A design method for near-field focusing lens antenna and near-field focusing lens antenna

Abstract

The present invention belongs to the field of antennas, and in particular, relates to a method for preparing a near-field focusing lens antenna for imaging and a near-field focusing lens antenna, the near-field focusing lens antenna comprising: a rectangular horn antenna with a smooth inner wall (1), a near-field focusing lens (2), and a fixing device (3); the method comprising: step 1) calculating the parameters of the horn antenna; step 2) calculating the external parameters of the near-field focusing lens; step 3) calculating the internal parameters of the near-field focusing lens, and performing tolerance analysis and calculation on the obtained near-field focusing lens antenna; step 4) calculating the near-field gain of the near-field focusing lens antenna, taking the near-field focusing 3dB diameter as the resolution value, and judging whether the calculated result of the resolution meets the design requirements; and step 5) simulating and calculating the influence of the fixing device on the mechanical and electrical properties of the lens antenna, and judging whether the influence degree is within an acceptable range.

Description

Technical Field

[0001] The present invention belongs to the technical field of antennas, and in particular, relates to a design method for a near-field focusing lens antenna and the near-field focusing lens antenna. Background Art

[0002] The wavelength of terahertz waves is between millimeter waves and visible light. It is widely used in space detection and close-range detection on the ground. Compared with the widely used millimeter waves, terahertz waves can achieve higher resolution than millimeter wave imaging when used for imaging. Terahertz imaging methods are divided into coherent and incoherent types. The point scanning method, as a basic imaging method of incoherent type, has the characteristics of high resolution and can improve the imaging resolution to a level close to the diffraction limit. The disadvantage is that imaging can only be performed point by point, so it takes a long time to scan for large-area imaging. Point scanning imaging belongs to a type of near-field incoherent imaging. Its principle is to place the emission source and the sample separately, focus the beam emitted by the terahertz emission source using a quasi-optical system, irradiate the sample to be imaged with the focused light spot, and receive the reflected / refracted signal by the receiver. In order to achieve near-field focusing, the use of a lens antenna is a relatively simple quasi-optical focusing method, which can realize the amplitude and phase modulation of the beam through the refraction of the dielectric material, improve the focusing performance, and achieve focusing close to the diffraction limit.

[0003] The terahertz frequency band needs to use a quasi-optical system to achieve the diffraction-limited focusing method in the near-field state. The lens antenna in the quasi-optical system is widely used and simple in design. Its design method can refer to the design method of visible light lens and improve it based on the characteristics of terahertz. However, the lens antenna in the terahertz frequency band has the following differences in the design process:

[0004] 1. The focusing of the terahertz band needs to be designed to the diffraction limit, while the focusing of visible light only needs to be designed to reach the resolution limit of the human eye. Therefore, the design difficulty of the lens antenna in the terahertz band is higher than that of the visible light lens.

[0005] 2. The beam emitted by the active transmitting source is a non-spherical wave. During the design phase, the emitted beam is designed as a spherical wave. Therefore, the design based on the spherical wave will cause a certain difference between the actual focusing effect and the quasi-light simulation. The resolution in the actual measurement is somewhat worse than that in the simulation phase. Summary of the invention

[0006] In order to solve the above-mentioned defects in the prior art, the present invention proposes a method for preparing a terahertz near-field focusing lens antenna. The method takes into account the current situation that the horn antenna emits a beam of aspherical waves, and optimizes the lens designed for the aforementioned spherical wave according to the surface shape of the beam emitted by the horn antenna.

