CN109239675A - A kind of distributed spaceborne radar LFM waveform determining method based on same bandwidth difference chirp rate - Google Patents
A kind of distributed spaceborne radar LFM waveform determining method based on same bandwidth difference chirp rate Download PDFInfo
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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
- 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
- G01S7/023—Interference mitigation, e.g. reducing or avoiding non-intentional interference with other HF-transmitters, base station transmitters for mobile communication or other radar systems, e.g. using electro-magnetic interference [EMI] reduction techniques
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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
- 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
- G01S7/28—Details of pulse systems
- G01S7/282—Transmitters
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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
- 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
- G01S7/42—Diversity systems specially adapted for radar
Abstract
A kind of distributed spaceborne radar LFM waveform determining method based on same bandwidth difference chirp rate, i.e. to same carrier frequency, the linear FM signal of same time width and bandwidth two sections of equal part on a timeline, every section is modulated using different chirp rate k, it establishes distributed radar difference chirp rate and emits signal model, analyze influence of the chirp rate difference to waveform orthogonality and Doppler sensitivity, transmitted waveform auto-correlation is set by theory analysis, the parameters such as cross-correlation and doppler tolerance, determine the double section transmitted waveform parameters of each radar cell, finally realize between multiple diclinic rate LFM signals that there is quasi- orthogonality and lower Doppler sensitivity, under conditions of not increasing radar system bandwidth, meets the needs of distributed radar is for transmitted waveform.Operation of the present invention is simple, can significantly improve distributed spaceborne radar system transmitted waveform intercept, reduces the requirement of crosstalk and distributed system to system bandwidth B between each unit radar.
Description
Technical field
The orthogonal waveforms design based on same bandwidth difference chirp rate that the present invention relates to a kind of, it is especially a kind of to be based on same band
The distributed spaceborne radar LFM waveform determining method of wide difference chirp rate, belongs to microwave remote sensing field.
Background technique
It is interfered with each other under distributed system due to existing between radar, transmitting orthogonal waveforms is had between each spaceborne radar
Each radar can be made to receive, and target echo is mutually indepedent, obtains the time delay of each radar relative target by autocorrelation matching and phase is believed
Breath, while the unstability and high-speed motion of distributed spaceborne radar platform, therefore it is required that transmitted waveform cope with Doppler compared with
It is insensitive.Traditional method is to realize waveform orthogonality by transmitting signal frequency division, determines wave using maximum likelihood estimate
The carat Metro thresholding of shape is analyzed, although improving the intercept of waveform, reduces the interference between each radar, significantly
Increase requirement of the station-keeping radar system to bandwidth.
Currently based on proposed in the methods of MIMO radar orthogonal frequency Design of Signal a kind of combination sparse model to it is orthogonal from
It dissipates frequency LFM waveform to optimize, but this method is the ambiguity function for analyzing orthogonal frequency signal, to cross-correlation peak
Value sidelobe level position is analyzed with amplitude, is not directed to the side of different chirp rate segment designs under same bandwidth condition
Method, while this method does not consider and illustrates influence of the target Doppler characteristic to Waveform Design.
Summary of the invention
Technology of the invention solves the problems, such as: overcome the deficiencies in the prior art, proposes a kind of based on the bandwidth not people having the same aspiration and interest
The distributed spaceborne radar LFM waveform design method of frequency slope, to the linear FM signal of same carrier frequency, same time width and bandwidth
Two sections of equal part on a timeline, every section is modulated using different chirp rate k, analyzes chirp rate difference to waveform orthogonality
Meet distributed radar for transmitting under conditions of not increasing radar system bandwidth with the influence of Doppler sensitivity
The demand of waveform realizes between multiple diclinic rate LFM signals there is quasi- orthogonality and lower Doppler sensitivity.
The technical solution of the invention is as follows: a kind of distributed spaceborne radar LFM based on same bandwidth difference chirp rate
Waveform determining method, steps are as follows:
(1) according to distributed radar element number, transmitting signal carrier frequency fcWith target range resolution ratio cr, establish the not people having the same aspiration and interest
The mathematical model S of frequency slope LFM signali(t)；
(2) the mathematical model S established according to step (1)i(t), using distance-Doppler two dimension fuzzy function, construction is double
The cross-correlation function of frequency modulation LFM signal；Determine the mathematical model S of the different chirp rate LFM signals of step (1)i(t) fuzzy letter
Number, and determine doppler tolerance；
(3) according to the cross-correlation function and doppler tolerance of the frequency modulation-frequency modulation LFM signal of step (2) building, each distribution is determined
The chirp rate difference Δ k of formula radar cellnWith the sub- slope time width T of frequency modulationb；
(4) the chirp rate difference and the sub- slope time width of frequency modulation of each distributed radar unit determined according to step (3) determines
The transmitted waveform of the linear frequency modulation (LFM) of each distribution spaceborne radar unit.
