Bandpass filtering and input impedance characterization for driven multielement transducer pair-delay line magnetostatic wave devices

Abstract

This paper reports results of theoretical and experimental studies of microwave delay line filters based on magnetostatic wave (MSW) propagation in epitaxial yttrium iron garnet (YIG) with multielement transducer pairs for wave launching and receiving. Filter transmission and input impedance characteristics for both magnetostatic surface wave (MSSW) and magnetostatic forward volume wave (MSFVW) devices have been calculated and measured experimentally. A planar, multilayer metal-dielectric-YIG geometry, permitting consideration of decoupling due to spacing between the transducers and YIG surface, is used to model the transducer. A ’’low’’ loss microstrip transmission line model is used to derive an equivalent transducer circuit. For assumed noninteraction of transducer element currents, the Poynting vector is used to determine the radiation resistance and the radiation reactance is derived from the Hilbert transform of this resistance. Experimental swept frequency measurements of insertion loss and input impedance versus frequency at S band have yielded experimental results which show good agreement with theoretical predictions of the model for a number of different configurations.