JPH07106999A - Portable radio - Google Patents

Abstract

(57) [Abstract] [Purpose] When the human body approaches or contacts the portable wireless device, it shall not affect the radiation characteristics of the antenna. [Structure] An elongated metal piece 9 for mounting the antenna element 1 is provided in a housing 4 in which an electronic circuit is mounted, and it effectively acts as a stub. That is, the housing 4
A conductor surface is formed on at least a part of the above, and the conductor surface and the metal piece 9 are set so as to form a parallel line. Then, one end of the metal piece 9 is short-circuited with the conductor surface of the housing 4 to form a short-circuit end, and the other end is an open end. The antenna element 1 is attached to this open end, the distance L between the open end and the short-circuited end of the metal piece 9 is effectively set to 1/4 of the usable wavelength, and the hot side of the feeding path 3 is set to the antenna element 1. The cold side to this piece of metal 9
Connect to. With this configuration, a complicated antenna current is not generated on the surface of the housing 4, and the influence of the human body of the person who holds the radio can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a cellular radio telephone,
It is used for cordless phones, portable call radios, and other portable wireless communication devices. The present invention relates to an antenna structure of a portable wireless device. The present invention relates to a technique for reducing the influence of wireless propagation characteristics from a human body holding a portable wireless device.

[0002]

2. Description of the Related Art An apparatus according to an embodiment has a structure in which an antenna element 1 is connected via a matching circuit 2 to an electronic circuit 6 mounted inside a housing 4 by a feeding path 3 as illustrated in FIG. At the end of the feeding path 3 on the antenna element 1 side, the hot side is connected to the antenna element 1 via the matching circuit 2 and the cold side is connected to the potential of the housing 4. Matching circuit 2
In order to improve the matching when the characteristic impedance of the electronic circuit 6 and the power feeding path 3 has a relatively low value (for example, 50Ω), the characteristic impedance of the antenna element 1 has a relatively high value. It is provided.

In such a structure, a large current is generated in the housing 4 except when the antenna element 1 is half the wavelength used. When the antenna element 1 is set to have a half of the used wavelength, a high frequency current distribution as illustrated in FIG. 9 is generated. That is, even if the antenna element 1 is set to a half wavelength, if a current distribution P ₁ is generated in the antenna element 1, a corresponding current distribution P ₄ is generated in the housing 4. Regarding the radiation characteristics of the antenna in this case, Tsunekawa et al. “Relationship between gain in small waves and housing length of small radio antenna” (IEICE Transactions B, Vol. J75BI)
I, No. 10, pages 705 to 707, published in October 1992).

[0004]

In the portable radio device having such a structure, the influence of the human body holding the case affects the radiation characteristics of the antenna. That is, since the current distribution P ₄ is generated in the housing 4 even when the matching is achieved as shown in FIG. 9, a so-called housing current flows on the surface of the housing 4. Therefore, when a human hand or other human body approaches or contacts the casing 4, a part of the casing current flows to the human body, and the form of the current distribution P ₄ fluctuates according to the movement of the human body, causing the antenna radiation. The characteristics will change according to the movement of the human body. If the matching of the antenna is poor, the housing current becomes more complicated and the human body affects it.
The radiation characteristic of the antenna changes according to the movement of the arm holding the wireless device or the part of the human body approaching the wireless device.

The present invention has been made against such a background, and it is an object of the present invention to provide a device in which the antenna radiation characteristics of a portable radio device are less affected by a human body approaching or contacting the portable radio device. With the goal.

[0006]

SUMMARY OF THE INVENTION The present invention is constructed so as to reduce the influence of the human body on the radio wave propagation characteristics of a portable wireless device when it is gripped, and an electronic circuit is mounted inside. A housing (4), an antenna element (1),
A portable wireless device comprising a power feeding path (3) for electrically connecting the electronic circuit and the antenna element. The present invention is characterized in that the casing (4) has a conductor surface on at least a part thereof, forms a parallel line with the conductor surface, and has one end short-circuited to the conductor surface and the other end. An elongated metal piece (9) serving as an open end is provided on the conductor surface, the antenna element (1) is attached to the open end of the metal piece (9), and the hot side of the feeding path (3) is the antenna. The cold sides of the elements are respectively connected to the metal pieces, and the distance L between the short-circuited end and the open end of the metal piece is L = ((1/4) + (1/2) m). λg (where λg is the wavelength in the parallel line corresponding to the resonance frequency of the antenna element, and m is 0 or a positive integer).

It is desirable that the longitudinal direction of the metal piece (9) and the antenna element (1) are arranged substantially linearly.

