Noise Suppression With Cryogenic Resonators

Abstract

We show that fast technical fluctuations of microwave signals can be strongly suppressed by cryogenic resonators. The experiments were carried out with sapphire resonators cooled to approximately 6 K at frequencies around 11 GHz. Each sapphire crystal was shaped like a spindle with the rotational and crystal axes aligned within a degree. Noise suppression factors in excess of 50 dB were measured at 10 kHz offset from the carrier. This was achieved by rotating the sapphire spindle and moving the coupling probes relative to its surface. Microwave signals with reduced fast technical fluctuations allow the high-precision tests of fundamental physics, as well as the development of better radars.

Frequency Stable Microwave Sapphire Oscillators

“…In the next stage of experiments, we studied how efficiently one can suppress the oscillator phase noise by extracting the output signal from the resonator transmission port. In [13], it was shown that the resonator in transmission acts as a bandpass filter suppressing both phase and amplitude fluctuations of the output signal outside its bandwidth, provided that the resonator transmission peak has sufficiently high contrast.…”