Abstract: A highly efficient resonant switching driver circuit includes a matching reactance coupled between an output resonant circuit and a driver circuit. The matching reactance performs a series to parallel impedance match from the driver circuit to the output resonant circuit.

Abstract: A multiple loop antenna is provided which may be connected to either a transmit circuit, a receive circuit, or a transmit/receive circuit. When powered by a transmit circuit, the antenna generates radio frequency magnetic fields in an area or zone proximate to the antenna, but which are substantially canceled at a distance approximately one wavelength and more from the antenna, thereby defining a surveillance zone proximate to the antenna. The loop antenna includes a first, upper loop and a second, lower loop. The upper and loser loops lie in separate, spaced, parallel planes and are preferably disposed at a fixed angle with respect to the surveillance zone.