Realization method of frequency control array jamming signal for anti-airborne MIMO radar space domain filtering

Abstract

The application discloses a frequency control array jamming signal implementation method for resisting space domain filtering of airborne MIMO radar, and belongs to the technical field of radar jammer design based on frequency control array. Firstly, the frequency control array jammer intercepts radar signals, and carries out digital radio frequency storage processing on the radar signals to obtain jamming signals, and loads a deceptive delay on the jamming signals; then, after different frequency offsets are added to different radiating antennas of the frequency control array jammer, the jamming signals are transmitted in the form of array antennas; after the airborne MIMO radar receives the jamming signals, space-time adaptive processing is carried out on the jamming signals. Through the matched filtering of the airborne MIMO radar, a single frequency control array jammer can generate dense false targets in the distance dimension, which cannot be realized by a single traditional jammer technology; the frequency control array jammer can reduce the output signal-to-interference-and-noise ratio of the space domain filtering of the airborne MIMO radar, reduce the probability of target detection, and make the radar jamming suppression performance decrease.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radar jammer design based on frequency diverse array (FDA), and particularly relates to a frequency diverse array jamming signal implementation method for countering spatial filtering of an airborne multiple input multiple output (MIMO) radar. BACKGROUND

[0002] An airborne radar can realize spatial adaptive beamforming by using the spatial degrees of freedom of an array, increase an output signal-to-interference-plus-noise ratio (SINR), improve a target detection probability, and effectively complete sidelobe jamming suppression. As an opponent of the radar, a jammer plays an important role in jamming the radar and protecting the target. An effective jamming technology can obtain an information advantage in radar electronic warfare.

[0003] Existing jammer technologies mainly affect the detection performance of the radar by increasing the degrees of freedom occupied by a jamming signal (such as dense jamming and multi-point source jamming), polluting training samples in a range dimension (such as delay forwarding jamming and intermittent sampling forwarding jamming), polluting a unit under test with false Doppler deception information (such as Doppler deception jamming), and destroying the authenticity of training samples (such as scattering jamming). However, these methods are all premised on that the jammer intercepts a radar signal and directly forwards the radar signal after adding deception information, that is, the jamming signal and the radar signal have the same phase-frequency response, which provides a fixed signal processing idea for radar jamming suppression, that is, forming a null in the jamming by using spatial resolution capability. At present, taking the above jammer technologies as research objects, a large number of airborne radar anti-jamming technologies are widely researched and gradually implemented in engineering applications. Therefore, in order to improve the effectiveness of the jammer against the airborne radar and reduce the jamming suppression capability of the radar, a new jamming technology needs to be invented and designed. SUMMARY

[0004] The present application aims at: in order to reduce the STAP anti-jamming performance of the airborne radar, make up for the deficiency of the existing scattering jamming technology, propose a scattering jamming signal based on a frequency diverse array for countering the STAP anti-jamming of the airborne radar, so as to reduce the jamming suppression performance of the radar.

[0005] The technical solution adopted by the present application is:

[0006] The frequency diverse array jamming signal implementation method for countering the spatial filtering of the airborne MIMO radar comprises the following steps:

[0007] Step J1, a frequency diverse array jammer intercepts a radar signal of an airborne MIMO radar;

[0008] Step J2, the frequency control array jammer carries out digital radio frequency storage processing on the intercepted radar signal, including sampling, storage, jamming modulation processing and copying, and loading deception delay on the jamming signal obtained by jamming adjustment processing;

[0009] Step J3, after different frequency offsets are added to different radiating antennas of the frequency control array jammer, the jamming signal is transmitted in the form of an array antenna;

[0010] After the airborne MIMO radar receives the jamming signal, it carries out space-time adaptive processing, including:

[0011] Step R1, the airborne MIMO radar carries out matched filtering sampling on each fast time sampling unit of the jamming signal, to obtain a matched filtering result;

[0012] Step R2, the airborne MIMO radar carries out adaptive spatial filtering on the matched filtering result, to complete jamming suppression.

