Abstract: A communications and computing based urban transit system based on digital cellular communication, GPS locating technology, and digital computers to provide real-time command and control of passengers and vehicles with the objective of minimizing the social costs of urban transportation.

Abstract: An emergency warning network including a base station for broadcasting a warning signal and a first, earth-orbiting satellite for receiving the warning signal and rebroadcasting such to extend the range of communications of the base station. A first substation receives the warning signal and broadcasts a first forwarding signal in response thereto to a first portable receiver. A second substation also receives the warning signal and broadcasts a second forwarding signal in response thereto via a second, earth-orbiting satellite to a first branch station. The first branch station broadcasts a third forwarding signal in response to the second forwarding signal to a second portable receiver. A second branch station also receives the second forwarding signal via the second, earth-orbiting satellite and broadcasts a fourth forwarding signal to a third portable receiver.

Abstract: A system and method for automatically directing a communication antenna to point to a desired wireless communication transceiver, is presented herein. The system includes a position location receiver, which receives signals indicating the position location information of the antenna and a position location transmitter and a processing mechanism, which determines calibration information of the antenna. The calibration information is achieved by first establishing a reference vector between the location of the antenna and position location transmitter and establishing a vector reference space and then calculate the necessary elevation and azimuthal components, within the vector reference space, to identify the proper calibration of the antenna. Once the calibration information has been determined, an alignment mechanism automatically orients the antenna.

Abstract: The invention relates generally to a digital broadcast system and receivers therein which are configured to allow the use of a reverse channel for transmitting responses to broadcast messages. The digital broadcast system is configured to receive requests for information from a mobile platform device (e.g., a GPS receiver) and broadcast information request messages. The receivers are configured to receive a broadcast information request message and communicate with a telematics-enabled device in a mobile platform such as a cellular telephone to initiate a transmission of a response message therefrom.

Abstract: A Search Domain Reducing Frequency Transfer in A Multi-Mode Global Positioning System Used With Wireless Networks is disclosed.

Abstract: A method and apparatus for creating and distributing satellite tracking data in a compact format to a remote receiver. At least a portion of the satellite tracking data is extracted from memory and is formatted into a compact format. The compact formatted data is transmitted to the remote receiver via a distribution network.

Abstract: A system for providing a communication link among a plurality of mobile units comprises a broadband RF transceiver with antenna, a GPS receiver, an audio-visual interface, an electro-mechanical interface and a microprocessor with associated memory incorporated into each a mobile unit.

Abstract: A receiver for direct sequence spread spectrum code division multiple access signals (DS-CDMA) particularly for GPS signals includes a plurality of correlators. Each correlator includes variable level threshold circuits (29, 30) which follow integrate and dump registers (27, 28). The threshold level is set using the correlation noise level and predicted signal strength.

Abstract: A broadcasting or transmitting system using an artificial satellite. The artificial satellite is placed into an orbit in which individual artificial satellites orbit on an elliptical orbit so that at least one of the artificial satellites is always viewable within a pre-defined range of operational elevational angles in a zenith direction from a service area. A group of the artificial satellites are satellites on respective different orbits obtained by combining an inclination angle and an eccentricity squared of said elliptical orbit so that a time period during which one artificial satellite of the group of the artificial satellites is viewable from ground is substantially identical to a time period during which another artificial satellite of the group is viewable from the ground.

Abstract: An elliptical satellite system which carries out communication. The satellite orbits a height above the earth less than that necessary for geosynchronous orbits. When the satellite is near the apogee portion of its orbit, its velocity approximates the rotational velocity of the earth, and during that period it appears to hover over the earth. Each ground station on the earth always communicates a satellite within a predetermined position of its apogee, and hence that satellite appears to the ground station to hover over the earth. The satellite hence does not communicate with any earth station when it is outside of that apogee portion. During the times when the satellite is outside the apogee portion, its communication is therefore shut off to prevent.any possibility of interfering with geosynchronous satellites. During this time, the power supply on the satellite is also used to charge a battery on the satellite.

Abstract: A radar surveillance system includes a plurality of satellites a plurality of medium earth orbit satellites to provide continuous, long dwell coverage of a region of interest. Each satellite has an antenna having a main reflector and a subreflector electromagnetically coupled to the main reflector. A phased array generates multiple electromagnetic beams positioned so the electromagnetic beams reflect from the subreflector onto said main reflector. The system may be used in determining slow moving targets using a combination of monopulse anomaly and target spectral width measurements. The system also performs synthetic aperture radar imagery and focussed area fast moving target detection using alternating slope linear frequency modulated pulses. The plurality of medium Earth orbit satellites include a self-contained communications system consisting of high bandwidth self-relay crosslinks, high bandwidth downlink, and direct broadcast downlinks for processed data.

