Low noise microwave signal generation: resonator/oscillator comparisons

The author compares existing and projected microwave signal spectral performance obtainable using various types of acoustic and non-acoustic high-Q resonators. Included is a discussion of recent progress in resonator technology such as improvements in conventional dielectric resonator and quartz crystal resonator performance, development of composite UHF resonators such as the high-overtone bulk acoustic resonator (HBAR) exhibiting tenfold increase in Q and decrease in vibration and sensitivity (compared to quartz), and superconducting cavity-type resonators exhibiting ultrahigh Q directly at microwave frequency. It is concluded that the generation of low-noise microwave signals depends, to a large extent, on resonator performance parameters including Q, short-term frequency stability, drive level, operating frequency, and are quite process-variable and consideration of device yield is important. Selection of optimum resonator technology (or multiple technologies) must be tailored to specific signal spectral performance requirements.<>