Optical transparent reflective array antenna and preparation method thereof

Abstract

The invention discloses an optical transparent reflective array antenna and a preparation method thereof. The optical transparent reflective array antenna comprises a conductive unit array, a dielectric substrate and a conductive grounding plate from top to bottom, the conductive unit array comprises a plurality of reflective array units, each reflective array unit comprises three concentric circular metal thin wires which are respectively a first circle, a second circle and a third circle from outside to inside, and the second circle and the third circle are connected through four centrosymmetric metal thin wires to form a circular ring structure; the length of the metal thin wire is fixed, and the reflection phase is regulated and controlled by adjusting the radius of the first circle and the radius of the second circle. And finally, the antenna array of the array is excited by the feed source horn, so that good performance of high gain, high efficiency and large bandwidth is realized, good visible light transparency is kept, and the technical problems of small phase shift range, large loss, narrow antenna working bandwidth and low efficiency of a traditional optical transparent reflective array antenna unit are solved.

Description

Technical Field

[0001] The invention relates to reflective array antenna technology, in particular to an optically transparent reflective array antenna and a preparation method thereof. Background Art

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

[0003] Most of the existing optically transparent reflective array antennas are based on pure optically transparent conductive oxides, such as indium tin oxide, as radiating elements to replace traditional opaque metals to achieve optical transparency. For example, existing solutions include an optically transparent reflective array antenna, which is composed of a square ring and a square patch to form a combined resonant unit, and the conductor structure unit is an indium tin oxide optically transparent conductive film. However, due to the large conductor loss of this type of transparent conductive material itself, the unit reflection loss of the planar reflective array is significantly higher than that of the unit realized by traditional metal materials, the phase shift variation range is small, and usually a multi-layer dielectric substrate is required to reduce the unit loss and increase the phase shift variation range, and the cross-section is higher. In addition, these optically transparent reflective array antennas usually also have problems such as poor optical brightness, low efficiency and narrow bandwidth. Summary of the invention

[0004] Purpose of the invention: The purpose of the present 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 the present invention is to provide a method for preparing 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 unit array, a dielectric substrate and a conductive ground plane;

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

[0007] The length of the metal thin wire is fixed, and the reflection phase is regulated by adjusting the radius of the first circle and the second circle;

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

[0009] Furthermore, the line widths of the circular metal wires and the metal wires do not exceed 50 micrometers and are almost invisible to the human eye.

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

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

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

[0013] Furthermore, the material of the dielectric substrate is a dielectric material with optical transparency, including at least one of modified mixed olefin polymer, cycloolefin copolymer, transparent resin, transparent plastic, glass, and acrylic. In order to further improve the performance of the device, low-loss dielectric materials such as optically transparent modified mixed olefin polymer and cycloolefin copolymer with low loss characteristics can be used.

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

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

[0016] Furthermore, the optically transparent reflective array antenna uses a conical horn as a feed source. A 15dBi conical horn can be selected as the feed source, and the array is irradiated at an offset of 18° on the E plane. The focal diameter ratio of the phase center of the feed horn to the reflective array antenna is 0.87. The optically transparent reflective array antenna as a whole includes 15×15 reflective array units, and the corresponding length and width are both 6.525 times the spatial wavelength (free space wavelength at 29GHz). When optimizing the array, it is necessary to adjust the energy distribution of the feed source irradiating the array, and select units with small reflection losses in the central area where the energy is more concentrated as the benchmark for array formation and overall design simulation.

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

[0018] Determine the size of the circular metal wire and the metal wire in each reflective array unit;

[0019] Depositing each reflective array unit on the top of a first optically transparent film; depositing a conductive ground plane on the bottom of a second optically transparent film; and bonding the first optically transparent film and the second optically transparent film to two sides of a dielectric substrate, respectively, to obtain the optically transparent reflective array antenna;

[0020] Alternatively, each reflective array unit and a conductive ground plane are deposited on both sides of a dielectric substrate to obtain the optically transparent reflective array antenna.

