Optically transparent reflectarray antenna and method of manufacturing the same

Abstract

The application discloses an optically transparent reflective array antenna and a preparation method thereof. The optically transparent reflective array antenna comprises, from top to bottom, a conductive unit array, a dielectric substrate and a conductive ground plate. The conductive unit array comprises a plurality of reflective array units. Each reflective array unit comprises three concentric circular metal thin wires, namely a first circle, a second circle and a third circle from outside to inside. The second circle and the third circle are connected by four center-symmetrical metal thin wires to form a circular ring structure. The length of the metal thin wire is fixed, and the radius of the first circle and the second circle is adjusted to realize the adjustment of the reflection phase. The finally assembled antenna array is excited by a feed horn to realize good performance of high gain, high efficiency and large bandwidth, while good visible light transparency is maintained. The technical problems of small phase shift range, large loss, narrow antenna operating bandwidth and low efficiency of the traditional optically transparent reflective array antenna unit are solved.

Description

Technical Field

[0001] This invention relates to reflective array antenna technology, and in particular to optically transparent reflective array antennas and their fabrication methods. Background Technology

[0002] With the rapid development of modern communication technology, the frequency bands used for radio are constantly expanding, which in turn promotes the urgent need for new multifunctional antennas with high gain, wide bandwidth, and high integration in the millimeter-wave and terahertz frequency bands. In recent years, optically transparent antennas have played an important role in satellite communication and solar-based energy harvesting applications. Optically transparent planar reflective array antennas can be integrated into solar panels to achieve antenna radiation and energy harvesting functions, and have high gain, high capacity, low profile, and high optical transparency characteristics.

[0003] Most existing optically transparent reflective array antennas are based on purely optically transparent conductive oxides, such as indium tin oxide (ITO), as radiating elements to replace traditional opaque metals and achieve optical transparency. For example, existing solutions include an optically transparent reflective array antenna composed of square rings and square patches forming a combined resonant unit, with the conductor structure unit being an ITO optically transparent conductive thin film. However, due to the high conductor loss of such transparent conductive materials, the reflection loss of the unit in the planar reflective array is significantly higher than that of units implemented with traditional metal materials. The phase shift range is also small, and multiple dielectric substrates are usually required to reduce unit loss and increase the phase shift range, resulting in a higher profile. Furthermore, these optically transparent reflective array antennas typically suffer from poor optical brightness, low efficiency, and narrow bandwidth. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a broadband high-efficiency optically transparent reflective array antenna with low unit reflection loss, high visible light transmittance, and large phase change. The second purpose of this invention is to provide a method for manufacturing the optically transparent reflective array antenna.

[0005] Technical solution: The optically transparent reflective array antenna of the present invention comprises, from top to bottom, a conductive element array, a dielectric substrate, and a conductive ground plane;

[0006] The conductive unit array includes several reflective array units, each of which includes three concentric circular metal wires, which are a first circle, a second circle, and a third circle from the outside to the inside. The second circle and the third circle are connected by four metal wires to form a ring structure. The four metal wires are perpendicular to each other and are parallel or perpendicular to the boundary of the dielectric substrate.

[0007] The length of the metal wire is fixed, and the reflection phase is controlled by adjusting the radii of the first and second circles;

[0008] Both the dielectric substrate and the conductive ground plane are made of materials with light-transparent properties.

[0009] Furthermore, the circular metal wire and the line width of the metal wire both do not exceed 50 micrometers, making them almost invisible to the human eye.

[0010] Furthermore, the circular metal wire and the metal wire material are both at least one of copper, silver, aluminum or gold.

[0011] Furthermore, the optically transparent reflective array antenna operates at frequencies of 26-32 GHz. The radius of the first circle is adjustable from 0.8 to 2.1 mm, and the radius of the second circle is adjustable from 0.6 to 1.8 mm. The thicknesses of the conductive element array, dielectric substrate, and conductive ground plane are 800 nm, 1.7 mm, and 650 nm, respectively. When the radius of the outer circular structure reaches its maximum size, the radius of the inner ring structure is further adjusted to achieve a reflection phase variation range greater than 360° at different frequencies, while maintaining low element loss.

[0012] Furthermore, the conductive unit array is etched and attached to the first optically transparent dielectric film, and the conductive ground plane is etched and attached to the second optically transparent dielectric film. The first and second optically transparent dielectric films are polyethylene terephthalate (PET) or polyimide (PI) dielectric films.

