A method for constructing a sky wave radar multi-domain joint interference perception architecture

Abstract

The application discloses a construction method of a sky wave radar multi-domain joint interference sensing architecture, comprising the following steps: Fourier transform is conducted on array element level baseband echoes in a radar coherent processing interval to obtain a space domain echo; the space domain echo envelope is taken and integration is conducted along fast time to obtain an echo space-time spectrum; the space-time spectrum is detected to estimate interference arrival angles and pulses and to judge main / auxiliary lobe interference; according to the estimated interference arrival angles and pulses, interference time domain samples are extracted from the space domain echo, and judgment and signal identification of interference time domain continuity / discontinuity and interference frequency domain wideband / narrowband are conducted; sensed interference space, time and frequency joint domain features and corresponding parameters are recorded in a structure body, and interference information is displayed on a radar terminal. The application does not need to change the system structure, only needs to adjust a signal processing algorithm, is convenient for engineering implementation, can be used in various electronic countermeasures and radar electronic reconnaissance equipment, is simple to realize, and has wide application prospects.

Description

Technical Field

[0001] This application relates to the technical field of interference filtering, and in particular to a method for constructing a multi-domain joint interference sensing architecture for skywave radar. Background Technology

[0002] Skywave over-the-horizon (OTHR) radar uses ionospheric reflection for target detection, overcoming the detection blind spots caused by the Earth's curvature. It boasts numerous advantages, including all-weather operation, long detection range, and protection against low-altitude penetration. However, OTHR operates at a low frequency, making it susceptible to unintentional interference from radio frequency and transient signals, as well as targeted active jamming from the enemy during wartime.

[0003] Currently, although numerous interference suppression algorithms exist, these algorithms generally have limited applicability. They typically only suppress interference models assumed by the algorithm. When the actual interference experienced by the radar does not match the model, the algorithm's effectiveness will significantly decrease. Therefore, accurately sensing interference in advance is a key technical challenge that urgently needs to be solved. Currently, there are many methods for interference sensing, but they are mainly single-domain sensing, with interference frequency, angle of arrival (DOA) estimation, and signal identification being the most common. OTHR employs an array pulse Doppler (PD) system, and direct application of existing methods presents four prominent problems: First, existing interference frequency and DOA estimation methods typically only target echoes with a single pulse repetition period, failing to capture the inter-pulse characteristics of the interference. Second, existing interference signal identification methods require prior access to clean interference samples, while OTHR lacks an independent reconnaissance receiver, and interference samples can only be obtained from the echoes. OTHR is typically a continuous wave system, and the echoes contain strong clutter and targets in addition to interference signals, failing to meet algorithm requirements. Third, existing suppression algorithms tend towards joint suppression across multiple spatial, temporal, and frequency domains; single-domain sensing is insufficient to meet the algorithm's prior requirements. Fourth, existing interference sensing methods involve matrix inversion, matrix decomposition, and sample training, resulting in high computational complexity and difficulty in ensuring timely performance.

[0004] Based on this, this application provides a method for constructing a multi-domain joint interference sensing architecture for skywave radar to solve the above-mentioned technical problems. Summary of the Invention

[0005] In order to provide accurate prior information for precise interference suppression and ensure the effective performance of radar detection, this application provides a method for constructing a multi-domain joint interference sensing architecture for skywave radar.

[0006] The method for constructing a multi-domain joint jamming perception architecture for skywave radar provided in this application adopts the following technical solution:

[0007] First aspect

[0008] A method for constructing a multi-domain joint jamming sensing architecture for skywave radar includes the following steps:

[0009] S1. Perform Fourier transform on the array element-level baseband echo within the coherent processing interval (CPI) of the low-frequency radar to obtain the spatial echo.

