Design of a thermal sensitive MEMS resonator and readout circuit for infrared sensing

This paper presents a novel thermal sensitive MEMS resonator (TSMR) and the readout circuit (ROIC) for uncooled infrared (IR) detection. The structure of the TSMR uses an optical resonance cavity co-constructed with a metal-oxide-metal (MIM) resonator to improve the IR sensing capability. The filling fraction and absorption coefficient of the micro-mechanical resonator can be up to 80%. In the ROIC design, the Maxwell-Wien bridge is adopted to detect the TSMR's impedance variation due to the IR radiation heating the resonator. A self-mixing mixer is also used to generate the corresponding dc output voltage for the following integrator and sample-and-hold circuit (SH) to do charge accumulation and hold the sampled-signal level. The simulated results show that the output voltage of the SH circuit is from 0.1 V to 2.3 V and the noise voltage is lower than 300 μVrms. The signal-to-noise ratio of the ROIC is higher than 77 dB.