FREQUENCY DOUBLING ANTENNA SENSOR FOR WIRELESS STRAIN AND CRACK SENSING

• US 20150047436A1
• Filed: 08/13/2014
• Published: 02/19/2015
• Est. Priority Date: 08/13/2013
• Status: Active Grant

• Current Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Cook, Benjamin, Tentzeris, Manos, Yi, Xiaohua, Cho, Chunhee, Wang, Yang, Leon, Roberto T.
• Granted Patent: US 9,506,848 B2
• Time in Patent Office: Days
• US Class Current: 73/775
• CPC Class Codes: G01M 5/0033 by determining damage, crack or wear
• CPC Class Codes: G01M 5/0083 by measuring variation of impedance, e.g. resistance, capacitance, induction
• CPC Class Codes: G01N 3/02 Details

Abstract

A strain and crack sensor senses an amount of strain induced in an object. A receiving planar antenna has a first resonant frequency and is configured to receive a querying signal at the first resonant frequency. A transmitting planar antenna has a second resonant frequency that is twice the first resonant frequency. At least one of the receiving planar antenna and the transmitting planar antenna is bonded to the object so that at least one of strain induced in the object or a crack formed in the object causes a shift in at least one of the first resonant frequency or the second resonant frequency. A matching element is in electrical communication with the first planar antenna and the second planar antenna. The matching element is configured to cause the transmitting planar antenna to radiate a response signal in response to the querying signal.

Claims

1. A strain and crack sensor for sensing an amount of stress concentration induced in an object, comprising:

(a) a receiving planar antenna having a first resonant frequency and configured to receive a querying signal at the first resonant frequency;

(b) a transmitting planar antenna having a second resonant frequency that is twice the first resonant frequency, at least one of the receiving planar antenna and the transmitting planar antenna being bonded to the object so that strain induced in the object or a crack formed in the object causes a shift in at least one of the first resonant frequency or the second resonant frequency; and

(c) a matching element in electrical communication with the first planar antenna and the second planar antenna, the matching element configured to cause the transmitting planar antenna to radiate a response signal in response to the querying signal.

2. The strain and crack sensor of claim 1, wherein the receiving planar antenna has a greater surface area that the transmitting planar antenna.

3. The strain and crack sensor of claim 2, wherein the receiving planar antenna and the transmitting planar antenna comprise:

(a) a conductive ground plane;

(b) a dielectric layer disposed on the ground plane; and

(c) a conductive radiating layer disposed on the dielectric layer.

4. The strain and crack sensor of claim 2, wherein the receiving planar antenna and the transmitting planar antenna comprise:

(a) a plurality of dielectric layers disposed on the ground plane; and

(b) a plurality of conductive radiating layers interleaved with the plurality of dielectric layers.

5. The strain and crack sensor of claim 1, wherein the receiving planar antenna and the transmitting planar each comprise an antenna selected from a group of antennas consisting of:

patch antennas;

wideband antennas frequency selection surface (FSS) antennas, and combinations thereof.

6. The strain and crack sensor of claim 1, wherein the matching element comprises:

(a) a Schottky diode; and

(b) electromagnetic matching lines.

7. The strain and crack sensor of claim 6, wherein the Schottky diode has a cathode side and an anode side, wherein the cathode side is in electrical communication with the transmitting planar antenna and wherein the anode side is in electrical communication with the receiving planar antenna.

8. The strain and crack sensor of claim 7, wherein the Schottky diode comprises a GaAs Schottky diode.

9. The strain and crack sensor of claim 1, further comprising:

(a) a transceiver that is configured to radiate the querying signal and to receive the response signal;

(b) a spectrum analyzing circuit configured to detect the response signal frequency; and

(c) a processor configured to calculate the amount of strain induced in an object.

10. A sensing system for sensing a strain and a crack in an object, comprising:

(a) a receiving planar antenna having a first resonant frequency and configured to receive a querying signal at the first resonant frequency;

(b) a transmitting planar antenna having a second resonant frequency that is twice the first resonant frequency, at least one of the receiving planar antenna and the transmitting planar antenna being bonded to the object so that strain induced in the object or a crack formed in the object causes a shift in at least one of the first resonant frequency or the second resonant frequency;

(c) a matching element in electrical communication with the receiving planar antenna and the transmitting planar antenna, the matching element configured to cause the transmitting planar antenna to radiate a response signal in response to the querying signal, the matching element including a Schottky diode having a cathode side that is in electrical communication with the transmitting planar antenna and an anode side that is in electrical communication with the receiving planar antenna, the matching element also including electromagnetic matching lines; and

(d) a sensing unit, that includes;

(i) a transceiver that is configured to radiate the querying signal and to receive the response signal;

(ii) a spectrum analyzing circuit configured to detect the response signal frequency; and

(iii) a processor configured to calculate the amount of strain induced in an object.

11. The sensing system of claim 10, wherein the receiving planar antenna comprises a first patch antenna and wherein the transmitting planar antenna comprises a second patch antenna, the first patch antenna having a greater surface area that the second patch antenna.

12. The sensing system of claim 10, wherein the receiving planar antenna and the transmitting planar each comprise an antenna selected from a group of antennas consisting of:

patch antennas;

wideband antennas frequency selection surface (FSS) antennas, and combinations thereof.

13. The sensing system of claim 10, wherein the Schottky diode comprises a GaAs Schottky diode.

14. A method of sensing stain and a crack in an object, comprising the steps of:

(a) transmitting a querying signal having a first frequency to a receiving planar antenna that has a first resonant frequency;

(b) receiving a response signal from a transmitting planar antenna that has a second resonant frequency that is twice the first resonant frequency, where at least one of the receiving planar antenna and the transmitting planar antenna is bonded to the object so that at least one of strain in the object or the crack in the object will cause a frequency shift in the response signal;

(c) detecting an amount of frequency shift between the response signal frequency and twice the querying signal frequency; and

(d) determining an amount of strain or the presence of a crack based on the amount of frequency shift.

15. The method of claim 14, wherein the receiving planar antenna comprises a first patch antenna and wherein the transmitting planar antenna comprises a second patch antenna, the first patch antenna having a greater surface area that the second patch antenna.

16. The method of claim 14, further comprising the step of matching the transmitting planar antenna with the receiving planar antenna with a matching element, wherein the matching element comprises:

(a) a Schottky diode; and

(b) electromagnetic matching lines.

17. The method of claim 16, wherein the Schottky diode has a cathode side and an anode side, an further comprising the steps of electrically coupling the cathode side to the transmitting planar antenna and electrically coupling the anode side to the receiving planar antenna.

18. The method of claim 17, wherein the Schottky diode comprises a GaAs Schottky diode.