EditorialThis research received no external funding

Ghinea, G

Nagarajan, R

Suriyan, K

Electronics

Brunel University Research Archive

Citation: Suriyan, K.; Nagarajan, R.;Ghinea, G. Smart AntennaOptimization Techniques for WirelessApplications. Electronics 2023, 12,2983. https://doi.org/10.3390/electronics12132983Received: 29 June 2023Accepted: 3 July 2023Published: 6 July 2023Copyright: © 2023 by the authors.Licensee MDPI, Basel, Switzerland.This article is an open access articledistributed under the terms andconditions of the Creative CommonsAttribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).electronicsEditorialSmart Antenna Optimization Techniques for Wireless ApplicationsKannadhasan Suriyan 1,* , R. Nagarajan 2 and George Ghinea 31 Department of Electronics and Communication Engineering, Study World College of Engineering,Coimbatore 641105, India2 Department of Electrical and Electronics Engineering, Gnanamani College of Technology,Namakkal 637018, India; krnaga71@yahoo.com3 Department of Computer Science, College of Engineering, Brunel University, London UB8 3PH, UK;george.ghinea@brunel.ac.uk* Correspondence: kannadhasan.ece@gmail.com or s.kannadasan@swehg.comIn recent years, antenna design has received a lot of attention. This is due to a surgein interest in a variety of applications, ranging from IoT to low-frequency, long-rangeapplications and to high-frequency mmWave 5G mobile technology. Wearable antennasthat build body area networks have also sparked interest. Wearable clothes and materialsthat adhere directly to the skin, such as e-skin, are examples of this. The supply of evenlarger data rates to mobile customers, the delivery of zero-latency multimedia content,and the connectivity of diverse services are all intimately linked on the path to designingand implementing next-generation broadband wireless networks. The goal is to createa cellular network environment in which sensors, appliances, automobiles, and dronesmay interact with one another. The cellular network’s capacity must be considerablyincreased in order to support such interactions. The notion of 5G, a new generation ofmobile wireless technology that offers multi-gigabit-per-second data rates with a highercapacity and lower latency than today’s wireless systems, was recently announced by thewireless communications industry. Future phones and base stations will need multimodeantenna technology that is both energy-efficient and can function in the millimeter waveband in conjunction with legacy 4G and sub-6 GHz 5G.Antennas should be small in size, but they must meet technical criteria, such as agreater power, wider bandwidth, higher gain, and insensitivity to human users’ hand-heldinfluence. The usage of the millimeter wave band, which will provide a network of tinycells enabling high-capacity and area-efficient hotspot zones, is critical to 5G. The next 5Gsystem will be a true mobile multimedia communication platform, including not just legacyheterogeneous mobile networks but also sophisticated radio interfaces and the ability tooperate at millimeter wave frequencies to make use of the vast amount of available capacity.This will impose stringent design standards that go beyond the most recent 5G rollout inthe sub-6GHz range.This Special Issue aims to shed light on recent breakthroughs in antenna design forthese new developing applications, as well as highlight more study possibilities in thisfascinating field of communications technology. We encourage scholars and practicingengineers to submit original research papers that address:• Multibeam antenna technologies for 5G wireless communications;• Millimeter wave (mmWave) and THz antennas for 5G wireless communications;• Propagation models at mmWave and THz bands;• Compact antenna arrays for massive MIMO systems;• mmWave and large-scale MIMO channel models;• Antennas for implantable systems and IoT applications;• Advanced antennas and transceivers for full-duplex communication;• Distributed antenna systems for 5G multiuser networks;• mmWave and THz cooperative relays for coverage extension;Electronics 2023, 12, 2983. https://doi.org/10.3390/electronics12132983 https://www.mdpi.com/journal/electronicsElectronics 2023, 12, 2983 2 of 5• Antenna design for the Internet of Things;• Beamforming and smart antennas for 5G;• Antenna design for wearable applications;• Antenna design for body area networks;• Antenna design for Chipless RFID;• Metamaterial-based antennas;• Smart antennas, beamforming and MIMO;• Aeronautical and space applications;• Antenna design for CubeSat;• Antenna design for deep space communication• Antenna design for biomedical systems and applications;• Implanted antennas;• UWB and multispectral technologies and systems;• mmWave and THz antennas;• Multiple