Array antenna sparse conversion method, computer equipment and readable storage medium

Abstract

The invention discloses an array antenna sparse conversion method, computer equipment and a readable storage medium. The method comprises the following steps: presetting uniform array elements of an array antenna; antenna array elements in the uniform array elements are uniformly distributed, and a plurality of antenna array elements are randomly selected or removed from the uniform array elements to form sparse array elements; converting a side lobe control region and a beam scanning region of the sparse array element in a geodetic coordinate system into a region of the sparse array element in an array surface spherical coordinate system; in the sparse array element, the output relative phase and the output relative amplitude of the T assembly of the antenna array element are adjusted, and the sidelobe control area and the beam scanning area are respectively controlled. Therefore, the sparse array element can reach or exceed the gain of the uniform array element.

Description

Technical Field

[0001] The present application relates to the technical field of array antennas, and in particular to an array antenna sparse conversion method, a computer device, and a readable storage medium. Background Art

[0002] A planar array antenna is an array antenna whose antenna elements are distributed on a plane and whose antenna beam can be electronically scanned in both azimuth and elevation. At present, most long-range array antenna radars and three-coordinate phased radars use planar array antennas. A planar array antenna can be decomposed into multiple sub-array antennas or multiple linear arrays. There are two main ways to arrange the elements of a planar array antenna: rectangular grid array arrangement and triangular grid array arrangement. The latter can be regarded as a planar array antenna composed of two antenna elements arranged in a rectangular grid array with a large spacing between them.

[0003] Large planar array antennas with uniform spacing have the characteristics of high gain, narrow beam, and easy electronic scanning in azimuth and elevation. However, they consume a large number of antenna elements, making the array antenna expensive. When considering cost and performance, it is necessary to reduce the number of antenna elements as much as possible. When the number of antenna elements is reduced, the sidelobe control area and beam scanning area of ​​the array antenna also change. In the existing technology, it is impossible to effectively control the sidelobe control area and beam scanning area of ​​the array antenna after reducing the number of antenna elements. Summary of the invention

[0004] The main technical problem solved by the present application is to provide a method for sparse conversion of array antennas, so as to solve the problem that the sidelobe control area and beam scanning area of ​​the array antenna cannot be effectively controlled after reducing the antenna elements.

[0005] In order to solve the above technical problems, a technical solution adopted in the present application is to provide a method for sparse conversion of an array antenna, comprising:

[0006] A uniform array element of a preset array antenna; the antenna elements in the uniform array element are uniformly distributed, and a plurality of the antenna elements are randomly selected or removed from the uniform array element to form a sparse array element;

[0007] Convert the sidelobe control area and beam scanning area of ​​the sparse array element in the geodetic coordinate system to the sparse array element in the array surface spherical coordinate system;

[0008] By adjusting the output relative phase and the output relative amplitude of the T component of the antenna array element in the sparse array element, the sidelobe control area and the beam scanning area are controlled respectively.

[0009] The present application also provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method when executing the computer program.

[0010] The present application also provides a computer-readable storage medium having a computer program stored thereon, characterized in that the steps of the method are implemented when the computer program is executed by a processor.

[0011] The beneficial effects of the present application are as follows: in the present application, a plurality of antenna elements are randomly selected or removed from uniform array elements to form sparse array elements, thereby reducing the cost of array antennas, and converting the sidelobe control area and beam scanning area of ​​the sparse array elements in the geodetic coordinate system to the sparse array elements in the array surface spherical coordinate system; and controlling the sidelobe control area and beam scanning area respectively through the output relative phase and output relative amplitude of the antenna element T component in the sparse array elements, thereby enabling the sparse array elements to reach or exceed the gain of the uniform array elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a flow chart according to an embodiment of the present application;

[0013] Figure 2 is a schematic diagram of an array antenna evenly arranged according to an embodiment of the present application;

[0014] Figure 3 is a schematic diagram of a ground and antenna coordinate system according to an embodiment of the present application;

[0015] Figure 4 is a schematic diagram of the relationship between two sets of coordinates in a ground coordinate system according to an embodiment of the present application;

[0016] Figure 5 is a schematic diagram of a coordinate transformation process according to an embodiment of the present application;

[0017] Figure 6 is a schematic diagram of a side lobe control area when the array face tilt angle is 0° according to an embodiment of the present application;

[0018] Figure 7 is a schematic diagram of the side lobe control area when the array face tilt angle is 5° according to an embodiment of the present application;

[0019] Figure 8 is a schematic diagram of the side lobe control area when the array face tilt angle is 10° according to an embodiment of the present application;

[0020] Fig. 9 is a schematic diagram of the side lobe control area when the array face tilt angle is 15° according to an embodiment of the present application;

[0021] Fig.10 is a schematic diagram of the side lobe control area when the array face tilt angle is 20° according to an embodiment of the present application;

[0022] Fig.11 is a schematic diagram of the side lobe control area when the array face tilt angle is 25° according to an embodiment of the present application;

[0023] Fig.12 This is a schematic diagram of the amplitude control centerline of the array antenna array coordinate system according to an embodiment of the present application;

[0024] Fig.13 is a flow chart of scanning angle and sidelobe control according to an embodiment of the present application;

[0025] Fig.14 is a schematic diagram of an array plane of a sparse array element according to an embodiment of the present application;

[0026] Fig.15 It is a schematic diagram of the array radiation pattern and the sidelobe control area in the 5.5 GHz array coordinate system according to an embodiment of the present application;

[0027] Fig.16 is a horizontal plane pattern of a normal beam in a 5.5 GHz array coordinate system according to an embodiment of the present application;

[0028] Fig.17 is a pitch plane pattern of a normal beam in a 5.5 GHz array coordinate system according to an embodiment of the present application;

[0029] Fig.18 is a schematic diagram of the dipole feeding power after the amplitude inverse weighting of the normal beam is performed according to an embodiment of the present application;

[0030] Fig.19 is a two-dimensional normalized directional pattern after amplitude inverse weighting according to an embodiment of the present application;

[0031] Fig. 20 is a normalized elevation pattern after amplitude inverse weighting according to an embodiment of the present application;

[0032] Fig.21 It is a schematic diagram of the dipole feeding power after the amplitude forward weighting of the edge beam at an azimuth of 0 degrees according to an embodiment of the present application;

[0033] Fig. 22 is a two-dimensional normalized directional pattern after amplitude inverse weighting according to an embodiment of the present application;

[0034] Fig.23 It is a normalized elevation pattern after amplitude inverse weighting according to an embodiment of the present application. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of this application.

[0036] It should be noted that when an element is referred to as being "fixed on" or "set on" another component, it can be directly on the other component or indirectly set on the other component; when a component is referred to as being "connected to" another component, it can be directly connected to the other component or indirectly connected to the other component.

[0037] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "vertical", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0038] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "multiple" and "several" mean two or more, unless otherwise clearly and specifically defined.

[0039] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification so that people familiar with this technology can understand and read them. They are not used to limit the conditions under which this application can be implemented, so they have no substantive technical significance. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in this application without affecting the effects and purposes that can be achieved by this application.

[0040] Figure 1-Figure 23 An embodiment of the sparse conversion method of the array antenna of the present application is shown, comprising the steps of:

[0041] A uniform array element of a preset array antenna; the antenna elements in the uniform array element are uniformly distributed, and a plurality of the antenna elements are randomly selected or removed from the uniform array element to form a sparse array element;

[0042] Convert the sidelobe control area and beam scanning area of ​​the sparse array element in the geodetic coordinate system to the sparse array element in the array surface spherical coordinate system;

[0043] The sidelobe control area and the beam scanning area are controlled respectively by the output relative phase and the output relative amplitude of the antenna array element T component in the sparse array array element.

[0044] In the present application, a plurality of antenna elements are randomly selected or removed from uniform array elements to form sparse array elements, thereby reducing the cost of array antennas, and converting the sidelobe control area and beam scanning area of ​​the sparse array elements in the geodetic coordinate system to the sparse array elements in the array surface spherical coordinate system; and controlling the sidelobe control area and beam scanning area respectively through the output relative phase and output relative amplitude of the antenna element T component in the sparse array elements, thereby enabling the sparse array elements to reach or exceed the gain of the uniform array elements.

[0045] The sidelobe control area and beam scanning area of ​​the array antenna are both defined in the geodetic coordinate system, and the actual array antenna array surface has an upward tilt angle. When the array antenna is working, the array antenna and its carrier are stationary relative to the ground. In addition, when the antenna carrier plane is parallel to the ground, the geodetic coordinate system can be considered to be the carrier coordinate system.

[0046] The array antenna pattern function uses Figure 2 The model shown. The array antenna is located on the xoy plane, with a total of M*N antenna elements. The N antenna elements along the x direction are evenly arranged with a spacing of dx, and the M antenna elements along the y direction are evenly arranged with a spacing of dy, thus forming a planar array of a rectangular grid array.

[0047] Assume that the direction of the antenna array element target (incoming wave) is expressed as direction cosine:

[0048]

[0049] in, is the direction of the target, is the x direction of the target, is the y direction of the target, is the z direction of the target, θ angle: is the angle between the target direction vector and the Z axis (front normal), and the definition domain is [0°, 180°]; Angle: It is the angle between the projection vector of the target direction vector on the XOY plane and the X-axis. The direction is increased by the right-hand spiral direction in the +Z-axis direction. The domain is [0°, 360°). The direction of the target refers to the source direction of the transmitted or received signal.

