Target feature agility system and method for target stealth

Abstract

The invention discloses a target feature agility system and method for target stealth, and the system comprises a signal processing subsystem which is used for sorting and recognizing signals, and deploying a complete RCS database and agility style of a target body; the intermediate frequency processing subsystem is used for collecting and analyzing intermediate frequency data, generating agile waveforms and outputting the intermediate frequency data; the radio frequency processing and transmitting subsystem is used for receiving the multiple paths of agile intermediate frequency signals, converting the multiple paths of agile intermediate frequency signals into multiple paths of radio frequency signals through frequency mixing, and outputting the multiple paths of radio frequency signals through power amplification; the radio frequency processing and receiving subsystem is used for mixing the radio frequency signals and then converting the radio frequency signals into intermediate frequency signals; and the air feed system is used for radiating the received signal to the space according to a specific polarization mode and receiving an enemy radar waveform at the same time. According to the method, the ground noise of the echo signal can be enhanced, the signal-to-noise ratio of the echo signal of the target body is weakened, the radar CFAR detection threshold is improved, and the radar detection distance is shortened; the agility mode is flexible and variable, the adaptive scene is wide, the engineering implementation is high, and an effective stealth means is provided.

Description

Technical Field

[0001] The present invention relates to the field of target stealth technology, and in particular to a target feature agile changing system and method for target stealth. Background Art

[0002] Under the current situation, stealth and anti-stealth means are developing rapidly in the field of electronic countermeasures. On the one hand, the development of stealth technology has improved the survivability of the target itself, which has posed a severe challenge to the radar detection system. On the other hand, in response to the development of target stealth technology, all parties are accelerating the research on radar anti-stealth technology. Radar detection performance is improved by adopting technologies such as meter-wave radar anti-stealth, air-based platform anti-stealth, dual / multi-base and networked radar anti-stealth. Therefore, how to further improve the stealth performance of the target on the basis of existing stealth technology is a problem that must be solved at present.

[0003] Currently, the commonly used target stealth technologies mainly include passive stealth technologies such as material stealth and shape stealth, as well as active stealth technologies such as active cancellation.

[0004] (1) Among passive stealth technologies, material stealth technology uses absorbing materials to reduce the radar cross-section (RCS) to achieve target stealth. However, absorbing materials have certain frequency selectivity, and usually have poor absorbing performance in low-frequency bands, which significantly reduces stealth performance. Shape stealth technology optimizes the shape structure to reflect radar signals to the direction with less threat, thereby achieving stealth. However, shape stealth is not omnidirectional. It mainly reduces the RCS in some directions, while the RCS in other directions is significantly increased, greatly reducing the stealth effect.

[0005] (2) In active stealth technology, active cancellation technology is to collect radar signals and modulate them to produce a coherent waveform with the same amplitude and opposite phase as the target echo, which is superimposed on the real echo signal to reduce the echo energy, thereby achieving the stealth effect. Active cancellation is only effective in the direction of the radar wave, and may even have an enhanced effect at other angles, and the engineering implementation is relatively difficult.

[0006] Therefore, it is necessary to design a target feature agility system and method for target stealth to solve the above problems. Summary of the invention

[0007] In order to solve the above problems, a target feature agility system and method for target stealth is provided, in which one or more high-performance active electronic devices capable of detecting the frequency and angle of the radar incident wave and having storage and forwarding capabilities are mounted on the target body, and the target feature agility system is provided. The coherent echo generated by the device has a randomly agile amplitude and phase, and the agility time can be as fast as hundreds of nanoseconds. The multi-agile source method is mainly aimed at target bodies with multiple strong scattering centers. This technology can enhance the background noise of the echo signal, weaken the signal-to-noise ratio of the target body echo signal, improve the radar CFAR detection threshold, and shorten the radar detection distance. The agile mode of this technology is flexible and variable, adaptable to a wide range of scenarios, and has strong engineering feasibility, providing an effective stealth means in the field of electronic countermeasures.

