JP3173711B2 - Transmission line type antenna and wireless 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 antenna and a wireless terminal, and more particularly, to an improvement of a small transmission line antenna suitable for a small and portable wireless terminal, and a wireless terminal using the antenna. About. In Japan, such wireless terminals are 900 MHz band and 1.5 MHz
Car phone or mobile phone using obi, or 1.9
There are PHS terminals and the like that use the GHz band. Moreover,
GSM using 900MHz band in European specification
Terminal.

[0002]

2. Description of the Related Art Conventionally, a transmission line type antenna having an inverted U-shape and a short-circuited transmission line end is known as an antenna wire having a planar structure for a wireless terminal. FIG. 8 shows a schematic configuration of the antenna wire 2. The antenna line 2 is composed of a vertical portion (both lengths H) on both ends and a horizontal portion (length L) between them, and one end is formed on 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 supply unit 3. Further, the antenna line 2 has an effective length (hereinafter referred to as an electric length) that determines an electric resonance frequency as an antenna.
Is set to be equal to a half wavelength of a radiated radio wave such as a desired carrier wave (= L + 2 × H).

In the transmission line antenna having such a configuration, the vertical portion (H) radiates vertically polarized waves, while the horizontal portion (L) has a capacity for impedance matching with the feed unit 3.
In this case, since the terminal is short-circuited, a large amount of current contributing to radiation flows in both terminal side portions (see the sine waveform i in FIG. 9), radiation is effectively performed, and the electrical length is half the wavelength. In (H), the amplitude and phase of the current are equalized, and the total radiation amount is doubled.

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

On the other hand, there is known an antenna wire in which a horizontal portion is bent in a U-shape in a horizontal plane of height H in order to reduce the maximum length of the antenna. FIG. 10 shows a schematic configuration thereof. The antenna line 2 has a total length C (= L0 + 2 ×
The lengths of (L1 + 2 × H) and the horizontal portion (L0 + 2 × L1) are 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 reduced (from L to L0), and the size is reduced 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. For this reason, the conventional transmission line type antenna as described above cannot withstand application to a wireless terminal. Therefore, it is necessary to further reduce the size of the antenna.

For this purpose, for example, the above-described bending of the horizontal portion is further repeated to reduce the maximum length (L0 → L
2) It is also possible (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. For this reason, it is difficult to put it to practical use.

Therefore, it is conceivable to push the folded antenna into a single plane to form a planar structure (see FIG. 7). However, if the plane is simply planarized, the radiation from the vertical portions on both ends is canceled by the radiation from the bent portion, so that the total radiation amount is reduced by almost half. In addition, since the capacitance between the bent portion and the conductor ground plane varies greatly for each individual, it is difficult to adjust this capacitance value to a constant appropriate value. It will be lost. Such an antenna is defective because the radiation efficiency is further deteriorated.
This is not practical.

The present invention has been made to solve such a problem, and an object of the present invention is to realize a transmission line antenna which is small, thin, and reliable in impedance matching. Another object of the present invention is to provide a wireless terminal having such a transmission line type antenna, which is smaller, thinner and more sensitive.

[0010]

Means for Solving the Problems Structures and operational effects of the first and second solving means invented to solve such problems will be described below.

According to a first aspect of the present invention, there is provided a transmission line type antenna (as described in claim 1 at the beginning of the application) in which an antenna wire having one end connected to a feeder and the other end connected to a conductive ground plane is provided. In the transmission line type antenna having the antenna line, the both ends are formed so as to be separated from the conductive ground plane while bending in a single plane, respectively, and the central part has a predetermined length. It is characterized in that it is formed so as to have a predetermined capacity by being brought close to the conductor ground plane within a predetermined distance within the plane.

Here, the term “aligned” means that they do not go in opposite directions with the conductor ground plane interposed therebetween, and it is desirable but not essential that they be parallel. The “predetermined capacity” is a capacity required for impedance matching, and the “predetermined length” and the “predetermined distance” are a length and a distance determined corresponding to the capacity.

In the transmission line type antenna according to the first solution, since the bent portions are formed at both ends of the antenna wire, a sufficient miniaturization is achieved.

Further, since the bent portion and the central portion of the antenna wire are both formed in the same plane, the connecting portion between the bent portion and the central portion is also formed in the same plane. The antenna line is formed generally in a single plane. Thereby, sufficient thickness reduction is achieved.

Further, since the central portion is formed close to the conductive 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 is possible to do. As a result, impedance matching can be ensured, and feed energy for radiation can be efficiently received.

[0016] When the power is supplied to one end, the two bent portions formed so as to be separated from the conductor ground plane are aligned.
In particular, large in-phase currents flow near both ends. on the other hand,
Only a small current flows in the remaining central part and connection part. Thus, while a large radiation is emitted from both bent portions, it is only slightly emitted from the connecting portion. As a result, the large radiation from both bent portions is hardly canceled out by the radiation from the connecting portion of the opposite phase,
A large total radiation is ensured.

