Abstract: A method comprises receiving a plurality of signals from a plurality of space-based satellites, wherein the plurality of space-based satellites comprises at least one space-based satellite from each of a plurality of Navigation Satellite System (NSS) constellations. The method also comprises determining, in a first domain, a first plurality of sub-solutions based on a respective sub-set of the plurality of signals, each respective sub-set in the first domain chosen according to a characteristic defining the first domain; and determining, in a second domain, a second plurality of sub-solutions based on a respective sub-set of the plurality of signals, each respective sub-set in the second domain chosen according to a characteristic defining the second domain. The method further comprises determining if an error is present in the navigation system based on the first plurality of sub-solutions and on the second plurality of sub-solutions.

Abstract: A global navigation satellite system (GNSS) receiver includes: at least one radio frequency (RF) front end configured to receive a GNSS signal from a single GNSS antenna and to digitize the GNSS signal into a digitized GNSS signal; at least one processor configured to: calculate weight to be applied to a sample of a block of samples of the digitized GNSS signal; apply the weight to at least one sample of the block of samples of the digitized GNSS signal to create a weighted GNSS signal; and perform signal processing on the weighted GNSS signal.

Abstract: In one embodiment, a method for selecting a sub-set of satellites from a set of N satellites is provided. The method includes recursively evaluating each sub-set of N?P satellites of a set of N satellites. If only one sub-set satisfies one or more first criterion, then the one sub-set that satisfies the one or more first criterions is selected. If, however, more than one sub-set satisfies the one or more first criterion, then the sub-sets that satisfy the one or more first criterion are evaluated with respect to one or more second criterion and the one sub-set that optimizes the one or more second criterion is selected. Once the selected set of N satellites is equal to the number of satellites from which a receiver is configured to calculate a navigation solution, then that selected set of N satellites is used to calculate a navigation solution.

Abstract: A global navigation satellite system (GNSS) receiver includes a processor to determine whether a first satellite is in view of GNSS receiver; whether a second satellite is in view of GNSS receiver when first satellite is in view of GNSS receiver; and whether a third satellite is in view of GNSS receiver when first satellite is not in view of GNSS receiver. Second satellite was previously determined more likely to be in view when first satellite is in view based on a first average distance between first satellite and second satellite based on a first orbit of first satellite and a second orbit of second satellite. Third satellite was previously determined more likely to be in view when first satellite is not in view based on a second average distance between first satellite and third satellite based on first orbit of first satellite and a third orbit of third satellite.

Abstract: A method of performing a discrete Fourier transform (DFT) on one or more data samples in a global navigation satellite system baseband tracking channel is provided. The method comprises loading a pseudorandom noise code generator with a constant value in the baseband tracking channel; setting a tracking loop integration time according to a selected frequency resolution; updating a carrier generator with a selected DFT frequency in the baseband tracking channel; integrating a data sample in the baseband tracking channel; and storing the integrated data sample in a DFT bin. The method determines whether all DFT bins have been received, and if all DFT bins have not been received, the method repeats starting with updating the carrier generator, until all DFT bins have been received.

Abstract: An efficient covariance matrix computation method is disclosed in connection with certain GNSS applications, including ARAIM and geometry screening. The system and method of the present application enable computation of multiple covariance matrices with substantially greater efficiency than previous approaches, including the rank-one update formula. For example, the system and method of the present application advantageously involves substantially fewer and simpler arithmetic operations than previous approaches. In addition, unlike the rank-one update formula, the system and method of the present application can be used to compute the subsolution in which all the satellites of a given constellation are removed.

Abstract: A global navigation satellite system (GNSS) receiver including a processing device configured to: group GNSS satellites in view of the GNSS receiver into subsets based on relative geometries of the GNSS satellites relative to the GNSS receiver, wherein a GNSS satellite of the GNSS satellites is included in at most one subset of the subsets, wherein each subset of the subsets includes at least one GNSS satellite of the GNSS satellites and less than all GNSS satellites of the GNSS satellites, and wherein at least one subset includes more than one GNSS satellite; calculate a plurality of navigation sub-solutions based on data received at the GNSS receiver from the GNSS satellites using at least one GNSS antenna, wherein each navigation sub-solution of the navigation sub-solutions is calculated with at least one different subset of the subsets excluded; and calculate a protection level based on the navigation sub-solutions.

