Key Technology Of PCM/FM Modulation And Demodulation And FPGA Implementation

Telemetry has developed rapidly in recent years and is widely used in the development of aerospace telemetry and strategic weapons.The pulse code modulation/frequency modulation(PCM/FM)telemetry system has high precision,anti-fading and anti-interference ability,and is a widely used telemetry system.With the rapid increase of signal propagation speed and distance of PCM/FM telemetry system,the demodulation performance requirements are getting higher and higher.The traditional non-coherent frequency demodulation demodulation technology has poor demodulation performance,which can not meet the existing equipment.Demand.In order to further improve the demodulation performance of PCM/FM signals,this paper first studies the Multi-Symbol Detection(MSD)technology.Through simulation analysis,it shows that when the observed symbol length is N=5,the MSD demodulation algorithm is more traditional.The non-coherent frequency demodulation improves the demodulation performance by 3dB.However,its computational complexity is large and it is difficult to implement in hardware.Aiming at this problem,an algorithm of Baseband Quadrature Complex Rotation Multi-Symbol Detection(BQCR-MSD)is introduced.This algorithm can reduce the computational complexity and make it easier in hardware without degrading the demodulation performance.Implemented in.Secondly,the Turbo Product Code(TPC)is analyzed and analyzed.The demodulation performance is better than MSD,and the demodulation performance is improved by 6dB compared with the traditional non-coherent frequency demodulation.However,its computational complexity and the required hardware storage space are large.Therefore,this paper proposes an optimization scheme to simplify the storage of external information and the storage capacity of the receiving matrix.Although the demodulation performance of the optimized TPC algorithm is reduced by 0.2 dB,the hardware implementation is greatly reduced.The complexity makes the TPC demodulation more suitable for implementation in hardware.Then the angle rotation MSD algorithm is combined with the optimized TPC algorithm for the demodulation of PCM/FM telemetry signals.Through simulation analysis,the demodulation performance is improved by 7.7dB compared with the traditional non-coherent frequency discrimination.In telemetry systems,data transmission is unreliable due to the presence of channel interference,which requires the use of synchronization techniques in demodulation.Therefore,this paper first introduces the symbol synchronization based on MSD algorithm,which is a digital phase-locked loop synchronization method.Its advantage is that it does not need to extract pilots,nor does it need to calculate the symbol phase,and it can automatically correct the error loop time.The code block synchronization algorithm based on TPC decoding is introduced to improve the TPC decoding performance.Finally,FPGA implementation is implemented for the modulation,demodulation,and synchronization techniques of the PCM/FM telemetry system.The module design was carried out in Verilog HDL language,simulated in Modelsim,and the indicators were tested with Xilinx FPGA zynq7010 development board,610 Zi oscilloscope and signal generator.The test results show that the angle rotation MSD and the optimized TPC algorithm are more traditional.The non-coherent frequency-demodulation demodulation improves the 6.6dB demodulation performance gain.Although it has certain errors with the software implementation,it is in line with the design purpose,so the design of the system is correct.