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Feed network for a dual circular and dual linear polarization antenna
| Details |
Inventors: Bains, Paramjit S.;
Assignee: Hughes Aircraft Company (Los Angeles, CA)
Primary Examiner: Hellner; Mark
Assistant Examiner:
Attorney, Agent or Firm: Westerlund; Robert A., Mitchell; Steven M., Denson-Low; Wanda K.
A feed network for an antenna system, e.g., a phased array antenna system, which is operatively associated with a signal source, e.g., satellite-based transponders, which generates first and second R.F. signals of circular polarization, and third and fourth R.F. signals of orthogonal linear polarizations. The feed network includes a 3dB hybrid coupler or the like for splitting each of the first and second R.F. signals into first and second signal components disposed in phase quadrature with each other. Facilities are provided for applying the first signal components of the first and second R.F. signals, and the third R.F. signal, to a first beam forming network (BFN); and, for separately applying the second signal components of the first and second R.F. signals, and the fourth R.F. signal, to a second BFN. Subsequent to their emergence from the BFN's, the first and second signal components of each of the first and second R.F. signals are applied to respective through and side ports of ortho-mode-tees (OMT's) which Function to re-combine the first and second signal components, in phase quadrature, in order to thereby produce output first and second R.F. signals of opposite-sense (i.e., dual) circular polarizations. The third and fourth R.F. signals pass unaffected through the OMT's as output third and fourth R.F. signals of orthogonal (i.e., dual) linear polarizations. The first, second, third, and fourth output R.F. signals are then fed through common transmission lines to excite the individual antenna elements of the antenna system. |
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DETAILED DESCRIPTION The present invention encompasses a feed network for an antenna system which is operatively associated with a signal source which generates at least one linearly polarized R.
F.
signal and at least one circularly polarized signal, with the feed network being common to all of these R.
F.
signals and functioning to feed all of these R.
F.
signals to the N individual antenna elements, e.
g.
, feed horns, of the antenna system, e.
g.
, a phased array antenna system of the direct radiating or reflector type, such as are employed in satellite communications systems.
In a preferred embodiment of the present invention, the feed network includes a 3 dB hydrid coupler for splitting each of first and second circularly polarized R.
F.
signals into first and second signal components disposed in phase quadrature with each other.
The feed network also includes first and second signal transmission lines for separately feeding the first and second signal components of the first and second R.
F.
signals to respective first and second beam forming networks (BFN's).
The first signal transmission line is preferably operatively associated with a first multiplexer for facilitating common transmission of the first signal components of the first and second R.
F.
signals, and a third R.
F.
signal having a prescribed linear polarization (e.
g.
, horizontal), to the first beam forming network.
The second signal transmission line is preferably operatively associated with a second multiplexer for facilitating common transmission of the second signal components of the first and second R.
F.
signals, and a fourth R.
F.
signal having a prescribed linear polarization (e.
g.
, vertical) orthogonal to that of the third R.
F.
signal.
The first and second BFN's distribute each of the signals applied thereto into N component signals.
The feed network further includes N ortho-mode-tees (OMT's) each of which has a through port and a side port.
The N component signals of the first signal components of the first and second R.
F
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