CN109462421B - Signal timing recovery method and recovery device, signal demodulation method and demodulation system - Google Patents

Signal timing recovery method and recovery device, signal demodulation method and demodulation system Download PDF

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CN109462421B
CN109462421B CN201811231045.4A CN201811231045A CN109462421B CN 109462421 B CN109462421 B CN 109462421B CN 201811231045 A CN201811231045 A CN 201811231045A CN 109462421 B CN109462421 B CN 109462421B
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熊军
王旭
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Ruixinfeng Aerospace Technology Beijing Co ltd
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Beijing Rinfon Technology Co ltd
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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
    • H04B1/7087—Carrier synchronisation aspects
    • 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
    • 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
    • H04L27/2662—Symbol synchronisation

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Abstract

The invention relates to a signal timing recovery method and a recovery device, a signal demodulation method and a demodulation system, wherein the signal timing recovery method comprises the following steps: receiving a plurality of sections of signals, wherein each section of signals comprises a plurality of symbol signals, sampling the symbol signals, and calculating the timing error of each symbol signal; adding and averaging the timing errors of a plurality of symbol signals in each section of signals to obtain the average value of the timing errors of each section of signals; and comparing the average value of the timing errors of each section of signals with a preset threshold, calculating the number of adjustment points of the sampling points when the number of times that the average value of the timing errors of the sections of signals is continuously larger than or smaller than the preset threshold exceeds the preset number of times, and performing timing recovery on each symbol signal according to the number of adjustment points of the sampling points. The signal timing recovery method and device, the signal demodulation method and the signal demodulation system can quickly determine the signal adjustment direction, are stable in adjustment and cannot cause the problems of over adjustment or missing adjustment.

Description

Signal timing recovery method and recovery device, signal demodulation method and demodulation system
Technical Field
The present invention relates to the field of wireless communications, and in particular, to a signal timing recovery method and recovery apparatus, a signal demodulation method and a demodulation system.
Background
In a software radio receiver, in order to correctly recover the signal carried by the transmitting end, the receiving end must know the start and stop time of each symbol, so as to perform periodic sampling decision to recover the binary signal at the middle time of each symbol. The delay of the signal in the transmission process is generally unknown, and due to the influence of noise, multipath effect and the like in the transmission process, the received signal is not synchronous with the local clock signal, so that a bit synchronization algorithm is needed to recover the clock signal with the same frequency and phase as the received code element. The correct synchronous clock is the basis for the correct judgment of the receiving end and is also an important factor influencing the error rate of the system; without an accurate bit synchronization algorithm, reliable data transmission is impossible, and the performance of the bit synchronization directly affects the performance of the whole communication system. The types of bit synchronization algorithms are very diverse, and the bit synchronization algorithms can be divided into three types of bit synchronization algorithm models, namely a full analog mode, a half digital mode and a full digital mode according to different processing modes, as shown in fig. 1.
The model in fig. 1(a) is a full-analog bit synchronization implementation technique, which calculates a bit synchronization timing control signal of an input signal in an analog domain to control a local clock, so as to perform synchronous sampling on the signal.
The model in fig. 1(b) is a semi-analog synchronization model, and the main idea of the model is to extract the deviation value of the input signal and the local clock by subjecting the sampled signal to a series of digital processing, and to change the phase of the local clock by the deviation to achieve bit synchronization. (a) Both the two modes need to change the phase of the local clock in time, which is not beneficial to the realization of high-speed digital signals and has low integration degree.
Fig. 1(c) shows that the bit synchronization in the all-digital mode is a relatively common method at present, and the bit synchronization algorithm in the all-digital mode is very suitable for the implementation of software radio. The method comprises the steps of sampling an input analog signal through a fixed local clock, and performing full digitalization processing on the sampled signal to realize synchronization; the method is simple to implement, convenient for digital implementation and greatly reduced in requirements on the local clock. The Gardner timing recovery algorithm based on interpolation is mainly adopted.
The principle of the Gan Gardner timing recovery algorithm is as follows: the Gardner timing recovery algorithm is based on an interpolation bit synchronization mode, and in a bit synchronization algorithm model of a full digital mode, a fixed local sampling clock cannot guarantee that sampling can be realized at an extreme point of a signal, so that sampling at the extreme point needs to be realized by changing a resampling clock or an input signal. The Gardner timing recovery algorithm is implemented by changing the input signal, and the maximum value of the signal is recovered by using an interpolation filter and then is resampled, and the principle of the Gardner timing recovery algorithm is shown in fig. 2.
