Abstract: A GNSS receiver receives GNSS signals from satellites of a plurality of Global Navigation Satellite Systems, and a front end section thereof outputs corresponding navigation signals. A plurality of baseband processing channels receive and process the navigation signals so as to output navigation measurements which are divided and grouped into a plurality of sets. Each of a plurality of first application processing blocks receives a respective set of the navigation measurements and calculates a navigation solution.

Abstract: A GNSS spoofing signal detection/elimination includes tracking acquired candidate GNSS signals for each target GNSS signal, identifying the acquired candidate GNSS signals as authentic, unauthenticated, or counterfeit, removing the counterfeit GNSS signal(s) from tracking, generating a first list of the authentic GNSS signals and a second list of unauthenticated candidate GNSS signals, creating a plurality of sets of GNSS signals by selecting at least four GNSS signals from among the first list and the second list, such that each set includes all of the authentic GNSS signals, if any, and at least one unauthenticated candidate GNSS signal such that each set includes only one candidate signal per target GNSS signal, calculating PVT solutions and post-fit residuals for each set, thereby obtaining a plurality of estimated solutions, estimating authenticity of unauthenticated GNSS signals by analyzing the plurality of estimated solutions.

Abstract: A GNSS receiver has a first antenna and a reference antenna. From the measurement of a carrier phase L1k of GNSS signals at the first antenna and a reference carrier phase L0k at the reference antenna, a single difference L10k is obtained, whereby calculating a double difference L10k0=L10k?L100 between a k-th GNSS satellite and a reference satellite (k=0). The double difference L10k0 is also predicted using known satellite position information as a function of a differencing vector ek0 between a unit line-of-sight direction vector ek of the k-th satellite and that of the reference satellite e0 and a base line vector ? with a second integer bias N10k0. A real time kinematic (RTK) positioning solution is calculated with ambiguity resolution based on the predicted value of L10k0 and the calculated value of L10k0. A spoofing is detected if the RTK positioning solution yields ?=0.

Abstract: In RTK positioning, a calibration memory stores calibration information for combinations of GNSS receivers. A memory processor retrieves the calibration information for a selected combination of a first GNSS receiver for a base station and a second GNSS receiver for a rover from the calibration memory. A calibration apparatus, by communicating with the rover and the memory processor, receives a first correction signal associated with the first GNSS receiver, obtains the calibration information and modifies the first correction signal therewith to generate a modified correction signal calibrated for the second GNSS receiver with respect to the first GNSS receiver, and transmits the modified correction signal to the rover. The rover performs the RTK positioning with respect to a known GNSS receiver of the base station using the modified correction signal, thereby automatically achieving the frequency-dependent hardware bias calibration for the second GNSS receiver with respect to the first GNSS receiver.

Abstract: A GNSS spoofing signal detection and elimination includes acquiring and tracking a plurality of GNSS signals, authenticating the acquired signals based on available authentication information to determine if the acquired signals are authentic, unverified, or counterfeit, creating a first list of the authentic signals and a second list of unverified signals, by removing the counterfeit signal(s), creating a plurality of sets of the signals by selecting at least four GNSS signals such that each set includes all of the authentic signals and at least one unverified signal, calculating PVT solutions and post-fit residuals for each set, estimating authenticity of unverified signals by analyzing the PVT solutions and post-fit residuals, estimating authenticity and accuracy of PVT solutions based on the estimation, and outputting a list of all of the acquired GNSS signals with the respective authenticity, and a list of all possible PVT solutions with the respective authenticity and accuracy.

Abstract: Sub-microsecond time transfer in a GPS/GNSS receiver using a weak GPS/GNSS signal is provided. The digitized complex baseband signal and the generated PN code are cross-correlated for each code period so as to output a complex correlation value at each code epoch of the generated PN code, where a sequence of the output correlation values form a data stream representing the navigation message. Bit synchronization generates bit sync pulses at bit boundaries. The location of a target segment having a known sequence at a known bit location in the navigation message is detected by searching through a plurality of subframes and accumulating search results for the plurality of subframes. Transmission time of the target segment is determined from the detected location of the target segment, with a certain time ambiguity. Accurate local time is determined by solving the time ambiguity using approximate time obtained from an external source.

Abstract: A method and apparatus provide high-sensitivity GPS/GNSS signal acquisition in a stationary GPS/GNSS receiver. The uncertainty in frequency due to apparent Doppler shift is partitioned into a plurality of contiguous frequency bins, and the uncertainty in location of navigation data bit boundaries is partitioned into equally spaced trial bit boundary locations. For each combination of the trial bit boundary location and the frequency bin, a signal block of captured complex baseband signal is Doppler-compensated using a phase rotator, and then synchronously summed with a periodicity of one period of C/A code so as to produce a compressed sample block having N samples. Each compressed sample block is cross-correlated with one period of reference C/A code to produce an N-value correlation function. A predetermined number of magnitudes of the N-value correlation functions are stack-accumulated into an array with precession compensation so as to find a correlation peak having the largest value.