antennas for advanced 5G transceivers;• Multiband 5G antenna;• 5G Dielectric Resonator antennas;• Antennas on flexible substrates for medical applications;• Antennas for wireless power transmission and harvesting;• RFID antennas;• Reconfigurable antennas and devices;• Mutual coupling and isolation techniques between antenna elements;• UWB antennas.Bluetooth low-energy beacons are active transmitters that send a radio signal at setintervals [1]. Most beacons are powered by small batteries. The problem with systems basedon such devices is the need to periodically replace the chemical cells. This is especiallytedious when a large number ofthe beacons is used. A solution to these problems is to usebeacons with a power supply supported by photovoltaic panels. Their obvious drawback isthe need to place them in good lighting conditions. To overcome this disadvantage, the useof a power source that gathers energy due to the Peltier effect is proposed in this paper. Sincethe temperature difference between two surfaces can be found in almost every environment,the authors analyzed the efficiency of this kind of energy source in the context of poweringthe beacons. In order to justify the idea, a multitude of measurements and simulationswas performed. The power supply demand of the beacon was measured in various modesof operation. Finally, the model of the proposed device was developed. The elaboratedsolution eliminates the need for batteries and makes the beacon maintenance-free.A novel compact fractally loaded two- and eight-element multiple-input–multiple-output (MIMO) with strong diversity is designed for 5G Sub 6 GHz and WLAN applica-tions [2]. The proposed layout features a partially grounded, protruding T-shaped stub onthe underside of the substrate and a set of fractally loaded circular patch antenna elementson the top. Four triangular slots on the substrate and a T-shaped stub on the ground areemployed to produce good isolation over the intended bands. The proposed antenna has afrequency range of (3.3–6.0) GHz, making it compatible with the 5G sub-6 GHz bands andthe WLAN band thanks to its high isolation of above 15 dB and good impedance-matchingcharacteristics. Good agreement is observed between the antenna results and the theory ofcharacteristic mode analysis approach.A frequency reconfigurable multiband multiple-input–multiple-output (MIMO) an-tenna is developed for 5G communication systems [3]. A split-ring resonator (SRR) isintroduced into the upper patch to cover multiple 5G application bands, and an RF PINdiode is embedded between the upper and lower patches to enable the frequency diversityfeature. In order to design a MIMO antenna with improved inter-element isolation, fourantenna elements are orthogonally located with ground planes connected to each other.The antenna design covers the n41/n46/n48/n79 5G application bands.Electronics 2023, 12, 2983 3 of 5Array imperfections may exist in an antenna system subject to non-ideal design andpractical limitations. It is difficult to accurately model array imperfections, and thuscomplicated algorithms are usually inevitable for model-based methods to estimate thedirection of arrival (DOA) with imperfect arrays. Deep neural network (DNN)-basedmethods do not need to rely on pre-modeled antenna array geometries, and have beenexplored to handle flawed array models because of their better flexibility than model-basedmethods.In this paper, we study the convolutional AE (CAE) method that substantiallyfocuses on the learning of local features in a different manner from the previous DAEmethod. The advantage of the convolutional operation using a kernel in CAE is to capturefeatures in a more efficient manner than the DAE, and thus be able to reduce the numberof parameters that are required to be trained in the neural networks. From the numericalevaluation of DOA estimation accuracy, the proposed CAE method is also more resistant tothe noise effect than the DAE method such that the CAE method has better accuracy at alower signal-to-noise ratio [4].Modern navigation requires high accuracy of position coordinate determination, par-ticularly in bathymetric surveys and aerial photogrammetry (Makar, A. et al.). In mostcases, the terrain conditions enable positioning with high accuracy and reliability. Theseparticularly involve the terrain conditions, i.e., high harbour infrastructure for bathymetricsurveys and trees for railway surveys that hinder the measurement performance with apre-determined accuracy. This article presents the limitations in unmanned survey vehicle(USV) positioning in an area restricted by a high quay, and difficult observational condi-tions in the surrounding high harbour infrastructure. The positioning used a four-systemreceiver that determined