CN100380135C - Anti-interference method for ground wave radar in high frequency based on submatrix of antenna - Google Patents

Abstract

The present invention relates to an interference resisting method for a ground wave radar in high frequency based on a sub-matrix of an antenna. An antenna matrix of the ground wave radar in high frequency is designed into the mode of front and back two rows of even linear matrixes, and the two front and back opposite antennas of the antenna matrix are arranged into the sub-matrix. A self-interference echo signal from an ionized layer in near vertical direction is eliminated by the front and back subtracting process of signals received by the two antennas in the sub-matrix. The interference resisting method for a ground wave radar in high frequency based on a sub-matrix of an antenna is based on the existing antenna matrix and does not need to increase receiving antennas, receiving channels and occupation area. The interference resisting method for a ground wave radar in high frequency based on a sub-matrix of an antenna does not need to use any reference signal and can eliminate outside strong interference seriously affecting the performance of the radar by using a software method. The strong outside interference and weak interference can be restrained by using an improved power inversion adaptive algorithm, a plurality of accelerating operation methods are adopted, and real time requirement can be met. The interference resisting method for a ground wave radar in high frequency based on a sub-matrix of an antenna can eliminate the strong interference of the ionized layer in the near vertical direction by adopting the front and back magic T subtracting method of the two antennas. The interference resisting method for a ground wave radar in high frequency based on a sub-matrix of an antenna raises detecting performance and simultaneously and greatly reduces the developing cost and the maintenance expense of the radar. The interference resisting method for a ground wave radar in high frequency based on a sub-matrix of an antenna has standout practical performance.

Description

High-frequency ground wave radar anti-interference method based on the antenna submatrix

Technical field

The present invention relates to a kind of high-frequency ground wave radar anti-interference method based on the antenna submatrix.

Background technology

The high frequency surface wave over-the-horizon radar utilizes the vertical polarization frequency electromagnetic waves in the little characteristics of conduction ocean surface diffraction propagation decay, can the following moving targets such as naval vessel, aircraft and guided missile that occur of over-the-horizon detection sea level sight line.In addition, the high frequency surface wave over-the-horizon radar utilizes single order and the second order dispersion mechanism of ocean surface to frequency electromagnetic waves, from the radar marine echo, extract drive marine mathematic(al) parameters such as wind field, Lang Chang, flow field, can realize to marine environment on a large scale, high precision and round-the-clock real-time monitoring.

Yet, according to the Classical Electromagnetic Field theory, when vertical polarized antenna is positioned at infinitely great ideal conducting plane, antenna is radiationless on its axis direction, but when antenna holder is established ground when being non-infinitely great ideal conducting plane, as earth mat is big or small and density is limited, there is loss etc. in ground, antenna beam not only can upwarp certain angle, and also has radiation on the axis direction of antenna.Fig. 1 represents the synoptic diagram of certain vertical polarization emitting antenna and earth mat.Represent that as Fig. 2 certain vertical polarization emitting antenna is having the antenna pattern (among the figure, solid line and dotted line are respectively to having consumption ground and laying the directional diagram of limited earth mat situation) that consumes ground and be covered with E face under the earth mat situation.In actual radar engineering, desirable infinitely great conductive plane can not be accomplished in the place of antenna installation, so emitting antenna certain electromagnetic radiation that exists closely vertically upward on its axis direction.There is certain lobe width owing to antenna at the E face simultaneously, so emitting antenna also certain electromagnetic radiation that exists obliquely on other elevation direction.

As everyone knows, from 60km overhead highly, the part atmospheric molecule is formed an ionization medium zone, space of being made up of electronics, positive ion and negative ion and neutral particle by solar electromagnetic radiation, particle radiation ionization.This ionization medium zone that is present in the upper atmosphere is called as ionosphere.Ionosphere extends to the space of several thousand kilometers height of atmospheric envelope outer rim always.According to the variation of electron concentration, ionosphere also can be divided into several zones, i.e. D layer (60-90km), E layer (90-140km), F1 layer (140-200km), F2 layer (200-1000km or 2000km) and outer ionosphere (more than the F2 layer).

