CN105388465B - Sea clutter simulation method based on wave spectrum model - Google Patents
Sea clutter simulation method based on wave spectrum model Download PDFInfo
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- CN105388465B CN105388465B CN201510952881.1A CN201510952881A CN105388465B CN 105388465 B CN105388465 B CN 105388465B CN 201510952881 A CN201510952881 A CN 201510952881A CN 105388465 B CN105388465 B CN 105388465B
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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
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Abstract
The invention discloses a kind of sea clutter simulation method based on wave spectrum model, the problem of prior art is difficult to embody extra large surface wave high details is mainly solved.Its implementation is：1. set up the extra large surface based on wave spectrum model；2. determine the extra large surface range under the irradiation of radar main beam；3. choose rectangle frame in extra large surface range, and to complex surface that the extra large surface discretization of inframe is configured to be spliced by the triangle scattering unit of many homalographics；4. calculate the property parameters and echo power of each triangle scattering unit；5. the echo model of triangle scattering unit is set up according to echo power；6. producing the echo of rectangle frame inland sea surface triangles scattering unit according to echo model, the radar visibility of triangle scattering unit is judged, calculate and be superimposed the echo of all visible triangle scattering units, produce the emulation data of sea clutter and analyze.The present invention improves the confidence level and practicality of sea clutter simulation, available for target detection.
Description
Technical field
The invention belongs to signal processing technology field, specifically a kind of sea clutter simulation method, available for target inspection
Survey.
Background technology
The emulation technology of radar sea clutter, experienced from shallow to deep, go from the simple to the complex and slightly arrive thin process.Be initially by
Sea clutter regards the random sequence with certain probability density function PDF as, is emulated using Monte-Carlo methods.Through
The sea clutter amplitude statistics model of allusion quotation has just too distribution, Wei Buer distributions and the K distributions of rayleigh distributed, logarithm.And actually encounter
Sea clutter not only there is statistical distribution characteristic in amplitude, while meet certain correlation again, this allows for the data of emulation
Certain specific power spectrum characteristic or correlation properties and amplitude distribution characteristic, relatively representative and ripe side are met simultaneously
Method has spherically invariant random processes SIRP and Zero memory nonlinearity transfrom method ZMNL, also a kind of stochastic differential equation seldom
Method SDE.But these are a kind of empirical models from the sea clutter amplitude statistics model of statistical theory, fail to consider radar
Actual operating conditions and environmental condition, it is impossible to directly apply to the clutter analysis of actual radar system.
So need for specific radar operative scenario carry out clutter simulation come research model parameter and radar parameter and
The relation of ambient parameter.Document《Any attitude records PD radar three-dimensional land clutter algorithm researches》By ground sea press distance-it is how general
Le has carried out scattering unit division, to Airborne Pulse Doppler Radar using it is lower depending on working method when ground sea clutter carry out
Modeling and simulation；Document《The modeling and simulation of PD radar seekers sea clutter spectrum》With reference to the revised surface scattering of measured data
The models such as coefficient, have carried out scattering unit division, to the radar being operated under pulse Doppler system by sea by equidistant ring
Target seeker sea clutter has carried out modeling and simulation.The former according to the scattering unit division methods of distance-Doppler in theory very
Accurately, but represent that these scattering units are more complicated using mathematical formulae, and calculating clutter power need to calculate dual-integration, it is real
Now get up relatively difficult；The latter is fairly simple according to the scattering unit division methods of equidistant ring, but scattering unit area with
The increase of distance and increase, extra large surface details are difficult to embody, and reduce the confidence level of sea clutter simulation.
The content of the invention
It is an object of the invention to the deficiency for above-mentioned prior art, a kind of sea clutter based on wave spectrum model is proposed
Analogy method, improves the confidence level and practicality of sea clutter simulation.
