JPH11234015A - Antenna system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a antenna system, which enables a stable mobile communication of high quality for a telephone call as an antenna system used for radio equipment by allowing operation with electrical length close to an element of such electrical length that the radiation resistance of the input impedance has a peak and the reactance component is ±∞ and longer than the electrical length. SOLUTION: This antenna system consists of a monopole antenna 1, a connection spring 2, a matching circuit 3, a radio circuit 4, and a radio equipment housing 5. Then the monopole antenna is placed in mode of electrical length close to the element of such electrical length that the radiation resistance of the input impedance has the peak, and the reactance component is ±∞ and longer tan the electric length. Consequently, a housing current can be made hard to flow and satisfactory radiation characteristics can be obtained in both standby mode and telephone call mode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna device used for a portable telephone, a mobile radio device, and the like, and more particularly to an antenna device having good antenna radiation characteristics at the time of standby and when a human body is used (call).

[0002]

2. Description of the Related Art Conventionally, an antenna having a substantially equivalent electric length such as 1/4 wavelength and 1/2 wavelength has been used for a mobile radio device or the like. In general, a quarter-wave antenna has a maximum current near the feeding point and a zero reactance component of impedance, so that it is easy to match and has a wide band. When used in portable radios due to factors such as disrupting the current distribution of
This is because even in an antenna with good gain when placed in free space, the current on the housing is disturbed when a person holds it in an actual call state, the impedance changes, and the radiation efficiency decreases. .

[0003] In the case of a half-wavelength antenna, the current near the feeding point becomes zero and the impedance becomes almost infinite, so that the influence of the housing current is small. Although the gain degradation when using the human body is less affected than when using a 1/4 wavelength antenna,
The current antenna having a substantially equivalent electrical length equivalent to a half wavelength has a very narrow band and very difficult impedance matching.

[0004] In order to solve this problem, the present inventors have proposed:
An application for Japanese Patent Application No. Hei 8-234634 was previously filed, in which an antenna used for a portable mobile communication terminal is configured to have a monopole antenna shape, and has an operation mode of 1/100.
By operating at two wavelengths + α, the radiation pattern radiated from the monopole antenna is directed upward, and the housing current is made difficult to flow, so that good radiation characteristics are obtained both during standby and during a call. We proposed an antenna device.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an antenna device having good antenna radiation characteristics both in free space and when a human body is used, in order to solve the same problems as in the prior application. It is.

[0006]

In order to solve the above-mentioned problems, an antenna device according to the present invention comprises an antenna used for a portable mobile radio terminal, wherein the antenna is configured as a monopole antenna. By operating the input impedance at an electrical length longer than the electrical length near the electrical length where the radiation resistance becomes a peak and the reactance component becomes ± ∞, it becomes difficult for the housing current to flow. In this way, a good antenna radiation characteristic is obtained both during standby and during a call.

[0007] As a result, the antenna radiation characteristics are such that the main lobe is less attenuated when held by a person than in free space, and is better in standby and talking than an antenna operating in another electrical length mode. It obtains an excellent radiation characteristic.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An antenna device according to a first aspect of the present invention is an antenna used for a portable mobile radio terminal, wherein the antenna device has a monopole antenna shape and radiates the input impedance of the monopole antenna. In the vicinity of the electrical length where the resistance becomes a peak and the reactance component becomes ± ∞, by operating at an electrical length longer than the electrical length, the housing current is made difficult to flow, so that the It is an antenna device characterized by obtaining good antenna radiation characteristics even during a call, and the antenna radiation characteristics have less attenuation of the main lobe when held by a person than in free space, It has the effect of obtaining better radiation characteristics both during standby and during a call than antennas operating in other electrical length modes.

According to a second aspect of the present invention, there is provided an antenna for use in a portable mobile communication terminal, wherein a monopole antenna is housed in a helical antenna shape when housed, and the electrical length of the helical antenna is determined by radiating an input impedance. By operating at an electrical length in the vicinity of the electrical length at which the resistance is a peak and a reactance component ± ∞ and longer than the electrical length, it is difficult to flow a housing current flowing on the portable mobile wireless terminal, so that the This is an antenna device characterized by obtaining good radiation characteristics even during a call.The antenna radiation characteristics show that the main lobe is less attenuated when held by a person than in free space, When listening from an antenna operating in electrical length mode,
It has the effect of obtaining good radiation characteristics even during a call.

