Method and system for generating simultaneous sub-pulse waveforms for low altitude surveillance radar

Abstract

The application discloses a low-altitude monitoring radar simultaneous sub-pulse waveform generation method and system, which comprises the following steps: acquiring radar detection parameters, determining the maximum pulse width and the minimum required pulse number of the simultaneous sub-pulse waveform, determining the parameters of each sub-pulse in each pulse according to the parameters, and finally judging whether the duty cycle meets the requirement according to the current sub-pulse parameters; if not, adaptive adjustment is performed to obtain the final sub-pulse waveform. The scheme adopts time-sharing frequency-division orthogonal waveform design, fully embodies the orthogonal non-interference concept, and means that the time domain and the frequency domain can be independently processed; the orthogonal waveform has high isolation, so that when multiple sub-pulses are detected in their respective action ranges at the receiving end, they are not affected by each other, the speed resolution of the detection near zone is greatly improved, the improvement of the speed resolution means that the influence of the strong clutter on the target in the detection near zone is greatly reduced, and the weak target detection capability is enhanced.

Description

Technical Field

[0001] This invention belongs to the field of low-altitude surveillance radar, specifically relating to a method and system for generating simultaneous subpulse waveforms in low-altitude surveillance radar. Background Technology

[0002] The electromagnetic propagation and scattering characteristics of low-altitude environments differ significantly from those of mid- and high-altitude environments. This makes the challenges faced by low-altitude surveillance radar in achieving effective target detection far more severe than those faced by high-altitude surveillance radar. High-altitude surveillance radar typically operates in relatively "clean" environments, while the detection beams of low-altitude surveillance radar inevitably encounter complex terrain and sea surfaces. This results in strong backscattered echoes from topography, buildings, vegetation, and ocean waves, creating extremely strong ground and sea clutter backgrounds. These clutters are not only high in power, often several orders of magnitude higher than the echo signals of small, slow, and small targets with low radar cross-sections, such as small drones and light aircraft, severely obscuring target signals; their spectral characteristics are also extremely complex. Due to the broadening of the clutter spectrum caused by the movement of surface objects (such as swaying trees) and the movement of the radar platform itself, the main lobe of the clutter severely overlaps with the Doppler band of slow, weak targets.

[0003] Therefore, in the context of strong low-altitude clutter, how to achieve stable and continuous detection of small targets with high detection probability and low false alarm probability has become the core technical bottleneck restricting the improvement of the effectiveness of low-altitude surveillance radar.

[0004] Currently, low-altitude surveillance radars mostly use time-division monopulse waveforms to complete full-range detection. These waveforms have varying pulse widths with different parameters; longer pulse widths are responsible for far-field detection, while shorter pulse widths are responsible for near-field detection. While this type of waveform is simple to design and process, its shortcomings are also apparent in low-altitude scenarios. Specifically, the near-field waveform has a short dwell time, resulting in extremely poor Doppler resolution. Furthermore, the near-field clutter intensity is higher, and small targets are indistinguishable from clutter in the Doppler domain, making it impossible to detect small targets. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a method and system for generating simultaneous subpulse waveforms in low-altitude surveillance radar.

[0006] The specific technical solution for achieving the objective of this invention is as follows:

[0007] A method for generating a simultaneous subpulse waveform for a low-altitude surveillance radar includes the following steps:

[0008] Step 1: Obtain radar detection parameters;

[0009] Step 2: Determine the maximum pulse width of the simultaneous sub-pulse waveform based on the radar detection parameters. And the minimum number of pulses N required for coherent accumulation;

[0010] Step 3: Determine the parameters of each sub-pulse in each pulse;

[0011] Step 4: Determine whether the duty cycle meets the requirements based on the current sub-pulse parameters. If not, make adaptive adjustments to obtain the final sub-pulse waveform.