[0050] The distance difference between the antenna element and the target direction determines the phase difference in the signal transmission process. for:

[0051]

[0052] Where: (d n ,d m ) are the coordinates of the mth and nth antenna array elements in the array plane coordinate system. m and n are the numbers of the antenna array elements in the horizontal and elevation dimensions, dx is the horizontal spacing of the antenna array elements, and dy is the elevation spacing of the antenna array elements.

[0053] The phase difference Δφ between the (m, n)th and (0, 0)th reference antenna elements caused by the antenna element spacing mn , expressed as:

[0054]

[0055] Wherein, λ is the free space wavelength corresponding to the electromagnetic wave of the working frequency. If the phase difference is positive, the phase of the electromagnetic wave received by the (m, n)th antenna array element is ahead of the (0, 0)th antenna array element. If the phase difference is negative, the phase of the electromagnetic wave received by the (m, n)th antenna array element lags behind the (0, 0)th antenna array element.

[0056] If at this time, each antenna element of the array antenna has a set of delayed phases, which are synthesized after delay, and this set of phases makes the maximum direction of the transmitted electromagnetic wave deviate to direction, according to the reciprocity principle of passive antenna transmission and reception, the weighted phase value a of this group mn satisfy:

[0057]

[0058] Under this set of weighted phase values, the radiation pattern of the array antenna is:

[0059]

[0060] The above formula is the radiation pattern function of the array antenna in the array coordinate system, where: N and M are the number of antenna elements in the horizontal and elevation dimensions of the array antenna, φ is the corresponding direction of the radiation pattern, j is an integer, θ0 and is the spatial angle that the array antenna pattern needs to cover, f mn (φ,θ) is the antenna array element array pattern of the (m, n)th antenna array element. If the differences in antenna array element patterns are not considered, the directions of all antenna array elements can be Figure 1 To. That is: f mn (φ,θ)=f0(φ,θ). mnIt is the feeding amplitude of the antenna element. When the array is sparse, there are only two values: 0 and 1.

[0061] The directional pattern of the antenna element in the array is quite different from that of the independent antenna element, especially the antenna element at the center of the array. The directional pattern will be distorted due to the mutual coupling of the antenna elements next to it, and the smaller the array spacing and the wider the directional pattern lobe width, the more serious the distortion. If the port isolation between the array antenna elements is relatively small, this change will generally not have a big impact on the main lobe of the array directional pattern, but it will have a relatively large impact on the side lobe, especially in most cases, it will deteriorate the side lobe performance. In practical applications, we have to consider the influence of the universality of mutual coupling on the directional pattern, but if mutual coupling is considered in the directional pattern model, it will become very complicated and not conducive to algorithm processing. Therefore, before the subsequent algorithm processing, it is necessary to make certain restrictions on the mutual coupling so that it does not affect the processing results of the algorithm.

[0062] Limiting the minimum spacing between antenna elements to more than half a wavelength can keep the mutual coupling of antenna elements within a controllable range. Even if the local radiation pattern exceeds the sidelobe index requirements, the feeding amplitude a of the antenna elements can be slightly adjusted. mn can be improved. Then:

[0063]

[0064] Wherein, f0(φ,θ) is the antenna array element radiation pattern.

[0065] Array antenna performance requirements: "The average sidelobe equivalent radiated power of the radiation source: within the commonly used scanning airspace (azimuth ±20°, elevation 0°~30°) is no more than 46dBW." The coordinate system at this time corresponds to Figure 3 In the OX1Y1Z1 coordinate system (carrier coordinate system), the pitch angle is 0°~30°, that is, the α1 angle in the figure satisfies α1∈[0°,30°], which is defined as: the angle between the unit vector of the incoming wave direction in the OX1Y1Z1 coordinate system, the projection vector on the OY1Z1 plane and the OZ1 axis; the azimuth angle range is ±20°, that is, the β1 angle (not shown in the figure) satisfies β1∈[-20°,20°], which is defined as: the angle between the unit vector of the incoming wave direction in the OX1Y1Z1 coordinate system, the projection vector on the OX1Z1 plane and the OZ1 axis. Similarly, the definitions of the α angle and the β angle in the OXYZ coordinate system are consistent with the above definitions.

[0066] Figure 4 The OXYZ coordinate system is the array coordinate system, the array normal points to the OZ axis, the OX axis is parallel to the OX1 axis in the carrier coordinate system, and the OX1Y1Z1 coordinate system (carrier coordinate system) is rotated around the OX1 axis by an angle of α0 to obtain the OXYZ coordinate system. The angle α0 in the figure is the upward angle of the array normal.

[0067] The spherical coordinate angle in the coordinate system OX1Y1Z1 is defined as The interplanar angles are defined as the α1 angle and the β1 angle.

[0068] The spherical coordinate angle in the coordinate system OXYZ is defined as The face angles are defined as angle α and angle β.

