Abstract: A GNSS receiver utilizes an antenna structure that two or more antennas that are spaced apart from their neighboring antennas by less than 1 wavelength of a GNSS satellite carrier signal of interest. The receiver calculates the orientation of the antennas directly from differences in the carrier phase angles measured at the two antennas, without resolving integer carrier cycle ambiguity.

Abstract: A system for generating and utilizing a look-up mechanism consisting of one or more phase difference error maps, tables and/or mathematical models calculates the respective maps, tables and/or models by placing a short baseline or ultra-short baseline antenna array in a known location and known orientation, determining angles of incidence of incoming GNSS satellite signals with respect the antenna array and calculating expected carrier phase differences between respective pairs of antennas, calculating measured carrier phase differences between the respective pairs of antennas, and determining carrier phase difference errors using the expected and measured carrier phase differences. The carrier phase difference errors are then recorded in the look-up mechanism, with the maps and, as appropriate, look-up tables for the respective pairs of antennas being indexed by angles of incidence. Thereafter, the system utilizes the look-up mechanism when determining the unknown orientation of the antenna structure.

Abstract: An anti-jamming subsystem for jamming signals originating along the horizon includes a two-dimensional horizontal array of antennas that effectively has a horizontal circular reception pattern for receiving signals originating along the horizon and a antenna that has a half hemispherical reception pattern and an upward looking view of the sky. The subsystem utilizes associated phase information to actively combine the signals received by the respective antennas in the array, to produce one or more anti jamming signals with narrow beams in the directions of the jammers. The subsystem combines the anti jamming signals with the signals received by the reference antenna, to produce signals for further processing in which the interference from the jamming signals originating along the horizon is minimized without adversely affecting the signals received by the reference antenna from at least higher elevation satellites.

Abstract: A GNSS receiver reduces the time to first fix by utilizing the properties of existing radiated signals of opportunity, such as AM or FM radio signals, television signals and so forth, to reduce the uncertainties associated with oscillator frequency and phase, and further utilizing an Almanac and battery backed-up date and time to determine the satellites in view and reduce the uncertainties associated with Doppler. The receiver may use multiple signals of opportunity to determine the city or local area in which the receiver is located based on the set of frequencies of the signals, and also to reduce search uncertainties for oscillator frequency by estimating an offset based on the differences between the frequencies of the respective signals of opportunity at the receiver and the nominal broadcast frequencies of the signals.

Abstract: A receiver includes a pre-correlation filter that forms an image of the average chip shape of a received signal over a specified period of time. The filter includes an array of complex accumulation registers that accumulate measurements that are associated with signal samples from specific ranges of locations, or code chip phase angles, along a spread-spectrum chip. Using the accumulated measurements, the receiver estimates the location of the chip transitions in a direct path signal component. The receiver may thereafter change the starting point, size and number of ranges, such that the accumulation registers accumulate more detail from the chip edges. The receiver in addition may compare the accumulated measurements with a reference pulse shape to determine if any interference is present in the received transmission that will distort ranging information calculated from the received signal.

Abstract: A receiver includes a pre-correlation filter that forms an image of the average chip shape of a received signal over a specified period of time. The filter includes an array of complex accumulation registers that accumulate measurements that are associated with signal samples from specific ranges of locations, or code chip phase angles, along a spread-spectrum chip. Using the accumulated measurements, the receiver estimates the location of the chip transitions in a direct path signal component. The receiver may thereafter change the starting points, sizes and numbers of ranges, such that the accumulation registers accumulate more detail from the chip edges. The receiver in addition may use the accumulated measurements from selected registers and/or selected groups of registers, to produce the correlation values that are needed to perform one or more correlation techniques and/or one or more multipath mitigation techniques.

