User`s guide

3-132 Agilent E6432A Microwave Synthesizer User’s Guide
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I/Q Calibration (Option UNG Only)
NOTE If the external I and Q source signals cannot be adjusted to a low
enough output level, attenuator values within the I/Q modulator
circuitry can be adjusted. For example, from the I/Q External Source
Adjustments dialog box, adjust the I Attenuation and Q Attenuation
controls. These I and Q Attenuation controls adjust the input level to
the mixers in the I/Q modulator circuitry to prevent overdriving. (Refer
to the drawing shown in Understanding I/Q Calibration.)
9. Adjust the ratio of I-gain to Q-gain (leave Q Gain fixed and adjust
I Gain) as well as the Quadrature to minimize the
Undesired-Sideband Signal. For optimum results, it is best to
iterate a few times between the gain adjustment and the quadrature
adjustment.
Adjust the I and Q Offset values to minimize the carrier feed
through signal. It is best to iterate a few times between the I and
Q Offset adjustments.
I/Q Calibration Example
As an example, set the synthesizer center frequency to 2 GHz, with
external I and Q source signals of approximately 0.35 Vrms, the I input
as a cosine wave at 10 kHz, and the Q input as a sine wave at 10 kHz.
(The synthesizer may be set to any center frequency from 10 MHz to
20 GHz; I/Q calibration is independent of the synthesizer center
frequency.)
The result, when viewing the RF output of the synthesizer on a
spectrum analyzer, should produce an undesired-sideband signal, a
carrier-feedthrough signal, and a desired-sideband signal.