According to a third aspect of the present invention, there is provided an antenna used for a portable mobile communication terminal, wherein the antenna has a spiral antenna shape, and the electrical length of the spiral antenna is such that the radiation resistance of the input impedance has a peak and the reactance. By operating at an electrical length in the vicinity of the electrical length that is the component ± ∞ and longer than the electrical length, it becomes difficult for the casing current flowing on the portable mobile radio terminal to flow, so that the standby mode and the call mode are good. The antenna device is characterized by obtaining radiation characteristics.
The main lobe is less attenuated when held by a person than in free space, and has an effect of obtaining better radiation characteristics both during standby and during a call than when the antenna operates in another electrical length mode.

According to a fourth aspect of the present invention, there is provided an antenna used in a portable mobile communication terminal, wherein the antenna is formed in an inductance-loaded antenna shape in which an inductance is loaded between antenna elements. The housing that flows on the portable mobile wireless terminal by operating the electrical length of the antenna element near the electrical length where the radiation resistance of the input impedance is a peak and the reactance component is ± ∞ and longer than the electrical length. This is an antenna device characterized by obtaining good radiation characteristics both during standby and during calls by making it difficult for current to flow.The antenna radiation characteristics are compared with those in free space when held by a person's hand When the main lobe is less attenuated than when the antenna operates in other electric length mode, Both during talk has the effect of obtaining a good radiation characteristic.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First Embodiment) FIG. 1 shows a configuration of an antenna device according to a first embodiment. The antenna device includes a monopole antenna 1, a connection spring 2, a matching circuit 3, a radio circuit 4, and a radio housing 5. The monopole antenna 1 is supplied with power from the wireless circuit 4 through the matching circuit 3 and the connection spring 2. Although the configuration is the same as that of FIG. 1 shown in the earlier application, the antenna device is designed so that the element length, the housing structure, and the center frequency assumed when designing the antenna are different.

FIGS. 2A and 2B show a schematic overall configuration of the antenna device according to the first embodiment. Fig. 2 (a) uses a 115mm x 30mm x 10mm metal box for the housing,
A monopole antenna having an electrical length of 0.48 wavelength for an assumed center frequency of 2040 MHz is used. FIG. 2 (b)
Uses a 123 mm × 36 mm substrate for the housing, and uses a monopole antenna having an electrical length of 波長 wavelength with respect to the assumed center frequency of 884 MHz.

In the prior application, a conductor plate of 123 mm × 36 mm is used as a housing, and a monopole antenna having an electrical length of 波長 wavelength + α with respect to a center frequency of 1920 MHz is used. However, the range of α is about 1% <α <10%.

FIG. 3 shows the radiation pattern in the free space of the monopole antenna and when the human body is used.
(A), (b) and FIGS. 4 (a), (b). In the case of FIG. 3A and FIG. 4A, an upward radiation pattern is obtained. In the case of FIG. 3B and FIG.
A radiation pattern with little attenuation of the main lobe is obtained.

Next, the operation characteristics of the antenna device of the present invention will be described using the power loss with respect to the electrical length of the linear antenna element and the input impedance (radiation resistance and reactance component) with respect to the electrical length of the linear antenna element.

FIG. 5 shows the power loss with respect to the electrical length of the linear antenna element of the antenna device according to the first embodiment of the present invention. Pa indicates the loss due to the head of the human body, and Ph indicates the loss due to the hand of the human body. In FIG. 5, as the electrical length of the antenna element increases, the shielding by the human head decreases, so that Pa decreases. Further, there is an electric length at which Ph is minimized due to the electric length of the antenna element. This indicates that the case current is the smallest, and the electrical length where the sum of Pa and Ph is usually the least, that is,
The element length that operates in the vicinity of the electrical length at which Ph becomes a minimum and that is longer than the electrical length is the element length that maximizes the antenna gain when a human body is used.

