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Oscillator with Optional Phase Noise Effects: OSC_S

Symbol

Summary

OSC_S imports the characteristics of a Microwave Office oscillator design into Visual System SimulatorTM (VSS) software. The power level, oscillation frequency and phase noise can be obtained from the Microwave Office simulation. The oscillation frequency is determined from the nonlinear simulation at the specified harmonic index while all other harmonics are ignored. The Microwave Office circuit must contain an oscillator phase noise simulation in order to model phase noise.

This block supports parameterized Microwave Office subcircuits and swept variables in the Microwave Office circuit. See Section 1.7 of the VSS Modeling Guide for details.

Parameters

Name Data Type Description Unit Type Default
ID N Element ID Text V1
NET S Microwave Office subcircuit name N/A M
PORT I Port number Scalar 1
FRQ R Oscillator frequency (if empty, it will be calculated from the nonlinear circuit) Frequency  
HARMIDX I Harmonic index (fundamental oscillation frequency=1) Scalar 1
PWR R Oscillator power (if empty, it will be calculated from the nonlinear circuit) Power in dB  
PHS R Phase offsets Angle 0
CTRFRQ R Center frequency Frequency  
SMPFRQ R Sampling frequency Frequency  
ZS C Source impedance Resistance _Z0
T R Output noise temperature Temperature _TAMB
NOISE E Thermal noise modeling N/A Auto
*TNRSEED I Thermal noise random number generator seeds Scalar  
PNOISE E Phase noise modeling N/A No phase noise
*PNTYP E Phase noise type N/A Traditional
*PNNFLT I Phase noise filter order Scalar 10000
*PNRSEED I Phase noise random number generator seeds Scalar  
*RFBSRC E RF Budget Analysis source frequency type N/A Auto
*SMPSYM R Samples per symbol Scalar _SMPSYM
*BLKSZ I Samples per pass Scalar _BLKSZ * _SMPSYM
*IVARTYP   Treatment of parameters for schematic swept variables   Allow any value for numeric

* indicates a secondary parameter

Parameter Details

NET. The name of the Microwave Office circuit. The name must be enclosed in quotation marks.

PORT. The port number in the Microwave Office schematic that is used as the measurement port.

FRQ. The oscillation frequency. If this parameter is empty, the value is calculated from the nonlinear oscillator simulation.

HARMIDX. Harmonic oscillation frequency. Most standard free-running oscillators have the harmonic index=1 (fundamental). Multiplier-type oscillators will operate at a harmonic of the fundamental. The frequency, power and phase noise are all calculated at this harmonic.

PWR. The oscillator power at the oscillation frequency. Leave empty to use the power from the Microwave Office simulation.

PHS. The phase offset for the oscillation frequency. Leave empty to use the phase from the Microwave Office simulation.

CTRFRQ. The center frequency for the complex envelope signal. If this is left empty, the center frequency will be automatically determined from either downstream blocks or the oscillation frequency.

SMPFRQ. The sampling frequency for the signal. If left empty this will be determined automatically, as follows. If there is nothing else in the signal path downstream to help determine a sampling frequency, then the sampling frequency is set to _SMPFRQ = _DRATE * _SMPSYM from the Options > Default System Options menu of the project. The sampling frequency can also be back-propagated to the block when it is specified somewhere else in the chain. For example, this happens when a signal with a specified sampling frequency goes through a mixer (or adder, combiner, etc.) for which this block is the LO. Then the sampling frequency of the block is set to the value back-propagated through the two-input block.

ZS. The source impedance of the generator.

T. The noise temperature of noise generated by the block if noise is enabled for the simulation type by NOISE. The noise generated is white noise.

NOISE. Determines how thermal noise is to be modeled:

  • RF Budget only: Noise is modeled for RF Budget Analysis simulations, but not Time Domain simulations.

  • RF Budget + Time Domain: Noise is modeled for both RF Budget Analysis and Time Domain simulations.

  • Noiseless: The block is assumed to be noiseless in all simulations.

  • Auto: The setting is determined from the RF Noise Modeling setting on the RF Optionstab of the System Simulator Options dialog box.

TNRSEED. Seeds for the random number generator used to generate thermal noise samples. Up to four values may be entered. If this is left empty, the seed will be generated based on the block name and ID parameter.

PNOISE. Determines how phase noise is to be modeled.

PNTYP. Determines how the phase noise mask is obtained from the Microwave Office circuit.

  • Traditional: Values are obtained similar to the Microwave Office PH_NOISE measurement with "Default" set for the noise computation method.

  • LSB Noise-to-Carrier: Values are obtained similar to the Microwave Office L_LSB measurement with "Default" set for the noise computation method.

  • USB Noise-to-Carrier: Values are obtained similar to the Microwave Office L_USB measurement with "Default" set for the noise computation method.

NOTE: The ability to generate time domain phase noise matching the phase noise mask is limited by the sampling frequency and the total phase noise to be generated. As the average phase noise generated by the FIR filter bins approaches or exceeds the inverse of the sampling frequency, the phase noise samples wrap around ±π and the phase noise samples effectively alias. Section 3.4.2 in the VSS Modeling Guide details the equations involved.

PNNFLT. The filter order of the FIR filter used to shape the phase noise spectrum. If an odd value is specified, one will be added to make the filter order even.

PNRSEED. Seeds for the random number generator used to generate phase noise samples. Up to four values may be entered. If this is left empty, the seed will be generated based on the block name and ID parameter.

RFBSRC. Determines how the RF Budget Analysis frequencies for this source are determined. The frequencies are computed by adding the frequency offsets specified in the RF Frequencies tab of the System Simulator Options dialog box to a base frequency, which is determined by the selected RFBSRC option:

  • Auto: If the signal is a real signal, and only one frequency offset was specified, the behavior will be the same as "Signal Frequency", otherwise the behavior will be the same as "Center Frequency (v7.5)". This behavior lets you easily configure an RF Budget Analysis simulation for mixers using real signals.

  • Center Frequency (v7.5): The frequencies are computed by adding the frequency offsets to the center frequency. This is the same behavior as VSS v7.5 software.

  • Signal Frequency: The frequencies are computed by adding the frequency offsets to the average of the frequencies in FRQ. This is useful if the center frequency cannot be the same as FRQ, or if a real signal is being generated.

SMPSYM. The number of samples per symbol associated with the signal. Although not directly applicable to RF tones, samples per symbol is used by various blocks to define a data bandwidth, which is the sampling frequency divided by the samples per symbol.

BLKSZ. The number of samples generated each time the block is visited.

IVARTYP. Determines the behavior of the dynamic parameters representing the swept variables of the Microwave Office schematic.

  • Allow any value for numeric, pin to nearest: The parameters allow any numeric value, and the data set with the swept variable closest to the parameter value is used.

  • Select from list: The parameters display a list of available values for the swept variables.

Data Output

Node No. Type Purpose
1 Real Oscillator signal

Implementation Details

OSC_S utilizes the same implementation as Tone(s) Source, TONE. Refer to TONE for details on the implementation.

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