JP2006186549A - Antenna with trapezoidal element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that it is difficult to satisfy a bandwidth by one element because the bandwidth of the element is narrow in the case of using a dipole antenna for receiving terrestrial digital broadcasting and employing the dipole antenna mounted on an automobile as an antenna for receiving the terrestrial digital broadcasting. <P>SOLUTION: An antenna 1 employing trapezoidal elements includes: the trapezoidal elements (2, 3); a feeding point 5; and a passive element 4. The trapezoidal elements 2 and 3 are symmetrical around a center axis passing through the feeding point 5, each width of the trapezoidal elements is H1, the length of the long side including the feeding point is L1, and the length of the short side is L1. Further, the passive element 4 is a conductor plate, not connected to the feeding point 5, the length is L3, the width is H3, and located apart from the trapezoidal elements (2, 3) by H2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an in-vehicle trapezoidal element antenna, and more particularly to a trapezoidal element antenna for a vehicle capable of receiving terrestrial digital broadcasting.

  FIG. 7 is a structural diagram of a dipole antenna in a conventional configuration. If the element length on one side of the dipole antenna is λ / 4, the total length of the element is λ / 2. In general, a λ / 2 dipole antenna is also called a half-wave dipole antenna. At this time, the antenna gain is 2.15 dBi.

  FIG. 8 is a characteristic diagram of a radiation pattern of a dipole antenna in a conventional configuration. The antenna pattern cut in the XY plane has a peak in the direction perpendicular to the dipole and becomes a radiation pattern such as “8” as shown in the figure.

  FIG. 9 is a characteristic diagram showing the return loss of the dipole antenna in the conventional configuration. According to the law of power conservation, the return loss measured electrically indicates the electromagnetic wave radiated to the space. Therefore, assuming that the resonance frequency of the radiated electromagnetic wave is 600 MHz and the target value of return loss is −10 dB, the bandwidth is 550 MHz to It becomes 650 MHz. However, in this state, sufficient characteristics cannot be expected for receiving terrestrial digital broadcasts having a bandwidth of 473 MHz to 701 MHz.

  Also, when a dipole antenna is used for terrestrial digital broadcast reception, and the antenna is mounted on an automobile and the dipole antenna is used as an antenna for terrestrial digital broadcast reception, the bandwidth is narrow, so the bandwidth is reduced with one element. Difficult to meet. For example, the bandwidth of the dipole is 17% with respect to the target bandwidth of 40% of the antenna, and the request cannot be satisfied.

  Thus, as disclosed in Patent Document 1, a technique for widening the bandwidth by flattening the element portion of the dipole antenna has been disclosed.

JP 2003-51708 A

  In order to widen the bandwidth, the total length can be shortened when compared with a dipole antenna when the dipole antenna is studied using the technique shown in Patent Document 1, but the length of the element portion is reduced. Increase in size. If this size is considered for mounting on a car, there is a problem that the mountable range becomes narrow and mounting is difficult.

  In order to solve the problems as described above, a trapezoidal element antenna according to the present invention is a trapezoidal element antenna for vehicle use, and a trapezoidal conductor formed by opposing long sides and short sides, and A planar dipole antenna having a feeding point that feeds the trapezoidal conductors arranged side by side, and a parasitic element arranged on the short side of the trapezoidal conductor.

  In the trapezoidal element antenna according to the present invention, the parasitic element is a narrow rectangle or trapezoid.

  The trapezoidal element antenna according to the present invention is an in-vehicle trapezoidal element antenna, a trapezoidal conductor formed of corresponding long sides and short sides, a trapezoidal feeding point, and a feeding point connected to the ground. , And a parasitic element disposed on the short side of the trapezoidal conductor and having one end connected to the ground.

  When a dipole antenna is used for terrestrial digital broadcast reception (bandwidth: 473 MHz to 701 MHz), the target bandwidth has not been achieved. However, by using a trapezoidal element antenna according to the present invention, There is an effect that the bandwidth can be increased and the target bandwidth can be satisfied.

  In addition, the element size can be reduced as compared with a dipole antenna that is planarized by using a parasitic element to reduce the size of the element portion.

  Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

  FIG. 1 is a pattern diagram of a trapezoidal element antenna according to the first embodiment of the present invention. The trapezoidal element antenna 1 includes a trapezoidal element (2, 3), a feeding point 5, and a parasitic element 4. The trapezoidal element 2 and the trapezoidal element 3 are symmetrical with respect to the feeding point 5 as a central axis.

  The width of the trapezoidal elements 2 and 3 is H1, including the feeding point, the long side length is L1, and the short side length is L2. Furthermore, these elements 2 and 3 are formed of a conductive plate. The parasitic element 4 has a length L3 and a width H3, and is disposed away from the trapezoidal element (2, 3) by H2. The parasitic element 4 is a narrow rectangular conductive plate and is not connected to the feeding point 5.

  FIG. 2 is a characteristic diagram showing an example of return loss 2 resonance in the first embodiment according to the present invention. There are resonance frequencies f1 and f2 within the target value of return loss, the resonance frequency f1 is experimentally determined by the relationship of λ / 2 = (L1 + L2) / 2, and the bandwidth at the target value of return loss is determined by H1. In this way, the shape of the trapezoidal element can be determined.

