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13.13. RFP RF Planning Tool Wizard

NI AWR’s frequency planning synthesis tool, the RFP RF Planning Tool Wizard, allows you to determine spurious free bandwidths. This wizard is an essential analysis tool when developing radio communications systems. It surpasses common spreadsheet analysis calculations and displays clear results in several formats. In addition to showing the power levels and frequencies of the signals, the root causes of the signals also displays. In addition to spur analysis, the RFP gives you the first cut of cascaded measurements such as NF, P1dB, SNR, and IM3, as well as spurious free dynamic range. The RFP is also seamlessly integrated with VSS software. You can generate designs in the NI AWR Design Environment software as VSS projects for further detailed analysis and optimization.

Using the RFP and VSS software to determine system specifications is better than a traditional spreadsheet-only method. VSS software provides a richer set of models, and calculations account for real world effects. In addition, yield analysis and optimization are available, and in-depth spur analysis is built in.

To access the RFP, open the Wizards node in the Project Browser and double-click RFP RF Planning Tool. The main RFP dialog box displays as shown in the following figure.

This first section of this chapter provides general information about the RFP Radio Frequency Planning Wizard through definitions, user interface graphics, and option descriptions. The second section includes an example that demonstrates the RFP tool's capabilities.

13.13.1. RFP RF Planning Tool Basics

Every RFP subnode of the RFP RF Planning Tool node in the Project Browser is an instance of the RFP wizard that contains one design object. A design object contains one or more system objects (also called "system states"). Most of the time, the main RFP dialog box displays the contents of the selected system, although there are other means and dialog boxes to access and modify all systems in the design. Each system object contains:

  • System Budget Specifications, which define the target values for gain, noise figure, compression point and other similar parameters for RF budget calculation. Budget specifications are located at the top left of the main RFP dialog box.

  • System Diagram, where components are cascaded. There is no restriction or certain template requirement for the order of components. They can be added in any order and RFP does necessary budget calculations, as well as finds a suitable frequency conversion scheme for a given order. The system diagram displays at the top of the main RFP dialog box. Each component is represented with a button you can click to edit. Some major parameters are also listed beneath the component buttons.

  • Input Signal Bands, (or Input Frequency Bands, or Input Bands), which define the RF inputs to each system. An input band is defined by three main values: min/max frequency and power level. There may be more than one input band for a system, and they can also be designated as threats. RFP has the capability to auto-adjust various parameters of components. One of the input bands is therefore called a “selected band”, whose frequencies the wizard uses to auto-adjust LO’s and IF frequencies.

  • Conversion Scheme, which defines how the RF to IF conversion through one or more mixer stages is performed. For example, in a two-stage frequency conversion system, one may take either RF-LO or RF+LO for the first IF. Depending on the conversion scheme chosen, RFP tries to auto-adjust all relevant LO’s and IF’s.

The RFP RF Planning Tool Wizard has the following system component types:

  • AMP - Amplifier

  • ATT - Passive or active attenuator

  • LPF - Lowpass filter

  • BPF - Bandpass filter

  • MIX - Mixer

  • SWT - RF Switch

  • SBP - Switched Bandpass Filter

  • ADC - Analog to Digital Converter

For details on parameters of components, see the Edit dialog boxes for the components.

13.13.2. Maintaining System States

The System States section of the main RFP dialog box provides access to all system states for editing.

The Wizard button displays the “Select Wizard Action Dialog Box”.

The Stages button displays the “System States - Conversion Stages Dialog Box” where you can edit input bands, and LO and IF frequencies of all systems in one place. For channelized downconverters, input bands are assigned to each channel. You can optimize input bands through this dialog box, where bands are easily edited and re-divided into channels.

13.13.2.1. Select Wizard Action Dialog Box

The Select Wizard Action dialog box includes buttons for creating pre-stored channelized frequency up/downconverter examples, as well as previously created designs. To access this dialog box, click the Wizard button in the main RFP dialog box.

  • Create New Design - Loads the selected built-in conversion settings into the wizard. These are typical frequency conversion examples that are pre-stored in the program.

  • Select a Previous Design - Loads the existing selected custom design. Each time the wizard runs, the design is stored and listed in the right pane of the dialog box for easy access.

  • Delete - Deletes the selected custom design from the pane on the right.

13.13.2.2. Up/Downconverter Wizard Dialog Box

The Up/Downconverter Wizard sets up RFP systems using the specified configuration settings. When you start this wizard, the diagrams and input bands in the main design dialog box are replaced with the new content as specified here. To access this dialog box, click the Create New Design button in the “Select Wizard Action Dialog Box”.

Under Number of Mixer Stages, select the number of conversion stages and the type of IF output as RF-LO, RF+LO or LO-RF. The LO behavior is selected from one of the following: Fixed LO(s) where LO's are user-specified and kept fixed, so the RF band maps to an IF band with the same bandwidth. Auto LO(x) - Fixed where the selected auto LO is automatically set, so the center of the RF band maps to the Final IF frequency and is fixed. The RF band maps to an IF band with the same bandwidth. Auto LO(x) - Tuning where LO is calculated to map every single frequency in the RF band into the single Final IF frequency. The RF band maps to a spot IF frequency.

Under Intermediate Frequency (IF), select IF centers as appropriate. Since only one of the LO(s) and IF(s) can be automatic, you must specify all other frequencies . RFP enables the frequencies that you should specify. Click the Search button to display the “LO/IF Search Dialog Box”.

Under Input Frequency (RF), specify the input RF bands that can be threatening or friendly. Select the Use Group BPF to cover all input bands check box to add an RF filter at the front end. Specify in Margin how much the filter must be extended on each side of the overall RF input range.

Under System Specifications, you enter specifications by clicking the Edit Specifications button. The Base name labels the system(s) with enumeration. If the Create one system per band check box is selected, RFP creates one system for each RF input band and assigns that band to the system as the active, friendly input. If this check box is cleared, only one system is created.

Under Components, you can select and edit the components you want to use. If Use Auto (Fo,BW) Parameters is selected, all filter frequency settings are turned into auto, and they are set to facilitate the intended RF/IF conversion. If this check box is cleared, the parameters remain as entered. Select the Use Auto (G,P1dB...) Parameters check box to automatically set all components with these parameters to auto mode. Select the Overall Gain[dB] check box to set the RF/IF conversion gain of the system.

13.13.2.3. LO/IF Search Dialog Box

The LO/IF Search dialog box is used for searching optimum, spur-free LO or IF frequencies. To access this dialog box, click the Search button in the “Up/Downconverter Wizard Dialog Box”.

To use this dialog box you first enter an RF input frequency range under RF specs, then select one of the following IF Conversion schemes:

  • RF – LO

  • RF + LO

  • LO – RF

Select either Fixed IF or Fixed LO as follows:

  • For Fixed IF, LO is swept according to RF to keep IF constant. IF BW determines the output window where the spurii is searched within. In practice, a bandpass filter follows the frequency conversion element (mixer) with a certain bandwidth, IF BW, which is only wide enough to allow data.

  • For Fixed LO, IF is calculated per the selected Conversion scheme. As a result, IF varies within a bandwidth that is the same as the RF bandwidth. In practice, the bandpass filter that follows the mixer has a fixed center frequency and bandwidth. The center frequency is calculated for the RF center frequency using the Conversion scheme. IF BW , where the spurii is searched within, is also equal to the RF bandwidth. As an example: For RF=3000-4000MHz and IF=RF-LO, when LO=2500MHz, IF varies between 3000-2500=500MHz and 4000-2500=1500MHz. This results in a fixed IF window of (500-1500MHz), which is centered at 1000MHz with 1000MHz bandwidth.

Under Search Limits, the options are used to limit the LO and IF ranges for search:

  • LOmin, LOmax, IFmin and IFmax determine the range of values LO and IF can take. They constraint the values when used as either a sweep variable or a resultant variable.

  • Freq Step is used as the increment value for search.

  • Ignore PdBc gives the threshold below which it is ignored as noise.

Click the Edit Spur Table button to display the “Spur Table Dialog Box” and set the spur level criteria, and then click the Search LO/IF button to search.

In an example with RFmin set to 6000, RFmax set to 6500, Conversion set to RF-LO, Fixed LO case, LOmin set to 1000, LOmin set to 5000, IFmin set to 100, IFmax set to 20000, Freq Step set to 100, and Ignore PdBc set to -80, since LO is fixed, IF is swept. The IF range to sweep is 100 to 20000MHz with a step of 100MHz. For each iteration of IF, LO is calculated from IF=RF-LO (or LO=RF-IF) and checked if it is between 1000-5000MHz. If so, it is recorded as a valid LO frequency and the resultant mixer spurs are calculated if they fall within the IF window. The IF window is centered at IF iteration value and its bandwidth is 500MHz (RF bandwidth). If the IF window cannot fit to positive frequencies, it is not a valid result, so the iteration is skipped to the next IF value. For example, when IF = 100MHz, a bandwidth of 500MHz cannot fit. In the previous example, the first valid IF frequency is 300MHz, where the IF window lies within (300-500/2=150) to (300+500/2=550). The first few lines of results for the search are:

LO                 IF-range                   Spurii
------             ------------               ----------------------------- 
2700,              3300-3800
1800,              4200-4700
1100,              4900-5400
4400,              1600-2100 S: [ 3x-4,        400-1900, -77]
4900,              1100-1600 S: [-3x 4,        100-1600, -77]

The results are given as sorted by the most spur-free frequencies. In the previous example, when LO is 2700MHz, 1800MHz, or 1100MHz, the corresponding IF windows do not contain any spurii above -80dBc. With slightly worse LO selections: LO=4400MHz, 4900MHz results in a 3x4 component at a level of -77dBc. The LO/IF Search utility can quickly search for a wide range of frequencies for spur-free conversions, and it is a strong alternative to the popular Spur Chart method.

