A phase array cross multi-beam amplitude comparison direction finding method

Abstract

The present invention discloses a phased array cross multi-beam amplitude comparison direction finding method, and the steps of the method are as follows: obtaining an initial signal from a radiation source; establishing an array model according to the physical characteristics of the array; selecting array weights according to the array model and actual requirements, and using digital beamforming (DBF) to construct simultaneous multi-beams in the azimuth direction within the search airspace range, and dividing the left and right half arrays in the elevation direction to construct dual beams by using analog beamforming (ABF), and respectively sending the corresponding parameters to the DBF and ABF; calculating the amplitude difference table between adjacent azimuth and elevation beams; for the obtained signal, according to the established amplitude difference table, performing look-up table calculation to obtain the signal position parameters. The present invention comprehensively applies digital phase weighting and analog phase weighting for cross multi-beam amplitude comparison direction finding, has the advantages of high gain and low sidelobe, and can ensure instantaneous azimuth and elevation airspace coverage while taking into account relatively high direction finding accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of radiation array synthesis, and in particular to a phase array cross multi-beam amplitude comparison direction finding method. Background Art

[0002] In modern warfare, the combat environment is becoming increasingly complex, and the frequency bands covered by various detection devices and interference devices are also becoming wider and wider. The influence on radar reconnaissance devices cannot be ignored. Especially in the sea battlefield environment, the sea conditions are complex and changeable, and detection signals and interference signals always cover in the form of multiple batches, multiple angles, and wide frequency bands, posing more severe challenges to our reconnaissance devices. Due to the flexibility of the front-end antenna design and the back-end signal processing of the phased array antenna, it has many excellent performances that traditional radar reconnaissance devices do not have, especially the all-digital array using digital beamforming technology.

[0003] Digital beamforming technology (DBF) is a technology that realizes beamforming by digital methods. By forming a main beam for the useful signal in a specific direction to make its output maximum and attenuating the interference signals in other directions for spatial filtering. Since all the information of the antenna array unit signals is retained in the baseband, DBF can use advanced digital signal processing technologies to process the antenna array signals to obtain excellent beam performances. It can adaptively form beams to achieve spatial anti-interference and can perform non-linear processing to improve angular resolution. Especially, it can simultaneously form multiple independently controllable beams without loss of signal-to-noise ratio, which provides strong technical support for multi-batch and wide-angle reconnaissance.

[0004] Compared with radar detection devices, the tasks undertaken by reconnaissance devices often cover a wider frequency band, even covering multiple octaves of themselves, which poses quite a challenge to both the front-end antenna design and the back-end signal processing.

[0005] By summarizing, in order to obtain reconnaissance targets with wide azimuth coverage, digital beamforming technology is adopted to form multiple independently controllable beams in the azimuth; each beam is weighted to achieve low sidelobes, thereby improving the anti-interference ability of the device. Common low-sidelobe weighting methods include: amplitude weighting, phase weighting, density weighting, and combined weighting methods of various single technologies; in order to achieve wide frequency band coverage, a wideband antenna such as a Vivaldi antenna array is required at the front end.

[0006] For a broadband array, if conventional narrowband beamforming methods are used, since the beam width is a function of frequency, without changing the weighting coefficients, the beam width will narrow with the increase of frequency. This will cause distortion of the output of signals incident from directions other than the axis of the maximum beam response, directly affecting the system's estimation of waveforms and the identification of target characteristics, etc., and thus unable to effectively cover the detection tasks of the entire working frequency band. An effective way to solve this problem is to design a constant beamwidth beamformer so that the array has the same beam pattern for input signals of different frequencies.

[0007] In the actual design of constant beamwidth beamforming, a commonly used design method is to divide the broadband signal into several narrow sub-bands, select a frequency point on each sub-band, use one of the frequency points as the reference frequency, and apply the narrowband beamforming weighting method to obtain the desired beam that meets the requirements at this frequency. Calculate the weighting coefficients at other narrowband frequency points so that the beams obtained at other frequency points have the same main lobe width as the desired beam at the reference frequency. For an array, taking the beam formed at a certain frequency within the bandwidth as the desired beam, in principle, for any other frequency within the bandwidth, it is always possible to design a set of frequency-varying weighting coefficients for each element in the array so that the main lobe width of the beam at that frequency is the same as that of the desired beam.

