Multi-stage transponder wake-up, method and structure
First Claim
1. A remote identification system comprising an interrogator and a transponder for identifying and locating a vehicle comprising:
- an interrogator having a transmitter for transmitting a wake-up signal, an interrogation signal and a continuous wave RF signal and a receiver for receiving a transponder response signal;
a transponder comprisinga wake-up circuit for receiving said wake-up signal and in response to said wake-up signal, applying a clock signal to a modulating circuit in said transponder;
a discriminator for receiving said interrogation signal and determining which lane said transponder is located;
said modulating circuit for modulating said received continuous wave RF signal with transponder reply data upon receipt of said clock signal.
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Accused Products
Abstract
A system and method which conserves energy in the operation of a transponder or tag (14) by providing that the transponder (14) be enabled or awakened in multiple stages. A threshold detector (62) is provided which measures the power level of received RF energy. If the RF energy received by the detector (62) exceeds a pre-determined level, the transponder (14) then employs a modulation detector (64) to ascertain whether it has been awakened by a valid interrogation signal from an interrogator (12) or whether the RF energy received was merely a spurious burst of RF energy from some other source. If a pre-determined modulation is detected by the modulation detector (64), the transponder (14) is then fully activated to its normal operational state.
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Citations
24 Claims
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1. A remote identification system comprising an interrogator and a transponder for identifying and locating a vehicle comprising:
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an interrogator having a transmitter for transmitting a wake-up signal, an interrogation signal and a continuous wave RF signal and a receiver for receiving a transponder response signal; a transponder comprising a wake-up circuit for receiving said wake-up signal and in response to said wake-up signal, applying a clock signal to a modulating circuit in said transponder; a discriminator for receiving said interrogation signal and determining which lane said transponder is located; said modulating circuit for modulating said received continuous wave RF signal with transponder reply data upon receipt of said clock signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification