Tunable wideband microwave band-stop and band-pass filters using YIG/GGG-GaAs layer structures

Magnetically tunable wideband microwave bandstop and bandpass filters using ferromagnetic resonance absorption in yttrium iron garnet/gadolinium gallium garnet-gallium arsenide (YIG/GGG-GaAs) layer structures are reported. The measured characteristics of the bandstop filter, with nonuniform bias magnetic field distribution along the YIG/GGG film, shows a large absorption bandwidth of 1900 MHz at the stopband center frequency of 11.0 GHz, average peak absorption of 13 dB, and an out-of-stopband insertion loss of 1.5 dB. The measured characteristics of the bandpass filter at the passband center frequency of 7.1 GHz demonstrates a 3-dB bandwidth of 1450 MHz, out-of-band rejection of 33 dB, and an insertion loss of 1.5 dB. A good agreement between the experimental results and the simulation results based on a lumped element equivalent circuit modeling of YIG bandstop filters has been achieved. Index Terms--Ferromagnetic resonance (FMR) absorption, tunable bandstop and bandpass filters, YIG filters.