CN101173985A - Passive radar detection method for detecting low-altitude objective by satellite signal - Google Patents

Abstract

The invention relates to a passive radar detection method by use of synergistic or asynergistic satellite signals to detect low altitude targets, belonging to the technical field of space technology, which comprises a satellite and a ground passive radar system; wherein, the system comprises a plurality of detection stations and a data processing station, and interactive communications are conducted between the detection stations and the data processing station by means of radio or optical fiber transmission method. The signals, expanded frequency measurement codes and the signals reflected on low altitude aircrafts by and of the satellite, especially high radiation power satellite, are received by the detection station receivers of the passive radar with high sensitivity. After correlation, the path difference between the direct radiation signals of the satellite and the signals from the same source reflected by the low altitude targets can be derived; then, a group of passive detection equations can be established; the solutions can be obtained simultaneously. And a three-dimensional position coordinate of the low or super low altitude targets can be thus acquired. The invention has the advantages of huge detection area, small blind area, the capability of detecting low or super low aircrafts like cruise missiles and super low altitude airplanes passively at long range, and extensive application value for military use.

Description

Utilize the passive radar detection method of satellite-signal detecting low-altitude objective

Technical field

The present invention relates to field of space technology, belong to extraterrestrial target passive detection technology.

Background technology

Invisbile plane, electronic interferences, antiradiation missile, extreme low-altitude surprise attack become four of traditional radar and threaten greatly.Development and maturation along with electronic technology and electromagnetic theory, also proposed the measure of the above-mentioned threat of many antagonism in field of radar, comprised the waveform that adopts particular design is realized low detectivity, the maneuverability that improves radar prevents antiradiation missile attack, adopt low elevation angle radar standard etc.But detection and early warning to the extreme low-altitude cruise missile that advances to attack have very big limitation, mainly be because the cruise missile of hedgehopping utilizes the physical restriction of earth curvature that the effective detection range of radar is reduced, and then pre-warning time is shortened.In addition, when surveying the configuration of the low elevation angle of radar for realization to treetop level target, the feeble signal of guided missile reflection is hidden in the land clutter noise, the very difficult resolution.Wherein the most promising counter-measure is a passive radar, self does not launch electromagnetic signal the passive radar system, the reflection of electric wave signal on target of launching for other purposes in the signal of dependence receiving target emission or the environment, by the location of signal Processing realization to target, this standard has embodied the purpose of radar invisible, can tackle above-mentioned nearly all threat.

The difference of the signal type that utilizes according to passive radar location, passive radar can be divided into radial pattern and reflection-type passive radar again.Comparatively speaking whether stealthy, the radial pattern passive radar is stronger because of the target emanation signal, be not subjected to target influence, and detection range is far away, but takes radio listening silence when target, when not transmitting, can make this passive radar lose usefulness; The electric wave signal of other signal source radiation of reflection-type passive radar employing target reflection is realized location and the tracking to specific objective, because the intensity of reflected signal is generally very weak, so detection range is nearer, detection range to the target of the stealthy target of the big high attenuation of radar scattering area (RCS) and low latitude hedgehopping is then nearer, also more difficult.

Be placed in ground passive radar and be subjected to the influence of earth curvature, its effective detection range is limited, for the low latitude, the detection range of hedgehopping target is then nearer, this point is identical with the monostatic radar principle, and can not reach by improving detection sensitivity merely, because this critical defect of ground radar has stayed many typical specific examples of a battle in modern war, in nineteen eighty-two English Armagh island contention war, Argentine at that time two super army flag fighter planes paste sea hedgehopping near Britain task force, closely launching 2 pieces of Exocet guided missiles, bombarded and sink the destroyer " Sheffield " number that Britain is worth 1.5 hundred million dollars, given Britain with heavy strike.

