Study On Parameters Estimation And Array Calibration With Sub-Nyquist Sampling

The problem of parameter estimation and array calibration with sub-Nyquist sampling is studied in this doctoral dissertation. Sampling the signals under Nyquist's theory is very difficult when they are in a wide band. It is urge to develop new techniques to deal with such difficulty. Sub-Nyquist sampling which is considered the perfect way to overcome this difficulty can allivate the burden with the system's design complexity. To estimate the directions-of-arrival(DOAs) from the samples of the array without ambiguity demands the interval between any two elements be less than the half of the wavelength of the signal with the maximum frequency. This restriction aggravates the mutual coupling of the signals with comparable low frequencies. Spatial sub-Nyquist which can not only allivate the mutual coupling between elements but also improve the estimation performance of DO As is considered a right technique to solve such problem. The problem of calibrate the highly sparse space- borne array is studied in the last two chapters. Two methods is proposed to remedy the sparse array through the analysis of the echoes from the illuminated area of the small satellite antenna. The detailed content included in every chapter is listed bellow:1. In chapter 2, a novel frequency estimation algorithm for wideband signal with sub-Nyquist sampling is proposed. With the aid of information provided by the auxiliary delayed sampling channel and the aliased frequency estimation for wideband signal with sub-Nyquist sampling, we can solve the frequency aliasing due to sub-Nyquist sampling. This method can reduce the complexity of the overall hardware at the cost of an auxiliary sampling channel. Furthermore, in order to alleviate the computation burden for its practicability, a more simplified algorithm based on propagator method(PM)is put forward. The simplified algorithm which is developed for practice in this chapter does not need to estimate the sample covariance matrix and only need to do one eigendecomposition with comparable lower dimensions to obtain the frequency estimation. A new method base on different sampling frequency to estimate frequencies from wide-band under-sampled data is also proposed in this chapter. The proposed method is not sensitive to the amplitude and phase errors of both channels and data obtained from two channels can be processed separately, thus it has a wider applied field than existing methods. At last, the effectiveness of the proposed algorithm is verified via computer simulations.2. In chapter 3, using the proposed frequency estimation method in chapter 2 and the state-space realization approach, a subspace based algorithm to estimate the frequency, DOA and range of near-field sources is proposed, which does not need any spectral peak searching and the 3-D parameters are automatically paired. Moreover, the proposed method is applicable to arbitrary additive Gaussian noise environment. The effectiveness of the proposed algorithm is verified via computer simulations.3. In chapter 4, a novel method for joint frequency, 2-D direction-of-arrrival and polarization estimation of transverse electromagnetic waves based on arbitrary L-shaped vector sensor(VS)array is proposed. VS consists of six co-located but diversely polarized antennas separately measuring all six electromagnetic-field components of an incident wavefield. Sub-Nyquist temporal sampling is introduced to reduce the complexity of the system design. Furthermore, sub-Nyquist spatial sampling, which can further reduce the mutual coupling among VSs, is combined to improve the estimation performance of spatial parameters. The CRLB is also derived in the end of this paper to verify the efficiency of this method.4. In chapter 5, a novel calibration method is proposed which is adapted to the distributed small satellites array. A constellation composed of several distributed small satellite radars can cooperate to improve the performance of multiple missions, therefore it has several advantages over a larger, single space-borne radar of being well in pe...