CN109981506A - A kind of all-digital demodulation method based on open loop structure - Google Patents
A kind of all-digital demodulation method based on open loop structure Download PDFInfo
- Publication number
- CN109981506A CN109981506A CN201910066137.XA CN201910066137A CN109981506A CN 109981506 A CN109981506 A CN 109981506A CN 201910066137 A CN201910066137 A CN 201910066137A CN 109981506 A CN109981506 A CN 109981506A
- Authority
- CN
- China
- Prior art keywords
- signal
- energy
- synchronization
- symbol
- burst
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
-
- 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
- H04L27/2656—Frame synchronisation, e.g. packet synchronisation, time division duplex [TDD] switching point detection or subframe 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
- H04L27/2657—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
- H04L27/2689—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation
- H04L27/2695—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation with channel estimation, e.g. determination of delay spread, derivative or peak tracking
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
- H04L2027/0044—Control loops for carrier regulation
- H04L2027/0046—Open loops
Abstract
The all-digital demodulation method based on open loop structure that the present invention provides a kind of, obtained digital baseband signal is filtered out out-of-band noise by matched filter first by receiver, it is then based on double sliding windows algorithm and detects burst signal, the Timing error estimate of burst signal is completed using O&M algorithm again, cube interpolation filter is controlled by timing error, and interpolation arithmetic is carried out to obtained sample value, again by the signal and local synchronization symbol progress cross-correlation operation after Timing Synchronization, complete frame synchronization, eliminate frequency offset error, the removing of carrier wave is completed finally by the phase deviation estimation algorithm removal skew based on maximum-likelihood criterion, baseband signal after being restored.Sampling rate of the present invention reduces, and reduces computation complexity.Method is simple, and demodulation effect is good, and noise tolerance is high, improves the reliability and efficiency of burst signal demodulation.
Description
Technical field
The present invention relates to fields of communication technology, especially to very high frequency(VHF) data broadcasting (VHF Data in ground strengthening system
BroadCast the burst signal completion timing that) eight phase phase-shift keying (PSK) (D8PSK) of differential encoding is modulated in subsystem is synchronous and carries
The synchronous method of reseptance of wave.
Background technique
Document " design of very high frequency(VHF) data broadcasting signal demodulating algorithm, computer application, 2013,33 (10): 2739-
A kind of demodulation method based on solution difference is disclosed in 2741. ", is first carried out guards escorting prisoners point to signal before the synchronization, is passed through docking
The collection of letters number carries out the delay of a symbol and takes conjugation, then receives signal multiplication with original, to eliminate frequency deviation to synchronous effect
It influences.Burst detection, Timing Synchronization and the offset estimation of system are completed using the good autocorrelation of sync symbols.Pass through docking
The over-sampling that the signal received carries out 10 times or more character rates comes so that comprising the sample close to the optimal judgement moment in sampled value
Point, while improving the accuracy of frame synchronization, bit synchronization and offset estimation.Method described in document is by increasing over-sampling rate come complete
At Timing Synchronization, but the unstable influence to over-sampling rate of sampling clock had not been considered, unstable over-sampling rate can be to frequency
Inclined calculating brings biggish error.The frequency deviation estimating method that document proposes simultaneously does not account for pulse-shaping and filters to waveform
Change, causes the frequency offset calculation precision of proposed method in practical situations not high.
Summary of the invention
For overcome the deficiencies in the prior art, the present invention provides a kind of all-digital demodulation method based on open loop structure.
The technical solution adopted by the present invention to solve the technical problems comprises the steps of:
Step 1: matched filtering: out-of-band noise being limited by matched filter, the transmitting terminal of VDB system is filtered using raised cosine
The matched filter of wave device, receiving end filters out out-of-band noise using low-pass filter, designs low-pass filter, and intermediate zone is set as 1
~1.2 times of character rate, passband allowable error are set as 0.01, and stopband allowable error is 0.01, and sample rate is set as 4 times of symbol speed
Rate；
Step 2: burst signal detection: two isometric and adjacent sliding windows of setting, by the letter in two sliding windows
Number energy calculated, solve the ratio of two sections of energy, if front window is completely in noise region, and rear window is completely in letter
Number plus noise region, then the ratio of back segment energy and leading portion energy will appear peak value, and the critical point of two windows is the start of message (SOM)
End；If rear window is completely in noise region, and front window is completely in signal plus noise region, then leading portion energy and back segment energy
Ratio will appear peak value, and the critical point of two windows is the message ends end, and the signal between starting point and end is to happen suddenly
The size of signal, peak value is not influenced by channel gain, only related with signal-to-noise ratio, is set a decision threshold, is worked as energy ratio
When more than decision threshold, it can be judged to detecting starting point and the end of burst signal；
Detailed step are as follows:
It detects to receive the burst message segment in signal by double sliding window mouth method, first calculates the two neighboring sliding in front and back
Signal energy in window, as shown in formula (1):
Wherein, r is the VDB signal received, W1nAnd W2nThe energy of signal in former and later two sliding windows is respectively indicated, L is
The length of sliding window, n are the position that two windows have a common boundary, and m and l respectively represent the serial number of front window and rear window；
Whether the size further according to energy ratio is more than decision threshold to determine starting point and the end of burst signal