[0007] The present invention provides a design method for a near-field focusing lens antenna, the near-field focusing lens antenna comprising: a rectangular horn antenna with a smooth inner wall (1), a near-field focusing lens (2) and a fixing device (3); the fixing device (3) fixes the rectangular horn antenna (1) and the near-field focusing lens (2); the method comprises:

[0008] Step 1) calculating the parameters of the smooth inner wall rectangular horn antenna according to the far field gain requirement and the operating frequency of the near field focusing lens antenna;

[0009] Step 2) calculating the external parameters of the near-field focusing lens according to the distance from the aperture of the rectangular horn antenna to the front surface of the lens;

[0010] Step 3) calculating the internal parameters of the near-field focusing lens according to the external parameters;

[0011] Step 4) according to the near-field focusing lens antenna obtained in step 1) to step 3), using the fast multi-level method, calculate the near-field gain of the near-field focusing lens antenna, and calculate whether the resolution result meets the requirements;

[0012] Step 5) Simulate and calculate the influence of the fixture on the mechanical and electrical properties of the near-field focusing lens antenna, determine whether the degree of influence of the deformation caused by the fixture on the electrical properties of the lens is within an acceptable range, and complete the design of the near-field focusing lens antenna.

[0013] As one of the improvements of the above technical solution, the parameters of the smooth inner wall rectangular horn antenna in step 1) include: the long side slant diameter R of the horn antenna h and the short side slope R e , the long side W and short side H of the rectangular aperture of the horn antenna are calculated as follows:

[0014]

[0015]

[0016] R h =0.0746·Gλ

[0017] R e =0.0531·Gλ

[0018] Where G is the far-field gain of the horn antenna and λ is the wavelength.

[0019] As one of the improvements of the above technical solution, in step 2), the external parameters of the near-field focusing lens include: the focal length of the near-field focusing lens, the numerical aperture of the near-field focusing lens and the caliber of the near-field focusing lens; wherein the calculation formula of the focal length f of the near-field focusing lens is:

[0020]

[0021] Wherein, L1 is the distance from the aperture of the rectangular horn antenna to the front surface of the lens, and L2 is the image distance of the lens.

[0022] As one of the improvements of the above technical solution, in step 2), the calculation formula of the numerical aperture NA of the near-field focusing lens is:

[0023] NA=sinθ

[0024] Where θ is half of the antenna transmit beam angle;

[0025] The calculation formula for the aperture D of the near-field focusing lens is:

[0026] D=l1·NA

[0027] Where l1 is the distance from the feeding end to the opening end of the horn antenna.

[0028] As one of the improvements of the above technical solution, in the step 2), the numerical aperture NA of the near-field focusing lens is set below 0.5.

[0029] As one of the improvements of the above technical solution, in step 3), the internal parameters of the near-field focusing lens include: the radius of curvature of the front surface of the lens, the radius of curvature of the rear surface of the lens, and the conic constant; specifically, the near-field focusing lens is set as a lens group consisting of two lenses, and the four surfaces of the lens group all meet:

[0030]

[0031] In the formula, z i is the optical axis of the lens group; r i k is the meridian coordinate of the lens group; i is the conic constant, which is used to represent quadratic surfaces using a unified expression; c i is the radius of curvature of the front surface or rear surface of any lens in the lens group; the subscript i=1,2,3,4 represents the four curved surfaces of the lens group from near to far from the rectangular horn antenna.

[0032] As one of the improvements of the above technical solution, the step 3) further includes:

[0033] Adjust c i and k i , in order to achieve near-field focusing of the outgoing beam of the near-field focusing lens antenna, and the focusing resolution is less than 0.6 mm;

[0034] And perform tolerance analysis on the obtained near-field focusing lens antenna; when the size tolerance is within the range of ±0.02mm and the unevenness tolerance is ±0.05mm, the spot radius of the spot diagram must be less than 1 / 3 of the Airy disk radius. If the requirements are met, go to step 4); if the spot radius of the near-field focusing lens antenna spot diagram is greater than 1 / 3 of the Airy disk radius, it is necessary to continue to adjust the internal parameters of the near-field focusing lens.

[0035] As one of the improvements of the above technical solution, in step 4), whether the calculated near-field resolution meets the requirements is determined as follows:

[0036] When the calculated resolution is less than 1 mm, the operation is terminated, and the preparation of the near-field focusing lens antenna is completed;

[0037] If the calculated resolution is lower than the design requirement of 1 mm, repeat steps 2)-4) until the calculated resolution is less than 1 mm.

