An Original Brick-Wall Bandstop Filter for Wideband Data-Link Avionics Systems

This paper presents the results of a unique bandstop filter whose characteristics and performances push the boundaries of what is generally recognized as practicable. For the first time, the full extracted-pole technique is successfully applied to a bandstop filter possessing high order and wide stopband, thus verging on an ideal brick-wall filtering function. The implementation of the filter is based on parallel-coupled slab lines technology, where an advanced stepped-impedance bandstop resonator structure is employed. Such a resonator allows for the realization of a wide spurious-free passband while enabling the strong coupling coefficients required to obtain a wide stopband. The experimental results presented at the end of this paper, including a remarkable match between measurements and simulations, validate the feasibility of the proposed brick-wall bandstop filter.