Patent ID: 7884682

Claim:
A waveguide structure comprising: a microstrip line; a waveguide; and a transmission mode transducer provided between the microstrip line and the waveguide, wherein the transmission mode transducer comprises a waveguide transducer, wherein the waveguide transducer is a ridged waveguide, wherein a characteristic impedance of the waveguide transducer is equal to or less than a characteristic impedance of the microstrip line, wherein a length of a shorter side of a rectangular cross-section opening of the ridged waveguide is twice or more than twice a thickness of a dielectric of the microstrip line, and wherein a ridge is provided near a center of one or both long sides of the ridged waveguide rectangular cross-sectional opening, projecting toward the center of the rectangular opening, wherein a distance from the ridge to the nearest part of the rectangular opening is twice or less than twice the thickness of the dielectric.