Apparatus and methods for symbol timing synchronization in a direct-sequence spread-spectrum receiver may use non-coherent integration, thresholding, peak selection, and curve fitting to determine appropriate timing instants at which to select despread samples for further processing, such as demodulation and decoding. The curve fitting may be used to search backwards and/or forwards in time to obtain the timing instants.

Correlation circuitry (2) includes selection circuitry (4) for selecting a sequence of symbol subsets comprising proper subsets of a candidate sequence of symbols and corresponding proper subsets of a target sequence of symbols. Correlation value determining circuitry (6) determines partial correlation values for these proper subsets which are then combined by correlation value combining circuitry (8) to generate a current combined correlation value. Early termination circuitry (10) compares the current combined correlation value with a early termination condition represented by a threshold value to determine whether or not early termination of the correlation determination may be performed. Early termination may be performed when the combined correlation value indicates a sufficient degree of confidence in the partial result determined such that continuing with determination of the full correlation is not justified.

A method between a geolocation receiver and an identified transmitting satellite, the receiver being able to receive a composite radio signal including a plurality of navigation signals each transmitted by a transmitting satellite that is part of a satellite constellation, a method for validating the synchronization between a geolocation receiver and a transmitting satellite during a phase for acquiring an augmentation signal including geolocation correction and integrity data; the methods include, for each identified transmitting satellite, extracting received ephemerid words or received words of any type of the received signal associated with the identified satellite as it is received, and comparing at least one received word with at least one word of the same rank or stored for the identified satellite and/or for at least one other satellite; the validation or non-validation of the synchronization with the identified transmitting satellite depends on a predetermined false alarm probability and/or non-detection probability.

Apparatus and methods for symbol timing synchronization in a direct-sequence spread-spectrum receiver may use non-coherent integration, thresholding, peak selection, and curve fitting to determine appropriate timing instants at which to select despread samples for further processing, such as demodulation and decoding. The curve fitting may be used to search backwards and/or forwards in time to obtain the timing instants.

A personal navigation device includes a correlator for processing GNNS 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.

An apparatus and method for detecting a burst signal. The apparatus includes circuitry that concatenates a predetermined number of samples and transmits the samples to a first programmable memory tap of a predetermined number of programmable memory taps. For each memory tap, a corresponding partial correlation is computed. A normalized sum of all the partial correlations is multiplexed and transmitted to a predetermined number of multipliers. A peak of the burst signal is determined by computing a summation of the complex multiplications of each multiplier, wherein the determined peak corresponds to a start of the burst signal.

A device and method for estimating a bias in a frequency estimate of a received signal. Circuitry generates a first signal including a number of sample-blocks, wherein the first signal is shifted in frequency from the received signal by a first frequency shift. Based on the first signal, a second signal and a third signal are generated, by shifting a frequency of each of the samples of the first generated signal by a second frequency shift and a third frequency shift, respectively. For each generated signal, a variance for each sample-block is computed. An average variance of the computed sample-block variances is further calculated and a bias of the received signal is determined as one of the first frequency shift, the second frequency shift, and the third frequency shift, corresponding to the generated signal having the smallest calculated average variance.

A device and method for unwrapping phase samples of a burst signal. The device generates a set of vectors including phase samples. A first mean and a first variance of the vectors is computed, and a set of unwrapped phase samples of the burst signal are computed by rotating phase samples of the vector having a smallest first variance by a first rotation amount. The set of vectors is updated based on a new phase sample and a second mean and a second variance of the updated set of vectors is computed. Differences between unwrapped phase samples and a number of phase samples included in the vector having the smallest computed second variance are computed. A next unwrapped phase sample is generated by rotating the new phase sample by a second rotation amount corresponding to a median value of the computed differences.

Apparatus and methods for symbol timing synchronization in a direct-sequence spread-spectrum receiver may use non-coherent integration, thresholding, peak selection, and curve fitting to determine appropriate timing instants at which to select despread samples for further processing, such as demodulation and decoding. The curve fitting may be used to search backwards and/or forwards in time to obtain the timing instants.