To achieve the above object, technical solution of the present invention includes as follows：
(1) it is theoretical according to random seaway, describe any point (x, y) on datum water level with wave height equation η (x, y, t) and exist
The extra large apparent height of t, sets up the Wave Model on extra large surface, and the wherein amplitude in wave height equation is determined by wave spectral function；
(2) antenna height is set up for H, beam angle is 2 ψ, wave beam sight line grazing angle is φ head-down radar, according to
Any point (x, y, z) and the position relationship of head-down radar on extra large surface under antenna main beam irradiation, calculate point motion
Track x2cos2ψ-2yHcosφsinφ+y2(cos2ψ-cos2φ)=H2(sin2φ-cos2ψ), it is determined that the scope on extra large surface：When
During φ ＜ ψ, extra large surface range is hyperbola and its internal sea surface；As φ=ψ, extra large surface range is parabola and its inside
Extra large surface；As φ ＞ ψ, extra large surface range is oval and its internal sea surface；
(3) it is determined that extra large surface range, choose size be p × q a rectangle frame, laterally sampled in the rectangle frame
Interval takesWith the rectangle frame inland sea surface arbitrfary point (x0,y0,z0) movement velocity v, azimuth angle alpha0, angle of pitch β0, protecting
Hold DOPPLER RESOLUTION and meet Doppler it is unambiguous under the conditions of calculate longitudinal sampling interval s δ, and distinguished with transverse and longitudinal interval
ForSampled point is taken on the extra large surface in rectangle frame with s δ, then a triangle scattering unit is constituted with every 3 sampled points,
Wherein c is the light velocity, fsFor radar signal sample frequency, s is that ripple door is originated in y-axis location of projection, and δ is between azimuth is split
Every,N is the umber of pulse in a coherent processing interval CPI, the length that p projects for the start-stop of ripple door in y-axis, q
For determination extra large surface range it is longitudinally wide；
(4) parameter of any one triangle scattering unit is calculated：
(4a) according to any one triangle scattering unit and the position relationship of radar, calculate the triangle scattering unit with
The distance between radar R, azimuth angle alpha and angle of pitch β, arrival bearingNormal directionArea A0, wherein triangle scattering unit
Area A0, byCalculate；
(4b) calculates the echo power P of the triangle scattering unit according to radar equationr；
(5) echo model of establishment step (4) intermediate cam shape scattering unitIts
Middle st() is the linear frequency modulation LFM signals of radar emission, and ζ (t) shakes for phase delay,Represent imaginary number, fdFor the triangle
The Doppler frequency of scattering unit；
(6) according to ray tracing principle, the hiding relation and triangle scattering unit between triangle scattering unit are judged
The hiding relation of itself：
If certain triangle scattering unit summit is α relative to the elevation angle of radar1, block unit summit is faced upward relative to radar
Angle is α2, work as α1≥α2When, the triangle scattering unit is blocked, and its echo is not calculated；Work as α1＜ α2When, triangle scattering is single
Member there is not occluded cell to block, then calculates the local incident angle α of the triangle scattering unitL, then judge that triangle scattering is single
First hiding relation of itself：
Work as αLDuring ＞ pi/2s, the triangle scattering unit is blocked by itself, and its echo is not calculated；
Work as αLDuring≤pi/2, the triangle scattering unit is not blocked, calculate and be superimposed all triangles not being blocked dissipate
The echo of unit is penetrated, the sea clutter emulation data of a coherent processing interval CPI echo is produced, completes the simulation to sea clutter.
The present invention has the following advantages that compared with prior art：
1. the extra large surface for the method emulation that the present invention is combined with wave spectrum model with radar running parameter, ambient parameter increases
The strong sea clutter of simulation and contacting for sea situation environment, more with practicality；
2. because discrete extra large surface can regard the complex surface being spliced by many triangle scattering units, and triangle as
Scattering unit is projected as right angled triangle bin horizontal plane, and the present invention is drawn to sea level using triangle scattering unit
Point, compared to the resolution cell division methods based on equidistant ring in the past, Triangular patch belongs to equal area partition, the bin of division
Area will not increase with the increase of distance, therefore the extra large surface of simulation can more embody unrestrained high details.While the division methods
It is simpler than distance-Doppler resolution cell division methods on mathematical notation, it is not necessary to complicated dual-integration computing；
Experiment simulation shows：1) sea clutter of single pulse echo of the present invention emulates the amplitude curve figure and sea clutter of data
The amplitude curve map sheet degree trend of measured data is basically identical, illustrates that the sea clutter that the present invention is produced has confidence level；2) this hair
The amplitude statistical distribution of the sea clutter emulation data of bright same range cell is examined with conventional statistics distributed model K fittings of distribution goodness
Test optimal, showing the sea clutter simulation method of the present invention has practicality there is provided Research statistics distributed model parameter and radar work
Make a kind of approach of relation between parameter and ambient parameter.
