Source: https://patents.justia.com/patent/9585150
Timestamp: 2020-02-24 11:49:44
Document Index: 320407462

Matched Legal Cases: ['Application No. 62', 'arth 630', 'arth 630', 'arth 630', 'arth 630', 'arth 630', 'arth 630', 'arth 630', 'arth 630', 'arth 630', 'arth 630', 'arth 630', 'arth 630', 'arth 630']

US Patent for EPFD coverage for NGSO satellites Patent (Patent # 9,585,150 issued February 28, 2017) - Justia Patents Search
Justia Patents Spacecraft Formation, Orbit, Or Interplanetary PathUS Patent for EPFD coverage for NGSO satellites Patent (Patent # 9,585,150)
This application claims priority under 35 USC 119(e) to co-pending and commonly owned U.S. Provisional Patent Application No. 62/136,075 entitled “IMPROVING EPFD COVERAGE FOR NGSO SATELLITES” filed on Mar. 20, 2015, the entirety of which is incorporated by reference herein.
More specifically, for the example of FIG. 7A, considering the second NGSO satellite 300B, the second NGSO satellite 300B may determine, for each point within the coverage areas of its beams on the Earth's surface (as an example, the coverage area 613B of the beam 612B), an angle between a first line extending from the point on Earth to the second NGSO satellite 300B and each of a plurality of second lines extending from the point on Earth to positions along the GSO arc 640 (e.g., the positions along the GSO arc 640 corresponding to possible locations of GSO satellites). For simplicity, the first and second lines are not shown in FIG. 7A. The determined angles may be referred to herein as the “arc angles (a).” Then, for the point on Earth, a minimum of the arc angles may be determined. This process may be repeated for all points within the coverage areas of the beams of second NGSO satellite 300B. Then, if the minimum arc angles are less than a threshold angle (e.g., 2°) for any point on Earth 630 within the beam coverage areas, the second NGSO satellite 300B may disable its interfering beams to avoid potential interference with GSO satellite communications.
The determined arc angles may correspond to an exclusion zone defined in accordance with the ITU's guidelines on EPFD limits for NGSO satellites. For example, FIG. 7B shows a diagram 701 depicting an example exclusion zone 710 that may be defined, in accordance with the ITU's guidelines on EPFD limits, for the example GSO ground station 625. From the field of view of the second NGSO satellite 300B, three iso-a lines 711 and 712A-712B may be “drawn” on the surface of Earth 630. Each of the iso-a lines 711 and 712A-712B may represent points on the surface of Earth 630 that share the same value of the arc angle α. More specifically, a first iso-a line 711 may represent points on the surface of Earth 630 for which α=0. The first iso-a line 711 may be defined by a plurality of sight lines 715 extending from points on the GSO arc 640 through NGSO satellite 300B to points on Earth 630. The points on Earth corresponding to sight lines 715 may then be used to define the first iso-a line 711 (e.g., for which the value of α=0). A second iso-α line 712A may represent points on the surface of Earth 630 for which α=+α0, and a third iso-a line 712B may represent points on the surface of Earth 630 for which α=−α0. The value of α0, which may be the threshold angle described above with respect to FIG. 7A, may correspond to a specified EPFD limit. In some aspects, the specified EPFD limit may be approximately −160 dB (W/Hz). The exclusion zone 710 may then be defined as the surface area on Earth 630 lying between the “boundary” iso-α lines 712A-712B. Accordingly, points on Earth 630 that lie within the exclusion zone 710 may experience an EPFD value equal to or greater than the specified EPFD limit (e.g., equal to or greater than −160 dB).
Per the ITU's guidelines on EPFD limits for NGSO satellites, the second NGSO satellite 300B is to disable any of its beams when one or more points on Earth see the second NGSO satellite 300B within the threshold angle α0 of the GSO arc 640 (e.g., for points lying within the exclusion zone 710). In other words, according to at least one conventional interference mitigation technique to comply with the ITU's EPFD limits on NGSO satellite transmissions, if the −160 dB PFD contour of a beam transmitted from second NGSO satellite 300B overlaps the exclusion zone 710, then the second NGSO satellite 300B is to turn off the beam. As used herein, a beam's PFD contour may indicate a portion of the beam's coverage area on Earth for which the beam's PFD is greater than or equal to a specified EPFD limit Thus, for example, a beam's −160 dB PFD contour may refer to the coverage area on Earth for which the beam's PFD is greater than or equal to −160 dB.
