CN106772284A - Consider radar far field prediction method in the formation of Layer Near The Sea Surface atmosphere environment impact - Google Patents

Abstract

The invention discloses a kind of radar far field prediction method in formation for considering Layer Near The Sea Surface atmosphere environment impact, comprise the following steps：According to radiation source radar setting height(from bottom) position in forming into columns, radar initial field distribution is calculated；(2) according to radar signal feature, Layer Near The Sea Surface air index model is set up；(3) according to the air index model on radiation source radar and observation station relative position, station-keeping radar propagation path, station-keeping radar electromagnetic signal propagated forward model is set up, the propagation attenuation factor for considering Layer Near The Sea Surface atmospheric effect is calculated using Two dimensional parabolic stability line algorithm；(4) shipborne radar pattern features are finally combined, the electromagnetic environment at far field, the prediction field intensity at calculating observation point in forming into columns is solved.The present invention considers radar far field intensity at the electromagnetic wave propagated forward model prediction observation station that Layer Near The Sea Surface Rough Sea Surfaces reflect, Layer Near The Sea Surface atmospheric environmental parameters influence by setting up, and ambient parameter can be provided for formation EMC analysis, for analysis of electromagnetic interference.

Description

Consider radar far field prediction method in the formation of Layer Near The Sea Surface atmosphere environment impact

Technical field

The invention belongs to ship electromagnetic compatibility prediction field, and in particular to a kind of consideration Layer Near The Sea Surface atmosphere environment impact Radar far field prediction method in forming into columns.

Background technology

With the development of naval's New Equipments, naval vessel is formed into columns has turned into the main operational mode of naval vessels, for abundant Play the fight capability on each naval vessel.With increase, the broadening of frequency spectrum, the continuing with frequency equipment quantity of various radar transmission powers The factors such as increase, electromagnetic environment is more complicated all the more in maritime formation, and the electromagnetic interference problem between platform becomes complex.It is no Then, once there is electromagnetic interference, overall fight capability of forming into columns certainly will be destroyed, has a strong impact on naval and carry out combat duty.To make Each platform of forming into columns can work to very reliable under electromagnetic environment in complicated formation and close coordination, it is necessary to eliminate whole formation Each high powered radar equipment of system and high sensitivity sensitive equipment interfere the influence for bringing, that is, ensure the electromagnetism of whole system Compatibility.

Therefore, being accomplished by the radar for electromagnetic environment principal element in forming into columns, far field calculating side in radar formation is set up Method, electromagnetic environment of the high powered radar at high sensitivity sensitive equipment in Accurate Prediction formation, and then it is dry to analyze sensitive equipment Response is disturbed, is control electromagnetic interference, properly settled emc issue and lay the foundation.In view of shipborne radar setting height(from bottom) limit System, radar emission is highly prone to the influences such as Layer Near The Sea Surface reflection, scattering, the shipborne radar in forming into columns in forming into columns during electromagnetic environment In the computation model of far field must with due regard to Layer Near The Sea Surface reflection, scattering etc. influence.

The content of the invention

The technical problem to be solved in the present invention is, for existing analysis of electromagnetic interference above shortcomings, there is provided a kind of Consider radar far field prediction method in the formation of Layer Near The Sea Surface atmosphere environment impact, the coarse sea of Layer Near The Sea Surface can be considered by setting up Radar far field intensity, energy at face reflection, the electromagnetic wave propagated forward model prediction observation station of Layer Near The Sea Surface atmospheric environmental parameters influence For formation EMC analysis provide ambient parameter, for analysis of electromagnetic interference.

The present invention is for the solution technical scheme that is used of above-mentioned technical problem：

Consider radar far field prediction method in the formation of Layer Near The Sea Surface atmosphere environment impact, comprise the following steps：

(1) according to radiation source radar setting height(from bottom) position and radar direction feature in forming into columns, radar initial fields point are calculated Cloth；

(2) according to radar signal feature, Layer Near The Sea Surface air index model is set up；

(3) according to the air index model on radiation source radar and observation station relative position, station-keeping radar propagation path, Station-keeping radar electromagnetic signal propagated forward model is set up, the biography for considering Layer Near The Sea Surface atmospheric effect is calculated using Two dimensional parabolic stability line algorithm Broadcast decay factor；

(4) shipborne radar pattern features are finally combined, the electromagnetic environment at far field in forming into columns is solved, according to consideration coastal waters The propagation attenuation factor of face atmospheric effect, the prediction field intensity at calculating observation point.

By such scheme, the step (1) is specially：

If radiation source pattern function is A (α) in forming into columns, antenna installation is highly H_t, then radar is in x₀Along height at position Initial field distribution u (x on short transverse z directions₀, z) computing formula is as follows：

ε′_r=ε_r+j60σλ (1c)

Wherein：k₀=2 π/λ is free-space propagation constant；λ is electromagnetic wavelength, is known quantity；α is antenna elevation angle, is Known quantity；R_||or⊥It is the horizontal or vertical reflectance factor in sea；P=k₀Sin α are free-space propagation constant in antenna elevation angle direction On projection；Z is terrain clearance on radar altitude direction；ε′_rIt is multiple relative dielectric constant, ε_r=ε/ε₀It is relative Jie of medium Electric constant, is known quantity, ε and ε₀The respectively dielectric constant of medium and vacuum, σ is sea water conductivity, is known quantity.

By such scheme, the step (2) is specially：

Atmospheric refraction index n is reduced to function only related to terrain clearance z, i.e. n=n (z)；

Reflect atmospheric strument using air index N, the relation between air index N and atmospheric refraction index n is

N=(n-1) × 10⁶ (2)

That is n=N/10⁶+1；

Calculated in level height in tens meters of altitude ranges, according to coastal waters in view of Radar emitter far field in forming into columns The characteristics of face atmospheric sphere sublayer, linear model, air index N are set up to the air index on station-keeping radar propagation path It is function only related to terrain clearance z, i.e. N=N (z), concrete model is as follows：

Wherein：N₀It is terrestrial refraction rate, is known quantity, dN/dz is gradients of the air index N on terrain clearance z, z Unit be km；It is exactly so-called normal atmospheric environment as dN/dh ≈ -40N/km.

By such scheme, the step (3) specifically includes following steps：

1) station-keeping radar electromagnetic signal propagated forward model is set up；

Under two-dimensional Cartesian coordinate system, if radar electromagnetic signal is horizontal polarized wave, only the electric field component E of non-zero_y； If radar electromagnetic signal is vertically polarized wave, only the magnetic-field component H of non-zero_y；Because no matter electric field component E_yOr magnetic-field component H_yTwo-dimentional scalar wave equation is satisfied by, in order to obtain general propagated forward model, two-dimentional scalar wave momentum ψ (x, z) of definition =H_yorE_y；So during radio wave propagation, ψ (x, z) meets following two dimension scalar wave equation：

In formula,It is medium refractive index, in rectangular coordinate system, the hamonic function used by solving wave equations (4) Usually e^-jkxForm, therefore, definition is along the wave function of x-axis forward-propagating

Formula (5) is brought into formula (4), is obtained：

In in view of station-keeping radar electromagnetic signal communication process, medium refractive index n (z) changes little with apart from x, i.e.,Formula (6) is then decomposed into two on the Parabolic Equation apart from x：

In formula, Q is referred to as pseudo-differential operator, and

Formula (7a) is exactly the Two dimensional parabolic stability line equation of the station-keeping radar electromagnetic signal propagated forward under rectangular coordinate system, is Station-keeping radar electromagnetic signal propagated forward model；Formula (7b) is the station-keeping radar electromagnetic signal back-propagating under rectangular coordinate system Equation, it is nonsensical to research station-keeping radar signal propagation attenuation, no longer it is analyzed；

2) for formula (7a), the distribution Fourier solution for using Fourier transform, obtaining (7a) is following formula：

Wherein, Δ x is mesh generation size on wave line, is known quantity；

For formula (8), algorithm flow is set up, specific calculating process is as follows：

