Abstract: A method of monitoring an enclosed environment includes disposing a sensor assembly in an environment enclosed by an enclosure, where the sensor assembly includes a transmitter configured to communicate using near-field magnetic induction. A receiver is disposed outside the enclosure and configured to communicate with the transmitter using near-field magnetic induction. The receiver is to a communications device. The sensor assembly detects a sensed condition of the environment enclosed by the enclosure. The transmitter communicates the sensed condition to the receiver using near-field magnetic induction. After receiving the sensed condition from the receiver, the communications device communicates the sensed condition to a user.

Abstract: A method of monitoring an enclosed environment includes disposing a sensor assembly in an environment enclosed by an enclosure, where the sensor assembly includes a transmitter configured to communicate using near-field magnetic induction. A receiver is disposed outside the enclosure and configured to communicate with the transmitter using near-field magnetic induction. The receiver is to a communications device. The sensor assembly detects a sensed condition of the environment enclosed by the enclosure. The transmitter communicates the sensed condition to the receiver using near-field magnetic induction. After receiving the sensed condition from the receiver, the communications device communicates the sensed condition to a user.

Abstract: A method of collecting location data from objects moving within a specified site includes providing at least one tag reader and a plurality of tags each configured to communicate via near-field magnetic induction across an open-air gap of at least two meters. The tag reader listens for a tag signal transmitted by any one or more of the tags. Each tag transmits a tag signal containing a unique identifier that is received at a tag reader. The tag signal is demodulated to determine the unique identifier associated with the particular tag. Also disclosed is a system for monitoring a condition within a shielded environment using a tag and a tag reader that communicate using near-field magnetic induction.

Abstract: A transceiver antenna has a transmit antenna coil defining a substantially closed transmit coil geometry circumscribing a transmit coil inner area. The transmit antenna coil is configured to conduct a current to generate a magnetic field. One or more receive antenna coils each define a closed receive coil geometry with a number of coil turns. The receive antenna coils are positioned to define one or more inner areas located within the transmit antenna coil inner area and one or more outer areas located outside of the transmit antenna coil. The inner areas and the outer areas of the receive antenna coil(s) are configured so that a first voltage induced by the transmit magnetic field into the outer areas of the receive antenna coils is attenuated by a second voltage induced by the transmit magnetic field into the inner areas of the receive antenna due to phase cancellation.

Abstract: A transceiver antenna has a transmit antenna coil defining a substantially closed transmit coil geometry circumscribing a transmit coil inner area. The transmit antenna coil is configured to conduct a current to generate a magnetic field. One or more receive antenna coils each define a closed receive coil geometry with a number of coil turns. The receive antenna coils are positioned to define one or more inner areas located within the transmit antenna coil inner area and one or more outer areas located outside of the transmit antenna coil. The inner areas and the outer areas of the receive antenna coil(s) are configured so that a first voltage induced by the transmit magnetic field into the outer areas of the receive antenna coils is attenuated by a second voltage induced by the transmit magnetic field into the inner areas of the receive antenna due to phase cancellation.

Abstract: A method of collecting location data from objects moving within a specified site includes providing at least one tag reader and a plurality of tags each configured to communicate via near-field magnetic induction across an open-air gap of at least two meters. The tag reader listens for a tag signal transmitted by any one or more of the tags. Each tag transmits a tag signal containing a unique identifier that is received at a tag reader. The tag signal is demodulated to determine the unique identifier associated with the particular tag. Also disclosed is a system for monitoring a condition within a shielded environment using a tag and a tag reader that communicate using near-field magnetic induction.

Abstract: An access control system includes a transmitter initiator that has a magnetic flux antenna constructed and arranged to direct magnetic energy in an angular direction, a plurality of RF tone detectors, a microcontroller, and a plurality of RF burst generators. The system includes at least one receiver responder that has a magnetic flux antenna, a plurality of RF tone detectors, a microcontroller, and a RF burst generator. The transmitter initiator's magnetic flux antenna and the receiver responder's magnetic flux antenna define an open-air gap therebetween. The transmitter initiator's magnetic flux antenna has a paramagnetic housing, electromagnetic windings within the paramagnetic housing, and at least one ferromagnetic element disposed within the open air gap. The paramagnetic housing and the ferromagnetic element are constructed and arranged to direct a magnetic field across the open air gap. The system is configured for wireless communication via near-field magnetic induction.

Abstract: An access control system includes a transmitter initiator that has a magnetic flux antenna constructed and arranged to direct magnetic energy in an angular direction, a plurality of RF tone detectors, a microcontroller, and a plurality of RF burst generators. The system includes at least one receiver responder that has a magnetic flux antenna, a plurality of RF tone detectors, a microcontroller, and a RF burst generator. The transmitter initiator's magnetic flux antenna and the receiver responder's magnetic flux antenna define an open-air gap therebetween. The transmitter initiator's magnetic flux antenna has a paramagnetic housing, electromagnetic windings within the paramagnetic housing, and at least one ferromagnetic element disposed within the open air gap. The paramagnetic housing and the ferromagnetic element are constructed and arranged to direct a magnetic field across the open air gap. The system is configured for wireless communication via near-field magnetic induction.