Abstract: In a vehicle navigation apparatus having a control section which calculates relative vehicle positions and travel direction by dead reckoning calculations based on outputs from on-board sensors and periodically acquires GPS measurement data via a GPS receiver and applies error-reduction filter processing to these data to obtain position and travel direction information for correcting the calculated relative positions, the apparatus has a function for detecting that a travel direction obtained by dead reckoning contains an excessive error, and when that condition is detected, for directly applying an estimated vehicle position and travel direction derived directly from the GPS data, without filter processing, to correct the corresponding relative position and travel direction estimates.

Abstract: In a method and apparatus for processing a received navigation signal x′(t) of a satellite navigation system, the received navigation signal x′(t) contains at least four navigation codes. The navigation codes are modulated by a complex BOC signal and a defined subcarrier frequency such that the resulting signal has a constant amplitude. The resulting signal is then also modulated by means of a carrier signal. The navigation signal x′(t) is processed by a complex correlation with at least one reference signal.

Abstract: Method in a Global Positioning System (GPS) receivers, including determining pseudorange (PNR) measurements for at least four satellites (210), determining a coarse time (220) corresponding to the pseudorange measurement, determining an offset time (240) between a periodic GPS event of one of the four satellites and the coarse time, determining a time correction delta (250) based upon the period of the Periodic GPS event, the offset time and the coarse time if an error of the coarse time is less than ½ the period of the periodic GPS event, and determining corrected time (260) based upon the coarse time and the time correction delta if the error of the coarse time is less than ½ the period of the periodic GPS event.

Abstract: An interruption free navigator includes an inertial measurement unit, a north finder, a velocity producer, a positioning assistant, a navigation processor, an altitude measurement, an object detection system, a wireless communication device, and a display device and map database. Output signals of the inertial measurement unit, the velocity producer, the positioning assistant, the altitude measurement, the object detection system, and the north finder are processed to obtain highly accurate position measurements of the person. The user's position information can be exchanged with other users through the wireless communication device, and the location and surrounding information can be displayed on the display device by accessing a map database with the person position information.

Abstract: A method of increasing location accuracy in an inertial navigational device (100) is described herein. The navigational device (100) generates real-time data to depict its location. The data comprises at least one of sensor data, motion data, and location data. The navigational device (100) transmits the real-time data to a second device (104) in a real-time fashion. The navigational device (100) receives an update message from the second device (104), based on a comparison of the real-time data generated by the navigational device (100) against a second set of data. The navigational device (100) adjusts its depicted location based on the update message in order to increase the location accuracy of the navigational device (100). Alternatively, the navigational device (100), absent the second device (104), can compare the real-time data generated against the second set of data internally and adjust its depicted location accordingly.

Abstract: A positioning and navigation method and system thereof can substantially solve the problems encountered in global positioning system-only and inertial navigation system-only, such as loss of global positioning satellite signal sensibility to jamming and spoofing, and inertial solution's drift over time, in which the velocity and acceleration from an inertial navigation processor and an attitude and heading solution from an AHRS processor are used to aid the code and carrier phase tracking of the global positioning system satellite signals, so as to enhance the performance of the global positioning and inertial integration system, even in heavy jamming and high dynamic environments and when the GPS satellite signals are not available.

Abstract: In accordance with this invention, an apparatus and method for aircraft navigation are provided that utilize a blended architecture consisting of a global positioning system (GPS) and micro-electromechanical sensors (MEMS) for the primary navigation system and a laser gyroscope system for the secondary navigation system. The blended architecture of the present invention provides a navigation system that is at least as accurate, redundant and fault-tolerant as conventional navigation systems. In addition, the navigation system components may be distributed throughout the aircraft and may share computing resources with other avionics systems to process signals and provide data to the avionics systems. Overall, the navigation system of the present invention is significantly less expensive and easier to maintain, but equally or more precise and redundant, relative to conventional navigation systems.

Abstract: A walking stick navigator (WSN) apparatus and process comprises an aided INS (AINS) on a staff assembly that has the “look and feel” of a GPS survey instrument. When GPS is available, the AINS is aided by GPS data, and the surveyor manipulates the staff assembly like a standard GPS survey instrument. When GPS is not available due to signal obstruction, the surveyor manipulates the staff assembly as a walking stick. A switch means coupled to the lower end of the staff assembly provides a stationary interval signal when the surveyor plants and holds the WSN on the ground while walking. An input process is coupled to the AINS output signals and to the stationary interval signals and provides at least one aiding input signal to the AINS for each successive stationary interval, thereby allowing the AINS to control its velocity error and position drift during a GPS outage.

Abstract: A real-time self Differential Global Positioning System (DGPS) is developed for positioning a moving station in a local area. This DGPS system enables not only to minimize the error ranges without any additional expansive transmitting-receiving equipment, but also to calculate an accurate correcting value through a DGPS receiver. A method of the real-time self DGPS system comprises the steps of: (1) receiving a GPS signal of moving station contained data of satellite time and pre-measured moving station position, (2) calculating a correcting value from the moving station, (3) positioning the accurate moving station according to the correcting value and the GPS signal of moving station.

Abstract: The present method and apparatus consists of storing past values of estimated IRU error and using these past values to update the coasting filter when switching from GPS to inertial mode. Through the storage of past IRU error estimates, it is possible to avoid misdirected guidance from an erroneous GPS signal. The MMR and ground station can require up to 6 seconds to identify a failed GLS signal.

Abstract: A method and system that provide WAAS like corrections using a server and processor on a network. For one method, satellite measurement data is collected. Satellite position error corrections are computed using the collected satellite measurement data. The computed satellite position error corrections are stored. The stored satellite position error corrections can then be later retrieved and used by a server and processor coupled to the Internet.

Abstract: A method and a system to synchronize a time of day clock of a clock system. The method and system include a portable satellite timing system at a first location receiving a satellite signal comprising a first time of day signal. An internal clock of the portable satellite timing system is calibrated based on the first time of day signal to generate a second time of day signal. The portable satellite timing system is transported to a second location and coupled to the clock system. The second time of day signal is transferred from the portable satellite timing system to the clock system and the time of day clock is synchronized based on the second time of day signal. After a time period, the portable satellite timing system is transported to the first location.

Abstract: A method and apparatus for locating mobile device over a broad coverage area using a wireless communications link that may have large and unknown latency. The apparatus comprises at least one mobile device, a reference network, a position server, a wireless carrier, and a location requester. The mobile device is in communication with the wireless carrier and receives global positioning system (GPS) signals from a plurality of satellites in the GPS satellite constellation. The reference network is coupled to the position server and provides GPS data. The mobile receiver receives GPS signals, performs rudimentary signal processing and transmits the processed signals to the wireless carrier. The wireless carrier passes the signals on to the position server. The position server processes the mobile receiver's GPS data and the reference network ephemeris data to identify the location of the mobile receiver. The location is sent to the location requester.

Abstract: A hybrid processing apparatus outputs current position data, indicating a current position of a movable body, on the basis of self-contained positioning data from a self-contained positioning apparatus (10) and GPS measurement data from a GPS receiver (18). In the hybrid apparatus, a judging device (20) judges whether or not an estimated error of the self-contained positioning data is greater than a predetermined threshold value. A first calculation device (20) calculates the current position by combining the GPS measurement data with the self-contained positioning data or a second calculation device (20) calculates the current position without combining the GPS measurement data, depending upon a judgment result of the judging device.

Abstract: A method of calibrating acceleration data signals from a set of accelerometers, and angular rate data signals from a set of gyroscopes within a combined GPS/IGS includes generating navigation data as a function of the acceleration data signals, the angular rate data signals, and prior navigation data. The method further includes combining the navigation data with GPS data via a Kalman filter, so as to produce corrected navigation data, navigation correction data, acceleration correction data and angular rate correction data. The method further includes modifying the acceleration data signals as a function of the acceleration correction data so as to calibrate the acceleration data signals, and modifying the angular rate data signals as a function of the angular rate correction data, so as to calibrate the angular data signals.

Abstract: A method and apparatus for locating mobile device over a broad coverage area using a wireless communications link that may have large and unknown latency. The apparatus comprises at least one mobile device, a reference network, a position server, a wireless carrier, and a location requester. The mobile device is in communication with the wireless carrier and receives global positioning system (GPS) signals from a plurality of satellites in the GPS satellite constellation. The reference network is coupled to the position server and provides GPS data. The mobile receiver receives GPS signals, performs rudimentary signal processing and transmits the processed signals to the wireless carrier. The wireless carrier passes the signals on to the position server. The position server processes the mobile receiver's GPS data and the reference network ephemeris data to identify the location of the mobile receiver. The location is sent to the location requester.

Abstract: An improved positioning and data integrating process and system can substantially solve the problems encountered in system integration for personal hand-held applications, air, land, and water vehicles, wherein an integrated global positioning system/inertial measurement unit, enhanced with optional other devices to derive user position, velocity, attitude, and body acceleration and rotation information, and distributes these data to other onboard systems, for example, in case of aircraft application, flight management system, flight control system, automatic dependent surveillance, cockpit display, enhanced ground proximity warning system, weather radar, and satellite communication system.

Abstract: A track model is created for use with a GPS receiver. In one embodiment, the track model is a set of planar surfaces which approximate the contiguous surface on which navigation takes place. The GPS receiver searches for an appropriate planar surface associated with its approximate position. Having found the appropriate planar surface, the GPS receiver constrains its position using the planar surface associated with its approximate position. Using the track model improves the accuracy of the computed position at the time and improves the ambiguity estimation process so that positions with greatly improved accuracy are available sooner.

Abstract: A method, an apparatus and a computer program product are provided for accurately determining the vertical speed of an aircraft in a manner independent of signals provided by an air data computer, an inertial reference system and an inertial navigation system. Initially, a first vertical velocity of the aircraft is determined based upon a pressure altitude value associated with the aircraft. A second vertical velocity of the aircraft is also obtained from a GPS receiver carried by the aircraft. The first and second vertical velocities are then combined to determine the vertical speed of the aircraft. In this regard, the first and second vertical velocities are combined by complimentarily filtering the first and second vertical velocities. More particularly, the first vertical velocity is typically low pass filtered to remove high frequency noise that is attributable to the relatively low resolution of the first vertical velocity value.

Abstract: A method is described which enables the location of a radio frequency emitting target in absolute or relative GPS coordinates from a single airborne platform within a few seconds. The method uses a signal processing technique which emulates an antenna moving at very high velocities to induce a Virtual Doppler shift on signals incident upon a linear antenna array. The Virtual Doppler shift is directly proportional to the signal direction of arrival as measured by its direction cosine. The method is shown to prevent single and multiple GPS jammers from being able to jam conventional GPS signals. Also disclosed is a means and method for developing virtual Doppler shifted signals to determine the angle-angle bearing of emitting targets to high resolution. This in turn, allows the position of the emitter to be determined in a GPS reference frame to be located to a high degree of accuracy from a single platform in extremely short times.

Abstract: In a vehicle navigation apparatus having a control section which calculates relative vehicle positions and travel direction by dead reckoning calculations based on outputs from on-board sensors and periodically acquires GPS measurement data via a GPS receiver and applies error-reduction filter processing to these data to obtain position and travel direction information for correcting the calculated relative positions, the apparatus has a function for detecting that a travel direction obtained by dead reckoning contains an excessive error, and when that condition is detected, for directly applying an estimated vehicle position and travel direction derived directly from the GPS data, without filter processing, to correct the corresponding relative position and travel direction estimates.

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: Performance of an inertial navigation system (INS) corrected with GPS position data is enhanced with the addition of a filter that smooths the GPS-INS position difference data and couples the smoothed data to the INS position data. Difference data provided to the filter is edited to eliminate GPS-INS position data that excceeds a predetermined level. Performance is further improved by applying position resets from the INS Kalman filter in a ramp like manner.

