Radio frequency filter of combline structure having frequency cut-off circuit and method for implementing the same

摘要

Disclosed is a radio frequency filter of a combline structure including a frequency cut-off circuit for cutting off a specific frequency from a frequency band having a given frequency bandwidth. The frequency cut-off circuit includes an inductive transmission line extending from the output terminal by a length determined to provide an approximate inductance corresponding to a calculated value approximate to an inductance for obtaining the specific frequency, and a capacitive element coupled to the approximate inductance provided by the inductive transmission line, so that it has a capacitance for obtaining the specific frequency. The inductive transmission line is connected to the capacitive element through a via hole formed at an end of the transmission line opposite to the output terminal, from which the transmission line extends. The invention also proposes a method for implementing the radio frequency filter.