Brief description of the drawings
Fig. 1 is the operational flowchart of the present invention；
Fig. 2 is the power density equi-energy divided method schematic diagram based on wave used in the present invention；
Fig. 3 be use in the present invention extra large surface range schematic diagram is determined under the irradiation of radar main beam；
Fig. 4 is that the extra large surface in rectangle frame used in the present invention takes sampled point schematic diagram；
Fig. 5 is the construction triangle scattering unit schematic diagram used in the present invention；
Fig. 6 be the calculating triangle scattering unit design parameter used in the present invention triangle scattering unit and radar it
Between location diagram；
Fig. 7 is the extra large surface X-Y scheme not in the same time that the present invention is emulated；
Fig. 8 is the contrast of the sea clutter emulation data amplitude curve map and sea clutter measured data amplitude curve figure of the present invention
Figure；
Fig. 9 is the sea clutter echo data analysis chart that the present invention is emulated；
Embodiment：
The present invention combines the extra large surface of Pierson-Moskowitz wave spectrum models emulation based on wind speed, according to all kinds of right
Sea level divides the advantage and disadvantage of scattering unit method, proposes the triangle scattering unit division methods of homalographic, calculates and be superimposed
The echo simulation sea clutter of all scattering units, has been additionally contemplates that radar running parameter and ambient parameter during emulation, such as antenna is high
The factors such as degree, beam angle and wave beam sight line grazing angle.
The present invention is described in further detail with specific embodiment below in conjunction with the accompanying drawings.
Reference picture 1, the sea clutter simulation method of the invention based on wave spectrum model, comprises the following steps：
Step 1, the Wave Model on extra large surface is set up.
Because wind speed etc. influences, the change that height rises and falls can occur for sea, therefore it is flat to understand that extra large surface can not possibly always be
Whole surface, therefore can be theoretical according to random seaway, actual wave is regarded as different angular frequencies, the different directions of propagation, difference
The result of wave height and the sine-wave superimposed of different initial phases.
1a) selection wave frequencies spectral function SΩ(ω) and directivity function D (Φ)：
Use International Towing Tank Conference ITTC propose suggestiveness form for：
Wave frequencies spectral function SΩ(ω) selects Pierson-Moskowitz wave spectrum models, Pierson-Moskowitz
Spectrum is the Wind Wave Spectra using wind speed as the Developed state of parameter, and its expression formula is：
Wherein ω be wave of the sea angular frequency, Φ be wave relative to the direction of propagation of x-axis, g is acceleration of gravity, Uw
For higher than the wind speed at extra large surface 19.5m；
1b) according to wave frequencies spectral function SΩ(ω) and directivity function D (Φ), calculates wave spectral function S (ω, Φ),
S (ω, Φ)=SΩ(ω)D(Φ)；
1c) calculate the amplitude of different angular frequencies and the simple sinusoidal ripple in direction：Wherein Δ ω and
ΔΦ is respectively ω and Φ increment；
Following three dimensional random wave wave height equation 1d) is set up according to above-mentioned parameter：
Wherein Am,lRepresent different angular frequencies and the sinusoidal amplitude in direction；kmFor wave number, according to the dispersion relation of deep water,
The angular frequency of wave of the seaAndkmx=km cosΦl, kmy=km sinΦl；εm,lFor random phase
Parallactic angle, obey [0,2 π) in be uniformly distributed；L represents direction segmentation number,LThe maximum fractionation number in direction is represented, its value is bigger
Segmentation precision is higher, l=1,2 ..., L；M represents angular frequency segmentation number, and M represents the maximum fractionation number of angular frequency, m=1,
2 ..., M；
The segmentation reference picture 2 of diagonal frequencies, because angular frequency can be by 1a) in Pierson-Moskowitz frequency spectral functions
SΩ(ω) is described, therefore can be split using the equi-energy divided method diagonal frequencies based on wave power density：First to selected
M segmentation of angular frequency, makes the energy Δ E at each angular frequency interval equal, it is then determined that the centre frequency of each sub- area；
Defining angular frequency accumulation spectrum is：
Have according to the concept of energy in part：
Wherein b is constant, and Mb=E (∞), mb is the centre frequency of each sub- area, and angular frequency is divided into ωm=mb；
1e) coordinate of the projection according to extra large surface point (x, y, z) on datum water level be (x, y), then with η (x, y,
T) the extra large apparent height at t point (x, y) place is represented, it therefore follows that the Wave Model on point (x, y, z) place sea surface is：Z=η
(x,y,t)。
Step 2, determine that antenna main beam irradiates the scope on surface of plunging into the commercial sea.
