Magnetically tunable filter from 72 GHz to 95 GHz

In this paper a magnetically tunable filter based on unilateral finlines is presented. The filter covers a tuning frequency range from 72 GHz to 95 GHz, achieving an insertion loss between 11.3 dB and 7.3 dB. In order to be able to adjust such high resonant frequencies, resonators made of hexaferrite material are used. Although the filter contains only two resonators, an off-resonance isolation of about 60 dB is achieved in the range from 70 GHz to 110 GHz. In the cutoff region of the finlines the filter exhibits an even higher off-resonance isolation of more than 70 dB. A Rogers 5880 high frequency laminate is used as substrate to carry the circuit layout. For structuring the metal cladding a rapid PCB prototyping system based on laser ablation technique has been applied. If resonator spheres with a higher anisotropic field are used the filter structure can work up to 110 GHz.