Microwave waveguide mode converter having a bevel output end
First Claim
1. A mode converter for a microwave system, said mode converter being able to receive microwave energy at an input thereof in the form of a TM01 mode of a perfectly circular waveguide, said mode converter being able to output microwave energy predominantly in the form of a fundamental TE mode where said fundamental mode radiates a single narrow beam of energy into space, said mode converter comprising:
- a transition section being a first section of elliptical waveguide having a straight axis and of predetermined length, said input of said mode converter being in said first section, said first section having a circular cross-sectional shape with a radius, r1, at a first position and an elliptical cross-sectional shape at a second position, an interior surface of the first section between the first and second positions described by a mathematical equation of the form x2 /a2 (z)+y2 /b2 (z)=1, wherein x, y, and z are Cartesian coordinates, a major axis function a(z) is a mathematical function describing a major axis radius of the elliptical waveguide, a minor axis function b(z) is a mathematical function describing a minor axis radius of the elliptical waveguide, said major axis function a(z) having values greater than said radius r1 such that the major axis radius is generally increasing in a non-abrupt fashion from the first position to the second position, the minor axis function b(z) having a range of values greater than zero and less than or equal to radius r1 such that the minor axis radius is generally decreasing in a non-abrupt fashion from the first position to the second position, andan output section being a second section of waveguide of elliptical cross-section of a predetermined length, the second section connected to said first section at said second position in a manner such that internal surfaces of both the first and the second sections establish a continuous and non-abrupt elliptical waveguide, said second section having an interior surface described by x2 /a2 (z)+(y-f(z))2 /b2 (z)=1, wherein a(z) and b(z) are said mathematical functions having changing values from the second position to a third position, an offset function f(z) is a mathematical function which offsets the second section of waveguide in a minor axis radius direction, said second section of waveguide terminated at a flat plane thereby establishing a beveled end beginning at a first intermediate position between the second position and the third position and ending at the third position, said flat plane having a predetermined angle, α
, with respect to said first section straight axis, and said predetermined angle α
having a value greater than zero degrees and less than 90 degrees, said flat plane further oriented perpendicular to a plane coincident with the second section waveguide minor axis radius, a bounded area produced by the second section waveguide internal surface at the flat plane establishing an output aperture having an approximately elliptical shape, said output aperture being able to have a waveguide of predetermined length and shape attached thereto;
whereby said transition section providing a means to preserve the input TM01 mode from the first position to the second position, said output section providing a means to convert the TM01 mode to a fundamental TE mode at the output aperture.
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Abstract
The present invention comprises a microwave mode convert having a cylindrical waveguide input. Attached to the waveguide input is a transition section which gradually changes from the elliptical or cylindrical waveguide input. The output section is also an elliptical waveguide. The output section may also have an elliptical or cylindrical waveguide attached to it. The mode converter of the present invention has input a TM01 mode microwave energy from a cylindrical waveguide and outputs TE11 or TEM mode microwave energy which is an elliptical or circular pencil beam of radiation with high directivity.
17 Citations
7 Claims
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1. A mode converter for a microwave system, said mode converter being able to receive microwave energy at an input thereof in the form of a TM01 mode of a perfectly circular waveguide, said mode converter being able to output microwave energy predominantly in the form of a fundamental TE mode where said fundamental mode radiates a single narrow beam of energy into space, said mode converter comprising:
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a transition section being a first section of elliptical waveguide having a straight axis and of predetermined length, said input of said mode converter being in said first section, said first section having a circular cross-sectional shape with a radius, r1, at a first position and an elliptical cross-sectional shape at a second position, an interior surface of the first section between the first and second positions described by a mathematical equation of the form x2 /a2 (z)+y2 /b2 (z)=1, wherein x, y, and z are Cartesian coordinates, a major axis function a(z) is a mathematical function describing a major axis radius of the elliptical waveguide, a minor axis function b(z) is a mathematical function describing a minor axis radius of the elliptical waveguide, said major axis function a(z) having values greater than said radius r1 such that the major axis radius is generally increasing in a non-abrupt fashion from the first position to the second position, the minor axis function b(z) having a range of values greater than zero and less than or equal to radius r1 such that the minor axis radius is generally decreasing in a non-abrupt fashion from the first position to the second position, and an output section being a second section of waveguide of elliptical cross-section of a predetermined length, the second section connected to said first section at said second position in a manner such that internal surfaces of both the first and the second sections establish a continuous and non-abrupt elliptical waveguide, said second section having an interior surface described by x2 /a2 (z)+(y-f(z))2 /b2 (z)=1, wherein a(z) and b(z) are said mathematical functions having changing values from the second position to a third position, an offset function f(z) is a mathematical function which offsets the second section of waveguide in a minor axis radius direction, said second section of waveguide terminated at a flat plane thereby establishing a beveled end beginning at a first intermediate position between the second position and the third position and ending at the third position, said flat plane having a predetermined angle, α
, with respect to said first section straight axis, and said predetermined angle α
having a value greater than zero degrees and less than 90 degrees, said flat plane further oriented perpendicular to a plane coincident with the second section waveguide minor axis radius, a bounded area produced by the second section waveguide internal surface at the flat plane establishing an output aperture having an approximately elliptical shape, said output aperture being able to have a waveguide of predetermined length and shape attached thereto;whereby said transition section providing a means to preserve the input TM01 mode from the first position to the second position, said output section providing a means to convert the TM01 mode to a fundamental TE mode at the output aperture. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification