Research On Signal Processing Technology Of Array Lidar

Array lidar has been a popular focus in the field of lidar in recent years because it doesn’t need the scanning equipment,and it can quickly detect the target entirely.The detector of array lidar is composed of multiple and parallel avalanche photodiodes(APD),and it is hard to detect weak laser echo signals.Therefore,the design of the signal processing system of detector is very important.In this paper,the research on the signal processing technology of array lidar with multi-pixel photon counter(MPPC)which is a kind of detectors based on APD arrays was carried out in the thesis.According to the technical indicators,a signal processing system and a time interval measurement system of MPPC were designed,and a test platform of systems was built to verify the function of the designed systems.The main research contents and results are as follows:(1)The theory and working principle of array lidar was studied.The system of array lidar was divided into pulse laser transmitting and receiving optical system,signal receiving and processing system,time interval measurement system for analysis.With the detection range of 150～200 m as the total technical indicators of the lidar system,the detector was selected,and signal processing system indicators were calculated according to the parameters of detector.(2)The signal processing system was studied.The signal processing system was designed by dividing into three parts:the detector bias power supply module,the weak signal detection module,and the time identification module.According to the signal processing system indicators,the circuit of these modules were designed and simulated,and the simulation results showed that the weak signal detection module could achieve a gain of 74 dB in 75～88 MHz bandwidth;the time identification module could effectively identify the pulse laser signals.(3)The time interval measurement system was studied.According to the total indicators of the lidar system,the specified timing chip which named TDC-GP22 was selected as the core chip of this system.After the timing finishing,the timing results were read out by STM32.According to the internal resources,communication method,working principle and other requirements of TDC-GP22,the external circuit of chip and the software program of the time interval measurement system was designed.(4)A system test platform was built for experiments.The results of experiments show that the designed signal processing system can detect,amplify and identify the laser echo signal which is reflected by target within the range of 150～200 m;the designed time interval measurement system has the maximum limit error of 9.75 cm in the range of 150～200 m.