Conformal leaky-wave antenna

Abstract

The invention discloses a conformal leaky-wave antenna, and belongs to the technical field of microwave device communication. According to the invention, the problems of insufficient conformal adaptive capability, poor stability, poor beam scanning capability and the like of the conformal leaky-wave antenna are solved. The upper surface of the upper PI substrate is etched by flexible copper foil and is provided with a Vivaldi unit and metal branch knot combined structure periodically distributed on the outer side of an SSPP transmission line in a staggered mode, the lower surface of the lower ABS substrate is completely covered with a metal grounding layer, and a closed guided wave channel is formed. When a radio frequency signal is input from a feed port, electromagnetic waves are spread along the wave guide structure in the PI substrate, directional radiation is realized through energy leakage of periodic metal branch gaps, and meanwhile, the antenna can realize stress-free conformal on a curved surface carrier by utilizing the excellent flexibility characteristic of a PI material; and the periodic design of the radiation structure and the effect of Vivaldi coupling enable the wave beam to realize continuous frequency sweeping from-71 degrees to 42 degrees.

Description

Technical Field

[0001] This invention relates to a conformal leaky wave antenna, belonging to the field of microwave device communication technology. Background Technology

[0002] Leaky wave antennas are high-frequency devices that achieve continuous electromagnetic wave radiation based on a traveling wave structure. With their wide bandwidth and beam frequency scanning characteristics, they are widely used in 5G / 6G communications, high-resolution radar, satellite communication on the move, and conformal communication for aircraft. Existing leaky wave antennas are mainly implemented using structures such as metallic waveguides, planar waveguides (microstrip / coplanar waveguides), substrate integrated waveguides (SIW), or artificial electromagnetic metamaterials. Metal waveguide-type leaky antennas have the advantages of high mechanical strength and low transmission loss, but they are limited by their three-dimensional closed structure, making them bulky and costly to manufacture. They are also difficult to integrate with planar circuits and cannot meet the conformal requirements of curved carriers. Planar waveguide-type leaky antennas have the characteristics of low profile, easy manufacturing, and good integration, but their open structure leads to severe parasitic mode interference in the high-frequency band, high loss, and difficulty in controlling radiation efficiency. Substrate-integrated waveguides and artificial electromagnetic metamaterial-based leaky antennas can achieve both low loss and integration, or extend the beam scanning range, but they are limited by the complexity of structural design and manufacturing process. The former has insufficient conformal adaptation capability, and the latter is difficult to guarantee in terms of structural consistency and electromagnetic stability during mass production, and the cost is also high.

[0003] Polyimide (PI) is a high-performance polymer material that combines excellent flexibility with stable physicochemical properties. As a core substrate material in the field of flexible electronics, its molecular chain structure exhibits good mechanical toughness and chemical stability. When bent, folded, or bonded to curved carriers, it can maintain structural integrity and dielectric consistency, thereby achieving conformal adaptation of antennas to complex curved carriers. This characteristic makes it suitable for the design of conformal leaky wave antennas. Compared with traditional structures such as metal waveguides, rigid microstrips, or substrate integrated waveguides, conformal leaky wave antennas based on PI materials have many advantages, including low profile, lightweight, strong mechanical compatibility, wide operating frequency coverage (from microwave to millimeter wave), and excellent environmental adaptability, making them particularly suitable for curved carrier scenarios such as aircraft, satellites, and smart wearable devices. However, existing PI-based conformal leaky wave antennas mostly adopt a single-period structure or a simple planar extension design, resulting in insufficient beam scanning continuity, poor control of high-frequency radiation loss, and difficulty in precisely controlling the consistency of electromagnetic performance in the conformal state, which seriously limits their practical application value in high-precision communication and radar systems. Summary of the Invention

[0004] This invention addresses the problems of insufficient conformal adaptation capability, poor stability, and poor beam scanning capability of existing conformal leaky wave antennas by providing a conformal leaky wave antenna.

[0005] The technical solution of the present invention: One objective of this invention is to provide a conformal leaky wave antenna, which is composed of a periodically arranged array of units. The array of units includes a PI substrate, a leaky wave radiation structure etched on the upper surface of the PI substrate, an ABS substrate tightly attached to the lower surface of the PI substrate, and a metal ground layer tightly attached to the lower surface of the ABS substrate.

