A Method for Suppressing Dense False Target Interference in FDA-MIMO Radar Network Access Positioning

Abstract

The present invention relates to a method for suppressing dense false target interference in the network access positioning of an FDA-MIMO radar, and relates to the technical field of radar anti-jamming. The method for suppressing dense false target interference in the network access positioning of an FDA-MIMO radar according to the present invention includes transmitting a signal in the form of linearly frequency-spaced signals, discriminating between true and false targets in the transmit-receive two-dimensional frequency domain, and then positioning real targets and interference sources in the angle-distance two-dimensional airspace by transmitting signals in the form of non-linearly frequency-spaced signals, instructing other radars in the radar network to be silent in the azimuth sector where the interference source is located to suppress dense false target interference. Further, the method is verified through simulation analysis. The verification results show that the method has good effects in true and false target recognition and interference source positioning. After adopting the sector silent mode, the ability of other radars to suppress false targets and detect real targets is significantly improved, and the larger the sector silent range, the greater the interference suppression ratio and target detection probability of the radar network.

Description

Technical Field

[0001] The present invention relates to the technical field of radar anti-jamming, and particularly to a method for suppressing dense false target interference in FDA-MIMO radar network access positioning. Background Art

[0002] FDA-MIMO radar, also known as frequency diverse array-multiple-input multiple-output (FDA-MIMO) radar, has a small carrier frequency difference between its radar array elements, and the signals transmitted by each element are orthogonal, making it have unique advantages in aspects such as main lobe interference suppression, anti-interception performance, signal detection, and parameter estimation. By making full use of the range-angle coupling characteristic of the radar beam of this system, deceptive false targets can be identified, the positions of real targets can be estimated, and main lobe false target interference can be adaptively suppressed.

[0003] In terms of differentiating true and false targets, FDA-MIMO radar mainly has three ideas: One is to utilize the phase difference and spatial angular frequency differences generated between false targets and real targets among array elements to differentiate true and false targets, but the calculation is relatively complex and the error influence is relatively large; the second is to utilize the range-angle coupling characteristic of the transmitting direction pattern, making the main lobe of the direction pattern pass through the target to be differentiated and not pass through other targets, and differentiating the type of target according to the received signals. However, this method requires accurate knowledge of the position information of all targets, and when the number of false target interferences increases and they are relatively close to the targets, the differentiation effect is poor; the third is to utilize the differences in range and polarization characteristics between true and false targets, and jointly use range parameters and polarization characteristic quantities to differentiate true and false targets, but this method has complex calculations and a large amount of computation. In terms of target positioning, FDA-MIMO radar mainly has two methods: One is to change the frequency interval to transmit and receive signals in sequence, decouple the target range and angle, extract range and angle information, and estimate the target position, but the calculation is relatively complex; the second is to divide the array into multiple sub-arrays, each sub-array transmits signals with different frequency intervals, and use the multiple signal classification algorithm to estimate the target position, but the range estimation error is relatively large. Moreover, existing technologies do not consider both true and false target differentiation and target position estimation at the same time, and there is almost no research on the influence of suppressing dense false targets on other radars after FDA-MIMO radar accesses the network.

[0004] In the prior art, dense false target jamming mainly uses the Digital Radio Frequency Memory (DRFM) technology by the jammer to generate the received target signal through its own time delay. It can generate different range offsets, and the generated false targets can appear in any range cell, causing the real target to be submerged in the false targets. Especially when the angle of the jammer is close to or the same as that of the target, the performance of the phased array that suppresses the jammer using the angle dimension degree of freedom will deteriorate sharply, seriously affecting the radar's detection ability for the target. Summary of the Invention

[0005] Therefore, the present invention provides a method for suppressing dense false target jamming in the networked positioning of an FDA-MIMO radar to overcome the problem in the prior art that in the case of dense false target jamming, the existing research does not simultaneously consider the identification of true and false targets and the position estimation, resulting in weak anti-jamming ability of the radar.

[0006] To achieve the above object, the present invention provides a method for suppressing dense false target jamming in the networked positioning of an FDA-MIMO radar, including:

[0007] Step S1: Transmit a linearly frequency-spaced signal through the FDA-MIMO radar, and identify true and false targets in the transmit-receive two-dimensional frequency domain.

[0008] Step S2: Transmit a non-linearly frequency-spaced signal through the FDA-MIMO radar to locate the real target and the jammer in the two-dimensional spatial domain of angle-range gate.

[0009] Step S3: When the positioning is completed, the networking center instructs the radars in the radar network to take corresponding anti-jamming measures (sector silence) in the direction where the jammer is located to suppress dense false target jamming.

[0010] Further, in the step S1, the identification of the true and false targets includes:

[0011] Step S11: The FDA-MIMO radar directly performs spatial spectrum estimation on the received signal in the space-time two-dimensional domain using linearly frequency-spaced to obtain the spatial position information of the received real target and false target.

[0012] Step S12: Calculate the distributions of the real target and the false target in the transmit-receive two-dimensional spatial frequency domain based on the obtained spatial positions of the real target and the false target.

[0013] Step S13: Directly perform spectrum estimation on the signals of all the received targets in the transmit-receive two-dimensional spatial frequency domain, and compare the spectrum estimation result with the spatial position of the false target jamming obtained in the step S12.

[0014] Step S14: Determine the real target and false target according to the comparison result in step S13. If the positions of two identical targets in the comparison result are the same in the two-dimensional spatial frequency domain, then determine that target as a real target; if the positions of the two identical targets are different in the two-dimensional spatial frequency domain, then determine that target as a false target.

[0015] Step S15: When the determination is completed, output the position of the real target.

[0016] Further, in step S2, the positioning of the real target and the interference source is to change the transmission frequency of the FDA-MIMO radar to a non-linear frequency spacing signal and perform spatial spectrum estimation on the received signal in the angle-distance domain to obtain the spatial positions of the real target and the interference source. After removing the position of the real target output in step S15, the positions of all the interference sources are obtained.

[0017] Further, in step S3, the suppression of false target interference is to, according to the information sharing mechanism of the radar network, feedback the positions of the interference sources obtained in step S2 to other radars in the radar network, and enable the networking center to instruct the radars in the radar network to take corresponding interference measures. The FDA-MIMO radar forms an adaptive beam in the transmit-receive two-dimensional frequency domain to suppress dense false target interference.

[0018] Further, in step S11, the space-time two dimensions include angle and time-domain distance.

[0019] Further, the interference measure is sector silent. Sector silent means that the other radars do not actively transmit signals in the direction where the jammer is located and perform scanning outside the sector silent area.

[0020] Further, the FDA-MIMO radar is an equally spaced linear array with N array elements.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows. In the case of dense false target interference, almost no existing literature has considered the problems of true and false target recognition and position estimation simultaneously. A method for suppressing dense false targets by an FDA-MIMO radar when accessing the network is proposed. The FDA-MIMO radar first emits signals with linearly frequency-spaced intervals to distinguish true and false targets in the transmit-receive two-dimensional frequency domain. Then, it emits signals in the form of non-linearly frequency-spaced intervals to decouple its beam, remove range dimension ambiguity, locate the target and the interference source, and instruct other radars in the network to be silent in the azimuth sector where the interference source is located, reducing the interference power entering the radar. The simulation results show that this method has good effects in true and false target recognition and interference source positioning. After adopting the sector silent mode, the ability of other radars to suppress false targets and detect true targets is significantly improved, and the larger the sector silent range, the greater the interference suppression ratio and the target detection probability of the radar network. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the FDA-MIMO radar signal array model for the method of suppressing dense false target interference by an FDA-MIMO radar for positioning when accessing the network according to the present invention;

[0023] Figure 2 Schematic diagram of the space-time two-dimensional distance domain distribution of true and false targets for the method of suppressing dense false target interference by an FDA-MIMO radar for positioning when accessing the network according to the present invention;

[0024] Figure 3 Schematic diagram of sector silent for the method of suppressing dense false target interference by an FDA-MIMO radar for positioning when accessing the network according to the present invention;

