A digital multi-beam direction finding method and system for unmanned aerial vehicle

Abstract

The present invention discloses a method and system for digital multi-beam direction finding of unmanned aerial vehicles, which belongs to the field of electronic countermeasure technology. The method determines the real-time evaluation environment measurement signal-to-noise ratio by acquiring the relative distance between the unmanned aerial vehicle and the target radar; determines the beam mode of the target radar according to the magnitude of the real-time evaluation environment measurement signal-to-noise ratio and the preset minimum environment signal-to-noise ratio; when the real-time evaluation environment measurement signal-to-noise ratio is greater than the preset minimum environment signal-to-noise ratio, the beam mode of the target radar is a sparse beam mode; when the real-time evaluation environment measurement signal-to-noise ratio is less than the preset minimum environment signal-to-noise ratio, the beam mode of the target radar is a conventional beam mode; according to the beam mode selected by the target radar, digital multi-beam direction finding is performed by determining the amplitude difference between different beams of the target radar to obtain the target radar direction finding angle. The method can optimize energy consumption while maintaining high direction finding accuracy and spectrum coverage.

Description

Technical Field

[0001] The present invention relates to the field of electronic countermeasure technology, and more specifically to a digital multi-beam direction-finding method and system for unmanned aerial vehicles. Background Art

[0002] Digital beamforming technology is a new technology developed on the basis of array antenna and signal processing, and has been widely used in the field of antenna technology. Its basic idea is to control the directional function of the antenna array by weighted processing of the received data of the antenna array elements, so that the antenna array pattern produces a high-gain narrow beam in the main lobe direction and a deeper null in the side lobe direction. Therefore, only the radiated signal in the direction of the beam pointing to the corresponding incoming wave will enter from the main lobe direction of the beam, and the angle range of the incoming wave direction of the received signal is limited to the main lobe beam width of the antenna. Other receiving beams are only interfered by the side lobe direction, which reduces the radar's interfered airspace range and improves the radar's anti-interference ability.

[0003] Digital beamforming technology uses a multi-beam detection form to achieve instantaneous full coverage of the airspace. At the same time, array signal processing with high antenna gain is also an important means to complete electronic signal reconnaissance. Secondly, based on the multi-beam characteristics of digital beamforming technology, combined with the amplitude comparison direction finding algorithm, the measurement of the target signal arrival angle is completed. Due to its high direction finding accuracy and strong anti-interference characteristics, digital beamforming technology has been increasingly valued in modern wireless communications, radar and other applications, especially in the field of reconnaissance drones. It has been rapidly promoted and applied. When performing long-term, large-area reconnaissance missions, drones often need to comprehensively consider environmental risks, mission requirements and energy supply to provide support for the formulation of intelligent and effective reconnaissance strategies.

[0004] In actual direction finding, in order to improve the direction finding accuracy as much as possible, a sufficient number of beam groups with small overlapping beam widths should be designed. However, the existing digital multi-beam technology cannot fully cover the detection area during digital signal processing due to the unstable environmental signal-to-noise ratio, which affects the transmission of massive sampling information. At the same time, the beam synthesis calculation and data transmission of digital beamforming occupy a very large amount of computing resources and require complex weighted operations, which in turn affects the direction finding accuracy and efficiency. Summary of the invention

[0005] In response to the problems existing in the above-mentioned fields, the present invention proposes a digital multi-beam direction-finding method and system for unmanned aerial vehicles, which can solve the technical problems that the existing digital multi-beam technology cannot fully cover the reconnaissance area during digital signal processing due to the unstable environmental signal-to-noise ratio, affecting the transmission of massive sampling information. At the same time, the beam synthesis calculation and data transmission of digital beamforming occupy a very large amount of computing power resources and require complex weighted operations, which in turn affects the direction-finding accuracy and efficiency.

[0006] In order to solve the above technical problems, the present invention discloses a UAV digital multi-beam direction finding method, comprising the following steps:

[0007] Get the relative distance between the UAV and the target radar;

[0008] Determine the signal-to-noise ratio of the real-time evaluation environment measurement based on the relative distance between the UAV and the target radar;

[0009] The beam mode of the target radar is determined according to the magnitude of the real-time evaluation environment measurement signal-to-noise ratio and the preset minimum environment signal-to-noise ratio; when the real-time evaluation environment measurement signal-to-noise ratio is greater than the preset minimum environment signal-to-noise ratio, the beam mode of the target radar is a sparse beam mode; when the real-time evaluation environment measurement signal-to-noise ratio is less than the preset minimum environment signal-to-noise ratio, the beam mode of the target radar is a conventional beam mode;

[0010] The sparse beam mode and the conventional beam mode are configured as follows:

[0011] Obtain the coverage of the drone reconnaissance airspace, the angle error threshold of the digital multi-beam generated by the drone to the target radar, the minimum receiving gain and the preset minimum environmental signal-to-noise ratio;

