Parameter Estimation Technology For Radar Signal Reconnaissance Based On Subsampling

The problem of parameter estimation and direction of arrival(DOA)estimation with sub-Nyquist spatio-temporal sampling is studied in this paper.In the face of complex electromagnetic environment,it's hard to use the traditional Nyquist sampling theorem to estimate the parameters of the received signals directly,and it will increase pressure of the system.With the existing hardware development level,it's difficult to efficiently process and store signals with high frequency and large bandwidth.The problem can be solved by sub-Nyquist sampling.In array signal processing,to estimate the DOA of signals without ambiguity demands the distance between the antenna elements be less than the half wavelength of the signal,but it is easy to cause the coupling of the low frequency signal in the antenna array element,which is not conducive to high-precision DOA estimation.When the aperture of the antenna array is increased,the resolution and accuracy of the DOA estimation can be improved effectively,and in this way only phase ambiguity problem needs to be solved.To estimate the parameters and DOA of signal with sub-Nyquist sampling is the core of the study.The main work of this paper can be summarized as follows.1.Research on parameter and DOA estimation theory of signal with sub-Nyquist sampling.The spectrum characteristics of signals in sub-Nyquist sampling are analyzed.The classical frequency estimation methods of sinusoidal signal are studied.The feasibility of transforming the non-stationary wideband LFM signal into a stationary sinusoidal signal in sub-Nyquist sampling condition is proved.Methods for parameter estimation of wideband linear frequency modulation(LFM)signal with sub-Nyquist sampling are proposed.The reason of ambiguity of array signal direction finding is analyzed,and the basic method of realizing non-ambiguity is introduced.2.Two methods of parameter estimation of wideband LFM signals with sub-Nyquist sampling are studied.Single channel sampling and multi-path delays of signal are adopted in the first method.Wideband LFM signal is translated into sinusoidal signal,and the non-fuzzy property of the remainder theorem is used to realize high accuracy parameters estimation.Multi-path sampling channels and signal delays are adopted to estimate the parameters of wideband LFM signal in the second method,which based on estimation of signal parameters via rotational invariance techniques(ESPRIT)algorithm and Quinn algorithm and Rife algorithm to estimate the parameters of signal.3.Research on two-dimensional DOA estimation method for wideband LFM signal.Based on the time-frequency characteristics and energy aggregation of the wideband LFM signal in the Fractional Fourier transform domain,a two-dimensional DOA estimation method for wideband LFM signal is proposed which based on Fractional Fourier transform.To solve the problem of phase ambiguity caused by sub-Nyquist sampling,integer search method is used.4.Research on two-dimensional DOA estimation method for narrowband signal.A non-uniform L antenna array model with special structure is constructed.A two-dimensional DOA estimation method which based on ESPRIT algorithm is proposed.To solve the problem of phase ambiguity caused by sub-Nyquist sampling,integer search method is used.