[0025] Figure 4 Two-dimensional power spectrum diagram of angle-distance gate for simulation analysis of true and false target discrimination and interference source positioning for the method of suppressing dense false target interference by an FDA-MIMO radar for positioning when accessing the network according to the present invention;

[0026] Figure 5 Distribution diagram of true and false targets in the transmit-receive two-dimensional frequency domain for simulation analysis of true and false target discrimination and interference source positioning for the method of suppressing dense false target interference by an FDA-MIMO radar for positioning when accessing the network according to the present invention;

[0027] Figure 6 Spatial position diagram of true target for simulation analysis of true and false target discrimination and interference source positioning for the method of suppressing dense false target interference by an FDA-MIMO radar for positioning when accessing the network according to the present invention;

[0028] Figure 7The angle-distance two-dimensional power spectrum diagram for true / false target discrimination and interference source localization simulation analysis of the method for suppressing dense false target interference in the network access positioning of an FDA-MIMO radar according to the present invention;

[0029] Figure 8 The distribution diagram of the networking radar, target, and jammer in the simulation analysis of false target suppression by sector silent operation of the networking radar for the method for suppressing dense false target interference in the network access positioning of an FDA-MIMO radar according to the present invention,

[0030] Figure 9 The localization distribution diagram of the S-band jammer and the true target in the simulation analysis of false target suppression by sector silent operation of the networking radar for the method for suppressing dense false target interference in the network access positioning of an FDA-MIMO radar according to the present invention;

[0031] Figure 10 The localization distribution diagram of the S-band jammer and the true target in the simulation analysis of false target suppression by sector silent operation of the networking radar for the method for suppressing dense false target interference in the network access positioning of an FDA-MIMO radar according to the present invention;

[0032] Figure 11 The time-domain filtering diagram of the L-band radar in the simulation analysis of false target suppression by sector silent operation of the networking radar for the method for suppressing dense false target interference in the network access positioning of an FDA-MIMO radar according to the present invention;

[0033] Figure 12 The time-domain filtering diagram of the S-band radar in the simulation analysis of false target suppression by sector silent operation of the networking radar for the method for suppressing dense false target interference in the network access positioning of an FDA-MIMO radar according to the present invention;

[0034] Figure 13 The transmit-receive frequency-domain beamforming diagram of the FDA-MIMO radar in the simulation analysis of false target suppression by sector silent operation of the networking radar for the method for suppressing dense false target interference in the network access positioning of an FDA-MIMO radar according to the present invention;

[0035] Figure 14 The time-domain filtering diagram of the FDA-MIMO radar in the simulation analysis of false target suppression by sector silent operation of the networking radar for the method for suppressing dense false target interference in the network access positioning of an FDA-MIMO radar according to the present invention. Detailed implementation manners

[0036] In order to make the objectives and advantages of the present invention clearer and more understandable, the present invention will be further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principle of the present invention and do not limit the protection scope of the present invention.

[0038] It should be noted that in the description of the present invention, the terms indicating directions or positional relationships such as "upper", "lower", "left", "right", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings. This is only for convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0039] In addition, it should also be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0040] Please refer to Figure 1 as shown, which is a schematic diagram of the FDA-MIMO radar signal array model of the method for suppressing dense false target interference in the FDA-MIMO radar network access positioning of the present invention;

[0041] The method for suppressing dense false target interference in the FDA-MIMO radar network access positioning of the present invention includes:

[0042] Step S1: Transmit linearly frequency-spaced signals through the FDA-MIMO radar and distinguish between true and false targets in the transmit-receive two-dimensional frequency domain;

[0043] Step S2: Transmit non-linearly frequency-spaced signals through the FDA-MIMO radar to locate real targets and interference sources in the angle-distance two-dimensional airspace;

[0044] Step S3: When the positioning is completed, the networking center instructs other radars in the radar network to take corresponding interference measures in the direction where the interference source is located to suppress dense false target interference.