[0069] If the side lobes of the α1∈[0°,30°],β1∈[-20°,20°] space in the geodetic coordinate system OX1Y1Z1 need to be controlled, the space should be transformed into the array coordinate system OXYZ and then controlled by the optimization design method. The angle transformation process is as follows: Figure 5 As shown, the description is as follows:

[0070] A process: Knowing the direction of the incoming wave in the geodetic coordinate system OX1Y1Z1 (α1∈(0°,30°),β1∈(-25°,25°)), according to its definition and the relationship between polar coordinates, such as Figure 4 As shown, the formula is expressed as:

[0071]

[0072] Solving the above equation yields:

[0073]

[0074] Process B:

[0075] The unit vector of any incoming wave direction in the coordinate system O1X1Y1Z1 (expressed as spherical coordinates) is:

[0076]

[0077] The coordinate vector in the coordinate system OXYZ is decomposed into the coordinate system O1X1Y1Z1:

[0078]

[0079] Then the direction of the incoming wave in the coordinate system OX1Y1Z1 is The transformation direction in the coordinate system OXYZ is:

[0080]

[0081] at this time:

[0082]

[0083] Through the above two equations, we can directly solve the relationship between the incoming wave direction angle in the geodetic coordinate system and the front spherical coordinate system:

[0084]

[0085] During the algorithm optimization process, the above formula can be used to determine whether a certain direction in the array coordinate system is located in the airspace of the control side lobe. That is, after the beam is tilted up by an angle of α0, the direction of the incoming wave in the array spherical coordinate system is The corresponding angles α1 and β1 in the carrier coordinate system. When α1∈[0°,30°], β1∈[-20°,20°], it is the area where the sidelobe index needs to be met.

[0086] Figures 6 to 11 The dark circle in the figure is the airspace diagram of the front half space of the array in the array antenna coordinate system, and the horizontal axis is Value, vertical axis is The value of θ ranges from -90 to 90 degrees. The value range is -90 to 90 degrees, which together constitute the front half of the airspace in the antenna array coordinate system. Figures 6 to 11 It can be seen that since the airspace for controlling the side lobes is defined in the geodetic coordinate system, the relative airspace for controlling the side lobes of the antenna array is different as the upward angle is different.

[0087] In practical applications, different array weighting coefficients need to be used according to different tilting angles, depending on the different terrain in the actual installation environment. This requires storing different array weighting coefficients or angle correction values ​​in the wave control network. However, this does not hinder the design of the system solution. When designing the system, the tilting angle can be predetermined to be 15 degrees. If the measured angle is not 15 degrees and it is inconvenient to adjust, the array weighting coefficient after angle correction can be called.

[0088] Phased beam scanning spatial transformation: The scanning spatial domain of the array antenna is defined as α2∈[0°,50°], β2∈[-35°,35°] in the geodetic coordinate system OX1Y1Z1. α2 is the scanning elevation angle in the geodetic coordinate system, and β2 is the angle between the scanning projection vector and the OZ1 axis in the geodetic coordinate system. First, transform the spatial domain into the array coordinate system OXYZ, and its corresponding direction Then the beam scanning is realized by phase control method. Figure 5 Consistent,

[0089] The transformation equation is as follows:

[0090]

[0091] By controlling the relative phase of the output of each T component (phase shifter), the sparse array antenna beam is realized; by controlling the relative amplitude of the output of each T component (attenuator), the sparse array antenna sidelobe level control is realized. All these controls need to be performed after the array calibration operation. The change in attenuation caused by the control phase shifter and the change in phase shift caused by the control attenuator can be corrected after testing.

[0092] Array antenna beam scanning needs to be achieved through the relative phase shift of each T component channel. The control of the relative phase shift of each T component is discussed based on the following formula.

[0093]

[0094] The above formula is the expression of sparse array pattern, where f0(φ,θ) is the antenna element pattern, N and M are the number of antenna elements in the horizontal and elevation dimensions of the array antenna, respectively, and a mn It is the phase difference between antenna elements in a certain radiation direction caused by the antenna element layout; is the feeding phase difference of antenna elements numbered m and n. mn is the antenna element feeding amplitude, 1 means there is an antenna element at the position numbered m or n, and 0 means there is no antenna element. Based on the above analysis:

[0095]

[0096] Where (θ, φ) is the preset scanning angle in the array coordinate system, (d n ,d m ) are the coordinates of the mth and nth antenna array elements in the array coordinate system. To make the maximum beam direction point to (θ, φ) = (θ0, φ0), it must satisfy:

[0097]

[0098] That is, the phase of the mth and nth antenna array elements must satisfy:

[0099]

[0100] According to the coordinates in the array coordinate system, the phase of the antenna array element numbered m=0, n=0 is zero. The phases of the antenna elements in the above formula are all relative to the phases of the antenna elements m = 0 and n = 0. For any set angle, the feed phase of each antenna element can be calculated according to the above formula, and then converted into a phase control word, and the relative phase shift of the phase shifter can be controlled at the same time to achieve beam scanning.