[0038] As one of the improvements of the above technical solution, the step 5) specifically includes:

[0039] A contact surface based on penalty function calculation is established between the fixture and the lens. A uniform boundary load per unit area is applied to the cylindrical shell of the fixture. Based on force analysis, a fixed constraint point is set at the center of the lens. The mechanical deformation of the lens under the extrusion of the fixture is calculated to evaluate the influence of mechanical deformation on the electrical properties of the lens.

[0040] The present invention also provides a near-field focusing lens antenna, the near-field focusing lens antenna comprising: a rectangular horn antenna (1), a near-field focusing lens (2) and a fixing device (3); the rectangular horn antenna (1) and the near-field focusing lens (2) are installed and fixed in the fixing device (3);

[0041] The long side W, short side H, and long side oblique diameter R of the rectangular horn antenna h and the short side slope R e Satisfy the following formulas respectively:

[0042]

[0043]

[0044] R h =0.0746·Gλ

[0045] R e =0.0531·Gλ

[0046] Where G is the far-field gain of the antenna and λ is the wavelength;

[0047] The focal length f of the near-field focusing lens (2) satisfies the following formula:

[0048]

[0049] Wherein, L2 is the image distance of the lens, and L1 is the distance from the rectangular horn antenna aperture to the front surface of the lens;

[0050] The numerical aperture NA of the near-field focusing lens (2) satisfies the following formula:

[0051] NA=sinθ

[0052] Where θ is the half angle of the horn antenna beam angle;

[0053] The aperture D of the near-field focusing lens satisfies the following formula:

[0054] D=l1·NA

[0055] Where l1 is the distance between the feeding end and the opening end of the horn antenna;

[0056] The near-field focusing lens (2) is a lens group consisting of two lenses, and the four surfaces of the two lenses all satisfy the following formula:

[0057]

[0058] In the formula, z i is the optical axis of the lens group; r i k is the meridian coordinate of the lens group; i is the conic constant, which is used to design a unified expression to represent the quadratic surface; c i is the radius of curvature of the front / rear surface of any lens in the lens group; the subscript i refers to the number of the lens surface, with the surface closest to the horn antenna being numbered 1, and so on;

[0059] The c i and k i The setting requires the near-field focusing of the outgoing beam of the near-field focusing lens antenna to be achieved, and the focusing resolution is less than 0.6 mm;

[0060] The relevant dimensional tolerances of the near-field focusing lens antenna meet the following requirements: dimensional tolerance is ±0.02 mm, non-uniformity tolerance is ±0.05 mm, and the spot radius of the spot diagram must be less than 1 / 3 of the radius of the Airy disk;

[0061] The near-field resolution of the near-field gain of the near-field focusing lens antenna at different frequencies is less than 1 mm.

[0062] The beneficial effects of the present invention compared with the prior art are:

[0063] The method proposed in the present invention realizes near-field focusing in the 500 GHz frequency band with a resolution of less than 0.7 mm. The design is relatively simple and easy to implement. A mechanical analysis of the influence of the fixing device is carried out to prove that the lens will not be deformed in the fixing device. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 is a flow chart of a method for preparing a near-field focusing lens antenna for imaging according to the present invention;

[0065] Figure 2 is to use Figure 1 A schematic structural diagram of a near-field focusing lens antenna prepared by the method flow chart;

[0066] Figure 3 is the use of Figure 1 Schematic diagram of the resolution of the center frequency near-field focusing lens antenna prepared by the method flow chart, wherein FIG3(a) is a focusing spot diagram, and FIG3(b) is a schematic diagram of the focusing resolution in the x direction;

[0067] Figure 4(a) and Figure 4(b) are respectively Figure 1 A deformation diagram of two lenses after the near-field focusing lens antenna prepared by the method flow chart is fixed by a fixing device;

[0068] Figure 5 This is the effect diagram of the lens being added to the fixing device.

