Compact quasi-Yagi antenna with short length microstrip-to-coplanar stripline transition

A compact ultra-wideband (UWB) quasi-Yagi antenna with microstrip-to-coplanar stripline transition balun is presented in this paper. A planar balun with very short length (5.1 mm) has a 3dB back-to-back insertion loss bandwidth from 4.3 GHz to 10.8 GH. The proposed antenna has end-fire pattern and a good front-to-back ratio of 11.7 dB at 8.5 GHz. The cross polarization levels are -22 dBi and -25 dBi in the H-plane and E-plane, respectively.