CA2255220C - Efficient high latitude service area satellite mobile broadcasting systems - Google Patents
Efficient high latitude service area satellite mobile broadcasting systems Download PDFInfo
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- CA2255220C CA2255220C CA2255220A CA2255220A CA2255220C CA 2255220 C CA2255220 C CA 2255220C CA 2255220 A CA2255220 A CA 2255220A CA 2255220 A CA2255220 A CA 2255220A CA 2255220 C CA2255220 C CA 2255220C
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04H—BROADCAST COMMUNICATION
- H04H40/00—Arrangements specially adapted for receiving broadcast information
- H04H40/18—Arrangements characterised by circuits or components specially adapted for receiving
- H04H40/27—Arrangements characterised by circuits or components specially adapted for receiving specially adapted for broadcast systems covered by groups H04H20/53 - H04H20/95
- H04H40/90—Arrangements characterised by circuits or components specially adapted for receiving specially adapted for broadcast systems covered by groups H04H20/53 - H04H20/95 specially adapted for satellite broadcast receiving
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- 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
- H04B7/195—Non-synchronous stations
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- 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
- H04B7/18523—Satellite systems for providing broadcast service to terrestrial stations, i.e. broadcast satellite service
Abstract
Satellite audio broadcasting systems include orbital constellations for providing high elevation angle coverage of audio broadcast signals from the constellation's satellites to fixed and mobile receivers within service areas located at geographical latitudes well removed from the equator.
Description
EFFICIENT HIGH LATITUDE SERVICE AREA SATELLITE
MOBILE BROADCASTING SYSTEMS
BACKGROUND OF THE INVENTION
Satellite broadcasting systems to mobile receivers have been proposed for radio ("Satellite DAB," International Journal of Communications; Robert D.
Briskman; Vol. 13, February 1995, pp. 259-266) and other broadcast services, such as television or data from satellites at 35,786 km altitude located at or near the equatorial plane. These satellites well serve geographical regions at low and mid-latitudes but, as the latitude becomes higher, the elevation angles to the satellites decrease as shown in Figure 1. High elevation angles are most desirable in satellite broadcast systems using mobile receivers to reduce service outages from physical blockage, multipath fading and foliage attenuation. Recognition of this has led to satellite systems using 12-hour inclined elliptical orbits such as the Molniya communications satellites and the proposed Archimedes radio broadcast system.
These systems are not efficient since many satellites are required for continuous coverage of practical service areas and the satellites' electronics and solar power subsystems are degraded by the four times daily passage through the Van Allen radiation belts surrounding the earth. The systems and methods of this invention surmount these problems.
C:\DM\CDRADIO\APPS\9347.OO1.wpd 1 SUMMARY OF THE INVENTION
The systems and methods of this invention use satellites in 24 sidereal hour orbits (geosynchronous) with inclinations, orbital planes, right ascensions and eccentricities chosen to optimize coverage of a particular service area, region or country located at high latitudes. In contrast to the elevation angles of Figure 1, a satellite constellation of two, three or more satellites can provide during all or most of every day 50 - 60 elevation angles throughout a large service area located at high latitudes. The satellites' orbits can also be configured to avoid most of the radiation from the Van Allen belts.
Satellite systems of this invention, in preferred embodiments, serve geographical latitude service areas located at greater than approximately 30 N or 30 S by providing high elevation angles to mobile receivers in such areas for reception of broadcasting transmissions over all or most of the day. The preferred systems use geosynchronous satellites (i.e., having a 24 sidereal hour orbital period 86, 164 seconds) in a constellation. The design-of the constellation is configured to optimize the elevation angle coverage of a particular geographical high latitude service area for achieving minimum physical blockage, low tree foliage attenuation and small probabilities of multipath fading. For instance, Figure 13 shows an improvement in foliage attenuation at a 1.5 GHz transmission frequency of many decibels for high service reliabilities when the reception elevation angel is doubled.
Similar improvements occur for other microwave frequencies and for other service reliabilities.
The configuration design optimization is achieved by selection of the orbital parameters of the constellation's satellites and the number of satellites in the constellation. Satellite audio broadcasting systems to mobile receivers generally = CA 02255220 1998-12-21 provide multichannel radio service and the satellite transmissions are nominally between 1 - 4 GHz.
Inclination. The inclination of the satellites is generally chosen between about 40 and about 80 so they cover the desired high latitude service areas during their transit overhead.
EccentriciLy. The eccentricity is chosen to have a high apogee over the service area so the satellites spend the maximum amount of time overhead. Practically, the eccentricity is limited by the increased distance that the higher is from the service area since this extra distance must be overcome either by higher satellite transmission power, a more directive satellite antenna during this portion of the orbit or combinations thereof. The eccentricity range in preferred embodiments is from about 0.15 to about 0.30. Eccentricities between about 0.15 and about 0.28 are highly preferred since they avoid most of the Van Allen belts.
Planes/Number of Satellites. The number of orbital planes equals the number of satellites, and their spacing at the equator is equal to 360 divided by the number of satellites. Preferred embodiments have satellite constellations between 2 and 4 satellites. To illustrate, for a 3-satellite constellation, the satellites would be in orbital planes separated by approximately 120 .
Argument of Perigee. For service to latitude areas above 30 N, the argument of perigee is in the vicinity of 270 so that the apogee is in the northern hemisphere and the perigee is in the southern hemisphere.
For service to latitude areas below 30 S, the argument of perigee is in the vicinity of 90 so that the apogee is in the southern hemisphere and C:\DM\CDRADIO\APPS\9347.OO1.wpd 3 n the perigee is in the northern hemisphere.
Longitude of the Ascending Node. The orbit planes are chosen with a longitude of the ascending node such that the satellites have a good view (i.e., are at high elevation angles as viewed by mobile receivers) of the complete service area. Generally, this is accomplished by choosing the right ascension of the ascending node and the mean anomaly such that the center of the ground trace bisects the service area.
Ground Trace. In the preferred embodiment, the satellites follow the same ground trace and pass over a given point on the earth at approximately equal time intervals. The orbit of each satellite occupies its own orbital plane. For satellites in neighboring planes in a constellation of n satellites, the difference in right ascensions of the ascending nodes is 3600/n, the difference in mean anomalies is 3600/n and the average time phasing between the satellites on the trace is 24 sidereal hours/n.
Orbit Control. Satellite constellations of this invention experience change in the aforementioned orbital parameters over time due to the earth's oblateness, gravity forces of the sun, moon and solar radiation pressure. These can be compensated by the satellites' on-board propulsion system. The amount of such propulsion can be minimized by analyzing the perturbations of each individual orbit parameter over the lifetimes of the satellites caused by the previously mentioned effects and choosing the initial conditions of the orbits so the minimum on-orbit changes are required. This choice is generally assisted by the fact that some perturbation sources partially cancel out others.
C:\DM\CDRADIO\APPS\9347.OO1.wpd 4 Satellite Spatial and Time Diversity. Figure 3 shows the elevation angle coverage from Seattle, WA to a three-satellite constellation optimized by the methods described herein for broadcast service to the United States of America. Two satellites are visible at all times. The techniques for satellite spatial and time diversity described in U.S. Patents #5319672 dated 6/7/94; #5278863 dated 1/11/94 and #5592471 dated 1/7/97 are fully applicable. US 5,592,471, for example, discloses some of the following features listed in this paragraph which form part of the common general knowledge in the art. In some implementations, a time delay can be provided between signals where the time delay is of sufficient length to reduce outages in substantial parts of the service area. As an example, in some implementations, the delay can be at least substantially 0.5 seconds. In some implementations, the delay is in the range of approximately one second to approximately five minutes. In addition, a first radio broadcast signal can be stored in each of the mobile receivers for a time period that is substantially the same as the time delay.
In some implementations, the output of a mobile receiver can be generated by combining signals or by selecting for output, in correct time order, portions of a first radio broadcast signal and a second radio broadcast signal. In some implementations the output is provided as a time-ordered stream. In addition, in some implementations, the broadcasts can be at substantially the same frequency. However, in other implementations the broadcasts can be at substantially different frequencies. In some implementations, the signals can be broadcast at different polarizations but at substantially the same frequency. In some implementations, the two separate satellite sources comprise at least two separate satellites. In some implementations, the two signals are broadcasted from a common terrestrial transmission source. In some implementations, the mobile receivers select the stronger of the signals. In some implementations, a buffer shift register can be used to store at least one of the signals. In some implementations, a buffer storage and a delay synchronizer connected to the buffer storage can he used to store at least one of the signals. In some implementations, the signals can be analog or digital, have any desired modulation, are the same or differ in frequency, and include the timing information for storage derived from the signals.
The satellite transmission power margin saved by using the invention for mitigation of multipath fading and for reduction of tree and foliage attenuation can be used to advantage. One use is by employing a smaller, less costly satellite. A second use is by transmitting more program channels.
BRIEF DESCRIPTION OF THE DRAWINGS
The systems and methods of this invention can better be understood by reference to the drawings, in which:
Figure 1 shows the elevation angles at mobile receivers in the 48 contiguous United States for the optimum location of a geostationary satellite (which is appropriately 101 W.