  Further, the resonance frequency f2 is experimentally determined by λ / 2 = L3 and H2, the bandwidth is determined by H3, and the element size of the trapezoidal element antenna is determined.

  The operation will be described. First, a current flows from the feed point 5 to the trapezoidal elements 2 and 3 which are feed elements, and resonates with respect to the resonance frequency f1. Next, a current is induced in the parasitic element 4 from the short side of the trapezoidal elements 2 and 3 that are feeding elements, and resonates at the resonance frequency f2. And each resonance overlaps and the broadband is realized.

  FIG. 3 is a comparison diagram of the element sizes of the planar dipole antenna 10 in the reference configuration and the trapezoidal element antenna 1 in the first embodiment. In order to reduce the size of the rectangular elements (6, 7) of the planar dipole antenna 10 on the left side of FIG. 3, a capacitor is formed by opening a gap between the trapezoidal elements 2, 3 on the right side of FIG. The antenna length was shortened.

  FIG. 4 is a characteristic diagram showing changes in return loss due to a dipole antenna and a trapezoidal antenna having a conventional configuration. According to the experiments shown in FIGS. 3 and 4, when the width H4 of the planar dipole antenna 10 is 1, the width H5 of the trapezoidal element antenna 1 is 0.6, and a 40% reduction in size can be realized. It has been confirmed. In general, when the parasitic element 4 is disposed in the vicinity of a rod-shaped dipole antenna, two resonance frequencies can be obtained, but a bandwidth at a target return loss cannot be obtained. Therefore, the result was obtained that the bandwidth can be covered by making the rod-shaped feeding element planar.

  Furthermore, the trapezoidal element antenna 1 of the present embodiment is 45% of the target bandwidth of 40% by making the shape of the planar element trapezoidal in order to suppress the decrease in bandwidth even if the element size is reduced. % Bandwidth could be obtained.

  It should be noted that a person skilled in the art can suitably adjust the frequency ratio and the bandwidth suitable for the conditions by changing the dimensional ratio of L1 to H3 in the present embodiment.

  Further, the material of the element is flexible, and it is preferable to use a conductive material, for example, conductive rubber, conductive paint, etc., and it can also be realized by a method of forming a conductive pattern on an insulating film. Furthermore, even if the material of the element is not a plate shape but a net shape, it is possible to suitably obtain the same performance as the current state.

  FIG. 5 is a pattern diagram of the trapezoidal element antenna 1 according to the second embodiment of the present invention. By making the parasitic element 9 a trapezoid instead of a narrow rectangle, the bandwidth can be made wider. However, since the width (H3) tends to increase, it is necessary to consider the trade-off between downsizing and widebanding related to mountability in vehicles.

  FIG. 6 is a pattern diagram of the monopole trapezoidal antenna 8 according to the third embodiment of the present invention. By making the trapezoidal element 3 into a monopole shape and connecting one end of the parasitic element 4 to the ground, the same performance can be obtained, and further miniaturization becomes possible.

  As described above, when the present invention is used, it is needless to say that not only terrestrial digital TV reception but also AM, FM radio, cellular phone, SDARS, ETC, etc. can be supported.

  According to the embodiment of the present invention, the trapezoidal element and the parasitic element 4 are trapezoidal so that the bandwidth can be increased, and the target bandwidth for terrestrial digital broadcast reception (bandwidth: 473 MHz to 701 MHz) can be satisfied. There is an effect that can be done.

It is a pattern diagram of the trapezoidal element antenna in the first embodiment according to the present invention. It is a characteristic figure showing an example of return loss 2 resonance in a 1st embodiment concerning the present invention. It is a comparison figure of the element size of the planar dipole antenna in a reference composition, and the trapezoidal element antenna in a 1st embodiment. It is the characteristic view which showed the change of the return loss by the dipole antenna and trapezoid antenna of a conventional structure. It is a pattern diagram of the trapezoidal element antenna in the second embodiment according to the present invention. It is a pattern diagram of the trapezoidal element antenna in the third embodiment according to the present invention. It is a structural diagram of a dipole antenna in a conventional configuration. It is a characteristic view of the radiation pattern of the dipole antenna in a conventional structure. It is the characteristic figure which showed the return loss of the dipole antenna in a conventional structure.

Explanation of symbols

  1 trapezoidal element antenna, 2,3 trapezoidal element, 4,9 parasitic element, 5 feeding point, 8 monopole trapezoidal antenna, 10 planar dipole antenna.

Claims (3)

A trapezoidal element antenna for in-vehicle use,
A planar dipole antenna having a trapezoidal conductor formed by opposing long sides and short sides, and a feeding point that feeds the trapezoidal conductors arranged side by side;
A parasitic element disposed on the short side of the trapezoidal conductor;
A trapezoidal element antenna comprising: The trapezoidal element antenna according to claim 1,
The parasitic element is a trapezoidal element antenna having a narrow rectangular or trapezoidal shape. A trapezoidal element antenna for in-vehicle use,
A planar monopole antenna having a trapezoidal conductor formed of corresponding long sides and short sides, a trapezoidal feed point and a feed point connected to the ground;
A parasitic element disposed on the short side of the trapezoidal conductor and having one end connected to the ground,
A trapezoidal element antenna comprising:

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