CN102508271B - Navigation satellite signal capturing method based on peak value location comparison - Google Patents
Navigation satellite signal capturing method based on peak value location comparison Download PDFInfo
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- CN102508271B CN102508271B CN 201110292691 CN201110292691A CN102508271B CN 102508271 B CN102508271 B CN 102508271B CN 201110292691 CN201110292691 CN 201110292691 CN 201110292691 A CN201110292691 A CN 201110292691A CN 102508271 B CN102508271 B CN 102508271B
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Abstract
The invention provides a navigation satellite signal capturing method based on peak value location comparison, relating to a navigation satellite signal capturing method and solving the problems that the conventional navigation satellite signal capturing method has lower detection probability of small correlating peak values in a weak signal condition and the system has high false-alarm rate. The method comprises the following steps of: carrying out correlation calculation on a signal for many times, searching for the maximum value after each correlation calculation, and recording the position of the maximum value; judging if the signal exists according to the position of the maximum value when the positions of the maximum values are enough recorded, and then determining if the navigation satellite signal capture is successful. The method provided by the invention is suitable for capturing the navigation satellite signal.
Description
Technical field
The present invention relates to a kind of capturing navigation satellite signal method.
Background technology
The work of catching of navigation satellite signal can be considered to be at the two-dimensional search that carries out on frequency and two dimensions of code phase, in search, whole hunting zone is divided into a plurality of unit and searches for and adjudicate.What the mode decision scheme that adopts in traditional capturing navigation satellite signal circuit adopted is to get the strategy of M in Tang's search and N.The workflow of Tang's search as shown in Figure 1.
Threshold value A and the initial value B of Tang's search by reasonably choosing K realizes the balance between search speed, verification and measurement ratio and false alarm rate.Determine that to being difficult to the unit whether signal exists appends more search time, and false-alarm is repeatedly adjudicated to reduce in the unit that surpasses thresholding.
Wherein there be M time over thresholding if the strategy of getting M in N carries out N search to each search unit, think acquisition success.
Two kinds of search patterns are all by the mode of repeated detection, uncertain search unit to be carried out repeat search, are also simultaneously that the mode by repeated detection reduces false-alarm.But under weak signal, in search unit, detected correlation peak may be smaller, although each detected correlation peak can not surpass thresholding, really exist, and these two kinds traditional judgement means can't be utilized this part energy.If the selection of threshold value is unreasonable in design simultaneously, can cause the maximal value of some noises also to surpass thresholding, bring false-alarm to system, or system pays extra cost.
Summary of the invention
The present invention is lower to the detection probability of correlation peak less under weak signal in order to solve existing capturing navigation satellite signal method, causes the high problem of system's false alarm rate, thereby provides a kind of based on peak capturing navigation satellite signal method relatively.
Based on peak capturing navigation satellite signal method relatively, it is realized by following steps:
Step 2, navigation satellite signal and local code that step 1 is received carry out related operation, obtain one group of related function;
Step 3, the related function that step 2 is obtained carry out peak value searching, the position of record peak value;
Step 4, repeating step one arrive step 3 k time, obtain a corresponding k peak, and K is the positive integer more than or equal to 2;
Step 5, all k peak is compared, obtain comparative result;
Step 6, judging that whether comparative result satisfies the Changing Pattern of expection, is that decision signal exists, and completes capturing navigation satellite signal if judgment result is that; If the determination result is NO, decision signal does not exist, and returns to step 1, and navigation satellite signal is received next time.
Expection Changing Pattern described in step 6 was determined according to the time interval between code Doppler size and every twice related operation.
Beneficial effect: capturing navigation satellite signal method of the present invention to weak signal (especially lower than-detection probability of less correlation peak is high under 128dBm), system's false alarm rate decrease.
Description of drawings
Fig. 1 is the workflow schematic diagram of the search of Tang described in background technology; Fig. 2 is the schematic flow sheet of method of the present invention.Fig. 3 is the center-control state machine prize judgment strategic process figure in embodiment one.
Embodiment
Embodiment one, in conjunction with Fig. 1, this embodiment is described, based on peak capturing navigation satellite signal method relatively, it is realized by following steps:
Step 2, navigation satellite signal and local code that step 1 is received carry out related operation, obtain one group of related function;
Step 3, the related function that step 2 is obtained carry out peak value searching, the position of record peak value;
Step 4, repeating step one arrive step 3 k time, obtain a corresponding k peak, and K is the positive integer more than or equal to 2;
Step 5, all k peak is compared, obtain comparative result;
Step 6, judging that whether comparative result satisfies the Changing Pattern of expection, is that decision signal exists, and completes capturing navigation satellite signal if judgment result is that; If the determination result is NO, decision signal does not exist, and returns to step 1, and navigation satellite signal is received next time.
Expection Changing Pattern described in step 6 is determined according to the factors such as the time interval between code Doppler size and every twice related operation.
Principle: must comprise a maximal value in the result of each related operation, this maximal value might be the correlativity generation by signal, may be also the maximal value in noise.The maximal value that is produced by noise can be along with signal intensity, perhaps the change of receiver accumulated time and changing.For the peak value that is obtained by signal correlation, the position should be constant, or gradual due to the code Doppler effect.And for the peak value in noise, its position is random variation.Utilize this point, can be by the peak that obtains after repeatedly adjudicating, whether analysis draws signal and exists.
In the middle of peak mode decision scheme relatively, remain and will carry out repeatedly related operation to signal, all to carry out peaked search after each related operation, and record the position that maximal value occurs.After having recorded abundant maximum value position, judge having or not of signal by peaked position relationship.
If the related function that the computing of k correlations is obtained is designated as C with the form of array
k, each element wherein, namely the correlation on each code phase is designated as a
kx, the value of x is from the 1 total sampling number n to system here.
