A broadband thin film reflective array antenna

Abstract

The present invention discloses a broadband thin film reflective array antenna. The broadband thin film reflective array antenna of the present invention is composed of a feed source and a reflective array, wherein the reflective array is composed of two layers of thin films, the two layers of thin films are separated by a certain distance, and both are parabolic or quasi-parabolic; a metal patch unit is attached to the upper surface of the upper film, and a metal ground is attached to the upper surface of the lower film. The present invention can greatly widen the antenna bandwidth by shortening the spatial phase shift difference between the feed source and the reflective array unit, and has the advantages of wide bandwidth, high efficiency and light weight. The bandwidth of conventional large-aperture thin film reflective array antennas is less than 5%, while the bandwidth of the thin film reflective array antenna of the present invention can reach more than 30%. The efficiency of the thin film reflective array antenna of the present invention can reach more than 60%, and the antenna surface density does not exceed 1kg / m 2 , with the advantage of lightweight.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave antennas, and in particular to a large-scale broadband thin-film planar reflective array antenna. Background Art

[0002] In aerospace applications such as satellite communications and deep space exploration, onboard antennas require high gain, narrow beamwidth, and high power handling capabilities. Furthermore, the antenna beam must be able to scan across space. While array antennas can achieve the former, they are complex, heavy, and power-hungry. While reflector antennas can achieve the latter, traditional mechanical movement can cause disturbances in the satellite's attitude, and the beam movement rate is low. Planar reflectarray antennas combine the advantages of both approaches without their drawbacks, offering significant potential for development in the aerospace field.

[0003] A planar reflectarray antenna uses a feed source to illuminate a set of flat or arbitrarily shaped surfaces. Radiating elements are artificially distributed across this surface, each precisely designed element providing a different reflection phase. These reflection phases precisely compensate for the phase differences in the beam emitted by the feed source in various directions after being reflected from the plane. This creates a plane wavefront in that direction, enhancing radiation. In other words, a planar reflectarray uses a precisely designed plane to achieve the curved effect of a parabolic antenna. Planar reflectarray antennas come in various forms, such as the national invention patent for "Planar Reflectarray Antenna" (Patent No. ZL201410090071.5) filed by An Wenxing et al. and the national invention patent for "Ku-band Dual-band Dual-polarization Microstrip Planar Reflectarray Antenna" (Patent No. ZL201310486023.3) filed by Sun Ke et al. The former design features a fixed-beam planar reflectarray antenna. Phase adjustment is achieved by adjusting the shape and size of the metal branches within each metal patch element, thereby forming a constant phase surface on the metal planar reflectarray. The latter designed a dual-frequency, dual-polarization, fixed-beam planar reflectarray antenna operating in the Ku band. By adjusting the size of each microstrip unit on the dielectric substrate and compensating for the spatial phase difference between the feed source and each unit of the array, the reflected waves are superimposed in phase in a specific direction to form a pencil beam, achieving high gain. The relative bandwidth of the two does not exceed 10%.

[0004] Planar reflectarray antennas have an inherent disadvantage, which is their narrowband characteristics. Generally, their bandwidth does not exceed 10%. Summary of the Invention

[0005] In light of this, the present invention provides a broadband thin-film reflectarray antenna that significantly broadens the antenna bandwidth by using a planar partitioning technique to reduce the spatial phase shift difference between the feed source and the different elements of the large-aperture reflectarray. For large-aperture reflectarray antennas, the aperture is divided into several regions, each of which is a planar reflectarray antenna. Finally, each planar reflectarray is fitted into a quasi-paraboloid according to a specific pattern, significantly broadening the antenna bandwidth.

[0006] The present invention provides a broadband thin film reflective array antenna, which is composed of a feed source and a reflective array, wherein the reflective array is composed of two layers of thin films; the two layers of thin films are spaced a certain distance apart, and foam or dielectric honeycomb can be filled between the two layers of thin films to ensure the spacing depending on the structural conditions; or no dielectric is filled, and the two layers of thin films are supported by supporting structures on all sides; a metal patch unit is attached to the upper surface of the upper film, and a metal ground is attached to the upper surface of the lower film; the upper and lower films are both parabolic or quasi-parabolic.

[0007] The present invention significantly broadens the antenna bandwidth by shortening the spatial phase shift difference between the feed source and the reflector array unit. The metal patch units at different locations on the aperture of a broadband thin-film reflector array antenna may have different path lengths from the feed source phase center. To achieve an equiphase surface after reflection, the metal patch units should provide a certain reflection phase to compensate for the spatial path length difference. The spatial path length difference can be used to determine the relative phase shift that each metal patch unit needs to provide. The relative size of each metal patch can then be determined based on the phase shift curve of the metal patch unit, thereby completing the antenna aperture design.