As shown in FIG. 2, the input signal is a discrete signal x (mT)s) With a sampling rate of TsSymbol period is T and resampling clock is TiHere the resampling clock period TiN x T (n is a small integer). The basic idea of the Gardner timing recovery algorithm is that the input signal x (mT)s) The digital signal is restored to an analog signal y (t) through a D/A device and an analog filter h (t) for resampling, and a synchronous output signal y (kT) is obtainedi). The interpolation filter model includes a virtual D/a conversion and an analog filter, but if the following three conditions are met, the interpolation can be completely realized digitally.
Input sample sequencex(mTs)
Interpolation filter impulse response h (t)
Input sample time TsAnd output sampling time Ti
That is, both the D/A and analog filters in the figure can be implemented by designing a digital interpolation filter. Here TsAnd TiBeing two variables fixed, Ts/TiNot necessarily integers, and T is obtained by conversion to show the conversion process between themiAnd TsThe relationship of (A) is shown in a formula.
Figure BDA0001837164830000021
mkIs the integer part of the ratio and can be regarded as a basic pointer, representing the local resampling clock TiFor the sampling rate of TsOf the input signal, and ukThe fractional part of the ratio indicates the interpolation instant of the filter on the input signal. A block diagram of a typical Gardner timing recovery algorithm is shown in fig. 3.
The analog input signal x (T) with symbol rate T goes through a local fixed clock period TsAfter sampling, the signal becomes a discrete signal x (mT)s)(TsSatisfies nyquist theorem with T). Sending the value obtained by the interpolation filter into a timing error detector to obtain the phase error tau (n) between the input signal and the local clock, filtering the noise and high-frequency components in the input signal by a loop filter, sending the obtained value e (n) into a numerically controlled oscillator to calculate the integer sampling time mkAnd interpolation filter interpolation point position ukThereby obtaining a timing output y (kT)i)。
It can be seen from fig. 3 that a complete timing recovery algorithm consists mainly of a timing error detector, a loop filter, a numerically controlled oscillator and an interpolation filter. The design method of the loop filter is the same as that of the carrier synchronization algorithm in the previous chapter.
The existing gardner algorithm needs interpolation filtering, consumes more resources, is easily influenced by the order and coefficient of the filter, and is more complex in design because the noise of the filter needs to be continuously corrected under different channel and noise conditions.
The garder algorithm is a timing error estimation algorithm that does not require prior carrier synchronization. The method is a non-decision pointing method, and the basic idea is as follows: the amplitude and polarity change information of the optimal sampling point of the adjacent code element is extracted, and the information of whether the transition point of the adjacent code element is zero or not is added, so that the timing error can be extracted from the sampling signal. The Gardner phase-locked loop is located behind the Costas carrier synchronization phase-locked loop in system design and generally mainly comprises four parts: interpolator, clock error extraction module, loop filter, and controller module. Sampling points of two paths of orthogonal signals I and Q generate a timing error sampling point by calculating each symbol period. And sending the timing error sequence to a numerical control oscillator after passing through a loop filter through timing error detection, generating a parameter by the numerical control oscillator to control an interpolation filter, and finally adjusting the sampling time by the interpolation filter, thereby completing the whole symbol synchronization process. How to generate the timing error sequence from the received sample points is the key to the Gardner algorithm. The current ganrder algorithm requires interpolation filtering, which is relatively resource-consuming.
Therefore, a signal timing recovery method and recovery apparatus, a signal demodulation method and a demodulation system are provided.
Disclosure of Invention
In view of the above problems, the present invention has been made to provide a signal timing recovery method and recovery apparatus, a signal demodulation method and a demodulation system that overcome or at least partially solve the above problems, save the filtering processing resources of the conventional gardner algorithm, can quickly determine the adjustment direction of the system, and are stable in adjustment without the problems of over-adjustment or missing adjustment.
According to an aspect of the present invention, there is provided a signal timing recovery method, including the steps of:
receiving a plurality of sections of signals, wherein each section of signals comprises a plurality of symbol signals, sampling the symbol signals, and calculating the timing error of each symbol signal;
adding and averaging the timing errors of a plurality of symbol signals in each section of signals to obtain the average value of the timing errors of each section of signals;
and comparing the average value of the timing errors of each section of signals with a preset threshold, calculating the number of adjustment points of the sampling points when the number of times that the average value of the timing errors of the sections of signals is continuously larger than or smaller than the preset threshold exceeds the preset number of times, and performing timing recovery on each symbol signal according to the number of adjustment points of the sampling points.
Further, the plurality of symbol signals are oversampled, and the number of sampling points in each symbol signal is calculated by the following formula:
BL＝fS/Rb
wherein BL is the number of sampling points in each symbol signal, fSRb is the symbol rate, the sampling rate.
