Small-unit-spacing array antenna of low-sidelobe cosecant square pattern

Abstract

The invention relates to a small unit spacing array antenna of a low sidelobe cosecant square pattern, which is composed of a plurality of unit antennas which are adjacently and sequentially overlapped and arranged, each unit antenna is composed of a top-layer metal structure (1), a first-layer dielectric substrate (2), a middle-layer metal structure (3), a second-layer dielectric substrate (4), a metal bottom plate (5) and a feed coaxial connector (6) in sequence from top to bottom. The top layer metal structure is in a long strip shape, the upper side is an opening type sawtooth edge (1-1), and the lower side, the left side and the right side are straight edges (1-2). Metalized via holes (1-3) are distributed and connected around the straight edge and are used for being conducted with an intermediate layer metal structure; in addition, a feed metallization via hole (1-4) is arranged in the top layer metal structure. And low-sidelobe cosecant square pattern shaping under a non-large-scale array condition is realized. Meanwhile, the array has the characteristics of small size and low profile height on the premise of ensuring the performance of a directional diagram.

Description

Technical Field

[0001] This invention relates to various microwave communication fields, and in particular to a small-cell-pitch array antenna with a low sidelobe co-secant square pattern. Background Technology

[0002] The cosecant square pattern refers to an antenna gain distribution that follows a cosecant square relationship with the elevation angle. It provides relatively balanced coverage for airspace targets at different distances under constant altitude conditions, making it suitable for applications such as air-to-ground coverage. In near-ground environments, obstructions such as trees and buildings, and their reflections, can introduce strong interference and may even conceal potential interference sources. To meet the needs of communication and sensing, the radiation pattern needs strong sidelobe suppression capabilities to improve received signal quality and system robustness. However, due to limitations in base station size and weight, large-scale antenna arrays are difficult to deploy; limited physical aperture also makes pattern synthesis more challenging. Compared to traditional array structures with half-wavelength or larger element spacing, small-element-spacing arrays are more compact with the same number of elements. Combining small-element-spacing arrays with low-sidelobe cosecant square patterns can simultaneously achieve compact array size and excellent pattern performance, possessing significant engineering and academic value.

[0003] Existing cosecant square-pattern antennas can be broadly categorized into four types: single antennas, transmission arrays, reflection arrays, and array antennas. Single-antenna schemes typically achieve the cosecant square-pattern through aperture curve design, but generally suffer from low aperture efficiency and large pattern shape deviations. In transmission and reflection array schemes, the feed antenna must be placed near the focal point, resulting in a high antenna profile, which is detrimental to system integration. Array antenna schemes achieve the amplitude and phase distribution of each element to obtain the cosecant square-pattern through the feed network, but often use element spacing of at least half a wavelength. Achieving a low-sidelobe cosecant square-pattern often requires a large number of array elements, resulting in a large overall array size.

[0004] Currently, there are no reports on small-element-pitch array antennas with low sidelobe cocut square patterns, and related designs remain a blank. Therefore, it is necessary to conduct research on compact small-element-pitch array antennas with low sidelobe cocut square patterns, in order to simultaneously achieve high sidelobe suppression, a smooth cocut square pattern shape, and a compact array size and profile height. Summary of the Invention

[0005] Technical Problem: The purpose of this invention is to propose a small-cell-pitch array antenna with a low sidelobe co-secant square pattern, addressing the shortcomings of existing co-secant square pattern antennas in terms of size and profile height control. Common solutions also suffer from low co-secant square pattern matching and limited sidelobe suppression capabilities. This invention achieves low sidelobe co-secant square pattern shaping under non-large-scale array conditions. Furthermore, this array combines miniaturization and low profile height while maintaining pattern performance.

[0006] Technical solution: The present invention proposes a small-pitch array antenna with low sidelobe co-cut square pattern. The array antenna is characterized by being composed of several adjacent and sequentially stacked unit antennas. Each unit antenna consists of a top metal structure, a first dielectric substrate, a middle metal structure, a second dielectric, a metal base plate, and a coaxial feed connector from top to bottom.

[0007] The top metal structure is elongated, with an open serrated edge on the top and straight edges on the bottom and left and right sides. Connecting metallized vias are arranged around the straight edges to communicate with the intermediate metal structure. In addition, power-feeding metallized vias are provided in the top metal structure.

