Abstract: The energy potential of a receiver receiving signals from a navigation satellite is calculated according to an algorithm which is a function of an estimate of the mean and an estimate of the variance of a correlation signal. Improving the accuracy of measuring the energy potential may be achieved by improving the variance estimate. The variance estimate may be determined from measurements of the correlation signal over long time intervals during operation of the receiver. The variance estimate may also be determined during a calibration procedure, or by mathematical modeling of the receiver.

Abstract: Disclosed is a micropatch antenna comprising a radiating element and a ground plane separated by an air gap. Small size, light weight, wide bandwidth, and wide directional pattern are achieved without the introduction of a high-permittivity dielectric substrate. Capacitive elements are configured along the perimeter of at least one of the radiating element and ground plane. Capacitive elements may comprise extended continuous structures or a series of localized structures. The geometry of the radiating element, ground plane, and capacitive elements may be varied to suit specific applications, such as linearly-polarized or circularly-polarized electromagnetic radiation.

Abstract: Disclosed is a method and apparatus for determining the relative position of a mobile unit that moves from an initial location to a plurality of successive positions. The mobile unit receives signals from a plurality of navigation satellites and tracks the carrier phases of the signals during movement. For each of the received signals, carrier phase increments are calculated over a plurality of epochs. Anomalous carrier phase increments are determined and eliminated from further calculations. The non-eliminated carrier phase increments are then used to calculate coordinate increments for each of the time epochs. If, after elimination, the remaining number of carrier-phase increments is less than a threshold for a particular epoch, then coordinate increments for the particular epoch may be extrapolated using data from prior epochs. In various embodiments, least squares method and Kalman filtering may be used to calculate the coordinate increments.

Abstract: Disclosed is an adaptive receiver configured to receive signals from satellite navigation systems to determine receiver coordinates and configured to use a co-op tracking system to evaluate full phases of carrier phases for N navigation satellites in view. The adaptive receiver includes channels with autonomous wideband phase lock loops (PLLs) in a guiding status. The wideband PLLs are configured to track phases of carrier signals from satellites having high SNR and configured to produce control codes for target designations of varying carrier frequency. The adaptive receiver also includes channels with narrow-band PLLs in a guided status. The narrow-band PLLs can track phases of carrier signals of satellites with low SNR and are configured to use target designations from the wideband PLLs in guiding status and a prediction of frequency change caused by satellite movement. The adaptive receiver also includes channels with open PLLs in a standby mode.

Abstract: Disclosed is a method for determining coordinates of a mobile rover. The method includes determining a vector of one-shot code coordinates of the mobile rover. The method also includes determining a vector of phase increments by determining full phase differences for each navigation satellite in a plurality of navigation satellites in view at a discrete time interval (called a time epoch) and at a previous time epoch in a plurality of time epochs. A vector of radial range increments is determined from the full phase differences. A vector of rover phase coordinate increments is also determined using the vector of radial range increments. The vector of one-shot code coordinates and the vector of rover phase coordinate increments are then filtered to determine, at each time epoch, smoothed code coordinates of the mobile rover. Measured phase increments are cleared up from abnormal measurements.

Abstract: Disclosed is an antenna calibration technique for performing absolute antenna calibration. An antenna to be calibrated is positioned in a first position, called a home position, and records data samples from received satellite signals. The antenna is then moved to another location, called a non-home position, and records data samples from received satellite signals while at the non-home position. The antenna is then returned to the home position and records additional data samples. During the time that the antenna to be calibrated is recording its data samples, an auxiliary antenna is also recording satellite signal data samples. The data samples taken by the antenna to be calibrated during the home and non-home positions are differenced with the data samples taken by the auxiliary antenna during the same time period.

