Dual-band pulse compression coding frequency agility anti-interference method and system

Abstract

The invention discloses a dual-band pulse compression coding frequency agility anti-interference method and system, and relates to the field of radar anti-interference, and the method comprises the following steps: 1, transmitting a mixed coding signal of an X wave band and a Ku wave band under the triggering of a synchronization signal; step 2, receiving an echo signal of the mixed coding signal, and down-converting the echo signal to an intermediate frequency to obtain an intermediate frequency echo signal; and step 3, performing pulse compression and signal accumulation processing on the intermediate frequency echo signal in sequence to obtain a target signal. According to the invention, the target is detected by emitting the X-band and Ku-band mixed coding signal, when one frequency band signal is suppressed by noise interference, the other frequency band can still work normally, and the anti-interference capability of a radar system is improved.

Description

Technical Field

[0001] The present invention relates to the field of radar anti - interference, and specifically, to a dual - band pulse compression coding frequency - agile anti - interference method and system. Background Art

[0002] At present, radar jamming methods include noise suppression jamming, towing jamming, and Doppler noise jamming, etc. Among them, noise suppression jamming generates a noise - modulated signal with a bandwidth greater than the radar signal bandwidth within the radar operating frequency band, blocking or deteriorating the signal reception of the radar echo, making it impossible for the radar to normally extract the echo signal. Towing jamming is when the radar locks on a false target, and the false target pulse causes the range gate and velocity gate to gradually deviate from the real target through continuous time - delay modulation or center - frequency offset. As the time - delay / frequency - offset change amount of the deception signal gradually increases, the jamming - to - signal - ratio (JSR) of the received signal approaches infinity, resulting in the radar completely tracking the false target. When the interference pulse drags the range tracking gate from the real target to a predetermined position, the jammer immediately shuts down, and at this time the radar loses the target.

[0003] These jamming means pose a severe challenge to the target detection and tracking capabilities of the radar. Conventional anti - jamming methods include anti - jamming in terms of antennas (such as sidelobe cancellation technology, beamforming), anti - jamming in terms of transmitters (such as frequency hopping method, transmit waveform coding), anti - jamming in terms of receivers (such as receiver anti - saturation method), and anti - jamming in terms of signal processing (such as signal selection method, accumulation method, intra - pulse frequency agility, inter - pulse frequency agility). However, the jamming technologies corresponding to these anti - jamming methods have also been very mature. Using the characteristics or implementation technologies of conventional anti - jamming methods to transmit targeted jamming signals, conventional anti - jamming methods are difficult to distinguish and are no longer able to counter their jamming signals. Summary of the Invention

[0004] The purpose of the present invention is to solve the problem that conventional anti - jamming methods are no longer able to counter jamming signals and to improve the anti - jamming ability of the radar.

[0005] To achieve the above - mentioned purpose, the present invention provides a dual - band pulse compression coding frequency - agile anti - jamming method, and the method includes the following steps: Step 1: Under the trigger of a synchronization signal, transmit a hybrid - coded signal in the X - band and Ku - band; Step 2: Receive the echo signal of the hybrid - coded signal and down - convert the echo signal to an intermediate - frequency, obtaining an intermediate - frequency echo signal; Step 3: Perform pulse compression and signal accumulation processing on the intermediate - frequency echo signal in sequence to obtain a target signal.

[0006] Among them, the present invention improves the anti - jamming ability of the radar from the following three aspects: First, the mixed coded signal contains X-band signal and Ku-band signal. The frequency of the X-band signal is between 8 GHz and 12 GHz, and the frequency of the Ku-band signal is between 12 GHz and 18 GHz. To achieve effective noise suppression interference, the jammer must cover both frequency bands simultaneously (with a total bandwidth of 10 GHz). However, the instantaneous bandwidth of traditional jammers usually does not exceed 2 GHz. Therefore, at most, it can only cover one of the frequency bands in the mixed coded signal. In the present invention, when the receiving channel of a certain frequency band is suppressed by interference noise, its limiter will saturate. Once the radar system detects the saturation, it will automatically determine that the frequency band is interfered and abandon the data of that frequency band, instead using the information collected from the signal of the other frequency band to avoid interference.

