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VSS System Load Pull Example
This example shows a common use case and setup procedure for a system level load pull simulation. This analysis should be used to look at system level characterizations, ACPR or EVM for example, while preforming load pull analysis on a specific device in the system chain such as a power amplifier. The setup of the project is slightly more involved and outlined below. Furthermore, there are setup instructions located on both the Load_Pull_System_Template and the circuit/device Load_Pull_Template. Note that both the circuit and system simulators must be run to populate all graphs.
• Add a system load pull template by choosing Scripts > Load Pull > Create_System_Load_Pull_Template (A circuit load pull template will be added automatically if one does not already exist)
• Follow the directions on both the system and circuit load pull templates to configure them correctly.
• Set up the system level characterization measurements. For example, ACPR and EVM, are show in this example. A few caveats below:
o Measurements must have the F1 variable set to Use for x-axis
o Output power, available source power and transducer gain measurements are automatically added when the load pull simulation is performed.
o Measurements must plot a single trace per sweep, and thus waveform measurements are not load pull compatible.
• After the system and circuit load pull templates are configured run load pull using Scripts > Load Pull > Load_Pull
• Follow the on screen dialog to set up the load pull parameters (very similar to the circuit load pull setup)
• After the load pull simulation the load pull data will show up as a data file under the Data Files node in the project browser. The data can be plotted using the new load pull measurements (Load Pull > G_******)
This is the system load pull template created from the Scripts > Load Pull > Create_System_Load_Pull_Template. This template points to the circuit load pull template via the NL_S or NL_S_ENV elements. Directions are provided on the created template to aid in the appropriate setup.
This is the circuit load pull template called into by the system level template. If not already present in a project, creating the system level template (as above) will also create the circuit level template. Directions are provided on the template to aid in the appropriate setup.
This is the load pull data file created from the load pull simulation. This data file contains not only simulation data but also useful information in the header regarding the setup and sweep information.
Load Pull ACPR Contours gph:Load Pull ACPR Contours
This graph shows the load pull gammas plotted using G_LPGPM, with overlaid contours for the ACPR. ACPR contours are show for the high side and low side of the spectrum aligned to the 1 dB compression point using the G_LPCM_A measurement. The minimum values for the high and low side ACPR are also show using the G_LCMMIN_A measurement.
Load Pull G_Compress gph:Load Pull G_Compress
This graph shows the compression vs input power (index) for the amplifier defined in the circuit load pull template. The compression point is plotted using PlotMD_R.
Load Pull G_Compress Alignment gph:Load Pull G_Compress Alignment
This graph shows the compression from linear gain aligned to the 1 dB compression point. This measurement is plotted using the PlotMD_R_A measurement.
Load Pull G_Trans gph:Load Pull G_Trans
This graph shows the transducer gain of the amplifier defined in the circuit load pull template.
Load Pull Gamma Pointsgph:Load Pull Gamma Points
This graph plots the load gammas used during the load pull simulation with G_LPGPM.
Load Pull Ploadgph:Load Pull Pload
This graph plots the power delivered to the load of the amplifier defined in the circuit load pull template.
Load Pull Source Powergph:Load Pull Source Power
This graph plots the power available from the source.
This graph shows the input and output spectrum of the system load pull template. The input spectrum is taken at the output of the modulated source and the output spectrum is taken directly after the signal goes through the amplifier pointed to by the NL_S block. Both measurements use the PWR_SPEC measurement to compute the power spectrum.
System ACPRgph:System ACPR
This graph shows the ACPR measurement that should be set up prior to running the load pull simulation. The measurement is made at the output of the amplifier (NL_S block) using the ACPR measurement.
System EVMgph:System EVM
This graph shows the EVM measurement that should be set up prior to running the load pull simulation. This measurement utilizes the VSA in the system load pull template and its associated EVM measurement.