CN108490401A - A kind of side lobe suppression method of frequency stepping phase-coded signal - Google Patents
A kind of side lobe suppression method of frequency stepping phase-coded signal Download PDFInfo
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Abstract
The present invention provides a kind of side lobe suppression methods of frequency stepping phase-coded signal, for frequency stepping phase-coded signal, the method that mismatched filter coefficient carries out Sidelobe Suppression is solved based on weighted iteration least square method, weighted iteration cross-correlation weighting matrix Central Plains Hankel matrix is replaced with into the former Hankel matrix and subtracts the new Hankel matrix that itself shift matrix obtains, then it is solved, exports auto-correlation mismatch filter and cross-correlation mismatch filter after suppressed sidelobes respectively.The present invention further suppresses cross-correlation secondary lobe on the basis of ensureing autocorrelation sidelobe level.
Description
Technical field
The present invention relates to signal processing technology fields, and in particular to a kind of secondary lobe suppression of frequency stepping phase-coded signal
Method processed.
Background technology
Identical pulse is used between traditional system radar signal pulse, is more than a pulse repetition period for time delay
(PRT) target echo, it will generate range ambiguity phenomenon.
In order to solve the problems, such as that above-mentioned range ambiguity, common mode are by the way of waveform agile between arteries and veins, wherein more
Effective mode is realized by frequency agility between arteries and veins, and stepped frequency radar is a type the most typical in this kind of signal
Type.
In the Waveform Design of stepped frequency radar, in order to improve the flexibility of Waveform Design, increase the isolation between arteries and veins
Degree carries out phase code modulation usually on the basis of simple stepped frequency radar to each subpulse.Due to phase code
The auto-correlation of signal has higher secondary lobe with cross-correlation, generally requires and carries out autocorrelation sidelobe suppression by the method for mismatch filter
System and cross-correlation Sidelobe Suppression.
For autocorrelation sidelobe, a variety of methods such as frequency domain mismatch filter or time domain mismatch filter may be used and carry out side
Valve inhibits, and for the side lobe suppression method of cross-correlation secondary lobe, existing achievement in research is mainly for same frequency point pulse group, above-mentioned side
Method stands good for frequency stepping phase-coded signal, but and unbonded this parameter of frequency hopping optimize processing, therefore,
For the cross-correlation Sidelobe Suppression under the conditions of frequency agile, still there is prodigious optimization space.
Invention content
In view of this, the present invention provides a kind of side lobe suppression methods of frequency stepping phase-coded signal, in conjunction with frequency hopping
This parameter optimizes processing, on the basis of ensureing autocorrelation sidelobe level, further suppresses cross-correlation secondary lobe.
The specific implementation mode of the present invention is as follows：
A kind of side lobe suppression method of frequency stepping phase-coded signal is based on for frequency stepping phase-coded signal
Weighted iteration least square method solves the method that mismatched filter coefficient carries out Sidelobe Suppression, and weighted iteration cross-correlation is weighted
Matrix Central Plains Hankel matrix replaces with the former Hankel matrix and subtracts the new Hankel matrix that itself shift matrix obtains,
Then it is solved, exports auto-correlation mismatch filter and cross-correlation mismatch filter after suppressed sidelobes respectively.
Further, the side lobe suppression method the specific steps are：
Step 1 selectes Current observation distance segment, and construction auto-correlation weights diagonal matrix, and solves the Chinese of current demand signal
Ke Er matrixes；It constructs cross-correlation and weights diagonal matrix, and solve the interference signal to be suppressed for folding into Current observation distance segment
The Hankel matrix of interference signal to be suppressed is subtracted itself shift matrix and obtains interference signal to be suppressed by Hankel matrix
New Hankel matrix；
Step 2, the Hankel matrix calculating auto-correlation that diagonal matrix and current demand signal are weighted using the auto-correlation are added
Weight matrix calculates cross-correlation using the cross-correlation weighting matrix and the new Hankel matrix of interference signal to be suppressed and weights square
The summation of both auto-correlation weighting matrix and cross-correlation weighting matrix is obtained the weighting matrix under current iteration by battle array；
Step 3 solves the mismatched filter coefficient under current iteration using weighting matrix；
Step 4, the mismatch that auto-correlation and cross-correlation are calculated separately using the mismatched filter coefficient under current iteration are filtered
Wave exports；Judge whether the mismatch filter output of auto-correlation and cross-correlation meets iteration termination condition, if it is satisfied, then exiting
Previous cycle, it is mismatched filter coefficient to take current mismatched filter coefficient, conversely, then correcting weighting diagonal matrix, returns to step
Rapid two, continue iteration.