[0006] Further defining the leakage radiation structure, it includes a gradient feed structure, an SSPP transmission line structure, and Vivaldi radiation elements. The gradient feed structure is located at both ends of the SSPP transmission line structure, and the Vivaldi radiation elements are periodically and alternately distributed on both sides of the SSPP transmission line structure.

[0007] To further define it, the SSPP transmission line structure includes two mirror-distributed SSPP transmission line units, each of which includes a metal conductor strip and periodically distributed metal stubs located on one side of the metal conductor strip.

[0008] Furthermore, the metal stubs of the SSPP transmission line unit are periodically serrated, with a width of w4 and a spacing of l3. The metal stubs located in the middle of the metal conductor are all the same length, l2, while the lengths of the three metal stubs on both sides gradually change, from the inside out, being l6, l5, and l4, respectively, with l6 > l5 > l4.

[0009] Further specified, the metal stub portions of the two SSPP transmission line units are adjacent and have a gap.

[0010] Further defining the gradient power supply structure, it consists of two gradient rectangular rings located at both ends of the SSPP transmission line unit, with the two gradient rectangular rings being mirror-symmetrical.

[0011] Furthermore, the gradient rectangular ring consists of five closely adjacent rectangular metal patches with outer dimensions of l7×w5, l9×w5, l11×w5, l13×w5 and l15×w6 respectively, and inner dimensions of l8×w8, l10×w8, l12×w8, l14×w8 and l16×w9 respectively, and one rectangular metal patch with a size of l17×w7. The rectangular metal patches are coaxially arranged, and l7 > l9 > l11 > l13 > l15 = l17.

[0012] Further specifying, the Vivaldi radiating element is a bullhorn-shaped metal patch with an included angle of 20° and a width of w3.

[0013] Furthermore, the tips of the horn-shaped metal patch are connected to the metal conductor strip of the SSPP transmission line unit.

[0014] Furthermore, the distance between the tips of adjacent horn-shaped metal patches on the same side of the SSPP transmission line structure is 5.9 mm.

[0015] Further specified, the PI substrate, the leakage radiation structure, the ABS substrate and the metal ground layer are bonded together by a flexible adhesive to form an integral conformal structure, and the leakage radiation structure and the metal ground layer are electrically connected through metal vias.

[0016] Further specified, the PI substrate, ABS substrate and metal ground layer have the same size, and the thickness of the leakage radiation structure is t, the thickness of the PI substrate is h1 and the thickness of the ABS substrate is h2.

[0017] Beneficial effects: This invention provides a PI-based artificial plasmon frequency-scannable conformal leaky wave antenna. This conformal leaky wave antenna is based on a PI flexible dielectric substrate and a periodically perturbed waveguide structure. The overall structure consists of a radiating metal layer, a PI dielectric substrate, an ABS dielectric substrate, and a metal ground layer. These four layers are bonded together by a flexible adhesive layer to form an integrated conformal structure that can closely fit the surface of a curved carrier. Furthermore, a leaky wave radiating structure is etched onto the upper surface of the upper PI dielectric substrate with a thickness of h1 using a flexible copper foil with a thickness of t. A periodic Vivaldi unit and metal stub combination structure is introduced, where the metal stubs are symmetrically distributed on both sides of the slots, and the Vivaldi radiating units are periodically staggered on the outside of the SSPP transmission line. The lower surface of the lower ABS dielectric substrate with a thickness of h2 completely covers the metal ground layer. The upper radiating structure and the lower ground layer are electrically connected through metal vias, forming a closed waveguide channel. When an RF signal is input from the feed port, the electromagnetic wave propagates along the waveguide structure in the PI substrate. Directional radiation is achieved through energy leakage via the periodic metal stub gaps. Utilizing the excellent flexibility of the PI material, the antenna can achieve stress-free conformal performance on curved surfaces with radii of 100mm, 60mm, and 40mm. Furthermore, the periodic design of the radiating structure and Vivaldi coupling enable continuous beam scanning from -71° to 42°. To further achieve wideband impedance matching and mode stability in the conformal state, the first three metal stubs adopt a gradient design. The metal stubs on both sides of the gap have a length of l2 and a width of w4, arranged periodically at a spacing of l3, with the stub ends also employing the aforementioned gradient transition design. This design allows the RF signal to propagate in a fast-wave mode with low loss within the closed waveguide structure. Periodic perturbations achieve efficient energy leakage and wide-angle beam scanning. Simultaneously, the flexible PI substrate and integrated composite structure ensure reliable conformal performance of the antenna on curved surfaces, effectively solving the problems of poor conformal adaptability and high high-frequency loss inherent in traditional leaky wave antennas. Furthermore, the conformal leaky wave antenna has an array length of l1 and a width of w1, which can be flexibly expanded according to the actual carrier size, and directly integrated into the curved surfaces of clothing and equipment to achieve seamless communication. It can also be manufactured using mature processes such as flexible printing and lamination, enabling mass production at a controllable cost. Attached Figure Description