In modern war, in order to tackle extreme low-altitude threat, generally early warning radar is configured on aircraft or the satellite, increase the detection range of radar by prior-warning plane even early warning satellite, but early warning plane is owing to transmitting thereby also having the possibility of being located and destroying by the enemy, early warning plane is subjected to the restriction of hang time simultaneously, the multiple-alarm machine replaces the space that also has handing-over on duty, sought loopholes by the enemy easily, and technical sophistication, cost, operation, maintenance cost are very high, and the zone that therefore generally only is used for wartime strengthens early warning.Early warning satellite is then because far away from space, weak output signal, so be interfered easily with cheat, in sum, the high way of employing ground passive radar frame can satisfy the detection range requirement to low altitude aircraft, cruise missile, concrete enforcement is that passive radar is installed on the hilltop or the grappling balloon, enlarges passive radar line of vision detection range.

Passive radar can receive the multiclass signal of various frequency ranges in theory, electric wave, other radiate source radiation signals of comprising the various electronic equipment radiation that target is carried, as the signal of frequency modulation broadcasting, TV, satellite, ground communication, other radar emission etc., but to make choice according to the function of design, the feature of signal usually.The directionless wave beam of the general emission level of frequency modulation broadcasting, terrestrial television and communication station is influenced by earth curvature and makes coverage less.When the radar another one place of relieving a garrison, the signal in corresponding broadcasting, radio station may just not possess location condition, so these signals are not desirable signals.In recent years along with the development of satellite mobile communication, navigation and mobile broadcast television cause, for the antenna that makes terrestrial mobile terminal as far as possible little, be easy to carry, begin to greatly develop high-power satellite system both at home and abroad, realize that for passive radar utilizes satellite-signal passive positioning provides possibility.

Summary of the invention

The objective of the invention is to overcome the deficiencies in the prior art, a kind of method of utilizing Aerospace Satellite radiation signal over the ground low flyers such as cruise missile, extreme low-altitude aircraft to be carried out passive detection and location is provided.

For achieving the above object, technical solution of the present invention provides a kind of passive radar detection method that utilizes the satellite-signal detecting low-altitude objective, comprise satellite and ground passive radar system, this system comprises several acquisition stations and a data treating stations, each other with wireless mode or with optical fiber transmission mode interactive communication; It utilizes the signal of high radiation power satellite and the signal of measuring sign indicating number and reflecting on low flyer, receive by each acquisition station passive radar high sensitivity, through relevant satellite direct radiation signal and the path difference between the same source signal of low flyer reflection of trying to achieve, set up the passive detection equation, simultaneous solution just obtains the three-dimensional location coordinates of low latitude or treetop level target.

According to the described method of claims, its described satellite is mobile broadcast, communication, telstar or the Navsat of high radiation power; Inject the pseudo-code spread spectrum distance measuring signal of low rate by the ground connecting station to above-mentioned satellite, more help signal identification and catch, it is poor the relevant time of arrival of obtaining signal also to help by ranging code; If adopt non-collaborative satellite-signal, can utilize domestic and international mobile broadcast television satellite, moving communication satellite signal, implement the relevant high precision path difference of asking of continuous waveform signal.

Described method is when the reflected signal that utilizes satellite direct radiation signal and low latitude or hedgehopping device is asked between the two path difference, for realizing that to the Three-dimension Target location compute passive radar system should have three acquisition stations and a data treating stations to form at least; During the reflected signal of complete utilization low latitude or hedgehopping device, the passive radar system should have four acquisition stations and a data treating stations to form at least, realizes the passive positioning of target.

Described method, its described acquisition station for fixing or move, is built on high mountain, lift-off balloon or the early warning plane.Up cell site can be a fixed station, can be the vehicle-carried mobile station also, helps enlarging the visual field that radar receives the reflected signal of low target.

Described method, its described path difference, its measurement data should be implemented error correction, mainly refer to revise do the transmission time delay difference of two antennas of correlation computations to the center processing station, measure transmission path delay and the receiver time delay of each acquisition station respectively with instrument to processing enter, the way that also can adopt the transmission line exchange to measure is obtained the delay inequality between two transmission lines, writes down this delay inequality, deducts when target is carried out location compute.Help improving the bearing accuracy of target like this.

