Abstract: A satellite-based cellular telecommunications system employing a constellation of telecommunications satellites in medium earth orbit to provide multibeam radio frequency (rf) communications links for worldwide cellular telephone service with a minimum number of satellites. The telecommunications satellites are placed in a plurality of inclined orbits about the earth at an altitude of between approximately 5600 and 10,000 nautical miles. The characteristics of the orbits, such as the number of orbits, the inclination of each orbit, the number of satellites in each orbit and the altitude of the satellites, are tailored to maximize the coverage area of the satellites and their related line-of-sight elevation angles, while minimizing propagation time delays, the number of beam-to-beam and satellite-to-satellites handovers, and the total number of satellites.

Abstract: There is provided a mechanism for networking satellite and terrestrial networks. It comprises: maintaining subscriber-received power levels of terrestrial network transmissions about one order of magnitude above co-channel satellite transmissions to overcome interference and maintaining subscriber transmissions to terrestrial networks at power levels about one order of magnitude of the below co-channel transmissions to satellite networks to avoid causing interference at the satellite. Such power level maintenance is provided by the network in communication with such subscriber. Moreover, a non-orbiting ("grounded") satellite cooperates as a switching node of both the satellite network and a terrestrial network to relay information between a terrestrial subscriber and the satellite radiotelephone network over a terrestrial network. The terrestrial network and the satellite network may communicate via either the inter-satellite spectrum or the terrestrial-to-satellite spectrum.

Abstract: A satellite-based navigation system providing improved accuracy and reliability over wide geographical areas, including remote regions, is disclosed. Ranging-type signals transmitted through two or more commercial geostationary telecommunication satellites are received at known reference locations where navigation and correction information is generated and transmitted back to remote users. At the same time, the reference stations receive signals from the Global Positioning System (GPS), generate corrections for the GPS measurements, then transmit these corrections to the remote user. The remote user receives all of this information plus direct measurements from both the GPS and the geostationary satellites and, using conditional error processing techniques, provides a position solution whose accuracy and reliability exceeds that of GPS alone.

Abstract: There is disclosed a global positioning system receiver method and system which converts the analog signals to digital signals prior to performing signal acquisition and GPS unique processing functions. The A/D converter uses full null zone processing to increase anti-jamming capability and 4-level output to reduce signal processing. A single analog and digital channel is used for both the L1 and L2 channels as well as for all P(Y)-code and C/A-code thus allowing full multi channel tracking with several channels each tracking a separate signal while the remainder of the channels rove over all of the signals on the alternate L-band with programmable duty cycles. The system allows for Y-code substitution for P-code by multiplexing a portion of the Y-code generated between multiple channels.

Abstract: A real time method of rectifying remotely sensed image data provided by a radiation measuring instrument, such as used on spin stabilized geostationary satellites, rectification being obtained by determining a number of satellite parameters including radiation measuring instrument pointing parameters, the method comprising the following steps:1) prediction of the rectification parameters by statistical analysis from a number of preceding images;2) reading a limited number of raw image lines to facilitate accurate position of the South or North horizon, depending on scan direction of the incoming image;3) determining the spin rate of the satellite from the limited number of raw image lines and predicting the spin rate variations for the rest of the image;4) refining the attitude and the radiation measuring instrument pointing parameters using the horizon information obtained in real time;5) computing the position of the other horizon and the center of the image based on the first detected horizon and geometric

Abstract: This invention relates to a satellite signalling system, such as a satellite paging system, having signal coverage over a very wide area. The satellite signalling system comprises a satellite to which is coupled an antenna for providing a signal beam having a variable beam area. The satellite can control the position of the antenna such that the signal beam can be directed in a predetermined sequence to a plurality of locations on earth. The antenna is arranged to vary the signal beam's area in dependence on the location to which the signal beam is directed. The signal beam comprises a data signal having a data rate which can be varied by the antenna in dependence on the beam area.

Abstract: A single axis tracking system for a satellite moving in an inclined orbit. A linear antenna mount is used which is equipped for longitudinal tilt adjustment to enable an antenna to accurately track the longitudinal centerline of the figure 8 path of a satellite in an inclined orbit from any geographic location within the footprint of the satellite. The trajectory of the satellite is determined relative to the geographic location of the antenna mount. A time referenced tracking control signal moves the antenna mount. The signal from the satellite is periodically sampled and compared with stored values to verify the calculated trajectory. If a significant deviation occurs over a predetermined period, a new trajectory is automatically calculated and the time referenced trajectory signal is adjusted accordingly.