Abstract: A system for determining the location of an object includes an interrogator remote from the object and a transponder located at the object. The interrogator receives GPS signals and transmits pre-positioning data and a tracking signal to the transponder. The pre-positioning data includes pseudorandom noise (PRN) code number, Doppler frequency offset and code phase offset while the tracking signal includes reference time and frequency information. The transponder collects RF samples of at least one of the GPS signals associated with one of the PRN code numbers and correlates the RF samples of the GPS signal against code replicas of the GPS signal based on the Doppler frequency offset, code phase offset and reference time and frequency information for that GPS signal to produce the correlation snapshot. The transponder transmits the correlation snapshot to the interrogator and the interrogator determines the pseudorange associated with the GPS signal using the correlation snapshot.

Abstract: The relative movement of a receiver and transmitter in a communications system is used to advantage by electronically synthesizing a larger apparent antenna aperture, thereby increasing signal-to-noise ratio. The approach may be used regardless of whether the transmitter is fixed and the user or vehicle is moving, or the user or vehicle is fixed and the transmitter is moving. According to the method, the apparent angle between the receiver and transmitter is determined relative to the direction of movement and used to produce time-delayed replicas of the received signaling stream which are coherently added to synthesize the increased apparent receiver antenna aperture. Since only the receiver is modified according to the invention, existing transmitters and infrastructures can be used without modification. Significant cost potentials can be realized via economy of scale, due to relatively simple FFT processing.

Abstract: A non-geostationary low earth orbit satellite constellation using elliptical orbits with apogees in the Northern Hemisphere to provide continuous coverage over the Continental United States of America (CONUS), and by extension to the other points in the Northern Hemisphere situated above 25° north latitude. The constellation provides time-continuous visibility with at least one satellite to any point above 25° North latitude. An extension of the constellation has a combination of the elliptical orbits and at least one equatorial orbit to provide virtual global coverage. The distribution of capacity is deployed in proportion to the distribution of populations in the land masses of the earth. Time continuous visibility with at least one satellite is maintained by any point on earth north of the 50° South latitude, with a minimum number of satellites deployed.

Abstract: In a communication satellite constellation which uses CDMA and multiple spot beams for point-to-point communication, a system is provided for broadcasting regionally related information within a spot beam by establishing a Frequency/Walsh Code Tiling over the Earth's surface, and enabling a user terminal at a given position to tune to an appropriate frequency and Walsh Code to receive the information broadcast from a satellite over a forward beam downlink. The information, e.g. regional messages such as local weather or traffic, is transmitted to the satellite from a ground station or gateway that receives the information from a Broadcast Processing Center. In a preferred embodiment a dedicated Frequency Division Multiplex (FDM) channel within each spot beam transmits the regional broadcast messages at the Tiles in accordance with the Walsh Code designations of the Tiles.

Abstract: A communications satellite method and are provided for controlling a configuration of spot beams produced by a communications satellite. A plurality of spot beams are generated by a communications satellite while maintained at a first orbital position with respect to a first portion of the earth. The plurality of spot beams are configured in a first cell pattern to substantially encompass a first portion of the Earth. The satellite is moved to a second orbital position with respect to a second portion of the earth. Once moved, the satellite is reconfigured such that a second plurality of spot beams form a second pattern 85 to substantially cover the new portion of the earth of interest. A network of switches allows the satellite 10 to be reconfigured for operation from multiple orbital positions. The switching network directs individual feeds to different signal paths having different bandwidth and power capabilities.

Abstract: Method for accounting for factors (such as temperature) causing systematic errors (time-varying or constant) in a clock, such as a clock used in a ranging receiver (for use with a positioning system such as the Global Positioning System), and a corresponding clock system (including a clock and a filter such as a Kalman filter) for providing clock time and error, used for example in a ranging receiver. The invention adds new state vector components to account for systematic error. The process update equation used in the navigation solution is accordingly extended to include the additional components of the state vector.

Abstract: A method and device for using a single antenna for simultaneously receiving radio frequency signals in a first radio frequency band and radio signals in a second radio frequency band different from the first radio frequency band.

