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Published July 2019 | public
Journal Article

Analysis and Design of Coupled Inductive Bridges for Magnetic Sensing Applications

Abstract

This paper presents the analysis and design of a novel magnetic sensor. We study the underlying physics of inductance shift sensors as a special case of the broader family of magnetic energy deviation sensors. The result is a quantitative definition of performance metrics with all assumptions and approximations explicitly stated. This analysis is then used to design a modified ac Wheatstone bridge that uses two inductor-pairs in a cross-coupled configuration, to half its size and double its transducer gain while maintaining a fully differential structure with a matched frequency response. A proof-of-concept sensor was fabricated with peripheral circuitry in a 65-nm bulk CMOS process to operate between 770 and 1450 MHz with an effective sensing area of 200 µm x 200 µm. The new bridge sensor is fully characterized at a frequency of 770 MHz and demonstrates a reliable and continuous detection of 4.5-µm iron-oxide magnetic beads over time periods longer than 30 min, appreciably longer than previously reported works.

Additional Information

© 2019 IEEE. Manuscript received November 16, 2018; revised January 26, 2019 and February 28, 2019; accepted March 12, 2019. Date of publication May 2, 2019; date of current version June 26, 2019. The authors would like to thank Dr. B. Abiri for technical discussions, G. Sullivan for his assistance with testing, and Analog Devices for synthesizer evaluation kits.

Additional details

Created:
August 19, 2023
Modified:
October 20, 2023