[0008] The intermediate layer metal structure has the same shape as the top layer metal structure. The connecting metallized vias are directly connected to the top layer metal structure, while the power supply metallized vias have anti-pads in this layer to form a clearance area.

[0009] The metal base plate has through holes for the coaxial connector to pass through and be fixed; the outer conductor of the coaxial connector is tightly fitted with the middle layer metal structure, and its inner conductor passes through the power-feeding metallized via and is electrically connected to the top layer metal structure.

[0010] The top metal structure has a vertical length of 0.12. -0.15 ,in This represents the waveguide wavelength corresponding to the antenna's center frequency; its horizontal length is 1.45. -1.55 .

[0011] The dimensions of the open-type serrated edge in the vertical and horizontal directions are 0.025. -0.030 and 0.050 -0.055 .

[0012] The diameter of the connected metallized via is 0.006. -0.007 The spacing between adjacent vias is 0.0040. -0.0045 .

[0013] The diameter of the power-fed metallized via is 0.008 mm. -0.009 .

[0014] The height between the top metal structure and the metal base plate is 0.21. -0.22 .

[0015] The antenna elements are spaced at a distance of less than 0.5 operating wavelengths in the vertical direction to reduce the overall size of the array; the antenna elements are larger than 1 operating wavelength in the horizontal direction to obtain higher element gain.

[0016] Connecting metallized vias helps improve cell gain and enhance inter-cell coupling characteristics; while serrated openings can extend the operating bandwidth and optimize impedance matching at the feed port.

[0017] Beneficial Effects: This invention, through innovation in physical structure and optimization of comprehensive algorithms, offers the following advantages compared to existing technologies: 1) Achieving array miniaturization and low-profile design: This invention employs a unit spacing of less than 0.5 operating wavelengths, combined with 0.21... ~ 0.22 The low-profile structural design effectively controls the overall physical size and profile height of the array. This overcomes the bulky size problem caused by the large element spacing of traditional array antennas, making it easier for system integration and deployment. 2) Significantly improves the electrical performance and mutual coupling characteristics of the elements: The open-cut sawtooth edge design of the top metal structure of the element expands the operating bandwidth while optimizing the impedance matching of the feed port; the metallized vias distributed on the three sides of the element can effectively improve the element gain and significantly improve the mutual coupling characteristics between small-pitch array elements. 3) Possesses high-precision radiation pattern shaping and sidelobe suppression capabilities: By introducing the complex plane region division method, the main lobe, transition region and sidelobe region are mapped to the complex plane for classification and constraint, so that the shape of the main lobe of the radiation pattern is highly consistent with the cosecant square function, and a high degree of sidelobe suppression is achieved. This enhances the antenna's anti-interference capability in complex near-ground environments and improves signal quality. 4) The optimization process is efficient and has global search capabilities: The accompanying algorithm adopts the cuckoo search algorithm with the Lévy flight mechanism, which can effectively avoid the optimization from getting trapped in local optima. It can quickly obtain the optimal complex excitation output under non-large-scale array conditions, and has extremely high engineering application value. Attached Figure Description

[0018] Figure 1 This is a structural diagram of a small-unit-pitch array antenna;

[0019] Figure 2 This is a side view of a single antenna unit;

[0020] Figure 3 This is a top view of a single-unit antenna;

[0021] Figure 4 This is a bottom view of the unit antenna feed structure;

[0022] Figure 5 This is a flowchart of the cosecant squared direction pattern synthesis algorithm;

[0023] Figure 6 It is the constraint boundary diagram of the cosecant square direction pattern;

[0024] Figure 7 It is a complex plane region division diagram of the cosecting square direction diagram. Detailed Implementation

[0025] like Figure 1 , 2 As shown in Figures 3 and 4, the low sidelobe co-cut square pattern small-cell array antenna of the present invention is composed of several adjacent, sequentially stacked element antennas. Each element antenna, from top to bottom, consists of a top metal structure 1, a first dielectric substrate 2, an intermediate metal structure 3, a second dielectric layer 4, a metal base plate 5, and a feed coaxial connector 6. The top metal structure 1 is elongated, with an open serrated edge 1-1 on the upper side and straight edges 1-2 on the lower and left / right sides. Connecting metallized vias 1-3 are arranged around the straight edges 1-2 for communication with the intermediate metal structure 3. In addition, feed metallized vias 1-4 are provided in the top metal structure 1.

