The advantages to be gained include better quality communications as well as cost-effective scalability.
A team of more than 20 researchers at Tokyo Institute of Technology (Tokyo Tech) and NEC Corporation has successfully demonstrated a 39 GHz transceiver that could be used in the next wave of 5G wireless equipment, including base stations, smartphones, tablets and Internet-of-Things (IoT) applications.
Although research groups, including the current team, have until now largely focused on developing 28 GHz systems, 39 GHz will be another important frequency band for realizing 5G in many parts of the world.
The new transceiver is based on a 64-element (4 × 16) phased-array1 design. Its built-in gain phase calibration means that it can improve beamforming2 accuracy, and thereby reduce undesired radiation and boost signal strength.
Fabricated in a standard 65-nanometer CMOS3 process, the transceiver's low-cost silicon-based components make it ideal for mass production a key consideration for accelerated deployment of 5G technologies.
The researchers showed that the built-in calibration has a very low root-mean-square (RMS) phase error of 0.08°. This figure is an order of magnitude lower than previous comparable results. While transceivers developed to date typically suffer from high gain variation of more than 1 dB, the new model has a maximum gain variation of just 0.04 dB over the full 360° tuning range.
"We were surprised to achieve such a low gain variation when actually using the calibration based on our local-oscillator (LO) phase-shifting approach," says project leader, Kenichi Okada of Tokyo Tech.
In addition, the transceiver has a maximum equivalent isotropic radiated power (EIRP)4 of 53 dBm. This is an impressive indication of the output power of the 64 antennas, the researchers say, particularly for low-cost CMOS implementation.
Indoor testing (under anechoic chamber conditions5), which involved a one-meter, over-the-air measurement, demonstrated that the transceiver supports wireless transmission of a 400 MHz signal with 64QAM.
"By increasing the array scale, we can achieve greater communication distance," Okada says. "The challenge will be to develop the transceiver for use in smartphones and base stations for 5G and beyond."
This work is being presented at the 2019 IEEE Radio Frequency Integrated Circuits Symposium (RFIC) in Boston, Massachusetts, US, as part of the morning session (Session RTu2E) to be held on 4 June 2019. The paper of this work "A 39GHz 64-Element Phased-Array CMOS Transceiver with Built-in Calibration" by Yun Wang et al., received the best student paper award.
• phased-array: Referring to an electrically steerable array of antennas.
• beamforming: A powerful signal processing technique used to control antenna patterns.
• CMOS: Complementary metal oxide semiconductor, the main processing method for creating integrated circuits.
• Equivalent isotropic radiated power (EIRP): A measure of the signal strength or output power of an antenna in decibels per meter (dBm).
• anechoic chamber conditions: A non-reflective environment that is designed to be free from echoes.
1. Authors:Yun Wang1, Rui Wu1, Jian Pang1, Dongwon You1, Ashbir Aviat Fadila1, Rattanan Saengchan1, Xi Fu1, Daiki Matsumoto1, Takeshi Nakamura1, Ryo Kubozoe1, Masaru Kawabuchi1, Bangan Liu1, Haosheng Zhang1, Junjun Qiu1, Hanli Liu1, Wei Deng1, Naoki Oshima2, Keiichi Motoi2, Shinichi Hori2, Kazuaki Kunihiro2, Tomoya Kaneko2, Atsushi Shirane1, Kenichi Okada1, • Affiliations:1 Department of Physical Electronics, Tokyo Institute of Technology
2. NEC Corporation Session:Session RTu2E Session title:A 39GHz 64-Element Phased-Array CMOS Transceiver with Built-in Calibration Conference:IEEE Radio Frequency Integrated Circuits Symposium
*Corresponding author's email: okada[.]ee.e.titech.ac.jp
About Tokyo Institute of Technology
Tokyo Tech (titech.ac.jp) stands at the forefront of research and higher education as the leading university for science and technology in Japan. Tokyo Tech researchers excel in fields ranging from materials science to biology, computer science, and physics. Founded in 1881, Tokyo Tech hosts over 10,000 undergraduate and graduate students per year, who develop into scientific leaders and some of the most sought-after engineers in industry. Embodying the Japanese philosophy of "monotsukuri," meaning "technical ingenuity and innovation," the Tokyo Tech community strives to contribute to society through high-impact research.
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