Magneto-Impedance Sensor Based on Time Analog to Digital Converter (TAD) for Circuit Integration

We propose a new magnetic field measurement system that consists of a magneto-impedance (MI) sensor based on a time analog-to-digital converter (TAD) for circuit integration onto chips. The proposed MI sensor system has neither a rectifier nor a differential amplifier, both of which are needed in the previous MI sensor system, as they largely impact the integration of the circuit. In order to demonstrate the proposed magnetic field measurement system, we experimentally determine its optimal operating conditions and then show its magnetic characteristics. We demonstrate that the proposed MI sensor system has a 22.2 pT/LSB resolution, which can be optimized by changing the sampling clock of the TAD. In addition, the proposed system has a 15 pT/Hz^1/2 noise level, which is better than the previous MI sensor system. Moreover, it has a high signal-to-noise ratio that is better than the previous one. These results suggest that the proposed MI sensor system is suitable for circuit integration and has a low noise measurement.