Automatic calibration method using transmitting signals of an adaptive array for TDD systems

Adaptive arrays are especially effective in reducing cochannel interference and increasing channel capacity in time-division duplex (TDD) mobile communication systems because, ideally, the optimum pattern formed in the receiving mode can be applied to the transmitting pattern. However, since the radiation pattern of the adaptive array is generally formed on a baseband, the amplitude and phase errors must be calibrated between the branches of the array due to individual differences in the radio frequency (RF) devices of the receivers and transmitters. Moreover, since these errors change over time due to temperature variations, real-time calibration is required. This correspondence proposes an automatic calibration method using transmitting signals (ACT) for adaptive base station antennas that is suitable for TDD communication systems, i.e., it enables real-time calibration. The effectiveness of the proposed calibration method is demonstrated using an experimental adaptive array testbed.