JPH0969718A - Transmission line type antenna and radio terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission line type antenna which has a compact and thin structure and can secure the sure impedance matching. SOLUTION: This antenna uses an antenna wire 22, and one of both ends of the wire 22 is connected to a feeding part 3 with the other end connected to a conductor bottom board 1 respectively. Both end parts 22a and 22b of the wire 22 are folded within a single plane and separated together from the board 1, and the center part 22c of the wire 22 comes close to the board 1 by a prescribed distance (r) within the same plane. Thus the wire 22 has the prescribed capacity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission line type antenna and a wireless terminal, and more particularly, to an improvement of a small transmission line type antenna suitable for a small and portable wireless terminal, and a wireless terminal using this antenna. Regarding As such a wireless terminal, in Japan, 900 MHz band and 1.5 MHz
Car phones and mobile phones using obi, or 1.9
There are PHS terminals and the like that use the GHz band. Furthermore,
GSM uses 900MHz band in European specifications
There are also terminals for use.

[0002]

2. Description of the Related Art Heretofore, a transmission line type antenna having an inverted U-shape and a transmission line terminal short-circuited has been known as a planar structure antenna line for a wireless terminal. The schematic configuration is shown in FIG. 8. The antenna wire 2 is composed of vertical portions (both of which are length H) on both ends and a horizontal portion (length L) between them, and one end of which is connected to the conductor ground plane 1. It is directly connected, and the other end is indirectly connected to the conductor ground plane 1 via the power feeding unit 3. Further, the antenna line 2 has an effective length (hereinafter, referred to as an electrical length) that determines an electrical resonance frequency of the antenna.
The total length C (= L + 2 × H) is determined so that γ coincides with a half wavelength of a radiated radio wave such as a desired carrier wave.

In the transmission line antenna having such a structure, the vertical portion (H) radiates vertically polarized waves, while the horizontal portion (L) has a capacitance for impedance matching with the power feeding portion 3.
In this case, since the termination is short-circuited, a large amount of current contributing to radiation flows in the portions on both terminal sides (see the sine waveform i in FIG. 9), radiation is effectively performed, and since the electrical length is half a wavelength, both vertical portions are At (H), the amplitude and phase of the current become equal and the total radiation dose is doubled.

As described above, the inverted U-shaped transmission line type antenna has an advantage that the radiation gain is larger than that of a general inverted L-shaped antenna. However, in the inverted U-shaped transmission line type antenna, the horizontal portion (L) needs to be made considerably longer than the vertical portion (H) in order to secure the required capacity, so that the antenna has a small space. There is also a drawback that it cannot fit inside.

On the other hand, there is also known an antenna wire in which a horizontal portion is bent in a U-shape in a horizontal plane having a height H in order to shorten the maximum length of the antenna. The schematic configuration is shown in FIG. 10. The antenna wire 2 has a total length C (= L0 + 2 ×).
The lengths of (L1 + 2 × H) and the horizontal portion (L0 + 2 × L1) are made the same as those described above, and the electrical length and the capacitance are maintained at appropriate values. Due to such bending of the horizontal portion, the maximum length is shortened (from L to L0), and the miniaturization is achieved accordingly.

[0006]

However, since mobile phones and the like tend to be smaller and thinner in recent years, restrictions on the antenna space are only increasing. Therefore, the conventional transmission line type antenna as described above cannot be applied to a wireless terminal. Therefore, it is necessary to further reduce the size of the antenna.

Therefore, for example, the above-mentioned horizontal portion is further bent to shorten the maximum length (L0 → L).
2) can be considered (see FIG. 6). However, in this case, even if a certain degree of miniaturization can be achieved, the thickness cannot be reduced because of the three-dimensional structure. Therefore, it is difficult to put it to practical use.

Therefore, it is possible to push the bent antenna into a single plane to form a planar structure (see FIG. 7). However, if the surface is simply flattened, the radiation from the vertical portions at both ends is canceled by the radiation from the bent portion, and the total radiation amount is halved. Not only that, but the capacitance between the bent portion and the conductor ground plate varies greatly from one individual to another, making it difficult to align this capacitance value to a certain appropriate value. It will also end up. Such an antenna is a defective product because the radiation efficiency is further deteriorated.
This is not practical.

The present invention has been made in order to solve such a problem, and an object thereof is to realize a transmission line type antenna which is small in size, thin, and has a reliable impedance matching. Another object of the present invention is to realize a wireless terminal which is equipped with such a transmission line type antenna and which is smaller and thinner and has good sensitivity.

