CN108880609A - PN synchronization method based on burst spread-spectrum signal - Google Patents
PN synchronization method based on burst spread-spectrum signal Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7073—Synchronisation aspects
- H04B1/7085—Synchronisation aspects using a code tracking loop, e.g. a delay-locked loop
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7073—Synchronisation aspects
- H04B1/7075—Synchronisation aspects with code phase acquisition
Abstract
The invention discloses a kind of PN synchronization method based on burst spread-spectrum signal, the spread-spectrum signal received is first passed through acquiring pseudo code module by this method, and a capture mark signal is exported after acquisition success.In conjunction with capture mark signal, after success to be captured, data are pre-processed, obtain a kind of data of new model, then data after pretreatment are sent into PN code tracking loop after down coversion.Acquiring pseudo code use constant false alarm adaptive threshold technology, by the output valve of matched filter compared with adaptive threshold value after result is obtained by the judgement mode of M/N again.Local pn code generator in tracking ring is made of phase accumulator and pseudo-code look-up table, after calculating phase error, it gives phase accumulator and makees accumulation process, the result of accumulator obtains corresponding pseudo- code value as the address of look-up table, and the purpose of pseudo-code tracing is so obtained with a kind of structure of closed loop.The present invention is suitable for the communication of a variety of pseudo- bit rates, and reduces the consumption of hardware resource.
Description
Technical field
The present invention relates to the spread and disposal plus methods in the communications field, and in particular to one kind is in original PN synchronization method
The improved synchronous method being directed in burst spread spectrum communication.
Background technique
PN synchronization is always a critical problem in spread spectrum communication, it includes capturing and tracking two steps.It catches
Obtaining is that will receive the phase difference of pseudo-code sequence and local pseudo-code in control in 0.5 chip, and tracking is to precisely control the phase
Position error, with reduce as asynchronous and caused by system processing gain loss.
The capture of spread-spectrum signal be using the sharp autocorrelation performance of pseudo noise code, by the signal received with it is locally generated
Pseudo noise code carry out related calculation, the result of related operation is compared with thresholding, it is no if more than threshold value then acquisition success
Acquisition procedure will then be continued.Basic catching method has sliding correlation method, matched filter method, sequential detection prize law and transmitting
Signal is with reference to method etc..Matched filter method is based on a kind of improvement of sliding correlation technique, and efficiency is very high, but works as PN-code capture
It when longer, needs largely to be postponed and add operation, implements too complex and resource consumption is excessive, be relatively specific for
The shorter spread spectrum communication of pseudo- code length.The synchronized tracking of pseudo-code sequence generallys use delay locked loop, and delay lock technique exists
It is quite similar with phase locking techniques in principle, it is all to realize output signal to input by a nonlinear feedback control loop
The tracking and synchronous effect of signal.
When communication system is spread spectrum burst communication, signal duration is very short, and signal starting point, initial position are all
It is uncertain.Often Content of Communication all can include part guide data, these guide's data are provided to receiving end and do capture use.
But in the case where transmitting terminal does not have guide's data, the detection of signal, the acquisition and tracking of spreading code require to consume many
Useful spread spectrum information, all data informations for how restoring to receive are one of problems.
Restore to receive all data informations it is avoided that the signal that will not originally receive stores, system to be received
System again demodulates initial signal extraction after all synchronizing again out, and under normal circumstances, system is established in synchronous condition
Afterwards, after pseudo-code tracing is stablized, all reception signals are demodulated extracting, the signal extracted can have one
The mutability of phase.But at this time due to closing track loop, it can make occur tracking essence in the demodulating process of initial data
Insufficient situation is spent, causes to demodulate effect decline.
In traditional pseudo-code tracing loop, receiving end is generated local pseudo-code, pseudo-code by pseudo-code NCO and pn code generator
The purpose of NCO is the work clock for generating pn code generator, and pn code generator generates pseudo- code value under the work clock.General feelings
Under condition, the work clock of pn code generator is generated by DDS, work clock is often pseudo- bit rate, however when pseudo- bit rate with
When the work clock of receiver is not much different, which can be very severe, and this scheme is unworkable in such situation, and
The hardware resource of this scheme consumption is larger.
Summary of the invention
The purpose of the present invention is to provide a kind of acquiring pseudo code trackings based on burst spread-spectrum signal, overcome and are spelling
Phase discontinuity problem caused by when reception signal, significantly reduces consumed resource in pseudo-code tracing loop, and
The case where suitable for a variety of pseudo-code rate communications.
The technical solution for realizing the aim of the invention is as follows：A kind of PN synchronization method based on burst spread-spectrum signal, should
Method is obtained assuming that carrier wave has synchronized, and is included the following steps：
(1)：Signal feeding acquiring pseudo code module will be received to detect, module exports a capture mark signal simultaneously,
When the signal is high level, show have spread spectrum data entrance at this time；When it is low level, indicate at this time without spread spectrum letter
Number enter.
(2)：To be checked to measure after capture mark signal drawn high by low level, local pn code generator is started to work, and is generated pseudo-
Code value, while Signal Pretreatment will be received and obtain a kind of new model data, preprocessing process exports a data forward and reverse sequence mark
Signal k.I, Q branch data after being multiplied to obtain down coversion with the carrier wave NCO cosine and sine signal generated respectively for the new model data.
(3)：The advanced branch pseudo-code PN that obtained I, Q branch data and local pn code generator are generatedE, lag branch
Pseudo-code PNLIt is multiplied, and it is obtained into four tunnel correlation accumulated result I by integrate-dumpES,ILS,QESAnd QLS。
(4)：By four obtained road correlated results by lag subtract leading power phase demodulation algorithm obtain local pseudo-code with
The phase difference between pseudo-code is received, and this phase difference is sent into loop filter.
(5)：The positive backward marking signal k of data provided in conjunction with step (2) and loop filter export as a result, obtaining phase
Phase accumulation value in bit accumulator.
(6)：Phase accumulator adds up under clock according to obtained phase accumulation value, the accumulation result that will be obtained
Address value as the look-up table for storing local pseudo-code.Look-up table obtains advanced branch pseudo-code PN by way of readingE, by PNE
Lag branch pseudo-code PN is obtained by register delayL。
The design method of acquiring pseudo code module described in step (1) is：
Acquiring pseudo code module mainly takes traditional matched filter tim e- domain detection method, will receive in data and the module
Local NCO generate cosine and sine signal be multiplied, respectively obtain SI、SQBranch data.The two paths of data is sent into matched filtering again
In device, y is obtainedIAnd yQData, the tap coefficient of matched filter are the inverted order form of spread spectrum code sequence.Data will be adjudicatedWith the threshold value V obtained by constant false alarm adaptive threshold technologyTIt is compared.In M judgement, there are n times
It adjudicates data and is greater than thresholding VTWhen, capture mark signal is drawn high, signal capture is otherwise continued.
Data preprocessing method described in step (2) is：
If the initial data received is r (n), total length L.It is to need to consume part due to capturing spread spectrum data
Spread spectrum data, it is assumed that the data length of consumption is X.When capture mark signal is drawn high, actual spread spectrum data is pass by
One section.Therefore data can will be received and postpone X point, it is therefore an objective to make practical received first spread spectrum data just with capture mark
Signal is corresponding after drawing high.
If signal after processing isThen
It is made of altogether four parts, first part is to receive signal, is equal to receives signal in the time domain.Mark to be captured
When will signal is drawn high,It is no longer equal to receive signal in the time domain.Its second part is the pure spread-spectrum signal r received
(n) data after delayed X sampled point.But the preceding L in its spread-spectrum signal only received0A sample point data, third portion
Divide the preceding L then to receive spread-spectrum signal0The backward form of -1 sample point data, Part IV are that the reception of complete i.e. L point is expanded
Frequency evidence.Phase due to receiving data is continuous, so the data phase of backward form is also continuous, structure in this form
AtIt ensure that the continuity of phase.A data forward and reverse sequence marking signal k is provided in preprocessing process simultaneously：
Here, whenIt is when being made of the r (n) of backward, k marking signal is 1；The k mark letter when being in other situations
Number be 0.
