CN1202633C - Method and device for quick capturing pseudo random codes in dynamic mass signal condition - Google Patents
Method and device for quick capturing pseudo random codes in dynamic mass signal condition Download PDFInfo
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Abstract
The present invention relates to a method and a device for quickly capturing pseudo-random codes under the dynamic condition of large signals. The whole dynamic range of signals can be divided into two areas according to the height of Signal-to-Noise, and two different PN code capture strategies are provided. The capture strategy suitable for the high Signal-to-Noise area is quick search, and the capture strategy suitable for low Signal-to-Noise area is general search. When the capture is started, the assumed Signal-to-Noise is low, the general search is used; if the Signal-to-Noise is indeed low, a low threshold can be used for the capture of a PN code. If the Signal-to-Noise is high, the judgment of positioning the high Signal-to-Noise in the process of general search can be made, and the quick search can be converted. Under the condition of introducing an AGC circuit device, compared with an ordinary fixed threshold receiver, the PN code capture proposal of the present invention can normally work under the dynamic condition of larger signals, and has ideal average capture time, and the effect is more obvious particularly under the condition of large frequency bias. The present invention does not need an additional and special device for measuring Signal-to-Noise, and can be widely used for the field of code division multiple access satellite communication and infinite communication.
Description
Technical field:
The present invention relates to the method for reseptance and the device of a kind of direct sequence spread spectrum/code division multiple access (DS/CDMA) communication system, it can be implemented in pseudo random sequence (PN sign indicating number) under large-signal dynamic condition and the big carrier wave frequency deviation condition synchronously.
Background technology:
In direct sequence spread spectrum communication system,, need at first make local pseudo random sequence (PN sign indicating number) correctly synchronous with the pseudo random sequence in the received signal for correct receiving demodulation signal.The synchronous process of PN sign indicating number generally is divided into sign indicating number catches and two stages of code tracking, and what this patent related to is the acquisition procedure of PN sign indicating number.
Usually the PN code capture method has utilized the autocorrelation performance of pseudo noise code, just be correlated with receiving the PN sign indicating number with local PN sign indicating number, when both complete matchings, the autocorrelation value maximum, and chip of phase phasic difference between the two is when above, and its autocorrelation value is less relatively.Owing in direct sequence spread spectrum communication system, be difficult to synchronously realize the synchronous of carrier wave, therefore often use noncoherent receiver to realize catching of PN sign indicating number at the PN sign indicating number.The principle of noncoherent receiver is that envelope detection is carried out in the output of correlator, thereby obtains a sign indicating number verification of synchronization statistic, when test statistics during greater than default thresholding, thinks that received signal and local PN sign indicating number realized synchronously.
The structure of the capture circuit of PN sign indicating number mainly can be divided into two kinds of sliding correlation detector mode and matched filter modes.The matched filter mode can realize catching fast of PN sign indicating number in the short period of time, but in all-digital signal, realizes the required hardware complexity height of digital matched filter, thereby limited its range of application.The sliding correlation detector mode thereby be widely used in engineering practice, but its capture time is longer because it realizes simply.In order to improve the acquisition speed of sliding correlation detector mode, can adopt the sliding correlation detector composition parallel correlator group of using the local PN sign indicating number of out of phase to carry out sign indicating number usually and catch.
In communication system, channel changes, the power and the signal to noise ratio of receiver input signal all change, digital receiver for limited wordlength, excessive or this too small receiver that all can cause of the dynamic amplitude of input signal can't operate as normal, so receiver front end often needs to use automatic gain control (AGC) to come the amplitude of control input signals.In spread spectrum system, often use incoherent AGC to come the power of control input signals, the gross power that is to say the useful signal that makes input and noise keeps constant, but when the signal to noise ratio of input signal changes greatly, the amplitude of useful signal also has bigger variation in the output signal of incoherent ACC, thereby the amplitude of the auto-correlation main peak of correlator output also has bigger variation.For some auto-correlation secondary lobes bigger pseudo noise code such as GOLD sign indicating number, the value of the sign indicating number verification of synchronization statistic when high s/n ratio under the asynchronous situation is the sign indicating number verification of synchronization statistic under the synchronous situation during often greater than low signal-to-noise ratio.Some occasion in addition, the carrier frequency of receiver local carrier frequency and received signal has than large deviation, and before realizing that the PN sign indicating number is synchronously, this frequency difference is difficult to be compensated, and unknown frequency difference will cause bigger observation space.Thereby for the receiver that adopts the fixed sentence thresholding, the dynamic range of signals that very difficult adaptation is bigger, and be difficult to realize that the PN sign indicating number is synchronous fast.
