CN103278804A - Waveguide over-the-horizon radar - Google Patents

Abstract

The invention discloses a waveguide over-the-horizon radar. The waveguide over-the-horizon radar is provided with a sensor unit, a waveguide calculation module and an over-the-horizon evaluation module, wherein the sensor unit measures hydro meteorology data which at least comprise sea surface water temperature, sea surface atmospheric temperature, wind speed and atmospheric humidity, the waveguide calculation module calculates atmospheric stability by calculating a Richardson number Ri and the length L' of a Monin-Obukhov dimension according to environmental parameters collected by the sensor unit, the waveguide calculation module calculates waveguide height and an atmospheric correction refractive index for evaporating a waveguide under the state of different atmospheric stabilities, and the over-the-horizon evaluation module judges whether a current radar has over-the-horizon performance or not according to the waveguide height and the atmospheric correction refractive index output by the waveguide calculation module. When the waveguide over-the-horizon radar works, the over-the-horizon evaluation module calculates the trapping frequency of the current radar according to the waveguide height and the atmospheric correction refractive index, and when the trapping frequency is larger than the inherent frequency of the current radar, and the waveguide height is larger than the height of a radar antenna, the fact that the current radar has the over-the-horizon performance is judged. Meanwhile, the size of a target under the over-the-horizon state can also be accurately judged.

Description

A kind of waveguide over-the-horizon radar

Technical field

The present invention relates to a kind of waveguide over-the-horizon radar and over the horizon decision method thereof.

Background technology

Up to now, still stand to such an extent that high looking far is guiding theory, to extra large radar antenna as far as possible frame to highest point, no matter can both see such layout aboard ship or on the longshore high mountain.Because earth curvature influence, the electromagnetic wave that radar sends and eye can see light wave the same all be rectilinear propagation, therefore be difficult to see outward anything of earth curvature.People are called the maximum visual distance to this phenomenon.How to see that the outer over the horizon target of earth curvature is the human dream of exploring always and pursuing.This invention has utilized the sea to occur the evaporation waveguide phenomenon often exactly---and be that the boundary layer that atmosphere and seawater intersect forms a kind of waveguide phenomenon.Allow the electromagnetic wave of radar antenna emission in waveguide, propagate, detect sighting distance over the horizon target in addition thereby just overcome the earth curvature influence.

In addition, selecting navar to improve, mainly is navar popularity rate height now, and it is convenient to improve, and navar can play key effect to navigation at night and greasy weather navigation.This invention provides technical support for navar improvement from now on, increase over the horizon warning function just.

Summary of the invention

The present invention is directed to the proposition of above problem, and development

A kind of waveguide over-the-horizon radar has:

Measure the sensor unit of the hydrometeorological data that comprise sea table water temperature, sea atmospheric temperature, wind speed and atmospheric humidity at least;

According to the described environmental parameter that described sensor unit is gathered, calculate described atmospheric stability by calculating Richardson number Ri and Monin-Obukhov scale length L '; Under the state of different atmospheric stabilities, calculate the waveguide computing module of the Atmospheric corrections refractive index of sea evaporation waveguide height and sea evaporation waveguide;

According to the described environmental parameter that described sensor unit is gathered, calculate described atmospheric stability by calculating Richardson number Ri and Monin-Obukhov scale length L '; Under the state of different atmospheric stabilities, calculate the waveguide computing module of the Atmospheric corrections refractive index of sea evaporation waveguide height and sea evaporation waveguide;

According to sea evaporation waveguide height and the Atmospheric corrections refractive index of described waveguide computing module output, judge whether current radar has the over the horizon assessment mould module of over the horizon performance;

During work, described over the horizon evaluation module is according to described duct height and Atmospheric corrections refractive index, calculate the trapping frequency of current sea evaporation waveguide, when described trapping frequency during greater than the natural frequency of current radar, and duct height is higher than height of radar antenna, judges that current radar has the over the horizon performance.

Also have the radar range evaluation module: by the radar return power of more different transmission ranges and the minimum detectable signal power of radar: if at the radar return power of inner certain distance of the sea evaporation waveguide minimum detectable signal power greater than radar, then current distance is the detectable distance of radar.

Also has radargrammetry error evaluation module: whether receive the initial elevation angle that current sea evaporation waveguide height that described waveguide computing module draws and Atmospheric corrections refractive index judge current radar greater than zero, calculate the total length in multilayer waveguide space (comprising sea evaporation waveguide and space waveguide), propagated at the ray that radar antenna sends and the overall height in multilayer space according to ray theory, compare apart from the actual range of radar and the apparent height of target with target, obtain height error and the distance error of radargrammetry.

The adjustable height of described sensing system: according to sea evaporation waveguide height and the current antenna height that described waveguide computing module calculates, rise or fall radar antenna, described radar wave is propagated in waveguide.

The changeable frequency of described sensing system, the trapping frequency of the current sea evaporation waveguide that calculates according to described over the horizon assessment mould module, the adjustment to self frequency is carried out makes described radar frequency greater than the trapping frequency of current sea evaporation waveguide.

Has the target identification module: calculate radar wave regularity of energy distribution in the evaporation waveguide pipe of sea by the radar emission power meter, for the over the horizon target, according to the energy of echo strength divided by this point of radar emission power in waveguide, just can judge the size of over the horizon target, target sizes can be divided into general objective, middle target and little target.