[0008] The film can be divided into several flat regions, each of which is fitted into a quasi-paraboloid according to a certain pattern, reducing the spatial phase shift between the feed source and the reflector array elements. A typical block structure is: a central square block surrounded by four trapezoidal blocks, fitted into a quasi-paraboloid.

[0009] The broadband thin-film reflectarray antenna achieves different phase shifts by adjusting the size of the metal patch. Different patch unit shapes can achieve different phase shift ranges. The metal patch unit consists of two square rings, with the outer side of the square ring being 0.2 to 0.95 times the half-wavelength. The outer side of the inner ring is smaller than the inner side, and the inner side can be reduced to zero, meaning the inner ring can be solid. The dual square ring unit can provide a phase shift exceeding 530 degrees, and the phase shift characteristic exhibits excellent linearity, which helps broaden the unit bandwidth.

[0010] The film may be a polyimide film, a polyester film, or any other dielectric film that can be surface-metallized.

[0011] The reflector array is illuminated by a feed source, which can be a horn antenna or other antenna form. The feed source position affects both the antenna bandwidth and the relative tilt angle of the film. The focal ratio is typically set between 0.7 and 1.6. Through design optimization, a focal ratio of 1.5 provides good electrical performance and engineering feasibility.

[0012] Beneficial effects:

[0013] Usually, reflector array antennas are in the form of microstrips, which are difficult to achieve large apertures and are not easy to unfold. The present invention adopts a thin film form, which can be printed in one go, is easy to achieve large apertures, and is unfolded by an unfolding mechanism. In addition, the existing technology mainly widens the bandwidth of the reflector array by widening the bandwidth of the reflector array unit, and the bandwidth of large-aperture reflector array antennas is mainly limited by the aperture, so this technology has little effect on improving large-aperture antennas. The present invention provides a way to greatly widen the antenna bandwidth by shortening the spatial phase shift difference between the feed source and the large-aperture reflector array unit. For large-aperture reflector array antennas, the aperture is divided into several areas, each area is a planar reflector array antenna, and finally each planar reflector array is fitted into a quasi-paraboloid according to a certain rule, which can greatly widen the antenna bandwidth.

[0014] The broadband thin film reflector array antenna of the present invention has the advantages of wide bandwidth, high efficiency and light weight. Conventional large-aperture thin film reflector array antennas have a bandwidth of less than 5%, while the bandwidth of the thin film reflector array antenna of the present invention can reach more than 30%. The efficiency of the thin film reflector array antenna of the present invention can reach more than 60%, and the antenna surface density does not exceed 1kg / m 2 , with the advantage of lightweight. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a cross-sectional view of the broadband thin film reflective array antenna unit of the present invention.

[0016] Figure 2 Schematic diagram of a metal patch unit.

[0017] Figure 3 This is the relationship curve between the side length of the square ring outside the metal patch unit and the reflection phase shift and reflection loss.

[0018] Figure 4 A layout of an ultra-wideband thin film antenna array.

[0019] Figure 5 A side view of the ultra-wideband thin-film antenna array.

[0020] Figure 6 It is a structure of an ultra-wideband thin film antenna.

[0021] Figure 7 To adopt Figure 4The gain pattern design results of the antenna layout at the lower sideband 9GHz.

[0022] Figure 8 To adopt Figure 4 The gain pattern design results of the layout antenna at the center frequency of 9.6GHz.

[0023] Figure 9 To adopt Figure 4 The gain pattern design results of the antenna layout at the upper sideband 10.2GHz. DETAILED DESCRIPTION

[0024] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0025] Figure 1 A cross-sectional view of a broadband thin-film reflectarray antenna element is shown. It comprises a dual-square ring metal patch 1, an upper film 2, an air cavity or foam layer 3, a metal ground 4, and a lower film 5. The element is designed to operate at 9.6 GHz and is square in shape, with a side length equal to 0.5λ0, where λ0 is the wavelength in free space. Both the upper polyimide film 2 and the lower polyimide film 5 are 0.05 mm thick and have a relative dielectric constant of 3.5. The air cavity or foam 3 is 5 mm thick, and the relative dielectric constant of the foam is 1.05. The dual-square ring metal patch 1 is attached to the upper polyimide film 2, and the metal ground 4 is attached to the lower polyimide film 5.

[0026] Figure 2 The front view of the unit is shown, where double square ring metal patches 1 are attached to the upper polyimide film 2, and the side length of each group of metal patches changes according to a certain rule.

[0027] Figure 3 The relationship between the length of the outer square ring of the unit cell and the reflection phase shift and return loss is shown. By controlling the outer square ring length, continuously varying reflection phase shift and return loss can be achieved. By optimizing the relevant parameters, a smooth and continuous phase shift and loss curve is formed. As the outer square ring changes, the reflection phase changes from -180° to 180°, and the phase change is relatively smooth, which facilitates precise antenna design. Furthermore, regardless of the outer square ring length, the reflection loss does not exceed 0.1dB, indicating that the loss introduced by the unit cell is minimal.