Burst signal is extracted in position, shown in the expression formula of energy ratio such as formula (2):
Wherein, SnFor the ratio between front window energy and rear window energy, EnRatio between rear window energy and front window energy
Value, according to analysis above, when burst signal is into window and exit window, SnAnd EnObviously triangular waveform, record three can be showed
Value at angular peak value is the peak value of energy ratio, first counts the average value of x minor peaks, x is more than or equal to 1, then takes peak value
0.4 times of decision threshold T as burst detectionhValue, work as SnMore than decision threshold ThWhen, expression detects burst signal
E is worked as in starting pointnMore than decision threshold ThWhen, indicate the end for detecting burst signal；
Step 3: to the burst signal for extracting each section, this section of burst signal Timing Synchronization: being calculated using O&M algorithm
Timing error, and then the fractional part between determination point and previous sampled point is calculated, so as to find out cube interpolation polynomial
Coefficient, the signal after cube interpolation are the signal for completing Timing Synchronization；
Detailed step are as follows:
Timing error is calculated using O&M algorithm, the timing error as whole section of message:
Wherein, X is the transmitting variable of formula (3) and formula (4), xkEnergy for the burst signal extracted, N are each symbol
Corresponding sampling number, Len are the symbol numbers for calculating, εmFor the unbiased esti-mator of timing error ε, and then calculate judgement
Fractional part μ between point and previous sampled point:
μ=N ε-int [N ε] (5)
The μ value that formula (5) is found out substitutes into formula (6), so as to find out the coefficient of cube interpolation polynomial:
Interpolation formula are as follows:
Signal y after cube interpolation is the signal for completing Timing Synchronization, and interpolation filter is tied using Farrow
Structure is realized；
Step 4: frame synchronization
One symbol of signal delay after Timing Synchronization is subjected to conjugate multiplication again and obtains differential signal, to local synchronization code
Metasequence carries out 8PSK and maps to obtain local modulated signal, and differential signal is carried out sliding with the conjugation of local modulated signal and is multiplied
The cross-correlation operation of cumulative summation, when differential signal and local synchronization sequence are fully synchronized, correlation is maximum, if correlation is big
It in the thresholding of setting, that is, can determine that the sync symbols found in burst signal, complete frame synchronization；
Detailed step are as follows:
Signal y (k) after Timing Synchronization is indicated are as follows:
Wherein fdFor carrier wave frequency deviation, TbFor the time span of a symbol, θ (k) is the corresponding carrier phase of k-th of character.
n0It is mean value be 0 variance is N0White Gaussian noise；
Signal y (k) one symbol of delay after Timing Synchronization is subjected to conjugation involution again and obtains differential signal y1(k):
Sync symbols in VDB message are 48 bit sequences: 010 001 111 101 111 110 001 100 011 101
100 000 011 110 010 000, emit first from low level；8PSK is carried out to local synchronization sequence of symhols to map to obtain local
Modulated signalDifferential signal and the conjugation of local modulated signal are in sliding cross-correlation, obtain correlation such as
Shown in formula (10):
Wherein, R (k) is calculated correlation,For the cross correlation value of noise sequence and local synchronization sequence；
By formula (10) it is found that when frame synchronization, correlation peak 1 can determine that and complete when correlation is greater than the thresholding 0.8 of setting
The frame synchronization of burst message；
Step 5: coarse frequency offset and elimination；
Using local synchronization symbol as the auxiliary sequencel based on data-aided Algorithm of Carrier Frequency Offset Estimation, pass through local
Sync symbols go to modulate with signal progress conjugate multiplication completion is received, so that the signal received is no longer by original message symbol
Modulation, only the influence of remaining frequency deviation and skew, inherent spurious frequency deviation can control within 20Hz；
Signal after Timing Synchronization is indicated again are as follows:
Wherein, ckIt is modulation intelligence, fdIt is carrier deviation, ph is that carrier wave initially differs, n0It (k) is white Gaussian noise, mean value
It is 0, variance N0；
Sync symbols in VDB message include 48 bit sequences: 010 001 111 101 111 110 001 100 011
101 100 000 011 110 010 000, and emit first from low level, by the modulated modulation intelligence length L of D8PSK0
It is 16, due to the modulation intelligence c of sync symbols sequencekIt is known that signal y will be received0Multiplied by ckConjugationObtain modulation letter
Breath:
WhereinWith n0(k) statistical property is identical, and obtaining length is L0Remove modulation sequence z0, when
Domain auto-correlation function is as follows:
Following algorithm is used to based on data-aided offset estimation:
Wherein fdcFor the thick frequency deviation of calculated carrier wave, NS=L0/ 2, window function1≤m
≤NS；
Step 6: smart offset estimation and elimination: carrying out the estimation of carrier wave essence frequency deviation using the method based on unbound nucleus,
Offset estimation is relatively accurately carried out under conditions of not knowing prior information；
Signal y will be received0Remove the thick frequency deviation of carrier wave, the signal y after obtaining thick frequency offset correction1:
Using 2 π/M rotational invariance of mpsk signal, modulation intelligence is removed by M power operation, is obtained:
Auto-correlation function R1(m) expression formula are as follows:
Wherein, L1For the sequence length for estimation, the present invention takes 128, the smart frequency excursion algorithm of use are as follows:
Wherein NS=L1/ 2, wherein window function1≤m≤NS,
fdfFor calculated carrier wave essence frequency deviation, smart frequency offset correction is done to signal, is obtained:
Step 7: skew estimation and elimination: using maximum likelihood estimate, carries out data auxiliary estimation using sync symbols,
Expression formula are as follows:
It eliminates remaining skew and obtains the original signal after final removing carrier wave later:
So far, the present invention completes to receive the Timing Synchronization and carrier synchronization of signal, demodulates through D8PSK and maps back two by symbol
System symbol completes signal demodulation.
The beneficial effects of the present invention are use the method for reseptance based on all-digital demodulation, the local carrier of receiver with adopt
Sample clock is respectively independent and oscillation is in fixed frequency, does not need for timing error and carrier error feedback to be adjusted to AD,
But timing error, frequency deviation and the skew of burst message are calculated using feed forward architecture, then compensate to signal is received, therefore
Avoid existing method there are the not high deficiency of timing error and frequency offset calculation precision and traditional Phase Lock Technique due to
The case where burst System will be difficult to use in there is loop stability settling time needs and effect far apart.Sampling rate reduces,
Reduce computation complexity.Method is simple, and demodulation effect is good, and noise tolerance is high, improves the reliability of burst signal demodulation
With efficiency.
Detailed description of the invention
Fig. 1 is the system flow chart of the method for the present invention.
Fig. 2 is the burst packet check flow chart of the method for the present invention.
Fig. 3 is Timing error estimate method schematic diagram in the method for the present invention.
Fig. 4 is Farrow structural schematic diagram used by cube interpolation in timing synchronization procedure in the method for the present invention.
Fig. 5 is frame synchornization method schematic diagram in the method for the present invention, and what is stored in ROM is that local synchronization symbol is reflected by 8PSK
The symbol penetrated exports frame start position Frame_start when correlation is more than decision threshold.
Fig. 6 is coarse frequency offset bearing calibration schematic diagram in the method for the present invention, and what is stored in ROM1 is local synchronization symbol
By the symbol that D8PSK maps, go to modulate with the realization of signal conjugate multiplication is received, stored in ROM2 to be in Fitz algorithm be
Number wm。
Fig. 7 is smart offset estimation bearing calibration schematic diagram in the method for the present invention, and phase of received signal is carried out phase multiplied by 8 again
Bit mapping realization goes to modulate, and that store in ROM is the coefficient w in M&M algorithmm。
Fig. 8 is that skew estimates bearing calibration schematic diagram in the method for the present invention, and what is stored in ROM is that local synchronization symbol is passed through
The symbol of D8PSK mapping.
Fig. 9 is the spectral contrast figure before and after the method for the present invention receives signal in emulation by matched filter.
Figure 10 is the ratio schematic diagram of the method for the present invention double sliding window energy during burst packet check in emulation.
Figure 11 and Figure 12 is the method for the present invention in emulation, and the planisphere of the synchronous front and back of signal completion timing compares signal
Figure.
Figure 13 is correlation schematic diagram of the method for the present invention in emulation in frame synchronizing process, it will be apparent that relevant peaks are frame
The position of head.
Figure 14 is the constellation diagrams after signal completion frame synchronization.
Figure 15 is that signal completes constellation diagrams after thick frequency offset correction.
Figure 16 is the constellation diagrams after the smart frequency offset correction of signal completion.
Figure 17 is the constellation diagrams after signal completion skew correction.
Specific embodiment
Present invention will be further explained below with reference to the attached drawings and examples.
In order to overcome the shortcomings of the existing method lock not high and traditional there are timing error and frequency offset calculation precision
Since there is loop stability settling time needs and effect far apart will be difficult to use in burst System, the present invention uses phase technology
Method of reseptance based on all-digital demodulation, as shown in Fig. 1-Figure 17.Its main feature is that the local carrier of receiver and sampling clock are each
From independent and oscillation in fixed frequency, does not need for timing error and carrier error feedback to be adjusted to AD, but use
Feed forward architecture calculates timing error, frequency deviation and the skew of burst message, then compensates to signal is received.Receiver first will
Obtained digital baseband signal filters out out-of-band noise by matched filter, improves signal-to-noise ratio.It is then based on double sliding window mental arithmetic
Method detects burst signal, then the Timing error estimate of burst signal is completed using O&M algorithm, passes through timing error control cube
Interpolation filter carries out interpolation arithmetic to obtained sample value, obtains approximation of the signal at each symbol optimum sampling moment,
Completion timing is synchronous and reduces subsequent calculation amount.Again by the signal and local synchronization symbol progress cross-correlation after Timing Synchronization
Frame synchronization is completed in operation, navigates to the position of sync symbols, and then successively use based on data-aided Fitz algorithm and be based on
The M&M algorithm of unbound nucleus calculates the thick frequency deviation and smart frequency deviation of signal, eliminates frequency offset error.Finally by based on it is maximum seemingly
The phase deviation estimation algorithm removal skew of right criterion is to complete the removing of carrier wave, the baseband signal after being restored.