The design method of local pn code generator described in step (3) is：
Local pn code generator is made of a phase accumulator and pseudo-code look-up table.It is right under out of phase to be ready in advance
The pseudo- code value answered stores the pseudo- code value under the phase for phase value as address, constitutes a look-up table.Phase accumulator when
Clock acts on lower one phase value of output every time, which exports a local pseudo-code as the address of look-up table.For
Length is the pseudo-code sequence of M, if its pseudo-code sequence length after receiver samples becomes Ms.When in order to improve pseudo-code tracing
Precision, it is assumed that with N number of value indicate one it is sampled after pseudo- code value, then the precision of pseudo-code is 1/N, the at this time depth of look-up table
For Ms*N。
The update method of phase accumulation value described in step (5) is：
Since in the design of pseudo-code look-up table, the pseudo- code value after one originally is sampled has been extended to N number of pseudo-code
Value, therefore the basic stepping Pinc of phase accumulator is set here0It is sent into for N if the error signal of loop output is Δ Pinc
The numerical value of phase accumulator is Pinc：
Pinc=Pinc0+ΔPinc
Since when input data is backward, corresponding pseudo-code phase also starts toward rollback, at this time if phase-accumulated
Device continues if adding up, and local pseudo-code phase must be not corresponding with input data pseudo-code phase, so accumulator obtains at this time
To phase value should be toward retracting, then the value for being sent into accumulator should be negative, and practical Pinc value should be such as following formula：
Compared with prior art, the present invention its remarkable advantage：The present invention is a kind of effective and simple pn code generator knot
Structure overcomes the SPA sudden phase anomalies in signal splicing, suitable for the communication of a variety of pseudo- bit rates, and reduces hardware money
The consumption in source.
Detailed description of the invention
Fig. 1 is structural schematic diagram of the invention.
Fig. 2 is signal capture modular structure schematic diagram of the invention.
Fig. 3 is the timing diagram of Signal Pretreatment of the invention.
Fig. 4 is of the invention to obtain the structural schematic diagram of constant false alarm thresholding.
Fig. 5 is the schematic diagram of pseudo-code look-up table configuration of the invention.
Fig. 6 is ModelSim part signal simulation waveform in trapping module work.
Fig. 7 is ModelSim part signal simulation waveform in tracking system work.
Specific embodiment
Present invention will be further explained below with reference to the attached drawings and examples.
The program is to be write on ISE14.7 developing instrument using VerilogHDL language, below will be from
The program is described in the angle of VerilogHDL language.
If the initial data received is r (n), total length L.
Here the function of generating local carrier is realized by calling the DDS core carried in ISE.
Structure such as Fig. 1 of entire processing system, if obtaining S after intermediate frequency spread-spectrum signal down coversionI、SQTwo-way baseband signal：
In formula, S is available signal power, for convenience here it is considered that S=1, Δ f are residual frequency (i.e. local carriers
With the difference on the frequency between reception carrier wave), τ is the loop unknown delay volume to be tracked, and unit is chip, nI(t) and nQIt (t) is equal
Value is zero, and bilateral power spectral density is N0/ 2 baseband Gaussian white noise.What it is due to discussion is PN synchronization method, is defaulted here
Δ f is zero in the formula being discussed below.
By the S after mixingI、SQTwo-way baseband signal passes through matched filter respectively, in hardware realization, can call FIR
Core realizes matched filter, length M after order, that is, spread spectrum code sequence of matched filter is sampleds, coefficient, that is, sampled
The inverted order form of spreading code afterwards.When the pseudo-code phase of baseband signal (namely receiving signal) and the pseudo-code phase of matched filter
When less than a chip, obtained matched filter result is：
In above formula, TbIt is related accumulation interval, TCIt is that there are the times for a pseudo-code.Judgment variables after correlation are：
In general communication system, carrier doppler frequency deviation is much smaller than pseudo- bit rate, at this time
Therefore influence judgment variables factor be mainly manifested in Doppler frequency shift Δ f, with local pseudo-code and receive pseudo-code phase difference on.
Be zero due to defaulting Doppler frequency shift here, thus when receive code and local code to it is upper when (), judgment variables E will
There is maximum value.Since noise signal does not have the acuteness of pseudo-code, a thresholding can be set, when judgment variables E is higher than
When the threshold value, it is believed that spread-spectrum signal is come, when judgment variables E is lower than the threshold value, it is believed that arrive without spread-spectrum signal.
