JP2004242297A - Antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a miniaturized antenna by reducing the height of antenna elements in the antenna that is used for mobile radio equipment or the like. <P>SOLUTION: An antenna is configured by providing: a first antenna element 13 of which one terminal 13a is connected to a power feeding point 2 and an intermediate portion 13b extending above a conductor earth plate 1 is bent a plurality of times; and a second antenna element 23 of which one terminal 23a is connected to another terminal 13c of the first antenna element 13, another terminal 23c is connected to a conductor earth plate 1 and an intermediate portion 23b extending above the conductor earth plate 1 is bent a plurality of times. By placing the first antenna element 13 and the second antenna element 23 opposite to each other at a predetermined gap therebetween, the miniaturized antenna of which the height of the antenna elements is reduced is obtained. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to an antenna used for a mobile wireless device such as a vehicle.

  2. Description of the Related Art In recent years, a linear monopole antenna or a folded monopole antenna has been generally used as an antenna of a mobile wireless device such as a vehicle.

  Such a conventional monopole antenna or folded monopole antenna will be described with reference to FIG.

  FIG. 11A is a side view of a conventional monopole antenna. In FIG. 11A, reference numeral 91 denotes a flat conductive ground plate made of copper or the like; 92, a feed point located at the center of the conductive ground plate 91; The antenna element 93 has one end connected to the feed point 92, the other end opened perpendicular to the conductor ground plate 91, and the height h extending to form an antenna. .

  FIG. 11B is a side view of a conventional folded monopole antenna. In FIG. 11B, reference numeral 103 denotes an antenna element such as a linear copper material formed by folding in a U-shape.

  One end of the antenna element 103 is connected to the feeding point 92, the upper end extending vertically to the conductor base plate 91 at a height h is folded in a U-shape, and the other end is connected to the conductor base plate 91 to form an antenna. It is configured.

  In the above configuration, when a high-frequency current having an operating frequency is supplied to the antenna elements 93 and 103 from the feeding point 92 in each of the antennas, the antenna elements 93 and 103 are excited to perform a transmission operation, and in the case of reception, operate. The antenna elements 93 and 103 are excited by the high frequency electromagnetic field of the frequency, and the receiving operation is performed.

  Since the monopole antenna is formed with one end of the antenna element 93 connected to the feeding point 92 and the other end opened perpendicular to the conductor ground plane 91, the current (i1) between a and b An image current (i1) corresponding to the portion between a and b flows through the ground plane 91 in the same phase, and is excited to emit a radio wave into the air.

  On the other hand, in the folded monopole antenna, since the antenna element 103 is formed by folding in a U-shape, in addition to the current (i1) between a and b and the current (i3) between cd and An image current (il, i3) corresponding to between a and b and between cd and flows in the conductor ground plane 91 in the same phase, the impedance of the antenna is increased, and the band can be widened.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP-A-62-122401

  However, in the above-mentioned conventional monopole antenna and folded monopole antenna, since the operation of the antenna is generally operated in a quarter wavelength mode, the mechanical height h is equal to or more than a quarter wavelength of the operating frequency. A height is required. For example, in the case of a 900 MHz band used for a mobile phone, a height of about ４ wavelength and 83 mm or more is required.

  Therefore, when the mechanical height h of the antenna element is made shorter than １ ／ wavelength of the operating frequency to reduce the antenna height in order to reduce the size of the antenna, the impedance of the antenna becomes small and impedance matching becomes difficult. there were.

  Further, when the above-mentioned conventional antenna is installed on a rear tray portion or a dashboard portion in a vehicle, it is preferable to install the antenna elements 93 and 103 upward so as to improve the efficiency of radio wave radiation of the antenna. Preferably, the antenna elements 93 and 103 occupy a large space in the height direction when the antenna is installed upward, so that there is a problem that a mounting place in the vehicle is restricted.

  An object of the present invention is to solve such a conventional problem and to provide a small-sized antenna with a reduced height of an antenna element.

