Modulated spread spectrum in RF identification systems method
First Claim
1. A communication system, comprising:
- signal conditioning and transmitting circuitry to produce and transmit a twice modulated data signal; and
a receiver system that is remote from the signal conditioning and transmitting circuitry and that comprises;
receiving and processing circuitry to receive the transmitted twice modulated data signal and to produce therefrom a recovered modulated data signal including acarrier component and a data signal component;
synthesizing and synchronizing circuitry to receive the recovered modulated data signal and produce a synthesized signal synchronized with the carrier component; and
processing and comparing circuitry to receive the recovered modulated data signal and the synthesized signal, and to produce a signal indicative of the data signal component responsive to signals including the recovered modulated data signal and the synthesized signal.
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Accused Products
Abstract
A method for RF communication between transceivers in a radio frequency identification system that improves range, decreases multipath errors and reduces the effect of outside RF source interference by employing spread spectrum techniques. By pulse amplitude modulating a spread spectrum carrier before transmission, the receiver can be designed for simple AM detection, suppressing the spread spectrum carrier and recovering the original data pulse code waveform. The data pulse code waveform has been further encrypted by a direct sequence pseudo-random pulse code. This additional conditioning prevents the original carrier frequency components from appearing in the broadcast power spectra and provides the basis for the clock and transmit carrier of the transceiver aboard an RFID tag. Other advantages include high resolution ranging, hiding transmissions from eavesdroppers, and selective addressing.
58 Citations
21 Claims
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1. A communication system, comprising:
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signal conditioning and transmitting circuitry to produce and transmit a twice modulated data signal; and a receiver system that is remote from the signal conditioning and transmitting circuitry and that comprises; receiving and processing circuitry to receive the transmitted twice modulated data signal and to produce therefrom a recovered modulated data signal including a carrier component and a data signal component; synthesizing and synchronizing circuitry to receive the recovered modulated data signal and produce a synthesized signal synchronized with the carrier component; and processing and comparing circuitry to receive the recovered modulated data signal and the synthesized signal, and to produce a signal indicative of the data signal component responsive to signals including the recovered modulated data signal and the synthesized signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A communication system, comprising:
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signal conditioning and transmitting circuitry to produce and transmit a modulated data signal; and a receiver system that is remote from the signal conditioning and transmitting circuitry and comprises; receiving and processing circuitry to receive the transmitted modulated data signal and to produce therefrom a recovered modulated data signal including a carrier component and a data signal component; synthesizing and synchronizing circuitry to receive the recovered modulated data signal and produce a synthesized signal synchronized with the carrier component, and produce an inverse of the synthesized signal; and processing and comparing circuitry to receive the recovered modulated data signal and the synthesized signal and to produce a signal indicative of the data signal component responsive to the recovered modulated data signal, the synthesized signal, and the inverse of the synthesized signal. - View Dependent Claims (16, 17, 18, 19, 20)
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21. A communication system, comprising:
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signal conditioning and transmitting circuitry to produce and transmit a modulated data signal, wherein the modulated data signal comprises a twice modulated data signal that is produced by modulating a second carrier with a first modulated data signal, which is produced by modulating a data signal with a first carrier, and the first and second carriers are pseudo noise signals; and a receiver system that is remote from the signal conditioning and transmitting circuitry and comprises; receiving and processing circuitry to receive the transmitted modulated data signal and to produce therefrom a recovered modulated data signal including a carrier component and a data signal component; signal production circuitry to produce a synchronized signal that is synchronized with the carrier component; and processing and comparing circuitry to receive the recovered modulated data signal and the synchronized signal, and to produce a signal indicative of the data signal component responsive to signals including the recovered modulated data signal and the synchronized signal.
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Specification