US3914764A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus for reducing cross coupling between orthogonal polarizations in satellite communication systems
Assignee: AT&T Inc
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Filing: 1974-03-04
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Granted: 1975-10-21
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Expires: 1994-03-04
Abstract
Abstract In satellite communications systems, linearly polarized orthogonal waves are used for simultaneously transmitting different signal information. In transmission, however, the linearly polarized transmitted waves experience adverse changes in their polarizations due to the polarization rotation and polarization conversion effects of the transmission channel. In particular, as a result of the rotational effect, the linearly polarized waves are rotated by the same variable amount so that the waves retain their linearly polarized states and orthogonality but take on new polarization directions which are inclined at the same angle relative to their original polarization directions. The polarization conversion effect of the channel, in turn, acts upon the rotated linearly polarized transmitted waves and converts these waves into a pair of elliptically polarized waves having arbitrary characteristics which change with changes in the angle of rotation of the rotated waves. The present apparatus involves an arrangement of microwave components having fixed characteristics which can be used to transform the two varying elliptically polarized waves exiting from the transmission channel into replicas of the rotated transmitted waves. In particular, a combination of 3 microwave components, namely a first differential phase-shifter, a differential attenuator comprising two differential attenuator sections, and a second differential phase-shifter having fixed magnitudes and orientations are employed to provide such transformation.
Inventors
- 👤 Edward Allen Ohm
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 07:29
CPC Classifications
H; H04; H04B; H04B7/00; H04B7/002
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
134 words
Apparatus responsive to first and second elliptically polarized waves which are formed by the action of a transmission channel on first and second linearly polarized waves, said first and second linearly polarized waves being polarized along first and second orthogonal polarization directions which rotate, thereby causing the characteristics of said first and second elliptically polarized waves to change, comprising: polarization conversion means including a first differential phase shifter, a first differential attenuator and a second differential phase-shifter; said first and second differential phaseshifters and said first differential attenuator having fixed characteristics which are adjusted to cause said first and second elliptically polarized waves to be converted, for all rotations of said first and second directions, into third and fourth linearly polarized waves which are replicas, respectively, of said first and second linearly polarized waves.
Claim 2
Dependent Claim
134 words
Apparatus responsive to first and second elliptically polarized waves which are formed by the action of a transmission channel on first and second linearly polarized waves, said first and second linearly polarized waves being polarized along first and second orthogonal polarization directions which rotate, thereby causing the characteristics of said first and second elliptically polarized waves to change, comprising: polarization conversion means including a first differential phase shifter, a first differential attenuator and a second differential phase-shifter; said first and second differential phaseshifters and said first differential attenuator having fixed characteristics which are adjusted to cause said first and second elliptically polarized waves to be converted, for all rotations of said first and second directions, into third and fourth linearly polarized waves which are replicas, respectively, of said first and second linearly polarized waves.
Claim 3
Dependent Claim
20 words
Apparatus in accordance with claim 1 in which said first phase-shifter, first attenuator and second phase-shifter are arranged in cascade.
Claim 4
Dependent Claim
19 words
Apparatus in accordance with claim 2 in which said first attenuator is disposed between said first and second phase-shifter.
Claim 5
Dependent Claim
17 words
Apparatus in accordance with claim 1 in which said attenuator comprises first and second differential attenuator sections.
Claim 6
Dependent Claim
360 words
Apparatus in accordance with claim 4 in which: said first phase-shifter and said first attenuator section are adjusted such that when said rotation is a given amount their combined effect is to convert said first and second elliptically polarized waves directly into said third and fourth waves and such that when said rotation is different from said given amount their combined effect is to convert said first and second elliptically polarized waves into first and second pairs of linearly polarized wave components corresponding, respectively, to said first and second linearly polarized waves, one of the wave components of each of said pairs being polarized along a third polarization direction and the other of said wave components of each of said pairs being polarized along a fourth ortHogonal polarization direction, said first pair having amplitudes whose ratio relative to that of the ratio of the amplitudes of the wave components along third and fourth directions which combine to form said first linearly polarized wave is a first constant amount, and phases which differ by a second constant amount, and said second pair having amplitudes whose ratio relative to that of the ratio of the amplitudes of the wave components in said third and fourth directions which combine to form said second linearly polarized wave is a constant amount equal to said first amount, and phases which differ by a constant amount equal to said second amount; said second attenuator section is adjusted to apply a differential attenuation to said first and second pairs such that the ratio of the amplitudes of said first pair is made equal to the ratio of the amplitudes of said components which combine to form said first linearly polarized wave, and the ratio of the amplitudes of said second pair is made equal to the ratio of the amplitudes of said components of which combine to form said second linearly polarized wave; and said second phase-shifter is adjusted to apply a differential phase-shift to said first and second pairs such that the phase difference between said first pair is made equal to zero and the phase difference between said second pair is made equal to zero.
Claim 7
Dependent Claim
67 words
Apparatus in accordance with claim 5 in which: said second attenuator is adjusted to apply a differential attenuation to said first and second pairs so as to cause said first amount to be made equal to unity: and said second phase-shifter is adjusted to apply a differential phase-shift to said first and second pairs so as to cause said second amount to be made equal to zero.
Claim 8
Dependent Claim
94 words
In a satellite communications system which includes a transmission channel which exhibits a polarization conversion effect and a polarization rotation effect, which effects act to transform linearly polarized waves transmitted through the channel into elliptically polarized waves having arbitrary characteristics which change with changes in said rotation effect; polarization conversion means including a first differential phase-shifter, a first differential attenuator and a second differential phase-shifter; said first and second differential phaseshifters and said first differential attenuator having fixed characteristics which are adjusted to counteract said conversion effect for all changes in said rotation effect.
Claim 9
Dependent Claim
94 words
In a satellite communications system which includes a transmission channel which exhibits a polarization conversion effect and a polarization rotation effect, which effects act to transform linearly polarized waves transmitted through the channel into elliptically polarized waves having arbitrary characteristics which change with changes in said rotation effect; polarization conversion means including a first differential phase-shifter, a first differential attenuator and a second differential phase-shifter; said first and second differential phaseshifters and said first differential attenuator having fixed characteristics which are adjusted to counteract said conversion effect for all changes in said rotation effect.
Claim 10
Dependent Claim
20 words
A system in accordance with claim 7 which includes, in addition, polarization rotation means for counteracting said polarization rotation effect.
Claim 11
Dependent Claim
24 words
A system in accordance with claim 7 which includes an earth station and in which said conversion means is disposed at said earth station.
Claim 12
Dependent Claim
87 words
A system in accordance with claim 7 in which: said polarization rotation effect acts to rotate the polarization directions of said linearly polarized waves by a changing amount to form rotated linearly polarized waves; said polarization conversion effect acts to transform said rotated waves into said elliptically polarized waves whose characteristics change with changes in said amount of rotation; and said conversion means, for all changes in said amount of rotation, converts said elliptically polarized waves into linearly polarized waves which are replicas of said rotated waves.
References Cited (Backward Citations)
US3728643A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-10-20 | 1979-04-21 | 1979-10-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-10-20 | 1983-04-21 | 1983-10-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-10-20 | 1987-04-21 | 1987-10-21 | $7700.00 | Window Closed / Lapsed |