A one-dimensional tightly coupled phased array with low cross-polarization

Abstract

The present invention relates to a one-dimensional tightly coupled phased array with low cross-polarization, comprising a plurality of periodic units, each of which includes a horizontally polarized interdigital dipole, a vertically polarized interdigital dipole, a feed structure, and a first metal floor. The horizontally and vertically polarized interdigital dipoles are printed on the upper and lower layers of a dielectric plate, respectively, and are positioned orthogonally to each other. The feed ports of the horizontally polarized interdigital dipoles are symmetrically distributed about the centerline of the elevation plane; the feed ports of the vertically polarized interdigital dipoles are staggered on the centerline of the elevation plane; the feed structure is used to feed the horizontally and vertically polarized interdigital dipoles; and the first metal floor serves as a reflective floor for the horizontally polarized interdigital dipoles and the vertically polarized interdigital dipoles. The present invention, through the symmetrical design of the array feed ports, achieves better symmetry for the radiator, optimizes the current path, reduces the current component causing cross-polarization, and thus enables the antenna to have a lower cross-polarization level.

Description

Technical Field

[0001] The present invention belongs to the field of microwave and antenna technology, and specifically relates to a one-dimensional tightly coupled phased array in the field of antenna technology, which can be used for long-distance communication or interference. Background Art

[0002] Array antennas offer the advantages of easily achieving specialized requirements such as strong directivity, high power, beam steerability, low sidelobes, and shaped beams. Tightly coupled arrays, as a form of array antenna, are attracting increasing attention due to their ultra-wideband, low profile, and conformal properties, which align well with the development of phased array radars. Conventional tightly coupled arrays are typically deployed in two dimensions. This is because they rely on capacitive coupling between elements to mitigate impedance variations and achieve broadband design. However, for some specialized applications, such as the narrow and long environments of airborne systems, a two-dimensional array design is impractical, limiting their application. Therefore, one-dimensional tightly coupled arrays are a worthy research area with high application value.

[0003] Yang Shiwen's team at the University of Electronic Science and Technology of China (UESTC) has disclosed a dual-polarization, one-dimensional, strongly coupled, ultra-wideband scanning phased array in their patent application, "A Dual-Polarized, One-Dimensional, Strongly Coupled, Ultra-Wideband Angle Scanning Phased Array" (Application No. 201610230021.1, Publication No. CN 105846081 A). The antenna consists of two rows of horizontally polarized and 26 rows of vertically polarized interdigital coupled dipole antennas. Its basic structure includes a vertical parasitic printed dielectric plate for wide-angle scanning, an upper layer of horizontally polarized interdigital dipoles, a dielectric plate, a lower layer of vertically polarized interdigital dipoles and their horizontal extensions, a vertically tapered extension of the vertically polarized dipoles, a tapered microstrip feed structure for feeding the dipole ports, a reflective floor, metal fencing on both sides of the floor, a power splitter, and a 50-ohm coaxial adapter. The tightly coupled structure between the elements helps the antenna achieve ultra-wideband performance. A parasitic printed dielectric plate replaces the bulky traditional wide-angle impedance matching layer, enabling wide-angle scanning while also achieving a lightweight design. While this antenna reduces the size of a strongly coupled two-dimensional array to a single dimension, broadening its application scenarios, it lacks consideration for cross-polarization, a key characteristic of dual-polarization antennas that directly determines the polarization purity of the antenna and the overall communication quality of the system.

[0004] The 724th Research Institute of China Shipbuilding Industry Corporation (CSIC) has filed a patent application titled "An Ultra-Wide Bandwidth Angular Coverage Low Cross-Polarization Array Antenna Unit" (Application No. 201810764050.5, Publication No. CN 108899639 A). The array antenna unit comprises a dielectric substrate, a tapered slot, a parasitic elliptical metal strip, a metalized through-hole, a stripline balun feed, and a metal guide. The proposed antenna radiating element features a five-fold operating bandwidth, wide angular scanning, wide angular matching, and easy integration with feed networks, making it suitable for phased array antennas. The array design utilizes a symmetrical double-layer radiator structure for low cross-polarization. However, a drawback of the array antenna is its two-dimensional array configuration, making it unsuitable for specialized applications and limiting its practical application.