[0008] In order to cover a wider airspace range, in addition to having a wide angular coverage in the azimuth angle, the elevation angle should also have a certain angular coverage. The existing constant beamwidth beam technologies only focus on the research and design in the azimuth angle, which will inevitably lead to missed detection and misdetection of elevation angle targets. Summary of the Invention

[0009] The purpose of the present invention is to provide a cross multi-beam amplitude comparison direction finding method with high gain, low sidelobe, comprehensive application of digital phase weighting and analog phase weighting, while taking into account higher direction finding accuracy, ensuring instantaneous azimuth and elevation airspace coverage.

[0010] The technical solution to achieve the purpose of the present invention is: a phased array cross multi-beam amplitude comparison direction finding method, specifically including the following steps:

[0011] Step 1, initial signal acquisition: Obtain the initial signal from the radiation source;

[0012] Step 2, model establishment: Establish an array model according to the physical characteristics of the array;

[0013] Step 3, Selection of objective function: According to the array model and actual requirements, select the array weights. In the azimuth direction within the search airspace range, use digital beamforming (DBF) to construct simultaneous multi-beams, and in the elevation direction, divide the left and right half arrays and use analog beamforming (ABF) to construct dual-beams, and send the corresponding parameters to DBF and ABF respectively;

[0014] Step 4, Establish the amplitude difference table: Calculate the amplitude difference table between adjacent beams in azimuth and elevation;

[0015] Step 5, Determine the target azimuth by looking up the table: For the signal obtained in Step 1, according to the amplitude difference table established in Step 4, perform look-up table calculation to obtain the signal position parameters.

[0016] Compared with the prior art, the significant advantages of the present invention are:

[0017] (1) On the premise of ensuring the gain of the front end of the array, effectively reduce the influence of sidelobe signals on the direction finding accuracy: By accurately establishing the mathematical model of the comprehensive array, comprehensively optimizing the design of multiple sidelobe suppression antennas at the front end, and selecting specific sub-array weighting coefficients; By optimally arranging the directions of each independent sidelobe suppression antenna so that its reception range covers the entire working area, and performing a maximum selection operation on the amplitudes in each direction; Select the sub-array weighting coefficients according to the maximum selected signal amplitude, so that the sidelobe signal amplitude of the corresponding azimuth of the array is less than the signal amplitude of the sidelobe antenna;

[0018] (2) Flexible aperture allocation design: Divide the antennas in each path in the azimuth into independent small sub-arrays, that is, combine the signals in the elevation direction and output them. In this way, each output signal can be independently collected, and the azimuth aperture size and direction can be rearranged through digital beamforming technology; In addition, each antenna can perform independent analog phase shift operations;

[0019] (3) It can have a wide instantaneous elevation coverage ability while instantaneously covering the azimuth angle: Combine digital multi-beamforming technology and analog multi-beamforming technology. Perform digital multi-beamforming in the azimuth angle direction. By dividing the aperture into two independent sub-arrays that are symmetric left and right, each sub-array performs multi-beam arrangement separately; In the elevation angle direction, perform analog beam arrangement. Through beam control, perform elevation direction phase shift operations on each phase shift unit of the left and right half arrays respectively, so that the elevation beam directions of the left and right half arrays are each offset by half a beam width relative to the center beam direction, and combine sidelobe suppression antennas and elevation phase weighting to reduce the influence of sidelobe signals on direction finding in the elevation direction. Brief description of the drawings

[0020] Figure 1 It is a schematic diagram of the amplitude comparison direction finding principle.

[0021] Figure 2It is a schematic diagram of the spatial model of the phased array scanning beam pattern.

[0022] Figure 3 It is a typical phased array spatial pattern.

[0023] Figure 4 It is the azimuth DBF pattern.

[0024] Figure 5 It is the elevation left and right half array dual beam ABF pattern.