Further, the timing error of each symbol signal is calculated by the following formula:
Figure BDA0001837164830000041
where u (r) is the timing error of the symbol signal r,
Figure BDA0001837164830000051
is the interpolation value of the middle time I path of the sampling points of the symbol signal r and the symbol signal r-1,
Figure BDA0001837164830000052
for interpolated values, x, of paths Q intermediate the sampling points of the sign signal r and the sign signal r-1I(r) is the sampling point, x, of the I path of the symbol signal rQ(r) is the sampling point, x, of the Q-path of the symbol signal rI(r-1) is a sampling point of path I of the symbol signal r-1, xQAnd (r-1) is a sampling point of a Q path of the symbol signal r-1.
Further, the timing errors of the plurality of symbol signals in each segment of the signal are summed and averaged by the following formula:
Figure BDA0001837164830000053
wherein, UiThe average value of u (r) in the ith symbol signal is shown, P is the number of ith symbol signals, and i is 1,2 and ….
Further, the preset threshold is 0.
Further, timing recovery is carried out on each symbol signal according to the number of sampling point adjustment points through the following formula:
newST＝newST+sign(▽)*move；
the new ST is the position of an original sampling point, v is a fractional timing error factor, sign (v) is a fractional timing error factor with a sign, move is the number of points moved at one time, and sign (v) move is the number of adjustment points of a sampling point.
Further, the fractional part timing error factor is calculated by the following equation:
Figure BDA0001837164830000054
wherein, UiIs the average value of u (r) within the ith segment sign signal +iThe error factor is timed for the fractional part of the ith segment of the symbol signal.
According to another aspect of the present invention, there is provided a signal timing recovery apparatus for implementing the method as described above, including:
a symbol signal timing error calculation module, configured to receive multiple segments of signals, where each segment of signals includes multiple symbol signals, sample the multiple symbol signals, and calculate a timing error of each symbol signal;
the timing error average value calculation module is used for adding and averaging the timing errors of a plurality of symbol signals in each section of signals to obtain a timing error average value of each section of signals;
and the signal timing recovery module is used for comparing the average value of the timing error of each section of signal with a preset threshold, calculating the number of adjustment points of the sampling points when the number of times that the average value of the timing error of the plurality of sections of signals is continuously greater than or less than the preset threshold exceeds the preset number of times, and performing timing recovery on each symbol signal according to the number of adjustment points of the sampling points.
According to still another aspect of the present invention, there is provided a signal demodulation system including the signal timing recovery apparatus as described above, comprising:
the signal acquisition device is used for acquiring signals and sending the signals to the pseudo code synchronization device;
the pseudo code synchronization device is used for performing pseudo code synchronization on the signals and sending the signals to the de-spreading device;
the de-spread device is used for receiving and de-spreading the signal after pseudo code synchronization and sending the signal to the signal timing recovery device;
the carrier synchronization device is used for receiving the signals after the bit synchronization sent by the signal timing recovery device and carrying out carrier synchronization on the signals;
and the signal demodulation device is used for receiving and demodulating the signal after the carrier synchronization to obtain a demodulated signal.
According to another aspect of the present invention, there is provided a signal demodulation method implemented based on the signal demodulation system, including the following steps:
collecting signals;
carrying out pseudo code synchronization on the acquired signals;
despreading the signals after pseudo code synchronization;
receiving a plurality of sections of despread signals, wherein each section of signals comprises a plurality of symbol signals, sampling the symbol signals, and calculating the timing error of each symbol signal;
adding and averaging the timing errors of a plurality of symbol signals in each section of signals to obtain the average value of the timing errors of each section of signals;
comparing the average value of the timing error of each section of signal with a preset threshold, calculating the number of adjustment points of the sampling points when the number of times that the average value of the timing error of the plurality of sections of signals is continuously larger than or smaller than the preset threshold exceeds the preset number of times, and performing timing recovery on each symbol signal according to the number of adjustment points of the sampling points;
carrying out carrier synchronization on the signals after timing recovery;
and demodulating the signal after carrier synchronization to obtain a demodulated signal.
Compared with the prior art, the invention has the following advantages:
1. the signal timing recovery method and the recovery device, the signal demodulation method and the demodulation system of the invention obtain the average timing error by calculating the average after calculating the arithmetic superposition of the timing errors for a plurality of times, judge the average timing error, and judge the superposition after exceeding the preset threshold, and perform real loop updating once after the number of times that the average timing error continuously exceeds the preset threshold is more than the preset number of times, so that the timing recovery of the signal does not need filtering interpolation, and can reach a stable state only by a two-dimensional average algorithm, thereby saving the filtering processing resource of the traditional gardner algorithm, being capable of rapidly determining the adjusting direction, being stable in adjustment, and having no problem of over-adjustment or missing adjustment;
2. the gardner bit synchronization algorithm in the signal timing recovery method and the recovery device, the signal demodulation method and the demodulation system can be independent of carrier synchronization and independent of a carrier synchronization device, thereby greatly reducing the algorithm complexity brought by algorithm association in signal demodulation.
