Auto-Calibration and element failure compensation in active phased

Solid state active phased array antennas promise to provide very low sidelobe capability. However, they will be subject to short term calibration drift and element failures. This compels an on-line, operational self calibration capability. TSC proposes a completely internal, on-line self calibration technique which utilizes the inherent mutual coupling among the radiating elements to accurately measure the transfer coefficients of each of the elements and their associated T/R module receivers and transmitters, transmission lines, and beamformers. The technique does not require knowledge of the absolute magnitude of the mutual coupling coefficients, but exploits the fact that the coupling coefficients will be very consistent across the array, and will remain very stable with time. Once the transfer coefficients are accurately measured, the appropriate corrections are applied to the T/R module phase shifters and attenuators. In case of a failed element, one of several algorithms is applied which optimally adjusts the other elements in the array to recover the antenna pattern sidelobe performance. The simplest of these to implement utilizes adjustments to the weights of the other elements in the array to synthesize, and add back, a close approximation of the missing array element pattern.