Carbon-fiber composite T-match folded bow-tie antenna for RFID applications

In this paper, the authors investigate the use of carbon-fiber composite material for the radiating element for an radiofrequency identification antenna, the T-match folded bow-tie antenna. We consider two kinds of composites that have relatively high electrical conductivity for the radiating element: (1) a braided tissue of carbon fibers embedded in epoxy resin, and (2) reinforced long carbon-fibers in an epoxy matrix. All simulations are performed using CST MWS software. Since braided-tissue of carbon-fiber composite shows isotropic behavior, the composite antenna has almost the same resonant frequency of 950 MHz as the metal antenna. However, the radiation efficiency degrades due to the low conductivity of composites compared to metals. By using anisotropic reinforced carbon-fiber composite as a material for the radiating element, the behavior of the antenna changes and the resonant frequency increases to 2.45 GHz. The anisotropic conductivity allows the antenna designer to largely restrict current flow to one direction, and this may lead to novel antenna designs.