[0010]

The constitutions and effects of the first and second solving means invented to solve the above problems will be described below.

The transmission line type antenna of the first solution (as described in claim 1 at the beginning of the application) has an antenna wire whose one end is a connecting end to the power feeding portion and the other end is connected to the conductor ground plane. In the transmission line type antenna having, the antenna wire is formed such that the portions on both end sides are bent in a single plane and are separated from the conductor ground plane evenly, and the central portion has a predetermined length. It is characterized in that it is formed so as to have a predetermined capacitance by being brought close to the conductor ground plane by a predetermined distance in the plane.

Here, the above "aligned" means that they do not go in opposite directions with the conductor ground plate in between, and it is desirable, but not essential, that they are parallel to each other. Further, the "predetermined capacity" is a capacity necessary for impedance matching, and the "predetermined length" and the "predetermined distance" are length and distance determined corresponding to the capacity.

In the transmission line type antenna of the first solving means as described above, since the bent portions are formed on both ends of the antenna wire, sufficient miniaturization is achieved.

Further, since both the bent portion and the central portion of the antenna wire are formed in the same plane, as a result, the connecting portion between the bent portion and the central portion is also formed in the same plane, at least. The entire antenna line is formed in a single plane. As a result, sufficient thinning is achieved.

Further, since the central portion is formed close to the conductor ground plane, the capacitance required for impedance matching can be easily and stably secured even if the predetermined length is shortened so as not to hinder miniaturization. It becomes possible to do. As a result, impedance matching can be ensured, and the feeding energy for radiation can be efficiently received.

Then, when electric power is supplied to one end, both bent portions formed so as to be separated from the conductor ground plane are
In particular, large in-phase currents flow near both ends. on the other hand,
Only a small current flows through the remaining central portion and the connecting portion. Therefore, a large amount of radiation is emitted from both bent portions, while a small amount is emitted from the connecting portion. As a result, the large radiation from both bent parts is almost never canceled out by the radiation from the connecting part in antiphase,
A large total radiation is secured.

Therefore, according to the present invention, it is possible to realize a transmission line type antenna which is small in size, thin, and sure in impedance matching.

[Second Solving Means] A wireless terminal of the second solving means (as described in claim 2 at the beginning of the application) is a flat plate unit in which the first transmission line type antenna is formed on one surface. A wireless terminal for performing communication by using the unit, wherein the unit is attached so as to be movable between a storage position and a communication position with respect to a terminal body, and the antenna formation surface is hidden at the storage position, and the communication is performed. It is characterized in that the antenna forming surface appears outside at a position.

In the wireless terminal of the second means as described above, by adopting the small flat plate-shaped unit of the transmission line type antenna, the wireless terminal as a whole becomes smaller and thinner.

An antenna unit is attached to the terminal body so as to be movable between a storage position and a communication position. Therefore, the user of the wireless terminal usually moves the antenna unit to the storage position and then carries the wireless terminal in a pocket or the like to take out the wireless terminal when carrying out communication such as a call using the antenna unit and the antenna unit. Move to the communication position and then communicate. Then, after the communication is completed, the antenna unit is returned to the storage position again.

As described above, the antenna surface is hidden at the storage position, so that the antenna is protected as in the conventional internal patch antenna. Therefore, the advantage that the user can easily carry and carry is maintained. There is. On the other hand, since the antenna surface is exposed to the outside at the communication position, the receiving sensitivity and the like are improved as compared with the conventional internal patch antenna. Moreover, even at the storage position, the receiving sensitivity and the like equivalent to those of the conventional internal patch antenna are ensured at a minimum, so that a call or the like when carried can be properly received.

Therefore, according to the present invention, it is possible to realize a wireless terminal which is smaller and thinner and has high sensitivity by including a small and thin transmission line type antenna. be able to.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION With respect to the transmission line type antenna and the wireless terminal of the present invention achieved by the first and second solving means described above, modes for carrying out this will be described. [First Embodiment of Transmission Line Type Antenna] The concrete configuration of the best thought example of the transmission line type antenna of the present invention will be described with reference to the drawings. 1A and 1B show the appearance of an antenna unit formed in a flat plate shape, FIG. 1A is a front view thereof, and FIG. 1B is a side view thereof.

In this antenna unit 20, an antenna wire 22 as a transmission line type antenna is patterned on one surface of a dielectric substrate 21, and the dielectric substrate 21 and a conductor ground plate 1 such as a copper plate are in contact with each other at their end faces. In this state, they are connected with an adhesive or the like. As a result, this unit has a flat plate shape as a whole.

