A Millimeter-Wave Sub-Harmonic Self-Oscillating Mixer Using Dual-Mode Substrate Integrated Waveguide Cavity

This paper presents a novel sub-harmonic self-oscillating mixer (SOM) topology that makes use of the transmission characteristics of two operating modes in a substrate integrated waveguide (SIW) cavity. The SOM circuit consists of a dual-mode SIW bandpass filter, a common source heterojunction field-effect transistor, and a low-pass filter. The fundamental mode ( H ₁₀₁) of the SIW cavity is used for RF mode operation, while the H ₂₀₂ mode is used for local oscillation. A K a-band experimental prototype has been designed and fabricated to demonstrate and validate our proposed circuit concept. The measured power levels of the self and second harmonic local oscillator signals are about 8.5 and -3 dBm, respectively. The mixer, implemented as a down-converter, achieves a 12-dB conversion loss and an IF phase noise of -81 dBc/Hz at 100-kHz offset with a 34-GHz RF input.