[0012] This solution also provides a system for generating subpulse waveforms for low-altitude surveillance radar, used to perform the above method, including the following modules:

[0013] Radar control module: Used to generate simultaneous sub-pulse waveform data based on radar parameters, form the waveform parameters of the current frame, and write the parameters into the radar control word of the frame to form the frame control command; Waveform parameter parsing module: The frequency source receives the current frame control command, parses the waveform parameters and sends the sub-pulse number, modulation form, frequency offset, pulse width, bandwidth, and gate information parameters to the intermediate frequency signal generation module, and sends the frequency control word to the local oscillator signal generation module; Intermediate Frequency Signal Generation Module: Used to receive parameters such as the number of sub-pulses, modulation form, frequency offset, pulse width, bandwidth, and gate information, and control the DDS arbitrary waveform generator to generate a corresponding number of sub-pulse waveforms within the intermediate frequency bandwidth. The sub-pulse waveforms do not overlap in the time domain, do not overlap in the frequency domain, and maintain orthogonality in the waveform domain. Finally, the digital quantity is converted into an analog quantity by the DAC and output at the intermediate frequency. Local oscillator signal generation module: used to receive the frequency control word information of the current frame, generate the frequency control code corresponding to the working frequency, generate the corresponding local oscillator intermediate frequency signal, and finally synthesize it into a local oscillator and a second local oscillator signal corresponding to the working frequency of the current frame; RF excitation generation module: The intermediate frequency signal and two local oscillator signals are input to the RF excitation generation module. After two mixing cycles, the RF signal is converted from intermediate frequency to RF. The RF signal is amplified by the T / R component and then transmitted to the antenna end to be radiated to the designated airspace.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] For low-altitude surveillance radar detection, achieving both a long operating range and high speed resolution across the entire range within a limited search period is equally important. Traditional time-division single-pulse waveforms are difficult to achieve both, while sub-pulse waveforms are the key technology to resolve this contradiction.

[0016] The multiple simultaneous sub-pulses in this scheme adopt a time-division and frequency-division orthogonal waveform design, which fully reflects the concept of orthogonal non-interference. Time-division and frequency division means that the time domain and frequency domain can be processed independently, and the orthogonal waveforms have high isolation, so that when the signal is detected by multiple sub-pulses within their respective ranges during processing at the receiving end, they are not affected by each other.

[0017] Meanwhile, the engineering basis for the implementation of the subpulse design lies in the full application of digital processing technology in digital array radar. When generating the transmitted waveform, DDS-based arbitrary waveform generation technology is used, which enables multiple subpulses to be generated simultaneously and orthogonal to each other. When receiving and processing, parallel processing, multi-signal separation, matched filtering and other technologies are used to recover the subpulse data.

[0018] Meanwhile, the outstanding application effect of the sub-pulse waveform is that it greatly improves the velocity resolution in the near-field detection area, which is precisely the area of ​​strong clutter that is easily encountered during low-altitude detection. The improvement in velocity resolution means that the target in the near-field detection area is greatly affected by strong clutter, thus enhancing the detection capability of small targets.

[0019] The present invention will be further described below with reference to specific embodiments. Attached Figure Description

[0020] Figure 1 This is a comparative diagram of the existing time-division monopulse and the simultaneous subpulse of this scheme, where (a) is the time-division monopulse, (b) is the simultaneous subpulse, and (c) is a schematic diagram of the effective range of the simultaneous subpulse.

[0021] Figure 2 This is a schematic diagram of the method for generating subpulse waveforms simultaneously in low-altitude surveillance radar according to the present invention.

[0022] Figure 3 This is a schematic diagram of the system architecture for the simultaneous generation of subpulse waveforms by a low-altitude surveillance radar in an embodiment of the present invention. Detailed Implementation

[0023] Example

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0026] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0027] Combination Figure 1 Sub-pulse waveforms refer to multiple pulse waveforms with different pulse widths, frequencies, and modulation forms that exist simultaneously within a certain time and bandwidth during transmission.

[0028] During transmission, all sub-pulse waveforms are emitted to the designated airspace within the transmission time span. Each sub-pulse is responsible for target detection at different ranges. The ranges corresponding to all sub-pulses are combined to form the full range.

[0029] During reception, the beamforming subsystem separates the detection data of each sub-pulse, and then the signal processing and data processing perform detection and tracking on each segment.

[0030] Currently, ground-based two-dimensional active phased array radars often employ time-division monopulse waveforms for long-range detection (i.e., first transmitting a large-pulse waveform for maximum range coverage, then transmitting a small-pulse waveform to fill the detection blind spots of the previous large-pulse waveform, and so on). This method is relatively simple and convenient in waveform design and processing. However, in low-altitude detection scenarios, strong clutter presents a challenge. To suppress strong clutter, improving spatial, temporal, and Doppler domain resolution is an effective solution. If time-division monopulse waveforms are still used, their near-field Doppler resolution is extremely poor, failing to effectively suppress strong near-field clutter and affecting the detection of small targets against a cluttered background.

