JPH09219617A - Planar antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a planar antenna which facilitates the adjustment of input impedance. SOLUTION: On the surface of a first dielectric substrate having a rectangular hole 12, a radiation conductive film 13 is formed. On the front surface, the rear surface and the side surface of a second dielectric substrate 14, a vibration proof conductive film 15, a ground conductive film 16 and a feeder electrode 18 are formed, respectively, and the vibration proof conductive film 15 is connected with the feeder electrode 18. Further, the first and second dielectric substrates 11 and 14 are integrated and the tip part of the vibration proof conductive film 15 is exposed from the hole 12 of the first dielectric substrate 11.

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. Furthermore, in the case of a configuration in which the antenna and the communication device body are connected by a connector, transmission and reception of high-frequency signals will be performed through the connector,
Problems such as insertion loss due to connectors 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. 6 is a perspective view showing a planar antenna for surface mounting proposed in Japanese Patent Laid-Open No. 7-235825, and FIG. 7 shows a radiation conductor film side (front side) of the planar antenna shown in FIG. 8 and 9 are views showing the ground conductor film and the excitation conductor film side (back surface side) of the planar antenna shown in FIG.
In the planar antenna 60 shown in FIG. 6, the radiation conductor film 62 is formed on the entire surface of the dielectric substrate 61. A ground conductor film 63 is formed on the back surface of the dielectric substrate 61. The ground conductor film 63 has a shape in which a part of one short side is cut out as shown in FIG. 8, and an excitation conductor film 64 which is a strip line is formed in the cutout part. Has been done. Further, the power supply electrode 6 is provided on the side surface of the dielectric substrate 61.
5 are formed. The power supply electrode 65 is the excitation conductor film 6
4 is connected. In addition, on the side surface of the dielectric substrate 61,
Ground electrodes 66 and 67 are formed at both ends sandwiching the power feeding electrode 65. These ground electrodes 66 and 67 are connected to the ground conductor film 63.

Further, a through hole 68 having a conductor on its inner wall is formed inside the dielectric substrate 61, and the through hole 68 electrically connects the tip end portions of the radiation conductor film 62 and the excitation conductor film 64. There is. The planar antenna 60 configured in this manner is surface-mounted on the circuit board built in the communication device body, and the radiation conductor film 62 is passed from the communication device body via the feeding electrode 65, the excitation conductor film 64, and the through hole 68. High-frequency power is supplied to the electromagnetic wave, and electromagnetic waves are radiated into the air from the radiation conductor film 62 due to electromagnetic coupling between the excitation conductor film 64 and the radiation conductor film 62.

[0005]

By the way, in a high frequency component such as the above-mentioned planar antenna, in order to efficiently transmit high frequency power, the impedance of the transmission path of the circuit board on which the component is mounted, and It is necessary to match the input impedance of the component. Generally, this impedance is 50Ω. The input impedance of the planar antenna described above depends on the position of the through hole for feeding with respect to the radiation conductor film or the length of the excitation conductor film that is electromagnetically coupled to the radiation conductor film. In this planar antenna, since the tip portion of the excitation conductor film and the radiation conductor film are connected by the through hole formed inside the dielectric substrate, it is difficult to adjust the input impedance of the manufactured planar antenna. is there. Therefore, in order to manufacture a planar antenna having an accurate input impedance, extremely high design accuracy and processing accuracy are required, which leads to an increase in cost and a decrease in yield.

In view of the above circumstances, the present invention provides a planar antenna whose input impedance can be easily adjusted.

[0007]

Means for Solving the Problems A planar antenna of the present invention which achieves the above object is (1) a dielectric substrate having a radiation conductor film on its surface (2) a dielectric substrate having a geometrical overlap with the radiation conductor film. Holes provided on the front side of the body substrate (3) Ground conductor film formed on the back side of the dielectric substrate (4) Extending into the inside of the dielectric substrate, and the tip portion from the hole of the dielectric substrate Exposed Exciting Conductor Film (5) The invention is characterized in that the exciting conductor film is provided with a feeding electrode formed on a side surface of the dielectric substrate and connected to a rear end of the exciting conductor film.

