An Asymmetric Coplanar Strip-Fed Compact Yagi-Uda Antenna Utilizing Ground as Director

This paper presents a novel approach to design a printed monopole driven compact Yagi-Uda antenna, where the printed monopole is fed using asymmetric coplanar strip (ACS) line to significantly reduce the size of the driven element of the Yagi-Uda array compared to the standard coplanar waveguide (CPW)-fed case. Further, the use of ground of the ACS as a director circumvent the need of incorporating a dedicated director element making the Yagi-Uda array even more compact. It is found that an ACS-fed Yagi-Uda antenna having reflector alone and no director provides a front-to-back ratio of only 6 dB, which improves to 15 dB after successfully using the ground as director. The designed antenna, which operates in the 2.4 GHz wireless local area network (WLAN) band with 5.71% bandwidth, has the footprint of only 47 x 24 mm(2).