editorial flexible and conformal antennas and applicationseditorial flexible and conformal antennas...

EditorialFlexible and Conformal Antennas and Applications

Maggie Y. Chen ,1 Félix A. Miranda,2 Xing Lan,3 and Xuejun Lu4

1Ingram School of Engineering, Texas State University, San Marcos, TX 78666, USA2NASA Glenn Research Center, Cleveland, OH 44135, USA3NG Next, Northrop Grumman Corporation, Redondo Beach, CA 90278, USA4Department of Electrical and Computer Engineering, University of Massachusetts, Lowell, MA 01854, USA

Correspondence should be addressed to Maggie Y. Chen; [email protected]

Received 14 March 2018; Accepted 14 March 2018; Published 6 June 2018

Copyright © 2018Maggie Y. Chen 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.

There are numerous ongoing research efforts in flexibleantenna technology since these antennas can enable commu-nications in curved surfaces not suitable for traditional rigidantennas, as well as exhibiting wide adaptability, low massdensity, small volume, lightweight, and low cost. A consid-erable effort is being carried out on the novel antennaconfigurations exhibiting agile operating frequencies, tunablebandwidth, switchable polarization, and reconfigurable radi-ation pattern. Due to the significant research efforts and fastdevelopment in the field, International Journal of Antennasand Propagation set out to publish a special issue devotedto the topic of Flexible and Conformal Antennas and Appli-cations. The result is a collection of ten outstanding articlessubmitted by investigators representing seven countriesacross Asia, Europe, and North America.

For additive manufacturing and direct write printing,material selection and manufacturing process are critical tothe antenna and radio frequency (RF) components’ overallelectrical and mechanical performance. M. A. Monne et al.from Texas State University, in “Material Selection andFabrication Processes for Flexible Conformal Antennas,”discuss extensively the major fabrication techniques andassociated materials used for the fabrication of flexible con-formal antennas, including 3D printing technology, wearabletextile technology, substrate-integrated waveguide technol-ogy, and membrane technology. The application of each typeof fabrication technique is analyzed through experimentalresults, which further underlines the importance of materialselection and the various fabrication processes. E. S. Roskeret al. from Northrop Grumman Corporation and UCLA, in

“Printable Materials for the Realization of High PerformanceRF Components: Challenges and Opportunities,” thoroughlydiscuss the attributes and challenges of additive manufactur-ing and direct writing techniques for the development of avariety of RF components including antennas, filters, andtransmission lines. In this very comprehensive paper, theauthors discuss printing methods, ink formulation, and post-processing approaches necessary to attain RF componentsand devices with performance comparable to those devel-oped using conventional techniques and address future areasof research where further work is needed to optimizethe performance and exploit the full potential of printedRF components.

Various types of flexible antennas were designed andreported. J. Zhou et al. from Xidian University, in “Design,Fabrication, and Testing of Active Skin Antenna with 3DPrinting Array Framework,” report the design, fabrication,and testing of a novel active skin antenna which consists ofan encapsulation shell, antenna skin, and RF and beamcontrol circuits. An active skin antenna prototype with 32microstrip antenna elements was fabricated using a hybridmanufacturing method. 3D printing technology was appliedto fabricate the array framework, and the different layerswere bonded to form the final antenna skin by using tradi-tional composite processes. The proposed design and fabrica-tion technique is suitable for the development of a conformalload-bearing antenna or smart skin antenna installed in thestructural surface of aircraft, warships, and armored vehicles.L. Zhao et al. from Nanjing University of Posts and Telecom-munications, in “A Ring-Focus Antenna with Splash Plate in

