A high frequency low phase-noise signal source generated using a self-oscillating mixer

A 21 GHz signal source is obtained from a 4 GHz voltage-controlled oscillator (VCO) using an integrated self-oscillating mixer which, in essence, contains a fixed frequency oscillator (FFO) and a mixer. The phase noise for the up-converted signal is about 5 dB worse than for the 4 GHz VCO, much less than the expected 14.7 dB degradation if a frequency multiplier would be used. The focus of the present work, however, is not on design optimization of the overall signal source performance, but rather to demonstrate how practical the proposed up-conversion method is in generation of low phase noise sources at high frequencies. This is experimentally done by manipulating the phase noise of the FFO using the so called self-injection lock technique.