Distortion Measurement Parameters

In this topic:

Spectrum Decomposition
Distortion Model
Accessing the Distortion Measurement Parameters
Main, Distortion Tab Measurement Parameters
Distortion Table

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
Select a trace by pressing Trace > Trace N > Trace N. Press Trace > Trace Setup > Measure.... Select a parameter.	Right-click on a trace. Select a parameter

Main, Distortion 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 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	Description	Default Format
PIn1	PIn1	Input power incident on 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	Output Power incident on the VNA test port	dBm/Hz
PDlvrIn1	PDlvrIn1	Power delivered to the DUT. This is calculated from the incident power (PIn) and the match of the DUT port; used for load-pull measurements.	dBm/Hz
PDlvrOut2	PDlvrOut2	Power delivered to the receiver on the output port. This is calculated from the incident power (POut) and the match of the receiver port; used for load-pull measurements.	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	Power gain - Y(f) / X(f) This gain is calculated tone-by-tone and includes the nonlinear distortion which appears as random noise in the frequency domain. As a result the PGain trace looks “noisy”.	dB
PGain1_Wav	PGain1_Wav	Power Gain = X(f)/(Ideal Waveform) at input,indicating channel flatness of source.	dB
PGain2_Wav	PGain2_Wav	Power Gain = Y(f)/(Ideal Waveform) at output,indicating channel flatness of DUT.	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	Description	Default Format
CarrIn1	CarrIn1	Input band power	dBm/Hz
CarrOut2	CarrOut2	Output band power	dBm/Hz
CarrGain21	CarrGain21	Band power gain	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	dBm/Hz
AcpPwrOut2	AcpPwrOut2	ACP output band power	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	dBm/Hz
EvmPwrOut2	EvmPwrOut2	EVM output band power	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	dBm/Hz
NprPwrOut2	NprPwrOut2	NPR output band power	dBm/Hz
ModFilter	ModFilter	Modulation filter used during measurement	dB

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:

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.
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.
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
Press Meas > Main > click the small button to the left of the Distortion Table... button.	Click Instrument. Select Display. Select Show Table.... In the Customize Display dialog, select the Show Table pull-down. Select Distortion. 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

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.