A gain enhancement structure for antenna array based on double-lens structure

Abstract

The present invention discloses an antenna array gain enhancement structure based on a dual-lens structure, which belongs to the field of radio frequency communication technology. The gain enhancement structure of the present invention includes two layers of lenses; the first layer of lenses is a primary mirror, which adopts a Fresnel lens and is used to convert spherical waves into plane waves, thereby achieving gain enhancement; the second layer of lenses is a secondary mirror, which is located between the antenna array and the primary mirror and is used to provide phase compensation for the antenna array elements. The antenna array gain enhancement structure based on the dual-lens structure of the present invention can effectively achieve gain improvement of the antenna array; the carrier is FSS, which has the characteristics of low profile and low cost; while improving the array gain, it does not change the characteristics of the antenna array itself, and has the characteristics of convenient detachability.

Description

Technical Field

[0001] The present invention belongs to the technical field of radio frequency communications, and in particular relates to an antenna array gain enhancement structure based on a dual-lens structure. Background Art

[0002] With the continuous development of wireless communication technology, the introduction of millimeter-wave technology can meet its requirements for high data rates, high reliability, and low power consumption. Millimeter-wave antennas play a key role in this, and therefore high-performance millimeter-wave antennas with high-gain characteristics have become the focus and difficulty of current research. Existing methods for improving antenna gain include array formation and the use of large-aperture antennas, but the implementation and application of these technologies are not flexible, and excessive array spacing will also change the structure of the antenna itself, thereby affecting the antenna's performance, such as the emergence of problems such as grating lobes. Therefore, how to effectively achieve high-gain characteristics of antenna arrays in the millimeter-wave frequency band through antenna gain enhancement structures remains an unresolved problem.

[0003] The prior art "A broadband circularly polarized Fabry-Perot resonant antenna using a single-layered PRS for 5G MIMO applications" discloses a millimeter-wave gain enhancement structure based on a partially reflective cladding with a high dielectric constant. However, the thickness and height of the dielectric layer are limited to half a wavelength, and the dielectric layer plate is constrained by the high dielectric constant, making it impossible to achieve the high gain characteristics of the antenna array.

[0004] The existing technology "Gain enhancement of a V-Band antenna using a Fabry-perotcavity with a self-sustained all-metal cap with FSS" forms an all-metal nut structure into a periodic structure to achieve antenna gain improvement in the V band. However, the all-metal structure also has disadvantages such as high cost and bulkiness. It also fails to achieve the high gain characteristics of the antenna array and causes the antenna gain bandwidth to narrow.

[0005] A Chinese patent application titled "Fabry-Perot resonant cavity broadband high-gain microstrip antenna based on a single-layer double-sided cladding structure" and publication number CN109802232A discloses a technical means of increasing the gain of an antenna through a single-layer double-sided electromagnetic periodic structure, but it also cannot achieve the high-gain characteristics of a millimeter-wave antenna array. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide an antenna array gain enhancement structure based on a dual-lens structure, which can improve the array gain of the millimeter wave antenna without changing the inherent characteristics of the antenna and its array.

[0007] The technical problem proposed by the present invention is solved as follows:

[0008] An antenna array gain enhancement structure based on a dual-lens structure includes two layers of lenses. The first layer is a primary mirror, which uses a Fresnel lens to convert spherical waves into plane waves, thereby achieving gain enhancement. The second layer is a secondary mirror, located between the antenna array and the primary mirror, and is used to provide phase compensation for the antenna array elements.

[0009] The center of the antenna array coincides with the focus of the primary mirror and is located at the origin of the rectangular coordinate system; a secondary mirror is configured for each antenna element between the antenna array and the primary mirror; the plane where the antenna array is located, the primary mirror, and the secondary mirror are parallel to the xoy plane;

[0010] The phase of the incident wave from the center of the antenna array to any point on the main mirror is:

[0011]

[0012] Where F is the focal length of the primary mirror, i.e., the distance from the focus to the primary mirror surface; k0 is the free space wave number corresponding to the center frequency; x and y are the horizontal and vertical coordinates of any point on the primary mirror surface, respectively.