The controller 850 includes at least a processor 851 and a memory 852. The memory 852 may include a non-transitory computer-readable storage medium (e.g., one or more nonvolatile memory elements, such as EPROM, EEPROM, Flash memory, a hard drive, and so on) that may store the following software modules (SW):
a beam location determination software module 852A to facilitate the determination of the current position of satellite 300, for example, as described for one or more operations of FIG. 11;
a GSO arc locating software module 852B to facilitate the determination of the location of the GSO arc relative to the determined current position of satellite 300, for example, as described for one or more operations of FIG. 11;
a beam enabling and configuration software module 852C to facilitate the enabling or disabling of one or more beams of satellite 300 and/or to adjust a number of parameters (e.g., antenna configurations, beam steering, antenna gain, and/or transmit power levels) of one or more beams of satellite 300, for example, as described for one or more operations of FIG. 11;
a region contour determination software module 852D to facilitate the determination of a PFD contour associated with boundaries between the first region and the second region of the beam coverage area of at least one of satellite 300's beams, for example, as described for one or more operations of FIG. 11; and
an arc angle measurement software module 852E to facilitate the determination of arc angles between the GSO arc and satellite 300 from points within the first region of the beam coverage area, for example, as described for one or more operations of FIG. 11.
Each software module includes instructions that, when executed by processor 851, cause controller 850 to perform the corresponding functions. The non-transitory computer-readable medium of memory 852 thus includes instructions for performing all or a portion of the operations of FIG. 11.
FIG. 9A shows a diagram 900 depicting an example definition of a first region and a second region within a beam coverage area using a cone projected onto the surface of the Earth. As shown in FIG. 9A, NGSO satellite 300 orbits the Earth 630 at a distance or altitude 903. A beam 910 transmitted from satellite 300 may have a coverage area 912 on the Earth's surface. In accordance with example implementations, a cone 920 may be “projected” onto the surface of the Earth 630. It is noted that the cone 920 may not actually be transmitted to or projected onto Earth 630 (e.g., in a physical manner), but rather may represent a simulation of antenna gains of the beam 910 (e.g., as a function of distance from a center of the beam's coverage area on Earth). The surface area on Earth 630 covered by the projected cone 920 may be denoted as a PFD contour 922. The cone 920 may be “sized” such that antenna gains within the PFD contour 922 are within a predetermined decibel limit of the peak antenna gain of beam 910. In some aspects, the first region of beam coverage area 912 may be defined as the PFD contour 922, for example, as depicted in FIG. 9A. The second region of coverage area 912 may be defined as including portions of beam coverage area 912 that lie outside (e.g., not within) the PFD contour 922. For purposes of discussion herein, the second region may be denoted as a PFD boundary zone 914, for example, as depicted in FIG. 9A.
For other implementations, the PFD contour 922 may correspond to a region containing all points (on the Earth's surface) that have a PFD value greater than a threshold PFD. The PFD function for the NGSO satellite's beam 910 may be determined based on factors including (but not limited to) the beam's antenna gain pattern and the expected path loss. For some aspects, the threshold PFD may be associated with the EPFD limits established by the ITU for the frequency band used by the NGSO satellite beam. For other aspects, the threshold PFD may be set to a value of approximately −160 dB/m2.
