The Amplitude Profile feature of the N7621 Multitone Distortion application allows you to modify the amplitude flatness of a Noise Power Ratio (NPR) signal. Two examples are presented here. Example 1 will work with most hardware configurations. Example 2 requires a PSG and a Wideband Arb. Both examples use the “TestAmplitudeProfile.txt” file included in the Multitone Distortion\ApiExample directory.
Start the software and configure
the system for a 
Internal Arb Waveform Generator
with Calibration
using a PSG, ESG, MXG or EXG.
From the Mode
menu, select Noise Power Ratio
(NPR).
Configure the NPR Signal Frequency and Amplitude as follows:
RF Output = On
Frequency = 1 GHz
Amplitude = 0 dBm
Configure the NPR Settings
as follows:
Tone Count = 801
Tone Spacing = 100 kHz (This results in an 80 MHz noise bandwidth.)
Amplitude Profile
= TestAmplitudeProfile.txt
example file
Corrections = Off
Click 
to download and play the waveform.
The text file TestAmplitudeProfile.txt
contains simulated data from 900 MHz to 1100 MHz and from 9 GHz to 11 GHz, and represents cable attenuation
versus frequency.
The Amplitude
Profile file
contains two columns. The first column is the absolute frequency in Hz,
the second column is the amplitude response in dB or dBm.
The data must be sorted from lowest frequency to highest frequency without duplicate frequency data points. The application interpolates between data points and uses the end points for frequencies beyond the lowest and highest frequencies.
The figure below shows the amplitude profile display of the NPR mode using the settings from step 1 through 4 above.
When the Apply Amplitude Accuracy Adjustment is disabled, the Amplitude Profile file must contain the measured amplitude response of both the signal generator and the signal path outside of the signal generator.
The figure below contains the amplitude
profile generated using the TestAmplitudeProfile.txt
data.
Start the software and configure
the system for a Wideband Arb Waveform Generator
with Calibration
using the N6030A Arb.
From the Mode
menu, select Noise Power Ratio
(NPR).
Configure the NPR Signal Frequency and Amplitude as follows:
RF Output = On
Frequency = 10 GHz
Amplitude = 0 dBm
Configure the NPR Settings
as follows:
Tone Count = 1001
Tone Spacing = 1 MHz (This results in a 1 GHz noise bandwidth.)
Amplitude Profile
= TestAmplitudeProfile.txt
example file
Corrections = Off
Click to download and play the waveform.
The text file TestAmplitudeProfile.txt
contains simulated data from 9 GHz to 11 GHz and represents cable attenuation
versus frequency, as shown in the figure below.
The Amplitude
Profile file
contains two columns. The first column is the absolute frequency in Hz,
the second column is the amplitude response in dB or dBm.
The data must be sorted from lowest frequency to highest frequency without duplicate frequency data points. The application interpolates between data points and uses the end points for frequencies beyond the lowest and highest frequencies.
The figure below shows the amplitude profile display of the NPR mode using the settings from step 1 through 4 above.
The Amplitude Profile can be used with or
without the NPR application's Apply Amplitude
Accuracy Adjustment.
When the Apply Amplitude Accuracy Adjustment is disabled, the Amplitude Profile file must contain the measured amplitude response of both the signal generator and the signal path outside of the signal generator.
The figure below contains the amplitude
profile generated using the TestAmplitudeProfile.txt
data.
|
|
The ripple in the plot is from the RF output path of the signal generator. The TestAmplitudeProfile.txt file does not contain any information to correct the RF signal generator output profile. |
When the Apply Amplitude Accuracy Adjustment is enabled, the correction measurement will characterize the amplitude profile of the signal generator and signal path up to the spectrum analyzer. It corrects for the signal generator flatness and then adds the correction needed by the response in the Amplitude Profile file. The figure below shows this correction.
|
|
When providing the amplitude profile of the signal generator by sweeping a sine wave in the wideband I or Q input, be sure to turn the ALC off. |
There are several harmonic and/or spur filters in the RF output path. Be sure to characterize the RF output on both sides of the filter switch points. The following figures show the signal generator amplitude response at 5 GHz and 5.000000001 GHz.
