Analog Lock-In Amplifier Design Using Subsampling for Accuracy Enhancement in GMI Sensor Applications.

Area of Science:

• Electrical Engineering
• Sensor Technology
• Signal Processing

Background:

• Analog lock-in amplifier (LIA) architectures are crucial for giant magneto-impedance (GMI) sensor applications.
• Enhancing the accuracy of LIAs, particularly at optimal GMI sensor operating frequencies, presents a significant challenge.
• Existing LIA designs may face limitations in precision and noise reduction at higher frequencies.

Purpose of the Study:

• To present a novel frequency downscaling technique for analog LIA architectures.
• To improve the measurement accuracy of GMI sensors by optimizing LIA performance.
• To validate the effectiveness of the proposed downscaling method on different LIA topologies.

Main Methods:

• A frequency downscaling technique was applied to LIA architectures for GMI sensor applications.
• The method involves subsampling input and reference signals using sample-and-hold (SH) circuits to reduce operating frequency.
• Two LIA topologies, utilizing analog and switching-based multiplication for phase-sensitive detection, were investigated.

Main Results:

• The frequency was successfully downscaled from 200 kHz to 1 kHz, leveraging low-frequency analog signal multiplication benefits.
• Measurement errors in signal magnitude were reduced by a factor of 8 (analog multipliers) and 21 (switched multipliers).
• In-phase detection error in a two-phase LIA was reduced by over 25%.

Conclusions:

• The proposed frequency downscaling technique significantly enhances the accuracy of analog LIA architectures for GMI sensors.
• The method offers a practical approach to improve GMI sensor measurement precision without altering the core phase-sensitive detector principles.
• Experimental validation confirms substantial error reduction, demonstrating the technique's efficacy in real-world applications.