Extraction of Signal Frequency in Laser Ranging of Space Target Based on FPGA

Aiming at the problems in a linear frequency modulation continuous wave(LFMCW)ranging lidar system,such as low signal-to-noise in echo beat frequency and difficult extraction of the signal frequency,a method with high-speed and high accuracy based on field programmable gate array(FPGA)is proposed.Firstly,the laser echo beat signal is sampled by high-speed analog to digital converter(ADC)and then processed in FPGA for data preprocessing.After the signal is processed by the 8192-point FPGA will obtain the frequency spectrum and then apply the frequency spectrum to data processing and adaptive noise signal peak detection.These two steps realize the real-time and accurate extraction process of the target echo beat signal frequency.Finally,the spectrum data is transmitted to the host computer and processed through the external data acquisition board for real-time spectrum display.Experimental results show that data preprocessing and spectrum data processing can effectively suppress DC bias and system modulation noise.Adaptive noise peak detection can accurately divide the threshold contour according to the dynamic noise of the system and realize the detection of target signal peak.When the sampling clock of the system is 100 MHz,the time needed for each calculation of the spectrum is 81.92μs,and the refresh rate of the spectrum reaches 12.2 kHz,which meets the real-time requirements of the system.