Patent US3174648A successfully refreshed from Google Patents.
Patent EP0665665B1 successfully refreshed from Google Patents.
EP0665665B1
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Method and device enabling a modem to synchronize on a transmitter of digital data via a radio channel in the presence of interferences
Assignee: Thales SA
•
Filing: 1995-01-13
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Granted: 2001-05-16
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Expires: 2015-01-13
Abstract
No abstract record available.
Inventors
- 👤 Pascal Chevalier
- 👤 François Pipon
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-28 21:19
CPC Classifications
H; H04; H04B; H04B7/00; H04B7/02; H04B7/04; H04B7/08; H04B7/0837; H04B7/0842; H04B7/0848; H04B7/0854; H04L; H04L7/00; H04L7/04; H04L7/041; H04L7/042; H04B7/0851; H04B7/0857; H04L7/02; H04L7/027
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
306 words
Method enabling a modem to be synchronized with
an RF digital signal transmitter in the presence of
jammers consisting in: estimating (9) the matrix of correlation R and xx of signals
received on a set of N reception sensors (1 1 ... 1 N ) by
blocks formed by a number of samples of a
synchronization sequence transmitted by the
transmitter, Computing (10) the reverse correlation matrix R and xx -1 , computing (11) vectors of intercorrelation r and xd between
the signals X(k) received on the set of the N sensors
and a known replica signal d(k), computing a criterion of synchronization (7)
calculating the scalar product between the
intercorrelation vector r XD and the vector obtained by
the product of the inverse of the correlation matrix R and xx -1 and the intercorrelation vector r xd , comparing (8) the value of the criterion obtained with
a determined threshold value η to place the
synchronization on the sample for which the value of
the criteria exceeds the threshold value η, characterized in that, in order to estimate the Doppler
shift inherent in the communications between
transmitters and receivers, said method consists in
subdividing the synchronization sequence into a
determined number
M of sections of k o symbols, carrying out (11, 13) computations, on these sections,
of partial intercorrelation vectors r and xd (i = 1 ... M)
in such a way that, on each of the sections of k o symbols, the Doppler shift causes the phase to rotate
by a value of less than 90°, carrying out (12, 14) fast Fourier transform (FFT)
computations on the vectors r and xdi obtained, and computing a value of the synchronization criterion
from the vectors r xd (kΔf), obtained as a result of the
fast Fourier transform computations and the correlation
matrix R and xx .
Claim 2
Dependent Claim
55 words
Method according to Claim 1, characterized in
that the estimation of the correlation matrix R and xx is
obtained by the relationship and the intercorrelation vector is estimated according
to the relationship. where p is the position of the first sample from which
the correlation is done between the vector X and the
replica d.
Claim 3
Dependent Claim
42 words
Method according to Claim 2, consisting in
choosing the computation bin of the fast Fourier
transform that gives a maximum value of the
synchronization criterion and in comparing the maximum
value obtained with a determined threshold value to
decide on the synchronization.
Claim 4
Dependent Claim
68 words
Method according to any one of Claims 1 to 3,
characterized in that to obtain an improved resolution
on the Doppler shift and a greater value of the maximum
of the criterion, consists in computing (13) frequency-shifted
vectors r xdi and in performing an FFT
computation on the shifted vectors r xdi so as to obtain
the value of the criterion with higher resolution on
the Doppler frequencies.
Claim 5
Dependent Claim
38 words
Method according to any one of Claims 1 to 4
characterized in that it consists in oversampling the
signals received on the N sensors with respect to the
symbol rate to improve the resolution on the
synchronization position.
Claim 6
Dependent Claim
47 words
Method according to any one of Claims 1 to 5,
characterized in that it consists in computing the
correlation matrix R and xx on a number of samples K'
greater than the number K of samples of the
synchronization sequence in order to reduce the
computing power.
Claim 7
Dependent Claim
116 words
Method according to any one of Claims 1 to 6,
characterized in that in order to reduce the computing
power and after having carried out an oversampling by a
factor L with respect to the symbol rate, it consists
in carrying out a pre-treatment step consisting of the
computation, for each sample p (p = 1 to L) forming a
symbol, of the values Ci of the criterion of
synchronization on each of the M sections of k 0 symbols
and computing the value of the criterion by taking the
sum of the criteria Ci obtained to keep, in the
subsequent processing, the sample giving the maximum
value of the criterion: C = ΣC i .
Claim 8
Dependent Claim
292 words
Device for implementing the method according to
any one of Claims 1 to 7 of the type comprising a
network of N sensors (1 1 ...1 N ) of reception signals
coupled with a network of adaptive filters comprising
amplitude-phase weighting circuits controlled by a
control processor, the control processor being
programmed to: estimate the inverse matrix of correlation R and xx -1 of the
received signals X(K) and compute the vectors of
intercorrelation r and xd between the signals X(k) and the
replica signal d(k) characterized in that it comprises
processing means (5...19) to compute a criterion of
synchronization (7) by calculating the scalar product
between the intercorrelation vector r xd and the vector
obtained by the product of the inverse of the
correlation matrix R xx -1 and the intercorrelation vector
r and xd , compare (8) the value of the criterion obtained
with the threshold value η to place the synchronization
on the sample for which the value of the criteria
exceeds the threshold value η, and estimate the Doppler shift inherent in the
communications between transmitters and receivers by
subdividing the synchronization into a determined
number M of sections of k o symbols, carrying out (11, 13) computation on these sections, of
partial intercorrelations vectors r and xd (i = 1...M) in
such a way that, on each of the sections of k o symbols,
the Doppler shift causes the phase to rotate by a value
of less than 90°, carrying out (12, 14) fast Fourier transform (FFT)
computations on the vectors r and xdi obtained, and computing a value of the synchronization criterion
from the vectors r xd (kΔf), obtained as a result of the
fast Fourier transform computations and the correlation
matrix R and xx .
References Cited (Backward Citations)
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