Abstract: Methods for synchronizing to a reference signal the timing of a received composite, code phase SATPS signal, which consists of a preferred, interference-free signal distorted by at least one interfering signal, to determine an undistorted timing point of the preferred signal. An idealized correlation function A.sub.I (t), formed from the product of a digital reference signal with a time-shifted reference signal, and a measured correlation signal A.sub.M (t), formed from the product of a received signal and a time-shifted reference signal, are computed. Peak amplitudes A.sub.M (p.sub.M) and A.sub.I (p.sub.I) are found for the respective measurable and idealized punctual code phase shifts p.sub.M and p.sub.I. In a first embodiment of the invention, the correlation measurements formed on the early side (or on the late side) of the peak for the correlation function A(t) are combined to form an estimate of the time delay associated with a multipath signal.

Abstract: A receiver embodiment of the present invention comprises a radio frequency section that down-converts frequency division signals received from the several orbiting GLONASS satellites into a composite pseudo-baseband with spectral fold-over, a Nyquist sampling unit for sampling the composite signal at twenty to twenty-five MHz, and a programmable carrier frequency in-phase (I) and quadrature-phase (Q) digital multiplier for sorting through the composite signal to find a particular GLONASS satellite's signal. The particular satellite is identified by comparing almanac and ephemeris information. Cross-correlations between L1 and L2 are performed by a correlation that is integrated over a whole data bit length and a proposed insertion bit is inverted or not inverted according to its sign before further summing.

Abstract: The GPS-map speed matching system for controlling the speed of the vehicle is described. The system includes a GPS navigation receiver, a database processing facility, a GPS computer, an engine computer, a video display, a speed sensor and a heading sensor. The database processing facility can be local or remote. The GPS computer obtains the latitude, longitude, heading and speed of the vehicle. The database processing facility processes the GPS data and obtains the location and the maximum posted speed of the vehicle. The GPS computer or an engine computer perform the comparison between the vehicle speed and the maximum posted speed and signal the odometer to decrease the vehicle speed if the vehicle speed exceeds the maximum posted speed plus some predetermined value.

Abstract: A GPS receiver comprises a data output port for communicating time code information formatted according to standards published by the Society of Motion Picture and Television Engineer (SMPTE). Such time code information is input to independent sound, film and video recorders at a performance event to create tracks on each recording for re-synchronizing the pictures and sounds in post-performance editing.

Abstract: Method and apparatus for providing GPS pseudorange correction information over a selected geographic region S with a diameter of up to 3000 km with an associated inaccuracy no greater than 5 cm. N spaced apart GPS fiducial stations (N.gtoreq.3), whose location coordinates (u.sub.n, v.sub.n, v.sub.n) are fixed and are known with high accuracy, are provided within or adjacent to the region R. Each fiducial station n (n=1, 2, . . . , N) receives GPS signals from at least four common-view GPS satellites, numbered m=1, 2, . . . , M (M.gtoreq.3), computes its own GPS-determined location coordinates, compares these coordinates with its known location coordinates determines the pseudorange corrections PRC(t;t0;m;n) for its GPS-determined location, and transmits these correction signals to a central station located within or adjacent to the region S. The central station retransmits the pseudorange correction signals throughout the region S.

Abstract: Apparatus for measuring surveying parameters, such as distances and angular displacements between survey stations, with improved accuracy. The invention combines a differential satellite positioning system (SATPS), available with positioning systems such as GPS and GLONASS, with electromagnetic measurements of distances and optically encoded angles by a conventional electro-optical survey instrument to provide survey measurements that can be accurate to within a few millimeters in favorable situations. The differential satellite positioning system relies upon carrier phase measurements, after removal of certain phase integer ambiguities associated with carrier phase SATPS signals. The SATPS may be retrofitted within the housing of the conventional electro-optical instrument.