The computing formula that described waveguide computing module calculates Richardson number Ri is:

$R_i=\frac{g}{T}\·\frac{\∂\mathrm{\θ}/\∂z}{{(\∂u/\∂z)}^2}$

When 0＜Ri＜1, current atmosphere is in neutrality or steady state (SS), when Ri＜0, judges that current atmosphere plays pendulum;

The Monion-Obukhov length L ' computing formula be:

$L^{\′}=\frac{u^{*}\∂u/\∂T}{\mathrm{kg}\∂\mathrm{\θ}/\∂T},$ U wherein ^*Be friction velocity $u^{*}=\sqrt{\frac{\mathrm{\τ}}{\mathrm{\ρ}}},$ τ is shearing stress;

Sea evaporation waveguide height for (0＜Ri＜1) under neutral and the stable atmospheric conditions:

$Z^{*}=\frac{{\mathrm{\ΔN}}_P}{-0.125({\log }_e\left(\frac{h_1}{h_0}\right)+\frac{5.2h_1}{L^{\′}})-\frac{5.2{\mathrm{\ΔN}}_p}{L^{\′}}},$ Wherein $L^{\′}=\frac{u^{*}\∂u/\∂T}{\mathrm{kg}\∂\mathrm{\θ}/\∂T}$

Np is the potential index of refraction, h ₀Be sea level height, h ₀=0.00000015, h ₁Be sensor height;

Work as z ^*＜0 o'clock or

＞1 o'clock, then:

$Z^{*}=\frac{{\mathrm{\ΔN}}_P(1+5.2)+0.65h_1}{-0.125{\log }_e\left(\frac{h_1}{h_0}\right)}$

For (R under the instability condition _i＜0 o'clock) sea evaporation waveguide height:

$Z^{*}=\frac{1}{\sqrt[4]{{\mathrm{\φ}}^4-\frac{18}{L^{\′}}{\mathrm{\φ}}^3}}$ φ is flux profile function

Wherein $\mathrm{\φ}=\frac{-0.125B}{{\mathrm{\ΔN}}_p},$ $B={\log }_e\left[\frac{h_1}{h_0}\right]-\mathrm{\ψ}$ B is flux profile parameter, and ψ is flux profile function;

The Atmospheric corrections refractive index of evaporation waveguide is under stable or neutral atmosphere state

$M\left(h\right)=M_s+\frac{h}{8}-\left[\frac{0.125Z^{*}}{1+\frac{5.2Z^{*}}{L^{\′}}}\right][{\log }_e\left(\frac{h_0+h}{h_0}\right)-\frac{5.2h}{L^{\′}}]$

Under the rough atmosphere state, the Atmospheric corrections of evaporation waveguide refraction ladder is

$M\left(h\right)=M_s+\frac{h}{8}-\left[\frac{0.125Z^{*}}{\mathrm{\φ}\left(\frac{Z^{*}}{L^{\′}}\right)}\right][{\log }_e\left(\frac{h_0+h}{h_0}\right)-\mathrm{\ψ}\left(\frac{Z^{*}}{L^{\′}}\right)],$ Wherein Ms is at h ₀The Atmospheric corrections refractive index of height can directly be measured.

Described over the horizon assessment mould module is calculated the electromagnetic maximum wavelength of described sea evaporation waveguide trapping and is:

${\mathrm{\λ}}_{\max }=\frac{8\sqrt{2}\×{10}^{-3}}{3}\·{\∫}_{z_0}^d\sqrt{M\left(z\right)-M\left(d\right)}\mathrm{dz}$ （m）

All the time d is sea evaporation waveguide height, is described Z*, and z represents differing heights, M(z) is the Atmospheric corrections refractive index of differing heights, z ₀Be sea level height;

Calculating the electromagnetic low-limit frequency of described evaporation waveguide trapping is:

$f_{\min }=\frac{c}{{\mathrm{\λ}}_{\max }}=\frac{79.49449}{{\∫}_{z_0}^d\sqrt{M\left(z\right)-M\left(d\right)}\mathrm{dz}}$ (GHz) in the formula, c is the light velocity (2.997925.10 ⁸M/s).

The method of work of described radar range evaluation module is as follows:

The target echo power that radar receives can be write as the form of one-way propagation loss:

P _r＝-8.55+10log ₁₀(P _tσf ²)+2G-L _s-L _a-2L _single

Receive theory according to radar, the minimum detectable signal power of radar is S _Imin, determined by the radar receiver performance,

$S_{i\min }=k{T}_0{B}_n{F}_0{D}_0={\mathrm{kT}}_0{B}_n{F}_0{\left(\frac{S_0}{N_0}\right)}_{\min }$

K is Boltzmann constant, k=1.38 * 10 ^-23(J/K); T is resistance temperature, with absolute temperature (K) metering, for 17 ℃ of room temperatures, T=T ₀=290K; B _nBe the passband of equipment,

τ is pulse width; F ₀Be the noise figure of receiver, Be the minimum signal to noise ratio (S/N ratio) of receiver output terminal;

When the power P that receives _rGreater than S _IminThe time, radar could be found target reliably, works as P _rJust in time equal S _IminThe time, just obtain the maximum operating range R of this target of detections of radar _Max, and P _rLess than S _IminThe time, target is in the radar electromagnetism blind area.

The method of work of described error-detecting module is as follows:

Use ray theory, set up the evaluation profile-raytrace pattern of radar range finding and altimetry error.

By Snell rule, α ₂Can obtain by following formula,

$\cos {\mathrm{\α}}_2=[1+(N_1-N_2)\×{10}^{-6}-\frac{\mathrm{dir}\·\mathrm{dh}}{r_0+h_1}]\cos {\mathrm{\α}}_1$

Dir is directions of rays, when ray is upwards propagated, and dir=1, when ray is propagated downwards, dir=-1, Ψ ₁Be bending of a ray angle,

${\mathrm{\Ψ}}_1=\frac{2(N_1-N_2)\×{10}^{-6}}{\tan {\mathrm{\α}}_1+\tan {\mathrm{\α}}_2}$

β is geocentric angle, according to Abel, and et.al, 1982,

β ₁＝Ψ ₁+α ₂-α ₁

According to the cosine law, TRGAPP1 represents that ray in the length of this sheaf space, can be obtained by following formula

${\mathrm{TRG}}_{\mathrm{APP}!}=\sqrt{{(r_0+h_1)}^2+{(r_0+h_2)}^2-2(r_0+h_1)(r_0+h_2)\cos {\mathrm{\β}}_1}$

