Wave transmission lines and networks – Plural channel systems – Having branched circuits
Reexamination Certificate
2001-10-05
2003-06-10
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Plural channel systems
Having branched circuits
C333S137000, C333S02100R
Reexamination Certificate
active
06577207
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to electromagnetic couplers, and especially to such couplers using mode transformation, and their use in conjunction with antenna arrangements.
BACKGROUND OF THE INVENTION
The invention arose out of consideration of the problems associated with the design of broadband antenna feed systems for use in spacecraft. Some current communication spacecraft operate in a transmit (Tx) band extending from 3.2 to 4.2 GHz and in a receive (Rx) band extending from 5.925 to 6.725 GHz. These bands may be referred to as a “4/6” GHz frequency band. The purpose of such couplers is to allow a single antenna to receive and transmit signals within its receive and transmit bands with isolation, and preferably high isolation, between Tx and Rx ports, or between the transmit and receive signals of two disparate frequency bands. Electromagnetic couplers for communications use tend to require a combination of broad bandwidth, low losses, isolation between Tx and Rx ports, light weight, simplicity and ruggedness. A compromise is ordinarily required among these and other limitations, such as cost.
Arrangements for frequency re-use of antennas are described beginning at page 371 and extending to page 445 of the text
Waveguide Components for Antenna Feed Systems: Theory and CAD
, by Uher et al., published 1993 by Artech House of Boston and London, ISBN 0-89006-582-9.
A coupler suitable for such use is described in U.S. Pat. No. 3,992,621, issued Nov. 25, 1975 in the name of Gruner. The Gruner arrangement includes an inner circular waveguide for propagating the 6 GHz signals and an outer circular waveguide for propagating the 4 GHz signals. The coupling section includes a plurality of inwardly projecting annular corrugations.
SUMMARY OF THE INVENTION
Thus, a coupler with mode transformer according to an aspect of the invention is for coupling (a) a common square waveguide port with at least one of nominally mutually independent (b) first external and (c) second external ports. The first external port is in the form of a cluster of first, second, third, and fourth clustered square waveguide ports. The second external port is in the form of first and second rectangular ridged waveguide ports, which are associated with corresponding waveguides. The first external port, in one embodiment, operates at a relatively high frequency band, namely 6 GHz, and the second external port operates at a relatively low frequency band, while the common port operates at both frequency bands. The common square waveguide associated with the common square waveguide port, and each of the four square clustered waveguides associated with the first external port, are capable of supporting either, or both, of two mutually orthogonal linear polarizations. In general, at any one time, one of the square waveguides may support a first linear polarization, a second linear polarization orthogonal to the first, or either of two hands of circular or elliptic polarization which has as components such linear polarizations. The second external port is in the form of first and second rectangular ridged waveguide ports, each of which is capable of supporting a single linear polarization, and each of which is associated with a corresponding ridged waveguide. The common port can couple signals with any of these polarizations with (or to) one or the other of the first and second nominally independent ports. The coupler includes a ridged square waveguide section defining a port coupled to, or in common with, the common square waveguide port and also defining a first internal square port. The ridged square waveguide section includes first and second mutually spatially orthogonal ridge structures lying between the first and first internal square ports of the ridged square waveguide section. These ridge structures tend to concentrate the fields of the dominant TE
1,0
mode of either of the two mutually spatially orthogonal linear polarizations in, or into, a region near the axis or center of the ridged square waveguide section. The ridged square waveguide section also includes first and second planar phase shifters. The first planar phase shifter lies parallel to the plane of the first ridge structure, and the second planar phase shifter lies parallel with the plane of the second ridge structure, so that the first and second planar phase shifters are mutually orthogonal. Each of the first and second planar phase shifters is located between that one of the ridge structures with which it is parallel and a side wall of the ridged square waveguide section. The locations of the phase shifters are selected for propagating either polarization of the dominant TE
1,0
mode from the first port to the second port of the ridged square waveguide section without substantially affecting the dominant TE
1,0
mode, and for delaying by substantially &pgr; a spatial portion of one of (a) a TE
2,0
and (b) a TE
0,2
mode propagating therein, to thereby convert between the dominant TE
1,0
mode at the first port of the square waveguide section and the one of the (a) TE
20
and (b) TEO
0,2
mode at the second port of the square waveguide section. The coupler includes a transition section of waveguide. The transition section of waveguide defines a first internal square waveguide port which is coupled to the first, internal, square waveguide port of the ridged square waveguide section, and also defines a second square waveguide internal port. The transition section of waveguide includes a first septum extending completely across the square cross-section at the second internal port of the transition section of waveguide to thereby define first and second internal rectangular waveguide ports. The first septum progressively reduces in size (becomes smaller) toward the first square waveguide port of the transition section of waveguide. The transition section of waveguide converts between either polarization of the TE
1,0
mode at the first internal square port of the ridged waveguide section and at least one of the TE
2,0
and TE
0,2
modes in the first and second internal rectangular ports of the transition section. The coupler further includes an eight-port waveguide branch section defining the first and second rectangular ridged waveguide ports of the second nominally independent port of the coupler. The branch section also includes first, second, third, and fourth clustered square waveguide ports of the first nominally independent port of the coupler, and third and fourth internal rectangular waveguide ports having a common or joined wall. The third and fourth internal rectangular waveguide ports of the branch section are coupled to the first and second internal rectangular waveguide ports of the transition waveguide section. The branch section further defines first and second H-plane walls parallel with the common wall, a first E-plane rectangular aperture in the first H-plane wall which is coupled to the first rectangular waveguide port of the second nominally independent port of the coupler, and a second rectangular aperture in the second H-plane wall which is coupled to the second rectangular waveguide port of the second nominally independent port of the coupler. The branch section further includes a second septum extending from that edge of the first rectangular aperture which is adjacent the first nominally independent waveguide port to the first nominally independent waveguide port, to thereby aid in defining the first and second clustered square waveguide ports, and further includes a third septum extending from that edge of the second rectangular aperture which is adjacent the first nominally independent waveguide port to the first nominally independent waveguide port, to thereby aid in defining the third and fourth clustered square waveguide ports.
In a particular avatar of this aspect of the invention, the coupler includes a first rectangular waveguide section extending from the first rectangular aperture to the first rectangular waveguide port of the second nominally independent port of the coupler. This particular avata
Duane Morris LLP
Lockheed Martin Corporation
Takaoka Dean
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