ABSTRACT
Antennas are an indispensable part of any communications, command, control. communication and Computer (C4) system. Traditionally, omnidirectional antennas are used in most C4 systems due to their simplicity and low cost. However, in today’s contested scenarios, it is imperative that C4 activities are done extremely secure with MINIMUM RADIO-FREQUENCY SIGNATURE. It is also important for C4 systems to provide protection/jam resistance for electronic countermeasure attacks. Both these requirements call for narrow beam antennas as opposed to omnidirectional antennas with massive RF signatures, which can be easily detected by enemy and jammed from almost any direction. Detecting, intercepting or jamming a C4 system with a narrow beam requires the intruder to be in the main beam coverage area (of a few degrees), which is operationally difficult without getting unnoticed. Ability to steer the narrow beam provides an additional layer of protection making it almost impossible to be intercepted or jammed even in an unlikely situation of it being detected. Various steerable narrow beam antenna technologies are being developed currently; including mechanically steered reflector (dish) type antenna systems, active phased array antenna systems, flat-panel antenna systems with massive numbers of electronically controlled tuned scatters on an liquid-crystal-display panel, Near-Field Meta-Steering (NFMS) antenna systems, Laterally translating transmit arrays, etc. each with own merits and limitations. In this paper we present recent advances in these antenna technologies and their potential applications in defence. The strengths and weaknesses of each technology for various C4 systems in maritime, land, aerospace and space applications will be discussed.

BIOGRAPHY
Karu Esselle is the Distinguished Professor in Electromagnetic and Antenna Engineering at the University of Technology Sydney and a Visiting Professor of Macquarie University, Sydney. Karu is a Fellow of the Royal Society of New South Wales, IEEE and Engineers Australia. Karu’s most recent awards include the top Defence Industry award in Australia – the “Winner of Winners” Excellence Award – as well as the Academic of Year Award at the 2021 Australian Defence Industry Awards, both the most prestigious Excellence Award and the Academic of the Year Award at 2022 Australian Space Awards, Finalist for 2021 Australian national Eureka Prize for Outstanding Mentor of Young Researchers, Runner-up to the same prize in 2020, 2019 Motohisa Kanda Award (from IEEE USA) for the most cited paper in IEEE Transactions on EMC in the past five years, 2021 IEEE Region 10 (Asia-Pacific) Outstanding Volunteer Award, and 2020 IEEE NSW Outstanding Volunteer Award. According to the Special Report on Research published by The Australian national newspaper, he is the 2019 National Research Field Leader in Australia in both Microelectronics and Electromagnetism fields. Karu has provided expert assistance to more than a dozen companies including Intel, Hewlett Packard Laboratory (USA), Cisco Systems (USA), Audacy (USA), Cochlear, Optus, ResMed and Katherine-Werke (Germany). His team designed the high-gain antenna system for the world’s first entirely Ka-band CubeSat made by Audacy, USA and launched to space by SpaceX in December 2018. This is believed to be the first Australian-designed high-gain antenna system launched to space, since CSIRO-designed antennas in Australia’s own FedSat launched in 2002. Since 2002, his research team has been involved with research grants, contracts and PhD scholarships worth over 22 million dollars, including 15 Australian Research Council grants, without counting the 245 million-dollar SmartSat Corporative Research Centre, which started in 2019. His research has been supported by many national and international organisations including Australian Research Council, Intel, US Air Force, Cisco Systems, Hewlett-Packard, Australian Department of Defence, Australian Department of industry, NSW Chief Scientist & Engineer Office and German and Indian governments. Previously he received 2019 Macquarie University Research Excellence Award for Innovative Technologies, 2019 ARC Discovery International Award, 2017 Excellence in Research Award from the Faculty of Science and Engineering, 2017 Engineering Excellence Award for Best Innovation, 2017 Highly Commended Research Excellence Award from Macquarie University, 2017 Certificate of Recognition from IEEE Region 10, 2016 and 2012 Engineering Excellence Awards for Best Published Paper from IESL NSW Chapter, 2011 Outstanding Branch Counsellor Award