[0010] S2. Take the spatial echo envelope and integrate it along the fast time to obtain the echo space-time spectrum (SPS);

[0011] S3. Detect the echo space-time spectrum, estimate the angle of arrival (DOA) and the pulse where the interference is located, and determine the main / side lobe interference;

[0012] S4. Based on the estimated angle of arrival (DOA) and the pulse, extract the time-domain sample of the interference from the spatial echo, and determine whether the interference is continuous / discontinuous in the time domain, wide-band / narrow-band in the frequency domain, and identify the signal.

[0013] S5. Record the perceived interference spatial, temporal, and frequency joint domain characteristics and corresponding parameters into the structure, and display the interference information on the radar terminal.

[0014] Optionally, step S1 includes:

[0015] S11. Let x be the baseband echo of the array element level within a coherent processing interval (CPI). r (t k ,t f ,t m ), t k For spatial time, t f For fast time, t m For slow time, the discrete forms are as follows:

[0016]

[0017] Where N is the number of array elements, L is the number of echo range gates, and M is the number of accumulated pulses; d is the array element interval, t is the number of echo range gates, and t is the number of echo range gates. s For echo sampling period, T r The radar pulse repetition period is c = f0λ, where c is the speed of light, f0 is the radar carrier frequency, and λ is the wavelength.

[0018] S12, along the spatial time t k Calculate x r (t k ,t f ,t m The Fourier transform of ) yields the spatial echo x. r (θ,t f ,t m ), represented as:

[0019]

[0020] Optionally, step S2 includes:

[0021] S21, Obtain spatial echo x r (θ,t f ,t m The envelope of ) along fast time t f Integrating, we obtain the echo space-time spectrum S. t (θ,t m ), represented as:

[0022]

[0023] Optionally, step S3 includes:

[0024] S31, Echo space-time spectrum S t (θ,t m Interference detection is performed to obtain the r-th interference label. For the estimated interference DOA, For the pulse in which the tag is located, r = 0, 1, 2, ..., R-1, where R is the number of tags.

[0025] S32. Let the left and right boundaries of the radar transmit beam be θ respectively. left and θ right The main / sidelobe interference can be determined using the following formula:

[0026]

[0027] Optionally, step S4 includes:

[0028] S41. Based on the detected interference tags echo from the airspace x r (θ,t f ,t m Extracting interference time-domain samples j) r (t f ), represented as:

[0029]

[0030] S42. For the extracted interference time-domain sample j r (t f The envelope is captured, and then temporal detection is performed to obtain P interference range gates. p p = 0, 1, 2, ... P-1; determine whether the interference is continuous or discontinuous in the time domain according to the following formula:

[0031]

[0032] In the formula, α is the threshold for distinguishing between continuous and discontinuous interference in the time domain, and 0 < α < 0.5;

[0033] S43, Regarding the interference time-domain sample j r (t f Intelligent identification is performed to obtain the form of the interference signal;

[0034] S44. Calculate the interference time-domain sample j r (t f The Fourier transform of ) yields the interference frequency domain sample j. r (f), for the interference frequency domain sample j r (f) Take the envelope and perform frequency domain detection to obtain Q interference frequency points f. q q = 0, 1, 2, ... Q-1; determine the bandwidth / narrowband of the interference frequency domain according to the following formula:

[0035]

[0036] In the formula, β is the interference frequency domain broadband / narrowband discrimination threshold, 0 < β < 0.5.

[0037] Optionally, step S5 includes:

[0038] S51. Construct a structure to record interference information. The structure contains the following elements: category, feature descriptor, and feature parameters.

[0039] S52, the echo space-time spectrum X(θ,t) m Interference time-domain sample j r (t f Interference frequency domain sample j r (f) and the structure content are displayed on the radar interference perception interface.

[0040] Optionally, the Fourier transform in step S1 is a Fast Fourier Transform (FFT).

[0041] Optionally, in step S3, a constant false alarm rate (CFAR) detector is used to detect the echo spatiotemporal spectrum.

[0042] Optionally, both the time-domain detection and frequency-domain detection in step S4 adopt the maximum outlier detection method. The criterion for maximum outlier detection is one of the following: 3 times the standard deviation criterion, 1.5 times the interquartile range criterion, and 2.5 times the median absolute deviation criterion.

