Ryosuke Hasaba

This work presents a D-band high-power-density four-element phased-array transceiver for 6G user equipment (UE). Conventional designs require large multi-stage LO generation circuits for D-band up/down conversion, making it difficult to achieve compact size and low-power consumption. To address this, we propose an integrated LO chain using an injection-locked tripling phase shifter (ILTPS), which enables both frequency tripling and phase shifting within a single circuit without multi-stage amplifiers. The ILTPS achieves an area of 0.088 mm² and a power consumption of 15 mW. In addition, to realize high power density, the transceiver integrates a bi-active sub-harmonic mixer (BA-SHM) and a D-band PA/LNA with PA-sharing TDD switching. An eight-element antenna-in-package (AiP) module using two transceiver ICs operates in the 142–164-GHz frequency range, achieving an EIRP of 25.7 dBm and a maximum data rate of 56 Gbps. The power consumption per element is 150 mW in TX mode and 93 mW in RX mode with 1 V VDD. The active area of this transceiver is 8.5 mm², and it is implemented using a 65 nm CMOS process.

Sub-terahertz (Sub-THz) communication systems are a promising technology for next-generation high-speed, high-capacity wireless networks. Achieving this requires highly integrated antenna-in-package (AiP) solutions combining antennas and radio frequency integrated circuits (RFICs). However, high-frequency operation and dense integration increase RFIC heat density, potentially degrading AiP performance and reliability. This article proposes a sub-THz AiP with both excellent RF and thermal performance. The design features a multilayer antenna structure on a low-loss dielectric substrate, minimizing RFIC-to-antenna connections and radiating toward the substrate edge. A dual-sided heat dissipation structure is also introduced for efficient thermal management in stacked configurations. Validation through simulations and measurements confirmed good reflection characteristics ( $\vert $ S $11\vert \lt $ –10 dB), 15 dBi gain, and thermal resistance below 4.1 K/W. 2-D beam steering was also demonstrated, highlighting the effectiveness of the proposed co-design approach.

To realize the practical application of sub-THz band wireless communication toward 6G, it is necessary to develop AiP modules with compact size and low cost. This letter discusses the design of a miniaturized AiP module for high-speed wireless communication targeting extended reality (XR) applications in medical operating rooms as an example of 6G use cases. By integrating waveguide antenna array along with a compact divider/combiner within the multilayer substrates, the module achieves a small form factor of $8.42\times 20.0\times 1.37$ mm while integrating radio frequency integrated circuit (RFIC) and peripheral surface mount components. The measurement shows a data rate of 40 Gb/s at a 3 m distance in the 150 GHz band with an excellent transmission energy efficiency of 35.7 pJ/bit.

The manuscript introduces a radio wave-based wireless communication system tailored for Autonomous Underwater Vehicles (AUVs), optimized for underwater deployment. Initial experiments to ascertain the fundamental properties of a loop antenna were conducted in a small-scale water tank, followed by comprehensive communication and video transmission trials in a larger tank with an AUV. A specialized waterproof enclosure was developed to house a waterproof antenna, a Vector Network Analyzer (VNA), and a communication board. This setup facilitated the evaluation of the loop antenna’s radio propagation attributes and the identification of frequencies conducive to underwater communication. Designed with practical deployment in mind, the system incorporates a 2-meter loop antenna for signal transmission and a 0.5m by 0.8m rectangular loop antenna integrated into the AUV for signal reception. Utilizing a wavelet Orthogonal Frequency Division Multiplexing (OFDM) communication board and tuning to lower frequencies, the system successfully established User Datagram Protocol (UDP) and Transfer Control Protocol (TCP) communications within a few meter radius from the transmitting antenna, achieving data transfer rates up to 6.8 Mbps.

An inverted-L monopole radiating element is proposed for antenna-in-package modules at the 151.5-164 GHz band. Its radiation pattern is half-isotropic and is well-suited for phased arrays for mobile communications. The ideal inverted-L monopole is analyzed and initial design parameters are found. A radiating element structure designed for planar technology is proposed, which consists of eight copper layers and is fed by a stripline. Impedance matching and fabrication constraints are taken into consideration when designing the structure. An array is designed and fabricated with the same size and technology as the module. To prove its scanning capabilities, a scaled-up version of the array is fabricated and measured at 28 GHz. The beam coverage of the proposed arrays is very high, able to cover 80% with a realized gain of 10 dBi by using just 2 modules.

Recently, microwave power transfer (MPT) for Internet-of-Things (IoT) devices has been actively studied. The distributed microwave power transfer (DMPT) can supply power efficiently by cooperating multiple transmit antenna arranged distributed in a relatively wide area. In this article, the advantages of DMPT are shown by using ray-trace-based Monte Carlo simulation. In addition, an algorithm for optimizing the phase is proposed and discussed its convergence. Furthermore, the implementation of DMPT using a backscatter-based closed-loop system is proposed. The system was built using the open-source platform GNU Radio. Experimental results show the effectiveness of the proposed system.

An autonomous underwater vehicle (AUV) is used for exploring marine resources and monitoring infrastructure facilities. Because an AUV is powered by batteries, it needs to be lifted out of the water to have them replaced or recharged. Thus, wirelessly feeding power to an AUV under the sea would improve the efficiency of marine activities. However, it is difficult to wirelessly power an object under the sea because seawater has high conductivity. We examine the electromagnetic field in lossy materials such as a conductor, a coil cover, and seawater. We design a wireless magnetic resonance-based power transfer system with multiple coils using bandpass filter (BPF) theory. The coil structure is sealed so that water cannot enter it. We perform experiments on this system completely immersed in seawater and measure the coil coupling coefficient, efficiency, and wattage. The results confirm wireless power transfer exceeding a distance of 10 m in an undersea setting. We verify the transmission efficiency by changing the receiving-coil position on the central axis of the transfer coils. Furthermore, we confirm a dependence on transfer on the order of 1 to 100 W.

In a system that feeds relatively small electric power using microwaves, it is a problem to improve received power in various arrival directions in a power receiving device that is generally small. In this paper, we propose a rectenna that converts power in a wide range of incoming direction to DC with an array antenna that performs power synthesis by a hybrid circuit and report the results of verification by simulation and actual measurement.