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4. Executing the Measurement and Viewing Results

  1. Click the triangle Run button on the menu bar.

  2. Once the measurement begins, the detailed information will be displayed in the Log view at the bottom of the window as shown below.

    During the running process, you can stop it any time by clicking the . When you see the "Complete!" message in the Log view, it indicates that the measurement is completed.

Viewing the Measurement Results

In the measurement view, there are four result windows: AM-AM, AM-PM, ACP, and EVM vs. Power. For DPD measurements, only the first three results are used. These three results give an insight of PA's improvement on linearity after using DPD. If the results are not satisfactory, you need to adjust the settings, such as PA model extraction parameters in the Digital Predistortion block under the block view, and rerun the measurement.

DPD measurement results are updated for each iteration if the Number of Iteration setting is larger than one in Digital Predistortion block.

You can double-click on each window to enlarge it and double-click it again to return to the four-window view.

On the Signal Analyzer, you can check the EVM and constellation graph improvements after DPD.

AM-AM

AM-AM curve displays ratio of the PA output signal amplitude to the PA input signal amplitude. So two signals are used use to plot the AM-AM curve. One is the reference signal, that is the PA input signal. The other is the PA output signal, which is the IQ waveform data captured by the Signal Analyzer in the IQ Analyzer(Basic) mode.

There are two results: the red one shows the AM-AM value without using DPD, and the green one shows the AM-AM value after using DPD.

There is also a "Normalized" check box in the window. Check it or uncheck it will decide whether to display the normalized value or not.

  1. Normalized: It displays the PAout/PAin value

  2. Not normalized: It displays the PA output value

AM-PM

AM-PM curve displays ratio of the PA output signal phase to the PA input signal amplitude.

There are two results: the red one shows the AM-PM value without using DPD, and the green one shows the AM-PM value after using DPD.

ACP

The ACP results are from the ACP measurement results in the Spectrum Analyzer mode of the Signal Analyzer. It displays the improvements in ACP (Adjacent Channel Power Ratio) after using DPD.

There are four ACP settings in the right panel, In-Channel Bandwidth, Adjacent Channel Count, Adjacent Channel BW, and Channel Offset, in which In-Channel Bandwidth, Adjacent Channel BW, and Channel Offset are coupled to the Bandwidth settings in the Waveform block in the block view. If you want to view the ACP results of more than one adjacent channel, you can adjust the Adjacent Channel Count value. The results will be updated after you rerun the measurement.