초록 ▼

The invention relates to a method for acquiring a receiver (1) into a code modulated spread spectrum signal received by the receiver (1). In the method at least one replica code (r) is used which corresponds to a code used with the modulation having a pre-determined number of chips, and an examinati

The invention relates to a method for acquiring a receiver (1) into a code modulated spread spectrum signal received by the receiver (1). In the method at least one replica code (r) is used which corresponds to a code used with the modulation having a pre-determined number of chips, and an examination phase is performed, in which a frequency shift of the signal within a selected frequency area is examined, and a code phase of the code used with the modulation is examined. In the method the frequency shift examination is divided into a first estimation phase and a second estimation phase, wherein in the first estimation phase the selected frequency area is divided into a first set of frequencies, and in the second estimation phase a second set of frequencies is examined nearby each frequency of the first set of frequencies. Further, a comparison for frequencies of the second set of frequencies is performed using the received signal and the replica code (r), and the results of the comparison are used to estimate the correct frequency shift.

대표청구항 ▼

1. A method for acquiring a receiver into a code modulated spread spectrum signal received by the receiver, in which method at least one replica code is used which corresponds to a code used with the modulation having a pre-determined number of chips, and an examination phase is performed, in which

1. A method for acquiring a receiver into a code modulated spread spectrum signal received by the receiver, in which method at least one replica code is used which corresponds to a code used with the modulation having a pre-determined number of chips, and an examination phase is performed, in which a frequency shift of the signal within a selected frequency area is examined, and a code phase of the code used with the modulation is examined, wherein the frequency shift examination is divided into a first estimation phase and a second estimation phase, wherein in the first estimation phase the selected frequency area is divided into a first set of frequencies, and in the second estimation phase a second set of frequencies is examined nearby each frequency of the first set of frequencies, that a comparison for frequencies of the second set of frequencies is performed using the received signal and the replica code, and that the results of the comparison are used to estimate a correct frequency shift.2. The method according to the claim 1, in which a reference oscillator signal is formed, wherein in each of the first estimation phases the received signal is mixed with said reference oscillator signal, that a frequency of the reference oscillator is set into a different frequency for different first estimation phases, and that the mixed signal is used in the second estimation phase.3. The method according to the claim 1, wherein a time-to-frequency transformation of a reversal of the replica code is produced, that in each of the first estimation phase a transformed, reversed replica code is shifted such that in different first estimation phases a different phase shift of the transformed, reversed replica code is used.4. The method according to claim 1, wherein the received signal is sampled for producing a set of samples, a matrix is formed from the samples, the matrix having a first dimension and a second dimension, and the second estimation phase having the steps of performing a first time-to-frequency transform on the matrix in said second dimension, and performing a second time-to-frequency transform on the time-to-frequency transformed matrix in said first dimension.5. The method according to claim 4, wherein a time-to-frequency transform is performed on a reversed replica code, the time-to-frequency transformed replica code is multiplied with a resulting matrix of the second time-to-frequency transformation, a frequency-to-time transform is performed on a resulting matrix of the multiplication.6. The method according to claim 5, wherein a non-coherent processing is performed on at least one frequency-to-time transformed matrix, in which non-coherent processing a maximum value is searched for finding a correct frequency shift and code phase.7. The method according to claim 4, wherein said first dimension equals the number of samples of the code period.8. The method according to claim 1, wherein the received signal is sampled for producing a set of samples, a matrix is formed from the samples, the matrix having a first dimension and a second dimension, a compensation matrix is formed, and the second estimation phase having the steps of performing a first time-to-frequency transform on the matrix in said second dimension, multiplying the time-to-frequency transformed matrix with the compensation matrix to form a compensated matrix, and performing a second time-to-frequency transform on the compensated matrix in said first dimension.9. The method according to claim 8, wherein said first dimension equals the number of chips of the code.10. A location system comprising at least:a receiver having means for receiving code modulated spread spectrum signal, means for acquiring the receiver into the received signal, means for using at least one replica code which corresponds to a code used with the modulation, which code having a pre-determined number of chips, and examination means for examining a frequency shift of the signal within a selected frequency area, and a code phase of the code used with the modulation, wherein the examination of the frequency shift is divided into a first estimation phase and a second estimation phase, wherein the location system further comprises:means for dividing the selected frequency area into a first set of frequencies for the first estimation phase, means for examining a second set of frequencies nearby each frequency of the first set of frequencies in the second estimation phase, and means for performing a comparison for frequencies of the second set of frequencies by using the received signal and the replica code, and the examination means comprise means for evaluating a the correct frequency shift by using the results of the comparison.11. The location system according to the claim 10, further comprising a reference oscillator for producing a reference oscillator signal, wherein the location system further comprises:means for mixing the received signal with said reference oscillator signal in the first estimation phases, and means for adjusting a frequency of the reference oscillator into a different frequency for different first estimation phases, and that the mixed signal is arranged to be used in the second estimation phase.12. The location system according to the claim 10, wherein it comprises means for producing a time-to-frequency transformation of a reversal of the replica, and for shifting the transformed, reversed replica code in each of the first estimation phase such that in different first estimation phases a different phase shift of the transformed, reversed replica code is arranged to be used.13. The location system according to claim 10, wherein it comprises:means for sampling the received signal for producing a set of samples, means for forming a matrix from the samples, the matrix having a first dimension and a second dimension, means for performing a first time-to-frequency transform on the matrix in said second dimension, and means for performing a second time-to-frequency transform on the time-to-frequency transformed matrix in said first dimension. 