JPH09153733A - Plane reverse-f-shaped antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain the adjustment of power feeding point impedance. SOLUTION: Slits 13 are formed at the respective apexes of triangular antenna element 9. By varying a slit length L2 of these slits 13, the power feeding point impedance can be adjusted. Besides, a short hole 10 connected to a ground board is provided at the central part of each side of antenna element 9, and a through hole 12 for feeding power is formed at the centroid position of antenna element 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat inverted F-shaped antenna having a plate shape, and is particularly suitable for application to an antenna of a mobile phone or the like installed on a ceiling or the like. .

[0002]

2. Description of the Related Art Conventionally, dipole antennas, monopole antennas or leak cables have been used as antennas for indoor radios, wireless microphones, public radio telephone lines, etc., which are used indoors or in underground malls. Among them, the dipole type antenna and the monopole antenna have a bad appearance because they are mounted in a state protruding from a side wall, a ceiling or the like in a room or a premises. In addition, since leaky cables are expensive to set up,
There is a drawback that it is too costly to use a leaky cable as an antenna. To solve this,
Planar antennas have been proposed. An inverted F-type antenna is shown in FIG. 7 as a conventional example of this plane type antenna.

FIG. 1A is a perspective view of an inverted F type antenna, and FIG. 1B is a top view thereof. In the inverted F-type antenna shown in these figures, the antenna 102 has a square plate shape, and a square ground plate 101 serving as a ground having a larger area than the antenna 102 is provided. The plate-shaped antenna 102 is arranged so as to face the ground plate 101 with a predetermined separation. A short plate 103 is formed on one side of the quadrangular antenna 102 so as to extend. The short plate 103 is bent at a right angle to the antenna 102 and its tip is electrically connected to the ground plate 101. There is.

Further, a feeding line 105 feeds power to a feeding point 104 which is a predetermined position of the antenna 102.
In this case, the impedance of the feeding point of the antenna 102 can be adjusted by selecting various positions of the feeding point 104. It should be noted that the length of one side of the antenna 102 is such that a current distribution of a quarter wavelength of the frequency signal used is generated in the antenna 102, and the directivity characteristic of the E surface is as shown in FIG. The maximum absolute gain of the inverted-F antenna is about 1.5 dB. Such an inverted F-type antenna is not limited to a quadrangular shape, and various shapes have been proposed. As an example, an inverted F-shaped antenna having a circular shape is shown in FIG.

FIG. 1A is a perspective view of an inverted-F type antenna, and FIG. 1B is a side view thereof. In the inverted F-type antenna shown in these drawings, the antenna 202 has a circular shape, and a circular ground plate 201 serving as a ground is provided. Antennas 202 are arranged on the ground plate 201 so as to face each other with a predetermined space therebetween. Also, one end of the short post 203 is electrically connected near the periphery of the circular antenna 202,
The other end of the short post 203 is electrically connected to the ground plate 201.

Further, power is fed from a power feeding line 205 to a power feeding point 204 which is a predetermined position of the antenna 202, and the antenna 20 is selected by variously selecting the position of this power feeding point.
It is possible to adjust the impedance of the feeding point of 2. The length of the diameter of the antenna 202 is 1 of the frequency signal used.
The length is such that the current distribution of / 4 wavelength is generated in the antenna 202. The above-described conventional inverted F-type antenna is a planar antenna, and is used as an antenna capable of transmitting and receiving vertically polarized waves and horizontally polarized waves.

[0007]

However, the directional characteristics of the E surface of the conventional inverted F-type antenna are such that the electric field strength radiated to the surroundings is unbalanced and the antenna gain is as shown in FIG. There was a problem that it was low.
Therefore, the present applicant proposes an inverted F-type antenna that solves the above-mentioned problems in Japanese Patent Application No. 5-237169, and also proposes an inverted F-type antenna that is made compact by using a printed circuit board. This compact inverted F-type antenna can solve the imbalance of the electric field strength and has a high antenna gain, but it is difficult to adjust the disturbance such as the resonance frequency and the impedance due to the variation of the dielectric constant and dimensions of the printed circuit board. There was a problem that was.

Therefore, according to the present invention, a compact planar inverted F whose resonance frequency and impedance can be adjusted.
The purpose is to provide a type antenna.

[0009]

In order to solve the above-mentioned problems, a planar inverted F type antenna according to the present invention comprises a triangular plate-shaped antenna element formed on the front surface of an insulating base material and the insulating material. A grounding plate formed on the back surface of the base material, a short hole connecting the outer edge of the triangular plate-shaped antenna element and the grounding plate, and feeding power to the center of gravity of the triangular plate-shaped antenna element And a through hole for use as a slit, and a slit is formed from each vertex of the triangular plate-shaped antenna element toward the position of the center of gravity.