Calculate TRGAPP1 and the β of each layer by iteration ₁, the result adds up with gained, can obtain the total length TRG that ray is propagated in the space _APPWith total geocentric angle β _Total

${\mathrm{TAG}}_{\mathrm{APP}}=\underset{l=1}{\overset{L}{\mathrm{\Σ}}}{\mathrm{TRG}}_{\mathrm{APPl}}$

${\mathrm{\β}}_{\mathrm{total}}=\underset{l=1}{\overset{L}{\mathrm{\Σ}}}{\mathrm{\β}}_1$

Target is TRG apart from the actual range of radar, is obtained by following formula:

$\mathrm{TRG}=\sqrt{{(r_0+h_{\mathrm{REL}})}^2+{(r_0+h_n)}^2-2(r_0+h_{\mathrm{REL}})\left(r_0{+h}_n\right)\cos {\mathrm{\β}}_{\mathrm{total}}}\·$

Then the distance error of target is:

TRGERR＝TRG _APP-TRG

The apparent height of target is THTAPP, uses 4/3 equivalent earth's radius, and actual ray is become approximate straight line, and gained target apparent height is:

${\mathrm{THT}}_{\mathrm{APP}}=\sqrt{{[4/3(r_0+h_{\mathrm{REL}})]}^2+{{\mathrm{TRG}}_{\mathrm{APP}}}^2-2[4/3(r_0+h_{\mathrm{REL}})]{\mathrm{TRG}}_{\mathrm{APP}}\cos {\mathrm{\α}}_0}-4/3(r_0+h_n)$

Can obtain the height error of target:

THTERR＝THT _APP-h _n

Utilize above-mentioned formula, the program that the available simulation ray that programs is propagated in the space is assessed the height and distance error of radargrammetry.

Owing to adopted technique scheme, provided by the invention hypo is led over-the-horizon radar, the evaporation waveguide phenomenon that can effectively utilize the sea to occur often realizes over-the-horizon detection owing to overcome the earth curvature influence and makes that warning becomes effectively to the target over the horizon.The objective of the invention is to improve target over the horizon monitoring validity, reliability, realize that simultaneously the accurate judgement of over the horizon target sizes is surveyed.

Description of drawings

Technical scheme for clearer explanation embodiments of the invention or prior art, to do one to the accompanying drawing of required use in embodiment or the description of the Prior Art below introduces simply, apparently, accompanying drawing in describing below only is some embodiments of the present invention, for those of ordinary skills, under the prerequisite of not paying creative work, can also obtain other accompanying drawing according to these accompanying drawings.

Fig. 1 is module diagram of the present invention

Fig. 2 is the workflow diagram of waveguide computing module of the present invention

Fig. 3 is over the horizon evaluation module workflow diagram of the present invention

Fig. 4 is principle of work Fig. 1 of radargrammetry error evaluation module of the present invention

Fig. 5 is principle of work Fig. 2 of radargrammetry error evaluation module of the present invention

Fig. 6 is the synoptic diagram of modified index of refraction in the embodiment of the invention 1

Fig. 7 is the spatial distribution map of radar one way Craft Loss in the embodiment of the invention 1

Fig. 8 be in the embodiment of the invention 1 radar under different communication environments to the maximum detectable range synoptic diagram of differing heights target

The shore line synoptic diagram that Fig. 9 obtains under the waveguide condition for radar in the embodiment of the invention 1

Figure 10 is the sea book of boats and ships in the embodiment of the invention 1

The synoptic diagram that Figure 11 propagates in the evaporation waveguide of sea for radar of the present invention

Embodiment

For the purpose, technical scheme and the advantage that make embodiments of the invention is clearer, below in conjunction with the accompanying drawing in the embodiment of the invention, the technical scheme in the embodiment of the invention is known complete description:

A kind of waveguide over-the-horizon radar mainly comprises: waveguide computing module and over the horizon evaluation module.

Multiple hydrometeorological data such as comprising temperature, atmospheric temperature, wind speed and atmospheric humidity at least can be measured and provide to sensor unit.

The waveguide computing module can be according to the described described multiple water temperature weather data that provides, by calculating the Atmospheric corrections refractive index that Richardson number Ri calculates described atmospheric stability with Monin-Obukhov scale length L ' and can calculate duct height and evaporation waveguide under the state of the different atmospheric stabilities that calculate.

Over the horizon assessment mould module is used for receiving and according to duct height and Atmospheric corrections refractive index that described waveguide computing module is exported, judging whether current radar has the over the horizon performance.

Under the duty, described sensor unit at first obtains current hydrometeorological data, data are sent to described waveguide computing unit, and the waveguide computing unit goes out atmospheric duct height and the Atmospheric corrections refractive index in the current environment and is sent to described over the horizon evaluation module according to hydrometeorological data computation; By the over the horizon evaluation module according to described duct height and Atmospheric corrections refractive index, calculate the trapping frequency of current waveguide, when described trapping frequency during greater than the natural frequency of current radar, and duct height is higher than height of radar antenna, judge that current radar has the over the horizon performance, control radar carries out the over the horizon search, obtains corresponding over the horizon search data.

