This document discusses direction of arrival (DOA) estimation using the MUSIC algorithm. It begins with an abstract that introduces DOA estimation and the MUSIC algorithm. It then provides background on smart antennas and switched beam arrays. The document presents the system model and mathematical formulation for signal propagation and antenna array output. It then describes the MUSIC algorithm, which uses eigendecomposition of the covariance matrix to estimate DOA. The algorithm is able to simultaneously measure multiple signals with high precision and resolution. The document concludes by discussing implementation of the algorithm using a 4-element antenna array to estimate DOA.