CN105871765A - Wireless communication carrier wave tracking method based on FFT assistant S-PLL - Google Patents
Wireless communication carrier wave tracking method based on FFT assistant S-PLL Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2657—Carrier synchronisation
- H04L27/2659—Coarse or integer frequency offset determination and synchronisation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2657—Carrier synchronisation
- H04L27/266—Fine or fractional frequency offset determination and synchronisation
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Abstract
The invention relates to a wireless communication carrier wave tracking method based on FFT assistant S-PLL. In a high-speed moving carrier wireless communication system, by adopting a carrier wave tracking method based on a fast Fourier transform assistant second-order phase-locked loop, the problem of receiving wireless communication under the condition of large-range Doppler frequency deviation can be solved, under the condition that the sampling frequency meets Nyquist sampling theorem, the general position of signal frequency can be rapidly acquired through FFT, and precise frequency deviation estimation can be further achieved through S-PLL. By adopting the method, frequency deviation estimation characteristics of FFT and PLL are sufficiently utilized, influence caused by large-range Doppler frequency deviation and signal noise can be overcome, and large dynamic variable carrier wave frequency deviation can be tracked; on the other hand, the method is simple in achieving structure, relatively low in complexity and relatively good in practicability.
Description
Technical field
The present invention relates to a kind of wireless communication carriers tracking based on FFT auxiliary S-PLL, belong to wireless communication carriers
Tracking technique field.
Background technology
The flourish requirement to cordless communication network of mobile Internet industry is more and more higher, round-the-clock, high-reliability, height
The network service of speed, high real-time and large user's capacity becomes the target that wireless communication technology development is constantly pursued.Make a general survey of whole
Individual Development of Wireless Communications history, particularly the Development of Wireless Communications history of China, is even more than the height of the velocity of sound towards speed per hour several hundred kilometers
The wireless communication problems of speed mobile vehicle is the most effectively solved.Stage in early days, by national economy level and skill
The restriction of art development, high-speed mobile wireless communications application market is relatively small, along with the enhancing of country's overall national strength, the highest
Developing rapidly of ferrum technology and related industry, towards wireless communications application demand the most urgent of high-speed mobile carrier.At a high speed
The main technological difficulties that the radio communication of mobile vehicle is faced are: during high-speed mobile, communication terminal launch or
Large range of Doppler shift (hereinafter referred frequency deviation) can be there is in the communication electromagnetism ripple received.On the one hand, Doppler's frequency
Wireless communication receiver partially can be caused to capture, demodulate, decode inefficacy, cause transmission information to extract；On the other hand, Doppler
Frequency deviation dynamically can change along with mobile vehicle speed, the acceleration even change of acceleration, thus gives wireless communication carriers
Technology of frequency tracking brings huge challenge.
In traditional wireless communication system, carrier frequency tracking mainly uses two class methods.The first kind is that open loop is estimated
Method, mainly includes frequency domain interpolation side based on fast Fourier transform (Fast Fourier Transformation, FFT)
Method, time domain smoothing method based on signal autocorrelation and based on time domain and frequency domain combined relevant method of estimation；Wherein, the most practical and have
Effect is the method for frequency domain interpolation based on FFT, and its ultimate principle is the corresponding mathematical relationship based on carrier signal time domain and frequency domain,
In conjunction with the spectral line periodogram after the FFT of carrier signal, the method using mathematical interpolation, such as two wires interpolation method, three lines are inserted
Value method, and then the carrier wave frequency deviation accurately obtained.This process employs the feature that FFT can quickly realize, make frequency deviation estimate
Implementation complexity is substantially reduced, thus the most widely used.Less in carrier wave frequency deviation constant magnitude or change
Under the conditions of, these methods can solve the estimation problem of frequency shift (FS) to a certain extent.But, theory analysis shows,
Under conditions of Doppler frequency deviation is relatively big, these open loop methods of estimation are all difficult to prove effective.Main reason is that: dynamic at carrier wave frequency deviation
Under conditions of change, either spectrum, or the correlation properties of time domain all present the characteristic of real-time change, thus it is difficult to standard
Really estimate carrier wave frequency deviation.