[0007] Second, the present invention performs pulse compression and signal accumulation processing on the intermediate frequency echo signal. Pulse compression processing converts the long pulse signal into a short pulse signal through matched filtering, which not only improves the range resolution of the radar system but also enhances the target echo intensity, and can effectively suppress the influence of interference signals. Pulse compression requires strict synchronization of the echo signal in the time domain. Signal accumulation processing coherently superimposes the intermediate frequency echo signals of multiple periods. Since the real echo signal has a stable phase relationship and periodic characteristics, the X-band echo signal and the Ku-band echo signal can completely coincide with their respective corresponding standard pulses at the same moment to achieve signal accumulation. The essence of towed jamming is digital storage frequency jamming. The jammer first receives the analog signal emitted by the radar, analyzes it and converts it into a digital signal, and then delays these digital signals and converts them back into an analog signal to be emitted as an interference signal. Among them, when the jammer performs delay processing on the pulse signals of different frequency bands, due to the differences in circuit characteristics, the delay degrees of different frequency points are different, resulting in the interference signal being unable to simultaneously meet the time domain synchronization condition required for pulse compression and the phase coherence condition required for signal accumulation, and thus unable to achieve effective pulse compression and signal accumulation, which enables the interference signal to be eliminated from the target signal.

[0008] Third, the present invention down-converts the echo signal to the same intermediate frequency through down-conversion, which is convenient for subsequent processing of the signal using the same hardware and reduces the complexity of the radar system. Down-converting the echo signal to the intermediate frequency signal for signal accumulation processing, since the echo signal of the real target has phase consistency in the X-band and Ku-band, the signal intensity is enhanced after superposition, while the phase of the interference signal is usually random. When performing signal accumulation processing, they may cancel each other out, resulting in a weakened signal intensity after superposition.

[0009] Therefore, to interfere with the radar signal of the present invention, the following conditions must be met: 1. Simultaneously analyze the frequency, pulse width, pulse repetition frequency, etc. of the X-band pulse signal and the Ku-band pulse signal within one radar sub-pulse period (1 μs); 2. Obtain the synchronous trigger time for the pulse compression of the echo signals in two bands. In practical applications, this trigger time is internal confidential information.

[0010] Further, in step 1, the hybrid coded signal includes a number of hybrid pulses; Among them, the hybrid pulse is generated by intra-pulse frequency coding of the X-band sub-pulse and the Ku-band sub-pulse.

[0011] Among them, intra-pulse frequency coding means that within a single pulse period, the frequency of the signal is coded. Since the spectrum of the intra-pulse frequency coded signal has multiple peaks, and the positions and amplitudes of these peaks can be adjusted flexibly, it is difficult for the jammer to accurately simulate a jamming signal that is exactly the same as the radar signal, thus improving the anti-jamming ability of the radar.

[0012] Further, the coding method of the intra-pulse frequency coding includes: Step 101: Perform linear frequency modulation on any X-band sub-pulse and Ku-band sub-pulse to be transmitted, and randomly determine the transmission carrier frequency; Step 102: Arrange the modulated X-band sub-pulse and Ku-band sub-pulse in the time domain to form the hybrid pulse.

[0013] Among them, the present invention adopts the method of hybrid coding of the X-band sub-pulse and the Ku-band sub-pulse, making the radar signal more complex and diverse in the spectrum, and further enhancing the anti-jamming ability of the radar.

[0014] Further, the X-band sub-pulse includes a first sub-pulse and a second sub-pulse, and the Ku-band sub-pulse includes a third sub-pulse and a fourth sub-pulse.

[0015] Among them, for different hybrid pulses, the carrier frequencies of the internal sub-pulses are all randomly determined, which means that each hybrid pulse has unique frequency domain characteristics, which greatly increases the complexity of the hybrid coded signal and increases the difficulty of jamming.

[0016] Further, in the hybrid pulse, the X-band sub-pulse and the Ku-band sub-pulse are arranged in the following order: the first sub-pulse, the third sub-pulse, the second sub-pulse, and the fourth sub-pulse. By increasing the number of sub-pulses with different frequencies, there are more arrangement ways inside the hybrid pulse.

[0017] Further, the coding method of the intra-pulse frequency coding also includes: inserting a cover pulse into the hybrid pulse; Inserting the cover pulse into the hybrid pulse includes: Insert an X-band cover pulse at the timing position corresponding to the Ku-band sub-pulse, and insert a Ku-band cover pulse at the timing position corresponding to the X-band sub-pulse.

[0018] Among them, the present invention further increases the difficulty for the jammer to obtain the true operating frequency of the radar by inserting cover pulses of false frequency points; by making the cover pulses and the true sub-pulses intertwined in the time domain and the frequency domain, thereby misleading the frequency information of the interference system, greatly increasing the probability of not being intercepted.

[0019] Further, the X-band sub-pulse and the Ku-band sub-pulse are both frequency-modulated waves.

[0020] Further, the frequencies of the first sub-pulse, the second sub-pulse, the third sub-pulse, and the fourth sub-pulse are mutually coherent. Among them, in step 3, the frequency of the synchronous trigger pulse for pulse compression and signal accumulation is coherent with the frequencies of the X-band sub-pulse and the Ku-band sub-pulse, and the frequencies of the X-band sub-pulse and the Ku-band sub-pulse are respectively integer multiples of the frequency of the synchronous trigger pulse.

[0021] Among them, the frequencies of the four sub-pulses are mutually coherent and coherent with the frequency of the synchronous trigger pulse, and the frequencies of the four sub-pulses are integer multiples of the synchronous trigger pulse. When this condition is met, the intermediate-frequency echo signal can achieve effective pulse compression and signal accumulation. Therefore, if effective interference is to be carried out on this method, the interfering party must also know the multiple between the frequency of the sub-pulse and the frequency of the synchronous trigger pulse, and this multiple is randomly selected by the radar system, with a low risk of being cracked.

[0022] The present invention also provides a dual-band pulse compression coding frequency agile anti-jamming system, and the system includes: A signal transmitting unit, configured to transmit a mixed coding signal of the X-band and the Ku-band under the trigger of a synchronization signal; A signal receiving unit, configured to receive the echo signal of the mixed coding signal and down-convert the echo signal to an intermediate frequency to obtain an intermediate-frequency echo signal; A signal accumulation unit, configured to perform pulse compression and signal accumulation processing on the intermediate-frequency echo signal in sequence to obtain a target signal.

[0023] One or more technical solutions provided by the present invention have at least the following technical effects or advantages: 1. The present invention detects a target by transmitting a mixed coding signal of the X-band and the Ku-band. When the signal of one frequency band is suppressed by noise interference, the other frequency band can still work normally, improving the anti-jamming ability of the radar system.

[0024] 2. The present invention combines dual - band frequency agile conversion and intra - pulse frequency coding methods to achieve dual anti - interference in the frequency domain and time domain of radar signals. In the frequency domain, through the dual - band frequency agile conversion technology, the radar signal can quickly switch between the X - band and Ku - band, reducing the possibility of interference equipment capturing and tracking the radar signal. In the time domain, the intra - pulse frequency coding technology finely codes the frequency characteristics inside the hybrid pulse, increasing the complexity and randomness of the radar signal and enhancing the anti - interference ability of the radar.