Advantageous effect：
The present invention is directed to frequency stepping phase-coded signal, since the difference of the two neighboring cross-correlation secondary lobe after pulse pressure is got over
It is small, it can achieve the purpose that inhibit cross-correlation secondary lobe, be based on this principle, mismatch filter is solved in weighted iteration least square method
On the basis of wave device coefficient carries out side lobe suppression method, weighted iteration cross-correlation weighting matrix Central Plains Hankel matrix is replaced
The new Hankel matrix that itself shift matrix obtains is subtracted for former Hankel matrix, is then solved, is being ensured by auto-correlation
On the basis of valve level, cross-correlation secondary lobe is further suppressed.
Description of the drawings
The time-frequency schematic diagram of Fig. 1 signal models；
Fig. 2 range ambiguity schematic diagram of a scenario；
Fig. 3 context of methods implementation flow charts；
Fig. 4 echo signal mismatch filters export；
Fig. 5 interference signal mismatch filters export.
Specific implementation mode
The present invention will now be described in detail with reference to the accompanying drawings and examples.
For signal by the way of frequency stepping between pulse, a frame signal includes N number of pulse, frequency between two neighboring pulse
Rate saltus step Δ f is modulated using M phase codes in each signal arteries and veins, the type of phase code can for phase Code or
The coded sequence of polyphase code, different pulses is different.The time-frequency schematic diagram of signal is as shown in Fig. 1.
Mode of the stepped frequency radar due to using waveform agile between arteries and veins can be with for the echo positioned at different PRT
By adjusting reference signal time delay, different distance segments is selected, to solve the problems, such as range ambiguity.Scene shown in Fig. 2 includes
One disclosed herein (target 1) can prolong all reference signals to detect target 2 with a remote target (target 2)
When one PRT, since carrier frequency is different between different pulses, intra-pulse modulation mode is also different, therefore the reference after the PRT that is delayed
Signal and the echo of target 2 match, and are mismatched with the echo of target 1, when handling the echo of this distance segment, target 1
Echo can be effectively suppressed.
In practical application, it is limited to the limitation of step frequency parameter designing, the number of frequency steps of two neighboring pulse needs
Less than or equal to the bandwidth of subpulse, in order to utilize time resource to greatest extent, and the correlation between adjacent pulse is reduced, for
Frequency stepping phase-coded signal, number of frequency steps can be equal to the bandwidth of subpulse between arteries and veins.Nevertheless, since phase is compiled
The frequency spectrum of code signal has certain energy dissipation in band outside, although centre frequency differs a sub- arteries and veins between two neighboring pulse
The bandwidth of punching, but cross-correlation still has certain energy output can shadow when the backward energy that remaining distance segment folds is higher
The detection of current distance segment signal is rung, as shown in Fig. 2, when 1 energy of target is higher, still with the cross-correlation of reference signal
Higher output is had, the detection of target 2 can be influenced, therefore, for the signal of frequency stepping between arteries and veins, it is still desirable to be considered mutual
The suppressing method of correlation side lobes.
The cross-correlation function characteristic of two different pulses of carrier frequency is different from cross correlation of carrier frequency when identical, considers
It is made of to phase-coded signal one group of continuous chip, the cross-correlation of the chip containing carrier frequency will be analyzed first below
Function is generalized to the cross-correlation function of the phase-coded signal containing carrier frequency on this basis.
Assuming that two pulse s1(t) and s2(t), carrier frequency f1、f2。
WhereinWithIt is the first phase of chip, rect () is rectangular window function, TcIt is symbol width.
s1(t) and s2(t) cross-correlation is
Wherein Δ f=f2-f1, τ is cross-correlation intermediate variable.