[0012] Based on the angle error threshold and minimum receiving gain of the digital multi-beam, the directivity pattern function of the synthesized beam is determined; by analyzing the direction finding error of the directivity pattern function, the beam overlap coefficient and the overlap beam width of the synthesized beam are determined to obtain the upper boundary value and the lower boundary value of the overlap beam width;

[0013] According to the upper boundary value and the lower boundary value of the overlapping beam width, the number of beams corresponding to the upper boundary value and the lower boundary value are determined;

[0014] The obtained upper boundary value of the overlapping beam width and the number of beams corresponding to the upper boundary value are set as parameters of the sparse beam mode; the obtained lower boundary value of the overlapping beam width and the number of beams corresponding to the lower boundary value are set as parameters of the normal beam mode;

[0015] The upper boundary value of the overlapping beam width is greater than the lower boundary value of the overlapping beam width, and the number of beams corresponding to the upper boundary value is less than the number of beams corresponding to the lower boundary value;

[0016] The number of beams of the conventional beam mode is greater than the number of beams of the sparse beam mode, and the overlapping beam width of the conventional beam mode is smaller than the overlapping beam width of the sparse beam mode;

[0017] According to the beam mode selected by the target radar, digital multi-beam direction finding is performed by determining the amplitude difference between different beams of the target radar to obtain the target radar direction finding angle.

[0018] Preferably, the determining of the real-time evaluation environment measurement signal-to-noise ratio comprises the following steps:

[0019] Get effective radiated power , the relative distance between the UAV and the target radar , the power of the intercepted signal is:

[0020]

[0021] in, is the ratio of the side lobe to the main lobe, is the signal wavelength;

[0022] The signal-to-noise ratio of the real-time evaluation environment measurement is:

[0023]

[0024] in, It is a relatively stable noise power value obtained through long-term average measurement.

[0025] Preferably, the method of obtaining the upper boundary value and the lower boundary value of the overlapping beam width comprises the following steps:

[0026] Get the number of array elements , the received signal frequency is , No. The narrowband analog signal received by each array element is:

[0027]

[0028] in, , , is the amplitude of the echo signal, j is a plural unit;

[0029] The element spacing of the uniform linear array is obtained as , determine the beam function according to the following formula:

[0030]

[0031] in, is the number of the antenna element, is the echo wavelength, is the complex weighting coefficient, Indicates the direction of incoming waves;

[0032] Pair After normalization, the directional diagram function of the synthesized beam is obtained as:

[0033]

[0034] in, , M is the number of beams, , is the beam overlap coefficient, is the overlapping beamwidth, The value is The overlapping beam width at ;

[0035] Get the center angle of the synthetic beam with maximum output at the same time and the composite beam center angle of the second largest output , the direction finding error is:

[0036]

[0037] in, , is the preset minimum environmental signal-to-noise ratio;

[0038] The characteristic value of the overlapped beam width includes an upper boundary value and a lower boundary value, where:

[0039] exist and When the direction finding error is known and fixed, the angle error is made less than or equal to the angle error threshold, that is, , substituting into the direction finding error formula, we get The upper boundary constraint value , ≤ ;

[0040] It is known that the minimum receiving gain of the receiver for the signal is , when the antenna gain is When the beam overlap coefficient D satisfy:

[0041]

[0042] Corresponding to Another upper bound constraint value of , ≤ ;

[0043] The upper boundary value of the overlapped beam width is obtained as ;

[0044] Get the maximum number of beamforming , based on the overlapping beamwidth Coverage of reconnaissance airspace The relationship between , we can conclude The corresponding lower boundary constraint value , ≥ ;

[0045] Another lower bound constraint for obtaining the overlapped beam width is , ≥ , is the engineering experience value of the overlapping beam width, and the lower boundary value of the overlapping beam width is obtained as .

[0046] Preferably, the corresponding determination of the number of beams corresponding to the upper boundary value and the lower boundary value comprises the following steps:

[0047] According to the upper boundary value of the overlapped beam width obtained , based on the overlapping beamwidth Coverage of reconnaissance airspace The relationship between , and the number of beams corresponding to the upper boundary value is obtained ;

[0048] According to the obtained overlap beam width lower boundary value , based on the overlapping beamwidth Coverage of reconnaissance airspace The relationship between , and the number of beams corresponding to the lower boundary value is obtained .

[0049] Preferably, obtaining the target radar direction finding angle comprises the following steps:

[0050] Determine the beam overlap coefficient based on the beam mode selected by the target radar The corresponding beam pattern is extracted Normalized antenna pattern data, respectively and The normalized antenna pattern data is subtracted to obtain the beam The amplitude-to-direction-finding table data;

[0051] The obtained beam The amplitude comparison direction-finding table data is limited, filtered, amplified and A / D quantized to obtain multiple independent beams with adjacent main lobes. The envelope amplitudes of signals received by two or more adjacent narrow beams among the simultaneously existing narrow beams are compared;

[0052] Get the The axis angle of the beam is , signal direction In the At the antenna axis of the beam, The first The signal amplitudes received by each beam are expressed as:

[0053]

[0054]

[0055] in, Representative m The signal amplitude of each beam receiving channel, Representative m -1 beam receiving channel signal amplitude, For the m -1 beam axis angle, is a constant;

[0056] The signal amplitude difference between two adjacent beams is , It is expressed as:

[0057]

[0058] Calculate the signal at m beam and the m-1 The signal amplitude difference of the beam , use the signal amplitude difference to find the corresponding m The amplitude ratio direction finding table of each beam can obtain the direction finding angle of the target radar.