Because ionospheric existence, when the emitting antenna radiation beam when vertical plane has certain width or certain elevation angle is upwards arranged, the electromagnetic wave energy of its radiation is except coastal diffraction propagation, some energy is with the radiation obliquely of certain angle, propagate with the sky waveshape with interaction back, ionosphere, after the interaction of air-sea target, get back to radar with original route again to scattered signal thereafter.Represent the one-hop propagation route of ground wave radar antenna energy between ocean surface and ionosphere as Fig. 3.

A large amount of radar observation experimental results show that the high-frequency ground wave radar Ionospheric Echo often occurs in E layer, F1 layer and F2 layer, sometimes in addition d-layer also have reflection (or scattering) characteristic.Daytime is strong from Ionospheric F layer echo, sometimes in addition can with coastal waters echo comparable (as shown in Figure 4), and this very seriously affects the performance of radar, sometimes even make the radar can't operate as normal.Represent current chart after sea echo is subjected to Ionospheric Echo " pollution " as Fig. 5.From these figure obviously as seen, in the distance element that is ionized layer " pollution ", marine echo is disappeared in powerful Ionospheric Echo entirely, be not finally inversed by ocean current by the distance element of " pollution " owing to ionospheric interference, thereby is forming the distance " blind area " of certain limit.

In addition, because high-frequency ground wave radar is operated in short-wave band, radar echo signal is extremely complicated, and the echoed signal, zero-frequency interference, ionosphere self-interference, Radio frequency interference (RFI), atmospheric noise, thunder and lightning interference, cosmic noise, man-made noise on sea echo signal, sea-surface target echoed signal, island and land etc. are arranged.

Existing high-frequency ground wave radar offsets the ionosphere interference method and all adopts polarized filtering method basically, and its method is by some horizontal antennas being set, utilizing certain algorithm to realize offseting of the strong self-interference in ionosphere.But this method need increase extra auxiliary antenna, receiving cable and antenna farm, this method wastes time and energy, the cost height, cost is big, big [the H Leong: ' Adaptive nulling of skywave interference using horizontal dipole antennas in acoastal surface HF surface wave radar system ' of antenna array aperture receiving cable loss, Radar 97, and 14-16October 1997, Publication No.49:26-30.].

This invention will be utilized existing receiving antenna array, and antenna array is designed to some submatrixs, from the spa-tial filter properties of antenna array, propose a kind of high-frequency ground wave radar anti-interference method based on the antenna submatrix.A large amount of observation experiment explanations, the method that the present invention proposes can effectively offset ionosphere and disturb, and has satisfied the anti-interference basic demand of the high-frequency ground wave radar based on the antenna submatrix that the present invention proposes, and therefore will introduce it below.

Summary of the invention

Limitation at existing method, the purpose of this invention is to provide a kind of high-frequency ground wave radar anti-interference method based on the antenna submatrix, this method is based on existing antenna array, need not increase receiving antenna, receiving cable and antenna floor area, can suppress strong external interference, when improving detection performance, reduce the development cost and the maintenance cost of radar.

To achieve these goals, the present invention adopts a kind of high-frequency ground wave radar anti-interference method based on the antenna submatrix, and two arranged the uniform straight line array forms before and after the high-frequency ground wave radar antenna array was designed to, and two relative antennas before and after the antenna array are arranged to submatrix; By subtracting each other before and after the signal that two antennas in the submatrix are received, to offset ionosphere self-interference echoed signal from nearly vertical direction.

The above-mentioned signal front and back that two antennas in the submatrix are received are kept to the signal that two antennas in the submatrix are received mutually directly subtracts each other, and perhaps utilizes isometric cable that the signal that two antennas receive is directly utilized the reverse addition of magic T.

The present invention also can be designed to main antenna with arbitrary antenna in the antenna array, two to four adjacent on every side antennas are designed to auxiliary antenna, offset the strong jamming in the forceful electric power absciss layer self-interference and/or other orientation except that ionosphere of non-nearly vertical direction with the power inversion algorithm.

