Dual-Polarized Microwave Imaging Probe

Near-field microwave imaging is increasingly finding utility for non-invasive inspection of various critical components in a wide range of industries. Conventionally, microwave imaging is performed using probes of linear electric field polarization such as a rectangular aperture probe excited with its dominant mode. Consequently, detecting polarized targets, e.g., cracks and highly conductive linear inserts, becomes challenging and highly dependent upon the orientation of the target with respect to the irradiating electric field vector. In practice, the orientation of the target could be unknown a priori. Hence, selecting a single suitable polarization is not always feasible. To address this challenge, a dual-polarized Teflon-loaded circular aperture-based microwave probe is proposed herein for imaging applications at 24 GHz. The proposed probe irradiates the target with two orthogonal polarizations and allows reconstructing the image using the average of the reflected signals due to these polarizations. The scattering parameters and electric field distribution of the proposed probe are analyzed using numerical electromagnetic simulations. A prototype of the proposed probe is fabricated and its characteristics are measured experimentally. The efficacy of the proposed imaging probe is demonstrated by acquiring phase and magnitude images of highly polarized targets. The images obtained using the proposed probe are compared to those obtained using a conventional open-ended rectangular waveguide probe. It is shown that unlike the conventional rectangular waveguide probe, the proposed probe could effectively detect polarized targets irrespective of their orientation.