[0043] Optionally, the low-frequency radar includes a skywave radar.

[0044] In summary, this application includes at least one of the following beneficial technical effects:

[0045] 1. This invention does not require modification to the system structure; only the signal processing algorithm needs adjustment, making it easy to implement in engineering. The technology of this invention can be used in various electronic countermeasures and radar electronic reconnaissance equipment, is simple to implement, and has broad application prospects.

[0046] 2. The FFT used in this invention has a small computational load, and the CFAR used is a mature radar technology.

[0047] 3. The method of this invention only involves the signal processing flow, that is, it only requires upgrading the processing system and software, without changing other system structures, and has the value of promotion and application.

[0048] 4. This invention is applicable not only to skywave radar, but also to other array and PD-type radars. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the interference sensing architecture of the present invention.

[0050] Figure 2 This is a flowchart of the construction method of the interference sensing architecture of the present invention.

[0051] Figure 3 This is the measured space-time spectrum of the interference echo of the present invention.

[0052] Figure 4 This is a graph showing the measured spatiotemporal spectrum detection effect of the interference echo of the present invention (displayed in polar coordinates).

[0053] Figure 5 This is a diagram showing the measured spatiotemporal spectrum detection effect of the interference echo of the present invention (displayed in rectangular coordinates).

[0054] Figure 6 This is the active interference time-domain waveform obtained by sensing in this invention.

[0055] Figure 7 This is the transient interference time-domain waveform obtained by sensing in this invention.

[0056] Explanation of reference numerals in the attached figures: Detailed Implementation

[0057] The following is in conjunction with the appendix Figure 1-7 This application will be described in further detail.

[0058] Reference Figure 1The embodiments of the present invention consist of an array element-level baseband echo 1, a spatial echo 2, an echo spatiotemporal spectrum 3, a spatiotemporal spectrum detection 4, an interference time-domain sample 5, a time-domain outlier detection 6, intelligent signal recognition 7, an interference frequency-domain sample 8, a frequency-domain outlier detection 9, recording interference information 10, and a radar terminal display 11. In these embodiments, the array element-level baseband echo 1 is an echo signal received by the radar containing components such as interference, targets, and clutter; the spatial echo 2 is obtained by calculating the Fourier transform of the array element-level baseband echo along the spatial domain; the echo spatiotemporal spectrum 3 is obtained by taking the envelope of the spatial echo and then integrating it along the fast time path; the spatiotemporal spectrum detection 4 performs constant false alarm rate (CFAR) detection on the echo spatiotemporal spectrum to obtain interference tags (each tag corresponds to one spatial domain and one pulse), and determines whether the interference originates from the main lobe or side lobe; the time-domain sample 5 is an interference time-domain sample obtained from the spatial echo based on the interference tags; and the time-domain outlier detection 6 performs maximum outlier detection on the interference time-domain sample and determines... Interference is interrupted continuously or intermittently, and the range gate of the affected area is recorded; Signal intelligent identification 7 uses machine learning to identify the form of interference signals; Interference frequency domain sample 8 is obtained by calculating the Fourier transform of interference time domain sample; Frequency domain outlier detection 9 performs maximum outlier detection on interference frequency domain sample to determine whether the interference signal is broadband or narrowband, and records the interference frequency point; Recording interference information 10 records the obtained interference information into the structure; Radar terminal display 11 displays the echo spatiotemporal spectrum, interference time domain sample, interference frequency domain sample, and structure information on the radar interface for operators to understand the current interference situation.

[0059] This application discloses a method for constructing a multi-domain joint jamming perception architecture for skywave radar. (Refer to...) Figure 2 This includes the following steps:

[0060] S1. Perform Fourier transform on the array element-level baseband echo within the coherent processing interval (CPI) of the low-frequency radar to obtain the spatial echo.

[0061] The low-frequency radar includes skywave radar or other array / PD-type radar. In this embodiment, the low-frequency range of the low-frequency radar is less than 30MHz.