[0026] The intermediate layer metal structure 3 has the same shape as the top layer metal structure 1. The connecting metallized vias 1-3 are directly connected to the top layer metal structure 1, while the power supply metallized vias 1-4 have anti-pads 3-1 in this layer to form a clearance area. The metal base plate 5 has through holes for the coaxial connector 6 to pass through and be fixed. The outer conductor of the coaxial connector 6 is tightly fitted to the intermediate layer metal structure 3, and its inner conductor passes through the power supply metallized vias 1-4 and is electrically connected to the top layer metal structure 1. The vertical length of the top layer metal structure 1 is 0.12 mm. -0.15 ,in This represents the waveguide wavelength corresponding to the antenna's center frequency; its horizontal length is 1.45. -1.55 The dimensions of the open-type serrated edge 1-1 in the vertical and horizontal directions are both 0.025. -0.030 and 0.050 -0.055 The diameter of the connecting metallized vias 1-3 is 0.006 mm. -0.007 The spacing between adjacent vias is 0.0040. -0.0045 The diameter of the metallized feed vias 1-4 is 0.008 mm. -0.009 The height between the top metal structure 1 and the metal base plate 5 is 0.21 meters. -0.22 The antenna elements are spaced at a distance of less than 0.5 operating wavelengths in the vertical direction to reduce the overall size of the array; the antenna elements are larger than 1 operating wavelength in the horizontal direction to obtain higher element gain.

[0027] The amplitude and phase excitation of each antenna element are generated by the cosecant squared pattern synthesis algorithm proposed in this invention, the process of which is as follows: Figure 5 As shown, the algorithm uses the real and imaginary parts of the exponential term of the complex root corresponding to the array pattern in the complex plane as optimization variables; it measures the deviation between the current pattern and the upper and lower constraint boundaries through an error function, and minimizes this error as the optimization objective; the optimization process is implemented using the cuckoo search algorithm.

[0028] Step 1 sets parameters including: number of array cells and cell spacing; population size of the Cuckoo algorithm, Lévy flight step size parameter, discovery probability and maximum number of iterations; upper and lower constraints of the cosecant squared pattern include: main lobe angle range, gain fluctuation within the main lobe, sidelobe suppression degree and transition region width, and the acceptable range of real and imaginary parts of the complex root exponent in each region of the complex plane.

[0029] Step 2: Initialize optimization variables and randomly generate a set of initial samples;

[0030] Step 3: Calculate the error function, which is to obtain the sum of squares of the portion of the current radiation pattern that exceeds the upper and lower boundaries, in order to quantify the degree of deviation between the radiation pattern and the constraint boundaries.

[0031] Step 4: Select the sample with the smallest error function value from the current sample as the historical best sample;

[0032] Step 5: Update and optimize variables based on Levy-flight;

[0033] Step 6: Update the variables further based on the discovery probability;

[0034] Step 7: Recalculate the updated error function values ​​for all samples;

[0035] Step 8, update the historical best sample: if a sample with smaller error appears in step 7, replace the original historical best sample with it; otherwise, leave it unchanged.

[0036] Step 9: Determine the iteration termination condition. If the current iteration count has reached the maximum iteration count, proceed to step 10; otherwise, return to step 5 to continue iterating.

[0037] Step 10: Output the final result and calculate the corresponding amplitude and phase excitation based on the historical best sample to obtain the optimized output of the pattern synthesis.

[0038] The algorithm employs a double-constraint boundary method to construct the target boundary of the cosecant squared direction pattern, such as... Figure 6 As shown. Where θ1, θ2, and θ3 are the angular parameters of the upper boundary, θ... a θ b The angle parameter for the lower boundary. Parameters θ2 and θ3 are used to control the width of the shaping region, and θ1 and θ... a Control the width of the transition zone on the left side of the shaping region, θ b θ3 controls the width of the transition region on the right side of the shaped region. RP represents the maximum allowable gain fluctuation in the shaped region, and SLL represents the maximum sidelobe level in the non-shaped region. The pattern synthesis employs a complex plane region division method, as shown in Figure 7. The pattern is divided into three sub-regions and mapped to the complex plane. Region I is the shaped region, corresponding to the main lobe portion of the pattern. Within this region, a pattern with roll-off characteristics close to the cosecant square function needs to be constructed, and the gain fluctuation within the main lobe must be controlled within the set range. Region II is the transition region, consisting of two intervals on the complex plane, corresponding to the transition between the main lobe and sidelobe in the pattern. Zeros need to be constructed in this region to achieve rapid gain roll-off. Region III is the non-shaped region, corresponding to the non-main lobe portion of the pattern and the non-visible area of ​​the complex plane. This division method meticulously partitions the complex plane, ensuring that each region in the divided complex plane corresponds to a different part of the array pattern, and constrains the number and location range of complex roots in each region, thereby helping to obtain the target cosecant square direction. Figure 1 This achieves the desired main lobe characteristics and a comprehensive effect of high-suppression sidelobe pattern.

