A MEMS Analog demodulator

This paper presents a method and a device to demodulate the front end Radio frequency (RF) signal by measuring the displacement of the micro-plate in an electrostatic MEMS paddle actuator. Specifically, it investigates the feasibility of demodulating Amplitude Modulated (AM) signals. The operating principle of the MEMS demodulator is explained and modeling and simulation results are presented to demonstrate the feasibility of AM demodulation. The MEMS demodulator was fabricated and tested. Experimental validation results are reported here. The measured displacement of the micro-plate were found to follow closely baseband signals with varying frequencies thus demonstrating a mechanical demodulator able to extract the baseband signal from the modulated RF signal. In concrete terms, the MEMS demodulator extracted a baseband signal corresponding to a micro-plate RMS displacement of 30.8 nm from a modulated input signal of 48.6 mV RMS and a carrier frequency of 138 kHz.