Step (1) is according to distributed radar element number, transmitting signal carrier frequency fcWith target range resolution ratio cr, establish not
With the mathematical model S of chirp rate LFM signali(t), specific as follows:
In formula, j is imaginary unit, fcTo emit signal carrier frequency, rect [] is rectangular window function, n=1,2 ..., N, N
For radar number, knm(m=1,2) is two sub- slopes of frequency modulation of n-th of radar, and T is entire transmitting pulse signal time width, Tb=
T/2 be will emit pulse time width T to be divided to be two sections after every of time.
The mathematical model S that step (2) is established according to step (1)i(t), distance-Doppler two dimension fuzzy function, structure are utilized
The cross-correlation function of frequency modulation-frequency modulation LFM signal is made, specific as follows:
In formula, p subsignal and q subsignal are that any two radar cell emits signal, knpAnd knqFor p subsignal and q
Signal chirp rate, τ are time of integration parameter, CnpqFor frequency modulation-frequency modulation LFM signal cross-correlation function, n=1,2,., N, N are thunder
Up to unit number, j is imaginary unit；
Using fresnel integral formula, the cross-correlation function of frequency modulation-frequency modulation LFM signal is expressed as
Step (2) determines doppler tolerance, specific as follows:
Using distance-Doppler two dimension fuzzy function, the mathematical modulo of the different chirp rate LFM signals of step (1) is determined
Type Si(t) ambiguity function, so that it is determined that doppler tolerance.
Doppler tolerance fndIt indicates are as follows:
In formula, B is the bandwidth of the transmitting signal of distributed radar unit, Δ knIt is expressed as the tune of each distributed radar unit
Frequency slope differences.
The cross-correlation function and doppler tolerance for the frequency modulation-frequency modulation LFM signal that step (3) is constructed according to step (2) determine each
The chirp rate difference Δ k of distributed radar unitn, steps are as follows:
(1) it according to the cross-correlation function of the frequency modulation-frequency modulation LFM signal of step (2) building, determines in the value of doppler tolerance
Limit and value lower limit；
(2) according to the value upper limit of doppler tolerance and value lower limit, Δ k is determinednValue range.
ΔknValue range are as follows:
In formula, N is radar cell number, and T is transmitting pulse signal time width, Δ knPoor, the f for two sections of chirp ratesmaxFor hair
Penetrate signal doppler tolerance.
Step (3) determines the sub- slope time width T of frequency modulationb, steps are as follows: according to Δ knValue range, determine the sub- slope of frequency modulation
Time width TbValue range:
In formula, Tb is the sub- slope time width of frequency modulation, and T is transmitting pulse signal time width, and N is radar cell number, and B is transmitting
Signal bandwidth.
Step (4) is according to the sub- slope time width T of chirp rate difference and frequency modulation of each distributed radar unitb, determine each distribution
Linear body frequency modulation (LFM) transmitted waveform of formula spaceborne radar unit, specific as follows:
(4.1) chirp rate according to each distributed radar unit is poor, determines frequency modulation of each distributed radar unit tiltedly
Rate,
(4.2) the sub- slope of frequency modulation of each distributed radar unit determined by (4.1), in conjunction with the sub- slope time width T of frequency modulationb,
Determine linear body frequency modulation (LFM) transmitted waveform of each distributed spaceborne radar unit.
Spaceborne radar is mounted on low orbit satellite, and the spaceborne radar networking of multi-satellite forms radar system network, each
Spaceborne radar is a distributed radar unit.
The advantages of the present invention over the prior art are that:
(1) the method for the present invention compared with prior art, in distributed radar system, by same section of bandwidth LFM wave
Shape carries out two slope over 10 and divides design, solves the problems, such as that Orthogonal injection waveform system bandwidth is larger, realizes same section of fixation
The quasi- orthogonalization of bandwidth emission waveform, reaches transmitted waveform mutually not crosstalk；
(2) the invention patent compared with prior art, by transmitted waveform cross correlation value Parameter analysis and design, solve
LFM orthogonal waveforms cross correlation larger problem is realized and is combined using different chirp rates, makes multiple distributed unit radars
Transmitting signal between have quasi- orthogonality.
