Weak signal detection technology for synthetic aperture ladar

Abstract

When remote objects are detected by use of SAL, weak echo signal is easy to be interfered by noises. To obtain high receiving performance, the amplifier and signal processing system should be carefully designed. In this paper, the circuit consisting of the microwave filter, the pre-amplifier and the main amplier is designed under the condition of photodiode impedance matching. The major noises of PIN photo diode are analyzed and a low noise pre-amplifier circuit is designed,which can improve the signal to noise ratio ( SNR ) effectively. The noises are filtered by a microwave filter. The circuit self-excited owing to high frequency operating is also taken into account. Some measures that the device is reasonably selected and the circuit is legitimately designed are implemented. The anti-interference of the circuit and the ability of restraining self-excited are improved by shielding box etc. Experimental results indicate that the receiving circuit has small volume and high reliability with high performance.