The major part that back scattering occurs for radar illumination sea surface depends on antenna height, beam angle and wave beam aiming
This 3 factors of line grazing angle.
2a) set up one and set up antenna height for H, beam angle is 2 ψ, wave beam sight line grazing angle is that the lower of φ is regarded
The intersection point of radar, antenna main beam sensing y-axis direction, wave beam sight line and y-axis is point C, then radar beam boresight direction is：Wherein, RaFor radar site,I, j, k be respectively unit in three reference axis to
Amount；
Any point on the basis of 2b) reference picture 3, P (x, y, 0) on horizontal plane in radar footprint, then radar point to the point
Direction vector be：If radar beam is needle-like wave beam or conical beam, vector equation is obtained：
WhereinRepresent vectorWith vectorInner product, | | represent calculate a vector field homoemorphism value；
2c) according to above-mentioned vector equation, point P (x, y, 0) track is calculated：
Lycos φ+LHsin φ=(x2+y2+H2)1/2Lcos ψ,
It can obtain after arrangement：
x2cos2ψ-2yHcosφsinφ+y2(cos2ψ-cos2φ)=H2(sin2φ-cos2ψ),
For given radar altitude H, given wave beam sight line grazing angle φ and the given ψ of beam angle 2, work as φ
During ＞ ψ, the track of the point is hyperbola；As φ=ψ, the track of the point is parabola；As φ ＞ ψ, the track of the point is
Ellipse, the track of the point and its internal extra large surface that includes are the extra large surface range of determination.
Step 3, it is determined that extra large surface range in, construct triangle scattering unit.
When radar signal processor is sampled to the extra large surface of above-mentioned determination, the echo-signal in a received wave door, so will
Choose and sampled point is taken on a rectangle frame, the extra large surface in rectangle frame region, construct scattering unit.
3a) choose rectangle frame：
Reference picture 4, the rectangle frame that selection size is p × q, the length that p projects for the start-stop of ripple door in y-axis, q is true
Fixed extra large surface range it is longitudinally wide, then take sampled point on the extra large surface in the rectangle frame scope；Wherein it there may be
Some extra large surfaces not it is determined that extra large surface range in but in rectangle frame, because antenna beam can be added to this partial echo
Power weakens, and this part sea surface does not interfere with emulation.
3b) calculate the lateral separation of sampled point：
If the coordinate of radar is (xR,yR,zR), the coordinate at extra large surface any point is (x0,y0,z0), antenna main beam refers to
To y-axis direction, radar signal processor is on datum water level between equidistantly sampling along the y-axis direction, the transverse direction for calculating sampled point
It is divided into：
Wherein c is the light velocity, fsFor sample frequency, φ0For the grazing angle at the point, φs＜ φ0＜ φe, φs、φePoint
Not Wei ripple door section start, ripple door end at grazing angle,
Point (x0,y0,z0) from radar distance R0For：
Grazing angle is：
With y0Increase, the point is from distance by radar R0Grazing angle φ at increase, the point0Reduce, Δ R reduces, and works as y0＞ ＞
During H, the lateral separation of sampled point can abbreviation be：
3c) calculate the longitudinally spaced of sampled point：
3c1) calculate point (x0,y0,z0) relative to the radial velocity of radar：vr=vcos α0cosβ0,
Wherein v is the movement velocity of scattering unit, α0For azimuth,
β0For the angle of pitch,
3c2) calculate point (x0,y0,z0) Doppler frequency：Wherein fcCarried for signal
Frequently；
3c3) calculate point (x0,y0,z0) azimuth resolution：
By 3c2) in Doppler frequency fDTo α0Differential, i.e.,Obtain azimuth
Resolution ratio is：Wherein d () is infinitesimal；
3c4) computer azimuth angle segmentation interval：
The DOPPLER RESOLUTION of radar signal isWherein N is the umber of pulse in a coherent processing interval CPI,
TrFor the pulse repetition period, in order to keep DOPPLER RESOLUTION, it should there is d (fD)≤ΔfD, take d (fD)=Δ fD、
V takes the maximum for making Doppler not in fuzzy ranges, if ambiguous Doppler frequency range is notThen v
Maximum occurrences meet：By above-mentioned d (fD)、α0, v parameters be updated to 3c3) in azimuth resolution d (α0) in,
Calculate azimuth segmentation at intervals of：
To reach not ambiguous Doppler frequencyIf N span is：N≥2；To make δ division as fine as possible,
It can carry out taking a little for r times, r=1,2 ..., obtain { β1,β2,...,βr, take β0=min { β1,β2,...,βr}；
3c5) according to 3c4) in the coordinate s that projects on the y axis of azimuth segmentation interval δ and ripple door starting distance, calculate
The longitudinally spaced of extra large surface sampled point is s δ；
3d) sampled point is taken on the extra large surface in rectangle frame：
Reference picture 5, with lateral separationWith longitudinally spaced s δ sampled point, sampled point are taken on the extra large surface in rectangle frame
The black round dot being projected as shown in Fig. 5 (a) on datum water level, then a triangle scattering is constituted with every 3 sampled points
Unit, the extra large surface in rectangle frame is divided into the complex surface being spliced by many triangle scattering units, scattering unit
The right angled triangle being projected as shown in Fig. 5 (b) on datum water level.
