On-line detection of the number of narrowband signals with a uniform linear array

For any practical direction estimation and tracking system in array processing, estimating the number of incident signals accurately and tracking its possible changes in an on-line way is a critical requirement. In this paper, a new QR-based adaptive detection algorithm is proposed to estimate the coherent/incoherent narrowband signals impinging on a uniform linear array (ULA), where the updating of eigenvalues and the threshold setting are avoided. The effectiveness of the proposed method is verified through numerical examples, and simulation results show that the proposed method has good detection performance to track the number of suddenly appearing/disappearing incident signals or that of closely-spaced signals with time-varying directions.