No abstract

Employing circular aperture probes for microwave imaging in the near-field has been proven to render high resolution images of a variety of samples under test (SUT) when compared to the conventionally utilized rectangular aperture probes. In this paper, it is proposed to further enhance the near-field imaging resolution and sensitivity by loading the circular aperture (operating in the K-band frequency range) with a resonant iris. It is shown that the probe exhibits a confined and localized near-field distribution close to the iris opening, thereby improving its resolution and sensitivity. The design and analysis of the probe presented herein are aided by 3D electromagnetic simulations and validated experimentally. The spatial resolution of the probe is established through line scans of the probe over a pair of targets interspaced at known distances. To further demonstrate the utility of the probe in critical non-destructive testing (NDT) applications, a manufactured prototype is devised to detect cracks on metal structures and map corrosion areas hidden under paint layers. It is shown here that the proposed probe provides significant resolution and sensitivity improvement over the un-loaded circular aperture probe. Specifically, for crack detection, the proposed probe provides two-fold and more than three-fold improvement in the resolution and sensitivity, respectively. For corrosion mapping, the proposed probe yields 2 to 5 times higher image signal-to-noise ratio compared to the unloaded aperture probe.

No abstract

The integration of antennas in composite structures is gaining popularity with advances in wireless communications and the ever-increasing demands for efficient smart structures. Efforts are ongoing to ensure that antenna-embedded composite structures are robust and resilient to inevitable impacts, loading and other external factors that threaten the structural integrity of these structures. Undoubtedly, the in situ inspection of such structures to identify anomalies and predict failures is required. In this paper, the microwave non-destructive testing (NDT) of antenna-embedded composite structures is introduced for the first time. The objective is accomplished using a planar resonator probe operating in the UHF frequency range (~525 MHz). High-resolution images of a C-band patch antenna fabricated on an aramid paper-based honeycomb substrate and covered with a glass fiber reinforced polymer (GFRP) sheet are presented. The imaging prowess of microwave NDT and its distinct advantages in inspecting such structures are highlighted. The qualitative as well as the quantitative evaluation of the images produced by the planar resonator probe and a conventional K-band rectangular aperture probe are included. Overall, the potential utility of microwave NDT for the inspection of smart structures is demonstrated.