1. formula (1a) is utilized, radar initial field distribution u (x are calculated₀,z)；

2. Fourier transform is utilized, auxiliary variable T (x are solved₀, p), F () represents Fourier transform：

3. inverse fourier transform is utilized, auxiliary variable TT (x are solved₀, z), F^-1() represents Fourier transform：

TT(x₀, z)=F^-1(T(x₀,p)) (10)

4. x is calculated₀U (x at+Δ x₀+Δx,z)：

Thus by radar initial field distribution u (x₀, z) calculating radar signal travels to x₀Field distribution at+Δ x.

5. repeat step 2.~4. iteration step to and intend calculating the field at position, that is, obtain field in whole zoning point Cloth u (x, z)；Exponential term in above-mentioned iterative processBarrier on path is reflected to make the diffraction of radar electromagnetic signal With,Reflect transmitting, refraction effect of the Layer Near The Sea Surface air medium to electromagnetic wave；

6. propagation attenuation factor PL (x, z) at any observation station for considering Layer Near The Sea Surface atmospheric effect is calculated according to formula (11)

PL (x, z)=| u (x, z)/u (x₀,z)| (12)

Wherein u (x, z) is the normalization field intensity at observation station (for power of radiation source and the normalization field intensity of gain).

By such scheme, the step (4) is specially：

Assuming that radar power is P, gain is G on observation station direction, and distance by radar observation station distance is R, then observation station The actual field intensity E (x, z) at (x, z) place is：

Beneficial effects of the present invention：

1st, the present invention does not rely on the type of D shipborne radar, and any antenna type can be using this computational methods come fast Field intensity at speed prediction radar antenna far field.

2nd, the present invention has taken into full account near field face air folding by air index model and Sea surface boundary condition model The influence to shipborne radar far-field distribution such as penetrate, reflect.

3rd, what the present invention set up considers the shipborne radar far field computational methods of Layer Near The Sea Surface influence, and all-wave numerical prediction side Method is compared, and can disclose the physical mechanism that shipborne radar far field is influenceed by sea from physical layer.

Brief description of the drawings

Fig. 1 is that station-keeping radar reflects schematic diagram across the sea；

Fig. 2 is station-keeping radar electromagnetic signal propagation model distribution Fourier calculation flow chart；

Fig. 3 is the atmospheric transmission factor figure of Layer Near The Sea Surface；

Fig. 4 is the field intensity map with sensitive equipment (observation station) height change.

Specific embodiment

Technical solution of the present invention is described in detail with example below in conjunction with the accompanying drawings.

Radar far field prediction method in the formation for considering Layer Near The Sea Surface atmosphere environment impact of the present invention, including following step Suddenly：

(1) station-keeping radar according to Fig. 1 reflects schematic diagram across the sea, obtains interior radiation source radar installation height of forming into columns Degree position, interior radiation source pattern function of forming into columns is A (α), and antenna installation is highly H_t, radar is calculated in x₀Along height at position Initial field distribution on the z directions of direction.

(2) according to radar signal feature, Layer Near The Sea Surface air index model is set up；

Can be influenceed by Layer Near The Sea Surface stratified atmosphere in view of propagation in the formation of radar electromagnetic signal, this influence air Refractive index n is described, and in general, atmospheric refraction index n has spatial distribution heterogeneous, this allows for radio wave and exists Spread speed in air is less than the light velocity, and corresponding spatial variations are presented, so as to cause the deflection of wave surface；

Substantial amounts of test shows that Layer Near The Sea Surface air is bigger by 1 to 3 than its change in the horizontal direction in the change of vertical direction Individual magnitude, therefore, in the range of tail clearance, the change in atmospheric level direction can be ignored, and nearly marine atmospheric is considered as ball Face hierarchy, so that atmospheric refraction index n is reduced to function only related to terrain clearance z, i.e. n=n (z)；

Although atmospheric refraction index n distributions are different, 1 is all generally in close proximity to, in general, n ≈ on sea Between 1.00026~1.00046；For the ease of studying and applying, atmospheric strument is generally reflected using air index N；Examine Consider Radar emitter far field in formation to calculate in level height in tens meters of altitude ranges, according to Layer Near The Sea Surface air sphere The characteristics of layering, set up linear model to the air index on station-keeping radar propagation path, air index N for only with it is liftoff Height z related function, i.e. N=N (z).