[0025] Figure 6 It is a schematic diagram of the relationship between the beam width and the elevation angle. Specific implementation mode

[0026] The present invention provides a phased array cross multi-beam amplitude comparison direction finding method, which is based on the comprehensive processing of constant beam width in a wide frequency domain, performs amplitude comparison direction finding and positioning on the received signals, and effectively takes into account the spatial coverage of the azimuth angle and the elevation angle while ensuring wide frequency domain coverage and low sidelobe suppression. The schematic diagram of the amplitude comparison direction finding principle is as Figure 1 shown.

[0027] The phased array cross multi-beam amplitude comparison direction finding method of the present invention utilizes the sub-array beam synthesis characteristics of the phased array surface, adopts digital beam synthesis (DBF) technology to construct simultaneous multi-beams in the azimuth direction within the search airspace range, divides the left and right half arrays in the elevation direction, and uses analog beam synthesis (ABF) to construct dual beams. Record the amplitudes of the beam patterns with different pointing directions covering the entire airspace range and generate a look-up table, and then compare according to the amplitude ratio within the adjacent beams where the received signal is located with the look-up table to finally determine the angle information of the elevation and azimuth of the target.

[0028] In order to effectively reduce the influence of sidelobe signals on the direction finding accuracy while ensuring the front-end gain, multiple sidelobe suppression antennas with different pointing directions are arranged around the array. By optimizing the arrangement of the pointing directions of each independent sidelobe suppression antenna, its receiving range covers the entire working area, and the amplitudes in each direction are selected for the larger value. Select the sub-array weighting coefficient according to the selected larger signal amplitude, so that the sidelobe signal amplitude of the array in the corresponding azimuth is less than the signal amplitude of the sidelobe antenna.

[0029] Divide the antennas in the azimuth into independent small sub-arrays, that is, combine and output the signals in the elevation direction. In this way, each output signal can be independently collected, and the azimuth aperture size and pointing are rearranged through digital beam forming technology. In addition, each antenna can perform independent analog phase shift operations.

[0030] The following specifically introduces the principle and process of the phased array cross multi-beam amplitude comparison direction finding method of the present invention, which mainly includes the following steps:

[0031] Step 1, Initial signal acquisition: Obtain the initial signal from the radiation source;

[0032] Step 2, Model establishment: Establish an array model according to the physical characteristics of the array;

[0033] Step 3, Selection of objective function: According to the array model and actual requirements, select the array weights. In the azimuth direction within the search airspace range, use digital beamforming (DBF) technology to construct simultaneous multi-beams. In the elevation direction, divide the left and right half arrays and use analog beamforming (ABF) to construct dual-beams, and send the corresponding parameters to DBF and ABF respectively;

[0034] Step 4, Establishment of amplitude difference table: Calculate the amplitude difference table between adjacent beams in azimuth and elevation;

[0035] Step 5, Determine the target azimuth by looking up the table: For the signal obtained in Step 1, according to the amplitude difference table established in Step 4, perform table lookup calculation to obtain the signal position parameters.

[0036] As a specific implementation manner, the establishment of the array model according to the physical characteristics of the array in Step 2 is as follows:

[0037] Perform spatial modeling of the scanning beam pattern based on the characteristics of the array layout, as Figure 2 shown. The units are arranged in a rectangular grid, and the half-wavelength of the designed center frequency is used as the spacing between each unit;

[0038] Assume that the initial weights between each unit are equal in amplitude and phase, then the array pattern is expressed as the following formula:

[0039]

[0040] where M and N are the numbers of antenna array elements in the z-axis and y-axis directions of the entire antenna array respectively, a ik corresponds to the amplitude of the element current excitation of the i-th row and k-th column, d 1 , d 2 are the antenna element spacings in the z-axis and y-axis directions in the two-dimensional array respectively, θ, correspond to the beam elevation angle and azimuth angle respectively, κ = 2π / λ is the wave number, λ is the wavelength, is the in-array phase difference in the z-axis and y-axis directions; F 1 (θ) represents the pattern of a one-dimensional linear array with the same element spacing and the same number of elements as the two-dimensional array in the z-axis direction, that is, the array gain of this one-dimensional linear array when the elevation angle is θ; represents the pattern projection of a one-dimensional linear array with the same element spacing and the same number of elements as the two-dimensional array in the y-axis direction when the elevation angle is θ, that is, the pattern of this one-dimensional linear array when the azimuth angle is The projection of the array gain at a certain time on the elevation angle θ plane. Typical simulation results of the model are as Figure 3 shown.

