High-speed reader for wireless resonant SAW sensors

A new reader is presented that is based on a narrowband pulsed excitation of two SAW resonators contained in a differential wireless resonant sensor such as a torque senor. Simultaneous excitation of the resonators working at 433–437 MHz allows achieving a flat system frequency response up to Nyquist frequency. An interrogation algorithm and a structure of the reader ensure a torque sampling rate of at least 16 kHz and the system bandwidth of at least 8 kHz achievable at the processor clock of 150 MHz. Systematic errors caused by mutual interference of the two SAW responses, intermodulation products and aliasing are discussed. Random errors caused by the phase noise of the local oscillators are analyzed theoretically. Experimental results are also presented.