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 method is described which enables the location of a radio frequency emitting target in absolute or relative GPS coordinates from a single airborne platform within a few seconds. The method uses a signal processing technique which emulates an antenna moving at very high velocities to induce a Virtual Doppler shift on signals incident upon a linear antenna array. The Virtual Doppler shift is directly proportional to the signal direction of arrival as measured by its direction cosine. The method is shown to prevent single and multiple GPS jammers from being able to jam conventional GPS signals. Also disclosed is a means and method for developing virtual Doppler shifted signals to determine the angle-angle bearing of emitting targets to high resolution. This in turn, allows the position of the emitter to be determined in a GPS reference frame to be located to a high degree of accuracy from a single platform in extremely short times.

Abstract: The data receiver device (100) of the present invention for reception of radio signals containing correction data for a global navigation satellite system includes at least two different radio receiving circuits (12,14) operating in three different frequency bands for receiving the radio signals containing the correction data; at least one demodulator (20) for conversion of these radio signals to a baseband; a memory for a frequency table (16) of frequencies of at least two different sources of the radio signals and for a decoding table (26) for decoding the radio signals and at least one decoding device (22) for decoding of the correction data from the radio signals. The at least one decoding device (22) is connected with the at least one demodulator (20) to receive the radio signals from it on the baseband and with the memory (26) for the decoding table for decoding of the radio signals.

Abstract: An infrastructure for implementing DGPS virtual reference stations is disclosed. The virtual reference station infrastructure is comprised of a network of real DGPS reference stations coupled to a central computer system. The real DGPS reference stations may be coupled to the central computer by a set of radio receivers that transmit the pseudorange corrections from each real reference station to the central computer system. The central computer system processes the pseudorange corrections from all the real DGPS reference stations to generate a dynamic satellite error vector and a clock error for each satellite. The dynamic satellite error vector and satellite clock error for each satellite are transmitted to plurality of “virtual” references stations. The virtual reference stations combine the dynamic satellite error vector and the satellite clock error with a local position to generate the local pseudorange corrections (PRC) for the observable satellites.

Abstract: Satellite identification data generated when using the Reduced Order GPS (ROGPS) system are compressed, allowing for shorter data transmission times, reduced transmitter energy and reduced satellite channel occupancy. An indexed list of all possible constellations of a subset of all satellites is created. This list is then used at both the tracked object location and the central station to which the satellite identifications must be sent. At the tracked object location, the chosen satellite GPS indices are identified and the list index is found, encoded, and transmitted with only enough bits to uniquely identify it from all other indices in the list. At the central station, the received list index is used to find the satellite constellation corresponding to the chosen satellite GPS indices. The number of bits used to encode the index can be further reduced by reducing the indexed list size.

Abstract: A car navigation apparatus includes a route setting unit for setting a route; an own car position detection unit for measuring an own car position and detecting the own car position; and an advance direction detection unit for detecting an advance direction of the own car. The car navigation apparatus further includes a turning intersection detection unit for detecting an intersection where the own car should turn next time, on the route located within a predetermined distance in the advance direction from the own car position; and a turning intersection display unit responsive to detection of a turning intersection to display the shape of the turning intersection and a direction to which the own car should turn, acquired from map information stored in a map information storage unit, on the display screen using figures, and to display the distance to the turning intersection and the name of the turning intersection on the display screen using characters.

Abstract: The present invention provides an open-loop method for determining uplink transmission power in a satellite communication system 200 that compensates for antenna pointing error attenuation and for rain attenuation. Satellite downlink signal 208 attenuation is measured. Antenna pointing information is then used in conjunction with antenna gain pattern information 400 to determine antenna pointing error attenuation. The measured downlink attenuation and antenna pointing error attenuation are then used to determine the amount of rain attenuation on the downlink 208. The downlink attenuation information is then used to determine the amount of uplink 216 attenuation to be expected. Uplink transmission power levels are then adjusted accordingly to overcome the expected uplink 216 attenuation.

Abstract: A system and method for improving the accuracy of altitude determinations in an inertial navigation system. The system utilizes pressure measurements which are taken by a barometric altimeter and converted into an estimated pressure altitude using any known pressure-to-altitude conversion. A pressure correction value is then generated using a correction value generating formula that is a function of altitude. The pressure correction value is then multiplied by a pressure offset value for the barometric altimeter to generate a pressure offset error for the barometric altimeter. This pressure offset error is used in the present invention to modify the pressure altitude estimation in order to generate an altitude determination having an improved accuracy. The present invention further determines an amount of observation noise in the barometric altimeter that is a function of pressure noise and altitude, where the altitude estimation is further modified to account for the observation noise.

Abstract: A system using GPS navigation signals to aid in distance determination on a golf course includes a cart-based unit, a hand-held distance determining unit that can be interconnected with the cart-based unit, and a central base station. The central base station includes an RF transceiver for wireless communications and a controller. The hand-held distance determining unit includes a GPS receiver, a display, memory for storing golf course location data, and a controller. The cart-based unit includes an RF transceiver, a display, and a connector cradle into which the hand-held unit can be inserted in order to share information with the cart-based unit. With the hybrid system of the invention, the benefits of the full features, large display screen and rich functionality of a cart-mounted GPS-based distance determining system are provided along with the benefits of a small, inexpensive, portable hand-held unit that a golfer can use away from the golf cart, such as in “cart path only” situations.

Abstract: A global positioning system (GPS) receiver has first circuitry for receiving and processing pseudorandom sequences transmitted by a number of GPS satellites. The first circuitry is configured to perform conventional correlation operations on the received pseudorandom sequences to determine pseudoranges from the GPS receiver to the GPS satellites. The GPS receiver also includes second circuitry coupled to the first circuitry. The second circuitry is configured to receive and process the pseudorandom sequences during blockage conditions. The second circuitry processes the pseudorandom sequences by digitizing and storing a predetermined record length of the received sequences and then performing fast convolution operations on the stored data to determine the pseudoranges. The GPS receiver may have a common circuitry for receiving GPS signals from in view satellites and downconverting the RF frequency of the received GPS signals to an intermediate frequency (IF).

Abstract: In a cellular communication system, positioning receiver disposed in a mobile station is tuned based on an reference frequency error transmitted from the base station. In accordance with the transmitted reference frequency error, the mobile station adjusts the tuning frequency of the positioning receiver. As a result, the GPS receiver locks onto the GPS satellite signals at a faster speed.

Abstract: A DGPS system using GPS almanac data for determining the locations-in-space and the DGPS corrections for GPS satellites for providing a differentially corrected location of a remote GPS user receiver. A GPS reference receiver determines almanac-based DGPS corrections from the differences between ranges that are measured to GPS satellites and ranges that are calculated to the GPS almanac-based locations-in-space of the GPS satellites from the known location of the GPS reference receiver. The GPS user receiver measures pseudoranges to the GPS satellites. Then, in a first embodiment, the GPS reference receiver radios the DGPS corrections to the GPS user receiver. The GPS user receiver uses almanac-based locations-in-space for the GPS satellites and the almanac-based DGPS corrections for differentially correcting the measured user pseudoranges for providing a differentially corrected user location. In a second embodiment, the GPS user receiver radios the measured user pseudoranges to the GPS reference receiver.

Abstract: Interrogator for an electronic identification system having a first oscillator arranged to vary in frequency in accordance with the frequency of a received signal, a second oscillator arranged to vary in accordance with the frequency of the first oscillator after a delay of a number of cycles of the received signal, a phase discriminator for detecting the phase difference between respective output signals of the first and second oscillators and a phase-change detector arranged to determine the frequency at which the phase changes occur. In this way, a modulation frequency of the received signal can be determined.

Abstract: The invention relates to a navigation system for a vehicle, in particular for a land vehicle, having at least one single-axis gyro for the vehicle vertical axis (z axis), having two accelerometers in the horizontal vehicle plane (x axis, y axis), and having a vehicle-axis velocity measurement device, for example, a distance-travelled sensor. In addition, supporting signal devices, in particular a satellite receiver and/or a map, are available as well as a controller, which uses a suitable Kalman filter to determine the vehicle position and/or the direction of travel from the measured and stored signals. The Kalman filter is assigned at least one partial filter, of which a first partial filter is used for dynamic levelling and/or a second partial filter is designed as a position filter which provides track calibration, position calibration and sensor calibration.

