JPH0685525A - 1/2 wavelength antenna - Google Patents

Abstract

PURPOSE:To provide the small size and wide band 1/2 wavelength antenna with reduced influences upon antenna characteristics caused by the approach of a human body. CONSTITUTION:In the 1/2 wavelength antenna provided with a helically formed 1/4 wavelength radiating element 1 driven by the circuit of a radio equipment and a 1/2 wavelength radiating element 2 coupled with the 1/4 wavelength radiating element 1 by an electromagnetic field, the 1/4 wavelength radiating element 1 is surrounded by a coaxial conductor 4 which periphery is grounded excepting for an open end face coupled with the 1/2 wavelength radiating element 2 by an electromagnetic field. Thus, since the 1/4 wavelength radiating element 1 can be provided by a compact coil and a gap between the 1/4 wavelength radiating element 1 and the 1/2 wavelength radiating element 2 can be reduced, this 1/2 wavelength antenna can be miniaturized, and the wide band 1/ 2 wavelength antenna can be provided while reducing the influences upon antenna characteristics caused by the approach of a human body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a 1/2 wavelength antenna suitable for mounting on a mobile phone or the like used for mobile communication.

[0002]

2. Description of the Related Art FIG. 4 is a diagram showing a configuration example of a 1/2 wavelength antenna having a 1/2 wavelength radiation element driven by a conventional 1/4 wavelength radiation element. In FIG. 4, 5 is a quarter-wavelength radiating element formed in a spiral shape, and is fed by the feeding terminal 3. Reference numeral 2 is a ½ wavelength radiating element which is formed in a spiral shape and is electromagnetically coupled to the ¼ wavelength radiating element.
The 1/4 wavelength radiating element 5 exhibits series resonance characteristics and the radiation resistance is set to about 50 ohms.
As disclosed in Japanese Patent No. 8604, quarter wavelength radiating elements 5 and 1
By minimizing the electromagnetic field coupling state with the 1/2 wavelength radiating element 2, only the 1/4 wavelength radiating element 5 operates, and when extended, it is driven by the 1/4 wavelength radiating element 5 by a predetermined amount of electromagnetic field coupling. The 1/2 wavelength radiating element 2 serves as a 1/2 wavelength antenna.

[0003]

However, in the above-mentioned conventional 1/2 wavelength antenna, since the 1/4 wavelength radiating element 5 exhibits parallel resonance characteristics, the radiation resistance becomes several hundred ohms, which is often used in a radio circuit. In order to match the used 50 ohms, it was necessary to make the electromagnetic field coupling between the quarter-wavelength radiating element 5 and the half-wavelength radiating element 2 extremely weak. Therefore, in the 800 MHz band ½ wavelength antenna used in the conventional portable telephone, the distance between the ¼ wavelength radiating element 5 and the ½ wavelength radiating element 2 is about 10 mm.
It is necessary to make it above, and in order to cope with the recent miniaturization of the antenna, it is necessary to make this interval shorter.

At this time, there are radiation by the half-wavelength radiation element 2 and radiation by the quarter-wavelength radiation element 5, and
When the four-wavelength radiating element 5 approaches the head of the human body, the characteristics of the ¼-wavelength radiating element 5 change significantly. Therefore 1
There is also a problem that the characteristics themselves of the / 2 wavelength antenna are greatly affected.

The present invention has been made in view of the above points, and when the 1/2 wavelength antenna is used only in the extended state, the distance between the 1/4 wavelength radiating element and the 1/2 wavelength radiating element can be reduced, 1/2 wavelength antenna in which the characteristics of the 1/4 wavelength radiating element do not change significantly when the 1/4 wavelength radiating element approaches the head of the human body, that is, the characteristics of the 1/2 wavelength antenna itself are not significantly affected. The purpose is to provide.

[0006]

In order to solve the above problems, the present invention provides a quarter wave radiating element formed in a spiral shape driven by a circuit of a radio, a quarter wave radiating element and an electromagnetic wave. 1/2 equipped with field-coupled 1/2 wavelength radiating element
In the wavelength antenna, the 1/4 wavelength radiating element 1 is 1/2
It is characterized in that it is surrounded by a coaxial conductor 4 which is grounded except for the open end face which is electromagnetically coupled with the wavelength radiating element 2.

[0007]

The 1/4 wavelength radiating element 1 can be obtained by covering the 1/4 wavelength radiating element 1 with the grounded conductor 4 as described above.
Does not work as an antenna but as a matching circuit. Since the electromagnetic field is hard to radiate to the outside, the radiation resistance is low and 1
The electromagnetic fields of the quarter-wavelength radiating element 1 and the half-wavelength radiating element 2 can be made extremely strong to match the radio circuit. In order to strengthen the electromagnetic field coupling, it is preferable to couple on the open surface side of the quarter-wavelength radiating element 1, and the gap is 1 to 2
It is possible to combine with the half-wavelength radiating element 2 at an extremely short distance of about mm so as to match with 50 ohms. As a result, the 1/2 wavelength radiating element 2 is in an extremely strong coupling state, and the electromagnetic field is radiated in a positionally high state (the 1/4 wavelength radiating element 1 emits almost no radiation). It is possible to reduce the deterioration of the antenna characteristics due to the approach of.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration example of a 1/2 wavelength antenna of the present invention. In FIG. 1, 1 is a quarter wavelength radiating element formed in a spiral shape which is driven by a circuit of a radio device (not shown), and 2 is a 1/4 wavelength radiating element which is electromagnetically coupled with the 1/4 wavelength radiating element. It is a two-wavelength radiating element. The 1/4 wavelength radiating element 1 is surrounded by a coaxial conductor 4 whose periphery is grounded except for the open end face which is electromagnetically coupled with the 1/2 wavelength radiating element 2.

