Chang Hee Hyoung

This paper proposes a non-destructive method for measuring the complex permittivity of thick slab specimens using the Improved Open Waveguide (IOW) method based on the NRW Method. Conventional methods, generally effective only for thin materials, face significant challenges in accurately measuring the complex permittivity of thick slab specimens. This study addresses the limitations of prior methods by applying a disambiguation technique under non-magnetic conditions. The accuracy of the proposed methods was validated through numerical analysis and experimental results. Specifically, Measurements were conducted on paper specimens of varying thicknesses and a concrete block. For the paper specimens, the results closely matched reference values obtained using the Split Cylinder Resonator (SCR) method, a widely used standard for thin specimens. For the concrete block, numerical analysis was used to validate the derived complex permittivity, confirming the reliability of the proposed methods. While the IOW method relies on numerical analysis, which increases processing time, it provides reliable and accurate measurements of complex permittivity, particularly for specimens where sample preparation is challenging.

Generally, various technologies, including waveguide below cutoff (WBC), gasket sealing, and bonding, are employed in metallic enclosures to achieve the high electromagnetic shielding performance required for EMP protection and EMC countermeasures in shielding structures or facilities. While the shielding structure or facility is properly constructed and maintained according to design specifications, its electromagnetic shielding performance can remain at the required level, effectively protecting internal electrical and electronic equipment from external electromagnetic interference. However, unintended apertures often occur during the construction or maintenance of shielding facilities, compromising their shielding performance. Therefore, it is crucial to develop technologies that prevent shielding effectiveness degradation caused by both intentional and unintentional apertures. This paper proposes a structure incorporating a composite absorber (made of dielectric and magnetic absorber) within a double metal panel of enclosure featuring an aperture, aimed at maintaining and improving the facility’s shielding performance. The effectiveness of the proposed structure was validated through numerical simulation.

This paper presents a testbed for unshielded facilities utilizing planar electromagnetic absorbers. These slabs demonstrate comparable shielding effectiveness to that of reinforced concrete in the frequency range from 1 GHz to 6 GHz. The testbed serves as a platform for developing a measurement method to assess unshielded facilities. It can be configured with different materials that have various levels of shielding effectiveness. We evaluate the shielding effectiveness of the absorber slab and extract its electromagnetic parameters. The testbed is implemented in a semi‐anechoic chamber with inner dimensions of 3.00 × 3.06 × 2.50 m³. The electromagnetic wave attenuation for the unshielded facilities is defined as the ratio of received power within the assessment space relative to the incident power. The measurement results provide quantitative information on the attenuation of electromagnetic waves within unshielded facilities. The testbed configured with two types of incident planes is evaluated and compared with the mean attenuation and distribution characteristics.

This article presents the performance-enhanced and improved power balance (PEIPWB) method for predicting the shielding characteristics of large structures by electromagnetic waves. The PEIPWB method is an improvement method that considers the electrical properties and size of the structure, allowing for interpretation regardless of the size or medium of the target. To improve the method, the transmission coefficient of the medium is considered, and the amount of incident waves on the target is restricted through scaling methods. To verify accuracy and usefulness, the simulation results of WinProp, a 3-D simulation tool based on a ray-tracing method, and the PEIPWB method are compared for various large structures. Additionally, it is confirmed that the method can be applied to actual measurement environments by comparing the results with the measured data of a large structure. As a result, it was confirmed that the PEIPWB method can be used for simple and efficient interpretation using only the transmission coefficient of the target, the area of the incident surface, and the specifications of the transmitting and receiving antennas.

한국전자파학회논문지 (The Journal of Korean Institute of Electromagnetic Engineering and Science)

한국전자파학회논문지 (The Journal of Korean Institute of Electromagnetic Engineering and Science)

한국전자파학회논문지 (The Journal of Korean Institute of Electromagnetic Engineering and Science)

This paper proposes a field probe to measure the power density (PD) at a millimeter-wave (mmWave) frequency band. The proposed probe is composed of a loop antenna in which one end is terminated with a load resistor. Such a structure enables the simultaneous measurement of electric (E)- and magnetic (H)-fields: the E-field is measured at a gap where the load resistor is placed, and the H-field is measured through the loop antenna. The simultaneous measurement makes it possible to measure PD for an incident wave even in the near field region where the E- and H-fields have different phases from each other. The proposed probe is fabricated and evaluated for its PD measurement performance. The measurement results show that the probe measures PD with an error less than 1.3 dB. Owing to the near field measurement, the proposed probe is useful in measuring the human body exposure to electromagnetic fields (EMFs) that are generated by 5G mmWave base stations.

한국전자파학회논문지 (The Journal of Korean Institute of Electromagnetic Engineering and Science)