摘要 |
In accordance with the present invention, a novel Time Division Multiple Access (TDMA) duplex radio communication system comprises an Interrogator which generates a first radio signal by modulating a first information signal onto a radio carrier signal. The Interrogator transmits t he first radio signal to at least one remote Tag of the system. The remote Tag receives and processes the received first radio signal. The remote Tag then modulates a second information signal onto a second radio carrier signal to form a second modulated signal. This second modulated signal is then 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 transmi t the second modulated signal. Other embodiments of this invention include the use of Modulated Backscatter to transmit the second modulated signal, and the us e of homodyne detection to demodulate the second modulated signal. A Frequency Division Multiple Access (FDMA) duplex radio communication system embodiment utilizes multiple subcarrier frequencies and another embodiment combines the FDMA and the TDMA methods. A Code Division Multiple Access (CDMA) embodiment utilizes multiple spreading codes; in addition, another embodiment combines the CDMA and the TDMA methods. A novel method for power control of the tag, using modulated backscatter, is also disclosed. Finally, a method for the Interrogator to instruct the Tag to dynamically alter the data rate of the second information signal is also disclosed.
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