[0059] Preferably, it also includes obtaining the measurement cycle in the actual measurement process , when the initial time passes After that, calculate the real-time evaluation environment measurement signal-to-noise ratio again ;

[0060] And calculate the real-time evaluation environment measurement signal-to-noise ratio The preset minimum environmental signal-to-noise ratio For comparison, Greater than When , select the sparse beam mode; when Less than , select the normal beam mode;

[0061] In the actual measurement process, each time , re-comparison of real-time evaluation of environmental measurement signal-to-noise ratio and the preset minimum environmental signal-to-noise ratio , and reselect the beam mode.

[0062] Preferably, a UAV digital multi-beam direction finding system is also included, comprising:

[0063] The signal-to-noise ratio acquisition module is used to obtain the relative distance between the UAV and the target radar; according to the relative distance between the UAV and the target radar, the signal-to-noise ratio of the real-time evaluation environment measurement is determined;

[0064] A beam mode selection module is used to determine the beam mode of the target radar according to the size of the real-time evaluation environment measurement signal-to-noise ratio and the preset minimum environment signal-to-noise ratio; when the real-time evaluation environment measurement signal-to-noise ratio is greater than the preset minimum environment signal-to-noise ratio, the beam mode of the target radar is a sparse beam mode; when the real-time evaluation environment measurement signal-to-noise ratio is less than the preset minimum environment signal-to-noise ratio, the beam mode of the target radar is a conventional beam mode; wherein the sparse beam mode and the conventional beam mode are set in a manner including: obtaining the coverage range of the UAV reconnaissance airspace, the angle error threshold of the digital multi-beam generated by the UAV to the target radar, the minimum receiving gain and the preset minimum environment signal-to-noise ratio; based on the angle error threshold and the minimum receiving gain of the digital multi-beam, determining the directional pattern function of the synthetic beam; and determining the direction finding error of the directional pattern function by analyzing the direction finding error of the directional pattern function. Determine the beam overlap coefficient and the overlap beam width of the synthetic beam to obtain the upper boundary value and the lower boundary value of the overlap beam width; determine the number of beams corresponding to the upper boundary value and the lower boundary value according to the upper boundary value and the lower boundary value of the overlap beam width; set the obtained upper boundary value of the overlap beam width and the number of beams corresponding to the upper boundary value as parameters of the sparse beam mode; set the obtained lower boundary value of the overlap beam width and the number of beams corresponding to the lower boundary value as parameters of the regular beam mode; wherein the upper boundary value of the overlap beam width is greater than the lower boundary value of the overlap beam width, and the number of beams corresponding to the upper boundary value is less than the number of beams corresponding to the lower boundary value; the number of beams of the regular beam mode is greater than the number of beams of the sparse beam mode, and the overlap beam width of the regular beam mode is less than the overlap beam width of the sparse beam mode;

[0065] The target radar direction finding angle acquisition module is used to perform digital multi-beam direction finding according to the beam mode selected by the target radar by determining the amplitude difference between different beams of the target radar to obtain the target radar direction finding angle.

[0066] Compared with the prior art, the present invention has the following beneficial effects:

[0067] The digital multi-beam direction-finding method for unmanned aerial vehicles proposed in the present invention determines the real-time evaluation of the environmental measurement signal-to-noise ratio by obtaining the relative distance between the unmanned aerial vehicle and the target radar, and provides theoretical support for the digital multi-beam direction-finding proposed in the present invention. By setting the conventional beam mode and the sparse beam mode, when the real-time evaluation of the environmental measurement signal-to-noise ratio is greater than the preset minimum environmental signal-to-noise ratio, the target radar selects the sparse beam mode for direction-finding. Since the number of waves in the sparse beam mode is smaller than the number of beams in the conventional beam mode, the requirements for the computing power of the hardware platform are reduced without affecting the direction-finding accuracy, the computing efficiency of the direction-finding process is improved, and power consumption is saved. When the real-time evaluation of the environmental measurement signal-to-noise ratio is less than the preset minimum environmental signal-to-noise ratio, the target radar selects the conventional beam mode for direction-finding. According to the selected beam mode, digital multi-beam direction-finding is performed by making a ratio amplitude direction-finding table, and the direction-finding angle of the target radar is determined, thereby improving the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 is a flow chart of a UAV digital multi-beam direction finding method proposed in an embodiment of the present invention;

[0069] Figure 2 It is a block diagram of a UAV digital multi-beam direction finding method proposed in an embodiment of the present invention;

[0070] Figure 3 is a beam pattern of a conventional beam mode proposed in an embodiment of the present invention;

