Electronic Warfare Digital Wireless Communication Signal Blind Receive Key Technology Research

With the extensive use of electronic and information technology in the militaryfield, the information war has become the major part of modern warfare. Electronicwarfare is the basic combat way for the modern high-tech information warfare.Electronic support, such as reconnaissance and surveillance, is one of communicationcountermeasures in electronic warfare, which is mainly for intercepting the enemy’sconfidential information. In order to fulfill the process of communicationreconnaissance, the receiver, without any a priori knowledge, first needs to find out thecoding and modulation schemes that the enemy uses, and then does the demodulationand decoding accordingly, and finally recovers the information. This is called the blindreceive technology.In the wireless digital communication system, the blind receiver, having no ideaabout the transmitter’s training sequence information, tries to accomplish the effectivesynchronous and equalization by using the non-data-aided methods. However, theexisting non-data-aided symbol and carrier synchronization methods are limited by thecapture range, and the estimation precision. The convergence speed and robustness ofblind channel equalizer are also need to be improved.To solve the above problems, we first investigate the method of capture assistedblind symbol synchronization, which combines dynamic searching and the method ofvariable bandwidth of loop filter. The method can capture the offset which is as large as10%of normalized symbol rate, and has the stable tracking ability. For AWGN channel,it is shown that the difference of BER between the theoretical analysis and thesimulation result is less than1dB.Secondly, this paper researches on the non-data-aided Closed-Loop andOpen-Loop carrier recovery technology. For the continuous signals, we design theparallel of slow and fast loop carrier recovery technology, which can capture10%of thenormalized frequency deviation. For the short burst signal, a improved algorithm isproposed based on the classical frequency offset estimation algorithms by utilizing themaximum likelihood parameter estimation so that the estimated range can be expandedto1/(2MT), without increasing the computing complexity. The analytical and simulationresults for AWGN channel show that when the signal-to-noise ratio (SNR) is more than10dB, the performance of our algorithm is closed to Modified Cramer-Rao Bound(MCRB). We also applied our algorithm to the frequency offset estimation for MSKsignal which had been already linear processed. The estimated range is improved to1/(4T). And the performance of frequency offset estimation can attain MCRB whenSNR is greater than15dB.Thirdly, the improved dual-mode decision feedback blind equalization algorithm issimulated. We designed the symbol interval dual-mode blind decision feedbackequalizer for the MPSK and MQAM signal，and the dual-mode T/4fractionally spaced blind decision feedback equalizer for the MSK signal. The analytical and simulationresults show that the blind equalization method helps to speed up the convergence rateand reduce the steady-state MSE more than5dB, when the Eb/N0is equal to20dB.Finally, we integrate the synchronization and equalization solutions according tothe project requirements, and test the performance of the integrated solution. We realizethe algorithm with software and test the software in simulation software platform. It isshown that the difference of BER between the theoretical analysis and the simulationresults is less than1dB in AWGN channel. And the bit error rate can be less than1104in the short-wave multipath channel, which meets the demand of the project. The resultsin simulation and evaluation software platform verify the effectiveness ofsynchronization and equalization solution.The research in this thesis is based on the background of blind digital wirelesscommunication signal receiver in electronic warfare. It explores the improved algorithmof blind symbol synchronization, blind carrier synchronization, and blind channelequalization. The result of integrated testing for the improved algorithm shows that thesolution meets the requirement of the project. The realization of the simulation softwaree system referring in this paper has significant guiding for the development of the actualplatform.