Longitude on the equator). Most of the northern United States has elevation angles in the 30 - 35 range which could be lower in practice due to mobile platform tilt.
Canada, Japan and most of Europe are at lower elevation angles from optimally located geostationary satellites due to their higher latitudes.
Figure 2 shows the elevation angles for a constellation of three satellites with orbits optimized for the 48 contiguous United States using the methods and 5a C) techniques of the invention for Bangor, Maine; Figure 3 for Seattle, Washington;
Figure 4 for San Diego, California; Figure 5 for Orlando, Florida; and Figure 6 for Kansas City, Missouri. The constellation provides one satellite at all times above 600 elevation angle throughout the northern United States and a second one at most times above 30 elevation angle.
Figure 7 depicts the ground trace of the satellites. With single satellite which provides no mitigation of multipath fading, a constellation of two satellites is feasible as shown in Figure 8 for New York City. Conversely, a four satellite constellation would provide multiple satellite coverage at higher elevation angles than Figure 2 -6.
Figure 9 shows the ground trace for a three satellite constellation serving Europe with Figure 10 - 12 showing the high elevation angles achieved in various cities.
Figure 13 shows the fade margin required to overcome roadside shadowing from trees and leaves measured at L-band frequencies (1-2 GHz) in the 48 contiguous United States as a function of service unavailability and elevation angle. In cases where modest availability (e.g., 90% or 10% unavailability) is required any where moderate improvement in elevation angle coverage is implemented, the fade margin improvement will be several decibels. In cases where high availability (e.g., 99% or 1% unavailability) is required and where large improvement in elevation angle coverage is implemented, the fade margin improvement will be in the 12-14 dB
range (i.e., 20 times). Reductions in required fade margins can be used by the satellite system designer to employ smaller, less expensive satellites or more audio program channels or combinations thereof.
Figure 14 is a simplified graph which shows the improvement the invention provides in reducing service outages from physical blockages (e.g., buildings, hills, C:\DM\CDRADIO\APPS\9347.OO1.wpd 6 etc.) of the satellite signal from the mobile receiver. The graph shows the worst case distance a car must be away from a building of a certain height to always avoid an outage from blockage as a function of elevation angle to a single satellite.
The amount of blockage avoidance varies significantly for an assumed building height with satellite elevation angle improvement. Depending on the improvement in satellite elevation angle coverage, the distance of a mobile receiver from the building can typically be as close as several feet to as far as many yards away and not be affected by blockage.
Figure 15 shows what would happen to the orbit of one of the constellation's satellites, whose ground trace is shown in Figure 7, if the orbital parameters are not chosen to minimize the orbital perturbations and if no satellite propulsion is used over a fifteen year period to correct the remaining perturbations. The perturbations, caused by gravitational effects of the sun, moon and earth oblateness, and by solar radiation pressure, are a function of the orbits and their epochs (i.e., the actual time of orbit insertion).
DESCRIPTION OF PREFERRED EMBODIMENTS
The systems and methods of the invention are best described by enumerating the steps employed in the design of an audio satellite broadcast system to mobile receivers for providing service throughout a service area geographically well removed from the equator. The mobile receivers have antennas configured to view the sky where satellites would be visible. The invention is also applicable to fixed location receiver radio broadcast systems. In fact, when a mobile receiver stops, it is essentially a fixed receiver. The fixed location receiver case is less technically simpler, since there is little multipath fading and the blockage encountered is static with time.
C:\DM\CDRADIO\APPS\9347.OO1.wpd 7 1) The important analysis input parameters are the definition of the geographical service area and the quality of service to be provided. The quality of service is defined as the percent of time service will be unavailable due to outage from physical blockage, multipath and tree/foliage attenuation. The desired satellite elevation angles for minimizing outage from single path physical blockage can be derived from calculations similar to those graphically shown in Figure 14.
Similarly, the desired satellite elevation angles for minimizing outage from tree/foliage attenuation can be derived from transmission measurements in the projected service area at the system's operating radio frequency, such as shown in Figure 13 for the United States at L-band frequencies, and knowledge of the satellites' transmission signal margin at the mobile receiver. Multipath and total blockage (i.e., all path blockage such as occurs when a mobile receiver passes under a large underpass) are dealt with by use of satellite spatial and time diversity. Diversity is analyzed as a requirement of the number of satellites simultaneously viewable by the mobile receivers and of the satellites' elevation angles.
The results of the aforementioned analyses are then used in the design of the satellite constellation which is a function of the orbital parameters and number of satellites in the constellation. Using known computer analysis programs, an optimization is performed of the elevation angles for the mobile receivers throughout the service area to the constellation's satellites throughout a day (i.e., since the satellites are geosynchronous, the elevation angles will repeat every day if perturbations are ignored). The optimization specifically varies inclination and eccentricity for given right ascensions to maximize the time the satellites remain over the service area (i.e., at high elevation angles). Also, the choice of the apogee and perigee of the orbit considers the avoidance of passage through the Van Allen belts so radiation damage to the satellites is minimized and avoids too high apogees C:\DM\CDRADIO\APPS\9347.OO1.wpd 8 so excess space loss or antenna beam forming is minimized as discussed subsequently.
Continuous coverage of a reasonably sized service area well removed from the equator cannot be achieved with a single satellite so analysis is generally performed on constellations with 2, 3 and 4 satellites. The analyses are performed using known computer programs. The amount of elevation angle coverage improvement diminishes for constellations with more than three satellites. Constellations with more than 4 satellites are technically feasible and only marginally improve both elevation angle coverage and redundancy. Figure 8 shows the elevation angle coverage of a two satellite constellation as seen from New York City. No appreciable satellite spatial diversity is possible making multipath mitigation from this technique unavailable. The selection of the number of satellites in the constellation from the analyses' data is based on the criteria adopted for the minimum required number of satellites visible to mobile receivers throughout the service area at the selected minimum elevation angles. The selection may also be influenced by system costs.
The next analyses take the selected satellite orbit constellation and further optimize it from the viewpoint of orbit perturbations. The purpose of this final optimization is to minimize the satellites' mass, particularly the amount of on-board propellant needed for correcting the orbits from long term perturbations. This is important since both the satellite and its launch vehicle will be less expensive. Thus, orbital parameters minimize satellite propulsion required to maintain each satellite in the constellation in its desired orbit.
The analyses are done by known computer programs. The programs calculate the perturbations of the satellites' orbits caused by the earth's oblateness, the gravity effects of the sun and moon and the solar radiation pressure.
Although those effects are individually small on a short term basis, satellites of this type generally have a 15 year lifetime. The magnitude of some of the perturbations are 9a a function of when the satellites are initially placed in orbit (i.e., epoch).
The analyses consider which perturbations are additive and which are subtractive, and the minimization of the perturbations by small changes in the initial orbital parameters, particularly inclination and eccentricity, and their subsequent in-orbit correction strategy. The result of the optimization is the amount of satellite on-board fuel required and reflects the minimum satellite mass.
The last analyses involve the optimization of the satellite antenna which is directive towards the service area. The analyses result in the required pointing angle of the satellite antenna boresight with time (i.e., over one sidereal day) to keep it accurately pointed at the service area. Depending on the difference between apogee and perigee altitude, if the apogee is very high, the analyses provide the beamshaping of the satellite antenna with time required to offset the change in range (i.e., space propagation loss change) and also provide antenna pattern rotation requirements with time for antenna beamshapes which are not circular.
Two systems using this invention were designed for audio satellite broadcasting. One system was designed for service to the contiguous 48 United States. The input requirements were to have one satellite in the northern portion of the service area always in view with at least 60 elevation angle to mobile receivers in the area and a second satellite always visible with at least 25 0 elevation angle. The analyses were conducted with an orbital computation program called "Satellite Tool Kit" from Analytical Graphics, Inc. of Malvern, Pennsylvania.
The results of the analyses resulted in a three satellite constellation. Figures 2 through 7 show specific final elevation angle coverage outputs of the program for the system.
A second system was designed for service to Europe using similar input C:\DM\CDRADIO\APPS\9347.OO1.wpd 10 requirements to the first system and the same computation program. Figures 9 through 12 reflect the final results regarding elevation angle coverage.
C:\DM\CDRADIO\APPS\9347.OO1.wpd 11
MOBILE BROADCASTING SYSTEMS
BACKGROUND OF THE INVENTION
Satellite broadcasting systems to mobile receivers have been proposed for radio ("Satellite DAB," International Journal of Communications; Robert D.
Briskman; Vol. 13, February 1995, pp. 259-266) and other broadcast services, such as television or data from satellites at 35,786 km altitude located at or near the equatorial plane. These satellites well serve geographical regions at low and mid-latitudes but, as the latitude becomes higher, the elevation angles to the satellites decrease as shown in Figure 1. High elevation angles are most desirable in satellite broadcast systems using mobile receivers to reduce service outages from physical blockage, multipath fading and foliage attenuation. Recognition of this has led to satellite systems using 12-hour inclined elliptical orbits such as the Molniya communications satellites and the proposed Archimedes radio broadcast system.
