Abstract: The invention is a radio-frequency identification system consisting of a reader and a tag. The reader comprises a transmit/receive resonant circuit comprising one or more coils, a means for repeatedly driving the transmit/receive resonant circuit with pulses of a periodic signal, a means for obtaining a tag response signal from the transmit/receive resonant circuit, a means for extracting tag information from the tag response signal obtained from the transmit/receive resonant circuit, a receive resonant circuit comprising one or more coils, a means for obtaining a tag response signal from the receive resonant circuit, and a means for extracting tag information from the tag response signal obtained from the receive resonant circuit. The tag comprises a plurality of resonant circuits, a means for recognizing he presence of an interrogating magnetic field, and a means for embedding information to be communicated to the interrogating reader in at least one coil current.

Abstract: The invention is a resonant-circuit structure for enhancing the interrogation range of a radio-frequency identification system. The resonant circuit structure consists of a coil assembly and a capacitor connected in parallel with a resonance frequency equal to the frequency of the interrogating signal of the radio-frequency identification system with which the resonant circuit structure is to operate. The coil assembly and the capacitor are embedded in a structure which provides physical support for the coil assembly and the capacitor and access to a region near the coil assembly.

Abstract: The invention is a resonant-circuit structure for enhancing the interrogation range of a radio-frequency identification system. The resonant circuit structure consists of a coil assembly and a capacitor connected in parallel with a resonance frequency equal to the frequency of the interrogating signal of the radio-frequency identification system with which the resonant circuit structure is to operate. The coil assembly and the capacitor are embedded in a structure which provides physical support for the coil assembly and the capacitor and access to a region near the coil assembly.

Abstract: The invention is a radio-frequency identification system consisting of a reader and a tag. The reader comprises a transmit/receive resonant circuit comprising one or more coils, a means for repeatedly driving the transmit/receive resonant circuit with pulses of a periodic signal, a means for obtaining a tag response signal from the transmit/receive resonant circuit, a means for extracting tag information from the tag response signal obtained from the transmit/receive resonant circuit, a receive resonant circuit comprising one or more coils, a means for obtaining a tag response signal from the receive resonant circuit, and a means for extracting tag information from the tag response signal obtained from the receive resonant circuit. The tag comprises a plurality of resonant circuits, a means for recognizing he presence of an interrogating magnetic field, and a means for embedding information to be communicated to the interrogating reader in at least one coil current.

Abstract: A reader (10) capable of efficiently reading tags (12) of differing protocols in a radio frequency identification system. The tag may be either a full-duplex tag or a half-duplex tag. The reader includes a display (16), a power switch (18) and a read switch (20) for enabling operation of the reader by a user. The reader further includes a coil (60); a driver circuit (32) coupled to the coil; and a signal analyzing circuit (82, 84, 90) coupled to the coil. The signal analyzing circuit analyzes tag identification signals sensed by the coil by detecting an initial data sequence of the tag identification signals and selecting from at least two different protocols the correct protocol of the tag identification signal.