The book focuses on angle-of-arrival estimation using radar interferometry and provides a unique perspective to angle estimation. Typically radars perform poorly when estimating angle to a target as opposed to range estimation. The interferometer provides a means to improve angle estimation but is subject to unique error effects. This book presents a comprehensive understanding of various radar interferometer architectures and will quantify interferometer angle estimation accuracy. It features some new material and alternative derivations on radar target tracking and identifies and quantifies radar-based measurement errors on the performance of angle-of-arrival estimation. It also includes a basic digital interferometer, a monopulse interferometer, an orthogonal interferometer and signal processing algorithms. By exploring interferometry and beyond, this book offers a unique perspective and an in depth look at the derivation of angle error equations for a radar interferometer. This book would suit practicing radar design engineers and researchers within both the radar community and the military industrial sector.