Abstract: A system (20) and method (30) for estimating the location of a terrestrial-based user terminal (23) is provided. The user terminal (23) is capable of measuring the relative signal strengths of a plurality of spot beams pilot signal emitted from a geostationary satellite (22). The user terminal (23) then estimates its position based on the measured relative signal strengths. Using this approach, the user terminal (23) can quickly determine its location without prior knowledge of its position or delay time.

Abstract: A method and apparatus for distributing satellite tracking data to a remote receiver. At least a portion of the satellite tracking data is extracted from memory and is formatted into a format prescribed by a remote receiver. The formatted data is transmitted to the remote receiver via a distribution network.

Abstract: A communications satellite method and are provided for controlling a configuration of spot beams produced by a communications satellite. A plurality of spot beams are generated by a communications satellite while maintained at a first orbital position with respect to a first portion of the earth. The plurality of spot beams are configured in a first cell pattern to substantially encompass a first portion of the Earth. The satellite is moved to a second orbital position with respect to a second portion of the earth. Once moved, the satellite is reconfigured such that a second plurality of spot beams form a second pattern 85 to substantially cover the new portion of the earth of interest. A network of switches allows the satellite 10 to be reconfigured for operation from multiple orbital positions. The switching network directs individual feeds to different signal paths having different bandwidth and power capabilities.

Abstract: An information providing method and apparatus for providing information to a moving body via an artificial satellite. Information for selecting a desired information and position information of the moving body is transmitted, from the moving body. Information is provided to the moving body from the artificial satellite depending upon the position information of the moving body and the desired information, on the basis of information from the moving body.

Abstract: A system for directing an antenna for transmission over a two-way satellite network is disclosed. A transceiver is coupled to the antenna; the transceiver transmits and receives signals over the two-way satellite network. A user terminal is coupled to the transceiver and executes an antenna pointing program. The program instructs a user to initially point the antenna to a beacon satellite using predefined pointing values based upon the location of the antenna. The program receives new antenna pointing parameters that are downloaded from a hub over a temporary channel that is established via the beacon satellite. The program displays the new antenna pointing parameters and instructs the user to selectively re-point the antenna based upon the downloaded new antenna pointing parameters.

Abstract: A first pair of antennas are mounted on a satellite spaced along a first axis and a second pair of antennas are spaced along a second axis for receiving signals from another satellite in orbit with the satellite, the first and second axes being orthogonal to a yaw axis that points toward the centroid of the celestial body about which the satellite orbits. Each pair of antennas are used to derive phase angle and signal strength differences, and these differences are used for deducing a yaw orientation of the satellite about the yaw axis.

Abstract: A communication satellite system (100) is established using one or more satellite constellations (110, 120). The two or more satellite groups (110, 120) are connected via long range crosslinks (145) which provide a communication path between the long range satellites (150, 170) in the two satellite groups (110, 120). Each satellite group (110, 120) comprises long range satellites (150, 170) and short range satellites (160, 180) which are interconnected using short range crosslinks (155, 175). A single antenna on each satellite provides both crosslinks. The long range crosslink (145) is established using the antenna's main beam and the short range crosslinks (155, 175) are established using the antenna's sidelobes.

Abstract: A satellite communication system including an interface device for distributing satellite signals received from an outdoor unit (ODU) to a plurality of indoor units (IDUs) connected to a local area network (LAN), at a particular site. Only two cables, a power cable and a cable connected to the LAN, must be installed between the interface device and the site containing the IDUs. Accordingly, the installation of IDUs at a site is simplified and has the flexibility of allowing future satellite based services to be added without requiring the installation of new cables between the ODU and the IDUs. The satellite communication system also permit flexibility among connected devices, including to which other devices they are connected, how they are connected to other devices and what types of connections are used.

Abstract: A system for and method of providing optimizing the antenna patterns on a first satellite and a second satellite that operate in conjunction to deliver content to a single radio receiver. The process begins by first selecting an objective predictive model for predicting link margin at a first location and a link margin at a second location. The model is used further to determine an initial required transmit power flux densities to achieve the first and second link margins. Then the power flux density is adjusted for the first location by decreasing the power flux density for the first satellite and simultaneously increasing the power flux density for the second satellite. The predicted joint availability for the first location is then predicted. In the event the required power flux density cannot be achieved to achieve a desired joint availability across an entire geographical region, the power flux density for both the first and second satellites for the first location are decreased.