Summary of the invention:
The object of the present invention is to provide a kind of method and circuit arrangement that direct sequence spread spectrum communication system PN sign indicating number is caught that be used for.Under the condition of introducing incoherent automatic gain controller (AGC), it can realize reliably catching of PN sign indicating number with short capture time and better simply full-digital circuit in very big dynamic range of signals, especially in the occasion of carrier beat much larger than information rate, its effect is more obvious.
The quick capturing method of pseudo noise code under the large-signal dynamic condition among the present invention, its step comprises:
1) according to the statistical property of sign indicating number verification of synchronization statistic and possible frequency difference scope the whole dynamic range of signal is divided into low signal-to-noise ratio district and high s/n ratio district according to the height of signal to noise ratio;
2) set low threshold TL that is adapted to the low signal-to-noise ratio district and the high threshold TH that is adapted to the high s/n ratio district respectively according to required acquisition performance; The setting of low threshold satisfy with low threshold false alarm probability when the low signal-to-noise ratio area searching PN code phase be tending towards 0 and detection probability be tending towards 1, and the probability that false lock takes place is tending towards 0; The setting of high threshold satisfy with high threshold false alarm probability when the high s/n ratio area searching PN code phase be tending towards 0 and detection probability be tending towards 1, and signal to noise ratio is when being positioned at the low signal-to-noise ratio district, the probability that sign indicating number verification of synchronization statistic is crossed high threshold is tending towards 0;
3) be suitable for routine search in the low signal-to-noise ratio district, use low threshold TL, residence time is long, and the each resident multisample of taking detects; Be suitable for fast search in the high s/n ratio district, residence time is short, and each resident sample number is less than the sample number of routine search;
4) carry out once omnidistance fast search after routine search is finished, all PN code phases are carried out one-time detection, if there is the pairing sign indicating number of certain phase place verification of synchronization statistic to surpass TH, judge that then this phase place is correct PN code phase, otherwise judge that the PN code phase of being caught is correct PN code phase.
Catching method of the present invention also comprises the method that search procedure is further quickened, and its step comprises:
1) set resident probability P for the first time, when satisfying high s/n ratio, the sign indicating number verification of synchronization statistic that routine search obtains is crossed for the first time resident probability greater than P;
2) be threshold value with TL earlier, adopt routine search to carry out the PN sign indicating number and catch, write down the number of times that for the first time resident number of times and code phase are adjusted simultaneously;
3) when the adjustment number of times of code phase had reached a fixing value N, whether check code verification of synchronization statistic crossed for the first time resident probability greater than P, if greater than P, judges that then be high s/n ratio this moment, directly changes fast search over to;
In described routine search, adopt how resident, multisample detection.The used sample number average of resident next time check of same observation station is greater than the used sample number of resident check last time.
Residence time is short in described fast search, and it is few to detect sample number.
Pseudo-random code catching device under the large-signal dynamic condition of the present invention, comprise being used to obtain yard correlator of verification of synchronization statistic or a correlator bank, comprise that also the independent correlator of the PN code phase that a tracking captures and the PN sign indicating number of respective phase thereof produce circuit; Also comprise and added up the counting device that for the first time resident number of times and code phase are adjusted number of times.
The invention provides a kind of PN sign indicating number Acquisition Scheme that in additive Gaussian channel, is used for the DS/CDMA system, its basic thought is the dynamic range of signal is divided into high s/n ratio and two districts of low signal-to-noise ratio, and set two thresholdings of height, wherein the relevant peaks that is used under the high s/n ratio of high threshold is caught, and the relevant peaks that low threshold is used under the low signal-to-noise ratio is caught.The search strategy also can according to the difference of signal to noise ratio divide under the low signal-to-noise ratio and high s/n ratio under search strategy.
