Apparatus and method for controlling crosspolarization of signals in a frequency reuse system

• US 4,292,685 A
• Filed: 05/31/1978
• Issued: 09/29/1981
• Est. Priority Date: 05/31/1978
• Status: Expired due to Term

• Current Assignee: Lin-Shan Lee
• Original Assignee: Lin-Shan Lee
• Inventors: Lee, Lin-Shan
• Primary Examiner(s): Bookbinder, Marc E.
• Application Number:
  US05/911,954
• Time in Patent Office: 1,217 Days
• Field of Search: 325/60, 325/65, 325/62, 325/63, 325/367, 325/371, 325/472, 325/476, 325/477, 325/1, 325/3, 325/4, 325/56, 179/15 BP, 179/15 AN, 179/15 BC, 333/18, 333/28 R, 333/70 T, 333/21 A, 328/162, 328/165, 328/167, 343/100 PE, 343/200, 343/100 ST, 455/11, 455/12, 455/52, 455/59, 455/63, 455/71, 455/295, 455/303-306, 370/6
• US Class Current: 455/13.2
• CPC Class Codes: H04B 7/002 Reducing depolarization effects

Abstract

Apparatus and method for controlling the crosspolarization of signals in a satellite communications, frequency reuse system. Each earth station in the system includes one crosscoupling network that compensates for the crosspolarization of signals transmitted by such earth station uplink to the satellite due to the propagative medium around such earth station, and an adaptive feedback control system having another crosscoupling network that compensates for the crosspolarization of signals received from the other earth stations due to such propagative medium around such earth station.

Claims

1. Apparatus for controlling the crosspolarization between dual reference signals propagated in a frequency reuse satellite communications system having a plurality of stations communicating via a satellite, in which the dual reference signals transmitted by each station are of different polarization, and the propagative medium around each station causes the crosspolarization of the dual reference signals transmitted and received by each station, the apparatus being for use at each station, comprising:

(a) first means for controllably crosscoupling the dual reference signals being transmitted by the station to the satellite to compensate for the crosspolarization due to the propagative medium, including first means for adjusting the amplitude and phase of the dual reference signals being crosscoupled and transmitted; and

(b) second means for controllably crosscoupling the dual reference signals being received by the station via the satellite to compensate for the crosspolarization due to the propagative medium, including second means for adjusting the amplitude and phase of the received dual reference signals being corsscoupled;

wherein

(c) said first crosscoupling means includes means, coupled to said second crosscoupling means, for generating output signals representing a correlation between the crosspolarization produced by the propagative medium acting on the dual reference signals transmitted by the station to the satellite and the dual reference signals received by the station, said first adjusting means being responsive to the output signals to adjust the amplitude and phase of the dual reference signals being crosscoupled and transmitted, said generating means including

(i) memory means, coupled to said second adjusting means, for storing predetermined pairs of first and second complex variable signals, each of the first and second complex variable signals having amplitude and phase information, said second adjusting means including means for producing control signals representing the adjustment in amplitude and phase of the received and crosscoupled dual reference signals, and said memory means having means for outputting one pair of the complex variable signals in response to one of the control signals, and

(ii) means, responsive to the one pair of complex variable signals and the control signals, for producing the output signals.

2. Apparatus for controlling the crosspolarization between first and second reference signals propagated in a frequency reuse satellite communications system having a plurality of stations communicating via a satellite, in which the first and second reference signals transmitted by each station are of different polarization, and the propagative medium around the station causes the crosspolarization of the first and second reference signals transmitted and received by each station, the apparatus being for use at each station, comprising:

(a) first means for controllably crosscoupling the first and second reference signals being transmitted by the station to the satellite to compensate for the crosspolarization due to the propagative medium, including means for adjusting the amplitude and phase of the first and second reference signals being crosscoupled; and

(b) second means for controllably crosscoupling the first and second reference signals being received by the station via the satellite to compensate for the crosspolarization due to the propagative medium;

wherein

(c) said first crosscoupling means includes means, responsive to the first and second reference signals which have been crosscoupled by said second crosscoupling means, for generating output signals representing the crosspolarization of the first and second reference signals transmitted to the satellite, said adjusting means being responsive to the output signals to adjust the amplitude and phase of the first and second reference signals being crosscoupled and transmitted, said generating means including

(i) first means for producing a first pair of signals, one corresponding to the first reference signal crosscoupled by said second crosscoupling means and the other corresponding to the first reference signal crosscoupled into the second reference signal by said first crosscoupling means; and

(ii) second means, connected to said first producing means, for producing a second pair of control signals representing the difference in amplitude and phase between the first pair of signals, the second pair being the output signals.

