A description is given of the modified SMI (sample matrix inversion) adaptive arrays in which the sample covariance matrix is redefined to reduce the effect of thermal noise on the weights of an adaptive array. This is accomplished by subtracting a fraction of the smallest eigenvalue of the original covariance matrix from its diagonal terms. In situations where the number of degrees of freedom of a modified SMI adaptive array is larger than the number of interfering signals incident on the array, the adaptive array provides the required interference suppression. An experimental modified SMI adaptive antenna array is described. Performance results are presented, and the experimental system is a three-element SMI adaptive antenna array and operates in a signal scenario consisting of a desired signal and an interfering signal whose source may be located at an arbitrary angular separation from the desired signal.
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