On the number of narrowband signals which can be resolved with a uniform linear array
Douglas B. Williams, D.H. Johnson · 1989
The problem of determining the maximum number of narrowband signals whose parameters can be estimated with a linear array of M equally spaced sensors is examined. While this number previously has been taken to be M - 1 when the signals are mutually uncorrelated, we show how to estimate directions and amplitudes for as many as 2M - 1 signals. This over twofold increase is accomplished by using length 2M real signal vectors rather than the usual length M complex vectors. We show that 2M of these real vectors are linearly independent with probability one, and, thus, in the presence of additive white noise, the parameters of 2M - 1 signals can be estimated. An algorithm for determining directions and amplitudes is presented. However, computational complexity limits this algorithm to small M and low time-bandwidth products.