Another inverted-F antenna according to the present invention is a triangular plate-shaped antenna element formed on the front surface of an insulating base material, and a ground plate formed on the back surface of the insulating base material. The triangular plate-shaped antenna element, an outer edge of the triangular plate-shaped antenna element, a short hole connecting the ground plate, and a through hole for feeding at a substantially center of gravity of the triangular plate-shaped antenna element. The slits are formed from the outer edge of the earth plate toward the back surface position of the center of gravity, passing through the back surface positions of the vertices of the plate antenna element.

Still another inverted-F antenna of the present invention is a triangular plate-shaped antenna element formed on the front surface of an insulating base material and a ground formed on the back surface of the insulating base material. A plate, an outer edge of the triangular plate-shaped antenna element, a short hole connecting the ground plate, and a through hole for feeding at a substantially center of gravity of the triangular plate-shaped antenna element, The first slit extending from each vertex of the shaped plate antenna element to the position of the center of gravity and the back surface position of each vertex of the triangular plate antenna element, and the back surface position of the center of gravity from the outer edge of the ground plate. The second slit facing toward is formed.

According to the present invention as described above, the resonance frequency and the feeding point impedance can be adjusted by changing the width and the length of the slit formed at the apex of the triangular plate antenna element. Further, the feed point impedance can be adjusted by adjusting the width and length of the slit that passes through the back surface position of the apex of the triangular plate-shaped antenna element formed on the ground plate.

[0013]

1 and 2 show the configuration of a first embodiment of a flat inverted F-type antenna according to the present invention. FIG.
FIG. 2A is a top view of the first embodiment of the flat inverted F-type antenna, FIG. 2B is an enlarged view of the configuration of the antenna element, and FIG. 2 is a side view of the flat inverted F-type antenna. Is.
The planar inverted F-type antenna shown in these figures has a ground plate 8 formed by a circular lower conductive layer provided on the entire lower surface of the conductive foil provided on both sides of an insulating base material 7 such as a circular printed circuit board. And the upper surface conductive layer provided on the upper surface of the base material 7 is etched to form a triangular antenna element 9
Is formed. Further, a short hole 10 penetrating the base material 7 is provided so as to be in contact with the outer edge of the antenna element 9, and a metal plating layer is provided in the short hole 10 to form a ground portion with the central portion of each side of the triangular antenna element 9. The plate 8 is electrically connected.

Further, a through hole 12 penetrating the base material 7 is provided substantially at the center of gravity of the triangular antenna element 9, and the core wire of the feeder line 11 is formed by the metal plating layer formed in the through hole 12. It is electrically connected to the antenna element 9. At each vertex of the triangular antenna element 9, as shown in FIG. 1B, a width L1 and a length L are set.
Two slits 13 are formed respectively. The extending direction of the slit 13 is the center of gravity of the antenna element, that is, the direction in which the through hole 12 is provided.
When the slit 13 is provided at each vertex, the substantial length L3 of one side of the antenna element 9 changes according to the width L1 of the slit 13, and the width L of the slit 13
The resonance frequency of the antenna element 9 can be adjusted by changing 1.

Further, the feed point impedance can be adjusted by changing the length L2 of the slit 13. The impedance characteristics when the width L1 and the length L2 of the slit 13 are changed are shown on the Smith chart shown in FIG. The impedance characteristic of A shown in FIG. 4 is when the slit width L1 is 4 mm and the slit length L2 is 16 mm, and the SWR is almost 1 at the use center frequency shown by ▽ 1, and the impedance of the feeding point is about 1. Four
It has a substantially pure resistance of 8.5Ω, which is a good characteristic. The impedance on the power feeding side is 50Ω. Next, the impedance characteristic of B shown in FIG. 4 is a case where the slit width L1 is 4 mm and the slit length L2 is 13 mm, and at the use center frequency shown by ▽ 2, its feeding point impedance is almost half. It is considered to be pure resistance.

Further, the impedance characteristic of C shown in FIG. 4 has a slit width L1 of 4 mm and a slit length L2 of 10.
mm, and at the center frequency of use indicated by ▽ 3, the impedance at the feeding point is about half, which is about 2
It consists of a pure resistance of 5.1Ω and a positive reactance component of about 0.68Ω. In this way, by changing the length L2 of the slit 13, it is possible to change the feeding point impedance of the planar inverted F-type antenna. Therefore, when the desired impedance cannot be obtained as the feeding point impedance of the planar inverted F-type antenna manufactured as shown in FIG. 1A, the length L2 of the slit 13 is varied to obtain the desired impedance. Can be adjusted.