Described method, its described satellite-signal, its signal frequency is L, S, C, X, the signal of multiple frequency ranges such as ku or ka.

Described method not only can be surveyed low flyer, can be used for surveying airbound target on all kinds of height and ground, waterborne target equally, comprises satellite, aircraft, guided missile, warship, tank etc.

The inventive method can be utilized various satellite-signals, but (EIRP＞70dBw), specific broad pulse, low rate are measured sign indicating number, the pseudo-code spread-spectrum signal is advisable with high radiation power satellite.Because the frequency of satellite-signal and sign indicating number type can predict in advance, help catching and relevant treatment of frequency and coded signal.

Passive radar of the present invention is different from the VERA type passive radar of having researched and developed in the world at present that utilizes TV station and radio signals reflection; Also be different from the Celldar passive radar that Britain utilizes the mobile communication base station.

Passive radar of the present invention has the ability of low latitudes such as search coverage is wide, the blind area is little, the passive long-range detection cruise missile of energy, extreme low-altitude aircraft, hedgehopping device, has application value in army.

Description of drawings

Fig. 1 passive radar of the present invention system's positioning principle synoptic diagram (1);

Fig. 2 passive radar of the present invention system's positioning principle synoptic diagram (2);

Fig. 3 passive radar of the present invention system's positioning principle synoptic diagram (3);

Fig. 4 passive radar system chart of the present invention;

Fig. 5 multistation signal time difference of the present invention is asked for synoptic diagram;

Fig. 6 signal processing flow synoptic diagram of the present invention.

Embodiment

It is wide that satellite-signal generally covers the region, and same satellite emission signal has same source coherency, is easier to use the occasion that needs sync correlation to survey at the many acquisition stations of passive radar.In addition, satellite-signal have coverage big, be subjected to terrain and its features to influence outstanding advantages such as little, that networking is convenient, can be used as collaborative source or non-collaborative irradiation source that low target is surveyed the passive radar system.Signal is from target top irradiation target, can also be according to the deployed position choose reasonable satellite-signal of passive radar, thus can make the radar angle of passive radar observed object reach more excellent, this moment, target had bigger RCS, helped the increase of radar horizon.

In order to realize the effective detection range of target echo, except the receiver sensitivity that as far as possible improves radar, the powerful satellite-signal of choose reasonable is a very effective approach.In recent years, along with the development of satellite mobile communication,, constantly there is high-power satellite to come out in order to reduce the antenna aperture of receiving terminal.The high-power Radiation Satellite that mobile communication, mobile TV have particularly been arranged, comprise after the Inmarsat-4 and Asia cellular satellite Aces and relay type satellite navigation system CAPS that covers China, utilization has the power of spread-spectrum pseudo code signal and realizes that than the large satellite signal passive positioning has had possibility, makes the condition that emerged of the novel passive radar of this class.Inmarsat-4 maritime communication satellite in March, 2005 emission is an example below, adjusts passive radar of the present invention operating distance in the cards:

The EIRP of satellite is 67dBW, is in the most of area of China in the Northern Hemisphere and the oblique distance R of synchronous satellite and is about 40000km (synchronous satellite is about 35800km apart from the terrestrial equator surface), and establishing target scattering area σ is 1m ²The distance that makes target and radar is d (undetermined), because d compares very little with R, the flying height of low-to-medium altitude target is also in 2 myriametres, think that the distance of target and satellite also is 40000km so be similar to, radar receiving antenna adopts the parabolic multiple-beam antenna of 3 meters bores, and antenna efficiency η is 0.6, the gain G of single beam _rBe about 31dB.

