Abstract: An apparatus for the detection of any intruder passing through an electronic fence is disclosed. The electronic fence is formed by a millimeter wave radar positioned at one end of the fence and a plurality of reflectors placed along the floor of the fence as well as on a structure at its far end. The fence is formed of a plurality of electromagnetic beams traversing between the radar antenna or antennas and each of the reflectors. A sufficient number of beams inhabit the fence volume to make traversing the fence by an intruder without detection essentially impossible. The radar reflection from the intruder's person is used to report the location of an intruder attempting to traverse the electronic fence near the radar end and is the secondary means of detection at greater ranges where breaking of one or more electromagnetic beams constitutes the primary means of detection.

Abstract: A transponding tag (14) and method for responding with a unique code signal (18) when it receives an interrogation signal (16). The tag (14) waits a random duration before responding to avoid interference with response code signals (18) from other tags (14). The tag (14) includes two antennae (22, 24) formed on opposing sides of a dielectric planar substrate (20). A protective coating (52) and printed indicia (72) overlie the antennae. An electrical circuit (34), decoupling capacitor (44) and inductive pickup coil (46) are embedded within the substrate (20). The electrical circuit (34) and capacitor (44) reside between the antennae (22, 24) to receive RF shielding from the antennae and to reduce thickness of the tag (14). A capacitance exists between the antennae (22, 24). This capacitance stores DC electrical energy for the electrical circuit (34). The tag (14) is programmed through a modulated magnetic field detected at the inductive pickup coil (46).