JP2006080609A - Planar antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a planar antenna, wherein a ground conductor plate is provided to one side of a dielectric board and a radiation conductor plate is provided to the other side, that has a higher degree of design freedom than that of conventional planar antennas of the same kind and can widen a transmittable/receptible radio wave frequency. <P>SOLUTION: The planar antenna is configured such that the ground conductor plate 2 is provided to one side of the dielectric board 1 and the radiation conductor plate 3 is provided onto the another side at opposite side. The dielectric board 1 is configured by arranging a plurality of dielectric bodies 11, 12, 13 and a group of a plurality of the dielectric bodies comprises at least two kinds of the dielectric body 11 (12, 13) whose dielectric constants differ from each other. For example, relations of εα>εβ and εα<2×εβ hold between the dielectric constant εα of the center dielectric body 11 and the dielectric εβ of both the outside dielectric bodies 12, 13. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a planar antenna that can be used as a small antenna for transmission / reception for mobile communication, in particular, a plane in which a ground conductor plate is provided on one surface of a dielectric substrate and a radiation conductor plate is provided on the other surface on the opposite side. Regarding antennas.

  A planar antenna with a grounding conductor plate on one side of a dielectric substrate and a radiation conductor plate on the other side on the other side is widely used today as a patch antenna or planar antenna in GPS navigation systems and wireless LANs. It will be widely used in the future.

  A dielectric substrate in such a planar antenna is formed by appropriately selecting a substrate material, a substrate thickness, and the like according to required antenna characteristics. A laminated plate obtained by appropriately laminating a sintered body, a prepreg and the like has been adopted. On the other hand, further research has been conducted on a substrate material for a planar antenna. For example, Japanese Patent No. 2873541 discloses a resin composition having a high dielectric constant and a low dielectric loss tangent that is useful as a substrate material that can cope with high frequency band radio waves. is doing.

Japanese Patent No. 2873541

  However, in any case, the dielectric substrate in the conventional planar antenna has a constant dielectric constant that determines the antenna characteristics regardless of whether it has a laminated structure or a single layer structure. The person must design the antenna on the premise of the constant dielectric constant and the like. As a result, the degree of freedom in antenna design is reduced, and the antenna characteristics, particularly the radio frequency band that can be transmitted and received, is constant. It was limited to a narrow range controlled by the dielectric constant.

  Such a dielectric substrate cannot cope with the sophisticated and complicated antenna shape and antenna characteristics required with the recent development of mobile communication. In particular, it is difficult to meet the demand for a wide band of radio frequencies that can be transmitted and received.

  Therefore, the present invention is a planar antenna in which a grounding conductor plate is provided on one surface of a dielectric substrate and a radiation conductor plate is provided on the other surface on the opposite side, and compared with a conventional planar antenna of the same type. It is an object of the present invention to provide a planar antenna that has a high degree of freedom and can broaden the frequency of radio waves that can be transmitted and received.

The present inventor has intensively studied to solve the above problems, and has come to focus on the following.
In a planar antenna in which a grounding conductor plate is provided on one surface of a dielectric substrate and a radiation conductor plate is provided on the other surface on the opposite side, at least the structure of the dielectric substrate and the dielectric constant of each part are determined by the antenna designer. If it can be entrusted to a free design, the degree of freedom in antenna design can be increased accordingly. In addition, if the dielectric constant that affects the transmittable / receivable radio frequency band can be left to the antenna designer to freely design the dielectric constant of each part of the dielectric substrate, the transmittable / receivable radio frequency band can be widened.

  The present inventor has further researched, and in order to realize this, a dielectric substrate in which a plurality of dielectrics including at least two kinds of dielectrics different in terms of dielectric constant are arranged is adopted. I found what I should do.

  Based on such attention and knowledge, the present invention provides a planar antenna in which a grounding conductor plate is provided on one surface of a dielectric substrate and a radiation conductor plate is provided on the other surface on the opposite side. The plurality of dielectric groups provide a planar antenna made of at least two types of dielectrics having different dielectric constants.

  According to the planar antenna according to the present invention, the dielectric substrate is configured by arranging a plurality of dielectrics including at least two types of dielectrics that differ in terms of dielectric constant. The frequency is high, and it is possible to widen the frequency band of radio waves that can be transmitted and received.

