Modulation field detection, method and structure
First Claim
1. A system for radio frequency identification of a transponder by an interrogator, the system comprising:
- a) said interrogator wherein said interrogator hasi) an oscillator operable to provide a carrier wave,ii) a first modulator operable to modulate data upon said carrier wave with a first modulation signal, andiii) a second modulator operable to superimpose a second modulation signal upon said modulated carrier, said second modulation signal operable to alert said transponder that an RF interrogation is being sent by said interrogator; and
b) said transponder wherein said transponder hasi) a modulation detector operable to be alerted to the presence of said RF interrogation by the presence of said second modulation signal,ii) means for enabling other transponder circuitry upon detection of said second modulation signal, said means in electrical communication with said modulation detector and enabling said other transponder circuitry only when said modulation detector detects the presence of said second modulation signal, thereby lessening the likelihood that said other transponder will be activated in the absence of an RF interrogation, such as by spurious Electro-Magnetic Interference, andiii) a demodulator operable to demodulate said data from said carrier wave.
1 Assignment
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Accused Products
Abstract
Disclosed is a system and method which protects a transponder or tag (14) from being enabled or awakened by spurious RF energy. A modulation detector (64) is provided which detects a modulation signal that is superimposed upon an RF modulation from an interrogator (12). Preferably this superimposed modulation is of a low frequency, below those typically existing as Electro-Magnetic Interference (EMI), such that the transponder (14) is less likely to be erroneously activated by an unintended RF signal. Upon reception of an RF interrogation having the proper modulation superimposed thereupon, the modulation detector (64) is operable to awaken other circuitry within the transponder (14) such that the transponder (14) is then operable to communicate with the interrogator (12).
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Citations
17 Claims
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1. A system for radio frequency identification of a transponder by an interrogator, the system comprising:
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a) said interrogator wherein said interrogator has i) an oscillator operable to provide a carrier wave, ii) a first modulator operable to modulate data upon said carrier wave with a first modulation signal, and iii) a second modulator operable to superimpose a second modulation signal upon said modulated carrier, said second modulation signal operable to alert said transponder that an RF interrogation is being sent by said interrogator; and b) said transponder wherein said transponder has i) a modulation detector operable to be alerted to the presence of said RF interrogation by the presence of said second modulation signal, ii) means for enabling other transponder circuitry upon detection of said second modulation signal, said means in electrical communication with said modulation detector and enabling said other transponder circuitry only when said modulation detector detects the presence of said second modulation signal, thereby lessening the likelihood that said other transponder will be activated in the absence of an RF interrogation, such as by spurious Electro-Magnetic Interference, and iii) a demodulator operable to demodulate said data from said carrier wave. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for interrogating a remote transponder, said method comprising the steps of:
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a) monitoring received RF signals by a modulation detector in said remote transponder, said modulation detector being sensitive to modulation having a known modulation frequency; b) sending an RF interrogation pulse from an interrogator, said RF interrogation pulse having said known modulation frequency superimposed thereon; c) detecting by said modulation detector presence of said known modulation frequency; and d) enabling by said modulation detector, other transponder circuitry whereby said transponder is operable to receive said RF interrogation pulse and perform actions based thereon. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification