Bounding the angular scale factor error for adaptive arrays

When compared with a conventional gimballed antenna a phased-array antenna conveys some important advantages to a tracking radar system, including inertialess beam-steering and the ability to modify the beam pattern to suppress interference. For successful tracking of a radar target the linearity of the antenna angular response must be carefully controlled. The effect of array calibration errors on the linearity of the response of an adaptive phased-array antenna is considered. Through analysis of the maximum likelihood estimate (MLE) of target angle, a lower bound is derived on the variance of the angular scale factor error achievable when tracking a target with an adaptive phased-array antenna in the presence of residual calibration errors and interference. It is shown that while the presence of a sidelobe interferer has little impact on the achievable variance, a strong mainbeam interferer can result in a very significant degradation.