Adaptive Antenna Arrays

Abstract

AbstractConventional adaptive techniques generally deal with antenna arrays that consist of omni directional isotropic radiating elements uniformly spaced. When the uniformity in the spacing is relaxed one then needs multiple snapshots in estimating the complex amplitude of the signal of interest (SOI) arriving from a known direction in the presence of multipaths, clutter and thermal noise. Usually a statistical methodology is used for the adaptive process which makes it difficult to incorporate the various electromagnetic effects like mutual coupling between the elements, presence of near field scatterers and so on and obtain a real time solution in a dynamic environment where the interference scenario may change from snap shot to snap shot.The object of this article is to present an adaptive methodology that can not only deal with realistic antenna elements operating in a real environment but can also handle the effects of mutual coupling between the antenna elements. In addition, one can incorporate in this methodology the effects of near field scatterers and use of dissimilar antenna elements in the array. The analysis is carried out by using a dynamic electromagnetic analysis tool. In addition, an array transformation technique is used to mitigate the various complex electromagnetic effects in a non‐uniformity spaced nonplanar array in the presence of the mutual coupling and transform the problem to that of a virtual linear array of uniformly spaced omni directional isotropic point radiators operating in free space. The preprocessed data from the interpolated virtual array is analyzed using a direct data domain least squares approach utilizing a single snapshot of data to estimate the strength of the signal of interest arriving from a known direction in the presence of coherent strong jammers, clutter and thermal noise. In addition, this methodology is quite amenable to real time processing.Thus this adaptive methodology is split into two parts. First one uses an electromagnetic analysis tool in conjunction with an interpolation algorithm to transform the induced voltages in the real antenna elements due to the presence of mutual coupling and near field scatterers to that of a virtual array containing isotropic omni directional point radiators. Then a direct data domain least square method is applied to the pre processed data to obtain the desired signal strength in the presence of strong interferers, clutter and thermal noise. Numerical results are represented to illustrate the efficiency and accuracy of this method. No attempt has been made to cite the earlier references; the bibliography provides a list where supplemental information may be available.