A Compact Flexible CPW-fed Circular Monopole UWB Antenna with Full Ground Plane Structure

A compact flexible Coplanar waveguide fed (CPW-fed) circular monopole ultra-wideband (UWB) antenna with full ground plane structure is proposed for wireless body-area network (WBAN) applications. A metal parasitic circular patch is introduced between the radiating element and the ground plane to extend the bandwidth. Multiple independent resonances are created by incorporating parasitic structures like semi-ring parasitic patch, semi-ring slots, via-hole to the mid-layer, and L-shape slots to further improve the impedance matching performance in the whole frequency range. The antenna uses denim as substrate to ensure good flexibility and wearing comfort. It has an overall size of 80×65×4.255 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (0.755λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> × 0.613λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> × 0.04λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> at the lowest operating frequency). The simulation results show that the proposed antenna has an operating frequency band of 2.83-10.88 GHz, and it has unidirectional radiation patterns with a highest realized gain of 7.35 dBi at 9.47 GHz. Due to the full ground plane structure, the antenna has minimized interference on human bodies, with a SAR value as low as 0.25 Watt/kg, proving to be a good candidate for WBAN applications.