This paper presents novel design procedures for a decoupling circuit, utilizing the coupling between antennas. The proposed decoupling circuit consists of, a Band-Stop Filter (BSF) based on Coupling Matrix Synthesis (CMS) theory, a pair of matching circuits, and microstrip connecting lines. By inserting a BSF into an antenna pair, high isolation can be achieved. By utilizing coupling between antennas, the proposed BSF can be designed only using 2 parallel resonators based on the CMS theory. To maintain impedance matching of patch antennas, a pair of matching circuits is inserted after the BSF for each port. Lastly, the decoupling circuit model was fabricated. The experimental results have a good agreement with the simulation result and the validity of the proposed design method is confirmed.

In this paper, we design one-dimensional (1D) magneto-metasurface for THz isolator application. In this optimization, frequency domain finite element method (FD-FEM) with periodic boundary condition (PBC) is employed as a numerical simulation method and two kinds of evolutionary algorithms were used to optimize design parameters. In order to optimize two objectives to maximize unidirectional transmission and isolation ratio, we propose a novel objective function using ELU function. The results show that designed metasurface isolator with relatively simple structure can realize unidirectional transmission. In addition, it is demonstrated that angular characteristics is improved by optimizing DC magnetic field and operating temperature.

We present first-time demonstration of short-reach and low-latency optical communication within a real network, employing a microresonator frequency comb as a light source. The modulated signal is transmitted through a 9-km single-mode optical fiber installed in a metropolitan network. This demonstration paves the way for realizing low-latency massively parallel optical communication, which is the key to beyond-5G and 6G network. For a proof-of-concept experiment, we employ an MgF₂ crystalline microresonator with a 20-GHz free-spectral range that could be used for dense wavelength division multiplexing communication. We generated a stable soliton comb and modulated it with simple 10-Gbps intensity modulation and direct detection to achieve a small excess delay of 3.1 μs.

In this paper, a position-aided beam training (PBT) in millimeter wave (mmWave) non-orthogonal multiple access (NOMA) systems method is proposed. Position information can be used to compute the angle of beam pointing and essentially eliminate the beam alignment overhead. Based on the angle, a clustering method based on k-means is conducted to cluster users. After clustering, the beamforming method based on the cluster center is developed to reduces interference between each cluster. Finally, power allocation for downlink NOMA is put forward to maximize sum rate with user position information. Simulation analysis confirm the superiority of the proposed method over the conventional ones in performance.

This study explores the use of a commercially available polymer optical fiber within an axially aligned offset-free single-mode-multimode-single-mode (SMS) structure for twist sensing. We analyze the transmitted light spectral response to twist angles from -360° to 360°, identifying distinct behaviors for clockwise and counterclockwise twists. Focusing on two specific wavelengths, we demonstrate that this configuration can effectively measure both the magnitude and direction of twists.

This paper proposes a jig structure for a large-diameter coaxial-feed type stepped cut-off circular waveguide to enable accurate measurement of permittivity for liquids with good repeatability in the MHz band. The jig combines an N connector and a metal sample holder with an inner diameter slightly larger than that of the connector flange’s outer conductor. The accuracy of S₁₁ evaluation under short termination conditions was improved by this construction. To verify the validity of the proposed structure, several jig sets and short metal rods for S₁₁ calibration were made. S₁₁ was measured multiple times using the VNA when the jig tip was short, open, and with a reference material inserted (here, pure water), with methanol and ethanol as unknown liquids. The permittivity of each liquid was estimated by substituting the measured S₁₁ value above into a formula involving comparison with SOM termination (short/open conditions and a known material). The liquid estimation results obtained were compared with those evaluated based on an inverse problem via MMT (mode-matching technique), with results showing good agreement, simple and stable evaluation with little variation over multiple dielectric evaluations at low frequency.