The Horizontal Monopole with Feed Point at Ground Level over a Finitely Conducting Ground

摘要

The horizontal dipole or monopole at or near the surface of the ground has received extensive treatment in recent years; however, one of the disadvantages of this type of antenna is its bidirectional antenna pattern. One way of overcoming this disadvantage is to raise the monopole slightly above ground while keeping the feed point at ground level. Expressions are developed for the input impedance, electric field vectors, patterns, and power gain of this type of antenna based on the assumptions: (1) the displacement currents in the homogeneous ground are negligible compared to the conduction currents; (2) the horizontal portion of the antenna is much longer than the vertical portion (the practical case for low profile antennas); and (3)the product of the vertical height and free-space phase constant is less than 0.1. A comparison of experimental and theoretical data indicates that the actual antenna is electrically longer than predicted by theory. This may possibly be taken into account by increasing the physical length of the antenna by an empirical correction factor of 4 to 6 percent in the theoretical calculations. (Author)