13.13.2.4. System States - Conversion Stages Dialog Box

The System States - Conversion Stages dialog box provides access to the RF inputs, LO’s, and IF’s of all systems in one location. To access this dialog box, click the Stages button on the main RFP dialog box. This dialog box is mainly used for, but not limited to, channelized converter designs. Systems are listed together with their current active input bands, LO and IF set frequencies. If a system has a fixed LO, that LO is available to edit, otherwise, the corresponding IF is available for editing. For channelized converters, input bands are covered by channels in a contiguous manner. In RFP, channels are represented by systems. In this dialog box, you can change input bands for each system. For example, you can widen the System 1 band and narrow the System 2 band while keeping the bands contiguous.

Select the Re-assign input bands of systems check box if the RF bands edited in the dialog box are intended to re-assign all systems. It is best to give an example for how the bands are reassigned. For example, the input band (RF band) for System 1 is called Band 1, the input band for System 2 is called Band 2, and so on, so there are N bands for N systems. When you select this option and Inactivate all other bands as Threat, System 1 has only one active band (Band 1) and all the other bands are inactive for this system. Similarly, System 2 has one active band (Band 2) with all the other bands set to inactive. When you select Re-assign input bands of systems, and Active all other bands as Threat, System 1 has one active band (Band 1) and N-1 threat bands (Band 2 to Band N). Similarly, System 2 has one active band (Band 2) and N-1 threat bands (Band 1 and Band3 to Band N). When you select Show center frequency for LO/IF only, the LO/IF frequency ranges only display as center frequencies, which is easier to interpret in some cases. This dialog box display only ten systems at a time. To see additional systems, click the Prev States or Next States buttons.

13.13.2.5. System States Dialog Box

The System States dialog box is used to sort, rename or delete systems from a design. To access this dialog box, click the Edit button under System States in the main RFP dialog box.

Click the Move up or Move down buttons to change the index of the selected system in the design. The systems are listed in the dialog box by their index. System indices are used for re-assignment of input bands, plotting responses, and reporting plot information. Their names are display only. For example, if you select System_3 and move it up in the list, it is named and treated as [System#2] internally although the name is still System_3. Similarly, in this case, System_2 is moved down to third place, and is treated as [System#3] internally. To delete the selected system, click the Delete button. To rename the selected system, enter the name in the edit box, and click the Rename button.

13.13.2.6. System Setup Shortcuts

A System Setup drop-down menu is available at the top left of the main RFP dialog box to provide you with shortcuts to system-wide actions.

Select from the following options:

  • Load Example Designs to display the Select Wizard Action dialog box.

  • Load Systems from a Text File to load system setup from a text-based file. The file can be externally edited in Notepad if needed.

  • Save Systems into a Text File to save system setup to a text-based file. The file can be externally edited in Notepad if needed. When problems occur, this is a convenient way to check the wizard data and exchange with NI AWR support if needed.

  • Clear Systems and Bands to reset the working RFP environment by clearing all user-edited settings.

13.13.3. Maintaining the Selected System

The following sections include information on dialog boxes that provide system control and configuration.

13.13.3.1. Mixer Stages Dialog Box

The Mixer Stages dialog box is used to change the frequency conversion scheme of the current system. To access this dialog box, click the Mixers button under System Diagram in the main RFP dialog box.

Frequency conversion to an intermediate frequency (IF) occurs by adding RF and LO or by subtracting one from the other. For a single conversion RF-LO case, the equation is: IF = RF - LO. RF is already specified by input bands. IF and LO are therefore interdependent.

The way RFP functions depends on your option selection:

  • Fixed LO(s) - where LO's are manually entered and kept fixed. RF band maps to an IF band with the same bandwidth.

  • Auto LO(x) - Fixed - where the selected auto LO is automatically set so that the center of RF band maps to Final IF frequency and kept fixed. RF band maps to an IF band with the same bandwidth.

  • Auto LO(x) - Tuning - where LO is calculated to map every single frequency in RF band into the single Final IF frequency. RF band maps to a spot IF frequency.

For double and triple conversion, similarly, there is always one parameter that must be free from specification and it is calculated by using other variables. They are called Auto LO1, Auto LO2, Auto LO3, or Fixed LO(s). When Auto LO2 is selected, all other variables (for example LO1 and IF) are available for editing, and LO2 is automatically calculated from the edited variables. In the simplified system diagram at the bottom of the dialog box, the free variable is displayed in red. A test case is provided for easy interpretation of the conversion scheme. RF test frequency, which is also available in the main RFP dialog box, is input to the system and the basic conversion frequencies are displayed in the simplified system diagram. As in any mixer conversion, there are two major IF outputs: difference and addition of RF and LO. In the dialog box, they are shown after each mixer in two different colors. The IF that belongs to the selected scheme for the mixer is shown in black/white, and the other is shown in gray. To select the grayed IF output, select the corresponding conversion from the drop-down box provided in the same row as that LO, or simply click the grayed output. If an IF BW entry is used for checking the spurii for the selected conversion scheme, it determines the bandwidth of the IF window, where the spurii is checked to fall into. You can view Mixer spurious information by clicking the i (Information) button to toggle its display in a separate “Mixer Spurious Information Window”.

13.13.3.2. Mixer Spurious Information Window

The Mixer Spurious Information window displays the problematic frequencies of the selected mixer conversion scheme. To access this dialog box, click thei (Information) button in the “Mixer Stages Dialog Box”.

When RF, LO, and/or IF of the conversion scheme are given, an IF window is determined around the desired/given IF. The IF window bandwidth (IF BW) is specified in the Mixer Stages dialog box. A spur search is then performed and any spurious component that falls into the IF window is reported. The location in which the spur occurs is also reported as 1st IF, 2nd IF, and so on. You can toggle the order of spur table entries for calculation in or out by clicking the Edit Spur Check Options button at the top of the window to display the “Spur Check Dialog Box”.

13.13.3.3. Spur Check Dialog Box

The Spur Check dialog box toggles the mixer spur components in or out of the spur search. To access this dialog box, click the Edit Spur Check Options button at the top of the “Mixer Spurious Information Window”.

By clicking the check boxes next to rows or columns, the entire m or n of the mRF+nLO is included or excluded in the search. When a cell displays a "+", that (m,n) cell is used in the spur search. The rows are for m (RF) and the columns are for n (LO).

If you select the Include LO intermix check box, combinations of LO’s are included in the spur check. In practical converters, LO’s can leak through stages to mix with other LO’s to create false IF. For example, in a double conversion design, a 20dBm 1st LO leaks through the 1st mixer by 30dB attenuation. It is further attenuated by 60dB in the bandpass filter after the 1st mixer. This means that the 1st LO presents itself as an RF input to the 2nd mixer as 20-(30+60) = -70dBm. The mixer can then generate a false IF output by mixing -70dBm LO1 and LO2, even when RF is terminated by a load. Select this check box to observe in the Mixer Spurious Information Window if there is any possibility of LO intermixing issues.

The Include (2nd, 3rd) LO mixing with RF check box is used to include leakage of 2nd and 3rd LO’s into 1st stage in spur checks. When selected, the spur search algorithm treats 2nd LO and 3rd LO as 1st LO and calculates spurii output of them and the RF input. If they fall into the 1st IF, they are reported as problematic. This situation occurs in systems where 2nd and 3rd LO are not well isolated from the 1st mixer’s LO port. They behave like LO and their mixing with the RF output may create in-band IF products that are not possible to remove.

13.13.3.4. Analysis Setting Dialog Box

The Analysis Settings dialog box is used to change global settings for spectrum calculation. To access this dialog box, click the Settings button in the main RFP dialog box.

This dialog box mainly gives limits below which signals are ignored from analysis. If the limit is for an input, then any signal level below the given limit is ignored as an input. If the limit is for an output, then any signal under that power level is omitted from reports or from inputs to the next component.

Under General, Ignore Outputs Below sets the minimum level of a signal at any output to be counted as a "high-enough" signal for the next stage.

Select the Calculate Harmonics check box to include harmonics of frequency outputs to be used in analysis. 2nd- and 3rd-order harmonic outputs are calculated by using OIP2 and OIP3:

2nd harmonic output = 2*Pout – OIP2 – 6
3rd harmonic output = 3*Pout – OIP3 – 9.54

These are only linear approximations of harmonics. When a component is in output compression or in saturation for the fundamental frequency, harmonics are extremely difficult to calculate and there is no generic way, so you should use harmonic outputs for guidance only.

Harmonics are calculated for all components except LPF, BPF and MIX.

Click the Calculate IM products check box to include inter-modulation calculation in the analysis for all active components. IM products for mixers are always calculated. This option is mainly used for amplifiers with high-input signals. The wizard calculates IM products of high-power inputs in combinations of 2 at six frequencies:

F1-F2, F2-F1, 2*F1-F2, 2*F2-F1, 2*F1+F2, 2*F2+F1

13.13.3.5. Specifications Group

The Specifications group presents major system budget specifications and a button to access the System Specifications dialog box to edit them in full.