  The arrangement of the plurality of dielectrics constituting the dielectric substrate is typically a planar arrangement in constructing the substrate. As such a planar arrangement state, a plurality of dielectric stripes are formed. An arrangement, a concentric ring arrangement of a plurality of dielectrics, and the like can be appropriately selected and employed depending on the required antenna characteristics.

  In any case, each of the plurality of dielectrics constituting the dielectric substrate may have a laminated structure or a single layer structure. Accordingly, as the dielectric substrate, a plurality of dielectrics each having a multilayer structure are arranged, a plurality of dielectrics each having a single layer structure are arranged, and at least one dielectric is a multilayer. Examples of the other dielectric material include a single layer structure and a plurality of dielectric materials arranged.

  In terms of the dielectric constant, among a plurality of dielectrics constituting the dielectric substrate, the dielectric material forming the central portion of the dielectric substrate is made wider in the range of radio frequencies that can be transmitted and received. The case where a dielectric constant is higher than the dielectric constant of the dielectric material located in the outer area | region of the dielectric material which forms this dielectric substrate center part can be illustrated. In this case, the dielectric constant of the dielectric located in the outer region may be constant for each part or may be different for each part.

  As an example where the dielectric constant of the dielectric located in the outer region is constant in each part, among the plurality of dielectrics constituting the dielectric substrate, the dielectric constant of the dielectric forming the central portion of the dielectric substrate Εα, the dielectric constant of the dielectric located in the outer region of the dielectric forming the central portion of the dielectric substrate is εβ, and the relationship of εα> εβ is satisfied. In this case, as a condition for achieving a wider band, the dielectric constants εα and εβ are preferably in a relationship of εα> εβ and εα <2 × εβ.

Out of the plurality of dielectrics constituting the dielectric substrate, the dielectric constant of the dielectric forming the central portion of the dielectric substrate is the outer region of the dielectric forming the central portion of the dielectric substrate. As a more specific example in the case where the dielectric constant is higher than that of the dielectric located in the plurality of dielectrics, a plurality of dielectrics constituting the dielectric substrate are arranged in a stripe shape (stripe shape). Of these, the dielectric constant of the dielectric at the center is εα, the dielectric constant of the dielectric located on both outer sides of the dielectric having the dielectric constant εα is εβ, and there is a relationship of εα> εβ.
Also in this case, the dielectric constants εα and εβ may satisfy the relationship of εα> εβ and εα <2 × εβ.

  The radiation conductor plate provided on the other surface of the dielectric substrate may be provided on any of the substrate surfaces as long as the antenna design condition is satisfied. However, as a representative example, the radiation conductor plate may be provided on the central portion of the substrate surface. Can be mentioned.

  Furthermore, the dielectric substrate, whether the plurality of dielectrics constituting the dielectric substrate are arranged in stripes as described above, or arranged in another arrangement state such as a concentric ring arrangement, etc. When the dielectric constant of the dielectric forming the central portion of the dielectric substrate is higher than the dielectric constant of the dielectric located in the outer region of the dielectric forming the central portion of the dielectric substrate, the radiation conductor plate is placed on the substrate surface. The case where it provides in a center part can be illustrated.

  The material of each of the plurality of dielectrics constituting the dielectric substrate is not particularly limited as long as a desired dielectric constant can be obtained. For example, at least one of the plurality of dielectrics is dielectric. The case where it forms from resin can be mentioned.

  For example, in a dielectric substrate in which a plurality of dielectrics are arranged in stripes, if a dielectric resin is used as each dielectric material, these are extruded by the same method as the two-color molding method by extrusion molding. The dielectric substrate can be easily obtained.

  As described above, according to the present invention, a planar antenna having a grounding conductor plate on one surface of a dielectric substrate and a radiation conductor plate on the other surface on the opposite side, which is a conventional planar antenna of the same type, In comparison, it is possible to provide a planar antenna that has a high degree of design freedom and can widen the frequency of radio waves that can be transmitted and received.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows an example of a planar antenna according to the present invention. In this planar antenna, a ground conductor plate 2 is provided on the lower surface of the dielectric substrate 1 and a radiation conductor plate 3 is provided on the upper surface. The substrate 1 of this antenna has a rectangular parallelepiped shape, and when viewed from the plane, the length of the XY plane presenting a quadrangle in the X-axis direction is a, and the length in the Y-axis direction is b. The length (thickness) in the Z-axis direction orthogonal to the X-axis and Y-axis is c.

