CN105305096B - The design method of compact planar structure parabolic reflector antenna based on Meta Materials - Google Patents

Abstract

The invention discloses a design method of a compact planar structure parabolic reflector antenna based on metamaterials, which includes the following steps: using the principle of transformation electromagnetics to design a feed source unit with a planar boundary; using a planar structure parabolic reflector to replace the conventional The parabolic reflector with curved surface structure is used as the reflecting surface of the reflector antenna; the planar reflector and the feed unit are combined to design a compact planar reflector antenna. The reflection surface of the present invention adopts a plane reflector, and its reflection characteristics are equivalent to conventional parabolic reflectors; the designed feed source unit itself is "transparent" to the rays, that is, it does not block the rays, and the feed source placed therein is due to The virtual displacement effect produced by the metamaterial is equivalent to the radiation characteristic of the feed source placed far away from the reflecting surface; the reflector and the feed unit in the reflector antenna are combined to form a compact structure, which avoids the The separation of the reflector from the feed in conventional reflector antennas.

Description

Design Method of Parabolic Reflector Antenna with Compact Planar Structure Based on Metamaterials

technical field

The invention belongs to the field of electromagnetic/optical device design. It relates to a theoretical design method of a parabolic reflector antenna with a compact planar structure. The designed reflector antenna is suitable for microwave, millimeter wave, terahertz and other frequency bands.

Background technique

As a broadband high-gain antenna, reflector antennas are widely used in satellite communications, radar, remote sensing, and radio astronomy. Its basic structure consists of two parts: reflector and feed. A reflector antenna whose reflective surface is a parabola (parabolic reflector antenna) is the most commonly used form.

The characteristics of the parabolic reflector antenna are mainly determined by its geometrical optical characteristics: the beam emitted at the focus is collimated after being reflected by the reflector, and the reflected beam propagates parallel to the main axis of the reflector; all the path lengths from the focus to the reflector to the aperture plane are equal and equal to 2 times the focal length.

Thus, a conventional parabolic reflector antenna consists of a parabolic reflector and a feed near the focal point. Such a structure makes the reflector antenna inconvenient in terms of installation, debugging and use, and because the reflector and the feed are separated in space, the possible shading between them will significantly affect the performance of the antenna. However, from the perspective of traditional reflector antenna design, an effective method has not yet been found to design a reflector antenna with a compact planar structure that can keep the antenna characteristics basically unchanged (compared with conventional parabolic reflector antennas). .

Contents of the invention

The purpose of the present invention is to provide a kind of design method based on the compact planar structure parabolic reflector antenna of metamaterial for the deficiencies in the prior art, this method utilizes the principle of transformation electromagnetism to design the feed source unit with plane boundary; The parabolic reflector of the planar structure is used as the reflecting surface of the antenna; the planar reflector and the feed unit are combined to design a compact planar reflector antenna. This reflector antenna has the same characteristics as a conventional parabolic reflector antenna.

The purpose of the present invention is achieved like this:

A method for designing a compact planar parabolic reflector antenna based on metamaterials, which includes the following specific steps: Step 1: Design a feed unit with a planar boundary by using the principle of transformation electromagnetics;

The second step: use a parabolic reflector with a planar structure instead of a parabolic reflector with a conventional curved surface structure as the reflecting surface of the reflector antenna;

Step 3: Attach the feed unit to the planar reflector to form a compact planar reflector antenna;

Wherein, the electromagnetic space transformation involved in the design process of the feed unit is described as follows. The closed space formed by the boundaries Γ1 and Γ4 is the original space [represented by s ₁ (x, y, z)]; this part of the space is compressed between the boundaries Γ1 and Γ2 by coordinate transformation [by s ₁ '(x _s1 ', y _s1 ', z _s1 ') means], which can be expressed as

x _s1 '=f ₁ (x,y,z), y _s1 '=g ₁ (x,y,z), z _s1 '=h ₁ (x,y,z) (1)

In the formula, f ₁ , g ₁ , h ₁ are coordinate transformation functions; the boundary conditions to be satisfied by this space transformation are: the boundary Γ1 remains unchanged before and after transformation, and Γ4 is mapped to Γ2;

In addition, in order to keep the electromagnetic space equivalent before and after the transformation, a boundary Γ3 is taken between the boundaries Γ2 and Γ4, so that the space between Γ2 and Γ4 is divided into two parts; the space between the boundaries Γ3 and Γ4 [by s ₂ (x, y, z)] is folded between the boundaries Γ3 and Γ2 through coordinate transformation [expressed by s ₂ '(x _s2 ', y _s2 ', z _s2 ')], which can be represented in the Cartesian coordinate system for:

x _s2 '=f ₂ (x,y,z), y _s2 '=g ₂ (x,y,z), z _s2 '=h ₂ (x,y,z) (2)