[0013] The phase of the outgoing wave with a pointing angle of α0 is:

[0014]

[0015] Then the phase distribution that needs to be compensated on the primary mirror aperture surface is:

[0016]

[0017] in, is the reference phase;

[0018] The electromagnetic wave passes through the corresponding secondary mirror from the position O' of any antenna element to obtain phase compensation The phase of the incident wave arriving at any point C of the primary mirror is:

[0019]

[0020] Where x' and y' are the horizontal and vertical coordinates of any point on the secondary mirror surface, respectively. O'C is the distance from point O' to point C, d is the thickness of the secondary mirror, and θ is the angle between the line connecting point O' and point C and the z-axis;

[0021] The phase of the incident wave from the origin O to point C is:

[0022]

[0023] Among them, d OC is the distance from the origin O to point C;

[0024] To achieve The phase distribution that needs to be compensated for the secondary mirror is as follows:

[0025]

[0026] Furthermore, the lens uses a slab or a frequency selective surface FSS as a phase control carrier.

[0027] Furthermore, the primary mirror includes a first dielectric substrate 11 and a first square patch 2. The first square patch 2 is located on the lower surface of the first dielectric substrate 11, has a side length of 0.4 mm, and a center periodic spacing of adjacent first square patches 2 is 2.5 mm. The 10×10 first square patch 2 located in the center is defective.

[0028] The secondary mirrors corresponding to all antenna elements in the antenna array are designed as a whole, including a second dielectric substrate 1 and a second square patch 3; the second square patch is located on the lower surface of the second dielectric substrate 1, with a side length of 0.35 mm, and the center period spacing of adjacent second square patches 3 is 2.5 mm.

[0029] The array antenna consists of 4×4 antenna elements arranged tightly in a rectangular shape. Each antenna element includes a parasitic patch 7, a radiating patch 5, an upper dielectric substrate 6, a lower dielectric substrate 4, a feed metal probe 8, an SMA connector 9, and a ground plane 10. The parasitic patch 7, the upper dielectric substrate 6, the radiating patch 5, the lower dielectric substrate 4, and the ground plane 10 are tightly fitted together from top to bottom. The SMA connector 9 is located at the bottom of the ground plane 10, with its outer conductor connected to the ground plane 10. The feed metal probe 8 passes through the lower dielectric substrate 4 and connects to the inner conductor of the radiating patch 5 and the SMA connector 9, respectively. The array antenna is fixedly mounted on a metal support structure 12 at uneven heights.

[0030] There is a 1mm air gap between the first dielectric substrate 11 and the second dielectric substrate 1; there is an 8.8mm air gap between the second dielectric substrate 1 and the upper dielectric substrate 6. The first dielectric substrate 11 has dimensions of 50mm*50mm, a dielectric constant of 2.67, a tangent loss of 0.0074, and a thickness of 6mm. The second dielectric substrate 1 has dimensions of 25mm*25mm, a dielectric constant of 2.67, a tangent loss of 0.0074, and a thickness of 3.5mm.

[0031] The beneficial effects of the present invention are:

[0032] The antenna array gain enhancement structure based on the dual-lens structure described in the present invention can effectively achieve gain improvement of the antenna array; the carrier is FSS, which has the characteristics of low profile and low cost; while improving the array gain, it does not change the characteristics of the antenna array itself and has the characteristics of convenient disassembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the principle of the primary mirror in the gain enhancement structure of the present invention;

[0034] Figure 2 Schematic diagram of the principle of the gain enhancement structure of the present invention;

[0035] Figure 3 Schematic diagram of the gain enhancement structure described in the embodiment;

[0036] Figure 4 A gain comparison diagram of the antenna array with and without the gain enhancement structure described in the embodiment;

[0037] Figure 5 This is a comparison diagram of the directional patterns of the antenna array described in the embodiment with and without the gain enhancement structure at 26.5 GHz;

[0038] Figure 6 This is a comparison diagram of the directional patterns of the antenna array described in the embodiment with and without the gain enhancement structure at 28 GHz;

[0039] Figure 7 This is a comparison diagram of the directional patterns of the antenna array described in the embodiment with and without the gain enhancement structure at 29.5 GHz. DETAILED DESCRIPTION

[0040] The present invention will be further described below with reference to the accompanying drawings and examples.

