Apparatus and method for interrogating a passive sensor
First Claim
1. An apparatus for determining the resonant frequency of a passive sensor, said apparatus comprising:
- means for transmitting signals of a plurality of frequencies to said passive sensor;
means for receiving signals from said passive sensor simultaneously with said transmitting of signals;
means for comparing the received signals with the transmitted signals to identify a characteristic change in the relationship between the received signals and the transmitted signals which occurs when the sensor is being driven at its resonant frequency; and
means for determining the frequency of the transmitted signal at the moment when the comparison indicates that the sensor is being driven at its resonant frequency.
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Accused Products
Abstract
Apparatus for determining the resonant frequency of a passive sensor, for example a saw device, includes a device (5, 7, 3) for transmitting signals of a plurality of frequencies to the passive sensor (2); a device (3, 7) for receiving signals from the passive sensor simultaneously with the transmitting of signals; a device (7) for comparing the received signals with the transmitted signals to identify a characteristic change in the relationship between the received signals and the transmitted signals which occurs when the sensor is being driven at its resonant frequency. As the frequency at which the passive sensor is driven passes through the resonant frequency of the sensor the phase and/or amplitude of the signal generated by the passive sensor will change. By identifying this change of phase and/or amplitude the point at which resonance occurs can be detected. The frequency of the transmitted signal at the moment when the comparison indicates that the sensor is being driven at its resonant frequency is the resonant frequency of the sensor.
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Citations
21 Claims
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1. An apparatus for determining the resonant frequency of a passive sensor, said apparatus comprising:
- means for transmitting signals of a plurality of frequencies to said passive sensor;
means for receiving signals from said passive sensor simultaneously with said transmitting of signals;
means for comparing the received signals with the transmitted signals to identify a characteristic change in the relationship between the received signals and the transmitted signals which occurs when the sensor is being driven at its resonant frequency; and
means for determining the frequency of the transmitted signal at the moment when the comparison indicates that the sensor is being driven at its resonant frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
- means for transmitting signals of a plurality of frequencies to said passive sensor;
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11. A method for determining the resonant frequency of a passive sensor, said method comprising the steps of:
- transmitting signals of a plurality of frequencies to said passive sensor;
receiving signals from said passive sensor simultaneously with said transmitting of signals;
comparing the received signals with the transmitted signals to identify a characteristic change in the relationship between the received signal and the transmitted signal which occurs when the sensor is being driven at its resonant frequency; and
determining the frequency of the transmitted signal at the moment when the comparison indicates that the sensor is being driven at its resonant frequency. - View Dependent Claims (12)
- transmitting signals of a plurality of frequencies to said passive sensor;
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13. An apparatus for determining a resonant frequency of a passive sensor, comprising:
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a transmitter/receiver which transmits signals of a plurality of frequencies to be received by a passive sensor, and which receives signals from the passive sensor simultaneously with transmitted signals sent by the transmitter; and
a comparing device which compares signals received from the sensor and the transmitter/receiver to identify a characteristic change in a relationship between the received sensor signals and the transmitted signals which occurs when the sensor is being driven at its resonant frequency to determine the frequency of the transmitted signal when the comparison indicates that the sensor is being driven at its resonant frequency. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21)
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Specification