Key Technologies Of Low-complexity Incoherent Demodulation In GMSK-FH Communication

In military communication systems,anti-jamming communication plays a more and more important role,and the frequency hopping(FH)technique is widely used because of its good anti-jamming performance.At the same time,Gaussian filtering minimum frequency shift keying(GMSK)is widely used in FH systems because of its advantages of narrow frequency band,good spectral characteristics,and stable envelope.Considering this,this paper studies the key technologies of incoherent demodulation in GMSK-FH communication systems,and verifies the feasibility of the scheme through both theoretical analysis and hardware implementation.The main research contents of this paper are as follows:Firstly,the development status of MSK modulation,GMSK modulation and demodulation,and FH technologies is summarized,and the coherent demodulation and incoherent demodulation algorithms for GMSK systems are analyzed to provide theoretical supports for the following system design.Secondly,the theory of GMSK demodulation algorithm is studied,and the low-complexity incoherent demodulation in GMSK-FH communication systems is determined as one-bit differential demodulation.In addition,the influence of frequency synchronization error and sampling offset on GMSK incoherent demodulation performance is given,and the complexity analysis of GMSK one-bit differential incoherent demodulation is provided.Thirdly,the overall implementation architecture of low-complexity incoherent demodulation of GMSK-FH communication is designed,and FPGA implementation and laboratory verification are completed.First,the independent design and implementation of each sub-module is completed,and the interface constraints of each sub-module are carried out.Then,the function simulation,logic synthesis and implementation of each sub-module are combined,and the timing is optimized according to the timing report.Next,the hardware resource consumption of GMSK incoherent demodulation is analyzed.Finally,the upper board test is carried out to analyze the test link bandwidth,constellation diagram,receiver sensitivity and error rate results,and compare the bandwidth in the simulation link,constellation diagram after demodulation and error rate curve.Experimental results show that in GMSK-FH,under the condition of Turbo coding and decoding,the bit error rate of GMSK demodulation is less than 10^-5,and the performance loss of fixed-point implementation is less than 2 d B.This paper completes the design and implementation of low-complexity incoherent demodulation scheme of GMSK-FH communication,which provides theoretical and experimental support for the application of GMSK-FH communication,and has certain reference and significance in practical engineering.