[0025] 3. The solution of the present invention can be implemented on a single - unit radar. Compared with the conventional multi - radar cooperative detection, it is synchronized with the same internal synchronous clock signal and does not require external devices such as Beidou satellites and GPS. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of the present invention, and do not limit the embodiments of the present invention; Figure 1 It is a schematic flow chart of a dual - band pulse compression coding frequency agile anti - interference method in Embodiment 1 of the present invention; Figure 2 It is a schematic diagram of the principle of the down - conversion process in Embodiment 1 of the present invention; Figure 3 It is a schematic diagram of the intra - pulse frequency coding methods of the X - band pulse signal and Ku - band pulse signal in Embodiment 1 of the present invention; Figure 4 A schematic diagram of inserting cover pulses in the hybrid pulse sequence in Embodiment 1 of the present invention; Figure 5 It is a schematic diagram of the composition of a dual - band pulse compression coding frequency agile anti - interference system in Embodiment 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] In order to more clearly understand the above - mentioned objects, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the drawings and specific embodiments. It should be noted that, without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0028] In the following description, many specific details are set forth to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0029] Embodiment 1

[0030] Please refer to Figure 1, Embodiment 1 of the present invention provides a dual-band pulse compression coding frequency agile anti-jamming method, and the method includes the following steps: Step 1: Under the trigger of a synchronization signal, transmit a hybrid coding signal in the X-band and Ku-band; Step 2: Receive the echo signal of the hybrid coding signal, and down-convert the echo signal to an intermediate frequency, obtaining an intermediate frequency echo signal; Step 3: Perform pulse compression and signal accumulation processing on the intermediate frequency echo signal in sequence to obtain a target signal.

[0031] Among them, the frequency source used in the anti-jamming method of this embodiment is the frequency source involved in the prior art CN213240505U, and this frequency source can achieve good phase consistency after broadband frequency hopping. In the hybrid coding signal, the X-band signal and the Ku-band signal are respectively transmitted through the X-band phased array active antenna and the Ku-band phased array active antenna. The specific process of down-conversion can refer to Figure 2 , first input a calibration signal through calibration, after being controlled by a calibration switch, limit the signal amplitude by a limiter, then control the signal flow direction through a radio frequency switch, enter a low-noise amplifier for low-noise amplification, then finely adjust the signal intensity through a digital control attenuator, filter out the image frequency signal generated by mixing through an image frequency filter, and then enter the intermediate frequency processing stage, including intermediate frequency amplification, filtering and switch control, and then mix with the local oscillator signal through two-stage mixers (LO2 and LO1) to gradually down-convert the radio frequency signal to the intermediate frequency. During this period, filter out unnecessary frequency components through a 50M filter, and increase the signal intensity by an amplifier. Finally, adjust the signal amplitude through a digital control attenuator again, control the input of the radio frequency signal through a radio frequency switch, and finally output an intermediate frequency signal of 210 MHz to complete the entire down-conversion process.

[0032] Among them, in Step 1, the hybrid coding signal includes several hybrid pulses; Among them, the hybrid pulse is generated by intra-pulse frequency coding of an X-band sub-pulse and a Ku-band sub-pulse.

[0033] Among them, the coding method of the intra-pulse frequency coding includes: Step 101: Perform linear frequency modulation on any X-band sub-pulse and Ku-band sub-pulse to be transmitted, and randomly determine the transmission carrier frequency; Step 102: Arrange the modulated X-band sub-pulse and Ku-band sub-pulse in the time domain to form the hybrid pulse.

[0034] Among them, the X-band sub-pulse includes a first sub-pulse and a second sub-pulse, and the Ku-band sub-pulse includes a third sub-pulse and a fourth sub-pulse.

[0035] Among them, in the mixed pulse, the X-band sub-pulses and the Ku-band sub-pulses are arranged in the following order: the first sub-pulse, the third sub-pulse, the second sub-pulse, and the fourth sub-pulse.

