Research And Implementation Of Short Wave Specific Signal Receiving Technology

Shortwave communication is a kind of effective wireless communication method of longdistance transmission without relay.It is widely used in military communication because of its advantages of strong anti-destruction,anti-jamming ability,flexible configuration and low cost.With the development of many HF adaptive communication link standards in recent decades,the stability and effectiveness of HF communication has been improved significantly.Among them,the U.S.Department of Defense proposed MIL-STD-188-110C(hereinafter referred to as 110 C protocol)short wave standard specification,the maximum signal bandwidth is 24 k Hz.Based on the current IC technology,this paper uses Xilinx XCZU9 EG So C chip as the platform to implement the baseband signal processing algorithm for the 110 C Appendix C signal with high transmission reliability,strong business adaptability and wide application range.It focuses on the analysis of the adaptive equalization algorithm commonly used by the receiver in the actual shortwave communication,and carries on the structural optimization.To ensure the real-time signal processing,to cope with modern war in the complex electromagnetic environment.In this paper,the main work and innovative points are summed up follows:Firstly,the development history of short wave communication is introduced.The development and optimization of the receiving hardware platform and the channel equalization of the key processing technology based on the software radio architecture are analyzed according to the transmission characteristics and application scenarios of the HF communication at present stage.The statistical characteristics of HF communication channels are discussed from the point of correlation bandwidth and coherence time.This paper briefly describes the Appendix C protocol110 C,analyzes the signal waveform characteristics of the protocol after interference and the performance testing environment for the protocol.Secondly,the shortwave channel equalization technology is illustrated.The principle and performance of LMS and RLS adaptive equalization algorithms based on the least mean square error criterion and the least square criterion are detailed analyzed.When the channel environment is poor,the classical adaptive equalization algorithm cannot effectively compensate the distortion caused by the channel.The idea of Turbo code is used to carry out the iterative exchange of soft information between equalizer and decoder to improve the channel equalization ability.The linear iterative equalization algorithm based on MMSE criterion and the iterative equalization algorithm based on Kalman framework are studied.The simulation results indicate that the performance of MMSE linear iterative equalization algorithm is obviously better than that of LMS adaptive equalization algorithm when the interference between signals is serious.For the sake of reducing the high computational complexity of MMSE linear iterative equalization algorithm due to decoding,an iterative equalization algorithm based on Kalman framework is adopted.The algorithm combines the Kalman filter and smoothing operation to estimate the signal state,and uses the statistical characteristics of the signal to realize the soft decision to complete the iterative equalization.In the end,a receiving and processing scheme is proposed in this parper for the signal in Appendix C of 110 C protocol.The short wave receiving process includes three parts: digital down conversion,signal equalization and synchronization.By using the pseudo-random sequence in the initial synchronization header of the frame,the signal equalization and synchronization acquisition are realized,the crosstalk between codes is eliminated and the rough delay information is obtained.Timing synchronization is realized by using repeated FH sequence in the initial synchronization head and Schmidl&Cox algorithm.The carrier frequency offset is estimated by the Barker code set in the frame data block and the signal frequency offset is tracked in real time.The performance simulation of the above receiving system shows that the bit error rate of the signal can reach 10-4.According to the design scheme,a short wave receiving and processing system on account of Xilinx ZCU102 evaluation board is realized.The low rate IQ complex signal is obtained from the short wave real signal through the digital down conversion module.Synchronization module based on signal correlation operation describes the realization of each thick and thin synchronization module.The carrier frequency deviation obtained by the carrier synchronization module is fed back to the DDS IP core in the digital down conversion module,and the local oscillator output frequency is adjusted to ensure a small deviation of digital mixing.The classical LMS algorithm structure and the adaptive equalization module of DLMS based on the pulsation array structure are researched and implemented.The filter throughput is improved by adding delay element to LMS algorithm to adjust the algorithm structure.Combined with the pulsation array structure,the flow capacity of the delay LMS algorithm is improved,and the good spatial and temporal locality is ensured.In conclusion,the short-wave receiving and processing platform has good feasibility and accuracy for the 110 C Appendix C signal,and has certain reference function for the design and implementation of the So C structure-based short-wave receiving and processing platform.