Abstract: A radio frequency identification transponder includes a power supply and a dynamic memory array that stores data. When power from the power supply ceases, the data in the dynamic memory array is validly maintained for a predetermined period of time. The dynamic memory array is responsive to an interrogating signal for selectively updating the data. A radio frequency identification transponder includes a signal processor that extracts an identifier from the interrogation signal and is responsive to the identifier and the stored data to determine whether some or all of the identifier is stored in the dynamic memory array.

Abstract: A radio frequency identification transponder includes a power supply and a dynamic memory array that stores data. When power from the power supply ceases, the data in the dynamic memory array is validly maintained for a predetermined period of time. The dynamic memory array is responsive to an interrogating signal for selectively updating the data. A radio frequency identification transponder includes a signal processor that extracts an identifier from the interrogation signal and is responsive to the identifier and the stored data to determine whether some or all of the identifier is stored in the dynamic memory array.

Abstract: A radio frequency identification transponder including a power supply and a dynamic memory array which stores data. When power from the power supply ceases, the data in the dynamic memory array is validly maintained for a predetermined period of time. The dynamic memory array is responsive to an interrogating signal for selectively updating the data. A signal processor extracts an identifier from the interrogation signal and is responsive to the identifier and the stored data to determine whether some or all of the identifier is stored in the dynamic memory array.

Abstract: A radio frequency identification transponder including a power supply and a dynamic memory array which stores data. When power from the power supply ceases, the data in the dynamic memory array is validly maintained for a predetermined period of time. The dynamic memory array is responsive to an interrogating signal for selectively updating the data. A signal processor extracts an identifier from the interrogation signal and is responsive to the identifier and the stored data to determine whether some or all of the identifier is stored in the dynamic memory array.

Abstract: A device having a switched impedance that can be switched between a first state and a second state wherein, in the first state, the device acts as a voltage multiplier and, in the second state, the device acts as a rectifier.

Abstract: A preferred embodiment of the invention includes: an identification device (1) for receiving a first signal and transmitting a second signal, the device including: a receiving means (35) for receiving the first signal to generate a voltage; an integrated circuit (37) having a state selection means (41) for selecting whether the device (1) is in a first state or a second state; a connection (39) between the receiving means (35) and the integrated circuit (37); a transmission means (45) for generating the second signal. The invention also includes a system (50) that includes an interrogator (43) for interrogating a plurality of the identification devices (1).

Abstract: A radio frequency identification transponder includes a power supply and a dynamic memory array that stores data. When power from the power supply ceases, the data in the dynamic memory array is validly maintained for a predetermined period of time. The dynamic memory array is responsive to an interrogating signal for selectively updating the data. A radio frequency identification transponder includes a signal processor that extracts an identifier from the interrogation signal and is responsive to the identifier and the stored data to determine whether some or all of the identifier is stored in the dynamic memory array.

Abstract: Apparatus and methods for transmitting data include using data to phase modulate a carrier signal to have side bands substantially lower in amplitude than the carrier. Phase modulation may be less than 90 degrees. The apparatus and methods may apply transponders, RFID apparatus and methods, passive signal devices, and single antenna equipment and methods.

Abstract: A transmitter or a method for transmitting data from a first antenna imposes a low level phase modulation, for example of less than 90°, on a carrier signal in accordance with a data signal to create a modulated signal, preferably having a carrier frequency and sidebands, and the sidebands may be substantially lower in amplitude than the carrier frequency. The method may be used in an identification system, for example for identifying luggage or other items. In another aspect of an apparatus or method for transmitting data, a phase modulation may be imposed on a carrier signal in accordance with a data signal to create a modulated signal having a carrier and sidebands, where the amount of phase modulation being selected is such that the amplitude of the sidebands is substantially lower than that of the carrier. Phase modulation may be imposed by a mixer.