HindawiInternational Journal of Antennas and PropagationVolume 2018, Article ID 6367571, 2 pageshttps://doi.org/10.1155/2018/6367571

http://orcid.org/0000-0003-2226-7112https://doi.org/10.1155/2018/6367571

Ka-Band,” report a ring-focus antenna fed by a splash platefor Ka-band communications. In this paper, the authorsintroduce a new theory for the splash-plate feed design. Theirsimulation also shows a very good agreement with themeasurement data. The measured efficiency satisfies therequirement for Ka-band communications. K. N. Parachaet al. from Universiti Teknologi Malaysia, in “Low-CostPrinted Flexible Antenna by Using an Office Printer for Con-formal Applications,” report a coplanar waveguide- (CPW-)fed Z-shaped planar antenna printed using an ink-jet printeron a flexible polyethylene terephthalate (PET) substrate. Theradiation efficiency of 62% was achieved at 2.45GHz. Theperformance of the printed antenna under various bendingconditions is also tested for conformal applications for thefuture 5G network. C. Y. Cheung et al. fromHong Kong havedemonstrated a printed inverted-F antenna (PIFA) in thepaper titled “Miniaturized Printed Inverted-F Antenna forInternet of Things: A Design on PCB with a MeanderingLine and Shorting Strip.” This antenna employs a smartmeandering line and shorting strip design technique to fur-ther reduce the overall size, profile, and cost and increase theantenna’s various electrical performances. This techniquecan be adapted and widely applied to various Internet ofThings (IoT) and numerous other wireless applications dueto its merits.

Flexible high-speed digital switching, amplifiers, anddigital beamforming networks are critical to realize flexiblephased-array antenna. M. A. Monne et al. from Texas StateUniversity, in “Inkjet-Printed Flexible MEMS Switches forPhased-Array Antennas,” report a fully ink-jet-printed flexi-ble MEMS switch for phased-array antennas. The physicalstructure of the printed MEMS switch consists of an anchorwith a clamp-clamp beam, a sacrificial layer, and bottomtransmission lines. 5mil Kapton® polyimide film is used asa flexible substrate material. Layer-by-layer fabrication pro-cess and material evaluation are illustrated. The MEMSswitch has a low actuation voltage of 1.2V, current capacityof 0.2195mA, a current on-off ratio of 2195 : 1, and an RFinsertion loss of 5 dB up to 13.5GHz. Printed MEMS switchtechnology is a promising candidate for flexible and reconfi-gurable phased-array antennas and other RF and microwavefrequency applications.

Numerical simulation of an antenna system can be usedas guidance towards flexible antenna development. S. Asalyet al. from Ariel University, in “Accurate 3D MappingAlgorithm for Flexible Antennas,” report a new accurate 3Dflexible antenna surface mapping technology using a small-sized monocamera and known patterns on the antennasurface. This method demonstrated up to 0.1-millimeterantenna mapping accuracy from 1m distance. The methodprovides an effective tool for accurate 3D mapping of a flex-ible antenna surface. D. Subitha and J. M. Mathana fromAnna University, in “Design of Low-Complexity Hybrid Pre-coder and Inkjet-Printed Antenna Array for Massive MIMODownlink Systems,” propose two design methodologies toreduce the complexity of massive multiple input multipleoutput (MIMO) systems. The first one is the design of alow-complexity hybrid precoder based on zero-forcing (ZF)precoding algorithm and Neumann series approximation.

The second one is the design of a flexible, environmentfriendly, simple 128-element Z-shaped coplanar waveguide(CPW) monopole array at the frequency of 2.4GHz. Theperformance of the proposed designs are evaluated in termsof probability of error in the hybrid precoding algorithmand radiation characteristics like gain, directivity, and returnloss for the printed antenna design.

Uniformly, these authors highlight both the promise andthe challenges faced by this emerging field of antenna devel-opment. In summary, this special issue provides a snapshotof the current development of flexible and conformal anten-nas across the globe. Hopefully, this publication will providea benchmark for future development of innovative, high-performance, low-cost, rapid deployable, and flexible anten-nas for various applications.

Maggie Y. ChenFélix A. Miranda

Xing LanXuejun Lu

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