Focusing pulsed electromagnetic radiation in the near field

Intense, subnanosecond electric fields can be used either to stimulate bioelectric effects, such as calcium release in cells (which can lead to various secondary physiological effects), or to generate local hyperthermia. High power wideband antennas radiating electromagnetic waves in the subnanosecond range allows us to treat deep lesions non-invasively. Electromagnetic waves launched at the first focal point of the reflector are focused at the second focal point. This allows us either to deposit substantial amount of energy to the target for therapy or to image the dielectric properties of tissue in the confocal configuration. Two antennas with prolate spheroidal reflectors but fed with different wave launchers were designed and built to focus the radiated electric field. Antenna I is immersed in coupling medium with high dielectric permittivity, allowing for a small aperture diameter (0.14 m). Antenna II has a larger aperture diameter (0.5 m) and is to be operated in air.