Abstract: A phase noise measurement system including a low noise programmable synthesizer and a receiver/down converter is provided. The low noise synthesizer provides L-Band Signals which can selectively exhibit low noise close-in or low noise far out. The receiver down converter provides for absolute, additive, and down converted/direct/multiple phase noise measurement.

Abstract: An improved circuit for phase noise measurements utilizing a frequency down conversion/multiplier and direct spectrum measurement technique. The circuit is particularly useful for field test environments where laboratory instrumentation is normally not available, and fast and accurate phase noise measurements are required. The phase noise measuring circuit includes a frequency mixer which has a first input signal from a device under test and a second input signal from a reference stable oscillator having ultra low phase noise with a fixed center frequency. The frequency mixer produces a down converted signal comprising the frequency difference signal of the first and second input signals. A lowpass filter passes the down converted signal to a frequency multiplier circuit which produces a second harmonic signal, a fourth harmonic signal, and higher harmonic signals of the down converted signal.