The latest breakthrough in the continuing miniaturization of electronic systems is made possible by the integration of circuit functions and radiating elements into single modules. In a typical system implementation, electronic circuits and antenna subsystems are often provided by different equipment vendors. Traditionally, electronic circuits and antenna systems have been designed by different groups of designers using different types of design tools, working independently on either side of a well-defined interface, very often with very little interaction. This approach leads to separately packaged circuit and antenna subsystems, connected by appropriate cables or waveguides.