CN109343044B - Method for improving Doppler resolution of Gray complementary waveform - Google Patents

Method for improving Doppler resolution of Gray complementary waveform Download PDF

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CN109343044B
CN109343044B CN201811184076.9A CN201811184076A CN109343044B CN 109343044 B CN109343044 B CN 109343044B CN 201811184076 A CN201811184076 A CN 201811184076A CN 109343044 B CN109343044 B CN 109343044B
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waveform
group
matched filtering
signals
complementary
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CN109343044A (en
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朱家华
黄晓涛
初宁
范崇祎
王学智
比尔莫兰
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National University of Defense Technology
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/006—Theoretical aspects
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
    • G01S7/418—Theoretical aspects

Abstract

The invention provides a method for improving Doppler resolution of a Gray complementary waveform. The technical scheme comprises the following steps: in a first step, a complementary waveform group signal is generated that propagates in the time domain. And secondly, transmitting the complementary waveform group signals according to a standard transmission sequence. And thirdly, designing two groups of specific matched filtering weight sequences. And fourthly, performing matched filtering on the echo signals of the first N/2 pulses according to the first group of specific matched filtering weight sequence to obtain a first group of waveform signals output after matched filtering. And fifthly, performing matched filtering on the echo signals of the N/2 pulses according to a second group of specific matched filtering weight sequences to obtain a second group of waveform signals output after matched filtering. And sixthly, adding the two groups of waveform signals output after matched filtering to obtain the finally output waveform signal. The present invention further improves the doppler resolution of the waveform so that targets with different velocities at the same location can be better distinguished.

