Development of a wide-band short backfire antenna excited by an unbalance-fed H-shaped slot

The short backfire antenna (SBA) has been widely used for mobile satellite communications, tracking, telemetry, and wireless local-area network applications due to its compact structure and excellent radiation characteristics. The most common excitation topology for the SBA is a balance-fed wire dipole, which has the disadvantage of a narrow frequency bandwidth for the input impedance. In this paper, an H-shaped slot is employed to excite the SBA for the first time. The H-shaped slot is unbalance-fed from a coaxial line. It is demonstrated that the H-shaped slot-excited SBA can achieve a bandwidth for input impedance of more than 20% (VSWR<2) while maintaining good radiation performance. The antenna structure is described and the simulation and experimental results are presented. The operating principle is investigated to explain why the slot-excited SBA can result in good impedance and radiation characteristics. A parametric study is conducted for the use of practical engineering design.