More specifically, the NGSO satellite beam 910 may have an associated antenna gain function G(θ), which depends on the angle θ of divergence from the center of the beam pattern. The NGSO satellite beam 910 may also have a transmission power P, and a transmission frequency f. At a point on the ground a distance d from the NGSO satellite, an example PFD including free space path loss may be determined using the following equation (1), where the value of P may be the beam's transmission power normalized to a reference bandwidth:
P ⁢ ⁢ F ⁢ ⁢ D = 10 ⁢ ⁢ log 10 ⁡ ( 10 P 10 * G ⁡ ( θ ) 4 ⁢ ⁢ π ⁢ ⁢ d 2 ) ( 1 )
Thus, the first region of the beam coverage area 912 may be defined as the region for which all points located therein have a PFD value that exceeds a PFD threshold, and the second region of the beam coverage area 912 may be defined as the region for which all points located therein have a PFD value that does not exceed the PFD threshold. When determined using a PFD function such as equation (1), the second region of the beam coverage area 912 may be removed from consideration for possible interference (e.g., with GSO satellite communications), for example, because a PFD value below the threshold PFD may indicate that the power of the satellite beam's signals that are received at points within the second region of the beam coverage area 912 is sufficiently low to make interference with GSO satellite communications unlikely. In contrast, a PFD value greater than the threshold PFD may indicate that the power of the satellite beam's signals that are received at points within the first region of the beam coverage area 912 is sufficiently large that interference with GSO satellite communications may be possible, thereby warranting consideration for possible beam disabling.
FIG. 10A shows a diagram 1000 depicting an example position and/or orientation of NGSO satellite 300 that may not result in NGSO satellite 300 disabling beam 910. As shown in FIG. 10A, NGSO satellite 300 transmits a beam 910 having an associated beam coverage area 912 on the Earth's surface (Earth's surface not shown in FIG. 10A for simplicity). The controller 850 may define (e.g., using a cone projection, discussed above with respect to FIG. 9A) a PFD contour 922 within beam coverage area 912 for which all points located therein have a PFD value that exceeds the threshold PFD, as discussed above. For each point within the PFD contour 922 of beam coverage area 912, the controller 850 may determine the minimum arc angle (α) between the GSO arc 640 and the NGSO satellite 300. For the example of FIG. 10A, an example point is located at the origin of the x-axis, y-axis, and z-axis, and an example arc angle (α) is depicted as the angle between a first line 1001 extending from the example point to an example position 1004 along the GSO arc 640 and a second line 1002 extending from the point to the NGSO satellite 300. Although not shown for simplicity, the arc angles between the example point and a plurality of positions along the GSO arc 640 are determined, and the arc angle having the minimum value is determined. The minimum arc angle is then compared with the threshold angle (e.g., to determine whether the PFD value at the example point exceeds the EPFD limits) For the simplified example of FIG. 10A, the depicted minimum arc angle (α) for the example point is greater than the threshold angle, and consequently the beam 910 transmitted from NGSO satellite 300 may not be disabled.
FIG. 10B shows a diagram 1050 depicting another example position and/or orientation of NGSO satellite 300 that may result in NGSO satellite 300 disabling beam 910. As shown in FIG. 10B, NGSO satellite 300 transmits beam 910 having an associated beam coverage area 912 on the Earth's surface (Earth's surface not shown in FIG. 10B for simplicity). The controller 850 may define (e.g., using a cone projection, discussed above with respect to FIG. 8) the PFD contour 922 within which all points have a PFD value that exceeds the threshold PFD, as discussed above. For the example of FIG. 10B, an example point is located at the origin of the x-axis, y-axis, and z-axis, and an example arc angle (a) is depicted as the angle between a first line 1001 extending from the point to an example position 1054 along the GSO arc 640 and a second line 1002 extending from the example point to the NGSO satellite 300. Although not shown for simplicity, the arc angles between the example point and a plurality of positions along the GSO arc 640 are determined, and the arc angle having the minimum value is determined. The minimum arc angle is then compared with the threshold angle (e.g., to determine whether the PFD value at the example point exceeds the EPFD limits). For the simplified example of FIG. 10B, the depicted minimum arc angle (α) is less than the threshold angle, and thus NGSO satellite 300 may consider disabling its beam 910 (e.g., to meet the EPFD limits and/or to avoid interference with GSO satellite communications).
for a selected one of the plurality of points within the first region, comparing the determined minimum arc angle for the selected point with a threshold angle; and selectively disabling the first beam based at least in part on the comparing.
4. The method of claim 3, wherein the selectively disabling comprises:
disabling the first beam based on the determined minimum arc angle being less than the threshold angle; and selecting another point of the plurality of points based on the determined minimum arc angle being not less than the threshold angle.