One end of this antenna wire 22 is the conductor ground plane 1.
Is directly connected to the conductor ground plate 1 at the ground point 1a, and the other end is indirectly connected to the conductor ground plane 1 with the power supply unit 3 interposed between the power supply point 3a and the ground point 1b. Moreover, the total length C is determined so that the electric length thereof matches the half wavelength of the radiated radio wave such as the desired carrier wave.

The portion of the antenna wire 22 having the height H on the grounding point 1a side and the feeding point 3a side is the dielectric substrate 2.
The bent portion 2 is bent symmetrically on the surface of 1 in a zigzag manner.
2a and 22b are formed, whereby the portions on both end sides are bent in a single plane and are separated from the conductor ground plane.

Further, the antenna wire 22 has a bent portion 22.
A portion between a and 22b is bent back into a substantially U shape, and a proximal portion 22c which is a bottom portion thereof is formed to be parallel to the end portion of the conductor ground plate 1 at a distance r. Moreover, this distance r
Indicates that the capacitance between the adjacent portion 22c and the conductor ground plane 1 is equal to the power feeding portion 3
Is set so that the output impedance of the antenna and the equivalent impedance of the antenna line 22 match. As a result, the antenna wire 22 also has a predetermined capacitance in which the central portion is brought close to the conductor ground plane by a predetermined length in the same plane to a predetermined distance.

By patterning the antenna wire 22 in this way, a small and thin antenna unit 20 can be mass-produced at low cost, and the variation in the distance r between individual units is small and the capacity of the proximity section 22c is small. Stabilizes to a specified value. Therefore, the transmission line type antenna of the first embodiment can easily and reliably perform impedance matching even during mass production.

The specific operation of the antenna unit 20 of this embodiment will be described. It should be noted that the description will be given only at the time of transmission when there is a problem with the radiation amount or impedance matching, and omitted at the time of reception.

At the time of transmission, a high frequency having a frequency such that the electric length of the antenna becomes a half wavelength is applied between the grounding point 1b and the feeding point 3a by the power feeding section 3. When electrical resonance occurs, the antenna wire 22
Since the ground is grounded, the bent portions 22a and 2
A large in-phase current flows through 2b. On the other hand, the bent portion 22
Only a very small current flows in the connecting portion between a and 22b and the adjacent portion 22c.

Therefore, the radiated radiation from the bent portions 22a and 22b is substantially effective as it is, and a large total radiation amount can be obtained while being small and thin.

[Second Embodiment of Transmission Line Type Antenna] Another embodiment of the transmission line type antenna of the present invention will be described. FIG. 2 shows a front view of the second embodiment of this mode. The difference between this and the first embodiment is that the zigzag bent portions 22a and 22b in FIG. 1 are shown in FIG. It is a point that is formed in a meander line shape as described above. In this case as well, the basic operation and effect are the same, but since there is no sharp corner, it is easy to handle.

The pattern of the antenna wire can be formed integrally with the printed circuit board by the printed wiring, or can be formed independently by etching or punching a thin plate.

[Third Embodiment of Transmission Line Type Antenna] Another embodiment of the transmission line type antenna of the present invention will be described. Regarding the third embodiment of this mode, an external view of the antenna wire is shown in FIG. 3, but the difference between this and the first embodiment is that
The point is that the antenna wire 22 in FIG. 1 is formed of a wire as shown in FIG. In this case as well, the basic operation and effect are the same, but since the wire rod can easily be deformed after being formed, it is possible to raise or lower the position of the central part when mounting it on the dielectric substrate or adjusting it after mounting. (By changing the distance r), the impedance matching capacitance can be easily adjusted.

The wire for the antenna wire is generally a drawn wire having a circular cross section, but is not limited to this and may be a gold-plated wire or a clad material. The bending process is performed by hand during the trial manufacture, but may be performed by an automatic machine equipped with a wire feeding mechanism or the like during mass production. Alternatively, it may be integrally formed with a synthetic resin that becomes the dielectric substrate.

[First Embodiment of Radio Terminal] A mobile telephone as a first embodiment of the radio terminal of the present invention will be described.
FIG. 4 is an external view thereof. This mobile phone 31 is
The mobile phone 31 having the antenna unit 20 of the embodiment
The main body is provided with a slidable storage space for the antenna unit 20.

When the antenna unit 20 is pushed into the main body from the opening of the storage space, the antenna unit 20 is almost entirely accommodated in the main body except a part such as a claw engaging portion.

