Coherent active bait design method

Abstract

The invention relates to a coherent active bait design method. The method comprises the following steps: time sequence synchronization: a radar data processing program transmits timing signals, beam pointing and control instruction information required by baits to the baits in advance; the bait receives an optical timing signal, converts the optical timing signal into an electric signal through photoelectric conversion equipment, processes the timing signal and an instruction signal, and sends the processed signals to each subsystem of the bait; frequency synchronization: a radar frequency source generates a frequency reference and synchronizes the frequency reference to each bait, the bait generates a radio frequency signal based on the received frequency reference, and it is ensured that a bait signal and a radar signal are coherent; and decoy beam forming: obtaining the direction of a protected radar transmitting beam in real time, and performing special phase weighting on each unit of the decoy phased-array antenna to enable the decoy transmitting beam to form a zero point in the direction of the radar beam direction. The coherent decoy is designed in the aspects of time-frequency synchronization, decoy beam forming and the like aiming at the coherent decoy, so that the coherent decoy is realized to decoy anti-radiation weapons and new-system anti-radiation seekers.

Description

Technical Field

[0001] This invention relates to the field of radar technology, and in particular to a coherent active decoy design method. Background Technology

[0002] With the continuous development and deployment of anti-radiation missiles and electronic warfare aircraft, the threat to early warning and intelligence radars and surface-to-air missile weapon systems is increasing. To improve the battlefield survivability of radar equipment, equipping it with decoy systems to counter anti-radiation missiles is particularly important.

[0003] Based on the phase relationship between the decoy's radiated signal and the protected radar's radiated signal, decoy systems can be divided into two types: coherent and non-coherent. In a coherent system, the decoy's radiated signal is at the same frequency as the protected radar's radiated signal and maintains a certain phase relationship. When the power of each radiation source received by the seeker antenna is approximately equal and the phase difference is close to 180°, the seeker's angle measurement value will have a significant error, causing the angle measurement direction to move away from both the decoy and the protected radar.

[0004] Some advanced anti-radiation missile seekers employ spatial spectrum estimation techniques to improve angular resolution. For non-coherent decoy signals and radar signals within the seeker's field of view, spatial spectrum estimation effectively enhances angular resolution. However, for coherent decoy signals, the seeker requires decoherent processing, which to some extent reduces the angular resolution performance of spatial spectrum estimation. Therefore, coherent decoys have a certain advantage in countering anti-radiation missile seekers that use spatial spectrum estimation for angle measurement. Summary of the Invention

[0005] To address the existing technical problems, this invention provides a coherent active decoy design method.

[0006] The specific content of this invention is as follows: A coherent active decoy design method, comprising the following steps:

[0007] (1) Radar and decoy timing synchronization: After the radar data processing program calculates the timing signal required by the decoy in advance, it transmits it to each decoy through fiber optic / wireless synchronization equipment. The radar also transmits beam pointing and control command information to each decoy. The decoy receives the optical timing signal and converts it into an electrical signal through photoelectric conversion equipment. After processing the timing signal and command signal, it sends them to each subsystem of the decoy.

[0008] (2) Radar and decoy frequency synchronization: The radar frequency source generates a frequency reference, which is converted into an optical signal by an electro-optical conversion device. After optical amplification and power division, the signal is transmitted / synchronized to each decoy through an optical fiber / wireless synchronization device. The decoy generates a radio frequency signal based on the received frequency reference to ensure that the decoy signal is correlated with the radar signal.

[0009] (3) Decoy beamforming: Real-time acquisition of the direction of the protected radar transmitting beam, and special phase weighting of each unit of the decoy phased array antenna, so that the decoy transmitting beam forms a null in the direction of the radar beam.

[0010] Further, the decoy waveform and timing need to be generated 30us in advance.

[0011] Further, when transmitted through optical fiber, first transmit the protected radar frequency reference optical signal, radar timing signal, and instructions to the control equipment cabinet; transmit the frequency reference optical signal, decoy timing signal processed by the decoy control module, and instructions to each decoy station; and complete the conversion of the frequency reference optical signal to an electrical signal in the decoy station.

[0012] Further, when synchronized through a wireless synchronization device, use distributed broadband wireless synchronization technology to synchronize the frequency reference from the control equipment cabinet to each decoy station, and transmit the decoy timing signal and instructions from the control equipment cabinet to each decoy station, to complete the interaction of the frequency reference, timing, and instructions between the control equipment cabinet and each decoy station.

[0013] Further, in step (3), decoy beamforming includes the following steps:

[0014] (31) Squared phase distribution method to expand the beam:

[0015] Based on the squared phase distribution to achieve beam expansion, the formula is as follows:

[0016]

[0017] Where N is the number of elements of the array, is the expansion factor, adjusting this value can get different beam expansion patterns;

[0018] (32) Nulling the main lobe direction of the beam:

[0019] Taking a one-dimensional linear array as an example, the phase weighting value is symmetrically inverted with the middle element, which realizes the formation of a null in the direction of the radar beam by the decoy transmitting beam, and the formula is as follows:

[0020]

[0021] (33) Beamforming:

[0022] Assuming that the decoy beam direction is , the decoy beam is obtained according to the following formula:

[0023]

[0024] In the formula, is the amplitude, is the ideal pattern of the antenna unit, is the interval of the linear array unit, is the position of the target.