[0062] Specifically, S1 includes:

[0063] S11. Let x be the baseband echo of the array element level within a coherent processing interval (CPI). r (t k ,t f ,t m ), t k For spatial time, t f For fast time, t m For slow time, the discrete forms are as follows:

[0064]

[0065] Where N is the number of array elements, L is the number of echo range gates, and M is the number of accumulated pulses; d is the array element interval, t is the number of echo range gates, and t is the number of echo range gates. s For echo sampling period, T r The radar pulse repetition period is c = f0λ, where c is the speed of light, f0 is the radar carrier frequency, and λ is the wavelength.

[0066] In this embodiment, the low-frequency radar is a skywave radar, which is a linear array. Therefore, its spatial time is one-dimensional, and the baseband echo of the skywave radar array is a three-dimensional echo. Furthermore, "fast time" refers to the range dimension, and "slow time" refers to the pulse dimension; these are academic terms used in radar coherent accumulation.

[0067] S12, along the spatial time t k Calculate x r (t k ,t f ,t m The Fourier transform of ) yields the spatial echo x. r (θ,t f ,t m ), represented as:

[0068]

[0069] In this embodiment, the Fourier transform is a Fast Fourier Transform (FFT) to reduce the computational load of the algorithm. Furthermore, since the baseband echo at the element level of the skywave radar array is a three-dimensional echo, the spatial echo is also a three-dimensional echo.

[0070] S2. Take the spatial echo envelope and integrate it along the fast time to obtain the echo space-time spectrum (SPS).

[0071] Specifically, S2 includes:

[0072] S21, Obtain spatial echo x r (θ,t f ,t m The envelope of ) along fast time t f Integrating, we obtain the echo space-time spectrum S. t (θ,t m ), represented as:

[0073]

[0074] In this embodiment, due to x r (θ,t f ,t m Since is a complex number, its envelope needs to be taken before integration when calculating the echo space-time spectrum.

[0075] S3. Detect the spatiotemporal spectrum, estimate the angle of arrival (DOA) of the interference and the pulse in which it is located, and determine the main / sidelobe interference.

[0076] Specifically, S3 includes:

[0077] S31, Echo space-time spectrum S t (θ,t m Interference detection is performed to obtain the r-th interference label. For the estimated interference DOA, Let r be the pulse in which the tag is located, and r = 0, 1, 2, ..., R-1, where R is the number of tags.

[0078] In this embodiment, a constant false alarm rate (CFAR) detector is used to detect the echo spatiotemporal spectrum, and the interference label reflects the interference spatial domain and slow-time information. For example, when the radar is subjected to interference from one interference source (DOA of 10 degrees, duration of pulses 1-50), then for all r, Both are 10 degrees, and The range is 1 to 50.

[0079] S32. Let the left and right boundaries of the radar transmit beam be θ respectively. left and θ right The main / sidelobe interference can be determined using the following formula:

[0080]

[0081] In this embodiment, the left and right boundaries of the transmitted beam are set to -5 degrees and 5 degrees, respectively, and the interference DOA is 10 degrees. Since it is located outside the interval, it is judged to be sidelobe interference.

[0082] S4. Based on the estimated angle of arrival (DOA) and the pulse, extract the time-domain sample of the interference from the spatial echo, and determine whether the interference is continuous / discontinuous in the time domain, wideband / narrowband in the frequency domain, and identify the signal.

[0083] Specifically, S4 includes:

[0084] S41. Based on the detected interference tags echo from the airspace x r (θ,t f ,t m Extracting interference time-domain samples j) r (t f ), represented as:

[0085]

[0086] In this embodiment, the interference time-domain sample is a fast-time sample selected from the spatial echo under the premise of knowing both the spatial domain and slow time dimensions.

[0087] S42. For the extracted interference time-domain sample j r (t f The envelope is captured, and then temporal detection is performed to obtain P interference range gates. p p = 0, 1, 2, ... P-1; determine whether the interference is continuous or discontinuous in the time domain according to the following formula.