Abstract: A global positioning system includes a base GNSS receiver that determines position and carrier phase measurements for GNSS satellites in view and a rover GNSS receiver, which is a single frequency receiver that captures GNSS satellite signals transmitted in the single frequency band during a capture window from a plurality of GNSS satellites, the plurality being large enough to provide a carrier phase data set from which a solution to associated integer carrier phase ambiguities is over determined. The system determining from the captured signals, a search space associated with the satellites in view, the code phase delays and associated position uncertainty. The system resolving the integer carrier cycle ambiguities using double difference carrier phase measurements associated with signal power values that are over a predetermined threshold value.

Abstract: A system for enhancing location estimates by movable rovers including one or more base stations that engage in two way time transfer (TWTT) with the rovers. Each TWTT operation between a given base station and a given rover provides range measurements and clock differences between the base station and rover. The range measurements are based on the travel time of return TWTT signals and the clock differences are based on a phase offset of a code in the return TWTT signal and/or timing information included in the return TWTT signals.

Abstract: A system to determine position, frequency and clock offsets over a network utilizing signals of opportunity transmitted by one or more transmitters with known locations, the system includes a base receiver with a clock and a known position that determines ranges to the transmitters, takes a series of samples of the signals of opportunity and time tags the series with times of receipt, calculated times of transmission based on the calculated ranges, or both. The base receiver transmits the time tagged series and, as appropriate, computed ranges to the remote receivers. A given remote receiver saves and time tags samples of the signals of opportunity, correlates the time-tagged series with the saved samples, and calculates a time offset as a time difference of the times of receipt at the remote receiver and either the time of receipt at the base receiver or the time of transmission calculated at the base receiver.

Abstract: A system to distribute accurate time and/or frequency over a network utilizing signals of opportunity transmitted by one or more local transmitters with known locations, the system includes a base receiver with a clock synchronized to a reference time scale such as GNSS or UTC time that saves a series of samples of the signals of opportunity and time tags the series with a calculated time of broadcast. A remote receiver saves samples of the signals of opportunity and correlates the series with the saved samples. The remote receiver calculates a time of transmission of saved samples that correspond to the series, determines a time offset as a difference in the time of broadcast calculated at the remote receiver and the time of broadcast calculated at the base receiver, and determines the time offset with respect to the base receiver.

Abstract: A system for determining positions of fixed-position satellite signal receivers that have restricted views of the sky includes a data recording control center, and one or more base satellite signal receivers with associated antennas that together have substantially unrestricted views of the sky. The system batch processes range information provided by the fixed-position receivers over an extended period of time, determining the three dimensional position of a given fixed-position receiver using range data from at least three relatively short time intervals associated with different sky positions in which the receiver is tracking any two or more satellite signals simultaneously.

Abstract: A global positioning system includes a base GNSS receiver that determines position and carrier phase measurements for GNSS satellites in view and a rover GNSS receiver, which is a single frequency receiver that captures GNSS satellite signals transmitted in the single frequency band during a capture window from a plurality of GNSS satellites, the plurality being large enough to provide a carrier phase data set from which a solution to associated integer carrier phase ambiguities is over determined. The system determining from the captured signals, a search space associated with the satellites in view, the code phase delays and associated position uncertainty. The system resolving the integer carrier cycle ambiguities using double difference carrier phase measurements associated with signal power values that are over a predetermined threshold value.

Abstract: A GNSS receiver utilizes an antenna structure that two or more antennas that are spaced apart from their neighboring antennas by less than 1 wavelength of a GNSS satellite carrier signal of interest. The receiver calculates the orientation of the antennas directly from differences in the carrier phase angles measured at the two antennas, without resolving integer carrier cycle ambiguity.

Abstract: A system for generating and utilizing a look-up mechanism consisting of one or more phase difference error maps, tables and/or mathematical models calculates the respective maps, tables and/or models by placing a short baseline or ultra-short baseline antenna array in a known location and known orientation, determining angles of incidence of incoming GNSS satellite signals with respect the antenna array and calculating expected carrier phase differences between respective pairs of antennas, calculating measured carrier phase differences between the respective pairs of antennas, and determining carrier phase difference errors using the expected and measured carrier phase differences. The carrier phase difference errors are then recorded in the look-up mechanism, with the maps and, as appropriate, look-up tables for the respective pairs of antennas being indexed by angles of incidence. Thereafter, the system utilizes the look-up mechanism when determining the unknown orientation of the antenna structure.

