JPH0697715A - Dual loop antenna - Google Patents

Abstract

PURPOSE:To provide a dual loop antenna containing two loops of the wound antenna lines which can secure the desired characteristic in regard of the directivity, the frequency characteristic, the voltage/stationary wave ratio, etc., and also can be miniaturized. CONSTITUTION:A dual loop antenna contains two loops of the wound antenna lines and is printed on the window glass. Each of both loops 1 and 2 has an isosceles triangle and these triangles are connected together at their optical angle parts opposite to each other. Then a loop back part 10 (20) is formed at the bottom side parts 13 and 14 (23 and 24) of each isosceles triangle. Loop back parts can also be provided at the bottom side part of each isosceles triangle. Then the directivity or the voltage/stationary wave ratio VSWR of the loop antenna is decided so that the antenna characteristic is decided. Thus the non-directivity is secured and the VSWR can be reduced in a wide frequency band. In other words, the wide band characteristic is secured and also the miniaturization of the loop antenna is attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a twin loop antenna which is formed by combining two loop antennas and is particularly suitable for installation in an automobile.

[0002]

2. Description of the Related Art An antenna device is required for transmitting and receiving various broadcasting communication waves of a car telephone or the like in a car. A pole antenna that has been widely used in the past is arranged so as to project from the vehicle body and has a transmission and reception performance. It cannot be said that the characteristics are sufficiently preferable, and in order to improve this point, a loop antenna formed by winding an antenna wire is used as an automobile antenna, and since the loop antenna has directivity, It is difficult to install at the optimum detection angle that is the angle formed by the vehicle body that can efficiently detect radio waves and the plane where the loop antenna is located.To solve this problem, a combination of multiple loop antennas is used. An antenna device for an automobile is known.

For example, the one disclosed in Japanese Patent Application Laid-Open No. 61-128609 is an electrostatic shield case attached to a vehicle body and having an opening formed facing the vehicle body, and a plurality of antenna wire windings. A loop antenna provided in the electrostatic shield case in close proximity to the shield case opening, and each loop forming the loop antenna is fan-shaped and expanded around the side on the shield case opening side. Therefore, regardless of the mounting angle of the electrostatic shield case with respect to the vehicle body, at least one loop of the plurality of loops forming the loop antenna is set to the optimum detection angle of the radio wave induced in the vehicle body by the broadcast wave. As it is located, radio waves can be efficiently detected.

[0004]

However, in the vehicle antenna device using the above-mentioned conventional loop antenna, the directivity, the frequency characteristic, and the voltage standing wave ratio (Voltage) are used.
Standing Wave Ratio; hereinafter referred to as VSWR), the shape of the antenna having desired characteristics,
It was difficult to design the size. For example, with regard to the directivity of the antenna, it is desirable that the antenna is non-directional during normal transmission / reception, particularly during reception, and that it is desirable that the antenna has a wide band characteristic, that is, the VSWR is low in a wide frequency band. There is a problem in that it is difficult to obtain an automobile antenna device having such characteristics, and in particular, it is difficult to have such characteristics and reduce the size.

An object of the present invention is to provide a twin loop antenna comprising two loops formed by winding an antenna wire,
It is an object of the present invention to provide a twin loop antenna which has desired characteristics such as directivity, frequency characteristics, and voltage standing wave ratio, and which can be downsized.

[0006]

In order to achieve the above object, the twin loop antenna of the present invention is a twin loop antenna which is printed on a window glass and is formed by connecting two loops formed by winding antenna wires. , Each of the loops is formed into an isosceles triangle and is connected to each other so as to face each other at the apex angle portions thereof, and a folded portion is formed at the bottom portion of the isosceles triangle. A plurality of antennas may be provided on the bottom side of the antenna, and the characteristics of the twin loop antenna are determined by determining the directivity of the antenna or the voltage standing wave ratio (VSWR). Therefore, the VSWR can be lowered in a wide frequency band, that is, a wide band characteristic can be provided, and miniaturization can be promoted.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, the structure of a twin loop antenna will be described. The twin loop antenna is formed by connecting two loops 1 and 2 formed by winding an antenna wire, and is printed on a window glass of an automobile. Has been installed.

The loop 1 (2) is formed entirely of straight portions, and the hypotenuse portions 11, 12 (21, 22) of equal length to each other.
And an apex angle α consisting of the bases 13, 14 (23, 24) divided at the center, and the apex side ends of the hypotenuses 11, 12 (21, 22) are formed into an isosceles triangle with the base A fold-back portion 10 (20) protruding outward of the isosceles triangle is provided at the central division position of the portions 13, 14 (23, 24), and the fold-back portion 10 (20) is parallel to the leg portions 15, 16 (25, 26) and legs 15, 16 (2
It is formed in a U-shape consisting of the outer end 17 (27) connecting the outer ends of 5, 26) and the distance w (w> 0) between the leg parts 15, 16 (25, 26) and , Leg length 15, 16 (25, 26) Length d
Means that the entire length of the loop 1 (2) is set within a range of a predetermined value, and has the effect of making it omnidirectional.