Here, it is effective that the exposed tip portion of the excitation conductor film is trimmed.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 is a perspective view showing a planar antenna of a first embodiment of the present invention, FIG. 2 is a view showing a radiation conductor film side of the planar antenna shown in FIG. 1, and FIG. 3 is a ground of the planar antenna shown in FIG. It is a figure which shows the conductor film side.

In this planar antenna 10, as shown in FIG. 1, a first dielectric substrate 11 and a second dielectric substrate 14 are superposed on each other and integrated. The combination of the integrated first and second dielectric substrates 11 and 14 is the dielectric substrate according to the present invention. The first dielectric substrate 11 has square holes 12 as shown in FIGS. This hole 12 forms a hole referred to in the present invention when the second dielectric substrate 12 is superposed on and integrated with the first dielectric substrate 11. A radiation conductor film 13 is formed on almost the entire surface of the first dielectric substrate 11. At this time, the radiation conductor film 13 geometrically includes the hole 12.

On the other hand, an exciting conductor film 15 as a microstrip line is formed on the surface of the second dielectric substrate 14 which is in contact with the first dielectric substrate 11. The tip portion of the excitation conductor film 15 is exposed from the hole 12 of the first dielectric substrate 11. A ground conductor film 16 is formed on the back surface of the second dielectric substrate 14. As shown in FIG. 3, the ground conductor film 16 has a shape in which a part of one short side is cut out, and the conductor film 17 is formed in the cut out part. A power supply electrode 18 is formed on the side surface of the second dielectric substrate 14. This feeding electrode 1
Reference numeral 8 is connected to the rear end of the exciting conductor film 15 and the conductor film 17.

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 18 of the planar antenna 10. Then, electromagnetic coupling is performed between the excitation conductor film 15 and the radiation conductor film 13 via the first dielectric substrate 11, and the electromagnetic wave is radiated from the radiation conductor film 13 into the air.

In the planar antenna 10 of this embodiment, the second antenna
The tip portion of the excitation conductor film 15 formed on the surface of the dielectric substrate 14 is exposed from the hole 12 of the first dielectric substrate 11. Here, the input impedance of the planar antenna 10 can be adjusted by trimming the exposed tip end portion of the excitation conductor film 15 by a method such as laser trimming and changing the length of the excitation conductor film 15. further,
Even after the manufactured planar antenna 10 is mounted on the circuit board, the input impedance of the planar antenna 10 can be adjusted by trimming the tip portion of the exciting conductor film 15.

FIG. 4 is a perspective view showing a planar antenna according to the second embodiment of the present invention. The planar antenna 40 shown in FIG.
On the surface of the first dielectric substrate 11, the U-shaped radiation conductor film 43 that replaces the square radiation conductor film 13 formed on almost the entire surface of the first dielectric substrate 11 shown in FIG. Are formed. When the present invention is carried out, the holes are provided for the purpose of trimming the exciting conductor film as described later, and therefore it is necessary to make a hole slightly larger than the exposed area of the exciting conductor film necessary for trimming. Further, in order to match the input impedance of the planar antenna according to the present invention with the transmission line impedance by trimming, it is necessary to set the excitation conductor film length to be slightly longer than the optimum value calculated. In the case of the planar antenna as in the present invention, the optimum value is approximately 1/2 of the length of the radiation conductor film, so that the hole may geometrically protrude from the radiation conductor film in some cases. In this case, even if the radiation conductor film has a U-shaped hole, the radiation conductor film can be excited by the excitation conductor film as in the first embodiment. Also in this embodiment,
Similar to the above-described embodiment, the input impedance of the planar antenna 40 can be easily adjusted by trimming the exposed tip portion of the excitation conductor film 15.

