Ultra-wideband dual-polarized antenna

Abstract

The invention discloses a tightly-coupled ultra-wideband dual-polarized antenna, and belongs to the technical field of antennas. The antenna is composed of a plurality of antenna units which are arranged in a two-dimensional period. The antenna unit comprises a wide-angle medium matching layer, an antenna radiation layer, a first supporting layer, a resistance type frequency selection surface layer, a second supporting layer and a metal floor layer which are sequentially arranged from top to bottom, and further comprises two feed baluns which are vertically arranged. Wherein the antenna radiation layer adopts an interdigital tight coupling dual-polarization dipole as a radiator. By introducing composite structures such as the wide-angle dielectric matching layer, the interdigital tight coupling dipole and the resistive frequency selective surface, the characteristics of ultra wide band, low profile and high gain are realized at the same time, the impedance matching performance of the antenna under a wide scanning angle is optimized, and the edge truncation effect and the grating lobe problem are effectively inhibited.

Description

Technical Field

[0001] The present invention belongs to the field of antenna technology, and specifically relates to a tightly coupled ultra-wideband dual-polarized antenna. More specifically, in response to the urgent needs of ultra-wideband, high gain, high integration and miniaturization of array antennas, a new interdigital tightly coupled antenna loaded with a resistive frequency selective surface (RFSS) and a wide-angle dielectric matching layer is proposed. Background Art

[0002] Tightly coupled antennas are a type of phased array antenna technology that leverages the strong mutual coupling between array elements to achieve ultra-wideband and low-profile characteristics. They are widely used in military radar, electronic warfare, 5G / 6G communications, satellite communications, and medical imaging. Compared to traditional microstrip antennas, they offer significant advantages in bandwidth, profile height, and scanning performance, but require high-precision manufacturing processes.

[0003] An interdigital tightly coupled antenna is a broadband antenna designed based on the tight coupling principle. Its core structure consists of multiple parallel metal finger electrodes, with adjacent electrodes having opposite polarity, forming a strong capacitive coupling. The spacing between the electrodes is much smaller than the operating wavelength to achieve the tight coupling effect. The antenna typically uses a high-dielectric constant or low-loss dielectric substrate to support the interdigitated structure and is fed via a coplanar waveguide, microstrip line, or coaxial line to ensure a 180° phase difference between adjacent electrodes, thereby stimulating a symmetrical radiation pattern. Some designs also load an impedance matching layer above the radiating surface, such as a metamaterial or gradient dielectric, to further broaden the bandwidth.

[0004] Resistive frequency selective surfaces (RFSS) are artificial electromagnetic structures that selectively control electromagnetic waves by introducing resistive materials into traditional frequency selective surfaces. They are widely used in stealth weaponry, microwave darkroom construction, and anti-interference applications in communication systems. Unlike ordinary metal FSS, RFSS embeds resistive materials with specific square resistance values, such as carbon films, conductive polymers, or indium tin oxide films, into a periodic unit structure. This allows RFSS to combine frequency selection with electromagnetic energy loss characteristics, offering significant advantages in broadband performance, angular stability, and stealth. The operating principle of RFSS is based on the synergistic effect of the ohmic loss effect of the resistive material and the resonant characteristics of the periodic structure, enabling precise control of the transmission, reflection, or absorption of electromagnetic waves in specific frequency bands. When an electromagnetic wave is incident, the loss characteristics of the resistive material are mainly reflected in the low-frequency band, the resonant characteristics of the periodic structure are exhibited in the high-frequency band, and the composite effect of the two is exhibited in the intermediate frequency band.

[0005] A wide-angle dielectric matching layer is a special dielectric structure used to improve the wide-angle incidence performance of antennas or electromagnetic systems. This is achieved by loading a dielectric layer with a specific dielectric constant distribution on the surface of the radiating element. This matching layer is usually composed of multiple layers of gradient dielectric constant materials or artificial electromagnetic metamaterials. Its core design concept is to compensate for the phase difference and impedance mismatch generated at different incident angles by controlling the propagation path and phase distribution of electromagnetic waves in the medium. The thickness and dielectric constant distribution of the matching layer are precisely calculated and optimized, enabling it to maintain stable impedance matching characteristics over a wide angle range. In practical applications, wide-angle dielectric matching layers often use honeycomb structures, foam materials, or periodic artificial structures to achieve the required equivalent dielectric constant, and control the propagation characteristics of electromagnetic waves by adjusting the unit size and arrangement. Summary of the Invention

[0006] To address the problems of existing ultra-wideband antennas, such as limited impedance matching bandwidth, high profile height, and insufficient wide-angle scanning performance, the present invention provides an ultra-wideband dual-polarized antenna. By incorporating a composite structure consisting of a wide-angle dielectric matching layer, interdigitated tightly coupled dipoles, and a resistive frequency selective surface, the present invention simultaneously achieves ultra-wideband, low profile, and high gain characteristics. It also optimizes the antenna's impedance matching performance over a wide scanning angle, effectively suppressing edge truncation and grating lobe issues.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] An ultra-wideband dual-polarized antenna, comprising a plurality of antenna units arranged in a two-dimensional periodic manner, wherein the antenna units comprise a wide-angle dielectric matching layer, an antenna radiation layer, a first support layer, a resistive frequency selective surface layer, a second support layer, and a metal floor layer, arranged sequentially from top to bottom, and further comprising two vertically placed feed baluns;

[0009] The wide-angle dielectric matching layer includes a first dielectric substrate and a matching patch provided on its upper surface, and is used to improve the antenna impedance characteristics at a wide scanning angle;

[0010] The antenna radiation layer includes a second dielectric substrate and an interdigital tightly coupled dual-polarized dipole disposed on its upper surface; the interdigital tightly coupled dual-polarized dipole includes a first dipole and a second dipole having identical structures and arranged orthogonally; the ends of the first dipole and the second dipole are loaded with bent metal patches, and the bent metal patches loaded on the first dipole respectively form an interdigital coupling structure with the bent metal patches loaded on the two intersecting second dipoles to enhance the mutual coupling effect between the antenna units;

[0011] The resistive frequency selective surface layer includes a third dielectric substrate and an impedance material thin film patch provided on its upper surface, which is used to eliminate the radiation zero point caused by floor reflection and improve the in-band gain;

[0012] The metal floor layer is used to suppress back radiation;

[0013] Two rectangular holes are opened on the antenna radiation layer, the first supporting layer, the resistive frequency selective surface layer, the second supporting layer and the metal floor layer, so as to allow two feeding baluns with mutually perpendicular surface normals to pass through and feed the interdigital tightly coupled dual-polarized dipole of the upper layer.

[0014] Furthermore, a coupling patch is provided on the lower surface of the second dielectric substrate, and the coupling patch is located directly below the interdigital coupling structure to further enhance the mutual coupling effect between the antenna units.

[0015] Furthermore, the resistive film patch is a square ring-shaped patch, and the outer side length of the square ring-shaped patch is the same as the period of the antenna unit.

[0016] Furthermore, the dipole arms of the first dipole and the second dipole are of square structure; the opposite vertices of the two dipole arms are cut at angles and used to connect to the feed balun; the bent metal patch is loaded on two sides that are not adjacent to the feed balun.

[0017] Furthermore, the matching patch includes a cross-shaped patch arranged at the center and eight rectangular patches arranged parallel to two arms of the cross-shaped patch. The matching patch as a whole has a 90° rotationally symmetrical structure.

[0018] Furthermore, the feeding balun includes a fourth dielectric substrate arranged vertically, a rectangular feeding line arranged on its front side, and a gradient feeding line arranged on its back side, for achieving impedance matching; wherein, a gap is left between the feeding balun and the rectangular opening of the metal floor layer, and the feeding balun is not directly connected to the metal floor layer.

[0019] Furthermore, the outermost units of the antenna are set as dummy elements to suppress the finite array edge truncation effect.

[0020] Furthermore, the first supporting layer and the second supporting layer are foam supporting layers.

[0021] Beneficial effects of the present invention:

[0022] 1. This invention achieves ultra-wideband impedance matching (VSWR < 3) in the 2-18 GHz frequency band through the collaborative design of interdigitated tightly coupled dipoles and resistive frequency selective surfaces. At the same time, the RFSS resistive frequency selective surface is used to eliminate radiation nulls caused by floor reflections, significantly improving in-band gain.

[0023] 2. The present invention adopts a wide-angle dielectric matching layer and a low-profile interdigital structure, so that the antenna maintains stable radiation characteristics under a wide scanning angle of ±45°, and the overall cross-sectional height of the array is only 0.1λ of the wavelength of the lowest operating frequency, meeting the requirements of device miniaturization.

[0024] 3. The antenna array composed of antenna units of the present invention can effectively suppress the grating lobe and edge truncation effects of large-scale arrays through dummy element layout and gradient balun integrated feeding design. The measured sidelobe level of the radiation pattern is lower than -15dB, and the maximum gain reaches 20.87dBi. It is suitable for high-precision beam control scenarios in complex electromagnetic environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. It should be noted that the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 This is a schematic diagram of the overall structure of the antenna unit provided by an embodiment of the present invention.

[0027] Figure 2 Schematic diagram of a wide-angle dielectric matching layer provided by an embodiment of the present invention.

[0028] Figure 3 A top view of the antenna radiation layer provided in an embodiment of the present invention.

[0029] Figure 4 A three-dimensional schematic diagram of the antenna radiation layer provided in an embodiment of the present invention.

[0030] Figure 5 A three-dimensional schematic diagram of a resistive frequency selective surface layer provided by an embodiment of the present invention.

[0031] Figure 6 A top view of a resistive frequency selective surface layer provided by an embodiment of the present invention.

[0032] Figure 7 Schematic diagram of the metal floor layer provided by an embodiment of the present invention.

[0033] Figure 8 Schematic diagram of a feed balun provided in an embodiment of the present invention.

[0034] Figure 9 Result diagram of the radiation pattern of the antenna unit in the embodiment of the present invention.

[0035] Figure 101 is a diagram showing the simulation results of the voltage standing wave ratio of the antenna unit in the 2-18 GHz operating frequency band according to an embodiment of the present invention.

[0036] Figure 11 This is a diagram of experimental results obtained by actual measurement of 10×10 array processing in an embodiment of the present invention.

[0037] Explanation of reference numerals: 1-wide-angle dielectric matching layer, 10-first dielectric substrate, 11-outer rectangular patch, 12-inner rectangular patch, 13-cross patch;

[0038] 2-antenna radiation layer, 20-second dielectric substrate, 21-first dipole, 22-second dipole, 23-interdigital tight coupling structure, 24-first rectangular hole, 25-second rectangular hole, 26-parasitic coupling patch;

[0039] 3-resistive frequency selective surface layer, 30-third dielectric substrate, 31-first rectangular hole, 32-second rectangular hole, 33-square ring resistor film;

[0040] 4-metal floor layer, 40-copper metal ground plate, 41-first rectangular hole, 42-second rectangular hole;

[0041] 5-first feeding balun, 50-fourth dielectric, 51-tapered microstrip transmission line, 52-microstrip transmission line with characteristic impedance of 50Ω, 53-coaxial feeding port;

[0042] 6- Second balun feeding structure. DETAILED DESCRIPTION

[0043] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0044] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0045] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or to implicitly indicate the quantity of the technical features indicated. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features.

[0046] This invention is funded by the National Key Laboratory of Electromagnetic Information Control and Effects. This embodiment provides an ultra-wideband dual-polarized antenna unit, such as Figure 1 As shown, the antenna comprises, from top to bottom, a wide-angle dielectric matching layer, an antenna radiating layer, a first foam support layer, a resistive frequency selective surface layer, a second foam support layer, and a metal floor layer. It also includes two vertically placed feed baluns. The overall cross-sectional height of the antenna unit is 15 mm, corresponding to 0.1λ of the lowest operating frequency wavelength, and the unit period is 9 mm × 9 mm.

[0047] The wide-angle dielectric matching layer, such as Figure 2 As shown, it includes a first dielectric substrate and a matching patch arranged on its upper surface, which is used to improve the antenna impedance characteristics under a wide scanning angle so that the voltage standing wave ratio of the antenna is less than 3 under a scanning angle of ±45°.

[0048] The first dielectric substrate is Rogers RO4350 with a side length of 9 mm and a thickness of 2 mm, and a dielectric constant of 3.66.

[0049] The matching patch includes a cross-shaped patch arranged at the center, and four inner rectangular patches and four outer rectangular patches arranged parallel to the two arms of the cross-shaped patch. The outer rectangular patch is located at the center of the four sides of the first dielectric substrate, close to the edge of the substrate, and has a length and width of 2.0 mm and 1.0 mm respectively. The inner rectangular patches are arranged 1.25 mm from the center of the outer rectangular patch to the first dielectric substrate, and have a length and width of 2.0 mm and 1.0 mm respectively. The cross-shaped patch is located at the center of the first dielectric substrate and is a square with a side length of 2.0 mm. The four corners of the cross are each hollowed out into a 0.5 mm square shape.

[0050] The antenna radiation layer, such as Figure 3 and Figure 4 As shown, it includes a second dielectric substrate and an interdigital tightly coupled dual-polarization dipole arranged on its upper surface, and a coupling patch arranged on its lower surface.

