# US 2014/0195104 A1 · Wheel speed sensor with support for indirect tire pressure monitoring > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0195104 A1 - Document ID: US20140195104A1 - Status: Published application - Kind: A1 - Application number: 13/734,320 - Filed: 2013-01-04 - Published: 2014-07-10 - Earliest claimed: 2013-01-04 - Assignees: Infineon Technologies AG - Applicants: Infineon Technologies AG - Inventors: Dirk Hammerschmidt - Web page: https://patentgrep.com/patent/US20140195104A1 ## CPC - B60C 23/062: {Frequency spectrum analysis of wheel speed signals, e.g. using Fourier transformation} - B60C: VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES ## Abstract The present disclosure relate to an indirect tire pressure monitoring system (TPMS). In some embodiments, the indirect TPMS has magnetic field sensor that detects a modulated magnetic field indicative of one or more resonance parameters of an automobile tire. The magnetic field sensor generates a modulated sensor signal based upon the modulated magnetic field. An analog-to-digital converter (ADC) converts the modulated sensor signal to a digital sensor signal, which is provided to a digital signal processing unit that perform analysis of the digital sensor signal to determine the one or more resonance parameters. A communication interface transmit data corresponding to the one or more resonance parameters to an electronic control unit (ECU). ## Claims ### Claim 1 An indirect tire pressure monitoring system (TPMS), comprising: a magnetic field sensor configured to detect a modulated magnetic field indicative of one or more resonance parameters of an automobile tire and to generate a modulated sensor signal based upon the modulated magnetic field; an analog-to-digital converter (ADC) configured to convert the modulated sensor signal to a digital sensor signal; a digital signal processing unit configured to receive the digital sensor signal and to perform analysis of the digital sensor signal to determine the one or more resonance parameters; and a communication interface configured to transmit data corresponding to the one or more resonance parameters to an electronic control unit (ECU). ### Claim 2 (depends on 1) The indirect TPMS of claim 1, wherein a sensor housing comprises the magnetic field sensor, the ADC, the digital signal processing unit, and the communication interface. ### Claim 3 (depends on 2) The indirect TPMS of claim 2, wherein the digital signal processing unit comprises: a demodulation element configured to demodulate the modulated sensor signal to generate a demodulated signal having a reduced bandwidth relative to the digital sensor signal; and a spectral analysis element configured to receive the demodulated signal, and from the demodulated signal to determine the one or more resonance parameters. ### Claim 4 (depends on 3) The indirect TPMS of claim 3, wherein the digital signal processing unit comprises a time frequency transform unit configured to perform a time to frequency transformation of the demodulated signal to generate a spectral density of the demodulated signal. ### Claim 5 (depends on 4) The indirect TPMS of claim 4, wherein the time frequency transform unit comprises a fast Fourier transform calculation unit. ### Claim 6 (depends on 4) The indirect TPMS of claim 4, further comprising: a decimation filter disposed within the sensor housing at a location downstream of the demodulation element and upstream of the time frequency transform unit, wherein the decimation filter is configured reduce a sampling frequency of the demodulated signal. ### Claim 7 (depends on 4) The indirect TPMS of claim 4, further comprising: a frequency identifier disposed within the sensor housing at a location downstream of the time frequency transform unit and configured to determine frequency peaks in the spectral density corresponding to the one or more resonance parameters. ### Claim 8 (depends on 3) The indirect TPMS of claim 3, wherein the digital signal processing unit comprises a phase-locked loop configured to receive the digital sensor signal, to lock onto a frequency of the digital sensor signal that represents the wheel speed, and to provide an output signal that controls the locked oscillator and represents the wheel speed. ### Claim 9 (depends on 3) The indirect TPMS of claim 3, further comprising: a bandpass filter disposed within the sensor housing at a location upstream of the demodulation element. ### Claim 10 (depends on 1) The indirect TPMS of claim 1, wherein the one or more resonance parameters comprise a resonance frequency or a q-factor of a resonance. ### Claim 11 An indirect tire pressure monitoring system (TPMS), comprising: a magnetic field sensor configured to generate a modulated sensor signal corresponding to a measured magnetic field indicative of one or more resonance parameters of an automobile tire; and an analog-to-digital converter (ADC) configured to sample the modulated sensor signal and to provide a digital signal, based upon the samples, to a demodulation element configured generate a demodulated signal having a lower frequency than the modulated sensor signal; a spectral analysis element configured to receive the demodulated sensor signal and to perform analysis of the sensor signal to determine the one or more resonance parameters; and a communication interface configured to transmit data corresponding to the one or more resonance parameters to an electronic control unit (ECU). ### Claim 12 (depends on 11) The indirect TPMS of claim 11, wherein the spectral analysis element comprises a time frequency transform unit configured to perform a time to frequency transformation of the demodulated signal to generate a spectral density of the demodulated signal. ### Claim 13 (depends on 12) The indirect TPMS of claim 12, further comprising: a decimation filter disposed at a location downstream of the demodulation element and upstream of the time frequency transform unit, wherein the decimation filter is configured to reduce a sampling rate of the demodulated signal. ### Claim 14 (depends on 11) The indirect TPMS of claim 11, wherein the spectral analysis element comprises a phase-locked loop configured to receive the digital sensor signal, to lock onto a frequency of the digital sensor signal that represents the wheel speed, and to provide an output signal that controls the locked oscillator and represents the wheel speed. ### Claim 15 (depends on 11) The indirect TPMS of claim 11, further comprising: a bandpass filter disposed at a location upstream of the demodulation element. ### Claim 16 (depends on 11) The indirect TPMS of claim 11, further comprising: a frequency identifier disposed within the sensor housing at a location downstream of the FFT calculation unit and configured to determine frequency peaks in the spectral density corresponding to a wheel speed and to one or more resonance frequencies. ### Claim 17 (depends on 11) The indirect TPMS of claim 11, wherein the communication interface is configured to transmit or compress and transmit a low frequency part of a spectral density of the demodulated signal to the ECU without detection frequency peaks in the spectral density. ### Claim 18 A method of measuring a tire pressure, comprising: receiving a modulated sensor signal from a magnetic field sensor configured to detect a modulated magnetic field indicative of a wheel speed and one or more resonance frequencies of an automobile tire; converting the modulated sensor signal to a digital sensor signal; performing analysis of the digital sensor signal to determine the one or more resonance parameters; and transmitting data corresponding to the one or more resonance parameters to an electronic control unit (ECU). ### Claim 19 (depends on 18) The method of claim 18, wherein performing analysis of the digital sensor signal comprises: demodulating the received digital sensor signal to generate a demodulated signal having a reduced bandwidth relative to the digital sensor signal; and performing spectral analysis of the demodulated signal to determine the one or more resonance parameters. ### Claim 20 (depends on 19) The method of claim 19, further comprising: filtering the digital sensor signal prior to demodulating the received digital sensor signal. ### Claim 21 (depends on 19) The method of claim 19, further comprising: decimating the demodulated signal prior to reduce a sampling rate of the demodulated signal. ### Claim 22 (depends on 18) The method of claim 18, wherein performing spectral analysis of the digital signal comprises performing a time to frequency transformation of the demodulated signal to generate a spectral density of the demodulated signal. ### Claim 23 (depends on 18) The method of claim 18, further comprising: identifying frequency peaks in the spectral density corresponding to a wheel speed and to one or more resonance frequencies. ### Claim 24 (depends on 18) The method of claim 18, further comprising: transmitting or compressing and transmitting a low frequency part of a spectral density of the demodulated signal without detection of frequency peaks in the spectral density.