Under the lower situation of signal to noise ratio,, thereby need to use a lower thresholding to catch because the useful signal amplitude is less in the signal of exporting in the AGC amplifier.And under low signal-to-noise ratio, use single sample to cause higher false alarm probability and lower detection probability easily with the method for thresholding comparison, thereby this moment adopted the multisample check, the mean value of just getting a plurality of yards verification of synchronization statistics is made comparisons to reduce the synchronously required time and to be locked in possibility on the wrong PN code phase with thresholding.In order further to reduce average lock in time, reduce the false alarm probability that sign indicating number catches and increase detection probability, when low signal-to-noise ratio, will carry out repeatedly resident check, and the used sample number average of often each resident check is greater than last.Search strategy under this low signal-to-noise ratio is referred to as routine search in the present invention.If but in higher signal to noise ratio, use routine search, because the autocorrelation performance of PN sign indicating number is often undesirable, thereby the amplitude of its auto-correlation secondary lobe is often bigger, thereby false alarm probability may be very high, thereby the decline that causes mean acquisition time might be locked in even on the wrong PN code phase, causes " false lock ".
Under high s/n ratio, because the amplitude of useful signal is bigger in the signal that the AGC amplifier is exported, thereby need use higher thresholding to carry out sign indicating number and catch, could guarantee lower false alarm probability like this so that the result of search is unlikely to be locked in mistakenly on the auto-correlation secondary lobe of PN sign indicating number.Owing to the signal to noise ratio height, just can obtain very high detection probability so can use the single even sample of less sample number to test, thereby can reduce and catch the required time in addition for each PN code phase.Search strategy under this high s/n ratio is referred to as fast search in this programme.If but in lower signal to noise ratio, use fast search strategy, because the amplitude at the sync correlation peak of PN sign indicating number is smaller, thereby its probability that surpasses high threshold is minimum, thereby can't correctly realize catching of PN code phase.
Among the present invention, when acquisition procedure was incipient, earlier hypothesis signal to noise ratio this moment was lower, thereby uses routine search, if this moment, signal to noise ratio was lower really, thereby to use low threshold to carry out catching of PN sign indicating number be suitable.Problem to be solved by this invention is that the signal to noise ratio of how judging in the routine search process at that time is to be positioned at the high s/n ratio district, thereby changes fast search strategy as quickly as possible over to, thereby reduces total mean acquisition time.
If in fact signal to noise ratio is higher, because the auto-correlation secondary lobe of PN sign indicating number is bigger, thereby the sign indicating number verification of synchronization statistic under the asynchronous situation of this moment is very high greater than the probability of low threshold, thereby by the first time of routine search resident probability also bigger, thereby can utilize these characteristics to judge signal to noise ratio.In acquisition procedure, be recorded in the detection of some continuous phases by for the first time resident number of times, if greater than a predefined value, then think the signal to noise ratio height of this moment, thereby can change the synchronization policy that uses under the high s/n ratio into.When signal to noise ratio was quite high, the situation of " false lock " might take place by repeatedly resident in routine search in the sign indicating number verification of synchronization statistic on a part of PN code phase.When false lock took place, routine search can't be withdrawed from false lock by repeatedly resident check.Among the present invention, after routine search is finished, adopt the strategy of fast search that all phase places are tested, under low signal-to-noise ratio, the auto-correlation secondary lobe of sign indicating number verification of synchronization statistic and main peak often all can not be by the high threshold of fast search, so if the sign indicating number verification of synchronization statistic on the neither one pseudo-random code phases can surpass high threshold, the PN code phase that conventional strategy is caught before then thinking is correct locking phase.Otherwise, if this moment the signal to noise ratio height, then the main peak of sign indicating number verification of synchronization statistic surpasses high threshold with very big probability and the auto-correlation secondary lobe has only minimum probability can pass through high threshold, if if thereby in fast search strategy, capture a sign indicating number verification of synchronization statistic on the phase place above high threshold, think that then this PN code phase is correct locking phase.Finish in routine search and to catch the fast search carried out of back we are referred to as omnidistance fast search.
Generally speaking, advantage of the present invention and good effect can be summarized as follows:
1, using under the condition incoherent automatic gain controller and that have frequency deviation, PN sign indicating number Acquisition Scheme provided by the present invention can be in bigger dynamic range of signals with respect to common simple gate limit receiver reliably working.
2, under the condition in above-mentioned 1, can obtain comparatively desirable mean acquisition time.
3, PN sign indicating number capture circuit provided by the present invention can be realized the Acquisition Scheme described in above-mentioned 1,2 with less hardware costs, and need not the extra equipment of measuring signal to noise ratio that is specifically designed to.
Description of drawings:
Fig. 1 is the theory diagram of the used digital signal receiver of the present invention.
Fig. 2 is the structure of employed noncoherent receiver in the embodiments of the invention
Fig. 3 is the structure chart of employed sign indicating number capture circuit in the embodiments of the invention.