The Equations of The Second Kind method that carrier wave frequency deviation is followed the tracks of is based on FLL (Frequency Lock Loop, FLL) or lock
The closed-loop policy of phase ring (Phase Lock Loop, PLL), its ultimate principle is to be adjusted tracking carrier wave dynamically by feedback loop
Frequency.Under conditions of feedback frequency is identical with carrier frequency, system loop tends to convergence, and then realizes carrier frequency accurately
Follow the tracks of.In the ideal case, the frequency deviation dynamic range that carrier wave tracing method based on FLL can be estimated is relatively big, but its carrier wave with
The precision of track is poor, and the frequency deviation remained after system stability is more than method based on PLL.Particularly there is noise in sampled signal
Under conditions of, the tracking performance of FLL can severe exacerbation.Carrier wave tracing method based on PLL can effectively resist link noise
The impact estimating system frequency deviation, and can adapt to the dynamic change of frequency deviation is practical communication system through frequently with method.
Particularly second order PLL(Second-order PLL, S-PLL), with the constringency performance that it is stable, wide by engineering design teacher
General favor.Dynamically change although carrier frequency bias estimation based on FLL or PLL can solve carrier wave frequency deviation to a certain extent
Estimation problem, but due to its intrinsic problem, it may be assumed that for following the tracks of large range of carrier wave frequency deviation, need to increase loop bandwidth, and
The increase of loop bandwidth causes the increase of system noise, causes the deterioration of system tracking performance.Therefore, side based on FLL or PLL
Method is difficult to be applicable to the wireless communication carriers tracking problem of high-speed mobile carrier.For solving this problem, researchers propose perhaps
Multi-method, mainly include based on card Raman filtering (Kalman Filter, KF) tracing, based on KF associating PLL method with
And the method for FLL associating PLL.But, these researchs are all based on greatly providing positioning and communicating service to launch, such as towards GPS or
The carrier tracking technique of BEI-DOU position system communications reception.It is known that the communication service speed of positioning service is the lowest, generally
Situation about tens baud (bps) per second.Under the support of spread spectrum system, symbols speed can be to million grades of bps so that unit
Symbol frequency change less, use the united method of KF, FLL or PLL can to a certain degree solve frequency change with
Track problem.But, time face to face to speech (Kbps), hundred Kbps level videos or data communication service, said method is still difficult to
It is suitable for.Therefore, design a kind of have follow the tracks of relatively Larger Dynamic frequency deviation change carrier wave tracing method to solve high-speed mobile carrier lead to
Letter problem has important value.
Existing research shows, under conditions of sample frequency meets nyquist sampling theorem, and can be quick based on FFT
Obtain the rough position of signal frequency, even if carrier frequency occurs quickly change in time domain, remain able to be positioned by FFT
Go out the constant interval of carrier frequency；On the other hand, it is less than or equal to the frequency-tracking interval of PLL when the constant interval of carrier frequency
Time, then utilize PLL necessarily can estimate carrier wave frequency deviation exactly.Visible based on above-mentioned analysis, there is large doppler frequency
During inclined carrier estimation, a frequency change less than or equal to PLL frequency offset estimation range can be estimated first with FFT
Interval, then utilizes PLL to realize accurate frequency deviation and estimates.Compared to other high-speed mobile communications carrier tracking techniques, the method
Have the advantage that 1) sufficiently make use of the frequency deviation evaluation characteristic of FFT and PLL so that system carrier follow the tracks of can overcome big
The impact that range Doppler frequency deviation and electromagnetic signal noise bring；2) simple in construction that method is corresponding, substantially by based on FFT
Rough estimate module and essence based on PLL estimate module serially concatenated composition, it is achieved complexity is relatively low；3) traceable frequency deviation excursion
Dynamic adjustment can be realized by amendment FFT and PLL parameter, improve the scope of application of method.