[0008]

In the device of the present invention (see FIG. 2), the parallel lines are effectively formed between the elongated metal piece (9) and the conductor surface of the housing (4). Moreover, the open end of the parallel line (A
The distance between the point) and the short-circuited end (point B) to the conductor surface of the housing (4) is effectively a quarter of the wavelength corresponding to the antenna resonance frequency (phase π, that is, a half as in the above equation). The length is repeated for each wavelength). That is,
The impedance Za at the wavelength when the side of the parallel line is viewed from the feeding point of the antenna element (1), which is the open end of the parallel line, is substantially infinite, and corresponds to the current distribution P ₁ in the antenna element (1). The current on the housing side is generated in the metal piece (9) like P ₄ , and the short-circuit point (B
At the point), the potential becomes zero. That is, this parallel line acts as a stub for the antenna, and the housing (4) is not affected by the current generated between the housing (4) and the antenna element (1). Therefore, when the human body approaches or contacts the housing (4) regardless of the human body contacting the metal piece (9), the human body is not directly affected by the housing current, The antenna radiation characteristics are not affected by the movement of the human body.

[0009]

Embodiments of the present invention will now be described with reference to the drawings.

(First Embodiment) FIG. 1 is a perspective view showing the configuration of the first embodiment of the present invention, and FIG. 2 is a diagram for explaining the operating principle of the first embodiment of the present invention.

In the first embodiment of the present invention, a housing 4 in which an electronic circuit 6 is mounted, an antenna element 1 mechanically attached to the housing 4, an electronic circuit 6 and the antenna element 1 are provided.
And a power feeding path 3 for electrically connecting the and. Further, as a feature of the present invention, the housing 4 has a conductor surface on at least a part thereof, and an elongated metal piece 9 forming a parallel line with the conductor surface is provided with a dielectric spacer 7 interposed therebetween. 9
The balanced line formed by and the conductor surface becomes an open end at point A,
At the point B, the short-circuit end is formed with respect to the conductor surface.
The hot side of the feeding path 3 is connected to the antenna element and the cold side is connected to the metal piece 9. This metal piece 9
The distance L between the open end and the shorted end of L is: L = ((1/4) + (1/2) m) .lambda.g (where .lambda.g is the parallel line in the parallel line corresponding to the resonance frequency of the antenna element). The wavelength and m are set to 0 or a positive integer.

The reason that m can be a positive integer other than 0 is that the wavelength becomes shorter as the used frequency becomes higher, but when the housing 4 is made to have a size convenient for use, the open end A
This is because the distance L between the point and the short-circuited point B cannot always be set to λg / 4. On the other hand, even if ½ of the wavelength λg in the parallel line corresponding to the resonance frequency of the antenna element 1 is added, it does not affect the radiation characteristics of the antenna. The distance L between the (Point A) and the short-circuited end (Point B) can be selected by the above equation. FIG. 1 shows an example in which the length of the metal piece 9 is adjusted to 1/4 of the wavelength λg of the antenna resonance frequency, and the metal piece 9 and the surface of the housing 4 constitute a wavelength stub.

The antenna element 1 in the first embodiment is 1
Assuming that the electric length is 1/2 wavelength, the antenna element 1
A half-wavelength current distribution P ₁ appears on the top as shown in FIG. On the other hand, the metal piece 9 and the metal surface of the housing 4 constitute a parallel two-wire stub, and its length is exactly 1 as described above.
Since its lower end is short-circuited to the housing 4 at / 4 wavelength, its current distribution becomes P ₉ , and the apparent impedance Z from the open end of this metal piece 9 becomes infinite. Therefore, the electric current appears on the antenna element 1 for one-half wavelength and is separated from the housing 4 by the metal piece 9 acting as a stub. Further, the power feeding path 3 is connected to the antenna element 1 via the matching circuit 2, and impedance conversion between the power feeding path 3 and the antenna element 1 is performed.

Thus, the half-wavelength antenna element 1
By connecting the lower part of the to a quarter-wave stub configured on the housing 4, it is possible to directly feed power with a low characteristic impedance of about 50Ω, which is equal to the terminal impedance of the electronic circuit 6, and on the housing 4. It is possible to configure a portable wireless device that can block the flowing current, has a good radiation pattern shape, and is less affected by the approach or contact of the human body.

(Second Embodiment) FIG. 3 is a perspective view showing the configuration of the second embodiment of the present invention.

In the second embodiment of the present invention, the strip line 3b is arranged on the metal piece 9 in the first embodiment, the strip line 3b and the feed line 3 are connected at a point B, and the coaxial line 3a is the metal piece 9. Connected to. Also, stripline 3
b and the antenna element 1 are connected via the matching circuit 2. The characteristic impedance of the strip line 3b is set to be equal to the characteristic impedance of the feeding line 3.

With such a configuration, the second embodiment also forms two parallel lines between the metal piece 9 and the housing 4 and short-circuits them at a quarter wavelength ahead, so that a quarter wavelength stub is formed. It
Therefore, also in the case of the second embodiment, as in the first embodiment,
Assuming that the antenna element 1 has an electric length of ½ wavelength, the current distribution on the antenna element 1 appears as P ₁ as shown in FIG. On the other hand, the metal piece 9 on which the strip line 3b is arranged and the metal surface of the housing 4 constitute a parallel two-wire stub, the length of which is 1/4 wavelength and the lower end thereof is short-circuited. The apparent impedance Z from the open end of the metal piece 9 becomes infinite. Therefore, the current distribution on the antenna element 1 becomes a half wavelength as shown in FIG. 2, and is separated from the housing 4 by the stub. As a result, the same effect as that of the first embodiment can be obtained.

