Research On Data Detection Techniques For HF Serial Digital Transmission

HF communication has played an important role in military field because of its inherent advantages. HF communication systems are constrained by the nonideal characteristics of HF channels such as bandwidth restrictions, signal fading, and multipath dispersion. These channel limitations present the major obstacles to achieving required reliability of the system.The objective is to improve the reliability of digital transmission over HF channels. This thesis lays emphasis on the key technologies in the two fields of channel estimation as well as data detection. First, according to the characteristics of HF channels, its influence on signal transmission is analyzed, and the equivalent baseband model of HF channels is provided. The convergence and tracking properties of two kinds of adaptive algorithm (LMS and RLS) are discussed, and in the light of HF conditions, a refined LMS algorithm using input decorrelation is presented with good performance and low computational complexity.Secondly, based on the construction of the decision feedback equalizer, both square root kalman(SRKalman) algorithms and block detection(DFBE) techniques are investigated. Simulation indicates that good stability is achieved by DFBE in the condition of time varying multipath channel. Aiming at the problem of DFBE degrading to linear equalizer(LE) in the presence of non minimum-phase channel, a solution is proposed by reversing the sequential order of the received signal samples in time prior to equalization. It is found that, assuming a non-minimum phase channel, this method can improve the performance of DFE considerably.Finally, based on MIL_STD₁88₁10A, some problems occurring in the DFBE algorithm implement of DSP are discussed, and fixed-point algorithm implement as well as C code optimization on TMS320C6416 are also given.