[0005] Therefore, one of the most pressing challenges in microwave technology is the design of a one-dimensional phased array with wide bandwidth, wide scanning angle, and low cross-polarization. Such a design is expected to improve the communication quality of the entire communication system and can be used in fields such as electronic countermeasures. Summary of the Invention

[0006] The technical problems to be solved by the present invention are:

[0007] In order to overcome the shortcomings of the prior art, the present invention provides a one-dimensional tightly coupled phased array with low cross-polarization, which is used to reduce the impact of cross-polarization on antenna performance and improve the communication quality of the entire communication system.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0009] A one-dimensional tightly coupled phased array with low cross-polarization, characterized by comprising a plurality of periodic units, each periodic unit comprising a horizontally polarized interdigital dipole, a vertically polarized interdigital dipole, a feed structure, and a first metal floor;

[0010] The horizontally polarized interdigital dipoles are printed on the upper layer of the first dielectric plate, and the vertically polarized interdigital dipoles are printed on the lower layer of the first dielectric plate, and the horizontally polarized interdigital dipoles and the vertically polarized interdigital dipoles are placed orthogonally to each other; the feeding ports of the horizontally polarized interdigital dipoles are symmetrically distributed about the center line of the pitch plane; the feeding ports of the vertically polarized interdigital dipoles are staggered on the center line of the pitch plane, that is, two adjacent columns of vertically polarized interdigital dipoles have one column offset above the center line of the pitch plane and one column offset below the center line of the pitch plane;

[0011] The feeding structure is used to feed the horizontally polarized interdigital dipole and the vertically polarized interdigital dipole;

[0012] The first metal floor is a reflection floor of horizontally polarized co-digital dipole and vertically polarized co-digital dipole.

[0013] A further technical solution of the present invention is that the sizes of the horizontally polarized interdigital dipole and the vertically polarized interdigital dipole are different.

[0014] A further technical solution of the present invention is as follows: the vertically polarized interdigital dipole is along the Y-axis direction, and the end of the vertically polarized interdigital dipole is connected to the vertical gradually extending portion.

[0015] A further technical solution of the present invention is that the lower portion of the vertical gradually extending portion is bent inward and then placed above a dielectric block, and the dielectric block is located above the first metal floor.

[0016] A further technical solution of the present invention is that the vertical gradually extending portion gradually widens from top to bottom.

[0017] A further technical solution of the present invention is as follows: the feeding structure includes an exponentially tapered feeding balun and a one-to-two power splitter, wherein the upper end of the exponentially tapered feeding balun is connected to the feeding port of the horizontally polarized co-digital dipole or the feeding port of the vertically polarized co-digital dipole, and the lower end is connected to the output port of the one-to-two power splitter.

[0018] A further technical solution of the present invention is as follows: the one-to-two power splitter is located on the second dielectric plate, and a second metal floor is provided below the second dielectric plate.

[0019] A further technical solution of the present invention is as follows: a circular through hole for installing a 50-ohm RF connector is provided on the second metal floor, so as to avoid the square groove of the exponential gradient feed balun.

[0020] A further technical solution of the present invention is that a square hole for passing the exponential gradient balun is provided on the first metal floor.

[0021] A further technical solution of the present invention further comprises a ferrite absorbing material, wherein the ferrite absorbing material is located above the first metal plate.

[0022] The beneficial effects of the present invention are:

[0023] The one-dimensional tightly coupled phased array with low cross-polarization provided by the present invention has the following advantages over the prior art:

[0024] First, the present invention adds a vertically downward-extending sheet metal structure to the end of the vertically polarized interdigital dipole to reduce the truncation effect of the one-dimensional linear array on the vertical polarization. This ensures the impedance bandwidth of the vertically polarized array and achieves broadband matching. Furthermore, this sheet metal structure offers high strength and provides excellent support for the antenna's radiating layer.

