Flexible organic polymer matrix composite antenna for wireless local area network application

Abstract

The growing demand for flexible antennas has resulted in intensified research on new materials for flexible antennas. The flexibility of antennas is a well-known requirement in wireless body area networks (WBAN), vehicle navigation system and wireless local area networks (WLAN) to improve seamless integration on devices. Compared with conventional rigid antennas, conformal antennas provide a larger coverage area with a broad beam radiation pattern due to the increase in the area of transmission and reception. This research aims to develop and explore a new organic polymer matrix composite (PMC) antenna with organic fibre to replace synthetic polymer composite which may release harmful chemical and also non-biodegradable. Organic PMC is not only low cost but able to promote sustainability for the environment. Size miniaturization also needs to be achieved for a more compact size antenna and also to enhance the bandwidth. The proposed antenna is a flexible monopole antenna based on organic PMC material produced from natural Basalt fibre and it proved to manage in operating at frequencies of 2.45 GHz and 5.8 GHz for WLAN application. The characterized Basalt composite substrate has a thickness of 0.42 mm, dielectric constant of 3.105 and tangent loss of 0.0299. The vacuum infusion technique is used to manufacture the composite material as this technique can increase the accuracy of fiber to resin ratio and give consistent resin usage. Before vacuum infusion, a layer of conductive fabric named ShieldIt with adhesive glue on its bottom layer will be ironed onto the basalt fiber fabric. Then, two layers of basalt fiber fabric with a layer of conductive fabric on the top layer were placed on the mold before vacuum conditions are created. Epoxy resin and hardener were then mixed in a ratio of 10:6. Vacuum pressure was turned on and pushed the epoxy mixture to the laminate through the tubing. The defected ground structure (DGS) were implemented to improve bandwidth and coplanar waveguide (CPW) as antenna feeding method. Top layer radiating element is conductive fabric and the lasercut machine cut out the antenna pattern precisely. Measured antenna gains at 2.45 GHz and 5.8 GHz are 3.865 and 4.8 with efficiency of 62.63% and 68.07%, respectively. As a flexible antenna, the bending test proved that the antenna performance did not compensate for bending at different curvature radii.