[0101] Sidelobe control: When the uniform array antenna radiates in the normal direction, the sidelobe level in other airspace is relatively low; as the scanning angle increases, the sidelobe level will increase relatively. However, if the average sidelobe level in a specified airspace is considered, it may fluctuate with the change of the scanning angle.

[0102] like Figure 3 As shown, the antenna array is tilted α0 = 25°. In the geodetic coordinate system O1X1Y1Z1, the scanning space of the array antenna is α2∈(0°, 50°), β2∈(-35°, 35°). The space where the side lobes need to be controlled is α1∈(0°, 30°), β1∈(-20°, 20°) in the geodetic coordinate system O1X1Y1Z1. Now, starting from the spherical coordinates of the array coordinate system OXYZ (where the OZ axis is the array normal), let's discuss how to control the side lobes.

[0103] Fig.12 is the front coordinate system, where The coordinates are the corresponding spherical coordinates. Beam scanning direction vector:

[0104]

[0105] There must be two straight lines in the OXY plane (front plane), and their unit vectors are set as and (either positive or negative direction is OK), satisfying:

[0106]

[0107] The names of these two straight lines on the array are defined as "amplitude control center lines". The feeding amplitudes of all antenna array elements are related to the distances from their centers to these two straight lines. Settings: Substituting into the above formula we get:

[0108]

[0109] The intersection of the two straight lines is the center of the array. The origin of the coordinate system is translated to the center of the array. At this time, the coordinates of the antenna element (m, n) are: Its arrival The distance of the straight line is:

[0110]

[0111] Its arrival The distance of the straight line is:

[0112]

[0113] The array is uniformly arranged, dx=dy.

[0114] If the array is a sparse array on a square grid, then M=N.

[0115]

[0116] When the side lobe is large and needs to be lowered, the relative amplitude control of each antenna array element satisfies the following formula:

[0117]

[0118] At this time, the amplitude is positively weighted. The antenna element feeding amplitude is higher at the center of the array, while the feeding amplitude is lower at the edge. s is the minimum feeding relative power, s∈(0,1), where D1 mn and D2 mn The minimum value is 0, at which point the midline of the amplitude passes through the antenna element; the maximum value is P mn The maximum value is 1 (the antenna element must be located at the center of the array. The even array will not have this maximum value, but it is very close to 1), and the minimum value is s. The relative amplitude range of the feeding of each antenna element on the array is between 1 and s.

[0119] When the side lobe is low and needs to be raised, the relative amplitude control of each antenna element satisfies the following formula:

[0120]

[0121] In this case, the amplitude is inversely weighted. The feeding amplitude of the antenna element at the center of the array is low, while the feeding amplitude at the edge is high. s is the minimum feeding relative power, s∈(0,1), P mn The maximum value is 1 (the antenna element needs to be located at the edge of the array. The even array will not have this maximum value, but it is very close to 1), and the minimum value is s. The relative amplitude range of the feeding of each antenna element on the array is between 1 and s.

[0122] The value of s is related to system indicators. If the average sidelobe level range to be controlled in the beam scanning state is not large, for example, only within 3dB, the value of s can be relatively close to 1; if the average sidelobe level range to be controlled is large, the value of s can be relatively close to 0; the smaller the value of s, the greater the output power dynamic range of the RF power amplifier component. Under the same EIRP requirement, the power output capacity required by the system will also be greater, and the system will be more expensive.

[0123] Reasonable sparse array can achieve the control of the sidelobe level in a certain area in a relatively small scanning space. The value of s can be close to 1. At this time, the amplitude control range of the array antenna power amplifier channel needs to meet the following requirements:

[0124] ΔP(dB)≥10·log 10 (s)

[0125] Scanning angle and sidelobe control process: In actual application, the angle of each incoming wave direction and the control word of its corresponding sidelobe level need to be stored in the wave control board in advance. The control process is as follows: Fig.13 The beam control board receives the beam scanning angle command from the host computer. If the angle is defined as the earth coordinate system, it is converted into the angle of the array coordinate system. The wave control board queries the average sidelobe level value and normal beam gain value of the specified airspace under the scanning angle. These two data can be obtained by testing the planar near field of the array antenna in advance and storing the results. Determine whether the average sidelobe level value is between -17dBc and -20dBc. If it is, no amplitude weighting is required, and only the channel relative phase needs to be changed; if not, determine whether it is less than -20dBc. If it is, it is necessary to reversely weight the array amplitude (that is, the feed power of the antenna element at the center of the array is low, and the feed power of the antenna element at the edge of the array is high), and obtain the array gain loss caused by weighting (the table can be obtained by prior testing), and uniformly calculate it into the channel amplitude control word; if it is greater than -17dBc, it is necessary to forward weight the array amplitude (that is, the feed power of the antenna element at the center of the array is high, and the feed power of the antenna element at the edge of the array is low), and obtain the array gain loss caused by weighting (the table can be obtained by prior testing), and uniformly calculate it into the channel amplitude control word.

