REACTIVELY LOADED DIRECTIVE ANTENNAS

摘要

The radiation characteristics of an N-port antenna system can be controlled by impedance loading the ports and feeding only one or a few of them. The use of reactive loads to produce high gain antenna systems is studied first. The theory employs the concept of modal resonance to resonate the real current that produces maximum gain. When the resonated current is the principal contributor to the radiation pattern, then the pattern is almost independent of the position of the feed. This usually requires large coupling between the antenna elements, and can result in supergain antennas. The theory of resonance is extended to include complex port currents and impedance loads. Numerical methods are developed and applied to arrays of linear dipoles arbitrarily distributed on a plane. Computations are made using both the method of moments and the sinusoidal current approximation. The two methods giv similar results. Computer programs are included to allow application of the theory to arrays of the user's choice.