(3) according to the air index model on radiation source radar and observation station relative position, station-keeping radar propagation path, Set up station-keeping radar electromagnetic signal propagated forward model, station-keeping radar electromagnetic signal propagation model distribution Fourier solution calculation process As shown in Fig. 2 calculating the propagation attenuation factor for considering Layer Near The Sea Surface atmospheric effect using Two dimensional parabolic stability line algorithm；

(4) shipborne radar pattern features are finally combined, the electromagnetic environment at far field in forming into columns is solved, according to consideration coastal waters The propagation attenuation factor of face atmospheric effect, the prediction field intensity at calculating observation point.

In embodiment, simulation calculation information is as follows：Certain shipborne radar is highly 40m, working frequency 1GHz, and distance observation is quick Apart from 6km, gain is 30dB to sense equipment, and radiation source 3dB beam angles are 3 degree, and directivity angle is 0 degree.

According to radar far field prediction method in the formation based on Two dimensional parabolic stability line algorithm proposed by the present invention, observation is calculated The transmission factor of point height change, the atmospheric transmission factor of Layer Near The Sea Surface is as shown in Figure 3；And shipborne radar environment distribution Curve, the field strength distribution with sensitive equipment (observation station) height change is as shown in Figure 4.In order to be compared, also given in figure The result of calculation of Double line model.What the present invention set up considers the shipborne radar far field computational methods of Layer Near The Sea Surface influence, and entirely Ripple Numerical Predicting Method is compared, and can disclose the physical mechanism that shipborne radar far field is influenceed by sea from physical layer.

Obviously, above-described embodiment is only intended to clearly illustrate example of the present invention, and is not to of the invention The restriction of implementation method.For those of ordinary skill in the field, what spirit under this invention was extended out is aobvious and easy Among the change or variation seen are still in protection scope of the present invention.

Claims (5)

1. radar far field prediction method in the formation of Layer Near The Sea Surface atmosphere environment impact is considered, it is characterised in that comprised the following steps：

(1) according to radiation source radar setting height(from bottom) position and radar direction feature in forming into columns, radar initial field distribution is calculated；

(2) according to radar signal feature, Layer Near The Sea Surface air index model is set up；

(3) according to the air index model on radiation source radar and observation station relative position, station-keeping radar propagation path, set up Station-keeping radar electromagnetic signal propagated forward model, is calculated using Two dimensional parabolic stability line algorithm and considers that the propagation of Layer Near The Sea Surface atmospheric effect declines Subtracting coefficient；

(4) shipborne radar pattern features are finally combined, the electromagnetic environment at far field in forming into columns is solved, it is big according to consideration Layer Near The Sea Surface The propagation attenuation factor of gas influence, the prediction field intensity at calculating observation point.

2. radar far field prediction method in the formation for considering Layer Near The Sea Surface atmosphere environment impact according to claim 1, it is special Levy and be, the step (1) is specially：

If radiation source pattern function is A (α) in forming into columns, antenna installation is highly H_t, then radar is in x₀Along height at position Initial field distribution u (x on the z directions of direction₀, z) computing formula is as follows：

$u(x_0,z)={\mathrm{ie}}^{i\mathrm{\π}/4}\sqrt{\frac{2k_0}{\mathrm{\π}}}\underset{0}{\overset{+\mathrm{\∞}}{\∫}}\frac{\[A\left(\mathrm{\α}\right)e^{-{\mathrm{ipH}}_t}+R_{\left|\right|or\⊥}A(-\mathrm{\α})e^{{\mathrm{ipH}}_t}\]sin\left(pz\right)}{{(k_0^2-p^2)}^{1/4}}dp---\left(1a\right)$

