Cross-correlation phase noise measurements

The noise floor of a typical two channel phase noise measurement system is set by the phase detector and amplifiers that follow the detector. If the phase noise of two oscillators is measured using two of these test systems, the output noise of the equipment is uncorrelated except for the component that is due to the phase noise between the oscillators. Examination of a system which uses matched power splitters, two phase detectors, and post amplifiers reveals that an exceptionally low noise floor is achievable. The time required to reach a given percentage of precision in the measurement at these low noise floors is lengthened due to the need to average away the uncorrelated noise. The details of the setup, including calibration procedures and confidence intervals for the measurement, are discussed