JP2015154368A - patch antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a patch antenna which can resonate with radio waves with a longer wavelength than an antenna with the same outer shape dimensions and which can maintain proper characteristics.SOLUTION: A patch antenna 1 includes a dielectric 11, a radiation electrode 12 that is formed on one surface of the dielectric 11, and an earth electrode 13 that is formed on the other surface of the dielectric 11. An outer shape of the radiation electrode 12 is formed of a polygonal or circular shape. A surface of the radiation electrode 12 is three-dimensionally formed in an uneven shape. A surface area of the radiation electrode 12 is larger than the outer shape.

Description

  The present invention relates to a patch antenna.

  Conventionally, patch antennas (also referred to as microstrip antennas) have been used for portable devices such as cellular phones, GPS devices used in such portable devices and in-vehicle fields, and the like. Since patch antennas are thin and have a flat plate characteristic, they have a high degree of freedom in antenna installation and are widely used.

  In general, a patch antenna includes a dielectric (dielectric substrate), a planar radiation electrode formed on one surface of the dielectric, and a ground electrode (ground electrode) formed on the other surface of the dielectric. And. The patch antenna is connected to a radiating electrode by a power feed pin that is insulated and penetrated from the ground electrode, so that power is supplied to perform communication.

  In recent years, there has been a growing need for miniaturization of antennas such as GPS used in the above-described portable devices and in-vehicle fields.

  As a method for reducing the size of the patch antenna, for example, a technique has been proposed in which a plurality of slits are provided on the outer peripheral portion of the rectangular radiation conductor by, for example, making a cut from each side toward the center (for example, (See Patent Documents 1 and 2).

JP-A-5-304413 JP 2012-049618 A

  However, when the slits are provided in this manner, there is a problem that the gain of the antenna is lowered, and the length of the slits is limited by the width of the patch antenna, so there is a limit to the range in which the frequency can be varied.

  The present invention has been made in view of the above circumstances, and since the surface area of the radiation electrode is substantially larger than the outer dimensions, it can resonate with radio waves having a longer wavelength than an antenna having the same outer dimensions. An object of the present invention is to provide a patch antenna that can maintain good characteristics.

  As a result of intensive studies in order to solve the above-mentioned problems, the present inventors have shifted the resonance point to the low frequency side in the same external dimensions as before by making the radiation electrode three-dimensional as an uneven shape. As a result, the present invention has been completed. That is, the present invention provides the following.

  (1) The present invention includes a dielectric, a radiation electrode formed on one surface of the dielectric, and a ground electrode formed on the other surface of the dielectric, and the outer shape of the radiation electrode is The surface of the radiation electrode is three-dimensionally formed in an uneven shape, and the surface area of the radiation electrode is a patch antenna wider than the outer shape.

  (2) The present invention provides the patch according to (1) described above, wherein the surface of the radiation electrode has a three-dimensional shape of the concavo-convex shape by forming a plurality of convex portions of a predetermined shape vertically and horizontally. It is an antenna.

  (3) According to the present invention, in the invention of (1) described above, the surface of the radiation electrode is formed in a three-dimensional manner by forming a plurality of grooves radially from the center to the outside. Is a patch antenna.

  (4) In the present invention according to any one of (1) to (3), the radiation electrode is formed of a metal plate having a predetermined thickness, and is insert-molded integrally with the dielectric. Or a patch antenna formed by plating with a predetermined thickness on the dielectric.

  According to the present invention, the resonance point can be shifted to the low frequency side, and good characteristics can be maintained.

It is the figure which showed an example of the patch antenna typically. It is a figure which shows typically the plane (A) of the radiation electrode which has an uneven | corrugated shape, and its side surface (B). It is a figure which shows typically the plane (A) of the radiation electrode which has an uneven | corrugated shape, and its side surface (B). It is a figure which shows the result of having calculated the resonant frequency by simulation using the FDTD method. It is a radiation characteristic figure in E side and H side obtained by simulation. It is the figure which showed typically the junction surface (A) with the dielectric material in the radiation electrode which formed uneven | corrugated shape, and a part (B) of the side surface. It is a figure which shows typically the plane (A) and the side surface (B) of the radiation electrode which the surface was formed by the unevenness | corrugation of a triangular wave shape. It is a figure which shows typically the plane (A) and the side surface (B) of the radiation electrode which the surface was formed by the unevenness | corrugation of a triangular wave shape. It is a figure which shows typically the plane (A) and the side surface (B) of the radiation electrode which the surface was formed by the unevenness | corrugation of a triangular wave shape. It is a figure which shows the result of having calculated the resonant frequency by simulation using the FDTD method.

