Sub-THz Antenna for High-Speed Wireless Communication Systems

Hindawi International Journal of Antennas and Propagation Volume 2019, Article ID 9573647, 9 pages https://doi.org/10.1155/2019/9573647 Research Article Sub-THz Antenna for High-Speed Wireless Communication Systems Hamsakutty Vettikalladi ,1 Waleed Tariq Sethi,2 Ahmad Fauzi Bin Abas ,1 Wonsuk Ko,1 Majeed A. Alkanhal,1 and Mohamed Himdi 2 1 2 Department of Electrical Engineering, College of Engineering, King Saud University, 11421 Riyadh, Saudi Arabia IETR University of Rennes 1, France Correspondence should be addressed to Hamsakutty Vettikalladi; Received 9 October 2018; Revised 27 December 2018; Accepted 1 January 2019; Published 27 March 2019 Academic Editor: Ikmo Park Copyright © 2019 Hamsakutty Vettikalladi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Terahertz (THz) links will play a major role in high data rate communication over a distance of few meters. In order to achieve this task, antenna designs with high gain and wideband characteristics will spearhead these links. In this contribution, we present different antenna designs that offer characteristics better suited to THz communication over short distances. Firstly, a single-element antenna having a dipole and reflector is designed to operate at 300 GHz, which is considered as a sub-terahertz band. That antenna achieves a wide impedance bandwidth of 38.6% from 294 GHz to 410 GHz with a gain of 5.14 dBi. Secondly, two designs based on the same dipole structure but with added directors are introduced to increase the gain while maintaining almost the same bandwidth. The gains achieved are 8.01 dBi and 9.6 dBi, respectively. Finally, an array of 1 × 4 elements is used to achieve the highest possible gain of 13.6 dBi with good efficiency about 89% and with limited director elements for a planar compact structure to state-of-the-art literature. All the results achieved make the proposed designs viable candidates for high-speed and short-distance wireless communication systems. 1. Introduction Over the last few years, wireless data traffic has been drastically increasing due to a change in the way today’s society creates, shares, and consumes information. This change has been accompanied by an increasing demand for much higher speed wireless communication anywhere at any time. In particular, wireless data rates have doubled every eighteen months over the last three decades and are quickly approaching the capacity of wired communication systems. Following this trend, wireless terabit-per-second (Tbps) links are expected to become a reality within the next five to ten years [1]. Advanced physical layer solutions and, more importantly, new spectral bands will be required to support these extremely high data rates [2]. Terahertz (THz) and sub-THz communication refers to the use of the band that coves region from (0.1–10) THz and sub-THz region is covered from (0.1–0.3) THz [1]. THz communication links will play a major role in which very high data rates are required over short distances. Terahertz band can be used for high-speed data transmission within a range of 10 m. This coverage area consists of small cells of cellular networks. Terahertz communication is applicable in the indoor as well as outdoor environments with stationary and mobile users. Terabit wireless local area networks (T-WLAN) can provide flawless communication between high-speed fiber optical links and personal laptops and tablets. Wired and wireless links enjoy the same speed in terahertz communication [2]. Very high path loss is imposed as one of the main challenges at THz band frequencies, which poses a major constraint on communication distances. Additional challenges range from the implementation of compact high-power THz band transceivers, the development of efficient ultra-broadband antennas at THz Band frequencies, and characterization of the frequency-selective path loss of the THz band channel to the development of novel 2 International Journal of Antennas and Propagation d1 Ld Gold Wf h3 Wff W Feed Lf Ls Driven dipole g Reflector d2 h2 BCB InP h1 Lr d3 Ws (a) (b) Figure 1: Geometric design of single-element dipole antenna: (a) perspective view and (b) front view. Table 1: Optimized dimensions of single-element dipole antenna. Dimensions y dBi 5.74 Value (μm) d1 78 d2 116 d3 82 h1 50 h2 6 h3 2 g 4 Lf 35 Lr 280 Ld 115 Wf 10 modulations, transmission schemes, and communication protocols tailored to the peculiarities of this paradigm. Many of these challenges are common to mm-wave communication systems, and as a result, the THz band is not yet regulated [3]. One of the major advantages of THz and sub-THz frequencies is the antenna size, which reduces to about submillimeter [4]. The implementation of these systems is now possible due to the advancements in the realization of the photonic and semiconductor devices with an operating frequency in the terahertz band. A common approach is to design the antenna in a low loss substrate and then integrate it to the active devices. On-chip antennas are easily integrated to the rest of the system but they have lower efficiencies due to the lossy substrate [5–7]. The substrate integration technology, one of the technologies used in THz, converts nonplanar antenna structures into their planar forms. Advanced microfabrication techniques are adopted for the design of terahertz antennas. Some of the substrate- Phi x z Theta y z y z Theta x 3.94 2.87 1.79 0.717 −2.14 −8.57 −15 −21.4 −27.8 −34.3 dB 5.14 3.54 2.57 1.61 0.643 Phi −2.18 x −8.71 −15.2 −21.8 y −28.3 x −34.9 z Figure 2: Reflection coefficient (S11 ) and gain (dB) of singleelement dipole antenna. integrated antenna structures used in THz technology are slot array, dipole, reflector, horn, and leaky wave antennas [8]. For the sub-THz designs, high gain with compact size and wide bandwidth is preferred. Some antennas have been presented in literature such as in [9] where authors presented three antenna designs (rectangular horn, Cassegrain, International Journal of Antennas and Propagation 3 dBi dBi 5.74 y 5.14 y 3.94 3.54 2.87 2.57 1.79 1.61 0.717 phi -8.57 x z 0.643 phi -2.14 -15 Theta x z -8.71 -15.2 Theta -21.4 -21.8 -27.8 -28.3 -34.3 -34.9 (a) 3D directivity of single-element dipole (b) 3D gain of single-element dipole 0 0 330 6 4 2 0 300 –2 –4 –6 –8 –10 –12 270 –12 –10 –8 –6 –4 240 –2 0 2 4 6 -2.18 30 60 90 120 150 210 180 6 4 2 0 300 –2 –4 –6 –8 –10 –12 270 –12 –10 –8 –6 –4 240 –2 0 2 4 6 330 30 60 90 120 150 210 180 CST_gain HSFF_gain CST_gain HSFF_gain ° (c) E-plane versus ϕ: Eϕ at θ=90 (d) H-plane versus θ: Eϕ at ϕ=0 ° Figure 3: Radiation pattern of the single-element dipole antenna at 300 GHz: (a) 3D directivity, (b) 3D gain, (c) E-plane, and (d) H-plane. Ld1 d1´ d1´ (...truncated)