Micromachined Tunable Magnetostatic Forward Volume Wave Bandstop Filter

We have successfully designed, fabricated, and characterized a planar monolithic yttrium iron garnet (YIG) Chebyshev bandstop filter on gadolinium gallium garnet (GGG) substrate with tunable frequency, low insertion loss (IL), and high rejection. This filter is created in YIG micromachining technology that allows direct placement of metal transducers on YIG for strong spin-wave coupling. With an out-of-plane 3900-Oe bias field, the bandstop filter exhibits 55-dB maximum stopband rejection at a center frequency of 6 GHz, with 2-dB passband IL and 37.8-dBm passband $\mathrm {IIP_{3}} $ . By applying different bias fields, the stopband center frequency is tuned from 4 to 8 GHz while maintaining more than 30-dB rejection. Incorporated with proper design of tunable compact electromagnet, this new filter design can provide attenuation of spurs appearing across the fifth generation (5G) and $X$ -band spectrum.