[0008] The present invention provides a target feature agile system and method for target stealth, which generates a coherent waveform with random amplitude and phase agility, enhances the noise floor of the echo signal of the target body, and weakens its signal-to-noise ratio, specifically including:

[0009] The signal processing subsystem is used to sort and identify signals and deploy the complete RCS database and agile patterns of the target entity;

[0010] The intermediate frequency processing subsystem is connected to the signal processing subsystem and is used for collecting and analyzing intermediate frequency data, generating agile waveforms, and outputting intermediate frequency data;

[0011] The radio frequency processing and transmitting subsystem is used to receive the agile multi-channel intermediate frequency signals output by the intermediate frequency processing subsystem, mix and convert them into multi-channel radio frequency signals, and output them after power amplification;

[0012] The RF processing receiving subsystem mixes the RF signal and converts it into an intermediate frequency signal, which is then transmitted to the intermediate frequency processing subsystem;

[0013] The air-feed system is used to radiate the signal received from the RF processing transmitting subsystem into space in a specific polarization mode, and at the same time receive the enemy radar waveform and transmit it to the RF processing receiving subsystem.

[0014] Preferably, the intermediate frequency processing subsystem includes a multi-channel AD unit, a multi-channel DA unit, an FPGA unit, and a DSP unit; the AD signal converted by the AD unit is processed in real time by the FPGA unit channelized receiver to obtain real-time pulse description word data and report it to the DSP unit, and the DSP reports the reconnaissance data to the signal processing subsystem after screening and identification; the FPGA unit generates an agility coefficient to modulate the target echo signal, which includes an M sequence generation module, a DDS amplitude and phase coefficient generation module, an amplitude coefficient modulation module and a target modulation module.

[0015] Preferably, the radio frequency processing transmitting subsystem includes an up-conversion unit and a power amplifier module; the radio frequency processing receiving subsystem includes a down-conversion unit and an instantaneous frequency measuring unit.

[0016] Preferably, the air-feed system comprises a transmitting antenna unit and a receiving antenna unit.

[0017] Preferably, it comprises a plurality of radio frequency processing transmitting subsystems and a plurality of radio frequency processing receiving subsystems.

[0018] Preferably, the target characteristic agility parameters include four dimensions: amplitude, phase, agility time, and pulse sequence number.

[0019] Preferably, multiple agile sources are generated for a target body having multiple strong scattering centers.

[0020] Preferably, for radar CFAR detection technology, the agile coherent waveform is superimposed with the real target echo signal to distort the echo signal received by the enemy radar, affecting the radar pulse compression processing, resulting in signal-to-noise ratio loss, and further affecting the radar detection power.

[0021] A target feature agility method for target stealth, comprising the following steps:

[0022] Step 1: Receive the detection waveform emitted by the enemy radar, convert it into an intermediate frequency signal through mixing, and screen and identify it;

[0023] Step 2, based on the screening and identification in step 1, generate corresponding agility parameters;

[0024] Step 3, generating an agile intermediate frequency signal according to the agile parameter, and then amplifying the power to obtain an agile signal;

[0025] Step 4: radiate the agile signal into space at respective angles according to specific polarization modes, and receive it together with the target real echo by the enemy radar, wherein the background noise of the echo signal received by the enemy radar is enhanced, and the signal-to-noise ratio of the target body is reduced;

[0026] Any of the above-described target feature agility systems for target stealth is used to implement the above steps.

[0027] The present invention proposes a new type of active stealth technology. Its characteristics are: first, the technology mounts one or more agile source electronic devices equipped with a target characteristic agile system on the target body, and the multiple agile sources are targeted at the target body with multiple strong scattering centers in different directions; second, the coherent waveform generated by the technology has amplitude and phase that are randomly agile within a range, and the agile speed can reach hundreds of nanoseconds at the fastest.

[0028] In terms of stealth effect, the present invention mainly targets radar constant false alarm rate (CFAR) detection technology. The coherent waveform after agility is superimposed on the real target echo signal, which distorts the echo signal received by the enemy radar, affects the radar pulse compression processing, causes signal-to-noise ratio loss, and further affects the radar detection power; at the same time, waveform distortion causes the pulse compression result to be broadened, affecting subsequent CFAR detection. For target bodies with multiple strong scattering centers, mounting agile source electronic devices at different positions can also have a significant stealth effect on broadband imaging radars. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of a target feature agility system for target stealth according to a preferred embodiment of the present invention;

[0030] Figure 2 A schematic diagram of target feature agility parameter settings in a preferred embodiment of the present invention;

[0031] Figure 3 A flow chart of target characteristic agile waveform generation according to a preferred embodiment of the present invention;

[0032] Figure 4 A time domain waveform comparison diagram before and after agility according to a preferred embodiment of the present invention;

[0033] Figure 5 This is a comparison diagram of pulse compression results before and after agility according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described below in conjunction with embodiments and drawings.

