LO-Free Self-Driven Down-Conversion via Combination Resonance in CMOS-MEMS Resonators

This letter demonstrates local-oscillator-(LO)-free frequency down-conversion using combination resonance (CR) in a CMOS-MEMS resonator. A single RF tone injected into an engineered three-mode cluster triggers CR and produces low-frequency components—including an IF tone selectable by a baseband filter—without any locally generated reference. The modal triplet is deterministically placed by optimizingVIAlocations using a particle swarm optimization (PSO) algorithm to satisfy the CR condition in a 0.35-μm CMOS-MEMS process. Measurements confirm LO-free translation and the emergence of a distinct IF component under single-tone excitation; representative spectra below and above the onset are presented. This work establishes the feasibility of LO-free down-conversion in standard CMOS-MEMS, offering a monolithic solution for secure wake-up receivers with intrinsic hardware-level interference rejection.