  In order to achieve the above object, the present invention has the following configuration.

  The invention according to claim 1 of the present invention is directed to a flat conductive base plate, a first antenna element having one end connected to a feeding point, and an intermediate portion extending above the conductive base plate turned back plural times, One end is connected to the other end of the first antenna element, the other end is connected to the conductive ground plane, and an intermediate part extending above the conductive ground plane is formed of a second antenna element which is turned back plural times. An antenna in which the first antenna element and the second antenna element are opposed to each other with a predetermined gap therebetween, and an intermediate portion between the first and second antenna elements has a plurality of diffraction turns. Since the antennas are formed facing each other with a predetermined gap therebetween, the impedance of the antenna is increased, impedance matching can be facilitated, and the height of the antenna can be reduced.

  According to a second aspect of the present invention, in the first aspect of the invention, the first antenna element and the second antenna element are arranged symmetrically facing each other on a plane, so that the antenna can be thinned. It has the action of:

  According to a third aspect of the present invention, in the first aspect of the present invention, the other end of the first antenna element and one end of the second antenna element are connected via a conductive plate. Since a capacitance is added to the ground plane to lower the resonance frequency of the antenna, the height of the antenna can be further reduced, and the capacitance can be changed by notching a part of the conductive plate. Has the effect of obtaining the resonance frequency of

  According to a fourth aspect of the present invention, in the first aspect of the present invention, the first and second antenna elements are formed in a plate shape, and the antenna elements can be easily formed by a press method, an etching method, or the like. This has the effect of stabilizing the characteristics of the antenna.

  According to a fifth aspect of the present invention, in the first aspect of the present invention, a base extending above the conductive ground plane is provided, a first antenna element is provided on one surface of the base, and a second antenna is provided on the other surface of the base. The antenna element is disposed, and has an effect that the first and second antenna elements and the base can be integrally formed, and the characteristics of the antenna can be stabilized.

  According to a sixth aspect of the present invention, in the first aspect of the invention, a parasitic antenna element having the same shape as the first or second antenna element is replaced with the first antenna element or the second antenna element. The antenna element is disposed opposite to the antenna with a predetermined gap, one end of the parasitic antenna element is connected to the conductive ground plane, and the other end is opened. It has the effect that the band can be widened.

  As described above, according to the present invention, an advantageous effect that a small antenna can be obtained by reducing the height of the antenna element can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

(Embodiment 1)
The first embodiment of the present invention will be described with reference to the first and third to fifth to fifth embodiments.

  FIG. 1 is a perspective view of an antenna according to a first embodiment of the present invention, and FIG. 2 is a side view of the antenna. In FIG. The ground plane 2 is a power feeding point located substantially at the center of the conductive ground plane 1.

  A linear or plate-like member 13 has one end 13a connected to the feeding point 2 and an intermediate portion 13b extending above the conductor ground plate 1 formed by being folded back multiple times in a substantially U-shape. This is a first antenna element such as a copper material.

  23 is connected to the other end 13c of the first antenna element 13 at one end 23a at the connection point 4, and the intermediate portion 23b is folded back in a substantially U-shape like the intermediate portion 13b. The second antenna 23 is disposed opposite to the back surface of the first antenna element 13 with a predetermined gap therebetween, and the other end 23 c is electrically connected to the conductive ground plane 1. 2 antenna element.

Further, the antenna 3 is configured such that the first antenna element 13 and the second antenna element 23 are symmetrically arranged on the front and back of the base member 7 such as a resin material so as to face each other with a predetermined gap t therebetween.
A specific production and evaluation method when the antenna configured as described above is used in a 900 MHz band of a mobile phone or the like will be described below with reference to the drawings.

  First, a plate-shaped copper plate having a plate thickness of 0.2 mm was press-processed, and two antenna elements 13 and 23 were manufactured in such a manner that the intermediate portion thereof was folded a plurality of times in a substantially U-shape.