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

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

[0023] 2) The reflectarray antenna uses an optically transparent low-loss cyclic olefin copolymer dielectric substrate and is made of fine metal wires with a line width not exceeding 50 microns. The optically transparent heterogeneous units designed with a combination of external circles and internal rings form a multi-resonance structure, which effectively improves the unit performance and visible light transparency of the reflectarray antenna.

[0024] 3) The reflectarray antenna adopts an optically transparent reflectarray unit designed with an outer circle and an inner ring. The reflection phase is controlled by adjusting the outer circle radius and the inner ring radius respectively. When the radius of the outer circle structure reaches the maximum size, the radius of the inner ring structure is further adjusted to ultimately achieve low unit 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 related communication applications with high transmittance requirements for the Internet of Things, building window glass, solar panels, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the hierarchical structure of the reflective array unit of the present invention;

[0026] Figure 2 A top view of a reflective array unit of the present invention;

[0027] Figure 3 is a reflection amplitude response diagram of the reflection array unit in the embodiment of the present invention within the frequency range of 26-32 GHz;

[0028] Figure 4 is a reflection phase response diagram of the reflection array unit in the embodiment of the present invention in the frequency range of 26-32 GHz;

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

[0030] Figure 6 It 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 pitch angles at a center frequency of 29 GHz;

[0031] Figure 7 It is a comparison diagram of reflection phase responses of a square reflection array unit and a reflection array unit in an embodiment of the present invention under oblique incidence at different pitch angles at a center frequency of 29 GHz;

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

[0033] Fig. 9 A top view of the surface of the optically transparent reflective array antenna in an embodiment of the present invention;

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

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

[0036] Fig.12 It is a comparison diagram of the simulated and measured gain and aperture efficiency of the optically transparent reflective array antenna in the embodiment of the present invention in the frequency range of 26-32 GHz. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0038] like Figure 1 As shown, the optically transparent reflective array antenna comprises an optically transparent conductive unit array 2, an optically transparent medium 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 etched and attached to a first optically transparent film 1 and a second optically transparent film 4 respectively.

[0039] The optically transparent conductive unit array 2 includes a plurality of reflective array units, which are made of metal fine wires with a line width not exceeding 50 microns, including an outer circular structure (including a first circle) and an inner circular ring structure (including a second circle, a third circle and metal fine wires) to ensure good light transmission performance, and the metal fine 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 made of copper metal fine wires with a thickness of 800 nanometers, the optically transparent medium substrate 3 is a cyclic olefin copolymer medium 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 unit, w is the width of the metal wire, and d is the distance between the inner rings, that is, the length of the metal wire, and its size and size are fixed. R1 is the radius of the outer circular structure, that is, the radius of the first circle, and R2 is the radius of the inner ring structure, that is, the radius of the second circle. The reflection phase is controlled by adjusting the radius of the outer circular structure and the radius of the inner ring structure 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 the maximum size R 1max When the reflection phase is reflected by the laser diode, the radius R2 of the inner ring structure is adjusted to achieve a larger reflection phase variation range while maintaining a lower unit loss. The conductor structure of the unit is a copper metal wire with a line width of 50 microns, and the conductor structure of the ground plane is an indium tin oxide optically transparent conductive film with a square resistance of 2.5 ohms.

[0041] In the process of adjusting the radius dimensions R1 and R2, the reflective array unit of the present invention has a good phase response in the range of 26-32 GHz, and the parallelism of the phase shift curve is close. Figure 3 , Figure 4 As shown, the horizontal axis is the size change, and the vertical axis is the reflection amplitude and reflection phase, respectively. The first unit structure with a change in the outer circular radius and the second unit structure with a change in the inner circular radius are separated by a black dotted line in the figure. The horizontal axis size unit is millimeter. The horizontal axis of the first unit structure on the left side of the dotted line is the outer circular structure radius R1, and its adjustment range is 0.8 to 2.1 mm; the horizontal axis of the second unit structure on the right side of the dotted line is the inner circular radius R2, and its adjustment range is 0.6 to 1.8 mm. Figure 3 and Figure 4 They are the amplitude response and phase response of the reflectarray unit in the frequency range of 26-32GHz. When the center frequency is 29GHz, the reflection loss of the reflectarray unit is less than 1.1dB and the phase change reaches 491°.

