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 Department of Electrical Engineering, College of Engineering, King Saud University, 11421 Riyadh, Saudi Arabia 2 IETR University of Rennes 1, France Correspondence should be addressed to Hamsakutty Vettikalladi; hvettikalladi@ksu.edu.sa 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 drasti- cally 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. Tera- hertz 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 appli- cable in the indoor as well as outdoor environments with sta- tionary and mobile users. Terabit wireless local area networks (T-WLAN) can provide flawless communication between high-speed fiber optical links and personal laptops and tab- lets. Wired and wireless links enjoy the same speed in tera- hertz 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. Addi- tional challenges range from the implementation of compact high-power THz band transceivers, the development of efficient ultra-broadband antennas at THz Band frequen- cies, and characterization of the frequency-selective path loss of the THz band channel to the development of novel Hindawi International Journal of Antennas and Propagation Volume 2019, Article ID 9573647, 9 pages https://doi.org/10.1155/2019/9573647