Electrical and Electronic Engineering News

Researchers develop a compact 28-GHz transceiver supporting dual-polarized MIMO

Study contributes to driving advances in 5G

June 29, 2020

Researchers at Tokyo Institute of Technology (Tokyo Tech) and NEC Corporation have jointly developed a 28-GHz phased-array¹ transceiver supporting dual-polarized MIMO² for fifth-generation mobile communications system (5G) radio units. Advances in 5G will benefit an array of industries ranging from healthcare, manufacturing and transportation to education and entertainment that require high bandwidth and high-quality connectivity.

Figure 1. The new transceiver is designed to limit signal degradation

An illustration of leakage cancellation between polarization signals and arbitrary angle polarization rotation.

Figure 2.Phased-array radio for polarization MIMO.

Figure 3. Printed circuit board with 64 antenna elements.

As countries launch or prepare for 5G services, researchers are continuing to step up efforts to facilitate deployment of 5G infrastructure. Dual-polarized phased-array transceivers are an attractive class of antenna systems that can transmit data simultaneously through horizontal and vertical-polarized waves. Numerous studies have shown that dual-polarized MIMO can improve the data rate and spectrum efficiency in 5G radio units. However, one problem encountered with these systems is cross-polarization leakage³, which results in degradation of signal quality especially in the millimeter wave band.

Now, Kenichi Okada’s Lab at Tokyo Tech’s Department of Electrical and Electronic Engineering and NEC corporation in Japan have developed a transceiver capable of canceling cross-polarization interference using a built-in so-called horizontal and vertical (H/V) canceller. Tests have shown that the error vector magnitude⁴ in 256 QAM⁵ can be improved from 7.6 % to a more desirable, lower figure of 3.3 % using this new leakage cancellation technique. "The cancellation signals are generated for horizontal and vertical polarization at the transmission side so that it can cancel the cross-polarization leakage caused by all through the transmitter/receiver chip, package, printed circuit board and antenna," the researchers say.

The transceiver was fabricated using low-cost, mass-producible silicon CMOS⁶ technology, occupying an area of just 16 mm². The researchers anticipate that the new circuitry could be installed in a wide range of applications that will be enabled by 5G in the future. Importantly, they point out that their transceiver will improve spectrum efficiency while keeping equipment size and set-up costs to a minimum.

The findings are being presented at the 2020 Symposia on VLSI Technology and Circuits (VLSI 2020), held online from 14 June. The paper has also been selected as one of the technical highlights at the conference.

This research is supported by the Ministry of Internal Affairs and Communications in Japan (JPJ000254).

Technical terms

¹ phased-array

Describing an electrically steerable array of antennas.

² Dual-polarized MIMO

Dual-polarized multiple-input multiple-output (MIMO) refers to an antenna system for wireless communications that can improve transmission capacity through the use of a plurality of antennae that transmit signals simultaneously.

³ cross-polarization leakage

A type of signal leakage caused by horizontal and vertical-polarized signals interfering with each other.

⁴ Error vector magnitude

A measure of the level of interference, calculated by the difference between the ideal transmitted signal and the actual received signal.

⁵ 256 QAM

The highest digital modulation method for converting digital data into radio waves and electric signals.

⁶ CMOS

Complementary metal-oxide-semiconductor, the main processing method for creating integrated circuits.

Reference

Technology Session :	CF2 - RF & mm-Wave Circuits
Session Title :	A 28-GHz CMOS Phased-Array Beamformer Supporting Dual-Polarized MIMO with Cross-Polarization Leakage Cancellation
Authors :	Pang, J. et al.
Conference :	2020 Symposia on VLSI Technology and Circuits
Affiliations :	¹ Department of Electrical and Electronic Engineering, Tokyo Institute of Technology, Tokyo, Japan ² NEC Corporation, Kawasaki, Japan