As shown in Fig. 1-Figure 17, simulated conditions of the present invention are that carrier wave frequency deviation is that official standard regulation VDB receiver needs connect
The maximum frequency deviation value 418Hz received, initial skew are 60 °, signal-to-noise ratio 20dB, and sliding window length is 48.
Step 1: low-pass filter being designed as matched filter by kaiser window, intermediate zone is set as 1~1.2 times of symbol
Rate, passband allowable error are set as 0.01, and stopband allowable error is also set as 0.01, and sample rate is set as 4 times of character rates, will be digital
Baseband signal limits out-of-band noise by matched filter, improves signal-to-noise ratio.
After the completion of step 2, matched filtering, detect to receive the burst message segment in signal by double sliding window mouth method.First
The signal energy in the two neighboring sliding window in front and back is calculated, as shown in formula (1):
Wherein, r is the VDB signal received, W1nAnd W2nThe energy of signal in former and later two sliding windows is respectively indicated, L is
The length of sliding window, n are the position that two windows have a common boundary, and m and l respectively represent the serial number of front window and rear window.
Whether the size further according to energy ratio is more than decision threshold to determine starting point and the end of burst message
Burst signal is extracted, shown in the expression formula of energy ratio such as formula (2) in position
Wherein, SnFor the ratio between front window energy and rear window energy, EnRatio between rear window energy and front window energy
Value, according to analysis above, when burst signal is into window and exit window, SnAnd EnObviously triangular waveform, record three can be showed
Value at angular peak value is the peak value of energy ratio.The average value of x minor peaks is first counted, x is more than or equal to 1, then takes peak value
0.4 times of decision threshold T as burst detectionhValue, can achieve the omission factor close to 0.Work as SnMore than decision threshold Th
When, it indicates the starting point for detecting burst signal, works as EnMore than decision threshold ThWhen, indicate the knot for detecting burst signal
Shu Duan.
Step 3, the burst signal extracted to each section, calculate its timing error；Because the burst signal duration is very
Short, timing error approximate can be regarded as constant in every section of message, therefore can use the partial data in every section of message, use
O&M algorithm calculates timing error, the timing error as whole section of message:
Wherein, X is the transmitting variable of formula (3) and formula (4), xkEnergy for the burst signal extracted, N are each symbol
Corresponding sampling number, Len are the symbol numbers for calculating, εmFor the unbiased esti-mator of timing error ε, and then calculate judgement
Fractional part μ between point and previous sampled point:
μ=N ε-int [N ε] (5)
The μ value that formula (5) is found out substitutes into formula (6) so as to find out the coefficient C of cube interpolation polynomial1, C0, C-1, C-2:
Interpolation formula are as follows:
Signal y after cube interpolation is the signal for completing Timing Synchronization, and interpolation filter is tied using Farrow
Structure is realized；
Step 4 indicates the signal y (k) after Timing Synchronization are as follows:
Wherein fdFor carrier wave frequency deviation, TbFor the time span of a symbol, θ (k) is the corresponding carrier phase of k-th of character.
n0It is mean value be 0 variance is N0White Gaussian noise.
Signal y (k) one symbol of delay after Timing Synchronization is subjected to conjugation involution again and obtains differential signal y1(k):
According to the normative document of civil aviaton, the sync symbols in VDB message are 48 bit sequences: 010 001 111 101 111
110 001 100 011 101 100 000 011 110 010 000, emit first from low level；To local synchronization sequence of symhols
8PSK is carried out to map to obtain local modulated signalDifferential signal and the conjugation of local modulated signal are slided
Dynamic cross-correlation obtains shown in correlation such as formula (10):
Wherein, R (k) is calculated correlation,For the cross correlation value of noise sequence and local synchronization sequence.
