I/Q calibration data is not affected by a preset or by a power cycle.
If the ESG/PSG I/Q calibration has not been performed recently, or the instrument's environment has changed, it is recommended that you run the I/Q calibration procedure by pressing the I/Q key on the front panel of your signal generator. The I/Q key accesses a menu that enables you to set the start and stop frequency for a user-defined I/Q calibration, or choose an I/Q calibration over the entire frequency range of the signal generator. In this menu you can also restore the original factory calibration data for the I/Q modulator. The N7621 software has a signal generator instrument control panel that allows you to adjust the I and Q offsets from the software as well as the instrument's front panel.
The I/Q calibration adjusts the DC offsets into the I/Q modulator to minimize carrier leakage. It also insures that the I/Q modulator is in Quadrature to help minimize images. It may be possible to reduce the carrier leakage even further by using the I and Q offset adjustments on the ESG/PSG.
An I/Q calibration should be performed approximately every 30 days, but it can be performed at any time to peak the performance of the I/Q modulator.
|
|
I/Q calibration data is not affected by a preset or by a power cycle. |
|
|
When performing an I/Q calibration on an E8267D-015, make sure there is no signal present at the wideband I/Q inputs while executing the IQ calibration. There are no internal switches to disconnect the I/Q inputs during a calibration. Having any signal present on the wideband I/Q inputs will cause the calibration to be incorrect and in some cases to fail outright. |
Use this procedure to match the time length and amplitude gain of the I and Q signal paths when using Wideband IQ modulation. Following this process will help the correction measurement to achieve its best results.
1. Start the software and configure the system for a 
Wideband Arb Waveform Generator with Calibration
using the N6030A or N8241A AWG.
From
the Control
menu, select Play Test Signal.
The analyzer display should look similar to the figure below — a typical IQ test signal with no adjustments.
Use
the IQ Skew and IQ Gain Balance parameters to minimize images.
|
|
The Gain Balance should be less than a few tenths of a dB. The IQ Skew should be less than a few hundred pico seconds. |
Click
to download and play the waveform. (A download and play is required to
apply each change to IQ Skew or IQ Gain Balance.)
The analyzer display should look similar to the figure below — a typical IQ test signal with IQ Skew and Gain Balance adjustments.
Experiment with different IQ Skew and IQ Gain Balance values until the images reach a minimum value.
|
|
The IQ Skew and IQ Gain Balance values determined here can also be used in the NPR application. |