Drawings
The invention is further illustrated by the following figures and examples.
FIG. 1(a) is a model of a fully analog mode bit synchronization algorithm;
FIG. 1(b) is a model of a half-digit mode bit synchronization algorithm;
FIG. 1(c) is a model of a full digital bit synchronization algorithm;
FIG. 2 is a Gardner timing recovery algorithm principle;
FIG. 3 is a block diagram of the Gardner timing recovery algorithm architecture;
FIG. 4 is a diagram of signal timing recovery method steps for an embodiment of the present invention;
FIG. 5 is a diagram of an embodiment of a signal timing recovery method according to the present invention;
FIG. 6 is a schematic diagram showing the comparison between the Ui value obtained after each averaging of u (r) and the preset threshold in the embodiment of the present invention;
FIG. 7 is a schematic diagram illustrating the direction of each actual adjustment of the signal sampling points according to the embodiment of the present invention;
FIG. 8 is a sample point amplitude before gardner symbol synchronization for an embodiment of the present invention;
FIG. 9 is the symbol amplitude after gardner symbol synchronization of an embodiment of the present invention;
FIG. 10 is a block diagram of a signal timing recovery apparatus according to an embodiment of the present invention;
FIG. 11 is a diagram of signal demodulation method steps for an embodiment of the present invention;
FIG. 12 is a signal constellation diagram after gardner symbol synchronization of an embodiment of the present invention;
fig. 13 is a block diagram of a signal demodulation system according to an embodiment of the present invention.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Fig. 4 is a diagram of steps of a signal timing recovery method according to an embodiment of the present invention, and as shown in fig. 4, the signal timing recovery method provided by the present invention includes the following steps:
receiving a plurality of sections of signals, wherein each section of signals comprises a plurality of symbol signals, sampling the symbol signals, and calculating the timing error of each symbol signal;
adding and averaging the timing errors of a plurality of symbol signals in each section of signals to obtain the average value of the timing errors of each section of signals;
and comparing the average value of the timing errors of each section of signals with a preset threshold, calculating the number of adjustment points of the sampling points when the number of times that the average value of the timing errors of the sections of signals is continuously larger than or smaller than the preset threshold exceeds the preset number of times, and performing timing recovery on each symbol signal according to the number of adjustment points of the sampling points.
The preset threshold and the preset times are set according to needs, for example, the preset threshold may be 0, and the preset times may be 2-5 times.
The plurality of symbol signals are subjected to oversampling, and the number of sampling points in each symbol signal is calculated by the following formula:
BL＝fS/Rb
wherein BL is the number of sampling points in each symbol signal, fSRb is the symbol rate, the sampling rate.
The timing error of each symbol signal is calculated by the following formula:
Figure BDA0001837164830000101
where u (r) is the timing error of the symbol signal r,
Figure BDA0001837164830000102
is the interpolation value of the middle time I path of the sampling points of the symbol signal r and the symbol signal r-1,
Figure BDA0001837164830000103
for interpolated values, x, of paths Q intermediate the sampling points of the sign signal r and the sign signal r-1I(r) is the sampling point, x, of the I path of the symbol signal rQ(r) is the sampling point, x, of the Q-path of the symbol signal rI(r-1) is a sampling point of path I of the symbol signal r-1, xQAnd (r-1) is a sampling point of a Q path of the symbol signal r-1.
In practical applications, a symbol or BIT is oversampled, for example, the sampling rate of the signal is fs-16 mhz, the symbol rate Rb is 32khz, then the oversampling BL-fs/Rb is 500, and a QPSK symbol is oversampled by BL-500 times, so that a symbol requires integration of BL-500 sampling points to obtain the value of the symbol. Thus x in the formulaI(r)，
Figure BDA0001837164830000104
xI(r-1), etc. are the result of BL point integration, xI(r) and xI(r-1) the difference is BL point, xI(r) and xI(r-1/2) differ by 250 points BL/2. Where a BIT represents a symbol, and the two are equivalent, and both contain BL sampling points.
The timing errors of a plurality of symbol signals in each signal segment are summed and averaged by the following formula:
Figure BDA0001837164830000105
wherein, UiThe average value of u (r) in the ith symbol signal is shown, P is the number of ith symbol signals, and i is 1,2 and ….
