The aim of this study is to demonstrate the design of an antenna with a high gain as well as almost constant gain characteristics over 3.1-10.6 GHz. The modified antipodal Vivaldi MAVARW antenna initially developed in an earlier study is used as the basic antenna. Three different gain enhancement methods such as increasing antenna size, using a phase compensation lens (PCL), and using a frequency selective surface (FSS) are applied and investigated on a comparative basis for this aim. The final MAVARW antenna is composed of a two-cut square ring PCL, and an FSS. The final antenna has a minimum 12.24 gain level with a maximum 1.66 dB gain deviation over 3.1-10.6 GHz in simulations. The simulation results for the final antenna are validated experimentally with very good agreement. A minimum 12.2 dB gain level as well as a maximum 1.8 dB gain deviation is obtained in measurements. (C) 2019 Elsevier GmbH. All rights reserved.