Interference reduction circuit
First Claim
1. An interference reduction circuit for use in a receiver of frequency reuse communications systems wherein a plurality of signals of the same frequency at predetermined different polarizations are transmitted from a remote location and the transmission media alters the relative polarizations between said plurality of signals thereby introducing cross-talk between the signals when they are received, said interference reduction circuit comprising:
- a. a first plurality of hybrid coupling networks each receiving one of said transmission media altered signals and dividing each of said signals into a number of circuit paths equal in number to the number of received signals,b. phase-shift means in each of said circuit paths for producing phase shifts in each of said signals, andc. a second plurality of hybrid coupling networks each connected to one of said circuit paths from each of said first plurality of hybrid coupling networks after said phase-shift means for cross-coupling said circuit paths and thereby adding a sample of all other signals of equal amplitude, but opposite phase, to the cross-talk interference in each signal and thereby substantially cancelling the cross-talk interference in each signal to provide uncorrupted output signals at the outputs of said second plurality of hybrid coupling networks.
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Accused Products
Abstract
An interference reduction circuit to provide isolation in frequency reuse systems operates on two or more non-isolated signals by cross-coupling the signals such that the interfering signals are cancelled on each channel. In a dual-polarized frequency reuse system, cancellation is effected by adding a sample of an oppositely polarized channel of equal amplitude, but of opposite phase, to the interference. Practical implementation includes closed-loop, digital feedback control to permit dynamic signal-to-interference improvement involving no a priori knowledge of the nature of the incoming signals. The circuit has applications in satellites and earth stations in a communications satellite system.
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Citations
13 Claims
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1. An interference reduction circuit for use in a receiver of frequency reuse communications systems wherein a plurality of signals of the same frequency at predetermined different polarizations are transmitted from a remote location and the transmission media alters the relative polarizations between said plurality of signals thereby introducing cross-talk between the signals when they are received, said interference reduction circuit comprising:
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a. a first plurality of hybrid coupling networks each receiving one of said transmission media altered signals and dividing each of said signals into a number of circuit paths equal in number to the number of received signals, b. phase-shift means in each of said circuit paths for producing phase shifts in each of said signals, and c. a second plurality of hybrid coupling networks each connected to one of said circuit paths from each of said first plurality of hybrid coupling networks after said phase-shift means for cross-coupling said circuit paths and thereby adding a sample of all other signals of equal amplitude, but opposite phase, to the cross-talk interference in each signal and thereby substantially cancelling the cross-talk interference in each signal to provide uncorrupted output signals at the outputs of said second plurality of hybrid coupling networks. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An interference reduction circuit for use in a receiver of frequency reuse communications systems wherein a plurality of signals of the same frequency at predetermined different polarizations are transmitted from a remote location and the transmission media alters the relative polarizations between said plurality of signals thereby introducing cross-talk between the signals when they are received, said interference reduction circuit comprising:
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a. a first plurality of power dividers each receiving one of said transmission media altered signals and dividing each of said signals into a number of circuit paths equal in number to the number of received signals, b. a plurality of variable phase shifters, one in each of said circuit paths for producing variable phase shifts in each of said signals, c. a second plurality of power dividers connected in a reciprocal manner to said first plurality of power dividers, each of said second plurality of power dividers being connected to one of said circuit paths from each of said first plurality of power dividers after said variable phase shifters for cross-coupling said circuit paths and thereby adding a sample of all other signals of equal amplitude, but opposite phase, to the cross-talk interference in each signal and thereby substantially cancelling the cross-talk interference in each signal to provide uncorrupted output signals at the outputs of said second plurality of power dividers, and d. amplifying means in said circuit paths for amplifying said signals.
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Specification