Description

Method for improving Doppler resolution of Gray complementary waveform
Technical Field
The invention belongs to the technical field of radar target detection, and relates to a method for improving Doppler resolution of Gray complementary waveforms.
Background
When the radar target detection performance is measured, a fuzzy function is often used for analysis and evaluation. Different radar emission waveforms correspond to different fuzzy functions, the time delay resolution and the Doppler resolution of the radar emission waveforms can be obtained by analyzing images of the fuzzy functions, and the range sidelobe suppression performance of the radar emission waveforms can be judged. The Golay complementary waveform (Golay complementary waveforms) has very high time delay resolution and good application prospect in the field of radar target detection. In addition, based on the existing binomial design method of the gray complementary waveform, the echo signal of the gray complementary waveform transmitting signal and the matched filtering signal of the matched filtering weight design at the receiving end are matched and filtered, and the obtained matched and filtered output waveform signal has a very large distance side lobe suppression area in the fuzzy function image (for the specific process of the method, the documents can be referred to as w.dang, a.pezeshki, s.howard, et., "coordinated complex wave for wideband suppression," 45th orthogonal conf.signals, Systems and digital outputs, 2011, pp.2096-2100.), namely, the radar transmitting waveform has very good distance side lobe suppression performance. However, this method has a drawback in that the doppler resolution of the radar transmission waveform described above is severely lowered, which makes it difficult to distinguish between targets having different velocities at the same position in actual target detection.
Complementary waveform groups (Complementary waveforms) are extensions of Golay Complementary waveforms (for a specific Complementary waveform group generation method, see C.C. Tsing and C. L. L iu, "Complementary waveforms of sequences," IEEETrans. Informam. Therory, vol.18, No.5, pp.644-652, Sep.1972.). A Complementary waveform group consisting of D (D is an integer of 2 or more) binary sequences can be expressed in the form of the following matrix
Figure GDA0002428515130000021
Wherein, l is 0,1,., L-1, each column of the matrix represents a binary sequence with the length of L digits and the value of 1 or-1, and the d +1 th column of the binary sequence is recorded as
Figure GDA0002428515130000022
D-1, 0, 1. In a binary sequence
Figure GDA0002428515130000023
Each element (i.e., 1 or-1) occupies a time width of TcThus each binary sequence
Figure GDA0002428515130000024
Has a time width of L Tc。
At baseband signal omega (t) using one unit of energy
Figure GDA0002428515130000025
For binary sequence
Figure GDA0002428515130000026
After modulation, the binary sequence
Figure GDA0002428515130000027
Become a train of pulse signals, denoted as A, which can propagate in the time domaind(t), where t represents time delay, D is 0,1, D-1 (modulation process can be referred to in the literature: m.a. richards, "fundamental of Radar signal processing", McGraw-Hill effect, NY, 2005).
The complementary waveform group signal propagated in the time domain is represented by D pulse signals as follows:
[A0(t),A1(t),...,AD-1(t)]
then, a D-system sequence P ═ P is used at the transmitting end0,...,pn,...,pN-1](N-0, 1.., N-1, N denotes the number of transmission pulses, pnIs an integer and pn∈ {0, 1.,. D-1}) to determine each pulse of the radar transmit waveform, referred to as a waveform transmit sequence, to represent A0(t)～AD-1(t) the transmission sequence. N +1 pulse transmitting pulse signal of radar transmitting waveform
Figure GDA0002428515130000028
The radar transmit waveform y (t) can be expressed as
Figure GDA0002428515130000029
Where T denotes the pulse repetition interval. When the value of the D-system sequence P is Pstd＝[0,1,...,D-1,0,1,...,D-1,...]And when the transmission sequence is referred to as a standard transmission sequence, the transmission sequence represented by the transmission sequence is referred to as a standard transmission sequence.
Let a positive sequence Q ═ Q0,...,qn,...,qN-1](qnPositive), the matched filtered signal of the radar transmission waveform y (t) at the receiving end is:
Figure GDA0002428515130000031
the sequence Q is used to determine the weight of the matched filtered signal z (t) on each pulse, called the matched filtered weight sequence, where the matched filtered weight for the (n + 1) th pulse is Qn. When all N values in the sequence Q are 1, it is called a standard matched filter weight sequence.
Next, by matched filtering, a waveform Signal outputted after matched filtering can be obtained, and then a fuzzy function image of the Radar emission waveform can be drawn by using the Signal (the process of matched filtering and the drawing method of the fuzzy function image can be referred to in the references: m.a. richards, "fundamental of Radar Signal Processing", McGraw-high efficiency, NY, 2005). According to the drawn fuzzy function image, the time delay resolution and the Doppler resolution of the radar transmitting waveform can be analyzed and evaluated, and the range sidelobe suppression performance of the radar transmitting waveform is judged.
Note that when D is 2, the complementary waveform group is equivalent to the foregoing gray complementary waveform, in which case, with the foregoing binomial design method, the waveform transmission order sequence P isBD＝[0,1,0,1,...]For standard transmit order sequences, matched filter weight sequences
Figure GDA0002428515130000032
Wherein
Figure GDA0002428515130000033
Which represents the number of combinations of N number of pulses taken out of N-1 different numbers of pulses.
Disclosure of Invention
The purpose of the invention is: a method for improving Doppler resolution of a Gray complementary waveform is provided.
The technical scheme of the invention comprises the following steps:
generating a group of complementary waveform groups consisting of D binary sequences, and then carrying out baseband modulation to obtain complementary waveform group signals transmitted in a time domain; d is an integer greater than 2, and the value of D is determined according to actual conditions.
Secondly, transmitting the complementary waveform group signals according to a standard transmitting sequence, setting the number of transmitting pulses to be N, and dividing echo signals of the complementary waveform group signals into a front N/2 pulse part and a rear N/2 pulse part at a receiving end; the number of transmit pulses N is chosen to ensure that it is divisible by 2D.
And thirdly, designing two groups of specific matched filtering weight sequences, and recording the two groups of specific matched filtering weight sequences as a first group and a second group.
And fourthly, performing matched filtering on the echo signals of the first N/2 pulses according to the first group of specific matched filtering weight sequence to obtain a first group of waveform signals output after matched filtering.
And fifthly, performing matched filtering on the echo signals of the N/2 pulses according to a second group of specific matched filtering weight sequences to obtain a second group of waveform signals output after matched filtering.
And sixthly, adding the two groups of waveform signals which are obtained in the fourth step and the fifth step and output after matched filtering to obtain finally output waveform signals.
