sensors Review The Recent Advancement in Unmanned Aerial Vehicle Tracking Antenna: A Review Anabi Hilary Kelechi 1, Mohammed H. Alsharif 2,* , Damilare Abdulbasit Oluwole 1, Philip Achimugu 3, Osichinaka Ubadike 1, Jamel Nebhen 4, Atayero Aaron-Anthony 5 and Peerapong Uthansakul 6,* 1 Department of Aerospace Engineering, Faculty of Air Engineering, AirForce Institute of Technology, Kaduna 800282, Nigeria; hk.anabi@afit.edu.ng (A.H.K.); damilareoluwole@afit.edu.ng (D.A.O.); ocubadike@afit.edu.ng (O.U.) 2 Department of Electrical Engineering, College of Electronics and Information Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 05006, Korea 3 Department of Computer Science, Faculty of Computing, AirForce Institute of Technology, Kaduna 800282, Nigeria; p.achimugu@afit.edu.ng 4 College of Computer Engineering and Sciences, Prince Sattam bin Abdulaziz University, P.O. Box 151, Alkharj 11942, Saudi Arabia; [email protected] 5 Department of Electrical and Information Engineering, Covenant University, Ota 112233, Ogun State, Nigeria; [email protected] 6 School of Telecommunication Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand * Correspondence: [email protected] (M.H.A.); [email protected] (P.U.) Abstract: Unmanned aerial vehicle (UAV) antenna tracking system is an electromechanical com- ponent designed to track and steer the signal beams from the ground control station (GCS) to the Citation: Kelechi, A.H.; Alsharif, airborne platform for optimum signal alignment. In a tracking system, an antenna continuously M.H.; Oluwole, D.A.; Achimugu, P.; tracks a moving target and records their position. A UAV tracking antenna system is susceptible Ubadike, O.; Nebhen, J.; to signal loss if omnidirectional antenna is deployed as the preferred design. Therefore, to achieve Aaron-Anthony, A.; Uthansakul, P. longer UAV distance communication, there is a need for directional high gain antenna. From design The Recent Advancement in principle, directional antennas are known to focus their signal energy in a particular direction viewed Unmanned Aerial Vehicle Tracking from their radiation pattern which is concentrated in a particular azimuth direction. Unfortunately, Antenna: A Review. Sensors 2021, 21, a directional antenna is limited by angle, thus, it must always be directed to the target. The other 5662. https://doi.org/10.3390/ s21165662 limitation of a UAV mechanical beam steering system is that the system is expensive to maintain and with low reliability. To solve this problem, we are proposing the use of MIMO technology as a readily Academic Editor: Luis Velasco available technology for UAV beyond line of sight technology. Although UAV antenna tracking is domiciled in the mechanical beam steering arrangement, this study shows that this native technology Received: 27 July 2021 could be usurped by MIMO beam forming. Accepted: 20 August 2021 Published: 23 August 2021 Keywords: UAV; tracking antenna system; azimuth angle; elevation angle; range; MIMO technology; beam steering; antenna array Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. 1. Introduction During the last two decades, unmanned aerial vehicle (UAV) has been deployed to per- form high risky operations where deploying humans presents great danger to their health notably in fire-fighting [1,2], chemical spraying [3–5], search and rescue missions [5,6], Copyright: © 2021 by the authors. disaster network communication [7,8] and surveillance operations [9]. Undoubtedly, UAV Licensee MDPI, Basel, Switzerland. will be pivotal in medical and blood delivery for troops in the frontline when it is danger- This article is an open access article ous to send in medical personnel. The market of UAV has a positive outlook, as could distributed under the terms and be seen from Figure1. The major drivers of the UAV market are the remotely operated conditions of the Creative Commons commercial UAV and the emergency management sector. Particular interest is the remotely Attribution (CC BY) license (https:// operated commercial UAV where the channel model ranges from direct line of sight (LoS) creativecommons.org/licenses/by/ 4.0/). to non-LoS propagation communication [10]. UAVs are deployed in urban, semi-rural, Sensors 2021, 21, 5662. https://doi.org/10.3390/s21165662 https://www.mdpi.com/journal/sensors Sensors 2021, 21, x FOR PEER REVIEW 2 of 28 Sensors 2021, 21, 5662 2 of 27 remotely operated commercial UAV where the channel model ranges from direct line of sight (LoS) to non-LoS propagation communication [10]. UAVs are deployed in urban, andsemi-rural, rural environments and rural environments which are fully which captured are fully using captured LoS and using non-LoS LoS and scenario. non-LoS Each