Summary of the invention
It is contemplated that provide a kind of based on fast Fourier transform (Fast in realizing radio communication for high-speed mobile carrier
Fourier Transformation, FFT) auxiliary second-order PLL (Second-order Phase Lock Loop, S-
PLL) wireless communication carriers tracking, on the one hand can solve the problem that the Doppler frequency deviation shadow to wireless communication receiver on a large scale
Ring；On the other hand performance and the complexity advantage of FFT and PLL can sufficiently be utilized, with simple structure and relatively low complexity
Degree, it is achieved effective estimation of carrier wave frequency deviation.
The present invention is achieved by the following technical solutions: a kind of wireless communication carriers based on FFT auxiliary S-PLL is followed the tracks of
Method, comprises the steps:
The first step: transmitting terminal processes；By information sequence to be sentAfter encoded modulation, it is converted into and can be sent out by antenna
The electromagnetic wave signal sent, can be by this signal modeling, the communication channel of system be modeled as additive white Gaussian noise (
Additive White Gaussian Noise, AWGN) channel, the shock response parameter constant of channel is 1, and signal passes through
, white Gaussian noise can be there is in awgn channelInterference, due to the versus high motion of transmitting terminal Yu receiving terminal, high-speed mobile institute
The Doppler frequency deviation producedIt is modeled as one about practical carrier frequency, carrier translational speed, acceleration, add
SpeedAnd the timeMulti-term expression, it may be assumed that
Wherein、、For coefficient function, expression is respectively as follows:
WhereinFor the spread speed of communication electromagnetism ripple,Angle for electromagnetic wave propagation direction Yu carrier relative movement direction；
Assume that the symbol sebolic addressing that transmitting terminal is sent is, the signal of transmission is, it is expressed as:
WhereinFor sending symbol period,For sending shaping function, it is ordinarily selected to square root raised cosine function,For
Carrier wave initial phase, through awgn channel, the signal received by receiving terminal is:
WhereinThe average of Gaussian noise is 0, and standard deviation is。
Second step: receiving terminal pretreatment；First to the signal receivedCarry out down-converted, pending to obtain
The baseband signal carrying frequency deviation, under conditions of meeting nyquist sampling theorem, rightCarry out sampling processing, enter
And obtain discrete digitized signal sequence, after capturing carrier and accurate bit timing synchronization process, carried
Doppler frequency deviationDiscrete sampling sequence, it is expressed as:
WhereinFor the sampling period, sample frequency meets nyquist sampling law, it may be assumed that
WhereinThe maximum Doppler frequency offset followed the tracks of it is designed to for system,Actual samples frequency for receiving terminal；At this
On the basis of, by all of sampled point according to time spanSegmentation,Size by the frequency-tracking model of PLL loop filter
EncloseWithTogether decide on, and meet:
。
3rd step: FFT frequency deviation rough estimate；By discrete sampling sequenceAccording to regular length segmentation, for each
Sampled data section, first extracts() individual sampled point does a length ofFFT, it may be assumed that
WhereinMeet:
On this basis, the peak value spectral line after FFT is utilized to obtain the rough estimate interval of carrier wave frequency deviation, it may be assumed that
WhereinMeet:
Pass throughFrequency calibration, can obtain existing the sample sequence of residual frequency deviation further, it may be assumed that
WhereinFor AWGN sequence.
