In last years, there has been an increasing need for high gain wide band directional antennas in some wireless applications, mobile communication systems and other applications. The backfire antenna may become one of the most competitive candidates for these applications, because of its high gain and simple structure. The backfire antenna principle is a highly effective technique for improving the pattern characteristics of an antenna. When the space between the reflectors(from 0.5 to ) the backfire antenna called short backfire antenna(SBFA) and its called long backfire antenna(LBFA) when...