Conformal array antenna monopulse direction-finding difference beam generation method

Abstract

The invention discloses a conformal array antenna monopulse direction-finding difference beam generation method. The method comprises the following steps: giving a conformal array expected difference beam index; selecting an effective array element according to the expected beam direction and the array element orientation; carrying out sum beam synthesis on an array formed by the effective array elements; calculating the amplitude difference of the two wave beams at the expected nulling position, and enabling the amplitude difference to meet the corresponding angle difference when the nulling depth is given; adjusting right beam pointing according to the calculated angle difference; repeating the step 4 and the step 5 until an iteration termination condition is reached; and performing phase compensation and weighted stacking on the excitation of the two beams obtained by calculation to realize difference beam forming. The method for effectively generating the difference beam is suitable for the conformal array, and deep null and low sidelobe difference beams at different angles can be achieved under the condition that the array element shielding problem and the array asymmetric layout are considered.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of array antennas, in particular to a method for generating a single-pulse direction-finding difference beam of a conformal array antenna. BACKGROUND

[0002] In modern radar, communication and navigation systems, difference beam synthesis is one of the key technologies to achieve accurate angle direction finding or target deviation measurement. Compared with the traditional sum beam, the difference beam usually has a deep null and steep slope characteristics in the main beam direction, making it have high precision and high sensitivity in target angle deviation measurement. Therefore, the combination of sum / difference beams is the core means of single-pulse radar systems.

[0003] In recent years, with the increasing demand for antenna integration capability of the platform, conformal array antennas have attracted widespread attention in the military (such as stealth fighter jets, missiles) and civilian (such as vehicle-mounted, 5G base stations, unmanned aerial vehicles) fields due to their advantages of closely fitting the body surface, reducing radar cross section, and improving aerodynamic performance. Compared with traditional planar arrays, the position, orientation, and element pattern of each element on the curved surface of the conformal array are inconsistent, which makes the conventional difference beam synthesis method for planar arrays unsuitable, and it is very difficult to achieve deep null (high slope) and low sidelobe (such as -25 dB) in asymmetric layout.

[0004] In view of the above difficulties, some methods have been tried in existing research, but there are still many shortcomings: Chinese patent 202210114302.6 discloses a dynamic array grouping method based on cone-shaped conformal phased array and difference beam forming. A conical surface conformal array is divided into sub-arrays along the circumferential fan-shaped region and the upper and lower conical surfaces and numbered. Considering the element occlusion at different angles, different sub-arrays are dynamically selected for sum and difference beam forming. Chinese patent 202410469706.6 discloses a spherical conformal array difference beam element activation region division. When generating elevation and azimuth difference beams, the array elements in the activation region of the spherical array are divided into two sub-arrays according to the half-space of the beam pointing coordinate system. The elements in one of the sub-arrays are excited based on the conventional pointing phase matching, and the elements in the other sub-array are excited based on the conventional pointing phase matching plus a certain phase shift. The two beams generated by the two sub-arrays are superimposed to obtain the difference beam. Chinese patent 202410694796.9 discloses a conformal array digital difference beam forming system and method, which generates two beams in the elevation and azimuth directions by shifting the phase of each sub-array of the conformal array, and then performs subtraction operation to generate the difference beam. The above methods do not consider the structural characteristics of conformal arrays. When generating difference beams, the asymmetric array structure causes the two beams to be asymmetric after phase shifting or the selected sub-arrays to be asymmetric, which results in unequal directional pattern values at the expected null position, causing the generated null to be not deep or even difficult to generate.

[0005] Overall, while existing research has provided several solutions for difference beamforming, no mature and practical method has yet been found to achieve difference beamforming on irregular conformal arrays while simultaneously meeting the single-pulse performance requirements of deep nulls, high slope, and low sidelobes. To address the aforementioned technical problems, this invention proposes a single-pulse direction-finding difference beamforming method for conformal array antennas. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to propose a method for generating a single-pulse direction-finding difference beam for a conformal array antenna. This method is applicable to any three-dimensional conformal array and can achieve the desired difference beam while maintaining high overall efficiency.