This group has two columns: the values on the left show the target specifications, while the values on the right show the actual values calculated for the system. An icon next to each row changes colors as targets are reached, approached, or missed. When a target value is reached or exceeded, the icon displays in green. If the actual value is slightly less than the target, the icon displays in orange. When the actual value reasonably falls short of the target, the icon displays in red.

You can directly edit values in this group. Due to the limited display area, not all of the budget specification parameters are displayed. To edit all of the specs, click the Edit Specifications button to display the System Specifications dialog box.

If attenuation or gain values of components are in Auto mode, the RFP RF Planning Tool Wizard tries to adjust them to match the overall gain specification by distributing the gain equally between auto-stages. For example, if G=10dB is specified and the system diagram is set up using a mixer with CL=6 and two auto-gain amplifiers, the gain of the amplifiers is set to 8dB each to make 16dB gain in cascade, which reduces to the desired 10dB when combined with the mixer’s conversion loss.

13.13.3.6. System Specifications Dialog Box

The System Specifications dialog box allows you to edit system budget parameters in detail. To access this dialog box, click the Edit Specifications button in the main RFP dialog box.

The two columns in the Specifications group display target and current values. You can edit the target values. The current values are calculated from the current system and are display only. Click the Set Target to Current Values button to set the target values to the current values. This auto-set is useful, especially when you want to set the system state as a reference and view changes in budget parameters when the system changes.

SNR and IF BW are used to calculate minimum discernible signal (MDS) and dynamic range. MDS and SFDR are calculated using the following equations:

MDS = -174 + 10*log10 (IFBW) + NF + SNR
SFDR = Phigh – Plow = (MDS + 2*IIP3)/3 – MDS = 2/3 * (IIP3 – MDS)

where IF BW is in Hz.

13.13.3.7. System Information Window

The System Information window displays the results of system budget calculations. To open or close this window, click the i (Information) button in the Specifications group in the main RFP dialog box to toggle its display.

This window shows live information with term descriptions. For more information, see RF Design Guide, a book by P. Vizmuller.

13.13.4. Maintaining Input Bands

Every system has input frequency bands. The Input Signals group in the main RFP dialog box contains options to maintain input bands.

To edit frequency band details, click the Edit button to display the Input Signal Bands dialog box. Additional options in the Input Signals group provide shortcuts to input band properties.

The text box next to the Edit button shows the index of the selected input band.

To select the previous or next input band, click the Previous Signal Band or Next Signal Band arrow buttons to the right of the text box.

The option to the right of the arrow buttons includes three options for band selection:

  • Traverse active bands only selects among the bands designated as active.

  • Traverse all bands, making unselected bands Inactive selects among all of the input bands, each time setting only one input band active and all others inactive.

  • Traverse all bands, making unselected bands Threat selects among all of the input bands, each time setting only one input band active and all others active but threat.

Every input band contains frequency and power ranges. Input bands also have a test frequency and test power that vary in the defined ranges. Power level is used in band or spot frequency analysis, whereas test frequency is only used in spot frequency analysis. The test frequency and power display as Fin and Pin. You can change these by typing new values, or by clicking in the option and then scrolling with the mouse wheel to change values. The buttons next to Fin and Pin are shortcuts for setting test frequency or test power to minimum, center, or maximum values in the range. The button color changes to green when you apply its test values.

IF displays the final IF frequency calculated for the test signal. When the conversion is any of the Auto LO(x) schemes (for example, fixed IF), you can edit the frequency here instead of opening the Mixers Stages dialog box.

Selecting the RF Image check box allows you to include RF image input for the first mixer in the system as a threat input. RF image for conversion schemes are:

For IF = RF – LO,	RF image input = LO – IF
For IF = RF + LO,	RF image input = LO + IF
For IF = LO – RF,	RF image input = LO + IF

Example: IF=RF-LO scheme is selected. RF=5000-6000MHz, LO=4000MHz, and RF test (Fin)=5500MHz.

In the spot frequency analysis, the intended IF=RF-LO=5500-4000=1500MHz. So, RF image occurs at LO-IF=4000-1500=2500MHz. If RF image is input to the system as a threat, it generates the same output as the intended IF: IF=|RFimage-LO|=|2500-4000|=1500MHz.

In the frequency band analysis, RF image is included as a threat band. RF image frequency for 5000MHz input is 3000MHz. Similarly, RF image frequency for 6000MHz input is 2000MHz. As a result, the RF image as a threat band is 2000-3000MHz.

When input bands pass mixer conversion stages in the LO-RF mode, they are inverted at the IF output. When a few mixing stages are combined, it becomes difficult to tell the inverted and non-inverted spectrum. You can select the Trapezoid Test Input check box to put a slant on the left-hand side of the RF input band so that the processed spectrum is more easily distinguished.

When you select RF Image, the threat input is automatically calculated and input in either spot frequency or frequency band mode.

Selecting the 1/2 IF input check box allows you to include RF threat input that generates half IF frequency at the first mixer output. Since the mixer generates multiples of differences as well, a 2nd order product of half IF falls exactly onto IF. Half IF threat inputs for conversion schemes are as follows:

For IF = RF – LO,	Half IF input = LO + IF/2 
For IF = RF + LO,	not practical
For IF = LO – RF,	Half IF input = LO – IF/2

Since this threat input is only IF/2 away from LO, it is difficult to remove half IF input by RF filtering. In practice, RF and LO are kept as far as possible to build immunity against half IF input.

Example: IF=RF-LO scheme is chosen. RF=5500-6000MHz, LO=4500MHz, and RF test (Fin)=5500MHz.

In the spot frequency analysis, the intended IF=RF-LO=5500-4500=1000MHz. So, half IF input occurs at LO+IF/2=4500+1000/2=5000MHz. If half IF threat is input to the system, the mixer’s 2*(RF-LO) generates 2*(5000-4500) = 1000MHz, which is exactly the intended IF.

In the frequency band analysis, half IF is included as a threat band. Half IF frequency for 5500MHz input is 4500MHz. Similarly, half IF frequency for 6000MHz input is 5250MHz. As a result, half IF input as a threat band is 4500-5250MHz. This example system normally has a pre-selection filter for 5500-6000MHz. With the mixer suppression, half IF input should be suppressed below system sensitivity so that it does not affect the dynamic range. A typical mixer suppression for 2*(RF-LO) product is 60dBc. If the maximum threat input power is 20dBm, and the sensitivity is -90dBm, the filter suppression is found as: 20dBm-60dB-S < -90dBm, which yields S > 50dB. 50dB suppression at just 250MHz away from the passband corner is a challenge. To overcome this, you need to choose a mixer with a high 2x2 suppression or a different LO.

13.13.4.1. Input Signal Bands Dialog Box

The Input Signal Bands dialog box is used to specify input signal frequency bands to a system. To access this dialog box, click the Edit Bands button in the Input Signals group in the main RFP dialog box.

Bands are listed in the Edit Bands group. Each band has frequency and power ranges, which have minimum, maximum, center, test and step values.

In the Band Properties group, Fmin and Fmax are the lower and upper frequency of an input band. In the frequency band analysis, these values determine the width of the input signal. In the spot frequency mode, Ftest (Fin in the main RFP dialog box) represents input signal frequency. Fstep is the step frequency used as the increment when clicking in the Fin option and then scrolling with the mouse wheel to change values. When you select the Auto check box, the program determines the frequency step automatically. Nominal frequency, Fnom, is not specified in this dialog box; it is automatically determined to be the center of the frequency range.

Pmin and Pmax are the lower and upper bounds of the power level. They do not contribute to analysis. In the main RFP dialog box, when you change Pin with the mouse wheel, these extrema come into effect to limit the value of Pin. Ptest is the test power of the input signal in both spot frequency and frequency band analysis. Pnom is the nominal power. When you click the Set Test Power to Nominal Power button next to Pin in the main RFP dialog box, Ptest is set to Pnom. Pstep is 1dB by default, but it is not specified in this dialog box.

Each band can be active or inactive (disabled). Active signals are always input to system during analysis. However, only one band is selected for the system to auto-adjust frequencies. To specify that band, select it and then click OK. Alternatively, click the Prev Signal Band or Next Signal Band button in the Input Signals group in the main RFP dialog box.

To activate a band for analysis, select the Active check box. Select the Threat check box to designate the selected band as a threat band. A band can be active but not threat; threat but not active; or inactive, so select check boxes accordingly.

By default, Fmin and Fmax are specified for frequency range. If you want to specify center frequency and bandwidth instead of corner frequencies, select the Fo,BW check box.

To add a new input band, click the Add New button.

To delete the selected input band, click the Delete button.

To set up multiple input bands with the same bandwidths and separated by the same frequency gap, click the Auto Setup button to display the Input Bands Auto Setup dialog box.

The Half IF/RF Image Interferers group contains options to generate half IF and RF image input threats to systems. The check boxes in this group activate the relevant threat band, while the edit boxes specify their power level. For details on interferers, see “Maintaining Input Bands”.

The Input Signal Bands dialog box applies to one system, however the System States group includes options to apply the input bands to all systems in the design. When you select the Apply Input Bands to All System States check box, Band 1 is assigned to System 1 as the selected band, Band 2 is assigned to System 2, Band 3 to System 3 and so on. Remaining bands are assigned either as threat or inactive. If you select Inactivate all other bands, then Bands 2 to N are set as inactive for System 1; Band 1 and Bands 3 to N are set as inactive for System 2, and so on. If you select Activate all other bands as Threat, those bands are activated and set as threat.

