Calibration for spaceborne phased array antennas without interrupting satellite communications

For spaceborne phased arrays, real-time antenna calibration plays a critically important role. It is the premise of high performance digital beamforming. Conventional antenna calibration approaches usually need to interrupt normal communication traffic flows to perform calibration and thus data satellite communications are interrupted. In this paper, an online calibration method without interrupting satellite communications is proposed for transmitting phased array antennas in the code division multiple access (CDMA) satellite communication system. Low-power calibration signals which are modulated with orthogonal signature codes are simultaneously injected into all the chains along with normal communication signals. To eliminate the multiple access interference (MAI) imposed by communication signals, we employ iterative partial parallel interference cancellation (PPIC) algorithm. At the end of this paper, the performance advantages of the proposed algorithm is demonstrated by simulation results in terms of the calibration accuracy.