[0025] The present application is directed to coherent decoys, and designs in time-frequency synchronization, decoy beamforming, etc., to realize coherent decoys to deceive anti-radiation weapons and new system anti-radiation seekers. BRIEF DESCRIPTION OF DRAWINGS

[0026] The present application will be further clarified by the following description with reference to the accompanying drawings.

[0027] Figure 1 is a schematic diagram of protected radar and decoy non-coherent synthesis;

[0028] Figure 2 is a schematic diagram of protected radar and decoy coherent synthesis;

[0029] Figure 3 is a beam weighting code. DETAILED DESCRIPTION

[0030] In combination Figures 1-3 The present application provides a coherent active decoy design method, which is designed based on the phased array system of active decoy, and realizes the coherent design of decoy through time-frequency synchronization and decoy beamforming. The steps are as follows:

[0031] I. Time sequence synchronization of decoy and protected radar

[0032] In order to effectively decoy anti-radiation missiles, the decoy system must emit the same or similar electromagnetic signals as the protected radar. In addition, in order to prevent the seeker from distinguishing the decoy signal from the radar signal in the time domain, the emission time of the decoy signal must be strictly controlled. Multiple decoy signals should arrive at the seeker antenna aperture at the same time, completely "covering" the radiation signal of the protected radar. At the same time, the signal emission time of the decoy station must be avoided to enter the receiving gate of the protected radar to ensure the normal operation of the radar.

[0033] The decoy control device needs to introduce the waveform, time sequence and beam pointing information provided by the protected radar, and these information should be transmitted to the decoy control device in advance to realize the "synchronous" emission of the decoy and the radar. This requires the protected radar to generate the waveform and time sequence of the decoy in advance according to the task, because the decoy is generally arranged at a distance of 300~600m from the protected radar, so the decoy waveform and time sequence should be generated at least 4us in advance. In fact, the time required for generating the decoy waveform and time sequence also needs to be considered, so generally it needs to be generated 30us in advance, so as to realize the time sequence synchronization of the decoy and the protected radar.

[0034] II. Frequency synchronization of decoy and protected radar

[0035] The frequency of the decoy radiation signal should be the same or similar to the protected radar (the difference should not exceed the frequency resolution of the passive radar seeker of the anti-radiation weapon, usually 0.5MHz-1MHz), and when the radar frequency is agile, the frequency of the decoy radiation signal can be switched in real time to synchronize with the radar, so as to avoid the anti-radiation weapon identifying the protected radar and the decoy from the frequency domain analysis with pre-attack information. By synchronizing the frequency reference of the protected radar to the decoy, the frequency of the decoy is synchronized with the protected radar.

[0036] The waveform, timing, command and beam pointing information between the decoy and the protected radar can be transmitted by optical fiber transmission and wireless synchronization, realizing time-frequency synchronization and information interaction.

[0037] 1. Optical fiber transmission

[0038] First, the protected radar frequency reference optical signal, radar timing and command are transmitted to the control equipment cabinet; the frequency reference optical signal and the decoy timing and command processed by the decoy control module are transmitted to each decoy station; the frequency reference optical signal is converted into an electrical signal in the decoy station.

[0039] 2. Wireless synchronization

[0040] The distributed wideband wireless synchronization technology is adopted to synchronize the frequency reference from the control equipment cabinet to each decoy station, and to transmit the decoy timing and command from the control equipment cabinet to each decoy station, completing the interaction of the frequency reference, timing and command between the control equipment cabinet and each decoy station.

[0041] a) Three, decoy beam shaping

[0042] The emission lobe of the protected radar is formed by the spatial interference superposition of the mutually coherent signals emitted by each radiation element of the array. When the decoy is in a coherent working state, its emission signal is consistent with the emission signal of the protected radar in frequency and phase, and the emission time period overlaps. At this time, the coherent radiation signal of the decoy will also interfere and superimpose with the emission signal of the protected radar in space, causing distortion of the main lobe of the protected radar. The main lobe distortion will cause additional fluctuations in the signal-to-noise ratio of the received signal, and the lifting of the side lobe may cause the generation of false target echoes.

[0043] To solve this problem, in order to reduce the influence of coherent decoy deflection on the main lobe distortion of the radar emission beam, a special shaping method for the decoy beam can be used. The specific implementation is to obtain the pointing of the protected radar emission beam in real time, and to perform special phase weighting on each element of the decoy phased array antenna, so that the decoy emission beam forms a zero point in the direction of the radar beam pointing. In addition, in order to more comprehensively cover the protected radar side lobe space, the decoy emission beam is widened. The steps of decoy beam shaping are as follows:

[0044] 1) Squaring rate phase distribution method to expand beam

[0045] The squaring rate phase distribution is used to expand the beam, and the formula is as follows:

[0046]

[0047] Wherein, N is the number of elements of the array, is the expansion factor, and adjusting the value can obtain different beam expansion patterns.