Step 4, the parameter and echo power of any one triangle scattering unit are calculated.
Any one the triangle scattering unit of reference picture 6 and radar site relation, the triangle scattering unit is in horizontal plane
Some right angled triangle being projected as in Fig. 5 (b).The parameter of the triangle scattering unit includes：Triangle scattering unit with
The distance between radar R, azimuth angle alpha and angle of pitch β, arrival bearingNormal directionArea A0。
4a) calculate the parameter of triangle scattering unit：
Three apex coordinates of any one triangle scattering unit are expressed as (x1,y1,z1), (x2,y2,z2), (x3,
y3,z3), its center position coordinates is：
4a1) calculate the distance between the triangle scattering unit and radar：
4a2) calculate direction (α, β) of the triangle scattering unit under radar antenna coordinate system：
Azimuth angle alpha：
Angle of pitch β：
4a3) calculate the arrival bearing of the triangle scattering unit：
4a4) calculate the normal direction of the triangle scattering unit：
4a5) calculate the area of the triangle scattering unit：
4b) calculate the echo power of the triangle scattering unit：
4b1) calculate the local grazing angle of the triangle scattering unit：Its effective value
Scope is
4b2) the calculation formula provided according to Guinard and Dalcy, calculates the sea under horizontal polarization and vertical polarization
Scattering coefficient ΓHHWith ΓVV：
Wherein ε is complex dielectric permittivity：ε=ε '-j ε ", whereinFor imaginary number, ε ' expressions ε single order is led, and ε " represents ε second order
Lead, ε ' and ε " value can be obtained by tabling look-up,
Table 1 gives ε ' and the ε " value of some seawater complex dielectric permittivities in different frequency and temperature：
The complex dielectric permittivity of the seawater of table 1
4b3) radar scattering for selecting corresponding formula to calculate the triangle scattering unit according to the polarization mode of antenna is cut
Area：
During antenna horizontal polarization, the Radar Cross Section of the triangle scattering unit：σ=ΓHHΑ0,
When antennas orthogonal polarizes, the Radar Cross Section of the triangle scattering unit：σ=ΓVVΑ0；
The triangle scattering unit echo power 4b4) is calculated according to above-mentioned parameter：
Wherein PtFor radar transmission power, G (αF,βF；α, β) point to (α for wave beam sight lineF,βF) when (α, β) direction on
Antenna gain, λ is signal wavelength, LsFor radar transmit-receive composite loss.
Step 5, the echo model of triangle scattering unit is set up.
5a) calculate radar transmitting wave：
If radar transmitting wave is chirp pulse signal：
st(t)=rect (t/T) exp (j2 π fct)exp(jπΒt2),
Wherein T is pulse width, and B is signal frequency modulation rate,
5b) calculate the point scattering echo-signal of triangle scattering unit：
Wherein fdFor the Doppler frequency of triangle scattering unit, can by triangle scattering unit between two pulses it is relative
Estimated in the distance change of radar,Δ t is the time difference of two pulses；
5c) set up the echo model of triangle scattering unit：
Triangle scattering unit belongs to surface scattering unit, will not be smooth triangle scattering surface, therefore to consider sea
Contribution of the texture component in face to radar return, to 3b) in point scattering echo model phase delay add jitter simulation texture
The effect of component, obtains the echo model of triangle scattering unit：
Wherein ζ (t) shakes for phase delay, is that average is that zero, variance is σ0White Gaussian noise, represent the play of shake
Strong degree, it is relevant with sea situation.
Step 6, hiding relation between triangle scattering unit and the triangle scattering unit hiding relation of itself are judged.
