Abstract: A modulated backscatter communication system (e.g., an Electronic Shelf Label (ESL) system) includes a central node (e.g., a ceiling node) and one or more remote nodes (e.g., ESL tags). The central node transmits a downlink radio signal which is reflectively modulated at a remote node to produce a modulated reflected radio signal. At the remote node, a precise-frequency subcarrier signal is modulated with an uplink information signal to produce a modulated signal which is used to produce the modulated reflected radio signal. At the central node, the modulated reflected radio signal is received, detected and narrowband filtered to obtain the modulated subcarrier signal which is then demodulated to obtain the uplink information signal, with great immunity to close to carrier downlink radio noise and fluorescent light backscatter interference.

Abstract: In accordance with the present invention, a duplex radio communication system comprises an Interrogator which generates a radio signal to at least one remote Tag. The remote Tag receives the radio signal. The Tag then generates a subcarrier signal, and using Quadrature Phase Shift Keying (QPSK), modulates an information signal onto the subcarrier. A Backscatter Modulator, using this modulated subcarrier, modulates the reflection of the radio signal, the reflected signal being a reflected modulated signal. The Interrogator receives and demodulates the reflected modulated signal to obtain the information signal. In one embodiment, demodulation utilizes a homodyne detector. In another embodiment, the Interrogator modulates an information signal onto the radio signal, transmits that modulated radio signal to the Tag, and the Tag demodulates that modulated radio signal to recover the information signal.

Abstract: A system provides a mobile transmitter and a plurality of boundary tags for receiving communication from the mobile transmitter. Preferably the mobile transmitter is coupled to a mobile unit, which can be an inanimate object capable of moving or being moved, or a living being. The boundary tags mark the boundaries of an area within which the mobile unit is allowed to move. The mobile transmitter transmits a signal to a boundary tag. The system determines if the mobile transmitter has come into proximity of a boundary tag by receiving a reflected modulated signal from the boundary tag. If the mobile transmitter has come into proximity of a boundary tag a response is generated. The response can be a stimulus or an alert, or both. The response can be generated at a central control station, or at a mobile transceiver that includes the mobile transmitter and a mobile receiver. In one embodiment, the boundary tag modulates a reflection of the signal transmitted by the mobile transmitter.

Abstract: The present invention provides for an inexpensive RFID Tag design which uses an inexpensive Backscatter Modulator. The modulator is simply a CMOS gate driven by a shift register containing a modulating signal. The CMOS gate is connected to the antenna such that it modulates the reflectivity of the antenna in accordance with the modulating signal. In a second embodiment, the Tag is incorporated into a single CMOS integrated circuit which comprises all of the components, except for the antenna, necessary to implement an inexpensive read-only RFID Tag.

Abstract: The present invention involves an adaptive digital radio communications architecture which can be reconfigured by reprogramming at least one programmable device, and thus more efficiently use the available bandwidth of a time-varying RF channel and/or to provide a flexible and adaptive digital communications system. In certain embodiments, the programmable device uses a Programmable Logic Device (PLD) to perform the digital communications processing functions of the transmitter or the receiver of a radio communications system. In this context, PLD is a general term representing a family of programmable logic devices; examples of this family are a Programmable Array Logic (PAL), a Complex PLD (CPLD), and a Field Programmable Gate Array (FPGA). The architecture is reconfigurable in the sense that any or all of the digital communications processing algorithms can be modified by reprogramming the PLD.

Abstract: In accordance with the present invention, a general antenna system is disclosed suitable for applications in which an RFID Tag passes by an Interrogator. We then disclose a specific antenna design that uses a single planar antenna for transmit and a multi-element planar antenna array for receive. The multi-element planar antenna array is spaced such that each of the planar elements is four inches apart, center-to-center, thus defining a narrow 30° receive beamwidth in the horizontal plane. The vertical receive bandwidth is much greater than 30°, facilitating the Interrogator receiving signals at a variety of elevations. Furthermore, a multi-way microstrip combiner is used to sum the signals received from each of the planar antennas. To block interference from the transmit antenna and to improve receive sensitivity, this multi-way microstrip combiner is shielded using, in one embodiment, copper tape along its edges. In a specific embodiment, a four element receive antenna design is disclosed.