[0041] As a specific implementation, in step 3, digital beamforming, i.e., DBF, is used to construct simultaneous multiple beams in the azimuth direction within the search airspace range, specifically as follows:

[0042] A significant advantage of the present invention is that, on the premise of ensuring the front-end gain, it effectively reduces the influence of sidelobe signals on the direction-finding accuracy. For this purpose, multiple sidelobe suppression antennas with different pointing directions are arranged around the array. For azimuth airspace coverage, the method adopted is digital multiple-beamforming technology, i.e., DBF; at this time, the front-end wave control sets the phase difference between each subarray in the azimuth angle to be equal, and the beam azimuth angle points to 0. The analog signals received by each path are sampled into corresponding digital signals by using an analog-to-digital converter ADC. Of course, limited by the sampling frequency of the ADC, before transmitting the analog signal to the AD, the radio frequency signal is down-converted to the corresponding intermediate frequency;

[0043] The signals collected in each path are synthesized in the digital domain, that is, after giving each signal a weight coefficient, vector addition operation is performed on each signal; the array is divided into left and right half arrays, and then the left and right subarrays will be separately vector synthesized during the synthesis operation;

[0044] The weight coefficient is obtained by the formula of Taylor weighting coefficient:

[0045]

[0046]

[0047]

[0048] where

[0049]

[0050] In the formula, f(p) is the weighted value of the weighting coefficient in the domain (0, π / 2), p corresponds to the phase within the domain; N is the number of array elements within the subarray, is the number of equal sidelobes on one side of the main lobe, m is the serial number of the equal-height sidelobes, n is the traversal item serial number during the calculation process, S(m) is the intermediate calculation quantity, J is the expansion term of the Taylor formula, δ is the broadening factor, and A is determined by the variable control sidelobe level parameter R 0 , and cosh -1 represents the inverse function of the hyperbolic cosine function;

[0051] It should be noted that the larger the main-to-side lobe ratio is, the greater the array gain loss will be. Therefore, it is necessary to select an appropriate side lobe level. Referring to the signal acquisition amplitude of the side lobe suppression antenna, the side lobe level height is set to a value slightly lower than this level, and the corresponding weight coefficient obtained therefrom can maximize the front-end gain without sacrificing the direction finding accuracy.

[0052] In order to implement DBF and form an azimuth spatial coverage, it is necessary to reuse the digital signals on the basis of the beams discussed above. By performing phase weighting on each signal path, the front-end signals of the array in different directions are obtained. The phase weighting coefficients α in different directions satisfy the following relationship:

[0053]

[0054] where θ represents the azimuth spatial size covered by the beam, num represents the number of simultaneous multi-beams, and i represents the beam number. The final weighted single-layer simultaneous multi-beam pattern is as Figure 4 shown, and the horizontal line under the main lobe represents the side lobe suppression level.

[0055] As a specific implementation manner, in step 3, by dividing the left and right half arrays in the elevation direction, two beams are constructed using analog beamforming, i.e., ABF, and the corresponding parameters are respectively sent to DBF and ABF, as follows:

[0056] In terms of the elevation angle test, in order to cover a certain elevation range, the sub-array is divided into left and right half arrays, and the analog beamforming method is used in the elevation angle direction to achieve it, i.e., ABF.

