Passive response communication system
First Claim
1. A method of passive response communication in which a first transponder transmits an interrogation signal to a remote second transponder, which responds by transmitting data back to the first transponder, the two transponders each comprising a transmitter and a receiver, and a communication signal exchanged between said transponders in at least one direction including a plurality of pulses, wherein at least one edge of at least one distinguishing pulse selected among said plurality of pulses has a rate of change different from the rate of change of a corresponding edge of at least another of said plurality of pulses so as to confer a distinctive shape on said distinguishing pulse and the receiver of said communication signal is selectively responsive to the shapes of said plurality of pulses.
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Accused Products
Abstract
A method of passive response communication, especially for an access control system, in which a first transponder (2) transmits an interrogation signal to a remote second transponder (3), which responds by transmitting data back to the first transponder (2), the two transponders each comprising a transmitter and a receiver, and a communication signal exchanged between said transponders (2, 3) in at least one direction including a plurality of anti-relay-attack pulses (13, 14). At least one distinguishing pulse (14) selected among the anti-relay-attack pulses has a distinctive shape and the receiver of said communication signal is selectively responsive to the shapes of said plurality of pulses (13, 14). Interception of the transmitted signal in a relay attack using digital transceivers will not relay the distinctive shape and the response of the second transponder is inhibited.
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Citations
15 Claims
- 1. A method of passive response communication in which a first transponder transmits an interrogation signal to a remote second transponder, which responds by transmitting data back to the first transponder, the two transponders each comprising a transmitter and a receiver, and a communication signal exchanged between said transponders in at least one direction including a plurality of pulses, wherein at least one edge of at least one distinguishing pulse selected among said plurality of pulses has a rate of change different from the rate of change of a corresponding edge of at least another of said plurality of pulses so as to confer a distinctive shape on said distinguishing pulse and the receiver of said communication signal is selectively responsive to the shapes of said plurality of pulses.
Specification