Source Separation and Localization Using Time-Frequency Distributions: An Overview

In this article, we describe the role of time-frequency distributions (TFDs) in array processing. We particularly focus on quadratic TFDs (QTFDs). We demonstrate how these distributions can be properly integrated with the spatial dimension to enhance individual source signal recovery and angular estimation. The framework that enables such integration is referred to as spatial TFD (STFD). We present the important milestones of STFDs that have been reached during the last 15 years. Most importantly, we show that array processing creates new perspectives of QTFDs and defines new roles to the autoterms and cross-terms in both problem formulation and solution. Multisensor configurations, in essence, establish a different paradigm and introduces new challenges that did not exist in a single-sensor time-frequency distribution.