[0069] Figure ID

[0070] 1. Rectangular horn antenna 2. Near-field focusing lens 3. Fixing device DETAILED DESCRIPTION

[0071] The near-field focusing lens antenna for imaging proposed in the present application comprises: a rectangular horn antenna with a smooth inner wall and a near-field focusing lens in the terahertz frequency band;

[0072] Step 1) calculating the parameters of the smooth inner wall rectangular horn antenna; the parameters of the smooth inner wall rectangular horn antenna include: the oblique diameters of the long and short sides of the horn antenna, and the dimensions of the long and short sides of the rectangular mouth of the horn antenna;

[0073] Step 2) calculating the external parameters of the terahertz near-field focusing lens; the external parameters of the terahertz lens include: the distance from the horn antenna aperture to the front surface of the terahertz near-field focusing lens, the focal length of the terahertz near-field focusing lens, the aperture and numerical aperture of the terahertz near-field focusing lens;

[0074] Step 3) calculating the internal parameters of the terahertz near-field focusing lens; the internal parameters of the terahertz lens include: the radius of curvature of the front surface of the lens, the radius of curvature of the rear surface of the lens and the conic constant, and performing tolerance analysis;

[0075] Step 4) Calculate the near-field gain of the near-field focusing lens antenna using the fast multi-level sub-method, and calculate whether the resolution result meets the requirements.

[0076] Step 5) Simulate and calculate the influence of the fixing device (3) on the mechanical and electrical properties of the lens antenna, determine whether the influence is within an acceptable range, and complete the preparation of the terahertz near-field focusing lens antenna.

[0077] As one of the improvements of the above technical solution, the step 1) specifically includes:

[0078] The smooth inner wall horn antenna is a rectangular horn antenna, the long side and the short side are W and H, and the length of the long side oblique diameter and the short side oblique diameter of the rectangular horn antenna is R h and R e According to the optimal rectangular horn antenna design, let the far-field gain of the antenna be G, λ be the wavelength, then the long side W, short side H, and long side slant diameter R h and the short side slope R e It can be expressed as:

[0079]

[0080]

[0081] R h =0.0746·Gλ

[0082] R e =0.0531·Gλ

[0083] Where λ is the wavelength and G is the far-field gain.

[0084] As one of the improvements of the above technical solution, the step 2) specifically includes:

[0085] Assume that the distance from the rectangular horn antenna to the front surface of the terahertz lens is L1, the focal length of the terahertz lens is f, and the numerical aperture of the terahertz lens is NA;

[0086] The focal length f of the lens:

[0087]

[0088] Among them, L2 is the image distance of the lens, and the numerical aperture NA of the lens is sinθ. The larger the value is, the higher the beam efficiency and the higher the resolution, but the more difficult it is to focus. Therefore, the numerical aperture NA should be below 0.5, taking into account the resolution and the difficulty of focusing.

[0089] Then it must satisfy: 0.4≤sinθ≤0.5.

[0090] As one of the improvements of the above technical solution, the step 3) specifically includes:

[0091] Assuming that the terahertz lens is a lens group consisting of two lenses, the expressions of the four surfaces of the lens can be uniformly expressed as

[0092]

[0093] In the formula, z i is the optical axis of the lens group; r i k is the meridian coordinate of the lens group; i is the conic constant, which can be used to represent the quadratic surface with a unified expression; c i is the radius of curvature of the front / back surface of any lens in the lens group;

[0094] Optimize c i , k i , realize the near-field focusing of the outgoing beam of the terahertz near-field focusing lens antenna, and the focusing resolution is less than 0.6 mm. And perform tolerance analysis on the obtained terahertz near-field focusing lens antenna; when the size tolerance is within the range of ±0.02mm and the unevenness tolerance is ±0.05mm, the spot radius of the spot diagram must be less than 1 / 3 of the radius of the Airy disk. If the requirements are met, go to step 4);

