JPH10200327A - Inverted f antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain miniaturization of a terminal by effectively utilizing antenna occupied volume while suppressing a power feeding line loss small with a simple configuration by composing a power feeding means of a power feeding line formed on a dielectric substrate and a connecting part for connecting a radiation conductor and the power feeding line. SOLUTION: An inverted F antenna is composed of a radiation conductor 11 ground conductor 14, 1st short-circuitting part 15 and 2nd short-circuitting part 16 and power is supplied by a power feeding conductor 17 connected with a strip line 19 on a dielectric substrate 12. By arranging the power feeding conductor 17 and the 1st short-circuitting part 15 separately for a prescribed distance, matching the characteristic impedance of strip line 19 is enabled. Since the strip line 19 is directly connected to an RF circuit part 110 constituted on the same dielectric substrate 12, it is not necessary to lay the power feeding line around with a coaxial cable or the like, power feeding configuration is simplified, the loss is suppressed small as well and high-efficiency characteristics can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a built-in inverted-F antenna used for a portable radio such as a portable radio telephone.

[0002]

2. Description of the Related Art In recent years, mobile communication such as a portable radio telephone has been in the limelight, and accordingly, further miniaturization of a portable terminal has been demanded. On the other hand, with the spread of such mobile terminals, the need to expand the communication frequency band in order to expand the communication capacity, and the demand for the integration of various mobile communication systems, etc., have led to a wider bandwidth characteristic. There is a need for an antenna having As a built-in antenna used in these portable terminals, an inverted F antenna is generally well known.

FIG. 5 shows an example of a conventional inverted F antenna. FIG. 5 is an example of a generally used plate-shaped inverted-F antenna, in which a rectangular radiating conductor 51 made of a conductive metal such as a sheet metal is installed so as to face a ground plate 52, and One end is connected to the ground plate 52 by a short-circuit element 53 to form an antenna. Power is supplied from the back of the ground plate by a coaxial cable 54, and the core wire of the coaxial cable is connected to an appropriate position of the rectangular radiation conductor so that the characteristic impedance of the coaxial cable matches the impedance of the antenna.

[0004]

As one method for realizing miniaturization of a portable terminal, a substrate for mounting a high-frequency signal processing circuit (RF circuit) such as a transmission / reception circuit and a baseband signal processing circuit (base) such as a digital circuit are known. Band circuit) A method of separating the mounting substrate from each other and forming a two-substrate configuration in which the two circuit substrates are installed in parallel with a space therebetween can be considered.

Normally, a terminal operation key, a button, a microphone, and the like are arranged on the baseband circuit board side. Therefore, of the two circuit boards, the RF circuit board is more distant from the human head during a call. Configuration.

In the case where an inverted F antenna as in the conventional example is used as the built-in antenna of the terminal, the built-in antenna has the following characteristics.
It is preferable that the radiation conductor be located away from the human head, that is, the radiation conductor be disposed on the RF circuit board side.

[0007] When a conventional inverted-F antenna is used as a built-in antenna of a portable terminal having the two-substrate configuration, the antenna is mounted on an RF circuit board,
There are two methods, a first configuration method in which the circuit board is used as a ground plane, and a second configuration method in which the antenna is installed on a baseband board and the baseband circuit board is used as a ground plane.

In the case of the first method of installing the inverted F antenna on the RF circuit board, the radiation conductor has a shape protruding in a direction opposite to the baseband substrate. Is added to the distance between the RF circuit board and the baseband circuit board, so that the thickness of the terminal increases, which is a major problem in reducing the size of the terminal. There is also a method of effectively using the space by mounting a high-frequency component such as a filter in the space between the radiation conductor and the RF circuit board.However, the wider the antenna, the larger the distance between the radiation conductor and the ground plane. On the other hand, various high-frequency components are rapidly becoming smaller and shorter, so even if the high-frequency components are mounted on a board, the low-profile components cannot fill the space. Since a dead space is generated, it is difficult to effectively use the space to reduce the size of the terminal.

In the case of the second method of installing the inverted F antenna on the baseband substrate, the radiation conductor is installed on the RF circuit substrate side. And the distance between the radiation conductor and the baseband substrate, whichever is greater. Thereby, the thickness of the terminal can be reduced as compared with the first method. However, since the baseband substrate is used as the ground plane of the inverted F antenna, the power is supplied to the ground plane, that is, on the baseband substrate or the baseband. It must be performed from the bottom of the substrate. However, since the RF signal from the antenna feed line needs to be guided to the transmission / reception circuit mounted on the RF circuit board, a coaxial line such as a semi-rigid cable is routed from the antenna feed point on the baseband board to the RF signal on the RF circuit board. It is necessary to connect to the transmission / reception circuit, which complicates the configuration and causes a problem that the loss due to the feeding line is increased.

