Array Based High Resolution Direction Finding Technique

Electronic surveillance equipment faces complex electromagnetism environments with a variety of impulsive non-gauss interferences and noises. In order that the devices wok well and exert fighting efficiency sufficiently in this bad situations, an exact and appropriate mathematical model needs to be established for impulsive interference or noise, what's more, signal processing methods and techniques are studied in the impulsive noise environments. If the desired detection, resolution, or DOA estimation performance is specified, array geometry tailored to subspace-based DF algorithms is optimally designed so that the electronic reconnaissance and measurement system can scout out the interesting major targets in detail. Meanwhile, Performance levels of super-resolution direction finding arrays are also analyzed. An ambiguous generator set can be estimated to augment reliability of information. Function space and reconnaissance ability are improved by utilizing signal processing techniques. In order to get the above research aims, integration of theory with Monte Carlo simulation experiment is used in this dissertation. Several key techniques in array-based high resolution direction finding system are studies, their corresponding theoretic analyses and deductions are given. A series of algorithms proposed in this dissertation are of practical background and applied value. The computer simulation results show the validity, versatility and robustness of these algorithms. The main contributions of this dissertation are in five aspects as follows:(1)With the help of differential geometry, geometric configuration of sensor array, array manifold, DF performance, ambiguous DOAs, and their relationships are studied. Influence of array geometries on the DF performance and ambiguity of array are analyzed. The expression characteristic of performance of array is derived. The meaningful conclusions are drawn. The construction methods of array geometries are discussed. The estimation method and corresponding steps of ambiguous generator set are given for the arbitrary array geometry.(2) The basic signal processing framework based on stable processeisestablished. (3) Several high-resolution array direction finding algorithms are formulated in the presence of impulsive noises. First, TLS-ESPRIT algorithm using fractional order correlation function, the covariation or the covariation matrices is put forward, then TLFOC-MUSIC algorithm using temporal and spatial processing of time lag fractional order correlation function, whose performance superior to the general MUSIC and ROC-MUSIC algorithms. Finally, the covariation-based 2-D DOA matrix method is proposed, which retains the advantage of the original DOA matrix algorithm. Additionally, this dissertation constructs also a particular array geometric configuration, and defines the cross-covariation matrices of the subarray sensor outputs. a new subspace-based 2-D bearing estimation algorithm using fractional lower order statistics is proposed in the presence of impulsive noise.(4) According to the signal environments and features, some adaptive beamforming algorithms based on different signal processing methods are addressed. First, a novel robust cyclostationary space-time beamforming algorithm is proposed. In this algorithm, multiple lag parameters and the spectrum correlation property are used to exploit the cyclic statistical information and time domain characteristics of signals sufficiently and effectively. Thus it avoids the choice of the optimal time lag. Then a cummulant-based blind beamformer for recovery of independent sources in the presence of coherent multipath propagation is developed. To reduce the accumulation errors of forth-order cummulant estimation, a new definition format is adopted owing to the flexibility of cummulant definition. A certain extent, it smoothes the different influences of the spatial colored noise on cummulant among sensor outputs. Thus it can supress the spatial colored noise more efficiently. Finally, by solving the optim...