[0057] Perform analog phase shift operations on each antenna sub-array in the column direction, where the phase shift number is is the corresponding phase shift amount, generally taken as half of the beam width, and the positive and negative signs correspond to different phase shift amounts of the left and right half arrays. k = λ / 2π is the wave number, λ is the wavelength, and d 2 is the antenna element spacing in the y-axis direction of the two-dimensional array;

[0058] To suppress the influence of signals entering from the sidelobe direction on direction finding, the commonly used method is the same as that in the azimuth direction, that is, the method combining amplitude-phase weighting and sidelobe suppression antenna. However, since there are only two beams in the elevation direction, when using monopulse amplitude comparison direction finding, there may be an impact on direction finding due to multiple measurement values, that is, the situation where different angles have the same amplitude comparison result. The solution is to limit the amplitude comparison result of the two beams within a certain range, and the typical value is the ratio of the main beam peak value to the measured value of the other beam at the corresponding angle. Of course, for different elevation scanning strategies, this amplitude ratio can be increased or decreased accordingly. Finally, in the phased array system, the array weight values are selected according to the array model and actual needs, and the corresponding parameters are sent to DBF and ABF respectively. The dual-beam ABF pattern (including the difference pattern) of the left and right half arrays is as shown in Figure 5 shown.

[0059] For horizontal direction scanning, that is, the case where the elevation angle is 0, the relationship between the 3dB beamwidth θ 3dB changing with frequency and scanning angle is expressed as: where N is the number of array elements in the subarray, θ 0 is the main lobe pointing angle of the beam, d is the element spacing, and λ is the signal operating frequency; for fixed angles and frequency points, the relationship between the beamwidth and the elevation angle is as shown in Figure 6 shown. Where N = 32, d = 10.5mm, the scanning range 0 ∈[-20°,20°], and the signal frequency is 18GHz.

[0060] Based on the above relationship, the main beamwidths corresponding to different azimuth and elevation angle pointings are calculated under the unweighted condition within the working frequency band.

[0061] As a specific implementation manner, when selecting the objective function, the wideband received signal is divided into narrow subbands, and the wideband signal is divided into multiple narrowband signals for processing, as follows:

[0062] Taking one of the frequency points as the reference frequency, using the narrowband beamforming method to obtain the desired beam that meets the requirements at this frequency;

[0063] Checking the beamwidths corresponding to different angles at each frequency point, determining the frequency band range that needs beam broadening, and calculating the weighting coefficients at other narrowband frequency points so that the beams obtained at other frequency points have the same main lobe width as the desired beam at the reference frequency;

[0064] For frequency bands that do not require beamwidth broadening, weights that meet the conditions, frequency bands that meet the spatial coverage requirements, and beam pointing are selected. According to specific system requirements, weighted coefficients that meet the requirements are selected. At this time, the beamwidth will be broadened accordingly, without affecting the spatial coverage of the multi-beams. For frequency bands that require beamwidth broadening, a matching main beamwidth is selected and processed using the spatial resampling method.

[0065] As a specific implementation manner, the establishment of the amplitude difference table described in step 4 is as follows:

[0066] An amplitude difference table is established. According to the data of the azimuth multiple scanning beam patterns and the elevation left and right half-array two scanning beam patterns, calculations are performed at each scanning table angle, the amplitude differences between adjacent azimuth and elevation beams are statistically calculated, and a comparison amplitude direction-finding lookup table is made.

[0067] The present invention has the following characteristics: First, through the optimized design of the multi-element sidelobe suppression antenna and the selection of specific sub-array weighting coefficients, the amplitude of the array sidelobe signal corresponding to the azimuth is made smaller than the signal amplitude of the sidelobe antenna, effectively reducing the influence of the sidelobe signal on the direction-finding accuracy while ensuring the gain at the front end of the array. Second, the antennas in each azimuth are divided into independent small sub-arrays, and the signals output from each path are independently collected. Through the DBF technology, the azimuth aperture size and pointing are rearranged, and the aperture allocation design is flexible. Third, by combining the digital multi-beamforming technology and the analog multi-beamforming technology, the present invention can have a wider instantaneous elevation coverage ability while instantaneously covering the azimuth angle.

[0068] The following combines Figures 1 to 6 and specific embodiments to further describe the present invention in detail.

[0069] Embodiment

[0070] In the multi-beam amplitude comparison direction-finding method based on the phased array surface proposed by the present invention, it is assumed that the phased array sub-array contains 32 array elements, the rectangular array element spacing is 10.5 mm both in the y-axis and the z-axis, 16 beams are simultaneously covered in the horizontal direction, and the elevation is divided into two beams for the left and right half-arrays.