Owing to existing power inversion algorithm formed zero falls into along with the increase of external interference is deepened, but when having weak relatively interference, what traditional adaptive algorithm formed is zero sunken dark inadequately, the present invention can be at traditional power inversion algorithm (R.T.Compton.Jr: ' The power inversion array:concept and performance ', IEEE Trans., 1979, AES-15:803-814.) on the basis, by improving traditional power inversion algorithm, feature space based on the array covariance matrix decomposes, by abandoning the interference characteristic component in the weight vector, obtain one group of new weights, and, deepen the zero limit degree of depth under the weak jamming condition, better to offset small and weak relatively interference with the product of signals formation adaptive beam that these weights and the antenna that constitutes submatrix receive.

Advantage of the present invention is the Practical Performance that it is outstanding: based on existing antenna array, need not increase receiving antenna, receiving cable and antenna floor area; Need not use any reference signal, adopt the method for software can offset the extraneous strong jamming that has a strong impact on radar performance; Be inverted adaptive algorithm by improved power and not only can suppress strong external interference, can also suppress faint relatively interference well; Adopt some to quicken operational method, the energy requirement of real time; Two antenna receiving signals evil spirit T subtracts each other or the way of software before and after adopting, and can offset the strong self-interference in ionosphere of nearly vertical direction; When improving detection performance, significantly reduced the development cost and the maintenance cost of radar; The present invention is simple in actual applications, and is practical, effective.

Description of drawings

Fig. 1 vertical polarization emitting antenna and earth mat structural representation;

Fig. 2 vertical polarization emitting antenna is having the antenna pattern that consumes ground and be covered with E face under the earth mat situation;

The round of Fig. 3 frequency electromagnetic waves between air-sea;

The forceful electric power absciss layer echo and the ocean hypo Doppler spectrogram of Fig. 4 actual measurement;

Fig. 5 sea echo is subjected to the current chart after the Ionospheric Echo " pollution ";

Double uniform straight line array of Fig. 6 and coordinate definition synoptic diagram;

Fig. 7 higher-frequency radar signal environment and the schematic diagram that offsets nearly vertical direction interference;

The submatrix that two antennas constituted before and after Fig. 8 utilized is at the directional diagram of H face;

Fig. 9 constitutes synoptic diagram based on the submatrix of power inversion algorithm;

Figure 10 radar array submatrix constitutes and the signal Processing schematic diagram;

Doppler spectrogram before and after Figure 11 70km echo interference cancellation;

Doppler spectrogram before and after Figure 12 140km echo interference cancellation;

Doppler spectrogram before and after Figure 13 200km echo interference cancellation;

Doppler spectrogram before and after Figure 14 meteoric trail echo interference cancellation;

Doppler after Figure 15 goes to disturb;

Current chart after Figure 16 goes to disturb.

Embodiment

Below in conjunction with drawings and Examples, the present invention is done more detailed explanation.

Key of the present invention is by foundation double uniform straight line array to be set, and by making up submatrix and the front and back two antenna interference technology that disappears mutually, and improved power is inverted adaptive algorithm, offsets from the outer strong jamming of radar.

Represent the double uniform straight line array that designs as Fig. 6.In order to offset self-interference from nearly vertical direction, front and back two antennas can be designed to submatrix respectively, the method for subtracting each other before and after then the signal that receives being adopted can offset the strong jamming of nearly vertical orientations.From hardware, also front and back two antennas can be utilized isometric cable directly utilize the anti-phase addition of magic T, to offset ionosphere self-interference from nearly vertical direction.The principle schematic of representing radar signal environment and nearly vertical direction interference cancellation as Fig. 7.Represent the directional diagram of submatrix as Fig. 8, the directional diagram of this antenna submatrix is very wide, about 8 meters of antenna distances.

In order to offset the strong jamming in addition of nearly vertical direction, the arbitrary antenna of aerial array is designed to main antenna, adjacent on every side two to three or four antennas are designed to auxiliary antenna (as shown in Figure 9), utilize the power inversion algorithm to offset the forceful electric power absciss layer self-interference of non-nearly vertical direction or the strong jamming of other form.Owing to existing power inversion algorithm formed zero falls into along with the increase of external interference is deepened, but when having weak relatively interference, what traditional adaptive algorithm formed is zero sunken dark inadequately, the present invention is by improving traditional power inversion algorithm, feature space based on the array covariance matrix decomposes, by abandoning the interference characteristic component in the weight vector, deepen the zero limit degree of depth under the weak jamming condition, better to offset faint relatively interference.

