This book delves deeply into the substrate integrated suspended line antenna technologies and evaluates its potential to replace conventional three-dimensional (3D) metal-based antennas. Over the years, studies on substrate integrated suspended line antennas have captivated engineers and scientists from the antennas and related engineering fields, all aiming to achieve low-cost and low-loss characteristics. The book establishes a fundamental framework for this topic, while emphasizing the importance of substrate integrated suspended line antennas in the wireless communication and radar systems. It is designed for undergraduate and graduate students who are interested in antenna technology, researchers investigating substrate integrated technology, and antenna engineers working on low-cost and low-loss antennas and arrays.