In this paper, a millimeter wave (mmWave) transmission technology applying a waffle-iron ridge guide (WRG) technology is described. A circuit layer is molded on an aluminum plate and an acrylonitrile butadiene styrene (ABS) plate using precision machine cutting technology. The ABS resin layer would be copper plated to get conductivity. Insertion loss (IL) in the 79 GHz band is approximately 0.4 to 0.6 dB (/30mm), the performance of the copper plated product is better. The skin effect (in consideration of surface roughness) is also mentioned using 3D EM simulator. The simulation results and the measurement results are in good agreement.
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 its high-directivity and high-gain antenna proved to be more sensitive in detecting crack structures than measurements made from a distance of 780 mm. In order to estimate the penetration length of MM waves into concrete, an experiment was conducted to measure the penetration of MM waves through a thin concrete slab with a thickness of 3.7 mm. As a result, Λ
Since the series fed microstrip patch array antenna has low feeding loss, it is especially effective for the millimeter wave application. In order to realize an array antenna with a high gain, low sidelobe level, and low VSWR, we have optimized the width and element spacing for each patch antenna by the parato genetic algorithm. As for such an evolution method as genetic algorithm, the calculation load is enormous. In this paper, to reduce the load, these parameters are optimized by a coarse mesh. After optimization, we check the performance by a fine mesh. By numerical simulation of a planar array, we confirmed the effectiveness of the proposed method.
Novel automotive radar of 76 GHz band has been manufactured and the field tests have been successfully carried out. The radar features by applying SAGE algorithm to the multi-beam dielectric lens. For simple structure and small size, we used a patch array antenna as feed. Under severe constraints of the size, the lens shape has been designed by multi-objective genetic algorithm. Through the field test, it is confirmed that 2 targets separated by 3.5m can be resolved over the range from 20m to 80m.
The development of non-destructive testing (NDT) methods for infrastructure facilities and residential buildings that may affect human life is urgent to prevent collapse due to aging or damage in the event of earthquakes and other events. In this study, we developed a single-input and multiple-output (SIMO) synthetic aperture radar (SAR) imaging system using a high-sensitivity millimeter-wave (MM-wave) array antenna module with high directivity and absolute gains of 13.5 dB and 14.5 dB for the transmit and receive antennas, respectively. After various performance evaluations, we successfully demonstrated the usefulness of this system in NDT. Specifically, we observed cracks hidden by fiberglass tape and black acrylic paint during measurements on concrete materials. In addition, we demonstrated the transmission performance of the MM-wave against a thin concrete plate and obtained the attenuation distance Λ_exp=6.0 mm. Furthermore, in the experiment using composite materials consisting of ceramic tiles and a refractory board bonded together, and another experiment using composite plywood which is used in ordinary residential construction materials in Japan, we were able to observe defects in the internal structure that are invisible to the human eye through a perspective view.
We have examined application of a planar patch array antenna to a multi-beam antenna of dielectric lens. Under several constraints of structure, the lens shape has been designed by the multi-objective genetic algorithm. We demonstrate that the designed antenna has high gain and low sidelobe for each beam through the trial manufacturing model and evaluation.
