Analysis of monopole antenna with ground wires

Abstract A monopole antenna with ground wires excited at the terminal between the vertical and several ground wires is analyzed by varying the length of the vertical element, the lengths and numbers of ground wires and their angles of inclination. the characteristics of the structure are analyzed for an antenna with a quarter‐wavelength monopole element on a perfectly conducting ground plane. In the numerical analysis the effect of the feeder is neglected and a Hallen‐type integral equation with a simplified kernel is used. In the experiment the center conductor of the coaxial feeder is connected to the monopole and the outer conductor is connected to the ground wires. the effect of a sperrtopf, which prevents leakage current from flowing on the outer conductor, is studied. From the analytical results it is found that the gain of the monopole antenna with ground wires does not exceed that of a half‐wave dipole even if the length of the monopole is made about a quarter wavelength and the ground wires are directed 60° downward. When the antenna is on a perfect ground plane, the directivity strongly depends on the distance between the feed and the conducting plane and becomes maximum when the distance is about 0.3 wavelength. When the ground wires are 0.2 wavelength long and the angle of inclination is 300 the antenna is matched with a 50‐Ω feed line and the gain becomes 4 dB.