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

An automatic wideband 90 degrees 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 degrees will cause 1 Hz change of the resonant frequency. In order to meet the continuous measurement of the geomagnetic field, an automatic wideband 90 degrees 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 degrees 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 degrees, and the relative error less than 0.1%. It has been proved the feasibility of the automatic wideband 90 degrees phase shifter applied to the cesium optically pumped magnetometer.