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A Synchronous Chopping Demodulator and Implementation for High-Frequency Inductive Position Sensors

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2 Author(s)
Rahal, M. ; Dept. of Electron. & Electr. Eng., Univ. Coll. London, London, UK ; Demosthenous, A.

We describe a new method for high-frequency precision sensing. The method combines synchronous detection with chopping in a fully differential architecture that includes an instrumentation amplifier. An integrated circuit implementation of the proposed synchronous chopping demodulator front end was designed and fabricated in a 0.35-mum CMOS process technology and tested with high-frequency inductive position sensors. The measured results show that the new technique offers considerable advantages in terms of offset reduction compared to traditional techniques for these sensors, which rely on a microcontroller to measure the offset before each position measurement is taken. The measured average input-referred offset for the 20 fabricated chip samples is 87 muV at a chopping frequency of 500 kHz when the resonant target is off and synchronous demodulation and transmitter excitation are both applied at 1 MHz. The technique, in addition to improving system resolution and immunity to common-mode interference, allows these high-frequency position sensors to work with multiple targets, thus increasing speed and functionality.

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Instrumentation and Measurement, IEEE Transactions on  (Volume:58 ,  Issue: 10 )