HF8PSK Demodulation Key Technology Research And Its Implementation

HF communication as important means of tactical communication has been paid much attention by the military of every country. Especially in recent years, HF adaptive communication becomes the main development direction of remote military communication. In HF adaptive communication system, the American military standard MIL-STD-188-110A protocol occupies an extremely important position; it standardizes the HF adaptive communication system architecture and performance standards. According to the standard of shortwave radio, production has also been used for the radio everyday. In this dissertation, single tone8PSK signal to the MIL-STD-188-110A protocol is defined as example, using the modern digital signal processing technology, the demodulation algorithm of HF8PSK software is realized, and used as the core technique, and the HF signal demodulation platform is finally designed. The main work can be summarized as the followings:Starting from the main content of MIL-STD-188-110A protocol, the basic frame of the soft demodulation algorithm is constructed. The basic structure of baseband demodulation and channel equalizer is used to remove inter-symbol interference and recovery the distortion of symbols.Because of the characteristics of the training sequence defined by MIL-STD-188-110A protocol is short, we use RLS equalizer in channel equalization. Since the classical RLS algorithm is poor on stability, this dissertation proposes an improved the method of RLS correlation matrix in terms of the stability, and the calculation speed, and improving the overall performance by around25%.In order to remove the residual carrier and recovery the symbol timing signal, input and output signals of the equalizer are used to extract the frequency offset and timing offset information. A feedback loop to feedback frequency offset and timing offset information is used. The frequency offset information drives the VCO to remove residual carrier in the baseband signal, the timing offset information control PID controller to recover the timing signal.This method is easy to implement.Finally, this paper discusses the design idea and system structure of HF signal demodulation software platform; and the platform is introduced. The demodulation algorithm is simulated; the validity of the algorithm is verified. For the requirements of the real time processing in engineering practice, the method of the implementation proposed in this paper has better applicable and reference value.