[0126] Send the amplitude control word to the transmitting component to complete the beam scanning control and sidelobe control. The entire beam control process can be completed by table lookup and simple calculation. Several tables that need to be pre-stored in the beam control board include: 1. Scanning angle and antenna array element phase correspondence table (in the array coordinate system); 2. Forward weighted amplitude control table; 3. Reverse weighted amplitude control table; the latter two tables only need to store the control coefficient s and the average sidelobe increase or decrease value.

[0127] The dispersion of C-band RF active devices is small, and the absolute channel delay changes little with the environment and time. The empty-feed self-calibration method can be used. The purpose of empty-feed self-calibration is to calibrate the phase shift of T components and cables in use.

[0128] The antenna should first be calibrated in a darkroom environment for channel amplitude and phase. The calibration bracket will set up the calibration receiving antenna on the normal axis of the array, with the normal direction of the receiving antenna facing the array direction. The distance between the receiving antenna and the antenna element antenna of this application should meet the far-field test conditions (D ≥ 0.5m).

[0129] Switch the antenna array element antenna as the transmitting antenna in turn (connect the matching load to the other antenna ports), and read the calibration S of the antenna's transmit and receive channels respectively. 21 The parameters are as follows:

[0130] is the amplitude of the horizontally polarized transmitting antenna;

[0131] is the phase of the horizontally polarized transmitting antenna;

[0132] After the antenna is fully set up and stabilized at the site, channel amplitude and phase calibration is required. The placement of the calibration bracket and the calibration receiving antenna relative to the antenna array must be strictly consistent with the darkroom environment to reduce calibration errors.

[0133] Power on the power amplifier transmitting components in turn, and do not power on other power amplifier components. Read the calibration S of the antenna transceiver channel respectively. 21 The parameters are as follows:

[0134] is the amplitude of the horizontally polarized transmitting antenna;

[0135] is the calibration delay of the horizontally polarized transmitting antenna;

[0136] Adjust the phase shifters and attenuators of each power amplifier so that: 1. Each value in the vector is equal and the largest; 2. Each value in the vector is equal. Calibration is complete.

[0137] Beam width and pointing accuracy design: Beam width of C-band sparse array at all scanning angles:

[0138]

[0139] The beam pointing accuracy is required to be no less than 1.5 degrees, therefore:

[0140]

[0141] To achieve such beam pointing accuracy, when virtual phase shift technology is used during beam scanning, the phase control accuracy between antenna array elements is:

[0142]

[0143] Therefore, the delay accuracy of the delay device in the RF circuit should be less than 5.6ps, corresponding to 0.018 wavelengths, and the longest delay should be greater than 1 wavelength.

[0144]

[0145] The selected delay device has a minimum delay of 14ps, 6 bits, and a maximum delay of 882ps, which meets the requirements of wave control accuracy and phase scanning.

[0146] The linear dynamic range of the system will be ensured by the attenuator in the RF T component. The RF channel requires two attenuators. One attenuator has a 30dB dynamic range to adjust the amplitude error (process error, matching error, chip difference, etc.) of the T component in the basic state. The other attenuator also needs to have a 30dB dynamic range for system sidelobe control and to compensate for the gain difference when the phase shifter is in different states.

[0147] When the system is calibrated, both attenuators are set to the maximum attenuation state. The system has a maximum dynamic range of 60dB.

[0148] According to the beam control accuracy of 1.5 degrees, the airspace is divided to obtain the total number of beams:

[0149]

[0150] The beam switching delay is defined as the total time for table lookup + calculation + sending + RF channel stabilization after receiving the beam switching instruction.

[0151] The tables that need to be stored in the system include: 1. Beam pointing to beam number table (scale 100); 2. Beam number to phase control word table (scale 100); 3. Beam number to amplitude control word table (scale 100). The table lookup process is serial, using a 50MHz clock frequency. The first table takes about 1us, the second and third tables take about 8us, and the total table lookup time is 17us.

[0152] The antenna array element feeding amplitude needs to be calculated, and the total calculation time is about 20us. The transmission time is about 4us. The time taken for a single T component from receiving the control word to stable power output is less than 50ns. Considering the serial control to make the transmission beam uninterrupted, it takes 5us. The transmission delay of a 30-meter line is 0.1us. In summary: from receiving the wave control command from the wave control board to forming a stable beam, it takes less than 45us, which meets the system index requirements.

[0153] Design the array of sparse array elements, the result is as follows Fig.14 As shown. The horizontal and vertical axes in the figure represent 20*20 grid points, and the horizontal and vertical distances between the grid points are both 0.7 center frequency (5.5GHz) free space wavelength, that is, 38.2mm. The circled grid points in the figure indicate that there is an antenna element at the grid point, and vice versa. It can be seen that the sparse array structure shows a clear distribution pattern of more antenna elements in the middle and fewer antenna elements at the edge. The average distance between the array antenna elements is increased, which reduces the mutual coupling between the antenna elements and is conducive to the synthesis of the normal gain of the array surface.