from IEEE headquarters (USA), 2009 Vice Chancellor’s Award for Excellence in Higher Degree Research Supervision and 2004 Innovation Award for best invention disclosure. His mentees have been awarded many fellowships, awards and prizes for their research achievements. Fifty-eight international experts who examined the theses of his PhD graduates ranked them in the top 5% or 10%. Two of his students were awarded PhD with the highest honour at Macquarie University – the Vice Chancellor’s Commendation, and one received University Medal for Master of Research. Karu has authored over 650 research publications and his papers have been cited ~12,500 times. In 2021 his publications received over 1,400 citations. His h-index is 53 and i-10 is 212. In addition to the IEEE Kanda Award mentioned above, several of his papers have been among most cited or most downloaded. For example, one he co-authored on All-metal Wideband Metasurface on Scientific Reports in May 2021 was selected by Web of Science-Clarivate as both a Highly cited paper (top 1% in the academic field of Engineering) as well as a Hot paper (to 1% in Engineering). He is in world’s top 100,000 most-cited scientists list by Mendeley Data. Karu received BSc degree in electronic and telecommunication engineering with First Class Honours from the University of Moratuwa, Sri Lanka, and MASc and PhD degrees with near-perfect GPA in electrical engineering from the University of Ottawa, Canada. Previously he was Director of WiMed Research Centre and Associate Dean – Higher Degree Research (HDR) of the Division of Information and Communication Sciences and directed the Centre for Collaboration in Electromagnetic and Antenna Engineering at Macquarie University. He has also served as a member of the Dean’s Advisory Council and the Division Executive and as the Head of the Department several times. Karu is a Director of Innovations for Humanity Pty Ltd. From 2018 to 2020, Karu chaired the prestigious Distinguished Lecturer Program Committee of the IEEE Antennas and Propagation (AP) Society – the premier global learned society dedicated for antennas and propagation - which has close to 10,000 members worldwide. After two stages in the selection process, Karu was also selected by this Society as one of two candidates in the ballot for 2019 President of the Society. Only three people from Asia or Pacific apparently have received this honour in the 68-year history of this Society. Karu is also one of the three Distinguished Lecturers (DL) selected by the Society in 2016. He is the only Australian to chair the AP DL Program ever, the only Australian AP DL in almost two decades, and second Australian AP DL ever (after UTS Distinguished Visiting Professor Trevor Bird). He has served the IEEE AP Society Administrative Committee in several elected or ex-officio positions 2015-20. Karu is also the Chair of the Board of management of Australian Antenna Measurement Facility, and was the elected Chair of both IEEE New South Wales (NSW), and IEEE NSW AP/MTT Chapter, in 2016 and 2017. Karu is in the College of Expert Reviewers of the European Science Foundation (2019-22) and he has been invited to serve as an international expert/research grant assessor by several other research funding bodies as well, including the European Research Council and funding agencies in Norway, Belgium, the Netherlands, Canada, Finland, Hong-Kong, Georgia, South Africa and Chile. He has been invited by Vice-Chancellors of Australian and overseas universities to assess applications for promotion to professorial levels. He has also been invited to assess grant applications submitted to Australia’s most prestigious schemes such as Australian Federation Fellowships and Australian Laureate Fellowships. In addition to the large number of invited conference speeches he has given, he has been an invited plenary/extended/keynote/distinguished speaker of several IEEE and other venues over 30 times, including EuCAP 2020 Copenhagen, Denmark; URSI’19, Seville, Spain; and 23rd ICECOM 2019, Dubrovnik, Croatia. Karu has served or is serving as a Senior Editor of IEEE Access and Associate Editor of both IEEE Transactions on Antennas Propagation and IEEE Antennas and Propagation Magazine. He is a Track Chair of IEEE AP-S/URSI 2022 Denver, 2021 Singapore and 2020 Montreal; Technical Program Committee Co-Chair of ISAP 2015, APMC 2011 and TENCON 2013 and the Publicity Chair of ICEAA/IEEE APWC 2016, IWAT 2014 and APMC 2000. His research activities are posted in the web at http://web.science.mq.edu.au/~esselle/ and https://www.uts.edu.au/staff/karu.esselle .