You can store input signals in an Input Signal Library and load from it as well. To add the current input bands to the library, click the Add Set button. To show the library click the Show button. When a library is shown and a signal set is selected, the name displays under Input Signal Library. When you edit signal properties, click the Update button to store the modified set back into the library.

The input signal library is stored in a text file in the User folder as ifp_SysInputs.txt. You can manually edit this file. If the file does not exist, click the Add Set button once to create the file and fill it with the current signal set. You can open the file and inspect for the format.

Input bands are displayed in graphical format at the bottom of the dialog box. The threat bands are drawn in red, and the normal (friendly) bands are drawn in blue. Change Plot Palette and Copy Plot Image to Clipboard buttons are provided to change the color palette and to copy the drawing onto the Clipboard as an image.

13.13.4.2. Input Bands Auto Setup Dialog Box

The Input Bands Auto Setup dialog box provides a quick way to set up input bands of the same widths and separated by identical gaps. To access this dialog box, click the Auto Setup button in the Input Signal Bands dialog box.

Number of Bands specifies the number of input frequency bands for a system.

Fmin of 1st Band is the lower corner of the first input band.

Channel Bandwidth is the bandwidth of each input band.

Guard Bandwidth is the separation between input bands. When this value is positive, the bands are separated from each other by this amount. When the value is negative, bands overlap, (the lower frequency of one band is lower than the upper frequency of the previous band by the guard bandwidth).

Input Pmin, Input Pmax, and Input Power are the minimum, maximum and nominal values of the input band power level.

The Make all signals active check box sets all of the input bands as active. When this check box is not selected, only the first input band is active; the other bands are disabled but ready for use.

The Vary power levels for distinction check box sets the nominal powers of input bands by decrementing 1dB. For example, if band 1 is 0dBm, band 2 is -1dBm, band 3 is -2dBm and so on.

13.13.4.3. System Input Signal Library Window

The System Input Signal Library window displays the input signal library and allows simple library operations. To access this window, click the Show button in the Input Signal Bands dialog box.

The list box at the top of the window lists the library items. Each item contains frequency bands and power levels as specified in the Input Signal Bands dialog box. When you select an item, its properties display in the lower half of the window.

Choose an item for use in the Input Signal Bands dialog box by selecting it and then clicking the Select button. In that dialog box under Edit Bands, the selected item shows "sel" appended to the band properties.

To delete a signal set from the library, click the Delete button.

To rename a signal set, click the Replace button.

To close the window, click the Close button.

13.13.5. Component Editing

The main RFP dialog box includes buttons for modifying components.

A drop-down box beneath each component button provides options for the following simple editing operations:

  • Click Delete to delete the selected component.

  • Click Insert to insert a component before the selected component. An Insert dialog box displays to allow you to select a position.

  • Click Clone to insert a copy of the selected component directly before the component.

  • Click Swap to exchange the selected component with the component that follows it.

  • Click Replace to replace the selected component with a component from the library. This option is only available when the component has an associated, opened library.

  • Click Same all to locate all components of the same kind and match their properties with those of the selected component. This command is useful, for example, when you change an amplifier in a cascade of amps and intend to replace all other amplifiers with that one.

13.13.5.1. Adding Component Shortcuts

The toolbar in the System Diagram group is used to add and modify system components.

To add a part from a library, click the Pick Part button. A Part Library window displays with a list of parts you can select.

When you click the Add Components with Auto-Parameters button, the system is in auto-parameter mode, where the auto-parameters of newly added components are set to Auto. For example, if you add a bandpass filter to the system in the auto-parameters mode, center frequency and bandwidth of the filter are set to Auto, so the system sets them automatically to pass the intended signal band.

When you click the Link Similar Parameters button, the system links parameters of similar components. For example, if you change the noise figure of an amplifier, the noise figure of all amplifiers in the diagram are synchronized to the new value.

The remaining buttons are for adding amplifier (AMP), attenuator (ATT), mixer (MIX), lowpass filter (LPF), bandpass filter (BPF), switched bandpass filter (SBP), RF switch (SWT), and analog-to-digital converter (ADC) components.

When you click the Clear Components button all components in the system diagram are deleted.

13.13.5.2. Part Library Window

The Part Library window allows you to select parts from a system parts library. To access this window, click the Pick Part button on the toolbar in the main RFP dialog box. You can also access this dialog box by clicking the Pick Part button in the component Edit dialog boxes.

RFP uses two sets of libraries: Factory shipped libraries and User libraries. The file format is the same for both types. Factory shipped libraries are read-only and provided only for reference. They are loaded from the NI AWR Design Environment installation folder. User libraries can be manually edited and stored anywhere on the computer. The location for User libraries is set using the top left Set Folder for Part Libraries button.

The parts are listed with A and U icons referring to factory shipped ( NI AWR) and User types. To display only the User libraries, select the Show User Parts Only check box. To filter out the displayed parts based on their operating frequency range, select the Frequency Range Filtering check box, enter minimum and maximum values and click the Apply button.

Part libraries are stored in simple text files with an intuitive format that you can edit for custom or commercial parts. Each part library has a unique file name and format. In library files, each line corresponds to a part, and properties are separated by a comma. Text beyond the "!" character is ignored.

RFP currently uses the following part libraries:

Amplifier library: ifp_AMP.txt

The following shows the format and some sample data for this library. Note that the data is wrapped into several lines for display purposes; the actual file must have one line per part.

!Make          PartNo      Type  Fmin  Fmax  Gain  NF    OCP1 OIP3 Gslop Fgain 
!
Mini Circuits, ZEL-0812LN, LNA,  800,  1200, 20.0, 1.5,  8.0, 18.0, 0.0,  0.0, 
Mini Circuits, ZEL-1217LN, LNA,  1200, 1700, 20.0, 1.5, 10.0, 25.0, 0.0,  0.0,

Vdd   Idd   IVSWR OVSWR  Pkg
!
15.0, 70.0, 2.5,  2.5,   Conn
15.0, 70.0, 2.5,  2.5,   Conn

The Make, PartNo, and Type properties can be any text and are used for classification and displaying the part in the tree. Fmin and Fmax give the usable range of the part in MHz. Gain, NF, OCP1, and OIP3 are budget parameters. Gslop is the gain slope [dB/GHz]; see “Edit AMP Dialog Box” for details on its use. Fgain is the frequency where Gain is defined. Vdd and Idd are supply parameters used to calculate total system power, which displays in the System Information window. IVSWR (input VSWR), OVSWR (output VSWR), and Pkg (package) data are reserved for future versions of the RFP Radio Frequency Planning Wizard.

Mixer library: ifp_MIX.txt

The following shows the format and some sample data for this library. Note that the data is wrapped into several lines for display purposes; the actual file must have one line per part.

!Make      PartNo    Type              RFmin   RFmax   LOmin   LOmax   IFmin   IFmax 
!                            
Marki MW,  M1-0204,  Double Balanced,  2000,   4000,    2000,   4000,    0,    2000,   
Marki MW,  M1-0208,  Double Balanced,  2000,   8000,    2000,   8000,    0,    2000,  

LOPow   ConvL   SSBNF    IIP3    ICP1  Is(R/I) Is(L/I) Is(L/R)  ImgRj  RefPin  M  N  
!
15.0,    5.0,    5.0,   16.0,    6.0,   20.0,   20.0,   38.0,    0.0,  -10.0,  5, 5, 
15.0,    6.0,    6.0,   16.0,    6.0,   20.0,   20.0,   38.0,    0.0,  -10.0,  5, 5, 
                       
(Spurii suppressions: MxN=(1x1),(2x1),(3x1),...,(1x2),(2x2),(3x2),..  M must be equal to N,
 1x1 will be overridden to 0dBc)     
!                         
(   0,  20,  10,  25,  20,  55,  50,  50,  50,  50,  50,  70,  55,  70,  60,  80,  95,    
(   0,  20,  10,  25,  20,  55,  50,  50,  50,  50,  50,  70,  55,  70,  60,  80,  95,  

!
95, 100,  90, 100, 100,  90, 110,  95),
95, 100,  90, 100, 100,  90, 110,  95),
                    
RSWR  LSWR  ISWR  Pkg
!
2.5,  1.5,  1.0, SMT
2.5,  1.5,  1.0, SMT

The Make, PartNo, and Type properties can be any text an are used for classification and displaying the part in the tree. RFmin, RFmax, LOmin, LOmax, IFmin, and IFmax give the usable range of the part in MHz. LOPow (LO Power), ConvL (conversion loss), SSBNF (noise figure), IIP3 (input IP3), and ICP1 (input compression point) are parameters as shown in the “Edit MIX”. Is(R/I), Is(L/I), and Is(L/R) are isolation in dB for RF/LO/IF leakages. Is(R/I) and Is(L/I) are used in the analysis as part of the Spur Table. Is(L/R) and ImgRj (image rejection) are reserved for future versions of the RFP RF Planning Tool Wizard. RefPin is the reference input power for the Mixer Spur Table. M and N are the dimensions of the Spur Table. The property in parentheses is a comma-separated Spur Table. Spur Table entries are given in positive numbers that correspond to suppression in dBc. The values are ordered by N first, and then M.

