Textbook in PDF format An antenna is a conductor or group of conductors used for radiating electromagnetic energy into space or collecting electromagnetic energy from space. When a radio frequency signal has been generated in a transmitter, some means must be used to radiate this signal through space to a receiver. The device that does this job is the antenna. In this book, the research advances on substrate integrated waveguide (SIW) technology and its application in microwave antennas, components, and subsystems are reviewed, which includes the propagation characteristics and discontinuity analysis of SIW, and its application in the design and implementation of directional antennas