[0007] To achieve the above-mentioned technical objectives, the present invention includes the following steps:

[0008] Step 1: For an arbitrary N-element three-dimensional conformal array, given the desired difference beam null position Generated differential beam type and corresponding generated differential beam pointing angle or ;

[0009] Step 2: Based on the desired beam direction or And the orientation of each array element, selecting effective radiation array elements that are not blocked under different beam directions;

[0010] Step 3: Perform beam synthesis on the arrays composed of effective array elements under the two beam directions to obtain the radiation pattern. and And obtain two beams in The amplitude of the directional pattern corresponding to each position , and phase , ;

[0011] Step 4: Determine , The size relationship, and calculate ;

[0012] Step 5: Calculation and amplitude Difference in observation angle at time By adjusting incentives The phase is used to obtain the radiation pattern. And at this time exist The amplitude of the directional pattern corresponding to the position ;

[0013] Step 6: Repeat steps 4 to 5 until the upper limit of the set number of iterations is reached, or the desired null depth is achieved, or the null depth changes less than a set value between two iterations;

[0014] Step 7: Perform reference phase alignment and peak equalization superposition on the corresponding excitation sequence to obtain a required conformal array difference beam excitation distribution, and the synthesis is completed; With corresponding to the excitation sequence, a required conformal array difference beam excitation distribution is obtained by performing reference phase alignment and peak equalization superposition, and the synthesis is completed;

[0015] Further, the difference beam type generated in step 1 includes elevation difference beam and azimuth difference beam, and the difference beam is generated by subtracting the sum beam, if the desired difference beam type is the elevation difference beam, two sum beams with beam pointing directions of are subtracted; if the desired difference beam type is the azimuth difference beam, two sum beams with beam pointing directions of are subtracted.

[0016] Further, in step 2, the array element screening is based on whether the included angle between the beam pointing direction and the array element orientation is greater than the given effective array element radiation angle When the included angle between the array element orientation and is greater than , the array element does not participate in the synthesis of the directional diagram because the radiation energy value in the radiation direction is too small or is physically blocked, so the effect of such array elements is not considered, and the N-element array is numbered, the array element serial number participating in the synthesis of the directional diagram is denoted as m, and the set can be expressed as

[0017] (1)

[0018] wherein, is the orientation vector of the array element ; , , ; is the expected beam pointing vector; , , ; and are selected as , , or , according to the expected beam type.

[0019] Further, the sum beam synthesis method in step 3 can adopt any synthesis method suitable for irregular conformal arrays, taking the elevation difference beam as an example, the excitation sequence corresponding to the beams with pointing directions of and is and​ , Direction chart and and two beams in The amplitude of the directional pattern corresponding to each position , and phase , .

[0020] Furthermore, the difference in observation angles in step 5 The calculation needs to refer to the judgment result in step 4. Taking pitch difference beam as an example, if... ,but ,like Then you need to find exist Within range and The two closest values and The corresponding pitch observation angle and ,in Obtained through linear interpolation amplitude The corresponding observation angle and difference :

[0021] (2)

[0022] according to Incentives The phase is compensated to obtain the compensated phase. :

[0023] (3)

[0024] in, The coordinates of the effective array elements; , , ; , , ;symbol This indicates Hadamard multiplication. (Used) renew .

[0025] Furthermore, in step 7, the excitation sequence reference phase alignment involves adding constant phase compensation to the excitation sequence, so that the two beams are aligned... The phase values ​​at each point are all 0; peak equalization superposition involves weighting the excitation sequence to make the peak values ​​of the two beams equal, and then superimposing them to obtain the final differential beam excitation distribution.

[0026] (4)

[0027] in, For the present exist The phase of the radiation pattern corresponding to the position.

[0028] The beneficial effects of adopting the above technical solution are as follows:

[0029] a) This invention can solve the problem of difference beam generation for asymmetric arrays, without specifying the position of array elements, and is applicable to conformal arrays with arbitrary layouts.

[0030] b) The present invention can dynamically adjust the array elements and the position of the differential beams involved in generating the differential beams according to the radar beam pointing direction, and can form a good array differential pattern for the entire airspace.

[0031] c) This invention uses sum beams to generate difference beams, which can achieve low sidelobe difference beams by adjusting the sum beams, and does not impose constraints on the synthesis method, making it widely applicable. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a flowchart of the method of the present invention;

[0034] Figure 2 This is a schematic diagram of the conformal array model of the present invention;

[0035] Figure 3 This is a schematic diagram illustrating the selection of effective array elements in this invention;

[0036] Figure 4 This is a three-dimensional radiation pattern of the integrated conformal array elevation difference in an embodiment of the present invention;

[0037] Figure 5 This is a composite conformal array elevation difference pattern in an embodiment of the present invention. Cross-sectional view. Detailed Implementation

[0038] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0039] Step 1: For an arbitrary N-element three-dimensional conformal array, given the desired difference beam null position Generated differential beam type and corresponding generated differential beam pointing angle or .