Therefore, according to the present invention, it is possible to realize a transmission line antenna which is small, thin, and has a reliable impedance matching.

[Second Solution] A wireless terminal according to a second solution (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 side. A wireless terminal that performs communication with the terminal, wherein the unit is attached to the terminal body so as to be movable between a storage position and a communication position, and the antenna formation surface is hidden at the storage position, and the communication is performed. In the position, the antenna forming surface is exposed to the outside.

In the wireless terminal according to the second solution, the small and thin transmission line antenna plate-shaped unit is employed, so that the wireless terminal as a whole becomes smaller and thinner.

Further, the antenna unit is provided so as to be movable between a storage position and a communication position with respect to the terminal body. 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. Is moved to the communication position and then communication is performed. Then, after the communication ends, the antenna unit is returned to the storage position again.

As described above, since the antenna surface is hidden at the storage position, the antenna is protected in the same manner as the conventional interior patch antenna, so that the advantage of easy and easy carrying and transport can be maintained. I have. On the other hand, by making the antenna surface appear outside at the communication position, the reception sensitivity and the like are improved as compared with the conventional interior patch antenna. Moreover, even at the stowed position, at least the same reception sensitivity as that of the conventional interior patch antenna is secured, so that it is possible to appropriately receive a call or the like when carried.

Therefore, according to the present invention, a wireless terminal having a small and thin transmission line type antenna and having a small size and a high sensitivity can be realized. be able to.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment for implementing a transmission line antenna and a radio terminal of the present invention achieved by the first and second means will be described. [First Embodiment of Transmission Line Type Antenna] A specific configuration of a transmission line type antenna according to a preferred embodiment of the present invention will be described with reference to the drawings. 1A and 1B show the appearance of an antenna unit having a flat plate shape, wherein FIG. 1A is a front view and FIG. 1B is a side view.

In this antenna unit 20, an antenna wire 22 as a transmission line type antenna is formed in a pattern on one surface of a dielectric substrate 21, and the dielectric substrate 21 and the conductive ground plate 1 such as a copper plate are brought into contact with the end surface. In this state, they are connected by an adhesive or the like. As a result, the unit is entirely formed in a flat plate shape.

One end of the antenna wire 22 is connected to the conductive ground plane 1.
And the other end is indirectly connected to the conductor ground plane 1 with the power supply section 3 interposed between the power supply point 3a and the ground point 1b. In addition, the total length C is determined so that the electrical length matches the half wavelength of a radiated radio wave such as a desired carrier wave.

The antenna wire 22 has a height H at the grounding point 1a and the feeding point 3a.
The bent part 2 is symmetrically bent on the surface of 1
2a and 22b are formed, so that both ends are bent away in a single plane, and are separated from the conductor ground plane.

Further, the antenna wire 22 is
The portion between a and 22b is bent back into a substantially U-shape so that the adjacent portion 22c corresponding to the bottom is parallel to the end of the conductive base plate 1 at a distance r. Moreover, this distance r
Means that the capacity between the adjacent portion 22c and the conductive ground plane 1 is
And the equivalent impedance of the antenna line 22 are set to match. As a result, the antenna wire 22 has a predetermined capacity in which the central portion is brought close to the conductor ground plate by a predetermined length within a same plane to a predetermined distance.

By forming the antenna wires 22 in a pattern as described above, it is possible to mass-produce the small and thin antenna units 20 at low cost, and the variation in the distance r for each individual is small, and the capacity of the proximity portion 22c is small. Stabilizes to a predetermined value. Therefore, the transmission line antenna of the first embodiment can easily and surely perform impedance matching even in mass production.

The specific operation of the antenna unit 20 of this embodiment will be described. In addition, only the transmission time when the radiation amount or the impedance matching becomes a problem will be described, and the reception time will be omitted.

At the time of transmission, a high frequency having a frequency such that the electrical length of the antenna becomes a half wavelength is applied between the ground point 1b and the feed point 3a by the feed unit 3. When electric resonance occurs, the antenna line 22 is connected to the ground point 1a.
Are grounded, the bent portion 22a and the bent portion 2
A large in-phase current flows through 2b. On the other hand, the bent part 22
Only a very small current flows through the connection between the a and 22b and the proximity portion 22c.

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

[Second Embodiment of Transmission Line Antenna] Another embodiment of the transmission line antenna of the present invention will be described. FIG. 2 shows a front view of the second embodiment of this embodiment. The difference from the first embodiment is that the zigzag bent portions 22a and 22b in FIG. 1 are shown in FIG. That is, they are 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 are no sharp corners, it is easy to handle.

The antenna line pattern can be formed integrally on a printed circuit board by printed wiring, or can be formed alone by etching or punching a thin plate.

[Third Embodiment of Transmission Line Antenna] Another embodiment of the transmission line antenna of the present invention will be described. FIG. 3 shows an external view of the antenna wire of the third embodiment of this embodiment. The difference between this embodiment and the first embodiment is as follows.
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 is easily deformable if it is slightly formed, the position of the center portion is raised and lowered when mounting on the dielectric substrate or the like after adjustment. (By changing the distance r), the impedance matching capacity can be easily adjusted.

