Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/14—Relay systems
  • H04B7/15—Active relay systems
  • H04B7/185—Space-based or airborne stations; Stations for satellite systems
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64G—COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR
  • B64G1/00—Cosmonautic vehicles
  • B64G1/10—Artificial satellites; Systems of such satellites; Interplanetary vehicles
  • B64G1/1007—Communications satellites
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64G—COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR
  • B64G1/00—Cosmonautic vehicles
  • B64G1/10—Artificial satellites; Systems of such satellites; Interplanetary vehicles
  • B64G1/1085—Swarms and constellations
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64G—COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR
  • B64G1/00—Cosmonautic vehicles
  • B64G1/22—Parts of, or equipment specially adapted for fitting in or to, cosmonautic vehicles
  • B64G1/24—Guiding or controlling apparatus, e.g. for attitude control
  • B64G1/242—Orbits and trajectories
  • B64G1/2425—Geosynchronous orbits
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/14—Relay systems
  • H04B7/15—Active relay systems
  • H04B7/185—Space-based or airborne stations; Stations for satellite systems
  • H04B7/1851—Systems using a satellite or space-based relay
  • H04B7/18513—Transmission in a satellite or space-based system
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/14—Relay systems
  • H04B7/15—Active relay systems
  • H04B7/185—Space-based or airborne stations; Stations for satellite systems
  • H04B7/19—Earth-synchronous stations

Definitions

• the present disclosure relates generally to satellite systems. More particularly, the present disclosure relates to inclined orbit satellite systems.
• geosynchronous satellite is used to describe a satellite having a period of revolution approximately equal to the period of rotation of the Earth about its axis. According to Article 11 of the 2012 Radio Regulations of the International
• a geostationary satellite is a geosynchronous satellite with an orbit the inclination of which is less than or equal to 15°.
• the Radio Regulations in Appendix 5 at Table 5-1 define a zone of satellite radio interference protection within an orbital arc of +/- 7° inclination. The Radio Regulations are hereby incorporated by reference in their entirety.
• An inclined satellite system is disclosed that can efficiently provide continuous communication to multiple regions across the world using satellites in inclined orbits.
• the inclined orbit satellites of the satellite system can turn off, mute, or attenuate service when they are near the equator.
• multiple inclined satellites may be required to provide continuous uninterrupted service.
• FIG. 1 illustrates examples of inclined geosynchronous satellite patterns.
• FIG. 2 illustrates an example of a satellite's spot beam movement during its inclined orbit.
• FIG. 3 illustrates an example of a satellite's regional beam changes during its inclined orbit.
• FIG. 4 illustrates an example of an overview of an inclined orbit satellite system.
• FIG. 5A illustrates an example of a two satellite inclined orbit satellite system.
• FIG. 5B illustrates an example of a three satellite inclined orbit satellite system.
• FIG. 6 illustrates an example of a user terminal or gateway antenna system.
• FIG. 7A illustrates an example of an upper latitude feed array elemental beam pattern.
• FIG. 7B illustrates an example of a lower latitude feed array elemental beam pattern.
• FIG. 8 illustrates an example block diagram for a receiver unit.
• FIG. 9 illustrates an example block diagram for a transmit unit.
• Inclined satellite systems are described herein that may efficiently provide continuous communication to geographic regions across the world using inclined orbit satellites. There are, however, a number of system challenges to be addressed. Those system challenges, and solutions to those challenges provided in accordance with the present disclosure, are described below.
• inclined orbit satellite is used to describe a satellite which has an orbit inclination that causes it to move north and south of the equator at a fixed longitude, defining a pattern over the course of a twenty four hour orbit which, when viewed from the Earth, generally resembles a figure eight.
• An inclined satellite can be a GSO satellite or a non-GSO satellite.
• Fig. 1 illustrates an example pattern of geosynchronous satellites with 20 and 30 degree inclinations.
• the satellites and the ground stations that the satellites may communicate with may be based, for example, on the satellites and ground stations described in U.S. Patent Application No. 13/803,449, entitled "Satellite Beamforming Using Split Switches" and filed on March 14, 2013, hereby incorporated by reference in its entirety.
• Satellite antenna coverage for a specific area may vary depending upon the position of the satellite in the figure eight orbital pattern. For example, there may be a large variation in coverage when a satellite in the Northern Hemisphere is serving a geographic area in the Southern Hemisphere or vice versa.
• Fig. 2 illustrates an example of a satellite's spot beam movement during a 24-hour geosynchronous orbit.
