Miniaturization of Low-profile Omnidirectional Vertical Polarization VHF Patch Antenna

There is an urgent demand for low profile omnidirectional vertical polarization VHF antennas in the vehicle applications. A low-profile patch antenna with several symmetric short vias is developed. By adjusting the position and number of vias, the resonant frequency of antenna can be regulated to work in VHF band. To ensure the omnidirectional radiation in the horizontal plane, the restraint condition of main lobe direction is developed, and the limit size of patch antenna and the permittivity of substrate is analyzed and optimized. Moreover, from the definition of quality factor, the radiation loss is increased to broaden the bandwidth. Slitting on patch can increase the equivalent magnetic currents which may help decrease the quality factor. In another side, a composite slot configuration is able to increase the current patch which decreases the resonant frequency of antenna.