Fig. 4 is the flow chart of PN sign indicating number harvesting policy used in the embodiments of the invention.
Fig. 5 is the flow chart of the routine search in the PN sign indicating number harvesting policy used in the embodiments of the invention.
Fig. 6 is the flow chart of the fast search in the PN sign indicating number harvesting policy used in the embodiments of the invention.
Embodiment:
The present invention has a specific embodiment.Related receiver input signal is the Direct swquence spread spectrum signal.Frequency expansion sequence is to be that 1023 GOLD sequence obtains by zero padding in the cycle, and the cycle is 1024.Information rate is 2.4kbps, spreading ratio 1024.Channel is an additive white Gaussian noise channel, E
b/ N
0Scope be 7.8dB to 60dB, frequency difference is less than 600Hz.Communication is burst mode, requires to realize in the short period of time catching fast of PN sign indicating number.
Come present embodiment is described below in conjunction with accompanying drawing.
Fig. 1 is the system construction drawing of baseband signal processing unit in the DS/CDMA all-digital receiver.The input signal of baseband signal processing unit is the base-band analog signal that obtains through down-conversion after the intermediate frequency process.The baseband signal of intermediate frequency unit output was controlled its amplitude respectively by automatic gain control module (AGC) 100 and 101 before sending into A/D converter 110 and 111, the reason of doing like this is: because the dynamic range of signal is very big among the embodiment, in order to guarantee the operate as normal of A/D conversion, before it, add the feasible level that enters the signal plus noise of A/D converter of AGC and remain within the constant scope (being the linear work district of A/D converter).Because the analog signal after the intermediate frequency down-conversion still has very big frequency difference,, correct the remaining frequency deviation in back within 600Hz so need through orthogonal digital down-conversion 120 correcting frequency offsets.The effect of digital matched filter 130 is to make signal to noise ratio maximum on the point that the digital correlator group sampled.I road that finally obtains and Q roadbed band digital signal are admitted among the pseudo-random code catching circuit 131 described in the invention to finish the synchronizing process of PN code phase.
Employed AGC is incoherent AGC in the present embodiment, and it is its work and does not rely on despreading signal afterwards with the difference of relevant AGC.In any case incoherent AGC makes the ratio of amplitude of the amplitude of useful signal in the input signal of A/D and noise signal change, the total signal strength of output (average power) all keeps constant.In the present embodiment, the total signal strength normalizing with output is 1.
In the present embodiment, the sign indicating number acquisition algorithm adopts the scheme of serial search, and the generation circuit that single sign indicating number is caught test statistics as shown in Figure 3.I way word correlator bank 200 is done the correlation intergal computing with the output of I, Q road matched filter with the output signal of local PN code generator 230 respectively with Q way word correlator bank 201, and integration cleaning control signal produces by 240.The output of I, Q road correlator bank is through just having obtained a sign indicating number verification of synchronization statistic by 220 additions again after squarer 210 and 211.
In the present embodiment, detection to the PN code phase is that step-length detects with 1/2 chip, each correlator bank is made up of 20 correlators, PN code phase in the received signal of two adjacent correlators differs 1/2 chip, and this correlator bank can detect 20 PN code phases in 10 PN chip range simultaneously.
Under the condition that adopts incoherent AGC, high s/n ratio is (as E
b/ N
0=the auto-correlation secondary lobe is discerned the average that detection limit has the main peak of sizable probability can be greater than low signal-to-noise ratio the time synchronously 40dB) time.Under the prerequisite that does not have the signal to noise ratio priori, if the statistical property according to the main peak under the low signal-to-noise ratio designs thresholding, then when the PN sign indicating number is discerned the detection limit average synchronously greater than decision threshold, can't judge it is auto-correlation secondary lobe under the high s/n ratio, or the auto-correlation main lobe under the low signal-to-noise ratio, and must utilize the amplitude information on other observation stations to come auxiliary judgement.
In routine search, because imagination signal to noise ratio at this moment is lower,, used resident detection method in the present embodiment three times in order to reduce mean acquisition time, each resident sample number is respectively 4,8,16.Three times resident in, adding up of sign indicating number verification of synchronization statistic all finished by multisample accumulator 300.Get the mean value of resident each PN code phase verification of synchronization statistic of gathering of this time in each resident, and make comparisons with low threshold by 320 by 310 maximums of selecting in a plurality of mean values, if should be worth greater than low threshold, then resident by this time, carry out next time resident by 330 pairs of these PN code phases of control module.If passed through three times resident, think that then this PN code phase is the correct PN code phase that routine search captured.
