ACCESSING LP TRANSPONDERS WITH CP TERMINALS VIA WAVEFRONT MULTIPLEXING TECHNIQUES

• US 20120026937A1
• Filed: 06/29/2011
• Published: 02/02/2012
• Est. Priority Date: 07/30/2010
• Status: Active Grant

• Current Assignee: Spatial Digital Systems Inc
• Original Assignee: Spatial Digital Systems Inc
• Inventors: CHANG, DONALD C. D.
• Granted Patent: US 8,538,326 B2
• Time in Patent Office: Days
• US Class Current: 370/316
• CPC Class Codes: H01Q 21/245 provided with means for varying the polarisation polarising devices H01Q15/24; tracking by comparing linear polarisation compounds G01S3/146; reducing depolarisation effects H04B7/00; polarisation diversity H04B7/10
• CPC Class Codes: H01Q 3/24 varying the orientation by switching energy from one active radiating element to another, e.g. for beam switching
• CPC Class Codes: H01Q 9/0407 Substantially flat resonant element parallel to ground plane, e.g. patch antenna dipole H01Q9/285; monopole H01Q9/40
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/1853 Satellite systems for providing telephony service to a mobile station, i.e. mobile satellite service for selecting H04W
• CPC Class Codes: H04J 14/06 Polarisation multiplex systems
• CPC Class Codes: H04L 5/005 of common pilots, i.e. pilots destined for multiple users or terminals
• CPC Class Codes: H04L 5/026 using code division
• CPC Class Codes: H04W 24/02 Arrangements for optimising operational condition
• CPC Class Codes: H04W 72/0446 Resources in time domain, e.g. slots or frames

Abstract

The invention is about a method and apparatus for grouping multiple satellite transponders with both (LP) polarization formats in different frequencies through Wave-Front (WF) Multiplexing (muxing) techniques for ground terminals with incompatible (CP) polarization formats. As a result of this invention, linear polarized (LP) transponders can be accessed and efficiently utilized by circularly polarized (CP) ground terminals and vice versa. This invention consists of conventional ground terminals, a unique organization of space assets, and a unique polarization alignment processor. The applications of wavefront multiplexing techniques to satellite communications offer many potential advantages, including improved flexibility and utility efficiency of existing space assets. Our proposed “Polarization Utility Waveforms” is an entirely new concept in VSAT and Earth Station Antenna diversity. The implementation enables antennas to switch between different polarization formats at the press of a button, and provides tele-port operators with greater flexibility in how they manage their assets.

Claims

1. A novel satellite communications method and apparatus for efficient communications among space assets and ground terminals with incompatible polarization formats comprising of:

2 transmitting ground terminals with circularly polarized (CP) formats,

2 separated linearly polarized (LP) communications channels at a common desired frequency slot on a space asset, and

a receiving ground terminal with circularly polarized formats.

2. The satellite communications system of claim 1, wherein a right hand circularly polarized (RHCP) format is assigned to a terminal transmitting signal s1 (t), wherein a left hand circularly polarized (LHCP) format is assigned to a terminal transmitting signal s2 (t).

3. The satellite communications system of claim 1, wherein a satellite provides two linearly polarized communications channels,

wherein a horizontally polarized (HP) communication channel with a bandwidth B centered at an input frequency f1

amplifies aggregated received signals from s1(t) and s2(t),

translates the amplified signals to an output frequency f2, and

radiates the transponded signals in HP to a coverage area on ground;

wherein a vertically polarized (VP) communication channel with a bandwidth B centered at an input frequency f1

amplifies aggregated received signals from s1(t) and s2(t),

translates the amplified signals to the same output frequency f2, and

radiates the transponded signals in VP to a coverage area on ground.