(3) the invention patent compared with prior art, by constructing Doppler's two dimension fuzzy function, joins doppler tolerance
Number is analyzed, and the restriction condition that transmitted waveform is influenced by target speed is given, and is the transmitting of distributed unit radar
There is lower Doppler sensitivity between signal.
(4) the invention patent compared with prior art, by dividing transmitted waveform cross correlation value and doppler tolerance
Analysis and design, transmitted waveform orthogonality is mutually restricted with Doppler sensitivity between solving the problems, such as multiple-unit radar, is future
The accurate estimation of spaceborne distributed radar Time Delay of Systems and phase provides technical support.
Detailed description of the invention
Fig. 1 is the flow chart of the method for the present invention；
Fig. 2 is multiple radar cell LFM signal time-frequency diagrams；
Fig. 3 is in the embodiment of the present invention using first radar emission signal amplitude-in three units of the method for the present invention
Frequency resultant schematic diagram；
Fig. 4 is in the embodiment of the present invention using second radar emission signal amplitude-in three units of the method for the present invention
Frequency resultant schematic diagram；
Fig. 5 is in the embodiment of the present invention using third radar emission signal amplitude-in three units of the method for the present invention
Frequency resultant schematic diagram；
Fig. 6 is in the embodiment of the present invention using result schematic diagram after the method for the present invention each unit radar cross-correlation.
Fig. 7 is in the embodiment of the present invention using result schematic diagram after the matching of the method for the present invention each unit radar return signal.
Specific embodiment
A kind of distributed spaceborne radar LFM waveform determining method based on same bandwidth difference chirp rate of the present invention, i.e., pair
Two sections of equal part, every section of different frequency modulation of use are oblique on a timeline for the linear FM signal of same carrier frequency, same time width and bandwidth
Rate k is modulated, and is established distributed radar difference chirp rate and is emitted signal model, analyzes chirp rate difference to waveform just
The influence of the property handed over and Doppler sensitivity sets transmitted waveform auto-correlation, cross-correlation and doppler tolerance etc. by theory analysis
Parameter determines the double section transmitted waveform parameters of each radar cell, finally realize between multiple diclinic rate LFM signals have quasi- orthogonality and
Lower Doppler sensitivity meets distributed radar for transmitted waveform under conditions of not increasing radar system bandwidth
Demand.Operation of the present invention is simple, can significantly improve distributed spaceborne radar system transmitted waveform intercept, reduces each unit
The requirement of crosstalk and distributed system to system bandwidth B between radar.
The spaceborne radar detection payload important as satellite platform is, it can be achieved that space, aerial, ground and sea mesh
Target degree of precision information measurement, but single spaceborne radar unit, which is difficult to realize big visual field, multiple target and distant object, to be surveyed
Amount, therefore networking is carried out according to certain design parallax range by multiple satellites equipped with spaceborne radar, form large aperture space
Radar network.But due to interfering with each other between spaceborne radar signal, more spaceborne radars, which must emit orthogonal waveforms, just be can guarantee
Each received target echo signal of radar is mutually indepedent, to realize the differentiation and processing of each transmitting signal.Therefore of the invention
Distributed spaceborne radar LFM waveform determining method based on same bandwidth difference chirp rate can not increase satellite platform complexity
Under conditions of degree, the orthogonalization of each radar cell transmitted waveform is realized.
A kind of distributed spaceborne radar LFM waveform determining method based on same bandwidth difference chirp rate of the present invention, step
It is as follows:
(1) according to distributed radar element number, transmitting signal carrier frequency fcWith target range resolution ratio cr, establish the not people having the same aspiration and interest
The mathematical model S of frequency slope LFM signali(t), specific as follows:
According to distributed radar element number, transmitting signal carrier frequency fcWith target range resolution ratio cr, it is oblique to establish different frequency modulation
The mathematical model S of rate LFM signali(t), specific as follows:
In formula, n=1,2 ..., N, N are radar number, knm(m=1,2) is two sub- slopes of frequency modulation of n-th of radar, T
Entirely to emit pulse signal time width, Tb=T/2 be will emit pulse time width T to be divided to be two sections after every of time, j is imaginary number list
Position, fcTo emit signal carrier frequency, rect [] is rectangular window function.
