Aperture Antennas on Probe-Fed Hemispherical Metallic Cavities

Aperture antennas cut onto probe-fed hemispherical cavities are investigated theoretically and experimentally. The result is valid for any aperture position and width. The operating frequencies of the antennas are primarily controlled by the resonant modes of the hemispherical cavity, with the input impedances easily matched by changing the probe length and/or aperture size. When the probe length and aperture size are designed properly, a very wide bandwidth of ~45% can be obtained. This bandwidth is nearly twice that of a bare monopole. The calculations are verified by measurements