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Figure 8-15 Measuring Carrier-to-sideband Ratio of the Modulated Port
Document Part No. E5500-90024Ed. 1.0
4
Measure the carrier-to-sideband ratio of the non-modulated side
of the phase detector. It must be at least 20 dB less than the
modulation level of the modulated port. This level is necessary to
prevent cancellation of the modulation in the phase detector.
Cancellation would result in a smaller phase detector constant,
or a measured noise level that is worse than the actual
performance. The modulation level is set by the port-to-port
isolation of the power splitter and the isolation of the phase
modulator. This isolation can be improved at the expense of
signal level by adding an attenuator between the phase modulator
and the power splitter.
5
Connect the phase detector.
6
Adjust the phase difference at the phase detector to 90 degrees
(quadrature) either by adjusting the test frequency or by
adjusting an optional variable phase shifter or line stretcher.
Quadrature is achieved when the meter in the phase noise
software is set to center scale
( ± 2 mV).
E5500 Phase Noise Measurement System Version A.02.00
Residual Measurement Fundamentals
Calibration Options
8
8-21
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