Abstract: A method and apparatus for estimating the changing frequency of a signal received by a satellite receiver from, illustratively, positioning system satellites is disclosed that enables a more accurate measurement of the change in frequency of that signal due to movement of the satellite receiver relative to those satellites. The system includes a PLL having a numerically controlled oscillator (NCO) and a filter of frequency estimates (FFE). In operation, an analog signal is received at the satellite receiver and the PLL tracks the changing signal frequency and outputs non-smoothed frequency estimates into the FFE. The FFE then smoothes noise in the signal to produce a more accurate smoothed frequency estimate of the input signal. Comparing multiple estimates over time allows Doppler shift of the signal frequency received by the satellite receiver to be calculated more precisely, thus resulting in more accurate satellite receiver velocity vector determinations and, hence, position measurements.

Abstract: A method and apparatus for resolving floating point and integer ambiguities in a satellite position navigation system is disclosed. A rover station is periodically positioned at unknown locations and has a satellite receiver capable of receiving the navigation signals. By calculating relative position coordinates between a base station in a known location and the rover station, and by calculating other position parameters relative to the satellite position, a geometric constraint based on a measured elevation angle between the rover and base station can be incorporated into data computations and processing to help resolve carrier phase ambiguities. The elevation angle is measured by transmitting multiple laser beams to an optical sensor on the rover station. This technique results in greater precision in determining the location of the rover.

Abstract: A satellite positioning device is disclosed for determining position based on received satellite navigation signals and a received non-satellite signal. A local clock controls the epoch period of a satellite signal processor. Correction signals are applied to the local clock in order to improve the synchronization between the satellite signal processor and the non-satellite signal processor.

Abstract: Disclosed are methods and apparatuses for estimating the floating ambiguities associated with the measurement of the carrier signals of a plurality of global positioning satellites, such that the floating ambiguities are preferably consist for a plurality of different time moments. In one aspect of the invention, a real-time iterative matrix refactorization process is provided which reduces processor load and retains history of the measurements.

Abstract: A method and apparatus for resolving floating point and integer ambiguities in a satellite position navigation system is disclosed. A rover station is periodically positioned at unknown locations and has a satellite receiver capable of receiving the navigation signals. By calculating relative position coordinates between a base station in a known location and the rover station, and by calculating other position parameters relative to the satellite position, a geometric constraint based on a measured elevation angle between the rover and base station can be incorporated into data computations and processing to help resolve carrier phase ambiguities. The elevation angle is measured by transmitting multiple laser beams to an optical sensor on the rover station. This technique results in greater precision in determining the location of the rover.

Abstract: Disclosed are methods and apparatuses for determining the position of a roving receiver in a coordinate system using at least two base-station receivers, which are located at fixed and known positions within the coordinate system. The knowledge of the precise locations of the base-station receivers makes it possible to better account for one or all of carrier ambiguities, receiver time offsets, and atmospheric effects encountered by the rover receiver, and to thereby increase the accuracy of the estimated receiver position of the rover. Baselines are established between the rover and each base-station, and baselines are established between the base stations. Navigation equations, which have known quantities and unknown quantities, are established for each baseline. Unknowns for the baseline between base stations are estimated, and then used to correlate and reduce the number of unknowns associated with rover baselines, thereby improving accuracy of the rover's estimated position.

Abstract: Disclosed is a method and apparatus for multipath mitigation using an antenna array. An antenna array made up of a plurality of antennas is used to receive satellite signals from satellites. Various configurations of antenna arrays is disclosed, including a linear vertical antenna array and a horizontal antenna array in which the antenna elements are located in a horizontal plane. A switch sequentially connects each of the antenna outputs to a single processing path to generate a common additive signal. The common additive signal is provided to satellite channel processors, each of which processes the signals from an associated satellite. A phase shift correction signal associated with each of the antennas is generated and synchronously applied to a carrier phase reference signal. A blocking signal may be applied to the satellite channel processors in order to block the processing of signals from an unwanted satellite.