Abstract: Sub-microsecond time transfer in a GPS/GNSS receiver using a weak GPS/GNSS signal is provided. The digitized complex baseband signal and the generated PN code are cross-correlated for each code period so as to output a complex correlation value at each code epoch of the generated PN code, where a sequence of the output correlation values form a data stream representing the navigation message. Bit synchronization generates bit sync pulses at bit boundaries. The location of a target segment having a known sequence at a known bit location in the navigation message is detected by searching through a plurality of subframes and accumulating search results for the plurality of subframes. Transmission time of the target segment is determined from the detected location of the target segment, with a certain time ambiguity. Accurate local time is determined by solving the time ambiguity using approximate time obtained from an external source.

Abstract: A method and apparatus provide high-sensitivity GPS/GNSS signal acquisition in a stationary GPS/GNSS receiver. The uncertainty in frequency due to apparent Doppler shift is partitioned into a plurality of contiguous frequency bins, and the uncertainty in location of navigation data bit boundaries is partitioned into equally spaced trial bit boundary locations. For each combination of the trial bit boundary location and the frequency bin, a signal block of captured complex baseband signal is Doppler-compensated using a phase rotator, and then synchronously summed with a periodicity of one period of C/A code so as to produce a compressed sample block having N samples. Each compressed sample block is cross-correlated with one period of reference C/A code to produce an N-value correlation function. A predetermined number of magnitudes of the N-value correlation functions are stack-accumulated into an array with precession compensation so as to find a correlation peak having the largest value.

Abstract: Sub-microsecond time transfer in a GPS/GNSS receiver using a weak GPS/GNSS signal is provided. The digitized complex baseband signal and the generated PN code are cross-correlated for each code period so as to output a complex correlation value at each code epoch of the generated PN code, where a sequence of the output correlation values form a data stream representing the navigation message. Bit synchronization generates bit sync pulses at bit boundaries. The location of a target segment having a known sequence at a known bit location in the navigation message is detected by searching through a plurality of sub-frames and accumulating search results for the plurality of subframes. Transmission time of the target segment is determined from the detected location of the target segment, with a certain time ambiguity. Accurate local time is determined by solving the time ambiguity using approximate time obtained from an external source.

Abstract: A low-cost GPS/GNSS receiver receives a satellite signal at an RF frequency (fRF). The GPS/GNSS receiver includes a front end section for receiving the satellite signal and generating a digital complex signal having a first bandwidth, the received satellite signal being converted into a complex signal before digitizing, a signal capturing section for searching for and acquiring the satellite signal, the signal capturing section including a capture memory, a baseband processor for tracking the acquired satellite signal, and a signal splitter coupled to the front end section. The signal splitter splits the digital complex signal into two bandwidths, by generating a narrowband digital complex signal having a second bandwidth substantially smaller than the first bandwidth. The signal splitter provides the narrowband digital signal to the capture memory and the wider first bandwidth digital complex signal to the baseband processor.

Abstract: A method and apparatus provide high-sensitivity GPS/GNSS signal acquisition in a stationary GPS/GNSS receiver. The uncertainty in frequency due to apparent Doppler shift is partitioned into a plurality of contiguous frequency bins, and the uncertainty in location of navigation data bit boundaries is partitioned into equally spaced trial bit boundary locations. For each combination of the trial bit boundary location and the frequency bin, a signal block of captured complex baseband signal is Doppler-compensated using a phase rotator, and then synchronously summed with a periodicity of one period of C/A code so as to produce a compressed sample block having N samples. Each compressed sample block is cross-correlated with one period of reference C/A code to produce an N-value correlation function. A predetermined number of magnitudes of the N-value correlation functions are stack-accumulated into an array with precession compensation so as to find a correlation peak having the largest value.

Abstract: A method and apparatus provide high-sensitivity GPS/GNSS signal acquisition in a stationary GPS/GNSS receiver. The uncertainty in frequency due to apparent Doppler shift is partitioned into a plurality of contiguous frequency bins, and the uncertainty in location of navigation data bit boundaries is partitioned into equally spaced trial bit boundary locations. For each combination of the trial bit boundary location and the frequency bin, a signal block of captured complex baseband signal is Doppler-compensated using a phase rotator, and then synchronously summed with a periodicity of one period of C/A code so as to produce a compressed sample block having N samples. Each compressed sample block is cross-correlated with one period of reference C/A code to produce an N-value correlation function. A predetermined number of magnitudes of the N-value correlation functions are stack-accumulated into an array with precession compensation so as to find a correlation peak having the largest value.