Further, described waveguide computing unit calculating duct height and Atmospheric corrections refractive index mainly adopt following method:

The computing formula that described waveguide computing module calculates Richardson number Ri is:

$R_i=\frac{g}{T}\·\frac{\∂\mathrm{\θ}/\∂z}{{(\∂u/\∂z)}^2}$

When 0＜Ri＜1, current atmosphere is in neutrality or steady state (SS), when Ri＜0, judges that current atmosphere plays pendulum;

The Monion-Obukhov length L ' computing formula be:

$L^{\′}=\frac{u^{*}\∂u/\∂T}{\mathrm{kg}\∂\mathrm{\θ}/\∂T},$ U wherein ^*Be friction velocity $u^{*}=\sqrt{\frac{\mathrm{\τ}}{\mathrm{\ρ}}},$ τ is shearing stress;

Evaporation waveguide height for (0＜Ri＜1) under neutral and the stable atmospheric conditions:

$Z^{*}=\frac{{\mathrm{\ΔN}}_P}{-0.125({\log }_e\left(\frac{h_1}{h_0}\right)+\frac{5.2h_1}{L^{\′}})-\frac{5.2{\mathrm{\ΔN}}_p}{L^{\′}}},$ Wherein $L^{\′}=\frac{u^{*}\∂u/\∂T}{\mathrm{kg}\∂\mathrm{\θ}/\∂T}$

Work as z ^*＜0 o'clock or

＞1 o'clock, then:

$Z^{*}=\frac{{\mathrm{\ΔN}}_P(1+5.2)+0.65h_1}{-0.125{\log }_e\left(\frac{h_1}{h_0}\right)}$

For (R under the instability condition _i＜0 o'clock) the evaporation waveguide height:

$Z^{*}=\frac{1}{\sqrt[4]{{\mathrm{\φ}}^4-\frac{18}{L^{\′}}{\mathrm{\φ}}^3}}$

Wherein $\mathrm{\φ}=\frac{-0.125B}{{\mathrm{\ΔN}}_p},$ $B={\log }_e\left[\frac{h_1}{h_0}\right]-\mathrm{\ψ}$

The Atmospheric corrections of evaporation waveguide refraction gradient is under stable or neutral atmosphere state

$M\left(h\right)=M_s+\frac{h}{8}-\left[\frac{0.125Z^{*}}{1+\frac{5.2Z^{*}}{L^{\′}}}\right][{\log }_e\left(\frac{h_0+h}{h_0}\right)-\frac{5.2h}{L^{\′}}]$

Under the rough atmosphere state, the Atmospheric corrections of evaporation waveguide refraction ladder is

$M\left(h\right)=M_s+\frac{h}{8}-\left[\frac{0.125Z^{*}}{\mathrm{\φ}\left(\frac{Z^{*}}{L^{\′}}\right)}\right][{\log }_e\left(\frac{h_0+h}{h_0}\right)-\mathrm{\ψ}\left(\frac{Z^{*}}{L^{\′}}\right)]\·$

In the research of ocean evaporation waveguide, usually use the concept of pseudo-refractive index Np, namely

$N_p=77.6\frac{P_0}{\mathrm{\θ}}+3.73\×{10}^6\frac{e_p}{{\mathrm{\θ}}^2}$

In the formula: θ is megadyne temperature, and closing with atmospheric temperature is θ=T (P ₀/ P) ^0.286(K);

e _pThe position vapour pressure, with the pass of vapour pressure be e _p=eP ₀/ P

In the surface layer, P ≈ P ₀, θ ≈ T, e _p=e, then formula becomes

$N_p=77.6\frac{P_0}{T}3.73\×{10}^6\frac{e}{T^2}$

Over the horizon assessment mould module is calculated the method that the electromagnetic maximum wavelength of described evaporation waveguide trapping mainly adopts:

${\mathrm{\λ}}_{\max }=\frac{8\sqrt{2}\×{10}^{-3}}{3}\·{\∫}_{z_0}^d\sqrt{M\left(z\right)-M\left(d\right)}\mathrm{dz}$ （m）

Calculating the electromagnetic low-limit frequency of described evaporation waveguide trapping is:

$f_{\min }=\frac{c}{{\mathrm{\λ}}_{\max }}=\frac{79.49449}{{\∫}_{z_0}^d\sqrt{M\left(z\right)-M\left(d\right)}\mathrm{dz}}$ (GHz) in the formula, c is the light velocity (2.997925.10 ⁸M/s).

Obtaining f _MinAfter, compare with the frequency of radar system self, if the frequency of current radar is greater than f _MinJudge that then current radar has the over the horizon performance, radar begins to carry out the over the horizon search; If the frequency of radar is less than f _Min, represent that then current radar does not have the over the horizon performance, can't carry out the over the horizon search.

Considering whether radar has over the horizon system energy at current waveguide environment, also need to consider the relation of current duct height and height of radar antenna, have only current waveguide to have height and when being higher than height of radar antenna, radar can be judged the radar over the horizon according to the trapping frequency.

After judging that current radar has the over the horizon performance, also need the radar performance of over the horizon is assessed, as a preferred implementation, the present invention also has the radar range evaluation module:

By the radar return power of more different transmission ranges and the minimum detectable signal power of radar: if the radar return power of certain distance is greater than the minimum detectable signal power of radar, then current distance is the detectable distance of radar.

Further, this radar range evaluation module adopts following method that detection range is assessed.The target echo power that radar receives can be write as the form of one-way propagation loss:

P _r＝-8.55+10log ₁₀(P _tσf ²)+2G-L _s-L _a-2L _single

Receive theory according to radar, the minimum detectable signal power of radar is S _Imin, determined by the radar receiver performance,

$S_{i\min }={\mathrm{kT}}_0{B}_n{F}_0{D}_0={\mathrm{kT}}_0{B}_n{F}_0{\left(\frac{S_0}{N_0}\right)}_{\min }$

K is Boltzmann constant, k=1.38 * 10 ^-23(J/K); T is resistance temperature, with absolute temperature (K) metering, for 17 ℃ of room temperatures, T=T ₀=290K; B _nBe the passband of equipment,

τ is pulse width; F ₀Be the noise figure of receiver,

For the minimum signal to noise ratio (S/N ratio) of receiver output terminal, be also referred to as the detection factor D ₀, it is by detection probability P _dWith false-alarm probability P _FaDetermine that the radar detection factor determines by following formula, have for the pulse accumulative means of non-coherent:

