Tight coupling phased array antenna based on broadband efficient electromagnetic structure

Abstract

The invention belongs to the technical field of microwave antennas, and particularly provides a tight coupling phased-array antenna based on a broadband efficient electromagnetic structure. The antenna comprises a broadband matching structure (I) which is an electromagnetic metasurface structure loaded on a broadband efficient electromagnetic structure; the radiation structure (II) is a broadband efficient electromagnetic structure; the feed structure (III) comprises a coaxial line, a gradient microstrip feeder line and a double-Y balun; and a floor (III). According to the invention, the broadband efficient electromagnetic structure is applied to the tightly-coupled antenna, which is equivalent to introduction of three currents in one unit aperture, so that the defect electromagnetic environment that only one current exists in one aperture when a traditional dipole antenna is cut off as an array element is made up, an infinite continuous current sheet model can be better simulated, and the antenna performance is improved. And therefore, a larger bandwidth and a lower profile can be realized. And meanwhile, the wide-angle scanning capability of the array is further improved by introducing the metasurface wide-angle matching.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave antennas, and specifically provides a tightly coupled phased array antenna based on a broadband and efficient electromagnetic structure. Background Art

[0002] With the rapid development of wireless communication technology and radar systems, modern electronic systems have placed more stringent requirements on antenna performance, including ultra-wideband operation, wide-angle scanning range, miniaturized integrated design, and high-efficiency transmission. To improve information transmission rates, extend communication distances, and increase airspace coverage, ultra-wideband angular scanning phased array technology has become a research hotspot. However, traditional ultra-wideband phased array design methods have many limitations: Designing broadband elements first and then assembling the array increases the number of antenna elements, leading to increased coupling between elements and thus affecting the antenna's broadband performance. Increasing the spacing between elements can suppress mutual coupling, but it can also lead to grating lobes in the radiation pattern and increase the array size. Loading special structures between elements can suppress mutual coupling, but it complicates the phased array structure.

[0003] To address these issues, tightly coupled phased array antenna technology, based on Wheeler's infinite current sheet theory, has emerged. Tightly coupled phased array antennas employ an array-based design approach, mimicking the radiation efficiency of an infinite current sheet with a finite array element. They actively utilize and enhance the mutual coupling between elements to overcome the limitations of traditional element spacing, achieving ultra-wideband, wide scanning angles, and a low profile.

[0004] Currently, the radiating metal sheets of tightly coupled phased array antennas are typically dipoles. However, the lack of periodicity perpendicular to the array arrangement direction in a one-dimensional linear array significantly affects the array's performance. Broadband, high-efficiency electromagnetic structures, as a new type of radiating structure, provide periodic currents perpendicular to the array arrangement direction. This, to a certain extent, can better simulate infinite current sheets, thereby improving the performance of one-dimensional linear tightly coupled arrays. Therefore, research on broadband, tightly coupled phased array antennas based on high-efficiency electromagnetic structures is of great significance. Summary of the Invention

[0005] The goal of the present invention is to make up for the lack of the technical field of tightly coupled phased array antennas based on broadband and efficient electromagnetic structures, and to realize a phased array antenna that can achieve broadband and wide scanning angles.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] The present invention primarily consists of a wide-angle scanning matching layer, a broadband high-efficiency electromagnetic structure, a feed structure, and a metal floor. The broadband high-efficiency electromagnetic structure utilizes a tightly coupled array design, achieving broadband characteristics through strong coupling between elements. The wide-angle scanning matching layer is positioned on the upper surface of a dielectric substrate, while the broadband high-efficiency electromagnetic structure is positioned on the lower surface. The dielectric substrate isolates the two from each other and maintains a predetermined spacing. The introduction of the wide-angle scanning matching layer effectively improves the antenna's impedance matching performance during wide-angle scanning, significantly increasing the antenna's scanning range.

[0008] The feed structure utilizes a tapered microstrip line design, whose width varies continuously along the transmission direction. This achieves a smooth impedance transition from the feed port to the radiating element, effectively addressing the challenge of broadband impedance matching. A metal floor, positioned beneath the tapered microstrip line, not only provides electromagnetic shielding and back-radiation suppression but also effectively absorbs reflected waves through specifically positioned absorbing resistors, improving isolation between array elements.

[0009] The innovation of the present invention is:

[0010] 1. Through the coordinated design of the wide-angle scanning matching layer and the broadband high-efficiency electromagnetic structure, the antenna maintains good impedance matching characteristics within a wide frequency band. At the same time, it significantly expands the scanning angle range of the antenna and solves the problem of the traditional tightly coupled array antenna's performance dropping sharply when scanning at large angles.

[0011] 2. The design scheme combining a gradient microstrip line feeding structure with an absorbing resistor not only achieves broadband impedance matching, but also effectively suppresses the mutual coupling between units, improves the isolation of the array, and ensures the high efficiency characteristics of the antenna.

