Abstract: Apparatus for electromagnetic radiation of living tissue, such as human tissue, or tissue simulating matter, comprises an electromagnetic radiation source having a dynamic frequency range of at least about 5 to 1, and preferably 10 to 1. Electrically connected to the source by a coaxial cable is a broadband applicator adapted for emitting electromagnetic radiation into tissue and the like. Parallel plate type radiation launching portions of the applicator are configured to have a characteristic impedance, throughout the dynamic frequency range, approximately equal to the impedance of specimens to be irradiated, which for human tissue, between 50 MHz-2000 MHz, is approximately 50 ohms. A transition for interconnecting the coaxial cable to the parallel plate launching portion is configured to provide a relatively gradual coaxial to parallel plate transition at constant characteristic impedance throughout the dynamic frequency range.