(Third Embodiment) FIG. 4 is a perspective view showing the structure of a third embodiment of the present invention.

In the third embodiment of the present invention, the matching circuit 2 is arranged between the metal piece 9 and the metal surface of the housing 4 via the dielectric spacer 7, and the feeding path 3 is provided directly in the vicinity of the matching circuit 2. Connected. Also in the case of this embodiment, since two parallel lines of the metal piece 9 and the housing 4 are formed, if the electrical length of this line is 1/4 wavelength, the same effect as in the first embodiment can be obtained. .

(Fourth Embodiment) FIG. 5 is a perspective view showing the structure of the fourth embodiment of the present invention.

In the fourth embodiment of the present invention, the antenna element 1 includes a linear element 1a and a coaxial sleeve element 1b continuous with the linear element 1a.
And the others are configured similarly to the second embodiment shown in FIG.

FIG. 6 is a diagram showing the dimensions of each part of the fourth embodiment, wherein the housing 4 is a metal box, and the distance between the metal surface and the metal piece 9 is 2 mm. 7A is a diagram showing a return loss characteristic of the fourth embodiment, FIG. 7B is a diagram showing a radiation pattern on an XY plane, and FIG. 7C is a diagram showing a radiation pattern on a YZ plane. The coordinate system for measuring this radiation pattern is as shown in FIG. 5, and the measured polarizations are Eφ and Eθ.

As shown in FIG. 7 (a), the return loss characteristic of the fourth embodiment shows a resonance at about 930 MHz, but when the stub by the metal piece 9 is not formed, this is true. No resonance appeared. 930MHz
Since the free space wavelength of the antenna element is about 32 cm, the length 17.7 (9 + 8.7) cm of the antenna element 1 (linear element 1a + coaxial sleeve element) in this case corresponds to about 1/2 wavelength. It can be seen that 1 operates as a 1/2 wavelength antenna. Furthermore, the length of the metal piece 9 is 8 cm.
Corresponds to about 1/4 of the wavelength in this case.

As for the radiation pattern, as shown in (b) and (c) of the same figure, the maximum value is equal to or greater than the 1/2 wavelength dipole ratio, and the radiation pattern is also vertically constricted, but in a substantially horizontal direction. You can see that it emits a large amount of radiation.

In the fourth embodiment, since the lower part of the antenna element 1 has a coaxial structure, the impedance of the antenna element can be lowered, so that the matching circuit is not required and the feeding of the characteristic impedance as low as about 50Ω is possible. Power can be supplied directly from the road. Further, since there is no matching circuit, wide band characteristics can be obtained.

[0026]

As described above, according to the present invention, a metal piece acts as a stub and is short-circuited to the housing portion at the maximum point of the current distribution, so that the antenna radiation characteristic is affected by the human body in contact with the housing. A device that can be received and does not fluctuate can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing the configuration of a first embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation principle in the first embodiment of the present invention.

FIG. 3 is a perspective view showing a configuration of a second embodiment of the present invention.

FIG. 4 is a perspective view showing the configuration of a third embodiment of the present invention.

FIG. 5 is a perspective view showing a configuration of a fourth embodiment of the present invention.

FIG. 6 is a diagram showing dimensions of each part in the fourth embodiment of the present invention.

7 (a), (b), and (c) are diagrams showing measurement results of return loss and radiation pattern in the fourth embodiment of the present invention.

FIG. 8 is a perspective view showing a configuration of a portable wireless device having a whip antenna in a conventional example.

FIG. 9 is a diagram showing a current distribution of a portable wireless device having a whip antenna in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Antenna element 1a Linear element 1b Coaxial sleeve element 2 Matching circuit 3 Feeding path 3a Strip line 3b Coaxial line 4 Housing 6 Electronic circuit 7 Dielectric spacer 9 Metal piece

Claims (3)

[Claims] 1. A housing (4) having an electronic circuit mounted therein.
And a portable wireless device including the antenna element (1) connected to the electronic circuit by a power feeding path (3), wherein the housing (4) has a conductor surface on at least a part thereof,
An elongated metal piece (9), which forms a parallel line with this conductor surface and has one end short-circuited to this conductor surface and the other end open to this conductor surface, is provided and the metal piece (9) is opened. The antenna element (1) is attached to the end side, the hot side of the feeding path (3) is connected to the antenna element and the cold side is connected to the metal piece, respectively, and between the short-circuited end and the open end of the metal piece. Is L = ((1/4) + (1/2) m) · λg, where λg is the wavelength in the parallel line corresponding to the resonance frequency of the antenna element, m is 0 or a positive integer, A portable wireless device characterized by being set to. 2. The feed line (3) includes a coaxial line (3a) wired inside the casing and a strip line (3b) wired on the metal piece, and the strip line and the antenna. Matching circuit (2) between element (1)
The portable wireless device according to claim 1, wherein the wireless communication device is inserted. 3. The antenna element (1) comprises a linear element (1a) and a coaxial sleeve element (1) continuous with the linear element (1a).
The portable wireless device according to claim 1, further comprising b).