position coordinates based on the signals from one, two, threeand four satellite navigation systems. The number of available satellites was determinedunder conditions of the open upper hemisphere and the partially obscured hemispherebased on the surrounding geometry. The determined position coordinates were related tothe position determined using robotic total station (RTS). An area was identified in which itbecomes difficult or impossible to maintain the required positioning accuracy [5].The goal of this work was to optimize a wire-bonded patch antenna to minimizelosses and maximize the gain in the frequency range from 81 to 83 GHz (Bogdan, G.et al.). Optimization was based on electromagnetic simulations of different variants of thewire bond. Results show that the optimized structure demonstrates two major advantages.Firstly, it does not require any external matching network; hence, it can be directly connectedto a contact pad of an MMIC die. Secondly, the wire bond radiation effect is utilized toenhance the patch antenna gain at the broadside direction [6].A fundamental feature of the functioning of antennas in this area is the possibility ofspatial focusing of electromagnetic energy. In this case, it is possible to realize the maximumfield strength at a given point in space and reduce the field strength outside this point.The focusing effect itself is provided by the in-phase addition of fields from elementarysources. Additionally, in addition to the formation of the maximum field strength at thefocusing point, it is also possible to realize a minimum field strength at the focusing pointby implementing antiphase addition of partial fields at the focusing point. The fundamentalpossibility of forming sum and difference amplitude distributions of electromagnetic fieldsin the near radiated field zone makes it possible to realize sum–difference signal processingin order to reduce the level of the secondary maximum of the focused field. This articlediscusses the features of the formation of the sum and difference amplitude distributionsand the principles of the sum–difference processing of focused electromagnetic fields, alongwith the implementation of technical solutions for non-destructive testing and technicaldiagnostic tasks [7].The technique relies on the definition of relevant figures of merit (FoM) and the use of agradient-based minimization algorithm. To this end, the volume where the NF is computedis divided into a number of disjoint regions where the FoM are defined. These FoMdefine the performance of the antenna and their direct optimization enables improvementcompared to previous approaches described in the literature, while reducing the memoryElectronics 2023, 12, 2983 4 of 5footprint of the algorithm and accelerating computation. The optimization procedureis divided into several stages to facilitate convergence towards a successful outcome.First, a phase-only synthesis is carried out at a single frequency. Then, a reflectarraylayout is obtained using a method of moments based on local periodicity, accounting formutual coupling between elements. Finally, an in-band DLO is performed at a number offrequencies directly optimizing the FoM. The results show that the obtained reflectarraylayout complies with the requirements in the frequency range 27 GHz–29 GHz within the5G new radio n257 band [8].When utilized in wireless communications, high-frequency electromagnetic wavesimpose several physical restrictions (Hadi, M.U. et al.). To overcome these difficultiesand to expand the service coverage, the radio-over-fibre (RoF)-based distributed antennasystem (DAS), in particular, can improve the usability of future mobile networks withadvantages such as seamless media conversion between wireless and optical signal, flexiblemultichannel aggregations, and efficiency. RoF technology’s inherent advantages are thatit improves the DAS network’s usability and transmission performance by allowing it toprovide both 5G and 6G THz services at the same time over a single optical fibre connection.We experimentally broadcast a single carrier-modulated 6G signal using a 256 quadratureamplitude modulation and a 5G new radio signal across a 10 km single mode fibre opticlink. Additionally, the 6G signal is received through a 3 m wireless medium providing,proof of concept for fibre wireless integration. The experimental trials are assessed in termsof error vector magnitude and carrier suppression ratio. The dynamic range of the allowedRF input power for a 6G signal is 10 dB, while the dynamic range for a 5G waveformsignal is 18 dB, which meets the 3GPP standardization criteria. Moreover, the bit error rateperformance significantly improved as the carrier suppression ratio was increased from0 to 20 Db [9].Future wireless