These systems are not efficient since many satellites are required for continuous coverage of practical service areas and the satellites' electronics and solar power subsystems are degraded by the four times daily passage through the Van Allen radiation belts surrounding the earth. The systems and methods of this invention surmount these problems.
C:\DM\CDRADIO\APPS\9347.OO1.wpd 1 SUMMARY OF THE INVENTION
The systems and methods of this invention use satellites in 24 sidereal hour orbits (geosynchronous) with inclinations, orbital planes, right ascensions and eccentricities chosen to optimize coverage of a particular service area, region or country located at high latitudes. In contrast to the elevation angles of Figure 1, a satellite constellation of two, three or more satellites can provide during all or most of every day 50 - 60 elevation angles throughout a large service area located at high latitudes. The satellites' orbits can also be configured to avoid most of the radiation from the Van Allen belts.
Satellite systems of this invention, in preferred embodiments, serve geographical latitude service areas located at greater than approximately 30 N or 30 S by providing high elevation angles to mobile receivers in such areas for reception of broadcasting transmissions over all or most of the day. The preferred systems use geosynchronous satellites (i.e., having a 24 sidereal hour orbital period 86, 164 seconds) in a constellation. The design-of the constellation is configured to optimize the elevation angle coverage of a particular geographical high latitude service area for achieving minimum physical blockage, low tree foliage attenuation and small probabilities of multipath fading. For instance, Figure 13 shows an improvement in foliage attenuation at a 1.5 GHz transmission frequency of many decibels for high service reliabilities when the reception elevation angel is doubled.
Similar improvements occur for other microwave frequencies and for other service reliabilities.
The configuration design optimization is achieved by selection of the orbital parameters of the constellation's satellites and the number of satellites in the constellation. Satellite audio broadcasting systems to mobile receivers generally = CA 02255220 1998-12-21 provide multichannel radio service and the satellite transmissions are nominally between 1 - 4 GHz.
Inclination. The inclination of the satellites is generally chosen between about 40 and about 80 so they cover the desired high latitude service areas during their transit overhead.
EccentriciLy. The eccentricity is chosen to have a high apogee over the service area so the satellites spend the maximum amount of time overhead. Practically, the eccentricity is limited by the increased distance that the higher is from the service area since this extra distance must be overcome either by higher satellite transmission power, a more directive satellite antenna during this portion of the orbit or combinations thereof. The eccentricity range in preferred embodiments is from about 0.15 to about 0.30. Eccentricities between about 0.15 and about 0.28 are highly preferred since they avoid most of the Van Allen belts.
Planes/Number of Satellites. The number of orbital planes equals the number of satellites, and their spacing at the equator is equal to 360 divided by the number of satellites. Preferred embodiments have satellite constellations between 2 and 4 satellites. To illustrate, for a 3-satellite constellation, the satellites would be in orbital planes separated by approximately 120 .
Argument of Perigee. For service to latitude areas above 30 N, the argument of perigee is in the vicinity of 270 so that the apogee is in the northern hemisphere and the perigee is in the southern hemisphere.
For service to latitude areas below 30 S, the argument of perigee is in the vicinity of 90 so that the apogee is in the southern hemisphere and C:\DM\CDRADIO\APPS\9347.OO1.wpd 3 n the perigee is in the northern hemisphere.
Longitude of the Ascending Node. The orbit planes are chosen with a longitude of the ascending node such that the satellites have a good view (i.e., are at high elevation angles as viewed by mobile receivers) of the complete service area. Generally, this is accomplished by choosing the right ascension of the ascending node and the mean anomaly such that the center of the ground trace bisects the service area.
Ground Trace. In the preferred embodiment, the satellites follow the same ground trace and pass over a given point on the earth at approximately equal time intervals. The orbit of each satellite occupies its own orbital plane. For satellites in neighboring planes in a constellation of n satellites, the difference in right ascensions of the ascending nodes is 3600/n, the difference in mean anomalies is 3600/n and the average time phasing between the satellites on the trace is 24 sidereal hours/n.
Orbit Control. Satellite constellations of this invention experience change in the aforementioned orbital parameters over time due to the earth's oblateness, gravity forces of the sun, moon and solar radiation pressure. These can be compensated by the satellites' on-board propulsion system. The amount of such propulsion can be minimized by analyzing the perturbations of each individual orbit parameter over the lifetimes of the satellites caused by the previously mentioned effects and choosing the initial conditions of the orbits so the minimum on-orbit changes are required. This choice is generally assisted by the fact that some perturbation sources partially cancel out others.
C:\DM\CDRADIO\APPS\9347.OO1.wpd 4 Satellite Spatial and Time Diversity. Figure 3 shows the elevation angle coverage from Seattle, WA to a three-satellite constellation optimized by the methods described herein for broadcast service to the United States of America. Two satellites are visible at all times. The techniques for satellite spatial and time diversity described in U.S. Patents #5319672 dated 6/7/94; #5278863 dated 1/11/94 and #5592471 dated 1/7/97 are fully applicable. US 5,592,471, for example, discloses some of the following features listed in this paragraph which form part of the common general knowledge in the art. In some implementations, a time delay can be provided between signals where the time delay is of sufficient length to reduce outages in substantial parts of the service area. As an example, in some implementations, the delay can be at least substantially 0.5 seconds. In some implementations, the delay is in the range of approximately one second to approximately five minutes. In addition, a first radio broadcast signal can be stored in each of the mobile receivers for a time period that is substantially the same as the time delay.
In some implementations, the output of a mobile receiver can be generated by combining signals or by selecting for output, in correct time order, portions of a first radio broadcast signal and a second radio broadcast signal. In some implementations the output is provided as a time-ordered stream. In addition, in some implementations, the broadcasts can be at substantially the same frequency. However, in other implementations the broadcasts can be at substantially different frequencies. In some implementations, the signals can be broadcast at different polarizations but at substantially the same frequency. In some implementations, the two separate satellite sources comprise at least two separate satellites. In some implementations, the two signals are broadcasted from a common terrestrial transmission source. In some implementations, the mobile receivers select the stronger of the signals. In some implementations, a buffer shift register can be used to store at least one of the signals. In some implementations, a buffer storage and a delay synchronizer connected to the buffer storage can he used to store at least one of the signals. In some implementations, the signals can be analog or digital, have any desired modulation, are the same or differ in frequency, and include the timing information for storage derived from the signals.
The satellite transmission power margin saved by using the invention for mitigation of multipath fading and for reduction of tree and foliage attenuation can be used to advantage. One use is by employing a smaller, less costly satellite. A second use is by transmitting more program channels.
BRIEF DESCRIPTION OF THE DRAWINGS
The systems and methods of this invention can better be understood by reference to the drawings, in which:
Figure 1 shows the elevation angles at mobile receivers in the 48 contiguous United States for the optimum location of a geostationary satellite (which is appropriately 101 W.
Longitude on the equator). Most of the northern United States has elevation angles in the 30 - 35 range which could be lower in practice due to mobile platform tilt.
Canada, Japan and most of Europe are at lower elevation angles from optimally located geostationary satellites due to their higher latitudes.
Figure 2 shows the elevation angles for a constellation of three satellites with orbits optimized for the 48 contiguous United States using the methods and 5a C) techniques of the invention for Bangor, Maine; Figure 3 for Seattle, Washington;
Figure 4 for San Diego, California; Figure 5 for Orlando, Florida; and Figure 6 for Kansas City, Missouri. The constellation provides one satellite at all times above 600 elevation angle throughout the northern United States and a second one at most times above 30 elevation angle.
Figure 7 depicts the ground trace of the satellites. With single satellite which provides no mitigation of multipath fading, a constellation of two satellites is feasible as shown in Figure 8 for New York City. Conversely, a four satellite constellation would provide multiple satellite coverage at higher elevation angles than Figure 2 -6.
Figure 9 shows the ground trace for a three satellite constellation serving Europe with Figure 10 - 12 showing the high elevation angles achieved in various cities.
Figure 13 shows the fade margin required to overcome roadside shadowing from trees and leaves measured at L-band frequencies (1-2 GHz) in the 48 contiguous United States as a function of service unavailability and elevation angle. In cases where modest availability (e.g., 90% or 10% unavailability) is required any where moderate improvement in elevation angle coverage is implemented, the fade margin improvement will be several decibels. In cases where high availability (e.g., 99% or 1% unavailability) is required and where large improvement in elevation angle coverage is implemented, the fade margin improvement will be in the 12-14 dB
range (i.e., 20 times). Reductions in required fade margins can be used by the satellite system designer to employ smaller, less expensive satellites or more audio program channels or combinations thereof.
Figure 14 is a simplified graph which shows the improvement the invention provides in reducing service outages from physical blockages (e.g., buildings, hills, C:\DM\CDRADIO\APPS\9347.OO1.wpd 6 etc.) of the satellite signal from the mobile receiver. The graph shows the worst case distance a car must be away from a building of a certain height to always avoid an outage from blockage as a function of elevation angle to a single satellite.