FIG. 6 shows the input impedance (radiation resistance and reactance component) with respect to the electrical length of the linear antenna element of the antenna device according to the first embodiment of the present invention. The point at which Ph in FIG. 5 is minimum is the point where the radiation resistance peaks in FIG. 6 and the reactance component becomes ± 成分. Therefore, the point at which the antenna gain is maximized when the human body is used is that the radiation resistance has a peak, and the element length operating near the electrical length where the reactance component is ± ∞ and operating at an electrical length longer than the electrical length is determined when the human body is used. The element length becomes the maximum antenna gain.

As described above, the electric lengths obtained from the center frequency assumed on the antenna design have different electric lengths at the peak points when the human body is used as shown in FIGS. However, it is because the housing current flows,
The operation of each antenna operates at the peak point shown in FIGS. 5 and 6, but the length of each element is determined by the balance between the housing and the antenna element due to the effect of the housing current.

(Second Embodiment) FIG. 7 shows a configuration of an antenna device according to a second embodiment. When the monopole antenna according to the first embodiment is housed, the shape of the antenna is changed. It is a helical antenna. In FIG. 7, (a) and (b) show the case where the same housing size as that of the first embodiment is used. By configuring the helical antennas having the same impedance characteristics as those of the monopole antenna according to the first embodiment (see FIG. 6), the input impedance characteristics of the helical antennas according to the second embodiment are different from each other. Although the electrical length of the whip antenna is different, the radiation pattern is close to figure 8 in free space even when the whip antenna is stored as a tip helical antenna, and the main lobe is slightly It faces upward, and the radiation directivity of each surface also becomes very large. Further, when a human body is used, a helical antenna in which the radiation pattern of the antenna is hardly distorted by the hand or the head can be configured.

(Third Embodiment) FIG. 8 shows the configuration of an antenna device according to a third embodiment. The monopole antenna according to the first embodiment is a spiral antenna, and It is a shortened version. In FIGS. 8A and 8B, (a) and (b) show cases where the same housing size as that of the first embodiment is used. The configuration can be realized by a simple configuration such as winding a belt-shaped tape around a resin such as ABS, and the impedance characteristic of the spiral antenna having a gentle spiral as shown in FIG. 8 is the same as that of the first embodiment. Since the impedance characteristics of the helical antennas are almost the same as the impedance characteristics of the monopole antenna (see FIG. 6), the electric lengths of the helical antennas are different. The pattern is close to figure 8, the main lobe is slightly upward, and the radiation directivity of each surface is very large. Further, when a human body is used, a helical antenna in which the radiation pattern of the antenna is hardly distorted by the hand or the head can be configured.

(Fourth Embodiment) FIG. 9 shows the configuration of an antenna device according to a fourth embodiment. In FIGS. 9A and 9B, (a) and (b) show cases where the same housing size as that of the first embodiment is used. When an antenna element as described in the first embodiment is used in a low frequency system such as an 800 MHz band,
At 800 MHz, the element length is as long as about 18 cm, which is a problem that cannot be accommodated in the current miniaturized mobile phones.Therefore, loading an inductance in the middle of the antenna element reduces the length and improves the gain. So that it can be removed. By making the impedance characteristic equal to that of the monopole antenna of the first embodiment, the electrical length of each of the inductance loaded antennas is different. In free space, the radiation pattern is close to figure 8, the main lobe is slightly upward, and the radiation directivity of each surface is very large. Further, when a human body is used, a helical antenna in which the radiation pattern of the antenna is hardly distorted by the hand or the head can be configured.