[0045] Specifically, assume that the FDA-MIMO radar is an equally spaced linear array with N array elements, d is the array element spacing, assume that the transmitted signal is a far-field narrowband signal, the angle between it and the array normal direction is θ, select the first array element as the reference array element, and the distance from the scattering point to the first array element is r, where is the envelope of the signal transmitted by the mth array element.

[0046] The transmission frequency of the m-th array element channel is

[0047] f m = f0 + (m - 1)Δf, m = 1, 2, …, N

[0048] where f0 is the carrier frequency of the first array element, and Δf is the frequency interval between two adjacent array elements.

[0049] Considering that the transmitted signal is a far-field narrowband signal, the phase difference between the m-th array element and the reference array element is

[0050]

[0051] It can be seen from the above formula that the phase difference of the transmitted signal of the FDA-MIMO radar is not only related to the spatial angle but also related to the propagation distance. Therefore, the antenna pattern of the FDA-MIMO radar has range-angle dependence. When the frequency interval is much smaller than the carrier frequency, that is, NΔf << f0, the phase difference brought by the first two terms can be ignored.

[0052] Since the transmitting beam of the FDA-MIMO radar is omnidirectional and various losses are ignored, the signal transmitted by the m-th array element of the target can be expressed as

[0053]

[0054] In the formula, E is the total energy of the transmitted signal, is the envelope of the signal transmitted by the m-th array element, and T is the pulse transmission duration. Different from the FDA radar, the FDA-MIMO radar combines the characteristics of the MIMO radar, making the envelopes of the signals transmitted by different array elements orthogonal, and there is

[0055]

[0056] In the formula, * represents conjugate calculation, and τ is an arbitrary delay time.

[0057] Then the frequency of the signal received by the m-th array element is f n and the signal is expressed as

[0058]

[0059] Therefore, the target signal received by the entire array is expressed as

[0060]

[0061] In the formula, ξ is the amplitude information of the target signal, T represents transpose, is the Kronecker product, v(θ, r, Δf) is the array steering vector, a(θ, r, Δf) is the transmitting steering vector, and b(θ) is the receiving steering vector. The specific expressions are

[0062]

[0063]

[0064] Among them, ⊙ represents the Hadamard product, and λ0 is the operating wavelength of the FDA-MIMO radar.

[0065] Please refer to Figure 2 shown in the figure, which is a schematic diagram of the space-time two-dimensional range domain distribution of the real target and false targets of the method for suppressing dense false target interference in the network access positioning of the FDA-MIMO radar according to the present invention;

[0066] For the method for suppressing dense false target interference in the network access positioning of the FDA-MIMO radar according to the present invention, in the step S1, the discrimination of the true and false targets includes:

[0067] Step S11, the FDA-MIMO radar directly performs spatial spectrum estimation on the received signal in the space-time two-dimensional domain with a linear frequency interval to obtain the spatial position information of the received real targets and interferences;

[0068] Step S12, calculate the distributions of the real targets and interferences in the transmit-receive two-dimensional spatial frequency domain based on the obtained spatial positions of the real targets and interferences;

[0069] Step S13, directly perform spectrum estimation on the signals of all the received targets in the transmit-receive two-dimensional spatial frequency domain, and compare the spectrum estimation result with the spatial position of the interference obtained in the step S12;

[0070] Step S14, determine the real targets and false targets according to the comparison result in the step S13. If the positions of two identical targets in the two-dimensional spatial frequency domain are consistent, then determine that the target is a real target; if the positions of two identical targets in the two-dimensional spatial frequency domain are inconsistent, then determine that the target is a false target;

[0071] Step S15, when the determination is completed, output the position of the real target.

[0072] Please continue to refer to Figure 2 shown in the figure, for the method for suppressing dense false target interference in the network access positioning of the FDA-MIMO radar according to the present invention, in the step S2, the positioning of the real targets and interference sources is to change the transmit frequency of the FDA-MIMO radar to a non-linear frequency interval signal and perform spatial spectrum estimation on the received signal in the angle-range domain to obtain the spatial positions of the real targets and interference sources, and obtain the positions of all the interference sources after removing the position of the real target output in the step S1.