The amount of blockage avoidance varies significantly for an assumed building height with satellite elevation angle improvement. Depending on the improvement in satellite elevation angle coverage, the distance of a mobile receiver from the building can typically be as close as several feet to as far as many yards away and not be affected by blockage.
Figure 15 shows what would happen to the orbit of one of the constellation's satellites, whose ground trace is shown in Figure 7, if the orbital parameters are not chosen to minimize the orbital perturbations and if no satellite propulsion is used over a fifteen year period to correct the remaining perturbations. The perturbations, caused by gravitational effects of the sun, moon and earth oblateness, and by solar radiation pressure, are a function of the orbits and their epochs (i.e., the actual time of orbit insertion).
DESCRIPTION OF PREFERRED EMBODIMENTS
The systems and methods of the invention are best described by enumerating the steps employed in the design of an audio satellite broadcast system to mobile receivers for providing service throughout a service area geographically well removed from the equator. The mobile receivers have antennas configured to view the sky where satellites would be visible. The invention is also applicable to fixed location receiver radio broadcast systems. In fact, when a mobile receiver stops, it is essentially a fixed receiver. The fixed location receiver case is less technically simpler, since there is little multipath fading and the blockage encountered is static with time.
C:\DM\CDRADIO\APPS\9347.OO1.wpd 7 1) The important analysis input parameters are the definition of the geographical service area and the quality of service to be provided. The quality of service is defined as the percent of time service will be unavailable due to outage from physical blockage, multipath and tree/foliage attenuation. The desired satellite elevation angles for minimizing outage from single path physical blockage can be derived from calculations similar to those graphically shown in Figure 14.
Similarly, the desired satellite elevation angles for minimizing outage from tree/foliage attenuation can be derived from transmission measurements in the projected service area at the system's operating radio frequency, such as shown in Figure 13 for the United States at L-band frequencies, and knowledge of the satellites' transmission signal margin at the mobile receiver. Multipath and total blockage (i.e., all path blockage such as occurs when a mobile receiver passes under a large underpass) are dealt with by use of satellite spatial and time diversity. Diversity is analyzed as a requirement of the number of satellites simultaneously viewable by the mobile receivers and of the satellites' elevation angles.
The results of the aforementioned analyses are then used in the design of the satellite constellation which is a function of the orbital parameters and number of satellites in the constellation. Using known computer analysis programs, an optimization is performed of the elevation angles for the mobile receivers throughout the service area to the constellation's satellites throughout a day (i.e., since the satellites are geosynchronous, the elevation angles will repeat every day if perturbations are ignored). The optimization specifically varies inclination and eccentricity for given right ascensions to maximize the time the satellites remain over the service area (i.e., at high elevation angles). Also, the choice of the apogee and perigee of the orbit considers the avoidance of passage through the Van Allen belts so radiation damage to the satellites is minimized and avoids too high apogees C:\DM\CDRADIO\APPS\9347.OO1.wpd 8 so excess space loss or antenna beam forming is minimized as discussed subsequently.
Continuous coverage of a reasonably sized service area well removed from the equator cannot be achieved with a single satellite so analysis is generally performed on constellations with 2, 3 and 4 satellites. The analyses are performed using known computer programs. The amount of elevation angle coverage improvement diminishes for constellations with more than three satellites. Constellations with more than 4 satellites are technically feasible and only marginally improve both elevation angle coverage and redundancy. Figure 8 shows the elevation angle coverage of a two satellite constellation as seen from New York City. No appreciable satellite spatial diversity is possible making multipath mitigation from this technique unavailable. The selection of the number of satellites in the constellation from the analyses' data is based on the criteria adopted for the minimum required number of satellites visible to mobile receivers throughout the service area at the selected minimum elevation angles. The selection may also be influenced by system costs.
The next analyses take the selected satellite orbit constellation and further optimize it from the viewpoint of orbit perturbations. The purpose of this final optimization is to minimize the satellites' mass, particularly the amount of on-board propellant needed for correcting the orbits from long term perturbations. This is important since both the satellite and its launch vehicle will be less expensive. Thus, orbital parameters minimize satellite propulsion required to maintain each satellite in the constellation in its desired orbit.
The analyses are done by known computer programs. The programs calculate the perturbations of the satellites' orbits caused by the earth's oblateness, the gravity effects of the sun and moon and the solar radiation pressure.
Although those effects are individually small on a short term basis, satellites of this type generally have a 15 year lifetime. The magnitude of some of the perturbations are 9a a function of when the satellites are initially placed in orbit (i.e., epoch).
The analyses consider which perturbations are additive and which are subtractive, and the minimization of the perturbations by small changes in the initial orbital parameters, particularly inclination and eccentricity, and their subsequent in-orbit correction strategy. The result of the optimization is the amount of satellite on-board fuel required and reflects the minimum satellite mass.
The last analyses involve the optimization of the satellite antenna which is directive towards the service area. The analyses result in the required pointing angle of the satellite antenna boresight with time (i.e., over one sidereal day) to keep it accurately pointed at the service area. Depending on the difference between apogee and perigee altitude, if the apogee is very high, the analyses provide the beamshaping of the satellite antenna with time required to offset the change in range (i.e., space propagation loss change) and also provide antenna pattern rotation requirements with time for antenna beamshapes which are not circular.
Two systems using this invention were designed for audio satellite broadcasting. One system was designed for service to the contiguous 48 United States. The input requirements were to have one satellite in the northern portion of the service area always in view with at least 60 elevation angle to mobile receivers in the area and a second satellite always visible with at least 25 0 elevation angle. The analyses were conducted with an orbital computation program called "Satellite Tool Kit" from Analytical Graphics, Inc. of Malvern, Pennsylvania.
The results of the analyses resulted in a three satellite constellation. Figures 2 through 7 show specific final elevation angle coverage outputs of the program for the system.
A second system was designed for service to Europe using similar input C:\DM\CDRADIO\APPS\9347.OO1.wpd 10 requirements to the first system and the same computation program. Figures 9 through 12 reflect the final results regarding elevation angle coverage.
C:\DM\CDRADIO\APPS\9347.OO1.wpd 11
Claims (43)
1. A method of providing satellite broadcasts to mobile receivers at or near the surface of the earth in a targeted geographical service area that is, at least in part, in a latitude above substantially 30° N or in a latitude below substantially 30° S, comprising:
providing a constellation of two or more satellites with each satellite during a part of its orbit, having elevation angles of at least substantially 35° in at least a part of said targeted geographic service area; having an orbit with a periodicity substantially the same as the period of rotation of the earth on its axis;
broadcasting from a satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, on one path, a signal having a frequency in the range of substantially 1 to 4 GHz that includes audio program information;
substantially simultaneously broadcasting from another satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, on a different path, another signal having a frequency in the range of substantially 1 to 4 GHz that includes substantially the same audio program information; and providing a time delay between said signals, said time delay being of sufficient length to reduce outages in substantial parts of said service area; and assembling and producing an output signal comprising audio program information derived from said satellite broadcast signals at a plurality of mobile receivers located in said service area.
providing a constellation of two or more satellites with each satellite during a part of its orbit, having elevation angles of at least substantially 35° in at least a part of said targeted geographic service area; having an orbit with a periodicity substantially the same as the period of rotation of the earth on its axis;
broadcasting from a satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, on one path, a signal having a frequency in the range of substantially 1 to 4 GHz that includes audio program information;
substantially simultaneously broadcasting from another satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, on a different path, another signal having a frequency in the range of substantially 1 to 4 GHz that includes substantially the same audio program information; and providing a time delay between said signals, said time delay being of sufficient length to reduce outages in substantial parts of said service area; and assembling and producing an output signal comprising audio program information derived from said satellite broadcast signals at a plurality of mobile receivers located in said service area.
2. The method of claim 1, where the broadcasts from the two said satellite sources are at substantially the same frequency.
3. A satellite broadcast system for mobile receivers in a targeted geographical service area at latitudes above substantially 30° N or in a latitude below substantially 30° S, comprising:
a constellation of two or more satellites with each satellite during a part of its orbit, having an elevation angle or angles of at least substantially 35° in at least a part of said targeted geographic service area; having an orbit with a periodicity substantially the same as the period of rotation of the earth on its axis;
a satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, for broadcasting on one path, a signal having a frequency in the range of substantially 1 to 4 GHz that includes audio program information;
another satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, for substantially simultaneously broadcasting, on a different path, another signal having a frequency in the range of substantially 1 to 4 GHz that includes substantially the same audio program information, with a time delay between said signals, said time delay being of sufficient length to reduce outages in substantial parts of said service area; and a plurality of mobile receivers for receiving the broadcast signals, said plurality of mobile receivers located in said service area at or near the surface of the earth, each of said plurality of mobile receivers being adapted to produce an output signal comprising audio program information derived from said satellite broadcast signals.
a constellation of two or more satellites with each satellite during a part of its orbit, having an elevation angle or angles of at least substantially 35° in at least a part of said targeted geographic service area; having an orbit with a periodicity substantially the same as the period of rotation of the earth on its axis;
a satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, for broadcasting on one path, a signal having a frequency in the range of substantially 1 to 4 GHz that includes audio program information;
another satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, for substantially simultaneously broadcasting, on a different path, another signal having a frequency in the range of substantially 1 to 4 GHz that includes substantially the same audio program information, with a time delay between said signals, said time delay being of sufficient length to reduce outages in substantial parts of said service area; and a plurality of mobile receivers for receiving the broadcast signals, said plurality of mobile receivers located in said service area at or near the surface of the earth, each of said plurality of mobile receivers being adapted to produce an output signal comprising audio program information derived from said satellite broadcast signals.