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

[0043] The optically transparent medium substrate 3 is a medium material with optically transparent properties, and is made of at least one of cycloolefin copolymer, transparent resin, transparent plastic, glass, and acrylic. In order to further improve device performance, low-loss medium materials such as optically transparent cycloolefin copolymer with low-loss properties may be used.

[0044] The prior art includes a transparent reflective array unit that uses a combination of an external square ring patch pattern and an internal square patch pattern, called a square reflective array unit. However, this method requires the use of a light-transparent semiconductor conductive film such as indium tin oxide to achieve transparency, and it is difficult to use a metal fine wire solution. In addition, the semiconductor conductive film solution will seriously affect the visible light transparency of the unit. In addition, if the combination of the external square ring and the internal square patch pattern is optimized and improved, and designed into a similar fine wire structure, such as Figure 5 As shown in (a) and (b), assuming that 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 metal wire width of the external square structure and the internal square ring structure, and d is the distance between the internal square rings. L1 is the side length of the external square structure, and L2 is the side length of the internal square ring structure, where L1 = 2R1 and L2 = 2R2. Similarly, by adjusting R1 and R2 respectively to achieve the reflection phase control of the external square structure and the internal square ring structure, at this time, the square reflective array unit structure has poor performance and is difficult to meet the requirements of practical applications.

[0045] like Figure 6 and Figure 7 As shown, the horizontal axis is the size change, and the vertical axis is the reflection amplitude and reflection phase respectively. The third unit structure with R1 change and the fourth unit structure with R2 change are separated by a black dotted line. The horizontal axis dimension unit is millimeter. The horizontal axis of the third unit structure on the left side of the dotted line is the outer circular structure radius R1, and its adjustment range is 0.8 to 2.1 mm; the horizontal axis of the fourth unit structure on the right side of the dotted line is the inner ring radius R2, and its adjustment range is 0.6 to 1.8 mm. Figure 6 and Figure 7 In the figure, the amplitude response and phase response of the reflective array unit of the present invention and the square reflective array unit in the prior art at the center frequency of 29 GHz and oblique incidence at different pitch angles. By comparison, when the center frequency is 29 GHz, the reflective array unit of the present invention has lower anti-loss, and the amplitude and phase response curves of the reflective unit remain stable within the range of pitch angles of 0-30°, and are insensitive to changes under oblique incidence, and have more stable phase modulation capabilities and smaller reflection loss changes.

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

[0047] The focal diameter ratio of the conical horn to the reflective array is selected as 0.87. The overall array contains 15×15 reflective array units, and the corresponding length and width are 6.525 times the spatial wavelength (free space wavelength at 29GHz). When optimizing the array, it is necessary to select units with small reflection loss in the central area where the energy is more concentrated as the benchmark for array formation and overall design simulation based on the energy distribution of the feed source irradiating the array. Finally, the optimized benchmark phase is determined to be 10°, and finally a light-transparent reflective array antenna is formed. Fig. 9 Shown is a top view of the surface of the optically transparent reflective array antenna.

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

[0049] S1: Calculate and determine the dimensions of the customized outer circular and inner ring combination 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 medium PET film by photolithography, magnetron sputtering or screen printing; similarly, deposit the light-transparent conductive ground plate on the bottom of the second light-transparent medium PET film by photolithography, magnetron sputtering or screen printing;

[0050] S2: Use transparent UV glue to adhere the PET film with a photo-transparent conductive unit array and the PET film with a photo-transparent conductive ground plane deposited on the two ends of the low-loss optically transparent medium substrate, and then align them. Then, under ultraviolet light, the UV glue is accelerated and fully solidified, and finally the broadband optically transparent reflective array antenna is quickly reinforced.