The fractional part timing error factor is calculated by the following equation:
Figure BDA0001837164830000111
wherein, UiIs the average value of u (r) within the ith segment sign signal +iThe error factor is timed for the fractional part of the ith segment of the symbol signal. Thus, a tracking architecture is employed, according to one paragraphSymbol-to-fractional part of timing error of u (r) average within a symbol
Figure BDA0001837164830000112
And (6) adjusting. Δ is the step of each adjustment. The larger Δ, the larger the range of code offsets that can be tracked, but the lower the accuracy of the timing error estimate, the application needs to determine Δ according to actual requirements. Initial fractional part timing error factor +iIs unknown, will generally +iIs set to +00. And not every time a new v is obtainediImmediately thereafter, the order of the front and back of the signal is updated, andigreater than a certain value indicates that | v is adjusted for a period of time in one directioni|＞Num。
Timing recovery is carried out on each symbol signal according to the number of the sampling point adjustment points through the following formula:
newST＝newST+sign(▽)*move；
the new ST is the position of an original sampling point, v is a fractional timing error factor, sign (v) is a fractional timing error factor with a sign, move is the number of points moved at one time, and sign (v) move is the number of adjustment points of a sampling point.
The signal timing recovery method obtains average timing error by averaging after timing error arithmetic superposition is obtained for multiple times, the average timing error is judged, superposition judgment is carried out after the average timing error exceeds a preset threshold, one real loop updating is carried out after the average timing error continuously exceeds the preset threshold for a time which is more than the preset time, so that the timing recovery of the signal can reach a stable state without filtering interpolation only by a two-dimensional average algorithm, the filtering processing resource of the traditional gardner algorithm is saved, the adjustment direction can be quickly determined, the adjustment is stable, the problem of excessive adjustment or missing adjustment is avoided, and the method can be suitable for overlapping the optimal sampling point of the search element of a large-scale spread spectrum signal and a related sequence.
The gardner bit synchronization algorithm in the signal timing recovery method can be independent of carrier synchronization and independent of a carrier synchronization device, so that the algorithm complexity caused by algorithm association in signal demodulation is greatly reduced, the gardner algorithm can save the filtering processing resource of the traditional gardner algorithm, can quickly determine the adjustment direction of a system, is stable in adjustment, does not have the problem of excessive adjustment or missing adjustment, and has great practicability. The method can be widely used for spread spectrum communication, BPSK/QPSK and other single carrier communication systems.
Fig. 5 is a diagram of an example of a signal timing recovery method according to an embodiment of the present invention, as shown in fig. 5, in a first step, a moving point number move is set to 1/8BIT, a P _ BIT number for averaging once is set, and a preset threshold THr for adjusting a zero value is set; secondly, obtaining the signal arithmetic sum of the previous BIT sample index1 and index1 to obtain x (r-1), the signal arithmetic sum of the current BIT sample index3 and index3 to obtain x (r), the second half of the index2 and index1 is combined with the first half of the index3 to obtain index2, and the signal arithmetic sum of the sample index of the index2 to obtain x (r-1/2), for example, the sample index of the previous BIT (symbol) is ABCD (1, 2, 3, 4), the index of the next BIT is EFGH (5, 6, 7, 8), the index of the middle position is CDEF (3, 4, 5, 6), and the signal output is x (r); third, the timing error of the symbol r is calculated by the formula
Figure BDA0001837164830000121
When P _ BIT symbols are accumulated, taking the P _ BIT symbols as a section of symbols, and calculating the average value U of U (r) in the section of symbols; according to the size relationship between U and the preset threshold THr, Δ ═ 1 when U is greater than THr, Δ ═ 1 when U is less than-THr, and Δ ═ 0 when U is between-THr and THr; v +, will generally be +iIs set to +0Not equal to 0, when | +iThe position of the sampling point is adjusted and ^ is granted again, | > Num0＝0。
The key point in fig. 5 is that after the signal is subjected to multiple gardner calculations, an average is obtained, the adjusted directivity is judged through the average directivity, and smoothing is performed again after the average is obtained, so that the integral trend of the continuous multiple BIT adjustment directions is averaged, and thus, the misjudgment of the signal directivity caused by noise or interference is avoided. Meanwhile, the gear is changed from the previous 2 gears to 3 gears, an unregulated gear is added, the stability of the system is enhanced, the precision is improved, and the regulation is not needed. A BIT represents a symbol, and the two are equivalent, and both contain BL sample points. A complete set of gardner tuning procedures is formed by the above 3 key points.
The input signal is adjusted according to the timing error calculated by the Gardner algorithm, the output rate of the adjusted signal is 2 times of the symbol rate, and the adjusted signal comprises the value of one path of optimal sampling point and is output as the result after symbol synchronization.
