(A) study on the receiver calibration in an array antenna system

Abstract

In an array antenna system, the accurate channel response and DOA(Direction of Arrival) estimation for optimal beamforming are required. In this thesis, we consider two problems in an array antenna system. First, we propose the online calibration for CDMA system in the presence of unknown complex gain of the receiver hardware by using the simulated annealing method. The proposed algorithm provides us with estimates of the DOAs and the calibration vector for the receiver hardware mismatch error, even under multiple access interference. The algorithm uses the code sequence of a reference user which is already known to the base station and is not dependent on the geometry of an array antenna. The proposed method overcomes the problem of the initial guessing in the previous subspace-based approach. Secondly, we consider the mutual coupling effects in an array antenna. The mutual coupling effects appear necessarily in an array antenna system and degrade performance of the system. Using the ICA(Independent Component Analysis) method, we estimate the mutual coupling effects, the calibration error by the receiver hardware mismatch and DOAs of the signals, respectively. The proposed algorithm only needs nongaussian and independent signals. With the computer simulations, we test the performances of the proposed algorithms.