A novel type of microstrip antenna is proposed for compact wideband wireless applications. The antenna is composed of six unit cells of left-handed metamaterial (LHM) and a dipole element. The dipole is directly connected to three of six LHM unit cells, which are arranged in a 2 3 antenna array form. In this aspect, the proposed antenna is regarded as LHM loaded dipole antenna. The antenna is matched with a stepped impedance transformer and rectangular slot in the truncated ground plane. The coupled LH resonances and simultaneous excitation of different sections of unit cells and dipole result into broad bandwidth. The proposed antenna has a maximum gain of 1 dBi at 2.5 GHz. The measured return loss indicates 63% bandwidth for S11 10 dB over the band of 1.3-2.5 GHz. The overall size of LHM loaded antenna is 0 2 87 0 11 27 0 315 80 at the center frequency. The radiation of the electrically small LHM unit cells is also demonstrated by the simulated radiation pattern, which is an important concept for the antenna miniaturization. Index Terms-Dipole antennas, left-handed metamaterials (LHMs), loaded antennas, periodic structure.

A dual‐band optically transparent antenna based on a slotted interconnected ring resonator as an efficient radiating element is proposed. The compact radiating element and partial ground plane are structured on a plexiglass substrate with Silver Tin Oxide as transparent conducting material. The radiation disadvantage of OTAs due to the low conductivity of conductive oxides has been overcome with the gain improvement technique of 2 × 1 antenna array design. The overall sizes of the proposed single element and 2 × 1 two element array antennas are λ/2.5 × λ/2.5 and λ/1.19 × λ/2.08 at the lower resonance frequency of 2.4 GHz, respectively. The operation bands of both OTA prototypes cover WLAN and WiMAX frequency bands with permissible bandwidth and sufficient gain therefore the 2 × 1 antenna array is utilized as one of two dual‐band antennas of a 2 × 2 MIMO transceiver system for WLAN and WiMAX band operations.

A transparent flexible co‐planar waveguide fed patch antenna using polyethylene terephthalate substrate is presented. The wideband high gain antenna having an overall dimension of 0.48λ × 0.64λ at the center frequency of 4.28 GHz is fabricated using a transparent sheet made up of Silver Tin Oxide (AgHT‐8). The performance of the proposed antenna is compared with four other nontransparent nonflexible and semitransparent flexible antennas. For the engineered design, patch geometry and feeding mechanism are kept constant whereas the substrate and patch materials are varied. Simulations are carried out using finite element method‐based full wave high‐frequency structure simulator after which the antennas are fabricated and tested. The proposed flexible transparent antenna has bandwidth in order of 40%, ranging from 3.89 to 5.9 GHz, with a notable gain over 3 dBi and efficiency greater than 80% for the entire frequency band. The bending conditions are also tested for the flexible transparent antenna which showed decent performance for sub‐6 GHz 5G and WLAN applications.

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An ultrathin dual-layer flexible metamaterial absorber with triple-band for RF energy harvesting applications has been reported in this article. The sub-wavelength unit cell of the proposed absorber is composed of six distinct concentric annular having outer circumference of ring and octagonal inner circumference. The metallic resonators are constructed from copper foil self-adhesive tape which are affixed on flexible neoprene rubber sheet terminated by metal ground plate. The proposed absorber prototype is ultrathin and compact with the thickness less than 0.037λ 0 and cell size less than 0.2λ 0 at the lower absorption frequency of 1.75 GHz. Flexible dual-layer absorber exhibits triple absorption peaks of 96.91%, 96.41% and 90.12% at 1.75 GHz, 2.17 GHz and 2.6 GHz with full width at half maximum (FWHM) bandwidth of about~6.5%. The RF performance of proposed absorber is numerically computed for different polarization and incidence angle variations. The absorption value is above 76% for the oblique incidence angle up to 45 in TE mode operation, whereas the absorption value is 94% for oblique incidence angle up to 60 in TM mode operation. The measured outcomes are in agreement with the numerically calculated results. The energy harvesting potential of the proposed absorber structure is numerically confirmed by the resulting improved RF absorption value in dependence to different resistive loading of the polarization insensitive unit cells. K E Y W O R D S energy harvesting, metamaterial, metamaterial absorber

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An engineered novel tunable dual-band metamaterial antenna based on stacked split ring resonator (SRR) array is presented. The μ-negative SRR array present at two sublayers of stacked microstrip patch antenna substrate adds tuning capability to the antenna with marginal trade-off between antenna gain and cross-polarization. If the size of resonator element is considerably smaller than resonance wavelength, ideally lesser than λ/10, the resonator would support the resonating mode of antenna. Compact SRR array embedded in radiator facilitate the antenna tuning to intended allocated spectrum of L5- and S-band frequencies without modifying external dimensions of patch antenna, which in turn helps the satellite payload design. The variations in SRR array dimensions and inter-element spacing are subsequently utilized to maintain the antenna gain and voltage-standing wave ratio. The proposed design of inset fed antenna, matched at 50 Ω, was validated by experimental results and it is suitable for global positioning satellite applications.

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