C
k＝[a
k1?a
k2?a
k3…a
kn]
Must there be a maximal value a in every group of related function
max, the position with it in sequence is designated as b,
a
max＝max(C)＝a
b
System carries out can obtaining m group related function sequence after the computing of m correlations, and consists of the related function matrix M of the capable n row of m.
Record the maximum value position b of every row in matrix M
y, the value of y from 1 to m, consists of the vectorial P of reaction peak, element b in P here
1To b
mBut between just having or not of reflected signal of relation.
P＝[b
1?b
2?b
3…b
m]
For example, in the situation that does not have Doppler shift, the maximum value position that at every turn searches should be fixed, or is subjected to the impact of system clock source degree of stability, floats within the specific limits.And in the situation that Doppler shift is arranged, the maximum value position that at every turn searches should be gradual according to certain rule, and its Changing Pattern can be according to being stipulated by the factors such as the time interval between code Doppler size, every twice related operation.When maximum value position did not satisfy the Changing Pattern of expection, decision signal did not exist.
The mode decision scheme of peak comparison both can use separately, also can be combined with other strategies.Such as setting a threshold value, maximal value is screened, get rid of that those are too small, to such an extent as to can not be the maximal value of relevant peaks.The strategy that also it can be got M in N is combined, if there be M peaked position to satisfy the rule change of expection in the maximal value that the N correlations obtains, be considered as signal and exist.
Below by concrete experimental verification effect of the present invention, adjudicate as example take twice contrast maximum value position and method that threshold value is set.Based on FPGA, system is realized in experiment, use Agilent 4438C signal generator as signal source.
In experiment, with the judgment variables that is compared to of the peak value of gained related function and average, carry out 1000 times and catch, and note is caught result and pre-conditioned consistent number of times, the number of times of catching result and the pre-conditioned number of times that is not inconsistent and could not catch.Test case is as shown in table 1.
Table 1 hardware testing result
Can find out from experimental result, consider transmission line and splicing loss, system sensitivity reached-145～-146dBm, according to the conventional method, threshold value is set to 0 o'clock system and can't works, but owing to having introduced maximum value position mode decision scheme relatively, native system still can be worked, and catches more weak signal.
Below by specific embodiment, the course of work of the present invention is described: take the C/A code sequence capturing process of GPS L1 frequency range as example, adopt peak-to-average force ratio as judgment variables, the mode of thresholding and twice code phase comparison of crossing by twice is adjudicated.Detailed process such as Fig. 3 show.System is when the enterprising line search of a certain frequency groove, when the peak-to-average force ratio of related function during greater than the peak-to-average force ratio thresholding that sets, system can record the phase value of catching, and again once catch on this frequency groove, if the peak-to-average force ratio of the correlation that obtains still surpasses thresholding, and catch the phase value that resulting code phase and front records and differ and be no more than half-chip, think changing frequently acquisition success on groove.In this judging process, if there is any one condition not satisfy, just is judged as this frequency groove and catches unsuccessfully.
Claims (1)
1. based on peak capturing navigation satellite signal method relatively, it is realized by following steps:
Step 1, reception navigation satellite signal;
Step 2, navigation satellite signal and local code that step 1 is received carry out related operation, obtain one group of related function;
Step 3, the related function that step 2 is obtained carry out peak value searching, the position of record peak value;
Step 4, repeating step one arrive step 3 k time, obtain a corresponding k peak, and k is the positive integer more than or equal to 2;
Step 5, all k peak is compared, obtain comparative result;
Step 6, judging that whether comparative result satisfies the Changing Pattern of expection, is that decision signal exists, and completes capturing navigation satellite signal if judgment result is that; If the determination result is NO, decision signal does not exist, and returns to step 1, and navigation satellite signal is received next time;
It is characterized in that: the expection Changing Pattern described in step 6 was determined according to the time interval between code Doppler size and every twice related operation.
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| CN105277294B (en) * | 2015-11-16 | 2018-05-15 | 北京华朔物联网科技有限公司 | The anti-interference method of frequency division multiplexing label based on Internet of Things electric power temperature measuring equipment |
| CN107015253B (en) * | 2017-03-09 | 2021-06-18 | 沈阳理工大学 | Search detection method capable of dynamically predicting threat in navigation receiver |
| CN109001772A (en) * | 2018-06-12 | 2018-12-14 | 桂林电子科技大学 | The Beidou navigation signal acquiring method compared based on peak position |
| CN113109846B (en) * | 2021-03-04 | 2023-06-30 | 北京北方联星科技有限公司 | Capturing verification strategy method based on signal strength trend |
| CN113872909B (en) * | 2021-09-28 | 2023-09-01 | 东方红卫星移动通信有限公司 | Short-time burst carrier capturing method and system for low-orbit satellite Internet of things |
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| CN1695069A (en) * | 2002-02-08 | 2005-11-09 | 高通股份有限公司 | Directly acquiring precision code GPS signals |
| WO2010005685A2 (en) * | 2008-06-14 | 2010-01-14 | Qualcomm Incorporated | Multiple correlation processing in code space search |
| CN101852849A (en) * | 2009-04-02 | 2010-10-06 | 深圳艾科创新微电子有限公司 | Method for acquiring GPS weak signals |
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|---|---|---|---|---|
| CN1695069A (en) * | 2002-02-08 | 2005-11-09 | 高通股份有限公司 | Directly acquiring precision code GPS signals |
| WO2010005685A2 (en) * | 2008-06-14 | 2010-01-14 | Qualcomm Incorporated | Multiple correlation processing in code space search |
| CN101852849A (en) * | 2009-04-02 | 2010-10-06 | 深圳艾科创新微电子有限公司 | Method for acquiring GPS weak signals |
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