[0013] Furthermore, the dielectric substrate is made of a dielectric material with optically transparent properties, including at least one of modified mixed olefin polymers, cyclic olefin copolymers, transparent resins, transparent plastics, glass, and acrylic. To further improve device performance, low-loss dielectric materials such as optically transparent modified mixed olefin polymers and cyclic olefin copolymers can be used.

[0014] Furthermore, the conductive ground plane is made of a conductive material with light-transparent properties, including at least one of indium tin oxide, silver-plated polyester film, and metal mesh.

[0015] Furthermore, the conductor structure of the conductive ground plane is an indium tin oxide optically transparent conductive film.

[0016] Furthermore, the optically transparent reflective array antenna uses a conical horn as its feed source. A 15dBi conical horn can be selected as the feed source, offset by 18° on the E-plane to illuminate the array. The focal diameter ratio from the phase center of the feed horn to the reflective array antenna is 0.87. The optically transparent reflective array antenna comprises 15×15 reflective array elements, each with a length and width of 6.525 times the spatial wavelength (free space wavelength at 29GHz). During array optimization, adjustments need to be made based on the energy distribution of the feed irradiation within the array. Elements with low reflection loss are selected as the benchmark for array assembly and overall design simulation in the central region where energy is more concentrated.

[0017] The method for fabricating the optically transparent reflective array antenna of the present invention includes the following steps:

[0018] Determine the size of the circular metal wires and the metal wires in each reflective array element;

[0019] Each reflective array element is deposited on top of a first optically transparent film; a conductive ground plane is deposited on the bottom of a second optically transparent film; the first and second optically transparent films are respectively bonded to both sides of a dielectric substrate to obtain the optically transparent reflective array antenna.

[0020] Alternatively, the optically transparent reflective array antenna can be obtained by depositing a dielectric substrate on both sides of each reflective array element and the conductive ground plane.

[0021] Beneficial effects: Compared with the prior art, the advantages of the present invention are as follows:

[0022] 1) The reflective array antenna is made of a custom patterned high visible light transparent conductive element array, a high visible light transparent indium tin oxide ground plane and a low loss light transparent dielectric layer, and has excellent antenna radiation performance in the millimeter wave band and extremely high transparency in the visible light band.

[0023] 2) The reflective array antenna utilizes a light-transparent, low-loss cyclic olefin copolymer dielectric substrate and is made with metal wires with a linewidth of no more than 50 micrometers. Its light-transparent heterogeneous units, designed with a combination of outer circles and inner rings, form a multi-resonant structure, which effectively improves the unit performance and visible light transparency of the reflective array antenna.

[0024] 3) The reflective array antenna adopts a light-transparent reflective array element with a combination of an outer circle and an inner ring. The reflection phase is controlled by adjusting the radius of the outer circle and the inner ring respectively. When the radius of the outer circle reaches its maximum size, the radius of the inner ring is further adjusted to achieve excellent characteristics such as low element reflection loss, large phase change, high visible light transmittance, large antenna operating bandwidth, high gain, high efficiency and low profile. It can be used in future 5G / 6G communication applications with high light transmittance requirements such as IoT, building windows, and solar panels. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the layered structure of the reflection array unit of the present invention;

[0026] Figure 2 This is a top view of the reflector array unit of the present invention;

[0027] Figure 3 The reflection amplitude response diagram of the reflection array element in the embodiment of the present invention in the frequency range of 26-32GHz is shown.

[0028] Figure 4 The reflection phase response diagram of the reflection array element in the embodiment of the present invention in the frequency range of 26-32GHz is shown.

[0029] Figure 5 This is a top view of a square reflective array unit in an embodiment of the present invention;

[0030] Figure 6 This is a comparison diagram of the reflection amplitude response of the square reflection array unit and the reflection array unit in the embodiment of the present invention under oblique incidence at different elevation angles at a center frequency of 29GHz.

[0031] Figure 7 This is a comparison diagram of the reflection phase response of the square reflection array unit and the reflection array unit in the embodiment of the present invention under oblique incidence at different elevation angles at a center frequency of 29GHz.

