Radiation pattern and directivity of mobile antenna at finite distance above the earth

The earth is modeled as a flat surface and the mobile vehicle is a conductive disk of finite size or part of a conductive sphere. Using the expanded induced current method, the radiation pattern in the vertical plane is obtained theoretically with consideration of the mobile vehicle and the earth. Confirming these results experimentally, the radiation patterns of mobile antennas are clarified with the effect of the earth taken into consideration. The earth curves ripple in the vertical plane of the pattern and the direction of the sharp beam closest to the horizon is affected little by the size or shape of the mobile vehicle, but depends on the height of the antenna from the earth. Moreover, when the mobile vehicle is assumed to be a conductive disk of finite size with radius over one wavelength, the directive gain is affected little.