[0048] 2) Beam main lobe direction zeroing

[0049] Taking a one-dimensional linear array as an example, the phase weighting value is symmetrically reversed with the middle vibration element, so that the decoy transmitting beam can form a zero point in the radar beam direction. The formula is as follows:

[0050]

[0051] 3) Beam forming

[0052] Suppose the decoy beam pointing direction is , and the decoy beam can be obtained according to the following formula.

[0053]

[0054] In the formula, is the amplitude, is the ideal directional diagram of the antenna element, is the linear array element spacing, is the position of the target.

[0055] Taking a linear array as an example, the beam forming design is carried out, the number of elements of the radiation source 1 is 66, which is used as a radar, the number of elements of the radiation source 2 at a distance of 260m is 12, which is used as a decoy; The element spacing of the radar and the decoy is 29.5cm, the wavelength is 5.65cm, the radiation power of each element is the same, the azimuth pointing directions of the radar and the decoy are consistent, and they are all pointed to-20 degrees.

[0056] The beam expansion code and the zeroing weighting code calculated according to formula (1) and formula (2) are set as shown in Figure 3 . The combined directional diagram of the radar transmitting beam before / without beam forming of the decoy can be seen in Figure 1 and Figure 2 . It can be seen that when the decoy beam is not shaped, the main lobe of the combined directional diagram is distorted and fluctuates, which will cause the signal-to-noise ratio of the radar receiving signal to fluctuate, and even cause unstable tracking and target loss; and after the decoy beam is shaped, the distortion of the combined directional diagram is obviously reduced.

[0057] The application analyzes the timing and frequency synchronization ability required by the phase comparison decoy design, and designs a synchronous transmission mode; based on the decoy beam broadening and decoy beam shaping design, the decoy beam achieves comprehensive coverage of the protected radar sidelobe space, and reduces the distortion of the decoy transmitting beam to the radar transmitting beam pattern main lobe.

[0058] In the above description, many specific details are set forth in order to provide a thorough understanding of the present application. However, the above description is merely a preferred embodiment of the present application, and the present application can be carried out in many different ways other than those described above, and therefore the present application is not limited by the specific implementation disclosed above. Meanwhile, any person skilled in the art can make many possible changes and modifications to the technical solutions of the present application, or modify them into equivalent embodiments, by using the methods and technical contents disclosed above, without departing from the scope of the technical solutions of the present application. Any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application, without departing from the content of the technical solutions of the present application, shall still fall within the scope of protection of the technical solutions of the present application.

Claims

1. A method for designing coherent active decoys, characterized in that: Includes the following steps: (1) Synchronization between radar and decoy: The radar data processing program transmits the timing signal, beam pointing and control command information required by the decoy to each decoy in advance; the decoy receives the optical timing signal and converts it into an electrical signal through the photoelectric conversion device, and then processes the timing signal and command signal and sends them to each subsystem of the decoy; (2) Radar and decoy frequency synchronization: The radar frequency source generates a frequency reference, which is synchronized to each decoy. The decoy generates radio frequency signals based on the received frequency reference to ensure that the decoy signal is correlated with the radar signal; (3) Decoy beamforming: The direction of the transmitted beam of the protected radar is obtained in real time, and special phase weighting is applied to each element of the decoy phased array antenna so that the transmitted beam of the decoy forms a null in the direction of the radar beam.

2. The coherent active decoy design method according to claim 1, characterized in that: The decoy waveform and timing need to be generated 30µs in advance.

3. The coherent active decoy design method according to claim 1, characterized in that: When transmitting via optical fiber, the protected radar frequency reference optical signal, radar timing signal, and command are first transmitted to the control equipment cabinet; the frequency reference optical signal, the decoy timing signal processed by the decoy control module, and the command are transmitted to each decoy station; and the frequency reference optical signal is converted into an electrical signal within the decoy station.

4. The coherent active decoy design method according to claim 1, characterized in that: When synchronizing via wireless synchronization equipment, distributed broadband wireless synchronization technology is used to synchronize the frequency reference from the control equipment cabinet to each decoy station, and to transmit the decoy timing signals and commands from the control equipment cabinet to each decoy station, thus completing the interaction of frequency reference, timing and commands between the control equipment cabinet and each decoy station.

5. The coherent active decoy design method according to claim 1, characterized in that: In step (3), the decoy beamforming includes the following steps: (31) Beam widening using the square law phase distribution method: Beam broadening is achieved based on the square-law phase distribution, as shown in the following formula: ， Where N is the number of elements in the array. This is the beamwidth factor; adjusting this value will yield different beamwidth patterns. (32) Set the main lobe direction of the beam to zero: Taking a one-dimensional linear array as an example, its phase weighting value is symmetrically reversed with respect to the middle element, so that the decoy's transmission beam forms a null point in the direction of the radar beam. The formula is as follows: ，， (33) Beamforming: Assuming the decoy beam is pointed as The decoy beam is obtained according to the following formula: ， In the formula, For amplitude, This represents the ideal radiation pattern of the antenna element. For the spacing of linear array elements, The location of the target.

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