Abstract: A demodulation frequency plan for use in a global positioning system (GPS) receiver, having three demodulation stages for L1 and L2 signal channels, in which identical local oscillator frequencies are used in the L1 and L2 channels at each demodulation stage, to minimize phase error differences between the two channels. The third stage provides an output at an intermediate frequency high enough to carry the full information bandwidth, thereby simplifying digital sampling of the signal, which is also performed in the third stage. Sampling is performed at a high enough rate to facilitate subsequent conversion to baseband. Moreover, the sampling rate is a binary multiple of the intermediate frequency, and this binary relationship further simplifies conversion to baseband.

Abstract: A satellite communication system includes first, second and third electromagnetic radiators, the first and second of which are a contiguous pair, and the second and third of which are also contiguous. Two channels of information are each modulated onto carriers at the same frequency by means of mutually independent modulations. The modulations may be by orthogonal pseudorandom codes. The first channel is applied to the first and second radiators, and the second channel is applied to the second and third radiators. The first and second radiators form a beam which if decoded for the first modulation is independent to that formed by the second and third radiators. Consequently, the feed apertures overlap in a manner which provides a more constant field intensity in each beam, and which saves size and weight by comparison with a single radiator of corresponding aperture for each channel.

Abstract: To reduce error introduced by the local oscillator in the velocity calculations, the receiver has two "tracking channels" and a microcomputer. With numbers required to, simultaneously, lock each of the "tracking channels" each to a respective satellite signal, the microcomputer employs a differential doppler technique to calculate the receiver velocity. The microcomputer calculates a number which represents the difference between the apparent doppler frequency shift of the carrier signal which is transmitted by the first "tracking channel" satellite and which is measured over a specific time period and the apparent doppler frequency shift of the carrier signal which is transmitted by the second "tracking channel" satellite and which is measured over substantially the same time period.

Abstract: A GPS receiver apparatus retrieves a maximum correlation point between a PN code involved in a satellite signal and a generated PN code with use of n detecting means each concurrently processing the retrieval operation to acquire the PN code of the satellite signal. The apparatus acquires the PN code of the satellite signal, unless said maximum correlation is yielded, by effecting a correlation processing or taking the synchronization among phases of the PN code in which the generated PN code is shifted in its phase by n/2 bits to retrieve the maximum correlation point. The apparatus further tracks GPS radiowaves with the use of a plurality of said detecting means which has been used to acquire the PN code.

Abstract: A land vehicle navigation system is adapted to display the present position of a vehicle by receiving signals from a combination of satellites under the global positioning navigation system. The present position of the vehicle is displayed on a screen, superposed over map data. To obtain the best global positioning data, the combination of satellites is selected in connectio with the visibility. To perform the positive reception of signals from the satellites as the vehicle is running in an urban area, data relating to the building height around the area can be obtained from a geographical information section including data indicative of the map and the building height distribution with respect to the area to determine the visibility.

Abstract: The system comprises at least two geosynchronous satellites (S-A, S-B) having the same elliptical orbit and the same trace on the ground. The longitudes of ascending node are displaced. The moving bodies have a vertically pointed fixed antenna. The system operates for 24 hours continuously with one or other of the satellites.

Abstract: On-board satellite switching is performed in three stages, an outer stage of switching on the up-link side for routing the received signals to either demodulators or frequency translators, a first inner stage of switching, preferably a baseband switch and processor, for routing and processing the outputs of the demodulators, a second inner stage of switching, e.g., a microwave switch matrix, for routing the outputs of the frequency translators, and an outer stage on the down-link side for assembling and routing the down-link spot beams. For a multiple hopping-beam system, the outer stages are microwave switch matrices, and for a hybrid scanning-hopping system the outer stages are beam forming matrices. A general purpose modified rearrangeable switch matrix is also disclosed.

