Automatic Gain Control for Pulse-Broadened Laser-Ranging System

In pulsed laser- ranging systems, the amplitude and pulse width of the echo pulse typically vary owing to the electrooptical/photoelectric conversion process and the changes in the target position or reflectivity, which results in significant errors when the fixed threshold method is used directly. Although an automatic gain control (AGC) system can minimize the error, most AGCs measure the peak value through the peak holding circuit, which causes problems such as peak holding attenuation, instability, and slow response speed. Therefore, a 250-MHz-high- speed analog-to-digital conversion module is used in this study to obtain the peak value of the echo pulse and achieve peak retention and zeroing in the field programmable logic gate array. Compared with the AGC system with a peak-holding circuit, the system has a simplified circuit, no attenuation of voltage peak, and a faster response. The experimental results show that the designed laser ranging system can effectively control the amplitude of the echo pulse within a narrow range (0. 76. 1. 44 V) to reduce measurement errors.