| Frequency Modulated Continuous Wave(FMCW)LiDAR is a new type of LiDAR technology that combines traditional radar technology with laser interferometry detection technology.FMCW lidar has the characteristics of no target,small blind spot,high detection accuracy,and strong antiinterference ability,playing an important role in fields such as autonomous driving,engineering measurement,and target recognition.However,in practical applications,the FMCW lidar system is limited by the modulation nonlinearity and linewidth of the laser light source,resulting in a decrease in its ranging accuracy.Therefore,studying the nonlinear suppression problem of laser frequency modulation is of great significance.This project studied a linear frequency modulation distributed feedback(DFB)laser based on Field Programmable Gate Array(FPGA),with a focus on designing the control circuit of the linear frequency modulation DFB laser.A nonlinear pre distortion compensation control program for the linear frequency modulation DFB laser is written using Verilog language and C language,and experimental and application studies are conducted.The main research content and results of this article are as follows:(1)We have developed a linear frequency modulation DFB laser driver circuit.The driving circuit includes a temperature control module and a current control module.The temperature control module is responsible for stabilizing the laser temperature and avoiding wavelength drift caused by temperature changes during frequency scanning.The temperature adjustment range is 5-50 ℃ and the resolution is 0.01.The current control module modulates the driving circuit of the DFB laser through an external modulation signal to achieve linear frequency modulation,with a modulation gain of 80 m A/V and a maximum modulation frequency of 10 MHz.This driver board can complete the pre distortion correction of linear frequency modulation DFB laser with FPGA development board.(2)A pre distortion correction algorithm based on FPGA is studied,and iterative pre distortion control technology is used to correct the nonlinearity of laser frequency modulation.The pre distortion correction algorithm is designed using a combination of Verilog language and C language.Verilog code is written to define multiple IP cores,which serve as the peripheral circuit for module design.At the same time,C code is written to complete the scheduling of each module,and multiple algorithms are used for iterative processing.(3)We have developed an experimental system for frequency modulation nonlinear correction of DFB lasers and conducted experimental and applied research.The experimental results show that at a scanning frequency of 5 k Hz,the modulation bandwidth is 19.91 GHz,and the nonlinearity is reduced from 0.324% uncorrected to 0.059%.The frequency modulation nonlinearity is significantly suppressed.A laser radar ranging system is designed based on a nonlinear correction light source,with a maximum measurement error of 0.868 m within a ranging range of 30 m. |