Abstract: A global navigation satellite system (GNSS) receiver includes radio frequency front end and digital processing functionality. Radio frequency front end includes radio frequency input; first variable gain amplifier adjusts first gain of first frequency range of first analog GNSS signal received from radio frequency input by first amount; and second variable gain amplifier adjusts second gain of second frequency range of second analog global navigation satellite system signal received from radio frequency input by second amount. Digital processing functionality compares first amount of adjustment of first gain of first frequency range with second amount of adjustment of second gain of second frequency range; and detects first interference signal present in first frequency range or second frequency range when first amount of adjustment of the first gain of first frequency range differs from second amount of adjustment of second gain of second frequency range by more than first threshold amount.

Abstract: A method of advanced receiver autonomous integrity monitoring of a navigation system is discussed and two modifications facilitating its implementation in a hybrid navigation system are disclosed. In the first approach, relations describing the effect of unmodeled biases in pseudo-measurement on the Kalman filter state estimate are analytically derived and their incorporation into the integrity monitoring algorithm is described. The method comprises receiving a plurality of signals transmitted from space-based satellites, determining a position full-solution and sub-solutions, specifying a pseudorange bias, computing a transformation matrix for the full-solution and all sub-solutions using a Kalman filter, computing a bias effect on an error of filtered state vectors of all sub-solutions, and adding the effect to computed vertical and horizontal protection levels.

Abstract: A method of advanced receiver autonomous integrity monitoring of a navigation system is discussed and two modifications facilitating its implementation in a hybrid navigation system are disclosed. In the first approach, relations describing the effect of unmodeled biases in pseudo-measurement on the Kalman filter state estimate are analytically derived and their incorporation into the integrity monitoring algorithm is described. The method comprises receiving a plurality of signals transmitted from space-based satellites, determining a position full-solution and sub-solutions, specifying a pseudorange bias, computing a transformation matrix for the full-solution and all sub-solutions using a Kalman filter, computing a bias effect on an error of filtered state vectors of all sub-solutions, and adding the effect to computed vertical and horizontal protection levels.

Abstract: Systems and methods for a scanning correlator for global navigation satellite system signal tracking are provided. In one embodiment, a method for Global Navigation Satellite System (GNSS) receiver tracking comprises: receiving a GNSS navigation signal; generating a local Pseudo Random Noise (PRN) sequence; sampling the GNSS navigation signal over a plurality of integration periods to produce a plurality of scanning values, wherein each scanning value has a respective time offset such that at least one first time offset is not equal to at least one second time offset; estimating at least two points of an autocorrelation function for the GNSS navigation signal based on the plurality of scanning values; and calculating an alignment between the GNSS signal and the local PRN sequence based on the autocorrelation function estimate.

Abstract: Systems and methods for a scanning correlator for global navigation satellite system signal tracking are provided. In one embodiment, a method for Global Navigation Satellite System (GNSS) receiver tracking comprises: receiving a GNSS navigation signal; generating a local Pseudo Random Noise (PRN) sequence; sampling the GNSS navigation signal over a plurality of integration periods to produce a plurality of scanning values, wherein each scanning value has a respective time offset such that at least one first time offset is not equal to at least one second time offset; estimating at least two points of an autocorrelation function for the GNSS navigation signal based on the plurality of scanning values; and calculating an alignment between the GNSS signal and the local PRN sequence based on the autocorrelation function estimate.

Abstract: Embodiments for satellite subset selection for use in monitoring the integrity of computed navigation solutions are disclosed. In one embodiment, a Global Navigation Satellite System (GNSS) receiver comprises: a processing device configured to: group a plurality of satellites in view of the GNSS receiver into a plurality of subsets, wherein a satellite of the plurality of satellites is included in at most one subset of the plurality of subsets, wherein each subset of the plurality of subsets includes at least one satellite of the plurality of satellites and less than all satellites of the plurality of satellites, and wherein at least one subset includes more than one satellite; calculate a plurality of navigation sub-solutions, wherein each navigation sub-solution of the plurality of navigation sub-solutions is calculated with at least one different subset of the plurality of subsets excluded; and calculate a protection level.

