Higher-order mode suppressor, waveguide filter device using same, spectrum analyzer, signal analyzer, signal generation device, higher-order mode suppression control method, and filter configuration method

A higher-order mode suppressor provided between a first waveguide and a second waveguide, the higher-order mode suppressor comprising:

• a ridge waveguide portion having a ridge structure in which a waveguide path penetrating in a longitudinal direction is provided and ridge portions are formed inside the waveguide path;
• a first ridge-waveguide conversion unit connected to one end surface of the ridge waveguide portion in a longitudinal direction and forming a ridge-waveguide converting waveguide path performing relay of radio wave propagation between the waveguide path having the ridge structure and a waveguide path of the first waveguide, between an end surface facing the one end surface and an opposite side end surface;
• and
• a second ridge-waveguide conversion unit connected to the other end surface of the ridge waveguide portion in the longitudinal direction and forming a ridge-waveguide converting waveguide path performing relay of radio wave propagation between the waveguide path having the ridge structure and a waveguide path of the second waveguide, between an end surface facing the other end surface and an opposite side end surface,
• wherein in the ridge waveguide portion, an inner diameter of the waveguide path is narrower than inner diameters of the waveguide paths of the first waveguide and the second waveguide,
• the first waveguide and the second waveguide are respectively connected to the opposite side end surface of the first ridge-waveguide conversion unit and the opposite side end surface of the second ridge-waveguide conversion unit, and
• when one of the first waveguide and the second waveguide is set as an input side and the other is set as an output side, and a frequency band exceeding a basic frequency band is input from the input side, the ridge waveguide portion is configured with dimensions for suppressing a higher-order mode occurring on the input side with respect to a frequency band of twice or more than a cutoff frequency band.