Allied Corporation

Other

Identitech

John J Torre

Philip M Anderson, Iii

Richard A Emanuel

Michael Drummy

Lounge and chair saver

A coplanar antenna system having a single-coil loop antenna provides both transmit and receive functions. The antenna operates in a tuned mode during transmitting and an untuned mode during receiving. Dead zone and transformer effect problems are virtually eliminated. The transmitter is highly efficient and the receiver is impulse noise immune.

Coplanar single-coil dual function transmit and receive antenna for

An article surveillance system includes a power line activated inductive magnetic field generator having an on duty cycle portion considerably less than 50%. A transformerless AC power line to DC converter and switching circuitry are connected to a series resonant circuit including a coil for deriving the AC inductive magnetic field. During on duty cycle portions, the switches are activated and connected to the series resonant circuit and the power supply to cause resonant current to flow in the series circuit at an activation frequency for the switches, causing the coil to generate the magnetic field at the activation frequency.

Inductive magnetic field generator

An inductive magnetic field article surveillance system includes a generator for a first inductive magnetic field having a predetermined frequency. The articles carry a structure which responds to the first magnetic field to derive a second inductive magnetic field having a predetermined frequency; the second field occurs immediately after expiration of the first magnetic field. A receiver for the second magnetic field responds to the predetermined frequency of the second magnetic field to indicate the presence of an article between the generator and receiver, if the frequency subsists for at least a predetermined time interval. The generator for the first magnetic field includes a tuned transmitting coil arrangement, while the receiver includes an untuned receiver coil arrangement. The second coil arrangement has a low Q and a resonant frequency considerably removed from the predetermined frequency of the second magnetic field so that impulse magnetic noise coupled to the receiver coil is not translated by the receiver coil into components of a signal at the frequency of the second magnetic field. Untuned, narrow band processing circuitry responds to a signal transduced by the receiver coil. The narrow band width of the processing circuitry is achieved by a synchronous demodulator driving an integrator.

System including tuned AC magnetic field transmit antenna and untuned AC

An article surveillance system includes a structure responsive to a first pulsed inductive magnetic field, periodically derived by a power line activated generator. The structure derives a second pulsed inductive magnetic field having a predetermined occurrence time relative to the occurrence time of the first magnetic field. A receiver for the second magnetic field is power line activated. The occurrence time of the first magnetic field and the activation time of the receiver to be responsive to the second magnetic field are synchronized. The synchronization of the transmitter and receiver is provided by separate zero crossing detectors for the power lines respectively activating the transmitter and receiver. The power lines activating the transmitter and receiver are likely to have zero crossings at different predetermined time positions because they are likely to be across two different phases of a three-phase power line. The receiver and transmitter includes separate circuits for compensating for the different zero crossing time positions.

Surveillance system including transmitter and receiver synchronized by

An inductive magnetic field article surveillance system includes a generator for a first magnetic field. Articles to be monitored include a structure responsive to the first magnetic field for deriving a second inductive magnetic field having a predetermined frequency. An inductive magnetic field receiver responsive to the second magnetic field includes a receiver coil arrangement for deriving a signal that is a replica of variations of the second magnetic field. Processing circuitry responds to the receiver coil arrangement to derive an indication of the presence of the structure. The receiver coil arrangement includes first and second coils likely to have different responses to the second magnetic field. Only one of the first and second coils is connected to the processing circuitry at a time, as a function of which coil is supplying a signal at the predetermined frequency of the second field to the processing circuitry for at least a predetermined time interval.

Selector for AC magnetic inductive field receiver coils

An article surveillance system includes a generator of a first inductive magneticc field having on and off duty cycle portions. The generator derives the first magnetic field at a predetermined AC frequency during the on duty cycle portions. The articles to be detected includes a structure which responds to the predetermined frequency of the first magnetic field to derive a second inductive magnetic field at a predetermined frequency. The second field is derived as a pulsed wave having a starting time at the expiration of each on-duty cycle portion and a predetermined carrier frequency. A receiver for the predetermined frequency of the second inductive magnetic field derives first and second different responses while an article including the structure is and is not in a detection region magnetically coupled to the receiver and transmitter. The receiver includes a synchronous detector for detecting first and second orthogonal components of the carrier frequency of the pulsed wave relative to a reference wave having a reference phase at the carrier frequency. The responses are derived independently of the amplitude of the carrier frequency components in the pulsed wave. The first and second responses are separately integrated over a predetermined interval, in synchronism with the occurrence time of each pulsed wave. The presence of the pulsed wave is indicated in response to either of the first or second responses having an absolute value in excess of a predetermined value during the interval.

Article surveillance system receiver using synchronous demodulation and

A coplanar antenna system has an interrogating means adapted to generate time varying magnetic field components within a region proximate thereto and a receiving means adapted to detect magnetic field components within a region proximate to the antenna system. The interrogating means has a plurality of coils configured such that the components thereof have near zero net resultant magnetic field. At least one coil of the receiving means is configured to detect components thereof having a preselected net resultant magnetic field.

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Monroe, NY, United States of America

John J Torre