JP2002171127A - Helical antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized helical antenna which resonates to a plurality of frequencies, and is easy to adjust antenna characteristics at each resonance frequency. SOLUTION: In a helical antenna which structures a radial element by winding around a conductor (3), the radial element is structured by a first element (5) having a first winding part (5a) which winds around the conductor and a second element (6) having a second winding part (6a) which winds around the conductor. The second element is disposed in a manner that the first winding part and the second winding part are coaxial so that the second winding part is projected from the first element, and the first element and the second element are fed from a common feeding point (4).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a helical antenna, and more particularly, to a helical antenna that resonates at a plurality of frequencies.

[0002]

2. Description of the Related Art A portable wireless device is provided with an antenna at an upper portion of a housing, and performs an operation of transmitting and receiving by radiating a radio wave with the antenna. In some mobile phones, a helical antenna is provided to reduce the amount of protrusion of the antenna from the housing. Furthermore, some recent portable wireless devices are compatible with a plurality of wireless communication systems, and the antenna also needs to resonate in a plurality of frequency bands.

[0003] Such an antenna corresponding to a plurality of frequencies has two elements having different electrical lengths, and is configured to resonate at mutually different frequencies. In FIG.
The side view of the helical antenna thus configured is shown. In this conventional helical antenna, two antenna elements 5 and 6 each formed by winding a conductive wire are horizontally arranged. The first element 5 and the second element 6 are connected at their lower ends, and a high-frequency current is supplied from a common power supply unit 4. The two antenna elements 5 and 6 are arranged at a distance from each other and diagonally above the housing of the mobile phone so as not to be electromagnetically coupled to each other.

[0004] In addition, an antenna corresponding to a plurality of frequencies is provided with an impedance element such that two elements resonate at a certain frequency and only one element resonates at another frequency. In some cases, the electrical length of the antenna element is changed.

[0005]

In such a conventional helical antenna, two separately provided elements are mutually coupled, and the characteristics of the antenna deteriorate. In particular, as shown in FIG. 5, when the two antenna elements 5 and 6 are horizontally arranged, the antenna elements 5 and 6 are coupled, the impedance characteristics of the elements change, and the resonance frequency changes. Also, depending on the arrangement of the antenna elements, the resonance frequency changes due to a change in the degree of coupling of the elements, and it has been difficult to adjust the antenna characteristics at each resonance frequency.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a small helical antenna which resonates at a plurality of frequencies and whose antenna characteristics can be easily adjusted at each resonance frequency.

[0007]

According to a first aspect of the present invention, there is provided a first element having a first winding portion wound with a conductor, and a second element having a second winding portion wound with a conductor. In the helical antenna configured with the radiation element, the first winding part and the second winding part may be configured such that the second element projects the second winding part from the first element. The first element and the second element are arranged coaxially and are fed from a common feeding point.

According to a second aspect, in the first aspect, a winding diameter of the first winding portion is equal to or larger than a winding diameter of the second winding portion.

In a third aspect based on the first or second aspect, the resonance frequency band of the first element and the second
The resonance frequency band of the element is adjacent to the element.

[0010]

According to the first aspect of the present invention, the first element having the first coil and the second element having the second coil constitute a radiating element, and the second element is provided above the first element. So that the coil protrudes
The two coils are arranged coaxially, and both elements are configured to be fed from a common feeding point, so that the first element and the second element are not electromagnetically coupled,
The antenna elements can be arranged close to each other, and the antenna characteristics of both elements can be easily adjusted.

In the second invention, the diameter of the first coil disposed at the lower part is equal to or larger than the diameter of the second coil disposed at the upper part. The antenna can be stably arranged.

In the third invention, since the resonance frequency band of the first element and the resonance frequency band of the second element are adjacent to each other, an antenna that resonates in a wide band by combining the frequency bands of both elements is provided. Can be.

[0013]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing the arrangement of the antenna of the portable radio device of the present invention.

The portable wireless device emits radio waves from a helical antenna 2 provided to protrude from the upper portion of the housing 1 and captures the radio waves to perform a transmission / reception operation. The power supply unit of the helical antenna 2 is connected to a transmission / reception unit (not shown) provided in the housing 1, and a high-frequency signal is supplied from the transmission / reception unit.

FIG. 2 is a side view showing the configuration of the helical antenna 2 according to the embodiment of the present invention.

Helical antenna 2 according to an embodiment of the present invention
Are two antenna elements 5, each having a winding,
6 are arranged so as to be stacked vertically.

The first element 5 is constituted by a coil 5a around which the conductive wire 3 is wound, and the lower end of the first element 5 is connected to the power supply unit 4.

The second element 6 is composed of a linear element loaded with a coil 6a having a conductive wire 3 wound at the tip, and a lower end of the second element 6 is provided with a feeder 4 common to the first element 5. It is connected to the. The lower part of the second element 6 is linear so as not to interfere with the first element 5, and the second element 6 is such that the winding part 6a of the second element is higher than the winding part 5a of the first element. At the projecting position, the centers of the winding part 6a and the winding part 5a are substantially the same, and are arranged coaxially.

In the present embodiment, the winding diameter of the second element 6 is smaller than the winding diameter of the first element 5. The diameter may be configured to be larger than the winding diameter of the first element 5.