[0073] Specifically, based on the correlation between the phase difference of the signals transmitted by the FDA-MIMO radar and the propagation distance, which is the distance from the array to the jammer and is reflected in the transmit steering vector, the steering vectors of the dense false target jamming released by the same jammer are the same. The dense false targets are generated by the jammer through time delay, and the range gate information they place does not match the real range information. By discriminating between true and false targets and locating the jammer source, and then according to the radar network information sharing mechanism, the direction of the jammer source is informed to other radars in the radar network, and corresponding anti-jamming measures such as sector silence are taken to suppress the dense false target jamming.

[0074] Specifically, due to the differences between the real target and the dense false target jamming in the spatio-temporal two-dimensional range domain, there will also be differences in the transmit-receive two-dimensional frequency domain. For the real target echo, the temporal range is equal to the spatial range. Then, the position in the transmit-receive two-dimensional frequency domain calculated based on the target angle and the temporal range coincides with the position obtained by spectral estimation directly in the transmit-receive two-dimensional spatial frequency domain. For the false target jamming, the temporal range is not equal to the spatial range. Then, the position in the transmit-receive two-dimensional frequency domain calculated based on the jammer angle and the temporal range does not coincide with the position obtained by spectral estimation directly in the transmit-receive two-dimensional spatial frequency domain. Using this difference, the false target jamming and the real target can be discriminated.

[0075] Specifically, assume that there is a real target located at (θ S ,r S ), and Q jammers release a total of P false target jammings (Q ≤ P). The k-th jammer is located at (θ Jk ,r Jk ). The signal received by the entire array can be expressed as

[0076]

[0077] where x S and x J represent the received target and interference signals respectively, n is Gaussian white noise with a mean of 0 and a variance of , ξ S is the received target amplitude information, ξ Jk is the amplitude information of the k-th interference, v S (θ S ,r S ,Δf) is the steering vector of the received target, v Jk (θ Jk ,r Jk ,Δf) is the steering vector of the k-th interference, where v S is the target and v Jk is the k-th interference.

[0078] Assume that the distance corresponding to the true target echo in the time domain is r St , and the positions of Q jammers are The positions of the P false target interferences released in the time domain can be expressed as Since the interferences released by the jammers are randomly placed on different range gates, which are generally different from the positions of the jammers, that is, r Ji ≠r Jkt (i = 1, …, Q; k = 1, …, P),

[0079] Therefore, the transmit steering vector a(θ j , r j , Δf) and the receive steering vector b(θ j ) of the interference are respectively as follows:

[0080]

[0081]

[0082] For the FDA-MIMO radar in the form of linear frequency spacing, define the transmit spatial frequency f T,J and the receive spatial frequency f R,J respectively as:

[0083]

[0084]

[0085] Please refer to Figure 3 shown, which is the sector silent schematic diagram of a method for suppressing dense false target interference in the grid positioning of an FDA-MIMO radar according to the present invention;

[0086] In the method for suppressing dense false target interference in the grid positioning of an FDA-MIMO radar according to the present invention, in the step S3, the suppression of false target interference is to feed back the position of the interference source obtained in the step S2 to other radars in the radar network according to the information sharing mechanism of the radar network, and make the networking center instruct other radars in the radar network to take sector silence, and the FDA-MIMO radar forms an adaptive beam in the transmit-receive two-dimensional frequency domain to suppress dense false target interference.

[0087] Specifically, since the FDA-MIMO radar in the form of linear frequency spacing will be ambiguous when positioning the true target and the interference source, after discriminating the true target and the interference signal, the FDA-MIMO radar can adopt a non-linear form of frequency spacing (such as exponential form: Δf n =(e n-1) Δf), locate the real target and the jamming sources, and then feed back the positions of the jamming sources to other radars in the radar network. Other radars in the network take corresponding anti-jamming measures. The FDA-MIMO radar can suppress the interference of dense false targets in the transmit-receive two-dimensional frequency domain.

[0088] In this embodiment, the anti-jamming measure is sector silent. Sector silent does not mean that signals are not received at all in the direction of the jammer. Instead, the radar does not actively transmit signals in this direction. However, it should be noted that when the radar scans outside the sector silent area, there are still sidelobes in the sector silent area.

