Terahertz near-field feed array amplitude and phase determination method based on plane wave incidence

Abstract

The invention discloses a terahertz near-field feed array amplitude and phase determination method based on plane wave incidence. The method comprises the following steps: 1, establishing a three-dimensional calculation model of an equiphase surface, a lens or a reflecting surface and an offset-focus feed surface; 2, the plane waves are propagated from the equiphase surface to the lens or the reflecting surface; 3, the position of a solving point is consistent with the center position of an actual feed source port plane; 4, calculating phase and amplitude parameters of each solving point of the offset-focus feed surface; 5, setting an included angle parameter between the equiphase surface and the normal of the aperture surface of the lens or the reflecting surface; 6, traversing the amplitude-phase distribution of the offset-focus array plane corresponding to each beam pointing angle in the beam scanning range; and 7, taking the amplitude-phase distribution parameter in the step 6 as input, and solving a conjugate phase of each solution point as an angle driving parameter applied by the phased-array antenna. According to the method, a unified calculation model is provided, so that the method is applicable to the two antenna designs, the calculation difference is reduced, and the design efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of terahertz antennas, and relates to a method for determining the amplitude and phase of a terahertz near-field feeding array based on plane-wave incidence. Background Art

[0002] Terahertz communication has the technical advantages of high speed and strong security, and has become a research hotspot at home and abroad in recent years. Due to the characteristics of terahertz quasi-optical propagation, it has strong directivity, and in long-distance communication, the configured high-gain antenna makes the communication beam relatively narrow. Therefore, terahertz communication between moving nodes needs to cooperate with high-precision beam control technology. Due to the narrow-beam characteristics of terahertz communication, for communication interconnection between fast-moving nodes, it is necessary to further improve the beam scanning speed, and the multi-beam flexible control ability of traditional fixed-surface antennas is very limited. Therefore, after the breakthrough of mechanical scanning beam pointing control technology, the current terahertz phased array technology has become a new focus in the field of terahertz communication. Terahertz phased arrays require arrayed channels. Since the implementation of high-performance terahertz RF circuits is more difficult than that of microwaves, and the efficiency also needs to be further improved. Considering the implementation difficulty and heat dissipation problems of the system, the achievable scale of terahertz phased arrays is generally not large. To further improve the gain, a reflector or lens is required for gain enhancement to increase its equivalent radiated power and extend the working distance of communication.

[0003] The antenna feed arrays using a lens or reflector for gain enhancement have a certain planar scale. In actual use, the feed array surface needs to be defocused, and to shorten the feed path, improve the feed efficiency and reduce the profile height of the antenna, the feed array is generally placed in near-field feeding. When feeding in the near field, the amplitude and phase configuration of the feed array elements has problems such as complex analysis and lack of reference for initial value setting. Implementing full-wave simulation for convenient amplitude and phase configuration calculation has a very large amount of calculation, and the time consumption cannot be ignored. Summary of the Invention

[0004] The present invention proposes a method for determining the amplitude and phase of a terahertz near-field feeding array based on plane-wave incidence, which can quickly determine the relationship between the amplitude and phase of each array element in the complex terahertz near-field feeding mode and the antenna beam pointing, effectively overcoming the problems of scale sensitivity in the terahertz band and the analytical difficulties caused by multiple couplings in the near-field feeding array.

[0005] To solve the above problems, the technical solutions adopted by the present invention include:

[0006] A method for determining the amplitude and phase of a terahertz near-field feeding array based on plane-wave incidence, comprising:

[0007] The first step: Establish a three-dimensional calculation model of an equiphase surface, a lens or a reflector, and a defocused feeding surface, and input the material and structural parameters of the lens or reflector, and define the size of the defocused feeding surface and the positional relationship with the focus of the lens or reflector;

[0008] Step 2: Set the plane wave to propagate from the equiphase surface to the lens or the reflecting surface. The lens calculates the propagation characteristics according to the medium, and the reflecting surface calculates the propagation characteristics according to the ideal metal surface;

[0009] Step 3: The position of the solution points on the defocused feed surface is consistent with the plane center position of the actual antenna feed surface to be fabricated;