$D_0=\frac{L_f{x}_0}{{4N}_p}(1+\sqrt{1+\frac{{16N}_p}{x_0}})$

x ₀＝(g _fa+g _d) ²

$g_{\mathrm{fa}}=2.36\sqrt{-{\log }_{10}\left(P_{\mathrm{fa}}\right)}-1.02$

$g_d=1.23t/\sqrt{1-t^2}$

t＝0.9(2P _d-1)

Pulse accumulative means for coherent then have:

$D_0=\frac{L_f{x}_0}{{4N}_p}(1+\sqrt{1+\frac{16}{x_0}})$

L _fFor target fluctuation loss, have for ripple disable target (Swail woods model 0): L _f=1, have for fluctuation target (as types such as Swail woods model 1, chi square-laws):

L _f＝-(ln(P _d)(1+g _d/g _fa) ^-1。

N _pBe pulse accumulation number, determined by the basic parameter of radar, for the radar of mechanical scanning:

$N_p=\frac{{\mathrm{\Θ}}_H{f}_p}{{6\mathrm{\φ}}_h\cos {\mathrm{\θ}}_0},$

Wherein, Θ _HBe the antenna horizontal beam width, degree; f _pBe pulse repetition rate, Hz; φ _hBe antenna horizontal direction sweep velocity, rpm; θ ₀Be target elevation, degree (being approximately 0 degree for low target); And for the radar of electric scanning, the pulse accumulation is several then by program setting.

The radar minimum detectable signal is write as the dB form:

S _imin＝kT ₀B _nF ₀D ₀＝-143.98+10log ₁₀B _n+F ₀+10log ₁₀(D ₀)

B _nUnit: MHz.Suppose that detections of radar is subjected to the influence of system noise, then the power P that ought receive _rGreater than S _IminThe time, radar could be found target reliably, works as P _rJust in time equal S _IminThe time, just obtain the maximum operating range R of this target of detections of radar _Ma, and P _rLess than S _IminThe time, target is in the radar electromagnetism blind area.

Further, consider the unevenness that atmospheric duct distributes, in traditional radar scanning zone, a plurality of skewness may occur, the blind area of shape inequality.Pretending is a preferred implementation, and the present invention also is provided with radar scanning regional determination module, divides grid in the radar scanning zone of radar, and the method for using above-mentioned judgement radar over-the-horizon detection distance is calculated the radar return power of each grid node; Travel through whole grid nodes, the echo power of total-grid node and the minimum detectable signal power of radar are compared: if the echo power that returns of certain described grid node is less than the minimum detectable signal power of described radar, then current grid node is the radar detection blind spot; Travel through all grid nodes, can finally obtain the surveyed area of current radar and detect the blind area.

Further, the present invention also is provided with under the multilayer atmospheric duct situation, the radargrammetry error evaluation module that the testing result of radar over the horizon is judged.

Whether receive the initial elevation angle that current duct height that described waveguide computing module draws and Atmospheric corrections refractive index judge current radar greater than zero, calculate the total length in the multilayer space, propagated at the ray that radar antenna sends and the overall height in multilayer space according to ray theory, compare apart from the actual range of radar and the apparent height of target with target, obtain height error and the distance error of radargrammetry.The concrete grammar that adopts is as follows: use ray theory, set up the evaluation profile-raytrace pattern of radar range finding and altimetry error.

By Snell rule, α ₂Can obtain by following formula,

$\cos {\mathrm{\α}}_2=[1+(N_1-N_2)\×{10}^{-6}-\frac{\mathrm{dir}\·\mathrm{dh}}{r_0+h_1}]\cos {\mathrm{\α}}_1$

Dir is directions of rays, when ray is upwards propagated, and dir=1, when ray is propagated downwards, dir=-1, Ψ ₁Be bending of a ray angle,

${\mathrm{\Ψ}}_1=\frac{2(N_1-N_2)\×{10}^{-6}}{\tan {\mathrm{\α}}_1+\tan {\mathrm{\α}}_2}$

β is geocentric angle, according to Abel, and et.al, 1982,

β ₁＝Ψ ₁+α ₂-α ₁

According to the cosine law, TRGAPP1 represents that ray in the length of this sheaf space, can be obtained by following formula

${\mathrm{TRG}}_{\mathrm{APP}!}=\sqrt{{(r_0+h_1)}^2+{(r_0+h_2)}^2-2(r_0+h_1)(r_0+h_2)\cos {\mathrm{\β}}_1}$

Calculate TRGAPP1 and the β of each layer by iteration ₁, the result adds up with gained, can obtain the total length TRG that ray is propagated in the space _APPWith total geocentric angle β _Total, as shown.

${\mathrm{TAG}}_{\mathrm{APP}}=\underset{l=1}{\overset{L}{\mathrm{\Σ}}}{\mathrm{TRG}}_{\mathrm{APPl}}$

${\mathrm{\β}}_{\mathrm{total}}=\underset{l=1}{\overset{L}{\mathrm{\Σ}}}{\mathrm{\β}}_1$

Target is TRG apart from the actual range of radar, can be obtained by following formula:

$\mathrm{TRG}=\sqrt{{(r_0+h_{\mathrm{REL}})}^2+{(r_0+h_n)}^2-2(r_0+h_{\mathrm{REL}})\left(r_0{+h}_n\right)\cos {\mathrm{\β}}_{\mathrm{total}}}\·$

Then the distance error of target is:

TRGERR＝TRG _APP-TRG

The apparent height of target is THTAPP, uses 4/3 equivalent earth's radius, and actual ray is become approximate straight line, and gained target apparent height is:

${\mathrm{THT}}_{\mathrm{APP}}=\sqrt{{[4/3(r_0+h_{\mathrm{REL}})]}^2+{{\mathrm{TRG}}_{\mathrm{APP}}}^2-2[4/3(r_0+h_{\mathrm{REL}})]{\mathrm{TRG}}_{\mathrm{APP}}\cos {\mathrm{\α}}_0}-4/3(r_0+h_n)$

Can obtain the height error of target:

THTERR＝THT _APP-h _n

Utilize above-mentioned formula, the program that the available simulation ray that programs is propagated in the space is assessed the height and distance error of radargrammetry.

