JP2003037428A - Linear antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make broaden the band width of a linear antenna. SOLUTION: A linear antenna is made of a belt-shaped conductor, in which a radiation element 14 is formed into a meandering shape. Chamfered parts 22 of isosceles triangular shape are formed at the outer edge of a bent part of the radiation element 14. Here, 12 is a dielectric board, and 16 is a metal plate as a parasitic element. When the chamfered part 22 is provided, a change in the impedance is made small, and decrease in the band width can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small linear antenna used for a mobile phone, a personal digital assistant, a wireless LAN (local area network) terminal device, and the like.

[0002]

2. Description of the Related Art A linear antenna (hereinafter referred to as an antenna) used for this type of application has a radiating element made of a conductor formed in a meandering shape (a meandering shape). In the usual case, the radiating element of the meander antenna is formed by pattern etching of a metal plate attached to a dielectric substrate, punching from the metal plate, or the like, so that the band-shaped conductor is thin and has a certain width. 11-4113, 11-243318, 11-317612
Issue).

[0003]

The meander antenna tends to have a narrower bandwidth as the number of bendings of the strip-shaped conductor increases.

In view of the above problems, an object of the present invention is to provide a meander antenna having a wider band.

[0005]

In order to achieve this object, the present invention provides an antenna comprising a conductor pattern in which a strip conductor is bent in the width direction of the strip, and a chamfered portion is provided on the outer edge of the bent portion of the strip conductor. It is characterized by being provided. By providing such a chamfered portion, it becomes possible to widen the band of the antenna. The total length of the conductor pattern is determined so that its electrical length is substantially n / 4 times the wavelength λ of the frequency transmitted and received by this antenna (n is a positive integer, usually n = 1).

In the antenna of the present invention, the size of the chamfer (the length of one side of the isosceles when chamfering into an isosceles triangle) is preferably 0.7 times or more the conductor width of the strip conductor.

[0007]

Embodiments of the present invention will be described below.
A detailed description will be given with reference to the drawings.

First Embodiment FIG. 1 shows an embodiment of the present invention. This meander antenna 10 includes a radiating element 14 made of a meander-shaped strip conductor on one surface of a dielectric substrate 12.
And a metal plate 16 is provided on the opposite surface.
The radiating element 14 has a length of about one-quarter wavelength, and has a feeding portion 18 at one end and an open end 20 at the other end.
The metal plate 16 is not grounded. That is, the metal plate 16 acts not as a ground plate but as a parasitic element. The radiating element 14 has a width direction straight line portion a that extends straight in the width direction of the meander and a pitch direction straight line portion b that extends straight in the pitch direction of the meander intersect at a right angle. This antenna is prepared by forming a radiating element 14 by preparing a double-sided copper foil substrate (copper foil thickness 36 μm) cut into a predetermined width and length, and etching, punching or printing one side of the copper foil. Manufactured.

A feature of this meander antenna 10 is that the outer edge of the portion of the radiating element 14 where the strip conductor bends at a right angle is cut into an isosceles triangle shape. That is, the chamfered portion 22 is formed by cutting along the line orthogonal to the line that divides the angle formed by the straight portions a and b into two. Specifically, the chamfered portion 22 is cut at an angle of 45 ° with respect to the pitch direction.

As in the case of this antenna, the radiating element 14 is shorter than the wavelength of the resonance frequency, and in a small antenna that operates by resonating, the details such as the corners of the meandering bent portion are It has not previously been considered that it affects the width of the antenna band. However, when the present inventor formed the chamfered portion 22 as described above, the bandwidth could be widened as compared with the case where the chamfered portion was not provided. The reason is not clear, but the present inventor
By providing the chamfered portion 22, the change in impedance at the bent portion of the radiating element 14 is reduced,
This is because unnecessary reflection can be prevented and the reduction in bandwidth can be suppressed.

[First Embodiment] The results of trial production of the meander antenna of the present invention and the conventional meander antenna will be described below. As a meander antenna of the present invention, a meander antenna 10 having a chamfered portion 22 as shown in FIG. 1 was prototyped. In this meander antenna 10, a dielectric substrate 12 has a length of 36 mm, a width of 8 mm and a thickness of 1.6 mm, a radiating element 14 has a conductor width of 1 mm, a conductor interval of 1 mm, a meandering width of 6 mm, and a metal plate 16 has a length and a width of a dielectric substrate. Same as twelve.

To compare with this, as a conventional meander antenna, the meander antenna 10 as shown in FIG. 2 is the same as the meander antenna 10 of FIG. 1 except that the bent portion of the radiating element 14 is not chamfered. I made a prototype.

