2. Configuring Parameters in the N7614B Software

The following figure shows the block view settings in N7614B for ET measurement. In this example, the Digital Predistortion block is turned Through and Envelope Tracking block is turned On.

The remaining section of this topic provides an example procedure of setting N7614B for the envelope tracking 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 Envelope Tracking Block

Step 4: Set the Envelope Signal Generator Block

Step 5: Set the ETPS Block

Step 6: Set the PA Block

Step 7: Set the RF Signal Generator Block

Step 8: Set the Signal Analyzer Block

Step 9: Set the Measurement View

Step 1: Set the Waveform Block

Click on the Waveform block icon on the UI. In the right panel, do the following:

1. Select Preloaded as the Waveform Type and select the "LTE_FDD_5M_QPSK_FullRB.wfm" file.

   Waveform Settings

   

   If you want to use a waveform generated by another Keysight signal studio, set Waveform Type to Signal Studio and select the file. Refer to Creating and Exporting Waveforms for details about exporting a waveform file.
   Note that to use a waveform generated by another signal studio software for ET test, the instrument needs to have the corresponding license. For this example, to use LTE waveform, the N7624B license needs to be installed in the instrument.

2. Set the bandwidth to 5 MHz according to the waveform bandwidth.

3. Set the Resampling Ratio to 3.

Step 2: Set the Crest Factor Reduction Block

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

Step 3: Set the Envelope Tracking Block

Click on the Envelope Tracking block icon and turn on Envelope Tracking on the UI. In the right panel, do the following:

1. Set the Envelope Source to From Non-predistorted Signal. Then the software will calculate the envelope signal using the signal before Digital Predistortion block.

2. Set the Trigger Master to Envelope Signal Generator if the RF Signal Generator in use is M9381 PXI VSG. Otherwise, set the Trigger Master to RF Signal Generator.

3. Set the OSR for Envelope to 3.

   For signals used for envelope tracking test, it is recommend that the overall oversampling ratio (OSR) is no less than three. In this software, there are three different places related with the overall OSR. One is the OSR in the waveform file imported in the Waveform block. Another is the Resampling ratio setting in the Waveform block. The other is the OSR setting here in the Envelope Tracking block. The overall oversampling ratio is the product of these three values. As you increase the overall OSR, make sure the final sample rate does not exceed the limit of the Envelope Signal Generator.

4. Set the Conversion Input Type to Absolute RF Output Voltage. This is to set the reference for the RF Voltage column in the shaping table.

5. Enter the shaping tables.This shaping table is used to map the selected Conversion Input Type, Normalized I/Q Amplitude, Absolute RF Output Voltage or Override Absolute RF, to the supply voltage of the PA (V_cc).

   Here a shaping table is used as an example and you can see the graphic view by clicking the Graph tab.

   

Step 4: Set the Envelope Signal Generator Block

Click on the Envelope Signal Generator block icon on the UI. In the right panel, do the following:

1. Select the type of Envelope Signal Generator in the Configuration setting. In this example, select M320xA PXIe AWG.

2. Enter the IP address or host name of the Envelope Signal Generator and the toggle the connect button on the top of the window to Connected state. After the instrument is connected, the model number and serial number of the instrument will be displayed in the Instrument cell.

   

3. For other values, you can use the default settings. Note that the Voltage and Voltage Offset value will be set automatically after the test flow is run.

   Refer to Voltage Mapping in Envelope Tracking Measurement for more details about Voltage Mapping.

Step 5: Set the ETPS Block

Click on the ETPS block icon on the UI. In the right panel, do the following:

1. Set the ETPS Gain to 7.0 dB.

2. Set the Vcc Offset to 2.75 V.

3. Set the Vcm to 450 mV.

Step 6: Set the PA Block

Click on the PA block icon on the UI. In the right panel, do the following:

1. Enter the PA information by setting the Loss In, Loss Out, and PA Gain.

2. Select PA Input as the Power Mode.

3. Set Power to -5 dBm. This is to set the input power of the PA. Then the Amplitude setting in RF Signal Generator block will be set to (Power + Loss In) automatically.

Step 7: Set the RF Signal Generator Block

Click on the RF Signal Generator block icon on the UI. In the right panel, do the following:

1. Select the type of RF Signal Generator in the Configuration setting. In this example, select M9381 PXIe VSG.

2. Enter the IP address or host name of the RF Signal Generator and the toggle the connect button on the top of the window to Connected state. After the instrument is connected, the model number and serial number of the instrument will be displayed in the Instrument cell.

   

3. Set Frequency to 2 GHz.

Step 8: Set the Signal Analyzer Block

Click on the Signal Analyzer block icon on the UI. In the right panel, do the following:

1. Select the type of RF Signal Analyzer in the Configuration setting. In this example, select M9391 PXIe VSA or M9393A PXIe VSA.

2. Enter the IP address or host name of the M9391 or M9393 PXIe Signal Analyzer and the toggle the connect button on the top of the window to Connected state. After the instrument is connected, the model number and serial number of the instrument will be displayed in the Instrument cell.

   

3. Note that the Frequency value is coupled to the frequency setting in RF Signal Generator block.

4. Set the Trigger Source to External 1 and adjust Trigger Delay value as needed. For most cases, you can use the default value.

Step 9: Set the Measurement View

Click the button on the UI to change the current view from block view to measurement view.

You can turn Intermediate Result to On and set the ACP parameters as required. In this example, the default settings are used.