Further, the height lifting of described radar antenna can be regulated the height of radar antenna in real time according to the height of current atmospheric duct in certain scope, have the over the horizon performance to guarantee current radar.

Accordingly, radar of the present invention is the changeable frequency radar, can change the wave band (frequency) of self, to adapt to the trapping frequency of different atmospheric duct environment, guarantees that as much as possible radar has the over-the-horizon detection performance.

Embodiment 1

Use low power navar (" Gu Ye " RF-7100D), its fundamental performance parameter sees the following form:

The Hangzhou Wan off-lying sea (30o35 ' N, 122o37 ' E) near, positive Beijing Institute of Aeronautics is capable.14:00 begins by measuring atmospheric temperature (19.8 ℃), humidity (43%), sea table water temperature (18 ℃) and sea wind speed key elements such as (10.4m/s), monitor marine site, boats and ships place and have available evaporation waveguide, duct height is 30.18m, and its modified index of refraction profile structure as shown in Figure 6.

Data handling procedure

Utilize the comprehensive numerical model of PEM-SSFA, radar electromagnetic wave under the actual measurement evaporation waveguide environment is carried out numerical evaluation, the space distribution of the one-way propagation loss that obtains, as shown in Figure 7.Here be a kind of approximate processing with the evaporation waveguide environment of single-point actual measurement as the single environment of radar detection area, this be similar to exposed waters in other words the marine site that has good uniformity of atmospheric level be rational.As can be seen: the evaporation waveguide height " trapping " propagation characteristic occurs greater than height of radar antenna, and transmission loss (TL) is less than under the normal atmospheric environment in the ducting layer, and the low latitude over-the-horizon detection appears in radar easily.

Radar is mainly surveyed the ship target on sea, and hypothetical target is large ship, and RCS is 20000m ², target does not have fluctuating or rises and falls slowly.The radar false alarm probability is 10-6, and it is 0.9 that detection probability requires, and utilizes the propagation loss computing formula to obtain transmission loss (TL) threshold value T _SingleBe 139.1dB.Utilize this threshold value that the transmission loss (TL) space distribution of Fig. 7 is carried out the threshold processing, obtain radar to the detection probability space distribution of large ship target, in fact, the result of simple gate limit value threshold process have only " energy " and " can not " detect two kinds of results of target.

For the simple gate limit threshold processing of intended target height, can directly lose with the assessment of carrying out radar maximum detectable range in the range distribution one-way propagation on this specified altitude assignment.The result of calculation of extracting respectively from Fig. 7 on 17.5m and the 25m height obtains the one-way propagation loss with the variation of distance, shown in circle sign and collimation mark will solid line among Fig. 8.For with normal atmospheric environment under compare, the space distribution of the transmission loss (TL) under the numerical evaluation normal atmospheric environment is extracted on two height of 17.5m and 25m transmission loss (TL) equally with the variation of distance, shown in Fig. 8 intermediate cam sign and positive sign sign dotted line.Satisfying the desired thresholding of detection probability and false-alarm probability is 139.1dB, as the no marks line among Fig. 8.Can Analysis of Radar among Fig. 8 under different communication environments to the maximum detectable range (distance that thresholding straight line and transmission loss (TL) variable in distance curve intersect farthest) of differing heights target.

Because radar is mainly surveyed the ship target on sea, usually with a maximum result as the radar performance assessment in the maximum detectable range on all height below the boats and ships significant height, from the numerical result of Fig. 8 as can be seen, radar has maximum detectable range at the 17.5m height under test evaporation waveguide environment.Following table has illustrated that radar is to the detectivity contrast of 17.5m height target under different communication environments.

Radar horizon R in the table _HorBeing to utilize the sighting distance equation to obtain, is the desirable maximum operating range that radar horizon is surveyed, and is 35.2km; Satisfy the ultimate range of radar under false alarm rate 10-6, detection probability 0.9 condition under the normal atmospheric environment, be 25.4km; And under the evaporation waveguide environment of actual measurement, the assessment radar can be surveyed the large ship target at 80.1km place, the detection range under desirable sighting distance and the normal atmospheric environment head and shoulders above.

In the process of the test, navar has observed the outer target echo of a large amount of sighting distances, has also enumerated the typical marine ships target (large vessel outside the PORT OF SHANGHAI) that radar observation is arrived in the table.In fact, radar has also observed a large amount of 100km outer island, sea, building and terrain return, typically as observing the outer Oriental Pearl TV Tower of 127.8km, Kingsoft echo outside the 124.1km etc., survey photo in kind as shown in Figure 9, the residing position of boats and ships as shown in figure 10.

Be beyond thought technique effect of the present invention herein, namely can obtain the profile in shore line accurately, can under the situation that the sea evaporation waveguide exists, survey the profile in shore line accurately, evade when flag-on-convenience vessel only reaches.

From radar maximum detectable range assessment result and radar actual detection effect relatively, both coincide better, this illustrates that also radar has low latitude over-the-horizon detection ability under the evaporation waveguide environment, also illustrates based on the comprehensive numerical model of PEM-SSFA and the accuracy of radar performance appraisal procedure simultaneously.

Yet, in the processing procedure of test figure, goal hypothesis and single evaporation waveguide environment approximate processing have been used, these hypothesis all also not exclusively conform to reality with approximate, as the hypothesis of ship target reflection cross section, consider that electromagnetic wave is limited in the ducting layer under the over-the-horizon detection situation, this moment, electromagnetic wave irradiation can only shine the ducting layer height with on the pontoon, some variations of ship target RCS when these features must cause over-the-horizon detection.In addition, marine evaporation waveguide environment has certain spatial-temporal distribution characteristic, and these must bring certain error for the radar performance assessment.

