Adaptive antenna arrays for weak interfering signals

The performance of adaptive antenna arrays in the presence of weak interfering signals (below noise level) is studied. It is shown that conventional adaptive arrays are unable to suppress such interfering signals. To overcome this problem, the feedback loops controlling the array weights are modified. In the modified feedback loops, the noise level in the feedback loops is reduced by reducing the correlation between the noise components of the two inputs to the loop correlator. Two techniques to decorrelate these noise components are discussed. It is shown that adaptive arrays with the modified feedback loops provide the desired interference suppression. An expression is given for the amount of noise decorrelation required to achieve a specified interference suppression.