A Printed CPW-fed Slot-Loop Antenna with Narrowband Omnidirectional Features

The design of a novel CPW-fed printed slot-loop antenna with narrowband omnidirectional attributes is proposed. The antenna geometry is selected to reduce slot coupling, thus achieving both a narrow bandwidth and an omnidirectional radiation pattern simultaneously. A gain of 2.1 dBi is accomplished with high radiation efficiency. Very narrow fractional impedance bandwidths as low as 2.9% are realised with good omnidirectional radiation characteristics. A technique providing unconstrained control of the bandwidth in the range of 1.7–6.9% is described.