Wave transmission lines and networks – Plural channel systems – Having branched circuits
Reexamination Certificate
1998-10-06
2001-05-01
Lee, Benny (Department: 2817)
Wave transmission lines and networks
Plural channel systems
Having branched circuits
C333S137000, C333S02100R
Reexamination Certificate
active
06225875
ABSTRACT:
The present invention relates generally to waveguides for guiding electrical fields. More specifically, the present invention relates to an orthomode transducer waveguide having dual sidewall feed ports.
BACKGROUND OF THE INVENTION
Waveguides are used to guide electrical fields. An orthomode transducer (OMT) is a type of waveguide which is designed to decompose an arbitrarily polaried electrical field into its various components. Prior art OMT's are typically of tubular construction, with one of the feed ports located on the cylindrical sidewall and the other feed port located on the circular endwall. Alternatively, the OMT may have a square or rectangular cross section with a corresponding square or rectangular endwall.
On prior art OMT's, the signal used to feed the endwall port must pass over the septum used to feed the sidewall port, thus causing interference. The length of the septum is resonant at some frequency, which decreases the usable band width of the endwall feed port. Moreover, the endwall port increases the overall length of the OMT, and thus coupling two OMT's together is made more difficult, as side mounted phase shifters must be employed.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, a waveguide or OMT includes a tubular housing having a pair of feed ports, both of which are mounted on the housing sidewall. One of the ports guides the horizontal component of an arbitrarily polarized electrical field, while the other port guides the vertical component of the electrical field. Preferably, the ports are oppositely disposed from each and are generally located at the same position along the axis of the housing. One port is oriented longitudinally and forms an H plane bend into the tubular waveguide. The second port is oriented transversely and forms an E plane bend into the tubular waveguide. A pair of planar septums are disposed within the housing, and intersect each other along a line parallel to the axis of the housing. Preferably, the line of intersection is spaced a fixed distance away from the centerline of the housing, with optimum results being obtained when the fixed distance is equal to approximately 48% of the housing radius measured from the housing centerline. Finally, each of the septums preferably includes a shaped or contoured leading edge. For example, the leading edge of the H plane bend septum preferably includes a pair of parabolic indentations spaced symmetrically about the housing centerline, while the E plane bend septum preferably includes a protrusion having an apex spaced from the housing centerline a distance equal to approximately 39% of the housing radius measured from the housing centerline. Horizontal and vertical tuning stubs are also provided along the housing sidewall.
According to another aspect of the invention, a waveguide includes a cylindrical housing having a sidewall and a pair of feed ports located on the sidewall, with each sidewall having a central axis extending away from the housing. Each of the ports is configured to guide one component of a polarized electrical field, and a pair of intersecting planes are disposed within the housing, each plane being generally perpendicular to the axis of its associated feed port. The planes intersect along a line generally parallel to the axis of the cylindrical housing.
According to yet another aspect of the present invention, a waveguide includes an elongated cylindrical housing that defines a central axis. A first feed port and a second feed port are disposed about the sidewall opposite from each other, and each of the ports are spaced at a common point along the central axis of the housing. Each of the ports includes a longitudinal axis that extends perpendicular from the central axis of the housing. A septum having a pair of intersecting planes is disposed within the housing. One of the planes is located perpendicular to the axis of the first feed port, while the second plane is located perpendicular to the axis of the second feed port.
A dual sidewall feed OMT according to the present invention will be shorter and more compact than a prior art OMT. The length of a variable power divider (VPD) constructed using the present OMT will be shorter by at least 12% than that obtainable using conventional OMT's. Performance is improved and usable bandwidth is increased because neither signal must pass through the septum used to feed the orthogonal mode. When used on VPD's, the shortened overall construction with an uninterrupted endwall allows the use of a simple motor and shaft mechanism rather than the more complicated sidewall motors for the phase shifters as is required by prior art OMT's.
REFERENCES:
patent: 3201717 (1965-08-01), Grosbois et al.
patent: 3668567 (1972-06-01), Rosen
patent: 114155 (1979-09-01), None
patent: 4304 (1985-01-01), None
patent: 158201 (1986-07-01), None
patent: 89401 (1990-03-01), None
patent: 4373201 (1992-12-01), None
European Search Report in Application No. EP 99 11 9563 dated Jan. 10, 2000.
Gudmestad T.
Hughes Electronics Corporation
Lee Benny
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