An omni-directional end-fire phased array based on reconfigurable elements

Abstract

The application discloses an omni-directional end-fire phased array based on reconfigurable array elements and belongs to the technical field of antennas. The phased array comprises N*N periodically arranged array elements, (N-2)*(N-2) central array elements periodically arranged in the array are azimuth plane omni-directional antenna elements, and 4(N-1) edge array elements located at the edges of the array are reconfigurable azimuth plane omni-directional antenna elements. The application introduces the azimuth plane omni-directional radiation antenna element into the end-fire phased array, realizes 360° omni-directional end-fire scanning of the phased array in the azimuth plane, and solves the impedance mismatch problem of the edge array elements in the end-fire scanning by designing the form of the reconfigurable array edge elements. The array designed in the application can realize 360° omni-directional end-fire scanning coverage in the azimuth plane, maintains low profile and vertical polarization characteristics, and has no impedance mismatch problem of the edge array elements.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of antennas, and particularly relates to an omnidirectional end-fire phased array based on reconfigurable elements. BACKGROUND

[0002] The main function of a military airborne radar detection system is to cooperate with a ground detection system to monitor and track air enemy targets in a complex electromagnetic environment, and to complete real-time monitoring of the battlefield situation. An ideal airborne radar system should have as few detection blind spots as possible without affecting the carrying capacity and flight aerodynamic performance of the platform. The antenna array of a traditional airborne radar system mostly uses a broadside array. Due to physical conditions, to make the broadside array produce a high-gain radiation beam in a specified direction, there must be a certain size of array aperture in the corresponding direction. If the flight aerodynamic performance of the platform is to be ensured, the scanning coverage capability in the front and rear directions of the platform axis will be sacrificed, which makes the radar system have a detection blind spot. In addition, under the current anti-stealth combat requirements, the antenna array is required to work at a lower frequency band, for example, a low-frequency meter-wave radar has become an important equipment for anti-stealth combat. However, at the same time, the antenna array at a lower frequency band must be larger in size, which makes the platform aperture resource limitation more stringent, and the application of the broadside array has more restrictions.

[0003] End-fire radiation refers to the radiation characteristic that the maximum gain direction of the radiation beam of the antenna array points to the axial direction of the element arrangement. Compared with an ordinary broadside array, the unique advantage of an end-fire phased array lies in that the size of an ideal end-fire array in the direction perpendicular to the end-fire beam is almost zero, which makes the end-fire array have a natural advantage in terms of flight aerodynamic performance and scanning coverage range, and can effectively utilize the limited aperture resource to supplement the scanning coverage of the detection blind spot of the traditional airborne radar system without affecting the flight aerodynamic performance of the platform.

[0004] At present, the mainstream end-fire phased array is mainly divided into two categories: one category is to use end-fire antenna elements to form a one-dimensional linear array, which can realize one-dimensional end-fire scanning in the azimuth plane. However, due to the limitation of the beam coverage range of the elements, the end-fire phased array cannot realize omnidirectional 360° end-fire scanning in the azimuth plane. The other category is to realize azimuth plane end-fire scanning through a circular or rectangular arrangement of monopole arrays. However, the end-fire phased array composed of such monopoles will have the problem of impedance mismatch of the edge elements in the end-fire scanning process, and this problem cannot be solved by setting array dummy elements, which has a great influence on the actual use of the array. Due to the many problems to be solved in the actual application of the above end-fire phased array, there are fewer cases of directly applying large end-fire phased arrays in past actual engineering cases. SUMMARY

[0005] In order to effectively utilize the inherent advantages of end-fire phased array, a blind scan scheme is provided for an airborne radar system, and problems such as narrow scanning coverage of a traditional end-fire phased array and impedance mismatch of array elements in the scanning process need to be solved. The application provides an omnidirectional end-fire phased array based on reconfigurable array elements, which can realize 360° omnidirectional end-fire scanning of the phased array in the azimuth plane by introducing azimuth plane omnidirectional antenna elements into the end-fire phased array, and can solve the problem of impedance mismatch of edge array elements in the end-fire scanning by designing the form of the reconfigurable array edge elements. The array designed in the application can realize 360° omnidirectional end-fire scanning coverage in the azimuth plane, maintain low profile and vertical polarization characteristics, and has no impedance mismatch problem of edge array elements.