Calculate the signal intensity that arrives the radar receiver input end:

If radar horizon d=200km, signal are L-band 1.5GHz, then

$S_{\mathrm{reflect}}=\mathrm{EIRP}+\mathrm{\σ}+G_r-10\lg ({\left(4\mathrm{\π}\right)}^3{R}^2{d}^2/{\mathrm{\λ}}_{1.5G}^2)=-207\mathrm{dBw}---\left(1\right)$

Direct signal power:

S _direct＝EIRP+G _r-20lg(4πR/λ _1.5G)＝-89dBw (2)

Because the satellite direct signal is than the high 118dB of target echo, can more easily receive direct signal, also can be used as the correlation receiver reference signal, get relevant with the signal that the target reflection passage receives, the suppression receiver noise, detect very faint reflected signal, and obtain direct signal and reflected signal poor time of arrival, and then resolve the locus coordinate of target.

Integral time got 1s by the radar correlation receiver, and noise figure is got 8dB, and signal to noise ratio snr is taken as 0dB, then

S _imin＝-174dBm+F ₀+10lg?B(Hz)-10lg(2BT _s)+SNR

＝-174dBm+8-10lg(2)+0＝-199dBw (3)

Therefore under the prerequisite of having considered receiver noise factor and signal to noise ratio (S/N ratio), the sensitivity of radar receiver is compared with the intensity of want received signal, the gap that 7dB is arranged, investigate link calculating formula (1), can realize reception to this signal, the required antenna aperture of so anti-release to 40dB by improving antenna gain:

$D=\sqrt{\frac{{10}^{\frac{G_r}{10}}\·{\mathrm{\λ}}^2}{0.6{\mathrm{\π}}^2}}=8.2m---\left(4\right)$

Therefore inquired into and analyzed by above-mentioned theory, employing 8.2m aperture antenna just can be realized the passive radar detection based on high-power telstar signal, and EFFECTIVE RANGE will reach more than the 200km.If detection range allows to shorten, then the receiving antenna bore also can reduce thereupon.Here SNR gets 0dB, mainly be to consider that the satellite direct signal is very strong, signal characteristic is obvious, the signal of target reflection can be submerged in the noise, because reflected signal and direct signal have same source coherency, therefore can with relevant reflected signal be extracted from noise by despreading, so the intensity of reflected signal can be lower than noise level, this is very favourable to practical application.

Because the earth is a conductor ball with certain curvature, for the target of hedgehopping, the detection range of passive radar also will be subject to the antenna height of radar receiving antenna and the flying height of target.The practical function distance will decide according to the line-of-sight propagation formula.

$d=4.1(\sqrt{h_1\left(m\right)}+\sqrt{h_2\left(m\right)})\left(\mathrm{km}\right)---\left(5\right)$

According to top formula, h ₁Be radar receiving antenna antenna height, h ₂Be target flying height, h ₁, h ₂Unit is kilometer with rice, the d unit of trying to achieve.Can get by following formula, when passive radar receiving antenna antenna height is 25 meters, the sighting distance detection range that to flying height is 15 meters target has only 36.38 kilometers, the sighting distance detection range that to flying height is 1000 meters target is about 151km, to flying height is 20000 meters target, and the sighting distance detection range is 603km.Therefore, mainly be subjected to the function influence that blocks of earth curvature for the detection range of low target, and the influence that improves receiver sensitivity to the detection range of low target because earth curvature restriction and can't increasing.We can't control the flying height of target, can only improve operating distance by increasing the radar receiving antenna antenna height to low target, this can solve by radar receiving antenna is set up on the coastal mountain top, calculate according to formula (5) equally, if the antenna installation height is 200～500 meters, the sighting distance detection range that to flying height is 5～30 meters treetop level target is 67～114 kilometers.As seen improving the radar receiving antenna antenna height is very significant to the effect that increases the low target detection range.