4th step: S-PLL carrier wave dynamic frequency offset essence is estimated；For obtaining accurate carrier wave frequency deviation, residual frequency deviation will be there is
Sample sequenceFurther across S-PLL process, particularly as follows:
1), phase discriminator:
WhereinFor sampled pointPhase place,For the feedback and tracking phase place of S-PLL,For phase demodulation function；
2), loop filter；By phase deviationAfter phase demodulation processes, input loop filter be filtered place
Reason, the transfer function of loop filterFor:
WhereinFor loop filter transfer functionTerritory expression formula,、For loop parameter；Wave filter inputsFor:
WhereinFor phase detector gain；
3), voltage controlled oscillator (VCO)；Further the output sequence of loop filter is input to voltage controlled oscillator
(VCO), transfer function is:
WhereinFor VCO transfer functionTerritory expression formula,For the gain control parameter of VCO, the input of VCO is loop
The output of wave filter, VCO is output as；
Through the process of S-PLL, it is estimated that sample sequenceMiddle remnants dynamically change Doppler frequency deviation, enter one
Step is passed throughCalibrating frequency process, can obtain final carrier track output sequence:
The goal satisfaction of carrier track:
。
5th step: FFT skew is calibrated；For estimating carrier phase deviation (hereinafter referred skew) further, can be according to symbol
Speed is to discrete sampling sequenceIt is sampled, recyclingEliminate the dynamic changing unit in carrier wave frequency deviation, enter
And obtain sequence:
Carrier wave skew is estimated further with frequency domain interpolation method based on FFT.
By technique scheme, the invention have the benefit that the present invention meets nyquist sampling in sample frequency
Under conditions of theorem, quickly obtained the rough position of signal frequency by FFT, realize accurate frequency deviation further with S-PLL
Estimating, compared to other tracking techniques, this method sufficiently make use of the frequency deviation evaluation characteristic of FFT and PLL, it is possible to overcomes big model
Enclose Doppler frequency deviation and impact that electromagnetic signal noise brings, Larger Dynamic change carrier wave frequency deviation can be followed the tracks of；On the other hand, this method
Corresponding realizes simple in construction, and complexity is relatively low, and practicality is higher.
Accompanying drawing explanation
Fig. 1 is high-speed mobile carrier communication system illustraton of model；
Fig. 2 is typical communication system receiver topology example figure；
Fig. 3 is the flowage structure figure corresponding to the carrier wave tracing method designed by the present invention；
Fig. 4 is S-PLL structure chart of the present invention；
Fig. 5 is that the carried carrier wave tracing method of the present invention is under the conditions of maximum Doppler frequency offset is 140KHz and signal to noise ratio is-1.0dB
Performance simulation figure；
Fig. 6 is that the carried carrier wave tracing method of the present invention is under the conditions of maximum Doppler frequency offset is 140KHz and signal to noise ratio is 0dB
Performance simulation figure.
Detailed description of the invention
Below in conjunction with accompanying drawing, the present invention is further described.
As Figure 1-4, a kind of wireless communication carriers tracking based on FFT auxiliary S-PLL, comprise the steps:
The first step: transmitting terminal processes；By information sequence to be sentAfter encoded modulation, it is converted into and can be sent by antenna
Electromagnetic wave signal, can be by this signal modeling；Through awgn channel, white Gaussian noise can be there is in signalInterference；Additionally, by
In the versus high motion of transmitting terminal Yu receiving terminal, can there is Doppler frequency deviation when arriving receiving terminal in the electromagnetic wave signal of transmission,
In conjunction with existing research work, can be byIt is modeled as one about practical carrier frequency, carrier translational speed, acceleration, accelerationAnd the timeMulti-term expression: i.e.:
Wherein、、For coefficient function, expression is respectively as follows:
WhereinFor the spread speed of communication electromagnetism ripple,Angle for electromagnetic wave propagation direction Yu carrier relative movement direction；
If the symbol sebolic addressing that transmitting terminal is sent is, the signal of transmission is, it is expressed as:
WhereinFor sending symbol period,For sending shaping function, it is ordinarily selected to square root raised cosine function,For
