Nondestructive imaging using a split-ring resonator sensing apparatus

1. A defect sensing apparatus comprising:

a microstrip transmission line along a length of the defect sensing apparatus;

a reference split-ring resonator coupled to the microstrip transmission line, the reference split-ring resonator being located on a reference side of the microstrip transmission line;

a first sensing split-ring resonator coupled to the microstrip transmission line, the first sensing split-ring resonator being located on a sensing side of the microstrip transmission line; and

a second sensing split-ring resonator coupled to the microstrip transmission line, the second sensing split-ring resonator being located on the sensing side of the microstrip transmission line, wherein the microstrip transmission line is configured to excite the reference split-ring resonator, the first sensing split-ring resonator, and the second sensing split-ring resonator,

wherein the first sensing split-ring resonator and the second sensing split-ring resonator are configured to scan a sample.

2. The defect sensing apparatus of claim 1 wherein the sensing side of the microstrip transmission line is opposite from the reference side of the microstrip transmission line.

3. The defect sensing apparatus of claim 1 wherein the reference split-ring resonator, the first sensing split-ring resonator, and the second sensing split-ring resonator include an inner ring and an outer ring.

4. The defect sensing apparatus of claim 3 wherein the outer ring of the first sensing split-ring resonator and the second sensing split-ring resonator includes an extended tip.

5. The defect sensing apparatus of claim 4 wherein the extended tip is extended in a direction opposite from the microstrip transmission line.

6. The defect sensing apparatus of claim 3 wherein:

the inner ring includes a first gap directed toward the microstrip transmission line, and

the outer ring includes a second gap directed opposite the first gap.

7. The defect sensing apparatus of claim 1 further comprising a third sensing split-ring resonator coupled to the microstrip transmission line and located on the sensing side of the microstrip transmission line.

8. The defect sensing apparatus of claim 1 wherein the first sensing split-ring resonator resonates at a first frequency and the second sensing split-ring resonator resonates at a second frequency, and wherein the first frequency is different from the second frequency.

9. The defect sensing apparatus of claim 1 further comprising:

at least one processor and a memory in data communication with the defect sensing apparatus, wherein:

the memory stores instructions for execution by the at least one processor and

the instructions include:

measuring a first frequency of the first sensing split-ring resonator;

storing the first frequency as a first resonant frequency;

for a predetermined period, measuring a subsequent first frequency of the first sensing split-ring resonator; and

in response to the subsequent first frequency shifting by a predetermined threshold from the first resonant frequency within the predetermined period, generating an alert.

10. The defect sensing apparatus of claim 9 wherein the instructions include:

measuring a second frequency of the second sensing split-ring resonator;

storing the second frequency as a second resonant frequency;

for the predetermined period, measuring a subsequent frequency of the second sensing split-ring resonator; and

in response to the subsequent second first frequency shifting by the predetermined threshold from the second resonant frequency within the predetermined period, generating the alert.

11. The defect sensing apparatus of claim 9 wherein the instructions include:

measuring a reference frequency of the reference split-ring resonator;

storing the reference frequency; and

in response to the first frequency shifting by the predetermined threshold from the reference frequency within the predetermined period, generating the alert.

12. A defect sensing system comprising:

a first sensing split-ring resonator, a second sensing split-ring resonator, and a reference sensing split-ring resonator mounted on a board, the board including a microstrip transmission line separating the reference sensing split-ring resonator;

at least one processor; and

a memory, wherein the memory stores a measured frequency database and instructions for execution by the at least one processor, the instructions include:

measuring (i) a first frequency of the first sensing split-ring resonator and (ii) a second frequency of the second sensing split-ring resonator;

storing, in the measured frequency database, the first frequency and the second frequency;

repeating measuring (i) the first frequency and (ii) the second frequency;

comparing the measured first frequency to the stored first frequency;

comparing the measured second frequency to the stored second frequency; and

in response to the comparison indicating a first frequency shift or a second frequency shift by a predetermined threshold, generating and transmitting an alert.

13. The defect sensing system of claim 12 further comprising:

a display interface,

wherein the instructions include:

repeating the measuring for a predetermined period;

plotting the measured first frequency and the measured second frequency on a frequency graph; and

displaying the frequency graph on the display interface.

14. The defect sensing system of claim 12 wherein the instructions include:

measuring a reference frequency of the reference sensing split-ring resonator, wherein the measured first frequency is compared to the measured reference frequency and, in response to the comparison indicating the first frequency shift by a first reference predetermined threshold, generating a reference alert.

15. The defect sensing system of claim 12 wherein the instructions include:

measuring a reference frequency of the reference sensing split-ring resonator, wherein the measured second frequency is compared to the measured reference frequency and, in response to the comparison indicating the second frequency shift by a second reference predetermined threshold, generating a reference alert.

16. The defect sensing system of claim 12 wherein the reference sensing split-ring resonator, the first sensing split-ring resonator, and the second sensing split-ring resonator include an inner ring and an outer ring.

17. The defect sensing system of claim 16 wherein the outer ring of the first sensing split-ring resonator and the second sensing split-ring resonator includes an extended tip.

18. The defect sensing system of claim 17 wherein the extended tip is extended in a direction opposite from the microstrip transmission line.

19. The defect sensing system of claim 16 wherein:

the inner ring includes a first gap directed toward the microstrip transmission line, and

the outer ring includes a second gap directed opposite the first gap.

20. A defect sensing apparatus comprising:

a microstrip transmission line along a length of the defect sensing apparatus, wherein the microstrip transmission line includes a first port and a second port, the second port being located on an opposite end from the first port;

a reference split-ring resonator coupled to the microstrip transmission line;

a first sensing split-ring resonator coupled to the microstrip transmission line;

a second sensing split-ring resonator coupled to the microstrip transmission line, wherein the microstrip transmission line is configured to excite the reference split-ring resonator, the first sensing split-ring resonator, and the second sensing split-ring resonator;

at least one processor; and

a memory in data communication with the microstrip transmission line, via the first port and the second port, and the at least one processor, wherein the memory stores instructions for execution by the at least one processor and the instructions include:

measuring (i) a first frequency of the first sensing split-ring resonator and (ii) a second frequency of the first sensing split-ring resonator;

storing the first frequency and the second frequency;

repeating measuring (i) the first frequency and (ii) the second frequency;

comparing the measured first frequency to the stored first frequency;

comparing the measured second frequency to the stored second frequency; and

in response to the comparison indicating a first frequency shift or a second frequency shift, generating and transmitting an alert.