(1) offsets the strongly disturbing signal model of nearly vertical direction

The high-frequency ground wave radar receiving antenna is designed to two row's planar array forms, and establishing antenna 1 is S from the backward scattered echoed signal in sea, is J from the ionosphere backward scattered echoed signal of nearly vertical direction ₁, noise is N ₁Equally, establishing antenna 2 is S from the backward scattered echoed signal in sea ₂, be J from the ionosphere backward scattered echoed signal of nearly vertical direction ₂, noise is N ₂(as shown in Figure 7).The signal that receives of antenna 1,2 then

x ₁＝S ₁+J ₁+N ₁(1)

x ₂＝S ₂+J ₂+N ₂(2)

Get by (1)-(2)

X＝x ₁-x ₂＝(S ₁-S ₂)+(J ₁-J ₂)+(N ₁-N ₂)(3)

Wherein can be expressed as from the ionosphere self-interference signal

$J_1\left(t\right)=\mathrm{\&sigma;\&rho;}\left(t\right)\exp \left(\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C20051001916200122.png,C20051001916200123.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;\&Delta;}{f}_{d}t\right)\exp \left[\mathrm{<figure-callout\; id="2"\; label="jk\; d"\; filenames="C20051001916200122.png,C20051001916200123.png"\; state="\{\{state\}\}">jk</figure-callout>}\frac{d}{}\frac{}{2}\sin \left({\mathrm{\&theta;}}_J\right)\right]---\left(4\right)$

$J_2\left(t\right)=\mathrm{\&sigma;\&rho;}\left(t\right)\exp \left(\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C20051001916200122.png,C20051001916200123.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;\&Delta;}{f}_{d}t\right)\exp [-\mathrm{<figure-callout\; id="2"\; label="jk\; d"\; filenames="C20051001916200122.png,C20051001916200123.png"\; state="\{\{state\}\}">jk</figure-callout>}\frac{d}{}\frac{}{2}\sin \left({\mathrm{\&theta;}}_J\right)]---\left(5\right)$

Wherein, the mean square value of σ ionosphere self-interference signal amplitude becomes the wide function of expansion, θ during ρ (t) Doppler _JIonosphere interference radiating way (with the angle of z axle), Δ f _dDoppler shift clocklike, d is the space length of 1,2 on antenna, and the typical multispectral spread function ρ (t) that reins in can be expressed as

ρ(t)＝exp(jxsin(2πεt))(6)

Thus

$X=x_1-x_2=(S_1-S_2)+2\mathrm{j\&sigma;\&rho;}\left(t\right)\exp \left(\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C20051001916200122.png,C20051001916200123.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;\&Delta;}{f}_{d}t\right)\sin \left[\mathrm{<figure-callout\; id="2"\; label="jk\; d"\; filenames="C20051001916200122.png,C20051001916200123.png"\; state="\{\{state\}\}">jk</figure-callout>}\frac{d}{}\frac{}{2}\sin \left({\mathrm{\&theta;}}_J\right)\right]+(N_1-N_2)---\left(7\right)$

When undesired signal during from the near vertical direction in ionosphere, i.e. θ _J0 ° of ≈, then

X＝x ₁-x ₂(S ₁-S ₂)+(N ₁-N ₂)(8)

Comprehensive above the analysis, when with front and back two adjacent antennas as a submatrix, and it is synthetic that antenna 1,2 received signals are carried out paraphase, then can directly offset from ionospheric nearly vertical direction self-interference signal.Or two element antennas form submatrix before and after utilizing, and utilize adaptive algorithm to realize offseting self-interference from nearly vertical direction again.It is easy to show that the pattern function of submatrix is

f(θ)＝1-exp(jkdcos)(9)

The submatrix directional diagram as shown in Figure 8.