[0040] For a given N-ary three-dimensional conformal array, with Figure 2 Taking the array shown as an example, the positions of each element are as follows: , , Array element The element radiation pattern is The far-field radiation pattern of this array is as follows:

[0041] (1)

[0042] in , , It is the wavelength at which the antenna operates; For array element Incentives; , , ; and These are the observation angles in the elevation and azimuth dimensions, respectively.

[0043] For this array, given the desired difference beam type, including elevation difference beams and azimuth difference beams, the difference beam is generated by subtracting the sum beam. If the desired difference beam type is an elevation difference beam, then the beam pointing... Subtract the two sum beams; if the desired difference beam type is azimuth difference beam, then use a beam pointing as... Two beam subtraction

[0044] (2)

[0045] Step 2: Based on the desired beam direction or And the orientation of each array element, selecting effective radiation array elements that are not blocked under different beam directions.

[0046] The selection criteria for array elements are beam pointing and element orientation. Is the included angle between them greater than the given effective element radiation angle? When the array elements face and Angle greater than In this case, if the radiation energy of an array element is too small or is physically blocked in that radiation direction and does not participate in the pattern synthesis, then the effect of this type of array element is not considered. The array element index participating in the pattern synthesis is denoted as m, and can be represented by a set.

[0047] (3)

[0048] wherein, is the orientation vector of the array element ; , , ; is the desired beam pointing vector; , , ; and is selected according to the desired beam type , , or , . For the array shown in Figure 2 , when the beam pointing is , set , the effective array elements are as shown in Figure 3 .

[0049] Step 3: Perform beam synthesis of the array composed of effective array elements in two beam pointing directions to obtain the directivity patterns and , and obtain the directivity pattern amplitudes , , and phases , corresponding to the two beams at the position, respectively;

[0050] The beam synthesis method can adopt any synthesis method suitable for irregular conformal arrays. Considering beam performance and synthesis efficiency, the alternating projection method is adopted in the present application. Taking the elevation difference beam as an example, set the beam pointing of the sum beam to be and ; if the desired difference beam sidelobe level is , the desired sidelobe level of the sum beam synthesis can be set to . The excitation sequence and , the directivity pattern and , and the directivity pattern amplitudes , and phases , corresponding to the two beams at the position, respectively.

[0051] Step 4: Determine the size relationship of , , and calculate .

[0052] Difference in observation angle The calculation needs to refer to the judgment result in step 4. Taking pitch difference beam as an example, if... ,but ,like Then you need to find exist Within range and The two closest values and and its corresponding pitch observation angle and ,in Obtained through linear interpolation amplitude The corresponding observation angle and difference :

[0053] (4)

[0054] according to Incentives The phase is compensated to obtain the compensated phase. :

[0055] (5)

[0056] in, The coordinates of the effective array elements; , , ; , , ;symbol This indicates Hadamard multiplication. (Used) renew .

[0057] Step 6: Repeat steps 4 to 5 until the set upper limit of the number of iterations is reached, or the desired zero depth can be achieved, or the change in zero depth between two iterations is less than the set value.

[0058] Set an iteration limit Q, the current iteration count q, and the expected depth of the zero trap. And the upper limit of the acceptable difference between two iterations of zero trap change. .when ,or ,or The iteration ends when the time is right, where Represents the q-th iteration .

[0059] Step 7: At this time With The corresponding excitation sequence is subjected to reference phase alignment and peak equalization superposition to obtain a required conformal array difference beam excitation distribution, and the synthesis is ended.

[0060] First, the current At The pattern phase corresponding to the position , the current With The corresponding excitation sequence is subjected to , Constant phase compensation. In order to ensure that the two peaks of the superposed difference beam are equal, the excitation sequence also needs to be weighted, and the final difference beam excitation distribution is

[0061] (6)

[0062] Wherein, is the pattern phase corresponding to the current At Position.