  The ground conductor plate 2 is provided on the entire lower surface of the substrate 1, and the radiation conductor plate 3 is provided on the center of the upper surface of the substrate 1. The radiating conductor plate 3 has a quadrangular shape when viewed from the plane, and the XY plane having the quadrangular shape has a length in the X-axis direction and a length in the Y-axis direction. In FIG. 1, a point P on the radiation conductor plate is a feeding point.

  In this example, the dielectric substrate 1 is arranged in a striped manner, and is composed of a central dielectric 11 and dielectrics 12 and 13 on both outer sides thereof. The dielectric substrate 1 can be obtained, for example, by employing a dielectric resin as the material of each of the dielectrics 11, 12, and 13, and extruding these resins by a technique similar to the two-color molding method by extrusion molding. .

The dielectric 11 at the center of the substrate has a width in the Y-axis direction d, and the widths of the dielectrics 12 and 13 in the Y-axis direction are the same here. The length of each dielectric in the X-axis direction is a, and the length (thickness) in the Z-axis direction is c.
The dielectric constant of the dielectric 11 is εα, the dielectric constant of the dielectrics 12 and 13 is εβ, and εα> εβ and εα <2 × εβ.
The dielectric constants of the dielectric bodies 12 and 13 do not have to be the same. However, in order to broaden the radio frequency that can be transmitted and received, the dielectric constant εα of the dielectric body 11 is set to the dielectric constant of the dielectric bodies 12 and 13. It should be larger than either.

  The grounding conductor plate 2 and the radiating conductor plate 3 can be provided on the substrate by sticking them to the substrate 1 with an adhesive or forming a conductor plate on the substrate 1 using various thin film forming techniques.

  According to this planar antenna, the dielectric substrate 1 is configured by arranging a plurality of dielectrics 11 to 13 including two types of dielectrics that are different in terms of permittivity that affects a radio frequency band that can be transmitted and received. Therefore, the degree of freedom in antenna design is high, and it is possible to widen the frequency of radio waves that can be transmitted and received.

  Next, with respect to the planar antenna shown in FIG. 1, the FDTD (Finite Difference Time Domain) method, that is, the Maxwell equation, which is a basic electromagnetic equation, is differentiated (Finite Difference) and solved in the time domain (Time Domain), The characteristics of the reflection coefficient S11 of the planar antenna, the width (bandwidth) of the transmittable / receivable radio frequency band, and the Eθ component will be described.

  With respect to the dimensions of each part of the planar antenna, the substrate 1 is constant a (64 mm) × b (64 mm) × c (3 mm), but the width d of the central dielectric 11 is changed as illustrated in FIG. It was. More specifically, as shown in FIG. 4, the width d [mm] was changed to 0, 10, 20, 22, 35, 64.

The radiation conductor plate 3 was constant a ′ (32 mm) × b ′ (32 mm). Regarding the dielectric constant, the dielectric constant εα = 5 of the dielectric 11 and the dielectric constant εβ = 3 of the dielectrics 12 and 13 were set. The width d = 0 of the central dielectric 11 means that the substrate 1 is composed only of the dielectrics 12 and 13 having a dielectric constant εβ = 3, and the width d = 64 mm means that the substrate 1 has a dielectric constant εα = 5. It means that it is composed only of the dielectric 11, and both correspond to comparative examples.
The feeding point P is arranged at the center of the radiation conductor 3.

  In the analysis by the FDTD method, the cell size was 0.5 mm, the time step was 0.963 ps (0.963 / sec), and Liao was adopted as the absorption boundary condition.