$R_{\left|\right|}=\frac{\sin \mathrm{\α}-\sqrt{{\mathrm{\ϵ}}_r^{\′}-{\cos }^2\mathrm{\α}}}{\sin \mathrm{\α}+\sqrt{{\mathrm{\ϵ}}_r^{\′}-{\cos }^2\mathrm{\α}}},R_{\⊥}=\frac{{\mathrm{\ϵ}}_r^{\′}\sin \mathrm{\α}-\sqrt{{\mathrm{\ϵ}}_r^{\′}-{\cos }^2\mathrm{\α}}}{{\mathrm{\ϵ}}_r^{\′}\sin \mathrm{\α}+\sqrt{{\mathrm{\ϵ}}_r^{\′}-{\cos }^2\mathrm{\α}}}---\left(1b\right)$

ε'_r=ε_r+j60σλ (1c)

Wherein：k₀=2 π/λ is free-space propagation constant；λ is electromagnetic wavelength, is known quantity；α is antenna elevation angle, is known Amount；R_||or⊥It is the horizontal or vertical reflectance factor in sea；P=k₀Sin α are free-space propagation constant on antenna elevation angle direction Projection；Z is terrain clearance on radar altitude direction；ε'_rIt is multiple relative dielectric constant, ε_r=ε/ε₀For the relative dielectric of medium is normal Number, is known quantity, ε and ε₀The respectively dielectric constant of medium and vacuum, σ is sea water conductivity, is known quantity.

3. radar far field prediction method in the formation for considering Layer Near The Sea Surface atmosphere environment impact according to claim 2, it is special Levy and be, atmospheric refraction index n is reduced to function only related to terrain clearance z, i.e. n=n (z)；

Reflect atmospheric strument using air index N, the relation between air index N and atmospheric refraction index n is

N=(n-1) × 10⁶ (2)

That is n=N/10⁶+1；

Calculated in level height in tens meters of altitude ranges in view of Radar emitter far field in forming into columns, it is big according to Layer Near The Sea Surface The characteristics of gas spherically stratified ionosphere, linear model is set up to the air index on station-keeping radar propagation path, air index N is for only The function related to terrain clearance z, i.e. N=N (z), concrete model are as follows：

$N\left(z\right)=N_0+\frac{dN}{dz}z---\left(3\right)$

Wherein：N₀It is terrestrial refraction rate, is known quantity, dN/dz is gradients of the air index N on terrain clearance z, the unit of z It is km；It is exactly so-called normal atmospheric environment as dN/dh ≈ -40N/km.

4. radar far field prediction method in the formation for considering Layer Near The Sea Surface atmosphere environment impact according to claim 3, it is special Levy and be, the step (3) specifically includes following steps：

1) station-keeping radar electromagnetic signal propagated forward model is set up；

Under two-dimensional Cartesian coordinate system, if radar electromagnetic signal is horizontal polarized wave, only the electric field component E of non-zero_y；If thunder It is vertically polarized wave, the then only magnetic-field component H of non-zero up to electromagnetic signal_y；Because no matter electric field component E_yOr magnetic-field component H_y Meet two-dimentional scalar wave equation, in order to obtain general propagated forward model, two-dimentional scalar wave momentum ψ (x, z) of definition= H_yorE_y；So during radio wave propagation, ψ (x, z) meets following two dimension scalar wave equation：

$\frac{{\∂}^2\mathrm{\ψ}}{\∂x^2}+\frac{{\∂}^2\mathrm{\ψ}}{\∂z^2}+k_0^{2}n{\left(z\right)}^2\mathrm{\ψ}=0---\left(4\right)$

In formula,It is medium refractive index, in rectangular coordinate system, the hamonic function used by solving wave equations (4) is usual It is e^-jkxForm, therefore, definition is along the wave function of x-axis forward-propagating

