Development of a High-Sensitivity Millimeter-Wave Radar Imaging System for Non-Destructive Testing

• Published in: Sensors
• Main Authors: Murakami, Hironaru, Fukuda, Taiga, Otera, Hiroshi, Kamo, Hiroyuki, Miyoshi, Akito
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG
• Subjects: millimeter wave; SAR; MIMO; imaging; NDT; radar module; taiga
• Online Access: https://doi.org/10.3390/s24154781; https://ir.library.osaka-u.ac.jp/repo/ouka/all/97289/Sensors_24_15_4781.pdf

Murakami Hironaru, Fukuda Taiga, Otera Hiroshi, et al. Development of a High-Sensitivity Millimeter-Wave Radar Imaging System for Non-Destructive Testing. Sensors 24, 4781 (2024); https://doi.org/https://doi.org/10.3390/s24154781. There is an urgent need to develop non-destructive testing (NDT) methods for infrastructure facilities and residences, etc., where human lives are at stake, to prevent collapse due to aging or natural disasters such as earthquakes before they occur. In such inspections, it is desirable to develop a remote, non-contact, non-destructive inspection method that can inspect cracks as small as 0.1 mm on the surface of a structure and damage inside and on the surface of the structure that cannot be seen by the human eye with high sensitivity, while ensuring the safety of the engineers inspecting the structure. Based on this perspective, we developed a radar module (absolute gain of the transmitting antenna: 13.5 dB; absolute gain of the receiving antenna: 14.5 dB) with very high directivity and minimal loss in the signal transmission path between the radar chip and the array antenna, using our previously developed technology. A single-input, multiple-output (SIMO) synthetic aperture radar (SAR) imaging system was developed using this module. As a result of various performance evaluations using this system, we were able to demonstrate that this system has a performance that fully satisfies the abovementioned indices. First, the SNR in millimeter-wave (MM-wave) imaging was improved by 5.4 dB compared to the previously constructed imaging system using the IWR1443BOOST EVM, even though the measured distance was 2.66 times longer. As a specific example of the results of measurements on infrastructure facilities, the system successfully observed cracks as small as 0.1 mm in concrete materials hidden under glass fiber-reinforced tape and black acrylic paint. In this case, measurements were also made from a distance of about 3 m to meet the remote observation requirements, but the radar module with ...