A method of manufacturing the flat antenna 10 shown in FIG. 1 will be described below. First, as the first and second dielectric substrates 11 and 14, the relative dielectric constant is 4.5 and the thickness is 1.6 mm.
Prepare two glass epoxy substrates. On the surface of the glass epoxy substrate as the first dielectric substrate 11 of these two glass epoxy substrates, a rectangular radiating conductor made of copper whose one side length is shorter than 1/2 wavelength of the resonance frequency in the dielectric substance. The film 13 is formed by etching. Further, a rectangular hole 12 smaller than the radiation conductor film 13 is provided in the portion of the first dielectric substrate 11 where the radiation conductor film 13 is formed. Here, the reason why the length of one side of the radiation conductor film 13 is made shorter than ½ wavelength is that the resonance wavelength becomes a little longer by providing the hole 12. Also the second
On the front surface and the back surface of the second glass epoxy substrate, which is the dielectric substrate 14 of FIG.
6 is formed by etching, and a conductor film 17 is formed on a portion of the back surface of the second dielectric substrate 14 other than the portion where the ground conductor film 16 is formed. Further, the conductor film 17 and the excitation conductor film 15 are soldered to each other by using a copper foil having a thickness of 50 μm to form a power supply electrode 18 on the side surface of the second dielectric substrate 14.

FIG. 5 is an assembly diagram of the planar antenna shown in FIG. With the back surface of the first dielectric substrate 11 facing downward,
Of the first dielectric substrate 11 and the back surface of the first dielectric substrate 11 are bonded to the front surface of the second dielectric substrate 14 by using an epoxy adhesive material. The dielectric substrates 11 and 14 are integrated. As a result, the tip portion of the exciting conductor film 15 is exposed from the hole 12. In this way, the planar antenna 10 is obtained. Since the input impedance of the planar antenna 10 depends on the length of the exciting conductor film 15, the exciting conductor film 15 is formed to be a little longer than the matching length of the input impedance, which is obtained by theoretical calculation at the time of design and is assembled. After that, the input impedance is adjusted by shortening the length of the excitation conductor film 15 by laser trimming or the like. Furthermore, the plane antenna 10
The impedance can be adjusted by the same method even after mounting on the circuit board. In this way, a planar antenna having an accurate input impedance can be obtained.

[0017]

As described above, in the planar antenna of the present invention, since the tip portion of the exciting conductor film is exposed from the hole of the dielectric substrate, the tip portion of the exciting conductor film is trimmed to provide a flat surface. The input impedance of the antenna can be easily adjusted.

[Brief description of drawings]

FIG. 1 is a perspective view showing a planar antenna according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a radiation conductor film side of the planar antenna shown in FIG.

FIG. 3 is a view showing the ground conductor film side of the planar antenna shown in FIG.

FIG. 4 is a perspective view showing a planar antenna according to a second embodiment of the present invention.

5 is an assembly diagram of the planar antenna shown in FIG. 1. FIG.

FIG. 6 is a perspective view showing a planar antenna for surface mounting proposed in Japanese Patent Laid-Open No. 7-235825.

7 is a diagram showing a radiation conductor film side of the planar antenna shown in FIG.

8 is a view showing the ground conductor film and the excitation conductor film side of the planar antenna shown in FIG.

[Explanation of symbols]

 10, 40 Planar antenna 11 First dielectric substrate 12 Hole 13, 43 Radiating conductor film 14 Second dielectric substrate 15 Excitation conductor film 16 Grounding conductor film 17 Conductor film 18 Feeding electrode

Claims (2)

[Claims] 1. A dielectric substrate having a radiation conductor film formed on a surface thereof, a dielectric substrate having a hole on its surface that geometrically overlaps a part of the radiation conductor film, and a dielectric substrate formed on the back surface of the dielectric substrate. A grounding conductor film, an exciting conductor film that extends inside the dielectric substrate, and has a tip portion exposed from the hole of the dielectric substrate, and an exciting conductor film formed on a side surface of the dielectric substrate. A planar antenna comprising a feeding electrode connected to a rear end. 2. The planar antenna according to claim 1, wherein the exposed tip portion of the excitation conductor film is trimmed.