Co-planar waveguide-fed zeroth-order resonant antenna with improved gain and efficiency

In this paper a co-planar waveguide (CPW)-fed zeroth-order resonant (ZOR) antenna with an improved gain and radiation efficiency was built and tested. The unit cell of the proposed antenna consists of a series metal-insulator-metal (MIM) capacitor and two shorted shunt stub inductors. In order to reduce the antenna size and to exhibit achieve excellent efficiency a straight strip bent by 90 degree was used as a shunt inductor instead of a meander line. The proposed antenna consisting of two unit cells has an open ended composite right/left handed (CRLH) transmission line structure. As a result the dominantly radiating part of the antenna comes from the shunt stub and vertical via. The total electrical size of the fabricated zeroth-order resonant antenna is 0.22λ₀ × 0.22λ₀. The measured gain and efficiency of the fabricated antenna have been enhanced to be 3.07 dBi and 75 %, respectively, at the zeroth-order resonant frequency of 2.97 GHz.