Phase noise measurements of low power signals

Measuring the phase fluctuation between a pair of low-power microwave signals, the signals must be amplified before detection. In such cases the phase noise of the amplifier pair is the main cause of 1/f residual noise. A new scheme is proposed that makes amplification possible while rejecting the 1/f (flicker) noise of the two amplifiers in real time. The first prototype, compared to a traditional saturated mixer system under the same conditions, shows a 24 dB noise reduction in the 1/f region.