Patent ID: 7821361

Claim:
A second-order band-pass filter comprising: a first signal terminal; a second signal terminal; a first transmission line resonator, formed with a plurality of bendings, having one end coupled to the first signal terminal and another end open-circuited in a first direction; a second transmission line resonator, symmetric to the first transmission line resonator and formed with a plurality of bendings, having one end coupled to the second signal terminal and another end open-circuited in a second direction opposite the first direction; and an impedance inverter, coupled between the first transmission line resonator and the second transmission line resonator, comprising: an inductor; a first micro strip line having one end coupled to the first signal terminal and another end coupled to a ground through the inductor; and a second micro strip line, symmetric to the first micro strip line, having one end coupled to the second signal terminal and another end coupled to the ground through the inductor.