A subspace-based online calibration algorithm for an asynchronous CDMA-based antenna array

Abstract

A new iterative calibration algorithm is presented for an asynchronous CDMA-based antenna array in the presence of unknown gain and phase errors. The algorithm is applicable to a non-linear array where the number of signals could be greater than the number of antennas. It does not require a prior knowledge of the direction of arrivals (DOAs) of the signals of any user but requires the code sequence of a reference user. The proposed algorithm provides us with estimates of the DOAs, the multi-path impulse response of the reference signal source, and the calibration of the antenna gain and phase, even under a multiple access interference. We verify the algorithm by using synthetic data as well as field data measured through a custom-built W-CDMA test bed. (C) 2002 Elsevier Science B.V. All rights reserved.