[0031] Unlike time-division single pulses, this scheme uses simultaneous sub-pulses, which divide the pulse width of a complete time-division single pulse into several different sub-pulse widths. Each sub-pulse width is arranged in front and behind according to the pulse width, and each sub-pulse width is responsible for target detection in different ranges.

[0032] Specifically, combined Figure 2 This solution provides a method for generating a simultaneous subpulse waveform for low-altitude surveillance radar, comprising the following steps:

[0033] Step 1: Obtain radar detection parameters;

[0034] Step 2: Determine the maximum pulse width of the simultaneous sub-pulse waveform based on the radar detection parameters. And the minimum number of pulses N required for coherent accumulation:

[0035]

[0036]

[0037] in, This is the maximum pulse width, which is the sum of the pulse widths of all sub-pulses. For radar detection range, The duty cycle of radar array transmission. For radar velocity resolution, For radar operating wavelength, The speed of light is constant. The minimum number of coherent pulses required for the radar to reach the detection range;

[0038] The minimum number of pulses here is different from the number of simultaneous sub-pulses; the minimum number of pulses refers to the number of coherent accumulation pulses required to reach the detection range, while the number of simultaneous sub-pulses refers to the number of sub-pulses that cover a complete range, with each sub-pulse covering a different detection range.

[0039] Step 3: Determine the parameters of each sub-pulse in each pulse:

[0040] Step 3-1: Based on the radar's maximum effective range and minimum required number of pulses Determine the pulse width of the first sub-pulse. :

[0041]

[0042] in, This represents the target detection signal-to-noise ratio required given the detection probability and false alarm probability, where k represents the Boltzmann constant. Indicates system noise temperature. Indicates system loss. G represents the peak transmit power, and G represents the array gain. Indicates the target's scattering cross-section;

[0043] Step 3-2: Determine the pulse width of the first sub-pulse. Corresponding detection blind zone distance Does it meet the system indicator of minimum detection blind zone? Requirements, such as meeting If the number of sub-pulses does not increase, then the number of sub-pulses will not increase; otherwise, the number of sub-pulses will increase, and the pulse width of the first sub-pulse will be reduced. Corresponding detection blind zone distance To determine the detection range, the pulse width of the second sub-pulse is then determined. :

[0044]

[0045] Step 3-3: Determine the pulse width of the second sub-pulse. Corresponding detection blind zone distance Does it meet the system indicator of minimum detection blind zone? Requirements, such as meeting If the number of sub-pulses does not increase, then repeat steps 3-2 and 3-3 to increase the number of sub-pulses to [the specified value]. until the minimum detection blind zone is met. Require.

[0046] Step 4: Determine if the duty cycle meets the requirements based on the current sub-pulse parameters. If not, make adaptive adjustments to obtain the final sub-pulse waveform.

[0047]

[0048] According to the proportion factor Check if it is greater than or equal to a set threshold, for example, 0.9. If yes, no adjustment is needed; otherwise, adjust according to the scaling factor. Adjust the pulse width of each sub-pulse in the pulse to: , … Repeat steps 3 and 4 until the requirements are met.

[0049] Compared to existing time-division single-pulse methods, the advantage of this scheme using simultaneous sub-pulse waveforms lies in the simultaneous emission of multiple sub-pulses, which reuses the dwell time and greatly improves time utilization. While ensuring the maximum effective range, it significantly enhances the full-range Doppler resolution, especially the near-range Doppler resolution. Doppler resolution is equivalent to velocity resolution; the following is a derivation and demonstration of the velocity resolution improvement achieved using the two waveform forms.

[0050] Table 1 shows the improvement in speed resolution using different waveforms:

[0051] Known probe range According to the radar array's transmission duty cycle Determine the pulse period pulse number From this, it can be deduced that the improvement in velocity resolution dimensionality between simultaneous sub-pulses and time-division monopulses in the near-field region is greater than that between... .