[0010] The present invention has been made in view of such a problem, and has two aspects of an RF circuit board and a baseband circuit board.
It is an object of the present invention to provide an inverted-F antenna suitable for miniaturization of a mobile terminal having a simple structure, by effectively utilizing the occupied volume of the antenna with a simple configuration while suppressing a feed line loss to be small. .

[0011]

According to the first aspect of the present invention, there is provided an inverted-F antenna, comprising: a radiation conductor; a ground conductor disposed so as to face the radiation conductor at an interval; and a radiation conductor and the ground conductor. And a short circuit means for connecting the radiation conductor and the ground conductor, and a power supply means for supplying power to the radiation conductor. And a feed line formed on the dielectric substrate, and a connecting portion connecting the radiation conductor and the feed line.

An inverted-F antenna according to a second aspect of the present invention is the inverted-F antenna, wherein the short-circuiting means connects the radiation conductor to a ground plane formed on the dielectric substrate; And a second short-circuit portion connecting to the ground conductor.

According to a third aspect of the present invention, in the inverted-F antenna, the feeding means is performed through capacitive coupling between conductor patterns formed on both surfaces of the dielectric substrate. The conductor pattern formed on one surface is connected to the power supply line, and the conductor pattern formed on the other surface of the dielectric substrate is connected to the radiation conductor.

According to a fourth aspect of the present invention, in the inverted-F antenna, the first short-circuit portion has a conductor line pattern formed on the dielectric substrate, and the conductor line pattern is a plurality of zigzags that are folded back. A shape pattern, one end of which is connected to the ground plane of the dielectric substrate, and the other end of which is directly or indirectly connected to the radiation conductor.

In the inverted F antenna according to the first aspect, a resonator is constituted by the radiation conductor, the short-circuit means, and the ground conductor. A dielectric substrate is arranged between a radiation conductor and a ground conductor, and the radiation conductor is fed at an appropriate position from a feeder line formed on the dielectric substrate. RF circuit components can be mounted on the radiating conductor and the space between the radiation conductor and the ground conductor can be effectively used even with a low-profile circuit component. In addition, since the power supply line and the RF circuit such as the transmission / reception circuit can be formed on the same dielectric substrate, it is not necessary to route the power supply line such as a coaxial line, so that the antenna power supply configuration can be simplified and the power supply line loss can be reduced. Can be

The inverted F antenna according to the second aspect is the first aspect of the invention.
In the inverted-F antenna according to the above, since the short-circuit means is configured to be divided by the first short-circuit part and the second short-circuit part, the first short-circuit part and the second short-circuit part are respectively different members. , And shape, and the degree of freedom in antenna design is increased. The first and second short-circuit portions are individually configured using a metal member such as a shield case or a part of a housing of the RF circuit portion or the baseband circuit portion, so that space is more effectively used. be able to.

The inverted F antenna according to the third aspect is the first aspect of the invention.
Alternatively, in the inverted F antenna according to claim 2, the power supply position on the radiation conductor is increased from the short-circuit portion by feeding the radiation conductor by capacitive coupling between the conductor patterns formed on both surfaces of the dielectric substrate. Release, opposite end of the short,
That is, power can be supplied from the open end. An inverted-F antenna is formed by bending both ends of a single metal member to form a radiating conductor, installing the radiating conductor on a dielectric substrate, and connecting one of the bent portions to a short-circuit portion and the other to a feed portion. , The antenna configuration can be simplified, and stable antenna characteristics with small variations can be realized.

In the inverted-F antenna according to the fourth aspect, since the short-circuit line formed on the dielectric substrate is formed in a zigzag shape, the electrical length from the open end to the short-circuit portion to the ground conductor is increased. And the reverse F
The antenna can be reduced in size.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of the inverted F antenna according to the first embodiment of the present invention. 1 includes a radiation conductor 11, dielectric substrates 12, 13, a ground conductor 14, a first short-circuit portion 15, and a second short-circuit portion 16.
, Power supply conductor 17, ground pattern 18, strip line 19, RF circuit section 110, RF circuit component 11
1, 112, a baseband circuit unit 113, and a baseband circuit component 114.