[0013] Further, in step J1, the kth pulse signal of the radar signal of the airborne MIMO radar intercepted by the frequency control array jammer is:

[0014]

[0015] Wherein, ξ j is the scattering coefficient of the frequency control array jammer, represents the transmission steering vector of the airborne MIMO radar, u(t-τ j represents the transmission baseband waveform vector of the airborne MIMO radar, τ j =R j / c is the propagation delay of the jamming signal, c represents the speed of light, f0 is the transmission signal carrier frequency, T represents the pulse signal period, and t represents the sampling time;

[0016] Based on the kth pulse signal e k (t) of the radar signal, the kth pulse jamming signal transmitted by the pth radiating antenna of the frequency control array jammer is:

[0017]

[0018] Wherein, ρ p represents the pth radiating antenna coefficient of the frequency control array jammer, Δf' represents the frequency offset added by the frequency control array jammer, represents the delay of signal propagation in the jammer antenna array, d j represents the spacing of the frequency control jammer antenna array, and P represents the number of radiating antennas of the frequency control array jammer.

[0019] Further, the airborne MIMO radar is a MIMO transceiving co-located airborne radar composed of S transmitting antennas and N receiving antennas.

[0020] Further, the kth pulse signal vector about the target received by the N receiving array elements of the airborne MIMO radar is:

[0021]

[0022] wherein, represents a MIMO radar receiving steering vector, θ t are the azimuth angle and the elevation angle of the target respectively, t is the scattering coefficient of the target, u(t-τ t ) represents a MIMO radar receiving baseband waveform vector, t t is the propagation time delay of the target signal, and t represents a sampling time.

[0023] The kth pulse signal about the frequency control array jammer received by the N receiving array elements of the airborne MIMO radar is:

[0024]

[0025] And for the target signal, the space-time data obtained by the airborne MIMO radar is represented as:

[0026]

[0027] wherein, represents a time-domain Doppler vector, represents a Kronecker product;

[0028] For the jamming signal transmitted by the frequency control array jammer, the space-time data of the MIMO radar is represented as:

[0029]

[0030] wherein, Y (FDA) represents a spectrum leakage matrix caused by the frequency offset of the jammer.

[0031] The technical solution provided by the present application at least brings the following beneficial effects:

[0032] Through the matched filtering of the airborne MIMO radar, a single frequency control array jammer can generate dense false targets in the range dimension, which cannot be realized by a single conventional jammer technology; the present application can reduce the output signal-to-interference-and-noise ratio of the space filtering of the airborne MIMO radar through the frequency control array jammer, reduce the probability of target detection, and make the radar jamming suppression performance decline. BRIEF DESCRIPTION OF DRAWINGS ​

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiments description. Obviously, the drawings in the following description only represent some of the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative effort based on these drawings.

[0034] Figure 1 The antenna structure diagram of the frequency control array jammer used in the embodiments of the present application.

[0035] Figure 2 The spatial coordinate scene diagram of the radar, the target to be detected and the frequency control array jammer involved in the embodiments of the present application.

[0036] Figure 3 The azimuth dimension beam pattern after the space domain filtering of the airborne MIMO radar is shown.

[0037] Figure 4 The output signal-to-noise ratio versus input signal-to-noise ratio graph under the conditions of different transmitting array element numbers and different interference frequency offsets is shown. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the following will describe the technical solutions in the embodiments of the present application in detail and completely with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings can be arranged and designed using different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not only to limit the scope of the claimed present application, but only to represent selected embodiments of the present application.