[0032] Figure 8 This is a schematic diagram of the optically transparent reflective array antenna under offset feeding in an embodiment of the present invention;

[0033] Figure 9 This is a top view of the surface of the optically transparent reflective array antenna in an embodiment of the present invention;

[0034] Figure 10 The simulated and measured radiation patterns of the E-plane of the optically transparent reflective array antenna in this embodiment of the invention at a center frequency of 29 GHz are shown.

[0035] Figure 11The simulated and measured radiation patterns of the H-plane of the optically transparent reflective array antenna in this embodiment of the invention at a center frequency of 29 GHz are shown.

[0036] Figure 12 This is a comparison chart of the simulated and measured gain and aperture efficiency of the optically transparent reflective array antenna in the 26-32GHz frequency range according to the embodiments of the present invention. Detailed Implementation

[0037] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0038] like Figure 1 As shown, the optically transparent reflective array antenna includes an optically transparent conductive unit array 2, an optically transparent dielectric substrate 3, and an optically transparent conductive ground plane 5, wherein the optically transparent conductive unit array 2 and the optically transparent conductive ground plane 5 are respectively etched and attached to the first optically transparent film 1 and the second optically transparent film 4.

[0039] The optically transparent conductive unit array 2 includes several reflective array units, fabricated using metal wires with a linewidth not exceeding 50 micrometers. It includes an outer circular structure (including a first circle) and an inner annular structure (including a second circle, a third circle, and the metal wires) to ensure good light transmission. The metal wires are made of at least one of copper, silver, aluminum, or gold. In this embodiment, the first optically transparent film 1 is a polyethylene terephthalate film with a thickness of 0.1 mm; the optically transparent conductive unit array 2 is fabricated using copper metal wires with a thickness of 800 nanometers; the optically transparent dielectric substrate 3 is a cyclic olefin copolymer dielectric substrate with a thickness of 1.7 mm; the second optically transparent film 4 is a polyethylene terephthalate film with a thickness of 0.125 mm; and the optically transparent conductive ground plane 5 is an indium tin oxide ground plane with a thickness of 650 mm.

[0040] like Figure 2 As shown in (a) and (b), P represents the side length of the reflective array element, w is the linewidth of the metal wire, and d is the distance between the inner rings, i.e., the length of the metal wire, whose size and dimensions are fixed. R1 is the radius of the outer circular structure, i.e., the radius of the first circle, and R2 is the radius of the inner ring structure, i.e., the radius of the second circle. The reflection phase is controlled by adjusting the radii of the outer and inner ring structures respectively. The adjustment range of radius R1 is 0.8 to 2.1 mm, and the adjustment range of radius R2 is 0.6 to 1.8 mm. When the radius of the outer circular structure reaches its maximum size R... 1max At the same time, a larger range of reflection phase change can be achieved by adjusting the radius R2 of the internal ring structure, while maintaining a low unit loss; the conductor structure of the unit is selected as a copper metal wire with a linewidth of 50 micrometers, and the conductor structure of the ground plane is selected as an indium tin oxide optically transparent conductive film with a sheet resistance of 2.5 ohms.

[0041] The reflector array element of this invention exhibits good phase response in the 26-32 GHz range and near-parallelism of phase shift curves during the adjustment of radius dimensions R1 and R2. For example... Figure 3 , Figure 4 As shown, the horizontal axis represents the size change, and the vertical axis represents the reflection amplitude and reflection phase, respectively. The first unit structure with a changing outer circular radius and the second unit structure with a changing inner ring radius are separated by the black dashed line in the figure. The unit of the horizontal axis is millimeters. The horizontal axis of the first unit structure to the left of the dashed line is the outer circular radius R1, which can be adjusted from 0.8 to 2.1 millimeters; the horizontal axis of the second unit structure to the right of the dashed line is the inner ring radius R2, which can be adjusted from 0.6 to 1.8 millimeters. Figure 3 and Figure 4 These are the amplitude and phase responses of the reflector array elements in the 26-32 GHz frequency range. At a center frequency of 29 GHz, the reflection loss of the reflector array elements is less than 1.1 dB, and the phase change reaches 491°.

[0042] The optically transparent conductive ground plane 5 is a conductive material and structure with certain optical transparency properties, and adopts at least one of optically transparent materials such as indium tin oxide, silver-plated polyester film or metal mesh.

[0043] The light-transparent dielectric substrate 3 is a dielectric material with light-transparent properties, and is made of at least one of cyclic olefin copolymers, transparent resins, transparent plastics, glass, and acrylic. In order to further improve the device performance, low-loss dielectric materials such as light-transparent cyclic olefin copolymers with low-loss properties can be used.

