The printed compound air-fed array (PCAFA) is an improved Fabry-Perot resonator (FPR) antenna, which exhibits wider bandwidth and higher aperture efficiency than traditional FPR antennas because the nonuniform phase and magnitude of field distribution on aperture are partly compensated in design. This letter proposes an essential method to enhance the gain bandwidth while keeping the high gain and aperture efficiency by means of forming a flattened gain-frequency response to enlarge the (gain × bandwidth) product. The detailed design example for 14 GHz is analyzed using CST-2006 simulator and tested in an anechoic chamber. The full-wave simulated results exhibit 19.1 dBi peak gain corresponding to 71% aperture efficiency and 9.9% bandwidth for -1 dB gain-drop or 14.1% bandwidth for -3 dB gain-drop. The measured data are in good agreement with the simulation .