Design Of Acquisition Card For Lidar Echo Signal Based On FPGA

Lidar is a kind of active remote sensing equipment which gets information of the target by emitting a laser beam towards a target actively and then acquisiting and analyzing echo signals reflected by the target.Data acquisition equipment of lidar echo signal is the critical part of lidar system.In order to improve signal-to-noise ratio(SNR),data acquisition equipment should have the function of filtering and high-speed data accumulation.In order to meet the requirement of lidars with different repetition frequency,the parameters such as sampling depth and accumulating time should be reconfigurable.In this paper,a universal lidar echo signal acquisition card with a sampling rate of 20MHz and reconfigurable parameters,which had the function of filtering and hardware accumulation,was realized by using FPGA as main control equipment and the detailed design content as follows.1.Firstly,this paper introduced the main noise components and their characteristics in the laser radar echo signal,analyzed the improvement of signal to noise ratio by cumulative average method and gave three method of accumulating the echo signal.2.The hardware design of echo signal acquisition card was introduced then:the analog-to-digital conversion circuit with its peripheral circuit,signal conditioning circuit,level converting circuit and RS232 interface circuit design was introduced in detail;the structure and function of digital circuit board was briefly introduced.3.The logic design of FPGA was introduced then.It introduced the method and process of FPGA project design,gave the design of the top-level module of the project,introduced the structure and function simulation result of all modules in the FPGA and showed the waveform diagram of the timing simulation of Top Module.4.Finally,the acquisition card was tested.It included the test of the hardware accumulation function,the signal to noise ratio and the bandwidth,as well as the live test on the lidar platform and the comparison test with Licel transient recorder.The test results showed that the acquisition card achieved the basic parameter configuration function and accumulation function,and the SNR was 71.9dB.Compared with a foreign echo signal acquisition equipment,the acquisition card had longer detection range and higher SNR in high repetition frequency lidar.