[0010] Step 4: Calculate the phase and amplitude parameters of each solution point on the defocused feed surface;

[0011] Step 5: Set the included angle parameter between the equiphase surface and the aperture normal of the lens or the reflecting surface with an angular step not exceeding the 3dB beam width, and repeat Steps 1 to 4;

[0012] Step 6: Repeat Step 5 to traverse one by one the amplitude-phase distributions of the defocused feed surfaces corresponding to the beam pointing angles within the beam scanning range to be solved;

[0013] Step 7: Take the amplitude-phase distribution parameters in Step 6 as the input, and obtain the conjugate phase of each solution point on the defocused feed surface as the angle driving parameter for phased array antenna applications.

[0014] Optionally, in the three-dimensional calculation model, the lens is located between the equiphase surface and the defocused feed surface.

[0015] Optionally, in the three-dimensional calculation model, the defocused feed surface is between the reflecting surface and the equiphase surface.

[0016] Optionally, the size of the defocused feed surface is the chord length corresponding to the position of the placed feed array under the angle subtended by the focus to the edge of the lens or the reflecting surface.

[0017] Optionally, the material and structure parameters of the lens or the reflecting surface include: the material properties and the material structure distribution of the lens or the reflecting surface.

[0018] Optionally, the definition of the size of the defocused feed surface and the positional relationship with the focus of the lens or the reflecting surface includes the size of the defocused feed surface, the center position of the actual antenna feed surface to be fabricated, and the overall three-dimensional coordinates of the defocused feed surface.

[0019] Optionally, in Step 2, the lens allows the electromagnetic wave to transmit and propagate, and the calculation of the propagation characteristics is characterized by the parameters of the permittivity and the permeability;

[0020] The electromagnetic wave propagation characteristic of the reflecting surface is total reflection, and only a 180° phase reversal is completed on the reflecting surface when calculating the propagation characteristics.

[0021] Optionally, in the fourth step, a finite element analysis solution method is adopted to perform full-wave simulation to calculate the phase and amplitude parameters of each solution point on the defocused feed surface;

[0022] Alternatively, for a regular lens or reflector, the Maxwell's equations are solved using the traveling wave method.

[0023] Advantages and beneficial effects of the present invention:

[0024] (1) Defocused surface amplitude-phase distribution inversion model based on plane wave incidence: The present invention proposes a unified calculation model for different architectures of in-field feeding of lens-enhanced and reflector-enhanced phased feed arrays, making the present invention applicable to both of these two antenna designs, reducing the calculation differences, and improving the design efficiency.

[0025] (2) Method for determining the amplitude-phase parameters of a quasi-optical gain-enhanced phased feed array: When the quasi-optical gain-enhanced phased feed array proposed by the present invention is in-field fed, the method for determining the amplitude-phase parameters of each array element utilizes the transmission reciprocity of the lens or reflector passive device, and the amplitude-phase parameters of the feed array elements for one beam angle can be determined through a single mapping, improving the design efficiency of the terahertz phased array antenna. Description of the Drawings

[0026] The drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. They are used together with the following specific embodiments to explain the present disclosure, but do not constitute a limitation to the present disclosure. In the drawings:

[0027] Figure 1 Schematic diagram of beamforming of a phased feed array, Figure 1 wherein TAA is the lens of the example of the present invention, PAA is the near-field feed array, F is the focal length of the lens, and H is the distance between the feed array and the lens;

[0028] Figure 2 Theoretical amplitude and amplitude-phase distribution diagrams of far-field plane wave incidence, S is free space, m and n are incident beams, and the subscripts represent the three stages before entering the lens, in the lens, and after passing through the lens respectively, and can be used as variables for the calculation in the fourth step of the method;

[0029] Figure 3 Hemispherical lens far-field 30° plane wave incidence intercepted amplitude-phase diagram, the left figure is the amplitude distribution diagram, and the right figure is the phase distribution diagram. Detailed Description of the Invention

[0030] In order to better elaborate on the technical solutions in the present invention in detail, the present application is further introduced in combination with the drawings in the embodiments.

