Omni-directional measurement of the geomagnetic field in satellites is necessary.Coherent population trapping(CPT)atomic magnetometer is theoretically capable of omni-directional measurement of magnetic fields,but it requires a reference signal in the direction of the magnetic field.To solve this problem,a new control method was proposed in this paper to trap four CPT signals.First,the control system demodulates the CPT differential signals with n=-3,n=-2,n=+2,and n=+3 by a time-division frequency modulation.Second,these CPT differential signals are fused to obtain two new feedback signals:one feedback signal used to calibrate the central frequency between n=±2 or n=±3,and the other feedback signal used to adjust the frequency between the central frequency and the CPT signals with n=±2 or n=±3.When a change in the magnetic field direction causes CPT signals with n=±2 or±3 to disappear,the two feedback signals remain unaffected.Therefore,this control method does not require a fluxgate magnetometer to provide the magnetic field direction for mode switching and can obtain continuous magnetic data without losing lock in the range of 0°-360°.This means that it is an autonomous omni-directional CPT atomic magnetometer.
atomic magnetometercoherent population trappingmagnetic fieldomni-directional measurement
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