Folded Loop Balanced Coplanar Antenna for WLAN Applications

A novel balanced rectangular loop antenna is proposed, having an ungrounded coplanar waveguide (CPW) feed configuration and a folded structure at both ends. This antenna is designed for operation over the 2.4 GHz and 5 GHz WLAN frequency bands. Bond-wire bridges are used along the CPW feed line to ensure the same potential across the CPW ground planes. The self-balancing structure that can be realized in a loop antenna offers operation without the need of a separate balun for connection to a RF source. A prototype of the optimized antenna with overall dimension of 31 mm x 16 mm x 3 mm was fabricated and tested. The calculated and measured results show good agreement, confirming good wideband characteristics with multiband operation. An example application of the proposed antenna is studied when used in handheld devices. The results show that this antenna has performance largely independent of perturbations of its associated ground plane, because the balanced feed created by the intrinsic balun structure minimizes ground plane currents.