Carrier wave initial phase, through awgn channel, finally, the signal received by receiving terminalFor:
WhereinThe average of Gaussian noise is 0, and standard deviation is。
Second step: receiving terminal pretreatment；First to the signal receivedCarry out down-converted, pending to obtain
The baseband signal carrying frequency deviation, under conditions of meeting nyquist sampling theorem, rightCarry out sampling processing, enter
And obtain discrete digitized signal sequence, after capturing carrier and accurate bit timing synchronization process, carried
Doppler frequency deviationDiscrete sampling sequence, whereinThe main process object of method designed by the present invention,
It is expressed as:
WhereinFor the sampling period, sample frequency meets nyquist sampling law, it may be assumed that
WhereinThe maximum Doppler frequency offset followed the tracks of it is designed to for system,Actual samples frequency for receiving terminal；At this
On the basis of, by all of sampled point according to time spanSegmentation,Size by the frequency-tracking model of PLL loop filter
EncloseWithTogether decide on, and meet:
。
3rd step: FFT frequency deviation rough estimate；By discrete sampling sequenceAccording to regular length segmentation, for each
Sampled data section, extraction() individual sampled point does a length ofFFT, it may be assumed that
WhereinMeet:
It follows that utilize the peak value spectral line after FFT to obtain the rough estimate interval of carrier wave frequency deviation, it may be assumed that
WhereinMeet:
；
Pass throughFrequency calibration, can obtain existing the sample sequence of residual frequency deviation further, it may be assumed that
WhereinFor AWGN sequence.
4th step: S-PLL carrier wave dynamic frequency offset essence is estimated；For obtaining accurate carrier wave frequency deviation, residual frequency deviation will be there is
Sample sequenceFurther across S-PLL process, particularly as follows:
1), phase discriminator；Extract the sample sequence that there is residual frequency deviationPhase sequence and input the phase discriminator of S-PLL:
WhereinFor sampled pointPhase place,For the feedback and tracking phase place of S-PLL,For phase demodulation function；
2), loop filter；By phase deviationAfter phase demodulation processes, input loop filter be filtered place
Reason, the transfer function of loop filterFor:
WhereinFor loop filter transfer functionTerritory expression formula,、For loop parameter；Wave filter inputsFor:
WhereinFor phase detector gain；
3), voltage controlled oscillator (VCO)；Further the output sequence of loop filter is input to voltage controlled oscillator
(VCO), transfer function is:
WhereinFor VCO transfer functionTerritory expression formula,For the gain control parameter of VCO, through said process
After serial process, can obtainThe dynamic frequency offset of middle remnants, pass throughFurther calibrating frequency, carrier wave can be obtained
Tracking output sequence:
The goal satisfaction of carrier track:
；
5th step: FFT skew is calibrated；For estimating carrier phase deviation, can be according to character rate to discrete sampling sequence
It is sampled, recyclingEliminate the dynamic changing unit (the fixing frequency deviation of residual) in carrier wave frequency deviation, and then obtain:
Final utilization frequency domain interpolation method based on FFT estimates carrier wave skew.
Hereafter illustrate that the concrete of institute of the present invention extracting method is applied with example:
At one towards in the wireless communication system of high-speed mobile carrier, the maximum flying speed of mobile vehicleRice is every
Second (m/s), the frequency of radio magnetic wave(Ka wave band).Assume that electromagnetic wave propagation speed ism/
S(is usually the 2/3 of the light velocity), then the maximum Doppler frequency offset produced in carrier moving process is.Channel is built
Mould is awgn channel, and noise average is 0, and variance is.The symbols speed of signal, mean power normalization
It is 1.Average power signal is defined as signal to noise ratio with the ratio of the monolateral spectrum density of interchannel noise, is designated as, unit is dB.Such as figure
Shown in 1-4, whole example to realize process as follows:
The first step: transmitting terminal processes；Transmitting terminal does not carry out coded treatment, directly uses quadriphase keying (QPSK) modulation system, right
The bit sequence arbitrarily generatedBeing modulated, the square root raised cosine function then utilizing roll-off factor to be 0.5 carries out symbol
It is transmitted molding.Finally signal to be sent is carried out up-conversion, be that signal is modulated onto frequency and isCarrier wave
On.
