Phase noise measurement system and method

Abstract

Three independent signal sources are used to statistically derive the power spectral density of the phase noise content of signals from each of them. This is accomplished by mixing each of the signals two at a time (i.e., signal one with signal two, signal one with signal three, and signal two with signal three) and capturing the resultant difference signals, such as with a waveform recorder, for example. A servo electronics loop is used to remove the carrier and any long term signal drift from the resultant difference signals. Statistical analysis is then used to compute the composite power spectral densities of the the resultant difference signals, and to solve for the individual power spectral densities of the original signals. The present system and method uses the mathematical relationships between the three sources that have similar magnitudes of phase noise, to compute the power spectral density of the noise content of signals from each source. The present system and method requires a minimum of interconnect hardware and only three inexpensive waveform recorders. Furthermore, the size, weight, and cost of producing the present phase noise test system is relatively low.