[0154] The normal direction of the array is tilted 25 degrees relative to the geodetic coordinate system. Fig.15The array pattern and sidelobe control area in the 5.5GHz array coordinate system (the airspace surrounded by the red line in the figure). The main lobe of the pattern in the figure points to The other airspaces in the upper half of the space are the grating lobes. When processing the radiation pattern, the antenna array element is the Yagi antenna unit.

[0155] Fig.16 and Fig.17 The horizontal and elevation patterns of the normal beam in the 5.5GHz array coordinate system. The 3dB beam width is 4.34° (horizontal) × 3.78° (elevation). Considering the amplitude inverse weighting and high-frequency factors, the beam width meets the overall design requirements. Table 1 shows the statistical information of the sparse planar array antenna at each scanning angle every 5 degrees between -25 degrees and 25 degrees in elevation.

[0156] Table 1 Statistics of scanning angles of sparse planar array antenna

[0157]

[0158] In Table 1: 1. Each column in the maximum directivity coefficient is relative to the decrease value of the normal beam, that is, the maximum directivity coefficient of the normal beam is normalized and logarithmically equal to 0, and the maximum decrease in other scanning areas is -3.78 dB.

[0159] 2. The maximum sidelobe is the logarithm of the sidelobe level of the unified beam divided by the main lobe level, multiplied by 10. From the statistical data, it can be seen that the maximum sidelobe is -7.2dB. No grating lobes appear in the entire airspace.

[0160] 3. If the level of the side lobe points in the airspace is lower than -30dBc, they will not be counted as side lobes;

[0161] 4. The average sidelobe level refers to the average sidelobe level value in the airspace of 0-50 degrees in elevation and ±30 degrees in the horizontal direction in the specified geodetic coordinate system. It can be seen that in the scanning state, the sidelobe level increases with the increase of the scanning angle. When the scanning angle is in the normal direction, the average sidelobe level is the lowest, with a value of -20.7dBc, which does not meet the requirement of the index being greater than -20dBc, so the array amplitude needs to be reversely weighted; when the scanning angle is at an elevation of 25 degrees and an azimuth of 0 degrees, the average sidelobe level is the highest, with a value of -16.1dBc, which meets the requirement of the index being greater than -20dBc, but the sidelobe level is too high, and the array amplitude needs to be positively weighted to control it.

[0162] Sidelobe control simulation: The normal beam is amplitude-inversely weighted, and the oscillator feeding power is as follows: Fig.18 As shown, the diameter of the red circle is proportional to the feed power. The feed power of the antenna element at the edge is the largest, which is 1W; the feed power of the antenna element in the middle is the smallest, which is 0.7W.

[0163] Fig.19 is the two-dimensional normalized directional pattern after amplitude inverse weighting, Fig. 20 is the normalized elevation pattern after amplitude inverse weighting, compared to Fig.16 , the side lobes are significantly enhanced. At this time, the array normal gain drops by 0.1dB, and the average feed power is 0.84W, which is reduced by 0.75dB. Therefore, the system needs to reserve a 1.0dB power design margin to control the regional average side lobes in the normal state. At this time, the side lobes in the horizontal ±25 degree airspace with an elevation angle of 0 to 30 degrees in the geodetic coordinate system increase from -20.7dBc to -19.1dBc, meeting the requirements.

[0164] The amplitude of the edge beam with an elevation angle of 25 degrees and an azimuth of 0 degrees is forward weighted, and the feed power of the vibrator is as follows: Fig.21 As shown, the diameter of the red circle is proportional to the feed power. The feed power of the antenna element at the edge is the largest, which is 0.3W; the feed power of the antenna element in the middle is the smallest, which is 1W.

[0165] Fig. 22 is the two-dimensional normalized directional pattern after amplitude inverse weighting, Fig.23 The normalized elevation pattern after amplitude inverse weighting, the side lobes are significantly reduced, the weighted array gain is reduced by 0.34dB, the average feed power is 0.72W, reduced by 1.4dB, and the total EIRP is reduced by 1.74dB. At this time, the elevation angle is 0-30 degrees in the geodetic coordinate system, and the side lobes in the horizontal ±25 degree airspace are reduced from -16.8dBc to -19.2dBc.

[0166] It can be seen that the present application discloses a method for sparse conversion of array antennas, which randomly selects or removes multiple antenna elements from uniform array elements to form sparse array elements, thereby reducing the cost of array antennas, and converting the sidelobe control area and beam scanning area of ​​the sparse array elements in the geodetic coordinate system to the sparse array elements in the array surface spherical coordinate system; and controlling the sidelobe control area and beam scanning area respectively through the output relative phase and output relative amplitude of the antenna element T component in the sparse array element, thereby enabling the sparse array element to reach or exceed the gain of the uniform array element.