[0039] In this invention, the antenna array employs an element spacing of less than 0.5 operating wavelengths, combined with a low profile height structural design, thereby effectively controlling the overall size and profile height of the array. By introducing a complex plane region partitioning method to synthesize the cosecant square pattern, a main lobe shape consistent with the height of the cosecant square function and a sidelobe pattern with high suppression can be obtained, thus achieving a high-performance cosecant square pattern synthesis effect.

Claims

1. A small-cell-pitch array antenna with a low sidelobe co-secant square pattern, characterized in that, The array antenna consists of several adjacent unit antennas stacked in sequence. Each unit antenna consists of a top metal structure (1), a first dielectric substrate (2), a middle metal structure (3), a second dielectric layer (4), a metal base plate (5), and a coaxial feed connector (6) from top to bottom.

2. The small-cell-pitch array antenna with low sidelobe co-cut square pattern according to claim 1, characterized in that, The top metal structure (1) is long and narrow, with an open serrated edge (1-1) on the upper side and straight edges (1-2) on the lower side and the left and right sides. Connecting metallized vias (1-3) are arranged around the straight edges (1-2) to communicate with the intermediate metal structure (3). In addition, a power supply metallized via (1-4) is provided in the top metal structure (1).

3. A small-cell-pitch array antenna with a low sidelobe co-cut square pattern according to claim 2, characterized in that, The intermediate metal structure (3) has the same shape as the top metal structure (1). The connecting metallized via (1-3) is directly connected to the top metal structure (1), while the power supply metallized via (1-4) has anti-pad (3-1) in this layer to form a clearance area.

4. A small-cell-pitch array antenna with a low sidelobe co-cut square pattern according to claim 6, characterized in that, The metal base plate (5) has through holes for the coaxial connector (6) to pass through and be fixed; the outer conductor of the coaxial connector (6) is closely fitted with the intermediate layer metal structure (3), and its inner conductor passes through the power-feeding metallized via (1-4) and is electrically connected to the top layer metal structure (1).

5. A small-cell-pitch array antenna with a low sidelobe co-cut square pattern according to claim 4, characterized in that, The length of the top metal structure (1) in the vertical direction is 0.

12. -0.15 ,in This represents the waveguide wavelength corresponding to the antenna's center frequency; its horizontal length is 1.

45. -1.55 .

6. A small-cell-pitch array antenna with a low sidelobe co-cut square pattern according to claim 5, characterized in that, The dimensions of the open-type serrated edge (1-1) in the vertical and horizontal directions are 0.025 respectively. -0.030 and 0.050 -0.055 .

7. A small-cell-pitch array antenna with a low sidelobe co-cut square pattern according to claim 6, characterized in that, The diameter of the connecting metallized vias (1-3) is 0.

006. -0.007 The spacing between adjacent vias is 0.0040. -0.0045 .

8. A small-cell-pitch array antenna with a low sidelobe co-cut square pattern according to claim 7, characterized in that, The diameter of the power-fed metallized vias (1-4) is 0.008 mm. -0.009 .

9. A small-cell-pitch array antenna with a low sidelobe co-cut square pattern according to claim 8, characterized in that, The height between the top metal structure (1) and the metal base plate (5) is 0.

21. -0.22 .

10. A small-cell-pitch array antenna with a low sidelobe co-cut square pattern according to claim 9, characterized in that, The antenna elements are spaced at a distance of less than 0.5 operating wavelengths in the vertical direction to reduce the overall size of the array; the antenna elements are larger than 1 operating wavelength in the horizontal direction to obtain higher element gain.

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