[0006] The technical scheme adopted by the application is as follows:

[0007] An omnidirectional end-fire phased array based on reconfigurable array elements, characterized in that the phased array comprises N*N periodically arranged array elements, wherein (N-2)*(N-2) central array elements periodically arranged in the array are azimuth plane omnidirectional antenna elements, and 4(N-1) edge array elements at the edges of the array are reconfigurable azimuth plane omnidirectional antenna elements; all the array elements have omnidirectional radiation capability in the azimuth plane, and the beam coverage range of the array elements can realize omnidirectional end-fire scanning coverage in the azimuth plane; the edge array elements have two different reconfigurable working states, and can maintain an active standing wave ratio less than 3 during the end-fire scanning of the array.

[0008] Further, the value of N is an integer greater than 4.

[0009] Further, the central array element is a rotationally symmetrical structure, comprising a dielectric substrate 5, a metal patch 1 located on the front surface of the dielectric substrate, a conical monopole 6 located on the back surface of the dielectric substrate, and four supporting metal columns 7.

[0010] The dielectric substrate 5 is a square dielectric substrate.

[0011] The metal patch 1 is a square metal patch, which is provided with a circular ring-shaped slot 2 and four progressive linear slots 3; the circular ring-shaped slot 2 is concentric with the square metal patch; the progressive linear slots 3 are respectively arranged adjacent to the four edges of the square metal patch, and adjacent progressive linear slots 3 are not connected; the middle part of the progressive linear slot 3 is provided with a rectangular protruding metal patch 4 for connecting the metal patch 1 and the supporting metal column 7.

[0012] The supporting metal column 7 is used for supporting the overall structure of the central array element and reducing the working frequency band.

[0013] The edge array element is provided with a ring-shaped metal patch 8 outside the metal patch of the central array element; the center position of each arm of the ring-shaped metal patch is connected to the internal metal patch through a PIN diode 9.

[0014] In order to break through the limitation of the end-on scanning range of the end-on phased array by the beam coverage range of the array element, the application selects an azimuth plane omnidirectional radiation element with low profile characteristics and vertical polarization radiation characteristics as a basic array element structure, optimizes the structure under the end-on phase boundary condition, so that the element can maintain a good working state during the end-on phased scanning process in the actual array, and realizes the azimuth plane omnidirectional end-on scanning of the end-on phased array by using the azimuth plane omnidirectional radiation characteristics. In addition, in order to solve the impedance mismatch problem of the edge element of the monopole end-on phased array, all the edge elements of the array are designed in the form of reconfigurable antenna elements, so that they can switch different reconfigurable working states to maintain good impedance matching during the end-on scanning process. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 (a) is a top view schematic diagram of the center element structure of the embodiment;

[0016] Figure 1 (b) is a side view schematic diagram of the center element structure of the embodiment;

[0017] Figure 2 (a) is a top view schematic diagram of the center element structure of the embodiment;

[0018] Figure 3 (b) is a side view schematic diagram of the center element structure of the embodiment;

[0019] Figure 4 (a) and (b) are schematic diagrams of the overall planar end-on phased array structure of the embodiment;

[0020] Figure 5 (a) and (b) are schematic diagrams of the overall planar end-on phased array structure of the embodiment;

[0021] Figure 6 (a) and (b) are schematic diagrams of the overall planar end-on phased array structure of the embodiment;

[0022] Figure 7 (a) and (b) are schematic diagrams of the overall planar end-on phased array structure of the embodiment;

[0023] Reference signs: 1, metal patch, 2, circular ring slot, 3, progressive line slot, 4, rectangular protruding metal patch, 5, dielectric substrate, 6, tapered monopole, 7, supporting metal column, 8, square ring metal patch, 9, PIN diode. DETAILED DESCRIPTION

[0024] The application will be described in detail below in combination with the drawings and specific embodiments.

[0025] As Figure 4As shown, the phased array in this embodiment includes 6*6 periodically arranged array elements, of which the 4*4 central array elements located in the center of the array are azimuth omnidirectional antenna elements, and the 20 edge array elements located at the edge of the array are reconfigurable azimuth omnidirectional antenna elements.

[0026] Figure 1 (a) and (b) are schematic diagrams of the structure of the central array element in this embodiment. The central array element is a 90° rotationally symmetric structure, including a square dielectric substrate 5, a metal patch 1 located on the front side of the dielectric substrate, a conical monopole 6 located on the back side of the dielectric substrate, and four supporting metal pillars 7.

[0027] The metal patch 1 is a square metal patch with an annular groove 2 and four progressive grooves 3. The annular groove 2 is concentric with the square metal patch. The progressive grooves 3 are respectively located adjacent to the four sides of the square metal patch, and adjacent progressive grooves 3 are not connected. A rectangular protruding metal patch 4 is provided in the middle of the progressive groove 3 to connect the metal patch 1 and the supporting metal column 7.

