Design of a Low‐Power and Temperature‐Compensated Readout Circuit for Surface Acoustic Wave Sensors

ABSTRACT Existing studies have extensively explored surface acoustic wave (SAW) sensors operating in both passive and active modes across a wide range of applications. Specifically, in remote sensing applications, active‐mode SAW sensors are preferred due to the communication range limitations inherent in passive operation. However, active‐mode SAW sensors face key challenges, including oscillator mode jumping, circuit dependency on SAW device parameters, high thermal sensitivity, and elevated power consumption. To address these challenges, this paper proposes a low‐power closed‐loop integrated circuit optimized for the reliable readout of two‐port SAW sensors in remote areas. The proposed circuit incorporates thermal compensation by employing two co‐located SAW elements, where only one is exposed to the target mass load. The output of the system is a digital count proportional to the frequency shift between the two SAW devices, which is temperature‐independent and depends only on device parameters and the mass load. While simulations assume ideally matched devices, calibration can be applied in practice to compensate for fabrication‐induced mismatches and enable accurate mass detection. The system operates in a power‐efficient pulsed mode, with automatic shutdown after measurement cycles and event‐based control of the external RF transmitter, significantly reducing power consumption. Simulation results using 0.18‐m CMOS technology demonstrate high resolution, thermal robustness, and energy efficiency for SAW devices with various center frequencies.