With respect to these meander antennas, a change in VSWR (voltage standing wave ratio) when the frequency was changed was measured. The measurement results are shown as a graph in FIG. The thick line with a cut (with a chamfer) is the meander antenna of the present invention, and the thin line without a cut is the conventional meander antenna. Table 1 shows the bandwidths at a plurality of VSWR levels obtained from the measurement results.

[0014]

[Table 1]

According to this result, it is clear that the frequency bandwidth can be made wider than that of the conventional meander antenna by providing the chamfered portion 22 at the outer edge of the bent portion of the radiating element.

[Embodiment 2] Next, the results of examining the size of the chamfered portion 22 will be described. As shown in FIG. 4 (B), for three types of meander antennas having conductor widths W of 5 mm, 10 mm, and 15 mm, the size of the chamfered portion (the length L of one side of an isosceles edge when chamfering into an isosceles right triangle) ) Was changed in the range of 0 to 2 times the conductor width W to measure the bandwidth. The result is shown in FIG. According to this, when the bandwidth without the chamfer is 1, the bandwidth changes as follows by providing the chamfer. (1) When the conductor width is 5 mm: Bandwidth 1.00 to 1.09 (maximum variation ΔM = 0.09) (2) When the conductor width is 10 mm: Bandwidth 1.00 to 1.16 (maximum variation ΔM = 0.16) (3) Conductor width 15 mm When: Bandwidth 1.00 to 1.40 (maximum variation ΔM = 0.40)

In FIG. 4A, the amount of change in bandwidth is ΔM / 2.
The above is when the size of the chamfer is 0.7 times or more the conductor width W, and the effect of widening the band is particularly remarkable in this range. Therefore, the size of the chamfered portion is preferably set to 0.7 times or more the conductor width W.

Embodiment 2 FIG. 5 shows another embodiment of the present invention. This meander antenna 10 has a dielectric substrate 12
Radiating element consisting of meander-shaped strip conductor on one side
14 is formed, and a metal plate is not provided on the surface opposite to the dielectric substrate 12. Other than that, it is the same as the meandering antenna of FIG. 1, and therefore the same parts are denoted by the same reference numerals and the description thereof is omitted. Even with such a configuration, the band of the antenna can be widened.

Other Embodiments The antenna shown in FIG. 6 is an example in which the present invention is applied to a dual frequency antenna. In this antenna, the conductor pattern is bifurcated in the vicinity of the feeding portion 30, and the first radiating element 14a and the second radiating element 14b are connected in series. Then, a chamfered portion 22 is formed by making a substantially V-shaped cut in the branch portion.

In the above embodiment, the chamfered portion obtained by cutting the corner portion of the strip-shaped conductor, which is most effective, along a straight line.
Although 22 is shown, the chamfered portion may be formed by cutting the outside of the corner portion where the straight line portion intersects with the straight line portion along a curved line such as an arc having a predetermined radius. Further, it is needless to say that the chamfered portion 22 may have a shape in which the conductor is swollen inside the corner portion, that is, a shape in which the chamfered portion is also chamfered inside the corner portion so that the conductor width is maintained. .

[0021]

As described above, according to the present invention,
By providing the chamfered portion on the outer edge of the bent portion of the strip-shaped conductor, it is possible to obtain an antenna with a wider band than in the past.

[Brief description of drawings]

FIG. 1 shows an embodiment of a meander antenna according to the present invention, (A) is a front view, (B) is a side view, and (C) is a rear view.

FIG. 2 is a front view, (B) is a side view, and (C) is a rear view showing a conventional meander antenna.

FIG. 3 is a graph showing the test results of the meander antenna of FIGS. 1 and 2.

FIG. 4A is a graph showing the relationship between the width (size) of the chamfered portion and the bandwidth of the meander antenna according to the present invention,
(B) is an explanatory view showing the definition of the size of the chamfered portion.

FIG. 5 shows another embodiment of a meander antenna according to the present invention, (A) is a front view, (B) is a side view, and (C) is a rear view.

FIG. 6 is a front view showing another embodiment of the present invention.

[Explanation of symbols]

10: Meanda antenna 12: Dielectric substrate 14: Radiating element 16: Metal plate 18: Power supply unit 20: Open end 22: Chamfer 30: Power supply unit

Claims (2)

[Claims] 1. A linear antenna comprising a conductor pattern formed by bending a strip-shaped conductor in the width direction of the strip, wherein a chamfered portion is provided at an outer edge of a bent portion of the strip-shaped conductor. 2. The line according to claim 1, wherein the size of the chamfered portion (the length of one side of the isosceles when chamfered into an isosceles triangle) is 0.7 times or more the conductor width of the strip conductor. Antenna.