Fig. 6 is a schematic diagram showing a comparison between the Ui value obtained after each averaging of u (r) and the preset threshold in the embodiment of the present invention, as shown in fig. 6, fig. 6 shows that the value obtained after one averaging is still oscillating or violent, in the initial stage, Ui is adjusted in one direction, the values are all positive numbers, and in the middle and later stages, positive and negative numbers are adjusted, and the directions change.
Fig. 7 is a schematic diagram of the direction of each actual adjustment of the signal sampling point in the embodiment of the present invention, and as the direction of each actual adjustment shown in fig. 7 obtains an adjustment increment value according to the direction during each oscillation, the increment value is continuously accumulated to a preset number of times to be actually adjusted. Wherein the adjustment size is fixed, 1 means backward adjustment, 0 means no adjustment, and-1 means backward adjustment.
Fig. 8 shows the amplitudes of the sampling points before the gardner symbol synchronization according to the embodiment of the present invention, and as shown in fig. 8, the amplitude of the signal before the gardner symbol synchronization fluctuates sharply and the signal cannot be demodulated at all.
FIG. 9 is the symbol amplitude after gardner symbol synchronization according to an embodiment of the present invention, as shown in FIG. 9, below is the signal amplitude after gardner symbol synchronization, which is the amplitude after integration of BL sample points, while the value size of BL is still being adjusted, the size and direction of which is sign ([ lambda ]) move.
For simplicity of explanation, the method embodiments are described as a series of acts or combinations, but those skilled in the art will appreciate that the embodiments are not limited by the order of acts described, as some steps may occur in other orders or concurrently with other steps in accordance with the embodiments of the invention. Further, those skilled in the art will appreciate that the embodiments described in the specification are presently preferred and that no particular act is required to implement the invention.
Fig. 10 is a block diagram of a signal timing recovery apparatus according to an embodiment of the present invention, and as shown in fig. 10, the signal timing recovery apparatus for implementing the method according to the present invention includes:
a symbol signal timing error calculation module, configured to receive multiple segments of signals, where each segment of signals includes multiple symbol signals, sample the multiple symbol signals, and calculate a timing error of each symbol signal;
the timing error average value calculation module is used for adding and averaging the timing errors of a plurality of symbol signals in each section of signals to obtain a timing error average value of each section of signals;
and the signal timing recovery module is used for comparing the average value of the timing error of each section of signal with a preset threshold, calculating the number of adjustment points of the sampling points when the number of times that the average value of the timing error of the plurality of sections of signals is continuously greater than or less than the preset threshold exceeds the preset number of times, and performing timing recovery on each symbol signal according to the number of adjustment points of the sampling points.
The signal timing recovery device of the embodiment of the invention is a two-stage superposition gardner loop optimal sampling point acquisition device, and the two-stage superposition specifically comprises the following steps: firstly, averaging and then superposing, and calculating the average after calculating and superposing the timing error U arithmetic for multiple times to obtain U; and secondly, judging U, performing superposition judgment after the U exceeds a certain threshold THr, and performing arithmetic superposition on Ui to obtain real loop updating after the U exceeds Num times.
The signal timing recovery device obtains average timing error by averaging after timing error arithmetic superposition is obtained for multiple times, the average timing error is judged, superposition judgment is carried out after the average timing error exceeds a preset threshold, one real loop updating is carried out after the average timing error continuously exceeds the preset threshold for a time which is more than the preset time, so that the timing recovery of the signal can reach a stable state without filtering interpolation only by a two-dimensional average algorithm, the filtering processing resource of the traditional gardner algorithm is saved, the adjustment direction can be quickly determined, the adjustment is stable, the problem of excessive adjustment or missing adjustment is avoided, and the device can be suitable for overlapping the optimal sampling point of the search element of a large-proportion spread spectrum signal and a related sequence.
The gardner bit synchronization algorithm in the signal timing recovery device can be independent of carrier synchronization and independent of a carrier synchronization device, so that the algorithm complexity caused by algorithm correlation in signal demodulation is greatly reduced, the gardner algorithm can save the filtering processing resource of the traditional gardner algorithm, can quickly determine the adjustment direction of a system, is stable in adjustment, does not have the problem of excessive adjustment or missing adjustment, and has great practicability. The method can be widely used for spread spectrum communication, BPSK/QPSK and other single carrier communication systems.
For the device embodiment, since it is basically similar to the method embodiment, the description is simple, and for the relevant points, refer to the partial description of the method embodiment.
Fig. 11 is a block diagram of a signal demodulation system according to an embodiment of the present invention, and as shown in fig. 11, the signal demodulation system including the signal timing recovery apparatus according to the present invention includes:
the signal acquisition device is used for acquiring signals and sending the signals to the pseudo code synchronization device;
the pseudo code synchronization device is used for performing pseudo code synchronization on the signals and sending the signals to the de-spreading device;
the de-spread device is used for receiving and de-spreading the signal after pseudo code synchronization and sending the signal to the signal timing recovery device;
the carrier synchronization device is used for receiving the signals after the bit synchronization sent by the signal timing recovery device and carrying out carrier synchronization on the signals;
and the signal demodulation device is used for receiving and demodulating the signal after the carrier synchronization to obtain a demodulated signal.