Abstract: A satellite broadcast system and method, particularly useful for television signals, allows for local as well as nationwide broadcast service by allocating greater satellite resources to the more important local service areas. This is accomplished by broadcasting a non-uniform pattern of local service beams and designing the system to establish different service area priorities through factors such as the individual beam powers, sizes, roll-off characteristics and peak-to-edge power differentials. Frequency reuse is enhanced by permitting a certain degree of cross-beam interference, with lower levels of interference established for the more important service areas.

Abstract: A satellite broadcast system and method, particularly useful for television signals, allows for local as well as nationwide broadcast service by allocating greater satellite resources to the more important local service areas. This is accomplished by broadcasting a non-uniform pattern of local service beams and designing the system to establish different service area priorities through factors such as the individual beam powers, sizes, roll-off characteristics and peak-to-edge power differentials. Frequency reuse is enhanced by permitting a certain degree of cross-beam interference, with lower levels of interference established for the more important service areas.

Abstract: In a satellite network with on-board switching and bandwidth on demand, traffic monitoring is required to facilitate billing data collection and to avoid congestion at the satellite. In addition to traffic monitoring, performance monitoring is necessary to quickly respond to link degradation or possible equipment anomalies. Monitoring terminals specially equipped with traffic measuring and policing and link performance measuring capabilities are used to monitor traffic and performance. The monitoring terminal is located in each satellite beam to perform the monitoring functions for that beam. The monitoring terminals are low-cost terminals that receive down-link traffic in their respective beam, and record statistics on a per transmit-terminal or per virtual connection basis. Records are periodically transmitted to a central location where they are processed for billing, enforcing traffic contracts, and taking actions against link degradations.

Abstract: A satellite broadcast system and method, particularly useful for television signals, allows for local as well as nationwide broadcast service by allocating greater satellite resources to the more important local service areas. This is accomplished by broadcasting a, non-uniform pattern of local service beams and designing the system to establish different service area priorities through factors such as the individual beam powers, sizes, roll-off characteristics and peak-to-edge power differentials. Frequency reuse is enhanced by permitting a certain degree of cross-beam interference, with lower levels of interference established for the more important service areas.

Abstract: Antenna elements 20 are arranged at intervals “d” greater than &lgr;/2, e.g., 5&lgr;. A signal received by an antenna element 20 is sent by way of an antenna multiplexer 21 to a receiver 23, where the signal is demodulated. The thus-demodulated signal is sent to a phase-and-power detection section 25, where a phase and power of the signal are detected. On the basis of the result of such detection, a control section 26 calculates the phase and power of a transmission signal. On the basis of the result of the calculation, a transmission signal generation circuit 27 transmits a transmission signal to each of the antenna elements 20 by way of the antenna multiplexer 21.

Abstract: A low-cost satellite system and method for using it for continuously monitoring near space and providing real-time data, both astronomical and space-environmental, is described and claimed. Low cost is achieved by disposing outwardly facing active and passive detection means aboard telecommunications and other satellites, and providing data from such means to subscribers. The system and method enable practical means to monitor space for approaching foreign bodies, providing high quality information for e.g., underfunded educational institutions while making enhanced use of geostationary orbits, a scarce resource, among other benefits.

Abstract: An electromagnetic wave radiation control apparatus includes an antenna, a modulator, an amplifier, and a radiation control unit. The modulator modulates a carrier wave based on a transmission signal to output a modulated signal, wherein the modulator stops the output of the modulated signal in response to a power off command. The amplifier amplifies the modulated signal such that the amplified signal is radiated as electromagnetic wave from the antenna, when the modulated signal is outputted from the modulator. The radiation control unit generates the power off command to the modulator, when radiation of electromagnetic wave in a current radiation direction of the antenna is inhibited, or when a level of a reception signal by the antenna is equal to or lower than a predetermined minimum level.

Abstract: Technique for determining the location of a mobile unit in a wireless communication system and presenting it to a remote party. In a scenario with first and second position estimates, the first position estimate is presented within a first predetermined time interval of call setup between the mobile unit and the remote party, and, if the second position estimate is available for presentation to the remote party, the second position estimate is presented within a second predetermined time interval after presentation of the first position estimate. Else, status information on availability of the second position estimate is presented within the second predetermined time interval.

