Tire pressure monitoring using half duplex transponder frequency shift
First Claim
1. A tire pressure sensor comprising:
- an analog half duplex RFID (radiofrequency identification) device powered by an RF signal charging a capacitor and having a parallel resonant circuit comprising an inductor and a first capacitor for generating a first radiofrequency (RF) signal for transmission to a reader circuit;
a variable capacitance pressure sensor being coupled across the parallel resonant circuit by a first switch for generating a RF frequency shift keying (FSK) signal having a frequency which varies with tire pressure for transmission to the reader, wherein a difference in frequency between the first radiofrequency (RF) signal and the FSK RF signal is the response data that is directly indicative of a pressure of a tire.
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Accused Products
Abstract
A tire pressure sensor has an RFID (radio frequency identification) device having a parallel resonant circuit including an inductor and a first capacitor for generating a first radio frequency (RF) signal for transmission to a reader circuit, and a second capacitor coupled across the parallel resonant circuit by a first switch in a first position and generating a second RF signal for transmission to the reader circuit. A capacitive pressure sensor is coupled across the parallel resonant circuit by the first switch in a second position for generating a third frequency RF signal for transmission to the reader, wherein a difference in frequency between the first and third RF signals is indicative of a pressure of a tire.
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Citations
15 Claims
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1. A tire pressure sensor comprising:
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an analog half duplex RFID (radiofrequency identification) device powered by an RF signal charging a capacitor and having a parallel resonant circuit comprising an inductor and a first capacitor for generating a first radiofrequency (RF) signal for transmission to a reader circuit; a variable capacitance pressure sensor being coupled across the parallel resonant circuit by a first switch for generating a RF frequency shift keying (FSK) signal having a frequency which varies with tire pressure for transmission to the reader, wherein a difference in frequency between the first radiofrequency (RF) signal and the FSK RF signal is the response data that is directly indicative of a pressure of a tire. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of measuring a tire pressure comprising:
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transmitting from a reader circuit a (RF) signal at a first frequency to a analog half duplex radio frequency identification (RFID) device to charge a capacitor and command a tire pressure sensor measure pressure in a tire to which the sensor is attached; transmitting a frequency shift keying (FSK) RF signal from the RFID device in response to a state of a digital signal, and a state of a capacitive pressure sensor coupled to a resonant circuit in response to the state of the digital signal causing the FSK signal frequency to vary with tire pressure; and determining a tire pressure in response to a difference between the FSK RF signal frequencies, wherein the difference in frequency is directly indicative of the tire pressure. - View Dependent Claims (9, 10, 11)
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12. A tire pressure sensor system utilizing a half duplex radio frequency identification (RFID) transponder frequency shift comprising:
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a reader circuit generating a RF signal at a first frequency to a RFID device to charge a capacitor therein and command tire pressure sensor measure pressure in a tire to which a sensor is attached; the RFID device transmitting a first RF signal to the reader circuit in response to a first state of a digital modulation signal; the RFID device transmitting a frequency shift keying (FSK) RF signal to the receiver in response to a second state of a digital signal and a state of a capacitive pressure sensor coupled to a resonant circuit in response to the second state of the digital signal causing the FSK signal frequency to vary with tire pressure; and determining a tire pressure in response to a difference between the FSK RF signal frequencies, wherein the difference in frequency is directly indicative of the tire pressure. - View Dependent Claims (13, 14, 15)
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Specification