The loops 1 and 2 are connected on the apex side of the isosceles triangle, and the apex side ends of the hypotenuse parts 11 and 21, 12 and 22 are connected by the short side parts 18 and 19 having the same length, respectively. Edge 18,
The feeding point is provided at the center of 19 and the positive (+) side feeding terminal and the negative (-) side feeding terminal are connected, and the band characteristic fluctuates according to the size of the distance between both feeding points. is there.

The positional relationship between loops 1 and 2 is such that the vertices of the isosceles triangles overlap, that is, the hypotenuse portion 11 of loop 1 and the hypotenuse portion 22 of loop 2, the hypotenuse portion 12 of loop 1 and the hypotenuse portion of loop 2.
21 and 21 are on the same straight line, and the intersections, that is, the vertices of the isosceles triangles of loops 1 and 2 are on the straight line connecting the feeding points A and B. When the vertices of a triangle are separated and a distance is created between them, directivity is generated in a direction parallel to the bases 13, 14 and 23, 24 (usually the front-back direction).

Further, since the target frequency band varies depending on the wire diameter d of the loops 1 and 2, it is possible to easily set the frequency band width that matches the purpose.

If the apex angle α of the loop 1 (2) is reduced, directivity is generated in a direction parallel to the bases 13, 14 (23, 24) (usually the front-back direction), and if it is increased, it becomes omnidirectional. Further, when the apex angle α changes, the gain at each frequency changes, and the VSWR at each frequency also changes.

Further, the omnidirectional gain at each frequency changes depending on the length of the one-side loop total length L, which is the total distance of the center line of the loop 1 (2) from the feeding point A to the feeding point B, and is most necessary. It is possible to set a target frequency that is a high frequency.

In the comparative example shown in FIG. 2, two loops a and b formed by winding an antenna wire to form an isosceles triangle are connected at the apex side of the isosceles triangle, and the hypotenuse parts a1 and a are formed.
2, b1 and b2 apex side ends are connected by short side parts c and d having the same length, and a feeding point is provided at the center of each of the short side parts c and d to form a positive (+) side feeding terminal. The negative (−) side power supply terminal is connected, and the expansion side ends of the hypotenuse parts a1 and a2 and b1 and b2 are connected by the bottom parts a3 and b3.

The above-described embodiment of the present invention in which the bottom portion 13, 14 (23, 24) of the isosceles triangle is provided with the folded portion 10 (20) and the bottom portion of the isosceles triangle of the loop is provided with the folded portion. Compared with the above comparative example which is not
The directivity in Z, that is, the gain in each direction is shown in Fig. 9
The directivity at 20 MHz is shown, and the example shows curve I.
The comparative example is shown by the curve II, and obviously the example (curve I) has no directivity, that is, the gain in each direction is higher.

Further, in FIG. 5, the horizontal axis represents frequency and the vertical axis represents the difference between the average gain and the minimum gain. The example is shown by curve III, and the comparative example is shown by curve IV. The difference between the average gain and the minimum gain over the curve III
It is shown that (Example) is lower than the curve IV (Comparative Example), and since the difference between the average gain and the minimum gain is closer to zero, a stable antenna gain can be obtained. The example shows that the VSWR becomes low in a wide frequency band, that is, a wide band characteristic can be provided.

In the above-mentioned embodiment, the folded portion provided at the bottom portion is located on the opposite side, that is, on the outer side of the apex of the isosceles triangle. The same effect can be obtained, and the antenna device can be further downsized.

Further, by providing a plurality of folded portions on the bottom portion of the isosceles triangle of the loop on one side, miniaturization of the antenna device can be promoted. Further, the folded portion may be formed in a lateral V-shape instead of the U-shape,
It is also possible to make them vertically asymmetric.

[0019]

Since the present invention is constructed as described above, it has the following effects. A twin loop antenna having two loops formed by winding antenna wires, in which a folded portion is formed at the bottom of an isosceles triangle, and a plurality of folded portions are provided at the bottom of the isosceles triangle of one loop. The directivity of the antenna and the VSWR are determined to determine the characteristics of the twin loop antenna, and the directivity can be made omnidirectional.
The VSWR can be lowered in a wide frequency band, that is, a wide band characteristic can be provided, and miniaturization can be promoted.

[Brief description of drawings]

FIG. 1 is a schematic plan view of a twin loop antenna that is an embodiment of the present invention.

FIG. 2 is a schematic plan view of a twin loop antenna of a comparative example having no folded portion.

FIG. 3 is a characteristic diagram in each azimuth of the example and the comparative example (frequency 880 MHz).

FIG. 4 is a characteristic diagram (frequency 920 MHZ) in each direction of the example and the comparative example.

FIG. 5 is a characteristic diagram at each frequency of the example and the comparative example.

[Explanation of symbols]

 1, 2 (one side) loop 11, 12, 21, 22 hypotenuse part 13, 14, 23, 24 bottom part 10, 20 folded part α vertex angle

Claims (2)

[Claims] 1. A twin-loop antenna comprising two loops formed by winding an antenna wire, each loop being formed into an isosceles triangle and facing each other at their apex angles to connect the two isosceles sides. A twin-loop antenna characterized in that a folded portion is formed at the base of a triangle. 2. The twin loop antenna according to claim 1, wherein each loop forming the twin loop antenna has a plurality of folded portions formed on a base portion of an isosceles triangle.