MAGNETO-STATIC SURFACE WAVE SENSOR

THERE IS A NEED FOR MINIATURE SINGLE AXIS MAGNETIC SENSOR CAPABLE OF DETECTING SMALL MAGNETIC FIELD PERTURBATIONS (NANOTESLAS). HOWEVER, UTILIZING RECENTLY DEVELOPED MAGNETO-STATIC SURFACE WAVE (MSWW) RESONATORS TOGETHER WITH SMALL RARE-EARTH MAGNETS, A SMALL (<10 CM[3]) AND SENSITIVE MAGNETIC FIELD DETECTOR CAN BE REALIZED. A PAIR OF MSSW RESONATOR CONTROLLED OSCILLATORS WHOSE DIFFERENTIAL OUTPUT FREQUENCY IS PROPORTIONAL TO MAGNETIC FIELD IS PROPOSED. A RARE-EARTH MAGNET PROVIDES THE NECESSARY BIAS WHILE REMAINING TRANSPARENT TO EXTERNAL MAGNET FIELDS. PRELIMINARY CALCULATIONS INDICATE A RESOLUTION OF <0.20 NANOTESLA AND A DYNAMIC RANGE OF 10 TO THE 9TH POWER (2000 OE) CAN BE ACHIEVED. EXTERNAL BIAS FIELDS OF OVER 100 OE CAN BE ACCOMMODATED AND FREQUENCIES FROM DC TO 1000 HZ COVERED. THE PROPOSED SENSOR REQUIRES MINIMAL CIRCUITRY AND UTILIZES LOW-POWER CMOS COUNTERS WHICH INTERFACE DIRECTLY TO DIGITAL EQUIPMENTS WITHOUT A/D CONVERTERS. APPLICATIONS ARE A MINIATURE SOLID-STATE COMPASS AND AS A LOW-FIELD MAGNETOMETER FOR MAPPING THE EARTH'S MAGNETIC FIELD OR SEARCHING FOR SUBMERGED UNDERWATER MINES AND SUBMARINES.