Heterogeneous networks (HetNets) which combine with macrocell and picocell in the same coverage are key technology to increase the system capacity. Millimeter wave (mmWave) technology is expected to achieve higher data rates or user throughput in fifth-generation (5G) mobile systems. In HetNets, cell range expansion (CRE) technique, which virtually expands the picocell coverage using cell selection offset (CSO), is very important. In this paper, we investigate average and 5-percentile user throughput of the mmWave HetNets using three-sector picocell as a function of CSO in the CRE using system-level computer simulations. We also compare the throughput with those of non-sector picocell, i.e., omni picocell. We confirmed that a CSO of 36 dB can provide the best performance, assuming that the signal bandwidth of picocell is 10 times wider than that of microcell. We also confirmed that the proposed “three-sector picocell” can improve the average and 5-percentile user throughputs by 2.1 and 1.8 times, respectively, compared with conventional “omni picocell”.

Vital signs measurement with phase analysis for mm-wave FMCW radar contains various kinds of noise. In this research, a phase accumulation-linear interpolation (PA-LI) method for mm-wave FMCW radar is proposed, which can quickly and efficiently reduce phase noise and improve the SNR of the radar vital sign before EMD/EEMD processing. Experimental results show that the proposed method can accurately extract the heartbeat signal with high SNR and the HR estimation is more accurate.

In this paper, a monopulse direction of arrival (DOA) estimation circularly polarized microstrip array antenna integrated with magic-Ts is proposed and its characteristics are investigated. The proposed antenna based on the monopulse system has a compact structure effectively utilizing an integration technology with microwave circuits. As the DOA estimation with a monopulse system is one of the attractive methods to realize a tracking function, the proposed antenna is suitable for communication systems which require the tracking function, such as the vehicle-to-vehicle (V2V) direct communications.

A general expression for the waveguide dispersion of a propagation mode is derived from the wave equation. Furthermore, a simple expression for the waveguide dispersion of high-order modes is derived as a function of the mode field radius by substituting an approximated function of the electrical field distribution of the mode into the general expression. The chromatic dispersions of the LP₀₁, LP₁₁, LP₀₂, and LP₂₁ modes in a four-mode fiber are estimated using the proposed expression, and their accuracies are evaluated through simulations.

In this study, we describe the design of a misalignment-resistant capacitive coupler under fresh water. The two main issues discussed in this study are: the relation between misalignment and efficiency when using a typical capacitive coupler, and the design of a misalignment-resistant capacitive coupler. Theoretical calculation and analytical results show no relation between misalignment and transmission efficiency in terms of monotonic reduction. Further, the relation between misalignment and transmission efficiency is discussed with respect to the coupling coefficient. Finally, we establish the design guideline using coupling factors that take into account misalignment and design a misalignment-resistant capacitive coupler.

Many automotive accidents are reported every year, some of which are attributed to fallen debris on road. For road debris detection, it would be difficult to find with imaging sensor while driving, especially in case of bad weather conditions such as rain and fog. The use of 79GHz-band ultra-wideband automotive radar is hence expected for road debris detection because of the high range-resolution and good weather resistance. The detection performance basically depends on the radar cross section (RCS) of road debris. For example, the maximum detection range is proportional to one quarter of the RCS. However, there is no report regarding to the RCS as far as the authors know. This paper presents the RCS characteristics of 11 typical road debris for 79GHz-band radar available in automotive radar which is also compared with 24GHz-band.

We investigated a novel demodulation technology based on our proposed electrical butterfly operation scheme which compensates for optical nonlinear distortion of conventional single-sideband (SSB) signals. In the scheme, phase-conjugated twin signals are transmitted as lower sideband (LSB) and upper sideband (USB) components of a dual sideband (DSB) signal modulated by a simple Mach-Zehnder modulator (MZM). The performance was evaluated by numerical simulation of 4-ary amplitude shift keying (4ASK) signals transmitted over a 100-km standard single mode fiber (SSMF). The error vector magnitude (EVM) was improved by about 20% when the input power was 10dBm, compared with a conventional SSB-4ASK signal.

In this paper, we propose loading layers of slit pairs with half-wavelength spacing over a corporate-feed waveguide slot array antenna in the 30 GHz band. This structure is expected to improve the isolation between transmitting and receiving antennas arranged in the E-plane. As a result of the design, the reflection of the radiating element is suppressed under -14 dB over a target band (27.8 GHz - 31.4 GHz). The isolation between two antennas using a 2×32-element model is improved by about 20 dB compared to the conventional structure without the slit-pair layers. We demonstrate this result by measurement using 64×32-element arrays.

Ultra-dense radio access network (RAN) with distributed multi-user multi-input multi-output (MU-MIMO) is considered as a promising approach to improve the coverage and link capacity. However, its prohibitively high computational complexity impacts its further extension and application. Our previous work has proved that forming users/antennas clusters can greatly alleviate the computational complexity, but the inter-cluster interference is produced, thereby reducing the spectrum efficiency. In this paper, we propose a graph coloring algorithm-based inter-cluster interference coordination for ultra-dense RAN with distributed MU-MIMO. It is confirmed by computer simulation that our proposed algorithm can improve both the sum capacity and the user capacity compared with no coloring case.