(2) improved power is inverted adaptive algorithm

Realize that radar offsets extraneous strong jamming, one of key is to select suitable adaptive algorithm.Be without loss of generality,, to simplify the analysis, establish reference array element and be positioned at true origin arbitrary plane battle array (array number is M), array element m (x, y) position on the plane with it to true origin apart from r _mWith with the angle theta of x axle _mRepresent (representing double uniform straight line array and coordinate definition synoptic diagram) as Fig. 6.The angle of elevation alpha of signal source _dBe defined as the angle of direction of arrival and z axle, azimuthal angle beta _dBe defined as direction of arrival in that (then space D signal source is with different two-dimensional directionals angle (α for x, the y) angle of plane projection and x axle _d, β _d) inciding M unit antenna array, array output data vector is

X(t)＝AS(t)+N(t)(10)

In the formula,

X(t)＝[x ₁(t)，x ₂(t)，...，x _M(t)] ^T

A＝[a(α ₁，β ₁)，a(α ₂，β ₂)，...，a(α _D，β _D)] ^T，

S(t)＝[s ₁(t)，s ₂(t)，...，s _M(t)] ^T

N(t)＝[n ₁(t)，n ₂(t)，...，n _M(t)] ^T

$a({\mathrm{\&alpha;}}_d,{\mathrm{\&beta;}}_d)=\{1,\exp [-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C20051001916200122.png,C20051001916200123.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}{\mathrm{\&Delta;}}_1],...,\exp [-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C20051001916200122.png,C20051001916200123.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}{\mathrm{\&Delta;}}_m],...,\exp [-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C20051001916200122.png,C20051001916200123.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}{\mathrm{\&Delta;}}_M\left]\right\}$

Δ _m＝r _m?sinα _d?cos(β _d-θ _m)

The basic thought that traditional power is inverted adaptive algorithm is to keep the output power of the first branch road array element constant, and the weighting coefficient of other array element can be adjusted, by adjusting the output minimum that other M-1 weighting coefficient makes last array element.Owing to there is the output power of an array element constant, so make output power hour adjusting weighting coefficient, promptly on interference radiating way, form zero point, and disturb strong more, zero fall into dark more.

The optimum power that power is inverted adaptive array is

w _opt＝R ^-1a(α ₀，β ₀)(11)

In the formula

a(α ₀，β ₀)＝[1，0，...，0] ^H(12)

Weigh by the optimum that (11) formula forms, can form zero and fall on interference radiating way, and interference is strong more, zero is sunken dark more.

Algorithm Analysis and improvement

Consider to receive vector covariance matrix R, R is done characteristic value decomposition

$R=\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&lambda;}}_i{q}_i{q}_i^H=\underset{i=1}{\overset{D}{\mathrm{\&Sigma;}}}{\mathrm{\&lambda;}}_i{q}_i{q}_i^H+\underset{i=D+1}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&sigma;}}^2{q}_i{q}_i^H---\left(13\right)$

In the formula, λ is i the eigenwert of matrix R, q _iFor changing eigenwert characteristic of correspondence vector, because R is a Hermitian matrix, so corresponding different eigenwerts, its proper vector is mutually orthogonal, then has

$R^{-1}=\underset{i=1}{\overset{D}{\mathrm{\&Sigma;}}}{{\mathrm{\&lambda;}}^{-1}}_i{q}_i{q}_i^H+\underset{i=D+1}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&sigma;}}^{-2}{q}_i{q}_i^H---\left(14\right)$

Will be in conjunction with (12) formula, and with (13) substitution (11)

$w_{\mathrm{opt}}=\underset{i=1}{\overset{D}{\mathrm{\&Sigma;}}}{{\mathrm{\&lambda;}}^{-1}}_{\mathrm{<figure-callout\; id="1"\; label="i\; q\; i"\; filenames="C20051001916200121.png,C20051001916200123.png"\; state="\{\{state\}\}">i</figure-callout>}}{q}_i^{}{1}_{*}^{}{q}_i^H+\underset{i=D+1}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&sigma;}}^{-2}{\mathrm{<figure-callout\; id="1"\; label="q\; i"\; filenames="C20051001916200121.png,C20051001916200123.png"\; state="\{\{state\}\}">q</figure-callout>}}_i^1{q}_i^H---\left(15\right)$