[0012] 3. The whole device is manufactured using PCB technology. The wide-angle scanning matching layer and broadband high-efficiency electromagnetic structure are printed on the upper and lower surfaces of the dielectric substrate respectively. It has a compact structure, simple process, low cost, easy mass production, and good engineering application value.

[0013] 4. By optimizing the electromagnetic parameters and geometric dimensions of each layer structure, the antenna achieves high efficiency and a stable radiation pattern within the operating frequency band, meeting the requirements of modern communication systems for high-performance antennas. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram of the overall structure of the present invention (including Ⅰ radiation structure and Ⅱ feeding structure from top to bottom);

[0015] Figure 2 Schematic diagram of the combination of the radiation structure and the feeding structure in the present invention;

[0016] Figure 3 is a front view of the antenna unit of the present invention;

[0017] Figure 4 1. It is a back view of the antenna unit of the present invention (showing the tapered microstrip feed line and the absorbing resistor);

[0018] Figure 5 A top view of the antenna unit of the present invention;

[0019] Figure 6 is a bottom view of the antenna unit of the present invention;

[0020] Figure 7 The directional patterns of the 1×8 array in the present invention at 2.75 GHz with E-plane end-fire and 30° and 50° scanning;

[0021] Figure 8 Schematic diagram of the change of active standing wave curve under the boundary of infinite array and 30° and 50° scanning on the E plane in the present invention. DETAILED DESCRIPTION

[0022] In order to make the objectives, technical solutions and innovations of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and examples.

[0023] Figure 1 This is the overall structure of the present invention, which includes a I radiation structure and a II feeding structure from top to bottom.

[0024] Figure 2 The feeding structure and radiation structure of the present invention are demonstrated. Figure 3 is its front view, Figure 4 is its back view, Figure 5 This is its top view. Figure 6 This is its bottom view.

[0025] Where 1 is the wide angle matching layer, and the side length of the square is W 10 =4.2mm, the spacing between patches W 11 =0.8mm, the distance between the patch and the edge is W 12 =0.4mm; 2 is a broadband high-efficiency electromagnetic structure, on which two opening structures are loaded. The loaded opening structures 2 are designed into two trapezoids. The long side W of the trapezoid 1 is 13 =12mm, short side W 14 = 2mm, height H4 = 10mm, the short side W of trapezoid 2 15 =1.3mm, long side W 16 = 22.3mm, height h5 = 24mm, the size of the introduced capacitance can be controlled by controlling the distance between the two inverted trapezoids and the size of the inverted trapezoids. 16 =3mm, the long side L of the coupling metal patch 17 =1mm, short side W19 =0.5mm, other parameters of broadband high-efficiency electromagnetic structure L 16 =22.5mm, W 17 =3.35mm, W 18 =1mm; 3 is a dielectric substrate connecting the wide-angle scanning matching layer and the broadband high-efficiency electromagnetic structure. The dielectric substrate 3 is a rectangular parallelepiped. The dielectric support 3 has a relative dielectric constant of 2.2, a relative magnetic permeability of 1, a loss tangent of 0.0009, and a long side L 15 =58mm, short side W1=30mm, height H1=3mm, dielectric substrate 3 fixes the feeding structure by embedding; 7 is the dielectric support of the feeding structure below the broadband high-efficiency electromagnetic structure, the thickness of the dielectric support 7 of the gradient structure is 0.762mm, and the height H3=25mm; 6 is the gradient microstrip feed line and its metal floor, Figure 3 Taking the front view as an example, the overall width of the metal floor is W5 = 2.6mm, L1 = 7mm, L2 = 8.1mm, L3 = 12.5mm, L4 = 7.93mm, L5 = 3.43mm, L6 = 6.6mm, W2 = 0.9mm, W3 = 2.6mm, and W4 = 1.4mm. The metal floor is integrated with absorbing resistors, which can effectively improve the isolation between array units. By adjusting the gradient size of the microstrip line, the impedance matching characteristics can be optimized; adjusting the position and resistance of the absorbing resistor can further improve the isolation performance. The gradient microstrip feeder can refer to the back view, and its parameters are: the first section impedance matching line W9 = 1.6mm, L7 = 4mm, the second section impedance matching line L8 = 2.18mm, L9 = 6.65mm, W8 = 1.15mm, L 10 =5mm, the third impedance matching line L 11 =5.79mm, W7=0.63mm, L 12 =5.5mm, L 13 =6.58mm, the fourth impedance matching line L 14 =2.8mm, L 15 =2.3mm, W6=0.34mm. The feed impedance increases from top to bottom, so that there is less reflected energy during the transmission process. 10 is the floor of the antenna, and the length of the floor is L 15 =58mm, width W1 =30mm. The function of the floor 10 is to suppress back radiation and improve antenna gain. 9 is the coaxial port of the antenna, which is used to feed energy to the antenna.