[0018] Figure 1 A three-dimensional structural schematic diagram of the unit array of the conformal leaky wave antenna provided by the present invention; Figure 2 A top view of the element array of the conformal leaky wave antenna provided by the present invention; Figure 3 The conformal leaky wave antenna provided in Example 1 and its S11 simulation results under conformal conditions; Figure 4 The conformal leaky wave antenna provided in Example 1 and its S21 simulation results under conformal state; Figure 5 The simulation results of the E-plane radiation pattern of the conformal leaky wave antenna provided in Example 1 at different frequency points from 12 to 18 GHz; Figure 6 The simulation results of the conformal leaky wave antenna provided in Example 1 and its E-plane radiation pattern at different frequency points from 12 to 18 GHz under conformal conditions are presented. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0020] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0021] Example 1: The conformal leaky antenna provided in this embodiment is as follows: Figure 1 and Figure 2 As shown, the structure consists of a periodically arranged array of cells. The cell array includes a PI substrate, a leakage radiation structure etched onto the upper surface of the PI substrate, an ABS substrate tightly bonded to the lower surface of the PI substrate, and a metal ground layer tightly bonded to the lower surface of the ABS substrate. The PI substrate, leakage radiation structure, ABS substrate, and metal ground layer are bonded together with a flexible adhesive to form an integral conformal structure, and the leakage radiation structure and metal ground layer are electrically connected through metal vias. The PI substrate, ABS substrate, and metal ground layer all have the same dimensions, l1×w1, with the leakage radiation structure having a thickness of t, the PI substrate having a thickness of h1, and the ABS substrate having a thickness of h2.

[0022] The leakage radiation structure includes a gradient feed structure, an SSPP transmission line structure, and Vivaldi radiating elements. The gradient feed structure is located at both ends of the SSPP transmission line structure, and the Vivaldi radiating elements are periodically and alternately distributed on both sides of the SSPP transmission line structure.

[0023] The SSPP transmission line structure comprises two mirror-distributed SSPP transmission line units. Each SSPP transmission line unit includes a metal conductor strip and periodically distributed metal stubs located on one side of the conductor strip. The metal stubs are arranged in a periodic zigzag pattern, with a width of w4 and a spacing of l3. The metal stubs in the middle of the conductor strip are all the same length, l2, while the three metal stubs on both sides have gradually changing lengths, from the inside out, l6, l5, and l4, with l6 > l5 > l4. The metal stub portions of the two SSPP transmission line units are adjacent and have gaps. The width of the metal conductor strip is w2.

[0024] The gradient feed structure consists of two gradient rectangular rings located at both ends of the SSPP transmission line unit, which are mirror-symmetrical. From the inside out, each gradient rectangular ring comprises five closely adjacent rectangular metal patches with outer dimensions of l7×w5, l9×w5, l11×w5, l13×w5, and l15×w6, and inner dimensions of l8×w8, l10×w8, l12×w8, l14×w8, and l16×w, respectively, and one rectangular metal patch with dimensions of l17×w7. The rectangular metal patches are coaxially arranged, with l7 > l9 > l11 > l13 > l15 = l17.

[0025] The Vivaldi radiating element is a horn-shaped metal patch with an included angle of 20° and a width of w3. The tips of the horn-shaped metal patch are connected to the metal conductor of the SSPP transmission line element. The distance between the tips of adjacent horn-shaped metal patches on the same side of the SSPP transmission line structure is 5.9 mm.

