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Design and implementation of a new high-accuracy interpolation encoder IC for magneto-resistive sensors

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Abstract

A new algorithm named the eight-section (ES) method for carrying out the interpolation for a magneto-resistive (MR) encoder is successfully developed and fabricated in a digital chip. It is known that a conventional magneto-resistive (MR) encoder employs the interpolation method, which converts incoming front-end analog signals in harmonics in sinusoids/co-sinusoids to moving displacement via calculating arc-tangents. This conventional interpolation requires divisions to be carried out for the displacement, which often leads to large noises while conducting digital computation, eventually undermining significantly the accuracy of the MR sensor. The proposed interpolation of eight-section (ES) is designed specially without divisions in the digital computation, leading to higher precision than the conventional interpolation conducting the computation of arc-tangents. The digital computation chip designed by this study consists of a cycle counter, two decimators for incoming analog signals of the MR sensor, a correcting circuit, and the proposal ES interpolation unit. The designed chip is successfully fabricated by TSMC 0.18-μm CMOS process, the area of which is 1643 × 1676 μm. The chip is than calibrated by a reference interferometer by experiments for further improving the measurement accuracy. The precision finally results in measuring displacement reaches as accurate as within 1.065 μm, which is much favorable to the existing performance around 2 μm by the conventional interpolation.

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Acknowledgements

This study is supported by Ministry of Science and Technology, Taiwan Grant Nos. -MOST 106-2218-E-009 -011, MOST 106-2634-F-009-001 -CC2, MOST 107-2221-E-009 -166 -MY2, MOST 107-2218-E-009 -006 -, MOST 107-3017-F-009-003, MOST 107-2622-E-009 -025 -CC2, MOST 108-2823-8-009 -002 -, and MOST 108-2623-E-009 -004 –D. It was also supported in part by the Novel Bioengineering and Technological Approaches to Solve Two Major Health Problems in Taiwan sponsored by the Taiwan Ministry of Science and Technology Academic Excellence Program under Grant Number: MOST 108-2633-B-009-001. This work was financially supported by the “Center for Intelligent Drug Systems and Smart Bio-devices (IDS2B)” from The Featured Areas Research Center Program within the framework of the Higher Education Sprout Project by the Ministry of Education (MOE) in Taiwan. It was also supported in part by Hsinchu Science Park Bureau, MOST Grant No. 108A31B.

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  1. Department of Electrical Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan

    Wen-Yu Chen, I-Feng Chang, Paul C.-P. Chao, Smriti Thakur & Tse-Yi Tu

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  1. Wen-Yu Chen
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  2. I-Feng Chang
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  3. Paul C.-P. Chao
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Correspondence to Paul C.-P. Chao.

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Chen, WY., Chang, IF., Chao, P.CP. et al. Design and implementation of a new high-accuracy interpolation encoder IC for magneto-resistive sensors. Microsyst Technol 26, 3547–3559 (2020). https://doi.org/10.1007/s00542-020-04949-9

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