[0071] Taking the received signal at 18 GHz as an example, the following specifically introduces the specific implementation manner of the phased array cross multi-beam amplitude comparison direction-finding in the present invention, which mainly includes the following steps:

[0072] 1) Initial signal acquisition: Obtain the initial signal from the radiation source.

[0073] 2) Model establishment: Establish an array model according to the physical characteristics of the array.

[0074] Based on the characteristics of the array layout, spatial modeling of the scanning beam pattern is performed. Assuming that the initial weights between each unit are equal in amplitude and phase, the array pattern can be expressed as the following formula:

[0075]

[0076] where M and N are the numbers of antenna elements of the entire antenna array in the z-axis and y-axis directions respectively, a ik is the excitation amplitude of the element current corresponding to the i-th row and k-th column, d 1 and d 2 are the antenna element spacings in the z-axis and y-axis directions in the two-dimensional array respectively, θ, correspond to the beam elevation angle and azimuth angle respectively, κ = 2π / λ is the wave number, λ is the wavelength, is the in-array phase difference in the z-axis and y-axis directions; F 1 (θ) represents the pattern of a one-dimensional linear array with the same element spacing and the same number of elements as the two-dimensional array in the z-axis direction, that is, the array gain of this one-dimensional linear array when the elevation angle is θ; represents the pattern projection of a one-dimensional linear array with the same element spacing and the same number of elements as the two-dimensional array in the y-axis direction when the elevation angle is θ, that is, the projection of the array gain of this one-dimensional linear array when the azimuth angle is on the elevation angle θ plane.

[0077] 3) Selection of objective function: According to the array model and actual needs, array weights are selected, and the corresponding parameters are sent to DBF and ABF respectively.

[0078] In the digital domain, the signals collected from each channel are synthesized, that is, after giving each signal a specific weighting coefficient, vector addition operation is performed on each signal. Among them, the array is divided into left and right half arrays, and during the synthesis operation, the left and right sub-arrays will perform vector synthesis separately. The weighting coefficient adopts the Taylor weighting coefficient. In order to implement DBF and form azimuth spatial coverage, it is necessary to reuse the digital signals on the basis of the beams discussed above. By performing phase weighting on each signal, the front-end signals of the array in different directions can be obtained, and the phase weighting coefficients in different directions satisfy the following relationship:

[0079]

[0080] where θ represents the azimuth spatial size covered by the beam, num represents the number of simultaneous multi-beams, and i represents the beam serial number.

[0081] In terms of elevation angle testing, in order to cover a certain elevation range, the sub-array is divided into left and right half arrays, and analog beam synthesis is used in the elevation angle direction to achieve it, that is, ABF. The specific implementation method is as follows: perform analog phase shift operation on each antenna sub-array in the column direction, where the phase shift number is is the corresponding phase shift amount, generally taken as half of the beam width. The positive and negative signs correspond to different phase shift amounts of the left and right half arrays.

[0082] To suppress the influence of signals entering from the sidelobe direction on direction finding, the commonly used method is the same as that in the azimuth direction, that is, the method combining amplitude-phase weighting and sidelobe suppression antenna. The ratio of the two-beam amplitude comparison results is clamped within a certain range, and the typical value is the ratio of the main beam peak value to the measured value of another beam at the corresponding angle. Finally, in the phased array system, the array weight values are selected according to the array model and actual needs, and the corresponding parameters are sent to DBF and ABF respectively. For horizontal scanning, that is, when the pitch angle is 0, the relationship between the beam width and the frequency and scanning angle can be expressed as: where N is the number of array elements in the subarray (32 in this example), θ 0 is the main lobe pointing angle of the beam, d is the element spacing (10.5 mm in this example), and λ is the signal operating frequency (16.67 mm in this example).

[0083] From the above relationship, the main beam widths corresponding to different azimuth and pitch angle pointings can be calculated under the unweighted condition within the working frequency band.

