The Design Of Power Spectrum Analysis System Based On FPGA

The coherent wind lidar measures the scattered echo signals of aerosol particles in the atmosphere and uses Doppler frequency shift to obtain the atmospheric wind speed.Compared with the traditional microwave radar,lidar has higher measurement accuracy and spatial resolution,and plays an important role in meteorological monitoring,wind power resource development,aviation security and other fields.In order to meet the requirements of signal acquisition and processing in coherent wind lidar system,a power spectrum analysis system based on FPGA is designed in this paper.Through the combination of hardware platform and algorithm logic,the system flexibly realizes a series of functions,such as data acquisition,trigger,cache,power spectrum estimation,result upload and so on.The host computer software is used to configure the key parameters to meet the measurement requirements in different situations.The whole system has the advantages of high integration,small size,wide measurement range and so on.The hardware platform of the system consists of a signal acquisition sub-board and a data processing motherboard.The sub-board uses a 12 bit 1GS/s ADC chip for high-speed sampling.The motherboard takes Virtex-6 series FPGA as the core,on the one hand,it controls the working mode of the sub-board through SPI interface,on the other hand,it realizes real-time power spectrum estimation by virtue of its rich computing resources.At the same time,it uses DDR3 memory bar and Gigabit Ethernet transmission module to complete high-speed data cache,command sending and receiving and result upload.According to the work flow of the system,the overall logical structure is divided into three parts:the data receiving part mainly completes the external trigger sampling control,data bit width conversion and DDR3 cache;the power spectrum estimation part realizes the functions of piecewise zero filling,real-time windowing,FFT processing and pulse accumulation;the communication module completes the parameter configuration and result upload through Gigabit Ethernet.Considering the calculation accuracy and processing speed,two FFT processing schemes are studied and implemented.The simulation results show that the relative error of single-precision floating-point parallel FFT module is 10-7,and the time of 1024-point transformation under 200MHz is 17.41?s.The relative error of pipelined FFT module of 24 bit fixed-point is 10-5 and the time of 1024-point transformation under 200MHz is 10.65?s.The control variable method is used to test the power spectrum analysis system,and the test results are consistent with the expectations,which verifies the correctness of the design.