Simultaneously as all transmitting signal distributions are in same bandwidth B (B=2cr/ C, C are the light velocity), and then obtain this method
Applicability condition, i.e. the constraint condition of the sub- slope of frequency modulation of each distributed radar unit transmitting signal waveform are as follows:
(2) the mathematical model S established according to step (1)i(t), using distance-Doppler two dimension fuzzy function, construction is double
The cross-correlation function of frequency modulation LFM signal；Determine the mathematical model S of the different chirp rate LFM signals of step (1)i(t) fuzzy letter
Number, and determine doppler tolerance, it is specific as follows；
The mathematical model S established according to step (1)i(t), using distance-Doppler two dimension fuzzy function, frequency modulation-frequency modulation is constructed
The cross-correlation function of LFM signal enables Doppler frequency fd=0, if CnpqFor the p letter of the wide interior different chirp rates of same subband
Number and q subsignal cross-correlation function, it is available:
It is specific as follows:
In formula, p subsignal and q subsignal are that any two radar cell emits signal.knpAnd knqFor p subsignal and q
Signal chirp rate, τ are time of integration parameter, CnpqFor frequency modulation-frequency modulation LFM signal cross-correlation function, n=1,2,., N, N are thunder
Up to unit number, j is imaginary unit.
Enable Δ knpq=knp-knq, using fresnel integral formula, whenWhen, Fresnel ripple very little, signal
Energy is concentrated mainly on [0, Δ knpqTb] or [Δ knpqTb, 0] and in range, withBe gradually increased, different frequency modulation
For the cross-correlation function of the signal of slope gradually close to rectangular function, energy peak is smaller, and cross correlation can be better, therefore double tune
The cross-correlation function C of frequency LFM signalnpq(τ) will be indicated as:
Doppler tolerance fndIt indicates are as follows:
F in formulandFor doppler tolerance, i.e. the doppler values corresponding when peak power drops to former power half, B is
Each radar cell transmitted signal bandwidth, T are entire transmitting pulse signal time width, Δ kn=kn1-kn2Frequency modulation for each subsignal is oblique
Rate is poor.
Determine doppler tolerance, specific as follows:
Using distance-Doppler two dimension fuzzy function, the mathematical modulo of the different chirp rate LFM signals of step (1) is determined
Type Si(t) ambiguity function χn(τ,fd), so that it is determined that doppler tolerance fnd。
F in formuladIt is the Doppler frequency obtained by target velocity, φnm1(τ,fd) it is the phase letter unrelated with chirp rate
Number, φnm2(τ,knm) it is phase function related with chirp rate, TbFor the sub- slope time width of frequency modulation, τ is time of integration parameter.
(3) according to the cross-correlation function and doppler tolerance of the frequency modulation-frequency modulation LFM signal of step (2) building, each distribution is determined
The chirp rate difference Δ k of formula radar cellnWith the sub- slope time width T of frequency modulationb, it is specific as follows:
According to the cross-correlation function and doppler tolerance of the frequency modulation-frequency modulation LFM signal of step (2) construction, each distributed thunder is determined
Up to the chirp rate difference Δ k of unitn, steps are as follows:
(3.1) according to the cross-correlation function of the frequency modulation-frequency modulation LFM signal of step (2) building, the value of doppler tolerance is determined
The upper limit and value lower limit；
(3.2) according to the value upper limit of doppler tolerance and value lower limit, the sub- slope differences Δ k of frequency modulation is determinednValue model
It encloses.
ΔknValue range are as follows:
In formula, N is radar cell number, and T is transmitting pulse signal time width, Δ knFor two sections of sub- slope differences of frequency modulation, fmaxFor
Emit signal doppler tolerance.
(4) the chirp rate difference and the sub- slope time width of frequency modulation of each distributed radar unit determined according to step (3) determines
The transmitted waveform of the linear frequency modulation (LFM) of each distribution spaceborne radar unit.
Determine the sub- slope time width T of frequency modulationb, steps are as follows: according to Δ knValue range, determine the sub- slope time width T of frequency modulationb
Value range:
In formula, TbFor the sub- slope time width of frequency modulation, T is transmitting pulse signal time width, and N is radar cell number, and B is transmitting
Signal bandwidth.
Step (4) is according to the sub- slope time width T of chirp rate difference and frequency modulation of each distributed radar unitb, determine each distribution
Linear body frequency modulation (LFM) transmitted waveform of formula spaceborne radar unit, specific as follows:
(4.1) chirp rate according to each distributed radar unit is poor, and the average tune of signal is calculated by k=B/T
Frequency slope recyclesAnd kn2=k-n Δ knDetermine two sub- slopes of frequency modulation of each satellite, wherein Δ kn
≤ k/2N, N are radar number, while utilizing relational expression 400 (N-1)2/T2≤ k/2N, it may be determined that the tune of each distributed radar unit
Frequently sub- slope.
