Theory and Applications of Multiport Structures using Magnetostatic Waves

This paper reports an electrodynamic analysis and possible applications of tunable multiport ferrite-dielectric structures with parallel transmission lines of an arbitrary type coupled through magnetostatic modes of magnetized multilayered thin ferrite films. The structures are supposed to be excited at one port by a falling electromagnetic wave and amplitudes and phases of electromagnetic waves at other ports are obtained in the result of an analytical procedure. The model is valid for an arbitrary direction of a magnetizing field and can describe the generation and interaction of magnetostatic modes due to the finite width of ferrite films. A reaction of magnetostatic waves on transducers´ magnetic fields which produce them is taken into account. Derived closed-form expressions for response functions of multiports provide the base for modeling and design of a wide class of magnetostatic wave devices: multichannel adjustable filters and delay lines, directional couplers, power dividers, multiport resonators. The theory is also applicable for the analysis of multiport and interdigital transducers. In conventional two-port filters and delay lines a mutual coupling of trarnsducers is proved to be responsible for passband ripples in frequency responses.