A new excitation technique for wide-band short backfire antennas

A new excitation technique is developed to improve the impedance bandwidth and to lower the manufacturing cost of a short backfire antenna (SBA). The new excitation structure consists of a planar monopole and a microstrip feed line, both of which are printed on the same dielectric substrate. By splitting the printed monopole with a slot, a wide-band performance can be achieved. The new split-monopole-excited SBA achieves an impedance bandwidth of about 15% [voltage standing wave ratio (VSWR <2)] while maintaining good radiation performance. As an example, an SBA configuration with the new excitation topology was designed and measured at the 5 GHz UNII band, and good agreement was observed between the simulation and experiment. The effects of the geometric parameters of the excitation structure on the impedance performance are investigated and the operating mechanism of the split-monopole-excited SBA is discussed. Being a low-cost, high-gain, and wide-band directional antenna, the new SBA can find applications in various wireless systems, such as LMDS, WLAN, and the emerging WiMAX networks.