Receiver for a position-finding system with improved sensitivity
View Patent ↗A receiver ( 1 ) of a position-finding system comprises a calculation unit ( 6, 7, 8 ) for calculation of a statistical value (Λ) on the basis of a received signal, and a detector unit ( 9 ) for comparison of the statistical value (Λ) with a threshold value (κ) and for determining whether the received signal is a synchronized location signal, an estimation unit ( 10 ) for estimation of the Rice factor (K) of the radio link via which the received signal has been transmitted, and a determination unit for calculation of the threshold value (κ) on the basis of the Rice factor (K).
1. A receiver for a position-finding system, which is based on the evaluation of different delay times of location signals, wherein the location signals are transmitted from two or more transmitters with known positions and being received by the receiver, the receiver comprising:
a calculation unit for calculation of a statistical value on the basis of a signal which is received by the receiver,
a detector unit, which is designed such that it compares the statistical value with a threshold value and determines on the basis of the comparison whether the received signal is a location signal and/or whether the received signal is used for finding the position of the receiver,
an estimation unit for estimation of the Rice factor of the radio link via which the received signal was transmitted, and
a determination unit for determination of the threshold value on the basis of the estimated Rice factor.
2. A receiver according to claim 1 , wherein
the determination unit is designed such that it calculates the probability density of the received, in particular preprocessed, signal on the basis of the estimated Rice factor, and that it calculates the threshold value on the basis of this probability density.
3. A receiver according to claim 1 , wherein
the determination unit is designed such that it calculates the probability density of the received, in particular preprocessed, signal on the basis of the estimated Rice factor, and that it determines the threshold value on the basis of this probability density by means of a table.
4. A receiver according to claim 1 , wherein
the determination unit is designed such that it determines the threshold value on the basis of the estimated Rice factor by means of a table.
5. A receiver according to claim 1 , wherein
the determination unit is designed such that it calculates the threshold value on the basis of a predetermined fixed incorrect detection probability, with the incorrect detection probability being the probability that the received signal is not a synchronized location signal but is considered by the detector unit to be a location signal.
6. A receiver according to claim 1 , wherein
in the calculation unit, sample values of the received signal feed a series circuit which has a first integrator for coherent integration, a magnitude squaring or magnitude forming device and a second integrator for non-coherent integration.
7. A receiver according to claim 1 , wherein
the location signals which are transmitted by the transmitters are spread-coded, and
a despreading unit is provided in the calculation unit, for despreading the received signal.
8. A receiver according to claim 1 , wherein
the estimation unit for estimation of the Rice factor is fed with the statistical value from the calculation unit, or with the despread sample values from the despreading unit.
9. A receiver according to claim 1 , wherein
the Rice factor is estimated by the estimation unit using
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where R is the amplitude of sample values of the received signal, and Ê {x} is approximated by forming a running average of x.
10. A receiver according to claim 1 , wherein
the Rice factor is estimated by the estimation unit using
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where R is the amplitude of sample values of the received signal, and Ê {x} is approximated by forming a running average of x.
11. A receiver according to claim 1 , wherein
the transmitter of the position-finding system is arranged on satellites or terrestrially.
12. A method for finding the position of a receiver in a position-finding system, which is based on the evaluation of different delay times of location signals, wherein the location signals are being transmitted by two or more transmitters with known positions, and being received by the receiver, the method comprising the steps of:
(a) calculating a statistical value on the basis of a signal which is received by the receiver;
(b) comparing the statistical value with a threshold value;
(c) determining on the basis of the result of the comparison whether the received signal is a location signal and/or whether the received signal is used for finding the position of the receiver,
(d) estimating the Rice factor of the radio link via which the received signal has been transmitted; and
(e) determining the threshold value on the basis of the estimated Rice factor.
13. A method according to claim 12 , wherein
the probability density of the received, in particular preprocessed, signal is calculated on the basis of the estimated Rice factor in step (e), and
the threshold value is calculated on the basis of this probability density.
14. A method according to claim 12 , wherein
the probability density of the received, in particular preprocessed, signal is calculated on the basis of the estimated Rice factor in step (e), and
the threshold value is determined on the basis of this probability density by means of a table.
15. A method according to claim 12 , wherein
the threshold value is determined on the basis of the estimated Rice factor by means of a table in step (e).
16. A method according to claim 12 , wherein
the threshold value is calculated on the basis of a predetermined fixed incorrect detection probability, with the incorrect detection probability being the probability that the received signal is not a synchronized location signal but is considered in step (c) to be a location signal.
17. A method according to claim 12 , wherein
sample values of the received spread-coded signal are despread in step (a),
the despread sample values are integrated coherently,
the squares of the magnitudes of the results of the coherent integration are formed, and
the squares of the magnitudes are integrated non-coherently.
18. A method according to claim 12 , wherein
the Rice factor is estimated on the basis of the statistical value or on the basis of despread sample values, or on the basis of coherently integrated despread sample values, or on the basis of the magnitude of coherently integrated despread sample values.
19. A method according to claim 12 , wherein
the Rice factor is estimated using
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where R is the amplitude of sample values of the received signal, and Ê {x} is approximated by forming a running average of x.
20. A method according to claim 12 , wherein
the Rice factor is estimated using
K
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4
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where R is the amplitude of sample values of the received signal, and Ê {x} is approximated by forming a running average of x.
21. A method according to claim 12 , wherein
the transmitters of the position-finding system are arranged on satellites or terrestrially.