[0028] Figure 4The layout of an ultra-wideband thin-film antenna array is shown, consisting of five subarrays: a central subarray 8 and four surrounding trapezoidal subarrays 6, 7, 9, and 10. Central subarray 8 is a square thin-film subarray, covered with 8×8 sets of double-square ring metal patches 1, arranged in a regular pattern. The four surrounding trapezoidal subarrays 6, 7, 9, and 10 are identical in size and tilted at the same angle relative to central subarray 8. Each subarray is covered with 120 sets of double-square ring metal patches 1, arranged in a regular pattern. Subarrays 6 and 10 share the same arrangement pattern, while subarrays 6, 7, and 9 each have different patterns.

[0029] Figure 5 A side view of the ultra-wideband thin film antenna array is shown. The surrounding trapezoidal sub-arrays form a certain angle with the central sub-array, and the angles between the four trapezoidal sub-arrays and the central sub-array are the same.

[0030] Figure 6 The structure of an ultra-wideband thin-film antenna is shown, including a feed source and a reflective array. The feed source uses a horn antenna, and the reflective array is offset-fed. The array edge taper drop is -10dB, and the focal diameter ratio of the antenna is 1.5.

[0031] Figure 7 The design results of the gain radiation pattern of the antenna using this layout at the lower sideband 9GHz are shown. The antenna gain is 30.7dBi, the sidelobe level is better than -20dB, and the cross-polarization is better than -40dB, which proves that the invented broadband thin film reflector array antenna has good performance in the lower sideband.

[0032] Figure 8 The design results of the gain pattern of the antenna using this layout at the center frequency of 9.6 GHz are shown. The antenna gain is 31.2 dBi, the sidelobe level is better than -20 dB, and the cross-polarization is better than -47 dB, proving that the invented broadband thin film reflector array antenna has good performance at the center frequency.

[0033] Figure 9 The design results of the gain pattern of the antenna using this layout at the upper sideband of 10.2GHz are shown. The antenna gain is 30.7dBi, the sidelobe level is better than -20dB, and the cross-polarization is better than -38dB, proving that the invented broadband thin film reflective array antenna has good performance at the upper sideband. Figure 7-9 By comparison, it can be seen that the 0.5dB gain bandwidth of the antenna is not less than 12.5%, which shows good broadband performance.

[0034] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A broadband thin film reflector array antenna, comprising a feed source and a reflector array, characterized in that: The reflective array is composed of two layers of thin films, which are separated by a certain distance, and each layer of thin film is divided into several blocks; each thin film is a plane, and multiple planes are fitted into a quasi-parabola; a metal patch unit is attached to the upper surface of the upper film, and a metal ground is attached to the upper surface of the lower film; the film contains a square central block and four trapezoidal blocks surrounding the central block, which are fitted into a quasi-parabola; the layout of the ultra-wideband thin film antenna array includes five sub-arrays, a central sub-array 8 and four trapezoidal sub-arrays 6, 7, 9, and 10 on the periphery; the central sub-array 8 is a square thin film sub-array, and 8×8 groups of double square ring metal patches are arranged on the sub-array, and the sizes of the patches are arranged according to a certain pattern; the four trapezoidal sub-arrays 6, 7, 9, and 10 on the periphery are the same size and have the same relative inclination angle with the central sub-array 8, and 120 groups of double square ring metal patches are evenly distributed on them, and the sizes of the patches are arranged according to a certain pattern; the arrangement pattern of sub-array 6 and sub-array 10 is exactly the same, and the arrangement patterns of sub-array 6, sub-array 7, and sub-array 9 are different.

2. The broadband thin film reflector array antenna according to claim 1, wherein: The space between the two layers of film is filled with foam or medium honeycomb; or no medium is filled, and the two layers of film are supported by the supporting structure around them.

3. The broadband thin film reflector array antenna according to claim 1 or 2, characterized in that: The film is a polyimide film or a polyester film.

4. The broadband thin film reflector array antenna according to claim 1, wherein: The metal patch unit consists of two inner and outer square rings.

5. The broadband thin film reflector array antenna according to claim 4, wherein: The outer side length of the square outer ring is 0.2 to 0.95 times of the half wavelength, and the outer side length of the inner ring is smaller than the inner side length of the outer ring.

6. The broadband thin film reflector array antenna according to claim 4 or 5, characterized in that: The inner side of the interior ring of a square has zero length.

7. The broadband thin film reflector array antenna according to claim 1, wherein: The feed source is a horn antenna.

8. The broadband thin film reflector array antenna according to claim 1 or 7, wherein: The feed focal ratio is 0.7-1.6.

Images