4. The satellite audio broadcasting system of claim 3 wherein said audio program information from said constellation is in the frequency range of substantially 1 to substantially 4 GHz.
5. The satellite audio broadcasting system of claim 3 or 4 wherein the satellites in said constellation are in orbital planes separated from one another by a number of degrees equal to 360° divided by the number of satellites in said constellation.
6. The satellite broadcasting system of claim 3 or 4 wherein said orbital parameters for at least one satellite in said constellation minimize passage of said satellite through the Van Allen radiation belts around the earth.
7. The satellite audio broadcasting system of claim 3 or 4 wherein said orbital parameters minimize onboard satellite propulsion required to maintain each satellite in said constellation in its desired orbit.
8. The satellite audio broadcasting system of claim 3 or 4 wherein said orbital parameters are selected from the group consisting of satellite antenna pointing angles, satellite pattern rotation angles and satellite antenna beam shapes.
9. The satellite audio broadcasting system of claim 3 or 4 wherein said orbital parameters are selected from the group consisting of the inclination of each satellite, the eccentricity of the orbit for each satellite, the argument of perigee for each satellite in said constellation, the longitude of the ascending node of each orbit for each satellite in said constellation, and the ground trace for each satellite in said constellation.
10. A method of providing satellite broadcasts to mobile receivers at or near the surface of the earth in a targeted geographical service area that is, at least in part, in a latitude above substantially 30° N or in a latitude below substantially 30° S, comprising:
providing a constellation of two or more satellites with each satellite during a part of its orbit, having an elevation angle or angles of at least substantially 35° in at least a part of said targeted geographic service area; having an orbit with a periodicity substantially the same as the period of rotation of the earth on its axis;
broadcasting from a satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, on one path, a signal having a frequency in the range of substantially 1 to 4 GHz that includes audio program information;
substantially simultaneously broadcasting from another satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, on a different path, said different path being spaced from said satellite source and said first path sufficiently to reduce blockage and foliage attenuation and to facilitate signal reception at the earth's surface, while said satellite sources are broadcasting; and assembling and producing an output signal comprising audio program information derived from said satellite broadcast signals at a plurality of mobile receivers located in said service area.
providing a constellation of two or more satellites with each satellite during a part of its orbit, having an elevation angle or angles of at least substantially 35° in at least a part of said targeted geographic service area; having an orbit with a periodicity substantially the same as the period of rotation of the earth on its axis;
broadcasting from a satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, on one path, a signal having a frequency in the range of substantially 1 to 4 GHz that includes audio program information;
substantially simultaneously broadcasting from another satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, on a different path, said different path being spaced from said satellite source and said first path sufficiently to reduce blockage and foliage attenuation and to facilitate signal reception at the earth's surface, while said satellite sources are broadcasting; and assembling and producing an output signal comprising audio program information derived from said satellite broadcast signals at a plurality of mobile receivers located in said service area.
11. The method of claim 10, comprising broadcasting said signals with frequencies that are substantially different one from the other.
12. The method of claim 10, comprising broadcasting said signals with frequencies that are substantially the same.
13. The method of anyone of claims 10 to 12 further comprising broadcasting said signal and said another signal at different polarizations but with substantially the same frequency.
14. The method of anyone of claims 10 to 12 comprising broadcasting signals wherein one of the two satellite sources comprises at least two separate satellites.
15. The method of anyone of claims 10 to 12 wherein said assembling step comprises selection of said signal and said another signal as the basis for the output from at least one of said receivers.
16. The method of anyone of claims 10 to 12 wherein said assembling step comprises combining said signal and said another signal.
17. A satellite broadcast system for mobile receivers in a targeted geographical service area at latitudes above substantially 30 N or below substantially 30 S
comprising:
a constellation of two or more satellites with each satellite during a part of its orbit, having an elevation angle or angles of at least substantially 35 in at least a part of said targeted geographic service area; having an orbit with a periodicity substantially the same as the period of rotation of the earth on its axis;
a satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, for broadcasting on one path, a signal having a frequency in the range of substantially 1 to 4 GHz that includes audio program information;
another satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, for substantially simultaneously broadcasting, on a different path, another signal having a frequency in the range of substantially 1 to 4 GHz that includes substantially the same audio program information, said different path being spaced from said satellite source and said first path sufficiently to reduce blockage and foliage attenuation and to facilitate signal reception at the earth's surface, while said satellites are broadcasting; and a plurality of mobile receivers for receiving the broadcast signals, said plurality of mobile receivers located in said service area at or near the surface of the earth, each of said plurality of mobile receivers being adapted to produce an output signal comprising audio program information derived from said satellite broadcast signals.
comprising:
a constellation of two or more satellites with each satellite during a part of its orbit, having an elevation angle or angles of at least substantially 35 in at least a part of said targeted geographic service area; having an orbit with a periodicity substantially the same as the period of rotation of the earth on its axis;
a satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, for broadcasting on one path, a signal having a frequency in the range of substantially 1 to 4 GHz that includes audio program information;
another satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, for substantially simultaneously broadcasting, on a different path, another signal having a frequency in the range of substantially 1 to 4 GHz that includes substantially the same audio program information, said different path being spaced from said satellite source and said first path sufficiently to reduce blockage and foliage attenuation and to facilitate signal reception at the earth's surface, while said satellites are broadcasting; and a plurality of mobile receivers for receiving the broadcast signals, said plurality of mobile receivers located in said service area at or near the surface of the earth, each of said plurality of mobile receivers being adapted to produce an output signal comprising audio program information derived from said satellite broadcast signals.
18. The system of claim 17 in which said signals have frequencies that are substantially different one from the other.
19. The system of claim 17 in which said signals have frequencies that are substantially the same.
20. The system of anyone of claims 17 to 19 wherein said mobile receivers select the stronger of said signal and said other signal.
21. The system of anyone of claims 17 to 19 wherein said signal and said another signal are at different polarizations but have substantially the same frequency.
22. The system of anyone of claims 17 to 19 wherein one of the two satellite sources comprises at least two separate satellites.
23. The system of anyone of claims 17 to 19 wherein said receiver combines said signal and said another signal.
24. The system of anyone of claims 17 to 19 wherein said receiver selects from said signal and said another signal as the basis for the output from at least one of said receivers.
25. The system of anyone of claims 17 to 19 wherein the time delay is in the range of approximately one second to approximately five minutes.
26. A method of providing satellite broadcasts to mobile receivers at or near the surface of the earth in a targeted geographical service area that is, at least in part, in a latitude above substantially 30° N or in a latitude below substantially 30° S, comprising:
providing a constellation of two or more satellites with each satellite during a part of its orbit, having an elevation angle or angles of at least substantially 35° in at least a part of said targeted geographic service area; having an orbit with a periodicity substantially the same as the period of rotation of the earth on its axis;
broadcasting from a satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, on one path, a signal having a frequency in the range of substantially 1 to 4 GHz that includes audio program information;
substantially simultaneously broadcasting from another satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, on a different path, said different path being spaced from said satellite source and said first path sufficiently to reduce blockage and foliage attenuation and to facilitate signal reception at the earth's surface, while said satellite sources are broadcasting;
providing a time delay between said signals, said time delay being of sufficient length to reduce outages in substantial parts of said service area; and assembling and producing an output signal comprising audio program information derived from said satellite broadcast signals at a plurality of mobile receivers located in said service area.
providing a constellation of two or more satellites with each satellite during a part of its orbit, having an elevation angle or angles of at least substantially 35° in at least a part of said targeted geographic service area; having an orbit with a periodicity substantially the same as the period of rotation of the earth on its axis;
broadcasting from a satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, on one path, a signal having a frequency in the range of substantially 1 to 4 GHz that includes audio program information;
substantially simultaneously broadcasting from another satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, on a different path, said different path being spaced from said satellite source and said first path sufficiently to reduce blockage and foliage attenuation and to facilitate signal reception at the earth's surface, while said satellite sources are broadcasting;
providing a time delay between said signals, said time delay being of sufficient length to reduce outages in substantial parts of said service area; and assembling and producing an output signal comprising audio program information derived from said satellite broadcast signals at a plurality of mobile receivers located in said service area.
27. The method of claim 26 comprising broadcasting said signal and said another signal are at different frequencies.
28. The method of claim 26 comprising broadcasting said signal and said another signal from a common terrestrial transmission source.
29. The method of claim 26 further comprising providing a time delay in the range of substantially 1 second to substantially 5 minutes.