Abstract: An AltBoc receiver accumulates power measurements over code chip ranges that are associated with time slots that span the code chips. The receiver combines a received signal with code and carrier phase offsets that correspond to the time slots to produce the power measurements, with the code phase offsets determined from compressed signals representing one or a combination of the codes in the AltBoc signal. The receiver recovers navigation data from the data channels of the received signal and combines the recovered data with the corresponding locally generated PRN codes to produce a locally generated 4 code signal that is then used track the full 8PSK AltBoc received signal. The receiver rotates and shifts the phase of the received signal in order to line up the subcarrier splitting code zero crossings. The pulse shape of this rotated and shifted signal is measured. The resulting sharp edges of the recovered subcarrier are used to control the code phase of the receiver.

Abstract: A receiver includes a pre-correlation filter that forms an image of the average chip shape of a received signal over a specified period of time. The filter includes an array of complex accumulation registers that accumulate measurements that are associated with signal samples from specific ranges of locations, or code chip phase angles, along a spread-spectrum chip. Using the accumulated measurements, the receiver estimates the location of the chip transitions in a direct path signal component. The receiver may thereafter change the starting points, sizes and numbers of ranges, such that the accumulation registers accumulate more detail from the chip edges. The receiver in addition may use the accumulated measurements from selected registers and/or selected groups of registers, to produce the correlation values that are needed to perform one or more correlation techniques and/or one or more multipath mitigation techniques.

Abstract: A system for enhancing location estimates by movable rovers including one or more base stations that engage in two way time transfer (TWTT) with the rovers. Each TWTT operation between a given base station and a given rover provides range measurements and clock differences between the base station and rover. The range measurements are based on the travel time of return TWTT signals and the clock differences are based on a phase offset of a code in the return TWTT signal and/or timing information included in the return TWTT signals.

Abstract: A pre-correlation filter determines the timing of a second pseudorandom number (“PRN”) code, using an image of the average chip shape formed for a first PRN code. The filter collects measurements corresponding to samples of a received signal over multiple code chips of the first PRN code at sample times that are asynchronous to code rate. A code phase decoder directs the measurements to accumulation registers that are associated with code chip ranges that are fractions of a code chip of the first PRN code based on the code phase angles of the samples in the first PRN code, to accumulate measurements relating to chip transitions in the first PRN code and measurements relating to chip transitions in the second PRN code. The chip edges of the second PRN code are detected from the image of average chip shape for the first PRN code formed from the accumulated measurements.

Abstract: A receiver includes a pre-correlation filter that forms an image of the average chip shape of a received signal over a specified period of time. The filter includes an array of complex accumulation registers that accumulate measurements that are associated with signal samples from specific ranges of locations, or code chip phase angles, along a spread-spectrum chip. Using the accumulated measurements, the receiver estimates the location of the chip transitions in a direct path signal component. The receiver may thereafter change the starting point, size and number of ranges, such that the accumulation registers accumulate more detail from the chip edges. The receiver in addition may compare the accumulated measurements with a reference pulse shape to determine if any interference is present in the received transmission that will distort ranging information calculated from the received signal.

Abstract: A system for determining positions of fixed-position satellite signal receivers that have restricted views of the sky includes a data recording control center, and one or more base satellite signal receivers with associated antennas that together have substantially unrestricted views of the sky. The system batch processes range information provided by the fixed-position receivers over an extended period of time, determining the three dimensional position of a given fixed-position receiver using range data from at least three relatively short time intervals associated with different sky positions in which the receiver is tracking any two or more satellite signals simultaneously.