The ground conductor 14 is formed by a copper foil pattern on the back surface of the dielectric substrate 13 and is arranged to face the radiation conductor 11 with a space therebetween. The dielectric substrate 12 is disposed substantially parallel between the radiation conductor 11 and the ground conductor 14, and a strip line 19 is formed on the front surface and a ground pattern 18 is formed on the back surface by etching or the like. Radiation conductor 11, ground conductor 14, first short-circuit portion 15
And the second short-circuit portion 16 constitute an inverted-F antenna, which is fed by the feed conductor 17 connected to the strip line 19 on the dielectric substrate 12.

The radiation conductor 11, the first short-circuit portion 15, and the power supply conductor 17 are integrally formed of the same conductive metal member such as a sheet metal. The first short-circuit part 15 is connected to the ground pattern 18, and the ground pattern 18 is connected to the ground conductor 14 via the second short-circuit part 16,
The radiation conductor 11 includes the first short-circuit portion 15 and the ground pattern 1.
8, short-circuited to the ground conductor via the second short-circuit portion 16.

By arranging the power supply conductor 17 and the first short-circuit portion 15 at a predetermined distance, matching with the characteristic impedance of the strip line 19 can be achieved. Since the strip line 19 is directly connected to the RF circuit unit 110 configured by a band-pass filter, a high-output amplifier, a mixer, and the like on the same dielectric substrate 12, it is not necessary to route a power supply line by a coaxial cable or the like. In addition, the loss can be suppressed to a small value with a simple power supply configuration, and high efficiency characteristics can be realized.

Further, low-frequency RF circuit components 111 such as a filter, a coil, a capacitor, and a transistor are mounted on both the front and rear surfaces of the dielectric substrate 12 and disposed between the radiation conductor 11 and the ground conductor 14. be able to.

The baseband circuit section 113 formed on the dielectric substrate 13 is composed of a digital circuit or the like for performing various kinds of signal processing. It can be arranged below the radiation conductor 11.

As described above, since components can be mounted in multiple stages in the space between the ground conductor 14 and the radiation conductor 11 of the inverted-F antenna, even if a small circuit component with a reduced height is used, The space in the F antenna can be effectively used, and the dead space in the portable terminal can be reduced, and the terminal can be downsized.

Further, since the power supply line and the transmission / reception circuit can be formed on the same circuit board, no wiring such as a coaxial line is required, the configuration can be simplified, and the power supply line loss can be suppressed to a low level. Efficiency characteristics can be obtained.

In the present embodiment, the ground conductor 14
Is formed of a copper foil ground pattern formed on the back surface of the dielectric substrate 13 on which the baseband circuit section 113 and the like are mounted, but may be a conductive metal member such as a sheet metal. Further, the second short-circuit portion may be a shield case (not shown) of the RF circuit portion 110 formed on the dielectric substrate 12 or the baseband circuit portion 11 formed on the dielectric substrate 13.
The shield case (not shown) of the third embodiment may be used.

The radiating conductor 11 includes a dielectric substrate 12,
13 may be formed of a dielectric substrate different from that of the terminal substrate, or may be formed of a conductor plated on the terminal housing. The dielectric substrates 12 and 13 may be a multilayer substrate having three or more layers, and the ground pattern, the ground conductor 14 and the strip line 19 may be formed by using the inner layers. As the feed line, other means such as a coplanar line may be used instead of the strip line 19.

FIG. 2 is a perspective view of a second embodiment of the inverted-F antenna according to the present invention, which uses a capacitive coupling power feeding system. 2 that are the same as those in FIG. 1 are given the same numbers. The inverted F antenna shown in FIG. 2 includes a radiation conductor 11, a short circuit board 21, a power supply board 22, and dielectric substrates 12 and 13. The short-circuiting substrate 21 is formed of a dielectric substrate, on one or both sides of which a short-circuiting conductor pattern 25 is formed by etching or the like, and has one or a plurality of convex substrate connecting portions 28 at the lower end.

The power supply substrate 24 is composed of a dielectric substrate, and has power supply conductor patterns 26 and 27 formed on both surfaces thereof, and one or a plurality of convex substrate connection portions 29 at the lower end. The power supply pattern 26 on one surface is formed near the upper end of the power supply substrate 24, the power supply pattern 27 on the other surface has a certain area overlapping the power supply pattern 26 on the back surface, and the other end side is the substrate connection portion. It is formed to extend to 29.

The radiation conductor 11 has a bent portion 23 at one end.
Has another bent portion 24 at the other end, and the bent portion 23
Denotes a conductor pattern 25 for short-circuit formed on the substrate 21 for short-circuit
The bent portion 24 is connected to a power supply conductor pattern 26 formed on the power supply substrate 22 by soldering or the like.