Second step: Channel Processing；First pass around awgn channel, add signal to noise ratio and meetNoise, then add maximum
Doppler frequency deviation isDoppler frequency deviation, andAbout the timeMeet:
Final receiving terminal obtains radiofrequency signal。
3rd step: receiving terminal processes-FFT carrier wave frequency deviation rough estimate；First the radiofrequency signal received is carried out down coversion,
Again withSignal is sampled by the sampling rate of (meeting nyquist sampling theorem), obtains discrete series sample
Point, willBeing within 0.1 second, to carry out segmentation according to time span, every section of extraction is a length ofData enter
Line length isPoint FFT computing, then from the frequency domain spectral line that FFT obtains, find peak point, and utilize
It is calculated the rough estimate value of carrier wave frequency deviation。
4th step: receiving terminal processes-S-PLL carrier wave dynamic frequency offset essence and estimates；Utilize the carrier wave frequency deviation pair of rough estimateCarry out frequency calibration, obtain existing the sequence of residual frequency deviation, to the most rightInIndividual sampling point does as follows
Process:
1) sampling point phase place is extracted
WhereinFor taking sign bit function,For taking real part functions,For taking imaginary part function,For mod；
2) phase contrast is extracted
；
3) loop filter input is obtained
Wherein；
4) loop filtering processes
；
5) VCO process
；
6) local trace phase place is updated；
It is right to repeatCarry out 1)-6) serial process of step obtains local trace phase sequence, recycling phase and frequency about
The relation of time obtains carrier track frequency。
5th step: receiving terminal processes the calibration of-FFT skew；First withEliminate the dynamic change in carrier wave frequency deviation
Partly (the fixing frequency deviation of residual), recycling FFT obtains skew.
The present invention quickly obtains the rough position of signal frequency by FFT, realizes accurate frequency deviation further with S-PLL
Estimate, overcome Doppler frequency deviation and the impact on carrier track of the electromagnetic signal noise on a large scale, it is adaptable to high-speed mobile carrier without
Line communications applications scene.Fig. 5 and Fig. 6 sets forth the present invention and proposed wireless communication carriers tracking based on FFT auxiliary S-PLL
Method at maximum Doppler frequency offset is, and signal to noise ratio is respectivelyDB anddB
Under the conditions of performance.As seen from Figure 5, meet when signal to noise ratioDuring dB, the carrier frequency that institute of the present invention extracting method is estimated
There is error in inclined and actual carrier frequency deviation.When it can be seen that this error is less than, follow-up demodulation will not be given
The performance of decoding brings impact.As can be seen from Figure 6, whenDuring dB, the carrier wave frequency deviation that institute of the present invention extracting method is estimated with
Actual carrier frequency deviation is identical.Result shown in Fig. 5 and Fig. 6 sufficiently illustrates the effectiveness of the carried tracking of the present invention.
The above is only the better embodiment of the present invention, thus all according to the structure described in present patent application scope,
The equivalence that feature and principle are done changes or modifies, in the range of being all included in present patent application.
