Distributed impedance matching with Foster and Non-Foster elements

A systematic approach for the design of a matching network distributed along the antenna structure, including the feed point, is discussed. This scheme, based on the Method of Characteristic Modes, is much more general than the traditional impedance matching methods that only consider a network at the feed point. The loads can be Foster or Non-Foster elements. A summary of Non-Foster circuit topologies will also be given, especially the issue of stability.