30. A satellite broadcast system for mobile receivers in a targeted geographical service area at latitudes above substantially 30° N or below substantially 30° S comprising:
a constellation of two or more satellites with each satellite during a part of its orbit, having an elevation angle or angles of at least substantially 35° in at least a part of said targeted geographic service area; having an orbit with a periodicity substantially the same as the period of rotation of the earth on its axis;
a satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, for broadcasting on one path, a signal having a frequency in the range of substantially 1 to 4 GHz that includes audio program information;
another satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, for substantially simultaneously broadcasting, on a different path, another signal having a frequency in the range of substantially 1 to 4 GHz that includes substantially the same audio program information, said different path being spaced from said satellite source and said first path sufficiently to reduce blockage and foliage attenuation and to facilitate signal reception at the earth's surface, while said satellites are broadcasting;
providing a time delay between said signals, said time delay being of sufficient length to reduce outages in substantial parts of said service area; and a plurality of mobile receivers, with the capability of storing, in each of said mobile receivers, at least one of said signals and outputting from each of said plurality of mobile receivers said audio program information from said signals by combining the signals for output or by selecting for output, in correct time-ordered progression, portions of said signals.
a constellation of two or more satellites with each satellite during a part of its orbit, having an elevation angle or angles of at least substantially 35° in at least a part of said targeted geographic service area; having an orbit with a periodicity substantially the same as the period of rotation of the earth on its axis;
a satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, for broadcasting on one path, a signal having a frequency in the range of substantially 1 to 4 GHz that includes audio program information;
another satellite source in said constellation at an elevation angle or angles greater than or equal to approximately 35°, for substantially simultaneously broadcasting, on a different path, another signal having a frequency in the range of substantially 1 to 4 GHz that includes substantially the same audio program information, said different path being spaced from said satellite source and said first path sufficiently to reduce blockage and foliage attenuation and to facilitate signal reception at the earth's surface, while said satellites are broadcasting;
providing a time delay between said signals, said time delay being of sufficient length to reduce outages in substantial parts of said service area; and a plurality of mobile receivers, with the capability of storing, in each of said mobile receivers, at least one of said signals and outputting from each of said plurality of mobile receivers said audio program information from said signals by combining the signals for output or by selecting for output, in correct time-ordered progression, portions of said signals.
31. The system of claim 30 further comprising a buffer shift register for storing at least one of said signals.
32. The system of claim 30 further comprising buffer storage and a delay synchronizer connected to said buffer storage for storing at least one of said signals.
33. The system of claim 30 in which at least some of said mobile receivers combine said two signals, or select for output, portions of one signal and portions of another signal to provide a time-ordered stream.
34. The system of claim 30 wherein said signals are analog or digital, have any desired modulation, are the same or differ in frequency, and include timing information for storage derived from the signals.
35. The system of claim 30 in which at least some of said mobile receivers select the stronger signal from said signal and said another signal for output.
36. The system of claim 30 wherein at least some of said mobile receivers combine said signal and said another signal.
37. The system of any one of claims 30 to 34 wherein said time delay is in the range of substantially one second to substantially five minutes.
38. A method of providing audio satellite broadcast transmissions to fixed and mobile receivers in a defined geographical service area that is, at least in part, in a latitude above substantially 30° N or in a latitude below substantially 30° S
comprising providing a constellation of satellites, with each satellite in its own orbital plane, each orbital plane having orbital parameters that provide elevation angles of more than 35° in said defined geographical service area, each satellite with a period of revolution around the earth substantially the same as the period of rotation of the earth on its axis;
transmitting, from two or more of said satellites, audio broadcast signals that are substantially identical in content;
transmitting at least two radio broadcast signals having frequencies in the range of substantially 1 to substantially 4 GHz from at least two satellites in said constellation substantially simultaneously, said radio broadcast signals having substantially the same content, to a plurality of mobile receivers for said signals in said area and at or near the earth's surface, including the steps of. broadcasting a first radio broadcast signal to said plurality of mobile receivers; after a time delay of sufficient length to substantially eliminate outages in said area, said delay being at least substantially 0.5 seconds, following the broadcast of said first radio broadcast signal, broadcasting a second radio broadcast signal containing substantially the same program content as said first radio broadcast to said plurality of mobile receivers; storing, in each of said mobile receivers, said first radio broadcast signal for a time period substantially the same as the time of said time delay; and outputting from each of said plurality of mobile receivers, the program contents of first and said second radio broadcast signals by combining said first and said second radio broadcast signals for output or by selecting for output, in correct time-order progression, portions of said first radio broadcast signal and portions of said second radio broadcast signal.
comprising providing a constellation of satellites, with each satellite in its own orbital plane, each orbital plane having orbital parameters that provide elevation angles of more than 35° in said defined geographical service area, each satellite with a period of revolution around the earth substantially the same as the period of rotation of the earth on its axis;
transmitting, from two or more of said satellites, audio broadcast signals that are substantially identical in content;
transmitting at least two radio broadcast signals having frequencies in the range of substantially 1 to substantially 4 GHz from at least two satellites in said constellation substantially simultaneously, said radio broadcast signals having substantially the same content, to a plurality of mobile receivers for said signals in said area and at or near the earth's surface, including the steps of. broadcasting a first radio broadcast signal to said plurality of mobile receivers; after a time delay of sufficient length to substantially eliminate outages in said area, said delay being at least substantially 0.5 seconds, following the broadcast of said first radio broadcast signal, broadcasting a second radio broadcast signal containing substantially the same program content as said first radio broadcast to said plurality of mobile receivers; storing, in each of said mobile receivers, said first radio broadcast signal for a time period substantially the same as the time of said time delay; and outputting from each of said plurality of mobile receivers, the program contents of first and said second radio broadcast signals by combining said first and said second radio broadcast signals for output or by selecting for output, in correct time-order progression, portions of said first radio broadcast signal and portions of said second radio broadcast signal.
39. The method of claim 38 wherein the satellites in said constellation are in orbital planes separated from one another by a number of degrees equal to 360° divided by the number of satellites in said constellation.
40. The method of claim 38 wherein said orbital parameters for at least one satellite in said constellation minimize passage of said satellites through the Van Allen radiation belts around the earth.
41. The method of claim 38 wherein said orbital parameters minimize onboard satellite propulsion required to maintain each satellite in said constellation in its desired orbit.
42. The method of claim 38 wherein said orbital parameters are selected from the group consisting of satellite antenna pointing angles, satellite pattern rotation angles and satellite antenna beam shapes.
43. The method of claim 38 wherein said orbital parameters are selected from the group consisting of the inclination of each satellite, the eccentricity of the orbit for each satellite, the argument of perigee for each satellite in said constellation, the longitude of the ascending node of each orbit for each satellite in said constellation, and the ground trace for each satellite in said constellation.
