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Distortion Measurement Parameters

In this topic:

Spectrum Decomposition

The DUT is stimulated with a low-level signal to measure its linear parameters and a high-level modulated signal to measure its distortion characteristics. The modulation distortion application processes the data and compares the input spectrum X(f) and the output spectrum Y(f) using a process known as spectral correlation. As a result, the modulation distortion application decomposes the output signal spectrum into two parts:  H(f)*X(f) and D(f).  H(f)*X(f) linearly correlates to the input while D(f) represents the distortion which does not correlate to the input.

Distortion Model

The following Distortion Model describes noise and distortion in an amplifier and will help in understanding the Distortion Measurement Parameters (shown below):

Y(f) = C(f) * S21(f) * X(f) + D(f)

[H(f) = C(f) * S21(f)]

where:

X(f) = Measured input signal

Y(f) = Measured output signal

C(f) = Compression

S21(f) =Linear flatness and gain

D(f) = Output modulation distortion

Accessing the Distortion Measurement Parameters

How to select and configure Measurement Parameters

Using Hardkey/SoftTab/Softkey

Using a mouse

  1. Select a trace by pressing Trace > Trace N >  Trace N.

  2. Press Trace > Trace Setup >  Measure....

  3. Select a parameter.

  1. Right-click on a trace.

  2. Select a parameter

Main, Distortion and External Tab Measurement Parameters

   

Select from the parameters to measure power, S-parameters, or distortion characteristics.

New Trace - Add a new trace.

Channel N - Select a channel number for the new modulation distortion trace.

Window N - Select to create the new trace in an existing window or new window.

Select All - Select all measurement parameters.

The following tables describe the available Distortion Measurement Parameters for each DUT type and for the Main, Distortion and External tabs.

Note: The parameter names in the table assume we are testing a DUT with Port 1= input and Port 2 = output.

Main Tab Measurement Parameters

DUT Type

Description

Default

Format

Amplifier

Mixer

PIn1

PIn1

Incident Input power to the DUT

dBm/Hz

PInWav

PInWav

Power of the ideal modulation file loaded into the source. RMS power equals the power incident on the DUT.

dBm/Hz

POut1

POut1

Power reflected from the DUT input

dBm/Hz

POut2

POut2

Incident Output Power on the VNA test port at the DUT output.

dBm/Hz

PDlvrIn1

PDlvrIn1

Power delivered to the DUT input. This is calculated from incident power on the DUT (PIn1) and reflected power from the DUT (Pout1).

dBm/Hz

PDlvrOut2

PDlvrOut2

Power delivered to the receiver on at the DUT output. This is calculated from the incident power on the VNA port at the DUT output (POut2) and the reflected power from the VNA port at the DUT output (PIn2).

dBm/Hz

DutNois2

DutNois2

Noise power delivered to the receiver, calculated from DUT NF value and measured DUT gain.

dBm/Hz

MSig2

MSig2

Output modulation signal - C(f) * S21(f) * X(f)

dBm/Hz

MDist2

MDist2

Output modulation distortion - D(f)

dBm/Hz

MGain21

MGain21

DUT modulation gain - C(f) * S21(f) = H(f)

This gain is a smooth complex function, with smooth referring to the mathematical property that it has continuous derivatives of infinite order

dB

MGain1_Wav

MGain1_Wav

Mod gain from Ideal Waveform to DUT Input, indicating modulation channel flatness of source.

dB

MGain2_Wav

MGain2_Wav

Mod gain from Ideal Waveform to DUT output, indicating modulation channel flatness of DUT.

dB

PGain21

PGain21

Incident Power Gain = Y(f) / X(f) = (Incident Pout)/(Incident Pin).

dB

PGain1_Wav

PGain1_Wav

Channel Flatness In = X(f) / (Ideal Waveform) = (Incident Pin)/(Ideal Waveform).

This indicates channel flatness of source.

dB

PGain2_Wav

PGain2_Wav

Channel Flatness Out = Y(f) / (Ideal Waveform) = (Incident Pout)/(Ideal Waveform) at output.

Indicates channel flatness of DUT.

dB

Gp21

Gp21

Operating Power Gain = (Delivered Pout) / (Delivered Pin).

dB

LMatch2

LMatch2

Load match of the VNA port.

dB

Distortion Tab Measurement Parameters

Note: Single Port EVM Analysis is a Licensed Feature and is only available on PNA/PNA-X instruments. Learn more about Licensed Features.