systems’ adoption of smart antenna techniques is anticipated to have asignificant impact on the effective use of the spectrum, the reduction instartup costs for newwireless networks, the enhancement of service quality, and the realisation of transparentoperation across multi-technology wireless networks. Its success, however, depends on twofactors that are frequently disregarded when researching smart antenna technologies: first,the features of smart antennas must be taken into account early in the design phase of futuresystems (top-down compatibility); second, a performance evaluation of smart antennatechnique must be carried out in accordance with the crucial parameters associated withfuture systems requirements (bottom-up feasibility). First, a summary of the advantagesof and most current developments in smart antenna transceiver architecture are providedin this article. The most significant developments in the use of smart antennas in futuresystems are then discussed, including reconfigurability to changing channel propagationand network conditions, cross-layer optimisation, and multi-user diversity. Additionally,problems with designing an appropriate simulation methodology and accurately mod-elling channel characteristics, interference, and implementation losses are discussed. Thepredicted financial impact of the implementation of smart antenna systems is then explored,along with market trends and future predictions.Author Contributions: K.S., conceptualization, methodology, writing, editing, review and conclusion;R.N., conceptualization, methodology, writing, editing, review and conclusion; G.G., conceptualiza-tion, methodology, writing, editing, review and conclusion. All authors have read and agreed to thepublished version of the manuscript.Funding: This research received no external funding.Acknowledgments: We would like to take this opportunity to appreciate and thank all authors fortheir outstanding contributions and the reviewers for their fruitful comments and feedback. Wewould also like to acknowledge all the reviewers for their careful and timely reviews to help improvethe quality of this Special Issue. Last but not least, we would like to thank the Editorial Team of theElectronics journal for all the support provided in the publication of this Special Issue, ElectronicsElectronics 2023, 12, 2983 5 of 5Editorial Office staff for their hard and precise work in maintaining a rigorous peer-review scheduleand timely publication.Conflicts of Interest: The author declares no conflict of interest.References1. Pyt, P.; Jankowski-Mihułowicz, P.; Węglarski, M. Bluetooth Low Energy Beacon Powered by the Temperature Difference.Electronics 2023, 12, 1278. [CrossRef]2. Addepalli, T.; Kumar, M.S.; Jetti, C.R.; Gollamudi, N.K.; Kumar, B.K.; Kulkarni, J. Fractal Loaded, Novel, and Compact Two- andEight-Element High Diversity MIMO Antenna for 5G Sub-6 GHz (N77/N78 and N79) and WLAN Applications, Verified withTCM Analysis. Electronics 2023, 12, 952. [CrossRef]3. Singh, G.; Kumar, S.; Abrol, A.; Kanaujia, B.K.; Pandey, V.K.; Marey, M.; Mostafa, H. Frequency Reconfigurable Quad-ElementMIMO Antenna with Improved Isolation for 5G Systems. Electronics 2023, 12, 796. [CrossRef]4. Chang, D.-C.; Liu, Y.-T. DOA Estimation Based on Convolutional Autoencoder in the Presence of Array Imperfections. Electronics2023, 12, 771. [CrossRef]5. Makar, A. Limitations of Multi-GNSS Positioning of USV in Area with High Harbour Infrastructure. Electronics 2023, 12, 697.[CrossRef]6. Bogdan, G.; Sobolewski, J.; Bajurko, P.; Yashchyshyn, Y.; Oklej, J.; Ostaszewski, D. A Wire-Bonded Patch Antenna for MillimeterWave Applications. Electronics 2023, 12, 632. [CrossRef]7. Vedenkin, D.; Morozov, O.; Sedelnikov, Y.; Agliullin, T.; Nasybullin, A. Increasing the Accuracy Characteristics of FocusedElectromagnetic Devices for Non-Destructive Testing and Technical Diagnostics by Implementing Sum–Difference SignalProcessing. Electronics 2023, 12, 436. [CrossRef]8. Prado, D.R. Plane-Wave Generation through General Near-Field In-Band Reflectarray Direct Layout Optimization with Figure ofMerit Constraints in mm-Wave Band. Electronics 2023, 12, 91. [CrossRef]9. Hadi, M.U.; Murtaza, G. Fibre Wireless Distributed Antenna Systems for 5G and 6G Services. Electronics 2023, 12, 64. [CrossRef]Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individualauthor(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury topeople or property resulting from any ideas, methods, instructions or products referred to in the content.

Smart Antenna Optimization Techniques for Wireless Applications

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Smart Antenna Optimization Techniques for Wireless Applications

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