Study Of Effect Of Mutual Coupling On The Performance Of Adaptive Arrays

The mutual coupling in adaptive array's is studied with emphasis on the array composed of dipoles. Based on the method of moments (MOM), the electric fields integral equation is derived with the effects of equivalent load impedance at each terminal of the elements taken into account. The formulae for the elements of the general impedance matrix are given and the voltage across the ports of each element is computed. In accordance with the general network theory, the analytical model of adaptive arrays with mutual coupling between elements taken into account is derived. The mutual coupling between the elements is expressed in terms of the normalized general impedance matrix of the arrays. By doing it, the characteristics of the covariance matrix of the adaptive array are analyzed, and the concise expressions for the optimized weight of the LMS algorithm and the signal-to-interference-plus-noise ratio (S1NR) are given. The effect of mutual coupling on the performance of the SINR and the transient response is illustrated with several examples. By using spectral method and MOM, an improved method for compensating the mutual coupling is presented. The expressions for the adaptive weight and the output pattern of the array with the mutual coupling compensated are derived. Some examples are also taken to verify the compensation effect of this method. A study is made of the effective Direct Data Domain method for analyzing adaptive arrays. The technique for constructing the matrix equations for finding the adaptive weight is demonstrated, and the conjugate gradient algorithm for fast solution of the equations is given, then the analytical expression for the recovered signal is derived. The effect of the mutual coupling on the performance of the adaptive array is analyzed by means of the above methods. The degradation of the adaptive system caused by the mutual coupling is simulated and analyzed in two different electromagnetic environments such as the weak and strong interference. According to the effect mechanism of mutual coupling on the system, two methods of mutual coupling compensation in adaptive arrays are proposed, that is MOM and the open-circuit voltage method. A comparison of compensation results between the two methods is made through some examples.