Abstract: Method and apparatus for reducing or cancelling impulse noise from a signal containing noise. The desired noise-free signal is assumed to have a representative frequency .omega..sub.3, but may have a range of frequencies adjacent to this frequency, and is assumed to have substantially zero amplitude for all frequencies .omega.<.omega..sub.1 and/or for all frequencies .omega.>.omega..sub.2, where .omega..sub.1 <.omega..sub.3 <.omega..sub.2 or .omega..sub.1 <.omega..sub.2. An input (noisy) signal is filtered and analyzed in a narrow frequency region surrounding .omega.=.omega..sub.1 and/or a narrow frequency region surrounding .omega.=.omega..sub.2 to obtain one or two output signal components n.sub.1 (t) and/or n.sub.2 (t), respectively, that, ideally, contain no contribution from the desired signal. The input signal is also filtered and analyzed in a narrow frequency region surrounding .omega.=.omega..sub.3 to obtain an output signal s(t)+n.sub.3 (t) component including the desired signal s(t).

Abstract: An embodiment of the present invention is a communications system for multiple users sharing the same maximal length code (MLC) in a code position modulation multiple access environment. A 1023 chip length code is transmitted with reference to an independent coordinated time source. The code repeats every time after 1023 chips have been transmitted. The MLC will begin each time period with the first through 1023.sup.rd chip, depending on the data to be sent and the identity of the user transmitting it. The chips belonging to the MLC that were not sent at the beginning of a time period are sent at the end to complete the MLC each time period in a wrap around fashion. Each time period can be arbitrarily divided into subsections embracing, for example, sixteen chip times. When so divided, more than sixty subsections are possible from one 1023 chip MLC. Respective users are each assigned a subsection.

Abstract: Method and apparatus for reducing the contributions of receiver noise signal error and multipath signal error from signals received in a Satellite Positioning System (SATPS) from one or more SATPS satellites by formation and appropriate filtering of differences of signals DD that are differences of SATPS signals received by the SATPS receiver/processor. A difference signal DD of code-phase-derived delta range signals and carder-phase-derived delta range signals is formed, and this difference signal is passed through a first statistical processing filter with an associated time constant .tau.1 in the approximate range 50-500 sec, to produce smoothed or filtered signal with the estimated receiver noise error reduced or removed. The difference signal DD is passed through second and third statistical processing filters having associated time constants .tau.2=5-20 sec and .tau.

Abstract: A GPS receiver comprises a data input/output port for communication of datum-less position fixes in an earth-centered, earth-fixed (ECEF) coordinate style to avoid the errors associated with not communicating the datum choice with latitude longitude data communication formats.

Abstract: A global positioning system (GPS) receiver having a radio frequency (RF) circuitry to receive position signals from a plurality of satellites and to provide an intermediate frequency (IF) signal to a correlator circuitry for generating a pseudo range and a Doppler measurement for calculating a position fix. The GPS receiver further has a power supply system which has at least one battery and an alternative external power connector for connecting to an external power source. The GPS receiver further has a microprocessor having a read only memory (ROM). The microprocessor is electrically connected to the RF circuitry and the power supply system. Since the GPS receiver does not need to constantly process all the GPS position signals that are available to it to provide a useful tool, the ROM includes a program for automatically controlling the power supply to the RF circuitry so that battery power is conserved.

Abstract: Methods for determining the integrity of pseudorange and pseudorange rate signals received from a plurality of M Satellite Positioning System satellites (SATPS, including GPS and GLONASS), numbered j=j1, j2, . . . , jM, at a reference SATPS station (RS), using pseudorange and pseudorange rate signals received from the same satellites at a signal integrity monitoring (SIM) station located near the reference station. Pseudorange correction values PRC(t;i;j).sub.RS and PRC(t;i;j).sub.SIM and pseudorange rate correction values PRRC(t;i;j).sub.RS and PRRC(t;i;j).sub.SIM for the signals received at the reference station (RS, number i) and at the SIM station are computed, and difference values DPRE(t;i;j)=PRC(t;i;j).sub.RS -PRC(t;i;j).sub.SIM and DRRE(t;i;j)=PRRC(t;i;j).sub.RS -PRRC(t;i;j).sub.SIM are computed from these correction values. If .vertline.DPRE(t;i;j).vertline..ltoreq.DPRE(i;j).sub.thr and .vertline.DPRRE(i;j).vertline..ltoreq.DPRRE(i;j).sub.thr, where DPRE(i;j).sub.thr and DPRRE(i;j).sub.

Abstract: A data/voice modem embodiment of the present invention comprises an asynchronous-to-synchronous data converter for interface with a GPS receiver, a minimum space keyed modem, and a continuous tone controlled sub-audible squelch controller that modulates a radio transceiver interface with a discrete tone such that both voice and data may share a common radio channel. The data/voice modem periodically keys-up the radio transmitter through its interface and transmits a packet of information that contains user position and velocity obtained through the GPS transceiver interface and adds a user identification code and time tag. Incoming message packets from the radio transceiver that are sent from other similarly equipped mobile units are used to supply individual network member absolute positions and velocities, and this information is stored by user identification number as goal or waypoint equivalents.

Abstract: An embodiment of the present invention comprises a GPS receiver including a conversion table memory index for storing latitude-longitude lookup conversions to standardized map coordinates and scale factors.

Abstract: An embodiment of the present invention is a GPS receiver comprising a GPS downconverter, a fast acquisition unit, a GPS digital signal processor (DSP), a static random access memory (SRAM) and a temperature compensated crystal oscillator (TCXO). The fast acquisition unit samples intermediate frequency signals from the GPS downconverter at 5.17 MHz and writes the samples to the SRAM memory. The memory then supplies the samples back out at a rate of 10.34 MHz. The GPS DSP is such that PRN code and code phase searches are conducted at two times the real-time transmission rate of a GPS satellite. Once a code lock is obtained, Doppler, code, code phase and ephemeris data are stored by a GPS processor. If lock is lost, past code phase and Doppler are projected forward in time using ephemeris and other relevant GPS satellite knowledge to constrain a new search to re-establish lock.

Abstract: Method and apparatus for determining the present location of a missing vehicle, such as an automobile or marine vessel, using a Global Positioning System that receives GPS signals from two or more GPS satellites. A GPS antenna, GPS signal receiver/processor, a paging responder, a cellular telephone and associated antenna, and a controller/modem are installed in a vehicle and electrically connected together. When the vehicle is determined to be missing, because the vehicle has been misplaced, lost or stolen, the vehicle owner or operator contacts a vehicle location service center, which broadcasts a paging request that is received by the paging responder on the vehicle. The paging responder causes the controller/modem to interrogate the GPS receiver/processor to determine the present location of the vehicle. The receiver/processor determines the present vehicle location and notifies the controller/modem of such location.

Abstract: A method for fast acquisition of Satellite Positioning System (SATPS) signals from a satellite-based positioning system, such as GPS or GLONASS, that does not require permanent storage of satellite almanac information at an SATPS ground station. This SATPS signal acquisition method can be used whenever the "new" station initially powers up or has lost lock on one or more SATPS signals that must be reacquired. A nearby reference SATPS station, whose location coordinates are known with high accuracy, provides the new SATPS station with differential positioning SATPS information, and, optionally, with SATPS satellite ephemeride information on each SATPS satellite visible from the reference station. The new station then uses this differential SATPS information to establish channels to search for (only) the SATPS satellites that are visible from the reference station.

Abstract: An embodiment of the present invention is a combined GPS and dead-reckoning (DR) navigation sensor for a vehicle in which a pair of modifications are made to an otherwise conventional Kalman filter. Process noise is adapted to cope with scale factor errors associated with odometer and turning rate sensors, and correlated measurement error processing is added. When only two Doppler measurements (PRRs), or three with an awkward three-satellite geometry, are available, DR error growth can nevertheless be controlled. The measurement error correlations in the conventional Kalman filter covariance propagation and update equations are explicitly accounted for. Errors induced by selective availability periods are minimized by these two modifications.

Abstract: An embodiment of the present invention includes a plurality of portable satellite terminals (PSTs) and a network control unit (NCU) in mutual communication by a communications satellite. Integrated services digital network (ISDN) basic rate interfaces (BRI) are provided at each PST and NCU such that commercially available equipment may be connected and link access procedure D-channel (LAPD) protocols are supported end-to-end. CCITT Recommendation V.42 link access procedure-modem (LAPM) with the selective frame reject option is used to carry whole LAPD frames within the information fields of LAPM frames over the satellite link. Protocol conversion units are employed at each PST and NCU to convert LAPD to LAPM and back again.

Abstract: An embodiment of the present invention comprises a series pass transistor with its emitter arranged to receive a source of DC power, its collector arranged to supply a DC load, and its base connected to the junction of a capacitor to ground and an inductor to the collector. An output capacitor from the collector to ground is alternatively included. In a second embodiment of the present invention, an operational amplifier is inserted in the base circuit to increase the effective circuit gain.