Non-cooperative Receiving Schemes For Frequency Hopping Signals

Frequency hopping (FH)communication system has been widely applied, due to its low probability of interception and detection, anti-decline performance and anti-fading performance, and high security. And it's a great challenge to carry on receiving technology in noncooperative mode of frequency hopping signals. Now, the research of receiving technology in noncooperative mode of frequency hopping signals, such as signal detection, parameter estimation, and signal sorting became hot. A series of key technologies of receiving technology in noncooperative mode of frequency hopping signals, including signal detection, parameter estimation, and signal sorting, etc. in this field were mainly researched in this thesis. Finally, signal sorting algorithm of FH signals is realized using software. The main tasks completed are lined out as follows.1. Time-frequency analysis are studied. Various time-frequency representations (THRs) for FH signals detection and the performance of various TFRs was quantificationally compared in time-frequency concentration and suppression cross-term interference.2. Blind estimation of parameters of single FH signal is mainly researched. Firstly, a new method based on normalized window based on S transform (NWST) is presented which improves the performance of the methods based on S transform. The various time-frequency analysis method is studied for improve estimation precision in the low SNR. a new THRs can be obtained through assemble spectrogram and modified smoothed pseudo Wigner-vile Distribution method, a new method estimation of parameters based on one dimentional two quadratic difference is proposed, using it along time axes search peak value and modify peak value and position, then, using various method estimation FH signals parameter, and can enhance performance under low SNR condition.3. Blind detection of FH signals in complex electromagnetic environment with all kinds of interferences is researched. Firstly, using power spectrum elimination method for restraining the frequency-fixed signals, a CASO-CFAR method is proposed for the purpose of making frequency hopping signals well-marked, Then, mathematics morphological technology is used to smooth signals and eliminate noises. Finally, using image enhancement for eliminating noises and detect FH signals.4. Blind sorting of FH signals is researched. paramenters of each segment acquired from direction searching and segementation, firstly, a new method for frequency-hopping signals sorting based on beamforming is proposed, which is well-used in FH signals sorting, restraining the interference of come from different direction. Then, clustering algorithm is proposed, which can select optimal initial cluster centers by searching parameters's histogram peak values, the iterations of clustering are reduced and the robust is swelled, design a clustering method based on without knowledge of the frequency-hopping network mode for receiving technology in noncooperative mode,which is well-used in FH signals sorting, and reduce the computational complexity.5. FH signals sorting based on clustering algorithm is carried out on software. Firstly, FH signals process platform is introduced. Then, the process of signals sorting is fixed by flow charts, finally, the sorting algorithm is programed, the results show the software meet system demands.