Example: 3,3 (0,5,10,15,20,25,30,35,40) is decoded as in (MxN) pairs as

(0x0)=0dBc,
(0x1)=Although it is specified here, it is overridden by L/I isolation.
(0x2)=10dBc
(1x0)= Although it is specified here, it is overridden by R/I isolation.
(1x1)=Although it is specified as 20dBc, it is overridden by RFP as 0 because this is the
 reference power.
(1x2)=25dBc
(2x0)=30dBc
(2x1)=35dBc
(2x2)=40dBc

RSWR (RF VSWR), LSWR (LO VSWR), ISWR (IF VSWR) and Pkg (package) are reserved for this version of the RFP RF Planning Tool Wizard.

RF Switch library: ifp_SWT.txt

The following shows the format and some sample data for this library. Note that the data is wrapped into several lines for display purposes; the actual file must have one line per part.

!Make     PartNo      Type   Fmin Fmax     IL      Isol    ICP1     IIP3    Vcont  Pkg
!
Hittite,  HMC190AMS8, SPDT,  1,   3000,    0.4,    30.0,   99.0,    99.0,    3.0 , MS8
Hittite,  HMC194MS8,  SPDT,  1,   3000,    0.7,    27.0,   30.0,    99.0,    5.0 , MS8
Hittite,  HMC197A,    SPDT,  1,   3000,    0.4,    50.0,   23.0,    99.0,    3.0 , SOT26

The Make, PartNo, and Type properties can be any text and are used for classification and displaying the part in the tree. Fmin and Fmax give the usable range of the part in MHz. IL, ICP1, and IIP3 are budget parameters. Isol is the isolation in dB when the switch is off. Vcont (control voltage) and Pkg (package) are reserved for future versions of the RFP Radio Frequency Planning Wizard.

RF Lowpass Filter library: ifp_LPF.txt

The following shows the format and some sample data for this library. Note that the data is wrapped into several lines for display purposes; the actual file must have one line per part.

!Make           PartNo          Type        Order   Fc      Datafile
FiltCompany1,    LP111,        Lumped,      5,      400,    Filter11.s2p
FiltCompany2,    LP121,        SSS,         7,      500,    Filter22.s2p
FiltCompany1,    LP131,        Cavity,      9,      600,    Filter33.s2p

The Make, PartNo, and Type properties can be any text and are used for classification and displaying the part in the tree. Order represents the degree of the filter, Fc is the passband cutoff frequency, and Datafile is the file name from which the S-parameters are read. The S-parameter file must exist in the User Library folder.

RF Bandpass Filter library: ifp_BPF.txt

The following shows the format and some sample data for this library. Note that the data is wrapped into several lines for display purposes; the actual file must have one line per part.

!Make           PartNo         Type        Order   Fmin     Fmax    Datafile 
FiltCompany1,    BP111,        Lumped,     5,      400,     600,    Filter1.s2p
FiltCompany2,    BP121,        SSS,        7,      400,     600,    Filter2.s2p
FiltCompany1,    BP131,        Cavity,     9,      400,     600,    Filter3.s2p

The Make, PartNo, and Type properties can be any text and are used for classification and displaying the part in the tree. Order represents the degree of the filter, Fmin and Fmax are the passband corners, and Datafile is the file name from which the S-parameters are read. The S-parameter file must exist in the User Library folder.

13.13.5.3. Edit AMP Dialog Box

The Edit AMP dialog box is used to edit the parameters of an amplifier. To access this dialog box, click an Amplifier component button in the System Diagram section of the main RFP dialog box.

Component Name is the name loaded from the library file when you select a part from the library.

Gain is the nominal gain of the amplifier. When you set it to auto by selecting the Auto check box, its value is calculated by the system to achieve the overall gain for the target specification.

Noise Figure, Output P1dB, Output IP3, and Output IP2 are all intuitive parameters. When set to Auto, Output IP3 and Output IP2 are calculated as follows:

OIP3 = OP1dB + 9.7
OIP2 = OIP2 + 20

Bias voltage and Bias current are supply parameters used to calculate total system power, which is calculated and displayed in the System Information window.

In the Frequency Dependence group, minimum and maximum frequency range for the component is specified. Outside the frequency range specified, the gain of the amplifier is changed by the Gain Slope. The equations that govern the gain variation at frequency F are given as:

G = Gnom – S * (Fmin – F) for F < Fmin
G = Gnom for Fmin < F < Fmax
G = Gnom – S * (F - Fmax) for F < Fmax 

13.13.5.4. Edit ATT Dialog Box

The Edit ATT dialog box is used to edit the parameters of an attenuator. To access this dialog box, click an Attenuator component button in the System Diagram section of the main RFP dialog box.

Component Name is the name loaded from the library file when you select a part from the library.

Attenuation is the set-attenuation of the attenuator. This is the fixed attenuator value for passive attenuators. When you set it to auto by selecting the Auto check box, its value is calculated by the system to achieve the overall gain for the target specification.

Output P1dB and Output IP3 are output compression point and third-order output intercept points. When you set it to auto by selecting the Auto check box, output IP3 is calculated as follows:

OIP3 = OP1dB + 9.7

Atten. Step is used in the main RFP dialog box when you scroll your mouse wheel over the attenuation to increase or decrease the attenuation step.

Min. Ins. Loss is a fixed loss associated with the component. For digital attenuators, this is the insertion loss in the data sheet when the attenuator is set to 0dB. Total attenuation for the component is therefore the sum of attenuation and the minimum insertion loss.

Max Attenuation is the upper limit of the attenuation and is mainly used for digital attenuators.

Example: For a 4-bit 15dB digital attenuator with 1.2dB insertion loss at its 0dB state, set the parameters as the following:

Attenuation = 0
Attenuation Step = 1
Minimum Insertion Loss = 1.2
Maximum Attenuation = 15

Then in the System Diagram section of the main RFP dialog box, you can scroll your mouse wheel over the attenuation to set it within the operating range of the component.

13.13.5.5. Edit MIX

The Edit MIX dialog box is used to edit the parameters of a mixer with input and output attenuators. To access this dialog box, click a Mixer component button in the System Diagram section of the main RFP dialog box.

Component Nameis the name loaded from the library file when you select a part from the library.

LO Frequency and LO Power are the local oscillator properties of the mixer. LO Frequency is only available for editing if the conversion scheme allows it.

Conv. Loss is the RF to IF conversion loss of the mixer. For most passive mixers, the value ranges from 6.5 to 8.

RF/IF port Att is the value of attenuators at both RF and IF ports of the mixer. This parameter is provided to save space in the system diagram. Alternatively, you can use individual attenuators by setting the parameter to 0.

Output P1dB, Output IP3, and Output IP2 are output compression point and third and second order output intercept points. When set to Auto, they are calculated as follows:

OP1dB = LO Power – 5
OIP3 = OP1dB + 9.7
OIP2 = OIP2 + 20

IF Conversion is the intended conversion scheme for this mixer. Three options are available:

  • IF = RF – LO

  • IF = RF + LO

  • IF = LO – RF

In some cases, the difference function (RF-LO or LO-RF) produces (-) frequency values due to improper selection of LO and RF inputs. In these cases, the program tries to use the alternative difference function momentarily to make the output frequency positive.

The Frequency Dependence group provides a mechanism to simulate out-of-band behavior of the mixer. You can specify RF and IF ranges through MinRF(LO), MaxRF(LO), MinIF and MaxIF parameters. Conversion loss slopes are specified by RF slope and IF slope. Outside the specified frequencies, the slope S modifies the conversion loss (CL) as follows:

CL = CL – S * (Fmin – F)		for F < Fmin
CL = CL				    for Fmin <F < Fmax
CL = CL – S * (F - Fmax)		for F > Fmax

Since there are two slope parameters, the effect is additive. You can set either RF or IF or both ranges and slope to simulate out-of-band conversion of the mixer.

To edit the spur suppression of the mixer, click the Spur Table button. A Spur Table dialog box displays for editing the 9x9 Spur Table.

To edit the spur suppression of the mixer and simulate a single stage conversion chart, click the Spur Chart button. A Spur Chart dialog box displays to enable editing the Spur Table.

13.13.5.6. Spur Table Dialog Box

The Spur Table dialog box is used to edit the spur suppression table of a mixer. To access this dialog box, click the Spur Table button in the “Edit MIX”.

You can enable editing and analysis of table rows and columns by selecting the check boxes next to M,N numbers. Spur Table rows belong to M (RF), and columns belong to N (LO). For example, the horizontal cells and check box (4) belong to the suppression m=4 in the equation IF = m*RF + n*LO. Similarly, the vertical cells and check box (4) belong to the suppression n=4 in the equation IF = m*RF + n*LO.

When cells are greyed, they are not editable and are not used in the analysis. Cells are color coded. The spur plots or spectrum plots use the same color codes as the table entries. Blue represents the intended 1x1 component as seen in the table. In the spur and spectrum plots, the intended signal is also drawn in blue.

The Use Mixer class drop-down allows quick setting of the table from standard double balanced mixer classes. The drive level in the selected option is used as a reference input power for the mixer.

13.13.5.7. Edit SWT Dialog Box

The Edit SWT dialog box is used to edit the parameters of an RF switch. To access this dialog box, click a Switch component button in the System Diagram section of the main RFP dialog box.

Component Name is the name loaded from the library file when you select a part from the library.

Insertion Loss is the loss of the switch in the ON state.

Isolation is the loss of the switch in the OFF state.

