Intermodulation sensor platform based on mechanical resonator

• US 20150128707A1
• Filed: 05/22/2013
• Published: 05/14/2015
• Est. Priority Date: 05/22/2012
• Status: Active Grant

• Current Assignee: Teknologian tutkimuskeskus VTT Oy
• Original Assignee: Teknologian tutkimuskeskus VTT Oy
• Inventors: Viikari, Ville, Sepp, Heikki
• Granted Patent: US 10,145,729 B2
• Time in Patent Office: Days
• US Class Current: 73/584
• CPC Class Codes: G01H 13/00 Measuring resonant frequency
• CPC Class Codes: H04B 1/28 the receiver comprising at least one semiconductor device having three or more electrodes

Abstract

The present invention related to a new passive wireless sensor platform which is based on the intermodulation communication principle. The platform may utilize a quartz crystal or other mechanical resonator. Additionally, the platform allows for a narrow bandwidth and/or ID-code of a sensor. Certain embodiments enable high frequencies and large read-out distances. It facilitates a generic sensor element and can thus be used to monitor virtually any quantity. Additionally, it offers a means to realize a wireless passive sensor using MEMS sensor technology.

Claims

1. A wireless sensor comprising;

an antenna,

a mixing element electrically connected to the antenna and to a low-frequency circuit, and

wherein the low frequency circuit comprises a mechanical resonator, and a sensing element.

2. A wireless sensor according to claim 1, wherein the mixing element is a Schottky diode.

3. A wireless sensor according to claim 1, wherein the mechanical resonator comprises a quartz crystal or MEMS resonator.

4. A wireless sensor according to claim 1, wherein the sensing element is a capacitive sensor element, resistive sensor element or inductive sensor element.

5. A wireless sensor according to claim 1, further comprising at least one additional mechanical resonator and sensing element pair.

6. A wireless sensor according to claim 5, wherein the mechanical resonator of each pair resonates at a unique frequency.

7. A wireless sensor according to claim 1, wherein the wireless sensor does not contain a battery.

8. A wireless sensor according to claim 1, wherein the antenna acts as the sole voltage source for the wireless sensor.

9. A wireless sensor according to claim 1, wherein the wireless sensor is a passive wireless sensor.

10. A wireless sensor according to claim 1, wherein the mixing element is coupled to the mechanical resonator and is capable of providing excitation to the mechanical resonator at the difference of two distinct received signal frequencies.

11. A wireless sensor according to claim 1, wherein the mixing element is capable of mixing a voltage modified by a mechanical resonator and sensing element pair with one of at least two signals received by the antenna.

12. A wireless sensor according to claim 1, wherein the antenna is coupled to the mixing element and is capable of receiving signals at least two distinct frequencies simultaneously and re-transmitting a modified form of at least one of said received signals.

13. A wireless sensor according to claim 1, wherein the mixing element and sensing element are separate elements.

14. A wireless sensor according to claim 1, wherein the antenna is coupled with a first matching circuit.

15. A wireless sensor according to claim 1, wherein the mixing element is coupled with a second matching circuit.

16. A method of wirelessly reading a sensor element comprising the steps of;

transmitting two signals from a reading device to a wireless sensor, wherein each signal is transmitted at a different frequency,

wherein the difference between the two signal frequencies induces an excitation of a mechanical resonator coupled to a sensing element,

receiving an intermodulation response from the wireless sensor,

determining the impedance of a sensing element based on the received intermodulation response, and

providing a readout of the sensor element based on the determined impedance and known resonance of the mechanical resonator coupled to the sensing element.

17. A method according to claim 16, wherein determining the impedance includes measuring the intermodulation response across a frequency range.

18. A method according to claim 16, wherein the difference between the frequencies of the two transmitted signals is between 0.1-100 kHz.