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Families Citing this family (34)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20030189136A1 (en) * | 1998-05-20 | 2003-10-09 | Toshihide Maeda | Communication system, communication receiving device and communication terminal in the system |
| US6257526B1 (en) * | 1998-11-09 | 2001-07-10 | Hughes Electronics Corporation | Satellite system and method of deploying same |
| US6327523B2 (en) | 1999-01-21 | 2001-12-04 | Hughes Electronics Corporation | Overhead system of inclined eccentric geosynchronous orbitting satellites |
| US6457678B1 (en) * | 1999-08-16 | 2002-10-01 | Mobile Communications Holdings, Inc. | Constellation of elliptical orbit satellites with line of apsides lying in or near the equatorial plane |
| US6491257B1 (en) * | 1999-10-13 | 2002-12-10 | Motorola, Inc. | Technique for satellite constellation growth |
| US6442385B1 (en) | 1999-11-04 | 2002-08-27 | Xm Satellite Radio, Inc. | Method and apparatus for selectively operating satellites in tundra orbits to reduce receiver buffering requirements for time diversity signals |
| US6347216B1 (en) | 1999-11-04 | 2002-02-12 | Xm Satellite Radio Inc. | Method and system for providing geographic specific services in a satellite communications network |
| US6778810B1 (en) * | 1999-12-03 | 2004-08-17 | The Directtv Group, Inc. | Method and apparatus for mitigating interference from terrestrial broadcasts sharing the same channel with satellite broadcasts using an antenna with posterior sidelobes |
| US7184761B1 (en) * | 2000-03-27 | 2007-02-27 | The Directv Group, Inc. | Satellite communications system |
| US7369809B1 (en) * | 2000-10-30 | 2008-05-06 | The Directv Group, Inc. | System and method for continuous broadcast service from non-geostationary orbits |
| JP2002157516A (en) * | 2000-11-17 | 2002-05-31 | Hitachi Ltd | Method and device for providing advertisement information |
| US6851651B2 (en) * | 2002-02-15 | 2005-02-08 | Lockheed Martin Corporation | Constellation of spacecraft, and broadcasting method using said constellation |
| US20030181159A1 (en) * | 2002-03-22 | 2003-09-25 | Paul Heinerscheid | Combination of multiple regional beams and a wide-area beam provided by a satellite system |
| US7624948B2 (en) * | 2004-12-07 | 2009-12-01 | Lockheed Martin Corporation | Optimized land mobile satellite configuration and steering method |
| US7669803B2 (en) * | 2004-12-07 | 2010-03-02 | Lockheed Martin Corporation | Optimized land mobile satellite system for north american coverage |
| US7519324B2 (en) * | 2005-03-16 | 2009-04-14 | Lockheed Martin Corporation | Geosynchronous satellite constellation |
| US7672638B1 (en) * | 2005-03-16 | 2010-03-02 | Lockheed Martin Corporation | Geosynchronous satellite constellation |
| US7454272B1 (en) * | 2005-08-25 | 2008-11-18 | Raytheon Company | Geostationary stationkeeping method |
| US20070063982A1 (en) * | 2005-09-19 | 2007-03-22 | Tran Bao Q | Integrated rendering of sound and image on a display |
| US20070171891A1 (en) * | 2006-01-26 | 2007-07-26 | Available For Licensing | Cellular device with broadcast radio or TV receiver |
| US20070222734A1 (en) * | 2006-03-25 | 2007-09-27 | Tran Bao Q | Mobile device capable of receiving music or video content from satellite radio providers |
| US7827491B2 (en) * | 2006-05-12 | 2010-11-02 | Tran Bao Q | Systems and methods for video editing |
| US7840180B2 (en) * | 2006-12-22 | 2010-11-23 | The Boeing Company | Molniya orbit satellite systems, apparatus, and methods |
| US20080178233A1 (en) * | 2007-01-22 | 2008-07-24 | Goc Richard J | Audio and video program purchasing |
| US8016240B2 (en) * | 2007-03-29 | 2011-09-13 | The Boeing Company | Satellites and satellite fleet implementation methods and apparatus |
| US9045239B2 (en) * | 2009-01-14 | 2015-06-02 | Space Systems/Loral, Llc | Spacecraft payload orientation steering |
| US8238903B2 (en) * | 2009-02-19 | 2012-08-07 | Korb C Laurence | Methods for optimizing the performance, cost and constellation design of satellites for full and partial earth coverage |
| US20120119034A1 (en) * | 2009-07-02 | 2012-05-17 | Space Systems/Loral, Inc. | Deorbiting a Spacecraft from a Highly Inclined Elliptical Orbit |
| FR2962411B1 (en) * | 2010-07-12 | 2014-03-14 | Astrium Sas | METHOD FOR PRODUCING A SPATIAL SLEEP SYSTEM FOR MONITORING NEAR-SPACE |
| CA2716174C (en) * | 2010-10-01 | 2019-11-26 | Telesat Canada | Satellite system |
| CN103888183B (en) * | 2014-03-28 | 2018-01-09 | 中国科学院国家天文台 | A kind of method that round-the-clock communication is realized using two IGSO telecommunication satellites |
| CN108430875B (en) * | 2015-11-27 | 2022-05-24 | 加拿大卫星公司 | Satellite system and method for global coverage |
| US10889388B2 (en) | 2016-02-26 | 2021-01-12 | Space Systems/Loral, Llc | Inclined geosynchronous orbit spacecraft constellations |
| US11662183B1 (en) | 2022-09-13 | 2023-05-30 | Guardiansat, Llc | Systems and methods for automomous protection of satellites from hostile orbital attackers |
Family Cites Families (87)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2959644A (en) | 1957-06-13 | 1960-11-08 | Motorola Inc | Electronic device |
| US3163820A (en) | 1961-05-22 | 1964-12-29 | Bell Telephone Labor Inc | Satellite communication system employing a retrograding orbit |
| US3836969A (en) | 1971-10-26 | 1974-09-17 | Rca Corp | Geo-synchronous satellites in quasi-equatorial orbits |
| US3825837A (en) | 1972-06-01 | 1974-07-23 | Communications Satellite Corp | Television radio frequency switch |
| JPS577490B2 (en) | 1974-02-26 | 1982-02-10 | ||
| US4021737A (en) | 1975-06-04 | 1977-05-03 | Trask Burdick S | System for processing and transmitting audio signals received from a television set for reproduction by a high fidelity FM receiver |
| US4286262A (en) | 1975-09-02 | 1981-08-25 | Mallard Manufacturing Corporation | Electronic transmitter device |
| US4038600A (en) | 1976-02-17 | 1977-07-26 | Westinghouse Electric Corporation | Power control on satellite uplinks |
| US4291409A (en) | 1978-06-20 | 1981-09-22 | The Mitre Corporation | Spread spectrum communications method and apparatus |
| US4291410A (en) | 1979-10-24 | 1981-09-22 | Rockwell International Corporation | Multipath diversity spread spectrum receiver |
| DE3145207A1 (en) | 1981-02-28 | 1982-09-23 | Siemens AG, 1000 Berlin und 8000 München | TELECOMMUNICATION SATELLITE SYSTEM WITH GEOSTATIONAL POSITION LOOPS |
| GB2098821A (en) | 1981-03-20 | 1982-11-24 | Chan Kong Philip | Radio receiver |
| JPS5819782A (en) | 1981-07-29 | 1983-02-04 | Tdk Corp | Receiver |
| US4630058A (en) | 1982-02-26 | 1986-12-16 | Rca Corporation | Satellite communication system |
| US4535476A (en) | 1982-12-01 | 1985-08-13 | At&T Bell Laboratories | Offset geometry, interference canceling receiver |
| US4660196A (en) | 1983-08-01 | 1987-04-21 | Scientific Atlanta, Inc. | Digital audio satellite transmission system |
| US4532635A (en) | 1983-08-19 | 1985-07-30 | Rca Corporation | System and method employing two hop spread spectrum signal transmissions between small earth stations via a satellite and a large earth station and structure and method for synchronizing such transmissions |
| US4742410A (en) | 1983-12-16 | 1988-05-03 | Josephine County Technology, Inc. | Disk drive system with head protection mechanism |
| US4640987A (en) | 1984-04-23 | 1987-02-03 | Keizo Tsukada | Cordless telephone |
| DE3426851C1 (en) | 1984-07-20 | 1985-10-17 | Deutsche Forschungs- und Versuchsanstalt für Luft- und Raumfahrt e.V., 5300 Bonn | Satellite navigation system |
| US4560945A (en) | 1984-09-04 | 1985-12-24 | Westinghouse Electric Corp. | Adaptive feedforward cancellation technique that is effective in reducing amplifier harmonic distortion products as well as intermodulation distortion products |
| US4588958A (en) | 1985-03-29 | 1986-05-13 | Rca Corporation | Adjustable reflective predistortion circuit |
| US4809935A (en) * | 1985-07-31 | 1989-03-07 | Analytic Services, Inc. | Satellite continuous coverage constellations |
| US4712250A (en) | 1985-08-12 | 1987-12-08 | Sound Sender, Inc. | Tape player adapter for car radio |
| JPS6258732A (en) | 1985-09-06 | 1987-03-14 | Nippon Soken Inc | On-vehicle communication equipment |
| JPS6261431A (en) | 1985-09-12 | 1987-03-18 | Kokusai Denshin Denwa Co Ltd <Kdd> | Transmission power control system |
| US4685133A (en) | 1985-09-16 | 1987-08-04 | Inr Technologies, Inc. | Wireless audio transmission system |
| US4720873A (en) | 1985-09-18 | 1988-01-19 | Ricky R. Goodman | Satellite audio broadcasting system |
| US4801940A (en) | 1985-10-30 | 1989-01-31 | Capetronic (Bsr) Ltd. | Satellite seeking system for earth-station antennas for TVRO systems |
| US4823341A (en) | 1986-08-14 | 1989-04-18 | Hughes Aircraft Company | Satellite communications system having frequency addressable high gain downlink beams |