[0095] If the spot radius of the terahertz near-field focusing lens antenna spot diagram is greater than 1 / 3 of the Airy disk radius, the lens parameters need to be further optimized;

[0096] As one of the improvements of the above technical solution, the step 4) specifically includes:

[0097] The fast multi-level method is used to calculate the near-field gain of the near-field focusing lens antenna at different frequencies, and to determine whether the calculated near-field resolution meets the requirements;

[0098] When the calculated resolution is less than 1 mm, the operation is terminated, and the preparation of the terahertz near-field focusing lens antenna is completed;

[0099] If the calculated resolution is lower than the design requirement of 1 mm, repeat steps 2)-4) until the calculated resolution is less than 1 mm.

[0100] As one of the improvements of the above technical solution, the step 5) specifically includes:

[0101] The influence of the fixture (3) on the mechanical and electrical properties of the lens antenna is simulated and calculated to determine whether the influence of the lens deformation caused by the fixture is within an acceptable range. That is, by simulating the electrical properties of the lens after deformation, it is found that there is almost no influence on the electrical properties of the lens before deformation, and the preparation of the terahertz near-field focusing lens antenna can be completed.

[0102] The present invention will now be further described with reference to the accompanying drawings and embodiments.

[0103] Example 1

[0104] like Figure 1 As shown, it is a flow chart of a method for preparing a near-field focusing lens antenna according to Embodiment 1 of the present invention. The present invention provides a method for preparing a terahertz near-field focusing lens antenna, the terahertz near-field focusing lens antenna comprising: a smooth internal rectangular horn antenna and a terahertz lens group;

[0105] Step 1) calculating the parameters of the smooth inner wall rectangular horn antenna; the parameters of the smooth inner wall rectangular horn antenna include: calculating the parameters of the smooth inner wall rectangular horn antenna; the parameters of the smooth inner wall rectangular horn antenna include: the oblique diameters of the long side and the short side of the smooth inner wall horn antenna, and the long side and short side dimensions of the rectangular mouth of the smooth inner wall horn antenna;

[0106] Specifically, the step 1) includes:

[0107] The smooth inner wall horn antenna is a rectangular horn antenna, the long side and the short side are W and H, and the length of the long side oblique diameter and the short side oblique diameter of the rectangular horn antenna is R h and R e According to the optimal rectangular horn antenna design, let the far-field gain of the antenna be G, λ be the wavelength, then the long side W, short side H, and long side slant diameter R h and the short side slope R e It can be expressed as:

[0108]

[0109]

[0110] R h =0.0746·Gλ

[0111] R e =0.0531·Gλ

[0112] Where λ is the wavelength and G is the far-field gain.

[0113] Step 2) calculating the external parameters of the near-field focusing terahertz lens; the external parameters of the near-field focusing terahertz lens include: the distance from the transmitting antenna aperture to the front surface of the terahertz lens, the focal length of the terahertz lens, the aperture of the terahertz lens and the numerical aperture of the terahertz near-field focusing lens;

[0114] Specifically, the step 2) includes:

[0115] Assume that the distance from the transmitting antenna aperture to the front surface of the terahertz lens is L1, the focal length of the terahertz near-field focusing lens is f, and the numerical aperture of the terahertz near-field focusing lens is NA;

[0116] The distance from the aperture of the transmitting antenna to the surface of the terahertz lens is L1, and L1 is 40 mm.

[0117] The focal length f of the lens:

[0118]

[0119] Where L2 is the image distance of the lens,

[0120] The aperture of the terahertz lens D = l1·NA

[0121] Where λ is the wavelength;

[0122] The sine of the angle θ corresponding to the -10dB far-field pattern of the feed antenna determines the numerical aperture NA of the lens. The numerical aperture NA of the lens = sinθ, which is between 0.4 and 0.5, that is, it satisfies:

[0123] 0.4≤sinθ≤0.5.

