US 2009/0289846 A1 · Method of processing a digital signal derived from an analog input signal of a GNSS receiver, a GNSS receiver base band circuit for carrying out the method and a GNSS receiver

Abstract

An acquisition unit of a GNSS receiver base band circuit comprises an integrator (27) with a number of preprocessors (29a-h) where an incoming digital signal is mixed with different frequency signals to compensate at least in part for clock drift and Doppler shifts. The resulting digital signals are in each case, after an accumulation step reducing sample frequency, integrated over an integration period extendinging over several, e.g., twenty, basic intervals of the length of a basic sequence characteristic for a GNSS satellite, usually 1 ms, in such a way that samples separated by a multiple of the basic interval are superposed. The resulting data sequence of 1,023 digital values is stored in one of two memories (34, 35) and then, in mixers (38, 39), sequentially shifted by post-integration frequencies which are multiples of the inverse of the length of the basic interval, usually 1 kHz, whereas the pre-integration frequencies employed in the preprocessors (29a-h) deviate, with one possible exception, from the said post-integration frequencies and are usually smaller, preferably multiples of the integration period, e.g., 50 Hz.

Claims28

Dependent claims

A method of processing a digital signal consisting of digital samples derived from an analog input signal of a GNSS receiver, the digital signal containing at least one encoded binary sequence of chips of equal lengths, the binary sequence being characteristic of at least one GNSS satellite and consisting of repetitions of a characteristic basic sequence which extends over a basic interval, where at least one finite length compensated data sequence consisting of digital data values is derived from the digital signal and at least one correlation value for the at least one compensated data sequence and a correlation sequence derived from the characteristic basic sequence of the at least one GNSS satellite is determined, where the derivation of the compensated data sequence involves

mixing of the digital signal with a first group of periodic frequency signals with pre-integration frequencies of which at least one differs from any multiple of the inverse of the basic interval to compensate at least in part for clock drift and Doppler shift,
subjecting each one of a resulting first group of part-compensated digital signals to an integration over an integration interval which extends over a multiple of the length of the basic interval where subsequent samples of the part-compensated digital data signal separated by the length of the basic interval are summed up to in each case form a digital data value of a fixed length part-compensated data sequence,
mixing each one of the part-compensated data sequences in the first group with at least one further periodic frequency signal having a post-integration frequency which is a multiple of the inverse of the basic interval to provide the at least one compensated data sequence.

A method of processing a digital signal consisting of digital samples derived from an analog input signal of a GNSS receiver, the digital signal containing at least one encoded binary sequence of chips of equal lengths, the binary sequence being characteristic of at least one GNSS satellite and consisting of repetitions of a characteristic basic sequence which extends over a basic interval, where at least one finite length data sequence consisting of digital data values is derived from the digital signal and a correlation is carried out by multiplying every data value of the at least one data sequence with a binary value of a correlation sequence derived from the characteristic basic sequence of the at least one GNSS satellite whose position in the same corresponds to the position of the data value in the data sequence except for a fixed phase shift and adding up the products to form a correlation value in that correlation steps are carried out sequentially where at each step

a contribution value is determined from an evaluation subsequence which is a subsequence of the data sequence having a fixed step length greater than one and consisting of consecutive data values of the data sequence in that
from each of the data values of the evaluation subsequence a pair of evaluation values consisting of the data value multiplied with a multiplier of +1 and of the data value multiplied by a multiplier of −1 is derived,
evaluation sums over all possible combinations of evaluation values, where for each one of the data values of the evaluation subsequence one of the two evaluation values has been selected, are calculated in parallel,
from an arbitration subsequence which is a step length subsequence of the correlation sequence consisting of consecutive binary values of the correlation sequence the contribution value is determined as the evaluation sum where the multiplier of each evaluation value corresponds to the binary value whose position in the arbitration subsequence corresponds to the position of the data value the evaluation value has been derived from in the evaluation subsequence,
the contribution value is added to zero if the step is the first step and to a sum of previous contribution values otherwise,
the evaluation subsequence is replaced by a step length subsequence of the data sequence consisting of the data values immediately subsequent to the said evaluation subsequence and the arbitration subsequence is replaced by a step length subsequence of the correlation sequence immediately subsequent to the said arbitration subsequence.

3 more elements

A GNSS receiver base band circuit with an acquisition unit for processing samples of a digital data signal, the acquisition unit comprising a correlator for determining at least one correlation value, where the correlator comprises:

a correlator shift register containing a plurality of consecutive cells for holding consecutive binary values of a correlation sequence,
at least one evaluation unit with a plurality of adding units, each configured to calculate one of a plurality of evaluation sums of possible combinations of evaluation values, each forming an evaluation subsequence whose length equals a step length, and data lines each connected to an output of one of the adding units,
at least one correlator cell containing a register and an adder with a first input connected to an output of the register and a second input connected to each one of the data lines extending from the at least one evaluation unit via a switching unit and an arbitration unit which is connected to each cell of the correlator shift register pertaining to a set of consecutive cells whose number is equal to the step length and configured to control the switching unit according to binary values of an arbitration subsequence of the correlation sequence which are each contained in one of the cells.

Dependencies are inferred from the claim text.

Method of processing a digital signal derived from an analog input signal of a GNSS receiver, a GNSS receiver base band circuit for carrying out the method and a GNSS receiver

Life of this patent

Method of processing a digital signal derived from an analog input signal of a GNSS receiver, a GNSS receiver base band circuit for carrying out the method and a GNSS receiver

Life of this patent

Abstract

Claims28