[0036] For example, please refer to Figure 3 , this embodiment provides a figure of in-pulse frequency coding for X-band sub-pulses and Ku-band sub-pulses. The duration of each sub-pulse is T sub , and the bandwidth is B sub , and the waveform is linear frequency modulation. For any X-band sub-pulse, its carrier frequency is randomly determined within the X frequency band. Similarly, for any Ku-band sub-pulse, its carrier frequency is randomly determined within the Ku frequency band, so that the carrier frequencies of each sub-pulse inside the mixed pulse are different, and the carrier frequency distributions of the sub-pulses of different mixed pulses are also different. Finally, the X-band sub-pulses and the Ku-band sub-pulses are arranged in the time domain in the order of the first sub-pulse, the third sub-pulse, the second sub-pulse, and the fourth sub-pulse.

[0037] Among them, in signal processing, the intermediate frequency echo signal is sorted by a narrowband filter bank to obtain sub-pulse signals corresponding to different frequency codings; the sub-pulse signals are subjected to AD sampling (analog-to-digital conversion), converted from analog signals to digital signals, and subjected to segmented pulse compression processing. Then, the system-given synchronous trigger pulse is used to adjust the timing of all sub-pulse data signals to ensure their alignment in time. Finally, the adjusted sub-pulse data are spliced to form a complete radar echo signal data set. After pulse compression is completed, signal accumulation processing is performed.

[0038] In this embodiment, when the radar system is powered on regularly, frequency correction and phase alignment operations must be performed.

[0039] Among them, the coding method of the in-pulse frequency coding further includes: inserting cover pulses into the mixed pulse; Inserting cover pulses into the mixed pulse includes: Inserting X-band cover pulses at the timing positions corresponding to the Ku-band sub-pulses, and inserting Ku-band cover pulses at the timing positions corresponding to the X-band sub-pulses.

[0040] Please refer to Figure 4 , Figure 4 gives a way to insert cover pulses. In some preferred embodiments, in order to further mislead the interference system, two Ku-band cover pulses can be inserted at the timing positions corresponding to the X-band sub-pulses by using two transmission channels of the third sub-pulse signal and the fourth sub-pulse signal. Similarly, two X-band cover pulses can also be inserted at the timing positions corresponding to the Ku-band sub-pulses.

[0041] Among them, the transmission carrier frequency of the X-band covering pulse is different from that of the X-band sub-pulse, and the transmission carrier frequency of the Ku-band covering pulse is different from that of the Ku-band sub-pulse. In some preferred embodiments, different carrier frequencies are adopted among the covering pulses of the same band.

[0042] Among them, both the X-band pulse signal and the Ku-band pulse signal are frequency-modulated waves.

[0043] Among them, the frequencies of the first sub-pulse, the second sub-pulse, the third sub-pulse, and the fourth sub-pulse are mutually coherent; Among them, in step 3, the frequency of the synchronous trigger pulse for pulse compression and signal accumulation is coherent with the frequencies of the X-band sub-pulse and the Ku-band sub-pulse, and the frequencies of the X-band sub-pulse and the Ku-band sub-pulse are respectively integer multiples of the frequency of the synchronous trigger pulse. For example, the frequencies of the first sub-pulse, the second sub-pulse, the third sub-pulse, and the fourth sub-pulse are respectively 1, 2, 3, and 4 times the frequency of the synchronous trigger pulse.

[0044] Embodiment 2

[0045] Please refer to Figure 5 , Embodiment 2 of the present invention provides a dual-band pulse compression coding frequency agile anti-jamming system, and the system includes: A signal transmitting unit, configured to transmit a mixed coding signal of the X-band and the Ku-band under the trigger of a synchronization signal; A signal receiving unit, configured to receive the echo signal of the mixed coding signal and down-convert the echo signal to an intermediate frequency to obtain an intermediate frequency echo signal; A signal accumulation unit, configured to perform pulse compression and signal accumulation processing on the intermediate frequency echo signal in sequence to obtain a target signal.

