SBIR Phase II: Delta-Sigma All-Digital Magnetometer

This Small Business Innovation Research (SBIR) Phase II project will develop and prototype a single-chip magnetometer based on an innovative approach to digital magnetic sensors. The traditional approach combines a physical sensor having an analog output with an electronic analog-to-digital converter. In this sensor, the analog-to-digital conversion occurs in the physical mechanism of the sensor itself. With this approach only inexpensive digital electronic circuits are needed to complete the sensor system, resulting in a robust design that can easily be manufactured. The unique properties of sub-micron sized magneto-resistive sensor elements are used. The small size of these elements allows only two magnetic states, i.e. the magnetic state represents a binary digit that is a function of the external magnetic fields. Using concepts borrowed from over-sampling delta-sigma analog-to-digital converters, it is possible to measure the analog magnitude of a magnetic field by repeatedly interrogating the magnetic state of the bit. Using the principles of delta-sigma converters, including noise shaping feedback and high over-sampling ratios, high resolution and an inherently linear response can be achieved. This single-chip digital magnetometer would be a revolutionary advance in sensor technology since it is based on standard wafer-level integrated circuit processing techniques. It will thus be much smaller and cheaper to fabricate than existing equivalent magnetic sensor systems. The highly integrated nature of this product, low power consumption and the digital output will make it extremely attractive for remote and/or bussed sensor applications. Applications include digital compasses, geomagnetic surveying equipment, vehicle sensors for traffic control, intrusion detection, currency/document validation and portable biomedical assay devices.