JPH09214240A - Plane antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plane antenna in which an excellent antenna characteristics is easily obtained and the cost is reduced. SOLUTION: A radiation conductive film 12 is formed to the front side of a dielectric board 11, and an exciting conductive film 13 and grounding conductor films 14, 15 are formed in parallel with each other on a rear side of the dielectric board 11, a feeding electrode 16 and short-circuit boards 17, 18 are formed to the side face of the dielectric board 11 and the exciting conductor film 13 is connected to the feeding electrode 16 and the short-circuit boards 17, 18 connect the radiation conductor film 12 and the grounding conductor films 14, 15 to make electromagnetic coupling between the exciting conductive film 13 and the radiation conductive film 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat antenna mounted on a circuit board incorporated in a portable communication device or the like.

[0002]

2. Description of the Related Art In recent years, with the widespread use of portable communication devices, there is an increasing demand for miniaturization of antennas used for transmitting and receiving high-frequency signals between the communication devices. In such a communication device, when the antenna is installed outside the communication device main body, it is difficult to downsize the communication device, and an external force directly acts on the antenna, so that the mechanical strength and the durability are improved. May cause problems such as deterioration of the characteristics and changes in characteristics. Further, in the case of a configuration in which the antenna and the communication device main body are connected by a connector, high-frequency signals are transmitted and received through the connector, so problems such as insertion loss due to the connector and changes in resonance frequency occur. Further, the use of the connector increases the number of parts, which is not preferable in terms of workability and cost. Therefore, a planar antenna for surface mounting has been proposed which can be directly surface mounted on a substrate without using a connector.

FIG. 4 is a perspective view showing a surface mounting planar antenna proposed in Japanese Patent Laid-Open No. 7-221537. In the planar antenna 40 shown in FIG. 4, the dielectric substrate 41
The radiation conductor film 42 is formed on the entire surface of the. Further, a ground conductor film 43 is formed on the back surface of the dielectric substrate 41 near one of the short sides and over almost half of the back surface. Further, a feeding electrode 44 is formed from the other short side of the back surface of the dielectric substrate 41 to the side surface of the dielectric substrate 41. Further, a through hole 45 having a conductor on its inner wall is formed inside the dielectric substrate 41, whereby the radiation conductor film 42 and the feeding electrode 44 are electrically connected. The planar antenna 40 configured in this manner is surface-mounted on the circuit board built in the communication device main body, and power is supplied from the communication device main body to the radiation conductor film 42 via the feeding electrode 44 and the through hole 45. Electromagnetic waves are radiated into the air from the radiation conductor film 42.

FIG. 5 is a perspective view showing a planar antenna proposed in Japanese Unexamined Patent Publication No. 7-249923, in which a plurality of dielectric substrates are stacked on each other. In the planar antenna 50 shown in FIG. 5, the radiation conductor film 52 is formed on almost the entire surface of the first dielectric substrate 51. The second dielectric substrate 53 has slots 54,
A ground conductor film 55 is formed on a portion of the surface of the second dielectric substrate 53 excluding the slots 54, and ground electrodes 56, 5 are formed on both end portions of the side surface of the second dielectric substrate 53.
7 are formed. These ground electrodes 56 and 57 are connected to the ground conductor film 55. Further, an exciting conductor film 59 which is a microstrip line is formed on the surface of the third dielectric substrate 58, and the third dielectric substrate 58 is formed.
A power supply electrode 60 is formed at the center of the side surface of the. The power feeding electrode 60 is connected to the exciting conductor film 59. Further, ground electrodes 61 and 62 connected to the ground electrodes 56 and 57 are formed on both sides of the side surface of the third dielectric substrate 58 with the feeding electrode 60 interposed therebetween. A ground conductor is formed on the back surface of the third dielectric substrate 58 except for the power supply electrode 60 and its periphery, and is connected to the ground electrodes 56, 57, 61, and 62. These first, second and third dielectric substrates 51, 53 and 58 are superposed on each other and integrated. When power is supplied to the feeding electrode 60 of the planar antenna 50 configured as described above, electromagnetic coupling is performed between the exciting conductor film 59 and the radiating conductor film 52 through the slot 54, whereby the radiating conductor film is formed. Electromagnetic waves are emitted from 52 to the air.

[0005]

However, in the planar antenna described with reference to FIG. 4 in which the radiation conductor film and the feed electrode are connected by the through hole, the feed electrode feeds the radiation conductor film through the through hole. Since it is carried out via the through-hole, the arrangement of the through-hole, the connecting portion between the feeding electrode and the through-hole, the connecting portion between the through-hole and the radiation conductor film, etc. are frequency characteristics, impedance matching, etc. It is difficult to design a planar antenna to improve its antenna characteristics. In addition, the processing accuracy of the through hole has a great influence on the antenna characteristics.
It is also difficult to manufacture a planar antenna having good antenna characteristics.