For PCSF signals, Δ f=1/TcHave
As can be seen that above-mentioned cross-correlation function is the time limit, it is zero in starting and final position cross-correlation function, in
Heart position cross-correlation function is also zero, and above-mentioned cross-correlation function is about center point symmetry.
For the cross-correlation function of two phase codes, can be regarded as after taking cross-correlation between any two to all chips
Summation as a result, having
Wherein ym,n(t) be m-th and n-th chip cross-correlation gk(t) it is the y with identical delaym,n(t) ask
With
As can be seen from the above equation, gk(t) characteristic and ym,n(t) identical, in symbol width TcIntegral multiple position on take
Value is to be similarly zero, the still characteristic with point symmetry.R (t) can be regarded as to gk(t) be delayed TcIntegral multiple after sum, because
This R (t) is with TcFor interval, periodically there is zero, due to gk(t) it is the time limit, the region between two neighboring zero is
By two groups of gk(t) it determines, for example, kTcTo (k+1) TcRegion, be by gk(t-kTc) and gk+1(t-(k+1)Tc) determine.Due to
gk(t) centre-symmetric properties, if gk(t-kTc) and gk+1(t-(k+1)Tc) identical, then kTcTo (k+1) TcIntermediate region
Completely zero.Since different chip first phases are different, this desired result is unable to reach, but this property can obtain above
Go out, if gk(t-kTc) and gk+1(t-(k+1)Tc) between difference it is smaller, then kTcTo (k+1) TcIntermediate region cross-correlation
Side lobe levels can be smaller.That is the difference of the two neighboring cross-correlation secondary lobe after pulse pressure is smaller, can reach and inhibit by cross-correlation
The purpose of valve.
Based on this principle, the characteristics of for frequency stepping phase-coded signal frequency agile, the present invention provides one kind
The side lobe suppression method of frequency stepping phase-coded signal inhibits cross-correlation secondary lobe.Press down in the autocorrelation sidelobe of least square method
On the basis of method processed, autocorrelative weighting matrix and the weighting matrix of cross-correlation are summed, and carry out successive ignition, is solved
Go out mismatched filter coefficient, changes the method for calculating cross-correlation weighting matrix, cross-correlation side lobe peak is further suppressed to reach
The purpose of secondary lobe ratio (PSL), specific method are：
Step 1: initialization auto-correlation weighting diagonal matrix and cross-correlation weight diagonal matrix；
Selected Current observation distance segment, the he number that each subpulse includes are M, and the length of mismatched filter is P (P
>=M), to current demand signal S1With the interference signal S to be suppressed for folding into Current observation distance segment2Trailing zero is carried out, its length is made
For P, have
S1=[S1[0] S1[1]…S1[M-1] 0 … 0]T (7)
S2=[S2[0] S2[1] … S2[M-1] 0 … 0]T (8)
Then construct the auto-correlation weighting diagonal matrix W of (2P-1) × (2P-1)1It is weighted with (2P-1) × (2P-1) cross-correlation
Diagonal matrix W2
diag(W1)=[1,1 ... 1,0,1 ..., 1,1]T (9)
diag(W2)=[1,1 ... 1,1,1 ..., 1,1]T (10)
Wherein diag () expressions take element on diagonal line to current matrix.
Calculate current demand signal S1Hankel matrixes
Calculate the interference signal S for folding into current distance section to be suppressed2Hankel matrixes
WhereinFor unit matrix,For shift matrix.
Step 2: calculating weighting matrix
Utilize S1With S2Hankel matrixes and weighting diagonal matrix W1With W2, calculate auto-correlation weighting matrix B1With it is mutual
Related weighing matrix B2It is as follows
B2=X2W2X2 H (14)
The two summation is the weighting matrix B under current iteration
B=B1+B2 (15)
Step 3: calculating mismatch filter coefficient
The mismatched filter coefficient under current iteration is calculated using the weighting matrix B solved in step 2
h0=B-1S1 (16)
Mismatch filter coefficient under current iteration is obtained to the normalization of above-mentioned coefficient
It is exported with cross-correlation mismatch filter Step 4: calculating auto-correlation
Under current iteration, the mismatch filter output for calculating auto-correlation and cross-correlation is as follows
y1=hHX1 (18)
y2=hHX2 (19)
Judge y1、y2Whether iteration termination condition is met, if it is satisfied, then exiting previous cycle, it is to lose to take current coefficient
With filter coefficient, conversely, then correcting weighting diagonal matrix W1With W2, return to step two, continuation iteration.