[0071] Figure 4 is a beam pattern of a sparse beam mode proposed in an embodiment of the present invention;

[0072] Figure 5 is a direction finding error distribution diagram of a conventional beam pattern of a specific environmental signal-to-noise ratio proposed in an embodiment of the present invention;

[0073] Figure 6 It is a distribution diagram of the direction finding error of the sparse beam mode of the specific environmental signal-to-noise ratio proposed in the embodiment of the present invention. DETAILED DESCRIPTION

[0074] The following will be combined with the embodiments of the present invention Figure 1-Figure 6 , the technical solutions in the embodiments of the present invention are clearly and completely described. It should be understood that the terms described in the present invention are only used to describe specific implementation methods and are not used to limit the present invention.

[0075] When the drone approaches the target, due to the relative distance Shorten, while ensuring line error While the angle error remains unchanged, the angle error can be appropriately relaxed. Therefore, it is considered to use a beam group with a larger overlapping beam width but fewer beams to estimate the direction of arrival (DOA) of the target radar signal, which greatly reduces the computing resources during beamforming and thus reduces power consumption.

[0076] The method first presets the coverage of the UAV reconnaissance airspace, the angle error threshold of the digital multi-beam generated by the UAV to the target radar, the minimum receiving gain and the minimum environmental signal-to-noise ratio; based on the minimum receiving gain and the angle error threshold, the conventional beam mode and the sparse beam mode are set respectively; by calculating the relative distance between the UAV and the target radar in real time, the real-time evaluation of the environmental measurement signal-to-noise ratio is determined, and by judging the size of the real-time evaluation of the environmental measurement signal-to-noise ratio and the preset minimum environmental signal-to-noise ratio, it is determined whether to adopt the conventional beam mode or the sparse beam mode; finally, according to the selected beam mode, digital multi-beam direction finding is performed by making a ratio amplitude direction finding table to determine the direction finding angle of the target radar.

[0077] Example

[0078] According to the above method principle, this embodiment provides a UAV digital multi-beam direction finding method, such as Figure 1 As shown, the following steps are included:

[0079] Step 1: Preset the coverage of the drone reconnaissance airspace, the angle error threshold of the digital multi-beam generated by the drone to the target radar, the minimum receiving gain and the minimum environmental signal-to-noise ratio:

[0080] Step 1.1: Preset the coverage of the drone reconnaissance airspace to , the angle error threshold of the digital multi-beam generated by the drone to the target radar , minimum receiving gain and minimum ambient signal-to-noise ratio The real-time evaluation environment measurement signal-to-noise ratio is obtained by evaluating the signal receiving device, and the real-time evaluation environment measurement signal-to-noise ratio is compared with the preset minimum environment signal-to-noise ratio. The corresponding beam mode is selected according to the comparison result, and the parameters of the beam mode are used for the digital multi-beam amplitude comparison direction finding technology.

[0081] Step 1.2: Assume that the drone’s airspace coverage is , preset the angle error threshold of the digital multi-beam generated by the drone to the target radar , minimum receiving gain , minimum environmental signal-to-noise ratio SNR 0=12dB.

[0082] Step 2: Based on the angle error threshold and the minimum receiving gain, the pattern function of the synthesized beam is analyzed, and the beam overlap coefficient and the overlapping beam width are determined by analyzing the direction finding error of the pattern function to obtain the characteristic value of the overlapping beam width; according to the characteristic value of the overlapping beam width and the coverage range of the reconnaissance airspace, the number of beams is determined, and the parameters of the conventional beam mode and the sparse beam mode are set to determine the conditions for entering low-power direction finding, so as to provide theoretical support for the digital multi-beam direction finding proposed in the present invention:

[0083] Step 2.1: Assume the number of array elements is , the received signal frequency is , No. The narrowband analog signal received by each array element is:

[0084]

[0085] in, , , is the amplitude of the echo signal, j A plural unit.

[0086] Assume that the element spacing of the uniform linear array is , according to the following formula, the beam function is determined as:

[0087]

[0088] in, is the number of the antenna element, is the echo wavelength, is the complex weighting coefficient. By changing the complex weighting coefficient, we can get beams with different requirements. The direction of the incoming wave.

[0089] In order to facilitate calculation, After normalization, the equivalent synthetic beam pattern function is:

[0090]

[0091] in, , M is the number of beams, , is the beam overlap coefficient, is the overlapping beamwidth, The value is The beam width at .

[0092] Step 2.2: Assumptions and are the center angle of the synthetic beam with the maximum output and the center angle of the synthetic beam with the second largest output at the same time, respectively. The direction finding error formula is:

[0093]

[0094] in, , is the minimum environmental signal-to-noise ratio preset in step 1.

[0095] exist and When the direction finding error is known and fixed, the angle error threshold of the digital multi-beam preset in step 1 is made smaller than or equal to the angle error threshold of the digital multi-beam preset in step 1, that is, , from which it can be concluded that The upper boundary constraint value , ≤ , .

