A High-Accuracy Lock-In Transceiver for Speed Over 8000-r/min Contactless Eddy-Current Angular Position Sensors

This article presents a customized low-power and high-linearity lock-in transceiver, including a dual-channel receiver and a one-channel transmitter for inductive continuous angular position sensing. Based on the dual-channel design, the measured angle error is immune to the gain variation and the phase deviation of receiver channels. To accommodate the liftoff of the target, a wide range tunable gain of 0–42.8 dB and an adjustable excitation frequency of 1–8 MHz are employed and optimized in the transceiver. In addition, the transmitter reuses the transmitter coil with the sensor and induces ~MHz-level carrier wave, mitigating skin effect and achieving the reduction of system size. Hence, the sensing module, consisting of the proposed transceiver and inductive sensor, could work in noisy environments for measuring continuous and full-range angles during high-speed rotations (over 8000 r/min), such as for electric power steering applications. The transceiver has been fabricated in a 0.18- $\mu \text{m}$ CMOS process. The measured results of transceiver with an emulated sensor show that the maximum and rms nonlinearity are 0.26% and 0.005%, respectively. The proposed transceiver has achieved 10-dB higher figure of merit (FoM) than state-of-the-art measurements.