Synchronized electronic identification system
First Claim
1. An identification system including an interrogator comprising:
- transmitter means for transmitting an interrogation signal to at least one transponder,receiver means for receiving a response signal from a transponder, andmeans for identifying the response signal;
and at least one transponder comprising;
means for receiving the interrogation signal,means for transmitting a signal in response to the interrogation signal;
wherein the interrogator includes clock extraction means for extracting a synchronizing clock signal from a received response signal and means to modify the interrogation signal synchronously with said synchronizing clock signal.
2 Assignments
0 Petitions
Accused Products
Abstract
The invention relates to an identification system comprising an interrogator and a plurality of transponders. The interrogator includes transmitter means for transmitting an interrogation signal to the transponder, receiver means for receiving a response signal from the transponder, and processor means for identifying the transponder from data in the response signal. Clock extraction means are further provided for extracting a transponder clock signal from the response signal which is used to synchronise the modification of the interrogation signal with the response signal from the transponder. Each transponder comprises receiver means for receiving the interrogation signal, a transponder clock generator, a code generator, transmitter means, and a modulator connected to the code generator, so that on receipt of the interrogation signal the transponder transmits a response signal containing data which identifies the transponder. The interrogator is adapted to detect successful reception of a response signal from any transponder, to derive a synchronisation signal from the response signal of that transponder, and to modify the interrogation signal synchronously with the response signal to indicate successful reception of the response signal. Each transponder further includes means responsive to a respective modification of the interrogation signal to cease transmission of its response signal.
94 Citations
45 Claims
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1. An identification system including an interrogator comprising:
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transmitter means for transmitting an interrogation signal to at least one transponder, receiver means for receiving a response signal from a transponder, and means for identifying the response signal; and at least one transponder comprising; means for receiving the interrogation signal, means for transmitting a signal in response to the interrogation signal; wherein the interrogator includes clock extraction means for extracting a synchronizing clock signal from a received response signal and means to modify the interrogation signal synchronously with said synchronizing clock signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A transponder comprising:
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means for receiving an interrogation signal; means for transmitting a signal in response to the interrogation signal; wherein transmission of the response signal ceases if the interrogation signal is modified synchronously with said transponder clock signal. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29)
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30. An interrogator for identifying at least one transponders comprising:
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transmitter means for transmitting an interrogation signal to at least one transponder; receiver means for receiving a response signal from a transponder; and means for identifying the response signals wherein the interrogator includes clock extraction means for extracting a synchronizing clock signal from a received response signal and means to modify the interrogation signal synchronously with said synchronizing clock signal. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37, 38)
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39. A method of identifying at least one transponder by an interrogator comprising;
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an interrogator transmitting an interrogation signal; a transponder receiving the interrogation and transmitting a response signal; the interrogator receiving the response signal and identifying said transponder; and wherein a synchronizing clock signal is derived from the received response signal and the interrogation signal is modified synchronously with said synchronizing clock signal. - View Dependent Claims (40, 41, 42, 43, 44, 45)
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Specification