[0026] The design of a conformal leaky wave antenna operating in the 12-18 GHz range is as follows: The specific structural parameters of the aforementioned element array are set as follows: wl=38mm, l1=291mm, l2=1.2mm, l3=0.2mm, w2=0.1mm, w3=0.4mm, w4=0.2mm, w5=2mm, w6=2mm, w7=14mm, w8=1mm, w9=1mm, h1=0.1mm, h2=1mm, t=0.017mm, l4=1.95mm, l5=2mm, l6=2.05mm, l7 =5.1mm, l8=4.3mm, l9=4.1mm, l10=3.3mm, l11=3.1mm, l12=2.3mm, l13=2.1mm, l14=1.3mm, l15=l17=1.1mm, l16=0.3mm. The relative permittivity of the PI substrate is 3.5, and the loss tangent is 0.002. The relative permittivity of the ABS substrate is 2.5, and the loss tangent is 0.001. The leakage radiation structure and the metal ground layer are made of copper foil.

[0027] Based on the above structural parameters and material properties, the simulation results of the conformal leaky wave antenna constructed with the above unit array are as follows: Figures 3-6 As shown.

[0028] from Figure 3 and Figure 4 As can be seen, this antenna achieves good and stable impedance matching under conformal conditions with cylinders of different radii, with a small variation range, and the open stopband phenomenon is suppressed. Figure 5 and Figure 6 As can be seen, this antenna can achieve continuous beam scanning from back to front in both its natural and bent states, with high gain and weak sidelobe levels. The simulation results demonstrate that the conformal leaky wave antenna proposed in this invention can effectively achieve wide-angle, high-gain, narrow-beam scanning from back to front, and has broad application prospects in future 5G / 6G communication, radar, and remote sensing systems.

[0029] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A conformal leaky wave antenna, characterized in that, It consists of a periodically arranged array of cells, which includes a PI substrate, a leakage radiation structure etched on the upper surface of the PI substrate, an ABS substrate tightly attached to the lower surface of the PI substrate, and a metal ground layer tightly attached to the lower surface of the ABS substrate. The leakage radiation structure includes a gradient feed structure, an SSPP transmission line structure, and Vivaldi radiation units. The gradient feed structure is located at both ends of the SSPP transmission line structure, and the Vivaldi radiation units are periodically staggered on both sides of the SSPP transmission line structure. The SSPP transmission line structure includes two mirror-distributed SSPP transmission line units. Each SSPP transmission line unit includes a metal conductor strip and periodically distributed metal stubs located on one side of the metal conductor strip.

2. The conformal leaky wave antenna according to claim 1, characterized in that, The metal stubs of the SSPP transmission line unit are periodically serrated, with a width of w4 and a spacing of l3. The metal stubs in the middle of the metal conductor are all the same length of l2, while the lengths of the three metal stubs on both sides gradually change, from the inside to the outside, being l6, l5 and l4 respectively, with l6 > l5 > l4.

3. The conformal leaky wave antenna according to claim 1, characterized in that, The metal stub sections of the two SSPP transmission line units are adjacent and have a gap.

4. The conformal leaky wave antenna according to claim 1, characterized in that, The gradient power supply structure consists of two gradient rectangular rings located at both ends of the SSPP transmission line unit, and the two gradient rectangular rings are mirror-symmetrical.

5. The conformal leaky wave antenna according to claim 4, characterized in that, The gradient rectangular ring consists of five closely adjacent rectangular metal patches with outer dimensions of l7×w5, l9×w5, l11×w5, l13×w5 and l15×w6 respectively, and inner dimensions of l8×w8, l10×w8, l12×w8, l14×w8 and l16×w9 respectively, and one rectangular metal patch with a size of l17×w7. The rectangular metal patches are coaxially arranged, and l7>l9>l11>l13>l15=l17.

6. The conformal leaky wave antenna according to claim 1, characterized in that, The Vivaldi radiating element is a horn-shaped metal patch with an included angle of 20° and a width of w3.

7. The conformal leaky wave antenna according to claim 6, characterized in that, The tips of the horn-shaped metal patch are connected to the metal conductor of the SSPP transmission line unit.

8. The conformal leaky wave antenna according to claim 6, characterized in that, The distance between the tips of adjacent horn-shaped metal patches on the same side of the SSPP transmission line structure is 5.9 mm.

9. The conformal leaky wave antenna according to claim 1, characterized in that, The PI substrate, the leakage radiation structure, the ABS substrate, and the metal ground layer are bonded together by a flexible adhesive to form an integral conformal structure, and the leakage radiation structure and the metal ground layer are electrically connected through metal vias.

10. The conformal leaky wave antenna according to claim 1, characterized in that, The PI substrate, ABS substrate, and metal ground layer have the same dimensions, and the thickness of the leakage radiation structure is t, the thickness of the PI substrate is h1, and the thickness of the ABS substrate is h2.

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