3. Configuring Parameters in the N7614B Software

The following figure shows the block view settings in N7614B for wideband DPD measurement.

The remaining section of this topic provides an example procedure of setting N7614B for DPD measurement. Note that for different PA, the settings are different.

Step 1: Set the Waveform Block

Step 2: Set the Crest Factor Reduction Block

Step 3: Set the Digital Predistortion Block

Step 4: Set the RF Signal Generator Block

Step 5: Set the PA Block

Step 6: Set the Signal Analyzer Block

Step 1: Set the Waveform Block

Since the Waveform block has been configured in calibration step, you can skip this step if no settings under Waveform block need to be changed.

Step 2: Set the Crest Factor Reduction Block

Click on the Crest Factor Reduction block icon and Closedturn Crest Factor Reduction to Through on the UI.

Step 3: Set the Digital Predistortion Block

Click on the Digital Predistortion block icon and Closedturn on Digital Predistortion on the UI. In the right panel, do the following:

  1. Select Extract and Apply as the DPD Mode.

    Two modes are supported to perform the digital predistortion.

    • Extract and apply is to extract the PA model using the signals captured by the Signal Analyzer, so there will be a Closedfeedback line from the Spectrum Analyzer block to the Digital Predistortion Block on the block diagram.

  2. Set the Number of Iteration to 1. By setting this parameter, the extraction model will be repeated by feeding its output to the input to minimize error. Typically, setting it to 3 is enough.

  3. Set the PA Model Type to Memory Polynomial. Refer to DPD Concept for details about different PA model types.

  4. Set the Memory Order to 1 and set Non-linear Order to 5.

Different PAs may have different characteristics, which will need different DPD models to simulate the DPD performance. In DPD test, if the measurement results are not as expected, you can try to change the the parameters for DPD model extraction. If the DUT is memoryless, it is recommended to set the PA Model Type to Look-up Table, or to set the PA Model Type to Memory Polynomial or Volterra Series and set the Memory Order to 0 or 1. If the DUT is memory device, it is recommended to set the PA Model Type to Memory Polynomial or Volterra Series.

Step 4: Set the RF Signal Generator Block

Click on the RF Signal Generator block icon on the UI. Set the PSG amplitude for PA input power. PA input power can also be set in PA block.

Step 5: Set the PA Block

Click on the PA block icon on the UI. Set the Loss In, Loss Out, and PA Gain. For example set PA Gain to 20 dB.

Step 6: Set the Signal Analyzer Block

Click on the Signal Analyzer block icon on the UI. Set the Trigger Source to External 1 and adjust Trigger Delay value as needed. If the high bandwidth channel is used for UXA H1G, the trigger source should be set to external 3.