[0041] This embodiment provides an antenna array gain enhancement structure based on a dual-lens structure, including two layers of lenses; the first layer of lenses is a primary mirror, which uses a Fresnel lens to convert spherical waves into plane waves, thereby achieving gain enhancement; the second layer of lenses is a secondary mirror, which is located between the antenna array and the primary mirror, parallel to the antenna array and the primary mirror, and is used to provide phase compensation for the antenna array elements.

[0042] For the primary mirror, the principle involved is to compensate for the phase difference of the incident wave caused by different spatial paths by adjusting the projection phase of each point on the lens aperture surface, so that the phase of the outgoing wave of the lens is the same, thereby forming a high-gain pencil beam. Figure 1As shown, the ideal point source coincides with the focus of the primary mirror and is located at the origin O in the rectangular coordinate system; the primary mirror is parallel to the xoy plane; point A is the point on the lens where x=y=0, and point C is any point on the lens surface that does not coincide with A; α0 is the pointing angle of the outgoing wave after the electromagnetic wave radiated by the ideal point source passes through the lens; according to the principle of equal optical path difference, the phase of the path of the electromagnetic wave from the origin O through point A to point B should be the same as the phase of the path from the origin O through point C to point D, and the angle between the line connecting B and D and the lens is α0.

[0043] It is known that the incident wave phase from an ideal point source to any point on the primary mirror is:

[0044]

[0045] Where F is the focal length of the primary mirror, i.e., the distance from the focus to the primary mirror surface; k0 is the free space wave number corresponding to the center frequency; x and y are the horizontal and vertical coordinates of any point on the primary mirror surface, respectively.

[0046] The phase of the outgoing wave with a pointing angle of α0 is:

[0047]

[0048] The phase distribution formula that needs to be compensated on the main lens aperture surface is:

[0049]

[0050] in, is the reference phase.

[0051] In the design of the high-gain planar lens antenna described in this embodiment, a phase distribution method with α0 = 0° is adopted. Based on the above formula, the phase distribution that needs to be compensated for the primary mirror can be obtained.

[0052] For antenna arrays, there is more than one ideal point source, so it is necessary to design an additional lens for each antenna element that deviates from the focus position to perform corresponding phase compensation. Figure 2 As shown in FIG, the gain enhancement structure of this embodiment uses a double-layer lens to enhance the gain of the antenna array. The gain enhancement structure model of the double-layer lens is shown in FIG. Figure 2 shown.

[0053] The center of the antenna array coincides with the focus of the primary mirror and is located at the origin O of the rectangular coordinate system; a secondary mirror is configured for each antenna element between the antenna array and the primary mirror; the plane where the antenna array is located, the primary mirror, and the secondary mirror are parallel to the xoy plane;

[0054] According to the principle of equal optical path difference, the electromagnetic wave passes through the corresponding secondary mirror TAA' from the position O' of any antenna array element to obtain phase compensation. The phase of the path reaching any point C of the primary mirror should be the same as the path from the origin O to point C.