Abstract: A system for directing an antenna for transmission over a two-way satellite network is disclosed. A transceiver is coupled to the antenna; the transceiver transmits and receives signals over the two-way satellite network. A user terminal is coupled to the transceiver and executes an antenna pointing program. The program instructs a user to initially point the antenna to a beacon satellite using predefined pointing values based upon the location of the antenna. The program receives new antenna pointing parameters that are downloaded from a hub over a temporary channel that is established via the beacon satellite. The program displays the new antenna pointing parameters and instructs the user to selectively re-point the antenna based upon the downloaded new antenna pointing parameters.

Abstract: A communications system for determining the position and velocity of an object using a plurality of GPS signals transmitted by a plurality of GPS sources includes an interrogator remote from the object and responsive to the plurality of GPS signals. The interrogator transmits an RF signal including GPS source information and at least one of frequency information and time and code phase information of at least one of the GPS signals. The system also includes a transponder positioned on the object and responsive to the RF signal and the plurality of GPS signals. The transponder tracks one of the plurality of GPS signals in response to the GPS source information and the frequency information and time and code phase information. The transponder generates a correlation snapshot and transmits the snapshot to the interrogator.

Abstract: The invention provides GPS navigational system for a satellite in space which comprises a front end section having an input for receiving GPS signals from a plurality of satellites, a digital preprocessor connected to the front end section for digitally preprocessing the GPS signals received from the front end section, and a signal processor connected to the digital preprocessor for decoding the GPS signals to determine a position of the satellite. An on-board computer is provided and a first data bus line connects the data processor and the signal processor for bi-directional data exchange therebetween and a second data bus line connects the signal processor and the on-board computer for bi-directional data exchange therebetween.

Abstract: A method and apparatus for mitigating multipath signal distortion using a multi-element antenna array is provided. The multi-element antenna array is used to discriminate between the desired signal and its multipath components based on spatial angle of arrival. A reference signal, provided by the positioning system receiver, is used to compute element weightings that are utilized to null out the multipath components before they reach the receiver.

Abstract: The invention relates to a method of locating a jammer (14) of a satellite telecommunications system (10). To locate the jammer, at least two of the following three measurements are performed: a measurement of the difference between the instant of arrival at the telecommunications satellite and at a detection satellite (16) of signals transmitted at the same time by the jammer (14), the detection satellite being used solely for detection purposes; a measurement of the difference between the frequencies received by the telecommunications satellite and by the detection satellite, for a signal transmitted by the jammer; and an interferometric measurement of the angle between a direction associated with the detection satellite and the straight line between said satellite and the jammer (14).

Abstract: A non-geostationary low earth orbit satellite constellation using elliptical orbits with apogees in the Northern Hemisphere to provide continuous coverage over the Continental United States of America (CONUS), and by extension to the other points in the Northern Hemisphere situated above 25° north latitude. The constellation provides time-continuous visibility with at least one satellite to any point above 25° North latitude. An extension of the constellation has a combination of the elliptical orbits and at least one equatorial orbit to provide virtual global coverage. The distribution of capacity is deployed in proportion to the distribution of populations in the land masses of the earth. Time continuous visibility with at least one satellite is maintained by any point on earth north of the 50° South latitude, with a minimum number of satellites deployed.

Abstract: Methods and systems are provided for determining a position of a mobile terminal that includes a satellite radiotelephone and a global positioning system (GPS) receiver based on knowledge of the position of the communication satellite spot-beam in which the mobile terminal is located. Using knowledge of the location of the communication satellite spot-beam, the present invention can resolve the one-millisecond ambiguity, that typically arises from the code repeat length where relative code phase may be determined but absolute code phase (i.e. one millisecond increments) could be off by one or more code periods. The spot-beam identifier is obtained from the satellite communication system and used to determine the geographic location of the spot-beam. Trial positions, i.e., candidate mobile terminal positions, are then selected to cover the spot-beam area, with spacing between trial positions provided to account for the one-millisecond ambiguity.

Abstract: A radar detection and imaging system provides for the simultaneous imaging of the stationary objects on the earth's surface and the detection and imaging of moving targets. The radar system includes at least one transmitting aperture and a plurality of receiving apertures that are simultaneously operated in a synthetic aperture radar (SAR) mode caused by the motion of the satellite or airborne platform on which they are mounted. Each receiving aperture is connected to its own coherent receiver and the digitized signals from all receivers are processed to image both stationary clutter and moving targets. The system employs space-time adaptive processing (STAP) algorithms to better compensate for channel mismatches, better suppress stationary clutter, and to suppress mainbeam jamming. Moving target detection and estimation modules are also included and are their performance is improved as a result of the STAP algorithms.

