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1. Microwave Nondestructive Testing Using an Array of Near-Field Sensors

   Gao, Y; K Amineh, R; Ravan, M (July 2023, IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting July 23–28, 2023 • Portland, Oregon, USA)

   Microwave imaging has been a popular high resolution, non-invasive, and non-contact nondestructive testing (NDT) method for detecting defects and objects in non-metallic media with applications toward testing dielectric slabs, printed circuit board testing, biomedical diagnosis, etc. In this paper, we employ an array of microwave sensors designed based on the complementary split ring resonators (CSRR) along with nearfield holographic microwave imaging (NH-MWI) to assess the hidden features in the dielectric media. In this array, each element resonates at a different frequency in the range of 1 GHz to 10 GHz. Performance of the proposed method is demonstrated via simulation and experimental results. 

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2. A Low-Cost and Compact Three-Dimensional Microwave Holographic Imaging System

   https://doi.org/10.3390/electronics8091036  

   Wu, Hailun; Amineh, Reza K. (September 2019, Electronics)

   With the significant growth in the use of non-metallic composite materials, the demands for new and robust non-destructive testing methodologies is high. Microwave imaging has attracted a lot of attention recently for such applications. This is in addition to the biomedical imaging applications of microwave that are also being pursued actively. Among these efforts, in this paper, we propose a compact and cost-effective three-dimensional microwave imaging system based on a fast and robust holographic technique. For this purpose, we employ narrow-band microwave data, instead of wideband data used in previous three-dimensional cylindrical holographic imaging systems. Three-dimensional imaging is accomplished by using an array of receiver antennas surrounding the object and scanning that along with a transmitter antenna over a cylindrical aperture. To achieve low cost and compact size, we employ off-the-shelf components to build a data acquisition system replacing the costly and bulky vector network analyzers. The simulation and experimental results demonstrate the satisfactory performance of the proposed imaging system. We also show the effect of number of frequencies and size of the objects on the quality of reconstructed images. 

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3. Fast and Robust Capacitive Imaging of Cylindrical Non-Metallic Media

   https://doi.org/10.3390/magnetism1010006  

   Raisa, Noshin; Gao, Yuki; Ganesh, Mahindra; Ravan, Maryam; Amineh, Reza K. (December 2021, Magnetism)

   In this paper, a unique approach to the imaging of non-metallic media using capacitive sensing is presented. By using customized sensor plates in single-ended and differential configurations, responses to hidden objects can be captured over a cylindrical aperture surrounding the inspected medium. Then, by processing the acquired data using a novel imaging technique based on the convolution theory, Fourier and inverse Fourier transforms, and exact low resolution electromagnetic tomography (eLORETA), images are reconstructed over multiple radial depths using the acquired sensor data. Imaging hidden objects over multiple depths has wide range of applications, from biomedical imaging to nondestructive testing of the materials. Performance of the proposed imaging technique is demonstrated via experimental results. 

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4. Fourier-Space Image Reconstruction Using Microwave Measurements: The Path Toward Real-Time Microwave and Millimeter-Wave Imaging

   https://doi.org/10.1109/MMM.2024.3403047  

   Amineh, Reza K; Nikolova, Natalia K (August 2024, IEEE Microwave Magazine)

   The use of electromagnetic waves at microwave and millimeter-wave (mm-wave) frequencies in imaging has been growing rapidly in the last two decades with applications in security screening, biomedical imaging, nondestructive testing, and the inspection of goods and packages. The nonionizing nature of the radiation renders microwave and mm-wave imaging (MMI) safe for humans and, thus, attractive, especially for frequent imaging of living tissue and humans. At the same time, the radiation penetrates many materials, which are optically opaque: e.g., fog and foliage, soil and living tissue, brick and drywall, wood, fabrics, and plastics. Importantly, modern MMI systems offer compact and relatively low-cost hardware due to advancements in high-frequency microelectronics. 

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5. Fast, Robust, and Low-Cost Microwave Imaging of Multiple Non-Metallic Pipes

   https://doi.org/10.3390/electronics10151762  

   Gao, Yuki; Ravan, Maryam; K. Amineh, Reza (August 2021, Electronics)

   The use of non-metallic pipes and composite components that are low-cost, durable, light-weight, and resilient to corrosion is growing rapidly in various industrial sectors such as oil and gas industries in the form of non-metallic composite pipes. While these components are still prone to damages, traditional non-destructive testing (NDT) techniques such as eddy current technique and magnetic flux leakage technique cannot be utilized for inspection of these components. Microwave imaging can fill this gap as a favorable technique to perform inspection of non-metallic pipes. Holographic microwave imaging techniques are fast and robust and have been successfully employed in applications such as airport security screening and underground imaging. Here, we extend the use of holographic microwave imaging to inspection of multiple concentric pipes. To increase the speed of data acquisition, we utilize antenna arrays along the azimuthal direction in a cylindrical setup. A parametric study and demonstration of the performance of the proposed imaging system will be provided. 

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