[0096] Step 2.3: Preset antenna gain , the beam overlap coefficient is , The minimum receiving gain and beam overlap coefficient preset in step 1 D satisfy:

[0097]

[0098] Corresponding to Another upper bound constraint value of , ≤ ;

[0099] Conclusion The upper bound value of another upper bound constraint value ;

[0100] The upper boundary value of the overlapped beam width is calculated from this , based on the overlapping beamwidth The reconnaissance airspace coverage preset in step 1 The relationship between , and the corresponding number of beams is obtained .

[0101] Step 2.4: Considering the limitation of device hardware resources, the number of beamformers must be strictly controlled within a predetermined maximum value to ensure the stability and performance of the system.

[0102] The maximum number of preset beamforming is =14, based on overlapping beamwidth The reconnaissance airspace coverage preset in step 1 The relationship between , and obtain the corresponding lower boundary constraint value , ≥ , .

[0103] Based on technical experience and expertise, D =3 dB is the engineering experience value of the overlapping beam width. Another lower boundary constraint value of the overlapping beam width is often set to , to ensure that the performance of the beamforming system meets the design requirements, while avoiding insufficient signal coverage or performance degradation due to too narrow a beam.

[0104] Calculate the lower boundary value of the overlapping beam width , based on the overlapping beamwidth The reconnaissance airspace coverage preset in step 1 The relationship between , and the corresponding number of beams is obtained .

[0105] Step 2.5: Set the overlapped beam width lower boundary value , Number of beams Sets the parameters for the normal beam mode.

[0106] like Figure 3 As shown, it is the beam pattern of the conventional beam mode, where the key simulation parameters of the beam pattern are: the array element spacing of the uniform linear array is , the number of array elements is , the received signal frequency is , , the reconnaissance airspace coverage is , overlapping beam width , Number of beams , root mean square error .

[0107] Overlap beam width upper boundary value , Number of beams Set the parameters for sparse beam mode, > , < .

[0108] like Figure 4 As shown, it is the beam pattern of the sparse beam mode, where the key simulation parameters of the beam pattern are: the array element spacing of the uniform linear array is , the number of array elements is , the received signal frequency is , , the reconnaissance airspace coverage is , overlapping beam width , Number of beams , root mean square error .

[0109] Step 3: Determine the real-time evaluation environment measurement signal-to-noise ratio based on the relative distance between the drone and the target radar:

[0110] Step 3.1: Assume that the signal reaches the target radar through free space, there is no obstacle between the UAV and the target radar, and the signal propagates in a straight line. Assume that the effective radiated power is , the relative distance between the UAV and the target radar is , the power of the intercepted signal is:

[0111]

[0112] in, is the ratio of the side lobe to the main lobe, is the signal wavelength.

[0113] Step 3.2: Assume that the relatively stable noise power value obtained through long-term average measurement is , the power of the intercepted signal is , the real-time evaluation environment measurement signal-to-noise ratio is obtained as:

[0114]

[0115] Step 4: compare the real-time evaluation environment measurement signal-to-noise ratio with the minimum environment signal-to-noise ratio preset in step 1 to determine the beam pattern of the target radar.

[0116] When the real-time evaluation of the environmental measurement signal-to-noise ratio is greater than the preset minimum environmental signal-to-noise ratio, the sparse beam mode is selected; when the real-time evaluation of the environmental measurement signal-to-noise ratio is less than the preset minimum environmental signal-to-noise ratio, the conventional beam mode is used. According to the beam mode selected by the target radar, digital multi-beam direction finding is performed, and a comparison amplitude direction finding table is prepared according to the selected beam mode to perform digital multi-beam direction finding.

[0117] Taking into account the limitation of equipment hardware resources, the number of beamforming must be strictly controlled within the predetermined maximum value to ensure the stability and performance of the direction finding system; the size of the overlapping beam width is set to avoid insufficient signal coverage or performance degradation due to too narrow beams. The set conventional beam mode and coefficient beam mode can fully cover the detection area by distinguishing the number of beams and the overlapping beam width, provide environmental protection for the transmission of massive sampling information, and then determine the conditions for entering low-power direction finding, thereby carrying out low-power direction finding.

[0118] Step 4.1: Obtain the initial environmental signal-to-noise ratio of the real-time evaluation environment measurement according to step 3 , and compare it with the minimum environmental signal-to-noise ratio preset in step 1 By comparison, we can see that When , select the normal beam mode set in step 2. The root mean square error is , the error distribution diagram is as follows Figure 5 As shown in FIG. 1 , it is a distribution diagram of the direction finding error of the conventional beam mode. Through analysis, it can be seen that the root mean square error is lower than the design threshold of 1°, that is, the conventional beam mode meets the direction finding angle error requirement preset in step 1.

