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.

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.

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.

Abstract: A method of tuning the resonance frequency of a transponder to a target frequency is described, wherein a transponder comprises a film antenna with an IC (IC) mounted to the film antenna (L) and an integrated resonance capacitor (C) is part of a IC. During testing of IC at chip probe to determine the pass/fail of the IC, the integrated resonance capacitor (C) is measured and the value is stored with the pass/fail data of the wafer map. Then after mounting a passed IC (IC) to a film antenna (L) with variable inductance, retrieve the integrated resonance capacitance value from the wafer map and calculate the amount of inductance necessary to achieve the target frequency. Tune the film antenna (L) to achieve the necessary inductance, measure the transponder resonance frequency, and compare the transponder resonance frequency to the target frequency.