Abstract: There is disclosed a system and technique for providing an audio verification of Global Positioning System (GPS) receiver signal acquisition. In a GPS receiver, the correlated output of the GPS signal is generally represented as a data modified CW signal with a Doppler component caused by the movement of a GPS satellite with respect to the receiver. Due to the Doppler component, this signal output provides a signature which is indicative of the particular satellite from which the signal is being received. The signal output is mixed with a local oscillator to produce a beat frequency in the audio band which may be filtered and coupled to an audio amplifier to produce an audio tone. The presence of the audio tone indicates the acquisition of a selected satellite signal and its audio frequency is indicative of the particular satellite signal being received.

Abstract: A satellite receiver which can selectively inhibit the reception of radio wave of the improper program. This receiver comprises: a receiver unit; a reproducer unit to reproduce the signal received by the receiver unit; a control unit including (a) a first memory to store the designated transponder number, (b) a second memory to store the transponder number which is parental locked, and (c) a generator to generate a parental lock signal when the memory contents of the first and second memories coincide; and means for disabling the signal from the designated transponder to be reproduced by the reproducer unit in response to the parental lock signal. With this receiver, the radio wave from the designated transponder cannot be received.

Abstract: A system for causing an antenna controller for a satellite antenna to determine the alignment position of the antenna for a given satellite, whereby antenna installation time may be substantially reduced when the alignment position of the antenna for a large number of satellites must be determined. The system includes means for measuring the alignment position of the antenna for at least two reference satellites; and means for processing said measurements with stored data indicating the relative positions of the reference satellites and other satellites in accordance with an algorithm to determine the alignment positions of the antenna for the other satellites. The system also includes means for causing an antenna controller for a satellite antenna to determine the skews of the linear polarization axis of the antenna for respectively matching the linear polarization axis of odd-numbered and even-numbered channels received from a satellite.

Abstract: In antenna arrays having normally unexcited or little-excited elements, a technique for configuring the array to provide both global and spot beam coverage, wherein the normally unexcited or little-excited elements are excited at a higher level, together with other normally excited elements to provide spot beam coverage, the normally unexcited elements being left unexcited to provide global beam coverage. Ring redundancy configurations for amplifiers in a transponder provided in the configuration are optimized to minimize additional hardware requirements. The specific example of the INMARSAT II satellite system is discussed.

Abstract: A satellite receiver which selects one of radio waves from a plurality of satellites and receives the selected radio wave. This receiver comprises; a satellite number designation switch; an antenna controller for allowing a parabola antenna to face the designated satellite in accordance with the designation by the designation switch; a memory to store the data corresponding to a correction amount of the position of a probe for each satellite; a drive motor to drive the probe to the position corresponding to the data outputted from the memory; and a control circuit to allow the data for the satellite designated by the designation switch to be supplied from the memory to the drive motor. The probe position is corrected in accordance with the designated satellite.

Abstract: In a telecommunications satellite system operating with quasi-stationary orbits and comprising a plurality of earth satellites having elliptical orbits appearing at nearly the same location in space in cyclical succession and relieving one another in radio operation, a different range of the respective satellites to be engaged and disengaged from the ground stations is guaranteed. This enables an additional transit time for storage of data transmitted about the switching time from one satellite to another. To this end, the apogee of the orbital ellipse is shifted to such a degree from the Northern-most or, respectively, Southern-most orbital point against the direction of flight of the respective satellite that an adequate signal repetition of the bits to be transmitted occurs about the switching time. In a specific system comprising three satellites on elliptical orbits having an eccentricity of 0.

Abstract: A satellite communications system employs separate subsystems for providing broadcast and point-to-point two-way communications using the same assigned frequency band. The broadcast and point-to-point subsystems employ an integrated satellite antenna system which uses a common reflector (12). The point-to-point subsystem achieves increased communication capacity through the reuse of the assigned frequency band over multiple, contiguous zones (32, 34, 36, 38) covering the area of the earth to be serviced. Small aperture terminals in the zones are serviced by a plurality of high gain downlink fan beams (29) steered in the east-west direction by frequency address. A special beam-forming network (98) provides in conjunction with an array antenna (20) the multiple zone frequency address function. The satellite (10) employs a filter interconnection matrix (90) for connecting earth terminals in different zones in a manner which permits multiple reuse of the entire band of assigned frequencies.