[0052] Combination Figure 3 The present invention also provides a system for generating a simultaneous subpulse waveform for a low-altitude surveillance radar, for performing the above method, comprising the following modules:

[0053] Radar control module: Used to generate simultaneous sub-pulse waveform data based on radar parameters, form the waveform parameters of the current frame, and write the parameters into the radar control word of the frame to form the frame control command; Waveform parameter parsing module: The frequency source receives the current frame control command, parses the waveform parameters and sends the sub-pulse number, modulation form, frequency offset, pulse width, bandwidth, and gate information parameters to the intermediate frequency signal generation module, and sends the frequency control word to the local oscillator signal generation module; Intermediate Frequency Signal Generation Module: Used to receive parameters such as the number of sub-pulses, modulation form, frequency offset, pulse width, bandwidth, and gate information, and control the DDS arbitrary waveform generator to generate a corresponding number of sub-pulse waveforms within a 40MHz intermediate frequency bandwidth. The sub-pulse waveforms do not overlap in the time domain, do not overlap in the frequency domain, and maintain orthogonality in the waveform domain. Finally, the digital quantity is converted into an analog quantity by the DAC and output at an intermediate frequency of 150MHz ± 20MHz. Local oscillator signal generation module: used to receive the frequency control word information of the current frame, generate the frequency control code corresponding to the working frequency, generate the corresponding local oscillator intermediate frequency signal, and finally synthesize it into a local oscillator (3450M~4150M) and a second local oscillator (900M) signal corresponding to the working frequency of the current frame; RF excitation generation module: The intermediate frequency (IF) signal and two local oscillator (LO) signals are input into the RF excitation generation module. After two mixing cycles, the IF to RF conversion is completed. The first mixing cycle has an LO frequency of 900MHz, resulting in an IF of 750MHz ± 20MHz. The second mixing cycle has an LO frequency (3450MHz to 4150MHz) determined by the operating frequency of the current frame. For example, if the system operates at 3100MHz, the corresponding LO frequency is 3850MHz. At this time, the 750MHz ± 20MHz signal is mixed with the 3850MHz signal to obtain an RF signal of 3100MHz ± 20MHz. The RF signal is amplified by the T / R component and then transmitted to the antenna to radiate to the designated airspace.

[0054] The design method and system of multiple simultaneous sub-pulses in this scheme adopts time-division and frequency-division orthogonal waveform design, which fully reflects the concept of orthogonal non-interference. Time-division and frequency division means that the time domain and frequency domain can be processed independently, and the orthogonal waveforms have high isolation. This ensures that when multiple sub-pulses are processed at the receiving end, the signals detected within their respective ranges are not affected by each other, which greatly improves the velocity resolution in the detection near-field. The detection near-field is precisely the strong clutter area that is easily encountered during low-altitude detection. The improvement in velocity resolution means that the degree of influence of strong clutter on targets in the detection near-field is greatly reduced, and the detection capability of weak targets is enhanced.

[0055] This solution also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to perform the following steps:

[0056] Step 1: Obtain radar detection parameters;

[0057] Step 2: Determine the maximum pulse width of the simultaneous sub-pulse waveform based on the radar detection parameters. And the minimum number of pulses N required for coherent accumulation;

[0058] Step 3: Determine the parameters of each sub-pulse in each pulse;

[0059] Step 4: Determine whether the duty cycle meets the requirements based on the current sub-pulse parameters. If not, make adaptive adjustments to obtain the final sub-pulse waveform.

[0060] This solution also provides a computer-storable medium storing a computer program thereon, characterized in that the computer program, when executed by a processor, performs the following steps:

[0061] Step 1: Obtain radar detection parameters;

[0062] Step 2: Determine the maximum pulse width of the simultaneous sub-pulse waveform based on the radar detection parameters. And the minimum number of pulses N required for coherent accumulation;

[0063] Step 3: Determine the parameters of each sub-pulse in each pulse;

[0064] Step 4: Determine whether the duty cycle meets the requirements based on the current sub-pulse parameters. If not, make adaptive adjustments to obtain the final sub-pulse waveform.