[0031] Terahertz communication has technical advantages such as high rate and strong security, becoming a research hotspot at home and abroad in recent years. Due to the characteristics of terahertz quasi-optical propagation, it has strong directivity, and in long-distance communication, the configured high-gain antenna makes the communication beam relatively narrow. Therefore, terahertz communication between moving nodes needs to cooperate with high-precision beam control technology. For the narrow-beam characteristics of terahertz communication, facing the communication interconnection of fast-moving nodes, it is necessary to further improve the beam scanning speed, and the multi-beam flexible control ability of traditional fixed-surface antennas is very limited. For this reason, following the breakthrough of mechanical scanning beam pointing control technology, the current terahertz phased array technology has become a new focus in the field of terahertz communication. Terahertz phased arrays require arrayed channels. Since the realization of high-performance terahertz radio frequency circuits is more difficult than that of microwaves and the efficiency also needs to be further improved, considering the difficulty of system implementation and heat dissipation problems, the achievable scale of terahertz phased arrays is generally not large. To further improve the gain, a reflector or lens is required for gain enhancement to increase its equivalent radiated power and expand the working distance of communication.

[0032] The antenna feed array with gain enhancement using a lens or reflector has a certain planar scale. In actual use, the feed array surface needs to be defocused, and to shorten the feed path, improve the feed efficiency and reduce the profile height of the antenna, the feed array is generally placed for near-field feeding. During near-field feeding, the amplitude and phase configuration of the feed array elements has problems such as complex analysis and lack of reference for the initial value setting. Implementing full-wave simulation for convenient amplitude and phase configuration calculation has a very large amount of computation, and the time consumption cannot be ignored.

[0033] The method for determining the amplitude and phase of a terahertz near-field feeding array based on plane-wave incidence of the present invention calculates the relationship between the amplitude and phase of each element of the feeding array and the beam pointing through the conjugate inversion of plane-wave incidence. It can effectively reduce the high computational cost brought by the amplitude and phase traversal of the feeding unit. Only by specifying the beam pointing position, the amplitude and phase distribution of the feeding array elements can be determined, and it can avoid the amplitude and phase errors caused by the strong coupling of size and amplitude and phase in the terahertz frequency band. It greatly improves the design ability of phased-feed array antennas in the terahertz frequency band and promotes the application process of terahertz communication and radar systems. It reversely transforms complex near-field problems into solvable problems that can be analyzed. It is suitable for the rapid solution of large-scale feeding arrays.

[0034] The method for determining the amplitude and phase of a terahertz near-field feeding array based on plane-wave incidence of the present invention has the following specific implementation steps:

[0035] The equal-phase surface of the present invention is specifically: the equal-phase surface is a plane composed of points with the same phase after the electromagnetic wave exits through the lens. For the far field of the antenna, the equal-phase surface is a plane, and for the near field, the equal-phase surface is a spherical surface.

[0036] Although the present invention does not focus on the type of lens, generally, the lens in the antenna must be a convex lens, and a concave lens does not generate positive gain, and the radius of curvature is not required.

[0037] The reflecting surface is a concave mirror, and generally a convex mirror is not used for the antenna either, and no positive gain is generated. There is no special requirement for the radius of curvature.

[0038] The focal point is the focal point of the lens or the reflecting surface;

[0039] The off-focus feed surface is another plane that is away from the plane where the focal point is located. Figure 2 The plane of the central feed source array is the off-focus feed surface, and it is different from Figure 1 the off-focus feed surface shown, Figure 1 inside the focal point, Figure 2 outside the focal point.

[0040] Step 1: Establish a three-dimensional calculation model of the equiphase surface, the lens or the reflecting surface, and the off-focus feed surface, and input the material and structural parameters of the lens or the reflecting surface, and define the size of the off-focus feed surface and the positional relationship from the focal point; as Figure 1 shown, TAA is the lens of the present invention example, PAA is the near-field feed array, F is the focal length of the lens, H is the distance between the feed array and the lens, o' is the focal point, F - H is the position from the focal point, and the size of the off-focus feed surface is the chord length corresponding to the position of the placed feed array under the included angle from the focal point to the edge of the lens;