[0051] The second dielectric substrate is Rogers RT / duroid 5880 with a side length of 9 mm and a thickness of 0.508 mm.

[0052] The interdigital tightly coupled dual-polarized dipole comprises a first dipole and a second dipole of identical structure and orthogonal arrangement; the dipole arms of the first dipole and the second dipole are square metal patches with a side length of 2.7 mm; in one antenna unit, the first dipole and the second dipole each comprise a complete square metal patch dipole arm and two incomplete dipole arms, and the incomplete dipole arm and the adjacent unit form a complete dipole arm, such as Figure 3 As shown, the incomplete dipole arm has a triangular shape with a base length of 4 mm and a height of 1.8 mm.

[0053] The ends of the first dipole and the second dipole are loaded with bent metal patches. The bent metal patches loaded on the first dipole respectively form an interdigital coupling structure with the bent metal patches loaded on the two intersecting second dipoles to enhance the mutual coupling effect between antenna units. The interdigital structure has a length of 1 mm, a width of 0.25 mm, an interdigital gap of 0.1 mm, and an overall square shape of 1.35 mm × 1.35 mm.

[0054] The coupling patch is located directly below the interdigital coupling structure and has a side length of 6 mm.

[0055] The resistive frequency selective surface layer, such as Figure 5 and Figure 6 As shown, it includes a third dielectric substrate and a resistive film patch arranged on its upper surface, which is used to eliminate the radiation zero point caused by floor reflection, improve the in-band gain, cover the antenna standing wave ratio convex band (12.5GHz~17.5GHz), and realize the optimization of the S11 parameters in the full frequency band.

[0056] The third dielectric substrate is Rogers 5880 with a side length of 9 mm and a thickness of 0.508 mm, and a relative dielectric constant of 2.2.

[0057] The resistor film patch is a square ring-shaped film with an outer ring side length of 9mm, which is consistent with the side length of the substrate. The inner ring side length is 7mm, the film width is 2mm, and its characteristic impedance is 50Ω.

[0058] The metal floor layer, such as Figure 7 As shown, it is used to suppress back radiation; its size is 9mm×9mm×0.508mm, and its relative dielectric constant is 1.

[0059] Two rectangular holes are provided on the antenna radiation layer, the first support layer, the resistive frequency selective surface layer, the second support layer and the metal floor layer, for allowing two feed baluns with mutually perpendicular surface normals to pass through to feed the interdigital tightly coupled dual-polarized dipole of the upper layer; wherein, the specific length × width dimensions of the rectangular holes of the antenna radiation layer, the first support layer, the resistive frequency selective surface layer and the second support layer are 1.9mm × 0.608mm, the distance between the right side of the first rectangular hole and the right edge of the substrate is 2mm, and the distance between the lower side and the lower edge of the substrate is 1.76mm, and the second rectangular hole is symmetrical to the first rectangular hole along the diagonal of the substrate; the rectangular hole of the metal floor layer is larger than the rectangular holes of other layers so that it does not contact the feed balun.

[0060] The feed balun, such as Figure 8As shown, it includes a vertically arranged fourth dielectric substrate and a rectangular feeder arranged on its front side and a gradient feeder arranged on its back side, achieving 50Ω impedance matching and high power carrying capacity.

[0061] The fourth dielectric substrate is Neltec NH9348 with a size of 1.8 mm×0.508 mm×13 mm and a relative dielectric constant of 3.48.

[0062] The rectangular feed line is a 50Ω impedance microstrip line with a line width of 0.34mm. The width of the gradient feed line gradually changes from 1.5mm to 0.336mm from bottom to top. The expression of the gradient curve is X = 0.75e -0.115Z In practical applications, the coaxial feed port is connected to a coaxial probe with a 50Ω impedance to introduce the feed source.

[0063] The thicknesses of the first foam support layer and the second foam support layer are 3.584 mm and 5.4 mm respectively.

[0064] See also Figure 9 and Figure 10 , is the radiation performance simulation result of the antenna unit of this embodiment; Figure 9 (a) with Figure 9 (b) is the radiation pattern of the antenna at 2GHz with phi = 0° and 90°, Figure 9 (c) with Figure 9 (d) is the radiation pattern of the antenna at 10 GHz with phi = 0° and 90°. Figure 9 (e) with Figure 9 (f) shows the antenna's radiation pattern at 18 GHz with phi = 0° and 90°. It can be seen that in the two typical directions of phi = 0° and phi = 90°, the antenna's gain in the 2 GHz to 18 GHz frequency band shows a uniform growth trend from -14.96 dBi to 4.9 dBi. Figure 10 This is the voltage standing wave ratio simulation result of the antenna unit of this embodiment in the 2-18 GHz operating frequency band. It can be seen that when the E-plane and H-plane scanning angles reach 45°, the voltage standing wave ratio of the antenna unit in the 2 GHz to 18 GHz frequency band is less than 3, and the antenna unit can achieve a ±45° scanning characteristic.

