X-Band Self Oscillating Mixer With Resonator-Antenna Filter

A simple self-oscillating mixer (SOM) with an excellent figure-of-merit (FOM) using a parallel feedback circuit composed of a planar resonator-antenna filter is proposed. By coupling a planar patch antenna and a Slotted Square Patch Resonator (SSPR), the feedback circuit shows two-pole bandpass filter (BPF) characteristic with a high group delay peak value. The SOM is designed near the group delay peak frequency, so that the phase noise and hence the FOM of the oscillator can be improved. As a negative resistance device, NE3512S02 is biased near the pinch off region for enhancement of power efficiency with proper mixing and oscillating functions. The measured phase noise is -102.38 dBc/Hz at 100 kHz offset with the FOM of -195.40 dBc/Hz. The output power, power efficiency and the conversion gain of the SOM are measured as 4.2 dBm, 46.7% and 4.45 dB, respectively.