A YIG/GGG/GaAs-based magnetically tunable wideband microwave band-pass filter using cascaded band-stop filters

A yttrium iron garnet/gadolinium gallium garnet-gallium arsenide (YIG/GGG-GaAs)-based magnetically-tunable wideband microwave band-pass filter with large tuning ranges for the center frequency (5.90-17.80 GHz) and the bandwidth (1.27-2.08 GHz) in the pass-band using a pair of cascaded band-stop filters is reported. The design and numerical simulation of the band-pass filter that incorporates multisegment microstrip meander-lines and 2-D nonuniform bias magnetic fields were first carried out using Ansoft High Frequency Structure Simulator (HFSS) software suite. The measured transmission characteristics of the band-pass filter at center frequency of 8.28 GHz, using 2-D nonuniform bias magnetic fields centered at 2,750 Oe and 4,150 Oe facilitated by Nd-Fe-B permanent magnets, shows a -3-dB bandwidth of 1.73 GHz, an out-of-band rejection of -33.5 dB, and an insertion loss of -4.2 dB. A good agreement between the simulation and experimental results for the band-pass filter in the center frequency and the bandwidths of the pass-band and the two guarding stop-bands has been accomplished. Index Terms--Bandpass filters, bandstop filters, ferromagnetic resonance (FMR), tunable filters, yttrium iron garnet (YIG) filters.