Claims (2)
1. a wireless communication carriers tracking based on FFT auxiliary S-PLL, it is characterised in that: comprise the steps:
The first step: transmitting terminal processes；By information sequence to be sentAfter encoded modulation, it is converted into and can be sent by antenna
Electromagnetic wave signal, can be by this signal modeling；Through awgn channel, white Gaussian noise can be there is in signalInterference；
Additionally, due to transmitting terminal and the versus high motion of receiving terminal, how general the electromagnetic wave signal of transmission can exist when arriving receiving terminal
Strangle frequency deviation, can be byIt is modeled as one about practical carrier frequency, carrier translational speed, acceleration, acceleration
DegreeAnd the timeMulti-term expression:
Wherein、、For coefficient function, expression is respectively as follows:
WhereinFor the spread speed of communication electromagnetism ripple,Angle for electromagnetic wave propagation direction Yu carrier relative movement direction；If
The symbol sebolic addressing that transmitting terminal is sent is, the signal of transmission is, it is expressed as:
WhereinFor sending symbol period,For sending shaping function, it is ordinarily selected to square root raised cosine function,For carrying
Ripple initial phase, through awgn channel, finally, the signal received by receiving terminalFor:
WhereinThe average of Gaussian noise is 0, and standard deviation is；
Second step: receiving terminal pretreatment；Receiving terminal is first to the signal receivedCarry out down-converted, wait to locate to obtain
The baseband signal carrying frequency deviation of reason, under conditions of meeting nyquist sampling theorem, rightCarry out sampling processing,
And then obtain discrete digitized signal sequence, after capturing carrier and accurate bit timing synchronization process, taken
Band Doppler frequency deviationDiscrete sampling sequence, whereinIt is expressed as:
WhereinFor the sampling period, sample frequency meets nyquist sampling law, it may be assumed that
WhereinThe maximum Doppler frequency offset followed the tracks of it is designed to for system,Actual samples frequency for receiving terminal；At this
On the basis of, by all of sampled point according to time spanSegmentation,Size by the frequency-tracking model of PLL loop filter
EncloseWithTogether decide on, and meet:
；
3rd step: FFT frequency deviation rough estimate；By discrete sampling sequenceAccording to regular length segmentation, for each hits
According to section, extraction () individual sampled point does a length ofFFT, it may be assumed that
WhereinMeet:
；
It follows that utilize the peak value spectral line after FFT to obtain the rough estimate interval of carrier wave frequency deviationThat is:
WhereinMeet:
；
Pass throughFrequency calibration, can obtain existing the sample sequence of residual frequency deviation further, it may be assumed that
WhereinFor AWGN sequence；
4th step: S-PLL carrier wave dynamic frequency offset essence is estimated: for obtaining accurate carrier wave frequency deviation, the sampling of residual frequency deviation will be there is
SequenceFurther across S-PLL process；
5th step: FFT skew is calibrated；For estimating carrier phase deviation, can be according to character rate to discrete sampling sequenceEnter
Line sampling, recyclingEliminate the dynamic changing unit in carrier wave frequency deviation, and then obtain:
Final utilization frequency domain interpolation method based on FFT estimates carrier wave skew.
A kind of wireless communication carriers tracking based on FFT auxiliary S-PLL the most according to claim 1, its feature exists
In: the sample sequence of residual frequency deviation will be there is in the 4th described stepFurther across S-PLL process, particularly as follows:
1), phase discriminator；Extract the sample sequence that there is residual frequency deviationPhase sequence and input the phase discriminator of S-PLL:
WhereinFor sampled pointPhase place,For the feedback and tracking phase place of S-PLL,For phase demodulation function；
2), loop filter；By phase deviationAfter phase demodulation processes, input loop filter be filtered processing,
The transfer function of loop filterFor:
WhereinFor loop filter transfer functionTerritory expression formula,、For loop parameter；Wave filter inputsFor:
WhereinFor phase detector gain；
3), voltage controlled oscillator (VCO)；Further the output sequence of loop filter is input to voltage controlled oscillator (VCO),
Transfer function is:
WhereinFor VCO transfer functionTerritory expression formula,For the gain control parameter of VCO, the input of VCO is loop
The output of wave filter, VCO is output as；After the serial process of said process, can obtainThe dynamic frequency offset of middle remnants, pass throughFurther calibrating frequency process, can obtain carrier track output sequence:
The goal satisfaction of carrier track:
。
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| CN116155668B (en) * | 2023-04-20 | 2023-07-14 | 北京中天星控科技开发有限公司 | Anti-frequency offset carrier recovery method, system and storage medium |
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