Table 2 Comparison of microwave crack detection methods.
From: See through metallic sensor implemented using proximity resonant coupling
Ref. | Freq. (GHz) | Crack width (mm) | Lift-off (mm) | Key innovation | Probe type |
|---|---|---|---|---|---|
26.5–40 | 0.15 | 9 | Far-field | Rectangular waveguide aperture | |
1 | 1 | 1 | Far-field | Cutoff-cavity probe | |
0.8 | 0.25 | 1 | Resonant coupling | Spiral resonator | |
1.5–3.5 | 1 | 0 | Resonant coupling | Complementary Split-Ring Resonator | |
9.5 | 0.2 | 0.2 | Resonant coupling | Complementary split-ring resonators (CSRRs) | |
2–6 | 1.5 | 0 | Resonant scattering | Passive RFID sensor tag | |
3–5 | 1 | 0 | Resonant scattering | Passive RFID sensor tag | |
Present work* | 1.45 | 1 | 5 | - Resonant coupling exclusive to metal objects - Maximum lift-off detection limit upto 8 cm - Supports see-through wall metal detection | Ground-less circular patch resonator |
