This dissertation presents a rigorous analysis for excitation of magnetostatic surface wave (MSSW) with an infinitely long microstrip line embedded in a multilayer structure which includes a ferrite layer. When operating at frequencies below and near the MSSW resonance, the microstrip line radiates MSSW's and becomes a MSSW transducer. In the previous papers, and magnetostatic approximation has been employed to split the fields into TE- and TM-modes to the MSSW propagation direction; i.e., retardation effects and the field variations along the microstrip line are ignored. And the uniform current distribution over the width of the transducer has been assumed.
In this dissertation, a self-consistent full-wave technique based on a 4*4 interface tangential field matrix method is used for anisotropic layered medium (ferrite). The Galerkin's moment method in the spectral domain is employed and the transducer currents in terms of a complete set of even and odd basis functions are expand to calculate the propagation constant of a microstrip transducer. In this case, retardation effects are considered. The results show that the propagation constant of the transducer mode is complex and has a large imaginary part (attenuation) tied to the excitation of MSSW's and the principal current is not symmetrically distributed across the transducer width.
The substitution of the calculated complex propagation constant into the transverse resonance condition for the interface normal direction gives the surface wave poles exciting the MSSW. The nonreciprocal properties of the MSSW field lead to the asymmetrical existences of the MSSW poles and the different excitations in each MSSW propagating direction. MSSW fields can be obtained from the residues of the Fourier integrals in the spectral domain approach. The complex radiation power is determined by a rigorous complex Poynting vector analysis where the current distribution is a result of a full-wave moment method solution. The total energy flux of the MSSW and the components of the flux in the different regions of the waveguiding structure are calculated. Thus the complex radiation impedance in terms of the geometrical and material parameters is obtained. The loss from EM wave propagating along the microstrip to the MSSW system can be expressed in terms of a radiation resistance.
The input impedance of a shorted transmission line is a complex quantity involving the propagation constant and the characteristic impedance of the line as well as the radiation impedance. As the radiation impedance increases, the propagation constant along the microstrip increases, and the total attenuation and phase shift through the shorted section cannot be neglected. The attenuation constant and phase shift, or the complex propagation constant, can be obtained only by a full-wave analysis. The calculated input impedances of shorted transmission lines for the various structures are compared with the experimental results of the another paper.