[0124] Step 3) calculating the internal parameters of the terahertz near-field focusing lens; the internal parameters of the terahertz lens include: the curvature radius and aspheric coefficient of the front surface of lens 1, the curvature radius and aspheric coefficient of the rear surface of lens 1, the curvature radius and aspheric coefficient of the front surface of lens 2, and the curvature radius and aspheric coefficient of the rear surface of lens 2; near-field focusing is achieved by optimizing the internal parameters of the terahertz lens;

[0125] Specifically, the step 3) includes:

[0126] The expressions of each surface of the terahertz lens are set as

[0127]

[0128] Among them, z i is the optical axis coordinate of each terahertz lens surface; r i is the meridian coordinate of each terahertz near-field focusing lens; k i is the conic constant of each terahertz near-field focusing lens; c i is the radius of curvature of the front and rear surfaces of each lens;

[0129] Adjust k i and c i Make the beam a near-field focused beam.

[0130] In this embodiment, if Figure 2As shown, the left side of each lens in the terahertz lens group is the front surface, and the right side is the back surface.

[0131] Step 4) according to the results of step 1) to step 3), a terahertz near-field focusing lens antenna is obtained, and it is determined whether the light beam emitted from the terahertz near-field focusing lens antenna obtains a focused spherical wave;

[0132] If the aberration of the beam emitted from the terahertz lens is greater than the threshold, it is determined that good near-field focusing is not achieved, and steps 1)-3) are repeated to adjust various parameters until the aberration is less than the threshold;

[0133] If the aberration of the beam emitted from the terahertz lens is less than or equal to a preset exit angle threshold, it is determined that good focusing is achieved;

[0134] Specifically, the step 4) includes:

[0135] The fast multi-level method is used to calculate the near-field gain of the near-field focusing lens antenna at different frequencies, and to determine whether the calculated near-field resolution meets the requirements;

[0136] When the calculated resolution is less than 1 mm, the operation is terminated, and the preparation of the terahertz near-field focusing lens antenna is completed;

[0137] If the calculated resolution is lower than the design requirement of 1 mm, repeat steps 2)-4) until the calculated resolution is less than 1 mm.

[0138] Step 5) simulate and calculate the influence of the fixing device on the mechanical and electrical properties of the lens antenna, determine whether the influence is within an acceptable range, and complete the preparation of the terahertz near-field focusing lens antenna.

[0139] Specifically, the step 5) includes:

[0140] A contact surface based on penalty function calculation is established between the fixture and the lens. A uniform boundary load per unit area is applied to the cylindrical shell of the fixture. Based on force analysis, a fixed constraint point is set at the center of the lens to calculate the mechanical deformation of the lens under the extrusion of the fixture, so as to avoid deformation of the lens caused by the fixture.

[0141] According to the above preparation method, the present invention provides a method for preparing a terahertz near-field focusing lens antenna, as shown in FIG3 . In this embodiment, the near-field focusing lens antenna includes a horn antenna and a terahertz near-field focusing lens;

[0142] Example 2

[0143] like Figure 2, which is a schematic diagram of the horn antenna and the near-field focusing lens in the near-field focusing lens antenna prepared in Example 2 of the present invention; in the terahertz near-field focusing lens antenna prepared in this embodiment, the distance L1 from the horn antenna aperture to the terahertz lens surface is 40 mm, and the numerical aperture NA of the lens is 0.5; the lens curvature radius from left to right is -492.262, -19.692, 11.136, 21.089, and the aspheric coefficient k i are 0, -0.481, -0.450, -0.725;

[0144] The main task of preparing terahertz near-field focusing lens antennas is to select and optimize the lens surface to ensure that the outgoing beam is a nearly spherical wave, thereby improving the resolution.

[0145] As shown in FIG. 3( a ) and FIG. 3( b ), the terahertz near-field focusing lens antenna prepared above achieves high-resolution focusing, with a resolution of 0.64 mm at 500 GHz.

