U.S. patent application number 14/106844 was filed with the patent office on 2014-04-17 for polarization re-alignment for mobile satellite terminals.
This patent application is currently assigned to Donald C.D. Chang. The applicant listed for this patent is Donald C.D. Chang. Invention is credited to Donald C.D. Chang, Frank Lu, Yulan Sun.
Application Number | 20140104105 14/106844 |
Document ID | / |
Family ID | 45527215 |
Filed Date | 2014-04-17 |
United States Patent
Application |
20140104105 |
Kind Code |
A1 |
Chang; Donald C.D. ; et
al. |
April 17, 2014 |
Polarization Re-alignment for Mobile Satellite Terminals
Abstract
A system for allowing ground terminals, specifically mobile
ground terminals, to dynamically and electronically realign signal
polarizations to match that of incoming and outgoing signal
polarizations from designated space assets, specifically
communications from satellites, comprising an adaptive
re-orientation technique based on a cost minimization function, and
a means of direct calculations of weighting components based on the
knowledge of the orientation and bearing of both the satellites and
the ground terminals. The embodiment will allow a mobile ground
terminal to electronically realign itself to the signals of a
satellite, without the need for mechanical processes to physically
re-orient the antenna array.
Inventors: |
Chang; Donald C.D.;
(Thousand Oaks, CA) ; Lu; Frank; (Reseda, CA)
; Sun; Yulan; (Canoga Park, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Chang; Donald C.D. |
Thoundsand Oaks |
CA |
US |
|
|
Assignee: |
Chang; Donald C.D.
Thousand Oaks
CA
|
Family ID: |
45527215 |
Appl. No.: |
14/106844 |
Filed: |
December 15, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12847997 |
Jul 30, 2010 |
8634760 |
|
|
14106844 |
|
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|
Current U.S.
Class: |
342/361 |
Current CPC
Class: |
H01Q 21/245 20130101;
H04J 14/06 20130101; H01Q 3/24 20130101; H04L 5/005 20130101; H04W
24/02 20130101; H01Q 9/0407 20130101; H04W 72/0446 20130101; H04B
7/0617 20130101; H04B 7/1853 20130101; H04L 5/026 20130101 |
Class at
Publication: |
342/361 |
International
Class: |
H01Q 3/24 20060101
H01Q003/24 |
Claims
1-16. (canceled)
17. A method for angle realignment, comprising: obtaining a first
vertical polarization component and a first horizontal polarization
component; resolving a second vertical polarization component based
on information comprising a polarization offset angle and said
first vertical and horizontal polarization components; resolving a
second horizontal polarization component based on information
comprising said polarization offset angle and said first vertical
and horizontal polarization components; calculating a cost based on
information comprising a cross correlation between said second
vertical and horizontal polarization components; and after said
calculating said cost, calculating a cost gradient.
18. The method of claim 17, wherein said polarization offset angle
has an accuracy between +6 degrees and -6 degrees.
19. The method of claim 17 further comprising said calculating said
cost gradient in response to finding said calculated cost is
greater than a threshold cost.
20. The method of claim 17 being performed on a mobile
terminal.
21. The method of claim 17 further comprising determining said
polarization offset angle via a compass.
22. The method of claim 17, wherein said first vertical and
horizontal polarization components are converted into ones in a
digital mode.
23. The method of claim 17 further comprising said resolving said
second vertical polarization component based on information
comprising a combination of said first vertical polarization
component multiplied by cosine of said polarization offset angle
minus said first horizontal polarization component multiplied by
sine of said polarization offset angle.
24. The method of claim 17 further comprising said resolving said
second horizontal polarization component based on information
comprising a combination of said first vertical polarization
component multiplied by sine of said polarization offset angle plus
said first horizontal polarization component multiplied by cosine
of said polarization offset angle.
25. A method for angle realignment, comprising: obtaining a first
vertical polarization component and a first horizontal polarization
component; resolving a second vertical polarization component based
on information comprising a polarization offset angle and said
first vertical and horizontal polarization components; resolving a
second horizontal polarization component based on information
comprising said polarization offset angle and said first vertical
and horizontal polarization components; calculating a cost based on
information comprising a cross correlation between said second
vertical and horizontal polarization components; and after said
calculating said cost, performing an angle rotation process to
output a third vertical polarization component based on information
comprising said polarization offset angle and said first vertical
and horizontal polarization components and to output a third
horizontal polarization component based on information comprising
said polarization offset angle and said first vertical and
horizontal polarization components.
26. The method of claim 25, after said performing said angle
rotation process, further comprising performing a decoding
process.