[0089] The normalized directional pattern gain of the spatial matched filtering with the beam pointing in the direction of θ0 is

[0090]

[0091] The main lobe width is

[0092]

[0093] When the main lobe of the radar antenna scans, only the sidelobes scan in the sector silent area. Moreover, the farther away from the main lobe of the antenna, the lower the antenna sidelobe level. That is, the larger the radar sector silent area, the lower the interference power entering the radar.

[0094] Example 1, please refer to Figures 4 - 7 as shown Figure 4 is the two-dimensional power spectrum diagram of angle-distance gates, Figure 5 is the true and false target distribution diagram in the transmit-receive two-dimensional frequency domain, Figure 6 is the real target spatial position diagram, Figure 7 is the angle-distance two-dimensional power spectrum diagram.

[0095] The simulation analysis of the true and false target discrimination and jamming source location of the FDA-MIMO radar in the method for an FDA-MIMO radar in a network to locate and suppress the interference of dense false targets of the present invention is as follows: Set the parameters as follows: Set the number of elements of the FDA-MIMO radar to 10, the carrier frequency to 3 GHz, the frequency interval to 3 kHz, the position of the real target to (0°, 180 km), located on the 100th range gate, the signal-to-noise ratio to 5 dB, there are 3 jammers, and the positions are (2°, 450 km), (15°, 300 km), (-25°, 200 km) respectively. Each jammer releases 3 false target interferences, located on the 40th, 100th, 160th, 70th, 100th, 130th, 20th, 100th, 180th range gates respectively. The interference-to-signal ratios of the interferences released by the 3 jammers are 15 dB, 25 dB, and 30 dB in sequence. When locating the real target and the jamming sources, an exponential form of frequency interval is adopted, and the base of the exponent is e = 1.2.

[0096] There are a total of 9 false targets and 1 real target in the two-dimensional angle-distance domain. Since there is no prior information about the position of the real target, it is impossible for the FDA-MIMO radar to distinguish which signal is the real target. Therefore, the FDA-MIMO radar cannot distinguish between false targets and real targets in the two-dimensional angle-distance gate domain. Since the false targets generated by the same jammer will be superimposed in the transmit-receive two-dimensional frequency domain, and the position is the position of the jammer in the transmit-receive two-dimensional frequency domain, rather than the position of the false target interference in the transmit-receive two-dimensional frequency domain. So when the positions of all signals in the two-dimensional angle-distance gate are transformed into the transmit-receive two-dimensional frequency domain and compared with the positions obtained by direct spatial spectrum estimation in the transmit-receive two-dimensional frequency domain space, only the position calculated for the real target coincides with the position obtained by direct spatial spectrum estimation; by accurately obtaining the distribution of true and false targets in the transmit-receive two-dimensional frequency domain, the output of the true target position is (0°, 180 km), which is consistent with the set parameters of the real target position.

[0097] Please refer to Figure 7 As shown, when performing spectrum estimation on signals in the two-dimensional angle-distance domain, the positions of the real target and the interference source (jammer) can be clearly estimated. After removing the position of the real target, the remaining is the position where the jammer is located, and the estimated value is basically consistent with the parameter settings.

[0098] Please refer to Figures 8 - 14 As shown, Figure 8 is a distribution diagram of a networked radar, targets, and jammers. Figure 9 is a positioning distribution diagram of an S-band jammer and a real target. Figure 10 is a positioning distribution diagram of an S-band jammer and a real target. Figure 11 is a time-domain filtering diagram of an L-band radar. Figure 12 is a time-domain filtering diagram of an S-band radar. Figure 13 is a transmit-receive frequency domain beamforming diagram of an FDA-MIMO radar. Figure 14 is a time-domain filtering diagram of an FDA-MIMO radar.

