Vivaldi antenna design procedure from a conventional slot antenna

The design procedure of a Vivaldi antenna is presented in this paper. This procedure starts from a conventional slot antenna with a two-layer feeding structure consisting of microstrip and coplanar waveguide (CPW). The original slot antenna resonates in two bands, the first between 0.9760 GHz and 1.3200 GHz and the second between 2.1680 GHz and 2.6240 GHz, with fractional bandwidths (FBW) of 29.97% and 19.03%, respectively. The designed Vivaldi antenna is matched in the range between 0.9520 GHz and 2.9200 GHz, which corresponds to an FBW of 101.65%. This antenna is obtained after sequentially applying linear and exponential tapering to the original slot antenna. It is found that the best performance of the Vivaldi antenna is achieved by setting a maximum width of the tapered slot at its end and introducing an impedance step at the transition between CPW and tapered slot. The gain of the designed Vivaldi antenna at 2.4 GHz is 1.2135 dB, which is an improvement over the 0.3013 dB gain of the original slot antenna.