The beneficial results of the invention are: compared with the waveform signal which is output after matched filtering and obtained by the existing quadratic form design method based on the Gray complementary waveform, the waveform signal which is finally output by the technical scheme obtains the distance sidelobe suppression performance and the time delay resolution which are equivalent to the radar transmission waveform under the condition of keeping the total pulse number of the radar transmission waveform unchanged, and further improves the Doppler resolution of the waveform, so that targets with different speeds at the same position can be better distinguished in the radar target detection process.
Drawings
FIG. 1 is a graph of simulation experiment results for a prior art method;
FIG. 2 is a flow chart of an implementation of the present invention;
fig. 3 is a simulation result of a simulation experiment performed using an embodiment of the present invention.
Detailed Description
Fig. 1 is a diagram of simulation experiment results of a conventional method, specifically, a comparison between a fuzzy function image of a waveform signal output after matched filtering obtained by a conventional golay complementary waveform-based binomial design method and a fuzzy function image of a waveform signal output after matched filtering (that is, a fuzzy function image of a waveform signal output after matched filtering obtained by performing matched filtering on a golay complementary waveform signal propagated in a time domain by using a standard transmission sequence and a standard matched filtering weight sequence) of a standard golay complementary waveform. Wherein the abscissa of fig. 1(a) and fig. 1(b) represents the doppler frequency (abbreviated as doppler) in units of "radian", and the radian is adopted as the unit of the parameter for the purpose of displaying in the image more clearly; the ordinate represents the time delay in seconds; the amplitude units are all "dB". The abscissa of fig. 1(c) represents the doppler frequency (abbreviated doppler) in units of "radians"; the ordinate represents the amplitude in "dB". Fig. 1(a) shows a blur function image of a waveform signal output after a standard gray complementary waveform matching filter, fig. 1(b) shows a blur function image of a waveform signal output after a matching filter obtained by a binomial design method based on a gray complementary waveform, and fig. 1(c) shows a comparison result of doppler resolutions of waveforms in the blur function image shown in fig. 1(a) and fig. 1 (b). Compared with the prior art, the matching-filtered waveform signal obtained by the binomial design method has a larger range sidelobe suppression area in the blur function image, but the Doppler resolution of the waveform is also seriously reduced.
Fig. 2 is a flow chart of an implementation of the present invention. The specific implementation mode comprises the following steps:
firstly, a group of complementary waveform groups consisting of D binary sequences is generated, and then baseband modulation is carried out to obtain complementary waveform group signals which are propagated in a time domain.
And secondly, transmitting the complementary waveform group signals according to a standard transmitting sequence, setting the number of the transmitted pulses to be N, and dividing the echo signals into a front N/2 pulses and a rear N/2 pulses at a receiving end.
And thirdly, designing two groups of specific matched filtering weight sequences, and recording the two groups of specific matched filtering weight sequences as a first group and a second group.
Designing a first group of specific matched filtering weight sequences for the first N/2 pulses, and recording the weight sequences as s0,...,sn1,...,sN/2-1]Wherein n is1＝0,1,...,N/2-1，
Figure GDA0002428515130000051
Wherein floor (n)1) Is expressed by taking less than n1Mod (n) is the maximum integer of1And D) represents taking n1The remainder of/D.
A second set of specific matched filter weight sequences is designed for the last N/2 pulses and is recorded as
Figure GDA0002428515130000052
Wherein n is2＝N/2,N/2+1,...,N-1，
Figure GDA0002428515130000053
And fourthly, performing matched filtering on the echo signals of the first N/2 pulses according to the first group of specific matched filtering weight sequence to obtain a first group of waveform signals output after matched filtering.
And fifthly, performing matched filtering on the echo signals of the N/2 pulses according to a second group of specific matched filtering weight sequences to obtain a second group of waveform signals output after matched filtering.
And sixthly, adding the two groups of waveform signals which are obtained in the fourth step and the fifth step and output after matched filtering to obtain finally output waveform signals.
Recording the waveform signals output after the matched filtering obtained in the fourth step and the fifth step as chi respectively1(t,FD) Hexix-2(t,FD) Where t denotes the time delay, FDIndicating doppler. The finally outputted waveform signal χ (t, F) obtained through the addition processingD) Is shown as
χ(t,FD)＝χ1(t,FD)+χ2(t,FD)
Then, a fuzzy function image of the radar transmitting waveform can be drawn by using the signal, and then the delay resolution and the Doppler resolution of the radar transmitting waveform are analyzed and evaluated according to the drawn fuzzy function image, so that the range sidelobe suppression performance of the radar transmitting waveform is judged.
Fig. 3 is a simulation result of a simulation experiment performed using an embodiment of the present invention. Wherein the abscissa of fig. 3(a) represents the doppler frequency (abbreviated as doppler) in units of "radians"; the ordinate represents the time delay in "seconds"; the amplitude unit is "dB". The abscissa of fig. 3(b) represents the doppler frequency (abbreviated as doppler) in units of "radians"; the ordinate represents the amplitude in "dB". Without loss of generality, a complementary waveform set consisting of D ═ 4 binary sequences is used here for comparison with the results of a binomial design based on gray complementary waveforms. Meanwhile, assuming that a target exists in the scene, the normalized amplitude, the normalized time delay and the normalized Doppler value of the target are respectively 0dB, tau is 0, fd＝0。
The parameters of the radar emission waveform signal are set as follows: operating frequency of radar is fcThe bandwidth of the signals of the Golay complementary waveform and the complementary waveform group which can be propagated in the time domain is B50 MHz, and the sampling rate fs2B, the pulse repetition interval T is 50 mus, the number of pulses is N64, each binary sequence in the complementary waveform and complementary waveform group has L time width T of 64c1 or-1 value of 0.1 μ s. Detecting complex white Gaussian noise obedience in a scene
Figure GDA0002428515130000061
Distribution, signal-to-noise ratio SNR is 10 dB. FIG. 3(a) is a blur function image χ (t, F) of a waveform signal finally outputted by the method of the present inventionD) Fig. 3(b) is a comparison result of doppler resolution of waveforms in the waveform signal finally output by the method of the present invention and the matching-filtered waveform signal obtained by the binomial design method based on the gray-complementary waveform. From the comparison results between fig. 3(a) and fig. 1(b) and 3(b), the method of the present invention and the method of the binomial design based on the complementary waveform of gray both transmit N-64 pulses, so there is no difference in the time required for signal transmission; on the other hand, the finally output waveform signal of the method has the distance sidelobe suppression performance and the time delay resolution which are equivalent to the latter, and the Doppler resolution of the waveform is further improved, so that the Doppler resolution is improved in the radar target detection processTargets with different velocities at the same location can be better distinguished.