By emulation and analysis, find because the effect of AGC makes the power (variance) of white noise at E to following yard verification of synchronization amount statistical property of different signal to noise ratios
b/ N
0Approximate constant in the scope of≤20dB, white noise has occupied most power in the despread unit input signal in this is interval, if according to E
b/ N
0The situation that equals 10dB designs thresholding, and this thresholding all can operate as normal in this scope.Work as E
b/ N
0When further increasing, the white noise variance begins to reduce, and the influence of signal autocorrelation secondary lobe increases gradually, thereby causes the possibility of detector " false lock " to increase.As 20dB＜E
b/ N
0During＜27dB, routine search obviously increases by resident probability for the first time, but " false lock " seldom occur.Work as E
b/ N
0" false lock " during＞27dB, appears easily, and the big more easy more generation of signal to noise ratio.Therefore define E
b/ N
0≤ 20dB is the low signal-to-noise ratio district and designs a thresholding that can satisfy mean acquisition time as the low threshold in the routine search process.The high s/n ratio district is taken as more than the 20dB, and the high threshold that sets according to this signal to noise ratio district satisfies at 20dB≤E
b/ N
0False alarm probability is near 0 in the scope of≤60dB, and detection probability is near 1.And in the low signal-to-noise ratio district, the probability that sign indicating number verification of synchronization statistic is crossed high threshold approaches 0, and therefore such high threshold setting is applicable to the fast search and omnidistance fast search under the high s/n ratio.
Set after high threshold and the low threshold, routine search and the omnidistance fast dynamic range that just can cover whole signal place of searching for, ensuing problem is how to distinguish the situation of low signal-to-noise ratio and high s/n ratio.Just beginning to carry out when sign indicating number catches, owing to, therefore can only begin to carry out sign indicating number and catch from routine search not about the priori of signal to noise ratio.Work as E
b/ N
0During≤20dB`, routine search can be worked well.As 20dB＜E
b/ N
0During＜27dB, because false alarm probability is too high, routine search increases by for the first time resident probability, therefore mean acquisition time increases, the decreased performance that causes receiver, but this moment, we can judge the signal to noise ratio of this moment by resident probability for the first time by receiver, then adopted more suitable fast search strategy.Probability P is exactly by 20dB＜E
b/ N
0Receiver is set by resident probability for the first time during＜27dB.Work as E
b/ N
0During＞27dB, the sign indicating number verification of synchronization statistic under the asynchronous condition increases by three resident probability, causes false lock easily.Therefore after routine search is finished, need to add the omnidistance fast search of using the high threshold search.Under high s/n ratio, the probability that sign indicating number verification of synchronization statistic under the asynchronous situation surpasses high threshold is very little, and that the relevant peaks under the synchronous situation surpasses the probability of this thresholding is very high, and the vacation that therefore omnidistance fast search can make receiver withdraw to cause because of high s/n ratio is at an easy rate locked and found correct PN code phase apace.
The employed hardware circuit resource of present embodiment is: AGC, a correlator bank that comprises 20 correlators, add up for the first time resident number of times and code phase and adjusted the counting device of number of times, the PN sign indicating number of free correlator and respective phase produces circuit, squarer, corresponding sign indicating number acquisition control circuit.
The process of the PN sign indicating number being caught below in conjunction with Fig. 4 briefly is described below:
As shown in Figure 5, step 1,2,3 is the routine search flow process:
1. code phase adjustment counter adds 1.Utilize correlator bank on continuous 20 PN code phase observation stations, to observe respectively 4 times, each observation station obtains 4 sample values, get average as sign indicating number verification of synchronization statistic, and will organize test statistics maximum (remembering that its corresponding correlator sequence number is L, L＜=20) and low threshold and compare.If less than low threshold, then adjust local PN code phase and repeat this step after for next group phase place.If greater than low threshold, then cross for the first time resident counter and add 1 as follows according to this Counter Value operation then: if cross for the first time resident Counter Value less than 15 then jump directly to step 2; If cross for the first time resident Counter Value greater than 15, then calculated resident probability (resident Counter Value is adjusted Counter Value divided by code phase excessively for the first time) for the first time, if this probability, then jumped to for the 4th step greater than default thresholding P and searches for soon otherwise will cross and jump to step 2 after resident counter and code phase are adjusted number of times counter reset (zero clearing) for the first time.