When the antenna performance was analyzed under these conditions, the reflection coefficient S11 shown in FIG. 4 and the bandwidth shown in FIG. 5 were obtained.
From FIG. 4, the reflection coefficient S11 with respect to the radio frequency changes when the width d of the central dielectric 11 is changed. From FIG. 5, the bandwidth changes when the width d of the central dielectric 11 is changed. I understand that The bandwidth is a bandwidth where each reflection coefficient S11 when the width d of the dielectric 11 is changed is −10 dB or less, and when the substrate dielectric constant is equalized to εα = 5 (when d = 64 mm). The ratio of the center frequency (3.96 GHz) is [%].
Here, the center frequency is a frequency at which S11 is minimized.

  As shown in FIG. 5, when the width d of the central dielectric 11 is 20 mm and 22 mm, the bandwidth is increased to 8.9% and 10%, and the substrate is the same as when the width d is 0 or 64 mm. Compared with the case where the dielectric constant of 1 is constant, the bandwidth is wide (about 6% for d = 0 and only about 1.5% for d = 64 mm). The antenna characteristics related to the band have been improved, in other words, a wider band has been achieved.

  FIG. 6 shows radio wave radiation patterns at point A (4.12 GHz) and point B (4.31 GHz) in FIG. In both cases, the Eθ component is the main polarization, and the maximum gain is 6.5 dBi at the point A and 3.7 dBi at the point B.

  In the planar antenna shown in FIGS. 1 and 2, the dielectrics 11, 12, and 13 constituting the substrate 1 are arranged in stripes. However, the arrangement of the dielectrics is not limited to this, and for example, FIG. As shown in FIG. 6, a dielectric substrate 1 ′ having a dielectric arrangement in which the outer dielectric 12 ′ surrounds the central dielectric 11 ′ can also be employed.

  INDUSTRIAL APPLICABILITY The present invention can be used for providing a planar antenna used as a small antenna for transmission / reception for mobile communication.

1 is a perspective view of an example of a planar antenna according to the present invention. FIGS. 1A to 1C show examples in which the dielectric width at the center of the substrate is changed in the planar antenna shown in FIG. FIGS. 4A to 4C are diagrams showing other examples of the arrangement of a plurality of dielectrics on a dielectric substrate. It is a figure which shows the reflection coefficient S11 characteristic of an antenna when a board | substrate center part dielectric material width is changed. It is a figure which shows the bandwidth change of an antenna when changing the board | substrate center part dielectric material width. It is a figure which shows the electromagnetic wave radiation pattern in A point of FIG. 4, and B point.

Explanation of symbols

1, 1 'Dielectric substrate 11, 11' Dielectric 12, 13, 12 'in the center part Dielectric outside 2, Ground conductor plate 3 Radiation conductor plate P Feeding point

Claims (7)

  In a planar antenna in which a grounding conductor plate is provided on one surface of a dielectric substrate and a radiation conductor plate is provided on the other surface on the opposite side, the dielectric substrate is configured by arranging a plurality of dielectrics, A planar antenna, wherein the plurality of dielectric groups are made of at least two types of dielectrics having different dielectric constants.   Among the plurality of dielectrics constituting the dielectric substrate, the dielectric constant of the dielectric forming the central portion of the dielectric substrate is outside the dielectric forming the central portion of the dielectric substrate. The planar antenna according to claim 1, wherein the dielectric constant is higher than a dielectric constant of the dielectric located in the region.   Of the plurality of dielectrics constituting the dielectric substrate, the dielectric constant of the dielectric forming the central portion of the dielectric substrate is εα, and the dielectric forming the central portion of the dielectric substrate is The planar antenna according to claim 2, wherein a dielectric constant of the dielectric located in the outer region is εβ, and εα> εβ.   The planar antenna according to claim 3, wherein the dielectric constants εα and εβ are in a relationship of εα> εβ and εα <2 × εβ.   A plurality of dielectrics constituting the dielectric substrate are arranged in a stripe pattern, and a dielectric constant of a central portion of the plurality of dielectrics is εα, and both outer sides of the dielectrics having the dielectric constant εα The planar antenna according to claim 1, wherein the dielectric constant of the dielectric located at ε is εβ, and εα> εβ.   6. The planar antenna according to claim 5, wherein the dielectric constants εα and εβ have a relationship of εα> εβ and εα <2 × εβ.   The planar antenna according to any one of claims 1 to 6, wherein at least one of a plurality of dielectrics constituting the dielectric substrate is made of a dielectric resin.