[0119] Step 4.2: Assume the measurement cycle in the actual measurement process , from the initial time through the time After that, calculate the real-time evaluation environment measurement signal-to-noise ratio again , and compare the real-time evaluation environment measurement signal-to-noise ratio with the minimum environment signal-to-noise ratio preset in step 1 By comparison, we can see , then select the sparse beam mode set in step 2. The root mean square error is , the error distribution diagram is as follows Figure 6 As shown in FIG. 1 , it is a distribution diagram of the direction finding error of the sparse beam mode. Through analysis, it can be seen that the root mean square error is lower than the design threshold of 1°, that is, the use of the sparse beam mode also meets the direction finding angle error requirement preset in step 1.

[0120] Step 4.3: During the actual measurement process, After that, the real-time evaluation environment measurement signal-to-noise ratio is calculated again, the real-time evaluation environment measurement signal-to-noise ratio is re-compared with the minimum environment signal-to-noise ratio preset in step 1, and the beam mode is reselected, thereby achieving the purpose of maintaining high flexibility and accuracy and optimizing energy consumption.

[0121] Step 5: The beam mode selected in the above step is used to perform digital multi-beam direction finding by making an amplitude comparison direction finding table to determine the target radar direction finding angle, thereby achieving low-power direction finding with almost no loss of direction finding accuracy, which specifically includes the following steps:

[0122] Step 5.1: Determine the beam pattern corresponding to the beam overlap coefficient according to the beam mode selected by the target radar; The corresponding beam pattern is extracted Normalized antenna pattern data, respectively, in the and The normalized antenna pattern data is subtracted to obtain the beam The amplitude-to-direction-finding table data is then loaded into the digital signal processing system.

[0123] Step 5.2: Use the self-check source designed at the front end to perform limiting filtering, amplification and A / D quantization processing on the received signal at the same time, and separate multiple independent beams with adjacent main lobes. The amplitudes of the echo signals received by two or more (including two) adjacent narrow beams in the simultaneously existing narrow beams are compared. Assuming that the amplitude characteristics of each channel are consistent, The axis angle of the beam is , signal direction In the The first The first The signal amplitudes received by each beam are expressed as:

[0124]

[0125]

[0126] in, Representative m The signal amplitude of each beam receiving channel, Representative m -1 beam receiving channel signal amplitude, For the m -1 beam axis angle, is a constant.

[0127] Assumptions is the signal amplitude difference between two adjacent beams, which can be expressed as:

[0128]

[0129] Step 5.3: Calculate the radar signal in the beam With beam The signal amplitude difference , use the signal amplitude difference to find the corresponding m The amplitude ratio direction finding table of each beam is used to obtain the direction finding angle of the target radar signal.

[0130] like Figure 2 FIG. 1 is a block diagram of a UAV digital multi-beam direction finding method according to an embodiment of the present invention. Based on the proposed UAV digital multi-beam direction finding method, the present invention also proposes a UAV digital multi-beam direction finding system, including:

[0131] The signal-to-noise ratio acquisition module is used to obtain the relative distance between the UAV and the target radar; according to the relative distance between the UAV and the target radar, the signal-to-noise ratio of the real-time evaluation environment measurement is determined.

[0132] The beam mode selection module is used to determine the beam mode of the target radar according to the size of the real-time evaluation environment measurement signal-to-noise ratio and the preset minimum environment signal-to-noise ratio; when the real-time evaluation environment measurement signal-to-noise ratio is greater than the preset minimum environment signal-to-noise ratio, the beam mode of the target radar is a sparse beam mode; when the real-time evaluation environment measurement signal-to-noise ratio is less than the preset minimum environment signal-to-noise ratio, the beam mode of the target radar is a conventional beam mode; wherein the sparse beam mode and the conventional beam mode are set in a manner including: obtaining the coverage range of the UAV reconnaissance airspace, the angle error threshold of the digital multi-beam generated by the UAV to the target radar, the minimum receiving gain and the preset minimum environment signal-to-noise ratio; based on the angle error threshold and the minimum receiving gain of the digital multi-beam, determining the directional pattern function of the synthetic beam; by analyzing the direction finding error of the directional pattern function, Determine the beam overlap coefficient and the overlapping beam width of the synthetic beam to obtain the upper boundary value and the lower boundary value of the overlapping beam width; determine the number of beams corresponding to the upper boundary value and the lower boundary value according to the upper boundary value and the lower boundary value of the overlapping beam width; set the obtained upper boundary value of the overlapping beam width and the number of beams corresponding to the upper boundary value as parameters of the sparse beam mode; set the obtained lower boundary value of the overlapping beam width and the number of beams corresponding to the lower boundary value as parameters of the regular beam mode; wherein the upper boundary value of the overlapping beam width is greater than the lower boundary value of the overlapping beam width, and the number of beams corresponding to the upper boundary value is less than the number of beams corresponding to the lower boundary value; the number of beams of the regular beam mode is greater than the number of beams of the sparse beam mode, and the overlapping beam width of the regular beam mode is less than the overlapping beam width of the sparse beam mode.

[0133] The target radar direction finding angle acquisition module is used to perform digital multi-beam direction finding according to the beam mode selected by the target radar by determining the amplitude difference between different beams of the target radar to obtain the target radar direction finding angle.

