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 four-element compact wide-band optically transparent MIMO antenna with a full ground plane is proposed. The four elements transparent MIMO system has a compact size of 24×20 mm 2 with the undivided ground plane as most of the real-time systems demand a common reference. The complete antenna system achieves around 85% transparency due to a combination of AgHT-8 and Plexiglas which forms the transparent conductive patch/ground and substrate, respectively. The antenna geometry leads dual-band operation ranging from 24.10-27.18 GHz (Impedance bandwidth = 12%) and 33-44.13 GHz (Impedance bandwidth = 28.86%) targeting the mm-wave 5G applications. The 4-element antenna system achieves isolation between inter-elements > 16 dB and maximum gain value of greater than 3 dBi with more than 75% efficiency. The proposed transparent MIMO antenna is evaluated in terms of diversity gain (DG), envelope correlation coefficient (ECC), total active reflection coefficient (TARC), and mean effective gain (MEG) where decent MIMO performance with isolation more than >16 dB between the adjacent and other elements is achieved. Transparent MIMO antenna achieves directional patterns for the operating band with the value of DG > 9, ECC < 0.1, TARC value less than-15dB, and the ratio of MEG within the agreed limit of ±3 dB confirming acceptable MIMO/diversity performance.

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.

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

A compact wideband transparent antenna designed on plexiglass substrate (10 × 12 × 1.48 mm3) is presented. The optically transparent antenna consists of a radiation patch and a ground plane fabricated using AgHT‐8. The antenna design comprises of rectangular shaped branches optimized to attain the wideband characteristics. The proposed antenna design has impedance bandwidth of 58.71% covering the frequency range of 23.92‐43.8 GHz. The radiation pattern of the proposed antenna shows directional radiation pattern with electrical tilt. All calculated and measured results show that proposed compact transparent antenna is an excellent candidate for 5G communication systems and wideband code division multiple access applications.