Abstract: A magnetic antenna system particularly useable in electronic article surveillance systems for detecting the presence of a resonant tag utilizes multiple loop shielded transmitting and receiving antennas. The antennas employ shield structures that are designed to minimize the electric field response and to provide a balanced magnetic field response. The magnetic field responses of different ones of the loops in each of the antennas are different and the loops are oriented so that more responsive loops of the transmitting antenna are positioned opposite less responsive loops of the receiving antenna and vice versa in order to reduce the coupling between antennas without reducing the sensitivity of the receiving antenna to a tag signal.

Abstract: A multiple loop antenna particularly suitable for use with an electronic article surveillance security system for detecting the presence of a resonant tag employs first and second shielded twisted loops lying in a common plane and having portions thereof interleaved with each other. The loops are electrically coupled to each other and to a common transmitter or receiver. The loops may be fabricated from coaxial cable to achieve the shielding function at low cost while providing design flexibility.

Abstract: A magnetic antenna particularly usable for deactivating electronic article surveillance tags that are attached to articles of merchandise to prevent unauthorized removal from a protected area. The antenna comprises a driven element in the form of a transmitting loop, preferably a pair of loops driven in opposite phase, and shield grids disposed on opposite sides of the driven elements. The shield grids serve to prevent electric field radiation from the driven element from propagating past the shield, but permit the passage of magnetic field radiation therethrough. The antenna may also be used at a protected exit to detect the presence of a tag.

Abstract: A multiple loop antenna particularly suitable for use with an electronic article surveillance security system for detecting the presence of a resonant tag employs first and second shielded twisted loops lying in a common plane and having portions thereof interleaves with each other. The loops are electrically coupled to each other and to a common transmitter or receiver. The loops may be fabricated from coaxial cable to achieve the shielding function at low cost while providing design flexibility.

Abstract: An anti-theft tag for use in an electronic article surveillance system has a housing, a lock for releasably attaching the housing to an article to be protected, and a marker on the housing, the marker having a resonant circuit including an inductor and a capacitor, the inductor including a solenoid type winding defining a winding opening, wherein the circuit has a Performance Factor P of at least 1.times.10.sup.6 in the equation P=QA.sup.1.5, wherein Q is equal to the circuit Q, and wherein A is equal to the area of the winding opening in square millimeters.