MICROWAVE BANDPASS FILTER WITH HIGHER HARMONICS REJECTION FUNCTION

摘要

A rectangular waveguide bandpass filter for transmitting fundamental electromagnetic waves f 0 in a fundamental mode TE101 and attenuating second harmonic waves 2f 0 therein, comprising two susceptance elements spaced apart a distance of one-third waveguide wavelength in a lengthwise direction interiorly of the waveguide to form a resonant cavity for passing a frequency band including the fundamental wave f 101, attenuating the second harmonic wave 2f 101, and preventing resonant frequencies of modes higher than the fundamental mode TE101 from decreasing into a frequency region below the second harmonic; and one or two adjustable screws disposed between the two susceptance elements in one or both waveguide wide walls to project into the interior of the cavity at a position which is one-twelth of the one-third waveguide wavelength susceptance element spacing and which is from an adjacent narrow waveguide wall one-third of the overall distance between the two narrow waveguide walls whereby the screws are restricted to function as one or two capacitive elements only for the TE101 mode.