[0044] Existing technology includes a transparent reflective array unit that employs a combination of an outer square ring patch pattern and an inner square patch pattern, referred to as a square reflective array unit. However, achieving transparency using this method requires the use of light-transparent conductive semiconductor films such as indium tin oxide (ITO), making it difficult to utilize fine metal wire schemes. Furthermore, the use of conductive semiconductor films would severely affect the visible light transparency of the unit. In addition, if the combination of the outer square ring and inner square patch patterns is optimized and designed into a similar fine wire structure, such as... Figure 5 As shown in (a) and (b), assuming the square reflective array unit has the same structural dimensions as the reflective array unit of the present invention, P represents the side length of the optically transparent conductive unit, w is the linewidth of the metal wires in the outer square structure and the inner square ring structure, and d is the distance between the inner square rings. L1 is the side length of the outer square structure, and L2 is the side length of the inner square ring structure, where L1 = 2R1 and L2 = 2R2. Similarly, by adjusting R1 and R2 respectively, the reflection phase of the outer square structure and the inner square ring structure can be controlled. At this time, the structural performance of the square reflective array unit is very poor and it is difficult to meet the requirements of practical applications.

[0045] like Figure 6 and Figure 7 As shown, the horizontal axis represents the size change, and the vertical axes represent the reflection amplitude and reflection phase, respectively. The third unit structure with varying R1 and the fourth unit structure with varying R2 are separated by a black dashed line. The horizontal axis dimensions are in millimeters. The horizontal axis of the third unit structure to the left of the dashed line represents the outer circular structure radius R1, which can be adjusted from 0.8 to 2.1 millimeters; the horizontal axis of the fourth unit structure to the right of the dashed line represents the inner ring radius R2, which can be adjusted from 0.6 to 1.8 millimeters. Figure 6 and Figure 7 The amplitude and phase responses of the reflector array unit of this invention and the square reflector array unit in the prior art are compared under oblique incidence at different elevation angles with a center frequency of 29 GHz. The comparison shows that at a center frequency of 29 GHz, the reflector array unit of this invention exhibits lower anti-loss, and the amplitude and phase response curves of the reflector unit remain stable within the elevation angle range of 0-30°. It is insensitive to changes under oblique incidence conditions, possesses more stable phase modulation capability, and exhibits smaller variations in reflection loss.

[0046] like Figure 8 As shown, to reduce the blocking effect of the feed horn, a 15dBi conical horn was used as the feed source, offset at 18° on the E-plane to illuminate the array. Figure 9 The incident wave direction is set at an 18° offset on the E plane, and the reflected beam of the target is also set at 18°. A coordinate system XYZ is established with the position of the reflection array. When the incident wave is set at an 18° offset on the E plane, for ease of explanation, the coordinate system XYZ is also rotated by 18° to form a new coordinate system X'YZ', with the E plane and the H plane perpendicular to each other.

[0047] The focal diameter ratio from the conical horn to the reflector array was chosen to be 0.87. The overall array comprises 15×15 reflector array elements, each with a length and width of 6.525 times the spatial wavelength (free space wavelength at 29 GHz). During array optimization, based on the energy distribution of the feed illumination within the array, elements with low reflection loss in the more energy-concentrated central region were selected as the benchmark for array assembly and overall design simulation. Ultimately, the optimized benchmark phase was determined to be 10°, resulting in a light-transparent reflector array antenna. Figure 9 The image shown is a top view of the surface of a light-transparent reflective array antenna.

[0048] The method for fabricating the optically transparent reflective array antenna of the present invention includes the following steps:

[0049] S1: Calculate and determine the external dimensions of the customized design of the combination of outer circles and inner rings of the light-transparent conductive unit array, and then deposit the light-transparent conductive array based on metal fine wires on the top of the first light-transparent dielectric PET film by photolithography, magnetron sputtering or screen printing; similarly, deposit the light-transparent conductive ground plane on the bottom of the second light-transparent dielectric PET film by photolithography, magnetron sputtering or screen printing.

[0050] S2: Using transparent UV adhesive, the PET film with photolithographically etched transparent conductive unit array and the PET film with deposited transparent conductive ground plane are respectively bonded to the two ends of a low-loss optically transparent dielectric substrate and aligned. Then, under ultraviolet light irradiation, the UV adhesive is accelerated and fully solidified, ultimately rapidly strengthening the broadband optically transparent reflective array antenna.

