User`s guide

Agilent E6432A Microwave Synthesizer User’s Guide 3-135
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I/Q Calibration (Option UNG Only)
Understanding I/Q Calibration
When a synthesizer I/Q calibration is run, an iterative algorithm makes
corrections for the impairments within the synthesizer by adjusting the
Gain, Offset, and Quadrature adjustment DACs. This calibration does
not account for impairments in external I/Q sources. After the
calibration is run, a separate, manual adjustment must be performed so
as to minimize the impairments in the external I/Q sources. The most
useful modulation type for minimizing the impairments in the external
I/Q sources is a single-sideband signal. A single-sideband signal may
be generated by adjusting the external source that is driving the I input
with a cosine wave, and the Q input with a sine wave at the same
frequency. The result is an undesired sideband signal, a carrier
feedthrough signal, and a desired sideband signal. Adjustments made
to the ratio of I-gain to Q-gain as well as adjustments to quadrature can
minimize the undesired sideband signal. Adjustment to the I and Q
offsets can minimize the carrier feedthrough signal.
NOTE Items shown as blue represent the impairments that are being
“calibrated-out” with the Calibration Settings (from the I/Q Calibration
dialog box) and Adjustments to Calibration Setting (on the I/Q External
Source Adjustments dialog box). These impairments are not physical
components in the I/Q modulator assembly or the external I/Q sources.