Tire pressure monitoring using half duplex transponder frequency shift
AssigneeTexas Instruments Deutschland GmbH
InventorAlfons Lichtenegger
Life of this patent
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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.
Claims15
A tire pressure sensor comprising:
- an RFID (radiofrequency identification) device 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, and a second capacitor coupled across the parallel resonant circuit by a first switch in a first position for generating a second RF signal for transmission to the reader circuit;
- a capacitive pressure sensor being 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.
A method of measuring a tire pressure comprising:
- transmitting from a reader circuit a (RF) signal at a first frequency to a radio frequency identification (RFID) device to charge a capacitor therein and command a tire pressure sensor measure pressure in a tire to which the sensor is attached;
- transmitting the first RF signal from the RFID device to the reader circuit in response to a first state of a digital modulation signal;
- transmitting a second RF signal from the RFID device in response to a second state of the 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;
- and
- determining a tire pressure in response to a difference between the first and third RF signal frequencies.
A tire pressure sensor using half duplex transponder frequency shift comprising:
- a capacitive pressure sensor (Cpres) instead, or in addition to CM, connected to the IC output CM1;
- capacitance change caused by pressure change varies the second frequency;
- the capacitive pressure sensor being calibrated at certain pressure points, measuring the first and second frequency calibration at the first frequency being substantially the same for all pressure points;
- application of the capacitance and High-bit frequency changes and the pressure is calculable out of the calibration values stored in the transponder memory.
Dependencies are inferred from the claim text.