Novel lattice-filter structures consisting of four-directional couplers are introduced, analyzed, and discussed. Four-directional couplers are discussed, and energy-conservation relations in a field-wave application are derived. A thick linear lattice filter is presented and studied as a simple extension to the traditional lattice. A two-dimensional lattice structure is also introduced and studied. Transfer functions are derived and discussed for several examples.

Electrochemical ͑Faradaic͒ effects play an important role in the unusual field-effect phenomenon observed in an all-organic transistor-type device that use films of doped electronic polymers, such as polyaniline ͑emeraldine-HCl͒ and poly-3,4-ethylenedioxythiophene polystyrene sulfonate, as the channel and gate. Small leakage currents through the dielectric are sufficient to affect reversible redox reactions in the polymer film in the active region of the device, i.e., where the channel and gate regions overlap. In the case of polyaniline, these redox reactions are accompanied by color changes corresponding to the different oxidation states of polyaniline that can be visually observed and also spectroscopically monitored.