[0035] like Figure 1 As shown, the target characteristic agile system for target stealth provided in this embodiment generates a coherent waveform with random agile amplitude and phase, which is used to enhance the noise floor of the echo signal of the target body and weaken its signal-to-noise ratio, and specifically includes: a signal processing subsystem, an intermediate frequency processing subsystem, a radio frequency processing transmitting subsystem, a radio frequency processing receiving subsystem and an air feed system. The same target body can be equipped with one or more radio frequency processing systems, that is, multiple radio frequency processing transmitting subsystems and multiple radio frequency processing receiving subsystems, and generate multiple agile signals at the same time.

[0036] Among them, the signal processing subsystem is used to sort and identify signals and deploy the complete RCS database and agile style of the target entity; in the agile mode, it can respond to the table at the fastest speed.

[0037] The intermediate frequency processing subsystem is connected to the signal processing subsystem and is used for the collection and analysis of intermediate frequency data, the generation of agile waveforms, and the output of intermediate frequency data. A digital channelized receiver is used to output pulse width, repetition, frequency, pulse arrival time and other pulse description words in real time and report them to the signal processing subsystem. The intermediate frequency processing subsystem is the core of the target feature agile technology, and is mainly composed of a multi-channel AD unit, a multi-channel DA unit, an FPGA unit, and a DSP unit. The AD signal converted by the AD unit is processed in real time by the FPGA unit channelized receiver to obtain real-time pulse description word data and report it to the DSP unit. After screening and identification, the DSP reports the reconnaissance data to the signal processing subsystem. The FPGA unit generates an agility coefficient to modulate the target echo signal, which includes an M sequence generation module, a DDS amplitude and phase coefficient generation module, an amplitude coefficient modulation module, and a target modulation module. The target feature agile parameters include four dimensions: amplitude, phase, agile time, and pulse number; in this embodiment, it includes amplitude agility enable, agile amplitude 1, agile amplitude 2, phase agility enable, phase agility enable 1, phase agility 2, and pulse number. The amplitude and phase of the generated coherent waveform are randomly agile, with the fastest agility speed being one hundred nanoseconds.

[0038] The RF processing and transmitting subsystem includes an up-conversion unit and a power amplifier module, which are used to receive the agile multi-channel intermediate frequency signals output by the intermediate frequency processing subsystem, mix and convert them into multi-channel RF signals, and output them after power amplification.

[0039] The RF processing receiving subsystem includes a down-conversion unit and an instantaneous frequency measurement unit, which mixes the RF signal and converts it into an intermediate frequency signal, and transmits it to the intermediate frequency processing subsystem. It also has the functions of fast frequency measurement and frequency reference.

[0040] The air-feed system includes a transmitting antenna unit and a receiving antenna unit, which are used to radiate the signal received from the RF processing transmitting subsystem into space in a specific polarization mode, and at the same time receive the enemy radar waveform and transmit it to the RF processing receiving subsystem.

[0041] The technology of the present invention can generate multiple agile sources, mainly targeting a target body with multiple strong scattering centers.

[0042] The present invention is mainly aimed at radar CFAR detection technology; the coherent waveform after agility is superimposed on the real target echo signal, which distorts the echo signal received by the enemy radar, affects the radar pulse compression processing, causes the signal-to-noise ratio loss, and further affects the radar detection power.

[0043] The method for making a target invisible using the target feature agile system comprises the following steps:

[0044] Step 1: Receive the detection waveform emitted by the enemy radar, convert it into an intermediate frequency signal through mixing, and screen and identify it;

[0045] Step 2, based on the screening and identification in step 1, generate corresponding agility parameters;

[0046] Step 3, generating an agile intermediate frequency signal according to the agile parameter, and then amplifying the power to obtain an agile signal;

[0047] Step 4: radiate the agile signal into space at respective angles according to specific polarization modes, and receive it together with the real echo of the target by the enemy radar. The background noise of the echo signal received by the enemy radar is enhanced, and the signal-to-noise ratio of the target body is reduced.

[0048] The target feature agility system workflow is as follows:

[0049] In the reconnaissance mode, the detection waveform emitted by the enemy radar enters the RF processing receiving subsystem through the receiving antenna. The RF processing receiving subsystem converts the RF signal into an intermediate frequency signal through mixing and outputs it. After receiving the intermediate frequency signal, the intermediate frequency processing subsystem screens and identifies it, and reports the preliminary screening results to the signal processing subsystem, which further sorts and identifies the reconnaissance results.