$u(x,z)=e^{-{\mathrm{jk}}_{0}x}\mathrm{\ψ}(x,z)---\left(5\right)$

Formula (5) is brought into formula (4), is obtained：

$\frac{{\∂}^{2}u}{\∂x^2}+2{\mathrm{jk}}_0\frac{\∂u}{\∂x}+\frac{{\∂}^{2}u}{\∂z^2}+k_0^2(n{\left(z\right)}^2-1)u=0---\left(6\right)$

In in view of station-keeping radar electromagnetic signal communication process, medium refractive index n (z) changes little with apart from x, i.e.,Formula (6) is then decomposed into two on the Parabolic Equation apart from x：

$\frac{\∂u}{\∂x}=-{\mathrm{jk}}_0(1-Q)---\left(7a\right)$

$\frac{\∂u}{\∂x}=-{\mathrm{jk}}_0(1+Q)u---\left(7b\right)$

In formula, Q is referred to as pseudo-differential operator, and

$Q=\sqrt{\frac{1}{k_0^2}\frac{\∂}{\∂z^2}+n{\left(z\right)}^2}$

Formula (7a) is exactly the Two dimensional parabolic stability line equation of the station-keeping radar electromagnetic signal propagated forward under rectangular coordinate system, is to form into columns Radar electromagnetic signal propagated forward model；Formula (7b) is the side of the station-keeping radar electromagnetic signal back-propagating under rectangular coordinate system Journey, it is nonsensical to research station-keeping radar signal propagation attenuation, no longer it is analyzed；

2) for formula (7a), the distribution Fourier solution for using Fourier transform, obtaining (7a) is following formula：

$u(x_0+\mathrm{\Δ}x,z)=e^{\frac{-{\mathrm{jk}}_0}{2}\left(n^2\right(x,z)-1)\mathrm{\Δ}x}{F}^{-1}\left(e^{\frac{j\mathrm{\Δ}x}{2k_0}{p}^2}F\right(u\left(x_0,z\right)\left)\right)---\left(8\right)$

Wherein, Δ x is mesh generation size on wave line, is known quantity；

For formula (8), algorithm flow is set up, specific calculating process is as follows：

1. formula (1a) is utilized, radar initial field distribution u (x are calculated₀,z)；

2. Fourier transform is utilized, auxiliary variable T (x are solved₀, p), F () represents Fourier transform：

$T(x_0,p)=e^{\frac{j\mathrm{\Δ}x}{2k_0}{p}^2}F\left(u\right(x_0,z\left)\right)---\left(9\right)$

3. inverse fourier transform is utilized, auxiliary variable TT (x are solved₀, z), F^-1() represents Fourier transform：

TT(x₀, z)=F^-1(T(x₀,p)) (10)

4. x is calculated₀U (x at+Δ x₀+Δx,z)：

$u(x_0+\mathrm{\Δ}x,z)=e^{\frac{-{\mathrm{jk}}_0}{2}\left(n^2\right(x,z)-1)\mathrm{\Δ}x}TT(x_0,z)---\left(11\right)$

Thus by radar initial field distribution u (x₀, z) calculating radar signal travels to x₀Field distribution at+Δ x.

5. repeat step 2.~4. iteration step to intend calculate position at field, that is, obtain the field distribution u in whole zoning (x,z)；Exponential term in above-mentioned iterative processDiffraction of the barrier to radar electromagnetic signal on path is reflected,Reflect transmitting, refraction effect of the Layer Near The Sea Surface air medium to electromagnetic wave；

6. propagation attenuation factor PL (x, z) at any observation station for considering Layer Near The Sea Surface atmospheric effect is calculated according to formula (11)

PL (x, z)=| u (x, z)/u (x₀,z)| (12)

Wherein u (x, z) is the normalization field intensity at observation station.

5. radar far field prediction method in the formation for considering Layer Near The Sea Surface atmosphere environment impact according to claim 4, it is special Levy and be, the step (4) is specially：

Assuming that radar power is P, gain is G on observation station direction, and distance by radar observation station distance is R, then observation station (x, z) Place actual field intensity E (x, z) be：

$E(x,z)=\sqrt{P*(G-PL(x,z\left)\right)*h/(4*\mathrm{\π}*R^2)}---\left(13\right).$