Abstract: A system provides short range wireless data communication from a central control point (e.g., interrogator) to inexpensive endpoints (e.g., tags). The endpoints utilize the technology of modulated backscatter for transmission from the tags to the interrogator. The system uses a new downlink protocol for data transmission from the interrogator to the tags and a new uplink protocol for data transmission from the tags to the interrogator. Both protocols use a backoff/retry algorithm to randomly retransmit any non-acknowledged messages. System capacity from the tags to the interrogator is further enhanced by the use of uplink subcarrier frequency division multiplexing.

Abstract: A modulated backscatter communication system (e.g., an Electronic Shelf Label (ESL) system) includes a central node (e.g., a ceiling node) and one or more remote nodes (e.g., ESL tags). The central node transmits a downlink radio signal which is reflectively modulated at a remote node to produce a modulated reflected radio signal. At the remote node, a precise-frequency subcarrier signal is modulated with an uplink information signal to produce a modulated signal which is used to produce the modulated reflected radio signal. At the central node, the modulated reflected radio signal is received, detected and narrowband filtered to obtain the modulated subcarrier signal which is then demodulated to obtain the uplink information signal, with great immunity to close to carrier downlink radio noise and fluorescent light backscatter interference.

Abstract: A radio communication system includes an Interrogator for generating and transmitting a radio signal. One or more Tags contained within the radio communication system receive the radio signal. A Backscatter Modulator modulates the reflection of the radio signal using a subcarrier signal, thereby forming a reflected modulated signal. The Interrogator receives and demodulates the reflected modulated signal. Based upon the characteristics of the demodulated signal, the Interrogator can determine the identity of the Tag, and the relative velocity of the Tag with respect to the Interrogator. The Interrogator can also determine if motion exists in the vicinity of the Interrogator, even when no Tag is present, without the need for a separate motion detection system. The characteristics of the demodulated signal, can also be used to determine the characteristics of motion of the Tag, such as the vibrational frequency.

Abstract: A radio communications system is that can determine the location of an RFID Tag. The radio communication system includes at least one Interrogator for generating and transmitting a modulated radio signal to one or more Tags. The Interrogator is at a known location, and is in motion with respect to the Tag at a known velocity. One or more Tags of the system receive and demodulate the modulated radio signal, which contains a first information signal which specifies which Tag or Tags should respond using Modulated Backscattering. The Tag generates a subcarrier signal, and backscatter modulates the reflection of the radio signal using the subcarrier signal, thereby forming a reflected signal. The Interrogator receives and demodulates the reflected signal. The Interrogator then determines the Tag's relative direction from the location and velocity of the Interrogator, and from the Doppler shift of the subcarrier signal. More than one of such measurements allow the location of the Tag to be determined.

Abstract: In accordance with the present invention, a radio communications system is disclosed that can operate in one of several Modes which integrate in-building security, location determination, messaging, and data communications capabilities. The radio communication system includes at least one Interrogator for generating and transmitting a radio signal. One or more Tags of the system receive the radio signal. A Backscatter Modulator modulates the reflection of the radio signal using a subcarrier signal, thereby forming a reflected modulated signal. The Interrogator receives and demodulates the reflected modulated signal. The Interrogator can also transmit a first information signal to one or more tags, specifying which tags should respond using the Backscatter Modulator. In the Interrogation Mode, the Interrogator can determine the identity of the Tags in the reading field, and can exchange data with those Tags that have been identified.