[0055] The electromagnetic wave passes through the corresponding secondary mirror TAA' from the position O' of any antenna array element to obtain phase compensation The phase of the incident wave arriving at any point C of the primary mirror is:

[0056]

[0057] Where x' and y' are the horizontal and vertical coordinates of any point on the surface of the secondary mirror TAA', respectively. O'C is the distance from point O' to point C, d is the thickness of the secondary mirror TAA', and θ is the angle between the line connecting point O' and point C and the z-axis;

[0058] The phase of the incident wave from the origin O to point C is:

[0059]

[0060] Among them, d OC is the distance from point O to point C;

[0061] To achieve The phase distribution that needs to be compensated for the secondary mirror is as follows:

[0062]

[0063] The above derivation can be used to obtain the phase compensation values ​​of the two lens layers. In practical cases, dielectric plates or frequency selective surfaces (FSSs) are usually used as phase control carriers. Considering the low profile and easy processing characteristics of FSSs, the present invention uses FSSs as the phase shift transmission unit.

[0064] This embodiment applies a dual-lens gain enhancement structure to a millimeter-wave stacked antenna to achieve broadband high gain in the millimeter-wave frequency band. Figure 3 shown.

[0065] In this embodiment, the primary mirror includes a first dielectric substrate 11 and a first square patch 2. The first square patch 2 is located on the lower surface of the first dielectric substrate 11, has a side length of 0.4 mm, and the center periodic spacing between adjacent first square patches 2 is 2.5 mm. The 10×10 first square patch 2 located in the center is defective.

[0066] The secondary mirrors corresponding to all antenna elements in the antenna array are designed as a whole, including a second dielectric substrate 1 and a second square patch 3; the second square patch is located on the lower surface of the second dielectric substrate 1, with a side length of 0.35 mm, and the center period spacing of adjacent second square patches 3 is 2.5 mm.

[0067] In this embodiment, the array antenna is composed of 4×4 antenna elements arranged tightly in a rectangular shape. Each antenna element includes a parasitic patch 7, a radiating patch 5, an upper dielectric substrate 6, a lower dielectric substrate 4, a feed metal probe 8, an SMA connector 9, and a ground plane 10. The parasitic patch 7, the upper dielectric substrate 6, the radiating patch 5, the lower dielectric substrate 4, and the ground plane 10 are tightly fitted in sequence from top to bottom. The SMA connector 9 is located at the bottom of the ground plane 10, and the outer conductor is connected to the ground plane 10. The feed metal probe 8 passes through the lower dielectric substrate 4 and is respectively connected to the inner conductor of the radiating patch 5 and the SMA connector 9.

[0068] There is a 1mm air gap between the first dielectric substrate 11 and the second dielectric substrate 1; there is an 8.8mm air gap between the second dielectric substrate 1 and the upper dielectric substrate 6. The first dielectric substrate 11 has dimensions of 50mm*50mm, a dielectric constant of 2.67, a tangent loss of 0.0074, and a thickness of 6mm. The second dielectric substrate 1 has dimensions of 25mm*25mm, a dielectric constant of 2.67, a tangent loss of 0.0074, and a thickness of 3.5mm.

[0069] The array antenna is fixedly mounted on a metal support structure 12 at different heights.

[0070] Figure 4 A gain comparison diagram of the antenna array with and without the gain enhancement structure described in the embodiment; Figure 5 This is a comparison diagram of the directional patterns of the antenna array described in the embodiment with and without the gain enhancement structure at 26.5 GHz; Figure 6 This is a comparison diagram of the directional patterns of the antenna array described in the embodiment with and without the gain enhancement structure at 28 GHz; Figure 7 This figure compares the antenna array patterns at 29.5 GHz with and without the gain enhancement structure. As can be seen from the figure, the peak gain of the antenna array is improved by 3 dB compared to the reference patch array without the millimeter-wave enhancement structure. This demonstrates that the dual-lens gain enhancement structure described in this embodiment achieves antenna array gain enhancement in the millimeter-wave frequency band, demonstrating the effectiveness of the gain enhancement structure described in this embodiment.

[0071] The above description of the present invention and its embodiments is provided for those skilled in the art. The above examples are intended to help readers understand the principles of the invention and should be considered illustrative rather than restrictive. Those skilled in the art may make modifications based on the technical concepts disclosed in the claims without departing from the core essence of the present invention. All of the above modifications should be considered within the scope of protection of the present invention.