(4.2) the sub- slope of frequency modulation of each distributed radar unit determined by (4.1), in conjunction with the sub- slope time width T of frequency modulationb,
Determine linear body frequency modulation (LFM) transmitted waveform of each distributed spaceborne radar unit.
Spaceborne radar is mounted on low orbit satellite, and the spaceborne radar networking of multi-satellite forms radar system network, each
Spaceborne radar is a distributed radar unit, is illustrated in figure 2 multiple radar cell LFM signal time-frequency diagrams.
As shown in Figure 1, being the flow diagram of the method for the present invention, key step is as follows:
(1) it for distributed spaceborne radar orthogonality problem, determines distributed radar unit number n, emits signal carrier frequency
fcWith target range resolution ratio cr, establish the mathematical model S of different chirp rate LFM signalsi(t), i.e., to same signal carrier frequency,
The LFM signal of same time width and bandwidth is halved on a timeline, and the different sub- slopes of frequency modulation are arranged for every segment signal, right
It is known as frequency modulation-frequency modulation slope waveform subsignal in the different occupied signals of chirp rate；
In formula, n=1,2 ..., N, N are radar number, knm(m=1,2) is two sub- slopes of frequency modulation of n-th of radar, T
Entirely to emit pulse signal time width, Tb=T/2 is that will emit pulse time width T to be divided to the time for being two.Multiple radar cell LFM
Signal time-frequency relation is as shown below.
Since all transmitting signal distributions are in same bandwidth B (B=2cr/ C, C are the light velocity), and then obtain each distributed thunder
Up to the constraint condition of the sub- slope of frequency modulation of transmitting signal are as follows:
(2) according to step 1 as a result, utilizing the mutual of distance-Doppler two dimension fuzzy construction of function frequency modulation-frequency modulation LFM signal
Correlation function determines multiple transmitted waveform orthogonal properties, and analyzes LFM transmitting signal doppler characterization.Enable fd=0, if CnpqFor
The wide interior different p subsignals of chirp rate of same subband and the cross-correlation function of q subsignal, available:
K in formulanpAnd knqFor p subsignal and q subsignal chirp rate, τ is time of integration parameter.
Enable Δ knpq=knp-knq, using fresnel integral formula, whenWhen, Fresnel ripple very little, signal
Energy is concentrated mainly on [0, Δ knpqTb] or [Δ knpqTb, 0] and in range, withBe gradually increased, different frequency modulation
For the cross-correlation function of the signal of slope gradually close to rectangular function, energy peak is smaller, and cross correlation can be better, therefore Cnpq
(τ) can be approximately:
The slope differences between each subsignal of two transmitting signals determine the peak value of cross-correlation function as available from the above equation, tiltedly
Rate difference is bigger, and the orthogonality of each radar emission signal is bigger, each easier differentiation of radar.
The cross correlation of similar signal analyzes the doppler characterization of signal using two dimension fuzzy function.The signal can be obtained
Ambiguity function:
F in formuladIt is the Doppler frequency obtained by target velocity, φnm1(τ,fd) it is the phase letter unrelated with chirp rate
Number, φnm2(τ,knm) it is phase function related with chirp rate, it can be obtained by derivation,
F in formulandFor doppler tolerance, the i.e. doppler values corresponding when peak power drops to former power half.Δ
kn=kn1-kn2Chirp rate for each subsignal is poor.
By that can obtain to transmitting signal doppler characterization analysis, wide when transmitting a signal and one timing of bandwidth, Doppler hold
Limit fndWith chirp rate difference Δ knIn inverse relation, therefore the Doppler sensitivity of diclinic rate transmitting signal is reduced, needed each
The chirp rate difference of subsignal is smaller.
Therefore, according to distributed radar to target resolution cr, it may be determined that overall system bandwidth B=2cr/ C, shines according to radar
The target scene speed variation penetrated determines Doppler frequency variation range [fmin, fmax], by doppler tolerance fnd≥fmax
Estimate T2·Δkn≤1.772B/fmaxThe value upper limit.Cross correlation value is set further according to cross-correlation function, that is, works as CnIt is less than
There is quasi- orthogonality between 0.1 multiple signal waveforms, T can be obtained2·ΔknLower limit value 400 (N-1)2。
(3) according to the result of step 2, it is assumed that the transmitting signal time width T of distributed radar system passes through T2·ΔknValue
Bound can determine Δ knValue range:
Simultaneously in order to keep the autocorrelation sidelobe of signal as low as possible, Δ knValue answer as small as possible, therefore value model
The minimum value enclosed, it may be assumed that
The average chirp rate of signal is calculated by k=B/T, is recycledAnd kn2=k-n Δ kn
Determine two sub- slopes of frequency modulation of each satellite, wherein Δ kn≤ k/2N, N are radar number.400 (N- of relational expression is utilized simultaneously
1)2/T2≤ k/2N, it may be determined that the value range of the sub- slope time width of frequency modulation:
Finally by above-mentioned design whole parameter, LFM frequency modulation-frequency modulation slope waveform subsignal expression formula is brought into, can obtain every
A unit radar Orthogonal injection waveform, while each parameter can carry out value in the range of distributed radar system allows.