  Hereinafter, specific embodiments of the patch antenna according to the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following embodiment, A various change is possible in the range which does not change the summary of this invention.

  As shown in FIG. 1, the patch antenna 1 according to the present invention includes a dielectric 11, a radiation electrode 12 formed on one surface of the dielectric 11, and a ground electrode formed on the other surface of the dielectric 11. 13 is a so-called microstrip antenna.

  The outer shape of the radiation electrode 12 is a quadrangular shape in FIG. 1, but is not limited thereto, and may be formed by, for example, a polygonal shape or a circular shape other than the quadrangular shape. Further, since the patch antenna 1 performs communication by circular polarization, strictly speaking, the outer shape of the radiation electrode 12 is not a quadrangle, but is provided with a notch at a corner. When communication is performed using right-handed circularly polarized waves, for example, notches are provided in the upper right corner and the lower left corner. When communication is performed using left-handed circularly polarized waves, for example, notches are provided in the upper left corner and the lower right corner.

  The surface of the radiation electrode 12 is three-dimensionally formed in an uneven shape. The surface area of the radiation electrode 12 is wider than the outer shape.

  Thus, the patch antenna 1 can increase the surface area by forming a three-dimensional uneven shape on the surface of the radiation electrode 12. Therefore, since the surface area of the radiation electrode 12 can be substantially larger than the outer dimension, the patch antenna 1 can resonate with a radio wave having a longer wavelength than the antenna having the same outer dimension, and maintain good characteristics. it can.

  Further, the patch antenna 1 can adjust the surface area of the radiation electrode 12 to substantially the same size as the radiation electrode of the antenna of the conventional configuration even when the external dimensions are made smaller than that of the antenna of the conventional configuration. Therefore, the antenna can resonate with a radio wave having the same wavelength as that of a conventional antenna and can maintain good characteristics.

  Furthermore, since the patch antenna 1 can be made smaller in outer dimensions than the antenna of the conventional configuration and can adjust the surface area of the radiation electrode 12 to be substantially larger than the radiation electrode of the antenna of the conventional configuration, The antenna can resonate with radio waves having a longer wavelength than that of the antenna and can maintain good characteristics.

  Moreover, as shown in FIG. 1, the uneven | corrugated shape may be formed in three dimensions on the surface of the radiation electrode 12 by forming the convex part of a predetermined shape vertically and horizontally.

  The radiation electrode 12 may be formed on the dielectric 11 by a plating process having a predetermined thickness. The radiation electrode 12 may be formed by forming a plurality of metal plates whose convex portions are processed into the same shape. Note that the thickness of the metal plate is constant.

Below, each element which comprises the patch antenna 1 is explained in full detail.
The material of the dielectric 11 is not particularly limited. For example, the dielectric 11 can be made of a resin, ceramic, a material obtained by mixing a resin at a predetermined ratio with ceramic, or the like.
Here, as resin which comprises the dielectric material 11, PPS (polyphenylene sulfide), LCP (liquid crystal polymer) etc. can be mentioned, for example.

  The dielectric 11 may be processed by injection molding, and can be formed into various shapes according to the thin shape and purpose. Furthermore, the dielectric 11 may be formed into a desired thickness and shape by using a composite material in which a ceramic having a high relative dielectric constant, PPS, and LCP are compounded and injection-molded.

  The dielectric constant of the dielectric 11 is not particularly limited, and can be set to a value corresponding to a desired size of the patch antenna 1. For example, the relative dielectric constant of the dielectric 11 is appropriately set according to the housing size of an electronic device or the like to which the patch antenna 1 is applied.

  The dielectric 11 may be formed in a desired thickness and shape integrally with the radiation electrode 12 by insert molding.

The radiation electrode 12 includes, for example, a copper metal such as phosphor bronze and a conductive metal material such as silver, nickel, or an alloy thereof.
The radiation electrode 12 will be described as adopting a direct coupling dielectric method in which power is directly fed from the back using a coaxial line or connector that penetrates the ground electrode 13 and the dielectric 11, but is not limited to this, and an electromagnetic coupling feeding method is also used. Good.

The ground electrode (ground electrode plate) 13 is a conductor containing a conductive metal material such as copper, silver, nickel, or an alloy thereof.
In this embodiment, it has been described that the single ground electrode 13 is formed on the dielectric 11. However, the present invention is not limited to this, and a circuit board disposed under the dielectric 11 may be used as the ground electrode 13.

  Next, the uneven shape of the radiation electrode 12 of the patch antenna 1 will be described. The uneven shape is not limited to the shape shown in the following embodiment, and may be other shapes as long as the effective area of the radiation electrode 12 can be effectively increased.

  FIG. 2 is a view showing a state in which the radiation electrode 12 is formed in a concavo-convex shape having a convex portion on the side opposite to the joint surface 12a with the dielectric 11, and a top view of the radiation electrode 12 as viewed from above (FIG. 2 (A)) and a side view thereof (FIG. 2B). The patch antenna shown in FIG. 2 is referred to as “patch antenna 1A”. Note that σ in FIG. 2 indicates a feeding point and is arranged at an optimum position for obtaining matching with the feeding line.

  The radiation electrode 12 allows a current to flow three-dimensionally along the concavo-convex shape, and the current path length can be made longer than that of a planar conventional radiation electrode. In this way, since the patch antenna 1 has a surface area of the radiation electrode 12 substantially larger than the outer dimensions, the patch antenna 1 can resonate with radio waves having a longer wavelength than the antenna having the same outer dimensions, and maintain good characteristics. can do.

  Note that the size of each region of the grid-like section having the convex portions 21 in the radiation electrode 12 is not particularly limited. For example, the radiation electrode 12 having a substantially square shape has a size that can be divided into 4 × 4 areas as shown in FIG. 2 or a size that can be divided into 6 × 6 areas as shown in FIG. be able to. In this embodiment, the patch antenna 1B formed in the 6 × 6 region shown in FIG. 3 has the same external dimensions as the patch antenna 1A, but the surface area of the radiation electrode 12 is increased.

  If the surface area of the radiation electrode 12 is not changed, the height decreases as the number of the convex portions 21 increases. Therefore, the patch antenna 1 has an advantage that it becomes thinner as the number of the convex portions 21 formed in the radiation electrode 12 is larger.

  Further, in the present embodiment, the shape of the convex portion 21 is described as being formed in a mountain shape (tapered shape) having a continuous slope in the height direction as shown in FIG. 2, but is not limited thereto. It may be a dome shape.

Next, a simulation by the FDTD method (finite difference time domain method) is performed on each of the patch antenna 1A in the mode illustrated in FIG. 2, the patch antenna 1B in the mode illustrated in FIG. 3 and the reference patch antenna. The obtained change in the resonance frequency will be described with reference to FIG. Note that the external dimensions of the patch antenna 1A, the patch antenna 1B, and the reference patch antenna are the same. Further, the reference patch antenna means a conventional patch antenna, that is, a patch antenna having a form obtained by forming a planar radiation electrode having no uneven shape on a dielectric.
The analysis conditions by simulation, the size of the radiation electrode 12 in the patch antenna 1A, the size of the uneven shape, and the like were set as follows.

[Analysis conditions, etc.]
Analysis method: FDTD (Finite-Difference Time-Domain) method Feeding method: Pin feeding Dielectric constant of dielectric substrate: εr = 8
Cell size: xs = ys = zs = 0.4 mm
Dielectric substrate thickness (dielectric substrate thickness): h = 1.6 mm
Patch diameter (size of one side of radiation electrode): L = 34.4 mm
Dielectric substrate diameter (size of one side of dielectric substrate): W = 51.2 mm
Feeding point distance: ρ = 3.6mm
Small patch diameter (size of one side of each partition area): a = 5.6 mm

  As shown in FIG. 4, in the patch antenna 1A and the patch antenna 1B, it can be seen that the peak of the resonance frequency f is shifted to the low frequency side (long wavelength side) compared to the reference patch antenna. Specifically, the peak of the resonance frequency f of the reference patch antenna is 1.52 GHz, whereas the peak of the resonance frequency f of the patch antenna 1A is 1.47 GHz, and the peak of the resonance frequency f of the patch antenna 1B is 1. It became 1.45 GHz.