In the signal demodulation system of the invention, the signal timing recovery device can be independent of carrier synchronization and independent of a carrier synchronization device, thus greatly reducing the algorithm complexity caused by algorithm association. Meanwhile, the gardner timing error is obtained according to the previous signal, the next signal and the intermediate signal, and the timing error signals are averaged and smoothed to obtain the adjustment of the optimal sampling point.
The signal demodulation system obtains average timing error by calculating average after calculating timing error arithmetic superposition for multiple times, judges the average timing error, carries out superposition judgment after the average timing error exceeds a preset threshold, carries out real loop updating once after the number of times that the average timing error continuously exceeds the preset threshold is greater than the preset number of times, ensures that the timing recovery of the signal can reach a stable state without filtering interpolation, only needs a two-dimensional average algorithm, saves the filtering processing resource of the traditional gardner algorithm, can quickly determine the adjusting direction, is stable in adjustment, does not have the problem of excessive adjustment or missing adjustment, and can be suitable for overlapping the optimal sampling point of the search element of a large-proportion spread spectrum signal and a related sequence.
Fig. 12 is a signal constellation diagram after gardner symbol synchronization according to an embodiment of the present invention, and as shown in fig. 12, in the signal constellation diagram after code synchronization, symbol synchronization, and carrier synchronization, positions of constellation points are very concentrated, and at this time, when a signal is demodulated, an error rate is greatly reduced.
Fig. 13 is a step diagram of a signal demodulation method according to an embodiment of the present invention, and as shown in fig. 13, the signal demodulation method implemented based on the signal demodulation system according to the present invention includes the following steps:
collecting signals;
carrying out pseudo code synchronization on the acquired signals;
despreading the signals after pseudo code synchronization;
receiving a plurality of sections of despread signals, wherein each section of signals comprises a plurality of symbol signals, sampling the symbol signals, and calculating the timing error of each symbol signal;
adding and averaging the timing errors of a plurality of symbol signals in each section of signals to obtain the average value of the timing errors of each section of signals;
comparing the average value of the timing error of each section of signal with a preset threshold, calculating the number of adjustment points of the sampling points when the number of times that the average value of the timing error of the plurality of sections of signals is continuously larger than or smaller than the preset threshold exceeds the preset number of times, and performing timing recovery on each symbol signal according to the number of adjustment points of the sampling points;
carrying out carrier synchronization on the signals after timing recovery;
and demodulating the signal after carrier synchronization to obtain a demodulated signal.
The signal demodulation system obtains average timing error by calculating average after calculating timing error arithmetic superposition for multiple times, judges the average timing error, carries out superposition judgment after the average timing error exceeds a preset threshold, carries out real loop updating once after the number of times that the average timing error continuously exceeds the preset threshold is greater than the preset number of times, ensures that the timing recovery of the signal can reach a stable state without filtering interpolation, only needs a two-dimensional average algorithm, saves the filtering processing resource of the traditional gardner algorithm, can quickly determine the adjusting direction, is stable in adjustment, does not have the problem of excessive adjustment or missing adjustment, and can be suitable for overlapping the optimal sampling point of the search element of a large-proportion spread spectrum signal and a related sequence. The improved device is called a two-stage superposition gardner loop, and is an optimal sampling device which obtains the real loop updating only after the arithmetic superposition of the timing error U is obtained for a plurality of times and the average is obtained, secondly, the U is judged, the superposition judgment is carried out after the U exceeds a certain threshold THr, and the Ui carries out the arithmetic superposition again to obtain the number exceeding Num times.
