User`s guide

Agilent Technologies E5500 Phase Noise Measurement System 8-23
Residual Measurement Fundamentals
The Calibration Options
Figure 8-14 Measuring Carrier-to-sideband Ratio of the Modulated Port
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
(±2mV).
NOTE For the system to accept the adjustment to quadrature, the meter must be
within ±2mVto±4mV.
7. Set the Type of Measurement to Phase Noise Without Using a PLL.
8. Set the Calibration Technique to Derive From Double-sided Spur and
enter the sideband amplitude and offset frequency.
9. Select New Measurement.