[0025] Second, the present invention employs a symmetrical design for the vertically polarized interdigital dipoles. Their feed ports are staggered in an up-and-down pattern on the elevation plane, centered approximately in the array. Simultaneously, the feed ports of the horizontally polarized dipole units are arranged centrally on the elevation plane. This symmetrical design of the array's feed ports imparts greater symmetry to the radiator, optimizing the current path and minimizing current asymmetry caused by radiator asymmetry, thereby reducing cross-polarization in the antenna. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like parts throughout the drawings.

[0027] Figure 1 This is a schematic diagram of a 2*18 linear array of a low cross-polarization tightly coupled phased array according to the present invention;

[0028] Figure 2 Schematic diagram of a periodic unit of the low cross-polarization tightly coupled phased array of the present invention;

[0029] Figure 3 This is an exploded view of a periodic unit of the low cross-polarization tightly coupled phased array of the present invention;

[0030] Figure 4 Schematic diagram of a radiator in a periodic unit of a low cross-polarization tightly coupled phased array of the present invention;

[0031] Figure 5 It is a side view of a periodic unit of the low cross-polarization tightly coupled phased array of the present invention;

[0032] FIG6( a ) is a graph showing the active standing wave ratio of the horizontally polarized port of the low cross-polarization tightly coupled phased array of the present invention at beam scanning angles of 0 degrees, 30 degrees, and 52 degrees, respectively;

[0033] FIG6( b ) is a graph showing the active standing wave ratio of the vertically polarized port of the low cross-polarization tightly coupled phased array of the present invention at beam scanning angles of 0 degrees, 30 degrees, and 52 degrees, respectively;

[0034] FIG7( a ) is a diagram showing the cross-polarization ratio of the horizontally polarized array of the low cross-polarization tightly coupled phased array of the present invention at beam scanning angles of 0 degrees, 30 degrees, and 52 degrees;

[0035] FIG7( b ) is a diagram showing the cross-polarization ratio of the vertically polarized array of the low cross-polarization tightly coupled phased array of the present invention at beam scanning angles of 0 degrees, 30 degrees, and 52 degrees;

[0036] FIG8( a ) is a scanning pattern of the horizontally polarized array of the low cross-polarization tightly coupled phased array of the present invention at frequencies of 0.35 GHz and 2 GHz;

[0037] FIG8( b ) is a scanning pattern of the vertically polarized array of the low cross-polarization tightly coupled phased array of the present invention at frequencies of 0.35 GHz and 2 GHz.

[0038] In the picture:

[0039] 1-first dielectric plate; 2-horizontally polarized co-digital dipole; 3-vertically polarized co-digital dipole; 4-vertical tapered extension; 5-dielectric block; 6-exponentially tapered feed balun; 7-ferrite absorbing material; 8-first metal floor; 9-one-to-two power divider; 10-second dielectric plate; 11-second metal floor; 12-50 ohm RF connector; 101-first feed port; 102-second feed port; 103-third feed port; 104-fourth feed port; 201-fifth feed port; 202-sixth feed port; 203-seventh feed port; 204-eighth feed port; 801-square hole; 901-input port; 902-second output port; 903-third output port; 1101-cylindrical through hole; 1102-square slot. DETAILED DESCRIPTION

[0040] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0041] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as limiting the present invention.