The present invention is based on the distributed spaceborne radar LFM waveform design methods of same bandwidth difference chirp rate, and steps are as follows:
(1) for distributed spaceborne radar orthogonality problem, it is first determined distributed satellites number n, in same bandwidth B and
Under the conditions of time width T, the mathematical model Si (t) of not frequency modulation-frequency modulation slope linear FM signal is established, and determines that chirp rate constrains item
Part,
(2) it is calculated according to step 1 as a result, using distance-Doppler two dimension fuzzy function and speed-Doppler relation
The cross correlation C of the waveform outnpq(τ) and doppler tolerance fndInput condition as design waveform；
(3) according to step 2 as a result, using chirp rate difference Δ k between different radars to each radar emission signal cross-correlation
Thresholding (thresholding preferably -20dB) and doppler tolerance (1.772B/T2·Δkn, wherein the parameters such as B, T are determined by operative scenario),
The value range that different radar slope differences Δ k can be obtained, is obtained by average chirp rate kAnd kn2=k-
N Δ k determines two sub- slopes of frequency modulation of each satellite, realizes the LFM waveform with bandwidth difference chirp rate；
(4) by it is wide at the same time, under bandwidth condition, using the design of LFM frequency modulation-frequency modulation slope waveform subsignal relevant parameter,
Transmitted waveform design and emulation, demonstrate frequency modulation-frequency modulation slope subsignal construction transmitted waveform correctness, while obtain compared to
The method that tradition realizes Distributed orthogonal transmitted waveform design using frequency division, this method are able to achieve multiple diclinic rate LFM transmitted waves
There is quasi- orthogonality (preferably cross-correlation preferably 0.1) and lower Doppler sensitivity (preferably doppler tolerance preferably 1.1 between shape
×105Hz), under conditions of not increasing radar system total bandwidth, meet distributed radar for Orthogonal injection waveform
Demand.
Mathematical simulation is carried out, simulated conditions are preferred are as follows: radar carrier frequency fcFor 9GHz, distance by radar is to resolution ratio crFor 1.5m,
I.e. each unit transmitted waveform bandwidth is 100MHz, and observed object maximum aggregate velocity is 167m/s, and radar cell number is 3, each to fill
There is the satellite platform orbit altitude of spaceborne radar load identical.By above-mentioned condition, different chirp rate LFM signals are established
Mathematical model Si(t), while distance-Doppler two dimension fuzzy function is utilized, constructs the cross-correlation letter of frequency modulation-frequency modulation LFM signal
Number, and determine doppler tolerance fnd.By cross-correlation function and doppler tolerance, each distributed radar unit is calculated
Chirp rate difference Δ knWith the sub- slope time width T of frequency modulationb, finally obtain the frequency modulation-frequency modulation slope linear frequency modulation letter of three radar cells
Number transmitted waveform.