Next, the second planar inverted F-type antenna of the present invention will be described.
FIG. 3 shows the configuration of this embodiment. This figure is a bottom view of the planar inverted F-type antenna according to the second embodiment. Compared to the configuration of the planar inverted F-type antenna according to the second embodiment, the triangular antenna element 9 has a base material 7. It is common that it is formed on the front surface. However, the slit 13 is not formed in the antenna element 9. Further, the entire surface of the conductor foil attached to the back surface of the base material 7 serves as a ground plate 8, and a short hole 10 penetrating the base material 7 connected to the outer edge of the antenna element 9 is provided. Then, a metal plating layer is applied in the short holes 10 to electrically connect the central portion of each side of the triangular antenna element 9 to the ground plate 8.

Further, a slit 14 is formed from the outer edge of the ground plate 8 through the back surface of the apex of the triangular antenna element 9 toward the back surface position of the center of gravity of the triangular antenna element 9. The slit 14 formed in the ground plate 8 has a slit width of L5 and a slit length of L4. Then, the feeding point impedance can be adjusted by changing the slit length L4 of the slit 14.

The relationship between the feeding impedance and the length of the slit 14 will be described with reference to the Smith chart shown in FIG. The impedance characteristic of A shown in FIG.
The slit width L5 of the slit 14 formed in 4 mm is 4 mm,
This is the impedance characteristic when the slit length L4 is 35 mm, and the SWR is approximately 1 at the use center frequency indicated by ∇1, and the impedance at the feeding point is substantially pure resistance, which is a good characteristic.

Next, the impedance characteristic of B shown in FIG. 5 has a slit width L5 of 4 mm and a slit length L4 of 25 m.
In case of m, the impedance at the feeding point is about half the resistance at the use center frequency shown by ▽ 2. Further, the impedance characteristic of C shown in FIG. 5 has a slit width L5 of 4 mm and a slit length L5.
Is 15 mm, and at the use center frequency indicated by ∇3, the impedance at the feeding point is made up of about half the pure resistance and some positive reactance.

As described above, even if the slit length L4 of the slit 14 formed in the ground plate 8 is made variable, the feeding point impedance of the planar inverted F type antenna can be made variable. Therefore, when the desired impedance cannot be obtained as the feeding point impedance of the planar inverted F-type antenna manufactured as shown in FIG. 1A, the desired impedance can be adjusted by adjusting the slit length L4 of the slit 14. Can be adjusted to.

The third aspect of the planar inverted F-type antenna of the present invention is as follows.
The flat inverted F-type antenna of the third embodiment is the same as the flat inverted F-type antenna of the first embodiment described above.
It is configured by combining the type antenna and the planar inverted F type antenna according to the second embodiment. That is, in the planar inverted F-type antenna according to the third embodiment, the first slit 13 is formed in the triangular antenna element 1, and the top view thereof is
With the configuration shown in FIG. 1, the ground plate 8 is provided with the second slit 14, and the bottom view thereof has the configuration shown in FIG.

Then, the slit width L1 of the first slit 13 formed in the antenna element 9 and the slit length L2,
By adjusting the slit width L5 and the slit length L4 of the second slit 14 formed in the ground plate 8, the resonance frequency of the planar inverted F-type antenna and the feeding point impedance can be adjusted. . In particular, when the slit width L1 of the first slit 13 formed in the antenna element 9 is large, the adjustment width of the feeding impedance becomes narrow even if the slit length L2 is changed. Second slit 14 formed in 8
By varying the slit length L4, the impedance of the feeding point can be adjusted.

The planar inverted F-type antenna according to the first to third embodiments of the present invention described above has the substrate 7
The conductor foils attached to both surfaces of the substrate are etched to form the triangular antenna element 9, and the metal plating layer is formed in the through hole 12 and the short hole 10 provided so as to penetrate the substrate 7. A planar inverted F-type antenna can be manufactured with. Therefore, it is possible to provide a planar inverted F-type antenna excellent in mass productivity.

The slit 13 and the slit 14 are also formed at the same time as the antenna element 9, but if the slit lengths L2 and L4 are adjusted from the center of gravity side toward the outer edge with solder or the like, the slit length is increased. The adjustment of L2 and L4 can be performed. Furthermore, since the wavelength is shortened by the dielectric constant of the base material 7, the planar inverted F-type antenna can be downsized.