5. The method of claim 3, wherein the selectively disabling comprises:
enabling the first beam based on the determined minimum arc angle being greater than or equal to the threshold angle for each of the plurality of points within the first region.
reducing a power level of the first beam based on the determined minimum arc angle being less than a threshold angle.
modifying a shape or size of the first beam based on the determined minimum arc angle being less than a threshold angle.
redirecting the first beam to another coverage area on Earth based on the determined minimum arc angle being less than a threshold angle, the minimum arc angles associated with the other coverage area being greater than or equal to the threshold angle.
based on the determined minimum arc angle being less than a threshold angle, disabling the first beam; and directing a second beam, transmitted from a second satellite in the NGSO satellite constellation, to one or more portions of the coverage area associated with the first beam.
for a selected one of the plurality of points within the first region, means for comparing the determined minimum arc angle for the selected point with a threshold angle; and means for selectively disabling the first beam based at least in part on the comparing.
13. The apparatus of claim 12, wherein the means for selectively disabling is to:
disable the first beam based on the determined minimum arc angle being less than the threshold angle; and
select another point of the plurality of points based on the determined minimum arc angle being not less than the threshold angle.
means for redirecting the first beam to another coverage area on Earth based on the determined minimum arc angle being less than a threshold angle, the minimum arc angles associated with the other coverage area being greater than or equal to the threshold angle.
based on the determined minimum arc angle being less than a threshold angle, means for disabling the first beam; and means for directing a second beam, transmitted from a second satellite in the NGSO satellite constellation, to one or more portions of the coverage area associated with the first beam.
19. The apparatus of claim 17, wherein execution of the instructions causes the apparatus to further:
for a selected one of the plurality of points within the first region,
compare the determined minimum arc angle for the selected point with a threshold angle; and
selectively disable the first beam based at least in part on the comparing.
20. The apparatus of claim 19, wherein execution of the instructions to selectively disable the first beam causes the apparatus to:
21. The apparatus of claim 19, wherein execution of the instructions to selectively disable the first beam causes the apparatus to:
enable the first beam based on the determined minimum arc angle being greater than or equal to the threshold angle for each of the plurality of points within the first region.
22. The apparatus of claim 17, wherein execution of the instructions causes the apparatus to further:
redirect the first beam to another coverage area on Earth based on the determined minimum arc angle being less than a threshold angle, the minimum arc angles associated with the other coverage area being greater than or equal to the threshold angle.
23. The apparatus of claim 17, wherein execution of the instructions causes the apparatus to further:
based on the determined minimum arc angle being less than a threshold angle, disable the first beam; and direct a second beam, transmitted from a second satellite in the NGSO satellite constellation, to one or more portions of the coverage area associated with the first beam.
26. The non-transitory computer-readable medium of claim 24, wherein execution of the instructions causes the apparatus to perform operations further comprising:
comparing the determined minimum arc angle for the selected point with a threshold angle; and
selectively disabling the first beam based at least in part on the comparing.
27. The non-transitory computer-readable medium of claim 26, wherein execution of the instructions for selectively disabling the first beam causes the apparatus to perform operations further comprising:
disabling the first beam based on the determined minimum arc angle being less than the threshold angle; and
selecting another point of the plurality of points based on the determined minimum arc angle being not less than the threshold angle.
28. The non-transitory computer-readable medium of claim 24, wherein execution of the instructions causes the apparatus to perform operations further comprising:
29. The non-transitory computer-readable medium of claim 24, wherein execution of the instructions causes the apparatus to perform operations further comprising:
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Patent Publication Number: 20160278064
Inventors: Gene Wesley Marsh (Encinitas, CA), Qiang Wu (San Diego, CA), Peter John Black (San Diego, CA), Dan Vassilovski (Del Mar, CA), Mehmet Izzet Gurelli (San Diego, CA)
Application Number: 14/864,791
International Classification: H04H 20/71 (20080101); H04W 72/04 (20090101); H04W 52/24 (20090101); H04B 7/185 (20060101); H04B 7/204 (20060101);