An Automatic Wideband 90° Phase Shifter for Optically Pumped Cesium Magnetometers

An automatic wideband 90° phase shifter for optically pumped cesium magnetometer has been investigated experimentally. As an important part of the self-oscillating optically pumped cesium magnetometer detecting circuit, the band and automation of the phase shifter directly affect the continuous measurement of the magnetic field. At the same time, a phase deviation of 1° will cause 1 Hz change of the resonant frequency. In order to meet the continuous measurement of the geomagnetic field, an automatic wideband 90° phase shifter based on the allpass filter has been designed. It can be used to precisely make the phase of the detected signal shifted by 90° in a wide range of frequencies from 50 to 350 kHz. Through the actual test and analysis, the phase shift error of the automatic phase shifter is less than 0.1°, and the relative error less than 0.1%. It has been proved the feasibility of the automatic wideband 90° phase shifter applied to the cesium optically pumped magnetometer.