In the formula, f ₂ , g ₂ , h ₂ are coordinate transformation functions; the boundary conditions to be satisfied by this space transformation are: the boundary Γ3 remains unchanged before and after transformation, and Γ4 is mapped to Γ2;

Among them, the coordinate transformation functions f ₁ , g ₁ , h ₁ and f ₂ , g ₂ , h ₂ are arbitrary function forms satisfying the boundary conditions; the boundary Γ1 is a plane, and Γ2, Γ3, Γ4 are arbitrary curved surfaces;

It can be seen from the coordinate mapping relationship that any point in the original space s ₁ has _a corresponding point in the transformed space _{s 1} '; Electric constant and relative permeability, the calculation formula is:

ε'＝AεA ^T /det(A), μ'＝AμA ^T /det(A) (3)

In the formula, A is the Jacobian transformation matrix;

The designed feed unit is a structure surrounded by Γ1 and Γ3; it contains two kinds of metamaterial dielectric layers, namely the metamaterial dielectric layer obtained by compressive transformation between Γ1 and Γ2 and the folded transformation obtained by Γ2 and Γ3 The metamaterial dielectric layer; the obtained metamaterial dielectric layer has a regulating effect on the propagation of rays, which enables the feed source placed in the structure to produce a virtual displacement, for example, when the feed source is placed at the point F', the radiation effect produced is equivalent to The radiation effect produced when the feed source is placed at point F in the original space.

The plane side of the designed feed unit (ie Γ1 plane) is close to the center of the concave dielectric layer of the planar structure parabolic reflector, thus forming a compact planar structure parabolic reflector antenna.

The design of the parabolic reflector with a planar structure can refer to Chinese patent ZL 201310577904.6. The designed planar reflector has a double-layer structure, which is a concave dielectric layer and a convex dielectric layer. Since the concave surface of the paraboloid in the parabolic reflector antenna is used as the reflecting surface , so in order to simplify the antenna structure, a single-layer structure is adopted here, that is, a flat reflective surface plus a concave dielectric layer. This simplified single-layer structure will not have a significant impact on the characteristics of the reflector antenna.

The technical effect of the present invention is that: the reflection surface of the antenna adopts a plane reflector, and its reflection characteristics are equivalent to a conventional parabolic reflector; the designed feed unit itself is "transparent" to rays, that is, it does not block rays, and The feed source placed in it is due to the virtual displacement effect of the metamaterial, and its radiation characteristics are equivalent to the radiation characteristics of the feed source placed far away from the reflecting surface; the reflector and the feed source unit are combined in the reflector antenna A compact structure is formed, which avoids the separation of the reflection surface and the feed source in the conventional reflector antenna. Therefore, compared with the conventional transmitter antenna, the antenna of the present invention has a flat and compact structure and is thus convenient for installation and use; it saves the space between the reflector and the feed source; influences.

Description of drawings

Fig. 1 is a schematic diagram of the spatial mapping of the feed unit of the present invention;

Fig. 2 is a schematic diagram of the antenna of the present invention;

Fig. 3 is a schematic diagram of a conventional parabolic reflector antenna;

Fig. 4 is the near-field distribution figure of antenna of the present invention;

Fig. 5 is the near-field distribution figure of conventional parabolic reflector antenna;

Figure 6 is the far-field distribution diagram of two antennas.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

Referring to Figure 2 and Figure 3, assuming that point F is the focus of the paraboloid, the conventional parabolic reflector antenna places a feed near point F, and the feed illuminates the parabolic reflector as shown in Figure 3, and the transmitted beam is formed after being reflected by the reflector Highly directional reflected beam. In Figure 2, the feed source is placed at the mapping point F' of point F, and the beam emitted by it is equivalent to the beam emitted by the feed source placed at point F; the transmitted beam will form a conventional parabolic reflection after being reflected by a planar transmitter The reflected beam equivalent to the receiver antenna, the antenna characteristics remain unchanged.

Example

The spatial mapping of the feed source unit is shown in Figure 1, which is given by formula (1) and formula (2).

The coordinate transformation function in formula (1) is specifically taken as

The coordinate transformation in formula (2) is calculated separately in the first and fourth quadrants. In the first quadrant, that is, AC'D is specifically taken as

The fourth quadrant part, that is, BC'D, is specifically taken as

The material parameters of each part of the feed unit can be calculated by using formula (3). The parameter in ABC' is

The parameter in AC'D is

The parameter in BC'D is

The material parameters of the dielectric layer of the parabolic reflector with planar structure are

Where p is the focal length of the standard parabolic equation, a is the thickness of the concave medium layer of the plane reflector, and h is the half-height of the plane reflector (marked in Figure 2).