[0050] After the target feature agility is turned on, the signal processing subsystem responds quickly according to the reconnaissance results, generates corresponding agility parameters and sends them to the intermediate frequency processing subsystem. The intermediate frequency processing subsystem generates the intermediate frequency signal after agility in real time according to the agility parameters, and inputs it to the RF processing and transmitting subsystem through the feeder. The RF processing and transmitting subsystem converts the intermediate frequency signal into an RF signal through up-conversion, then amplifies the power through the power amplifier module, and finally radiates the agile signal into space at their respective angles in a fixed polarization mode through the transmitting antenna, and is received by the enemy radar together with the target's real echo.

[0051] When implementing:

[0052] In the reconnaissance mode, the RF signal is received by the air feed system and sent to the RF processing receiving subsystem. The RF processing receiving subsystem has a wide frequency coverage range, and needs to quickly measure the enemy radar operating frequency through the instantaneous frequency measurement unit, quickly guide the frequency, and switch the local oscillator. The RF signal is converted into an intermediate frequency signal that can be received by the AD board.

[0053] The AD signal is processed in real time by the FPGA unit channelized receiver to obtain real-time pulse description word data, which is reported to the DSP unit through SRIO. After screening and identification, the DSP reports the reconnaissance data to the signal processing subsystem.

[0054] After turning on the target feature agility, the signal processing subsystem quickly looks up the table to obtain the agility mode and sends it to the DSP unit. Since the amplitude value set in the agility mode is a relative ratio, the DSP unit calculates the actual amplitude range value after quantization according to the decibel calculation formula dB=10*log(p1 / p2), and passes it to the FPGA through the SRIO bus interface together with the actual phase agility range.

[0055] The target feature agility pattern is as follows Figure 2 As shown, there are four dimensional parameters that can be set, namely amplitude, phase, agility time, and pulse number. The parameters can be further refined and decomposed into amplitude agility enable, agility amplitude 1, agility amplitude 2, phase agility enable, phase agility enable 1, phase agility 2, and pulse number. When amplitude agility is turned off, the amplitude of the agile signal remains unchanged. When amplitude agility is turned on, the signal amplitude can be randomly changed between agility amplitude 1 and agility amplitude 2. The set agility amplitude refers to the ratio of the amplitude value of the agile signal to the RCS of the target body, in dB. When phase agility is turned off, the phase of the agile signal remains unchanged. When phase agility is turned on, the agile signal supports binomial agility between phase 1 and phase 2, and also supports random agility between phase 1 and phase 2.

[0056] The agile mode between pulses can be set independently. The host computer sets the agile mode of N pulses at the same time. The FPGA unit stores the agile parameters of each pulse and traverses them in sequence. The agile time can be set, and the fastest supported is within 100ns.

[0057] FPGA generates agility coefficients to modulate the target echo signal. The FPGA target feature agility signal processing flow is as follows: Figure 3 As shown, it is mainly composed of four functional modules, namely, M sequence generation module, DDS (Direct Digital Synthesizer) amplitude and phase coefficient generation module, amplitude coefficient modulation module, and target modulation module.

[0058] The M sequence generation module uses the M sequence to generate 16 levels of pseudo-random numbers. The M sequence is the longest linear feedback shift register sequence. The random number cycle can be up to 65535 beats, and the random base is large. The processing clock for random number generation is 10MHz, and the clock cycle is 100ns. The agility coefficient changes once per clock cycle, and the fastest can reach 100ns. This module mainly generates the amplitude and phase of random agility.

[0059] The random agile amplitude and phase are input to the DDS module, which converts the phase into the real and imaginary parts required for signal modulation. The phase word is configured to 16 bits, which is consistent with the bit width of the M sequence. The initial phase interface is configurable. The random agile phase generated by the M sequence is the initial phase word of the DDS module, which is calculated by the Euler formula e iθ=cosθ+isinθ, we can see that the real and imaginary parts of the DDS module output are the agility coefficients.

[0060] The DDS outputs the agility coefficient and sends it to the amplitude coefficient modulation module, which can modulate the amplitude of the agility coefficient according to the host computer settings. The DDS outputs the agility coefficient according to the full-scale quantization output, and this module outputs the agile amplitude and phase coefficient within the specified range.

[0061] The modulated amplitude and phase coefficients are input to the target modulation module, which uses a complex multiplier. The intermediate frequency signal and the agility coefficient are multiplied by complex numbers and then output to the RF processing subsystem for up-conversion and power amplification.