sce- environmentnario. Each environment characterized characterized by different linkby different obstacle link topology. obstacle For topology. instance, For in the instance, rural areain the where rural there area where is less obstacle,there is less the obstacle, channel the model channel conforms model to conforms the free spaceto the pathfree space loss modelpath loss suitable model for suitable LoS communication. for LoS communication. Different from Different the NLoS from model, the theNLoS UAV model, ground the controlUAV ground station control (GCS) deploysstation (G theCS) LoS deploys model the to LoS focus model the antennato focus beamthe antenna directly beam to the di- airbornerectly to UAVthe airborne using a highlyUAV using directional a highly antenna directional rather antenna than an rather omni-directional than an omni-direc- antenna totional maximize antenna the to received maximize signal the power.received signal power. Furthermore,Furthermore, thethe assignedassigned UAVUAV transmittransmit powerspowers whichwhich varies might become inade- inad- equatequate as as communication communication range range increases. increases. For For instance, instance, wifi wifi operated operated UAV UAV is islimited limited to to 20 20dBm dBm while while the the LTE LTE operated operated UAV UAV is limited is limited to 24 to dBm 24 dBm in uplink in uplink and 43–48 and 43–48 dBm in dBm down- in downlink)link) [10]. Hence, [10]. Hence, there thereis a need is a to need rely to on rely tracking on tracking antenna antenna to deliver to deliver the needed the needed signals signalsover a wider over a communication wider communication range in rangeunpredictable in unpredictable wireless communications wireless communications link. Obvi- link.ously, Obviously, using highly using directional highly directional antenna enhances antenna the enhances received the signal received strength signal (RSS) strength of the (RSS)airborne of the platform. airborne Thus, platform. there Thus,is a need there to is reduce a need co-channel to reduce co-channeland cross channel and cross interfer- chan- nelences. interferences. Additionally, Additionally, the need for the automatic need for re automaticpeat request repeat (ARQ) request as well (ARQ) as hybrid as well auto- as hybridmatic repeat automatic request repeat (HARQ) request in (HARQ)the face of in loss the faceof signal of loss when of signal deployed when in deployedautonomous in autonomousfashion are also fashion reduced. are also Moreover, reduced. the Moreover, aerial platform the aerial records platform a higher records signal-to-inter- a higher signal-to-interference-noiseference-noise ratio (SINR) ratiowhen (SINR) a packet when is successfully a packet is successfully delivered. From delivered. the perspective From the perspectiveof energy efficiency of energy and efficiency network and lifetime, network deploying lifetime, deploying omni-directional omni-directional antenna antennaconnotes connotesthe use of the more use energy of more to energy achieve to a achieve targeted a targetedreliable communication reliable communication link between link between the GCS theand GCS the andair-borne the air-borne platforms. platforms. Intuitively, Intuitively, directional directional antenna antenna is highly is highly desirable desirable for UAV for UAVcommunication communication because because it improves it improves pointing pointing accuracy, accuracy, and andminimizes minimizes the antenna the antenna side- sidelobeslobes and and antenna antenna beamwidth. beamwidth. In high-freque In high-frequencyncy band band communication, communication, sustaining sustaining preci- precisionsion communication communication between between the ground the ground statio stationn and and the theairborne airborne platform platform requires requires sig- significant improved pointing accuracy because of the short wavelength and range [11,12]. nificant improved pointing accuracy because of the short wavelength and range [11,12] FigureFigure 1. 1.UAV UAV market market outlook outlook [ 13[13].]. Meanwhile,Meanwhile, usingusing aa directional directional antenna antenna isis limited limited by by azimuth azimuth and and elevation elevation angles, angles, andand must must always always bebe directed directed toto the the target target [ 14[14].]. ItIt isis important important toto notenote thatthat optimaloptimal direc-direc- tionaltional antenna antenna should should consider consider UAV UAV look look angles angles (yaw, (yaw, pitch, pitch, and and roll) roll) which which are are dynamic dynamic asas they they are are motion-based. motion-based. Therefore,Therefore, thethe UAVUAV tracking tracking antenna antenna