Dfh System, The G Function And Its Performance Analysis

The Differential Frequency Hopping (DFH) technology combined with modulation, encoding and frequency hopping technology, highly improved the data transmission, anti-interference and anti-fading ability of the system, represents the developing direction of new generation HF anti-jamming communication scheme.The paper focuses on the research of some key technology of the differential frequency hopping communication system and gets some helpful conclusions. The design of the function G is the core of the DFH system. The design must consider anti-tracking, anti-jamming and bit error rate. According to these design demands, the paper overviews the basic design rules of the function G. Taking advantage of a serial of equivalent description of the function G, the paper analyzes the distance specific and the theory of maximum free distance. Base on the frequancy transfer matrix and the graphy theory, the paper deduces the rules of the judgement of the free distance and the shortage of the time invariable G function. Then the paper discusses some methods for creating new G function to avoid this shortage. Morever the derivation theory demonstrates that there exists a serial of functions G, which have the equivalent distance. It also illustrates the value of the derivation theory in the DFH system design that makes the derivation theory of the frequancy transfer much richer.Studies have also been made on frequency trellis decoding which is the key technology in the Differential Frequency Hopping system. Basing on this technology, the paper introduces a new decoding method named glide window frequency trellis decoding. Finally we bring forward a certain method based on jamming suppression in the frequency trellis decoding which is called adjacent hopping frequency subtract method. Then the dissertation compares and analyses the system performances in the Partial Band Jamming, Multi-Tone Jamming and Sigle-Tone Jamming environment with or without this anti-jamming algorithm.Above all, the paper discusses about the design of the DFH system, key technology of analysis, improvement and etc. The serial conclusions drawn in the paper has important reference value for researching and developing the future HF military communication system.