[0062] The simulation effect of target feature agility is as follows Figure 4 and Figure 5 As shown in the figure, the amplitude of the agility parameter setting remains unchanged, and the phase randomly changes between 0 and 180 degrees. From the time domain waveform, it can be seen that the phase of the waveform is randomly flipped after the agility, that is, 180-degree agility occurs. From the pulse compression results, it can be seen that the background noise energy in a large range near the target after the agility is enhanced. The noise near the same position is raised from the original 73.657 to 89.7041, but the energy of the target is still 126 at the peak of the pulse compression.

[0063] This technology is mainly aimed at radar CFAR detection. It significantly increases the background noise near the real target body, reduces the signal-to-noise ratio of the echo signal, raises the radar CFAR detection threshold, and thus affects the radar detection power, achieving a significant stealth effect.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A target feature agility system for target stealth, characterized by: Generate a coherent waveform with random amplitude and phase changes, enhance the noise floor of the target echo signal, and weaken its signal-to-noise ratio, including: The signal processing subsystem is used to sort and identify signals and deploy the complete RCS database and agile patterns of the target entity; The intermediate frequency processing subsystem is connected to the signal processing subsystem and is used for collecting and analyzing intermediate frequency data, generating agile waveforms, and outputting intermediate frequency data; The radio frequency processing and transmitting subsystem is used to receive the agile multi-channel intermediate frequency signals output by the intermediate frequency processing subsystem, mix and convert them into multi-channel radio frequency signals, and output them after power amplification; The RF processing receiving subsystem mixes the RF signal and converts it into an intermediate frequency signal, which is then transmitted to the intermediate frequency processing subsystem; The air-feed system is used to radiate the signal received from the RF processing transmitting subsystem into space in a specific polarization mode, and at the same time receive the enemy radar waveform and transmit it to the RF processing receiving subsystem.

2. The target characteristic agility system for target stealth as claimed in claim 1, characterized in that: The intermediate frequency processing subsystem includes a multi-channel AD unit, a multi-channel DA unit, an FPGA unit, and a DSP unit; the AD signal converted by the AD unit is processed in real time by the FPGA unit channelized receiver to obtain real-time pulse description word data and report it to the DSP unit. After screening and identification, the DSP reports the reconnaissance data to the signal processing subsystem; the FPGA unit generates agility coefficients to modulate the target echo signal, which includes an M sequence generation module, a DDS amplitude and phase coefficient generation module, an amplitude coefficient modulation module, and a target modulation module.

3. The target characteristic agility system for target stealth as claimed in claim 1, characterized in that: The RF processing transmitting subsystem includes an up-conversion unit and a power amplifier module; the RF processing receiving subsystem includes a down-conversion unit and an instantaneous frequency measurement unit.

4. The target characteristic agility system for target stealth as claimed in claim 1, characterized in that: The air-feed system includes a transmitting antenna unit and a receiving antenna unit.

5. The target characteristic agility system for target stealth as claimed in claim 1, characterized in that: It includes multiple radio frequency processing transmitting subsystems and multiple radio frequency processing receiving subsystems.

6. The target characteristic agility system for target stealth as claimed in claim 1, characterized in that: The target characteristic agility parameters include four dimensions: amplitude, phase, agility time, and pulse sequence number.

7. The target characteristic agility system for target stealth as claimed in claim 1, characterized in that: Multiple agile sources are generated for a target body with multiple strong scattering centers.

8. The target characteristic agility system for target stealth as claimed in claim 1, characterized in that: For radar CFAR detection technology, the coherent waveform after agile change is superimposed on the real target echo signal, which distorts the echo signal received by the enemy radar, affects the radar pulse compression processing, causes signal-to-noise ratio loss, and further affects the radar detection power.

9. The target feature agility method for target stealth as claimed in claim 1, characterized in that: The steps include: Step 1: Receive the detection waveform emitted by the enemy radar, convert it into an intermediate frequency signal through mixing, and screen and identify it; Step 2, based on the screening and identification in step 1, generate corresponding agility parameters; Step 3, generating an agile intermediate frequency signal according to the agile parameter, and then amplifying the power to obtain an agile signal; Step 4: radiate the agile signal into space at respective angles according to specific polarization modes, and receive it together with the target real echo by the enemy radar, wherein the background noise of the echo signal received by the enemy radar is enhanced, and the signal-to-noise ratio of the target body is reduced; The target characteristic agility system for target stealth as described in any one of claims 1 to 8 is used to implement the above steps.

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