27. The method of claim 25 further comprising said performing said
angle rotation process in response to finding said calculated cost
is less than a threshold cost.
28. The method of claim 25 being performed on a movable
terminal
29. The method of claim 25, wherein said third vertical
polarization component is associated with a combination of said
first vertical polarization component multiplied by cosine of said
polarization offset angle minus said first horizontal polarization
component multiplied by sine of said polarization offset angle.
30. The method of claim 25, wherein said third horizontal
polarization component is associated with a combination of said
first vertical polarization component multiplied by sine of said
polarization offset angle plus said first horizontal polarization
component multiplied by cosine of said polarization offset
angle.
31. A method for angle realignment, comprising: obtaining a first
vertical polarization component and a first horizontal polarization
component; resolving a second vertical polarization component based
on information comprising a first polarization offset angle and
said first vertical and horizontal polarization components;
resolving a second horizontal polarization component based on
information comprising said polarization offset angle and said
first vertical and horizontal polarization components; calculating
a first cost based on information comprising a cross correlation
between said second vertical and horizontal polarization
components; and after said calculating said first cost, calculating
a cost gradient; obtaining a second polarization offset angle based
on information comprising said cost gradient; resolving a third
vertical polarization component based on information comprising
said second polarization offset angle and said first vertical and
horizontal polarization components; resolving a third horizontal
polarization component based on information comprising said second
polarization offset angle and said first vertical and horizontal
polarization components; calculating a second cost based on
information comprising a cross correlation between said third
vertical and horizontal polarization components; and after said
calculating said cost, performing an angle rotation process to
output a fourth vertical polarization component and a fourth
horizontal polarization component based on information comprising
said second polarization offset angle and said first vertical and
horizontal polarization components.
32. The method of claim 31 further comprising said calculating said
cost gradient in response to finding said first cost is greater
than a threshold cost.
33. The method of claim 31 further comprising said performing said
angle rotation process in response to finding said second cost is
less than a threshold cost.
34. The method of claim 31 being performed on a mobile
terminal.
35. The method of claim 31, wherein said fourth vertical
polarization component is associated with a combination of said
first vertical polarization component multiplied by cosine of said
second polarization offset angle minus said first horizontal
polarization component multiplied by sine of said second
polarization offset angle.
36. The method of claim 31 further comprising said resolving said
third vertical polarization component based on information
comprising a combination of said first vertical polarization
component multiplied by cosine of said second polarization offset
angle minus said first horizontal polarization component multiplied
by sine of said second polarization offset angle.
Description
[0001] This application is a continuation of application No.
12/847,997, filed on Jul. 30, 2010, now bending.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to the field of wireless
communication systems and electronic processing and, in particular,
transmission and reception architectures between a radio frequency
(RF) receiver and transmitter. More specifically, but without
limitation thereto, the present invention pertains to a
communications system and method that allows mobile ground
terminals, or smart antennas to, dynamically realign itself to the
signal polarizations of a designated asset (primarily satellites)
utilizing a cost optimization program, reuse frequencies via
orthogonal polarization beams, and switch receiving polarizations
between circular polarizations (CP) and linear polarizations
(LP).
[0004] 2. Description of Related Art
[0005] In wireless communications, satellite to ground terminal
communication technologies are currently utilized in two different
ways. Fixed Service Satellites (FSS) utilize satellites placed in
geostationary orbit (GEO) transmitting and receiving signals from
ground terminals that are fixed in position. Direct-to-Home (DTH)
satellite dishes that serve to bring satellite-beamed television
into private homes are an example of FSS. On the other hand, Mobile
Service Satellites (MSS) rely on GEO satellites to transmit and
receive signals to and from mobile terminals, such as a Global
Positioning System (GPS) receiver in a car, boat, etc.
[0006] FSS and MSS are just two methods of wireless communications
that utilize polarization diversity, each with differing
applications and requirements. Polarization diversity has enabled
the same frequency to be reused over the same spectra, allowing one
frequency to transmit two or more distinct sets of information.
This has proved to be beneficial to both RF communications and RF
radar applications. RF transmissions are usually either circularly
polarized (CP), or linearly polarized (LP). LP signals can be
polarized either vertically (VP) or horizontally (HP).
Additionally, CP signals can either be right-hand circularly
polarized (RHCP) or left-hand circularly polarized (LHCP).
