US 12,756,082 B2Granted

Notch filter

AssigneeInter-University Research Institute Corporation National Institutes of Natural Sciences

InventorsMasaki Nishiura, Takashi Shimizu, Sakuji Kobayashi, Shin Kubo

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Abstract

The present disclosure aims to improve the performance of a notch filter using a rectangular waveguide and a cavity. A notch filter has a rectangular opening that is formed in an end face thereof. Inside of the notch filter, a waveguide is connected with circular cavities and by connecting pipes. In a planar shape of the waveguide, from an inlet side thereof, a wide path portion, a tapered portion and a narrow path portion are formed and are further connected with a tapered portion and a wide path portion. The circular cavities and designed according to the frequency of the electromagnetic wave that is to be trapped are provided in the middle of the narrow path portion. The configuration of decreasing the width of the waveguide in a location where the circular cavities are provided improves the performance of removal of the electromagnetic wave by the circular cavities.

Claims9

Dependent claims

A notch filter for removing an electromagnetic wave of a specific frequency, the notch filter comprising:

a rectangular waveguide having a rectangular cross-section and configured to allow a predetermined frequency band to pass therethrough, the rectangular cross-section having long sides each forming an E plane and short sides;
and
at least one cavity formed in dimensions according to the specific frequency and provided along an axis direction of the rectangular waveguide, the at least one cavity being in a cylindrical shape and protruding in a direction perpendicular to the E plane,
wherein the long sides and the short sides of the rectangular cross-section at an opening of the rectangular waveguide have respective lengths in accordance with the predetermined frequency band,
wherein the rectangular waveguide includes:
a narrow path portion at which the short sides of the rectangular cross-section have a length smaller than that of the short sides of the rectangular cross-section at the opening of the rectangular waveguide, the at least one cavity being provided to the narrow path portion,
and wherein the length of the short sides of the rectangular cross-section in the narrow path portion is set such that the electromagnetic wave of the specific frequency propagates in a predetermined mode.

4 more elements

Dependencies are inferred from the claim text.