Since sync symbols sequence has extraordinary autocorrelation performance, so when differential signal and local synchronization sequence are fully synchronized
When, it may appear that obviously correlation peak, and after conjugation involution processing, pass through formula (10) calculated correlation peak
Size is not influenced by carrier deviation.By formula (10) it is found that when frame synchronization, correlation is up to 1, therefore sets when correlation is greater than
When fixed thresholding 0.8, that is, it can determine that the frame synchronization for completing burst message；
Step 5, using local synchronization symbol as the auxiliary sequencel based on data-aided Algorithm of Carrier Frequency Offset Estimation, lead to
It crosses local synchronization symbol and goes to modulate with signal progress conjugate multiplication completion is received, so that the signal received is no longer by original message
The modulation of symbol, only the influence of remaining frequency deviation and skew, inherent spurious frequency deviation can control within 20Hz；
Signal after Timing Synchronization is indicated again are as follows:
Wherein, ckIt is modulation intelligence, fdIt is carrier deviation, ph is that carrier wave initially differs, n0It (k) is white Gaussian noise, mean value
It is 0, variance N0；
According to the normative document of civil aviaton, the sync symbols in VDB message include 48 bit sequences: 010 001 111 101
111 110 001 100 011 101 100 000 011 110 010 000, and emit first from low level, by D8PSK tune
Modulation intelligence length L after system0It is 16, due to the modulation intelligence c of sync symbols sequencekIt is known that signal y will be received0Multiplied by ck's
ConjugationObtain modulation intelligence:
WhereinWith n0(k) statistical property is identical, and obtaining length is L0Remove modulation sequence z0, when
Domain auto-correlation function is as follows:
Following algorithm is used to based on data-aided offset estimation:
Wherein fdcFor the thick frequency deviation of calculated carrier wave, NS=L0/ 2, window function1≤m
≤NS；
Step 6 will receive signal y0The thick frequency deviation of carrier wave is removed, obtains removing the signal y after thick frequency offset correction1:
Using 2 π/M rotational invariance of mpsk signal, modulation intelligence is removed by M power operation, is obtained:
Auto-correlation function R1(m) expression formula are as follows:
Wherein, L1For the sequence length for estimation, the present invention takes 128.The smart frequency excursion algorithm used are as follows:
Wherein NS=L1/ 2, wherein window function1≤m≤NS,
fdfFor calculated carrier wave essence frequency deviation, smart frequency offset correction is done to signal, is obtained:
Step 7, the estimation for doing remaining skew to the signal of removal frequency deviation utilize synchronous code using maximum likelihood estimate
Member carries out data auxiliary estimation, expression formula are as follows:
It eliminates remaining skew and obtains the original signal after final removing carrier wave later:
So far, the present invention completes to receive the Timing Synchronization and carrier synchronization of signal, demodulates through D8PSK and maps back two by symbol
System symbol completes signal demodulation.
Claims (1)
1. a kind of all-digital demodulation method based on open loop structure, it is characterised in that include the following steps:
Step 1: matched filtering: out-of-band noise being limited by matched filter, the transmitting terminal of VDB system uses raised cosine filter
Device, the matched filter of receiving end filter out out-of-band noise using low-pass filter, design low-pass filter, and intermediate zone is set as 1~
1.2 times of character rate, passband allowable error are set as 0.01, and stopband allowable error is 0.01, and sample rate is set as 4 times of symbol speed
Rate；
Step 2: burst signal detection: two isometric and adjacent sliding windows of setting, by the signal in two sliding windows
Energy is calculated, and the ratio of two sections of energy is solved, if front window is completely in noise region, and rear window is completely in signal and adds
Noise region, then the ratio of back segment energy and leading portion energy will appear peak value, and the critical point of two windows is start of message (SOM) end；If
Rear window is completely in noise region, and front window is completely in signal plus noise region, then the ratio of leading portion energy and back segment energy
Will appear peak value, the critical point of two windows is the message ends end, and the signal between starting point and end is burst signal,
The size of peak value is not influenced by channel gain, only related with signal-to-noise ratio, sets a decision threshold, when energy ratio is more than to sentence
Certainly when thresholding, it can be judged to detecting starting point and the end of burst signal；
Detailed step are as follows:
It detects to receive the burst message segment in signal by double sliding window mouth method, first calculate in the two neighboring sliding window in front and back
Signal energy, as shown in formula (1):
Wherein, r is the VDB signal received, W1nAnd W2nThe energy of signal in former and later two sliding windows is respectively indicated, L is sliding
The length of window, n are the position that two windows have a common boundary, and m and l respectively represent the serial number of front window and rear window；
Whether the size further according to energy ratio is more than decision threshold to determine the starting point of burst signal and the position of end,
Burst signal is extracted, shown in the expression formula of energy ratio such as formula (2):
