Direction of Arrival (DOA) Estimation for Wideband Sources Using Incoherent Signal Subspace Method (ISM) with Algorithm Enhancements

In this paper, we first analyze the Direction of Arrival (DOA) estimation method for wideband sources based on the Incoherent Signal Subspace Method (ISM). We implement a modified MUSIC algorithm featuring data matrix conjugate reconstruction within the ISM framework, which enhances angular resolution and enables coherent source identification through improved subspace separation. Algorithm implementation involves constructing frequency-dependent covariance matrices and applying signal subspace projection across multiple frequency bins. Subsequently, we examine the Coherent Signal Subspace Method (CSM) for wideband coherent source DOA estimation. Our analysis investigates how focusing matrices and focusing frequencies impact DOA estimation performance, establishing selection criteria for optimal focusing matrices and methodologies for optimal focusing frequency selection. Key implementation aspects include designing focusing matrices that transform wideband signals to a reference frequency while preserving signal subspace coherence. Furthermore, we develop a novel DOA estimation method for wideband signals in colored noise environments by integrating propagator operator concepts with TCT (Toeplitz Covariance Transformation) focusing matrices. This approach directly estimates the noise covariance matrix from array received signals using propagator operators, creating an efficient TCT focusing matrix implementation. The propagator-based technique eliminates the need for complex eigenvalue decomposition in traditional TCT algorithms, significantly reducing computational complexity while maintaining estimation accuracy in colored noise conditions. Code implementation would involve linear operations for noise subspace estimation rather than full matrix decomposition. Finally, computer simulations validate the effectiveness and feasibility of the proposed method, demonstrating improved performance in colored noise scenarios. Simulation code typically includes array signal generation, covariance matrix computation, and performance metrics calculation for comparative analysis. In summary, this paper provides a comprehensive investigation of DOA estimation for wideband array signals, with detailed analysis of ISM and CSM methods alongside novel solutions for colored noise environments. The research contributions establish theoretical foundations and practical applications for related fields. Keywords: Wideband Array Signals, Direction of Arrival Estimation, Colored Noise, Signal Subspace Focusing Matrices.