Abstract: A method and apparatus for rapidly and accurately determining the position coordinates of a remote, movable receiver relative to a fixed reference receiver. The technique utilizes successive code measurements and carrier phase measurements of both the L.sub.1 and L.sub.2 carrier signals broadcast from four or more orbiting GPS satellites. Code measurements based on a weighted average of the individual L.sub.1 and L.sub.2 code measurements in each satellite/receiver link are adjusted in accordance with the corresponding carrier phase measurement for an L.sub.1 -L.sub.2 carrier difference signal and are further smoothed over time. This yields a rapid determination of the remote receiver's position coordinates, with progressively increasing accuracy. After merely about two to three minutes of processing, a wide laning carrier phase procedure can be implemented to yield a position determination that is accurate to within about one centimeter.

Abstract: A TVRO earth station having a satellite seeking system comprising at least one controllable motor for adjusting the position of an antenna for receiving signals from a satellite having multiple transponders transmitting signals at prescribed nominal center frequencies and with different polarizations, control means for energizing the motor to move said antenna along a predetermined satellite-searching path, a receiver for receiving the incoming signals from the antenna and successively tuning to the center frequencies at each of a succession of intervals along the searching path, means responsive to the signals detected by the receiver for producing a signal or value representing the quality of the detected signals at each of the successive intervals along the searching path, and means responsive to the quality-representing signal or value for identifying the locations along the searching path at which the antenna receives signals from a satellite.

Abstract: In the storing mode, an operator section is operated to direct a parabolic antenna toward a broadcasting satellite and to select a desired channel. After the desired channel is seized, a predetermined label is input from a label input part. The satellite position and the selected channel are stored in a memory with the label attached thereto. When a search operation is performed, the direction of the antenna is gradually adjusted. Whenever the direction of the antenna is adjusted, the receiving frequency is scanned to receive each channel. When a signal is received by the frequency scanning, the type of the satellite is recognized depending on the odd or even group of channels and on whether the antenna is set to horizontally or vertically polarized wave reception. The type of the satellite as recognized, the antenna direction at that time, and the desired receiving channel transmitted from the satellite are stored into memory with a given label attached thereto.

Abstract: Improvement to satellite telecommunication systems using SS-TDMA (Satellite Switch Time Domain Multiple Access) technique equipped with on board regenerative repeaters consisting of: 1. Transmitting from ground to the satellite a signal (CM) with high frequency stability and in harmonic relationship with digital data rate by modulating the carrier sent by a beacon station for fine tracking of on-board antennas. The signal (CM) being synchronized to the plesiochronous clock (CPL) common to all ground stations is used for: a. on board bit re-synchronization of the data stream after demodulation and re-generation on board of the asynchronous data arriving at the satellite; b. synchronization of reference words related to start of frames sent by the satellite. 2. Modulating the signal CM with digital signals, to be used as high speed telecommand which operate in a totally independent way of the telecommand system usually adopted for satellite control.

Abstract: A differential navigation system applicable to mobile users and covering a wide range geographic area, including remote regions. A reference receiver of known location tracks a navigation information service, computes differential data with respect to that information and communicates the data to a transmitting unit. The transmitting unit transmits differential data via a commercial geosynchronous earth satellite relay to a mobile user located no more than 500 miles from the reference receiver, but possibly located in a remote region. The mobile user receives the relayed signal with a non-directional, circularly polarized, non-stabilized antenna. Reception at a sufficient data rate with sufficient reliability is made possible by formatting the differential data using spread spectrum techniques.

Abstract: A method of and apparatus for setting the direction of a parabolic antenna towards a broadcasting satellite, suitable for use in the case where a plurality of satellites are available for service. The elevation angle and the azimuth angle of the antenna with respect to each satellite are minutely adjusted while the state of receiving of waves from the satellite is watched, and the values of the elevation and azimuth angles for each satellite are stored in a memory section when the optimum state of receiving is attained. When the user selects one of the satellites through a selecting section, a control section operates to activate a driving section to swing the antenna vertically and horizontally in accordance with the stored optimum data, thus directing the antenna correctly towards the designated satellite.