Here Background Noise Power is estimated using short distance element method, referring to Fig. 4.Wherein input signal isIt is passed in the buffer that length is 2R-1, when input signal is noise, these signals are independent same
Distribution, there can be the estimated value μ an of noise power to update out under each clock, the value of μ be used ask equal here
The mode of value (value and averaging of the value at preceding R-1 moment and rear R-1 moment) obtains, then it can be obtained multiplied by threshold factor ρ
To decision threshold value UT.By comparing filter output value ZR+1With threshold value UTRelationship court verdict can be obtained.
After the decision method by M/N detects spread-spectrum signal, signal significant level is drawn high, at the same treated letter
NumberIt should be first spread spectrum data received (variation takes place in pretreated signal).
For data preprocessing module, in hardware realization, three RAM cores are called altogether.
Referring to Fig. 2, Fig. 3, first core mainly does time delay processing to reception signal r (n), and the sampled point number of delay is
The data sampling point sum that the data capture stage is consumed, exports conductIn second part.
Second RAM core is that a depth is L0RAM core store the L received0A sample point data, each sampling
Point corresponds to an address, after the completion of data are stored, obtains preceding L by way of reading address0- 1 sample point data
Backward form, asIn Part III.
Third RAM core is that a depth is 2L0- 2 RAM core is used to the spread spectrum data for postponing to receive, asIn Part IV.
Pretreated signal is equally multiplied with the local NCO cosine and sine signal generated, the two-way letter after obtaining down coversion
Number I, Q.After the completion of code acquisition, I, Q two paths of signals carry out phase with locally generated advanced, lag branch pseudo-code respectively
It closes and adds up, general accumulation length is a pseudo-code sequence length M.Assuming that Δ f is constant in related accumulation interval, accumulator every
MTCTime exports an accumulation result value, wherein TCIt is that there are the times for a pseudo-code.Its four roads signal is in tkThe expression formula at moment
For：
In above formula,It is the valuation to τ, Rc() is the auto-correlation function of pseudo noise code,It is related accumulation interval,
nIe, nQe, nId, nQdIt is the noise component(s) of related cumulative rear each branch.
Here the discriminator algorithm of leading power is subtracted using lag, the output error signal for obtaining discriminator is：
In formula,It is phase tracking error, residual frequency very little after general frequency acquisition, it is believed that sinc
(πΔfTb) ≈ 1, Ne(tk, ε) be phase discriminator output phase error signal in noise contribution.When noiseless, error signal e
(tk, ε) and directly proportional to D (ε), D (ε) is the function of phase tracking error ε, directly reflects the time delay of tracking loop output signal
ValuationTo the tracking error of the delay, τ of input signal.
As can be seen that working asWhen, D (ε) is the linear function of error ε.Due to before loop starts tracking
Reception system has been completed acquiring pseudo code, so ε at this time has met above-mentioned condition.Obtained error signal is sent into
After loop filter filters out high fdrequency component, it is re-fed into the mesh that pn code generator module adjusts the phase completion tracking of local pseudo-code
's.
Since during the tracking of pseudo-code, pseudo-code is periodic, therefore it can also regarded as special shape just
String wave (its difference be the value range of sine wave between positive and negative 1, and the value of pseudo-code only have 0 or 1 two kind of situation).
Referring herein to the concept of DDS, it is used to store the look-up table of local pseudo-code data with phase accumulator and one to constitute local puppet
Code generation module.
Wherein, it gets out corresponding puppet code value under out of phase in advance, equally stores the phase for phase value as address
Under pseudo- code value, constitute a look-up table.In FPGA, the function of look-up table is realized by calling ROM core, by each phase
Corresponding pseudo-code information is written in coe file, and directly coe file is imported into ROM core and produces look-up table.Phase is tired
Device is added to export a phase value every time under clock effect, which exports a local puppet as the address of look-up table
Code.Using the pseudo-code of output as advanced branch pseudo-code, then pass through register delay TCThe method of (PN-code capture) obtains stagnant
Branch code afterwards.The pseudo-code sequence for being M for length, pseudo-code sequence length becomes M after samplings.In order to improve pseudo-code tracing
When precision, it is assumed that with N number of value indicate one it is sampled after pseudo- code value, then the precision of pseudo-code is 1/N, the at this time depth of look-up table
Degree is Ms*N。
Referring to Fig. 5, here, since original one pseudo- code value has been extended to N number of pseudo- code value, phase is set here
The basic stepping Pinc of accumulator0For N, the error signal of loop output is that (i.e. phase error D (ε) is filtered Δ Pinc by loop
Result after wave device), it is sent into numerical value (i.e. frequency control word) Pinc of phase accumulator at this time：
Pinc=Pinc0+ΔPinc (20)
Since when input data is backward, corresponding pseudo-code phase also starts toward rollback, at this time if phase-accumulated
Device continues if adding up, and local pseudo-code phase must be not corresponding with input data pseudo-code phase, so accumulator obtains at this time
To phase value should be toward retracting (being gradually reduced), then the value for being sent into accumulator should be negative.Here above formula is repaired
Just：
By the amendment to above formula, the tracking to pseudo-code also may be implemented when input data is backward, so protect
The reliability that loop is synchronous when demodulating first information bit is demonstrate,proved.
