The performance of a defocused adaptive array with a finite-distance signal source

An approximate expression for the output signal-to-noise ratio (SNR) is obtained as a function of the steering distance and the steering angle. From that expression, a rule of thumb is drawn to determine both the steering angle and the steering distance which result in a given loss. The simulations show that the introduction of a single interferer does not affect the performance because of the interference nulling ability of the array for nonmain beam interferers. For the purpose of comparison with a conventional beamforming array, the range beamwidth and 3-dB degradation steering angle of an Applebaum adaptive array was derived. It is shown that the parameters for the conventional beamforming array cannot be directly applied to an Applebaum-type adaptive array