Won-Ho Choi

This paper investigates different dc-link voltage control strategies in a three-phase four-wire LC coupling hybrid active power filter (LC -HAPF) for reactive power compensation. By using direct current (current reference) pulsewidth modulation (PWM) control method, to achieve dc-link voltage self-charging function during LC -HAPF start-up process, the dc-link voltage control signal feedback as reactive current component is more effective than the traditional method as an active current componen

In this study, first, a circuit analog (CA) absorber consisting of a periodic pattern resistive sheet, glass-fiber/epoxy composite as a spacer, and carbon fabric composite was applied to the leading edge of a wing-shaped structure to reduce the echo radar cross section (RCS). This CA absorber was designed in a flat-plate shape through a parametric study that was performed to optimize the device in the X-band (8.2-12.4 GHz). The reflection loss of the fabricated flat-plate CA absorber was measure

A novel broadband microwave absorber design concept using a honeycomb sandwich structure is proposed. Unlike the conventional microwave absorbing honeycomb sandwich structure, the newly proposed design concept uses the transverse direction of a honeycomb structure with a coated lossy material. When the incident waves reach the inside of the honeycomb coated with the lossy material, multiple scattering occurs inside the honeycomb due to the two different refractive indices. Then, the trapped elec

This paper presents a simple line coupler with adaptive impedance matching between the output impedance of the amplifier for signaling and the access impedance of the power line. The proposed line coupler that is suitable for amplitude shift keying (ASK) or phase shift keying (PSK) modems at the CENELEC B,C and D bands provides the simple structure and simple control. In this paper, the method that control variable components of the line coupler is used. In order to verify the effect of the prop

A new design concept of a wideband radar absorbing structure consisting of load‐bearing glass/MWCNT added epoxy composite and having low density/lightweight characteristics for C‐ to X‐band and X‐ to Ku‐band radar is presented. The proposed radar absorbing structures have triple layers which are the low density and light weight layer to reduce the total weight, covering layers to protect the foam layer from humidity absorption, and a load‐bearing layer as the actual structural layer. The propose

In this study, a novel broadband radar absorbing volume structure (RAVS) is proposed and demonstrated with a practical point of view from design to fabrication. The proposed RAVS uses a design concept of repeatedly stacked carbon nanotube (CNT) composites and foam cores of the same thickness to improve the applicability to real structures while maintaining absorption performance. The repeatedly stacked CNT composites, which act as electrically lossy materials, result in the multiple scattering o