4. The satellite communications systems in claim 1, wherein the receiving ground terminals comprising of:

two separated concurrent CP receiving functions, comprising of

an RHCP format with an output signal stream yr(t) and

a LHCP format with an output signal stream yl(t), and

a polarization realignment processor to reconstitute the desired received signals s′

1(t) and s′

2(t) by performing linear combinations on output streams yr(t) and yl(t), wherein

s1′

(t)=c1r*yr(t)+c1l*yl(t), and

s2′

(t)=c2r*yr(t)+c2l*yl(t).

5. A polarization realignment processor comprising of:

a realignment mechanism,

a diagnostic network,

and an optimization processor,

wherein the realignment mechanisms comprising of calculations using two simultaneous linear equations with two circularly polarized (CP) inputs yi1 and yi2, two outputs yo1 and yo2, and four coupling coefficients c11, c12, c21, and c22,

yo1=c11*yi1+c12*yi2,

yo2=c21*yi1+c22*yi2,

wherein the four coupling coefficients are iteratively updated.

6. The polarization realignment processor in claim 5, wherein the diagnostic network

evaluates measured output signals yo1 and yo2 against anticipated received signal structures,

quantifies the measured performances into a set of positively defined numbers as performance indexes such as cost functions, and

produces a current total cost for the optimization processor by summing all performance indexes,

wherein the optimization processor

derives the gradients of the total cost with respect to various current coupling coefficients,

calculates a new set of coupling coefficients based on the cost gradients, and uploads the new coefficients to the realignment mechanism as updates.

7. A novel satellite communications method and apparatus for efficient communications among space assets and ground terminals with incompatible polarization formats comprising of:

two transmitting ground terminals with circularly polarized (CP) formats,

two separated linearly polarized (LP) communications channels at a common desired frequency slot on a space asset, and

two receiving ground terminals with circularly polarized formats.

8. The satellite communications system of claim 7, wherein the right hand circularly polarized (RHCP) format is assigned to the first terminal transmitting signal s1 (t) and the left hand circularly polarized (LHCP) format is assigned to the second terminal transmitting signal s2 (t).

9. The satellite communications system of claim 7, wherein a space asset provides two linearly polarized communications channels,

wherein a horizontally polarized (HP) communication channel, with a bandwidth B centered at an input frequency f1,

amplifies aggregated received signals s1(t) and s2(t), and

translates the amplified signals to an output frequency f2, and

radiates the transponded signals in HP to a coverage area on ground;

wherein a vertically polarized (VP) communication channel, with a bandwidth B centered at an input frequency f1,

amplifies another aggregated received signals s1(t) and s2(t), and

translates the amplified signals to the same output frequency f2, and

radiates the transponded signals in VP to a coverage area on ground.

10. The satellite communications systems in claim 7, wherein the first receiving ground terminal comprising of:

two separated concurrent CP receiving functions comprising of

an RHCP format with an output signal stream yr(t) and

a LHCP format with an output signal stream yl(t), and

a polarization realignment processor

performing linear combinations on the yr(t) and yl(t) to reconstitute the first desired received signals s′

1(t), wherein

s1′

(t)=c1r*yr(t)+c1l*yl(t).

11. The satellite communications systems in claim 7, wherein the second receiving ground terminal comprising of:

two separated concurrent CP receiving functions comprising of

an RHCP format with an output signal stream yr(t) and

a LHCP format with an output signal stream yl(t), and

a polarization realignment processor

performing linear combinations on the yr(t) and yl(t) to reconstitute the

second desired received signals s′

2(t), wherein

s2′

(t)=c2r*yr(t)+c2l*yl(t).

12. A novel satellite communications method and apparatus for efficient communications among space assets and ground terminals with incompatible polarization formats comprising of:

a transmitting ground terminal with circularly polarized (CP) formats,

two separated linearly polarized (LP) communications channels at a frequency slot on a satellite, and

two receiving ground terminals with circularly polarized formats.