[0146] As shown in Figure 4(a) and Figure 4(b), Figure 1 The deformation diagram of the two lenses of the near-field focusing lens antenna prepared by the method flow chart after being fixed by a fixing device; after adding the fixing device, the deformation of the two lenses is shown in the figure. The deformation is mostly concentrated at the contact position between the lens and the fixing device, and has almost no effect on optical parameters such as lens curvature.

[0147] like Figure 5 The figure shows the effect of adding a fixture to the lens. The rectangular horn antenna is mounted on the fixture via a flange.

[0148] It can be seen from the above specific description of the present invention that the terahertz near-field focusing lens antenna prepared by the method of the present invention achieves high-resolution focusing.

[0149] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the embodiments, it should be understood by those skilled in the art that any modification or equivalent replacement of the technical solutions of the present invention does not depart from the spirit and scope of the technical solutions of the present invention and should be included in the scope of the claims of the present invention.

Claims

1. A design method for a near-field focusing lens antenna, the near-field focusing lens antenna comprising: A rectangular horn antenna with a smooth inner wall (1), a near-field focusing lens (2) and a fixing device (3); The fixing device (3) fixes the rectangular horn antenna (1) and the near-field focusing lens (2); the method comprises: Step 1) calculating the parameters of the smooth inner wall rectangular horn antenna according to the far field gain requirement and the operating frequency of the near field focusing lens antenna; Step 2) calculating the external parameters of the near-field focusing lens according to the distance from the aperture of the rectangular horn antenna to the front surface of the lens; Step 3) calculating the internal parameters of the near-field focusing lens according to the external parameters; Step 4) according to the near-field focusing lens antenna obtained in step 1) to step 3), using the fast multi-level method, calculate the near-field gain of the near-field focusing lens antenna, and calculate whether the resolution result meets the requirements; Step 5) Simulate and calculate the influence of the fixture on the mechanical and electrical properties of the near-field focusing lens antenna, determine whether the degree of influence of the deformation caused by the fixture on the electrical properties of the lens is within an acceptable range, and complete the design of the near-field focusing lens antenna.

2. The design method of the near-field focusing lens antenna according to claim 1, characterized in that: The parameters of the smooth inner wall rectangular horn antenna in step 1) include: the long side slant diameter R of the horn antenna h and the short side slope R e , the long side W and short side H of the rectangular aperture of the horn antenna are calculated as follows: R h =0.0746·Gλ R e =0.0531·Gλ Where G is the far-field gain of the horn antenna and λ is the wavelength.

3. The design method of the near-field focusing lens antenna according to claim 1, characterized in that: In the step 2), the external parameters of the near-field focusing lens include: the focal length of the near-field focusing lens, the numerical aperture of the near-field focusing lens and the caliber of the near-field focusing lens; wherein the calculation formula of the focal length f of the near-field focusing lens is: Wherein, L1 is the distance from the aperture of the rectangular horn antenna to the front surface of the lens, and L2 is the image distance of the lens.

4. The design method of the near-field focusing lens antenna according to claim 3, characterized in that: In the step 2), the calculation formula of the numerical aperture NA of the near-field focusing lens is: NA=sinθ Where θ is half of the antenna transmit beam angle; The calculation formula for the aperture D of the near-field focusing lens is: D=l1·NA Where l1 is the distance from the feeding end to the opening end of the horn antenna.

5. The design method of the near-field focusing lens antenna according to claim 4, characterized in that: In the step 2), the numerical aperture NA of the near-field focusing lens is set below 0.

5.

6. The design method of the near-field focusing lens antenna according to claim 1, characterized in that: In step 3), the internal parameters of the near-field focusing lens include: the radius of curvature of the front surface of the lens, the radius of curvature of the rear surface of the lens, and the conic constant; specifically, the near-field focusing lens is set as a lens group consisting of two lenses, and the four surfaces of the lens group all meet: In the formula, z i is the optical axis of the lens group; r i k is the meridian coordinate of the lens group; i is the conic constant, which is used to represent quadratic surfaces using a unified expression; c i is the radius of curvature of the front surface or rear surface of any lens in the lens group; the subscript i=1,2,3,4 represents the four curved surfaces of the lens group from near to far from the rectangular horn antenna.