[0065] The above antenna units are used to form a 10×10 array, and the outermost circle of antenna units are set as dummy elements. Figure 11 (a) is the antenna radiation performance test result of the antenna array in the 6 GHz operating frequency band. Figure 11 (b) is the antenna radiation performance test result of the antenna array in the 10 GHz operating frequency band. Figure 11(c) shows the antenna radiation performance test results of the antenna array in the 18 GHz operating frequency band. It can be seen that the antenna array has good directivity. Its maximum gain at the typical frequencies of 2 GHz, 10 GHz, and 18 GHz is greater than 10 dBi, and its sidelobes are small, indicating that the array as a whole has good performance.

Claims

1. An ultra-wideband dual-polarized antenna, comprising a plurality of antenna units arranged in a two-dimensional periodic pattern, characterized in that: The antenna unit includes a wide-angle dielectric matching layer, an antenna radiation layer, a first support layer, a resistive frequency selective surface layer, a second support layer, and a metal floor layer, which are arranged in sequence from top to bottom, and also includes two vertically placed feed baluns; The wide-angle dielectric matching layer includes a first dielectric substrate and a matching patch provided on its upper surface, and is used to improve the antenna impedance characteristics at a wide scanning angle; The antenna radiation layer includes a second dielectric substrate and an interdigital tightly coupled dual-polarized dipole disposed on its upper surface; the interdigital tightly coupled dual-polarized dipole includes a first dipole and a second dipole having identical structures and arranged orthogonally; the ends of the first dipole and the second dipole are loaded with bent metal patches, and the bent metal patches loaded on the first dipole respectively form an interdigital coupling structure with the bent metal patches loaded on the two intersecting second dipoles to enhance the mutual coupling effect between the antenna units; The resistive frequency selective surface layer includes a third dielectric substrate and an impedance material thin film patch provided on its upper surface, which is used to eliminate the radiation zero point caused by floor reflection and improve the in-band gain; The metal floor layer is used to suppress back radiation; Two rectangular holes are opened on the antenna radiation layer, the first supporting layer, the resistive frequency selective surface layer, the second supporting layer and the metal floor layer, so as to allow two feeding baluns with mutually perpendicular surface normals to pass through and feed the interdigital tightly coupled dual-polarized dipole of the upper layer.

2. The ultra-wideband dual-polarization antenna according to claim 1, wherein: A coupling patch is provided on the lower surface of the second dielectric substrate, and the coupling patch is located directly below the interdigital coupling structure to further enhance the mutual coupling effect between antenna units.

3. The ultra-wideband dual-polarization antenna according to claim 2, wherein: The dipole arms of the first dipole and the second dipole are of square structure; the opposite vertices of the two dipole arms are cut at angles and used to connect to the feeding balun; the bent metal patch is loaded on two sides that are not adjacent to the feeding balun.

4. The ultra-wideband dual-polarization antenna according to claim 3, wherein: The resistor film patch is a square ring patch, and the outer side length of the square ring patch is the same as the period of the antenna unit.

5. An ultra-wideband dual-polarization antenna according to claim 3 or 4, characterized in that: The matching patch includes a cross-shaped patch arranged at the center and eight rectangular patches arranged parallel to the two arms of the cross-shaped patch. The matching patch as a whole has a 90° rotationally symmetrical structure.

6. The ultra-wideband dual-polarization antenna according to claim 5, wherein: The feeding balun includes a fourth dielectric substrate arranged vertically, a rectangular feeding line arranged on its front side, and a gradient feeding line arranged on its back side, for achieving impedance matching. A gap is left between the feeding balun and the rectangular opening of the metal floor layer, and the feeding balun is not directly connected to the metal floor layer.

7. The ultra-wideband dual-polarization antenna according to claim 6, wherein: The first supporting layer and the second supporting layer are foam supporting layers.

8. The ultra-wideband dual-polarization antenna according to claim 6, wherein: The outermost units of the antenna are set as dummy elements to suppress the finite array edge truncation effect.

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