Very high frequency and microwave interferometric phase and amplitude noise measurements

The interferometric technique allows close-to-the-carrier measurements of both phase and amplitude noise, improving the instrument noise floor by 10-25 dB as compared to the traditional method based on a saturated mixer. Principles and basic equations describing the noise measurement system are given, together with design strategies suitable to microwave and very high frequency bands. Two prototypes, operating at 9 GHz and 100 MHz are discussed in detail. The relevant features of these prototypes are the capability to operate in a wide power range, below 0 dBm and above 20 dBm, and low noise floor. The latter is about -180 dB rad(2)/Hz (white) and 150 dB rad(2)/Hz (flicker) at 1 Hz Fourier frequency, at carrier power from 9 to 15 dBm. (C) 1999 American Institute of Physics. [S0034-6748(99)02301-1].