Abstract: Sub-microsecond time transfer in a GPS/GNSS receiver using a weak GPS/GNSS signal is provided. The digitized complex baseband signal and the generated PN code are cross-correlated for each code period so as to output a complex correlation value at each code epoch of the generated PN code, where a sequence of the output correlation values form a data stream representing the navigation message. Bit synchronization generates bit sync pulses at bit boundaries. The location of a target segment having a known sequence at a known bit location in the navigation message is detected by searching through a plurality of sub-frames and accumulating search results for the plurality of subframes. Transmission time of the target segment is determined from the detected location of the target segment, with a certain time ambiguity. Accurate local time is determined by solving the time ambiguity using approximate time obtained from an external source.

Abstract: A low-cost GPS/GNSS receiver receives a satellite signal at an RF frequency (fRF). The GPS/GNSS receiver includes a front end section for receiving the satellite signal and generating a digital complex signal having a first bandwidth, the received satellite signal being converted into a complex signal before digitizing, a signal capturing section for searching for and acquiring the satellite signal, the signal capturing section including a capture memory, a baseband processor for tracking the acquired satellite signal, and a signal splitter coupled to the front end section. The signal splitter splits the digital complex signal into two bandwidths, by generating a narrowband digital complex signal having a second bandwidth substantially smaller than the first bandwidth. The signal splitter provides the narrowband digital signal to the capture memory and the wider first bandwidth digital complex signal to the baseband processor.

Abstract: A positioning apparatus includes a correlator 30 for calculating a correlation between the pseudo pattern code of each of satellites 1 and 2 and each of SPS signals associated with the satellites 1 and 2, and for outputting a correlation value indicating the correlation, sets up effective ranges ?1 and ?2 for the correlation values outputted from the correlator 30 on the basis of a pseudo distance PR1 between the satellite 1 and a SPS reference station 4, and a pseudo distance PR2 between the satellite 2 and the SPS reference station 4, and detects peak values which fall within the effective ranges ?1 and ?2, respectively. As a result, the positioning apparatus can determine the current position correctly even under a receiving environment in which the electric waves directly from the satellites 1 and 2 may become weak.

Abstract: A positioning apparatus includes a correlator 30 for calculating a correlation between the pseudo pattern code of each of satellites 1 and 2 and each of SPS signals associated with the satellites 1 and 2, and for outputting a correlation value indicating the correlation, sets up effective ranges ?1 and ?2 for the correlation values outputted from the correlator 30 on the basis of a pseudo distance PR1 between the satellite 1 and a SPS reference station 4, and a pseudo distance PR2 between the satellite 2 and the SPS reference station 4, and detects peak values which fall within the effective ranges ?1 and ?2, respectively. As a result, the positioning apparatus can determine the current position correctly even under a receiving environment in which the electric waves directly from the satellites 1 and 2 may become weak.

Abstract: A GPS positioning method to obtain pseudorange between a receiver terminal and a satellite by capturing a portion of received satellite signals of a predetermined time duration. A predetermined number of first input signals, equivalent to 1-bit of navigation data, are obtained with various delays in the starting point of processing. The first input signals are synchronously summed up to obtain second input signals. A PN code replica (pseudopattern) prepared by the receiver terminal operates on the second input signals to detect the polarity of the navigation bits and correct the polarity of the bits so that the bit polarity of the second input signals are always positive.

Abstract: A base station (server) transmits assisting information to the user's receiver (rover). Signals from at least 5 satellites are used for 3-dimensional positioning. Pseudorange measurements are made in a system of equations having a minimum set of unknowns X,Y,Z, and T. (X,Y,Z) is the 3D rover position in a predefined coordinate system, and T is the time at which simultaneous measurements are made to determine pseudoranges to all satellites. The position of each satellite is a vector-valued function ƒk (T) of said time T, where fk is determined from satellite ephemeris data or its equivalent, sent to the rover over a communication link, as well as from knowledge of the approximate position of the rover.

Abstract: A process is provided for accurate location determination in assisted satellite-based positioning systems in which a base station (server) transmits assisting information to the user's receiver (rover). Signals from at least 5 satellites are used for 3-dimensional positioning. Pseudorange measurements are made in a system of equations having a minimum set of unknowns X,Y,Z, and T. (X,Y,Z) is the 3D rover position in a predefined coordinate system, and T is the time at which simultaneous measurements are made to determine pseudoranges to all satellites. The position of each satellite is a vector-valued function fk (T) of said time T, where fk is determined from satellite ephemeris data or its equivalent, sent to the rover over a communication link, as well as from knowledge of the approximate position of the rover.