Next, FIG. 6 shows an example of the antenna characteristics of the flat inverted F-type antennas according to the first to third embodiments of the present invention. The ground plate has a diameter of about 140 mm and a triangular shape. Shaped plate antenna with one side length of about 81 mm
On the other hand, the diameter of the ground plate is about 1.75 times. In this case, V.S. at the center frequency of 1905 MHz of PHS (Personal Handyphone System). S. W. R is the same figure (a)
Is about 1.54, and the directional characteristic is a balanced directional characteristic as shown in FIG. However, although the beam width is slightly narrow, the antenna has a high absolute gain of about 2.56 dB. However, in this case, the relative permittivity of the base material 7 is set to 1, and when the relative permittivity of the base material 7 is set to a relative permittivity exceeding 1 and the wavelength is shortened, the wavelength shortening rate It is necessary to determine the size of the ground plate and the length of one side of the plate-shaped antenna element according to the above.

Although the ground plate shown in each of the above-described embodiments has a triangular shape, the present invention is not limited to this and may have a polygonal shape. Further, by making the shape of the triangular antenna to be a triangle other than the equilateral triangle, the radiation pattern may be changed so that a communication antenna other than the PHS may be used.

[0028]

Since the planar inverted-F antenna of the present invention is constructed as described above, the resonance frequency and the resonance frequency can be changed by changing the width and length of the slit formed at the apex of the triangular plate-shaped antenna element. The feed point impedance can be adjusted. Further, the feed point impedance can be adjusted by adjusting the width and length of the slit that passes through the back surface position of the apex of the triangular plate-shaped antenna element formed on the ground plate. Therefore, in a planar inverted-F antenna formed by etching conductor foils attached to both sides of a base material such as a printed circuit board, the resonance frequency and the impedance are different due to variations in the dielectric constant and thickness of the base material of the printed circuit board. Even if a disturbance occurs in the above, the disturbance can be adjusted.

[Brief description of the drawings]

FIG. 1 is a top view of a flat inverted F-type antenna according to a first embodiment of the present invention and an enlarged view showing the configuration of its antenna element.

FIG. 2 is a side view of the planar inverted F type antenna according to the first embodiment of the present invention.

FIG. 3 is a back view of a flat inverted F-type antenna according to a second embodiment of the present invention.

FIG. 4 is an impedance characteristic showing that the feeding point impedance can be adjusted in the planar inverted F type antenna according to the first embodiment of the present invention.

FIG. 5 is an impedance characteristic showing that the feeding point impedance can be adjusted in the planar inverted F type antenna according to the second embodiment of the present invention.

FIG. 6 shows a planer inverted F-type antenna according to each embodiment of the present invention.
V. S. W. It is a figure which shows an example of R characteristic and E surface directional characteristic.

FIG. 7 is a diagram showing a conventional square inverted F antenna.

FIG. 8 is a diagram showing E-plane directional characteristics of a conventional inverted F-type antenna.

FIG. 9 is a diagram showing a conventional circular inverted F-type antenna.

[Explanation of symbols]

 7 Base Material 8 Ground Plate 9 Antenna Element 10 Short Hole 11 Feed Line 12 Through Hole 13 Slit 14 Slit

Claims (3)

[Claims] 1. A triangular plate-shaped antenna element formed on a front surface of an insulating base material, a ground plate formed on a rear surface of the insulating base material, and a triangular plate-shaped antenna element An outer edge, a short hole connecting the ground plate, and a through hole for feeding at substantially the center of gravity of the triangular plate-shaped antenna element are provided, and from each vertex of the triangular plate-shaped antenna element, A planar inverted F-type antenna characterized in that a slit is formed toward the position of the center of gravity. 2. A triangular plate-shaped antenna element formed on a front surface of an insulating base material, a ground plate formed on a back surface of the insulating base material, and a triangular plate-shaped antenna element. An outer edge, a short hole that connects the ground plate, and a through hole for feeding at substantially the center of gravity of the triangular plate antenna element are provided, and the back surface positions of the vertices of the triangular plate antenna element are provided. A planar inverted F-shaped antenna, characterized in that a slit is formed from the outer edge of the ground plate toward the back surface position of the center of gravity. 3. A triangular plate-shaped antenna element formed on a front surface of an insulating base material, a ground plate formed on a back surface of the insulating base material, and a triangular plate-shaped antenna element. An outer edge, a short hole connecting the ground plate, and a through hole for feeding at substantially the center of gravity of the triangular plate-shaped antenna element are provided, and from each vertex of the triangular plate-shaped antenna element, A first slit directed to the position of the center of gravity and a second slit passing through the back surface positions of the vertices of the triangular plate antenna element and extending from the outer edge of the ground plate to the back surface position of the center of gravity are formed. A characteristic planar inverted F-type antenna.