System constitutes

The passive radar system of detecting low-altitude objective and usually said passive radar system constitute similar, radar truck by four space distributions is formed, multiple cloth station mode can be arranged, see accompanying drawing 1,2,3, wherein O is the center processing station, A, B, C are for dividing acquisition station, and each station location coordinate and satellite position are known, and target location coordinate is waited to ask.The center processing station is equipped with two antennas, receives the reflected signal of the direct signal and the target of satellite respectively, as shown in Figure 1; Each minute, the acquisition station antenna can receive satellite direct signal and target echo simultaneously, as shown in Figure 2; Also can avoid very strong direct signal, receive only target echo, as shown in Figure 3 by the antenna beam of particular design; After each minute, acquisition station passed through the pre-service digitizing to the satellite reflection signal that receives, pass to the center processing station without distortion, implement resolving of relevant treatment and target location coordinate.

At the center processing station, correlation receiver adopts the target echo coherent integration of direct signal as reference signal and acquisition station reception, obtain target and arrive each station and the mistiming that arrives the center processing station, can be listed as the passive positioning system of equations of writing similar satellite navigation equation:

$\left\{\begin{array}{c}\mathrm{ST}+\mathrm{TO}-\mathrm{SO}=c\·\mathrm{\Δ}{t}_O\\ \mathrm{ST}+\mathrm{TA}+\mathrm{AO}-\mathrm{SO}=c\·\mathrm{\Δ}{t}_{\mathrm{AO}}\\ \mathrm{ST}+\mathrm{TB}+\mathrm{BO}-\mathrm{SO}=c\·\mathrm{\Δ}{t}_{\mathrm{BO}}\\ \mathrm{ST}+\mathrm{TC}+\mathrm{CO}-\mathrm{SO}=c\·\mathrm{\Δ}{t}_{\mathrm{CO}}\end{array}\right.---\left(6\right)$

System of equations (6) is can abbreviation as follows:

$\left\{\begin{array}{c}\mathrm{TA}+\mathrm{AO}-\mathrm{TO}=c\·{\mathrm{\Δt}}_{\mathrm{AO}}^{\′}\\ \mathrm{TB}+\mathrm{BO}-\mathrm{TO}=c\·\mathrm{\Δ}{t}_{\mathrm{BO}}^{\′}\\ \mathrm{TC}+\mathrm{CO}-\mathrm{TO}=c\·{\mathrm{\Δt}}_{\mathrm{CO}}^{\′}\end{array}\right.---\left(7\right)$

$\left\{\begin{array}{c}\mathrm{ST}+\mathrm{TA}-\mathrm{SA}=c\·{\mathrm{\Δt}}_A\\ \mathrm{ST}+\mathrm{TB}-\mathrm{SB}=c\·{\mathrm{\Δt}}_B\\ \mathrm{ST}+\mathrm{TC}-\mathrm{SC}=c\·{\mathrm{\Δt}}_C\end{array}\right.---\left(8\right)$

System of equations (7), (8) are write as the corresponding system of equations with coordinate representation respectively:

$\left\{\begin{array}{c}\sqrt{{(\mathrm{xa}-\mathrm{xt})}^2+{(\mathrm{ya}-\mathrm{yt})}^2+{(\mathrm{za}-\mathrm{zt})}^2}+\sqrt{{(\mathrm{xa}-\mathrm{xo})}^2+{(\mathrm{ya}-\mathrm{yo})}^2+{(\mathrm{za}-\mathrm{zo})}^2}-\\ \sqrt{{(\mathrm{xo}-\mathrm{xt})}^2+{(\mathrm{yo}-\mathrm{yt})}^2+{(\mathrm{zo}-\mathrm{zt})}^2}=c\·\mathrm{\Δ}{t}_{\mathrm{AO}}-c\·{\mathrm{\Δt}}_O\\ \sqrt{{(\mathrm{xb}-\mathrm{xt})}^2+{(\mathrm{yb}-\mathrm{yt})}^2+{(\mathrm{zb}-\mathrm{zt})}^2}+\sqrt{{(\mathrm{xb}-\mathrm{xo})}^2+{(\mathrm{yb}-\mathrm{yo})}^2+{(\mathrm{zb}-\mathrm{zo})}^2}----\left(9\right)\\ \sqrt{{(\mathrm{xo}-\mathrm{xt})}^2+{(\mathrm{yo}-\mathrm{yt})}^2+{(\mathrm{zo}-\mathrm{zt})}^2}=c\·{\mathrm{\Δt}}_{\mathrm{BO}}-c\·{\mathrm{\Δt}}_O\\ \sqrt{{(\mathrm{xc}-\mathrm{xt})}^2+{(\mathrm{yc}-\mathrm{yt})}^2+{(\mathrm{zc}-\mathrm{zt})}^2}+\sqrt{{(\mathrm{xc}-\mathrm{xo})}^2+{(\mathrm{yc}-\mathrm{yo})}^2+{(\mathrm{zc}-\mathrm{zo})}^2}-\\ \sqrt{{(\mathrm{xo}-\mathrm{xt})}^2+{(\mathrm{yo}-\mathrm{yt})}^2+{(\mathrm{zo}-\mathrm{zt})}^2}=c\·{\mathrm{\Δt}}_{\mathrm{CO}}-c\·\mathrm{\Δ}{t}_O\end{array}\right.$