[0088]

[0089] In the formula, α is the threshold for distinguishing between continuous and discontinuous interference in the time domain, and 0 < α < 0.5;

[0090] In this embodiment, it is assumed that α = 0.1, the number of radar range gates L is 500, and the number of outliers P detected is 100. Since 100 > 0.1 × 500, it is judged as intermittent interference. The value of α is not strictly defined, as long as 0 < α < 0.5 is satisfied.

[0091] S43, Regarding the interference time-domain sample j r (t f Intelligent identification is performed to obtain the form of interference signals.

[0092] In this embodiment, the intelligent recognition method adopts machine learning.

[0093] S44. Calculate the interference time-domain sample j r (t f The Fourier transform of ) yields the interference frequency domain sample j. r (f), for the interference frequency domain sample j r (f) Take the envelope and perform frequency domain detection to obtain Q interference frequency points f. q q = 0, 1, 2, ... Q-1; determine the bandwidth / narrowband of the interference frequency domain according to the following formula:

[0094]

[0095] In the formula, β is the interference frequency domain broadband / narrowband discrimination threshold, 0 < β < 0.5.

[0096] Both time-domain and frequency-domain detection employ the maximum outlier detection method, with the maximum outlier detection criteria being one of the following: 3 times the standard deviation criterion, 1.5 times the interquartile range criterion, or 2.5 times the absolute deviation of the median criterion.

[0097] In this embodiment, assuming β = 0.1, the number of radar range gates L is 500, and the number of detected outliers Q is 100, since 100 > 0.1 × 500, it is judged as narrowband interference. The value of β is not strictly defined, as long as 0 < β < 0.5.

[0098] S5. Record the perceived interference spatial, temporal, and frequency joint domain characteristics and corresponding parameters into the structure, and display the interference information on the radar terminal.

[0099] Specifically, S5 includes:

[0100] S51. Construct a structure to record interference information. The structure contains the following elements: category, feature descriptor, and feature parameters.

[0101] In this embodiment, as shown in Table 1 below.

[0102] Table 1

[0103]

[0104] S52, the echo space-time spectrum X(θ,t) m Interference time-domain sample j r (t f Interference frequency domain sample j r (f) and the structure content are displayed on the radar interference perception interface. This provides prior information for the selection of interference suppression algorithms, allowing operators to intuitively grasp the current interference situation.

[0105] In this embodiment, Figure 3 It is the measured space-time spectrum of the interference echo. Figure 4 This is a graph showing the measured spatiotemporal spectrum of the interfered echo (displayed in polar coordinates). Figure 5 This is a graph showing the measured spatiotemporal spectrum of the interfered echo (displayed on rectangular coordinates). Figure 6 It is a time-domain waveform diagram of active interference obtained through sensing. Figure 7 This is the time-domain waveform of the transient interference obtained through sensing. The frequency-domain waveform can be obtained by performing a Fourier transform on the time-domain waveform; the frequency-domain waveform is not shown here.

[0106] As can be seen from the measured data in the figure, this technology can not only accurately measure the DOA of intentional interference, but also obtain the spatiotemporal distribution of unintentional interference, providing reliable prior information for radar anti-jamming.