Abstract: A method and apparatus for detecting and correcting anomalous measurements in a satellite navigation receiver is disclosed. Anomalous measurements are detected using the redundancy of observed satellite signals, or by analyzing the relationship between phase measurements at two frequencies when using dual frequency receivers. Upon determination that an anomalous measurement exists, the particular channel on which the anomalous measurement has occurred is determined. In addition, the extent of the anomalous measurement is estimated to produce an estimated error value. This information may then be used by the satellite navigation receiver in order to increase the accuracy of a navigation task.

Abstract: Compact antenna systems for reducing the reception of multipath signals are disclosed. An exemplary antenna system comprises a ground plane, a receiving antenna disposed above the ground plane and providing an output signal of the antenna system, and a passive antenna disposed below the ground plane.

Abstract: Prediction methods for navigation message symbols of satellite systems, such as GPS (Global Positioning System) and GLONASS (Global Orbiting Navigation System), that use information repetition in navigation data messages are disclosed. The methods enable one to eliminate the impact of symbol modulation for a received signal on the threshold performance of any navigation receiver, thereby permitting its operation in severe environments when the carrier-to-noise ratio C/N0 of “weak” satellite signals falls to levels below C/N0=20 dB*Hz.

Abstract: GPS and GLONASS Satellites broadcast code signals which are modulated onto respective carrier signals, and which are received by two receivers on Earth. The first receiver is situated at a point with known coordinates. The results of its measurements are transmitted to a user at a second receiver through a connection link, the user wanting to know the position of the second receiver. The measurements of two receivers are related to a common time moment by extrapolating measurement data that has arrived through the connection link with a delay. An extrapolating unit examines the measurements to find and discard measurements with abnormal errors, and generates extrapolated measurement data (e.g., predictions) for the common time based upon the most reliable data. This enables the measurements of code delays and carrier phase shifts in the satellite signals received by two receivers to be processed for the position of the second receiver.

Abstract: Methods and systems for measuring coordinates of a target, particularly under strong multipath conditions, are described. A satellite navigation system antenna and a tilt sensor are mounted on a range pole, with the sensor at the pole's bottom tip. Signals from the antenna and tilt sensor are provided to a receiver, which computes the antenna's coordinates from the antenna signals, and the pole tips position from the computed coordinates and the tilt data. The operator places the pole tip on the target and swings the pole by hand over an angle sector of 15 degrees while keeping the tip on the target. Height of the target can be computed with a single measurement set, and X-Y coordinates with just three measurement sets. The use of additional measurements reduces errors in the target's coordinates since multipath errors are uncorrelated during movement of the antenna. Vertical alignment of the pole is unnecessary.

Abstract: The present application is applicable to receivers for Global Positions (GP) systems which use delay-lock loops (DLLs) and, optionally, phase-lock loops (PLLs). The application discloses multipath error reduction techniques which enable the multipath errors in DLL systems to be made much less than the error present in known narrow “early-late” correlators, or their corresponding implementations which use strobe representations of the PR-code. Also disclosed are multipath error reduction techniques that enable multipath errors in the PLL systems to be reduced. The techniques, when applied to both the DLL and PLL systems work synergistically to further reduce multipath errors.

Abstract: The measurements of two GPS and/or GLONASS receivers are related to a common time moment by extrapolating measurement data that has arrived through a connection link with a delay. This common time moment is defined by the user. Cycle slips in the phase-lock loops (PLLs) of the receivers, which may be caused by blockage of direct signals from the satellites, strong interference signals, and reflections, are deflected and corrected in a multi-loop nonlinear tracking system. The procedure of resolution of phase measurement ambiguities comprises the preliminary estimation of floating ambiguities by a recurrent (e.g., iterative) procedure including the simultaneous processing of code and phase measurements for all satellites for each processing time interval, and the gradual improvement of the result as the information is accumulated. After the resolution of ambiguity, the user coordinates are estimated with centimeter accuracy on the basis of phase measurements on the carrier frequency.