Abstract: A method for dynamically obtaining a unified classification information graph which provides a navigation system for a user to access sought information. The method includes providing a multiple information resources that include hierarchy of categories that are associated, each, with a category. Leaf categories in the hierarchy are connected to information pages. The method filter provides generating a unified classification information graph by using the hierarchy of categories and the categories of the multiple information resources. The unified classification graph includes hierarchy of unified categories. Leaf unified categories in the hierarchy are connected to inflation pages, whereby, information pages accessible through the hierarchy of the multiple information resources are also accessible through the hierarchy of the unified classification information graph.

Abstract: A system for improving the accuracy of location coordinate determined in a survey of a chosen region. A grid of spaced apart points is imposed on the region, and a set of survey control points is provided. A “near set” of nearest survey control points is associated with each grid point, and the number of elements in this new set may vary with the grid point. Definition of a near set can vary from one grid point to the next. For each grid point, a transformation T from a first coordinate system to a second coordinate system is determined that minimizes a collective difference between coordinates of each survey control point in the near set and the corresponding coordinates of that survey control point under the transformation T. For one, two or three coordinates of each grid point, the difference(s) between the coordinate(s) of the grid point in the near set and the corresponding coordinate(s) of that grid point under the transformation T are computed.

Abstract: A system and method for providing remote viewing of satellite transponder plots. The system and method piovides for remote viewing of transponder plots derived from transponders located on a satellite that communicate with ground terminals having an antenna. The system comprises an antenna switch for receiving transponder signals from the antenna. A spectrum analyzer is coupled to the antenna switch for generating transponder plots. An equipment control computer is coupled to the antenna switch and the spectrum analyzer that selectively routes signals from the antenna switch to the spectrum analyzer and routes transponder plots generated by the spectrum analyzer. A server computer is coupled to the equipment control computer that stores the transponder plots generated by the spectrum analyzer that are routed by the equipment control computer.

Abstract: Faraday Rotation causes rotation of the plane of polarization of plane polarised radiation emitted by a radar e.g. a synthetic aperture radar and, if returns polarized in orthogonal planes are measured at the synthetic aperture radar in order to determine polarimetric characteristics of the ground, which could show up features of the ground such as crop patterns, the measurements made at the SAR are contaminated by the Faraday Rotation. In the invention, the transmitted plane polarized beam is pre-rotated in transmitter 9, the radar returns in receiver 13 are mathematically adjusted in signal formatting 14, 15 to compensate for just the pre-rotated angle, to produce data streams on downlink 16 uncontaminated by the Faraday Rotation.

Abstract: An apparatus and method is disclosed for providing a user with task-specific information that includes a portable instruction system that may be worn by a user, and includes, a computer sufficiently lightweight and designed to be worn by a user to which a memory has been connected. The system includes a display device that can receive display signals from the computer for visual display to the user and an input device by which the user enters commands to the computer. An instructional program is provided that the computer accesses and stores in memory in response to a user command and displays information concerning a task to be performed by the user on the display device in response to commands from the user.

Abstract: A dynamic repeater configuration for satellite systems is disclosed that allows for multiple broadcast of channel information and multiple subchannel allocations on uplink and downlink beam signals. The apparatus comprises an input multiplexer, a subchannel routing switch matrix, a channel routing switch matrix, and an output multiplexer. The input multiplexer receives the uplink signal and produces at least a first channel signal therefrom. The subchannel routing switch matrix receives the uplink signal, separates at least one channel signal into at least one subchannel, routes the subchannel from a selected uplink subchannel into a selected downlink subchannel, and recombines the selected downlink subchannels into a second channel signal. The channel routing switch matrix routes the first channel signal into a first downlink channel signal and the second channel signal into a second downlink channel signal. The output multiplexer combines the first and second downlink channels into the downlink signal.

Abstract: A communication system, wherein plural elliptical orbits in which an apogee is located on a specified service area are so defined that an individual right ascension of north-bound node may be established with a designated angle. A satellite is made to travel on an individual elliptical orbit and a group of satellites to be arranged on said elliptical orbits are used so that at least one of artificial satellites having a communication system may be always viewable within a pre-defined range of ascending vertical angle in a zenith direction from the service area.