A low phase noise local oscillator module for instrumentation application

In this paper we have developed a novel Local Oscillator Module for down conversion application in Signal Source Analyzer with low phase noise, which covers 3-10 GHz frequency range. The local oscillator is a multi-loop YTO based frequency synthesizer, which is implemented with ultra low phase noise OCXO, low phase noise YIG-tuned oscillator, low conversion loss, and low noise sampling phase detector. In this project in order to have a good phase noise of local oscillator, key circuits have been analyzed, designed and implemented. The output signal of local oscillator has a pretty good phase noise, and the measured phase noise at 10 kHz offset is about -128dBc/Hz at 3.05GHz and -120dBc/Hz at 9.95GHz respectively. The frequency switching time is less than 2 millisecond in the entire operating range.