[0028] The supporting metal column 7 is used to support the overall structure of the central array element and reduce the operating frequency band.

[0029] The central array element is located in the center of the actual planar end-fire phased array, maintaining an active VSWR of less than 2 at all end-fire scanning angles, while also possessing low profile and azimuth omnidirectional radiation characteristics. The main structural parameters of the optimized central array element are: W1 = 135.713 mm, W2 = 20.358 mm, L1 = 91.35 mm, g = 4.3589 mm, r1 = 32.2335 mm, h = 45 mm.

[0030] like Figure 2 The diagram illustrates the impedance mismatch problem of edge elements in a monopole end-fire phased array. Although the optimized central element maintains good impedance matching within the planar end-fire phased array, during end-fire scanning, impedance mismatch occurs in some edge elements in the direction opposite to the maximum end-fire gain due to the severe special coupling effect of the end-fire array and the edge effect of the finite floor size when scanning to different end-fire directions. The arrows in the diagram indicate different end-fire azimuth scanning directions; white boxes represent elements with normal impedance matching, and gray boxes represent elements with impedance mismatch.

[0031] To address the impedance mismatch issue at the edge of the array, a reconfigurable antenna element is designed based on the existing array element structure, such as... Figure 3As shown, a circle of square ring-shaped metal patches 8 is arranged outside the metal patch of the center element, with a peripheral size of 170.2mm*170.2mm; the center position of each arm of the square ring-shaped metal patch is communicated with the internal metal patch through a PIN diode 9. When the diode is in a conductive state, the original patch and the external patch are in a conductive state, and in this state, the reconfigurable element can replace the impedance mismatch edge element in the end-fire scanning process to maintain a good matching state; when the diode is in a cut-off state, the antenna element maintains an operating state similar to the original element structure.

[0032] As shown in Figure 5 Fig. 6 shows the active standing wave coefficients of all edge elements except the dummy element in the end-fire scanning process of the array of the embodiment, and it can be seen that in the scanning process, all the reconfigurable elements maintain a good match, and can maintain an active standing wave ratio of less than 3 in the operating frequency band of 420-480MHz.

[0033] As shown in Figure 6 Figs. 8(a) and 8(b) show the radiation patterns of the array in the positive end-fire scanning direction of the embodiment, and it can be seen that the designed array can realize a good and stable 360° omnidirectional end-fire scanning in the azimuth plane. Figure 7 Figs. 9(a) and 9(b) show the radiation patterns of the array in the maximum squint angle end-fire scanning direction of the embodiment, and it can be seen that the designed array can realize a good and stable 360° omnidirectional end-fire scanning in the azimuth plane.

Claims

1. A reconfigurable-element-based omni-directional end-fire phased array, characterized in that, The phased array includes N*N array elements arranged periodically, N is an integer greater than 4; wherein (N-2)*(N-2) center array elements arranged periodically in the array are azimuth plane omnidirectional antenna elements, 4(N-1) edge array elements located at the edges of the array are reconfigurable azimuth plane omnidirectional antenna elements; all array elements have omnidirectional radiation capability in the azimuth plane, and the beam coverage range of the array elements can realize azimuth plane omnidirectional end-fire scanning coverage; the edge array elements have two different reconfigurable working states and can maintain an active standing wave ratio less than 3 during array end-fire scanning; The center array element has a rotational symmetry structure, including a dielectric substrate (5), a metal patch (1) located on the front surface of the dielectric substrate, a conical monopole (6) located on the back surface of the dielectric substrate, and four supporting metal columns (7); The dielectric substrate (5) is a square dielectric substrate; The metal patch (1) is a square metal patch, which is provided with a circular ring slot (2) and four progressive linear slots (3); the circular ring slot (2) is concentric with the square metal patch; the progressive linear slots (3) are respectively arranged adjacent to the four edges of the square metal patch, and adjacent progressive linear slots (3) are not connected; the middle part of the progressive linear slot (3) is provided with a rectangular protruding metal patch (4) for connecting the metal patch (1) and the supporting metal column (7); The supporting metal column (7) is used for supporting the overall structure of the center array element and reducing the working frequency band; The edge array element is provided with a ring of square ring metal patches (8) outside the metal patch of the center array element; the center position of each arm of the square ring metal patch is connected to the internal metal patch through a PIN diode (9).

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