Research on target positioning and signal processing based on the four-quadrant detector

Abstract

In a target location system, the spot size and spot position of the laser light, which are received by a four-quadrant detector, are closely related to the accuracy of the target location. To acquire a pA-level current, according to the characteristics of the signals generated by the four-quadrant detector and the related signal processing circuits, this paper designs signal processing circuits with amplification multiples of 140 dB and 160 dB. Meanwhile, a T‑shaped compensation network is added to the circuit to solve the problem of bandwidth and gain not being increased simultaneously. Theoretical calculations and numerical simulations are carried out to verify this circuit gain, phase margin, and other parameters. Simulation results show that the bandwidth of the signal processing circuit with an amplification of 140 dB is 199.256 kHz, the bandwidth of the signal processing circuit with an amplification of 160 dB is 100 kHz, and the test bandwidth is 96 kHz in 140 dB, which provides a strong support for the calculation of the spot position of the four-quadrant detector.