[0167] The above are merely embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structural transformations made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for sparse conversion of an array antenna, characterized in that: A uniform array element of a preset array antenna; the antenna elements in the uniform array element are uniformly distributed, and a plurality of the antenna elements are randomly selected or removed from the uniform array element to form a sparse array element; Convert the sidelobe control area and beam scanning area of ​​the sparse array element in the geodetic coordinate system to the sparse array element in the array surface spherical coordinate system; By adjusting the output relative phase and the output relative amplitude of the T component of the antenna array element in the sparse array element, the sidelobe control area and the beam scanning area are controlled respectively.

2. The array antenna sparse conversion method according to claim 1, characterized in that: The sparse array element is formed based on the directional pattern of the array antenna, and the target direction of the array antenna is expressed as direction cosine: in, is the direction of the target, is the x-coordinate of the target, is the y coordinate of the target, is the z-coordinate of the target, θ is the angle between the target direction vector and the Z-axis, is the projection vector of the target direction vector on the XOY plane and the angle between the X axis; The antenna element position vector for: Where: (d n ,d m ) is the coordinate of the mth and nth numbered antenna array element in the array plane coordinate system; m and n are the numbers of the antenna array elements in the horizontal and elevation dimensions, dx is the spacing of the antenna array elements in the horizontal dimension, and dy is the spacing of the antenna array elements in the elevation dimension; The spacing between the antenna array elements makes the phase difference Δφ between the (m, n)th and (0, 0)th antenna array elements mn , expressed as: Wherein, λ is the free space wavelength corresponding to the electromagnetic wave of the working frequency, and the phase difference Δφ mn is positive, then the phase of the electromagnetic wave received by the (m, n)th antenna array element is ahead of the (0, 0)th antenna array element; the phase difference Δφ mn is negative, the phase of the electromagnetic wave received by the (m, n)th antenna array element lags behind that of the (0, 0)th antenna array element; Each antenna element of the array antenna has a set of delayed phases, which are synthesized after delay, and the set of phases causes the maximum direction of the transmitted electromagnetic wave to deviate to Direction, weighted phase value a mn satisfy: The directional pattern of the array antenna is: Where N and M are the number of antenna elements in the horizontal and elevation dimensions of the array antenna, respectively; j is an integer; θ0 and is the spatial angle that the array antenna pattern needs to cover, f mn (φ,θ) is the unit array pattern of the (m,n)th antenna element, g mn The antenna array element feeding amplitude.

3. The array antenna sparse conversion method according to claim 2, characterized in that: If the minimum spacing between the antenna elements is limited to more than half a wavelength, then: By adjusting the feeding amplitude of the antenna array element, the local radiation pattern of the array antenna is adjusted, and the radiation pattern of the array antenna is rewritten as: Wherein, f0(φ,θ) is the antenna array element radiation pattern.

4. The array antenna sparse conversion method according to claim 3, characterized in that: The sidelobe control area and beam scanning area of ​​the sparse array element in the geodetic coordinate system are converted to the sparse array element in the array spherical coordinate system; the relationship between the incoming wave direction angle in the geodetic coordinate system and the array spherical coordinate system is: Among them, α1 is the pitch angle in the geodetic coordinate system, β1 is the angle between the projection vector and the OZ1 axis in the geodetic coordinate system, and α0 is the upward angle of the array spherical coordinate system.

5. The array antenna sparse conversion method according to claim 4, characterized in that: For the scanning space of the array antenna, the scanning space is first transformed into the array coordinate system, and the corresponding direction Then the beam scanning is realized by the phase control method; The transformation method of the scanning space domain to the array coordinate system is: Among them, α2 is the scanning pitch angle in the geodetic coordinate system, and β2 is the angle between the scanning projection vector and the OZ1 axis in the geodetic coordinate system.

6. The array antenna sparse conversion method according to claim 5, characterized in that: The beam scanning of the array antenna is achieved by the relative phase shift of each T component channel. The control relationship between the sparse array pattern and the relative phase shift of the T component is shown in the following formula:

7. The array antenna sparse conversion method according to claim 6, characterized in that: The minimum spacing between the antenna array elements is limited to more than half a wavelength, and the sparse array pattern is expressed as:

8. The array antenna sparse conversion method according to claim 6, characterized in that: In controlling the side lobe control area and the beam scanning area, the array center is set, the origin of the coordinate system is translated to the array center, and the array center is The distance of the straight line is: The array is centered to The distance of the straight line is: If the sidelobe control area is large and needs to be lowered, the relative amplitude control of each antenna array element satisfies the following formula: If the sidelobe control area is low and needs to be raised, the relative amplitude control of each antenna array element satisfies the following formula:

9. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 8 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 8 are implemented.

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