Further, since the planar antenna described with reference to FIG. 5 in which the first, second and third dielectric substrates are superposed on each other has a multi-layer structure, the number of parts and the work procedure increase. Not cost effective. In view of the above circumstances, it is an object of the present invention to provide a planar antenna that can easily obtain good antenna characteristics and can be reduced in cost.

[0007]

Means for Solving the Problems A planar antenna of the present invention which achieves the above object is (1) a dielectric substrate (2) a radiating conductor film formed on the surface of the dielectric substrate (3) the dielectric substrate An exciting conductor film and a grounding conductor film are formed on the back surface of the substrate in parallel with each other. (4) A power supply electrode is formed on a side surface of the dielectric substrate and connected to the exciting conductor film.

Here, it is preferable to provide a short-circuit plate for short-circuiting the radiation conductor film and the ground conductor film on a portion of the side surface of the dielectric substrate excluding the feeding electrode.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 is a perspective view (a) showing a radiating conductor film side of a planar antenna according to a first embodiment of the present invention, and a coplanar line side of the planar antenna composed of an exciting conductor film and a grounding conductor film. It is a perspective view (b).

In this planar antenna 10, as shown in FIG. 1A, a radiating conductor having a length of about 1/4 of the wavelength of the resonance frequency of the planar antenna 10 on one side is formed on the surface of the dielectric substrate 11. The film 12 is formed. Also, FIG.
As shown in (b), an excitation conductor film 13 is formed on the back surface of the dielectric substrate 11, and the excitation conductor film 13 is sandwiched between the ground conductor film 14 and the ground conductor film 14 in parallel with each other. 15 is formed, and thereby a coplanar type line is formed. Further, the power supply electrode 16 is formed on the side surface of the dielectric substrate 11. This feeding electrode 1
Reference numeral 6 is connected to the excitation conductor film 13. In addition, the short-circuit plate 1 is provided on both sides of the side surface of the dielectric substrate 11 with the feeding electrode 16 interposed therebetween.
7 and 18 are formed, and the radiation conductor film 12 and the ground conductor films 14 and 15 are short-circuited by the short-circuit plates 17 and 18.

The planar antenna 10 having the above structure
However, for example, it is mounted on a circuit board of a portable communication device, and power is supplied from the portable communication device to the feeding electrode 16 of the planar antenna 10. Then, the excitation conductor film 13 and the radiation conductor film 1 connected to the power feeding electrode 16 via the dielectric substrate 11
Electromagnetic coupling is performed between the two and the electromagnetic wave is radiated from the radiation conductor film 12 into the air.

Thus, the planar antenna 1 of this embodiment is
At 0, since the radiation conductor film 12 formed on the front surface of the dielectric substrate 11 and the excitation conductor film 13 formed on the back surface of the dielectric substrate 11 are connected by electromagnetic coupling, A through hole such as a planar antenna in which power feeding electrodes are connected by a through hole is unnecessary, and therefore, antenna characteristics are not adversely affected, and the design and manufacture of the planar antenna 10 having good antenna characteristics are facilitated.
Further, by forming the short-circuit plates 17 and 18 on the side surface of the dielectric substrate 11, the short-circuit plates 17 and 18 can also serve as the ground electrode, which is effective in surface mounting and the number of parts can be reduced. . Further, since the structure is simple by using one dielectric substrate 11, the number of components and work steps are different from those of the conventional planar antenna having a multi-layer structure using the first, second, and third dielectric substrates. The number is small and the cost is reduced. Further, impedance matching is easily performed by the coplanar type line composed of the excitation conductor film 13 and the ground conductor films 14 and 15 formed in parallel with each other, and the transmission loss is also reduced.

Generally, in a patch antenna mounted on a circuit board, such as the planar antenna 10 of this embodiment, the length of the radiating element (radiating conductor) is set to 1/2 the wavelength used. It becomes a resonance state and operates as an antenna by passing a current through the radiating element. Here, the voltage / current distribution on the element is shown in FIG.
As shown in (a), the voltage is maximum and the current is 0 at both ends of the element, and the voltage is 0 and the current is maximum at the center of the element. Therefore, the patch antenna shown in FIG. 2B is cut at the center of the element. However, even if the patch antenna shown in FIG. 2 (c) is used and all the side surfaces of the element are short-circuited by the short-circuit plate (hatched portion), the current / voltage relationship on the element shown in FIG. 2 (a) can be maintained. Operates as an antenna. Further, when a part of the side surface of the element is short-circuited by a short-circuit plate (hatched portion) as shown in FIG. 2 (d), the current path is in the longitudinal direction of the element shown in FIGS. 2 (b) and 2 (c). Since the direction is changed from the parallel direction to the short-circuit plate in the diagonal direction, the element size can be reduced.