Abstract: A position determining system takes the form of a cellular radio system including at least one base station having a base station satellite receiver (6) and a mobile unit including a cellular mobile station (50) coupled to a local satellite receiver (58). The base station transmits base station satellite data via a cellular radio link to the mobile unit, the data including data representing a carrier phase measurement derived from a satellite signal (70) received by the base station satellite receiver (6). The mobile unit determines its position relative to the base station using local satellite data received by the local satellite receiver (58) and corrects errors in this position determination using base station satellite data. The relative positions of the base stations are determined automatically with reference to an external positional reference which may be a satellite-based position determining system.

Abstract: The present invention involves a system and method for determining a position of an object. The system comprises at least one ground transmitter configured to generate ground transmitter position signals comprising position information. The at least one ground transmitter has a known position. The system also comprises at least one ground transceiver having a known position and configured to receive the ground transmitter position signals and transmit ground transceiver position signals that are synchronized to the clock of the at least one ground transmitter. The object is configured to receive the ground transmitter position signals, the ground transceiver position signals and calculate the position of the object based on the received signals and the known positions of the at least one ground transmitter and the at least one ground transceiver.

Abstract: The apparatus of the present invention uses radar altimeter measurements and stored terrain altitude profiles to provide pre-filtered observations to a Kalman filter for estimating barometric offset at the airport runway, and barometric scale factor for offsets above the runway. These offsets are used with the smoothed baro-inertial output from an inertial reference system to provide 3 dimensional constant rate of descent approach procedures to replace non-precision approach procedures based on constant barometric altitude step approaches. The horizontal positions used as reference for the stored terrain altitude profiles are obtained from a prior art navigation apparatus. The integrity of all measurements is assured by using long term averages of the Kalman filter residuals to detect failures. In addition, the estimated baro offset at the runway is compared for consistency with the baro offset obtained by the pilot from the airport by radio.

Abstract: A differential GPS landing system having at least three GPS receivers at known locations in spatial proximity to each other, wherein each GPS receiver independently receives GPS signals from the plurality of GPS satellites and at least three reference stations, wherein each reference station receives a signal from a different two of the at least three GPS receivers and calculates two separate differential corrections for each satellite, wherein each differential correction is independently calculated using the signals received from a different one of the two GPS receivers. The reference stations preferably average the two calculated differential corrections for each satellite to produce an averaged differential correction for each satellite.

Abstract: A system and method for determining which of a plurality of correction signals is to be used in a position determination system for determining position. An antenna receives broadcasts of correction data on designated frequencies. The received correction data is analyzed to determine the best correction data signal to use to accurately determine position. The correction data from the selected best source of correction data is coupled to a position determination system for accurate determination of position. Thus, the present invention provides a seamless correction system that determines the best source of correction data from available sources and uses the selected correction data to determine location. The seamless correction system updates the source of correction data automatically.

Abstract: A communication system and a method of providing a feeder link to an earth orbiting satellite transponder having a mobile link illuminating spot beams with associated access channels, control channels and traffic channels for multiple user terminals (UTs) using the satellite transponder as the reference point to correct for dynamic frequency errors including the Doppler in the feeder link and in the mobile link caused by the satellite motion and the satellite translation error. A satellite access node (SAN) includes one or several radio frequency terminals (RFTs) and a satellite basestation subsystem (SBS). The RFT performs the center Doppler correction for each of the channels of the feeder link to the satellite transponder. The SBS corrects the feeder link residual Doppler and the satellite translation error for each channel and calculates the Doppler in the mobile link between the satellite transponder and the median Doppler line of each spot beam on the earth or each UT.

Abstract: A vehicle-mounted satellite signal receiving system adopting a satellite tracking system combining gyro tracking and hybrid tracking is disclosed which can correct a sensitivity coefficient for correcting a gyro sensor output signal to make up for a sensitivity error, even when a drift is produced in the sensitivity error. In this system, gyro tracking is caused when the received power level is above a threshold power level. The gyro tracking is done by determining the angular velocity .omega. of an antenna as .omega.=-(.omega.G.times..DELTA.SB+.omega.G from a value obtained by inverting the sign of the product of a gyro tracking angular velocity .omega.G and a sensitivity coefficient .DELTA.SB for dealing with the sensitivity error and a predetermined offset error correction value .omega.G and setting the antenna to .omega.. When .DELTA.SB is inaccurate and a sensitivity error is generated in the gyro sensor output signal, the received power level is reduced.

