Estimating Angle of Arrival and Output Signals to Noise Ratio for Wideband Signals

Abstract

Multiple Signal Classification (MUSIC) algorithm is the most popular algorithm to estimate angle of arrival (AOA) for narrowband signals. This algorithm is based on the use of subspace noise Eigenvectors (Q_n) matrix related to the smallest set of Eigen values of received signal covariance matrix (ϕ_xx). These set of Eigen values are corresponding to thechannels thermal noise. It is found that when the received signal has none zero bandwidth the distribution of Eigen Values magnitudes is changed according to the value of received signals bandwidth. The Eigenvalues magnitudes which are relating to the received sources are spreading on expense of noise sub space Eigen values .This new distribution causes a change in the relating eigenvectors, and now the Eigenvalues corresponding to thermal noise is no longer exist .Since Music algorithm is based on the use of these eigenvectors relating to the thermal noise Eigenvalues, and all these thermal noise subspace Eigenvalues are occupied by wideband signals, Music algorithm is no longer work. In this paper we suggest a new approach to estimate angle of arrival (AOA) as well as output signal to noise ratio (SNR) for wide band signals by using linear adaptive array antenna with transversal filter as a wide band beam-former processor in conjunction with Linearly Constrained Minimum Variance beam-former algorithm (LCMV). A general mathematical model for M array sensors with J taps behind each sensor and with a delay time between taps equivalent to a phase shift (90o) at center frequency is presented. The proposed approach is simulated and tested in different cases for different input levels and different received signals relative bandwidth (10%, 15%, 20% up to 40%) the result shows that with a proper number of taps behind each sensor the system is excellently Compensate the effect of signals bandwidth and estimate the angles of arrivals well the output SNR's of all received signals simultaneously with high accuracy. Under the same assumptions MUSIC technique is tested with transversal filter as a broadband processor, the results were very poor.