Signal transmission in a tire pressure sensing system
First Claim
1. Signal transmission apparatus comprising:
- transmitter circuitry comprising a resonator having at least one component whose effective value influences a natural resonant frequency of the resonator and can be changed in use of the circuitry;
an excitation unit which applies to the resonator an excitation signal having an excitation frequency, said excitation signal serving to bring about oscillations having said excitation frequency in said resonator;
receiver circuitry; and
a coupling arrangement which provides a coupling between said resonator and said receiver circuitry, the receiver circuitry being operable to detect such a change in said effective value via said coupling;
wherein said excitation frequency is a predetermined excitation frequency that does not change when said effective value changes and that differs from each value of said natural resonant frequency of said resonator as said effective value changes in use of the transmitter circuitry.
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Accused Products
Abstract
Signal transmission apparatus for use, for example, in a passive sensor system such as an in-vehicle tyre pressure sensing system, comprises transmitter circuitry and receiver circuitry coupled together by a coupling, preferably a wireless coupling such as two opposed plate-form antennae. The transmitter circuitry includes a resonator having at least one component whose value influences a natural resonant frequency of the resonator and can be changed in use of the circuitry. The effective value is changed, for example, by a physical parameter being sensed or by a control signal to be transmitted. The receiver circuitry includes a driver section for applying to the resonator an excitation signal having a predetermined excitation frequency that is different from the natural resonant frequency. The transmitter circuitry preferably derives its power supply from the excitation signal via a rectifier circuit. The receiver circuitry detects such a change in the effective value via the coupling. Such signal transmission apparatus can operate accurately and reliably in electronically and environmentally inhospitable environments.
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Citations
22 Claims
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1. Signal transmission apparatus comprising:
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transmitter circuitry comprising a resonator having at least one component whose effective value influences a natural resonant frequency of the resonator and can be changed in use of the circuitry;
an excitation unit which applies to the resonator an excitation signal having an excitation frequency, said excitation signal serving to bring about oscillations having said excitation frequency in said resonator;
receiver circuitry; and
a coupling arrangement which provides a coupling between said resonator and said receiver circuitry, the receiver circuitry being operable to detect such a change in said effective value via said coupling;
wherein said excitation frequency is a predetermined excitation frequency that does not change when said effective value changes and that differs from each value of said natural resonant frequency of said resonator as said effective value changes in use of the transmitter circuitry. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
said receiver circuitry comprises a modulator which amplitude-modulates said excitation signal in dependence upon a further signal to be transmitted from the receiver circuitry to said transmitter circuitry; and
said transmitter circuitry comprises an amplitude detector which detects said further signal based on the amplitude of the excitation signal received thereby.
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17. Apparatus as claimed in claim 16, wherein said receiver circuitry further comprises a demodulator which demodulates a sensing signal, derived from the resonator in the transmitter circuitry, with said further signal so as to tend to cancel out from said sensing signal variations arising from the amplitude modulation of the excitation signal, the demodulated sensing signal being used to detect said change in said effective value.
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18. Sensing apparatus, for transmitting sensor data from a first lenient to a second element, the first and second elements being movable relative to one another, which apparatus comprises:
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transmitter circuitry adapted to be carried by the first element and comprising;
a resonator having at least one component whose effective value influences a natural resonant frequency of the resonator and can be changed in use of the circuitry; and
a sensor which senses one or more predetermined parameters, such a change in said effective value being brought about by a change in at least one of said predetermined parameters;
an excitation unit which applies to the resonator an excitation signal having an excitation frequency, said excitation signal serving to bring about oscillations having said excitation frequency in said resonator;
receiver circuitry adapted to be carried by the second element, and a coupling arrangement which provides a coupling between said resonator and said receiver circuitry, the receiver circuitry being operable to detect said change in said effective value via said coupling;
wherein said excitation frequency is a predetermined excitation frequency that does not change when said effective value changes and that differs from each value of said natural resonant frequency of said resonator as said effective value changes in use of the transmitter circuitry.
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19. Tyre pressure measuring apparatus, adapted to be carried by a vehicle, comprising:
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transmitter circuitry adapted to be carried by one of the vehicle wheels and comprising;
a resonator having at least one component whose effective value influences a natural resonant frequency of the resonator and can be changed in use of the circuitry; and
a sensor which senses a tyre pressure of said one wheel, such a change in said effective value being brought about by a change in said tyre pressure;
an excitation unit which applies to the resonator an excitation signal having an excitation frequency, said excitation signal serving to bring about oscillations having said excitation frequency in said resonator;
receiver circuitry adapted to be carried by a chassis of the vehicle; and
a coupling arrangement which provides a coupling between said resonator and said receiver circuitry, the receiver circuitry being operable to detect said change in said effective value via said coupling;
wherein said excitation frequency is a predetermined excitation frequency that does not change when said effective value changes and that differs from each value of said natural resonant frequency of said resonator as said effective value changes in use of the transmitter circuitry. - View Dependent Claims (20, 21)
the transmitter circuitry comprises a pressure sensor which measures pressure and a temperature sensor, independent of the pressure sensor, which measures tyre temperature;
said pressure sensor has a capacitance Cp that varies with absolute tyre pressure P, at least in a desired operating range of pressures of the pressure sensor, approximately in accordance with
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21. Apparatus as claimed in claim 19, wherein said receiver circuitry comprises first and second modules connected together by a hard-wire link through which a current flows between the two modules when the apparatus is in use, the first module comprising a current modulator which modulates said current in dependence upon the detected change in said effective value, and said second module comprising a current detector which detects such modulation of said current by said current modulator in the first module.
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22. A signal transmission method, for use with transmitter circuitry that comprises a resonator having at least one component whose effective value influences a natural resonant frequency of the resonator, and with receiver circuitry that has a coupling when in use to said resonator, the method comprising:
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applying to the resonator an excitation signal having an excitation frequency so that oscillations having said excitation frequency are brought about in said resonator;
bringing about a change in said effective value of said at least one component in the transmitter circuitry; and
detecting such a change in said effective value in the receiver circuitry via said coupling;
wherein said excitation frequency is a predetermined excitation frequency that does not change when said effective value changes and that differs from each value of said natural resonant frequency of said resonator as said effective value changes in use of the transmitter circuitry.
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Specification