[0063] The specific implementation of the conformal array antenna monopulse direction finding difference beam generation method proposed in the application can be further given through the following simulation examples and results:

[0064] In this simulation example, the array model shown in Figure 2 The array is composed of a hemispherical crown array with 144 elements and a cylindrical array with 224 elements. The element spacing is ; the radius of the spherical crown array is ; the conformal array element with a direction of is approximately represented by formula (7):

[0065] (7)

[0066] The pattern of the remaining elements is obtained by coordinate rotation of the element.

[0067] To verify the applicability of the method, for the array shown in Figure 2 The generation of the elevation difference beam is considered, and the expected null position is ; the expected sidelobe level is ; the expected null level is ; and the expected difference beam peak position is . The synthesis results are shown in Figure 4 and Figure 5 . As can be seen from the results, the proposed method can be used to synthesize the azimuth difference beam of the irregular conformal array. The synthesized azimuth difference beam pattern is shown in The null depth is -54.6 dB. The sidelobes are -20.0 dB.

Claims

1. A method for generating a single-pulse direction-finding difference beam for a conformal array antenna, characterized in that... Includes the following steps: Step 1: For an arbitrary N-element three-dimensional conformal array, given the desired difference beam null position Generated differential beam type and corresponding generated differential beam pointing angle or ; Step 2: Based on the desired beam direction or And the orientation of each array element, selecting effective radiation array elements that are not blocked under different beam directions; Step 3: Perform beam synthesis on the arrays composed of effective array elements under the two beam directions to obtain the radiation pattern. and And obtain two beams in The amplitude of the directional pattern corresponding to each position , and phase , ; Step 4: Determine , The size relationship, and calculate ; Step 5: Calculation and amplitude Difference in observation angle at time By adjusting incentives The phase is used to obtain the radiation pattern. And at this time exist The amplitude of the directional pattern corresponding to the position ; Step 6: Repeat steps 4 to 5 until the set upper limit of the number of iterations is reached, or the desired zero depth can be achieved, or the change in zero depth between two iterations is less than the set value. Step 7: At this time and The corresponding excitation sequences are reference phase aligned and peak equalized and superimposed to obtain a conformal array difference beam excitation distribution that meets the requirements, and the synthesis is completed.

2. The method for generating a single-pulse direction-finding difference beam for a conformal array antenna according to claim 1, characterized in that: Step 1 generates differential beam types including elevation differential beams and azimuth differential beams. The differential beam is generated by subtracting the sum beam from the azimuth beam. If the desired differential beam type is an elevation differential beam, the beam pointing direction is... Subtract the two sum beams; if the desired difference beam type is azimuth difference beam, then use a beam pointing as... The two beams are subtracted.

3. The method for generating a single-pulse direction-finding difference beam for a conformal array antenna according to claim 1, characterized in that: In step 2, the selection criteria for array elements are beam pointing and element orientation. Is the included angle between them greater than the given effective element radiation angle? When the array elements face and Angle greater than At that time, because the radiation energy value of this array element in that radiation direction is too small or it is physically blocked and does not participate in the pattern synthesis, the role of this type of array element is not considered, and the N-element array is processed. The element number participating in the pattern synthesis is denoted as m, and can be represented by a set. (1)； in, For array element Orientation vector; , , ; The desired beam pointing vector; , , ; and Selected based on the desired beam type. , ,or , .

4. The method for generating a single-pulse direction-finding difference beam for a conformal array antenna according to claim 1, characterized in that: Observation angle difference in step 5 The calculation needs to refer to the judgment result in step 4. Taking pitch difference beam as an example, if... ,but ,like Then you need to find exist Within range and The two closest values and and its corresponding pitch observation angle and ,in Obtained through linear interpolation amplitude The corresponding observation angle and difference : (2)； according to Incentives The phase is compensated to obtain the compensated phase. : (3)； in, The coordinates of the effective array elements; , , ; , , ;symbol This indicates Hadamard multiplication. (Used) renew .

5. The method for generating a single-pulse direction-finding difference beam for a conformal array antenna according to claim 1, characterized in that: In step 7, the excitation sequence reference phase alignment involves adding constant phase compensation to the excitation sequence so that the two beams are aligned in the same direction. The phase values ​​at each point are all 0; peak equalization superposition involves weighting the excitation sequence to make the peak values ​​of the two beams equal, and then superimposing them to obtain the final differential beam excitation distribution. (4)； in, For the present exist The phase of the radiation pattern corresponding to the position.

Images