The estimation of the directions of arrival of the spread-spectrum signals with three orthogonal sensors

An effective technique in estimating the directions of arrival (DOAs) of incoming signals using three orthogonal sensors is proposed. The channel model with multipath transmissions for code-division multiple access (CDMA) users whose signals are modulated with binary phase-shift keying (BPSK) is used. Utilizing the maximum-likelihood (ML) method, the channel impulse response vectors of the three sensors can be estimated, then all of the corresponding propagation delays and amplitude weights of the three sensors´ channels can be obtained. By comparing the propagation delays of the three channels, we can identify the same signal replica, then its DOA can be estimated by the relation of the three corresponding attenuation weights. Calculating results show this method can reach fairly high accuracy, and it needs only three sensors while in other techniques the required number of sensors is greater than the number of estimated signals.