[0041] In the three-dimensional calculation model: the lens is located between the equiphase surface and the off-focus surface, and the focal point can be between the off-focus feed surface and the lens or not (here it is mainly stipulated that the lens must be located between the equiphase surface and the off-focus feed surface, but there is no constraint on the focal point position of the lens); in the reflecting surface model, the off-focus feed surface is between the reflecting surface and the equiphase surface;

[0042] Step 2: Set the plane wave to propagate from the equiphase surface to the lens or the reflecting surface. The lens calculates the propagation characteristics according to the medium (because the lens allows electromagnetic waves to transmit and propagate, and it serves as a propagation medium, and the calculation of this medium should be treated as a medium. The so-called medium can be characterized by the parameters of permittivity and permeability), and the reflecting surface calculates the propagation characteristics according to the ideal metal surface (the reflecting surface generally uses an approximation of an ideal metal, so the propagation characteristics of electromagnetic waves are total reflection, and only a 180° phase reversal is completed on the reflecting surface).

[0043] Step 3: Keep the position of the solution point of the off-focus feed surface consistent with the center position of the actual feed source port plane (the main meaning described here is that the solution position of the calculated off-focus feed surface must be consistent with the position of the antenna feed surface to be actually fabricated. Otherwise, even if the calculation is accurate, amplitude-phase errors will be generated), and reduce the amplitude-phase errors caused by position approximation.

[0044] Step 4: Calculate the phase and amplitude parameters of each solution point on the defocused feed surface. (Use a full-wave simulation software for finite element analysis (such as HFSS or CST, etc.) to calculate the phase and amplitude parameters of each solution point on the defocused feed surface. For regular lenses or reflectors, the self-programming method (such as MATLAB) is also used to solve by the traveling wave method using Maxwell's equations.) These are used as the amplitude and phase configuration parameters for the beam in this direction.

[0045] Step 5: Set the angle parameter between the equiphase surface and the normal of the lens or reflector aperture surface with an angular step not exceeding the 3dB beamwidth, and repeat steps 1 to 4.

[0046] Step 6: Repeat step 5 to traverse one by one the amplitude and phase distributions of the defocused array surfaces corresponding to the beam pointing angles within the beam scanning range to be solved.

[0047] Step 7: Use the amplitude and phase distribution parameters in step 6 as the input to obtain the conjugate phase of each solution point (the conjugate phase is the negative value of the phase extracted from the distribution parameters), which is used as the angle drive parameter for the phased array antenna application.

[0048] Example 1:

[0049] Step 1: According to Figure 2 , establish a three-dimensional calculation model of the equiphase surface, lens, and defocused feed surface (feed array plane). The lens is located between the equiphase surface and the feed array plane, and the focus formed by the lens is located between the feed array plane and the lens. The plane wave beam from free space S passes through the equiphase surface and the lens in sequence, converges to the focus, and forms a mapped area on the feed array plane. Input the material properties and structural distribution parameters of the lens, and define the size of the defocused feed surface and its positional relationship with the focus. Figure 2 In

[0050] S is free space, m and n are incident plane wave beams, and the subscripts represent the three stages before entering the lens, in the lens, and after passing through the lens respectively, which are used as variables for the calculation in step 4 of the method. n1 and m1 are the propagation distances of different plane wave beams from the equiphase surface to the lens, n2 and m2 are the propagation distances of different plane wave beams in the lens, and n3 and m3 are the propagation distances of different plane wave beams from the lens to the focus.

[0051] Step 2: Set the plane wave to propagate from the equiphase surface to the lens, and the lens calculates the propagation characteristics according to the medium.

[0052] Step 3: Keep the position of the solution point on the defocused feed surface consistent with the center position of the actual antenna feed surface to be fabricated, reducing the amplitude and phase errors caused by position approximation. Figure 3After the incident wave is projected from the 30° direction, a spatial field distribution is formed, and the amplitude distribution and phase distribution of the spatial field in two dimensions can be separately extracted;

[0053] Step 5: Set the angle parameter between the equal phase surface and the normal of the lens aperture surface with an angular step not exceeding 3 dB beam width, and repeat Steps 1 to 4;

[0054] Step 6: Repeat Step 5 to sequentially obtain the amplitude-phase distributions of the defocused array surfaces corresponding to the beam pointing angles within the beam scanning range to be solved;

[0055] Step 7: Use the amplitude-phase distribution parameters in Step 6 as inputs to obtain the conjugate phases of the solution points as the angle drive parameters for phased array antenna applications.