[0099] Network radar sector silent suppression of false target simulation analysis for the method of suppressing dense false target interference in the FDA-MIMO radar network positioning of the present invention. Suppose there is an S-band radar and an L-band radar networking with the FDA-MIMO radar. The operating frequency of the L-band radar is 1.2 GHz, the operating frequency of the S-band radar is 2.7 GHz, the carrier frequency of the FDA-MIMO radar is 3 GHz, and the frequency interval is 3 kHz. The L-band radar is located 60° east of north of the FDA-MIMO radar, with a distance of 250 km. The S-band radar is located 80° west of north of the FDA-MIMO radar, with a distance of 150 km. The antennas of all three radars are linear arrays, and the number of array elements is 20. When calculating at the networking center, a unified rectangular coordinate system is adopted, with the FDA-MIMO radar as the origin, and the counterclockwise deflection angle is the azimuth angle. Suppose there is a real target located at (0°, 180 km), the echo peak is located at the 180th range gate of the FDA-MIMO radar, and the signal-to-noise ratio is 5 dB. There is a jammer located at (2°, 450 km) of the FDA-MIMO radar, where 2° is the degree east of north of the FDA-MIMO radar. This jammer releases dense false target interference to the three radars, and the echo peaks are all located at the 40th, 60th, 80th, 100th, 120th, 140th, 160th, 180th, 200th, 220th, 240th, 260th, 280th, 300th, 320th, 340th, 360th, 380th range gates of the three radars, and the signal-to-noise ratio of the jammer is 25 dB. The FDA-MIMO radar can identify and locate the target and the interference source. Considering the positioning error, suppose the position of the located jammer is (1°, 470 km). When the positioning is completed, the position information of the interference source is sent to other radars in the radar network through the radar network. At this time, the L-band radar and the S-band radar estimate the position of the jammer with their own coordinate systems as the reference. In this embodiment, east of north is positive and west of north is negative.

[0100] Through estimation, the position of the jammer located by the L-band radar is (-59°, 403 km), the real target is located at (-14°, 223 km), the position of the jammer located by the S-band radar is (19°, 470 km), and the real target is located at (44°, 213 km). The jammer and the real target are far apart. Since the L-band radar and the S-band radar are different from the FDA-MIMO radar, their beam directions are independent of distance and only related to angle. Therefore, the interference can be suppressed by using the angle difference between the jammer and the real target. For example, sector silent can be carried out in the azimuth of the jammer.

[0101] Considering the possible range and angle errors in estimating the jammer position by L- and S-band radars, as well as the robust performance of sector blanking, the azimuth region centered on the azimuth of the jammer and deviating 5° to 10° up and down is defined as the sector blanking region. That is, the L-band radar sector blanking region is (-65°, -55°), and the S-band radar sector blanking region is (14°, 24°). Considering the worst-case scenario, the highest sidelobe level in the sector blanking region during the radar scanning process is used as the radar antenna gain when interference enters the radar. The simulation diagrams of the FDA-MIMO radar before and after filtering, and the simulation diagrams of the L- and S-band radars before and after sector blanking are as Figures 11 - 14 shown.

[0102] Since the L- and S-band radars adopt the sector blanking method to counter dense false target interference, the interference can only enter the radar through the antenna sidelobes. Through time-domain filtering, the L-band radar has basically removed the dense false target interference. Since the S-band radar is closer to the jammer, although the false target interference has not been completely filtered out, the energy of the false target interference has been weakened, and the output SINR has been increased. The FDA-MIMO radar utilizes its characteristic that the beam pointing is related to both range and angle, and points the beam to the location of the target in the transmit-receive two-dimensional frequency domain. At the same time, a null is adaptively formed at the location of the jammer, so that the false target interference can be directly suppressed during time-domain filtering, greatly improving the ability of the radar network to detect real targets.

[0103] According to the above analysis, the division of the sector blanking angle range directly affects the interference energy entering the L- and S-band radars, and thus affects the anti-jamming effect of the radar network. The present invention studies the influence of the setting of the sector blanking azimuth range of the L- and S-band radars (the sector blanking azimuth ranges of the two are set the same) on the evaluation of the anti-jamming effectiveness of the radar network. The main indicators include the network interference suppression ratio and the target detection probability. The network interference suppression ratio is the ratio of the sum of the output SINRs of all radars in the network before and after taking anti-jamming measures, and the target detection probability refers to the probability that the radar network correctly detects the target in the presence of interference. The influence of the sector blanking range on the anti-jamming effectiveness of the network is shown in the following table.