The above; only be the preferable embodiment of the present invention; but protection scope of the present invention is not limited thereto; anyly be familiar with those skilled in the art in the technical scope that the present invention discloses; be equal to replacement or change according to technical scheme of the present invention and inventive concept thereof, all should be encompassed within protection scope of the present invention.

Claims (10)

1. waveguide over-the-horizon radar has:

Measure the sensor unit of the hydrometeorological data that comprise sea table water temperature, sea atmospheric temperature, wind speed and atmospheric humidity at least;

According to the described environmental parameter that described sensor unit is gathered, calculate described atmospheric stability by calculating Richardson number Ri and Monin-Obukhov scale length L '; Under the state of different atmospheric stabilities, calculate the waveguide computing module of the Atmospheric corrections refractive index of sea evaporation waveguide height and sea evaporation waveguide;

According to sea evaporation waveguide height and the Atmospheric corrections refractive index of described waveguide computing module output, judge whether current radar has the over the horizon assessment mould module of over the horizon performance;

During work, described over the horizon evaluation module is according to described duct height and Atmospheric corrections refractive index, calculate the trapping frequency of current sea evaporation waveguide, when described trapping frequency during greater than the natural frequency of current radar, and duct height is higher than height of radar antenna, judges that current radar has the over the horizon performance.

2. a kind of waveguide over-the-horizon radar according to claim 1, be further characterized in that and have the radar range evaluation module: by the radar return power of more different transmission ranges and the minimum detectable signal power of radar: if at the radar return power of inner certain distance of the sea evaporation waveguide minimum detectable signal power greater than radar, then current distance is the detectable distance of radar.

3. a kind of waveguide over-the-horizon radar according to claim 1, be further characterized in that and have radargrammetry error evaluation module: whether receive the initial elevation angle that current sea evaporation waveguide height that described waveguide computing module draws and Atmospheric corrections refractive index judge current radar greater than zero, calculate the total length in multilayer waveguide space (comprising sea evaporation waveguide and space waveguide), propagated at the ray that radar antenna sends and the overall height in multilayer space according to ray theory, compare apart from the actual range of radar and the apparent height of target with target, obtain height error and the distance error of radargrammetry.

4. a kind of waveguide over-the-horizon radar according to claim 1, be further characterized in that: have adjustable for height radar antenna: the sea evaporation waveguide height and the current antenna height that calculate according to described waveguide computing module, rise or fall radar antenna, described radar wave is propagated in waveguide.

5. a kind of waveguide over-the-horizon radar according to claim 1, be further characterized in that: the radar antenna with changeable frequency, the trapping frequency of the current sea evaporation waveguide that calculates according to described over the horizon assessment mould module, adjustment to self frequency is carried out makes described radar frequency greater than the trapping frequency of current sea evaporation waveguide.

6. a kind of waveguide over-the-horizon radar according to claim 1, be further characterized in that: have the target identification module: calculate radar wave regularity of energy distribution in the evaporation waveguide pipe of sea by the radar emission power meter, for the over the horizon target, according to the energy of echo strength divided by this point of radar emission power in waveguide, just can judge the size of over the horizon target, target sizes can be divided into general objective, middle target and little target.

7. a kind of waveguide over-the-horizon radar according to claim 1 is further characterized in that: the computing formula that described waveguide computing module calculates Richardson number Ri is:

$R_i=\frac{g}{T}\·\frac{\∂\mathrm{\θ}/\∂z}{{(\∂u/\∂z)}^2}$

When 0＜Ri＜1, current atmosphere is in neutrality or steady state (SS), when Ri＜0, judges that current atmosphere plays pendulum;

The Monion-Obukhov length L ' computing formula be:

$L^{\′}=\frac{u^{*}\∂u/\∂T}{\mathrm{kg}\∂\mathrm{\θ}/\∂T},$ U wherein ^*Be friction velocity $u^{*}=\sqrt{\frac{\mathrm{\τ}}{\mathrm{\ρ}}},$ τ is shearing stress;

Sea evaporation waveguide height for (0＜Ri＜1) under neutral and the stable atmospheric conditions:

$Z^{*}=\frac{{\mathrm{\ΔN}}_P}{-0.125({\log }_e\left(\frac{h_1}{h_0}\right)+\frac{5.2h_1}{L^{\′}})-\frac{5.2{\mathrm{\ΔN}}_p}{L^{\′}}},$ Wherein $L^{\′}=\frac{u^{*}\∂u/\∂T}{\mathrm{kg}\∂\mathrm{\θ}/\∂T}$

Np is the potential index of refraction, h ₀Be sea level height, h ₀=0.00000015, h ₁Be sensor height;

Work as z ^*＜0 o'clock or

The time, then:

$Z^{*}=\frac{{\mathrm{\ΔN}}_P(1+5.2)+0.65h_1}{-0.125{\log }_e\left(\frac{h_1}{h_0}\right)}$

For (R under the instability condition _i＜0 o'clock) sea evaporation waveguide height:

$Z^{*}=\frac{1}{\sqrt[4]{{\mathrm{\φ}}^4-\frac{18}{L^{\′}}{\mathrm{\φ}}^3}}$ φ is flux profile function

Wherein $\mathrm{\φ}=\frac{-0.125B}{{\mathrm{\ΔN}}_p},$ $B={\log }_e\left[\frac{h_1}{h_0}\right]-\mathrm{\ψ}$ B is flux profile parameter, and ψ is flux profile function;

The Atmospheric corrections refractive index of evaporation waveguide is under stable or neutral atmosphere state

$M\left(h\right)=M_s+\frac{h}{8}-\left[\frac{0.125Z^{*}}{1+\frac{5.2Z^{*}}{L^{\′}}}\right][{\log }_e\left(\frac{h_0+h}{h_0}\right)-\frac{5.2h}{L^{\′}}]$

Under the rough atmosphere state, the Atmospheric corrections of evaporation waveguide refraction ladder is

$M\left(h\right)=M_s+\frac{h}{8}-\left[\frac{0.125Z^{*}}{\mathrm{\φ}\left(\frac{Z^{*}}{L^{\′}}\right)}\right][{\log }_e\left(\frac{h_0+h}{h_0}\right)-\mathrm{\ψ}\left(\frac{Z^{*}}{L^{\′}}\right)]$ , wherein Ms is at h ₀The Atmospheric corrections refractive index of height can directly be measured.

