Miniaturized flexible metamaterial antenna of circularly polarized high gain‐bandwidth product for radio frequency energy harvesting

Summary A discussion of using an ultrawide band (UWB) Hilbert‐shaped metamaterial (MTM) antenna structure for RF energy harvesting is exemplified in this article to conduct the use of organic substrates. Therefore, the proposed design is structured as a low profile rectangular MTM array in the context of wearable systems. The antenna is mounted on a prepared indium‐nickel oxide‐based polymerized Palm fiber (INP) substrate and backed with a ground plane of square electromagnetic band gap (EBG) defects. Fifteen samples of INP substrate are prepared for this study. Thus, the prepared INP substrates characterizations are tested using a T‐resonator transmission line technique printed on an FR4 substrate. In this technique, the measured scattering parameters are interpreted from two resonators with two different characteristics impedance to be employed for retrieving the relative permittivity ( ε r ) and permeability ( μ r ). This process is included to ensure the prepared substrate properties controllability for microwave devices manufacturing. After that, the proposed antenna is manufactured from silver nanoparticle (SNP) printout. The performance of the proposed antenna is tested numerically and experimentally. It is found that the proposed antenna shows an UWB response to start from 3 and up to 10 GHz that suits different applications including IoT, 5G, and WiMAX system networks. The measured gain spectrum shows four peaks at 3.5, 4.2, 5.4, and 6 GHz with gain values of 1.1, 2, 3.4, and 3.9 dBi, respectively. Finally, the conversion efficiency of RF harvesting is measured experimentally for the antenna in case of flat profile and bended structure at the frequency bands of interest to reveal insignificant changes.