3. Apparatus for controlling the crosspolarization between dual reference signals propagated in a frequency reuse satellite communications system having a plurality of stations communicating via a satellite, in which the dual reference signals transmitted by each station are of a different polarization, and the propagative medium around each station causes the crosspolarization of the dual reference signals transmitted and received by each station , the apparatus being for use at each station, comprising:

(a) first means for controllably crosscoupling in phase and amplitude the dual reference signals being transmitted by the station to the satellite to compensate for the corsspolarization due to the propagative medium;

(b) second means for controllably crosscoupling and for adjusting in phase and amplitude the dual reference signals being received by the station via the satellite to compensate for the crosspolarization due to the propagative medium, including means for generating first, second, third and fourth control signals proportional to the adjustment in amplitude and phase of the dual reference signals, respectively, and

(c) means, responsive to said control signals, for generating output signals representing a correlation between the crosspolarization produced by the propagative medium acting on the dual reference signals transmitted by the station to the satellite and the dual reference signals received by the station, including

(i) memory means, responsive to one of said control signals, for producing a pair of complex variable signals, the pair having a first amplitude signal, a first phase signal, a second amplitude signal and a second phase signal; and

(ii) parameter generator means for generating a first output amplitude signal, a first output phase signal, a second output amplitude signal and a second output phase signal, including a first adder for adding the first phase control signal and the second phase signal of the pair to produce the second output phase signal, a second adder for adding the second phase control signal and the first phase signal of the pair to produce the second output phase signal, a first multiplier to multiply the first amplitude control signal and the second amplitude signal of the pair to produce the second output amplitude signal, and a second multiplier to multiply the second amplitude control signal and the first amplitude signal of the pair to produce the first output amplitude signal, wherein said first crosscoupling means is responsive to the first output signal, the second output signal, the third output signal and the fourth output signal.

4. Apparatus for controlling the crosspolarization between first dual signals propagated in a frequency reuse satellite communications system having a plurality of remote stations and a local station communicating via a satellite, in which the first dual signals transmitted by each station are of different polarization and the propagative medium around the local station causes the crosspolarization of the first dual signals transmitted by the remote stations and the local station, the apparatus being for use at the local station, comprising:

(a) first adjustable means for controllably crosscoupling the first dual signals transmitted by the local station to the satellite to compensate for the crosspolarization due to the propagative medium;

(b) second adjustable means for controllably crosscoupling the first dual signals received by the local station via the satellite to compensate for the crosspolarization due to the propagative medium; and

(c) closed-loop control means for transmitting second dual-polarized reference signals via said first adjustable means and through the propagative medium, and for receiving the transmitted reference signals through the propagative medium and via said second adjustable means, said second adjustable means being adjusted in response to the received reference signals to control the crosscoupling of the received first dual signals and said first adjustable means being adjusted in response to the received reference signals to control the crosscoupling of the transmitted first dual signals.

5. Apparatus according to claim 4 wherein said first adjustable means comprises first crosscoupling network means for adjusting the amplitude and phase of the first dual signals and the second reference signals and wherein said second adjustable means comprises second crosscoupling network means for adjusting the amplitude and phase of the first dual signals and the second reference signals.

6. Apparatus according to claim 5 wherein said closed-loop control means comprises:

(a) filter and second reference signal detector means for adjusting said second crosscoupling means in response to the second reference signals; and

(b) function generator means for adjusting said first crosscoupling network means in response to the amplitude and phase adjustment of said second crosscroupling network means.

7. Apparatus for controlling the crosspolarization between first dual signals propagated in a frequency reuse satellite communications system having a plurality of remote stations and a local station communicating via a satellite, in which the first dual signals transmitted by each station are of different polarization, and the propagative medium around the local station causes the crosspolarization of the first dual signals transmitted by the remote stations and the local station. comprising:

(a) first adjustable means for controllably crosscoupling the first dual signals transmitted by the local station to the satellite to compensate for the crosspolarization due to the propagative medium;

(b) second adjustable means for controllably crosscoupling the first dual signals received by the local station via the satellite to compensate for the crosspolarization due to the propagative medium;

(d) first closed-loop control means, including said first adjustable means, for transmitting second dual-polarized reference signals uplink via said first adjustable means through the propagative medium, and for receiving the second transmitted reference signals through the propagative medium down-link via said second adjustable means, said first adjustable means being adjusted in response to the second reference signals received down-link via said second adjustable means; and

(e) second closed-loop control means, including said second adjustable means, for receiving third dual-polarized reference signals being received down-link through the propagative medium into said second adjustable means, the third reference signals having substantially only down-link crosspolarization due to the propagative medium, said second adjustable means being adjusted in response to the third reference signals received via said second adjustable means.

8. Apparatus according to claim 7 wherein said first adjustable means comprises first crosscoupling network means for adjusting the amplitude and phase of the first dual signals and the second reference signals and wherein said second adjustable means comprises second crosscoupling network means for adjusting the amplitude and phase of the first dual signals, the second reference signals and the third reference signals.

9. Apparatus according to claim 8 wherein said first closed-loop control means comprises function generator means for adjusting said first crosscoupling network means in response to the second reference signals adjusted by said second crosscoupling means.

10. Apparatus according to claim 9 wherein said second closed-loop control means comprises filter and third reference signal detector means for adjusting said second crosscoupling network means in response to the third reference signals.

11. Apparatus according to claim 10 wherein said means for receiving receives the third reference signals from said satellite, and said satellite also relays the transmitted second reference signals to said second crosscoupling network means.

12. Apparatus according to claim 11 wherein said function generator means includes means, responsive to the second reference signals adjusted by said second crosscoupling network means, for compensating the first transmitted signals for amplitude and phase shifts introduced by said satellite.