[0104]

[0105] Since the FDA-MIMO radar can identify and locate false target jammers and real targets, after it is networked with the L- and S-band radars, the located jammer source information is sent to other radars in the network, and sector blanking is performed on the location of the jammer source, which can well suppress the dense false target interference. And as the azimuth range of the sector blanking becomes larger and larger, the number of radars in the network that can detect real targets becomes more and more, and the probability of the L- and S-band radars in the network to detect targets increases sharply. The interference suppression ratio and the target detection probability of the three-radar network also become larger and larger.

[0106] So far, the technical solution of the present invention has been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, those skilled in the art can easily understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

[0107] The above are only the preferred embodiments of the present invention and are not used to limit the present invention; for those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for suppressing dense false target interference in the positioning of an FDA-MIMO radar when accessing the network, characterized in that, Including: Step S1: Transmit a linearly frequency-spaced signal through an FDA-MIMO radar and discriminate between true and false targets in the transmit-receive two-dimensional frequency domain, including: Step S11: The FDA-MIMO radar directly performs spatial spectrum estimation on the received signal in the spatio-temporal two-dimensional domain using linearly frequency-spaced signals to obtain the spatial position information of the received true and false targets; Step S12: Calculate the distributions of the true and false targets in the transmit-receive two-dimensional spatial frequency domain based on the obtained spatial positions of the true and false targets; Step S13: Directly perform spectrum estimation on the signals of all the received targets in the transmit-receive two-dimensional spatial frequency domain and compare the spectrum estimation result with the spatial position of the false target interference obtained in Step S12; Step S14: Determine the true and false targets based on the comparison result in Step S13. If the positions of two identical targets in the two-dimensional spatial frequency domain are the same, then determine that target as a true target; if the positions of two identical targets in the two-dimensional spatial frequency domain are different, then determine that target as a false target; Step S15: When the determination is completed, output the position of the true target; Step S2: Transmit a non-linearly frequency-spaced signal through the FDA-MIMO radar to locate the true target and interference sources in the two-dimensional airspace of angle-range gate; Step S3: When the positioning is completed, the networking center instructs the radars in the radar network to take corresponding interference measures in the direction where the interference sources are located to suppress the dense false target interference.

2. The method for suppressing dense false target interference in FDA-MIMO radar network access positioning according to claim 1, characterized in that In Step S2, the positioning of the true target and interference sources includes: changing the transmit frequency of the FDA-MIMO radar to a non-linearly frequency-spaced signal and performing spatial spectrum estimation on the received signal in the angle-range domain to obtain the spatial positions of the true target and interference sources, and obtaining the positions of all the interference sources after removing the position of the true target output in Step S15.

3. The method for suppressing dense false target interference in the network access positioning of the FDA-MIMO radar according to claim 2, wherein In Step S3, the suppression of the dense false target interference includes: according to the information sharing mechanism of the radar network, feeding back the positions of the interference sources obtained in Step S2 to the radars in the radar network, and enabling the networking center to instruct the radars in the radar network to take corresponding interference measures, and the FDA-MIMO radar forms an adaptive beam in the transmit-receive two-dimensional frequency domain to suppress the dense false target interference.

4. The method for suppressing dense false target interference in FDA-MIMO radar network access positioning according to claim 3, characterized in that, In Step S11, the spatio-temporal two-dimensional domain includes angle and time-domain distance.

5. The method for suppressing dense false target interference in FDA-MIMO radar network access positioning according to claim 4, characterized in that, The interference measure is sector silent, where sector silent means that other radars do not actively transmit signals in the direction where the jammer is located and perform scanning outside the sector silent area.

6. The method for suppressing dense false target interference in FDA-MIMO radar network access positioning according to claim 5, characterized in that, The FDA-MIMO radar is an equally spaced linear array with N array elements.

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