Abstract: A global navigation satellite system (GNSS) receiver includes radio frequency front end and digital processing functionality. Radio frequency front end includes radio frequency input; first variable gain amplifier adjusts first gain of first frequency range of first analog GNSS signal received from radio frequency input by first amount; and second variable gain amplifier adjusts second gain of second frequency range of second analog global navigation satellite system signal received from radio frequency input by second amount. Digital processing functionality compares first amount of adjustment of first gain of first frequency range with second amount of adjustment of second gain of second frequency range; and detects first interference signal present in first frequency range or second frequency range when first amount of adjustment of the first gain of first frequency range differs from second amount of adjustment of second gain of second frequency range by more than first threshold amount.

Abstract: A global navigation satellite system (GNSS) receiver includes a processor to determine whether a first satellite is in view of GNSS receiver; whether a second satellite is in view of GNSS receiver when first satellite is in view of GNSS receiver; and whether a third satellite is in view of GNSS receiver when first satellite is not in view of GNSS receiver. Second satellite was previously determined more likely to be in view when first satellite is in view based on a first average distance between first satellite and second satellite based on a first orbit of first satellite and a second orbit of second satellite. Third satellite was previously determined more likely to be in view when first satellite is not in view based on a second average distance between first satellite and third satellite based on first orbit of first satellite and a third orbit of third satellite.

Abstract: Systems and methods for satellite signal tracking are provided. In one embodiment, a GNSS tracking system comprises: a carrier demodulator that receives a navigation signal including pilot and data signal components; a correlator block that implements early, prompt and late correlators, generates prompt values from the pilot signal, and generates early and late values from the data signal; a carrier tracking loop that generates a reference signal using the prompt values, and outputs the reference signal to the carrier demodulator; a code tracking loop that outputs a pilot signal local replica to the prompt correlator and a data signal local replica to the early and late correlators, wherein a chip rate for the local replicas is adjusted by the code tracking loop as a function of the early and late values; and a symbol demodulator that extracts navigation data from the data signal component using the early and late values.

Abstract: In one embodiment, a method for selecting a sub-set of satellites from a set of N satellites is provided. The method includes recursively evaluating each sub-set of N?P satellites of a set of N satellites. If only one sub-set satisfies one or more first criterion, then the one sub-set that satisfies the one or more first criterions is selected. If, however, more than one sub-set satisfies the one or more first criterion, then the sub-sets that satisfy the one or more first criterion are evaluated with respect to one or more second criterion and the one sub-set that optimizes the one or more second criterion is selected. Once the selected set of N satellites is equal to the number of satellites from which a receiver is configured to calculate a navigation solution, then that selected set of N satellites is used to calculate a navigation solution.

Abstract: A method comprises receiving a plurality of signals from a plurality of space-based satellites, wherein the plurality of space-based satellites comprises at least one space-based satellite from each of a plurality of Navigation Satellite System (NSS) constellations. The method also comprises determining, in a first domain, a first plurality of sub-solutions based on a respective sub-set of the plurality of signals, each respective sub-set in the first domain chosen according to a characteristic defining the first domain; and determining, in a second domain, a second plurality of sub-solutions based on a respective sub-set of the plurality of signals, each respective sub-set in the second domain chosen according to a characteristic defining the second domain. The method further comprises determining if an error is present in the navigation system based on the first plurality of sub-solutions and on the second plurality of sub-solutions.

Abstract: Systems and methods for enhancing numerically controlled oscillators are provided. In certain embodiments, a numerically controlled oscillator enhancer includes a desired rate interface configured to receive a desired numerically controlled oscillator rate from an external device and a closest quantized rate identifier configured to identify a closest quantization rate that is closest to the desired numerically controlled oscillator rate. Further, the numerically controlled oscillator enhancer includes a quantization rate corrector configured to identify the quantization rate correction that, when applied to the closest quantization rate, constrains an accumulated quantization error within an error range and a rate output configured to output a corrected quantized numerically controlled oscillator rate.

Abstract: Systems and methods for enhancing numerically controlled oscillators are provided. In certain embodiments, a numerically controlled oscillator enhancer includes a desired rate interface configured to receive a desired numerically controlled oscillator rate from an external device and a closest quantized rate identifier configured to identify a closest quantization rate that is closest to the desired numerically controlled oscillator rate. Further, the numerically controlled oscillator enhancer includes a quantization rate corrector configured to identify the quantization rate correction that, when applied to the closest quantization rate, constrains an accumulated quantization error within an error range and a rate output configured to output a corrected quantized numerically controlled oscillator rate.