$\left\{\begin{array}{c}\sqrt{{(\mathrm{xt}-\mathrm{xs})}^2+{(\mathrm{yt}-\mathrm{ys})}^2+{(\mathrm{zt}-\mathrm{zs})}^2}+\sqrt{{(\mathrm{xa}-\mathrm{xt})}^2+{(\mathrm{ya}-\mathrm{yt})}^2+{(\mathrm{za}-\mathrm{zt})}^2}-\\ \sqrt{{(\mathrm{xa}-\mathrm{xs})}^2+{(\mathrm{ya}-\mathrm{ys})}^2+{(\mathrm{za}-\mathrm{zs})}^2}=c\·\mathrm{\Δ}{t}_{\mathrm{AO}}\\ \sqrt{{(\mathrm{xt}-\mathrm{xs})}^2+{(\mathrm{yt}-\mathrm{ys})}^2+{(\mathrm{zt}-\mathrm{zs})}^2}+\sqrt{{(\mathrm{xb}-\mathrm{xt})}^2+{(\mathrm{yb}-\mathrm{yt})}^2+{(\mathrm{zb}-\mathrm{zt})}^2}-\\ \sqrt{{(\mathrm{xb}-\mathrm{xs})}^2+{(\mathrm{yb}-\mathrm{ys})}^2+{(\mathrm{zb}-\mathrm{zs})}^2}=c\·{\mathrm{\Δt}}_{\mathrm{BO}}\\ \sqrt{{(\mathrm{xt}-\mathrm{xs})}^2+{(\mathrm{yt}-\mathrm{ys})}^2+{(\mathrm{zt}-\mathrm{zs})}^2}+\sqrt{{(\mathrm{xc}-\mathrm{xt})}^2+{(\mathrm{yc}-\mathrm{yt})}^2+{(\mathrm{zc}-\mathrm{zt})}^2}-\\ \sqrt{{(\mathrm{xc}-\mathrm{xs})}^2+{(\mathrm{yc}-\mathrm{ys})}^2+{(\mathrm{zc}-\mathrm{zs})}^2}=c\·{\mathrm{\Δt}}_{\mathrm{CO}}\end{array}---\left(10\right)\right.$

In the formula, Δ t _IO(i=A, B, C) for target echo arrives the mistiming that center processing station O and target echo directly arrive the center processing station through the i acquisition station, above Δ t in various _AO, Δ t _BO, Δ t _COBe respectively acquisition station A, B, C are to the signal time delay at center processing station, and signal can be communication by the link that acquisition station arrives the center processing station, also can use Optical Fiber Transmission, the time elongatedness of actual computation is the equivalence time-delay of the signal transmission link between acquisition station and the center processing station.

Find the solution top measurement and positioning system of equations and just can obtain the Three-dimension Target coordinate.The position calculation method of computing method and satellite navigation is similar, repeats no more here.