In practice, can exist between sea triangle scattering unit and block, triangle scattering unit can also exist certainly in itself
Body is blocked, and is judged using ray trace and following principle and criterion：
If certain triangle scattering unit summit is α relative to the elevation angle of radar1, block unit summit is faced upward relative to radar
Angle is α2, work as α1≥α2When, the triangle scattering unit is blocked, and its echo is not calculated；Work as α1＜ α2When, triangle scattering is single
Member there is not occluded cell to block, then calculates the local incident angle α of the triangle scattering unitL, then judge that triangle scattering is single
First hiding relation of itself：
Work as αLDuring ＞ pi/2s, the triangle scattering unit is blocked by itself, and its echo is not calculated；
Work as αLDuring≤pi/2, triangle scattering unit is not blocked, calculates and is superimposed all triangle scatterings not being blocked
The echo of unit, produces the sea clutter emulation data of a coherent processing interval CPI echo, completes the simulation to sea clutter.
Step 7, the emulation data of sea clutter are analyzed.
The sea clutter of produced in step 6 coherent processing interval CPI echo 7a) is emulated into data storage is in size
In u × v matrix Q, wherein u is the umber of pulse that a CPI is included, and v is the number of range cell；
7b) change antenna height parameter, produce two groups of sea clutter emulation data, respectively Q1、Q2, every group takes u1It is individual
Pulse emulates data as the sea clutter of single pulse echo, is respectivelyWherein u1Represent umber of pulse；Draw respectivelyWithEmulation amplitude-range cell curve map, compare the amplitude of two curves；
7c) the sea clutter measured data Q of the single pulse echo gathered according to chirp-pulse compression radarreDraw reality
Survey amplitude-range cell curve map, willQreThe curve map of three is made comparisons, and analysis emulation amplitude-range cell is bent
The amplitude trend of line chart and actual measurement amplitude-range cell curve map is distributed；
7d) produce multigroup sea clutter emulation data, optional one group of Q3, two-dimentional reflectogram is drawn, v therein is selected1It is individual away from
Sea clutter from unit emulates dataIts amplitude-pulse curve figure and amplitude statistical distribution curve map are drawn, by its width
Spend statistical distribution curve and carry out the least mean-square error MSD test of fitness of fots, wherein v with conventional statistics distributed model curve1Table
Show range cell number.
Beneficial effects of the present invention are further illustrated with reference to specific the simulation results.
1. simulated conditions
As listed in table 2：
The simulation parameter of table 2
Emulation 1：Under the conditions of table 2, the extra large surface wave of slow time is emulated, as a result such as Fig. 7.When Fig. 7 shows 4 differences
The extra large surface X-Y scheme of the 100m × 100m at quarter emulation, shows the extra large surface Wave Model that the present invention is set up, can emulate the table that goes to sea
The dynamic change of face wave.
Emulation 2：The condition that antenna height is respectively H=30m and H=500m is added under the conditions of table 2, is imitated on extra large surface
True sea clutter, the sea clutter emulation data and the emulation data and measured data of sea clutter of com-parison and analysis different antennae height,
As a result such as Fig. 8.Wherein：
Fig. 8 (a) is emulation amplitude-range cell curve of the sea clutter of single pulse echo when antenna height is 30m
Figure；
Fig. 8 (b) is sea clutter emulation amplitude-range cell curve of single pulse echo when antenna height is 500m
Figure；
Fig. 8 (c) surveys the actual measurement of amplitude-range cell curve map, wherein sea clutter for the sea clutter of single pulse echo
Data are collected by linear frequency modulation LFM pulse compression radars, and the radar is located at certain mountain top and irradiates the Pacific Ocean, and antenna height is
500m, grazing angle is about 1 °, bandwidth 5MHz, the μ s of pulsewidth 42；
Compare Fig. 8 (a) and Fig. 8 (b) and understand that Fig. 8 (b) echo amplitudes are slightly larger compared with Fig. 8 (a) echo amplitudes, show the present invention
The sea clutter of generation meet sea clutter backscattering coefficient with the increase of wave beam sight line grazing angle increased conclusion；
Emulation amplitude-range cell curve map in Fig. 8 (a) and 8 (b) sees that all to show middle high both sides low from overall
Trend, it is consistent with actual measurement amplitude-range cell curve map trend in 8 (c), because Bo Menkai get is smaller, in ripple door
The scattering unit echo on both sides is not completely included into Bo Men.
Fig. 8 shows that the sea clutter that the present invention is produced has confidence level.