Claims

1. An antenna array gain enhancement structure based on a dual-lens structure, characterized in that: It includes two layers of lenses. The first layer is the primary mirror, which uses a Fresnel lens to convert spherical waves into plane waves, thereby achieving gain enhancement. The second lens is the secondary mirror, located between the antenna array and the primary mirror, and is used to provide phase compensation for the antenna array elements. The center of the antenna array coincides with the focus of the primary mirror and is located at the origin of the rectangular coordinate system; a secondary mirror is configured for each antenna element between the antenna array and the primary mirror; the plane where the antenna array is located, the primary mirror, and the secondary mirror are parallel to the xoy plane; The phase of the incident wave from the center of the antenna array to any point on the main mirror is: Where F is the focal length of the primary mirror, i.e., the distance from the focus to the primary mirror surface; k0 is the free space wave number corresponding to the center frequency; x and y are the horizontal and vertical coordinates of any point on the primary mirror surface, respectively. The phase of the outgoing wave with a pointing angle of α0 is: Then the phase distribution that needs to be compensated on the primary mirror aperture surface is: in, is the reference phase; The electromagnetic wave passes through the corresponding secondary mirror from the position O' of any antenna element to obtain phase compensation The phase of the incident wave arriving at any point C of the primary mirror is: Where x' and y' are the horizontal and vertical coordinates of any point on the secondary mirror surface, respectively. O'C is the distance from point O' to point C, d is the thickness of the secondary mirror, and θ is the angle between the line connecting point O' and point C and the z-axis; The phase of the incident wave from the origin O to point C is: Among them, d OC is the distance from the origin O to point C; To achieve The phase distribution that needs to be compensated for the secondary mirror is as follows:

2. The antenna array gain enhancement structure based on a dual-lens structure according to claim 1, characterized in that: The lens uses a solid plate or a frequency selective surface FSS as a phase control carrier.

3. The antenna array gain enhancement structure based on a dual-lens structure according to claim 1, characterized in that: The primary mirror comprises a first dielectric substrate (11) and a first square patch (2), wherein the first square patch (2) is located on the lower surface of the first dielectric substrate (11), has a side length of 0.4 mm, and a central periodic spacing between adjacent first square patches (2) is 2.5 mm, and a 10×10 first square patch (2) located at the center is defective; The secondary mirrors corresponding to all antenna elements in the antenna array are designed as a whole, comprising a second dielectric substrate (1) and a second square patch (3); the second square patch is located on the lower surface of the second dielectric substrate (1), has a side length of 0.35 mm, and the center period spacing between adjacent second square patches (3) is 2.5 mm; The array antenna is composed of 4×4 antenna elements tightly arranged in a rectangular shape, and each antenna element comprises a parasitic patch (7), a radiating patch (5), an upper dielectric substrate (6), a lower dielectric substrate (4), a feeding metal probe (8), an SMA connector (9) and a grounding plate (10); the parasitic patch (7), the upper dielectric substrate (6), the radiating patch (5), the lower dielectric substrate (4) and the grounding plate (10) are tightly fitted in sequence from top to bottom; the SMA connector (9) is located at the bottom of the grounding plate (10), the outer conductor is connected to the grounding plate (10), and the feeding metal probe (8) passes through the lower dielectric substrate (4) and is respectively connected to the inner conductor of the radiating patch (5) and the SMA connector (9); the array antenna is fixedly mounted on a metal support structure (12) of unequal heights; There is an air gap of 1 mm between the first dielectric substrate (11) and the second dielectric substrate (1); There is an air gap of 8.8 mm between the second dielectric substrate (1) and the upper dielectric substrate (6); the first dielectric substrate (11) has a size of 50 mm*50 mm, a dielectric constant of 2.67, a tangent loss of 0.0074, and a thickness of 6 mm; the second dielectric substrate (1) has a size of 25 mm*25 mm, a dielectric constant of 2.67, a tangent loss of 0.0074, and a thickness of 3.5 mm.

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