Compact waveguide converter apparatus
First Claim
1. Waveguide mode converter apparatus for converting microwave energy from a whispering gallery mode to a single rectangular waveguide mode having low mode numbers, said apparatus comprising:
- a circular waveguide;
a coaxial waveguide overlapping a portion of said circular waveguide, a common wall separating said circular waveguide from said coaxial waveguide;
means for applying microwave energy in a whispering gallery mode to the circular waveguide;
means for coupling the microwave energy in the whispering gallery mode in said circular waveguide to a corresponding coaxial transmission mode in the coaxial waveguide, said coupling means including an array of N equally spaced axial slots placed in said common wall, where N is an integer;
means for converting the microwave energy in said coaxial transmission mode within said coaxial waveguide to a quasi parallel plate mode, said microwave energy propagating in accordance with said quasi parallel plate mode along a spiral path through said coaxial waveguide, said coaxial waveguide having inner and outer walls that function as parallel plates that are wrapped to form said circular waveguide, said quasi parallel plate mode exhibiting an electric field that is transverse to the spiraling direction of propagation and parallel to the walls of said coaxial waveguide, and further exhibiting a magnetic field having a component transverse to the spiraling direction of propagation that is perpendicular to the inner and outer walls of said coaxial waveguide, said means for converting including helical grooves on the inside of the outer wall of said coaxial waveguide, said helical grooves being oriented to run transverse to said spiral path;
means for extracting said microwave energy in said quasi parallel plate mode from said coaxial waveguide, said extracting means including means for helically unwinding the walls of said coaxial waveguide to form a rectangular waveguide, said quasi parallel plate mode becoming a rectangular waveguide mode within said rectangular waveguide;
whereby microwave energy within said whispering gallery mode is converted to microwave energy in said rectangular waveguide mode.
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Abstract
Conversion from a whispering gallery or volume mode to a more useable mode, such as the HE1,1 mode is achieved in a waveguide mode converter that includes input and output sections. The input section includes overlapping circular and coaxial waveguides. Microwave energy in a whispering gallery or volume mode within the circular waveguide is coupled through an array of N equally spaced axial slots placed in the common wall separating the circular waveguide and the coaxial waveguide to coaxial TE and TM modes. Helical grooves placed in one of walls of the coaxial waveguide convert the coaxial mode to a quasi parallel plate mode wherein the common wall separating the inner circular waveguide from the outer coaxial waveguide functions as one plate, and the outer wall of the coaxial waveguide functions as the other plate. The quasi parallel plate mode propagates microwave energy spirally through the coaxial waveguide in a direction k, where k makes an angle θ to the waveguide axis. The helical grooves are placed transverse to k. Such grooves cause the normal modes to no longer be the coaxial TE and TM modes, but modified linear combinations thereof. One such linear combination is a desired TE0,1 mode, which normal mode is only slightly affected by the grooves. The other normal mode is analogous to the parallel plate TM0,1 mode, which mode is strongly affected by the grooves. The output section extracts the TE0,1 energy by helically unwinding the walls of the coaxial waveguide. Additional conversion to the HE1,1 mode is accomplished by using a compact configuration that makes the wavefront cylindrical using a lens or mirror coupled to a sectoral horn.
42 Citations
30 Claims
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1. Waveguide mode converter apparatus for converting microwave energy from a whispering gallery mode to a single rectangular waveguide mode having low mode numbers, said apparatus comprising:
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a circular waveguide; a coaxial waveguide overlapping a portion of said circular waveguide, a common wall separating said circular waveguide from said coaxial waveguide; means for applying microwave energy in a whispering gallery mode to the circular waveguide; means for coupling the microwave energy in the whispering gallery mode in said circular waveguide to a corresponding coaxial transmission mode in the coaxial waveguide, said coupling means including an array of N equally spaced axial slots placed in said common wall, where N is an integer; means for converting the microwave energy in said coaxial transmission mode within said coaxial waveguide to a quasi parallel plate mode, said microwave energy propagating in accordance with said quasi parallel plate mode along a spiral path through said coaxial waveguide, said coaxial waveguide having inner and outer walls that function as parallel plates that are wrapped to form said circular waveguide, said quasi parallel plate mode exhibiting an electric field that is transverse to the spiraling direction of propagation and parallel to the walls of said coaxial waveguide, and further exhibiting a magnetic field having a component transverse to the spiraling direction of propagation that is perpendicular to the inner and outer walls of said coaxial waveguide, said means for converting including helical grooves on the inside of the outer wall of said coaxial waveguide, said helical grooves being oriented to run transverse to said spiral path; means for extracting said microwave energy in said quasi parallel plate mode from said coaxial waveguide, said extracting means including means for helically unwinding the walls of said coaxial waveguide to form a rectangular waveguide, said quasi parallel plate mode becoming a rectangular waveguide mode within said rectangular waveguide; whereby microwave energy within said whispering gallery mode is converted to microwave energy in said rectangular waveguide mode. - View Dependent Claims (2, 3, 4, 5, 6)
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7. Waveguide mode converter apparatus comprising:
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a circular waveguide; a coaxial waveguide overlapping a portion of said circular waveguide, a common wall separating said circular waveguide from said coaxial waveguide; an array of N equally spaced axial slots placed in said common wall, where N is an integer, microwave energy in a first transverse electric mode within said circular waveguide being converted to a second transverse electric mode within said coaxial waveguide through said axial slots, said first transverse electric mode propagating in said circular waveguide in a longitudinal direction, said second transverse electric mode propagating in said coaxial waveguide along a spiral path. - View Dependent Claims (8, 9, 10)
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11. Waveguide mode converter apparatus for converting microwave energy from a whispering gallery or volume mode to a rectangular TE0,1 mode comprising:
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first conversion means including an input circular waveguide section coupled to an output coaxial waveguide section for converting microwave energy applied to said input circular waveguide section to an intermediate TE mode that spirally propagates through said output coaxial waveguide section, said output coaxial waveguide section having inner and outer curved walls that are parallel to each other; second conversion means for converting said intermediate TE mode from said coaxial waveguide section to said rectangular TE0,1 mode, said second conversion means including an aperture in the outer wall of said coaxial waveguide section through which microwave energy in said spirally propagating intermediate TE mode may pass, and a curved parallel plate waveguide section to said aperture for collecting the microwave energy passing through said aperture, said curved parallel plate waveguide section gradually curving and forming a straightened section of rectangular waveguide wherein the microwave energy propagates in said TE0,1 mode. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
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19. A method for converting microwave energy from a whispering gallery mode applied to an input circular waveguide section to a TE0,1 mode in an output rectangular waveguide section comprising the steps of:
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coupling the microwave energy in said input circular waveguide section to an intermediate coaxial waveguide section that is coaxial with said input circular waveguide section, said intermediate coaxial waveguide section having inner and outer curved walls that are parallel to each other and coaxial with said circular waveguide section, said coupling being performed in a manner that causes the microwave energy coupled to said intermediate coaxial waveguide section to spirally propagate through said intermediate coaxial waveguide section in an intermediate TE mode; converting said intermediate TE mode in said coaxial waveguide section to said TE0,1 mode in said output rectangular waveguide section by placing an aperture in the outer wall of said coaxial waveguide section through which microwave energy in said spirally propagating intermediate TE mode may pass, and coupling a curved parallel plate waveguide section to said aperture, collecting the microwave energy passing through said aperture, and gradually curving said curved parallel plate waveguide section to form said output rectangular waveguide section in which said microwave energy propagates in said TE0,1 mode. - View Dependent Claims (20, 21, 22, 23, 24)
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25. A method for making a microwave energy converter that converts microwave energy between a circular waveguide and a coaxial waveguide, said method comprising the steps of:
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overlapping a portion of a circular waveguide with a coaxial waveguide, there being a common wall separating the circular waveguide from the coaxial waveguide; inserting an array of N equally spaced axial slots in said common wall; and placing helical grooves on the inside of the outer wall of said coaxial waveguide.
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26. Waveguide mode converter apparatus comprising:
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a circular waveguide; a coaxial waveguide overlapping a portion of said circular waveguide, a common wall separating said circular waveguide from said coaxial waveguide, an array of N equally spaced axial slots placed in said common wall, where N is an integer; and helical grooves on the inside of said coaxial waveguide; microwave energy propagating in a first transverse electric mode in said circular waveguide being coupled to said coaxial waveguide through said axial slots and converted to a second transverse electric mode. - View Dependent Claims (27)
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28. Waveguide mode converter apparatus for converting microwave energy propagating in a first mode having a first angular mode number to a selected second mode having a second angular mode number comprising:
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a circular waveguide; a coaxial waveguide overlapping a portion of said circular waveguide, a common wall separating said circular waveguide from said coaxial waveguide; helical grooves on the inside of said coaxial waveguide; an array of N equally spaced axial slots placed in said common wall, where N is an integer, microwave energy being coupled through said axial slots from one of said circular or coaxial waveguides to the other, the second angular mode number being determined by the number of axial slots N in accordance with a prescribed relationship; whereby said selected second angular mode number of said second mode is controlled by selecting the number of axial slots N placed in said common wall. - View Dependent Claims (29)
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30. A method of changing the angular mode number of microwave energy coupled between circular and coaxial waveguides comprising:
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overlapping a portion of a circular waveguide with a coaxial waveguide, there being a common wall separating the circular waveguide from the coaxial waveguide in the overlapped portion; placing a prescribed number N of equally spaced axial slots in said common wall; placing helical grooves on the inside of an outer wall of said coaxial waveguide in the portion of overlap; and coupling microwave energy through said axial slots between said circular and coaxial waveguides; the angular mode number being changed as a function of the number N of equally spaced axial slots.
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Specification