In the planar antenna 10 of this embodiment, short-circuit plates 17 and 18 are formed on both sides of the dielectric substrate 11 with the feeding electrode 16 sandwiched therebetween.
7 and 18, the radiation conductor film 12 and the ground conductor films 14 and 15
Is short-circuited, the high-frequency current flowing through the radiation conductor film 12 flows toward the short-circuit plates 17 and 18. Therefore, the dimension of the radiation conductor film 12 in the longitudinal direction can be short, and the planar antenna 10 can be downsized.

FIG. 3 is a perspective view (a) showing the radiating conductor film side of the planar antenna of the second embodiment of the present invention, and the planar antenna side of the planar antenna composed of an exciting conductor film and a grounding conductor film. It is a perspective view (b) which shows. The planar antenna 30 includes a dielectric substrate 3 as shown in FIG.
The radiation conductor film 32 is formed on the entire surface of 1. Further, as shown in FIG. 3B, on the back surface of the dielectric substrate 31,
The excitation conductor film 33 and the ground conductor films 34 and 35 are formed in parallel with each other. These form a coplanar line. Further, a power supply electrode 36 is formed on the side surface of the dielectric substrate 31. The power supply electrode 36 is connected to the exciting conductor film 33. Further, the ground terminals 37, 38 are provided on both sides of the side surface of the dielectric substrate 11 with the feeding electrode 36 interposed therebetween.
Are formed. These ground terminals 37 and 38 are connected to the ground conductor films 34 and 35.

The planar antenna 30 having the above structure
Is mounted on, for example, a circuit board of a portable communication device, and power is supplied from the portable communication device to the feeding electrode 36 of the planar antenna 30 to electromagnetically couple between the excitation conductor film 33 and the radiation conductor film 32. May be performed. The method of manufacturing the planar antenna 10 shown in FIG. 1 will be described below.

First, as the dielectric substrate 11, a relative dielectric constant of 4.
5. Prepare a glass epoxy substrate having a thickness of 1.6 mm.
A rectangular radiating conductor film 12 made of copper is formed on the surface of this glass epoxy substrate by etching, the length of one side being approximately ¼ wavelength of the resonance frequency in the dielectric. Further, the excitation conductor film 13 and the ground conductor films 14 and 15 are formed on the back surface of the glass epoxy substrate by etching to obtain a coplanar line. Further, the power supply electrode 16 is formed on the side surface of the glass epoxy substrate by soldering using a copper foil having a thickness of 50 μm.

Next, the radiation conductor film 12 and the ground conductor films 14 and 15 are soldered to each other on both sides of the glass epoxy substrate sandwiching the power supply electrode 16 by using a copper foil having a thickness of 50 μm to short-circuit the plate. 17 and 18 are formed. In this way, the flat antenna 10 having good antenna characteristics can be obtained.

[0019]

As described above, in the planar antenna of the present invention, electromagnetic coupling is performed between the radiation conductor film formed on the surface of the plane antenna and the excitation conductor film formed on the back surface thereof. Therefore, good antenna characteristics can be easily obtained, and the cost can be reduced.

[Brief description of drawings]

FIG. 1A is a perspective view showing a radiation conductor film side of a planar antenna according to a first embodiment of the present invention, and a coplanar line side of the planar antenna composed of an excitation conductor film and a ground conductor film. It is a perspective view (b).

FIG. 2 is a diagram showing voltage and current distributions on elements of a patch antenna, and element size of each patch antenna.

FIG. 3A is a perspective view showing a radiation conductor film side of a planar antenna of a second embodiment of the present invention, and a perspective view showing a coplanar line side of the planar antenna composed of an excitation conductor film and a ground conductor film. It is a figure (b).

FIG. 4 is a perspective view showing a planar antenna for surface mounting proposed in JP-A-7-221537.

FIG. 5 is proposed in Japanese Patent Laid-Open No. 7-249923.
It is a perspective view showing a plane antenna constituted by laminating a plurality of dielectric substrates.

[Explanation of symbols]

 10,30 Planar antenna 11,31 Dielectric substrate 12,32 Radiation conductor film 13,33 Excitation conductor film 14,15,34,35 Ground conductor film 16,36 Feed electrode 17,18 Short circuit plate 37,38 Ground terminal

Claims (2)

[Claims] 1. A dielectric substrate, a radiation conductor film formed on the front surface of the dielectric substrate, an excitation conductor film and a ground conductor film formed on the back surface of the dielectric substrate in parallel with each other, and the dielectric member. A planar antenna comprising a feed electrode formed on a side surface of a substrate and connected to the excitation conductor film. 2. The plane according to claim 1, wherein a short-circuit plate for short-circuiting the radiation conductor film and the ground conductor film is provided on a portion of the side surface of the dielectric substrate excluding the power feeding electrode. antenna.