Abstract: A filter (20) includes an input part (200), an output part (202), a first portion (22), a second portion (24), and a third portion (26). The input part is for receiving electromagnetic signals, and the output part is for transmitting the electromagnetic signals. The first portion with high impedance is electronically connected to the input part and the output part. The second portion with low impedance is electronically connected to two ends of the first portion. The third portion partially surrounds the second portion, and is electro-magnetically coupled to the second portion.

Abstract: A low-pass filter (10) is provided. The low-pass filter includes an input part (100), an output part (120), a high impedance part (140), a first low impedance part (160), and a second low impedance part (180). The input part is electronically connected to the high impedance part for input of electromagnetic signals thereinto. The output part is electronically connected to the high impedance part for output of electromagnetic signals therefrom. The input part and the output part are asymmetrical to a resonator defined by the high impedance part, the first low impedance part and the second low impedance part. One end of the high impedance part is electronically connected to the first low impedance part, the other end of that is electronically connected to the second low impedance part. Wherein the high impedance part is disposed partly between the first low impedance part and the second low impedance part.

Abstract: A low-pass filter (10) includes an input line (100), an output line (120), a high impedance transmission line (140), a first low impedance transmission line (160), a second low impedance transmission line (180), and a stub (190). The high impedance transmission line includes a first connecting portion (142) electronically connected to the input line, and a second connecting portion (144) electronically connected to the output line. The first low impedance transmission line includes a third connecting portion (162) electronically connected to the first connecting portion, and a first free end (164). The second low impedance transmission line includes a fourth connecting portion (182) electronically connected to the second connecting portion, and a second free end (184). The stub includes a fifth connecting portion (192) electronically connected to the first connecting portion and the second connecting portion, and a third free end (194).