Null broadening is an effective method to suppress the motion interference, but most methods are suitable for the uniform linear array. To solve this problem, an adaptive null broadening method based on uniform rectangular array (URA) is proposed in this paper. The method first estimates the power of interference and adds virtual interference with the same power near the real interference. Then, the method estimates the noise power and reconstructs the interference plus noise covariance matrix (INCM) which contains the null broadening information. Finally, the desired signal steering vector is corrected to obtain the optimal weighting vector. Simulation results show that the method can form wide nulls in the interference direction to suppress the motion interference and is robust to the desired signal steering vector mismatch.
KEYWORDS: Antennas, Signal to noise ratio, Optical simulations, Communication engineering, Virtual reality, Telecommunications, Signal processing, Scientific research, Radar, Neodymium
The virtual antenna array technology focuses on the methods of transforming the real antenna array into virtual antenna array. Virtual array transformation (VAT) can be used to realize virtual antenna array beamforming. The degrees of freedom of antenna array can be increased and more interference is inhibited. The robustness of the VAT beamforming against jammer motion can be improved by forming broad nulls. The performance of the VAT null broadening beamforming is better than that of the conventional VAT beamforming. A modified beamforming approach is proposed, and the performance of the VAT null broadening beamforming can be further improved. The reference position of the virtual antenna array is adjusted. The position that is one element space away from the antenna array is chosen as the reference position instead of the position that is at one end side of the antenna array. Besides, the conjugate covariance matrix is introduced into the expended covariance matrix, which is constructed by the Kronecker product of the covariance matrix of virtual array and its conjugate. According to theoretical analysis, more information can be obtained by the modified approach, so the performance of VAT null broadening beamforming can be improved.
KEYWORDS: Phased arrays, Lithium, Signal to noise ratio, Antennas, Control systems, Communication engineering, Signal processing, Monte Carlo methods, Data modeling, Chemical elements
When the adaptive antenna array encounters motion interference, the interference may overflow the null position which leads to a sharp decline in the output performance. At present, most of the solutions are to widen the null to improve the fault-tolerance of interference incidence angle. This will consume more degrees of freedom of the antenna array. For the adaptive antenna array with large number of elements, although it can provide enough degrees of freedom, the computational complexity is very large. To solve the above problems, a flexible adaptive null broadening beamforming based on symmetric non-overlapping subarray is proposed in this paper. The proposed method has three main contributions. The first is to widen the null to suppress the motion interference. Secondly, the proposed method flexibly controls the wide null according to the actual needs to reduce the waste of degrees of freedom. Finally, subarray level adaptive beamforming is used to replace element level adaptive beamforming, so as to reduce the computational complexity of the method. Simulation results verify the high performance and effectiveness of the proposed method.
KEYWORDS: Smoothing, Communication engineering, Signal to noise ratio, Optical simulations, Eye, Chemical elements, Mendelevium, Telecommunications, Scientific research, Radio astronomy
In order to improve the performance of beamforming of uniform planar array (UPA) against jammer motion, an improved null broadening beamforming approach of UPA is introduced based on covariance matrix expansion. The linear constraint sector suppressed (LCSS) beamforming is further used to form broad nulls in case of UPA, by which jammer motion can be inhibited. Then, the covariance matrix expansion (CME) and spatial smoothing techniques are combined. Virtual arrays are constructed by the CME technique, so the performance of null broadening can be greatly improved. The spatial smoothing technique is combined, by which the coherent interference can be candled. Simulation results show that, broad nulls can be formed by the improved approach, and coherent interference can be suppressed effectively.
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