Ground reflection effects upon radiated and received signals as viewed via image theory

The ground surface affects radiated and received signals of antennas near the surface of ground. By considering spatially extended current distributions, we obtain both positive and negative image results for both horizontal and vertical antennas. We present numerical results for HF with ground surfaces of soil, seawater, and a perfect electrical conductor. To illustrate the angle and frequency-to-height dependence of the constructive and destructive interference, we plot contours (of equal amplitude) of the four different image factors in terms of\thetaand height/wavelength (h/\lambda). These results provide insight into design considerations involving antennas in the near vicinity of ground.