[0007] FSS systems typically employ a LP signals, as the ground
receiver (terminal) is fixed, and there is no issue with the
signals falling out of phase, interfering with each other, or
unable to be received because the ground terminal does not move in
relation to the satellite. On the other hand, due to the mobile
nature of MSS platforms (such as a truck moving both directionally
and spatially to the satellite), a CP signal offers a better option
as it offers an omnidirectional radio wave signal that can be
received and decoded regardless of the direction or spatial
displacement of the terminal. However, there are some DBS (direct
broadcast satellites) that utilize CP as well as LP signals.
[0008] Because of this, polarization alignment techniques are
important on satellite communications to reduce interference due to
misalignment of the orientations of transmission signals and
received antennas either for large earth station antennas as well
as the small aperture antennas found in VSAT (very small aperture
terminals) and Direct-to-Home (DTH) services, such as those used
for satellite-based television (e.g. DirecTV or Dish Network).
Currently, the techniques used for polarization realignment are
mechanical-based, using gimbals and tracks to physically rotate and
re-orient the ground terminal to the satellite.
[0009] While mechanically driving the satellite receiver (also
known as the ground terminal) is a practical method of re-orienting
the dish to properly receive the RF signals, the gimbals and tracks
pose a problem for mobile ground terminals. However, mobile ground
terminals are limited in two important ways. The extra machinery
necessary for mechanized terminal re-orientation adds unnecessary
weight and complexity to these mobile terminals, when their chief
aim is simplicity with low cost and weight. This is because these
mobile terminals do not have the physical space or power
requirements that the FSS systems have.
[0010] For the foregoing reasons, there is a need in satellite
communications for a system to electronically re-orient,
specifically but without limitation thereto, mobile ground terminal
receivers to match the polarizations of satellite RF signals, thus
removing the requirement of mechanically re-orienting the ground
terminals. Furthermore, there is a need to create a system that
allows mobile ground terminals to seamlessly switch between
polarizations, allowing these mobile ground terminals to receive
both circularly polarized RF signals as well as linearly polarized
RF signals.
[0011] An embodiment of the present invention involves a dynamic
improvement of how ground terminals receive RF signals from
satellites by utilizing an electronic method of decoding
transmitted RF signals from satellites, whether they are circularly
polarized or linearly polarized. The proposed architecture will
allow ground terminals, in particular mobile VSAT or DTV operators,
to use satellite assets either with LP or CP satellites for their
services. The ground terminals will dynamically realign itself via
electronics, and not physically moving the receiver, to the
polarizations of radiation from a targeted satellite.
[0012] The following references are presented for further
background information: [0013] 1. R. G. Vaughan, J. B. Anderson;
"Antenna Diversity in Mobile Communications;" IEEE Transactions on
Vehicular Technology; Nov. 1987; pp. 149-172; and [0014] 2. R. G.
Vaughan; "Polarization Diversity in Mobile Communications;" IEEE
Transactions on Vehicular Technology; Aug. 1990; pp. 177-186; and
[0015] 3. K. Aydin, T. A. Seliga; "Remote Sensing of Hail with a
Dual Linear Polarization Radar;" Journal of Climate and Applied
Meteorology; Oct. 1986; V. 25; pp. 1475-1484; and [0016] 4. S.
Fiedler, F. Fresia, E. Pagana; "Method and System for Polarization
Alignment of an Earth Station Antenna with the Polarization Axis of
a Satellite Antenna;" EU Patent No. EP1303002; Mar. 9, 2008.
SUMMARY OF THE INVENTION
[0017] The present invention provides a dynamic communication
system suitable for allowing dynamic signal polarization
realignment by ground terminals, specifically but with no
limitation thereto, mobile ground terminals, realigning the signals
to those of radiated and/or received signals by designated space
assets, specifically satellites. These satellites may be in GEO
(geostationary earth orbit), LEO (low earth orbit), and MEO (medium
earth orbit) as well as in slightly inclined orbits from GEO
orbits.
[0018] Due to the fact that satellites and mobile ground terminals
are constantly in motion, the orientation of polarizations relative
to one another between a user terminal and the targeted satellite
must be known. Thus, the following information is needed for
implementation of the polarization realignment: [0019] 1.
Information on current locations and orientations of user
terminals; and [0020] 2. Information on current orbital slots and
orientations of targeted satellites.
[0021] More specifically, the present invention provides a means of
electronically realigning polarizations of incoming and outgoing
signals for mobile ground terminals via a cost minimization
technique (or, an angle optimization process) comprising: a set of
inputs, specifically an antenna array, electronically connected to
an angle optimization process module, which in turn is connected to
an angle rotation process module. This embodiment removes the
requirement for a means of mechanically reorienting the ground
terminal antenna array for continually matching the space asset's
signal polarizations, as the processing for realignment is done
electronically.
