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 rad2/Hz (white) and 150 dB rad2/Hz (flicker) at 1 Hz Fourier frequency, at carrier power from 9 to 15 dBm.