Output P1dB and Output IP3 are output compression point and third-order output intercept points. When set to Auto, output IP3 is calculated as:

OIP3 = OP1dB + 9.7

The Through path selected (On) check box sets the switch ON or OFF. When selected, the switch is selected ON (through path).

13.13.5.8. Edit BPF Dialog Box

The Edit BPF dialog box is used to edit the parameters of a bandpass filter. To access this dialog box, click a BPF component button in the System Diagram section of the main RFP dialog box.

Component Name is the name loaded from the library file when you select a part from the library.

Degree is the prototype order of the bandpass filter. It is also equal to the number of resonators for microwave filters.

Center Freq and Bandwidth are major passband parameters for bandpass filters. When you set Center Freq to Auto, the program automatically sets it to where the intended signal center or IF center is. When you set Bandwidth to Auto, the bandwidth is automatically set wide enough to allow the desired frequency range (or converted IF range) to go through. For example, if RF=5000-6000 is input to a mixer with LO=4000 and the conversion scheme is RF-LO, a bandpass filter used at the mixer output automatically sets itself to 1000-2000 to allow the desired IF to pass.

Insertion Loss is the loss for the whole passband.

PB Ripple is the passband ripple for Chebyshev filter types. Together with Degree, ripple helps determine the attenuation of a filter outside its passband. Due to its diminishing value in analysis, it is ignored for frequencies that fall in the passband of the filter.

Filter Type lists the filter types available. There are mainly Chebyshev and Maximally Flat types with three frequency mapping options: Standard, Quasi HP, and Distributed. You can add a bandpass filter to a system and compare filter responses by changing the filter type.

When you set Filter Type to Custom, the Edit button is enabled to allow custom frequency-loss editing for the filter in the Edit Custom Filter dialog box.

When the design is generated in the VSS program, the Custom filter type is mapped to the AMP_B component with gain and frequency data set in its GAIN and FREQS parameters. Chebyshev (standard) and Max. Flat (standard) filter types are mapped to BPFC and BPFB respectively. Other filter types are mapped to LIN_S, where the S2P data is stored in the Project Browser as a separate file.

13.13.5.9. Edit Custom Filter Dialog Box

The Edit Custom Filter dialog box is used to edit parameters for a custom lowpass/bandpass filter. To access this dialog box, select Custom as the Filter Type and then click the Edit button in the “Edit BPF Dialog Box” or “Edit LPF Dialog Box”.

At the top of the dialog box, the current passband frequencies display.

The Frequency Specification group specifies how the custom filter frequency points are interpreted. For Absolute Frequencies, the frequency points are assumed fixed and they are not changed by the program. For Offset Frequencies, the frequency points are updated as the reference frequency needs changing due to a changing input signal range. If, for example, the custom filter is a bandpass filter that follows a mixer, when the LO frequency changes, the IF center also changes. When Offset Frequencies is selected, this custom filter moves all frequency points accordingly so that the filter center frequency corresponds to the IF center and the shape of the filter is still preserved.

The list box in the middle of the dialog box displays frequency-loss (F,L) points of the filter. You can edit each (F,L) by changing the Freq and Loss under Point Data. Click elsewhere in the dialog box to update the data. You can also click in an option and scroll the mouse wheel to increment/decrement the values. The selected data point displays with a circle in the response plot.

The Losses at Freq Extrema group contains the loss parameters [dB] at F=0 and F=infinity. These frequency extrema do not have to be added to the list, as they are internally added to the analysis.

To add a new data point, click the Add button.

To delete the selected data point, click the Delete button.

Custom (F,L) data is used by interpolation. During analysis, if a frequency point falls between two data points, the attenuation of the filter is calculated by using a linear approximation.

The Auto-Set Points group contains options for quickly setting up the (F,L) data with Filter Order, PB Ripple, and # (F,L) points options. By clicking the Create Points button, you can create the exact attenuation data for the given filter type for frequencies that are program-selected. Frequencies are estimated by the program depending on the bandwidth and number of points. If the current frequency values are good and only a new attenuation profile is desired, then select the Calculate Loss only for Frequencies in the list check box.

13.13.5.10. Edit LPF Dialog Box

The Edit LPF dialog box is used to edit the parameters of a lowpass filter. To access this dialog box, click an LPF component button in the System Diagram section of the main RFP dialog box.

Component Name is the name loaded from the library file when you select a part from the library.

Degree is the order of the lowpass filter.

Corner Freq is the cutoff frequency of the filter. For maximally flat filters, it corresponds to 3dB point. For Chebyshev filters, it corresponds to the ripple corner. You can set this option to Auto to allow the desired frequency range to go through.

PB Ripple is the passband ripple for Chebyshev filter types. Together with Degree, this option helps determine the attenuation of a filter outside its passband. Due to its diminishing value in analysis, it is ignored for frequencies that fall in the passband of the filter.

Filter Type lists the filter types available. When this option is set as Custom, the Edit button is enabled to allow custom frequency-loss editing for the filter in the Edit Custom Filter dialog box.

When the design is generated in the VSS program, the Custom filter type is mapped to the AMP_B component with gain and frequency data set in its GAIN and FREQS parameters. Chebyshev (standard) and Max. Flat (standard) filter types are mapped to LPFC and LPFB respectively.

13.13.5.11. Edit SBP Dialog Box

The Edit SBP dialog box is used to edit the parameters of a switched bandpass filter. To access this dialog box, click an Sw.BPF component button in the System Diagram section of the main RFP dialog box.

A switched bandpass filter contains an RF switch, followed by a list of filter channels with one actively selected, followed by another RF switch. It is provided for convenience and to save space in the system diagram. You can use individual switches and auto-set bandpass filters if preferred.

Component Name is the name loaded from the library file when you select a part from the library.

In the Filter Banks group, the bandpass filter channels and the Selected channel display. The channels display in (F1, F2, InsLoss) format. For example, 4000,4250,1 corresponds to a bandpass filter in the 4000-4250MHz range with an insertion loss of 1dB. The Selected channel shows the selected bandpass filter index in the list.

The Filter Parameters group contains options for the common parameters of filter channels.

Degree is the prototype order of the bandpass filter. It is also equal to the number of resonators for microwave filters

PB Ripple is the passband ripple for Chebyshev filter types. With Degree, PB Ripple helps determine the attenuation of a filter outside its passband. Due to its diminishing value in analysis, it is ignored for frequencies that fall in the passband of the filter.

Filter Type displays a list of filter types available. There are mainly Chebyshev and Maximally Flat types with three frequency mapping options: standard, quasi HP and distributed. You can add a bandpass filter to a system and compare filter responses by changing the filter type.

Degree, PB Ripple, and Filter Type are bandpass filter properties that are identical for all channels.

The Switch Parameters group contains the parameters of the input and output RF switches.

Insertion Loss is the loss of the switches. There are two switches in SBP, one at the input and one at the output. Therefore, the overall insertion loss of SBP is 2*Switch IL + Selected channel IL.

Isolation is the loss of the switches. This parameter is reserved for future use.

Output P1dB and Output IP3 are output compression point and third-order output intercept points used when system budget is calculated.

13.13.5.12. Edit ADC Dialog Box

The Edit ADC dialog box is used to edit the parameters of an analog-to-digital converter. To access this dialog box, click an ADC component button in the System Diagram section of the main RFP dialog box.

Component Name is the name loaded from the library file when you select a part from the library.

Sampling rate is the analog-to-digital sampling rate in Mega samples per second.

13.13.6. Viewing System Response

There are four groups of buttons on the System Response toolbar.

The first group of buttons change response viewing mode. From left to right, the buttons are for:

  • Viewing the System Budget response

  • Viewing the System Budget response with Sweep Parameter

  • Viewing Spot Frequency Spur Schematic

  • Viewing Spot Frequency Response

  • Viewing Frequency Band Response

  • Viewing Spot Frequency/Frequency Band Response for all systems in the design

  • Viewing Spot Frequency/Frequency Band Response for the conversion stages in the selected system

The second group of buttons provide various options for the system response. From left to right, the buttons are for:

  • Changing the color palette of the drawing/graph

  • Changing the data pattern of the drawing/graph (click to experiment)

  • Showing/Hiding Nyquist zones. When shown, the dashed triangles show the Nyquist zones as determined by the ADC sampling frequency. The peak of the first triangle is FS/2. The vertical dashed lines show the actual input frequency band.

  • Showing/Hiding plot information in the System Response Window

  • Copying the System Response information to the Clipboard as text

  • Copying the drawing/graph to the Clipboard as an image

The third group of buttons provide Y-axis scaling for graphs. From left to right, the buttons are for:

  • Changing the Y-axes scale/div. Toggles between 1, 2, 5, 10, and 20dB per division.

  • Increasing the Y-axis reference level. Reference level is the value on top of the Y-axis.

  • Decreasing the Y-axis reference level. Reference level is the value on top of the Y-axis.

  • Editing Y-axis properties. This option is only available in the System Budget Response mode.

The fourth group of buttons provide X-axis (frequency) scaling for graphs. From left to right, the buttons are for:

  • Setting the analysis frequency range to Auto.

  • Increasing the analysis frequency span.

  • Decreasing the analysis frequency span.

  • Increasing the maximum analysis frequency.

  • Editing the analysis frequency span. This option is only available when the frequency range is not Auto.

13.13.6.1. Budget Response

System Budget Response viewing modes plot various parameters of popular system budget calculations on a conveniently laid out graph. To select this mode, click the Show Budget Response button on the System Response group toolbar. The X-axis displays system components from left to right, and data traces show how the budget parameters change after each stage.