When the claw engaging portion of the antenna unit 20 is hooked and pulled, the antenna wire 22 of the antenna unit 20 is pulled out of the main body through the opening of the housing space.

As a result, the mobile phone 31 is attached so that the antenna unit 20 can be moved between the storage position when the antenna unit 20 is pushed in and the communication position when the antenna unit 20 is pulled out from the main body. The antenna forming surface of 20 is hidden, and the antenna forming surface of the antenna unit 20 is exposed outside at the communication position.

Although not shown, a spring-biased power receiving pin is provided at the feeding point (3a) of the antenna unit 20, and the corresponding position in the storage space of the mobile phone 31 extends over the sliding range. And a power feeding path in which a slide groove is formed is provided. Then, the power receiving pin moves in the slide groove as the antenna unit 20 slides. As a result, regardless of whether the antenna unit 20 is in the storage position, the communication position, or the position between these positions, the spring-biased power receiving pin surely contacts the power feeding path, so that the function of the antenna is always maintained. Reserved. Moreover, the sensitivity becomes higher as compared to the conventional case as the storage position is closer to the communication position.

[Second Embodiment of Wireless Terminal] A portable telephone as a second embodiment of the wireless terminal of the present invention will be described.
FIG. 5 is an external view of the antenna unit 2 and FIG.
0 is placed in the communication position, and (b) is placed in the storage position. This mobile phone 32 has the antenna unit 20 of the first embodiment and is attached to the main body so that the antenna unit 20 bidirectionally rotates about 180 ° at the bent portion 33 at the end of the conductor ground plate side and opens and closes like a lid. It has been done. Although illustration is omitted, power feeding from the main body to the antenna unit 20 is performed via a flexible cable. Further, a thin film is attached to the antenna forming surface of the antenna unit 20 to protect this surface.

As a result, the mobile phone 32 is attached so that the antenna unit 20 can be moved between the storage position when the antenna unit 20 is closed and the communication position when the antenna unit 20 is open. The antenna formation surface is hidden, and the antenna formation surface of the antenna unit 20 is exposed outside at the communication position. Then, the sensitivity becomes higher as compared with the conventional one as it goes from the closed state to the open state.

[0043]

As is apparent from the above description, in the transmission line type antenna of the first solution of the present invention, the transmission line type antenna is formed in a plane, both ends are bent, and the central part is a conductor ground plate. Close to. As a result, there is an advantageous effect that it is possible to realize a transmission line type antenna that is small in size, thin, and has a reliable impedance matching.

Further, in the wireless terminal of the second solving means of the present invention, such a transmission line type antenna is adopted, and when moving to the communication position, the antenna surface is exposed to the outside. As a result, there is an advantageous effect that it is possible to realize a wireless terminal that is small in size, thin, and has high sensitivity.

[Brief description of drawings]

FIG. 1A is a front view and FIG. 1B is a side view of a first embodiment of a transmission line antenna according to the present invention.

FIG. 2 is a diagram showing a second embodiment of the transmission line type antenna of the present invention.

FIG. 3 is a diagram showing a third embodiment of the transmission line type antenna of the present invention.

FIG. 4 is a diagram showing a first embodiment of a wireless terminal of the present invention.

FIG. 5 is a diagram showing a second embodiment of the wireless terminal of the present invention.

FIG. 6 is a diagram when the antenna wire having a three-dimensional structure is further bent.

FIG. 7 is a diagram when it is accommodated in a single plane.

FIG. 8 is a conventional planar structure antenna wire.

FIG. 9 is the current distribution.

FIG. 10 is a conventional antenna wire having a three-dimensional structure.

[Explanation of symbols]

 1 conductor ground plane 1a grounding point 1b grounding point 2 antenna line 3 feeding part 3a feeding point 20 antenna unit 21 dielectric substrate 22 antenna line 22a bent part 22b bent part 22c proximity part 31 mobile phone 32 mobile phone 33 bending part

Claims (2)

[Claims] 1. A transmission line type antenna having an antenna wire, one end of which is connected to a power feeding portion and the other end of which is connected to a conductor ground plane. It is formed so that it bends inward and separates from the conductor ground plane evenly, and the center portion is brought close to the conductor ground plane in the plane by a predetermined length to a predetermined distance and has a predetermined capacity. A transmission line type antenna characterized by being formed as described above. 2. A wireless terminal for communication, comprising a flat plate-shaped unit having the transmission line antenna according to claim 1 formed on one side thereof, wherein the unit has a storage position and a communication position with respect to the terminal body. And movably attached so that the antenna formation surface is hidden at the storage position, and the antenna formation surface appears outside at the communication position.