Abstract: A satellite communications system and method of communication which results in increased frequency-reusage within assigned frequency bands and allows for a reduction in satellite transponder requirements per unit of bandwidth employed. The disclosed system employs a satellite in a geostationary orbit having transponders and one or more large-aperture, high-gain antennas that provide a broad-area beam for a relatively wide service area and for transmitting to and receiving signals from N narrow-area beams for N respective sub-areas, the sub-areas corresponding to the high-traffic nodes. Both beam types operate in the same allocated frequency bands but with opposite linear or opposite handed circular polarizations, or, alternatively, with arbitrarily determined portions of the allocated frequency band pairs with dual polarization so that the allocated frequency spectrum is used at least N+1 times.

Abstract: An antenna tracking device comprising an antenna which is so controlled in direction as to receive a plurality of beacon signals at different frequencies transmitted from a plurality of stationary satellites, respectively, which are spaced apart from each other by a relatively small distance, error detector connected to the feed of the antenna for detecting error signals each representing the difference between the incoming direction of each beacon signal and the axial direction of the main beam of the antenna, reference signal generator responsive to each beacon signal delivered to a receiver for generating a reference signal, and a tracking receiver which receives the reference signals and the error signals to generate the tracking error signals each consisting of mutually orthogonal components.

Abstract: A system and method for nagivating using satellites for transmitting coded ime signals as well as additional data for the purpose of determining position, locating operations, navigation, etc., which includes, transmitting only a time signal consisting of an identification code from a plurality of orbiting navigational satellites directly to users, and distributing any data required for determining position, locating operations and navigation as well as any data on orbiting satellites and ground stations by transmission from a small number of synchronous satellites positioned in geosynchronous orbit, to users. Data from the synchronous satellites may be transmitted to users, together with a time signal, at precisely the same frequency at which the navigational satellites emit their time signals.

Abstract: A NAVSTAR receiver in which the received signals are processed to produce digitized quadrature signals at zero i.f. Baseband phasor rotation to effect Doppler tracking in the receiver loop is accomplished by deriving digital signals representing sin .omega.T and cos .omega.T for the required rotation angle .omega.T, multiplying the quadrature signals separately and summing the outputs according to the algorithm I.sup.1 =I cos .omega.T+Q sin .omega.T and Q.sup.1 =Q cos .omega.T-I sin .omega.T, where I & Q are the digitized quadrature signals.

Abstract: A circuit is shown which utilizes signals transmitted from global positioning system satellites to create change in phase signals. The change in phase signals are measured over a predetermined time interval, one second, and stored. The stored signals are applied to a Kalman filter and back to the storage unit so that each one second time interval includes the information from all previous time intervals. This accumulated information is referred to as accumulated Delta-Range information which permits a more rapid determination of position by the circuit.

Abstract: An apparatus to confirm an orientation of the stem of ship by making use of a satellite included in the Global Positioning System. Radio wave signals from the satellite are received by a directional or omnidirectional antenna and the phase difference between a rotating period of said antenna and either the period of distance fluctuation, Doppler fluctuation, phase fluctuation or amplitude fluctuation is detected to obtain an orientation of the satellite which is used to obtain an accurate orientation of the stem relative to a reference direction such as due North.

Abstract: An improved signal generator and method for radio navigation in accordance with systems of the type in which location is determined in accordance with radio fixings with respect to multiple points of reference, each of such points providing a coded transmission. Multiple coded bit sequences are stored in an adddressable read only memory. Phantom signals comprising a plurality of coded sequences are generated by addressing the memory in accordance with preselected sequences. Further, predetermined phase shifts are applied to the coded sequences to facilitate signal detection and associated computational processes.

Abstract: A beacon signal is radiated from both the communications antenna and from a separate beacon antenna, the latter having a broader radiation pattern than the communications antenna pattern and overlapping the communications antenna pattern. The radiated signals are sensed at ground stations located about the periphery of a desired communications antenna radiation pattern coverage area on earth to provide sensor signals proportional to the ratios of the amplitudes of the two signals. The sensor signals are compared with one another to provide an error signal indicative of any departure of the communications antenna pattern from said desired coverage area. A control system in the satellite is responsive to this error signal for maintaining the communications antenna radiation pattern directed to the desired coverage area on earth as, for example, by controlling the attitude of the satellite.