DUT Type

Description

Default

Format

Amplifier

Mixer

CarrIn1

CarrIn1

Incident Band Power In on the DUT input.

dBm/Hz

CarrOut2

CarrOut2

Incident Band Power Out on the VNA test port at the DUT output.

dBm/Hz

CarrGain21

CarrGain21

Incident Band Power Gain = (Incident Pout)/(Incident Pin)

dB

CarrGp21

CarrGp21

Operating Band Power Gain = (Delivered Pout)/(Delivered Pin)

dB

AcpIn1

AcpIn1

Ratio of in-band channel power to channel power of the adjacent channel band at the input

dBc

AcpLoIn1

AcpLoIn1

ACPR low-side at the input

dBc

AcpUpIn1

AcpUpIn1

ACPR upper-side at the input

dBc

AcpAvgIn1

AcpAvgIn1

ACPR average at the input

dBc

AcpOut2

AcpOut2

Ratio of in-band channel power to channel power of the adjacent channel band at the output

dBc

AcploOut2

AcploOut2

ACPR low-side at the output

dBc

AcpUpOut2

AcpUpOut2

ACPR upper-side at the output

dBc

AcpAvgOut2

AcpAvgOut2

ACPR average at the output

dBc

AcpDist21

AcpDist21

ACP distortion added by DUT

dBc

AcpLoDist21

AcpLoDist21

ACPR low-side distortion

dBc

AcpUpDist21

AcpUpDist21

ACPR upper-side distortion

dBc

AcpAvgDist21

AcpAvgDist21

ACPR average distortion

dBc

AcpPwrIn1

AcpPwrIn1

ACP Input Band Power incident on the DUT input.

dBm/Hz

AcpPwrOut2

AcpPwrOut2

ACP Output Band Power incident on the VNA test port at the DUT output.

dBm/Hz

EvmDistEq21

EvmDistEq21

EVM equalized distortion added by DUT (non-linear contribution)

%

EvmDistUn21

EvmDistUn21

EVM unequalized distortion added by DUT (includes non-linear and linear distortion due to frequency dispersion)

%

EvmPwrIn1

EvmPwrIn1

EVM Input Band Power incident on the DUT input.

dBm/Hz

EvmPwrOut2

EvmPwrOut2

EVM Output Band Power incident on the VNA test port at the DUT output.

dBm/Hz

NprIn1

NprIn1

NPR at input

dBc

NprOut2

NprOut2

NPR at output

dBc

NprDist21

NprDist21

NPR distortion added by DUT

dBc

NprPwrIn1

NprPwrIn1

NPR Input Band Power Incident at the DUT input.

dBm/Hz

NprPwrOut2

NprPwrOut2

NPR Output Band Power incident on the VNA test port at the DUT output.

dBm/Hz

ModFilter

ModFilter

Modulation filter used during measurement

dB

External Tab Measurement Parameters

Right-clicking on the dialog accesses a pop up menu. Select Show Expert Tabs to display the Receivers tab for selecting one of the VNA receivers:

Distortion Table

The Distortion Table is displayed below the measurement area. Each row represents a measurement band. Each column represents a measurement parameter.

Total EVM

If there is more than one EVM band, then an extra band labeled Total EVM is added at the bottom of the table. The band power column sums the band power. The EVM and power density columns are a weighted average. The columns that do not apply are blank (for example, Carrier Offset Frequency).

Saving the Distortion Table

The Distortion Table can be saved to a .csv file in one of three ways:

  1. Using a mouse, right-click in the Distortion Table area, select Save Table As..., then select Distortion Table (*.csv) from the Save as type pulldown menu in the Save Data As dialog.
  2. Press Save Recall > Save Other >  Save Data..., then select Distortion Table (*.csv) from the Save as type pulldown menu in the Save Data As dialog.
  3. Using a mouse, select Utility, Save, Save Data, then select Distortion Table (*.csv) from the Save as type pulldown menu in the Save Data As dialog.

Accessing Distortion Table

Using Hardkey/SoftTab/Softkey

Using a mouse

  1. Press Meas > Main > click the small button to the left of the Distortion Table... button.

  1. Click Instrument.

  2. Select Display.

  3. Select Show Table....

  4. In the Customize Display dialog, select the Show Table pull-down.

  5. Select Distortion.

  6. Click OK.

Distortion Table help

Save Table As...

Specifies the Modulation Distortion Table path and file name (*.csv).

Editing Columns

The columns may be edited by clicking on Meas > Main > Distortion Table... button or by right-clicking in the distortion table at the bottom of the measurement area to access the pop up menu then selecting Edit Columns....

The Distortion Table Setup dialog is displayed with tabs for adding/removing measurement parameters for each measurement type.

Show Table

Check to display the Distortion Table at the bottom of the VNA display area.

Sort Table By

Select Band to sort the Distortion Table by band or Power to sort the Distortion Table by power.

Font Size

Select Small or Medium font size for the Distortion Table.

Carrier tab

EVM tab

NPR tab

ACP tab

External tab

  • List DC Meters and SMUs that are defined in External Device Configuration.

  • Only list the receivers for which Active-Show in UI is enabled.

  • For Sweep type set to Fixed, the data will be a constant valuel.

  • For Sweep type set to Power, the data will be one value at each power level.

  • Data will be displayed in the Distortion Table using the following formats:

    • Current = Amps

    • Voltage = Volts

    • Power = dBm

Editing Rows

The rows may be edited by right-clicking in the distortion table at the bottom of the measurement area to access the pop up menu then selecting Edit Rows....

The Modulation Distortion Setup Measure tab dialog is displayed. Click on the Measurement Type pulldown menu then select Multi-Band to access the table for adding, editing, and deleting band rows. Learn more.

Buttons

Defaults - Resets the dialog to its default selections.

MOD Setup... - Accesses the Modulation Distortion Setup Measure tab dialog. Learn more.