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This paper presents a broadband frequency tunable and polarization reconfigurable circularly polarized (CP) antenna, using a novel active electromagnetic band gap (EBG) structure. The EBG surface employs identical metallic rectangular patch arrays on both sides of a thin substrate, but rotated by 90 from each other. The active bias circuits are also orthogonal for each surface, enabling the reflection phases for orthogonal incident waves to be tuned independently in a wide frequency range. By placing a wideband coplanar waveguide (CPW) fed monopole antenna above the EBG surface, and properly tuning the bias voltages across the varactors in each direction, CP waves can be generated at any desired frequency over a broad band. In accordance with simulations, the measured 3 dB axial ratio (AR) bandwidth reaches 40% (1.03-1.54 GHz), with good input matching and radiation patterns at six presented sampling frequencies. The polarization reconfigurability is verified by simulations and measurements, and shown to be capable of switching between left hand circular polarization (LHCP) and right hand circular polarization (RHCP).

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The present work describes the inkjet printing and low temperature sintering of silver nanoparticle inks onto transfer tattoo paper. Our approach results in silver features of excellent resolution and conductivity and, subsequently the first passive UHF RFID transfer tattoo tags functional mounted on human skin of improved performance when compared to screen printed passive UHF RFID transfer tattoo paper tags.Moreover, inkjet printed passive UHF RFID transfer tattoo tags show similar performance to copper etched passive UHF RFID tags on plastic substrates. This study compares the image quality (resolution) and electrical performance of two commercial silver nanoparticle inks inkjet printed on transfer tattoo paper.The optimal printing and sintering parameters to obtain high resolution features of resistivities 20 to 57 times the resistivity of bulk silver (1.59 Â 10 À6 ohm cm) are described. We demonstrate how, by selectively depositing ink in specific areas of the antenna, read distance of passive UHF RFID tags can be increased from 54 to 68 cm whilst decreasing the amount of ink used by 33%. Furthermore, this approach results in inkjet printed passive UHF RFID tattoo tags with larger read distance than silver screen printed passive UHF RFID tattoo tags, 45 cm, and similar to copper etched passive UHF RFID plastic tags, 75 cm. Moreover, inkjet printed passive UHF RFID tattoo tags in this work are considerably thinner (1-5 mm) than screen and etched passive UHF RFID tags (tens of micrometers) hence, making the former more appealing to the end user. In addition to this, inkjet printing is compatible with large area manufacturing techniques and has the potential to evolve as one of the most promising RFID mass-production techniques. Therefore, this work represents a step towards the commercialization of on-body transfer tattoo paper passive UHF RFID tags.