Microwave interferometry: application to precision measurements andnoise reduction techniques

摘要

A concept of interferometric measurements has been applied to thendevelopment of ultra-sensitive microwave noise measurement systems.nThese systems are capable of reaching a noise performance limited onlynby the thermal fluctuations in their lossy components. The noise floornof a real time microwave measurement system has been measured to benequal to -193 dBc/Hz at Fourier frequencies above 1 kHz. Thisnperformance is 40 dB better than that of conventional systems and hasnallowed the first experimental evidence of the intrinsic phasenfluctuations in microwave isolators and circulators. Microwave frequencyndiscriminators with interferometric signal processing have proved to benextremely effective for measuring and cancelling the phase noise innoscillators. This technique has allowed the design of X-band microwavenoscillators with a phase noise spectral density of order -150 dBc/Hz atn1 kHz Fourier frequency, without the use of cryogenics. Another possiblenapplication of the interferometric noise measurements systems includen“flicker noise-free” microwave amplifiers and advanced twonoscillator noise measurement systems