[0065] The embodiments described above are merely one implementation method of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for generating a simultaneous subpulse waveform for a low-altitude surveillance radar, characterized in that, Includes the following steps: Step 1: Obtain radar detection parameters; Step 2: Determine the maximum pulse width of the simultaneous sub-pulse waveform based on the radar detection parameters. And the minimum number of pulses N required for coherent accumulation; Step 3: Determine the parameters of each sub-pulse in each pulse: Step 3-1: Based on the radar's maximum effective range The pulse width of the first sub-pulse is determined by the minimum number of coherent accumulation pulses N required. : ； in, This represents the target detection signal-to-noise ratio required given the detection probability and false alarm probability, where k represents the Boltzmann constant. Indicates system noise temperature. Indicates system loss. G represents the peak transmit power, and G represents the array gain. Represents the target scattering cross-section. The operating wavelength of the radar; Step 3-2: Determine the pulse width of the first sub-pulse. Corresponding detection blind zone distance Does it meet the system indicator of minimum detection blind zone? Requirements, such as meeting If the number of sub-pulses does not increase, then the number of sub-pulses will not increase; otherwise, the number of sub-pulses will increase, and the pulse width of the first sub-pulse will be reduced. Corresponding detection blind zone distance To determine the detection range, the pulse width of the second sub-pulse is then determined. : ； Step 3-3: Determine the pulse width of the second sub-pulse. Corresponding detection blind zone distance Does it meet the system indicator of minimum detection blind zone? Requirements, such as meeting If the number of sub-pulses does not increase, then repeat steps 3-2 and 3-3 to increase the number of sub-pulses to [the specified value]. until the minimum detection blind zone is met. Require; At the same time, the sub-pulse slices the pulse width of a complete time-division single pulse into several different sub-pulse widths. Each sub-pulse width is arranged in front and behind according to the pulse width, and each sub-pulse width is responsible for target detection in different range segments. Sub-pulse waveforms refer to multiple pulse waveforms with different pulse widths, frequencies, and modulation schemes that exist simultaneously within a certain time and bandwidth during transmission. During transmission, all sub-pulse waveforms are sent to the designated airspace within the transmission time span. Each sub-pulse is responsible for target detection in a different range segment. The range segments corresponding to all sub-pulses are combined to form the full range. The multiple simultaneous sub-pulses adopt a time-division and frequency-division orthogonal waveform design, and the waveforms of each sub-pulse do not overlap in the time domain, do not overlap in the frequency domain, and remain orthogonal in the waveform domain; Step 4: Determine whether the duty cycle meets the requirements based on the current sub-pulse parameters. If not, make adaptive adjustments to obtain the final sub-pulse waveform. Determining whether the duty cycle meets the requirements is based on the percentage factor. Sure: ； According to the proportion factor If the value is greater than or equal to the set threshold, no adjustment is needed; otherwise, adjust according to the scaling factor. Adjust the pulse width of each sub-pulse in the pulse to: , … Repeat steps 3 and 4 until the requirements are met.

2. The method for generating a simultaneous subpulse waveform for low-altitude surveillance radar according to claim 1, characterized in that, In step 2, determining the maximum pulse width of the simultaneous sub-pulse waveform The minimum number of pulses N required for coherent accumulation is: ； ； in, The maximum pulse width is the sum of the pulse widths of all simultaneous sub-pulses. For radar detection range, The duty cycle of radar array transmission. For radar velocity resolution, The speed of light is constant. The minimum number of coherent pulses required for the radar to achieve the required detection range.

3. A system for generating a simultaneous subpulse waveform for a low-altitude surveillance radar, used to execute the method of any one of claims 1-2, characterized in that, Includes the following modules: Radar control module: Used to generate simultaneous sub-pulse waveform data based on radar parameters, form the waveform parameters of the current frame, and write the parameters into the radar control word of the frame to form the frame control command; Waveform parameter parsing module: The frequency source receives the current frame control command, parses the waveform parameters and sends the sub-pulse number, modulation form, frequency offset, pulse width, bandwidth, and gate information parameters to the intermediate frequency signal generation module, and sends the frequency control word to the local oscillator signal generation module; Intermediate Frequency Signal Generation Module: Used to receive parameters such as the number of sub-pulses, modulation form, frequency offset, pulse width, bandwidth, and gate information, and control the DDS arbitrary waveform generator to generate a corresponding number of sub-pulse waveforms within the intermediate frequency bandwidth. The sub-pulse waveforms do not overlap in the time domain, do not overlap in the frequency domain, and maintain orthogonality in the waveform domain. Finally, the digital quantity is converted into an analog quantity by the DAC and output at the intermediate frequency. Local oscillator signal generation module: used to receive the frequency control word information of the current frame, generate the frequency control code corresponding to the working frequency, generate the corresponding local oscillator intermediate frequency signal, and finally synthesize it into a local oscillator and a second local oscillator signal corresponding to the working frequency of the current frame; RF excitation generation module: The intermediate frequency signal and two local oscillator signals are input to the RF excitation generation module. After two mixing cycles, the RF signal is converted from intermediate frequency to RF. The RF signal is amplified by the T / R component and then transmitted to the antenna end to be radiated to the designated airspace.

4. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1-2.

5. A computer-storable medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1-2.

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