Go to www.awrcorp.com
Back to search page Click to download printable version of this guide.

13.18. Load Pull Script

The Load Pull Script allows you to perform load pull simulations on a device model. To run this script choose Scripts > Load Pull > Load_Pull. This script has a number of features:

13.18.1. Generating a Load Pull Template

Load pull simulation is run from a load pull template schematic that defines the source and load tuners, the voltage and current meters where simulation data is measured, and simulation sweeps.

13.18.1.1. Standard Load Pull Template with Two Tuners

To add a template schematic to a project, choose Scripts > Load Pull > Create Load Pull Template (if the project already contains a load pull template schematic this script adds an additional template), or choose Scripts > Load Pull > Load_Pull to add a template schematic to a project if one does not already exist.

13.18.1.2. Modified Load Pull Template with One Tuner and One Fixed Termination

If the source termination needs to be modeled by a fixed and frequency-dependent reflection coefficient for a swept frequency load pull analysis, then the template schematic can be edited to replace the source tuner with a linear network and a GPROBE2 element in series with it. In the following figure, the "Input_Match" SUBCKT could contain, for example, an LPTUNER2 element (with ports 1 and 2 swapped), or a previously designed matching and biasing circuit, or a 2-port s-parameter data file and a BIASTEE in series.

13.18.2. Generating a System Load Pull Template

System load pull simulations are run from a system load pull template that defines the complex source and sinks for any associated measurements along with any system level sweeps.

To add a system template to a project, choose Scripts > Load Pull > Create System Load Pull Template (if the project does not contain a circuit load pull template, a template is auto-created.)

13.18.3. Performing Load Pull Simulations

To perform a load pull simulation, choose Scripts > Load Pull > Load_Pull. If the project has only one load pull template schematic or if the current active window is a load pull template schematic then the first dialog box to display is the Load Pull Gamma Sweeps dialog box.

If there are multiple load pull template schematics in the project and the current active window is not one of them, the first dialog box to display is the Choose Load Pull Template Schematic dialog box.

When performing system load pull simulations you should read the template carefully and note the following:

  • System level measurements must be set up prior to the simulation.

  • Measurements such as ACPR and EVM must plot a single point for each sweep.

  • Waveform measurement are not compatible because they need more than one point per sweep.

  • The derived values of Output Power, Available Source Power, and Transducer Gain are automatically added to the load pull data file when the load pull simulation is preformed.

  • The simulation is run the same as a circuit load pull by choosing Scripts > Load Pull > Load_Pull. The rest of the interface is the same as circuit load pull.

13.18.3.1. Load Pull Gamma Sweeps

The Load Pull Gamma Sweeps dialog box is used to select which tuner and harmonics to sweep during the load or source pull. You can select as many check boxes as needed. For example, Load Harmonic 1 is a fundamental load pull only, Source Harmonic 1 is a fundamental source pull only, and Load Harmonic 1 and Source Harmonic 1 are a nested fundamental source and load pull.

13.18.3.2. Load Pull Gamma Points

The Load Pull Gamma Points dialog box and associated graph guide you through the load pull gamma point selection. There are two methods for setting up gamma points:

  • Custom - define your own points with the dialog box controls

  • Existing Measurement - choose the points from an existing LPGPM, G_LPGPM, or LPGPT measurement (useful for using points defined in an existing load pull data file)

If you choose Custom as the Gamma Point Type you need to define the load pull points using the controls in the Load Pull Gamma Points dialog box. There are four point computation modes from which to choose:

  1. Circle Fixed Angle - You control the radius, center of the circles, and number of circles. The number of points on each circle depends on the radius of the circle.

  2. Circle Fixed Points - You control the radius, center of the circles, number of circles, and number of points per circle. The number of points on each circle is a fixed number.

  3. Uniform Distribution - You control the radius, center of the circles, and density of the point distribution within the circles.

  4. Square - You control the radius, center of the squares, and number of rows and columns.

The filtering control allows you to apply a 90-degree window outside of which the points are not used in the load pull analysis. The angle of the filtering window can be set to a fixed quadrant of the Smith Chart or to the angle specified under Custom Gamma Points Center Angle. If you choose Existing Measurement as the Gamma Point Type the load pull data points are taken from the chosen LPGPM, G_LPGPM, or LPGPT. measurement.

13.18.3.3. Load Pull Setup

In the Load Pull Setup dialog box you select the source and load tuners, the voltage and current meters used to record the load pull data, the name of the data file generated, and the number of harmonics to capture in the data file. If you have not edited the names of the tuners and meters in the load pull template schematic, those fields are correctly configured.

If you modified the template to implement a fixed frequency-dependent source termination, then you must set the Source Tuner in this dialog box to the GPROBE2 in series with it. NOTE: Measurements dependent on available input power (PSrc_Ava) will be invalid if the fixed matching network is lossy.

After the load pull analysis is complete, you can make measurements on the generated data file. The following is an example of a load pull script result run on the schematic shown. To re-run a load pull without the dialog boxes, right-click the Load_Pull_Template node and choose Options to display the Options - Load _Pull_Template dialog box. On the User Attributes tab, set Skip Dialogs to "1". For information on other attributes contact NI AWR support.

The following graph shows the simulated gamma points (G_LPGPM measurement) and Output Power and PAE contours (G_LPCM measurement). Obviously these gamma points were not optimally selected for this device, but the mechanics of the load pull simulation and subsequent data plotting are shown.

Please send email to awr.support@ni.com if you would like to provide feedback on this article. Please make sure to include the article link in the email.

Legal and Trademark Notice