Wherein, SnFor the ratio between front window energy and rear window energy, EnFor the ratio between rear window energy and front window energy, root
According to analysis above, when burst signal is into window and exit window, SnAnd EnObviously triangular waveform can be showed, triangle is recorded
Value at peak value is the peak value of energy ratio, first counts the average value of x minor peaks, and x is more than or equal to 1, then takes 0.4 times of peak value
Decision threshold T as burst detectionhValue, work as SnMore than decision threshold ThWhen, indicate the starting for detecting burst signal
End, works as EnMore than decision threshold ThWhen, indicate the end for detecting burst signal；
Step 3: to the burst signal for extracting each section, the timing of this section of burst signal Timing Synchronization: is calculated using O&M algorithm
Error, and then calculate the fractional part between determination point and previous sampled point, so as to find out the coefficient of cube interpolation polynomial,
Signal after cube interpolation is the signal for completing Timing Synchronization；
Detailed step are as follows:
Timing error is calculated using O&M algorithm, the timing error as whole section of message:
Wherein, X is the transmitting variable of formula (3) and formula (4), xkEnergy for the burst signal extracted, N are corresponding for each symbol
Sampling number, Len is for the symbol numbers that calculate, εmFor the unbiased esti-mator of timing error ε, so calculate determination point with
Fractional part μ between previous sampled point:
μ=N ε-int [N ε] (5)
The μ value that formula (5) is found out substitutes into formula (6), so as to find out the coefficient of cube interpolation polynomial:
Interpolation formula are as follows:
Signal y after cube interpolation is the signal for completing Timing Synchronization, and interpolation filter is real using Farrow structure
It is existing；
Step 4: frame synchronization
One symbol of signal delay after Timing Synchronization is subjected to conjugate multiplication again and obtains differential signal, to local synchronization symbol sequence
Column carry out 8PSK and map to obtain local modulated signal, and the conjugation of differential signal and local modulated signal is slided and is mutually multiplied accumulating
The cross-correlation operation of summation, when differential signal and local synchronization sequence are fully synchronized, correlation is maximum, sets if correlation is greater than
Fixed thresholding can determine that the sync symbols found in burst signal, complete frame synchronization；
Detailed step are as follows:
Signal y (k) after Timing Synchronization is indicated are as follows:
Wherein fdFor carrier wave frequency deviation, TbFor the time span of a symbol, θ (k) is the corresponding carrier phase of k-th of character, n0It is
Mean value is that 0 variance is N0White Gaussian noise；
Signal y (k) one symbol of delay after Timing Synchronization is subjected to conjugation involution again and obtains differential signal y1(k):
Sync symbols in VDB message are 48 bit sequences: 010 001 111 101 111 110 001 100 011 101 100
000 011 110 010 000, emit first from low level；8PSK is carried out to local synchronization sequence of symhols to map to obtain local modulation
SignalDifferential signal and the conjugation of local modulated signal are in sliding cross-correlation, correlation such as formula is obtained
(10) shown in:
Wherein, R (k) is calculated correlation,For the cross correlation value of noise sequence and local synchronization sequence；By formula
(10) it is found that when frame synchronization, correlation peak 1 can determine that when correlation is greater than the thresholding 0.8 of setting and complete burst
The frame synchronization of message；
Step 5: coarse frequency offset and elimination；
Using local synchronization symbol as the auxiliary sequencel based on data-aided Algorithm of Carrier Frequency Offset Estimation, pass through local synchronization
Symbol goes to modulate with signal progress conjugate multiplication completion is received, so that the signal received is no longer by the tune of original message symbol
System, only the influence of remaining frequency deviation and skew, inherent spurious frequency deviation can control within 20Hz；
Signal after Timing Synchronization is indicated again are as follows:
Wherein, ckIt is modulation intelligence, fdIt is carrier deviation, ph is that carrier wave initially differs, n0It (k) is white Gaussian noise, mean value 0,
Variance is N0；
Sync symbols in VDB message include 48 bit sequences: 010 001 111 101 111 110 001 100 011 101
100 000 011 110 010 000, and emit first from low level, by the modulated modulation intelligence length L of D8PSK0It is 16,
Due to the modulation intelligence c of sync symbols sequencekIt is known that signal y will be received0Multiplied by ckConjugationObtain modulation intelligence:
WhereinWith n0(k) statistical property is identical, and obtaining length is L0Remove modulation sequence z0, time domain is certainly
Correlation function is as follows:
Following algorithm is used to based on data-aided offset estimation:
Wherein fdcFor the thick frequency deviation of calculated carrier wave, NS=L0/ 2, window function1≤m≤NS；
Step 6: smart offset estimation and elimination: the estimation of carrier wave essence frequency deviation is carried out using the method based on unbound nucleus, not
Know and relatively accurately carries out offset estimation under conditions of prior information；
Signal y will be received0Remove the thick frequency deviation of carrier wave, the signal y after obtaining thick frequency offset correction1:
