Patent ID: 9525199
Filing Date: 2016-12-20
CPC Classification: H01P

Claim Text:
1. A millimeter waveband filter comprising: a first waveguide; a second waveguide, the second waveguide being connected to the first waveguide in a state where one end of the second waveguide is inserted into the first waveguide to constitute a transmission line allowing electromagnetic waves in a predetermined frequency range of a millimeter waveband to propagate in a TE10 mode; a pair of flat electric wave half mirrors which have characteristics to transmit a part of the electromagnetic waves in the predetermined frequency range and to reflect a part of the electromagnetic waves and are arranged to face each other at an interval in a state where the first waveguide and the second waveguide are blocked; and variable interval means for relatively moving the first waveguide and the second waveguide in a longitudinal direction of the transmission line in a state connected together to change the interval between the pair of electric wave half mirrors, wherein frequency components centering on a resonance frequency of a resonator formed between the pair of electric wave half mirrors are selectively transmitted, the first waveguide is a rectangular waveguide in which the sectional shape of the inside of the first waveguide is a rectangular shape such that a lower limit frequency of a propagatable frequency band of the first waveguide in the TE10 mode is equal to or less than a lower limit of the predetermined frequency range, the second waveguide is a ridge waveguide in which the outside thereof is a rectangular shape at a predetermined interval with respect to the inside of the first waveguide and the sectional shape of the inside thereof has a central portion having a height smaller than the height of both side portions, and the height and width of each of both side portions and the central portion are set such that a lower limit frequency of a propagatable frequency band of the second waveguide in the TE10 mode is equal to or less than the lower limit frequency of the propagatable frequency band of the first waveguide.