• the figure eight in the center of Fig. 2 represents the satellite's inclined orbit relative to the equator (which is depicted as the central horizontal line in Fig. 2).
• Reference letter A designates the satellite's northernmost position in its orbital path.
• Reference letter B designates the satellite's southernmost position in its orbital path.
• the beams may be shifted north, providing a coverage area over the African continent (for example) similar to that depicted on the left hand side of Fig. 2.
• the beams may be shifted south, providing a coverage area over Africa similar to that depicted on the right hand side of Fig. 2.
• Satellite regional beam coverage for a specific area may vary depending upon the position of the satellite in the figure eight orbital pattern. For example, satellite beam coverage may be stretched when a satellite in the Northern Hemisphere is serving a geographic area in the Southern Hemisphere or vice versa.
• Fig. 3 illustrates an example of how regional beams may change as the satellite moves through its inclined orbit. As in Fig. 2, the figure eight in the center of Fig. 3 represents a satellite's inclined orbit relative to the equator. Reference letter A represents the satellite's northernmost position in its orbital path, and reference letter B represents the satellite's southernmost position. As the satellite reaches position A, countries (such as the U.S.
• the northern Hemisphere countries located in the northern hemisphere will receive the maximum signal strength from the beam, as illustrated, for example, on the right hand side of Fig. 3.
• the signal strength received by Northern Hemisphere countries will be relatively less optimal, due to the curvature of the Earth and the greater distance between the Northern Hemisphere and the satellite in position B (as shown on the left hand side of Fig. 3).
• Spot beams may move relative to gateway and user terminal locations.
• Coverage may be improved by providing the satellite with a number of beams greater than the number of service areas. Interference between user terminals located in the same or adjacent spot beam coverage areas may be reduced by providing assigned satellite information to gateway and user terminals and/or by coordinating beam and frequency plans.
• gateways may have to be able to change to a new feeder link beam and may have to be able to assign capacity (a combination of beam (transmit and/or receive) , polarization, power and frequency assignments) to satellite beams with active users; (4) a satellite may have to be able to switch capacity to the geographic area with active users; and/or (5) user terminals and Gateway Earth stations may also need to switch its earth station transmit and receive beams to another satellite.
• An inclined satellite may share the same frequencies as certain GSO satellites and may serve the same geographic area. This can be accomplished by operating a satellite outside a specified GSO Satellite Exclusion Region about the equator (+/- 7 degrees inclination). Two or more satellites may be used in order to optimize the coverage of a specific geographic area using the same frequencies. By shutting off, muting, reducing, or attenuating transmissions (e.g., radiated outputs of a satellite) when the satellite passes near the equator, sharing with certain geostationary satellites may be possible. Muting or attenuating a satellite's signal can include reducing or backing off the satellite's transmitter amplifier drive level to a sufficient degree such that radiating levels output from the satellite causes minimal interference to other systems.
• Muting or attenuating a satellite's signal can include reducing or backing off the satellite's transmitter amplifier drive level to a sufficient degree such that radiating levels output from the satellite causes minimal interference to other systems.
• a second satellite can be used to provide uninterrupted service.
• Two or more satellites can be used to cover individual longitudes. If the relative position of each satellite within its figure eight pattern is designed in accordance with the techniques described herein, then a single additional satellite may serve as a backup for multiple pairs of satellites across multiple longitudes.
• a satellite system in accordance with the present disclosure can consist of one or more satellites deployed in a constellation about a constant Equatorial Crossover Point.
• the satellite system of the present disclosure may be able to use all frequencies allowed in the GSO plane (C, Ka, Ku, X, and others). For example, assuming a 6-degree orbital spacing at the cross over point at the equator, 60 of these satellite systems may be deployed.
• C, Ka, Ku, X, and others For example, assuming a 6-degree orbital spacing at the cross over point at the equator, 60 of these satellite systems may be deployed.
• Fig. 4 One example of a satellite system is illustrated in Fig. 4. In this example, three satellites have the same longitude crossing. Two of these satellites may be active and one may be a backup satellite. The three satellites can travel the same inclined orbital path, each satellite crossing the equator at the same longitude at an Equatorial Crossover Point. The satellites can be positioned so that, at any given time, at least one satellite
• a constellation that coordinates satellites, beams, power, coverage, capacity and frequency assignments throughout the orbit period may be described as follows.
• two satellites in inclined geosynchronous orbits may provide uplink and/or downlink services to multiple geographically distributed ground terminals.
• Each of these satellites may turn off, mute or attenuate transmissions near the equator in an exclusion zone in order not to cause interference to ground users of certain geostationary satellites or satellite with higher priority.
