A Miniaturized Microstrip-to-Coplanar-Strip Transition Loaded with Artificial Transmission Lines and 2.4-GHz Antenna Application

A miniaturized microstrip-to-coplanar strip transition and its antenna application are presented in this letter. A composite right/left-handed transmission line and planar artificial transmission lines are used to design the transition in the 2.4-GHz band and to balance the output of the transition over a wider frequency range. In addition, the occupied area of the transition is only 0.087λg
²
. The 3-dB back-to-back insertion loss bandwidth is around 84%. Based on the proposed transition, a quasi-Yagi antenna is demonstrated. The impedance bandwidth is 30.3%. The antenna offers excellent endfire radiation performance. The maximum gain and front-to-back ratio are 5.1 dBi and 21 dB, respectively, at the endfire direction in the operating band. The design process and the measured results of the proposed design are presented in detail.