Abstract: An improved receptor-reradiator, for use in a surveillance system employing a carrier frequency of UHF or higher in combination with a low frequency electrostatic field signal to be modulated on the carrier signal by the reradiator, is provided by an antenna frame wherein the metallic foil of which it is made is divided into three parts. The first part is U-shape of substantially one width and joins to a central portion of substantially reduced width which is predominantly inductive at the carrier frequency. A semiconductor diode, preferably a Schottky barrier diode or PIN switching diode, is connected in said central portion in series therewith. The opposite end of the central portion joins to an enlarged rectangular portion. At the low frequency the component has effectively two capacitive arms, one on each side of the diode, of different surface area to ensure bias signal for the diode.

Abstract: A microstrip antenna is incorporated in a floor mat, the latter consisting of a conductive grid laminated to a conductive sheet with a layer of dielectric material therebetween to form a capacitor. The microstrip antenna is connected to a source of microwave energy for the purpose of radiating a microwave signal through a surveillance area. A low frequency signal is applied to the capacitor section of the mat for direct capacitive coupling through the body of a pedestrian to any surveillance tag carried thereupon.

Abstract: A continuous loop transmitting winding assembly is disposed in one panel and a vertically oriented figure eight receiving coil winding assembly is disposed in a second panel, the two panels being mounted on pivots for swinging gate type movement straddling the pathway to be controlled by a magnetic surveillance system. This arrangement confines the surveillance field to the pathway and tends to follow the passage of an object bearing a marker therealong. No marker detecting backfield is generated. Alternatively, one winding assembly is moveable while the other is stationary thereby similarly confining the field.Special winding configurations are used to reduce interference from third harmonic signals produced in adjacent metallic counters. The arrangement also imposes immunity to signals emanating from cash registers, motors and the like.Door and single gate mounted magnetic and microwave surveillance systems are also disclosed.