[0046] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications once they know the basic creative concept. Therefore, the appended claims are intended to be interpreted to include the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0047] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims

1. A dual-band pulse compression coding frequency agile anti-jamming method, characterized in that The method includes the following steps: Step 1: Triggered by a synchronization signal, transmit a hybrid coded signal in the X-band and Ku-band; Step 2: Receive the echo signal of the hybrid coded signal, and down-convert the echo signal to an intermediate frequency to obtain an intermediate frequency echo signal; Step 3: Perform pulse compression and signal accumulation processing on the intermediate frequency echo signal in sequence to obtain a target signal.

2. The dual-band pulse compression coding frequency-agile anti-jamming method according to claim 1, characterized in that, In Step 1, the hybrid coded signal includes a number of hybrid pulses; Among them, the hybrid pulse is generated by intra-pulse frequency coding of an X-band sub-pulse and a Ku-band sub-pulse.

3. A dual-band pulse compression coding frequency agile anti-jamming method according to claim 2, characterized in that, The coding method of the intra-pulse frequency coding includes: Step 101: Perform linear frequency modulation on any X-band sub-pulse and Ku-band sub-pulse to be transmitted, and randomly determine the transmission carrier frequency; Step 102: Arrange the modulated X-band sub-pulse and Ku-band sub-pulse in the time domain to form the hybrid pulse.

4. A dual-band pulse compression coding frequency agile anti-jamming method according to claim 3, characterized in that, The X-band sub-pulse includes a first sub-pulse and a second sub-pulse, and the Ku-band sub-pulse includes a third sub-pulse and a fourth sub-pulse.

5. A dual-band pulse compression coding frequency agile anti-jamming method according to claim 4, characterized in that In the hybrid pulse, the X-band sub-pulse and the Ku-band sub-pulse are arranged in the following order: the first sub-pulse, the third sub-pulse, the second sub-pulse, and the fourth sub-pulse.

6. A dual-band pulse compression coding frequency agile anti-jamming method according to claim 3, characterized in that, The coding method of the intra-pulse frequency coding further includes: inserting a cover pulse in the hybrid pulse; The inserting a cover pulse in the hybrid pulse includes: Inserting an X-band cover pulse at the timing position corresponding to the Ku-band sub-pulse, and inserting a Ku-band cover pulse at the timing position corresponding to the X-band sub-pulse.

7. A dual-band pulse compression coding frequency agile anti-jamming method according to claim 6, characterized in that, The transmission carrier frequency of the X-band cover pulse is different from that of the X-band sub-pulse, and the transmission carrier frequency of the Ku-band cover pulse is different from that of the Ku-band sub-pulse.

8. A dual-band pulse compression coding frequency agile anti-jamming method according to claim 2, characterized in that Both the X-band sub-pulse and the Ku-band sub-pulse are frequency modulation waves.

9. A dual-band pulse compression coding frequency-agile anti-jamming method according to claim 4, characterized in that The frequencies of the first sub-pulse, the second sub-pulse, the third sub-pulse, and the fourth sub-pulse are mutually coherent; Among them, in Step 3, the frequency of the synchronization trigger pulse for pulse compression and signal accumulation is coherent with the frequencies of the X-band sub-pulse and the Ku-band sub-pulse, and the frequencies of the X-band sub-pulse and the Ku-band sub-pulse are respectively integer multiples of the frequency of the synchronization trigger pulse.

10. A dual-band pulse compression coding frequency agile anti-jamming system, characterized in that, The system includes: A signal transmitting unit, configured to transmit a hybrid coded signal in the X-band and Ku-band under the trigger of a synchronization signal; A signal receiving unit, configured to receive the echo signal of the hybrid coded signal, and down-convert the echo signal to an intermediate frequency to obtain an intermediate frequency echo signal; A signal accumulation unit, configured to perform pulse compression and signal accumulation processing on the intermediate frequency echo signal in sequence to obtain a target signal.

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