• ground users of the satellites may also be able to shut down, mute, or attenuate service so as not to interfere with certain geostationary satellite uplink signals.
• the inclined satellites may not turn off, mute, or attenuate
• the two inclined satellites can be separated by four hours so that one satellite is over the same location within the figure 8 after four hours.
• the exclusion for both uplink from ground terminals and downlink from the satellite can be, for example, at 9° inclination. This can ensure a 2° separation between the satellite and the 7° protection zone.
• the exclusion zone may be less or more than 9° inclination depending upon the radio interference potential between the services on the inclined and certain GSO satellites. If any inclined satellite is less than 9° inclination angle, then all uplink and downlink signals to and from the inclined satellite may be shut down. In this way, there may always be one inclined satellite out of the exclusion zone at all times.
• Fig. 5B an example is described in which three satellites in inclined orbits may provide uplink and/or downlink services to multiple geographically distributed ground terminals.
• the relative position of the two inclined satellites may be positioned so that if a third inclined satellite were to be added, the third inclined satellite may be positioned so that two inclined satellites are always out of the exclusion zone.
• one of the satellites may provide backup communications or all three can be used to provide continuous coverage communications.
• the three satellites may be placed at four hour delays with respect to each other so that the third satellite is 8 hours behind the first satellite and the second satellite is four hours behind the first. Any one of these satellites may be the backup satellite.
• Additional inclined satellites at additional longitudes can also be used to provide service to the same or different geographic areas.
• the first satellite located at each longitude may be in the same inertial orbital plane.
• the second satellite in each longitude can be in a common orbital plane.
• a single launch vehicle can be used to launch a first set of one to three inclined satellites and a second launch vehicle can be used to launch a second set of inclined satellites.
• An additional satellite may be in an orbital plane that serves as backup to all of the satellites at all of the longitudes.
• the backup satellites may be delayed by:
• Delay 24*(lon B )/360 hours + 8, where lon B is the longitude of the backup satellite. This may be done to ensure that satellites at different longitudes are in the same orbital plane. In case of a satellite failure, any one of the satellites in the same orbital plane can back up any other satellite by drifting from one longitude to another longitude orbit. Keeping the satellites in the same plane can minimize the fuel required to perform this backup maneuver.
• An inclined satellite providing regional coverage can use two or more antennas.
• One or more of the satellites may be optimized for coverage from the Northern Hemisphere and one or more optimized for coverage from the Southern Hemisphere.
• a satellite may switch between antennas depending on which Hemisphere it is covering. For example, this can be accomplished by: (1) separate reflectors or feed systems for the two antennas; (2) a single satellite antenna that tracks the coverage area as it moves through its figure 8 orbit; or (3) a single satellite beam forming system that could provide optimum satellite beam coverages from each Hemisphere.
• An inclined satellite system which does not provide service to geographic areas when the satellite is located near the equator, may eliminate interference to and from its associated earth stations with directional antennas from and into certain GSO satellites.
• An inclined satellite providing spot beam coverage may form excess beams to take into account the inclined satellite movement through its twenty four hour
• geosynchronous orbit For example, this can be accomplished by: (1) adding extra satellite antenna feeds that take into account the north and south satellite variation in the orbit; or (2) a satellite beam forming system with sufficient feeds that provide coverage taking into account the inclined satellite orbital variation.
• An inclined satellite may flexibly switch capacity between feed elements or separate antennas. For example, this can be accomplished by: (1) a frequency
• channelizing system (2) a switch matrix on the satellite; or (3) Earth stations with directional antennas that can switch capacity within beams of one satellite and between inclined satellites.
• the inclined system may operate autonomously, or with use of a global resource management system (GRM) that operates at the Network Operations Center and generates user terminal and gateway connectivity maps and user and gateway frequency beam and polarization assignments for each satellite.
• GRM global resource management system
• the GRM may be connected to each gateway over a low data rate link (terrestrial or satellite).
• the gateways may notify users of specific satellite beam and polarization assignments, frequency assignments, and handoffs to new gateways or satellites over the satellite link.
• the gateways may notify each of the users, over the satellite link, of handoffs to new satellites and beams, new frequency, and polarization assignments and assignments to new gateways. Since orbits are repeating every twenty-four hours, the GRM may generate repeating schedules for each inclined satellite for both users and gateways that can remain fixed as long as service requirements remain fixed.
• the gateway, satellite, and user terminals may receive a schedule from the GRM, which may describe the time dependent frequency assignments, beam and polarization assignments, and earth station and satellite beam pointing directions.