In order to verify the reliability of the program, below by taking the intermediate frequency spread-spectrum signal of BPSK modulation as an example.The spread-spectrum signal
Carrier frequency f0=50MHz, pseudo- code length Nc=32, pseudo- code frequency fc=40MHz, receiving end sample frequency fs=200MHz, it is former
Beginning bit rate fbit=1.25MHz.Using 5/4 (carrying out 5 judgements, be believed that judgement is effective when there is 4 times to succeed)
Judgement mode captures signal.Here the data length L=350bit received is set, for synchronous data length L0=
28bit.Here (the f due to sample rates/fc=5), originally the period is that the pseudo-code of M=32 point have now becomes MS=160
Point.N=100 is enabled here in order to improve the precision of pseudo-code, so the depth of pseudo-code look-up table is 16000 at this time.It uses below
Modelsim software emulates it：
The analogous diagram of acquisition phase is generated by matlab, is spread as shown in fig. 6, wherein din is the spread spectrum data received
Data be latter section of noise the last period be spread spectrum data.Adjust_gate is the threshold value that constant false alarm adaptive technique obtains,
Match_out is the output of matched filterIt can be seen that when input signal is spread spectrum data, match_
Periodic peak value is presented in out value, and (period is PN-code capture Tc).After 5 judgements, it is seen that 5 minor peaks are all larger than thresholding
Value, it is believed that captured spread-spectrum signal.
As shown in fig. 7, wherein din is the intermediate frequency data received, din_fixed is the waveform diagram of PN code tracking loop emulation
What din was obtained after data prediction, k is then the positive backward marking signal of above-mentioned data, and code_error is to receive
Phase difference between pseudo-code and local pseudo-code.Waveform diagram by observing code_error can be seen that acquisition phase not
Completion reception pseudo-code is fully synchronized with local pseudo-code, however uses the program, (locates in advance when the failing edge of k signal arrives
Manage the third section in obtained block signal), code_error illustrates this near obviously going to zero from an original biggish value
PN code tracking loop plays the role of pseudo-code phase tracking.
The present invention is mainly based upon the PN synchronization method of burst spread-spectrum signal, is on the basis of carrier synchronization is completed
Method is relatively specific for the shorter spread spectrum communication of pseudo- code length, is realized based on the constant false alarm threshold technique of matched filter
Acquiring pseudo code and the synchronous method that pseudo-code tracing is realized based on the mode of delay lock loop, tracking are based on original delay lock
Track improved a kind of technology on ring.First spread spectrum data can be captured simultaneously in the case where guide's data are not present
Unsuccessful demodulation comes out, and overcomes and splices phase discontinuity caused by when receiving signal in the case where receiving and happening suddenly spread-spectrum signal
Problem is a kind of effective and simple pn code generator structure, suitable for the communication of a variety of pseudo- bit rates, and reduces hardware money
The consumption in source.It can be currently to provide a kind of good thinking and scheme to the method for synchronization in burst communication, and adapt to
Signal is more than and is confined to spread-spectrum signal.