Claims (1)

1. A method for improving golay complementary waveform doppler resolution, comprising the steps of:
generating a group of complementary waveform groups consisting of D binary sequences, and then carrying out baseband modulation to obtain complementary waveform group signals transmitted in a time domain;
secondly, transmitting the complementary waveform group signals according to a standard transmitting sequence, setting the number of transmitting pulses to be N, and dividing echo signals of the complementary waveform group signals into a front N/2 pulse part and a rear N/2 pulse part at a receiving end;
thirdly, designing two groups of specific matched filtering weight sequences, and recording the sequences as a first group and a second group;
fourthly, the echo signals of the first N/2 pulses are taken to carry out matched filtering according to a first group of specific matched filtering weight sequence to obtain a first group of waveform signals output after matched filtering;
fifthly, the echo signals of the last N/2 pulses are subjected to matched filtering according to a second group of specific matched filtering weight sequence to obtain a second group of waveform signals output after matched filtering;
sixthly, adding the two groups of waveform signals which are obtained in the fourth step and the fifth step and output after matched filtering to obtain finally output waveform signals;
d is an integer greater than 2, and the value of D is determined according to the actual situation; the value of the number N of the transmitted pulses is ensured to be evenly divided by 2D;
a first set of specific matched filter weight sequences, denoted
Figure FDA0002448759320000011
Wherein n is1＝0,1,...,N/2-1，
Figure FDA0002448759320000012
Wherein floor (n)1The expression/D) is taken to be less than n1Maximum integer of/D, mod (n)1And D) represents taking n1of/DThe remainder;
a second set of specific matched filter weight sequences, denoted
Figure FDA0002448759320000013
Wherein n is2＝N/2,N/2+1,...,N-1，
Figure FDA0002448759320000014
Wherein floor (2 n)2The expression,/D) is taken to be less than 2n2The largest integer of/D.
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US20090256739A1 (en) * 2004-10-14 2009-10-15 Tasuku Teshirogi Short range radar small in size and low in power consumption and controlling method thereof
CN106814352A (en) * 2017-01-19 2017-06-09 中国人民解放军国防科学技术大学 A kind of multi-target detection method based on Golay complementary waveform

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