A wideband electronically tunable microwave notch filter in yttrium iron garnet–gallium arsenide material structure

A wideband electronically tunable microwave notch (band-stop) filter has been constructed in an yttrium iron garnet (YIG)/gallium arsenide (GaAs) material structure. An incident microwave propagating along the microstrip transmission line in the GaAs substrate is coupled into and to excite the magnetostatic surface waves in the YIG layer, which is laid upon the microstrip transmission line. Maximum coupling and thus the peak absorption of the output microwave power occur at the ferromagnetic resonance frequency in the YIG film as determined by a bias magnetic field. A tuning range as large as 2.5–23.0 GHz in the peak absorption frequency with the corresponding magnetic field tuning range of 290–7300 Oe has been accomplished. Peak absorption of 15–38 dB in the microwave output power has also been measured.