Claims (5)
1. a kind of PN synchronization method based on burst spread-spectrum signal, it is characterised in that include the following steps：
(1) in the case where assuming that carrier wave has synchronized, signal feeding acquiring pseudo code module will be received and detected, the module is defeated simultaneously
A capture mark signal out shows have spread spectrum data entrance at this time when the signal is high level；When it is low level
When, it indicates to enter without spread-spectrum signal at this time；
(2) to be checked to measure after capture mark signal drawn high by low level, local pn code generator is started to work, and generates pseudo- code value,
Signal Pretreatment is received simultaneously and obtains a kind of new model data, and preprocessing process exports a data forward and reverse sequence marking signal k, will
I, Q branch data after the new model data are multiplied to obtain down coversion with the carrier wave NCO cosine and sine signal generated respectively；
(3) the advanced branch pseudo-code PN for generating obtained I, Q branch data and local pn code generatorE, lag branch pseudo-code
PNLIt is multiplied, and it is obtained into four tunnel correlation accumulated result I by integrate-dumpES, ILS, QESAnd QLS；
(4) the phase demodulation algorithm that four obtained road correlated results are subtracted to leading power by lag obtains local pseudo-code and receives
Phase difference between pseudo-code, and this phase difference is sent into loop filter；
(5) the positive backward marking signal k of data and the loop filter output for combining step (2) to provide are tired out as a result, obtaining phase
Add the phase accumulation value in device；
(6) phase accumulator adds up under clock according to obtained phase accumulation value, using obtained accumulation result as depositing
Put the address value of the look-up table of local pseudo-code；Look-up table obtains advanced branch pseudo-code PN by way of readingE, by PNEBy posting
Storage postpones to obtain lag branch pseudo-code PNL。
2. PN synchronization method according to claim 1, it is characterised in that：Acquiring pseudo code module described in step (1)
Design method be：
Acquiring pseudo code module takes matched filter tim e- domain detection method, will receive what the local NCO in data and the module was generated
Cosine and sine signal is multiplied, and respectively obtains SI、SQBranch data；The two paths of data is sent into matched filter again, obtains yIAnd yQ
Data, the tap coefficient of matched filter are the inverted order form of spread spectrum code sequence；Data will be adjudicatedWith pass through perseverance
The threshold value V that false-alarm adaptive threshold technology obtainsTIt is compared, in M judgement, there are n times judgement data to be greater than thresholding VT
When, capture mark signal is drawn high, signal capture is otherwise continued.
3. PN synchronization method according to claim 1, it is characterised in that：Data prediction side described in step (2)
Method is：
If the initial data received is r (n), total length L；Assuming that the data length of consumption is X, if signal after processing
ForThen
It is made of altogether four parts, first part is to receive signal, is equal to receives signal in the time domain；Mark letter to be captured
When number drawing high,It is no longer equal to receive signal in the time domain；The pure spread-spectrum signal r (n) that second part as receives is through prolonging
Data after slow X sampled point, the preceding L in spread-spectrum signal only received0A sample point data, Part III are then reception
The preceding L of spread-spectrum signal0The backward form of -1 sample point data, Part IV are the reception spread spectrum data of complete i.e. L point；Pre- place
A data forward and reverse sequence marking signal k is provided during reason：
WhenIt is when being made of the r (n) of backward, k marking signal is 1；When being in other situations, k marking signal is 0.
4. PN synchronization method according to claim 1, it is characterised in that：Local pseudo-code described in step (3) generates
The design method of device is：
Local pn code generator is made of a phase accumulator and pseudo-code look-up table；Get out corresponding pseudo-code under out of phase
Value, stores the pseudo- code value under the phase for phase value as address, constitutes a look-up table；Phase accumulator is under clock effect
One phase value of output every time, the phase value export a local pseudo-code as the address of look-up table；It is M's for length
Pseudo-code sequence, if its pseudo-code sequence length after receiver samples becomes Ms；Assuming that with N number of value indicate one it is sampled after
Pseudo- code value, then the precision of pseudo-code be 1/N, at this time the depth of look-up table be Ms*N。
5. PN synchronization method according to claim 1, it is characterised in that：Phase accumulation value described in step (5)
Update method is：
The basic stepping Pinc of phase accumulator is set0It is sent into phase-accumulated for N if the error signal of loop output is Δ Pinc
The numerical value of device is Pinc：
Pinc=Pinc0+ΔPinc
Since when input data is backward, corresponding pseudo-code phase also starts toward rollback, at this time if phase accumulator after
It is continuous carry out it is cumulative if, local pseudo-code phase must be not corresponding with input data pseudo-code phase, so accumulator obtains at this time
Phase value is toward retracting, then the value for being sent into accumulator should be negative, and practical Pinc value should be such as following formula：
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