[0039] The embodiments of the present application provide a frequency control array jamming signal implementation method against the space domain filtering of the airborne MIMO radar, and the frequency control array jammer including a plurality of radiation antennas, a jammer receiver and a digital radio frequency memory performs the following processing on the radar signal:

[0040] Step J1, the frequency control array jammer intercepts the radar signal;

[0041] Step J2, the frequency control array jammer performs high-speed sampling, storage, jamming modulation processing and copying on the intercepted radar signal based on the digital radio frequency memory (DRFM) (i.e. realized based on the jammer receiver and the digital radio frequency memory), and loads a deceptive delay on the jamming signal obtained by the jamming adjustment processing;

[0042] Step J3, after adding different frequency offsets to different radiating antennas of the frequency control array jammer, the jamming signal is transmitted in the form of array antenna;

[0043] After the airborne radar receives the jamming signal, the airborne radar performs space-time adaptive processing on the received jamming signal to achieve interference suppression, including:

[0044] Step R1, the airborne radar receives the jamming signal transmitted by the frequency control array jammer;

[0045] Step R2, the airborne radar performs matched filtering sampling on each fast time sampling unit of the jamming signal to obtain a matched filtering result;

[0046] Step R3, the airborne radar performs adaptive space filtering on the matched filtering result to complete interference suppression.

[0047] Consider a frequency control array jammer composed of P radiating antennas and a MIMO transceiver co-located airborne radar composed of S transmitting antennas and N receiving antennas. Assuming the number of coherent pulses is K, the height and flight speed of the airborne radar are H and v a , the spatial coordinate scene diagram of the airborne radar, the target to be detected and the jammer is shown in Figure 2 . The azimuth angle of the target is The elevation angle is θ t (distance R t = H / sinθ t ), the speed is v t , and the scattering coefficient is ξ t . The azimuth angle of the jammer is The elevation angle is θ j (distance R j = H / sinθ j ).

[0048] In step J1, the kth pulse signal intercepted by the jammer can be expressed as

[0049]

[0050] where, represents the MIMO radar transmit steering vector, and u(t) represents the MIMO radar transmit baseband waveform vector.

[0051]

[0052] u(t) = [A(t) A(t)e j2πΔft … A(t)e j2π(S-1)Δft ] T

[0053] where d is the MIMO radar transmitting array element spacing, f0is the transmitting signal carrier frequency, A(t) is the time length T p unit energy baseband envelope signal, Δf ensures that the different transmitting array element signal spectrums do not overlap, Δf » 1 / T p . τ j = R j / c is the propagation time delay of the interference signal.

[0054] In steps J2 and J3, the interference signal of the kth pulse transmitted by the pth radiating antenna of the frequency control array jammer is

[0055]

[0056] where ρ p represents the pth radiating antenna coefficient of the frequency control array jammer, Δf' represents the additional frequency offset of the frequency control array jammer, represents the propagation delay of the signal at the jammer antenna array, d j represents the jammer antenna array spacing.

[0057] In step R1, the kth pulse signal vector received by the N receiving array elements of the airborne MIMO radar with respect to the target is

[0058]

[0059] where represents the MIMO radar receiving steering vector, τ t = R t / c is the propagation time delay of the target signal.

[0060]

[0061] The kth pulse signal received by the N receiving array elements of the airborne MIMO radar with respect to the frequency control array jammer is

[0062]

[0063] In step R2, for the target signal, the space-time data output by the MIMO radar matched filter can be expressed as

[0064]

[0065] where represents the time domain Doppler vector, represents the Kronecker product.

[0066]

[0067] For the frequency control array jamming signal, the space-time data outputted by the MIMO radar matched filter can be expressed as

[0068]

[0069] wherein Y (FDA) represents the spectrum leakage matrix caused by the frequency offset of the jammer, which can be expressed as

[0070]

[0071] The correlation vector p, g(R j , Δf'), z(t), X(t) can be respectively expressed as

[0072] p = [p1 p2 … p P ]

[0073]

[0074]

[0075] z(t) = [1 e j2πΔf't … e j2π(P-1)Δf't ] T

[0076]

[0077] In step R3, the airborne MIMO radar can realize space domain filtering by using the minimum variance distortionless response (MVDR) beamformer, and the optimal weight vector of the filter can be expressed as

[0078]

[0079] wherein R u represents the target-free covariance matrix,

[0080]

[0081] wherein n represents the zero-mean Gaussian white noise sampling sequence after the MIMO radar matched filtering, and the variance is E represents the mathematical expectation.