The dielectric substrate 12 has a ground pattern 18 formed on the back surface and a strip line 19 formed on the front surface by etching or the like, and has a mounting hole 210 at one end and a mounting hole 211 at the other end.

Short-circuit board 21 connected to radiation conductor 11
Substrate connecting portion 28 of the power supply substrate 24
9 are mounting holes 2 provided in the dielectric substrate 12 respectively.
The short circuit pattern 25 is connected to the ground pattern 18, and the power supply pattern 27 is connected to the strip line 19.

With the above configuration, the first short-circuit portion is formed by the short-circuit pattern 25 and the ground pattern 18, and the radiation conductor 11 is connected to the ground conductor 14 via the second short-circuit portion 16.

In the power feeding system, the radiation conductor 11 is fed from the strip line 19 via the capacitance between the power feeding patterns 26 and 27.

In the first embodiment, since the feeding point and the short-circuiting portion cannot be separated too much due to the necessity of matching with the feeding line, only one end of the radiation conductor 11 is provided on the dielectric substrate. However, in this embodiment, the feeding point on the radiation conductor 11 can be largely separated from the short-circuit portion by using the capacitive coupling feeding.

As a result, the short-circuit board 21 and the power supply board 22 can be provided at both ends of the radiating conductor 11, respectively, so that the radiating conductor 11 is firmly supported by the two boards 21 and 22. Since it is easy to keep the distance between the ground conductors 14 constant, it is possible to obtain stable characteristics in which variations in antenna characteristics are suppressed.

The power supply conductor patterns 26 and 27 have their respective pattern areas and the power supply substrate 2 so as to obtain good matching with the characteristic impedance of the strip line 19.
2 can be adjusted.

Although not shown in FIG. 2 for easy understanding of the configuration of the inverted-F antenna unit, various types of RF are provided on one or both sides of the dielectric substrate 12 as in the first embodiment.
The circuit components can be mounted on the dielectric substrate 13 by mounting the baseband circuit components, whereby the space can be efficiently used and the terminal can be miniaturized.

FIG. 3 is a perspective view of an inverted-F antenna according to a third embodiment of the present invention. In FIG. 3, components common to those in FIGS. 1 and 2 are denoted by the same reference numerals. Reverse F of FIG.
The antenna has a radiating conductor 11 whose both ends are bent at substantially right angles to form a U-shape, and dielectric substrates 12 and 13.

The radiating conductor 11 has both ends bent at substantially right angles, and has a plurality of convex protrusions 31 and 32 at one end of a bent portion thereof, and a plurality of projections 31 and 32 at the other bent end. The projections 36 and 37 have a convex shape. The dielectric substrate 12 has a strip line 19 formed on the surface by etching or the like and a power supply pattern 33 connected to the tip thereof, and a ground pattern 18 and a power supply pattern 33 similarly formed on the back surface. The power supply pattern 34 is provided so as to overlap a certain area.

The power supply pattern 34 is connected to at least one of a plurality of mounting holes 211 provided at one end of the dielectric substrate 12, and the ground pattern 1 on the back surface.
8 is connected to at least one of the plurality of mounting holes 210 provided at the other end.

The projections 31 and 32 on one side of the radiation conductor 11 are fitted into mounting holes 211 of the dielectric substrate 12, respectively.
One protruding portion 31 is connected to the power supply pattern 34 via the mounting hole 211.

The projections 36 and 37 of the other bent portion of the radiation conductor 11 are fitted into the mounting holes 210, respectively, and are connected to the ground pattern 18 via the mounting holes 210.

With the above configuration, the radiation conductor 11 is connected to the ground conductor 14 via the projections 36 and 37, the ground pattern 18, and the second short-circuit portion 16, and the other end of the radiation conductor 11 is an open end. Thus, an inverted F antenna is configured. Power is supplied to the radiation conductor 11 from the strip line 19 through the power supply patterns 33 and 34 on both surfaces of the dielectric substrate 12.
This is done via the capacitance between them.

As in the second embodiment, by appropriately adjusting the overlapping of the power supply conductor patterns 33 and 34 via the dielectric, the pattern area, and the thickness of the dielectric substrate, the strip line 19 can be formed. Good matching with the characteristic impedance can be achieved.

In the present embodiment, the dielectric substrate 11
Since a capacitive coupling pattern is formed thereon, and the radiation conductor 11 can be bent into a U-shape and fixed to the dielectric substrate 12,
The same effects as those of the first and second embodiments can be obtained while further simplifying the configuration.