13. The satellite communications system of claim 12, wherein the transmit terminal comprising of:

two independent concurrent CP transmission output signal streams yr(t) in a RHCP format and yl(t) in a LHCP format,

an auxiliary channel to receive a(t), and

a pre-processing unit performing polarization alignment functions, wherein

linear combinations on s1(t) and s2(t) to optimize two transmitting signals yr(t) and yl(t), wherein

yr(t)=cr1*s1(t)+cr2*s2(t) and

yl(t)=cl1*s1(t)+cl2*s2(t),

wherein the complex coefficients [cr1, cr2, cl1, and cl2] are estimated based on the output from the auxiliary channel a(t).

14. The satellite communications system of claim 12, wherein a space asset provides two linearly polarized communications channels,

wherein a horizontally polarized (HP) communication channel, with a bandwidth B centered at an input frequency f1,

amplifies a stream of aggregated received signals yr(t) and yl(t), and

translates the amplified signals to an output frequency f2, and

radiates the transponded signals in HP to a coverage area on ground, and

wherein a vertically polarized (VP) communication channel, with a bandwidth B centered at an input frequency f1,

amplifies a stream of another aggregated received signals yr(t) and yl(t),

translates the amplified signals to the same output frequency f2, and

radiates the transponded signals in VP to a coverage area on ground.

15. The satellite communications systems in claim 12, wherein the first receiving ground terminal comprising the RHCP receiving functions with an output signal stream s1(t), and wherein the second receiving ground terminal comprising the LHCP receiving functions with an output signal stream s2(t).

16. A novel satellite communications method and apparatus for efficient communications among space assets and ground terminals with incompatible polarization formats comprising of:

two transmitting ground terminal with circularly polarized (CP) formats,

two separated linearly polarized (LP) communications channels at a frequency slot on a satellite, and

two receiving ground terminals with circularly polarized formats.

17. The satellite communications method and apparatus of claim 16, wherein the first transmit terminal comprising of:

two concurrent independent CP transmission outputs are signal streams,

yr1(t) in a RHCP format and yl1(t) in a LHCP format,

an auxiliary receiving channel to receive a1(t),

a pre-processing unit performing polarization alignment functions, wherein

complex weightings are applied on the s1(t) for the two transmitting signals yr1(t) and yl1(t);

whereas

yr1(t)=cr1*s1(t) and yl1(t)=cl1*s1(t)

wherein the complex coefficients [cr1, and cl1] are estimated based on the output of the auxiliary channel a1(t).

18. The satellite communications method and apparatus of claim 16, wherein the second transmit terminal comprising of:

two concurrent independent CP transmission outputs are signal streams yr2(t) in a RHCP format and yl2(t) in a LHCP format,

an auxiliary receiving channel to receive a2(t),

a pre-processing unit performing polarization alignment functions, wherein complex weightings are applied on s2(t) for the two transmitting signal streams yr2(t) and yl2(t);

whereas

yr2(t)=cr2*s2(t) and yl2(t)=cl2*s2(t)

wherein the complex coefficients [cr2, and cl2] are estimated based on the output of the auxiliary channel a2(t).

19. The satellite communications system of claim 16, whereas a space asset provides two linearly polarized communications channels,

wherein a horizontally polarized (HP) communication channel, with a bandwidth B is centered at an input frequency f1,

amplifies aggregated received signals from yr1(t), yl1(t), yr2(t), and yl2(t),

translates the amplified signals to an output frequency f2, and

radiates the transponded signals in HP to a coverage area on ground, and

wherein a vertically polarized (VP) communication channel with a bandwidth B centered at an input frequency f1

amplifies another aggregated received signals from yr1(t), yl1(t), yr2(t), and yl2(t),

translates the amplified signals to the same output frequency f2, and

radiates the transponded signals in VP to a coverage area on ground;

20. The satellite communications systems in claim 16, wherein the first receiving ground terminal comprising the RHCP receives functions with an output signal stream s1(t), and whereas the second receiving ground terminal comprising the LHCP receives functions with an output signal stream s2(t).