Dfh Anti Intercepted The Key Technologies

High frequency (HF) communications play a unique important role in the field of military communication due to its skywave propagation characteristic and its ionospheric invulnerability. The Differential Frequency Hopping(DFH) technology which combines modulation encoding and frequency hopping technology can highly improve the data transmission rate, anti-interference characteristic and anti-fading ability of the system. Nevertheless, with the sharp development of interferencation technique and investigation technique in morden information warfare and of software radio technology, the anti-interference characteristic and the anti-intercept characteristic of DFH communication technology become the new challenge of mordon military communication.In several years, new researches in and aboard are mainly about the anti-interference characteristic of DFH communication technology, but the anti-intercept characteristic of the technology is barely mentioned. Comparing with its reliability, the security of the communication system should have higher importance. This paper according to the lack of nowadays research about hopping signal time-frequency detection and hopping pattern detection, above the foundation of today s DFH system, develops a profound research in the performance of time-frequency and pattern anti-intercept characteristic.This papar is composed of five chapters. The first chapter presents the unique military status of HF. Accroding to the feature of HF it introduces the main communication-technology and its present situation. According to the lack of research on anti-intercept characteristic, the whole purpose and content are given. In chapter 2, the DFH technique is assorted and a new DFH system which is called high density DFH in this paper is raised in the context of coding mode. The author gives the analysis methods and mathematic principle on the research of anti-intercept characteristic. Hopping patterns in different coding structure are analyz in their 1-dimensional (1D), 2-dimensional (2D) continuity and randomicity in chapter 3, the convolution-frequency-pair upper bound is raised to analysis. In chapter 4, the time-frequency distributions with hopping signals are derived and the judgment performance of optimal detection is testified. The Discrete Wigner-Ville Distribution (DWVD) self formula and the Discrete Smoothed Pseudo Wigner-Ville Distribution (DSPWVD) self formula are derived and testified through the peak detection. The formula of DSPWVD error-detected-probability is derived and compared with the simulation result.Anaysis on anti-intercept characteristic of high density DFH technique has been given. A conclusion is given and a prospect of the development of DFH technique is given at last.