Method for synchronizing a receiver, a system, and an electronic device
View Patent ↗A method for synchronizing a receiver ( 1 ) with a transmitted code-modulated spread spectrum signal, uses at least one reference code (r(x)), which corresponds to a code used in the modulation, and determines the frequency shift of the transmitted signal and the code phase of the code used in the modulation. In the method, a correlation step is taken to form a correlation function matrix on the basis of the received signal and said reference code. A non-coherent search matrix is formed of said correlation function matrix. In the method, elements in said non-coherent search matrix are modified on the basis of at least one statistical property of the elements in said non-coherent search matrix, and/or high-pass filtering is performed before the formation of said correlation function matrix. The invention also relates to a system and a receiver in which the method is applied.
1. A method for synchronizing a receiver with a transmitted code-modulated spread spectrum signal comprising:
forming correlation results on the basis of a received code-modulated spread spectrum signal and a reference code which corresponds to a code used in the modulation of said signal;
forming a correlation function matrix of the correlation results; and
forming a non-coherent search matrix of said correlation function matrix; and further comprising at least one of the following:
modifying the elements of said non-coherent search matrix on the basis of at least one statistical property of the elements of said non-coherent search matrix,
high-pass filtering the correlation results before forming said correlation function matrix.
2. A method for synchronizing a receiver with a transmitted code-modulated spread spectrum signal, in which method at least one reference code is used, which corresponds to a code used in the modulation, and the frequency shift of the transmitted signal and the code phase of the code used in the modulation are determined, wherein a correlation step is taken to form a correlation function matrix on the basis of the received signal and said reference code, a non-coherent search matrix is formed of said correlation function matrix, and that the method comprises at least one of the following steps:
modifying the elements of said non-coherent search matrix on the basis of at least one statistical property of the elements of said non-coherent search matrix, performing high-pass filtering before forming said correlation function matrix, wherein the formed non-coherent search matrix is two-dimensional, wherein one dimension of the non-coherent search matrix is the frequency and the other dimension is the code phase of the reference code.
3. The method according to claim 2 , wherein in the modification of the elements, a parameter describing the deviation of signals is calculated from the values of the different code phases for each frequency value in the non-coherent search matrix, and said parameter describing the deviation of signals, multiplied with a scaling factor, is subtracted from each value of the code phase of said frequency value.
4. The method according to claim 2 , wherein in the modification of the elements, the average is calculated from the values of the different code phases of each frequency value in the non-coherent search matrix, and said calculated average is subtracted from each value of the code phase of said frequency value.
5. A method for synchronizing a receiver with a transmitted code-modulated spread spectrum signal, in which method at least one reference code is used, which corresponds to a code used in the modulation, and the frequency shift of the transmitted signal and the code phase of the code used in the modulation are determined, wherein a correlation step is taken to form a correlation function matrix on the basis of the received signal and said reference code, a non-coherent search matrix is formed of said correlation function matrix, and that the method comprises at least one of the following steps:
modifying the elements of said non-coherent search matrix on the basis of at least one statistical property of the elements of said non-coherent search matrix. performing high-pass filtering before forming said correlation function matrix, comprising forming said correlation function matrix, sampling the signal after the formation of said correlation function matrix at a predetermined sampling frequency, and determining the frequency of at least one spurious signal in said signal after the sampling, to suppress the effect of the interference, which is at least one of the following:
a spurious signal close to the frequency of the signal to be received,
DC shift interference.
6. The method according to claim 5 , wherein the received signal is subjected to frequency conversion by mixing the received signal with a local oscillator signal, and that said determination of the frequency of at least one spurious signal is made on the basis of the frequency of said local oscillator signal.
7. A system comprising:
a receiver configured for acquiring a code-modulated spread spectrum signal, for generating at least one reference code corresponding to the code used in the modulation, for determining the frequency shift of the transmitted signal and the code phase of the code used in the modulation; wherein the system is configured for forming a correlation function matrix on the basis of the received signal and said reference code, for forming a non-coherent search matrix from said correlation function matrix, and for at least one of the following:
for modifying the elements of said non-coherent search matrix on the basis of at least one statistical property of the elements of said non-coherent search matrix,
for high-pass filtering correlation results before forming said correlation function matrix.
8. An electronic device comprising:
a receiver configured for acquiring a code-modulated spread spectrum signal, for generating at least one reference code corresponding to the code used in the modulation, for determining the frequency shift of the transmitted signal and the code phase of the code used in the modulation; wherein the electronic device is configured for forming a correlation function matrix on the basis of the received signal and said reference code, for forming a non-coherent search matrix from said correlation function matrix, and is configured for at least one of the following:
for modifying the elements of said non-coherent search matrix on the basis of at least one statistical property of the elements of said non-coherent search matrix,
for high-pass filtering correlation results before forming said correlation function matrix.
9. An electronic device comprising a receiver with means for acquisition of configured for acquiring a code-modulated spread spectrum signal, means for generating at least one reference code corresponding to the code used in the modulation, and means for determining the frequency shift of the transmitted signal and the code phase of the code used in the modulation, wherein the electronic device also comprises correlation means is configured for forming a correlation function matrix on the basis of the received signal and said reference code, means for forming a non-coherent search matrix from said correlation function matrix, and is configured for at least one of the following means:
means for modifying the elements of said non-coherent search matrix on the basis of at least one statistical property of the elements of said non-coherent search matrix,
means for performing high-pass filtering before the formation of said correlation results before forming said correlation function matrix.
wherein said non-coherent search matrix is two-dimensional, wherein one dimension is the frequency and the other dimension is the code phase of the reference code.
10. The electronic device according to claim 9 , wherein the means for modifying the elements in said non-coherent search matrix comprise means for computing the standard deviation from the values of the different code phases for each frequency value in the non-coherent search matrix, and means for subtracting said computed standard deviation, multiplied by a scaling factor, from each code phase value for said frequency value.
11. The electronic device according to claim 9 , wherein the means for modifying the elements in said non-coherent search matrix comprise means for computing the average from the values of the different code phases for each frequency value in the non-coherent search matrix, and means for subtracting said computed average from each code phase value for said frequency value.
12. The electronic device according to claim 9 , comprising means for sampling the signal after the forming of said correlation function matrix.
13. The electronic device according to claim 8 , comprising means for performing functions of a mobile station.
14. The electronic device according to claim 8 , wherein the receiver is a satellite positioning receiver.
15. The electronic device according to claim 8 , wherein the correlation means comprise a matched filter.
16. The electronic device according to claim 8 , wherein said non-coherent search matrix is two-dimensional, wherein one dimension is the frequency and the other dimension is the code phase of the reference code.