7. The design method of the near-field focusing lens antenna according to claim 6, characterized in that: The step 3) also includes: Adjust c i and k i , in order to achieve near-field focusing of the outgoing beam of the near-field focusing lens antenna, and the focusing resolution is less than 0.6 mm; And perform tolerance analysis on the obtained near-field focusing lens antenna; when the size tolerance is within the range of ±0.02mm and the unevenness tolerance is ±0.05mm, the spot radius of the spot diagram must be less than 1 / 3 of the Airy disk radius. If the requirements are met, go to step 4); if the spot radius of the near-field focusing lens antenna spot diagram is greater than 1 / 3 of the Airy disk radius, it is necessary to continue to adjust the internal parameters of the near-field focusing lens.

8. The design method of the near-field focusing lens antenna according to claim 1, characterized in that: In step 4), it is determined whether the calculated near-field resolution meets the requirements, specifically: When the calculated resolution is less than 1 mm, the operation is terminated, and the preparation of the near-field focusing lens antenna is completed; Otherwise, repeat steps 2)-4) until the calculated resolution is less than 1 mm.

9. The design method of the near-field focusing lens antenna according to claim 1, characterized in that: The step 5) specifically includes: A contact surface based on penalty function calculation is established between the fixture and the lens. A uniform boundary load per unit area is applied to the cylindrical shell of the fixture. Based on force analysis, a fixed constraint point is set at the center of the lens. The mechanical deformation of the lens under the extrusion of the fixture is calculated to evaluate the influence of mechanical deformation on the electrical properties of the lens.

10. A near-field focusing lens antenna, characterized in that: The near-field focusing lens antenna comprises: a rectangular horn antenna (1), a near-field focusing lens (2) and a fixing device (3); the rectangular horn antenna (1) and the near-field focusing lens (2) are installed and fixed in the fixing device (3); The long side W, short side H, and long side oblique diameter R of the rectangular horn antenna h and the short side slope R e Satisfy the following formulas respectively: R h =0.0746·Gλ R e =0.0531·Gλ Where G is the far-field gain of the antenna and λ is the wavelength; The focal length f of the near-field focusing lens (2) satisfies the following formula: Wherein, L2 is the image distance of the lens, and L1 is the distance from the rectangular horn antenna aperture to the front surface of the lens; The numerical aperture NA of the near-field focusing lens (2) satisfies the following formula: NA=sinθ Where θ is the half angle of the horn antenna beam angle; The aperture D of the near-field focusing lens satisfies the following formula: D=l1·NA Where l1 is the distance between the feeding end and the opening end of the horn antenna; The near-field focusing lens (2) is a lens group consisting of two lenses, and the four surfaces of the two lenses all satisfy the following formula: In the formula, z i is the optical axis of the lens group; r i k is the meridian coordinate of the lens group; i is the conic constant, which is used to design a unified expression to represent quadratic surfaces; c i is the radius of curvature of the front / rear surface of any lens in the lens group; the subscript i refers to the number of the lens surface, with the surface closest to the horn antenna being numbered 1, and so on; The c i and k i The setting requires the near-field focusing of the outgoing beam of the near-field focusing lens antenna to be achieved, and the focusing resolution is less than 0.6 mm; The relevant dimensional tolerances of the near-field focusing lens antenna meet the following requirements: dimensional tolerance is ±0.02 mm, non-uniformity tolerance is ±0.05 mm, and the spot radius of the spot diagram must be less than 1 / 3 of the radius of the Airy disk; The near-field resolution of the near-field gain of the near-field focusing lens antenna at different frequencies is less than 1 mm.

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