  From this result, it can be seen that the patch antenna 1A and the patch antenna 1B can resonate with radio waves having a longer wavelength even though the outer dimensions are the same as those of the reference patch antenna.

FIG. 5 shows an E plane (horizontal plane) obtained by simulation for the patch antenna 1A (FIG. 5A), the patch antenna 1B (FIG. 5B), and the reference patch antenna (FIG. 5C). FIG. 6 is a diagram showing radiation characteristics on the H plane (vertical plane).
From this result, it can be seen that the characteristics of the patch antenna 1A and the patch antenna 1B are not inferior to those of the reference patch antenna and maintain good characteristics.

Further, as shown in FIG. 6, the surface of the radiation electrode 12 may have a configuration in which the uneven shape is three-dimensionally formed by forming a plurality of grooves 31 radially from the center to the outside.
Specifically, when a metal plate is used as the radiation electrode 12, striped or radial uneven shapes are formed on the front surface, back surface (bonding surface with the dielectric), or both surfaces thereof. As shown in FIG. 6, the uneven grooves 31 are formed in stripes or radial shapes from the center to the outside.

In addition, the uneven | corrugated shape mentioned above is not restricted to a rectangular wave shape, A triangular wave shape, a sawtooth shape, or a sine wave shape etc. may be sufficient.
Moreover, the pattern of the surface of the radiation electrode 12 is not restricted to the above, Other patterns may be sufficient, for example, the following patterns may be sufficient.

1. As shown in FIG. 7A, the surface of the radiation electrode 12 is conceptually divided into nine blocks. The surface of the four outer blocks B1 arranged in the vertical and horizontal directions with respect to the central block is formed with an uneven shape along the horizontal line. Concavities and convexities are formed on the surfaces of the four outer blocks B2 arranged in the angular direction with respect to the central block so as to be horizontal or perpendicular to the diagonal line. As shown in FIG. 7A, the block B1 and the block B2 are arranged so that the grooves due to the unevenness are radially outward from the central block. In the above description, for convenience of explanation, the surface of the radiation electrode 12 is divided into nine blocks. However, the surface is not actually formed for each block.
FIG. 7A is a plan view showing a state in which the radiation electrode 12 is formed on the dielectric 11, and FIG. 7B shows a state in which the radiation electrode 12 is formed on the dielectric 11. FIG. In FIG. 7B, the uneven shape of the radiation electrode 12 is shown as a triangular wave shape, but is not limited thereto.

2. Similarly to the above, as shown in FIG. 8A, the surface of the radiation electrode 12 is conceptually divided into nine blocks. The surface of the four outer blocks B1 arranged in the vertical and horizontal directions with respect to the central block is formed with an uneven shape along the horizontal line. The surface of the four outer blocks B2 arranged in the angular direction with respect to the central block has an uneven shape formed from one side to a diagonal line, and the uneven shape is formed symmetrically with respect to the diagonal line. As shown in FIG. 8A, the block B1 is arranged so that the grooves due to the unevenness are radially outward from the central block. As shown in FIG. 8A, the block B2 is arranged so that the grooves due to the unevenness are aligned in the same direction as the grooves due to the unevenness of the adjacent upper, lower, left and right blocks. In the above description, for convenience of explanation, the surface of the radiation electrode 12 is divided into nine blocks. However, the surface is not actually formed for each block.
FIG. 8A is a plan view showing a state in which the radiation electrode 12 is formed on the dielectric 11, and FIG. 8B shows a state in which the radiation electrode 12 is formed on the dielectric 11. FIG. In FIG. 8B, the uneven shape of the radiation electrode 12 is shown as a triangular wave shape, but is not limited thereto.

3. As shown in FIG. 9A, the surface of the radiation electrode 12 has grooves formed by irregularities that are radially formed from the center to the outside. The concavo-convex shape is formed so that the width is narrower as it is closer to the center and the width is wider as it is farther from the center.
FIG. 9A is a plan view showing a state where the radiation electrode 12 is formed on the dielectric 11, and FIG. 9B shows a state where the radiation electrode 12 is formed on the dielectric 11. FIG. In FIG. 9B, the uneven shape of the radiation electrode 12 is shown as a triangular wave shape, but is not limited thereto.