14. The location system according to claim 13, wherein it comprises:means for forming a time-to-frequency transformed reversed replica code, means for multiplying the time-to-frequency transformed reversed replica code with the resulting matrix of the second time-to-frequency transformation, and means for performing a frequency-to-time transform on the resulting matrix of the multiplication. 15. The location system according to the claim 14, wherein it comprises means for performing a non-coherent processing on the frequency-to-time transformed matrix, in which non-coherent processing a maximum value is arranged to be searched for finding a correct frequency shift and code phase.16. The location system according to claim 13, wherein said first dimension equals the number of samples of the code period.17. The location system according to claim 10, wherein it comprises:means for sampling the received signal for producing a set of samples, means for forming a matrix from the samples, the matrix having a first dimension and a second dimension, means for forming a compensation matrix, means for multiplying the time-to-frequency transformed matrix with the compensation matrix to form a compensated matrix, and means for performing a second time-to-frequency transform on the compensated matrix in said first dimension. 18. The location system according to claim 17, wherein said first dimension equals the number of samples of the code period.19. A receiver comprising at least:means for receiving code modulated spread spectrum signal, means for acquiring the receiver into the received signal, means for using at least one replica code which corresponds to a code used with the modulation, which code having a pre-determined number of chips, and examination means for examining a frequency shift of the signal within a selected frequency area, and a code phase of the code used with the modulation, wherein the examination of the frequency shift is divided into a first estimation phase and a second estimation phase, wherein the receiver further comprises:means for dividing the selected frequency area into a first set of frequencies for the first estimation phase, means for examining a second set of frequencies nearby each frequency of the first set of frequencies in the second estimation phase, and means for performing a comparison for frequencies of the second set of frequencies by using the received signal and the replica code, and the examination means comprise means for evaluating a correct frequency shift by using the results of the comparison.20. The receiver according to the claim 19, further comprising a reference oscillator for producing a reference oscillator signal, wherein the receiver further comprises:means for mixing the received signal with said reference oscillator signal in the first estimation phases, and means for adjusting the frequency of the reference oscillator into a different frequency for different first estimation phases, and that the mixed signal is arranged to be used in the second estimation phase.21. The receiver according to the claim 19, wherein it comprises means for producing a time-to-frequency transformation of a reversal of the replica code, and for shifting the transformed, reversed replica code in each of the first estimation phase such that in different first estimation phases a different phase shift of the transformed, reversed replica code is arranged to be used.22. The receiver according to claim 19, wherein it comprises:means for sampling the received signal for producing a set of samples means for forming a matrix from the samples, the matrix having a first dimension and a second dimension, means for performing a first time-to-frequency transform on the matrix in said second dimension, and means for performing a second time-to-frequency transform on the time-to-frequency transformed matrix in said first dimension. 23. The receiver according to claim 22, wherein said first dimension equals the number of samples of the code period.24. The receiver according to claim 19, wherein it comprises:means for sampling the received signal for producing a set of samples, means for forming a matrix from the samples, the matrix having a first dimension and a second dimension, means for forming a compensation matrix, means for multiplying the time-to-frequency transformed matrix with the compensation matrix to form a compensated matrix, and means for performing a second time-to-frequency transform on the compensated matrix in said first dimension. 25. The receiver according to claim 24, wherein said first dimension equals the number of samples of the code period.26. The receiver according to claim 22, wherein it comprises:means for forming a time-to-frequency transformed reversed replica code, means for multiplying the time-to-frequency transformed reversed replica code with a resulting matrix of the second time-to-frequency transformation, and means for performing a frequency-to-time transform on a resulting matrix of the multiplication. 27. The receiver according to the claim 26, wherein it comprises means for performing a non-coherent processing on the frequency-to-time transformed matrix, in which non-coherent processing a maximum value is arranged to be searched for finding a correct frequency shift and code phase.28. An electronic device comprising at least:a receiver having means for receiving code modulated spread spectrum signal, means for acquiring the receiver into the received signal, means for using at least one replica code which corresponds to a code used with the modulation, which code having a pre-determined number of chips, and examination means for examining a frequency shift of the signal within a selected frequency area, and a code phase of the code used with the modulation, wherein the examination of the frequency shift is divided into a first estimation phase and a second estimation phase, wherein the electronic device further comprises:means for dividing the selected frequency area into a first set of frequencies for the first estimation phase, means for examining a second set of frequencies nearby each frequency of the first set of frequencies in the second estimation phase, and means for performing a comparison for frequencies of the second set of frequencies by using the received signal and the replica code, and the examination means comprise means for evaluating a correct frequency shift by using the results of the comparison.29. The electronic device according to the claim 28, wherein it further comprises means for communicating with a mobile communication network.