A blind calibration method for an adaptive array antenna in DS-CDMA systems using an MMSE algorithm

A new blind calibration method is proposed to compensate for the amplitude and phase errors in the antenna branches of DS-CDMA base stations with adaptive array antennas. The proposed method calibrates these errors using the MMSE (minimum mean square error) algorithm, requiring only the received (or transmitted) signals at the array antenna and not requiring any additional reference signal to be inserted for calibration. The proposed method and structure can be applied to both the downlink and uplink. The fast convergence property of this method ensures a tracking capability against amplitude-phase variances. In an uplink, using the proposed calibrator, a beam steering adaptive array antenna based on a directional finding algorithm of a desired signal has a BER performance that improves by about 2 dB at the BER of 10^-3 when a non-linear RF amplifier is used. We have also evaluated the downlink performance of this method when a non-linear RF amplifier is used and have confirmed its robustness against that of the amplifier