[0082] wherein the azimuth dimension beam pattern of the MIMO radar space domain filtering can be expressed as:

[0083]

[0084] The output signal-to-interference-and-noise ratio can be expressed as

[0085]

[0086] wherein

[0087]

[0088]

[0089]

[0090] The spatial filtering results of the conventional jammer and the frequency control array jammer are simulated according to the parameters in Table 1, so as to show the technical advantages of the present application.

[0091] Table 1 Parameter setting

[0092]

[0093] Figure 3 The azimuth beam pattern of the airborne MIMO radar after spatial filtering is shown, wherein Δf' = 0 kHz represents the conventional jammer as a comparative experiment. It can be obviously seen that when Δf' ≠ 0 kHz, the interference null at the azimuth angle of 15° rises, which shows that the interference suppression capability of the radar spatial filtering is reduced. With the increase of Δf', the null depth is shallower and shallower, because the frequency deviation of the frequency control array jammer causes a large phase difference, so that the phase of the covariance matrix element is mismatched.

[0094] Figure 4 The simulation diagram of the output signal-to-noise ratio under the influence of different interference frequency deviations under different transmitting array element numbers is shown, wherein Δf' = 0 kHz represents the conventional jammer as a comparative experiment. It can be seen from the diagram that with the increase of Δf', the output signal-to-noise ratio decreases, which shows that the interference suppression effect of the radar spatial filtering is deteriorated. With the increase of the transmitting array element number, the influence of the frequency control array jammer on the MIMO radar is greater, and the interference suppression capability of the radar is worse.

[0095] The above theoretical analysis and simulation experiment show the effectiveness of the frequency control array jammer provided by the embodiment of the present application against the spatial filtering of the airborne MIMO radar.

[0096] Embodiment

[0097] Consider that an airborne MIMO radar will detect a ground moving target, and the radar detection scene is as follows Figure 1The radar flies along the X axis at a height of 300 m and a speed of 150 m / s. There is a moving target in the ground area of interest, which is 6 km away from the radar and located at an azimuth angle of 0°. The airborne MIMO radar has 16 transmitting antennas and 16 receiving antennas, transmits a rectangular pulse signal to probe the target at a pulse repetition frequency of 20 kHz, the number of pulses in a coherent processing interval (CPI) is 8, the carrier frequency is 10 GHz, and the distance between the transmitting and receiving elements is half a wavelength.

[0098] In this embodiment, the frequency control array jammer is placed near the target at an azimuth angle of 15°, and the transmitted jamming signal enters from the sidelobe of the radar array antenna. The frequency control array jammer has 4 radiating antennas with a half-wavelength spacing. The frequency offset of the frequency control array jammer is set to be different from 0 to 20 kHz. The specific working process of the frequency control array jammer is as follows: when the radar transmits a pulse signal to probe the target, the frequency control array jammer intercepts the radar signal, copies and modulates the radar signal through a digital radio frequency memory, and transmits a frequency control array jamming signal to the radar after adding a frequency offset to the radiating antenna.

[0099] The airborne MIMO radar receives the reflected signal from the target and the signal from the frequency control array jammer, obtains a data sequence after sampling through a matched filter, and performs adaptive beamforming by using an MVDR spatial filter to suppress the interference energy in the direction of 15°. Figure 3 The azimuth dimension beam pattern after MVDR beamforming is shown, and it can be seen that, compared with the conventional jammer technology (Δf' = 0 kHz), the frequency control array jammer with a frequency offset of 9.6 kHz can make the interference null rise by 10 dB, and as the frequency offset increases to 12 kHz, the interference null can be increased by 20 dB, which shows that the frequency control array jammer can effectively reduce the energy of the radar spatial filtering interference suppression and alleviate the elimination of interference energy. Figure 4 The simulation diagram showing the change of the output signal-to-interference-and-noise ratio of the airborne MIMO radar with the input signal-to-noise ratio after spatial filtering is shown, and compared with the conventional jammer technology (Δf' = 0 kHz), the frequency control array jammer with a frequency offset of 2.4 kHz can make the output signal-to-interference-and-noise ratio decrease by 6 to 8 dB, and the frequency control array jammer with a frequency offset of 4.8 kHz can make the output signal-to-interference-and-noise ratio decrease by more than 10 dB.