Abstract: A method and apparatus for Doppler compensation in a satellite communications system such as Inmarsat's SATCOM network are disclosed. An aircraft terminal provides satellite communications services in one of several user-selectable modes including a circuit-mode services only mode and other modes providing some data packet services. The terminal includes multiple channel units coupled to a processing circuit. The channel units communicate radio signals via data or circuit channels between the aircraft and a satellite. Each channel unit can receive a channel input transmitted at a known frequency, and measure its frequency. Each channel unit can also transmit a channel output at an adjustable frequency. Each channel unit is operated as a circuit channel when circuit-mode services only is selected. Doppler shift is measured using the difference between the measured and known transmitted frequencies of at least one channel input.

Abstract: Communications equipment for use in a combat vehicle with at least one transmitting antenna and at least one receiving antenna and with more communications terminals than transmitting antennas or receiving antennas. Control logic accordingly contains a signal-path matrix by which any communications terminal can be connected, depending on its operating state "transmit" or "receive", either to a transmitting antenna along a high-frequency transmission path that includes a power adder or to the receiving antenna along a high-frequency reception path that includes a level distributor.

Abstract: A TV graphical user interface (GUI) is provided to enable a user to input antenna location information required for setting up a dish antenna. When the TV GUI is set in a dish set-up mode, the user may activate a U.S. map button to display a map of the United States or another area on the earth's surface. When a remote pointing device is directed at a point on the map that represents the current location of a satellite receiver, the TV GUI displays a regional map that shows in more detail a region where the receiver is located. When the user selects the receiver location within the regional map, the CPU determines the latitude and longitude values of the selected location, and calculates magnetic north and elevation angles for the antenna installation. To provide the user with visual feedback, the TV GUI may indicate the city nearest to the selected location, and a distance to the nearest city.

Abstract: A method and apparatus for determining frequency offsets caused by oscillator error or Doppler effects in a user terminal (for example, a mobile wireless telephone) in a communication system. The system (100) includes at least one user terminal (124, 126) and a base station (112), or gateway (120, 122) for communicating with the user terminal (124, 126) through a satellite (116, 118) with predetermined known orbital positions or patterns. A communication signal (130, 132, 146, 148) is precorrected for known Doppler effects, such as between a gateway and a transferring satellite (146, 148), when used, and transmitted to a user terminal. The user terminal (124, 126) determines the signal frequency relative to a reference oscillator (240), and treats any detected difference as resulting completely from Doppler. The frequency difference is either transferred as data in reverse link transmissions (130, 132, 140, 142), or used as a pre-correction factor for such transmissions.

Abstract: A satellite navigation receiver system detects faulty range measurement signals from navigation satellites and excludes them from future position estimates. This system includes a receiver coupled to a movable object. The receiver includes a stable clock with a constant frequency drift rate over a predetermined period of time. A processor coupled to the receiver models the behavior of the clock over a time period equivalent to the period of constant frequency drift rate. The processor then generates predicted clock bias estimates over a future period of time equivalent in length to the period modeled, generates an instantaneous clock bias estimate using satellite signals, and determines the difference between the instantaneous clock bias estimate and a predicted instantaneous clock bias estimate. If the difference does not fall within an acceptable limit, one or more signals are determined to be faulty.

Abstract: A method and apparatus to enable high-quality digital transmissions to a satellite terminal operating in proximity to a radar source combines interleaving a sequence of channel symbols at a land station before transmission of an RF signal to a satellite, increasing the satellite's EIRP to compensate for the effects of the radar's duty factor on received signal power and code distance, detecting the radar pulses at a satellite terminal, blanking the received RF signal to prevent reception of the signal by the modem at the satellite terminal during the radar's ON time, having the modem recognize and eliminate the effect of the gap in the channel signals on its metric calculation, and de-interleaving the sequence of channel symbols. As a result, satellite terminals operating in proximity to radar sources can provide the same quality of service as if there were no radars operating.