Fig. 3, Fig. 4 and Fig. 5 are three unit radar emission signal amplitudes-that the method for the present invention is used in the embodiment of the present invention
Frequency resultant analogous diagram, wherein abscissa is each radar cell bandwidth range, and ordinate is the spectral density of transmitted waveform, can be with
Find out that designed radar emission waveform is all to be realized by the sub- slope of two frequency modulation, while the sub- slope of each frequency modulation does not repeat, respectively
Sub- slope has time width T/2 having the same, and the bandwidth and frequency range of different sub- slopes are all different, and verifies the method for the present invention
The mathematical model S of structure buildingi(t) correctness.Fig. 6 is mutual using the method for the present invention each unit radar in the embodiment of the present invention
Result analogous diagram behind pass, wherein abscissa is that Unit two receive the time width after signal Cross Correlation Matching, and ordinate is that Unit two connect
Normalization range value after collection of letters Cross Correlation Matching, it can be seen from the figure that compare left figure low for the cross-correlation peak value of right figure
0.02 or so, and the chirp rate difference between radar 1 and radar 3 is greater than radar 1 and radar 2, i.e. frequency modulation between each subsignal
Slope differences are bigger, and cross-correlation peak value is smaller, and the orthogonal performance of transmitted waveform is better, demonstrate the condition of wide same bandwidth at the same time
Down, it can be achieved that the orthogonality of multiple distributed radar unit transmitted waveforms.Fig. 7 is that the method for the present invention is used in the embodiment of the present invention
Each unit radar return signal matching after result schematic diagram, wherein abscissa be each unit receive signal autocorrelation matching after when
Width, ordinate are that each unit receives the normalization range value after signal autocorrelation matching, it can be seen that cross-correlation peak value is less than master
The 1/10 of valve peak value, therefore can further illustrate that each transmitting signal has good orthogonality.Meanwhile the matching output of radar 1
Cross-correlation peak value in the left side of the peak value of main lobe, radar 2 appears in main lobe peak value two sides, and radar 3 is concentrated mainly on the main lobe right side
Side also illustrates wide at the same time and under bandwidth condition, Different Slope this is because caused by three signal chirp rates difference differences
The linear FM signal of difference is different, can distinguish to the echo-signal of each unit in distributed radar system.Finally, according to
It is 10KHz that target speed, which obtains target maximum doppler frequency amount, in the condition of emulation, much smaller than analyzing in this method
Doppler tolerance 1.1 × 105Hz, therefore each unit radar return signal matching output valve is not substantially by the shadow of Doppler frequency
It rings, demonstrates the insensitivity of Doppler frequency in this method.
First verify that this method mathematical model is established, frequency modulation-frequency modulation slope is determining, each unit cross-correlation by the embodiment
It is worth the small correctness low with Doppler frequency sensibility.Next is also illustrated before not increasing distributed radar system complexity
It puts, it can be achieved that with identical Orthogonal injection waveform in existing big wide frequency point waveform design method, and considers distribution
The problem of system how general for target rate frequency displacement.Finally, the embodiment only simulates the case where three radar cells, but this method
It can expand to N number of radar cell, the orthogonalization for the following distributed spaceborne radar transmitted waveform provides practical technological approaches.
The content that description in the present invention is not described in detail belongs to the well-known technique of those skilled in the art.
Claims (10)
1. a kind of distributed spaceborne radar LFM waveform determining method based on same bandwidth difference chirp rate, it is characterised in that step
It is rapid as follows:
(1) according to distributed radar element number, transmitting signal carrier frequency fcWith target range resolution ratio cr, it is oblique to establish different frequency modulation
The mathematical model S of rate LFM signali(t)；
(2) the mathematical model S established according to step (1)i(t), using distance-Doppler two dimension fuzzy function, frequency modulation-frequency modulation is constructed
The cross-correlation function of LFM signal；Determine the mathematical model S of the different chirp rate LFM signals of step (1)i(t) ambiguity function,
And determine doppler tolerance；
(3) according to the cross-correlation function and doppler tolerance of the frequency modulation-frequency modulation LFM signal of step (2) building, each distributed thunder is determined
Up to the chirp rate difference Δ k of unitnWith the sub- slope time width T of frequency modulationb；
(4) the chirp rate difference and the sub- slope time width of frequency modulation of each distributed radar unit determined according to step (3), determines each point
The transmitted waveform of the linear frequency modulation (LFM) of cloth spaceborne radar unit.
2. a kind of distributed spaceborne radar LFM waveform based on same bandwidth difference chirp rate according to claim 1 is true
Determine method, it is characterised in that: step (1) is according to distributed radar element number, transmitting signal carrier frequency fcIt is differentiated with target range
Rate cr, establish the mathematical model S of different chirp rate LFM signalsi(t), specific as follows:
In formula, j is imaginary unit, fcTo emit signal carrier frequency, rect [] is rectangular window function, and n=1,2 ..., N, N is radar
Number, knm(m=1,2) is two sub- slopes of frequency modulation of n-th of radar, and T is entire transmitting pulse signal time width, Tb=T/2 is
Pulse time width T will be emitted be divided to be two sections after every of time.