From formula (13) as seen, the optimum weights of power inversion adaptive algorithm are the weighted sum of eigenwert character pair vector in fact.Last be interference characteristic value characteristic of correspondence vector and, back one be interference characteristic value characteristic of correspondence vector weighting with; One of back is to be made of noise characteristic value vector, learn by the subspace theory, noise characteristic vector and interference steering vector quadrature, and the subspace that the interference characteristic vector is formed is identical with the subspace of disturbing steering vector to form, and for strong interferers, its eigenwert is bigger, reciprocal proportion is less, just smaller for formed optimum weighted contributions, thus darker zero falling into can be formed in strongly disturbing place, and for small and weak relatively interference.Strange eigenwert is near the noise characteristic value, so the influence of interference characteristic vector in optimum power is bigger, can not form darker zero falling into.If but give up first, and only adopt the weighting of noise characteristic vector to weigh as optimum, can form darker zero falling in the place of disturbing, the weights of this moment are

$w_{\mathrm{opt}}=\underset{i=D+1}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&sigma;}}^{-2}{\mathrm{<figure-callout\; id="1"\; label="q\; i"\; filenames="C20051001916200121.png,C20051001916200123.png"\; state="\{\{state\}\}">q</figure-callout>}}_i^1{q}_i^H=Q_n{Q}_n^H---\left(16\right)$

In the formula, Q _n=[q _D+1, q _D+2..., q _M1]

Noise subspace for the noise feature vector composition.

(3) submatrix constructive method

Key of the present invention is to make up a kind of double uniform straight line array, and by design submatrix and the front and back two antenna interference technology that disappears mutually, and improved power is inverted adaptive algorithm, offsets from the outer strong jamming of radar.

In order to offset self-interference from nearly vertical direction, front and back two antennas can be designed to submatrix respectively, the method for subtracting each other before and after then the signal that receives being adopted can offset the strong jamming of nearly vertical orientations.From hardware, also front and back two antennas can be utilized isometric cable directly utilize the anti-phase addition of magic T, to offset ionosphere self-interference (as shown in Figure 7) from nearly vertical direction.

In order to offset the strong jamming in addition of nearly vertical direction, the arbitrary antenna of aerial array is designed to main antenna (as making main antenna with 1,2,3,4 antennas among Figure 10 A, or make main antenna with 5,6,7,8 antennas among Figure 10 B), adjacent on every side two to three or four antennas are designed to auxiliary antenna, utilize improved power inversion algorithm to offset the forceful electric power absciss layer self-interference of non-nearly vertical direction or the strong jamming of other form.Represent that as Figure 10 the radar array submatrix constitutes and the signal Processing schematic diagram.

Theory and practice shows that method proposed by the invention can reasonably well offset extraneous strong jamming.For the validity of the inventive method is described, the OSMARXP higher-frequency radar system test data instance with Wuhan University's wave propagation laboratory development illustrates that invention proposes the validity of the nearly vertical direction of antagonism ionosphere interference method below.

(1) general document claims that all d-layer is an absorption layer, and it does not reflect frequency electromagnetic waves, but we on daytime every day, sometimes even also can observe the Ionospheric Echo of this distance evening.For example, the author finds in experiment, a lot of by day identical time periods, often find to have echo from the nearly vertical direction at 60-70km place, and this echo is also very strong sometimes, even marine echo has all been flooded fully.The echo Doppler spectrogram of representing 70km as Figure 11.Wherein, dotted line represents to offset the echo spectrogram that nearly vertical direction is come wavefront, and solid line represents to offset echo spectrogram behind the nearly vertical direction incoming wave (down with).From then on scheme as seen, because ionospheric reflection, marine echo is disappeared fully in Ionospheric Echo, and always the distance of wave interference is seen, this disturbs obviously from d-layer.This result illustrates that not only d-layer has certain reflection or scattering properties to frequency electromagnetic waves, illustrates that also the present invention proposes to offset the validity of interference method.

