A four-pole parallel-coupled dual-mode resonator bandpass filter

A dual-mode resonator can be used as a doubly tuned resonant circuit, and n dual-mode resonators can, therefore, comprise a 2n-pole filter. This paper presents a four-pole parallel-coupled line filter that uses two dual-mode resonators. Compared to the conventional parallel-coupled line filter that uses four half-wavelength line resonators, the proposed dual-mode resonator filter achieves smaller size and better performance as demonstrated in Section III.