Performance evaluation of an injection-locked self-oscillating mixer as a down-converter and phase shifter element for communication system applications

Self-oscillating mixers (SOM) are used in phased arrays and other communication systems due to their potential application as both down-converters that do not require an external local oscillator (LO) signal, and phase shifters. Phase shifting properties are introduced to the SOM by injection locking it to an external reference. In this work, the effects of the injection signal power on the performance of an SOM element are investigated. In addition the performance variation along the stable phase shift range is examined. Conversion gain, noise figure and distortion are evaluated. Simulation results are presented using harmonic balance and conversion matrix analyses to trace the various solutions. In addition, the stability of the solutions is verified with envelope transient analysis. The simulation results are compared with measurements on a 3.5 GHz SOM, designed to down-covert an RF signal of 7.1-7.25 GHz to an IF frequency in the range of 100-250 MHz, by mixing it with the 2^nd harmonic of the SOM.