[0042] The idea for achieving the purpose of the present invention is that the present invention prints a horizontally polarized interdigital dipole on top of the first dielectric plate and a vertically polarized interdigital dipole on the bottom of the first dielectric plate, with the two polarized dipoles placed orthogonally. The scale of the horizontally polarized interdigital dipole is 2*18, and the scale of the vertically polarized interdigital dipole is 2*18. The two co-polarized feed ports along the pitch plane are combined through an exponentially tapered feed balun and a one-to-two power splitter. The exponentially tapered feed balun can achieve the conversion from unbalanced feeding to balanced feeding. The end of the vertically polarized interdigital dipole extends vertically downward to extend the current path, ensure impedance matching, and reduce the impact of the truncation effect. The vertically extended portion of the vertically polarized dipole is supported by a dielectric block and placed above the first metal floor. The first metal floor 8 is located slightly below the center of the exponentially tapered feed balun, and a square hole 801 is opened inside it for passing the exponentially tapered feed balun. The first metal floor serves as the antenna's reflective floor. Ferrite absorbing material 7 is placed above it. This material reduces the impact of floor-reflected waves on the input impedance, simplifying impedance matching. The second metal floor serves as the metal ground for the one-to-two power splitter. The second dielectric plate is placed directly above it.

[0043] The present invention staggers vertically polarized interdigital dipoles along the elevation plane. That is, two adjacent vertically polarized dipoles have one column offset above the centerline and the other offset below it. When the number of array elements is sufficient, the vertically polarized interdigital dipoles can be considered to be centrally located in the elevation plane. Horizontally polarized interdigital dipoles are arranged along the center of the elevation plane. This centrally symmetrical placement achieves a low cross-polarization antenna design while ensuring an impedance bandwidth of 140.4% with a standing wave ratio of less than 2. Within a scanning angle range of ±52°, the cross-polarization ratio (cross-polarization (dB) minus main polarization (dB)) is less than -35dB for horizontal polarization and less than -27.5dB for vertical polarization. The minimum cross-polarization ratio within the band can reach -52.5dB.

[0044] In order to enable those skilled in the art to better understand the present invention, the present invention is described in detail below with reference to specific embodiments.

[0045] The application scenario of the embodiment of the present invention is long-distance communication or interference.

[0046] Reference Figure 1 , the simulation array model of the low cross-polarization tightly coupled phased array of the present invention is described. Figure 1 The array in the figure is a 2*18 linear array, where one antenna unit on each side is used as a dummy element to reduce the influence of the truncation effect. The actual fed array is a 2*16 linear array.

[0047] Reference Figure 2The simulation model of the periodic unit of the low cross-polarization tightly coupled phased array of the present invention is further described. The antenna is divided into three layers: the first layer where the first dielectric plate 1 is located, the second layer where the first metal floor 8 is located, and the third layer where the second metal floor 11 is located.

[0048] Reference Figure 3 , an exploded view of the periodic unit of the low cross-polarization tightly coupled phased array of the present invention is described in more detail. One periodic unit includes four horizontally polarized interdigital dipoles 2 and four vertically polarized interdigital dipoles 3. The horizontally polarized interdigital dipoles 2 are along the X-axis direction, and the vertically polarized interdigital dipoles 3 are along the Y-axis direction. The horizontally polarized interdigital dipoles 2 and the vertically polarized interdigital dipoles 3 have different sizes. The horizontally polarized interdigital dipoles 2 are printed on the upper layer of the first dielectric plate 1, and the vertically polarized interdigital dipoles 3 are printed on the lower layer of the first dielectric plate 1, and the horizontally polarized interdigital dipoles 2 and the vertically polarized interdigital dipoles 3 are placed orthogonally to each other. The end of the vertically polarized interdigital dipole 3 is connected to the vertical tapered extension part 4, and the lower part of the vertical tapered extension part 4 is bent inward and placed above the dielectric block 5, and the dielectric block 5 is located above the first metal floor 8. The exponentially tapered feed balun 6 is connected to the feed port of the dipole at the top and to the first output port 902 and the second output port 903 of the one-to-two power splitter 9 at the bottom. The one-to-two power splitter 9 is printed on the upper surface of the second dielectric plate 10, with its input port connected to the 50-ohm RF connector 12 and its output port connected to the exponentially tapered balun 6. The second dielectric plate 10 is located above the second metal floor 11. A circular through hole 1101 is provided inside the second metal floor 11 for installing the 50-ohm RF connector 12, and a square groove 1102 is provided to avoid the exponentially tapered feed balun 6. The horizontally polarized co-digital dipole 2 and the vertically polarized co-digital dipole 3 each have two feed ports on the elevation plane. The two ports along the elevation plane in the same polarization are combined through the exponentially tapered balun 6 and the one-to-two power splitter 9.