[0024]

As is apparent from the above description, as an antenna of a mobile communication terminal such as a cellular phone, the input impedance of the element length is determined by the electrical length such that the radiation resistance becomes a peak and the reactance component becomes ± ∞. By using an element length that is close to the element and that operates with an electrical length longer than the electrical length, it is possible to reduce the case current flowing on the portable mobile wireless terminal, and it is favorable both in free space and when using a human body. This has the effect that the radiation characteristics of a simple antenna can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an antenna device at the time of extension according to a first embodiment of the present invention;

FIGS. 2A and 2B are diagrams showing the overall configuration of the antenna device according to the first embodiment of the present invention, in which (a) a housing is 115 mm × 3;
Using a metal box of 0mm x 10mm, assumed center frequency 2040MHz
Example using a monopole antenna with an electrical length of 0.48 wavelength for (b) A monopole antenna with an electrical length of 1/2 wavelength for an assumed center frequency of 884 MHz using a 123 mm x 36 mm substrate for the housing Example using,

FIG. 3 is a diagram showing radiation characteristics of the antenna device in the free space and the human body of the antenna device of FIG. 2A;

FIG. 4 is a view showing radiation characteristics of the antenna device in a free space and a human body of the antenna device of FIG. 2 (b);

FIG. 5 is a diagram showing a power loss with respect to an electrical length of a linear antenna element of the antenna device according to the first embodiment of the present invention;

FIG. 6 is a diagram showing an input impedance (radiation resistance and reactance component) with respect to an electrical length of a linear antenna element of the antenna device according to the first embodiment of the present invention;

FIG. 7 is a diagram showing the overall configuration of an antenna device according to a second embodiment of the present invention, in which (a) a housing has a size of 115 mm × 3;
Example of helical antenna using a metal box of 0 mm × 10 mm,
(B) An example of a helical antenna using a 123 mm x 36 mm substrate for the housing,

FIG. 8 is a diagram showing an overall configuration of an antenna device according to a third embodiment of the present invention, in which (a) a housing is provided with 115 mm × 3
Example of spiral antenna using metal box of 0mm x 10mm, (b)
Example of a spiral antenna using a 123 mm × 36 mm substrate for the housing,

FIG. 9 is a diagram showing an overall configuration of an antenna device according to a fourth embodiment of the present invention.
Example of loading coil antenna using a metal box of 0 mm × 10 mm,
(B) This is an example of a loading coil antenna using a 123 mm × 36 mm substrate for the housing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Monopole antenna 2 Connection spring 3 Matching circuit 4 Radio circuit 5 Radio case 6 Helical antenna 9 Spiral antenna 10 Loading coil 11 Metal case 12 Mobile radio terminal

Claims (4)

[Claims] 1. An antenna used for a portable mobile radio terminal, wherein the antenna has a monopole antenna shape, and the input impedance of the monopole antenna is such that the radiation resistance has a peak and the reactance component is ± ∞. By operating near the element having a short electrical length and at an electrical length longer than the electrical length, it becomes difficult for the casing current flowing on the portable mobile wireless terminal to flow,
An antenna device characterized by obtaining good radiation characteristics both during standby and during a call. 2. An antenna used for a portable mobile radio terminal, wherein the antenna has a helical antenna shape,
By operating the input impedance of the helical antenna in the vicinity of an element having an electric length such that the radiation resistance becomes a peak and the reactance component becomes ± ∞ and an electric length longer than the electric length longer than the electric length, a portable type is provided. An antenna device characterized in that a casing current flowing on a mobile wireless terminal is made difficult to flow, so that good radiation characteristics can be obtained both during standby and during a call. 3. An antenna used for a portable mobile radio terminal, wherein the antenna is formed in a spiral antenna shape, and the input impedance of the spiral antenna is such that the radiation resistance has a peak and the reactance component is ± ∞. By operating near the long element and at an electrical length longer than the electrical length, it is possible to make it difficult for the casing current flowing on the portable mobile radio terminal to flow, thereby obtaining good radiation characteristics both during standby and during a call. An antenna device, comprising: 4. An antenna used for a portable mobile radio terminal, wherein the antenna is configured in the form of an inductance-loaded antenna having a structure in which an inductance is loaded between antenna elements, and a radiation resistance of an input impedance of the inductance-loaded antenna is changed by a radiation resistance. By operating near the element having an electric length such that the reactance component becomes ± ∞ and having an electric length longer than the electric length, it becomes difficult to flow the housing current flowing on the portable mobile wireless terminal. An antenna device characterized by obtaining good radiation characteristics both during standby and during a call.