Effects of desired signal arrival angle errors on the steady‐state performance of a howells‐applebaum adaptive array

When a Howells-Applebaum adaptive array is used in a communication system, the receiving side must know the frequency and arrival angle of the desired signal. However, it is often impractical to assume that the arrival angle is accurately known. It is of importance to determine the degradation of output characteristics due to the angular error in arrival angle of the desired signal. This paper first presents a theoretical analysis of the steady-state performance of the array when only the desired signal exists and angular error is contained in it. A condition is found under which the desired SNR is obtainable from the angle error profile. A formula is derived by which the upper limit of the amplifier gain or the allowable upper limit in the angle error is obtained. These limits are important criteria in the array design. Some numerical calculations are conducted for angle error characteristics in the presence of interference and the effectiveness of the derived design criteria. It is found that these criteria are sufficiently useful if the amplifier gain g normalized by the thermal noise power is larger than unity or if for a small g the interference power is reasonably large. This is because the angle error characteristics are better than those in the absence of interference.