Sensor, sensor system, and method for remotely sensing a variable

• US 6,897,775 B2
• Filed: 04/05/2001
• Issued: 05/24/2005
• Est. Priority Date: 05/23/2000
• Status: Expired due to Fees

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Elsner, Bernhard, Heidemeyer, Henry
• Primary Examiner(s): Wu, Daniel
• Assistant Examiner(s): Walk, Samuel J.
• Application Number:
  US10/275,162
• Publication Number:
  US 20030102984A1
• Time in Patent Office: 1,510 Days
• Field of Search: 340/539.22, 340/439, 340/440, 340/442, 340/447, 340/448, 340/686.3, 731/46
• US Class Current: 340/539.22
• CPC Class Codes: G01S 13/753 using frequency selective elements, e.g. resonator
• CPC Class Codes: G08C 17/02 using a radio link

Abstract

A sensor system for remote detection of a measurable variable includes a sensor, with a first resonator (5) which has a resonant frequency that is variable under the influence of the measurable variable; an antenna (1) for sending and receiving a modulated high-frequency signal; a modem (2) for coupling the first resonator (5) to the antenna; and a second resonator (3) that can be excited by a carrier frequency of the high-frequency signal. An interrogation unit generates an inquiry radio signal for exciting the two resonators and interrupts the broadcasting of the inquiry radio signal in order to receive a response radio signal broadcast by the sensor.

Claims

1. A sensor for remote detection of a measurable variable, having a first resonator (5), which has a resonant frequency that is variable under the influence of the measurable variable, having an antenna (1) for sending and receiving a modulated high-frequency signal and a modulator (2) for coupling the first resonator (5) to the antenna (1), characterized in that it includes a second resonator (3), which is excitable by a carrier frequency of the modulated high-frequency signal.

2. The sensor of claim 1, characterized in that the modulator (2) is a demodulation diode selected from the group consisting of a Schottky diode and a detector diode.

3. The sensor of claim 1, characterized in that the first resonator (5) includes a surface wave resonator or a quartz oscillator.

4. The sensor of claim 3, characterized in that the first resonator (5) further includes a discrete component (6) that is sensitive to the measurable variable.

5. The sensor of claim 1, characterized in that the measurable variable is a pressure or a temperature.

6. The sensor of claim 1, characterized in that the damping of the second resonator (3) is less than that of the first resonator (5).

7. The sensor of claim 1, characterized in that the second resonator (3) is a surface wave resonator, which is capable of generating a delayed output oscillation pulse in reaction to an excitation oscillation pulse.

8. The sensor of claim 7, characterized in that the second resonator has two three-dimensionally spaced-apart pairs (25, 26) of electrodes (21, 22).

9. The sensor of claim 7, characterized in that the second resonator (5) has a pair (27) of electrodes (21, 22) for exciting and picking up a surface wave and has reflector electrodes (23) spaced apart from the electrode pair (27).

10. A sensor system, having a plurally of sensors of claim 1, and at least one interrogation unit for sending an inquiry radio signal to the sensors and for receiving a response radio signal from the sensors, characterized in that the first resonators (5) each have different resonant frequency ranges.

11. The sensor system of claim 10, characterized in that each interrogation unit is assigned a first specific carrier frequency (f_T) of the inquiry radio signal and at least one sensor whose second resonator (5) is excitable selectively by the specific carrier frequency (f_T).

12. An interrogation unit for a sensor of claim 1, characterized in that it has oscillators (13, 14) for generating an inquiry radio signal, which includes an inquiry carrier signal at a second frequency (f_T), which signal is modulated with an inquiry measurement signal at a first frequency (f_M), and has a common antenna (11) for broadcasting the inquiry radio signal and receiving a response radio signal from one of the sensors, and the interrogation unit interrupts the broadcasting of the inquiry radio signal in order to receive the response radio signal.

13. The interrogation unit of claim 12, characterized in that the frequency of the inquiry carrier signal (f_T) is variable.

14. A method for remote detection of a measurable variable using the sensor of claim 1, in which the two oscillators (3, 5) of one sensor are excited by an inquiry radio signal which includes an inquiry carrier signal at a second frequency (f_T), which signal is modulated with an inquiry measurement signal at a first frequency (f_M), and a response radio signal, broadcast by the sensor, is received and evaluated, which includes a response carrier signal at the resonant frequency of the second oscillator (3), modulated with a response measurement signal at the resonant frequency of the first oscillator (5), and for receiving the answer radio signal, the sending of the inquiry carrier signal is interrupted.

15. The method of claim 14, characterized in that the inquiry radio signal and the response radio signal are sent and received via the same antenna (11).

16. The method of claim 14, characterized in that if no adequate response measurement signal is received, the frequency of the inquiry response signal is varied.