Y-axis scaling, the line color, and the legend all display in the same color as a parameter for easy distinction. On the right, the data legend shows the reference level and scale/div. for parameters. The Y-axis scaling on the left is given for the selected parameter. To select a different parameter, click the parameter in the legend. The traces do not move in the plot; the Y-axis values are updated to reflect selected parameter reference levels and scale/divs.

When a specific parameter misses the target system specs (for example Gain or NF) at a system stage, the value that corresponds to the violation point is circled twice as a warning. It is useful for parameters such as NF, which cannot be improved by further stages once it falls out of spec at any stage.

You can change the text values and the trace types by clicking the Change Data Pattern button.

To display the parameter values, click the i (Information) button to display the System Response window, which provides a comprehensive list of budget parameters calculated at the output of each stage. A legend displays at the bottom of the window.

13.13.6.2. Budget Response with Sweep Parameter

You can view Budget Response by using a component parameter as a sweep variable. This mode is very useful when seeking an optimum value of a parameter. For example, what is the minimum LNA gain needed to maintain a specified NF? Although NF, P1dB are mostly intuitive, specifications such as SFDR are difficult to predict. In this view mode, you can plot SFDR against a component parameter with one mouse click.

To select this mode, click the Show Budget Response with Sweep Parameter button on the System Response toolbar.

RFP now varies the selected component parameter and calculates overall system responses, then uses the parameter values as the X-axis and plots the responses. The selected parameter is a different color, as shown in the following figure.

Also shown in the figure is the amplifier's gain parameter selected (clicked on). RFP then varies the selected gain between 0 and 40dB and plots the overall Gain, NF and SFDR. The variation ranges are predefined and do not need specifying.

13.13.6.3. System Budget Plot Options Dialog Box

The System Budget Plot Options dialog box allows you to edit trace properties of the system budget plot. To access this dialog box, click the Edit Left-axis scale/div button on the System Response group toolbar.

This dialog box contains all of the parameters you can plot. When you select the check box associated with a parameter, the parameter is plotted in the graph as a trace. You can select the Reference level and scaling for each parameter individually, and set the Small Signal Gain, P1dB, IP3, Actual Gain, and Noise Figure parameters to Auto. When set to auto, the reference level and scale/div of Small Signal Gain are used for these traces.

There is a difference between Small Signal Gain and Actual Gain parameters. Small Signal Gain is the cascaded calculation of gain and attenuation values that are specified for components, while Actual Gain is the gain calculated for the given input power. Since the gain may be compressed after stages, the actual gain may come out lower than expected. As the input power is decreased, actual gain approaches the small signal gain.

You can select P1dB and IP3 as Input or Output parameters when plotting by selecting the Input side or Output side option at the bottom right of the dialog box. Output values are calculated by adding Small to the Input values for P1dB and IP3.

13.13.6.4. Spot Freq Schematic View Mode

Spot Frequency Schematic is a view mode that provides a simplified schematic of the system with spot frequency progression through stages. To save space, only frequency-contributing stages display. To select this mode, click the Show Spot Freq Schematic button on the System Response toolbar.

The RF test frequency (Fin in the Input Signals group) is assumed to be input to the system. To the right of each stage, a list of output frequencies, power levels, and signal histories display. On top of the line that connects stages, the desired signal propagation displays. Underneath the connecting line, the spurii or harmonics are listed.

The information for each output displays in a color-coded format. The information contains Freq, History, and Level but it may be shortened, depending on the Data Pattern selection. Click the Change Data Pattern button to experiment. Some typical formatted lines are decoded as follows:

1000   0,1  -11   Fout=1000, Pout=-11dBm, it is calculated by IF=0*RF + 1*LO
2000  -1,3  -27   Fout=2000, Pout=-27dBm, it is calculated by IF=-1*RF + 3*LO
2000   2H   -57   Fout=2000, Pout=-57dBm, it is a 2nd harmonic.

To display all of the values stage-by-stage in a window, click the i (Information) button to display the System Response window.

13.13.6.5. Spot Freq Response View Mode

Spot Frequency Response is a view mode that displays the final output of the system for a spot frequency input. To select this mode, click the Show Spot Freq Response button on the System Response toolbar.

Each trace is color-coded with the same colors used in the Spur Tables. The signals are plotted in relation to Y-axis settings: Reference level and scale/div, which you can change with the Toggle Left-axis scale/div and Increase/Decrease Left-axis Reference Level buttons on the toolbar.

When a trace is resultant of a threat input, the arrow is red.

The RF test frequency (Fin in the Input Signals group) is assumed to be input to the system. The frequency shown on top of the traces corresponds to the calculated output frequencies.

On top of each trace, formatted data information displays. From top to bottom, the information reads Freq, Power, a separator line, and frequency history lines. Frequency history given as the bottom line corresponds to the first stage, and the top history line corresponds to the last stage. Frequency history contains data only for actual frequency changes. Components that do not contribute to frequency conversion (or harmonics, for example attenuators and filters) are not recorded as history.

If the system diagram contains a bandpass/lowpass filter through the end of stages, its response is plotted as an overlay. The filter trace draws in light green. Although the filter trace uses the scale/division of the graph, the reference level is ignored and the 0dB point of the trace is drawn near the top of the graph. The trace is provided for guidance only to understand how the output spectrum is shaped.

The filter trace is only drawn for the last filter in the diagram. The filter must not be followed by a mixer, either immediately, or after other components. Since the mixer converts the whole frequency spectrum, plotting a filter response for the spectrum before a mixer is pointless.

To display trace data in a window, click the i (Information) button to open the System Response window. Frequency information is also shown in the frequency history data.

13.13.6.6. Frequency Band Response View Mode

Frequency Band Response is a view mode that displays the final output of the system for a frequency band input. To select this mode, click the Show Frequency Band Response button on the System Response group toolbar.

Each trace is color-coded with the same colors used in the Spur Tables. The signals are plotted in relation to Y-axis settings: Reference level and scale/div, which you can change with the Toggle Left-axis scale/div and Increase/Decrease Left-axis Reference Level buttons on the toolbar.

The RF test frequency band (as selected in the Input Signals group) is assumed to be input to the system. The band is processed through stages and it evolves into more than one band at the output of each stage. For example, each input band to an amplifier produces three outputs: fundamental, 2nd, and 3rd harmonic. The width of the input band may also become longer through stages. For example, a 1-2GHz input to an amplifier produces 1-2GHz fundamental, 2-4GHz 2nd harmonic, and 3-6GHz 3rd harmonic.

On top of each trace, formatted data information displays. From top to bottom, the information shows the frequency history lines. Frequency history given as the bottom line corresponds to the first stage, and the top history line corresponds to the last stage. Frequency history contains data only for actual frequency changes. Components that do not contribute to frequency conversion (or harmonics, for example attenuators and filters) are not recorded as history.

If the system diagram contains a bandpass/lowpass filter through the end of stages, its response is plotted as an overlay. The filter trace draws in light green. Although the filter trace uses the scale/division of the graph, the reference level is ignored and the 0dB point of the trace is drawn near the top of the graph. The trace is provided for guidance only, to understand how the output spectrum is shaped.

The filter trace is only drawn for the last filter in the diagram. The filter must not be followed by a mixer, either immediately, or after other components. Since the mixer converts the whole frequency spectrum, plotting a filter response for the spectrum before a mixer is pointless.

To display trace data in a window, click the i (Information) button to open the System Response window to view the number of points that make up the trace, its minimum and maximum frequency, and maximum power level.

13.13.6.7. Viewing Responses of All Systems

To view the response of all systems in the Spot Freq Response or Frequency Response Band Response mode, click the Plot All System States button on the System Response toolbar.

The response, spot frequency, or frequency band displays for all systems in the same plot. Depending on the number of systems in the design, the plot layout is automatically arranged in columns and rows.

13.13.6.8. Viewing Spot/Band Responses of All Stages

To view the response of conversion stages of the selected system in the Spot Freq Response or Frequency Band Response mode, click the Plot Conversion Stages button on the System Response group toolbar.

The response, spot frequency, or frequency band displays for all conversion stages in the same plot. The input signal, spot, or band, is shown as stage 0. The first conversion stage (the first mixer output), displays as stage 1, and so on.

For every stage, a filtering trace can display if there is such a filter following a mixer output.

13.13.7. Generating Designs in the NI AWR Design Environment Software

After initial frequency planning is finished in the RFP RF Planning Tool Wizard, you can generate the design in the NI AWR Design Environment software as a VSS project for further detailed analysis and optimization. The Generate Design dialog box allows you to generate a VSS system diagram for the selected system in the RFP. To access this dialog box, click the Generate Design button in the main RFP dialog box.

Diagram Name is the title of the VSS diagram to generate.

Select the Overwrite existing items check box to overwrite generated items in the NI AWR Design Environment software. If the generated item already exists and this check box is not selected, RFP does not create the new item and a warning that the item already exists is issued.

In the Graphs and Simulation group, there are options to generate analysis setups and initiate them upon generation. Click Generate graphs and one or both of the RF check boxes beneath it to create graphs. Select the Simulate after generating the system diagram check box to start analysis after generation.

13.13.8. Utilities

RFP provides some popular utilities for system design. To access the following utilities, click the Utilities or Spur Chart buttons in the main RFP dialog box to display the Utilities dialog box or Spur Chart dialog box respectively.