Since the 1/4 wavelength radiating element 1 is surrounded by the conductor 4, it emits almost no radiation and can be realized by a small coil, and is fed from the feeding terminal 3. 1/4
The end face of the wavelength radiating element 1 which is open from the conductor 4 is electromagnetically coupled to the ½ wavelength radiating element 2 at a very close distance. The operation of the 1/2 wavelength antenna having the configuration shown in FIG. 1 will be described below.

By covering the periphery of the 1/4 wavelength radiating element 1 with the grounded conductor 4, the TEM mode is set, and it becomes extremely difficult for the electromagnetic field to radiate to the outside, and the 1/4 wavelength radiating element 1 does not operate as an antenna and is matched. Operates as a circuit. Since the electromagnetic field is hard to radiate to the outside, the radiation resistance can be lowered to several ohms, and since the radiation resistance of the ½ wavelength radiating element 2 is several hundred ohms, the ¼ wavelength surrounded by the conductor 4 The electromagnetic fields of the radiating element 1 and the half-wave radiating element 2 can be set to a very strong state to match the radio circuit with 50 ohms.

In order to strengthen the electromagnetic field coupling, the electric field of the 1/4 wavelength radiating element is extremely strong, and it is preferable to couple on the open surface side opposite to the side to which power is fed. The distance from the open end face can be combined with the half-wavelength radiating element 2 at an extremely short distance of about 1 to 2 mm to match with 50 ohms. As a result, the periphery of the 1/4 wavelength radiating element 1 is covered with the grounded conductor 4, and
Because the electromagnetic field is radiated in a state in which the / 2 wavelength radiating element 2 is extremely strongly coupled and is in a high position (because there is almost no radiation from the ¼ wavelength radiating element 1), the human body approaches the head. Less deterioration of antenna characteristics.

Further, since the radiation resistance of the 1/4 wavelength radiating element 2 is low, the 1/4 wavelength radiating element 1 can be realized with a small coil. Since the electromagnetic field coupling between the quarter-wavelength radiating element 1 and the half-wavelength radiating element 2 can be strengthened, the coupling is performed at an interval distance of several mm, so that the ½-wavelength element 2 and the matching circuit are realized in a small size. Therefore, the size can be reduced as compared with the conventional 1/2 wavelength antenna shown in FIG.

FIG. 3 shows an example of measurement of the present half-wavelength antenna of the above construction realized with a total length of about 100 mm.
As shown in the figure, according to the present half-wave antenna, the frequency bandwidth in which the voltage standing wave ratio (VSWR) is 2.0 or less is about 1
A very wide band characteristic of 70 MHz can be obtained. Further, in order to make the matching impedance as high as 75 ohms or the like, the conductor 4 on the open surface side is largely removed to increase the radiation resistance of the quarter-wave radiating element 1, and impedance matching can be easily achieved. it can.

In the half-wavelength antenna having the structure shown in FIG. 1, the half-wavelength radiation element 2 has a spiral shape. However, the invention is not limited to this, and the half-wavelength radiation element has a linear shape. Similar characteristics can be obtained even when formed in a plate shape. In addition, in the 1/2 wavelength antenna having the configuration shown in FIG. 1, the 1/4 wavelength radiating element formed in a spiral shape and the 1/4 wavelength radiating element formed in a spiral shape
A so-called coaxial structure in which the two-wavelength radiating elements are coaxially arranged is used. However, in order to strengthen the electromagnetic field coupling, it is not necessary to have the coaxial structure, and they may be adjacently arranged as shown in FIG.
It can be realized even in a structure that is restricted in size such as a mobile phone.

[0015]

As described above, according to the present invention, 1
A quarter-wave radiating element is surrounded by a coaxial conductor grounded except for the open end face that is electromagnetically coupled to the ½-wave radiating element, so it is not easily affected by the approach of the human body, and is compact and has a wide band width. An excellent effect of providing a / 2 wavelength antenna can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a ½ wavelength antenna of the present invention.

FIG. 2 is a diagram showing another configuration example of the half-wave antenna of the present invention.

FIG. 3 is a diagram showing a measurement example of the present antenna characteristics in which the half-wavelength antenna having the configuration shown in FIG. 1 is realized with a total length of about 100 mm.

FIG. 4 is a diagram showing another configuration example of a conventional 1/2 wavelength antenna.

[Explanation of symbols]

 1 1/4 wavelength radiating element 2 1/2 wavelength radiating element 3 feeding terminal 4 conductor

Claims (1)

[Claims] 1. A 1/4 wavelength radiating element formed in a spiral shape driven by a circuit of a radio device, and a 1/2 wavelength radiating element electromagnetically coupled to the 1/4 wavelength radiating element.
In the / 2 wavelength antenna, the 1/4 wavelength radiating element is surrounded by a coaxial conductor whose periphery is grounded except for an open end face for electromagnetically coupling with the 1/2 wavelength radiating element. / 2 wavelength antenna.