[0100] The simulation experiment results show that the embodiment of the present application is effective in countering the spatial filtering processing of the airborne MIMO radar based on the frequency control array jammer.

[0101] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the same; although the present application has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some technical features therein can be replaced by equivalents; and such modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

[0102] The above only describes some embodiments of the present application. For those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are all within the protection scope of the present application.

Claims

1. A method for implementing frequency control array jamming signals against space domain filtering of airborne MIMO radars, characterized in that, The method comprises the following steps: Step J1, the frequency control array jammer intercepts the radar signal of the airborne MIMO radar; Step J2, the frequency control array jammer carries out digital radio frequency modulation storage processing on the intercepted radar signal to obtain an interference signal, and loads a deception delay on the interference adjustment processed interference signal; Step J3, after different frequency offsets are added to different radiating antennas of the frequency control array jammer, the interference signal is transmitted in the form of an array antenna; After the airborne MIMO radar receives the interference signal, the airborne MIMO radar carries out space-time adaptive processing, comprising: Step R1, the airborne MIMO radar carries out matched filtering sampling on each fast time sampling unit of the interference signal to obtain a matched filtering result; Step R2, the airborne MIMO radar carries out adaptive space filtering on the matched filtering result to complete interference suppression; In step J1, the kth pulse signal of the radar signal of the airborne MIMO radar intercepted by the frequency control array jammer is: wherein, is the scattering coefficient of the frequency control array jammer, denotes the transmit steering vector of the airborne MIMO radar, denotes the azimuth and elevation angles of the jammer, respectively; denotes the transmit baseband waveform vector of the airborne MIMO radar, is the propagation time delay of the jamming signal, the distance , denotes the height of the airborne MIMO radar, denotes the speed of light, is the carrier frequency of the transmit signal, T denotes the period of the pulse signal, and t denotes the sampling time; The kth pulse signal based on the radar signal The kth pulse interference signal emitted by the pth radiating antenna of the frequency control array jammer is: wherein, represents the pth radiation antenna coefficient of the frequency-controlled array jammer, P represents the number of radiation antennas of the frequency-controlled array jammer, e represents the natural base, represents the frequency offset added by the frequency-controlled array jammer, represents the delay of the signal propagating through the antenna array of the jammer, represents the spacing of the antenna array of the frequency-controlled jammer.

2. The method of claim 1, wherein, The airborne MIMO radar is a MIMO transmitting-receiving co-located airborne radar composed of S transmitting antennas and N receiving antennas.

3. The method of claim 2, wherein, The kth pulse signal vector about a target received by the N receiving array elements of the airborne MIMO radar is: wherein a scattering coefficient of interest, denotes a MIMO radar receive steering vector, , denote an azimuth angle and an elevation angle of interest, respectively, denotes a MIMO radar receive baseband waveform vector, is a propagation time delay of the target signal, t denotes a sampling time, ; The kth pulse signal about the frequency control array jammer received by the N receiving array elements of the airborne MIMO radar is: ； And for the target signal, the space-time data obtained by the airborne MIMO radar is represented as: wherein denotes the time-domain Doppler vector, denotes the Kronecker product; For the interference signal transmitted by the frequency control array jammer, the space-time data of the MIMO radar is represented as: wherein represents the spectrum leakage matrix caused by the jammer frequency offset.

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