[0049] Reference Figure 4, the arrangement of the radiators of the periodic unit of the low cross-polarization tightly coupled phased array of the present invention is further described. The horizontally polarized co-digital dipole antenna unit 2 has four feeding ports in one periodic unit, namely the first feeding port 101, the second feeding port 102, the third feeding port 103, and the fourth feeding port 104, wherein the first feeding port 101 and the second feeding port 102 are located in the same column, the third feeding port 103 and the fourth feeding port 104 are located in the same column, and the four feeding ports are mirror-symmetrical along the center line L of the pitch plane; the vertically polarized co-digital dipole 3 has four feeding ports in one periodic unit, namely the first feeding port 101, the second feeding port 102, the third feeding port 103, and the fourth feeding port 104. There are also four feeding ports, namely the fifth feeding port 201, the sixth feeding port 202, the seventh feeding port 203, and the eighth feeding port 204, wherein the fifth feeding port 201 and the sixth feeding port 202 are located in the same column, the seventh feeding port 203 and the eighth feeding port 204 are located in the same column, the fifth feeding port 201 and the eighth feeding port 204 are at the same vertical distance from the center line L, and the sixth feeding port 202 and the seventh feeding port 203 are at the same vertical distance from the center line L.

[0050] Reference Figure 5 The following further illustrates a side view of a periodic unit of the low cross-polarization tightly coupled phased array of the present invention. The vertically polarized dipole's vertical extension 4 has a tapered structure, gradually widening from top to bottom. Below it is a dielectric block 5, sandwiched between the first dielectric plate 1 and the first metal floor 8. The dielectric block 5 prevents electrical connection to the first metal floor.

[0051] The following is a detailed description of the effects of this application in conjunction with simulation:

[0052] 1. Simulation conditions

[0053] Use High Frequency Structure Simulator simulation software to simulate Figure 1 The 2*18 one-dimensional linear array shown.

[0054] 2. Simulation content

[0055] Simulation 1: Figure 1 The low cross-polarization tightly coupled phased array shown in FIG6 is brought into the simulation software for simulation, and the curves of the active standing wave at the horizontal polarization port changing with frequency and scanning angle as shown in FIG6(a) and the curves of the active standing wave at the vertical polarization port changing with frequency and scanning angle as shown in FIG6(b) are obtained.

[0056] As shown in Figures 6(a) and 6(b), the standing wave of the low cross-polarization tightly coupled phased array of the present invention has a frequency range of 0.35 to 2 GHz below 3.5. This shows that the low cross-polarization tightly coupled phased array of the present invention has ultra-wideband characteristics.

[0057] Simulation 2: Figure 1 The low cross-polarization tightly coupled phased array shown in the figure is brought into the simulation software for simulation, and the cross-polarization ratio variation curve of the horizontally polarized array as shown in Figure 7 (a) and the cross-polarization ratio variation curve of the vertically polarized array as shown in Figure 7 (b) are obtained.

[0058] As shown in Figures 7(a) and 7(b), due to the symmetry of the horizontally polarized and vertically polarized dipoles about the centerline L, the low cross-polarization tightly coupled phased array of the present invention exhibits a low cross-polarization ratio within the operating frequency band. Within a scanning angle range of ±52°, the horizontal cross-polarization ratio is less than -35dB, and the vertical cross-polarization ratio is less than 27.5dB, achieving a minimum cross-polarization ratio of -52.5dB within the frequency band.

[0059] Simulation 3: Figure 1 The low cross-polarization tightly coupled phased array shown in the figure is brought into the simulation software for simulation, and the scanning pattern shown in Figure 8 is obtained. Figure 8 shows the scanning patterns of 0 degrees, 30 degrees, and 52 degrees at the two frequency points of 0.35 GHz and 2 GHz.

