Research Article A 3-Dimensional Multiband Antenna for Vehicular 5G Sub-6 GHz/ GNSS/V2X Applications Ahmad S. Ibrahim , Ahmad M. Yacoub , and Daniel N. Aloi Electrical and Computer Engineering Department, Oakland University, Rochester Hills, MI 48309, USA Correspondence should be addressed to Ahmad S. Ibrahim; asalihibrahim@oakland.edu Received 27 February 2022; Revised 19 April 2022; Accepted 12 May 2022; Published 4 July 2022 Academic Editor: Claudio Gennarelli Copyright © 2022 Ahmad S. Ibrahim et al. is 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. A compact multiband monopole antenna is proposed for vehicular roof top shark-fin applications. e proposed multiband antenna covers 5G sub-6 GHz and LTE bands starting at 617 MHz to 5000 MHz and the higher GNSS band from 1559 to 1606 MHz as well as the V2X band at 5900 MHz. e presented antenna is a three-dimensional monopole antenna with two branches to cover the required bands with compact size to fit inside a roof top shark-fin. e long antenna branch covers the lower cellular frequency band from 617 to 960 MHz, while the short branch covers the higher frequency band from 1559 to 6000 MHz. e presented antenna is mounted on a double-sided FR4 PCB and is feeded through a short cable. e proposed antenna covers multiple frequency bands with compact size (H xLx W) of 58 × 37 × 17 mm 3 . e antenna is simulated and optimized, and then, a prototype is fabricated, and its radiation characteristics are measured when mounted on one-meter ground plane and on a vehicle’s roof. e maximum measured linear average gain is 3 dBi at 1900 MHz, and the maximum measured efficiency is 88% at 787 MHz. e active GNSS antenna gain is measured using an LNA with good isolation. A good agreement is achieved between the simulated and measured results when compared in terms of voltage standing wave ratio (VSWR), radiation patterns, linear average gain (LAG), and antenna efficiency. 1. Introduction Vehicular communication research and development has spiked recently due to the introduction of autonomous driving and intelligent vehicles, which requires many communication systems and protocols to be implemented [1]. To improve safety and efficiency in vehicles and the whole transportation system, vehicle-to-everything (V2X) is introduced, which mainly includes vehicle-to-vehicle (V2V), vehicle-to-pedestrian (V2P), vehicle-to-infrastructure (V2I), and vehicle-to-network (V2N). By exchanging messages between vehicles, infrastructure, and pedestrians, V2X can support many use cases such as forward collision warning, parking search, and optimizing a vehicle’s traffic [2]. An- other revolutionary technology for vehicle autonomy is the 5G cellular communications, which provides a reliable and low latency communications as well as high data rates. 5G wireless network provides an essential role by providing a reliable and fast communication between vehicles and other objects which means it can be integrated with V2X and this integration called later as cellular V2X (C–V2X). Global Navigation Satellite System (GNSS) is the main positioning system for self-driving vehicles, but it is not accurate enough, so it is integrated with other systems such as light detection and ranging (LiDAR) and inertial navigation systems (INS) to increase the positioning accuracy and availability, espe- cially in urban areas [3]. Placement of antennas on vehicles has large impact on the antenna’s performance, so most of the antennas are placed on the vehicle’s roof to avoid signal blockage by metal. Roof antennas are usually placed in one cast called a shark-fin due to its shape. Shark-fins have limited size due to the vehicle’s aerodynamic design, and recently, many an- tennas are placed inside these limited size shark-fins, which increase the coupling and shadowing effects between dif- ferent antennas [4]. One solution to reduce the shadowing Hindawi International Journal of Antennas and Propagation Volume 2022, Article ID 5609110, 13 pages https://doi.org/10.1155/2022/5609110