Amplitude and Phase Tuning of Microwave Signals in Magnetically Biased Permalloy Structures

In this paper, a permalloy layer has been employed in the fabrication of a coupled lineelectromagnetic bandgap (EMBG) device to tune both amplitude and phase. A magnetically biasedmicrowave coplanar configuration manufactured with evaporated permalloy has been measured, and a circuitmodelling has been studied to evaluate the measured effects in terms of variable attenuation and phaseshift. Starting from a permalloy made by the mixture 80% nickel and 20% iron content, we fabricatedan electromagnetic bandgap (EMBG) structure based on a periodic arrangement of single sections ofa transmission line with variable impedance, also including a central region with coupled lines. Thebandpass characteristics of the EMBG device can be tuned by changing permalloy's permeability through theapplication of a DC magnetic field H0 (parallel to the plane of the structure). In particular, using a magneticfield up to 3000 Oe, it was possible to change the phase by ca. 45oand the amplitude by ca. 7 dB in theX band.