Correct weighting diagonal matrix W1With W2Method be
diag(W1)=(abs (y1)+b)·diag(W1) (20)
diag(W2)=(abs (y2)+b)·diag(W2) (21)
Wherein b is a constant of very little, the influence with the zero to avoid correlation output to subsequently solving；Abs is represented
Modulus of access.
To verify the validity of context of methods, below by taking 64 quadri-phase codes as an example, provides auto-correlation and filtered with cross-correlation mismatch
Wave with conventional method as a result, and compared.Signal parameter is as follows
1 simulation parameter table of table
| Signal type | Optimal quadri-phase code |
| Signal element number | 64 |
| Mismatched filter exponent number | 80 |
| Chip width | 0.1us |
| Sample rate | 100MHz |
| Signal bandwidth | 10MHz |
| Receiver filtering bandwidth | 12MHz |
| Simulated receiver filter order | 48 |
Receiving the output of signal (with frequency point echo) mismatch filter with current distance section, the results are shown in Figure 4, with remaining distance
Section folds into the interference signal (non-same frequency point interference signal) of current distance section, and the results are shown in Figure 5 for mismatch filter.Above-mentioned two figure
Middle dotted line indicates the mismatch filter of conventional method as a result, solid line indicates the method for the invention mismatch filter as a result, can see
Go out, method of the invention maintains inhibition energy of the conventional method to autocorrelation sidelobe on to same frequency point Echo Processing result
Power, and in the handling result to non-same frequency point interference signal, it is better than conventional method 4.6dB.
In conclusion the above is merely preferred embodiments of the present invention, being not intended to limit the protection model of the present invention
It encloses.All within the spirits and principles of the present invention, any modification, equivalent replacement, improvement and so on should be included in this hair
Within bright protection domain.
Claims (2)
1. a kind of side lobe suppression method of frequency stepping phase-coded signal, which is characterized in that be directed to frequency stepping phase code
Signal solves the method that mismatched filter coefficient carries out Sidelobe Suppression based on weighted iteration least square method, and weighted iteration is mutual
Related weighing matrix Central Plains Hankel matrix replaces with the former Hankel matrix and subtracts the new Hunk that itself shift matrix obtains
That matrix, is then solved, and exports auto-correlation mismatch filter and cross-correlation mismatch filter after suppressed sidelobes respectively.
2. the side lobe suppression method of frequency stepping phase-coded signal as described in claim 1, which is characterized in that the secondary lobe
Suppressing method the specific steps are：
Step 1 selectes Current observation distance segment, and construction auto-correlation weights diagonal matrix, and solves the Hunk that square of current demand signal
Battle array；It constructs cross-correlation and weights diagonal matrix, and solve the Hunk that for the interference signal to be suppressed for folding into Current observation distance segment
The Hankel matrix of interference signal to be suppressed is subtracted itself shift matrix and obtains the Xin Hankeer of interference signal to be suppressed by matrix
Matrix；
Step 2, the Hankel matrix that diagonal matrix and current demand signal are weighted using the auto-correlation calculate auto-correlation weighting square
Battle array calculates cross-correlation weighting matrix using the cross-correlation weighting matrix and the new Hankel matrix of interference signal to be suppressed, will
The summation of both auto-correlation weighting matrix and cross-correlation weighting matrix obtains the weighting matrix under current iteration；
Step 3 solves the mismatched filter coefficient under current iteration using weighting matrix；
Step 4, the mismatch filter that auto-correlation and cross-correlation are calculated separately using the mismatched filter coefficient under current iteration are defeated
Go out；Judge whether the mismatch filter output of auto-correlation and cross-correlation meets iteration termination condition, is currently followed if it is satisfied, then exiting
Ring, it is mismatched filter coefficient to take current mismatched filter coefficient, conversely, weighting diagonal matrix is then corrected, return to step two, after
Continuous iteration.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113640752A (en) * | 2021-07-13 | 2021-11-12 | 北京理工大学 | Waveform design method based on inter-pulse phase spectrum double agility |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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