13.13.8.1. Sensitivity

The Sensitivity utility provides a quick way to calculate system sensitivity and related information. To access the Sensitivity utility, click the Utilities button in the main RFP dialog box to display the Utilities dialog box, then click the Sensitivity tab.

Sensitivity or minimum discernible signal (MDS) [dBm] of a receiver system is defined by the following equation:

MDS = -174 + 10*log10 (IFBW) + NF + SNR

where IFBW is the IF bandwidth [Hz], NF is the input referred noise figure [dB] and SNR is the minimum required signal to noise ratio for reception of a signal [dB].

Spurious free dynamic range (SFDR) of a system is given by the difference between maximum and minimum receivable signal levels:

SFDR = (MDS + 2*IIP3)/3 – MDS

where IIP3 is the third-order input intercept point.

MDS and SFDR are the resultant values and therefore grayed. All other parameters are available for editing. Noise Figure, Noise Factor (F) and Effective Noise Temp [K] are interrelated and you can specify any of them:

NF = 10 * log10 (F) Te = 290 * (F-1)

MDS[uV] is the microvolts equivalent of MDS[dBm] of power on 50 ohms load.

13.13.8.2. Path Loss

The Path Loss utility provides a quick way to calculate free space path loss. To access the Path Loss utility, click the Utilities button in the main RFP dialog box to display the Utilities dialog box, then click the Path Loss tab.

Free Space Path Loss is given by:

Path Loss = 92.44 + 20*log10(D) + 20*log10(F)

where D is the distance from the transmitter and receiver [km] and F is the frequency [GHz].

In this dialog box you specify Freq (frequency) and Distance, while wavelength and Free Space Path Loss are resultant values, so uneditable.

13.13.9. Spur Chart

Spur Chart is a conventional and useful technique to assess spurious free regions for a single-stage frequency conversion. To access spur chart, click the Spur Chart button under Control Panel in the main dialog box.

In the RF/IF Window group, you enter the main frequency conversion parameters. RFmin and RFmax determine the range for the input frequencies. You specify a conversion scheme in the IF drop-down. For up-conversion select RF+LO and for downconversion, select RF-LO or LO-RF. Next, select the behavior of LO:

  • For fixed LO conversions, select LO. RFP tries to map the center of the desired RF band into the center of the IF band by using the specified LO. For example, if RF=4000-5000, and LO=7000, and LO-RF is selected, IF is centered at 7000-4500=2500. In the previous figure, RF is plotted on the X-axis and IF is plotted on the Y-axis with the band centers clearly seen. The RF-to-IF mapping window displays in light blue.

  • For variable LO conversion, select IF and specify IF for the target IF center and BW for the sub-band widths. RFP calculates the necessary LO values to map separate RF sub-bands into the same IF window. For example, the following figure shows 200MHz sub-bands being converted into IF=2500. The LO value for the sub-band 4000-4200 is 6600, and for the 4200-4400 it is 6800, and so on. The plot shows five separate IF windows, with spurii coming from all conversions plotted in the same place. It is useful to plot multiple spurii when RF channelizing filter is not used. In this case, spurii are generated for all signals in the RF band, not only the sub-band of interest. This conversion mode makes it easy to visualize all different LO conditions in one plot.

The Analysis Range group is used to determine the X- and Y- ranges for the chart. If auto-scaling is needed, select the Auto range check box. To quickly fit and center the IF window in the chart, click the Fit button.

The Spur Table group presents the spurii levels in clickable rows and columns for mxn products. You display the desired m or n products by selecting the row or column. Rows correspond to m and columns correspond to n in +/-mRF+/-nLO.

Table entries and plotted traces are color-coded. If you click on a table entry, the corresponding trace is highlighted on the plot. Similarly, clicking on a trace highlights the corresponding table entry.

You specify the Spur Table reference input power in Ref. Input Power. The entries are automatically populated if a predefined Mixer class is specified by changing the Load. This selection is only used to load values into the Spur Table and is not used afterwards. You can also populate the table by clicking the Pick Mixer button to select a mixer from the part library.

You can display the actual spurii levels by selecting the Test with Pin check box to calculate the actual spurii levels in [dBm] and display them in the grayed-out table. The entries are not editable when this check box is selected.

Often, many less important spurii traces clutter the Spur chart. You can hide from the plot those that fall below a set threshold by selecting Hide Spurs if below Warning Level [dBc] and specifying the threshold in Warn if |dBc| is <.

13.13.10. RFP RF Planning Tool Wizard Example

The following example demonstrates RFP RF Planning Tool Wizard capabilities. A final step for VSS program use is also presented. Any changes you make prompt the wizard to recalculate the auto parameters, analyze the system response, and display all results in graphs and windows. No action is necessary to update the results as they are live data.

  1. In the main RFP dialog box, under System States, click the Wizard button to display the Select Wizard Action dialog box.

  2. Select Clear Systems and Input Bands.

  3. In the main RFP dialog box, under the Input Signals group, click the Edit button to display the Input Signal Bands dialog box.

  4. Under Band Properties, change Fmin to "960" and Fmax to "1010", then click OK.

  5. In the main RFP dialog box, on the System Response toolbar, click the Show Spot Freq Schematic button, then click the Add Mixer button at the bottom of the System Diagram window, as shown in the following figure.

  6. Change LO to "650" (MHz), and under RF Test Signal, set Fin to "1000" (MHz) and Pin to "-10" (dBm).

  7. Click the Change Data Pattern button to change the display of IM products and power levels, as shown in the following figure, then click the Mixer icon to display the Edit MIX dialog box.

  8. In the Edit MIX dialog box, click the Spur Table button to display the Spur Table dialog box.

  9. Ensure the Spur Table values match the following, then click OK.

  10. Click the Spur Chart button next to the Spur Table button to display the Spur Chart dialog box.

  11. Under RF/IF window, set RFmin to "990" (MHz) and RFMax to "1010" (MHz). You can also optionally select Use Henderson's tables to use a pre-defined behavioral mixer.

  12. Click the Show/Hide Plot Info button to toggle the display of Spur Chart information in tabular format in a System Response window. You can leave this window open while changing any frequency in the Spur Chart by selecting the frequency and typing a new value or scrolling the mouse wheel to change the frequency in 10 MHz steps (or press the Ctrl key while scrolling to change the frequency in 1 MHz steps). When you change a frequency, the Spur Chart and System Response windows both reflect the change.

  13. Set RFmin to "980" and display the Spur Chart information.

  14. Click the Show/Hide Plot button to hide the Spur Chart information, then set RFmin to "960" and click outside of the option. Three more spurs are generated in the band and shown as new lines in the Spur chart.

  15. Click on trace (-3,5) and note that the dBc value is highlighted in the Spur Table.

  16. Click the Show/Hide Plot button to display the Spur Chart information. The band spurs shown in tabular format show RFMin as 960 MHz and RFmax as 1010 MHz.

  17. Close all open windows and return to the main RFP dialog box. On the System Response toolbar, click the Show Spot Freq Response button, and then click the Auto Frequency Span button to manually set the frequency span.

  18. Click the Set Frequency Span button to display the Analysis Range dialog box. Set the Fmin and Fmax values as shown, then click OK.

  19. You can use the Increase Left-axis Reference Level and Decrease Left-axis Reference Level toolbar buttons to adjust the left axis scale, and the Toggle Left-axis scale/div button to adjust y-axis scaling 1dB/div, 2dB/div, 5dB/div and 10dB/div.

  20. The spectrum plot displays as follows. You can click the Change Data Pattern button to change the values that display on the spurs.

  21. Select the LO frequency and press the Ctrl key while scrolling the mouse wheel to change its value in 1 MHz steps. As you sweep, the LO the spectrum changes. The following figure shows LO set to 653 MHz. After viewing the results, set LO back to "650" MHz.

  22. Use the Increase Left-axis Reference Level and Decrease Left-axis Reference Level toolbar buttons to adjust the left axis scale, and the Toggle Left-axis scale/div button to adjust y-axis scaling to the values shown in the following figure. Click the Add Bandpass Filter button to add a filter, and then click the BPF icon to display the Edit BPF: Bandpass Filter dialog box. Note the settings in this dialog box and then close it. Click the Show Frequency Band Response button and note the filter response displayed on the graph.

  23. Click the Change Data Pattern button and use the Increase Left-axis Reference Level and Decrease Left-axis Reference Level toolbar buttons to adjust the left axis scale to the values shown in the following figure.

  24. Click the Add Amplifier button to add an amplifier, and then on the System Response toolbar, click the Show Plot Information button to display the System Response window with Spur Chart information in tabular format. Click the Decrease Left-axis Reference Level button to adjust the left axis as shown in the following figure.

  25. Click the Mixers: Fixed LO button to display the Mixer Stages dialog box. In the Mixer Stages dialog box, select Auto LO1 - Fixed to fix the IF. Now as you sweep on the RF the LO tracks it.

  26. To export the design to the NI AWR Design Environment platform, under Control Panel, click the Generate Design button to display the Generate Design dialog box and specify a diagram name and graph and simulation options.

    NOTE: Subsequent new designs use the latest frequency plan properties instead of requiring you to re-enter specifications.

  27. You can continue with the VSS program to:

    • consider account impedance mismatch

    • account for frequency dependency

    • run yield analysis

    • perform optimization

    • simulate with modulated signals: EVM, BER, and ACPR

    • replace ideal models with circuits created in Microwave Office or Analog Office programs and/or measured data

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