  As shown in FIG. 2, the intermediate portion 13b of the first antenna element 13, which has one end 13a soldered to the feeding point 2 and electrically connected thereto, extends above the conductor ground plate 1 to the first bending point 13d. The height h1 of the linear portion is 3 mm of 1/100 wavelength, the U-shaped gap h2 of the intermediate portion 13b, and the conductor width h3 of the copper plate are each 0.4 mm of 1/1000 wavelength.

  Further, one end 23a of the second antenna element 23 is connected to the other end 13c of the first antenna element 13 at the connection point 4, and the symmetrically formed intermediate portion 23b faces the first antenna element 13. And the other end 23c was electrically connected to the conductive ground plane 1 to form the antenna 3.

  The antenna elements 13 and 23 were held opposite to each other on the front and back surfaces of the base 7 using a base 7 having a dielectric constant of about 1.0 and a plate thickness t of 2 mm made of a resin material such as a cuboid foamed polystyrene foam.

  As described above, the respective line lengths, which are the total lengths of the first and second antenna elements 13 and 23 formed by performing a plurality of diffraction turns in a substantially U-shape, are approximately 5/4 operating in the quarter wavelength mode. Since the antenna 3 is formed to have a wavelength length, the antenna 3 can be operated in the quarter wavelength mode.

  In other words, by making the intermediate portions 13b and 23b a plurality of times, the height can be reduced even if the length of each line of the antenna element is increased. The antenna of the present invention has a radiation efficiency from the antenna to the air in comparison with a conventional monopole antenna having a line length of 1/4 wavelength by forming the antenna to a length of approximately 5/4 wavelength which operates in the 4-wavelength mode. Can be reduced without lowering the height.

  In other words, the mechanical height h is required to be 83 mm of 1/4 wavelength in the conventional antenna, but the height h of the antenna of the present invention is reduced to 1/22 by setting the width w to 15 mm of 1/22 wavelength. It is 23 mm with 15 wavelengths.

  3A and 3B are antenna characteristic diagrams showing evaluation results of the antenna manufactured as described above. FIG. 3A is a Smith chart showing impedance at an operating frequency, and FIG. 3B is a band characteristic diagram at an operating frequency. 3A, each point in the Smith chart of FIG. 3A represents the impedance at each operating frequency (B1 is 810 MHz, B2 is 900 MHz, B3 is 960 MHz), and the impedance is shown on the line AA ′. Is that the A side is small, the A 'side is large, and the center position B is impedance matched (in this case, 50Ω is shown).

  Here, from FIG. 3 (a), the impedance of each of the operating frequencies B1, B2, and B3 of the manufactured antenna is located near the center position B, and is determined by selecting a constant of an impedance matching circuit (not shown). This indicates that impedance matching can be easily achieved.

  In FIG. 3B, the horizontal axis is a frequency of 700 MHz to 1100 MHz, and the vertical axis is a VSWR (Voltage standing Wave ratio) indicating a voltage standing wave ratio. 810 MHz, B2 is 900 MHz, and B3 is 960 MHz). A smaller value indicates a smaller loss due to impedance mismatch at the antenna at the operating frequency.

  Here, if the horizontal line indicated by CC ′ in the drawing is a line of VSWR = 3 and VSWR = 3 or less is defined as an operating frequency band in which the antenna can be used, the bandwidth below VSWR = 3 is 192 MHz, This shows that a bandwidth of 150 MHz of B1 (810 MHz) to B3 (960 MHz) required for the 900 MHz band used for the mobile phone can be secured.

  As described above, the antenna elements 13 and 23 are symmetrically arranged opposite to each other with a predetermined gap therebetween above the conductor ground plate 1 to form a rectangular parallelepiped. The product of the dimensions is 0.8 × 10−6 cubic meters (0.8 ml), so that miniaturization and volume reduction can be achieved.

