The Research Of High-speed Signal Processing In The Time-of-flight Rangefinder Of Femtosecond Laser Based On FPGA

The satellite formation flying is the research background of this article.However,the rapid and precise measurements of absolute distance between the satellites are critical for satellite maintaining formation-flying.Traditional ranging methods with laser can be mainly divided into two categories: pulse time of flight ranging,and optical interference ranging.However,they both can't satisfy the large-scale and high-precise absolute distance measurement.Because the width of femtosecond laser pulses is in femtosecond level,it has an ultra-high time resolution,which brings a breakthrough for distance measurement.In addition,it also could be made up of all polarization maintaining fiber,which makes them with high integration and stability.Therefore,this artic,with the following research work,is to develop an integrated femtosecond rangefinder which could satisfy satellite formation-flying and precision industry manufacture,etc.1.A high repetition frequency femtosecond laser is built as light source,based on balanced optical cross-correlation,to measure the absolute distance from an about 3 meters target.The experiment result indicates that this method has a high precision,up to 52 nm.However,this method can only measure some points,existing big dead zone.Besides,it needs high-tension apparatus to adjust cavity,owning big volume.Therefore,this method is not suitable for applications of satellite.2.Then two fiber lasers with 2 KHz difference are built as light source,based on non-linier optical sampling,to measure absolute distance from an about 2 meters target.Through averaging the continuous measurement results,a ranging precision of 0.8 ?m is achieved at a 2 KHz update rate,which basically meet our demand.But the digitizer used to process signal in our experiment is too big to integrate.3.Therefore,according to the principle of distance measurement by two femtosecond laser,a high-speed signal processing unit is developed,which carries an 14 bits 105 MSPS AD9640 to sample the signal,and used a high-speed parallel FPGA to process the disperse signals.This article analysis the principle of Gaussian Fitting firstly,and then use the basic operations designed the arithmetic including adaptive filtering,Gaussian Fitting and solving equations,which are realized with logic Les in FPGA at last.When a standard clock is used for this board,the measurement results can trace to the standard.In conclusion,this article almost realize a femtosecond laser rangefinder based on FPGA according to the research of high-speed signal processing,which could achieve a precision of absolute distance measurement among meters,with results tracing to the standard.In addition,it has the characteristics of good stability,little volume,fast update rate and available boot,etc.