The wire of the antenna wire is generally drawn with 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 bending at the time of trial production, but may be performed by an automatic machine having a wire feeding mechanism or the like at the time of mass production. Further, it may be formed integrally with a synthetic resin to be a dielectric substrate.

[First Embodiment of Wireless Terminal] A mobile phone as a first embodiment of a wireless terminal according to the present invention will be described.
FIG. 4 is an external view thereof. This mobile phone 31 has a first
The mobile phone 31 having the antenna unit 20 of the embodiment
Is provided with a storage space in which the antenna unit 20 can slide.

When the antenna unit 20 is pushed into the main body through the opening of the storage space, the whole of the antenna unit 20 except for a part such as a claw engaging portion is substantially entirely contained in the main body.

When a hook is hooked on the hook engaging portion of the antenna unit 20 and the hook is pulled, at least the portion of the antenna line 22 of the antenna unit 20 is drawn out of the main body from the opening of the storage space.

Accordingly, the portable telephone 31 is provided so as to be movable between a storage position where the antenna unit 20 is pushed into the main body and a communication position where the antenna unit 20 is pulled out. The antenna forming surface of the antenna unit 20 is hidden at the communication position while the antenna forming surface of the antenna unit 20 is hidden.

Although illustration is omitted, a spring-loaded power receiving pin is provided at the feeding point (3a) of the antenna unit 20, and a corresponding position in the storage space of the mobile phone 31 extends over a sliding range. A power supply path having a slide groove is provided. Then, the power receiving pin moves in the slide groove as the antenna unit 20 slides. Thus, regardless of the position of the antenna unit 20 between the storage position, the communication position, and the position between them, the spring-loaded power receiving pin surely comes into contact with the power supply path. Secured. In addition, the sensitivity increases as the distance from the storage position to the communication position increases.

[Second Embodiment of Wireless Terminal] A mobile phone 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, and FIG.
0 is placed at the communication position, and (b) is the case placed at the storage position. This mobile phone 32 has the antenna unit 20 of the first embodiment, and is attached to the main body such that the antenna unit 20 rotates about 180 ° bidirectionally at the bent portion 33 at the end of the conductor ground plane and opens and closes like a lid. It was done. Although illustration is omitted, power supply from the main body to the antenna unit 20 is performed via a flexible cable. Further, a thin film is adhered to the antenna forming surface of the antenna unit 20 to protect this surface.

Thus, the portable telephone 32 is provided so as to be movable between a storage position when the antenna unit 20 is closed and a communication position when the antenna unit 20 is open with respect to the main body. The antenna formation surface is hidden, and the antenna formation surface of the antenna unit 20 appears outside at the communication position. Then, the sensitivity becomes better as compared with the conventional one as the state changes from the closed state to the opened state.

[0043]

As is apparent from the above description, the transmission line antenna according to the first solving means of the present invention is formed in a plane, bent at both ends, and has a center portion at the conductor ground plane. In close proximity. Thereby, there is an advantageous effect that it is possible to realize a transmission line antenna that is small, thin, and reliable in impedance matching.

Further, in the radio terminal according to the second solution of the present invention, such a transmission line type antenna is employed, and when the terminal is moved to the communication position, the antenna surface appears outside. Thereby, there is an advantageous effect that a small, thin, and highly sensitive wireless terminal can be realized.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating a transmission line antenna according to a second embodiment of the present invention.

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

FIG. 4 is a diagram showing a first embodiment of the 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 an antenna wire having a three-dimensional structure is further bent.

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

FIG. 8 is an antenna line having a conventional planar structure.

FIG. 9 is a current distribution.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conductive ground plane 1a Grounding point 1b Grounding point 2 Antenna wire 3 Feeding part 3a Feeding point 20 Antenna unit 21 Dielectric substrate 22 Antenna wire 22a Bent part 22b Bent part 22c Proximity part 31 Mobile phone 32 Mobile phone 33 Bend

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01Q 1/38 H01Q 1/24 H01Q 9/42 H04Q 7/32

Claims (2)

(57) [Claims] 1. A transmission line type antenna having an antenna line having one end connected to a power supply unit and the other end connected to a conductive ground plane, wherein said antenna line has a single plane at both ends. It is formed so as to be spaced apart from the conductor ground plane while being bent in the center, and a central part is brought close to the conductor ground plane by a predetermined length to a predetermined distance within the plane and has a predetermined capacity. A transmission line type antenna characterized by being formed as described above. 2. A wireless terminal for performing communication by using a transmission line type antenna according to claim 1 having a flat unit formed on one side, wherein said unit is located at a storage position and a communication position with respect to the terminal body. And a mobile terminal, wherein the antenna forming surface is hidden at the storage position, and the antenna forming surface appears outside at the communication position.