8. a kind of waveguide over-the-horizon radar according to claim 7 is further characterized in that: described over the horizon assessment mould module is calculated the electromagnetic maximum wavelength of described sea evaporation waveguide trapping and is:

${\mathrm{\λ}}_{\max }=\frac{8\sqrt{2}\×{10}^{-3}}{3}\·{\∫}_{z_0}^d\sqrt{M\left(z\right)-M\left(d\right)}\mathrm{dz}$ （m）

All the time d is sea evaporation waveguide height, is described Z ^*, z represents differing heights, M(z) is the Atmospheric corrections refractive index of differing heights, z ₀Be sea level height;

Calculating the electromagnetic low-limit frequency of described evaporation waveguide trapping is:

$f_{\min }=\frac{c}{{\mathrm{\λ}}_{\max }}=\frac{79.49449}{{\∫}_{z_0}^d\sqrt{M\left(z\right)-M\left(d\right)}\mathrm{dz}}$ (GHz) in the formula, c is the light velocity (2.997925.10 ⁸M/s).

9. a kind of waveguide over-the-horizon radar according to claim 3, be further characterized in that: the method for work of described radar range evaluation module is as follows:

The target echo power that radar receives can be write as the form of one-way propagation loss:

P _r＝-8.55+10log ₁₀(P _tσf ²)+2G-L _s-L _a-2L _single

Receive theory according to radar, the minimum detectable signal power of radar is S _Imin, determined by the radar receiver performance,

$S_{i\min }={\mathrm{kT}}_0{B}_n{F}_0{D}_0={\mathrm{kT}}_0{B}_n{F}_0{\left(\frac{S_0}{N_0}\right)}_{\min }$

K is Boltzmann constant, k=1.38 * 10 ^-23(J/K); T is resistance temperature, with absolute temperature (K) metering, for 17 ℃ of room temperatures, T=T ₀=290K; B _nBe the passband of equipment,

τ is pulse width; F ₀Be the noise figure of receiver,

Be the minimum signal to noise ratio (S/N ratio) of receiver output terminal;

When the power P that receives _rGreater than S _IminThe time, radar could be found target reliably, works as P _rJust in time equal S _IminThe time, just obtain the maximum operating range R of this target of detections of radar _Max, and P _rLess than S _IminThe time, target is in the radar electromagnetism blind area.

10. a kind of waveguide over-the-horizon radar according to claim 3, be further characterized in that: the method for work of described error-detecting module is as follows:

Use ray theory, set up the evaluation profile-raytrace pattern of radar range finding and altimetry error.

By Snell rule, α ₂Can obtain by following formula,

$\cos {\mathrm{\α}}_2=[1+(N_1-N_2)\×{10}^{-6}-\frac{\mathrm{dir}\·\mathrm{dh}}{r_0+h_1}]\cos {\mathrm{\α}}_1$

Dir is directions of rays, when ray is upwards propagated, and dir=1, when ray is propagated downwards, dir=-1, Ψ ₁Be bending of a ray angle,

${\mathrm{\Ψ}}_1=\frac{2(N_1-N_2)\×{10}^{-6}}{\tan {\mathrm{\α}}_1+\tan {\mathrm{\α}}_2}$

β is geocentric angle, according to Abel, and et.al, 1982,

β ₁＝Ψ ₁+α ₂-α ₁

According to the cosine law, TRGAPP1 represents that ray in the length of this sheaf space, can be obtained by following formula

${\mathrm{TRG}}_{\mathrm{APP}!}=\sqrt{{(r_0+h_1)}^2+{(r_0+h_2)}^2-2(r_0+h_1)(r_0+h_2)\cos {\mathrm{\β}}_1}$

Calculate TRGAPP1 and the β of each layer by iteration ₁, the result adds up with gained, can obtain the total length TRG that ray is propagated in the space _APPWith total geocentric angle β _Total

${\mathrm{TAG}}_{\mathrm{APP}}=\underset{l=1}{\overset{L}{\mathrm{\Σ}}}{\mathrm{TRG}}_{\mathrm{APPl}}$

${\mathrm{\β}}_{\mathrm{total}}=\underset{l=1}{\overset{L}{\mathrm{\Σ}}}{\mathrm{\β}}_1$

Target is TRG apart from the actual range of radar, is obtained by following formula:

$\mathrm{TRG}=\sqrt{{(r_0+h_{\mathrm{REL}})}^2+{(r_0+h_n)}^2-2(r_0+h_{\mathrm{REL}})\left(r_0{+h}_n\right)\cos {\mathrm{\β}}_{\mathrm{total}}}\·$

Then the distance error of target is:

TRGERR＝TRG _APP-TRG

The apparent height of target is THTAPP, uses 4/3 equivalent earth's radius, and actual ray is become approximate straight line, and gained target apparent height is:

${\mathrm{THT}}_{\mathrm{APP}}=\sqrt{{[4/3(r_0+h_{\mathrm{REL}})]}^2+{{\mathrm{TRG}}_{\mathrm{APP}}}^2-2[4/3(r_0+h_{\mathrm{REL}})]{\mathrm{TRG}}_{\mathrm{APP}}\cos {\mathrm{\α}}_0}-4/3(r_0+h_n)$

Can obtain the height error of target:

THTERR＝THT _APP-h _n

Utilize above-mentioned formula, the program that the available simulation ray that programs is propagated in the space is assessed the height and distance error of radargrammetry.

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