[0056] Those of ordinary skill in the art will realize that the examples described herein are to assist the reader in understanding the principles of the present invention and should be understood that the scope of protection of the present invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific deformations and combinations without departing from the technical revelations disclosed in the present invention, and these deformations and combinations are still within the scope of protection of the present invention.

Claims

1. A method for determining amplitude and phase of a terahertz near-field feeding array based on plane wave incidence, characterized in that: include: Step 1: Establish a three-dimensional calculation model of the equiphase surface, lens or reflection surface and defocused feeding surface, input the material and structural parameters of the lens or reflection surface, define the size of the defocused feeding surface and its positional relationship from the focus of the lens or reflection surface; Step 2: Set the plane wave to propagate from the equal phase plane to the lens or reflective surface. The propagation characteristics of the lens are calculated according to the medium, and the propagation characteristics of the reflective surface are calculated according to the ideal metal surface. Step 3: The solution point position of the defocused feed surface is consistent with the plane center position of the actual antenna feed surface to be manufactured; Step 4: Calculate the phase and amplitude parameters of each solution point on the defocused feeding surface; Step 5: Set the angle parameter between the equal phase plane and the normal line of the lens or reflective surface according to the angle step not exceeding 3dB beam width, and repeat steps 1 to 4; Step 6: Repeat step 5, and traverse the amplitude and phase distribution of the defocused feeding surface corresponding to each beam pointing angle within the beam scanning range to be solved one by one; Step 7: Using the amplitude and phase distribution parameters from step 6 as input, calculate the conjugate phase of each solution point on the offset feed surface as the angle driving parameter for the phased array antenna application.

2. The method for determining amplitude and phase of a terahertz near-field feeding array based on plane wave incidence according to claim 1, characterized in that: In the three-dimensional calculation model, the lens is located between the equal phase plane and the defocused feeding plane.

3. The method for determining amplitude and phase of a terahertz near-field feeding array based on plane wave incidence according to claim 1, characterized in that: In the three-dimensional calculation model, the defocused feeding surface is between the reflection surface and the equal phase surface.

4. The method for determining amplitude and phase of a terahertz near-field feeding array based on plane wave incidence according to claim 1, 2 or 3, characterized in that: The size of the defocused feeding surface is the chord length corresponding to the position of the placed feeding array under the angle from the focus to the edge of the lens or the reflecting surface.

5. The method for determining amplitude and phase of a terahertz near-field feeding array based on plane wave incidence according to claim 1, 2 or 3, characterized in that: The material and structural parameters of the lens or reflective surface include: Material properties and material structure distribution of lenses or reflective surfaces.

6. The method for determining amplitude and phase of a terahertz near-field feeding array based on plane wave incidence according to claim 1, 2 or 3, characterized in that: The definition of the size of the defocused feed surface and its positional relationship from the focus of the lens or the reflective surface includes the size of the defocused feed surface, the center position of the actual antenna feed surface to be manufactured, and the overall three-dimensional coordinates of the defocused feed surface.

7. The method for determining amplitude and phase of a terahertz near-field feeding array based on plane wave incidence according to claim 1, 2 or 3, characterized in that: In the second step, the lens allows electromagnetic waves to propagate through, and the propagation characteristics are calculated using parameters of dielectric constant and magnetic permeability to characterize; The electromagnetic wave propagation characteristic of the reflecting surface is total reflection. When calculating the propagation characteristics, only the 180° phase reversal is completed on the reflecting surface.

8. The method for determining amplitude and phase of a terahertz near-field feeding array based on plane wave incidence according to claim 1, 2 or 3, characterized in that: The fourth step is to use a finite element analysis solution method to perform full-wave simulation to calculate the phase and amplitude parameters of each solution point on the defocused feeding surface; Alternatively, for a regular lens or reflecting surface, Maxwell's equations can be solved using the traveling wave method.

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