[0022] Accordingly, several advantages of one or more aspects are
as follows: to provide a means of electronically realigning a
ground terminal to match signal polarizations (regardless of
whether they are CP or LP) to that of incoming or outgoing signals
by a designated space asset, that do not need a mechanical means of
realigning polarizations, and that can seamlessly switch between
signal polarizations thus giving ground terminals the ability to
communicate with different satellites, thus increasing the
flexibility of ground terminals.
BRIEF DESCRIPTIONS OF THE DRAWINGS
[0023] The objects, features and advantages of the present
invention will become better understood from the following detailed
descriptions of the preferred embodiment of the invention in
conjunction with reference to the following appended claims, and
accompany drawings where:
[0024] FIG. 1 shows polarization orientations for both the signals
from a targeted satellite and that of a user terminal.
[0025] FIG. 2 shows the use of dynamic polarization re-alignment
via cost minimization technique.
[0026] The 201 is a patch antenna.
[0027] The 202 is an amplifier.
[0028] The 203 is a frequency down converter.
[0029] The 204 is an A/D (analog-to-digital) converter.
[0030] The 205 is an Angle optimization process module.
[0031] The 206 is an Angle rotation process module.
[0032] The 207 is a compass.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0033] The present invention relates to the fields of communication
systems, and in particular, satellite to ground terminal
communications. More specifically, but without limitation thereto,
the present invention pertains to a communication system and method
that dynamically realigns incoming and outgoing signal
polarizations for ground terminals to those of designated space
assets, specifically satellites.
[0034] In order to determine the orientation of polarizations
relative to one another between a user terminal and a targeted
satellite, the following information is needed for implementation
of dynamic polarization realignments: [0035] 1) information on
current locations and orientations of user terminals [0036] 2)
information on current orbital slots and orientations of targeted
satellites.
[0037] The relative geometries are illustrated in FIG. 1, assuming
both polarizations from satellite and users are LPs. (x,y) are the
coordinate for satellite signals, and (x.sub.tm, y.sub.tm) are
those for user terminals. For GEO satellites, it is common to
orient the E-field of the HP to the "North" when the satellites are
in orbit. Therefore, the offset angle, .theta., can be roughly
determined via an electronic compass on a mobile user terminal. The
polarization realignment, with the knowledge of .theta., can be
achieved via the following equations:
VP=VPtm*cos .theta.-HPtm sin .theta. (1)
HP=VPtm*sin .theta.+HPtm cos .theta. (2)
[0038] The accuracy of the offset angle shall be better than
.about..+-.6.degree. to achieve a 20 dB isolation requirement
between the two LP signals.
[0039] The concept of linear polarization re-orientation to
dynamically match polarizations of incoming signals of for mobile
terminals with a set of linearly polarized output ports comprising:
[0040] a. direct calculations of weighting components based on
knowledge of orientation of the terminals to a moving platform and
bearing of the platform; [0041] b. In order to achieve better
isolation, it is possible to use optimization loop to re-align the
polarizations for the mobile terminals, as indicated in FIG. 2.
Described as below:
[0042] As indicated in FIG. 2, the antenna array 201 has two
orthogonal polarization output ports. Each signal component goes
through an amplifier 202, which boosts the strength of the signal.
The boosted signal then passes through a frequency down converter
203, then passing to an analog-to-digital (A/D) converter 204 to
convert the analog signal into a digital one. Finally, the digital
signals then go through an angle optimization process module 205.
Here, a process determines the difference of .theta. between (x,y)
and (x.sub.tm, y.sub.tm). After determining the difference of
.theta., the signals undergo a cost optimization program that
determines the cross correlation between the VP and HP. This is
compared with the initial .theta. from an electronic compass 207.
Once the new optimal angle (.theta.) is determined, information is
sent to angle rotation process module 206 to electronically
reorient antenna array 201 to receive the highest quality
signal.
[0043] In the angle optimization process module 205, first
resolving the mixed signals to VP (vertical polarization) and HP
(horizontal) polarization components according to the initial
.theta. provided by compass, then calculating the cost by cross
correlation between VP and HP, comparing the cost with a predefined
threshold cost. If the cost is greater than the threshold,
calculating the cost gradient will result in a new .theta.. The
loop continues until the cost is less than the threshold cost. The
final .theta. will be delivered to the angle rotation process
module and output better set of isolated VP and HP, at which point
the signal polarizations are matching and the ground terminal will
begin decoding the information.
* * * * *