Passive wireless temperature sensing with piezoelectric MEMS resonators

For the first time, a lateral-extensional piezoelectric MEMS resonator is utilized to enable wireless passive temperature sensing with an accuracy of less than 0.1°C at 1m distance. The high quality factor (2900) and low motional resistance (147Ω) of a 990MHz thin-film piezoelectric-on-silicon (TPoS) resonator are exploited to accurately determine the temperature of the subject by monitoring the induced change in the resonance frequency. The resonator is directly connected to an antenna and is excited wirelessly by a pulse-modulated sinusoidal signal. The decaying signal from the resonator is then recorded and the resonance frequency is determined from the frequency spectrum of the resonator's decaying response. The wireless temperature measurement was extended to a 3m distance with an interrogation signal power of 500mW using 5dBi gain antennas.