Another kind method is that the center processing station can be in the hope of the mistiming Δ t of target echo and direct signal arrival _O, other acquisition stations are also adopted and are tried to achieve Δ t in the same way respectively _A, Δ t _B, Δ t _C, the moveout equation group that also can listing whenever stands erectly penetrates signal and reflected signal is obtained the position of target.

Above-mentioned listed measurement equation solution is three set of equations, can be in the hope of Three-dimension Target coordinate figure x _t, y _t, z _tAfter the equation number surpassed three, available least square method was found the solution.When time difference of only surveying between target echo, measuring equation is shown in (9) formula.

When finding the solution above-mentioned equation, four acquisition station collaborative works should be arranged at least, list three time difference measurement solving simultaneous equations, obtain the Three-dimension Target coordinate.When equation during,, can improve target location accuracy for redundancy is found the solution more than four groups.

According to the function that passive radar will be realized, the structure of each acquisition station can be divided into the functional module shown in the accompanying drawing 4 substantially, is achieved respectively in system and function design.

Gordian technique among the present invention:

(1) development of high sensitive receiver and flat beams directed antenna.

Satellite radiation signal through target reflection is very faint, must adopt highly sensitive receiver in order effectively to receive, the direct signal of satellite-signal can have very big interference to target echo simultaneously, therefore the acquisition station antenna must be designed to that direct signal is had certain ability of blocking, avoid direct signal and enter feed, in order to guarantee radar range, designed antenna will have certain directivity simultaneously.

(2) tiny signal separates in the separation of multiple goal coherent signal and the strong clutter.

Because multiple goal is under the covering of same satellite-signal, it is typical coherent signal, simultaneously, satellite-signal all can reflect on ground, buildings, form the land clutter signal, signal may be flooded (SNR＜＜0dB), therefore separate based on the multiple goal of same satellite-signal in order to realize, except adopting the spread spectrum decoding technology, also must design the coherent signal isolation technics under the low signal-to-noise ratio condition.

(3) high precision time difference measuring system.

Passive radar of the present invention system is based upon on the basis, time difference method location, and the precision of time difference measurement directly has influence on the passive radar locating accuracy, therefore must design and improve high-precision time difference measurement algorithm.These can be from (the patent of invention number: further improve on the basis 02101392.6) and be resolved of the time difference measurement algorithm the new celestial navigation system.Wherein be noted that correction to the path difference measuring error.Measuring error mainly refers to the two-way received signal that will carry out related calculation when the acquisition station antenna transfers to the signal Processing center respectively, the delay inequality of transmission path.Can be when system initialization measure the phase error that this error causes, in addition phase place correction when back end signal is handled by the exchange Transmission line method.

(4) to effective identification of target.

Because the identical target of volume, different radar scattering areas (RCS) is arranged under different flight attitudes, sometimes differ greatly, even for invisbile plane, though its positive scattering area is very little, but, may scattering area increase during from rear and side reception, so passive radar need adapt to this violent variation from for transmitting-receiving radar separately.

Signal processing technology:

The signal Processing design of passive radar has been adopted and has been split but 4 acquisition stations of collaborative work, and receiver carries out Doppler shift extraction and cross correlation process to direct signal and reflected signal.Relevant treatment is complicated ambiguity function, and it is that matched filter is corresponding with Doppler shift comprehensive to the time delay of satellite-signal, and matching formula provides as follows

$x(\mathrm{\τ},f)={\∫}_{-\∞}^{\∞}s*(t+\mathrm{\τ})s\left(t\right)e^{j2\mathrm{\πft}}\mathrm{dt}---\left(11\right)$

Wherein s (t) is the complicated envelope of direct signal carrier signal, s (t+ τ) is the signal of s (t) through target reflection, because the prolongation in path, the reflected signal time τ that lagged behind, τ and f are respectively retardation time and deviation frequency parameter, they correspond respectively to x (τ, the parameter value when f) reaching peak value.Signal processing such as accompanying drawing 5, shown in Figure 6 based on the passive radar of satellite-signal:

In the Signal Pretreatment stage, each acquisition station carries out data formatting, signal rectification, bandpass filtering and data balancing to direct signal and reflected signal, for subsequent treatment is prepared.Reflected signal receiving antenna definite object direction, to run into subject matter be that also be reflected the simultaneously secondary lobe of receiving antenna of direct projection path components receives into.The receiving ability of reflected signal depends on the inhibition level of receiving antenna secondary lobe and the multipath transport phenomena in the communication environments to a great extent.Because the amplitude of direct signal is higher than 100 decibels of target echoes, the direct signal that the secondary lobe of reflected signal receiving antenna leaks will produce serious influence to the detection and the estimation of target.Therefore the secondary lobe technology for eliminating is also very limited to the direct signal inhibiting effect, also need be thought of as Antenna Design and adopt technology such as mask, eliminates the direct signal component in the reflected signal that receives.

About target detection, adopt ambiguity function that time delay/Doppler shift is carried out Combined Treatment as previously mentioned, then non-collaborative integration is carried out in two outputs apart from storer.The optional parameter corresponding with target hysteretic time and Doppler shift will integral result time-form a peak value on the Doppler plane.In conjunction with base length can at an easy rate calculate target range and speed thereafter.

Claims (8)

1. a passive radar detection method that utilizes the satellite-signal detecting low-altitude objective comprises satellite, ground passive radar system and ground signal connecting station; Ground passive radar system comprises several acquisition stations and a data treating stations, each other with wireless mode or with optical fiber transmission mode interactive communication; It is characterized in that, utilize the signal of satellite and the signal that spread spectrum is measured sign indicating number and reflected on low flyer, receive by each acquisition station passive radar high sensitivity, through relevant satellite direct radiation signal and the path difference between the same source signal of low flyer reflection of trying to achieve, set up the passive positioning system of equations, simultaneous solution promptly obtains three-dimensional location coordinates, the speed of low latitude or treetop level target, the technical parameter of flight path.

2. according to claims 1 described method, it is characterized in that, described satellite is mobile broadcast, communication, TV, Navsat, inject the pseudo-code spread-spectrum signal of low rate to these satellites by the ground signal connecting station, synergistic signal source as low latitude passive radar system, so more help the identification of signal and catch, also help by the relevant path difference of asking of pseudo-code signal; Or utilizing all kinds of broadcast communication TV signal of other mobile TV satellites, moving communication satellite, the waveform of implementing the same source signal that sends with a satellite is relevant, in the hope of the high precision path difference.

3. according to claims 1 described method, it is characterized in that when the reflected signal that utilizes satellite direct radiation signal and low latitude or hedgehopping device was asked between the two path difference, the passive radar system had three acquisition stations and a data treating stations at least; If do not utilize the direct radiation signal, and during the reflected signal of complete utilization low latitude or hedgehopping device, the passive radar system has four acquisition stations and a data treating stations at least, to realize the passive positioning of target.

4. according to claims 1 described method, it is characterized in that described acquisition station for fixing or move, is built on high mountain, lift-off balloon or the early warning plane, the operating distance when helping enlarging radar low target being surveyed.

5. according to claims 1 described method, it is characterized in that, described path difference, it is measured and must implement error correction, helps improving the bearing accuracy to target like this.

6. according to claims 1 described method, it is characterized in that, described satellite-signal, its signal frequency is L, S, C, X, the signal of ku or many kinds of frequency ranges of ka.

7. according to claims 1 or 2 described methods, it is characterized in that described satellite is mobile communication, mobile broadcast, the telstar of radiation high-power signal, for realizing valuable detection range, its equivalent isotropically radiated power EIRP＞70dBw.

8. according to claims 1,2,6 described methods is characterized in that, it can survey aerial, ground, waterborne target on each height equally, implements the location to satellite, aircraft, guided missile, warship, surface car.

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