This letter presents a novel method for designing the radiating elements of a corporate-feed array antenna using eigenmode analysis. This approach numerically determines the eigenmodes, resonant frequencies, and radiation Q-factors of the radiating elements, enabling their evaluation without requiring impedance matching. A printed circuit board (PCB) slit array antenna structure was designed with three eigenmodes contributing to the primary polarization and low radiation Q-factors. Through parameter optimization, a 300-GHz-band antenna was designed, achieving a 24% bandwidth while satisfying manufacturing constraints of a PCB process. The proposed method offers a universal approach for realizing wideband performance in various antenna designs.

This letter presents a numerical method for analyzing the radiation characteristics of beam-steering folded reflectarray (FRA) antennas. With the aid of the fast Fourier transform, near-field to near-field transformation between the two surfaces constituting the FRA antenna, as well as the computation of the co- and cross-polar far-field patterns and directivity, are performed computationally efficiently using the plane-wave spectrum. The proposed method was used to analyze a beam-steering FRA antenna with a 16-λ diameter (λ: wavelength). The radiation characteristics were computed in the order of milliseconds.

For the faster and higher capacity communication using higher frequencies in Beyond 5G era, we have proposed the switched analog radio over fiber (Switched-RoF) system, in which optical switches are inserted between antennas and Central units (CUs)/ Distributed units (DUs), in order to efficiently use and provide additional features to a large number of small optically powered antennas using the power over fiber technology with the hollow core fiber. One of the features of Switched-RoF is DU aggregation, which reduces system power consumption by optical path switching. This paper presents analytical results of the effectiveness of Switched-RoF in terms of power consumption and call blocking rate based on two different user equipment distribution scenarios.

An ultra-high splitting ratio passive optical network (PON) architecture using a hollow-core fiber cable has been proposed. To verify whether existing PON implementation is applicable to emulate the proposed architecture using the small number of actual equipment environment, we examined commercially available 10Gbps Ethernet PON (10G-EPON) equipment. The verification was performed by configuring a dual-fiber transmission 10G-EPON with a maximum distance difference of 11km between the upstream and downstream fibers. We report that we confirm the stable operation of dynamic bandwidth allocation under high load conditions with actual traffic flows.