[0026] Figure 7The present invention demonstrates endfire E-plane beam scanning patterns of 30 and 50 degrees at 2.75 GHz using a 1×8 array. This demonstrates that the 1×8 array can achieve ±45-degree E-plane beam scanning with minimal gain loss. The profile height of the present invention is 0.072 times the low-frequency wavelength, achieving an extremely low profile compared to traditional all-metal Vivaldi antennas.

[0027] Figure 8 The active standing waves of the side-firing, E-plane 30- and 50-degree scanning of the tightly coupled phased array antenna based on the broadband high-efficiency electromagnetic structure under infinite boundary conditions are demonstrated. It can be seen that in the frequency band of 0.74GHz-3.75GHz, the active standing waves of the present invention are less than 3 when the side-firing and H-plane scanning are 45 degrees, achieving a 5.1:1 frequency octave bandwidth; in the frequency band of 0.74GHz-3.75GHz, the active standing waves of the present invention are less than 3 when the E-plane scanning is 45 degrees, achieving a 5.1:1 frequency octave bandwidth, which also meets the requirements for active standing waves of tightly coupled phased array antennas in engineering.

[0028] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A tightly coupled phased array antenna based on a broadband and efficient electromagnetic structure, comprising a radiating structure and a feeding structure, characterized in that: The radiation structure comprises a wide-angle matching layer (1) located at the top of the overall structure for improving the scanning angle, a broadband high-efficiency electromagnetic structure (2), a dielectric substrate (3) supporting the wide-angle matching layer, and a dielectric substrate (4) supporting the broadband high-efficiency electromagnetic structure; a metal short-circuit column (5) for improving matching, a microstrip line and a matching balun (6) for achieving impedance transformation, a dielectric substrate (7) supporting a feeding network, a resistor (8) for suppressing reflection, a coaxial feeding port (9), and a floor (10) for suppressing back radiation.

2. The radiation structure of the tightly coupled phased array antenna based on a broadband and efficient electromagnetic structure according to claim 1 is characterized by: The broadband high-efficiency electromagnetic structure (2) is connected via a dielectric substrate (3); two trapezoidal opening structures (equivalent to two short-circuited transmission lines, capable of supporting TEM wave transmission) are formed on the structure (2) by etching; the wide-angle scanning matching layer (1) is arranged on the upper surface of the dielectric substrate (3); the broadband high-efficiency electromagnetic structure (2) is arranged on the lower surface of the dielectric substrate (3); the wide-angle scanning matching layer (1) and the broadband high-efficiency electromagnetic structure (2) are isolated from each other by the dielectric substrate (3) and maintain a predetermined distance, thereby improving the phased array scanning angle performance.

3. The feeding structure of the tightly coupled phased array antenna based on a broadband high-efficiency electromagnetic structure according to claim 1, characterized in that: The width of the gradient microstrip line (6) is designed to be gradient along the transmission direction, which can realize continuous impedance transformation, thereby realizing broadband impedance matching; the metal floor (10) is arranged below the gradient microstrip line, and is used to provide electromagnetic shielding and suppress back radiation, thereby improving antenna gain; the resistance element (8) is arranged at a predetermined position on the metal floor, and is used to absorb reflected wave energy and improve the isolation between ports; the coaxial line (9) is connected to the microstrip matching network (6) to realize energy feeding, and the floor (10) is used to suppress back radiation and improve gain.

4. The tightly coupled phased array antenna based on a broadband and efficient electromagnetic structure according to claim 1, characterized in that: The antenna unit has a lateral dimension of 58 mm×30 mm and a cross-sectional height of 29 mm.

5. The radiation structure of the tightly coupled phased array antenna based on a broadband and efficient electromagnetic structure according to claim 1 or claim 2, characterized in that: The dielectric substrate (3) connecting the broadband high-efficiency electromagnetic structure and the wide-angle matching layer has a relative dielectric constant of 2.2, a relative magnetic permeability of 1, a loss tangent of 0.0009, a lateral size of 58 mm×30 mm, and a height of 3 mm.

6. The broadband high-efficiency electromagnetic structure according to claim 1 or claim 2, characterized in that: The opening structure (2) loaded on the butterfly structure is designed in an inverted trapezoidal shape. The height of trapezoid 1 is 10 mm, the short side is 2 mm, and the long side is 12 mm. The height of trapezoid 2 is 24 mm, the short side is 1.3 mm, and the long side is 22.3 mm. A rectangular opening of 24 mm*3 mm is loaded on the long side of trapezoid 2.

7. The feeding structure of the tightly coupled phased array antenna based on a broadband high-efficiency electromagnetic structure according to claim 1 or claim 3, characterized in that: The microstrip line (6) with a gradually changing width is in a serpentine structure, and the widths of the grooves from bottom to top are 0.63 mm, 1.15 mm, and 1.6 mm, respectively, and the lengths of the grooves from bottom to top are 17.235 mm, 21.425 mm, and 4 mm, respectively. The width of the metal ground on the back is 2.6mm.

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