Emulation 3：It is highly 500m that fixed antenna is added under the conditions of table 2, and wave beam sight line grazing angle is 1 ° of bar
Part, emulates sea clutter, and least mean-square error MSD fittings are carried out to the amplitude statistical distribution and conventional statistics distributed model of sea clutter
Goodness is examined, as a result such as Fig. 9, wherein：
Fig. 9 (a) is the sea clutter artificial echo X-Y scheme at a coherent processing interval；
Fig. 9 (b) is sea clutter echo simulation amplitude-pulse curve figure of the 500th range cell；
Fig. 9 (c) is the amplitude statistical distribution of emulation amplitude-pulse curve figure and the fitting knot of conventional statistics distributed model
Really；
Fig. 9 (d) is the doppler spectral of the 500th range cell echo simulation data；
To emulating the result for using the least mean-square error MSD test of fitness of fots to obtain as shown in table 3 in Fig. 9 (c), by table
Preferably, rayleigh distributed fitting result takes second place 3 visible K fittings of distribution results；
The statistical distribution fitting result of table 3
The doppler spectral of the 500th range cell emulation data in Fig. 9 (d) has certain frequency displacement and spectrum width, because imitative
Triangle scattering unit is different relative to the azimuth of radar on true sea, and with the distance between radar and distance change not
Together；Doppler spectral can regard the speed mapping for the triangle scattering unit that sea is irradiated by antenna main beam, Fig. 9 (c) and Fig. 9 as
(d) it is consistent with conventional statistics modeling results.
Fig. 9 results show：The sea clutter simulation method of the present invention has practicality, can join for Research statistics model
Relation between number, radar running parameter and ambient parameter.
Claims (3)
1. the sea clutter simulation method based on wave spectrum model, including：
(1) it is theoretical according to random seaway, with any point (x, y) on wave height equation η (x, y, t) description datum water levels in t
The extra large apparent height at quarter, sets up the Wave Model on extra large surface, and the wherein amplitude in wave height equation is determined by wave spectral function；
(2) antenna height is set up for H, and beam angle is 2 ψ, and wave beam sight line grazing angle is φ head-down radar, according to antenna
Any point (x, y, z) and the position relationship of head-down radar, calculate the movement locus on extra large surface under main beam irradiation
x2cos2ψ-2yHcosφsinφ+y2(cos2ψ-cos2φ)=H2(sin2φ-cos2ψ), it is determined that the scope on extra large surface：As φ ＜
During ψ, extra large surface range is hyperbola and its internal sea surface；As φ=ψ, extra large surface range is parabola and its internal sea table
Face；As φ ＞ ψ, extra large surface range is oval and its internal sea surface；
(3) it is determined that extra large surface range, choose the rectangle frame that size is p × q, the horizontal sampling interval in the rectangle frame
TakeWith the rectangle frame inland sea surface arbitrfary point (x0,y0,z0) movement velocity v, azimuth angle alpha0, angle of pitch β0, keeping many
General Le resolution ratio and meet Doppler it is unambiguous under the conditions of calculate longitudinal sampling interval s δ, and be respectively with transverse and longitudinal intervalSampled point is taken on the extra large surface in rectangle frame with s δ, then a triangle scattering unit is constituted with every 3 sampled points, its
Middle c is the light velocity, fsFor radar signal sample frequency, s is that ripple door is originated in y-axis location of projection, and δ is that interval is split at azimuth,N is the umber of pulse in coherent processing interval CPI, and p is the length that is projected in y-axis of start-stop of ripple door, and q is true
Fixed extra large surface range it is longitudinally wide；
(4) parameter of any one triangle scattering unit is calculated：
(4a) calculates the triangle scattering unit and radar according to any one triangle scattering unit and the position relationship of radar
The distance between R, azimuth angle alpha and angle of pitch β, arrival bearingNormal directionArea A0, the wherein face of triangle scattering unit
Product A0, byCalculate；
(4b) calculates the echo power P of the triangle scattering unit according to radar equationr；
(5) echo model of establishment step (4) intermediate cam shape scattering unitWherein
st() is the linear frequency modulation LFM signals of radar emission, and ζ (t) shakes for phase delay,Represent imaginary number, fdDissipated for the triangle
Penetrate the Doppler frequency of unit；
(6) according to ray tracing principle, the hiding relation and triangle scattering unit itself between triangle scattering unit are judged
Hiding relation：
If certain triangle scattering unit summit is α relative to the elevation angle of radar1, block unit summit is relative to the elevation angle of radar
α2, work as α1≥α2When, the triangle scattering unit is blocked, and its echo is not calculated；Work as α1＜ α2When, the triangle scattering unit does not have
Occluded cell is blocked, then calculates the local grazing angle α of the triangle scattering unitL, then judge the triangle scattering unit
The hiding relation of itself：
Work as αLDuring ＞ pi/2s, the triangle scattering unit is blocked by itself, and its echo is not calculated；
Work as αLDuring≤pi/2, the triangle scattering unit is not blocked, calculates and is superimposed all triangle scattering lists not being blocked
The echo of member, produces the sea clutter emulation data of a coherent processing interval CPI echo, completes the simulation to sea clutter.