[0134] In summary, the UAV digital multi-beam direction-finding method and system proposed in the present invention can solve the problem of high power consumption of small and medium-sized UAVs performing long-term and large-area reconnaissance missions, while reducing the requirements for the computing power of the hardware platform, ensuring sufficient DOA estimation accuracy, reducing the dynamic energy consumption of the digital multi-beam reconnaissance system, and effectively improving the system's reconnaissance range and direction-finding efficiency, laying a technical foundation for the airspace and frequency domain coverage capabilities of UAV electronic reconnaissance.

[0135] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0136] In addition, unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as commonly understood by those skilled in the art to which the present invention belongs. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods related to the documents. In the event of any conflict with any incorporated document, the content of this specification shall prevail.

Claims

1. A UAV digital multi-beam direction finding method, characterized in that: The following steps are involved: Get the relative distance between the UAV and the target radar; Determine the signal-to-noise ratio of the real-time evaluation environment measurement based on the relative distance between the UAV and the target radar; The beam mode of the target radar is determined according to the magnitude of the real-time evaluation environment measurement signal-to-noise ratio and the preset minimum environment signal-to-noise ratio; when the real-time evaluation environment measurement signal-to-noise ratio is greater than the preset minimum environment signal-to-noise ratio, the beam mode of the target radar is a sparse beam mode; when the real-time evaluation environment measurement signal-to-noise ratio is less than the preset minimum environment signal-to-noise ratio, the beam mode of the target radar is a conventional beam mode; The sparse beam mode and the conventional beam mode are configured as follows: Obtain the coverage of the drone reconnaissance airspace, the angle error threshold of the digital multi-beam generated by the drone to the target radar, the minimum receiving gain and the preset minimum environmental signal-to-noise ratio; Based on the angle error threshold and minimum receiving gain of the digital multi-beam, the directivity pattern function of the synthesized beam is determined; by analyzing the direction finding error of the directivity pattern function, the beam overlap coefficient and the overlap beam width of the synthesized beam are determined to obtain the upper boundary value and the lower boundary value of the overlap beam width; According to the upper boundary value and the lower boundary value of the overlapping beam width, the number of beams corresponding to the upper boundary value and the lower boundary value are determined; The obtained upper boundary value of the overlapping beam width and the number of beams corresponding to the upper boundary value are set as parameters of the sparse beam mode; the obtained lower boundary value of the overlapping beam width and the number of beams corresponding to the lower boundary value are set as parameters of the normal beam mode; The upper boundary value of the overlapping beam width is greater than the lower boundary value of the overlapping beam width, and the number of beams corresponding to the upper boundary value is less than the number of beams corresponding to the lower boundary value; The number of beams of the conventional beam mode is greater than the number of beams of the sparse beam mode, and the overlapping beam width of the conventional beam mode is smaller than the overlapping beam width of the sparse beam mode; According to the beam mode selected by the target radar, digital multi-beam direction finding is performed by determining the amplitude difference between different beams of the target radar to obtain the target radar direction finding angle.

2. The UAV digital multi-beam direction finding method according to claim 1, characterized in that: The method of determining the real-time evaluation environment measurement signal-to-noise ratio comprises the following steps: Get effective radiated power , the relative distance between the UAV and the target radar , the power of the intercepted signal is: in, is the ratio of the side lobe to the main lobe, is the signal wavelength; The signal-to-noise ratio of the real-time evaluation environment measurement is: in, It is a relatively stable noise power value obtained through long-term average measurement.

3. The UAV digital multi-beam direction finding method according to claim 2, characterized in that: The method of obtaining the upper boundary value and the lower boundary value of the overlapping beam width includes the following steps: Get the number of array elements as , the received signal frequency is , No. The narrowband analog signal received by each array element is: in, , , is the amplitude of the echo signal, j is a plural unit; The element spacing of the uniform linear array is obtained as , determine the beam function according to the following formula: in, is the number of the antenna element, is the echo wavelength, is the complex weighting coefficient, Indicates the direction of incoming waves; Pair After normalization, the directional diagram function of the synthesized beam is obtained as: in, , M is the number of beams, , is the beam overlap coefficient, is the overlapping beamwidth, The value is The overlapping beam width at ; Get the center angle of the synthetic beam with maximum output at the same time and the composite beam center angle of the second largest output , the direction finding error is: in, , is the preset minimum environmental signal-to-noise ratio; The characteristic value of the overlapped beam width includes an upper boundary value and a lower boundary value, where: exist and When the direction finding error is known and fixed, the angle error is made less than or equal to the angle error threshold, that is, , substituting into the direction finding error formula, we get The upper boundary constraint value , ≤ ; It is known that the minimum receiving gain of the receiver for the signal is , when the antenna gain is When the beam overlap coefficient D satisfy: Corresponding to Another upper bound constraint value of , ≤ ; The upper boundary value of the overlapped beam width is obtained as ; Get the maximum number of beamforming , based on the overlapping beamwidth Coverage of reconnaissance airspace The relationship between , we can conclude The corresponding lower boundary constraint value , ≥ ; Another lower bound constraint for obtaining the overlapped beam width is , ≥ , is the engineering experience value of the overlapping beam width, and the lower boundary value of the overlapping beam width is obtained as .

