Study And Realization Of The Key Techniques Of HF/VHF Communication Signal Analysis

As the development of communication techniques, many new modulation types in the HF/VHF channel are emerging, for example, hybrid and Multi-Carrier Modulation, which make it more and more difficult for radio monitoring and signal analysis. Based on the non-cooperation communication, a number of key techniques which are involving in the process of recognition and parameter estimation of Multiplicative Hybrid Modulation and Multi-Carrier Modulation signals are studied. These relevant algorithms have also been realized on a universal signal processing platform. The main work can be summarized as follows:1. Based on the simulation of Watterson model, the paper analyzes the influence of some complicated time-varying factors including Multi-path effects, Doppler frequency shift and Doppler frequency spread on the signals, which is useful for the selecting and researching on signal analysis algorithms.2. Starting with modulation principle and mathematic description of the Multiplicative Hybrid Modulation signal, the paper studies the effects of some modulation parameters on it. After discussing the outer-features, two new characteristics which can achieve the recognition of Multiplicative Hybrid Modulation and non-Multiplicative Hybrid Modulation signal are proposed. Then the classification among the Multiplicative Hybrid Modulation signals is finished by the Spectral lines of nonlinear transformations based on signal cyclostationarity. Finally, a corresponding classifier based on decision tree has been designed which can accomplish the online classification. The simulation results show that these features exploited are immune to Multi-path effects and its good classification performance.3. Taking the practical characteristics of Multiplicative Hybrid Modulation signal into account, a novel carrier frequency estimation algorithm is proposed. After summing up the discrete spectral lines standing for the symbol rate, the paper discussed the relationship between symbol rate and the spectral lines of signal nonlinear transformation. By extracting these lines, symbol rate is precisely estimated.4. The paper also studies the parameter estimation of the Multi-Carrier Modulation signals in HF/VHF channel. Analytical expressions are derived for the power spectral density of this kind of signals which means that the PSD of these signals behaves as a cosine function. The number of subcarriers of some Multi-Carrier Modulation signals in HF/VHF channel is estimated using Power Cepstrum analysis.5. System realization of the related algorithms has been completed. The testing results show that the system is pragmatic and these relevant algorithms are efficient.