[0084] For wideband received signals, reasonable narrow sub-band division is required. The wideband signal is divided into several narrowband signals for processing. Taking one of the frequency points as the reference frequency, using the narrowband beamforming method, the desired beam meeting the requirements at this frequency is obtained. Check the beam widths corresponding to different angles at each frequency point, determine the frequency band range that needs beam broadening, calculate the weighting coefficients at other narrowband frequency points, so that the beams obtained at other frequency points have the same main lobe width as the desired beam at the reference frequency. For the frequency bands that do not need to be broadened, select the weights that meet the conditions, the frequency bands that meet the spatial coverage requirements, and the beam pointing. According to the specific system requirements, select the weighting coefficients that meet the requirements. At this time, the beam width will be broadened accordingly, and it will not affect the spatial coverage of the multi-beam; for the frequency bands that need to be broadened, select an appropriate main beam width and process it using the spatial resampling method.

[0085] 4) Establish an amplitude difference table. Calculate according to the data of the azimuth multiple scanning beam patterns and the pitch left and right half-array two scanning beam patterns at each scanning table angle, and count the amplitude differences between adjacent azimuth and pitch beams and make an amplitude comparison direction finding lookup table.

[0086] 5) Look up the table to determine the target azimuth. Perform a lookup table calculation on the table made in step 4) for the signal obtained in step 1) to obtain the signal position parameters.

[0087] In summary, the above is only the preferred embodiment of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc., made within the spirit and principle of the present invention, including changes in the different frequency band ranges included in the wideband phased receiving array surface, shall be included in the protection scope of the present invention.

Claims

1. A phase array cross multi-beam amplitude comparison direction finding method, characterized in that, it specifically includes the following steps: Step 1, initial signal acquisition: Obtain the initial signal from the radiation source; Step 2, model establishment: Establish an array model according to the physical characteristics of the array; Step 3, selection of objective function: According to the array model and actual needs, select the array weights. In the azimuth direction within the search airspace range, use digital beamforming (DBF) to construct simultaneous multi-beams. In the elevation direction, divide the left and right half arrays, and use analog beamforming (ABF) to construct dual beams, and send the corresponding parameters to DBF and ABF respectively; Step 4, establish an amplitude difference table: Calculate the amplitude difference table between adjacent beams in azimuth and elevation; Step 5, determine the target azimuth by looking up the table: For the signal obtained in Step 1, according to the amplitude difference table established in Step 4, perform look-up table calculation to obtain the signal position parameters; In Step 3, in the elevation direction, divide the left and right half arrays, use analog beamforming (ABF) to construct dual beams, and send the corresponding parameters to DBF and ABF respectively, specifically as follows: Perform simulated phase shift operations on each antenna subarray in the column direction, where the number of phase shifts is the corresponding phase shift amount, and the positive and negative signs correspond to different phase shift amounts for the left and right half arrays. κ = 2π / λ is the wave number, λ is the wavelength, and d 2 is the antenna element spacing in the y-axis direction of the two-dimensional array; Adopt the combination of amplitude-phase weighting and sidelobe suppression antenna to set the amplitude comparison result of the two beams within the required range; In the phased array system, select the array weights according to the array model and actual needs, and send the corresponding parameters to DBF and ABF respectively; For horizontal scanning, i.e., the case where the elevation angle is 0, the 3dB beamwidth θ 3dB The relationship varying with frequency and scan angle is expressed as: where N is the number of array elements within the subarray, θ 0 is the pointing angle of the main lobe of the beam, and d is the element spacing; Calculate the main beam widths corresponding to different azimuth and elevation angle directions under the unweighted condition within the working frequency band according to the above relationship.

2. The phase array cross multi-beam amplitude comparison direction finding method according to claim 1, characterized in that, In Step 2, the establishment of the array model according to the physical characteristics of the array is specifically as follows: Based on the characteristics of the array layout, perform spatial modeling of the scanning beam pattern. The units are arranged in a rectangular grid, and the half-wavelength of the design center frequency is used as the spacing between each unit; Assume that the initial weights between each unit are of equal amplitude and equal phase, then the array pattern is expressed as the following formula: where M and N are the numbers of antenna elements of the entire antenna array in the z-axis and y-axis directions, respectively, a ik corresponds to the amplitude of the element current excitation of the i-th row and k-th column, d 1 , d 2 are the antenna element spacings in the z-axis and y-axis directions of the two-dimensional array, respectively, θ, correspond to the beam elevation angle and azimuth angle, respectively, is the in-array phase difference in the z-axis and y-axis directions; F 1 (θ) represents the radiation pattern of a one-dimensional linear array with the same element spacing and the same number of elements as the two-dimensional array in the z-axis direction, that is, the array gain of this one-dimensional linear array when the elevation angle is θ; represents the projection of the radiation pattern of a one-dimensional linear array with the same element spacing and the same number of elements as the two-dimensional array in the y-axis direction when the elevation angle is θ, that is, the projection of the array gain of this one-dimensional linear array when the azimuth angle is on the elevation angle θ plane.