In this embodiment, the radiating conductor 11 has a U-shape bent at a substantially right angle. However, the radiating conductor 11 may be bent at an angle other than a right angle, and may have a semicircular shape. It may be configured in a curved shape.

FIG. 4 is a perspective view of a fourth embodiment of the inverted-F antenna according to the present invention. In FIG. 4, the same reference numerals are given to components common to FIGS. 1, 2, and 3. FIG.
In the third embodiment, the ground pattern 18 formed on the dielectric substrate 12 and the plurality of mounting holes 210
Line 41 for connecting to any one of
, And the short-circuit line 41 has a zigzag shape folded a plurality of times.

With the above-described configuration, the projection 37 provided on the bent portion of the radiation conductor 11, the mounting hole 210 on the dielectric substrate 12, and the first connection to the ground pattern 18 via the short-circuit line 41. Since the electrical length of the short-circuit portion becomes longer, the size of the inverted F antenna can be easily reduced.

Also, since the resonance frequency of the inverted antenna is usually determined by the size of the radiating conductor or the distance between the radiating conductor and the ground conductor, it is difficult to adjust the frequency when the antenna is built in the housing of the portable terminal. It is possible that the size and shape of the housing must be changed.

According to the present embodiment as described above,
Since the short-circuit line 41 is formed on the dielectric substrate 12 by etching or the like, fine frequency adjustment can be performed by fine-tuning the line pattern, and can be easily performed without changing the external shape of the inverted-F antenna at all. It is possible to perform frequency adjustment that matches the terminal housing.

This embodiment can also be applied to a structure using the power supply board 24 and the short-circuit board 21 as shown in the second embodiment.

[0054]

In the inverted F antenna according to the first and second aspects, the space inside the antenna is effectively used without complicating the antenna configuration and maintaining high efficiency characteristics with small feed line loss. Therefore, miniaturization of the portable terminal can be realized.

In the inverted F antenna according to the third aspect,
In addition to the above effects, simplification of the antenna configuration can be realized, and stable antenna characteristics with small variations can be realized.

In the inverted F antenna according to the fourth aspect,
In addition to the above effects, it is possible to further reduce the size of the antenna,
Further, the adjustment of the resonance frequency can be easily performed.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of an inverted-F antenna according to the present invention.

FIG. 2 is a perspective view showing a second embodiment of the inverted-F antenna of the present invention.

FIG. 3 is a perspective view showing a third embodiment of the inverted-F antenna of the present invention.

FIG. 4 is a perspective view showing a fourth embodiment of the inverted-F antenna of the present invention.

FIG. 5 is a perspective view of a conventional inverted F antenna.

DESCRIPTION OF SYMBOLS 11 Radiation conductor 12 Dielectric substrate 13 Dielectric substrate 14 Ground conductor 15 First short-circuit part 16 Second short-circuit part 17 Feeding conductor 18 Ground pattern 19 Strip line 110 RF circuit part 111 RF circuit part 112 RF Circuit parts 113 Baseband circuit part 114 Baseband circuit parts

Claims (4)

[Claims] A radiating conductor, a grounding conductor facing the radiating conductor at a distance from the radiating conductor, a dielectric substrate disposed substantially in parallel between the radiating conductor and the grounding conductor, In an inverted-F antenna having a short-circuiting means for connecting a radiation conductor to the ground conductor and a feeding means for feeding the radiation conductor, the feeding means comprises: a feeding line formed on the dielectric substrate; An inverted-F antenna comprising a conductor and a connecting portion for connecting the feeder line. 2. The short-circuit means includes: a first short-circuit portion connecting the radiation conductor to a ground plane formed on the dielectric substrate; and a second short-circuit section connecting the ground plane to the ground conductor. 2. The inverted-F antenna according to claim 1, wherein the inverted-F antenna comprises a short-circuit portion. 3. The power supply means is performed via capacitive coupling between conductor patterns formed on both surfaces of the dielectric substrate, respectively, and the power supply means is provided on one surface of the dielectric substrate. The inverted-F antenna according to claim 1 or 2, wherein the inverted F antenna is connected to the feed line, and the conductor pattern formed on the other surface is connected to the radiation conductor. 4. The first short-circuit portion includes a conductor line pattern formed on the dielectric substrate, wherein the conductor line pattern is a zigzag pattern that is bent a plurality of times, and one end of the conductor line pattern is the dielectric line pattern. 3. The inverted-F antenna according to claim 2, wherein the antenna is connected to a ground plane of the body substrate, and the other end is directly or indirectly connected to the radiation conductor.