Abstract: A Time Division Multiple Access (TDMA) duplex radio communication system uses an Interrogator to generate a first radio signal by modulating a first information signal onto a radio carrier signal which is sent to at least one remote Tag of the system. The remote Tag receives and modulates a second information signal onto a second radio carrier signal to form a second modulated signal which is transmitted, in a time-slotted manner, back to the Interrogator. The remote Tag selects, or is instructed, how many times it should repetitively transmit the second modulated signal; and selects, or is instructed, over how many of the time slots following receipt of the first radio signal the remote Tag should repetitively transmit the second modulated signal. Other embodiments use Modulated Backscatter to transmit the second modulated signal, and use homodyne detection to demodulate the second modulated signal.

Abstract: A modulated backscatter communication system (e.g., an Electronic Shelf Label (ESL) system) includes a central node (e.g., a ceiling node) and one or more remote nodes (e.g., ESL tags). The central node transmits a downlink radio signal which is reflectively modulated at a remote node to produce a modulated reflected radio signal. At the remote node, a precise-frequency subcarrier signal is modulated with an uplink information signal to produce a modulated signal which is used to produce the modulated reflected radio signal. At the central node, the modulated reflected radio signal is received, detected and narrowband filtered to obtain the modulated subcarrier signal which is then demodulated to obtain the uplink information signal, with great immunity to close to carrier downlink radio noise and fluorescent light backscatter interference.

Abstract: In accordance with the present invention, an RFID system has a homodyne receiver having two outputs; the in-phase or I output and the quadrature or Q output. The modulated backscattered signal is composed of an information signal, modulated onto a single frequency subcarrier signal, generating a modulated subcarrier signal; this modulated subcarrier signal is then backscatter modulated onto the incoming RF signal. To demodulate this modulated backscattered signal, the I and Q outputs are combined using an IQ combiner. This IQ combiner introduces a 90.degree. phase shift, with respect to the frequency of the subcarrier signal, onto one of the demodulator outputs and then combines the outputs of the demodulator.

Abstract: A duplex radio communication system includes an Interrogator which generates a first modulated signal by modulating a first information signal onto a radio carrier signal. The Interrogator transmits the first modulated signal to at least one remote Tag of the system. The remote Tag receives and processes the first modulated signal received at its Antenna. A Backscatter Modulator uses a second information signal to modulate the reflection of the first modulated signal from the Antenna, the reflected signal being a second modulated signal. The Interrogator receives and demodulates the second modulated signal to obtain the second information signal.

Abstract: A radio communication system includes an Interrogator for generating and transmitting a first modulated signal by modulating a first information signal onto a radio carrier signal, the first information signal indicating in which of multiple response modes a receiving Tag should respond. One or more Tags of the system receive the first modulated signal and decode it to obtain the first information signal. A Backscatter Modulator modulates the reflection of the first modulated signal using a second information signal whose content, data rate, or modulation is determined by said first information signal, thereby forming a second modulated signal. The Interrogator receives and demodulates the second modulated signal to obtain the indicated second information signal.

Abstract: A modulated backscatter communication system (e.g., an Electronic Shelf Label (ESL) system) includes a central node (e.g., a ceiling node) and one or more remote nodes (e.g., ESL tags). The central node transmits a downlink radio signal which is reflectively modulated at a remote node to produce a modulated reflected radio signal. At the remote node, a precise-frequency subcarrier signal is modulated with an uplink information signal to produce a modulated signal which is used to produce the modulated reflected radio signal. At the central node, the modulated reflected radio signal is received, detected and narrowband filtered to obtain the modulated subcarrier signal which is then demodulated to obtain the uplink information signal, with great immunity to close to carrier downlink radio noise and fluorescent light backscatter interference.

Abstract: An electronic label device includes a display device and a microcomputer connected to control the display device. The microcomputer includes a memory having a plurality of registers. Data received via an antenna is stored in the registers. The microcomputer is indirectly controlled to selectively display data stored in the registers on said display device. The indirect control is effected by coupling signals to the said microcomputer without physical contact with elements of the label device, such as by a magnetic reed switch, capacitor coupling or inductive coupling.