FULL-WAVE ANALYSIS OF AN INFINITELY LONG MAGNETIC SURFACE-WAVE TRANSDUCER

A rigorous analysis of an infinitely long microstrip line embedded in a multilayer structure which includes a ferrite layer is presented. In certain frequency ranges, such a line launches magnetic surface waves in the ferrite layer and thus becomes a surface wave transducer. The analysis is a self-consistent, full-wave solution which rigorously includes the effect of radiating magnetic waves. By expanding the transducer currents in terms of both even and odd functions, it is shown that the principal current is not symmetrically distributed across the transducer width. The propagation constant of the transducer mode is complex and shows a large, imaginary part (attenuation) tied to the excitation of magnetostatic surface waves. In addition, the propagation constant remains complex even for frequencies above the magnetostatic surface wave bandwidth because the excitation of magnetic surface waves has complex propagation constants. Insertion loss measurements of a multilayer microstrip transducer are in reasonable agreement with the calculated attenuation.