A case (not shown) made of resin is provided on the outer periphery of the first element 5 and the second element 6, and the helical antenna 2 is attached to the housing 1 of the portable radio by the case. I have. The inside of the case may be hollow or filled with resin. However, if the case is filled with resin, the elements 5 and 6 do not move and the resonance frequency and the frequency characteristics do not change.

FIG. 3 is a diagram showing a resonance state of the antenna according to the embodiment of the present invention. In the figure, (a) shows a current distribution when the first element 5 resonates at a low resonance frequency (first resonance frequency), and (b) shows a current distribution when the second element 6 resonates at the second resonance frequency. (C) shows the current distribution when the third element is resonating at a high resonance frequency (third resonance frequency).

In the helical antenna 2, at the first resonance frequency, the first element 5 has an electrical length of １ ／ wavelength, and at the third resonance frequency whose frequency is slightly less than three times the first resonance frequency, the first element 5 has three electric lengths. It is an electrical length of / 4 wavelength, which is the length of resonance. On the other hand, at the second resonance frequency, the second element 6 has an electrical length of １ ／ wavelength and has a length that resonates. Therefore, the helical antenna 2 resonates at three frequencies.

FIG. 4 is a characteristic diagram of the helical antenna 2 according to the embodiment of the present invention. In the figure, the vertical axis indicates gain, and the horizontal axis indicates frequency.

In the helical antenna 2 of the present embodiment, resonance occurs near the first resonance frequency (f1 = 900 MHz), near the second resonance frequency (f2 = 1800 MHz), and near the third resonance frequency (f3 = 2000 MHz). And the antenna gain is in a good state.

These resonance frequencies (f1, f2, f3)
Among the characteristics in the above, the first resonance frequency (f1) and the third resonance frequency (f3) are the characteristics due to the resonance of the first element 5, and the second resonance frequency (f2) is the characteristic due to the resonance of the second element 6. Is as described in FIG.

At this time, the resonance frequencies of the first element 5 and the second element 6 are selected such that the second resonance frequency (f2) and the third resonance frequency (f3) are adjacent to each other.

The frequency identification of the helical antenna according to the present invention in which both the first element 5 and the second element 6 are coaxially arranged, and the helical antenna having only the element corresponding to the first element 5 or the second element 6
In comparison with the frequency characteristics (not shown) of the helical antenna having only the element corresponding to the above, there is no difference in the resonance frequency between the two. Therefore, in the helical antenna according to the present invention, the first element 5 and the second element 6 is hardly electromagnetically coupled.

As described above, the helical antenna 2 according to the embodiment of the present invention has the first element 5 having the first winding portion 5a around which the conductor 3 is wound, and the second element 5 around which the conductor 3 is wound.
A radiation element is constituted by the second element 6 having the winding portion 6a, and the second element 6 is composed of the first element 5
So that the second winding portion 6a projects above the first winding portion 5a.
a and the second winding portion 6a are arranged coaxially, and the first element 5 and the second element 6 are configured to be fed from the common feeding point 3, so that the first element 5 and the second element 6 resonates at a plurality of frequencies and the two elements 5 and 6 have a small amount of electromagnetic coupling, so that the antenna characteristics of both elements can be individually adjusted.

Further, since the second element 6 is disposed above the first element 5 so that the second winding portion 6a protrudes, the first element 5 and the second element 6 resonate at a plurality of frequencies. Even if the two elements 5 and 6 are arranged close to each other, the electromagnetic coupling between them is small, so that the antenna can be downsized.

Whether the diameter of the first winding part 5a arranged at the lower part is the same as the diameter of the second winding part 6a arranged at the upper part,
Since the antenna is made thicker than this, the antenna does not become thicker as it goes upward, so that the antenna can be stably arranged and an antenna excellent in aesthetic sense can be obtained.

The first winding part 5a and the second winding part 5a are arranged such that the third resonance frequency (f3) of the first element 5 and the second resonance frequency (f2) of the second element 6 are adjacent to each other. With the configuration of the unit 6a, an antenna that resonates in a wide band by combining the resonance frequency bands of both elements can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an arrangement of an antenna of a portable wireless device of the present invention.

FIG. 2 is a side view of the antenna according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating a resonance state of the antenna according to the embodiment of the present invention.

FIG. 4 is a characteristic diagram of the antenna according to the embodiment of the present invention.

FIG. 5 is a side view of a conventional helical antenna.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cellular phone (housing) 2 Helical antenna 3 Conductive wire 4 Feeding part 5 1st element 5a Coil (winding part) 6 2nd element 6a Coil (winding part)

Claims (3)

[Claims] 1. A helical antenna in which a radiating element is constituted by a first element having a first winding portion wound with a conductor and a second element having a second winding portion wound with a conductor. The second element has the first winding part and the second winding part disposed coaxially so that the second winding part protrudes from the first element. A helical antenna, wherein the element and the second element are fed from a common feeding point. 2. The helical antenna according to claim 1, wherein a winding diameter of the first winding part is equal to or larger than a winding diameter of the second winding part. 3. The helical antenna according to claim 1, wherein a resonance frequency band of the first element and a resonance frequency band of the second element are adjacent to each other.