3. a kind of distributed spaceborne radar LFM waveform based on same bandwidth difference chirp rate according to claim 1 is true
Determine method, it is characterised in that: the mathematical model S that step (2) is established according to step (1)i(t), distance-Doppler two dimension mould is utilized
Function is pasted, the cross-correlation function of frequency modulation-frequency modulation LFM signal is constructed, specific as follows:
In formula, p subsignal and q subsignal are that any two radar cell emits signal, knpAnd knqFor p subsignal and q subsignal
Chirp rate, τ are time of integration parameter, CnpqFor frequency modulation-frequency modulation LFM signal cross-correlation function, n=1,2 ..., N, N is radar cell
Number, j are imaginary unit；
Using fresnel integral formula, the cross-correlation function of frequency modulation-frequency modulation LFM signal is expressed as
4. a kind of distributed spaceborne radar LFM waveform based on same bandwidth difference chirp rate according to claim 1 is true
Determine method, it is characterised in that: step (2) determines doppler tolerance, specific as follows:
Using distance-Doppler two dimension fuzzy function, the mathematical model S of the different chirp rate LFM signals of step (1) is determinedi
(t) ambiguity function, so that it is determined that doppler tolerance.
5. a kind of distributed spaceborne radar LFM waveform based on same bandwidth difference chirp rate according to claim 4 is true
Determine method, it is characterised in that: doppler tolerance fndIt indicates are as follows:
In formula, B is the bandwidth of the transmitting signal of distributed radar unit, Δ knThe frequency modulation for being expressed as each distributed radar unit is oblique
Rate is poor.
6. a kind of distributed spaceborne radar LFM waveform based on same bandwidth difference chirp rate according to claim 1 is true
Determine method, it is characterised in that: the cross-correlation function for the frequency modulation-frequency modulation LFM signal that step (3) is constructed according to step (2) and Doppler hold
Limit, determines the chirp rate difference Δ k of each distributed radar unitn, steps are as follows:
(1) according to step (2) building frequency modulation-frequency modulation LFM signal cross-correlation function, determine doppler tolerance the value upper limit and
Value lower limit；
(2) according to the value upper limit of doppler tolerance and value lower limit, Δ k is determinednValue range.
7. a kind of distributed spaceborne radar LFM waveform based on same bandwidth difference chirp rate according to claim 6 is true
Determine method, it is characterised in that: Δ knValue range are as follows:
In formula, N is radar cell number, and T is transmitting pulse signal time width, Δ knPoor, the f for two sections of chirp ratesmaxFor transmitting letter
Number doppler tolerance.
8. a kind of distributed spaceborne radar LFM waveform based on same bandwidth difference chirp rate according to claim 1 is true
Determine method, it is characterised in that: determine the sub- slope time width T of frequency modulationb, steps are as follows: according to Δ knValue range, determine frequency modulation
Slope time width TbValue range:
In formula, Tb is the sub- slope time width of frequency modulation, and T is transmitting pulse signal time width, and N is radar cell number, and B is transmitting signal band
It is wide.
9. a kind of distributed spaceborne radar LFM waveform based on same bandwidth difference chirp rate according to claim 1 is true
Determine method, it is characterised in that: step (4) is according to the sub- slope time width T of chirp rate difference and frequency modulation of each distributed radar unitb,
Determine linear body frequency modulation (LFM) transmitted waveform of each distributed spaceborne radar unit, specific as follows:
(4.1) chirp rate according to each distributed radar unit is poor, determines the sub- slope of frequency modulation of each distributed radar unit,
(4.2) the sub- slope of frequency modulation of each distributed radar unit determined by (4.1), in conjunction with the sub- slope time width T of frequency modulationb, determine each
Linear body frequency modulation (LFM) transmitted waveform of distributed spaceborne radar unit.
10. a kind of distributed spaceborne radar LFM waveform based on same bandwidth difference chirp rate according to claim 1 is true
Determine method, it is characterised in that: spaceborne radar is mounted on low orbit satellite, and the spaceborne radar networking of multi-satellite forms radar system
Network, each spaceborne radar are a distributed radar unit.
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| CN111190189A (en) * | 2020-01-13 | 2020-05-22 | 中国科学院上海光学精密机械研究所 | Multifunctional double frequency modulation coherent laser radar |
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| CN112965034A (en) * | 2021-04-13 | 2021-06-15 | 哈尔滨工业大学 | Method for improving Doppler tolerance of slow time phase coding signal of sky wave radar |
| CN112965034B (en) * | 2021-04-13 | 2023-11-17 | 哈尔滨工业大学 | Method for improving Doppler tolerance of slow time phase coded signal of sky-wave radar |
| CN113325417A (en) * | 2021-05-24 | 2021-08-31 | 西安空间无线电技术研究所 | Millimeter wave and terahertz multi-band radar detection imaging system and method |
| CN113325417B (en) * | 2021-05-24 | 2024-03-15 | 西安空间无线电技术研究所 | Millimeter wave and terahertz multi-band radar detection imaging system and method |
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