[0107] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for constructing a multi-domain joint interference sensing architecture for skywave radar, characterized in that, Includes the following steps: S1. Perform Fourier transform on the baseband echo of the array element level within the coherent processing interval CPI of the low-frequency radar to obtain the spatial echo. S2. Take the spatial echo envelope and integrate it along the fast time to obtain the echo space-time spectrum (SPS). S3. Detect the echo space-time spectrum, estimate the angle of arrival (DOA) of the interference and the pulse it is located in, and determine the main / side lobe interference; S4. Based on the estimated angle of arrival (DOA) and the pulse in which the interference occurs, extract the time-domain sample of the interference from the spatial echo, and determine whether the interference is continuous / discontinuous in the time domain and wide / narrow in the frequency domain, and identify the signal; S5. Record the sensed spatial, temporal, and frequency joint domain characteristics and corresponding parameters of the interference into the structure, and display the interference information on the radar terminal; Step S1 includes: S11, setting the array element-level baseband echo within a coherent processing interval CPI as x. r (t k ,t f ,t m ), t k For spatial time, t f For fast time, t m For slow time, the discrete forms are as follows: Where N is the number of array elements, L is the number of echo range gates, and M is the number of accumulated pulses; d is the array element interval, t is the number of echo range gates, and t is the number of echo range gates. s For echo sampling period, T r The radar pulse repetition period; c = f0λ, where c is the speed of light, f0 is the radar carrier frequency, and λ is the wavelength; S12, along the spatial time t k Calculate x r (t k ,t f ,t m The Fourier transform of ) yields the spatial echo x. r (θ,t f ,t m ), represented as: ; Step S2 includes: S21, obtaining the spatial echo x r (θ,t f ,t m The envelope of ) along fast time t f Integrating, we obtain the echo space-time spectrum S. t (θ,t m ), represented as: ; Step S3 includes: S31, analyzing the echo space-time spectrum S t (θ,t m Interference detection is performed to obtain the r-th interference label. For the estimated interference DOA, / > Let r be the pulse in which the tag is located, r = 0, 1, 2, ..., R-1, where R is the number of tags; S32, let the left and right boundaries of the radar transmit beam be θ respectively. left and θ right The main / sidelobe interference can be determined using the following formula: ; Step S4 includes: S41, based on the detected interference tags echo from the airspace x r (θ,t f ,t m Extracting interference time-domain samples j) r (t f ), represented as: S42. For the extracted interference time-domain sample j r (t f The envelope is captured, and then temporal detection is performed to obtain P interference range gates. p p = 0, 1, 2, ... P-1; determine whether the interference is continuous or discontinuous in the time domain according to the following formula: In the formula, α is the threshold for distinguishing between continuous and discontinuous interference in the time domain, 0 < α < 0.5; S43, for interference time domain sample j r (t f S44. Perform intelligent identification to obtain the form of interference signal; S45. Calculate the interference time-domain sample j r (t f The Fourier transform of ) yields the interference frequency domain sample j. r (f), for the interference frequency domain sample j r (f) Take the envelope and perform frequency domain detection to obtain Q interference frequency points f. q q = 0, 1, 2, ... Q-1; determine the bandwidth / narrowband of the interference frequency domain according to the following formula: In the formula, β is the interference frequency domain broadband / narrowband discrimination threshold, 0 < β < 0.

5.

2. The method for constructing a multi-domain joint interference sensing architecture for skywave radar according to claim 1, characterized in that, Step S5 includes: S51, constructing a structure for recording interference information, the structure containing the following elements: category, feature descriptor, and feature parameters; S52, processing the echo spatiotemporal spectrum X(θ,t) m Interference time-domain sample j r (t f Interference frequency domain sample j r (f) and the structure content are displayed on the radar interference perception interface.

3. The method for constructing a multi-domain joint interference sensing architecture for skywave radar according to claim 1, characterized in that, The Fourier transform in step S1 is the Fast Fourier Transform (FFT).

4. The method for constructing a multi-domain joint interference sensing architecture for skywave radar according to claim 1, characterized in that, In step S3, the echo spatiotemporal spectrum is detected using a constant false alarm rate (CFAR) detector.

5. The method for constructing a multi-domain joint interference sensing architecture for skywave radar according to claim 1, characterized in that, The time-domain detection and frequency-domain detection in step S4 both adopt the maximum outlier detection method. The criteria for maximum outlier detection are one of the following: 3 times the standard deviation criterion, 1.5 times the interquartile range criterion, and 2.5 times the median absolute deviation criterion.

6. The method for constructing a multi-domain joint interference sensing architecture for skywave radar according to claim 1, characterized in that, The low-frequency radar includes skywave radar.

Images