  Further, compared to the conventional monopole antenna and the folded monopole antenna, which have a height of 83 mm, the height of the antenna can be reduced to 23 mm, which is approximately 1/4, so that the antenna 3 can be mounted on the rear tray of the vehicle. Even if it is installed on the dashboard part facing upward to the space for radiating radio waves, the space in the height direction occupied by the antenna elements 13 and 23 can be reduced.

  In the above embodiment, the base 7 is described as a rectangular parallelepiped. However, the present invention is not limited to this. The base 7 may be cylindrical or polygonal as shown in FIG. The same effect can be obtained as long as the two antenna elements 23 face each other and are symmetrical.

  Further, the configuration in which the first antenna element 13 and the second antenna element 23 are arranged on the front and back of the base 7 has been described. However, the present invention is not limited to this. The first antenna element 13 and the second antenna element 23 may be arranged on the mating surface. In the case where the base 7 is a quadrangular prism or more, the first antenna element 13 and the second antenna element 23 The same effect can be obtained by disposing the element 13 and the second antenna element 23.

  As shown in the perspective view of the antenna in FIG. 5, the other end 13c of the first antenna element 13 and one end 23a of the second antenna element 23 are placed at the top of the head via a conductive plate 8 such as a copper material. By connecting, a capacitance is generated between the conductive ground plane 1 and the conductive plate 8, so that the impedance of the antenna at the feeding point 2 can be further increased. For example, in the case of a 900 MHz band used for a mobile phone or the like, Can further reduce the mechanical height h from 23 mm, and reduce the size of the antenna.

  Furthermore, since the capacitance between the conductive ground plate 1 and the conductive ground plate 1 can be changed by cutting out a part 8a of the conductive plate 8, a desired resonance frequency can be easily obtained.

  FIG. 6 is a plan view showing a method of manufacturing the antenna. The first antenna element 13, the second antenna element 23, and the conductive plate 8 are formed by pressing a flat plate made of a plate-like copper material or the like by a pressing method, an etching method, or the like. Are integrally connected to the hoop frame 51 by a connecting margin 51a, and are formed in a plate shape at the same time.

  Then, after the joining margin 51a is cut by a press or the like, the first antenna element 13, the second antenna element 23, and the conductive plate 8 are integrally bent by a press or the like, and are three-dimensionally integrated with a resin or the like. By molding, the antenna as shown in FIG. 5 can be manufactured.

  That is, when the first and second antenna elements are made of a plate-like copper material or the like, the antenna elements can be easily formed by a pressing method, an etching method, or the like, and the characteristics of the antenna can be stabilized.

(Embodiment 2)
The second embodiment of the present invention will be described with reference to the second embodiment.

  FIG. 7 is a side view of an antenna according to a second embodiment of the present invention. In FIG. 7, unlike the first embodiment, a first antenna element 13 such as a linear or plate-like copper material and a Two antenna elements 23 are formed on the same plane on the left and right in line symmetry with respect to the Z-axis to constitute an antenna.

  In the above configuration, in the case of transmission, when a high-frequency signal is fed to the first antenna element 13 and the second antenna element 23 from the feed point 2 at the center of the conductive ground plane 1, the high-frequency current of the first antenna element 13 (I13) and the high-frequency current (i23) of the second antenna element 23 are excited in phase to radiate radio waves into the air. In the case of reception, reception is performed by the reverse operation.

  As described above, according to the present embodiment, the first antenna element 13 and the second antenna element 23 are formed on the same plane in line symmetry on the left and right, so that the antenna characteristics equivalent to those of the first embodiment are obtained. At the same time, it is possible to obtain an antenna in which the antenna element can be thinned and can be mounted on a glass surface of a vehicle.

  Note that the same effect can be obtained by disposing the first antenna element 13 and the second antenna element 23 in a substantially L-shape, a substantially L-shape, or a curved surface.

