Channel tracking errors and the adaptive multiple-beam antenna

The ability of an adaptive antenna to reject wide-band interference sources is limited by the differences between the transfer functions of the different channels. An examination of the quantitative relationship between the rejection and the tracking errors shows that the multiple-beam antenna (MBA) achieves greater rejection than an array antenna. This is because, in forming a null in the direction of an interference source, the MBA achieves much of its total rejection by simply turning off the channel principally affected by the source. The array, on the other hand, must depend upon cancellation between channels to provide all its rejection. A simple formula exists, and is presented in the test, relating the interference cancellation to the rms mismatch between the channel transfer functions.