Not half bad

Abstract

Researchers from the Samsung Electronics Network R&D Center in Shenzhen, China, have fabricated and tested a prototype compact substrate-integrated-waveguide (SIW) cavity multiple-input-multiple-output (MIMO) antenna with potential applications in 5G communications. The triangular half mode design achieves an enhanced bandwidth by merging together two coupled modes in the required operating band and boasts high isolation and radiation efficiency. Since it was first introduced a decade ago, SIW technology has drawn significant attention from researchers, with particular appeal in the antenna community. It can be fabricated in planar form using periodic metallic vias and has the advantages of high-Q factor and high-power capacity. In addition to this, cavity antennas resonating at cavity modes and radiating energy through opened cavity edges or etched slots are well-known for good radiation performance. The SIW cavity antenna is an antenna type created by introducing SIW technology into a cavity antenna design. Antennas transmitting and receiving wireless signals are important components in communication systems. The SIW cavity antenna can not only combine the attractive characteristics of conventional cavity antennas, such as good radiation performance and unidirectional radiation pattern, and but also offers the advantages of planar SIW technology, such as low profile, convenient fabrication, and easy integration with planar circuits. Author Bing-Jian Niu in anechoic chamber holding the proposed antenna. Analytical model of the proposed SIW cavity antenna. The SIW cavity antenna reported in the teams published Letter is designed for MIMO applications. By etching three slots, a half-mode SIW cavity was divided into four eighth-mode sub-cavities. Two large sub-cavities are excited by two coaxial ports to construct two antenna elements and cavity energy is coupled from the excited sub-cavities to the unexcited sub-cavities to enhance bandwidth. Thus, a compact two-element MIMO antenna with enhanced bandwidth can be designed and achieved. As is well-known, MIMO antennas have been widely adopted in modern wireless systems. Co-author Bing-Jing Niu, however, notes that: “Two major challenges faced in the design are narrow bandwidth and poor isolation among antenna elements. In our proposed design, three slots are etched in the half-mode SIW cavity. The width, length, and position of these slots are carefully selected in our Letter.” To meet the stringent requirements on antenna fabrication for wearable and portable devices, antenna designs are becoming more and more complex. Compact two-element MIMO antennas with enhanced bandwidth and high isolation are in great demand. With an enhanced bandwidth of 160 MHz, high isolation of 19.5 dB, antenna gain of 4.9 dBi, and radiation efficiency of 72.8%, the proposed SIW cavity MIMO antenna has good specifications and properties, making it suitable for potential applications for forthcoming fifth-generation wireless communications. Etched slots in the antenna provide new perspectives and opportunities for designing SIW cavity antennas, which not only radiate cavity energy into free space but also control the coupling between adjacent sub-cavities. The challenges the group overcome were the ideal selection of slot width, length, and position to optimise their prototype for its intended applications. In the proposed design, a wide rectangle slot is considered as the de-coupler to enhance the antenna isolation while two narrow T-shaped slot are utilised as the coupler to enhance the impedance bandwidth. The novel design makes it possible to increase the channel capacity and link reliability in wireless communication channels. In the short term, this work is expected to be utilised in the sub-6 GHz band. In the longer term, massive MIMO antenna based on SIW cavities will likely be successfully developed and integrated successfully into communication networks. Mr Niu discusses the groups upcoming work and views on the future of the field: “To improve the conformal performance of planar antennas, we are considering liquid crystal polymers (LCP) as a manufacturing substrate. It has the ability to support 3D integration and low tangents up to and including millimetre-wave (MMW) applications. In addition, to improve the MIMO performance, multiple-element MIMO antennas such as four-element and eight-element, have been developed in our own research group. As one of the most pervasive core technologies, massive MIMO antennas will lead to an accelerated pace of research and development in wireless communication with the promise of significant new breakthroughs over the next decade. An unprecedented number of antennas result in major technical challenges as well as new opportunities in antenna design, channel propagation, electronic components and circuit design, and communication theory. We hope the SIW cavity antenna is a good candidate to address this issue.”