  Further, in the above description, the first antenna element 13 and the second antenna element 23 are obtained by turning a conductor such as a linear or plate-shaped copper material into a plurality of substantially U-shapes. Even if the first and second antenna elements are formed in a substantially V shape as shown in FIG. 8A, a substantially U shape as shown in FIG. The same effect can be obtained if the high-frequency current is formed by a plurality of diffraction turns and is excited in the same phase.

  Furthermore, the folded shape of the intermediate portion of the first antenna element 13 and the second antenna element 23 is not limited to the same shape. For example, one is formed in a substantially U-shape and the other is formed in a substantially V-shape. Has the same effect.

  Also, the first antenna element 13 and the second antenna element 23 have been described as processing a linear or plate-like copper material or the like, but as shown in FIGS. 5, the first antenna element 13 and the second antenna element 23 may be formed by etching the copper foil of the copper-clad board 6 into a desired shape. good.

  Thus, by forming the first and second antenna elements in a foil shape and forming them by an etching method or the like, it is possible to obtain stable antenna characteristics with little dimensional change.

  Then, as shown in FIG. 9, the same effect can be obtained even if the intermediate portion between the first antenna element 13 and the second antenna element 23 is formed in a lateral direction parallel to the conductor ground plane 1.

  Also, the mechanical height h of the first and second antenna elements 13 and 23 is such that the line length of each antenna element is 5/4 wavelength (that is, not only the height of 1/15 wavelength). The same effect can be obtained by appropriately selecting the gap h2 and the width w, which are the folded shapes of the lengths of the respective line lengths at which the operation of the antenna is in the quarter wavelength mode).

  Further, as shown in FIG. 10, one of the first antenna element 13 and the second antenna element 23, or both opposing surfaces, has one end connected to the conductive ground plane 1 and an intermediate portion connected to the first antenna element. By providing a parasitic antenna element 33 having the same shape as that of the second antenna element 13 or the second antenna element 23 and having the other end opened, a high-frequency current also flows through the antenna element 33 in the same phase to enhance excitation. Thus, the band of the antenna can be further widened.

  INDUSTRIAL APPLICABILITY The antenna according to the present invention can reduce the height of an antenna element and can obtain a small antenna, and is useful for an antenna used in a mobile wireless device such as a vehicle.

1 is a perspective view of an antenna according to a first embodiment of the present invention. Side view Antenna characteristic diagram Perspective view of another embodiment Same perspective view Plan view showing the same manufacturing method example Side view of an antenna according to a second embodiment of the present invention Plan view according to another embodiment Same perspective view Same perspective view Side view of conventional antenna

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Conductive ground plane 2 Feeding point 3 Antenna 4 Connection point 7 Base 8 Conductive plate 13 First antenna element 23 Second antenna element 33 Non-feeding antenna element

Claims (6)

A plate-shaped conductor ground plate, a first antenna element having one end connected to a feeding point, and an intermediate portion extending above the conductor ground plate turned a plurality of times;
One end is connected to the other end of the first antenna element, the other end is connected to the conductor ground plane, and an intermediate part extending above the conductor ground plane is formed by a second antenna element which is turned back plural times. ,
An antenna in which the first antenna element and the second antenna element are opposed to each other with a predetermined gap. The antenna according to claim 1, wherein the first antenna element and the second antenna element are symmetrically arranged on a plane so as to face each other. The antenna according to claim 1, wherein the other end of the first antenna element and one end of the second antenna element are connected via a conductive plate. The antenna according to claim 1, wherein the first and second antenna elements are plate-shaped. Along with providing a base extending above the conductive ground plane,
2. The antenna according to claim 1, wherein a first antenna element is arranged on one surface of the base, and a second antenna element is arranged on the other surface of the base. A parasitic antenna element having the same shape as the first or second antenna element
Along with the first antenna element or the second antenna element being opposed to each other with a predetermined gap therebetween,
2. The antenna according to claim 1, wherein one end of the parasitic antenna element is connected to a conductive ground plane and the other end is open.

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