[0060] As can be seen from FIG8 , the low cross-polarization tightly coupled phased array of the present invention has good scanning performance at 0.35 GHz and 2 GHz.

[0061] The simulation results demonstrate that the low cross-polarization tightly coupled phased array of the present invention exhibits a low cross-polarization ratio and excellent impedance matching performance within the operating frequency band. Within a scanning angle range of ±52°, the cross-polarization ratio for horizontal polarization is less than -35dB, and the cross-polarization ratio for vertical polarization is less than -27.5dB, with the minimum cross-polarization ratio within the band reaching -52.5dB. The relative bandwidth for standing waves below 2 is 140.4%, demonstrating excellent broadband characteristics.

[0062] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present invention, and these modifications or replacements should all be included in the scope of protection of the present invention.

Claims

1. A one-dimensional tightly coupled phased array with low cross-polarization, characterized in that: It comprises a plurality of periodic units, each periodic unit comprising a horizontally polarized interdigital dipole (2), a vertically polarized interdigital dipole (3), a feeding structure, and a first metal floor (8); The horizontally polarized cochineal dipole (2) is printed on the upper layer of the first dielectric plate (1), and the vertically polarized cochineal dipole (3) is printed on the lower layer of the first dielectric plate (1), and the horizontally polarized cochineal dipole (2) and the vertically polarized cochineal dipole (3) are placed orthogonally to each other; the vertically polarized cochineal dipole (3) is along the Y-axis direction, and the end of the vertically polarized cochineal dipole (3) is connected to the vertical gradient extension part (4); the lower part of the vertical gradient extension part (4) is bent inward and placed above the dielectric block (5), and the dielectric block (5) is located above the first metal floor (8); The feeding ports of the horizontally polarized interdigital dipoles (2) are symmetrically distributed about the center line of the pitch plane; the feeding ports of the vertically polarized interdigital dipoles (3) are staggered on the center line of the pitch plane, that is, one column of two adjacent vertically polarized interdigital dipoles (3) is offset above the center line of the pitch plane, and the other column is offset below the center line of the pitch plane; The feeding structure is used to feed the horizontally polarized co-digital dipole (2) and the vertically polarized co-digital dipole (3); The first metal floor (8) is a reflection floor for the horizontally polarized co-digital dipole (2) and the vertically polarized co-digital dipole (3).

2. The one-dimensional tightly coupled phased array with low cross-polarization according to claim 1, characterized in that: The horizontally polarized interdigital dipole (2) and the vertically polarized interdigital dipole (3) have different sizes.

3. The one-dimensional tightly coupled phased array with low cross-polarization according to claim 1, characterized in that: The vertical gradually extending portion (4) gradually widens from top to bottom.

4. The one-dimensional tightly coupled phased array with low cross-polarization according to claim 1, characterized in that: The feeding structure comprises an exponentially tapered feeding balun (6) and a one-to-two power splitter (9), wherein the upper end of the exponentially tapered feeding balun (6) is connected to the feeding port of the horizontally polarized co-digital dipole (2) or the feeding port of the vertically polarized co-digital dipole (3), and the lower end is connected to the output port of the one-to-two power splitter (9).

5. The one-dimensional tightly coupled phased array with low cross-polarization according to claim 4, characterized in that: The one-to-two power splitter (9) is located on the second dielectric plate (10), and a second metal floor (11) is provided below the second dielectric plate (10).

6. The one-dimensional tightly coupled phased array with low cross-polarization according to claim 5, characterized in that: A circular through hole (1101) for installing a 50-ohm radio frequency connector (12) is provided on the second metal floor (11) to avoid a square groove (1102) of the exponential gradient feed balun (6).

7. The one-dimensional tightly coupled phased array with low cross-polarization according to claim 4, characterized in that: The first metal floor (8) is provided with a square hole (801) for passing the exponential gradient balun (6).

8. The one-dimensional tightly coupled phased array with low cross-polarization according to claim 1, characterized in that: It also includes a ferrite absorbing material (7), which is located above the first metal floor (8).

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