2. according to the method described in claim 1, setting up the Wave Model on extra large surface wherein in step (1), enter as follows
OK：
(1a) is theoretical according to random seaway, obtains the mathematical description of three dimensional random wave wave height equationWherein m represents angular frequency segmentation number, and M represents angular frequency
Maximum fractionation number, l is that number is split in direction, and L represents the maximum fractionation number in direction；kmFor the wave number of wave of the sea, ωmFor sea
The angular frequency of wave, εm,lFor random phase angle, ΦlThe direction of propagation for wave relative to x-axis；Am,lFor different angular frequencies and side
To simple sinusoidal ripple amplitude,ΔωmAnd ΔΦlω is represented respectivelymAnd ΦlIncrement, S
(ωm,Φl) it is that different frequency and the Wave energy in direction are distributed, S (ωm,Φl)=SΩ(ωm)D(Φl), SΩ(ωm) it is wave
Frequency spectral function, selects Pierson-Moskowitz wave spectrum models here：g
For acceleration of gravity, UwFor higher than the wind speed at extra large surface 19.5m；D(Φl) it is directivity function, using international ship model experimental tank
The suggestiveness form that meeting ITTC is proposed：
Any point (x, y, z) on extra large surface is projected on datum water level (x, y) point by (1b), is retouched with wave height equation η (x, y, t)
Extra large apparent height z of the point (x, y) in t is stated, the Wave Model for setting up extra large surface is：Z=η (x, y, t).
3. according to the method described in claim 1, wherein step (4) calculates the echo power P of the triangle scattering unitr, by such as
Lower formula is calculated：
<mrow>
<msub>
<mi>P</mi>
<mi>r</mi>
</msub>
<mo>=</mo>
<msqrt>
<mfrac>
<mrow>
<msub>
<mi>P</mi>
<mi>t</mi>
</msub>
<msup>
<mi>&lambda;</mi>
<mn>2</mn>
</msup>
<mi>&sigma;</mi>
</mrow>
<mrow>
<msup>
<mrow>
<mo>(</mo>
<mn>4</mn>
<mi>&pi;</mi>
<mo>)</mo>
</mrow>
<mn>3</mn>
</msup>
<msub>
<mi>L</mi>
<mi>s</mi>
</msub>
</mrow>
</mfrac>
</msqrt>
<mo>&CenterDot;</mo>
<mfrac>
<mrow>
<mi>G</mi>
<mrow>
<mo>(</mo>
<msub>
<mi>&alpha;</mi>
<mi>F</mi>
</msub>
<mo>,</mo>
<msub>
<mi>&beta;</mi>
<mi>F</mi>
</msub>
<mo>;</mo>
<mi>&alpha;</mi>
<mo>,</mo>
<mi>&beta;</mi>
<mo>)</mo>
</mrow>
</mrow>
<msup>
<mi>R</mi>
<mn>2</mn>
</msup>
</mfrac>
<mo>,</mo>
</mrow>
Wherein PtFor radar transmission power, λ is signal wavelength, LsFor radar transmit-receive composite loss, G (αF,βF；α, β) taken aim at for wave beam
Directrix points to (αF,βF) when (α, β) direction on antenna gain, σ be triangle scattering unit Radar Cross Section, it is by σ
=ΓHHA0Or σ=ΓVVA0Calculate, ΓHHFor the surface scattering coefficient under horizontal polarization,
ΓVVFor the surface scattering coefficient under vertical polarization,ε is multiple Jie
Electric constant, αLFor the local grazing angle of triangle scattering unit, it is by triangle scattering unit arrival bearingWith normal directionIt is determined that：
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| CN112255607B (en) * | 2020-09-30 | 2022-06-07 | 中国人民解放军海军工程大学 | Sea clutter suppression method |
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