2. correlator bank continues observation in same observation station and carries out verification 8 times, the average of getting 8 sample values is as judgement amount, get the judgement amount of L correlator and low threshold relatively,, repeated for the 1st step if less than thresholding then the phase place of adjusting local PN sign indicating number is organized phase place to next.
3. correlator bank continues to observe 16 times to confirm in same observation station, the average of getting 16 sample values is as judgement amount, with the judgement amount of L correlator and low threshold relatively, if less than thresholding then the phase place of adjusting local PN sign indicating number is organized phase place to next, repeated for the 1st step; Greater than thresholding, then the PN code phase information of L correlator to be put to free correlator, free correlator enters the code tracking process, changes for the 5th step simultaneously over to.
As shown in Figure 6, step 4,5 is fast search routine:
4. correlator bank is used fast search strategy continuation instead at the enterprising line search of all phase places, uses high threshold during search, and each observation station is only observed 1 sample and got average as sign indicating number verification of synchronization statistic, up to all phase places of traversal.If judgement amount surpasses thresholding in this process, then observe 1 sample again in corresponding observation station position, if still surpass thresholding, then think to skip to for the 11st step by the real main peak of being sought.If instead traveled through a week, do not find the point of thresholding, then returned for the 1st step.
5. correlator bank is used fast search strategy continuation instead at the enterprising line search of all phase places, uses high threshold during search, and each observation station is only observed 1 sample and got its average as sign indicating number verification of synchronization statistic, up to all phase places of traversal.If test statistics surpasses thresholding in this process, then observe 1 sample again in corresponding observation station position, if judgement amount still surpasses thresholding, think that then the phase place of this point is the real main peak of being sought.If instead travel through a week, there is not to find to surpass the observation station of high threshold, the current location of then assert free correlator is real main peak.
Claims (4)
1, pseudo-random code catching method under a kind of large-signal dynamic condition, its step comprises:
1) according to the statistical property of sign indicating number verification of synchronization statistic and possible frequency difference scope the whole dynamic range of signal is divided into low signal-to-noise ratio district and high s/n ratio district according to the height of signal to noise ratio;
2) set low threshold TL that is adapted to the low signal-to-noise ratio district and the high threshold TH that is adapted to the high s/n ratio district respectively according to required acquisition performance; The setting of low threshold satisfy with low threshold false alarm probability when the low signal-to-noise ratio area searching PN code phase be tending towards 0 and detection probability be tending towards 1, and the probability that false lock takes place is tending towards 0; The setting of high threshold satisfy with high threshold false alarm probability when the high s/n ratio area searching PN code phase be tending towards 0 and detection probability be tending towards 1, and signal to noise ratio is when being positioned at the low signal-to-noise ratio district, the probability that sign indicating number verification of synchronization statistic is crossed high threshold is tending towards 0;
3) be suitable for routine search in the low signal-to-noise ratio district, use low threshold TL, residence time is long, and the each resident multisample of taking detects; Be suitable for fast search in the high s/n ratio district, residence time is short, and each resident sample number is less than the sample number of routine search;
4) carry out once omnidistance fast search after routine search is finished, all PN code phases are carried out one-time detection, if there is the pairing sign indicating number of certain phase place verification of synchronization statistic to surpass TH, judge that then this phase place is correct PN code phase, otherwise judge that the PN code phase of being caught is correct PN code phase.
2, pseudo-random code catching method under the large-signal dynamic condition as claimed in claim 1 is characterized in that this method also comprises the method that search procedure is further quickened, and its step comprises:
1) set resident thresholding probability P for the first time, the sign indicating number verification of synchronization statistic that routine search obtains when satisfying high s/n ratio is crossed for the first time resident probability greater than P;
2) with TL be threshold value, adopt routine search to carry out the PN sign indicating number and catch, detected for the first time resident probability, if this probability greater than P then judge and be high s/n ratio this moment, directly changes over to and omnidistancely searches for soon.
3, pseudo-random code catching method under the large-signal dynamic condition as claimed in claim 1 is characterized in that adopting how resident, multisample detection in described routine search; The used sample number average of resident next time check of same observation station is greater than the used sample number of resident check last time.
4, pseudo-random code catching method under the large-signal dynamic condition as claimed in claim 1 is characterized in that residence time is short in the described fast search, and it is few to detect sample number.
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