A specific simulation verification is given below. The design parameters of the feed unit are: x ₁ =0.05m, x ₂ =0.1m, x ₃ =0.2m, y ₁ =0.05m. The design parameters of the planar structure parabolic reflector are: p=0.45, a=0.05m, h=0.6m.

Place a feed source with frequency f=3GHz in the feed unit of the planar antenna system [coordinates are (x=0.18m, y=0)]. At this time, the total electric field distribution of the antenna system is shown in Figure 4. It can be seen from the figure that although the feed is placed inside the feed unit, due to the virtual displacement effect, the beam seems to be emitted from a point outside the feed unit [coordinates are (x=0.27m, y=0)]. For clear comparison, Fig. 5 shows the simulation result of a conventional parabolic reflector antenna, where the feed source is placed at (x=0.27m, y=0). Through comparison, it can be found that the designed compact planar parabolic reflector antenna in this embodiment has the same near-field distribution as the conventional parabolic reflector antenna. In order to quantitatively compare the two antenna systems, Figure 6 shows their far-field distributions, where the thick solid gray line represents the compact planar structure reflector antenna designed in the embodiment, and the dotted line with a black body circle represents the conventional parabolic reflector antenna . The results shown show that the far-field distributions of the two antennas are also nearly identical. The above design examples and numerical experiments prove the correctness of the design method and design results.

Claims (1)

1. a kind of design method of the compact planar structure parabolic reflector antenna based on Meta Materials, it is characterised in that this method Including step in detail below：

The first step：The feed unit with planar boundary is designed with transformation electromagnetic principles；

Second step：The paraboloid of conventional curved-surface structure is substituted as reflector using the paraboloid of planar structure The reflecting surface of antenna；

Third walks：Feed unit is close to plane reflector, forms compact-sized plane reflector antenna；

Wherein, the electromagnetic space transformation involved in the feed unit design process is described below；What boundary Γ 1 and Γ 4 was constituted Enclosure space is luv space [by s₁(x, y, z) is indicated]；The segment space is compressed to boundary Γ 1 and Γ 2 by coordinate transform Between [by s₁'(x_s1',y_s1',z_s1') indicate], it is represented by rectangular coordinate system

x_s1'=f₁(x,y,z),y_s1'=g₁(x,y,z),z_s1'=h₁(x,y,z) (1)

F in formula₁, g₁, h₁For coordinate transform function；The boundary condition that the spatial alternation need to meet is：The front and back boundary Γ 1 of transformation is protected Hold constant, Γ 4 is mapped to Γ 2；

In addition, it is equivalent in order to keep converting front and back electromagnetic space, a boundary Γ 3, in this way handle are taken between boundary Γ 2 and Γ 4 Space between Γ 2 and Γ 4 is divided into two parts；Wherein by the space between boundary Γ 3 and Γ 4 [by s₂(x, y, z) is indicated] it is logical Coordinate transform is crossed to fold between boundary Γ 3 and Γ 2 [by s₂'(x_s2',y_s2',z_s2') indicate], it can table in rectangular coordinate system It is shown as：

x_s2'=f₂(x,y,z),y_s2'=g₂(x,y,z),z_s2'=h₂(x,y,z) (2)

F in formula₂, g₂, h₂For coordinate transform function；The boundary condition that the spatial alternation need to meet is：The front and back boundary Γ 3 of transformation is protected Hold constant, Γ 4 is mapped to Γ 2；

Wherein, coordinate transform function f₁, g₁, h₁And f₂, g₂, h₂To meet the arbitrary function form of boundary condition；Boundary Γ 1 is flat Face, Γ 2, Γ 3, Γ 4 are arbitrary surface；

By coordinate mapping relations it is found that luv space s₁In any point, in transformation space s₁' in there are one point be corresponding to it Map；

S is calculated by coordinate transform₁' and s₂' in material parameter, that is, relative dielectric constant and relative permeability, calculation formula be：

ε '=A ε A^T/ det (A), μ '=A μ A^T/det(A) (3)

A is Jacobi transformation matrix in formula；

It is designed go out feed unit be Γ 1 and 3 closed structures of Γ；It includes two kinds of Meta Materials dielectric layers, respectively Γ 1 and Γ The Meta Materials medium obtained by being converted by folding between the Meta Materials dielectric layer obtained by compressed transform between 2 and Γ 2 and Γ 3 Layer.