Using 2 π/M rotational invariance of mpsk signal, modulation intelligence is removed by M power operation, is obtained:
Auto-correlation function R1(m) expression formula are as follows:
Wherein, L1For the sequence length for estimation, the present invention takes 128, the smart frequency excursion algorithm of use are as follows:
Wherein NS=L1/ 2, wherein window functionfdfFor
Calculated carrier wave essence frequency deviation is done smart frequency offset correction to signal, is obtained:
Step 7: skew estimation and elimination: using maximum likelihood estimate, utilizes sync symbols to carry out data auxiliary estimation, expresses
Formula are as follows:
It eliminates remaining skew and obtains the original signal after final removing carrier wave later:
So far, the present invention completes to receive the Timing Synchronization and carrier synchronization of signal, demodulates through D8PSK and maps back binary system by symbol
Symbol completes signal demodulation.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910066137.XA CN109981506B (en) | 2019-01-24 | 2019-01-24 | All-digital demodulation method based on open-loop structure |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910066137.XA CN109981506B (en) | 2019-01-24 | 2019-01-24 | All-digital demodulation method based on open-loop structure |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN109981506A true CN109981506A (en) | 2019-07-05 |
| CN109981506B CN109981506B (en) | 2021-05-07 |
Family
ID=67076623
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201910066137.XA Active CN109981506B (en) | 2019-01-24 | 2019-01-24 | All-digital demodulation method based on open-loop structure |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN109981506B (en) |
Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110545550A (en) * | 2019-08-12 | 2019-12-06 | 北京国电通网络技术有限公司 | Synchronous detection method for burst broadband communication |
| CN111555797A (en) * | 2020-04-23 | 2020-08-18 | 中国电子科技集团公司第五十四研究所 | Demodulation method for RACH burst of satellite mobile communication system |
| CN111585690A (en) * | 2020-04-28 | 2020-08-25 | 成都云溯新起点科技有限公司 | Multi-system same-frequency interference cancellation method |
| CN111600647A (en) * | 2020-05-22 | 2020-08-28 | 上海航天电子通讯设备研究所 | System and method for detecting collision energy of satellite-borne AIS signal multiple time slots |
| CN111740814A (en) * | 2020-06-30 | 2020-10-02 | 西安烽火电子科技有限责任公司 | Low-complexity folding product synchronization algorithm suitable for short-wave communication |
| CN111865859A (en) * | 2020-06-15 | 2020-10-30 | 北京遥测技术研究所 | Timing synchronization method based on SC-FDE burst signal 2-time oversampling |
| CN112003806A (en) * | 2020-10-28 | 2020-11-27 | 易兆微电子(杭州)股份有限公司 | Synchronous demodulation method of baseband signal and signal receiver |
| CN114362839A (en) * | 2021-12-07 | 2022-04-15 | 北京四季豆信息技术有限公司 | Signal detection method and device based on HPLC dual-mode wireless system and electronic equipment |
| CN114866214A (en) * | 2022-03-25 | 2022-08-05 | 中国电子科技集团公司第二十九研究所 | Method, device and medium for dynamically adjusting long burst communication bit synchronization |
| CN115022145A (en) * | 2022-07-01 | 2022-09-06 | 舟山美通信息技术有限责任公司 | LFM signal and HFM signal distinguishing method based on time delay autocorrelation |
| CN116032709A (en) * | 2022-12-06 | 2023-04-28 | 中国电子科技集团公司第三十研究所 | Method and device for blind demodulation and modulation feature analysis of FSK signal without priori knowledge |
| CN116055271A (en) * | 2023-01-13 | 2023-05-02 | 重庆大学 | Burst signal detection method of double sliding windows under specific waveform structure |
| CN114362839B (en) * | 2021-12-07 | 2024-05-03 | 芯象半导体科技(北京)有限公司 | Signal detection method and device based on HPLC dual-mode wireless system and electronic equipment |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7477707B2 (en) * | 2003-07-10 | 2009-01-13 | Honeywell International Inc. | Computationally efficient demodulation for differential phase shift keying |
| CN101414990A (en) * | 2008-12-02 | 2009-04-22 | 北京韦加航通科技有限责任公司 | Method for capturing carrier frequency bias and time delay of single carrier frequency domain equalizing system |
| US20110090991A1 (en) * | 2009-10-19 | 2011-04-21 | Integrated System Solution Corp. | Method and apparatus for phase reference tracking of digital phase modulated signals in the receiver |
| CN102111374A (en) * | 2010-12-22 | 2011-06-29 | 北京邮电大学 | Differential 8-phase shift keying (D8PSK)/amplitude shift keying (ASK) orthogonal light label switching method and system based on differential biphasic codes |
| CN105721375A (en) * | 2016-03-28 | 2016-06-29 | 电子科技大学 | Low signal-to-noise ratio short preamble burst signal demodulation system and method |
-
2019
- 2019-01-24 CN CN201910066137.XA patent/CN109981506B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7477707B2 (en) * | 2003-07-10 | 2009-01-13 | Honeywell International Inc. | Computationally efficient demodulation for differential phase shift keying |
| CN101414990A (en) * | 2008-12-02 | 2009-04-22 | 北京韦加航通科技有限责任公司 | Method for capturing carrier frequency bias and time delay of single carrier frequency domain equalizing system |
| US20110090991A1 (en) * | 2009-10-19 | 2011-04-21 | Integrated System Solution Corp. | Method and apparatus for phase reference tracking of digital phase modulated signals in the receiver |
| CN102111374A (en) * | 2010-12-22 | 2011-06-29 | 北京邮电大学 | Differential 8-phase shift keying (D8PSK)/amplitude shift keying (ASK) orthogonal light label switching method and system based on differential biphasic codes |
| CN105721375A (en) * | 2016-03-28 | 2016-06-29 | 电子科技大学 | Low signal-to-noise ratio short preamble burst signal demodulation system and method |
Non-Patent Citations (3)
| Title |
|---|
