A Miniatured Fully Integrated High Resolution and Accuracy Capacitive Angle Encoder

Abstract

In this paper, a capacitive angle encoder monitored and sensed by ASIC with a sensitive structure fabricated by MEMS technology is proposed. The sensitive structure with a 27.5mm outer diameter is designed and optimized in a limited footprint to realize higher accuracy. After being fabricated by MEMS technology, it is integrated with an ASIC, realizing high fabrication accuracy and a small footprint at the same time. The ASIC is designed in an analog-digital hybrid architecture to achieve low power consumption as well as a small footprint. The analog part of the ASIC consists of a charge to voltage converter with capacitance cancellation array and a sigma-delta modulator (SDM) with a 3-bit quantizer. In the digital part of ASIC, the processor based on Cortex-M3 core is designed to perform angle calculation. The measurement result of the proposed angle sensor reveals that the power consumption is 250 mW from a single 5V supply, the bandwidth is over 130Hz, the resolution is 0.002° and the accuracy over the full range is 0.024°, indicating that the encoder has considerable potential for use in high-precision applications.