3. The phase array cross multi-beam amplitude comparison direction finding method according to claim 2, characterized in that, In Step 3, in the azimuth direction within the search airspace range, use digital beamforming (DBF) to construct simultaneous multi-beams, specifically as follows: Arrange multiple sidelobe suppression antennas with different directions around the array. For azimuth airspace coverage, the adopted method is digital multi-beam synthesis technology (DBF); at this time, the front-end wave control sets the phase difference between each sub-array in the azimuth angle to be equal, and the beam azimuth angle points to 0; use the analog-to-digital converter (ADC) to sample each received analog signal into the corresponding digital signal; before transmitting the analog signal to the AD, down-convert the RF signal to the corresponding intermediate frequency; Perform synthesis on the collected signals in the digital domain, that is, give each signal a weight coefficient and then perform vector addition operation on each signal; divide the array into left and right half arrays, then the left and right sub-arrays will perform vector synthesis separately during the synthesis operation; The weight coefficient is obtained from the formula of Taylor weighting coefficient: where where \(f(p)\) is the weighted value of the weighting coefficient in the domain \((0, \pi / 2)\), \(p\) corresponds to the phase within the domain; \(N\) is the number of array elements within the sub-array, is the number of equal side-lobes on one side of the main lobe, \(m\) is the serial number of the equal height side-lobes, \(n\) is the serial number of the traversal term in the calculation process, \(S(m)\) is the intermediate calculation quantity, \(J\) is the expansion term of the Taylor formula, \(\delta\) is the broadening factor, and A is determined by the variable control sidelobe level parameter R 0 determined, cosh -1 represents the inverse function of the hyperbolic cosine function; Refer to the signal acquisition amplitude of the reference pressure sidelobe antenna, and set the sidelobe level height to a value lower than this level; obtain the front-end signals of the array in different directions by performing phase weighting on each signal. The phase weighting coefficients α in different directions satisfy the following relationship: where θ represents the azimuthal spatial domain size covered by the beam, num represents the number of simultaneous multi-beams, and i represents the beam sequence number.

4. The phased array cross multi-beam amplitude comparison direction finding method according to claim 2, characterized in that, when selecting the objective function, the wideband received signal is divided into narrow sub-bands, and the wideband signal is divided into multiple narrowband signals for processing, specifically as follows: Taking one of the frequency points as the reference frequency, using the narrowband beamforming method to obtain the desired beam that meets the requirements at this frequency; Checking the beam widths corresponding to each frequency point at different angles, determining the frequency band range that needs to be beamwidth-expanded, calculating the weighting coefficients at other narrowband frequency points, so that the beams obtained at other frequency points have the same main lobe width as the desired beam at the reference frequency; For the frequency bands that do not need to be beamwidth-expanded, select the weights that meet the conditions, the frequency bands that meet the airspace coverage requirements and the beam pointing, and select the weighting coefficients that meet the requirements according to the specific system requirements. At this time, the beamwidth will be correspondingly expanded; for the frequency bands that need to be beamwidth-expanded, select the matching main beam width and process it using the spatial resampling method.

5. The phased array cross multi-beam amplitude comparison direction finding method according to claim 2, characterized in that, The establishment of the amplitude difference table described in step 4 is specifically as follows: Establish an amplitude difference table, calculate according to the data of the azimuth multiple scan beam patterns and the pitch left and right half array two scan beam patterns at each scan table angle, count the amplitude differences between adjacent azimuth and pitch beams, and make an amplitude comparison direction finding look-up table.

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