4. The UAV digital multi-beam direction finding method according to claim 3, characterized in that: The corresponding determination of the number of beams corresponding to the upper boundary value and the lower boundary value comprises the following steps: According to the upper boundary value of the overlapped beam width obtained , based on the overlapping beamwidth Coverage of reconnaissance airspace The relationship between , and the number of beams corresponding to the upper boundary value is obtained ; According to the obtained overlap beam width lower boundary value , based on the overlapping beamwidth Coverage of reconnaissance airspace The relationship between , and the number of beams corresponding to the lower boundary value is obtained .

5. The UAV digital multi-beam direction finding method according to claim 4, characterized in that: The step of obtaining the target radar direction finding angle comprises the following steps: Determine the beam overlap coefficient based on the beam mode selected by the target radar The corresponding beam pattern is extracted Normalized antenna pattern data, respectively and The normalized antenna pattern data is subtracted to obtain the beam The amplitude-to-direction-finding table data; The obtained beam The amplitude comparison direction-finding table data is limited, filtered, amplified and A / D quantized to obtain multiple independent beams with adjacent main lobes. The envelope amplitudes of signals received by two or more adjacent narrow beams among the simultaneously existing narrow beams are compared; Get the The axis angle of the beam is , signal direction In the At the antenna axis of the beam, The first The signal amplitudes received by each beam are expressed as: in, Representative m The signal amplitude of each beam receiving channel, Representative m -1 beam receiving channel signal amplitude, For the m -1 beam axis angle, is a constant; The signal amplitude difference between two adjacent beams is , It is expressed as: Calculate the signal at m beam and the m-1 The signal amplitude difference of the beam , use the signal amplitude difference to find the corresponding m The amplitude ratio direction finding table of each beam can obtain the direction finding angle of the target radar.

6. The UAV digital multi-beam direction finding method according to claim 5, characterized in that: It also includes the measurement cycle to obtain the actual measurement process , when the initial time passes After that, calculate the real-time evaluation environment measurement signal-to-noise ratio again ; The calculated real-time evaluation environment measurement signal-to-noise ratio The preset minimum environmental signal-to-noise ratio For comparison, Greater than When , select the sparse beam mode; when Less than , select the normal beam mode; In the actual measurement process, each time , re-comparison of real-time evaluation of environmental measurement signal-to-noise ratio and the preset minimum environmental signal-to-noise ratio , and reselect the beam mode.

7. A UAV digital multi-beam direction finding system, characterized in that: include: The signal-to-noise ratio acquisition module is used to obtain the relative distance between the UAV and the target radar; according to the relative distance between the UAV and the target radar, the signal-to-noise ratio of the real-time evaluation environment measurement is determined; A beam mode selection module is used to determine the beam mode of the target radar according to the size of the real-time evaluation environment measurement signal-to-noise ratio and the preset minimum environment signal-to-noise ratio; when the real-time evaluation environment measurement signal-to-noise ratio is greater than the preset minimum environment signal-to-noise ratio, the beam mode of the target radar is a sparse beam mode; when the real-time evaluation environment measurement signal-to-noise ratio is less than the preset minimum environment signal-to-noise ratio, the beam mode of the target radar is a conventional beam mode; wherein the sparse beam mode and the conventional beam mode are set in a manner including: obtaining the coverage range of the UAV reconnaissance airspace, the angle error threshold of the digital multi-beam generated by the UAV to the target radar, the minimum receiving gain and the preset minimum environment signal-to-noise ratio; based on the angle error threshold and the minimum receiving gain of the digital multi-beam, determining the directional pattern function of the synthetic beam; and determining the direction finding error of the directional pattern function by analyzing the direction finding error of the directional pattern function. Determine the beam overlap coefficient and the overlap beam width of the synthetic beam to obtain the upper boundary value and the lower boundary value of the overlap beam width; determine the number of beams corresponding to the upper boundary value and the lower boundary value according to the upper boundary value and the lower boundary value of the overlap beam width; set the obtained upper boundary value of the overlap beam width and the number of beams corresponding to the upper boundary value as parameters of the sparse beam mode; set the obtained lower boundary value of the overlap beam width and the number of beams corresponding to the lower boundary value as parameters of the regular beam mode; wherein the upper boundary value of the overlap beam width is greater than the lower boundary value of the overlap beam width, and the number of beams corresponding to the upper boundary value is less than the number of beams corresponding to the lower boundary value; the number of beams of the regular beam mode is greater than the number of beams of the sparse beam mode, and the overlap beam width of the regular beam mode is less than the overlap beam width of the sparse beam mode; The target radar direction finding angle acquisition module is used to perform digital multi-beam direction finding according to the beam mode selected by the target radar by determining the amplitude difference between different beams of the target radar to obtain the target radar direction finding angle.

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