| US4879711A (en) | 1986-08-14 | 1989-11-07 | Hughes Aircraft Company | Satellite communications system employing frequency reuse |
| US4831619A (en) | 1986-08-14 | 1989-05-16 | Hughes Aircraft Company | Satellite communications system having multiple downlink beams powered by pooled transmitters |
| JPS6346824A (en) | 1986-08-14 | 1988-02-27 | Kokusai Denshin Denwa Co Ltd <Kdd> | Transmission power control system |
| CA1334292C (en) | 1986-10-06 | 1995-02-07 | Andrew E. Turner | Apogee at constant time-of-day equatorial (ace) orbit |
| US4901307A (en) | 1986-10-17 | 1990-02-13 | Qualcomm, Inc. | Spread spectrum multiple access communication system using satellite or terrestrial repeaters |
| US4829570A (en) | 1987-05-22 | 1989-05-09 | Recoton Corporation | Wireless remote speaker system |
| FR2628274B1 (en) | 1988-03-02 | 1990-08-10 | Centre Nat Etd Spatiales | COMMUNICATIONS SYSTEM WITH MOBILES USING SATELLITES |
| JPH01307302A (en) | 1988-06-06 | 1989-12-12 | Nec Corp | Loop antenna for portable radio equipment |
| US4908847A (en) | 1988-11-10 | 1990-03-13 | Telcor, Inc. | Adaptor set for converting standard telephone into cordless telephone |
| JPH0338932A (en) | 1989-07-06 | 1991-02-20 | Oki Electric Ind Co Ltd | Space diversity system |
| US5048118A (en) | 1989-07-10 | 1991-09-10 | Motorola, Inc. | Combination dual loop antenna and bezel with detachable lens cap |
| FR2650135B1 (en) | 1989-07-19 | 1994-05-20 | Centre Nal Etudes Spatiales | SATELLITE AND METHOD OF ORBITTING BY GRAVITATIONAL ASSISTANCE |
| US5036523A (en) | 1989-10-03 | 1991-07-30 | Geostar Corporation | Automatic frequency control of satellite transmitted spread spectrum signals |
| US5274840A (en) | 1989-11-06 | 1993-12-28 | Motorola, Inc. | Satellite communication system |
| DE69019825T2 (en) | 1989-11-06 | 1995-12-21 | Motorola Inc | SATELLITE TRANSMISSION SYSTEM. |
| US5015965A (en) | 1989-11-22 | 1991-05-14 | General Electric Company | Predistortion equalizer with resistive combiners and dividers |
| US5239670A (en) | 1989-11-30 | 1993-08-24 | Motorola, Inc. | Satellite based global paging system |
| US5038341A (en) | 1989-12-01 | 1991-08-06 | Hughes Aircraft Company | Relay communication system |
| US5126748A (en) | 1989-12-05 | 1992-06-30 | Qualcomm Incorporated | Dual satellite navigation system and method |
| US5017926A (en) | 1989-12-05 | 1991-05-21 | Qualcomm, Inc. | Dual satellite navigation system |
| US5099252A (en) | 1989-12-08 | 1992-03-24 | Larsen Electronics, Inc. | Mobile cellular antenna system |
| US5073900A (en) | 1990-03-19 | 1991-12-17 | Mallinckrodt Albert J | Integrated cellular communications system |
| IT1239472B (en) | 1990-04-09 | 1993-11-02 | Sits Soc It Telecom Siemens | LINEARIZER OF THE PRE-DISTORTION TYPE FOR MICROWAVE POWER AMPLIFIERS |
| DE4111705C2 (en) | 1990-04-28 | 1998-03-19 | Pioneer Electronic Corp | Sound signal modulation system |
| JP2873872B2 (en) | 1990-09-06 | 1999-03-24 | 株式会社ソキア | C / A code removal type frequency diversity correlation reception system in GPS |
| US5283780A (en) | 1990-10-18 | 1994-02-01 | Stanford Telecommunications, Inc. | Digital audio broadcasting system |
| US5455823A (en) * | 1990-11-06 | 1995-10-03 | Radio Satellite Corporation | Integrated communications terminal |
| US5303393A (en) | 1990-11-06 | 1994-04-12 | Radio Satellite Corporation | Integrated radio satellite response system and method |
| US5251328A (en) | 1990-12-20 | 1993-10-05 | At&T Bell Laboratories | Predistortion technique for communications systems |
| US5148452A (en) | 1990-12-31 | 1992-09-15 | Motorola, Inc. | Global positioning system digital receiver |
| US5408686A (en) | 1991-02-19 | 1995-04-18 | Mankovitz; Roy J. | Apparatus and methods for music and lyrics broadcasting |
| US5439190A (en) | 1991-04-22 | 1995-08-08 | Trw Inc. | Medium-earth-altitude satellite-based cellular telecommunications |
| US5433726A (en) | 1991-04-22 | 1995-07-18 | Trw Inc. | Medium-earth-altitude satellite-based cellular telecommunications system |
| US5175557A (en) | 1991-07-18 | 1992-12-29 | Motorola, Inc. | Two channel global positioning system receiver |
| IL98893A (en) * | 1991-07-19 | 1996-07-23 | Mass Jonathan | Artificial satellite communication system |
| US5319716A (en) | 1991-09-17 | 1994-06-07 | Recoton Corporation | Wireless CD/automobile radio adapter |
| US5153598A (en) | 1991-09-26 | 1992-10-06 | Alves Jr Daniel F | Global Positioning System telecommand link |
| US5485485A (en) | 1992-04-10 | 1996-01-16 | Cd Radio Inc. | Radio frequency broadcasting systems and methods using two low-cost geosynchronous satellites and hemispherical coverage antennas |
| US5278863A (en) | 1992-04-10 | 1994-01-11 | Cd Radio Incorporated | Radio frequency broadcasting systems and methods using two low-cost geosynchronous satellites |
| US5233626A (en) | 1992-05-11 | 1993-08-03 | Space Systems/Loral Inc. | Repeater diversity spread spectrum communication system |
| JP2706600B2 (en) * | 1992-05-28 | 1998-01-28 | ティアールダブリュー インコーポレイテッド | Cellular telecommunications systems based on mid-earth altitude satellites. |
| US5582367A (en) | 1992-06-02 | 1996-12-10 | Mobile Communications Holdings, Inc. | Elliptical orbit satellite, system, and deployment with controllable coverage characteristics |
| US5349606A (en) | 1992-12-31 | 1994-09-20 | Gte Government Systems Corporation | Apparatus for multipath DSSS communications |
| US5345244A (en) | 1993-01-12 | 1994-09-06 | Trimble Navigation Limited | Cordless SPS smart antenna device |
| FR2703199B1 (en) | 1993-03-26 | 1995-06-02 | Matra Communication | Radio transmission method using repeating spectrum inverting stations. |
| JP3181440B2 (en) | 1993-07-30 | 2001-07-03 | 松下通信工業株式会社 | CDMA communication device |
| EP0668662A4 (en) | 1993-08-06 | 1997-02-12 | Nippon Telegraph & Telephone | Receiver and repeater for spread spectrum communication. |
| TW239242B (en) | 1994-03-28 | 1995-01-21 | Leo One Ip L L C | Satellite system using equatorial & polar orbit relays |
| US5638399A (en) * | 1994-11-15 | 1997-06-10 | Stanford Telecommunications, Inc. | Multi-beam satellite communication system with user terminal frequencies having transceivers using the same set of frequency hopping |
| US5551065A (en) | 1994-12-19 | 1996-08-27 | Honore; David | Wireless solar entertainment system |
| US5641134A (en) | 1994-12-27 | 1997-06-24 | Motorola, Inc. | Satellite cellular telephone and data communication system at an inclined orbit |
| FR2729116A1 (en) * | 1995-01-06 | 1996-07-12 | Matra Marconi Space France | METHOD FOR CONTROLLING ATTITUDE OF SATELLITE ON INCLINED ORBIT ON THE TERRESTRIAL ECUADOR |
| US5508756A (en) | 1995-02-08 | 1996-04-16 | Landy; Bruce | T.V. signal tuner in a tape cassette body and method therefor |
| US5592471A (en) | 1995-04-21 | 1997-01-07 | Cd Radio Inc. | Mobile radio receivers using time diversity to avoid service outages in multichannel broadcast transmission systems |
| US6226493B1 (en) | 1996-05-31 | 2001-05-01 | Motorola, Inc. | Geosynchronous satellite communication system and method |
| US6019318A (en) * | 1997-06-16 | 2000-02-01 | Hugehs Electronics Corporation | Coordinatable system of inclined geosynchronous satellite orbits |
| US5907582A (en) * | 1997-08-11 | 1999-05-25 | Orbital Sciences Corporation | System for turbo-coded satellite digital audio broadcasting |
-
1998
- 1998-05-20 US US09/082,489 patent/US6223019B1/en not_active Expired - Lifetime
- 1998-12-10 AU AU97030/98A patent/AU759284B2/en not_active Ceased
- 1998-12-21 CA CA2255220A patent/CA2255220C/en not_active Expired - Fee Related
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1999
- 1999-01-07 CN CNB991010132A patent/CN1174563C/en not_active Expired - Fee Related
- 1999-01-12 NO NO19990114A patent/NO318038B1/en not_active IP Right Cessation
- 1999-02-09 MX MXPA99001381A patent/MXPA99001381A/en active IP Right Grant
- 1999-05-17 EP EP99303823A patent/EP0959573A3/en not_active Ceased
- 1999-05-19 JP JP13846499A patent/JP3108689B2/en not_active Expired - Fee Related
-
2000
- 2000-10-19 US US09/692,780 patent/US6564053B1/en not_active Expired - Lifetime
Also Published As
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| MXPA99001381A (en) | 2005-04-11 |
| NO318038B1 (en) | 2005-01-24 |
| JP3108689B2 (en) | 2000-11-13 |
| NO990114L (en) | 1999-11-22 |
| AU9703098A (en) | 1999-12-02 |
| EP0959573A2 (en) | 1999-11-24 |
| JP2000013297A (en) | 2000-01-14 |
| CN1236232A (en) | 1999-11-24 |
| NO990114D0 (en) | 1999-01-12 |
| US6564053B1 (en) | 2003-05-13 |
| CA2255220A1 (en) | 1999-11-20 |
| US6223019B1 (en) | 2001-04-24 |
| CN1174563C (en) | 2004-11-03 |
| EP0959573A3 (en) | 2002-05-02 |
| AU759284B2 (en) | 2003-04-10 |
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