A half mode inkjet printed tunable ferrite isolator

Abstract

-A novel half mode waveguide based ferrite isolator design is presented in this work. For the first time, tunability of the isolation band is demonstrated for a ferrite isolator. Instead of using the conventional antisymmetric bias the isolator requires a single direction of the magnetic bias field due to the half mode operation. Yttrium Iron Garnet (YIG) is used as the substrate for the device. The metallic walls of the waveguide are realized using inkjet printing. The magnetic biasing applied to the waveguide causes the RF waves to experience negative permeability in one direction of propagation hence providing isolation for this direction. For an applied bias of 3000 Oe, the device provides a maximum isolation figure of merit of 76.7 dB at 7.5 GHz. The isolation band can be controlled by changing the applied magnetostatic bias. As the bias is varied from 1500 Oe to 3500 Oe the center frequency of the isolation band varies from 4.45 GHz to 9 GHz. The measured response of the isolator shows that it can be integrated in any RF system requiring lower cost and good isolation.Index Terms-isolator, ferrite, waveguide, isolator figure of merit (IFM)

Theory and Design of Tunable Full-Mode and Half-Mode Ferrite Waveguide Isolators

“…This work uses the unidirectional MSW mode rather than the resonance absorption obtained from two different modes in the half-mode isolator of [16]. In [19], the authors themselves presented a half-mode isolator design but its performance was not optimized and no theory was proposed for such a design.…”