  FIG. 6 is a diagram illustrating a state in which a plurality of grooves 31 are provided on the bonding surface 12a of the radiation electrode 12 with the dielectric 11 to form a concavo-convex shape, and the bonding surface 12a of the radiation electrode 12 with the dielectric 11 is illustrated. It is a figure (FIG. 6 (A)) and sectional drawing (FIG. 6 (B)) of a part of side surface. Hereinafter, the patch antenna formed of the radiation electrode 12 shown in FIG. 6 is referred to as “patch antenna 1C”.

  As shown in FIG. 6, in the patch antenna 1 </ b> C, a plurality of grooves 31 are provided on the joint surface 12 a of the radiation electrode 12 with the dielectric 11, and a groove portion 31 a and a peak portion 32 obtained by the plurality of grooves are provided. It has an uneven shape formed by The surface of the radiation electrode 12 may be formed with an uneven shape by irradiating laser light, or may be formed with an uneven shape by etching.

  Thus, the surface area of the patch antenna 1 </ b> C can be increased by increasing the number of grooves 31 on the surface of the radiation electrode 12. Therefore, since the patch antenna 1C can substantially increase the surface area of the radiation electrode 12 from the outer dimensions, the patch antenna 1C can resonate with a radio wave having a longer wavelength than the antenna having the same outer dimensions and can maintain good characteristics. it can.

  Next, changes in the resonance frequency obtained by performing a simulation by the FDTD method for the patch antenna 1C and the reference patch antenna of the aspect shown in FIG. 6 will be described with reference to FIG. The patch antenna 1C and the reference patch antenna have the same external dimensions.

  The analysis conditions by simulation, the size of the patch antenna 1C, etc. are as follows. As the patch antenna 1C, the radiation electrode 12 has a thickness of 0.4 mm, and a groove 31 having a horizontal stripe shape as shown in FIG. The simulation was performed with the setting.

[Analysis conditions, etc.]
Analysis method: FDTD method Feeding method: Pin feeding Dielectric constant of dielectric substrate: εr = 8
Cell size: xs = ys = zs = 0.2 mm
Dielectric substrate thickness (dielectric substrate thickness): h = 2.0 mm
Patch diameter (size of one side of radiation electrode): L = 12 mm
Patch radius: L1 = 2.0mm, L2 = 6.0mm
Dielectric substrate diameter (size of one side of dielectric substrate): W = 16 mm
Feeding point distance: ρ = 1.0mm

  As shown in FIG. 10, in the patch antenna 1C, the peak of the resonance frequency f is shifted to the low frequency side (long wavelength side) compared to the reference patch antenna. Specifically, the peak of the resonance frequency f of the reference patch antenna was 3.95 GHz, whereas the peak of the resonance frequency f of the patch antenna 1C was 3.87 GHz.

  From this result, it can be seen that the patch antenna 1 </ b> C can resonate with radio waves having a longer wavelength even though the outer dimensions are the same as those of the reference patch antenna.

DESCRIPTION OF SYMBOLS 1 Patch antenna 11 Dielectric 12 Radiation electrode 12a Joint surface 12b Upper surface of a radiation electrode 13 Ground electrode

Claims (4)

A dielectric, a radiation electrode formed on one surface of the dielectric, and a ground electrode formed on the other surface of the dielectric;
The outer shape of the radiation electrode is formed by a polygonal shape or a circular shape,
The surface of the radiation electrode is three-dimensionally formed in an uneven shape,
The patch antenna has a surface area greater than that of the outer shape.   2. The patch antenna according to claim 1, wherein the surface of the radiation electrode is formed in a three-dimensional manner by forming a plurality of convex portions having a predetermined shape vertically and horizontally.   The patch antenna according to claim 1, wherein the surface of the radiation electrode has a three-dimensional shape of the concavo-convex shape by forming a plurality of grooves radially outward from the center.   The radiation electrode is made of a metal plate having a predetermined thickness, and is formed by insert molding integrally with the dielectric, or formed by a plating process having a predetermined thickness on the dielectric. The patch antenna according to any one of claims 1 to 3.

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