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: 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: 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 tag and an interrogator exchange proprietary information using Modulated BackScatter (MBS) technology. A method for encrypting the RFID user's PIN and thereby making the interception and the subsequent illegal use of RFID accounts at least as difficult as a present day ATM cards. For example, the encryption method can be based upon the US Digital Encryption Standard (DES), either first or third level. The Tag's personal encryption key is only known by the financial database and the RFID Tag. This method can be applied to any type of financial, debt, identification, or credit card.

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: In a radio frequency identification communication system, a communication protocol advantageously controls communication between an interrogator and one or more identifying labels or read/write tags. This protocol is configurable in two modes in which a read/write tag can be expected to operate. In the first mode, a rapid transfer of a limited amount of data takes place between the interrogator and one or more tags. In the second mode, a slower or less time critical transfer of a large quantity of data in a packet format takes place. In this second mode, a communication to the other tags causes these tags to remain "silent" so that they do not corrupt the data transfer in progress. The interrogator automatically determines the quantity of data and the correct mode in which to operate. Either mode can be initiated on successive communication periods by the communication protocol.

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.