[0051] like Figure 10 and Figure 11 The figure shows the simulated and measured radiation patterns of the fabricated optically transparent reflective array antenna at a center frequency of 29 GHz. The results are for the E-plane and H-plane, respectively. The horizontal axis represents the elevation angle in degrees, and the vertical axis represents the normalized radiation pattern in dB. Figure 12 The figure shows a comparison of the simulated and measured gain of the fabricated optically transparent reflective array antenna in the 26-33 GHz frequency range. The horizontal axis represents frequency, the left vertical axis represents the antenna gain, and the right vertical axis represents the aperture efficiency. The measured and simulated results are in good agreement. The test results show that the optically transparent reflective array antenna has good radiation characteristics, with a measured gain of 23.36 dBi, an aperture efficiency of 40.7%, and a 1 dB gain bandwidth of 22.41%. The method of this invention can simultaneously achieve low reflection loss, large phase change, high visible light transmittance, large bandwidth, high efficiency, and low profile characteristics, and can be applied to 5G / 6G wireless communication systems as well as IoT and related communication applications with high aesthetic requirements.

Claims

1. An optically transparent reflectarray antenna, characterized by, The optical transparent reflective array antenna comprises, from top to bottom, an array of conductive units, a dielectric substrate and a conductive ground plate. The array of conductive units comprises a plurality of reflective array units, each of which comprises three concentric circular metal wires, namely a first circle, a second circle and a third circle, from outside to inside, wherein the second circle and the third circle are connected by four metal wires to form a circular ring structure; the four metal wires are perpendicular to each other and parallel or perpendicular to the boundary of the dielectric substrate. The length of the metal wire is fixed, and the adjustment of the radii of the first circle and the second circle is used to realize the adjustment of the reflection phase. The dielectric substrate and the conductive ground plate are both materials with light transparent properties.

2. The optically transparent reflectarray antenna of claim 1, wherein, The line width of the circular metal wire and the metal wire is not more than 50 microns.

3. The optically transparent reflectarray antenna of claim 1, wherein, The circular metal wire and the metal wire are made of at least one of copper, silver, aluminum or gold.

4. The optically transparent reflectarray antenna of claim 1, wherein, The frequency of the optical transparent reflective array antenna is 26-32 GHz, the radius adjustment range of the first circle is 0.8 to 2.1 mm, and the radius adjustment range of the second circle is 0.6 to 1.8 mm. The thickness of the array of conductive units, the dielectric substrate and the conductive ground plate is 800 nm, 1.7 mm and 650 nm, respectively.

5. The optically transparent reflectarray antenna of claim 1, wherein, The array of conductive units is etched and attached to a first light transparent film, and the conductive ground plate is etched and attached to a second light transparent film. The first light transparent film and the second light transparent film are polyethylene terephthalate or polyimide dielectric film.

6. The optically transparent reflectarray antenna of claim 1, wherein, The material of the dielectric substrate is a dielectric material with light transparent properties, including at least one of modified mixed olefin polymer, cyclic olefin copolymer, transparent resin, transparent plastic, glass and acrylic.

7. The optically transparent reflectarray antenna of claim 1, wherein, The material of the conductive ground plate is a conductive material with light transparent properties, including at least one of indium tin oxide, silver-coated polyester film and metal mesh.

8. The optically transparent reflectarray antenna of claim 7, wherein, The conductor structure of the conductive ground plate is an indium tin oxide light transparent conductive film.

9. The optically transparent reflectarray antenna of claim 1, wherein, The optical transparent reflective array antenna uses a conical horn as a feed source.

10. A method of fabricating the optically transparent reflectarray antenna of any one of claims 1 to 9, characterized in that, The method comprises the following steps: determining the size of the circular metal wire and the metal wire in each reflective array unit; etching each reflective array unit on the surface of a first light transparent film and etching a conductive ground plate on the bottom of a second light transparent film; and adhering the first light transparent film and the second light transparent film to the two sides of a dielectric substrate, respectively, to obtain the optical transparent reflective array antenna. Alternatively, etching each reflective array unit and the conductive ground plate on the two sides of a dielectric substrate to obtain the optical transparent reflective array antenna.

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