Design of a Multiband Quasi-Yagi-Type Antenna With CPW-to-CPS Transition

A novel coplanar waveguide-fed planar quasi-Yagi antenna for multiband operation is presented in this letter. The antenna consists of a basic quasi-Yagi element and a coplanar-waveguide-to-coplanar-strip (CPW-to-CPS) transition, which can excite the odd-mode electric fields at the CPS line though the CPW feed line. The proposed antenna can be used in multiband operation with directional radiation patterns whose front-to-back ratios approximate to 10 dB for desired bands. Its impedance bandwidth, determined by -10-dB reflection coefficient, covers numbers of present wireless communication systems, and the antenna can be simply integrated with other circuit components for its planar structure. Experimental data obtained from a laboratory prototype are also presented. The experimental results confirm the good performances observed by the electromagnetic simulations.