| OGUZ CELIKEL: "Establishment of All Digital Closed-Loop Interferometric Fiber-Optic Gyroscope and Scale Factor Comparison for Open-Loop and All Digital Closed-Loop Configurations", 《IEEE SENSORS JOURNAL》 * |
| 张坤峰: "甚高频数据广播信号解调算法设计", 《计算机应用》 * |
| 高文捷: "高速突发通信的全数字解调器设计与实现", 《万方数据库》 * |
Cited By (20)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110545550A (en) * | 2019-08-12 | 2019-12-06 | 北京国电通网络技术有限公司 | Synchronous detection method for burst broadband communication |
| CN110545550B (en) * | 2019-08-12 | 2023-03-10 | 北京国电通网络技术有限公司 | Synchronous detection method for burst broadband communication |
| CN111555797A (en) * | 2020-04-23 | 2020-08-18 | 中国电子科技集团公司第五十四研究所 | Demodulation method for RACH burst of satellite mobile communication system |
| CN111585690A (en) * | 2020-04-28 | 2020-08-25 | 成都云溯新起点科技有限公司 | Multi-system same-frequency interference cancellation method |
| CN111585690B (en) * | 2020-04-28 | 2021-02-12 | 成都云溯新起点科技有限公司 | Multi-system same-frequency interference cancellation method |
| CN111600647A (en) * | 2020-05-22 | 2020-08-28 | 上海航天电子通讯设备研究所 | System and method for detecting collision energy of satellite-borne AIS signal multiple time slots |
| CN111865859A (en) * | 2020-06-15 | 2020-10-30 | 北京遥测技术研究所 | Timing synchronization method based on SC-FDE burst signal 2-time oversampling |
| CN111865859B (en) * | 2020-06-15 | 2023-04-14 | 北京遥测技术研究所 | Timing synchronization method based on SC-FDE burst signal 2-time oversampling |
| CN111740814A (en) * | 2020-06-30 | 2020-10-02 | 西安烽火电子科技有限责任公司 | Low-complexity folding product synchronization algorithm suitable for short-wave communication |
| CN111740814B (en) * | 2020-06-30 | 2023-03-31 | 西安烽火电子科技有限责任公司 | Low-complexity folding product synchronization algorithm suitable for short-wave communication |
| CN112003806A (en) * | 2020-10-28 | 2020-11-27 | 易兆微电子(杭州)股份有限公司 | Synchronous demodulation method of baseband signal and signal receiver |
| CN112003806B (en) * | 2020-10-28 | 2021-02-09 | 易兆微电子(杭州)股份有限公司 | Synchronous demodulation method of baseband signal and signal receiver |
| CN114362839B (en) * | 2021-12-07 | 2024-05-03 | 芯象半导体科技(北京)有限公司 | Signal detection method and device based on HPLC dual-mode wireless system and electronic equipment |
| CN114362839A (en) * | 2021-12-07 | 2022-04-15 | 北京四季豆信息技术有限公司 | Signal detection method and device based on HPLC dual-mode wireless system and electronic equipment |
| CN114866214A (en) * | 2022-03-25 | 2022-08-05 | 中国电子科技集团公司第二十九研究所 | Method, device and medium for dynamically adjusting long burst communication bit synchronization |
| CN115022145B (en) * | 2022-07-01 | 2023-09-29 | 舟山美通信息技术有限责任公司 | LFM signal and HFM signal distinguishing method based on delay autocorrelation |
| CN115022145A (en) * | 2022-07-01 | 2022-09-06 | 舟山美通信息技术有限责任公司 | LFM signal and HFM signal distinguishing method based on time delay autocorrelation |
| CN116032709A (en) * | 2022-12-06 | 2023-04-28 | 中国电子科技集团公司第三十研究所 | Method and device for blind demodulation and modulation feature analysis of FSK signal without priori knowledge |
| CN116032709B (en) * | 2022-12-06 | 2024-04-12 | 中国电子科技集团公司第三十研究所 | Method and device for blind demodulation and modulation feature analysis of FSK signal without priori knowledge |
| CN116055271A (en) * | 2023-01-13 | 2023-05-02 | 重庆大学 | Burst signal detection method of double sliding windows under specific waveform structure |
Also Published As
| Publication number | Publication date |
|---|---|
| CN109981506B (en) | 2021-05-07 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN109981506A (en) | A kind of all-digital demodulation method based on open loop structure | |
| CN105721375B (en) | A kind of demodulating system and method for the short preamble burst signal of low signal-to-noise ratio | |
| CN102449950B (en) | Method and apparatus for symbol timing recovery | |
| US9729366B2 (en) | Digital radio transmissions | |
| CN104852876B (en) | A kind of aviation wireless burst communication system | |
| CN101110602A (en) | Carrier wave catching system and method based on multimode operation | |
| CN112399551B (en) | High-precision synchronization method for short-time burst signals | |
| CN110300079B (en) | MSK signal coherent demodulation method and system | |
| EP1913705B1 (en) | Adaptive synchronization enhancement technique for serial modulated waveforms | |
| CN110233719B (en) | Modulation index CPM signal clock false lock detection and correction method larger than 1 | |
| WO2007014394A2 (en) | Synchronization technique for serial modulated waveforms | |
| Morelli et al. | Feedforward carrier frequency estimation with MSK-type signals | |
| CN111131110A (en) | Decision-directed carrier recovery system and method suitable for reverse order combination of burst communication | |
| CN112671684B (en) | Self-adaptive demodulation method of short-time burst BPSK signal | |
| CN111083082B (en) | Multiple synchronization method of FHSS-GMSK system | |
| US20070248189A1 (en) | Symbol timing detector and wireless terminal | |
| CN101577604B (en) | PN carrier acquisition device and method | |
| JP4551180B2 (en) | ASK demodulator and radio apparatus using the same | |
| CN109672515A (en) | A kind of bit synchronization method of Low SNR signal | |
| JP4328008B2 (en) | Reception synchronization method | |
| Gunther et al. | Burst mode synchronization of QPSK on AWGN channels using kurtosis | |
| CN112953594B (en) | Burst MSK direct sequence spread spectrum communication synchronous detection device and method | |
| JP3100281B2 (en) | Slot synchronizer | |
| Lasanen et al. | Timing synchronization of the WIND-FLEX OFDM prototype | |
| KR100330236B1 (en) | Timing recovery circuit of receiver in wireless communication system |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |