Research On The Algorithms Of Multi-parameter Estimation Of The Complex Wideband Signal

Signal parameters estimation, which is considered as the keystone of the real-time panoramic analysis and specifications measurement of complex wideband signal, is widely utilized in the field of mobile communication test, digital television broadcasting surveillance, spectrum sensing and radar detection, etc.. Since the traditional signal parameters estimation algorithms are generally devised for the signal parameter test of the narrowband stationary signal, those methods cannot be employed to satisfy the real-time and precision requirements of parameters estimation in the real-time multi-domain analysis and test for modern wideband complex signal under the condition of complex electromagnetic environment. How to realize the high-precision, real-time estimation and analysis of the characteristic parameters of the wideband complex signal in the absence of prior knowledge is an extrmely difficult and urgent problem to be solved.To solve this critical problem, combining with the real-time multi-domain analysis structure of complex wideband signals, the high accuracy real-time estimation methods and key algorithms for complex broadband signals are intensively investigated in this dissertation. The main contribution and innovative achievements of the dissertation are shown as follows:In order to improve the efficiency of DFT in real-time signal parameters estimation, the potential problems in precision and stability of the existing Hopping Discrete Fourier Transform(HDFT) are theoretically analysised intensively, and an innovative modulated Hopping Discrete Fourier Transform(mHDFT) algorithm which is characterized by its merits of high accuracy and constant stability is presented. The proposed algorithm, which is based on the circular frequency shift property of DFT, directly moves the k-th DFT bin to the position of k ?0, and computes the DFT by incorporating the successive DFT outputs with arbitrary time hop L. Compared to previous works, since the pole of mHDFT precisely settles on the unit circle in the Z-plane and the twiddle factor in the resonator of HDFT is completely removed, the accumulated errors and potential instabilities, which are caused by the quantization of the twiddle factor, are always eliminated without increasing much computational effort.Since the frequency randomness of the measured signal in the real-time analysis bandwidth results in the large carrier frequency offset, the carrier synchronization cannot be achieved in the real-time multi-domain signal analysis for M-QAM communication. To solve this prolem, a novel high-efficiency blind carrier frequency estimation algorithm, which is based on the power spectrum iterative correction, is presented. The proposed algorithm, which utilizes the symmetry of M-QAM spectrum, iteratively identifies the carrier frequency in according to the power difference between the upper sideband and lower sideband, which is defined and revised by the estimated carrier frequency in each iteration. The carrier frequency offset can be achieved when the residue error converges to the preset threshold, and the bandwidth, symbol rate and signal-noise ratio can also be calculated simultaneously. Compared with previous works, the error, which is introduced by the fluctuation of the spectrum power level caused by the randomness of transmitted symbols, is effectively eliminated, and the carrier frequency estimation accuracy and speed can be significantly improved without increasing the computational effort.For real-time multi-domain signal analysis and specification measurement for M-PSK burst communication, Based on the theoretical analysis of the maximum likelihood estimation of carrier frequency and phase offset for M-PSK burst communication signal, a novel blind joined carrier frequency and phase estimation algorithm based on interpolated DFT is presented. According to maximum likelihood estimation theory, the proposed algorithm firstly uses non-linear transform to remove modulation information from timing synchronized input. Then, the carrier frequency and phase offsets are estimated using DFT. Finally, the linear interpolation is applied to improve the estimation accuracy. The presented algorithm can improve the frequency and phase resolution capabilities of DFT without increasing the size of DFT. Experimental results show that the carrier estimation error is only half of the existing algorithms, and the variance of carrier estimation error closely converges to the Cramer-Rao bound.For the parameters estimation of the exponential signal, a novel parameter estimation algorithm based on interpolated all-phase DFT is presented. The proposed algorithm ingeniously introduces the all-phase preprocessing into the signal paramters estimation. a new signal sequence is constructed by continuously cycle shifting sample points and summing up N buffered exponential signal sample sequences, then an interpolation DFT engine to obtain accurate parameter estimation of the exponential signal based on the new signal sequence. Compared to previous works, the tedious iteration for spectral leakage elimination can be removed, and remarkable improvements are achieved in terms of estimation accuracy and speed.