A personal navigation device includes a correlator for processing GNSS signals from a constellation of satellites A signal is received from a navigation beacon containing a repeating code word, in which the code word includes a number N of samples corresponding to N phases, and in which reception of each code word occurs within a defined time period T. The sequence of N code samples is correlated with a known code word to determine a maximum value of correlation for a particular phase of the received signal. The correlation is performed using a correlator of size M, in which M is less than N, such that N/M=P complete correlations for a partial code phase are performed such that each correlation of a partial code phase is performed within a time period of approximately T/P. All P correlations of partial code phases are completed within time T.

Circuits and methods concerning signal detection are disclosed. In some example embodiments, an apparatus is configured to detect presence of a spreading sequence in a sample data sequence. Phase differences between samples in a sample sequence are determined. Presence of a spreading sequence in the sample sequence is detected by evaluating correlation of reference sub-sequences, of a reference spreading sequence, to the phase differences between samples in a sample sequence. Each of the reference sub-sequences includes fewer chips than the spreading sequence to be detected.

Systems and methods for improving correlation. In at least one system and method, a signal is received and divided into a plurality of slices. Each of the slices is divided into a plurality of sub-slices. A plurality of chips of a PN code are generated, and sub-slice correlation results are generated in parallel. Summation of the sub-slice correlation results generates a slice correlation results, and the accumulated slice correlation results provide a correlation result.

A method of detecting transient changes in the distribution of a discrete time series includes: operating in a sparse mode wherein, at sniff periods successively repeated at a first rate, at most K test phases are performed, K being an integer superior or equal to two, each test phase consisting of analyzing, by a sampling stopping time determination unit, samples of the time series captured by a sampler at sampling times according to a second rate which is higher than the first rate to provide a positive or negative result of the test phase. If the results of K successive test phases of a sniff period are each positive, the method switches to operate in a dense mode wherein the sampler is operated to continuously capture samples of the time series at sampling times according to the second sampling rate.

A method of generating a BOC correlation function based on partial correlation functions, an apparatus for tracking a BOC signal, and a spread spectrum signal receiver system using the same are disclosed herein. The apparatus includes a frequency offset compensation unit, a local code generation unit, a mixer, a delay lock loop (DLL), a phase lock loop (PLL), and a data extraction unit. The frequency offset compensation unit outputs a compensated received signal with respect to a received signal. The local code generation unit generates a delay-compensated local code based on a code delay value. The mixer mixes the delay-compensated local code with the frequency offset-compensated received signal. The DLL repeatedly tracks and calculates a code delay value. The PLL repeatedly calculates a carrier frequency compensation value. The data extraction unit extracts spreading data from a mixture of the delay-compensated local code and the compensated received signal.

This detection method is carried out after a phase for acquiring a navigation signal during a convergence phase and comprises at least one of the following steps: —determining a plurality of pilot channel periodic correlations and a plurality of data channel periodic correlations, and determining a first value as a function of these periodic correlations; —determining a plurality of pilot channel partial correlations, and determining a second value as a function of these partial correlations; —determining a plurality of shifted pilot channel correlations, and determining a third value as a function of these shifted pilot channel correlations. The convergence phase further comprises the step for determining a wrong synchronization when at least one of the first value, the second value, and the third value exceeds a predetermined threshold.

A round-trip, spread-spectrum navigation and locating system achieves high capacity and large processing gains in one-to-many and many-to-one configurations using round-trip signaling with frequency division based upon precise responding device carrier frequency offsets. Reduced cross-correlation is achieved by assigning these very small disparate frequency offsets to replies from interrogated devices so that the long-term correlation between disparate reply sequences is reduced almost to that of random noise of equivalent energy. The invention supports simultaneous interrogation of multiple responding devices, which responding devices respond essentially simultaneously at a fixed delay after receiving the query. The originating and/or responding devices may be fixed or mobile, permanently or temporarily deployed, terrestrial, airbourne or space-based with any source of power including batteries and solar without limitation. The signaling may be electromagnetic or acoustic with the potential for under-water use.

A round-trip, spread-spectrum navigation and locating system achieves high capacity and large processing gains in one-to-many and many-to-one configurations using round-trip signaling with frequency division based upon precise responding device carrier frequency offsets. Reduced cross-correlation is achieved by assigning these very small disparate frequency offsets to replies from interrogated devices so that the long-term correlation between disparate reply sequences is reduced almost to that of random noise of equivalent energy. The invention supports simultaneous interrogation of multiple responding devices, which responding devices respond essentially simultaneously at a fixed delay after receiving the query. The originating and/or responding devices may be fixed or mobile, permanently or temporarily deployed, terrestrial, airbourne or space-based with any source of power including batteries and solar without limitation. The signaling may be electromagnetic or acoustic with the potential for under-water use.

A GNSS correlator comprises a buffer and a processing unit. The buffer is configured to store input data representing sample values of a GNSS signal captured over a pre-defined time window. The processing unit is configured to receive one or more correlation parameters in a control signal, and, in a first pass, read the input data from the buffer and perform a first correlation operation on the input data, and, in a second pass, re-read the same input data from the buffer and perform a second correlation operation on the same input data, wherein the second correlation operation is different to the first correlation operation.

This detection method is carried out after a phase for acquiring a navigation signal during a convergence phase and comprises at least one of the following steps: determining a plurality of pilot channel periodic correlations and a plurality of data channel periodic correlations, and determining a first value as a function of these periodic correlations; determining a plurality of pilot channel partial correlations, and determining a second value as a function of these partial correlations; determining a plurality of shifted pilot channel correlations, and determining a third value as a function of these shifted pilot channel correlations.

The convergence phase further comprises the step for determining a wrong synchronization when at least one of the first value, the second value, and the third value exceeds a predetermined threshold.