199results about "Screened loop antennas" patented technology

In an electronic article surveillance system, quadrature transmitting and receiving antennas are used to improve field distribution. A transmitting antenna arrangement includes first and second adjacent co-planar antenna loops and excitation circuitry for generating respective alternating currents in the first and second loops such that the respective alternating currents are 90 DEG out of phase. In a receiving arrangement, respective signals received from two adjacent co-planar antenna loops are respectively phase-shifted by +45 DEG and -45 DEG , and the resulting phase-shifted signals are summed. A far-field cancelling transmitting antenna arrangement includes four loops operated at phases of 0 DEG , 90 DEG , 180 DEG and 270 DEG respectively. All four loops may be co-planar, with any bucking vertical segments being horizontally displaced from each other. Alternatively, the 0 DEG and 180 DEG loops may also be arranged in a common plane that is close to and parallel with another plane in which the 90 DEG and 270 DEG loops are arranged.

An antenna apparatus (60) is provided which is used in a recorder and / or player to write and read data to and from a contactless IC card (1). The antenna apparatus (60) includes a loop coil (61) to radiate an electromagnetic field for magnetic coupling with a loop coil (4) at the IC card (1) to send and receive data to and from the IC card (1), and a magnetic sheet (62) disposed to face the main side of the loop coil (61), opposite to the main side facing the IC card (1). The magnetic sheet (62) has the specific permeability μ′ and product Ms·t of saturation magnetization Ms and thickness t thereof set in accordance with a necessary range of communications with the contactless IC card (1).

A communication-capable electronic device is provided which includes a metallic housing (122) to accommodate electronic parts of the device, and a communication terminal (90) that makes communications with a communication-cable IC card (110) incorporating an antenna (115). The communication antenna (90) is located such that when the IC card is placed near the housing (122), the antenna (115) built in the IC card (110) faces, at a part thereof, a part of the communication terminal (90) while the rest of the antenna (115) of the IC Card (110) does not face the housing (122). Thus, it is possible to prevent the inductance in the antenna (115) of the IC card (110) from being reduced.

An arrangement for providing protection to wireless portable transponders (including resonant tags such as RFID tags) from unauthorized interrogation by employing a mechanical arrangement for disabling reception by or from the antenna of the transponder. The tags can be protected from receiving or providing unauthorized or unwanted information. Contemplated are mechanical arrangements that permit the owner to decide when reception / interrogation of personal or other information is not desired by employing the provided mechanical disable control arrangement. Also broadly contemplated herein is the altering interrogation characteristics of RFID tags to such an extent that they may still be read at a close range instead of the original range, and this result of this altering is visible to the user.