Research Of The Blind Equalization Technology In The Non-Cooperative Digital Receiving System

The modulation information of the received signal, such as the symbol rate, the carrier frequency, the roll-off factor and the modulation scheme, can not be known in advance to the receiver in the non-cooperative conditions. In order to complete the correct demodulation of the signal, it is necessary to use blind signal processing techniques to estimate and extract the parameters of the received signal.The whole process of the receiving and the analysis of the received signal under the non-cooperative conditions is referred to the non-cooperative digital receiving system. In the case of the transmitted signal and the channel characteristics are both unknown, blind equalization is an effective method to against the channel distortion and eliminate inter-symbol interference in the digital communication. Therefore, blind equalization technique is one of the key technologies of the blind demodulation.Under the background of the non-cooperative digital receiving system, this thesis studies blind equalization algorithm and its application. The main research work includes(1)Introduced the principle and algorithms of blind equalization, and based on constant modulus algorithm, a new variable step-size multi-modulus blind equalization algorithm is proposed. The simulation results show that the new algorithm has faster convergence speed and lower steady error after convergence with respect to the traditional blind equalization algorithms.(2) Described the basic structure of the blind demodulator of the non-cooperative digital receiving system. The roll-off factor of the shaping filter between the receiver and the transmitter may be inconsistent, the equalization performance is analyzed when the roll-off factor does not match.(3)Discussed the relationship between the synchronization module and equalization module, the influence of timing recovery loop based on different interpolation filtering to equalization results is studied.The simulation results show that the timing recovery loop based on cubic interpolation filter has smaller detection error than the timing recovery loop based on parabolic interpolation filter for4QAM signal, the constellation points after equalization are more aggregated and the inter-symbol interference is smaller.(4) Analyzed the propagation characteristics of the wireless ultrashort wave signal, discussed several practical channel model,then, the general processing flow of the ultrashort wave reconnaissance signal is given. Finally, combined with the typical modulation schemes of the ultrashort wave signal, the equalization performance of different blind equalization algorithms under different modulation types is simulated.