(2) Es is rinforzando E district, an ionosphere thin layer, is the ionosphere that appears at the overhead 120km eminence of the earth once in a while.The morphosis of Es is very complicated, and the factor that influences its formation is also a lot.2003 Leonid meteor shower burst periods, radar monitoring are found, the influence that the meteor shower outburst is certain to being formed with of Es layer.The echo Doppler spectrogram (seldom occurring this type of phenomenon in several days) of representing 140km time period radar as Figure 12 in these meteor shower outburst front and back.Figure as seen thus, the Es layer appears in the meteor shower burst period, and marine echo is disappeared fully in the reflection echo of Ionospheric Es, but the method that offsets interference of utilizing the present invention to propose, echo spectrum after offseting is improved greatly, and the Bragg peak of marine echo is obviously visible.

(3) for short wave communication and high frequency sky wave radar, the F layer is most important, and in the ordinary course of things, telecommunication all selects for use the F layer to do the reflection horizon.The F layer has two-layer by day: the F1 layer is positioned at the overhead 150km-200km of the earth and highly locates; The F2 layer is positioned at more than the overhead 200km of the earth.Their height was different in different seasons with one day different moment.The F2 layer is different with other level, does not have complete obiteration at post sunset, still maintains remaining ionization.The echo Doppler spectrogram of representing 200km as Figure 13.From then on scheme as seen, because ionospheric reflection, marine echo is disappeared in Ionospheric Echo fully.Always the distance of wave interference is seen, this disturbs obviously from the Ionospheric F layer.From then on the result who offsets sees that it is also very obvious to offset effects of jamming.

(4) the similar pulsating wave of meteoric trail echo, amplitude is increased to maximum fast, continues to disappear after several seconds.According to the echo character of meteor shower, in the experiment at midnight and noon, often can observe meteor shower echo (generally a few hours in less) in the afternoon, its echo is generally in the scope from sky 80-120km.Meteor shower echo Doppler composes broad, and their amplitude exceeds the about 30-40dB of noise floor.Seriousness as the marine echo Doppler spectrum that it is right that Figure 14 has shown the meteoric trail echo on the one hand influences also illustrates the feasibility that offsets nearly vertical orientations meteoric trail echo that the present invention proposes on the other hand.

(5) in order to illustrate that the present invention proposes to offset the validity of nearly vertical direction ionosphere interference method, the data of Fig. 4 and Fig. 5 are carried out further processing here, obtained the result of Figure 15 and Figure 16.From then on the result is not difficult to find out, the ionosphere self-interference is eliminated substantially to the multispectral influence of reining in spectrum of sea echo, and also eliminate the ocean current blind area of inverting.

Claims (5)

1. the high-frequency ground wave radar anti-interference method based on the antenna submatrix is characterized in that: the high-frequency ground wave radar antenna array is designed to front and back two row's uniform straight line array forms, and two relative antennas before and after the antenna array are arranged to submatrix; By subtracting each other before and after the signal that two antennas in the submatrix are received, to offset ionosphere self-interference echoed signal from nearly vertical direction.

2. method according to claim 1 is characterized in that: the signal that the signal front and back that two antennas in the submatrix are received are kept to mutually with two antennas reception in the submatrix directly subtracts each other.

3. method according to claim 1 is characterized in that: be kept to mutually before and after the signal to two antennas reception in the submatrix and utilize isometric cable that the signal that two antennas receive is directly utilized the reverse addition of magic T.

4. according to claim 1 or 2 or 3 described methods, it is characterized in that: arbitrary antenna in the antenna array is designed to main antenna, two to four adjacent on every side antennas are designed to auxiliary antenna, offset the strong jamming in the forceful electric power absciss layer self-interference and/or other orientation except that ionosphere of non-nearly vertical direction with the power inversion algorithm.

5. according to claim 1 or 2 or 3 described methods, it is characterized in that: arbitrary antenna in the antenna array is designed to main antenna, two to four adjacent on every side antennas are designed to auxiliary antenna, feature space based on the array covariance matrix decomposes, abandon the interference characteristic component in the weight vector then, obtain one group of new weights, and, offset the interference in the ionosphere self-interference and/or other orientation except that ionosphere of non-nearly vertical direction with the product of signals formation adaptive beam that these weights and the antenna that constitutes submatrix receive.

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