Design of compact dual-band quasi-elliptic filter with high selectivity and wide stopband rejection

A novel dual-band quasi-elliptic filter with compact size and wide stopband has been proposed in this paper. It is realized by embedding two open loops between two coupled half wavelength resonators. Thus, the filter is compact in size. Two inner open loops are placed far enough to avoid mutual coupling. In addition, by loading two semi-lumped anti-coupled structures, a broad upper stopband can be obtained without adding extra circuit size. To verify the proposed idea, a dualband filter sample has been designed and fabricated using single-layer printed circuit board (PCB) technology, and the measured S-parameters agree well with the simulated ones.