Broadband tunable YIG film resonator with high loaded-Q and spurious mode suppression

Abstract

In this work, a broadband tunable high load factor ($Q_L$) resonator based on yttrium iron garnet (YIG) films is proposed. Single-crystal YIG wafers were prepared on [111] crystal-oriented GGG substrates by liquid phase epitaxy (LPE) technique, and the samples were thinned to 100 um by chemical–mechanical polishing process to obtain excellent crystal quality with magnetic resonance linewidths as low as 1.8 $Oe$. The resonator structure consists of an alumina ceramic substrate, a coplanar waveguide (CPW), and an open resonance ring (SRR). The CPW is used to excite magnetic resonance in the YIG film, and placing the YIG film on the backside of the CPW effectively enhances the uniformity of the microwave field, while the SRR structure further improves the uniformity of the magnetic field distribution. Experimental results demonstrate that the resonator exhibits excellent performance in the 5–25 GHz tuning range, with $S_{11}$ parameters better than −5.2 dB, $Q_L$ values above 700 and the maximum figure of merit (FOM) is 17.21 at 14 GHz. In addition, the resonator successfully suppresses the higher-order spurious modes and maintains good spectral characteristics, which is promising for the application in the field of ultra-wideband tunable devices and microwave systems.