Scientists at the Tokyo Institute of Technology (Tokyo Tech) have developed a wireless relay network for 5G systems. The proposed batteryless communication addresses the challenges of the flexible use of relay networks. This design is both economical and energy efficient. Such advances in 5G communications will create tremendous opportunities for a wide variety of sectors.

The ever-increasing demand for wireless data bandwidth shows no signs of slowing down anytime soon. Millimeter waves, a short-wave spectrum, have shown great potential in 5G communication and beyond. To take advantage of high capacity millimeter wave frequencies, phased array antennas (antenna elements that work together to increase signal strength in a specific direction) are adjusted. However, the current use case is limited to spreading over the line of sight.

Therefore, relay nodes are considered for non-line of sight communication (Figure 1). While relaying can provide improved bandwidth, coverage, and reliability, deploying a relay network flexibly poses some challenges. The greatest challenge in relay networks is the power supply. A typical relay node has its own power supply or is connected to an external power source.

Fortunately, a team of Tokyo Tech scientists, led by Prof. Kenichi Okada, has proposed a 28GHz wireless phased array relay transceiver for the 5G network. Their work is set to be presented at the 2021 Symposia on VLSI Technology and Circuits, an international conference that explores emerging trends and new concepts in semiconductor technology and circuits.

A vector summation backscatter technique is used to implement the proposed design. The transmitter works as a backscatter with 24 GHz local oscillator (LO) and 4 GHz intermediate frequency (IF) signals (Figure 2). Okada explains: “Backscatter communication makes it possible to extract energy from incoming signals and reflects parts of the same signals back while the data is being modulated. In this design, Backscatter upconverts the 5G New Radio (5G NR) spectrum at 4 GHz and transmits at 28 GHz. ”The transmitter also acts as a phase shifter, allowing it to change the phase of an incoming signal. The transmitter’s backscattering and phase shifting capabilities make beamforming easier, and an antenna array can be controlled to send signals in a particular direction. This means that information is transmitted more efficiently and with less interference.

Receiver and rectifier operation is another critical feature of the transceiver. Passive phase shifters and power combiners (that combine power supplied at multiple ports) are used to amplify the received signal power for wireless power transmission (WPT). The proposed rectifier acts as a self-superimposed mixer. In other words, the rectifier splits and recombines an incoming beam with a modulated version of itself. It also works as a full wave rectifier on the 24 GHz WPT signal.

The entire phased array relay transceiver is configured in an area of ​​only 1.8 mm²2 (Figure 3). In receive mode, the wirelessly operated 4 × 8 array module generates 3.1 mW of power. In transmit mode, it produces -2.2 dBm of saturated equivalent isotropic radiated power (EIRP), which is the output power radiated by an antenna in a single direction. The vector-summing backscattering covers a 360 ° phase range with 7-bit phase resolution and consumes only 0.03 mW in both transmit and receive mode.

Okada closes enthusiastically: “The proposed batteryless transceiver improves 5G connectivity by acting as a repeater between indoor and outdoor environments. This in turn will improve the user experience and create new opportunities for operational efficiency in the Internet of Things, industrial automation and new communication services. “

Talk about efficiency in person!



Session: Session 11 Advanced Wireless for 5G, C11-1
(Jun 17,8:40, JST)

Session Title: A 28 GHz phased array relay transceiver for 5G networks with vector summing backscattering with 24 GHz wireless performance and LO transmission

Conference: 2021 symposia on VLSI technology and circuits

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About the Tokyo Institute of Technology

Tokyo Tech is at the forefront of research and higher education as Japan’s leading science and technology university. Tokyo Tech researchers excel in areas that range from materials science to biology, computer science and physics. Tokyo Tech was founded in 1881 and is home to over 10,000 undergraduate and graduate students annually who develop into science leaders and some of the most sought-after engineers in the industry. The Tokyo Tech community embodies the Japanese philosophy of “Monotsukuri,” which means “technical ingenuity and innovation,” and strives to contribute to society through effective research.

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