Research On Hardware Processing Of Receiving Error Of Echo Signal In Pulse Lidar

Nowadays,lidar technology has been widely used in many fields,and has become a new tool and new means for target data acquisition.One of the important parameters to evaluate the performance of lidar is the measurement accuracy.The factors that affect the accuracy of the lidar exist in three main aspects,including the laser transmitting system,the echo signal receiving system and the external interference factors.In order to improve the accuracy of pulsed lidar measurement,this paper aims to eliminate the receiving error of the echo signal,and studies the processing of high-precision signal in the receiving channel.It is devoted to the innovation of signal processing technology in the traditional receiving channel of lidar,and ultimately improves the application performance of lidar.First of all,the development of pulsed lidar technology at home and abroad is reviewed and summarized in this paper,and then the working principle of lidar is introduced in detail.The system composition of lidar,the principle of lidar ranging and the formula of pulse measurement are introduced in detail in this paper.Then,the working mechanism of the pulsed lidar receiving channel is described in detail,and the related technical schemes are listed from the three signal processing steps,such as the front-end amplifier circuit,timing discrimination,time-interval measurement,and the advantages and disadvantages of various technologies in each processing stage are compared.Finally,after summarizing a series of defects in signal processing of receiving channel,corresponding solutions are proposed in the above three steps of signal processing and implemented.In the process of implementing the technical scheme,the feasibility of theory and technology is verified by simulation experiment,and then the practical circuit is designed and experimented to make the scheme more rigorous and reliable.The results show that the time error of received signal is effectively reduced and the measurement accuracy of lidar is improved by the new technical scheme.Firstly,aiming at the large walk error in traditional timing discrimination technology,a timing discrimination method of third-order high-pass filtering is proposed in this paper,which is based on the traditional first-order high-pass filtering method to increase the differential operation of the signal.The third-order high-pass filtering method with three times of differential processing of the echo signal,which causes the rise of the echo signal to produce three peak points,so that the timing point moves forward twich to achieve the compression of the timing error and improve the measurement accuracy.Then,the merits and demerits of the pre amplification and the traditional leading-edge timing discrimination in the receiving channel are combined,and a high-order amplification and fitting method is proposed to achieve the timing point acquisition.This method amplifies the echo signal by fixing the threshold of the comparator,and generates a series of timing points.Then,the model is established according to the amplify coefficient,timing point and the amplitude of the different magnified output signals,and the relation functions between the three is fitted,and the minimum walk error is calculated.Finally,a simulation-fitting method is proposed,which converts the measurement of time interval into the form of capacitor charging to fit the time interval.In the time-interval measurement of simulated fitting method,the capacitor charging is controlled by starting and stopping signals of laser pulse,and the charge capacitance change curve is sampled and fitted,and the actual time-interval of the laser pulse flight time is calculated according to the fitting time amplitude function model.With the theoretical analysis of three kinds of high-precision hardware processing techniques for receiving error in lidar echo signal,and the establishing of simulation experiments.The theories are proved through the simulation rsults.The actual circuit module was designed and tested.The experimental results show that the three schemes have significantly reduced the error compared with the traditional methods,which proves the effectiveness and reliability of the proposed method.