• the gateway, user terminals, and satellites may follow this schedule in order to provide continuous service across multiple inclined satellites and orbit locations within the same twenty-four hour figure 8 orbit with the same Equatorial Crossing Point.
• a user terminal or gateway antenna system may dynamically cover various regions as the inclined satellite moves through its orbit. Additionally or alternatively, a user terminal or gateway antenna may simultaneously receive and/or transmit signals to/from multiple satellites as it follows the inclined satellites throughout their orbit.
• An example of a user terminal or gateway antenna system is illustrated in Fig. 6.
• the user terminal or gateway antenna system may include a reflector, an array of feed elements for an upper latitude satellite, an array of feed elements for a lower latitude satellite, a transmitter unit and/or a receive unit, and a control unit.
• the transmit unit may transmit the signals to an inclined satellite
• the receiver unit may receive the signals from an inclined satellite
• the control unit may configure these units so that the user terminal or gateway antennas track the inclined satellite(s).
• the user terminal or gateway feed arrays may be designed to cover the orbit of the active inclined satellite as seen from the Earth.
• Fig. 7A illustrates an example of the elemental beams generated from the feed array for the user terminal or gateway communicating with inclined satellites in the upper latitudes.
• Fig. 7B illustrates an example of elemental beams generated from the feed array for the user terminal or gateway communicating with inclined satellites located in the lower latitudes.
• These elemental beam patterns may be designed to cover the inclined satellites during the active inclined transmission periods as the inclined satellites travel over their orbit.
• the user terminal or gateway feed arrays may also be designed to receive and/or transmit signals.
• Each of these user terminal or gateway feeds may be connected to a receiver unit and a transmitter unit, respectively.
• the transmitter unit and/or receiver unit may employ two of these feed elements at any one time. Additionally or alternatively, more than two feed elements may be employed as well.
• the two feed elements may be selected such that their feed elemental beam patterns overlap the inclined satellite.
• Complex weights may be applied to transmit and/or receive feed elements, respectively, and the resulting signals received or transmitted from each feed element may be added to create a virtual receiver or transmit beam, respectively, that has its peak gain focused at the inclined satellite.
• Fig. 8 illustrates an example block diagram for a user terminal or gateway receiver unit in accordance with the present disclosure.
• the upper and lower latitude feed element arrays may be first amplified and then switched. Only one pair of adjacent element paths may be output from the switch.
• Complex weights may control amplitudes and phases of the received signals and may be applied to each of these element paths.
• the complex weights may be configurable so an intelligent controller can point the virtual beam at the satellite.
• the signals may then be added to form a beam focused at the inclined satellite.
• the received signals in each feed element array can be amplified and phase shifted according to a specific algorithm to provide a virtual beam with maximum gain focused at the inclined satellite.
• the receiver may then detect and process the received signals. More than one inclined satellite may be simultaneously served by using different feed elements through the switch matrix and a separate receiver in the user terminal or gateway. Such an operational mode is depicted with the dotted line box labeled optional in Fig. 8.
• Fig. 9 illustrates an example block diagram for a transmit unit for a user terminal or gateway in accordance with the present disclosure.
• a signal from the transmitter may be split along two paths.
• Configurable complex amplitude attenuation and phase shifting may be applied to each respective signal path before each signal path is amplified.
• the two paths may then be applied via a switch matrix to two adjacent transmit feed elements.
• the energy transmitted from these two feed elements can be combined in space to form a virtual beam that has its peak gain focused on the inclined satellite.
• More than one inclined satellite may be simultaneously served by using different feed elements through the switch matrix, a separate set of amplitude attenuators, phase shifters, and transmitters.
• Such an operational mode is depicted with the dotted line box labeled optional in Fig. 9.
• a control unit may provide the intelligence for the user terminal or gateway system.
• the control unit may follow a schedule that repeats over a twenty four hour orbit period.
• the control unit can calculate, using a specific algorithm, which transmit and receive elements are active at any given time to communicate with the inclined satellite(s).
• the control unit may also change the transmit and receive amplitude attenuators and phase shifters continually in order to maintain maximum gain and focus of the virtual beam at the inclined satellite as it moves throughout its orbit.

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• Aviation & Aerospace Engineering (AREA)
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• 2014
  • 2014-07-16 RU RU2016127529A patent/RU2660958C2/ru not_active IP Right Cessation
  • 2014-07-16 EP EP14869420.1A patent/EP3080930A4/de not_active Withdrawn
  • 2014-07-16 WO PCT/US2014/046855 patent/WO2015088588A1/en active Application Filing

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