The gardner bit synchronization algorithm in the signal demodulation system can be independent of carrier synchronization and independent of a carrier synchronization device, so that the algorithm complexity caused by algorithm correlation in signal demodulation is greatly reduced, the gardner algorithm can save the filtering processing resource of the traditional gardner algorithm, can quickly determine the adjustment direction of the system, is stable in adjustment, does not have the problem of excessive adjustment or missing adjustment, and has great practicability. The method can be widely used for spread spectrum communication, BPSK/QPSK and other single carrier communication systems.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (4)

1. A method for signal timing recovery, comprising the steps of:
receiving a plurality of sections of signals, wherein each section of signals comprises a plurality of symbol signals, sampling the symbol signals, and calculating the timing error of each symbol signal;
adding and averaging the timing errors of a plurality of symbol signals in each section of signals to obtain the average value of the timing errors of each section of signals;
comparing the average value of the timing error of each section of signal with a preset threshold, calculating the number of adjustment points of the sampling points when the number of times that the average value of the timing error of the plurality of sections of signals is continuously larger than or smaller than the preset threshold exceeds the preset number of times, and performing timing recovery on each symbol signal according to the number of adjustment points of the sampling points;
the plurality of symbol signals are subjected to oversampling, and the number of sampling points in each symbol signal is calculated by the following formula:
BL＝fS/Rb
wherein BL is the number of sampling points in each symbol signal, fSRb is the symbol rate, for the sampling rate;
the timing error of each symbol signal is calculated by the following formula:
Figure FDA0002566610510000011
where u (r) is the timing error of the symbol signal r,
Figure FDA0002566610510000012
is the interpolation value of the middle time I path of the sampling points of the symbol signal r and the symbol signal r-1,
Figure FDA0002566610510000013
for interpolated values, x, of paths Q intermediate the sampling points of the sign signal r and the sign signal r-1I(r) is the sampling point, x, of the I path of the symbol signal rQ(r) is the sampling point, x, of the Q-path of the symbol signal rI(r-1) is a sampling point of path I of the symbol signal r-1, xQ(r-1) is a sampling point of a Q path of the symbol signal r-1;
the timing errors of a plurality of symbol signals in each signal segment are summed and averaged by the following formula:
Figure FDA0002566610510000021
wherein, UiThe average value of u (r) in the ith symbol signal is shown, P is the number of the ith symbol signal, and i is 1,2 and …;
the preset threshold is 0;
timing recovery is carried out on each symbol signal according to the number of the sampling point adjustment points through the following formula:
Figure FDA0002566610510000022
wherein newST is the original sampling point position,
Figure FDA0002566610510000023
the timing error factor is a fractional part of the timing error factor,
Figure FDA0002566610510000024
the timing error factor is the signed fractional part, move is the number of points moved at a time,
Figure FDA0002566610510000025
adjusting the number of points for the sampling points;
the fractional part timing error factor is calculated by the following equation:
Figure FDA0002566610510000026
wherein, UiIs the average value of u (r) in the ith symbol signal,
Figure FDA0002566610510000027
the error factor is timed for the fractional part of the ith segment of the symbol signal.
2. A signal timing recovery apparatus for implementing the method of claim 1, comprising:
a symbol signal timing error calculation module, configured to receive multiple segments of signals, where each segment of signals includes multiple symbol signals, sample the multiple symbol signals, and calculate a timing error of each symbol signal;
the timing error average value calculation module is used for adding and averaging the timing errors of a plurality of symbol signals in each section of signals to obtain a timing error average value of each section of signals;
and the signal timing recovery module is used for comparing the average value of the timing error of each section of signal with a preset threshold, calculating the number of adjustment points of the sampling points when the number of times that the average value of the timing error of the plurality of sections of signals is continuously greater than or less than the preset threshold exceeds the preset number of times, and performing timing recovery on each symbol signal according to the number of adjustment points of the sampling points.
3. A signal demodulation system comprising the signal timing recovery apparatus of claim 2, comprising:
the signal acquisition device is used for acquiring signals and sending the signals to the pseudo code synchronization device;
the pseudo code synchronization device is used for performing pseudo code synchronization on the signals and sending the signals to the de-spreading device;
the de-spread device is used for receiving and de-spreading the signal after pseudo code synchronization and sending the signal to the signal timing recovery device;
the carrier synchronization device is used for receiving the signals after the bit synchronization sent by the signal timing recovery device and carrying out carrier synchronization on the signals;
and the signal demodulation device is used for receiving and demodulating the signal after the carrier synchronization to obtain a demodulated signal.
4. A signal demodulation method based on the system of claim 3, comprising the steps of:
collecting signals;
carrying out pseudo code synchronization on the acquired signals;
despreading the signals after pseudo code synchronization;
receiving a plurality of sections of despread signals, wherein each section of signals comprises a plurality of symbol signals, sampling the symbol signals, and calculating the timing error of each symbol signal;
adding and averaging the timing errors of a plurality of symbol signals in each section of signals to obtain the average value of the timing errors of each section of signals;
comparing the average value of the timing error of each section of signal with a preset threshold, calculating the number of adjustment points of the sampling points when the number of times that the average value of the timing error of the plurality of sections of signals is continuously larger than or smaller than the preset threshold exceeds the preset number of times, and performing timing recovery on each symbol signal according to the number of adjustment points of the sampling points;
carrying out carrier synchronization on the signals after timing recovery;
and demodulating the signal after carrier synchronization to obtain a demodulated signal.
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