[0051] like Fig.10 and Fig.11 Shown are the simulated and measured radiation patterns of the processed optically transparent reflective array antenna at a center frequency of 29 GHz, which are the E-plane and H-plane results respectively. The horizontal axis in the figure is the elevation angle in degrees; the vertical axis is the normalized pattern in dB. Fig.12 The figure shows the comparison of the simulated and measured gain of the processed optically transparent reflective array antenna in the frequency range of 26-33GHz. The horizontal axis is the frequency, the left vertical axis is the reflective array antenna gain, and the right vertical axis is the aperture efficiency. The measured results are consistent with the simulation results. The test results show that the optically transparent reflective array antenna has good radiation characteristics, with a measured gain of 23.36dBi, an aperture efficiency of 40.7%, and a 1dB gain bandwidth of 22.41%. The method of the present 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 and Internet of Things and related communication applications with high aesthetic requirements.

Claims

1. An optically transparent reflective array antenna, characterized in that: The optically transparent reflective array antenna comprises, from top to bottom, a conductive unit array, a dielectric substrate and a conductive ground plane; The conductive unit array includes a plurality of reflective array units, each of which includes three concentric circular metal thin wires, which are respectively a first circle, a second circle and a third circle from the outside to the inside, wherein the second circle and the third circle are connected by four metal thin wires to form a circular ring structure; the four metal thin wires are perpendicular to each other and parallel or perpendicular to the boundary of the dielectric substrate; The length of the metal thin wire is fixed, and the reflection phase is regulated by adjusting the radius of the first circle and the second circle; The dielectric substrate and the conductive ground plane are both made of materials with light-transparent properties.

2. The optically transparent reflective array antenna according to claim 1, characterized in that: The line widths of the circular metal fine wires and the metal fine wires are both no more than 50 microns.

3. The optically transparent reflective array antenna according to claim 1, characterized in that: The circular metal wire and the metal wire are made of at least one of copper, silver, aluminum or gold.

4. The optically transparent reflective array antenna according to claim 1, characterized in that: The frequency of the optically 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 thicknesses of the conductive unit array, the dielectric substrate and the conductive ground plane are 800 nanometers, 1.7 millimeters and 650 nanometers respectively.

5. The optically transparent reflective array antenna according to claim 1, characterized in that: The conductive unit array is etched and attached to the first optically transparent dielectric film, and the conductive ground plate is etched and attached to the second optically transparent dielectric film; The first light transparent dielectric film and the second light transparent dielectric film are polyethylene terephthalate or polyimide dielectric films.

6. The optically transparent reflective array antenna according to claim 1, characterized in that: The material of the dielectric substrate is a dielectric material with optical transparency, including at least one of modified mixed olefin polymer, cycloolefin copolymer, transparent resin, transparent plastic, glass, and acrylic.

7. The optically transparent reflective array antenna according to claim 1, characterized in that: The material of the conductive ground plate is a conductive material with optical transparency, including at least one of indium tin oxide, silver-plated polyester film, and metal grid.

8. The optically transparent reflective array antenna according to claim 7, characterized in that: The conductor structure of the conductive ground plate is an indium tin oxide optically transparent conductive film.

9. The optically transparent reflective array antenna according to claim 1, characterized in that: The optically transparent reflective array antenna uses a conical horn as a feed source.

10. A method for preparing the optically transparent reflective array antenna according to any one of claims 1 to 9, characterized in that: The steps include: Determine the size of the circular metal wire and the metal wire in each reflective array unit; Depositing each reflective array unit on the top of a first optically transparent film; depositing a conductive ground plane on the bottom of a second optically transparent film; and bonding the first optically transparent film and the second optically transparent film to two sides of a dielectric substrate, respectively, to obtain the optically transparent reflective array antenna; Alternatively, each reflective array unit and a conductive ground plane are deposited on both sides of a dielectric substrate to obtain the optically transparent reflective array antenna.

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