JP2005252659A - Monopole antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small monopole antenna that operates in a plurality of frequencies about a monopole antenna used in mobile communication of an automobile or the like. <P>SOLUTION: This monopole antenna 40 is provided integrally with a flat plate-shaped conductor 10 arranged oppositely from a ground conductor 1 with a spaced interval h by concentrically connecting the innermost, intermediate, and outermost conductors 11, 12 and 13 from the inside with connection conductors 31 and 32 between the respective conductors, and has a linear conductor 3 and a short circuit conductor 5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a monopole antenna used for mobile communication such as an automobile.

  2. Description of the Related Art In recent years, mobile vehicles such as automobiles have been used in mobile phones, satellite-based positioning systems called GPS [Global Positioning System], road traffic information systems called VICS [Vehicle Information and Communication System], and toll road automatic toll collection called ETC [Electronic. Services such as the Toll Collection system have been put into practical use.

  In order to cope with these services, there is an increasing demand for antennas for mobile radio apparatuses for in-vehicle use and the like that are compatible with a plurality of operating frequencies for these systems.

  As an example of such a conventional antenna, a monopole antenna corresponding to three operating frequencies will be described with reference to FIG.

  FIG. 7 is a schematic perspective view of a conventional monopole antenna. In this figure, the flat conductors are a concentric circle from the inside on the same plane, a disc conductor 61, an annular conductor 62, and an annular conductor 63 having a maximum diameter d. Formed from.

  Here, the outer edge of the disk conductor 61 is connected to the inner edge of the ring-shaped conductor 62 via the resonance circuit 71, and the outer edge of the ring-shaped conductor 62 is connected to the inner edge of the ring-shaped conductor 63 via the resonance circuit 72. Yes.

  The antenna element 54 is formed by the linear conductor 53, the disk conductor 61, the ring-shaped conductor 62, and the ring-shaped conductor 63.

  The monopole antenna 80 includes an antenna element 54 and a disk-shaped ground conductor 51 having a power feeding portion 52 that supplies power to the disk conductor 61 of the antenna element 54.

  Here, the resonance circuits 71 and 72 are configured to have a predetermined resonance frequency by, for example, a parallel circuit of a coil and a capacitor.

  In the above-described configuration, the antenna element 54 is next supplied with power from the power supply unit 52 to the disk conductor 61 from the highest first frequency f1 to the second highest frequency f2 and the lowest third frequency f3. Behaves like

  First, the operation of the antenna element 54 at the first frequency f1 is that the resonance circuit 71 that resonates at the first frequency f1 has a high impedance with respect to the first frequency f1, and therefore the disk conductor 61 and the ring-shaped conductor. 62 is electrically insulated from the linear conductor 53 to the disk conductor 61.

  Next, at the second and third frequencies f2 and f3 lower than the first frequency f1, the resonance circuit 71 becomes low impedance, and the disk conductor 61 and the ring-shaped conductor 62 become substantially conductive, and the second and third frequencies f1 and f3. The frequencies f2 and f3 are transmitted to the ring-shaped conductor 62.

  The operation of the antenna element 54 at the second frequency f2 is that the resonance circuit 72 that resonates at the second frequency f2 has a high impedance with respect to the second frequency f2. 63 is electrically insulated from the linear conductor 53 to the ring-shaped conductor 62.

  Further, the operation of the antenna element 54 at the third frequency f3 lower than the second frequency f2 is such that the resonance circuit 72 that resonates at the second frequency f2 has a low impedance at the third frequency f3, and the annular conductor 62 The ring-shaped conductor 63 is in a substantially conductive state, and the third frequency f3 is transmitted to the ring-shaped conductor 63, and the linear conductor 53 to the ring-shaped conductor 63 are excited.

  As described above, the monopole antenna 80 operating at three frequencies has been realized.

  Here, in general, the monopole antenna is configured to excite at a quarter wavelength of the operating frequency, and the configuration is the height h of the linear conductor 53 in the case of the third frequency f3. The sum of the ring-shaped conductor 63 and the diameter d (hereinafter referred to as a dimension) was set to be a quarter wavelength of the third frequency f3.

  For example, when the third frequency f3 is 900 MHz, the dimension a is 33 mm, which is 0.10 of h / λ (λ is the wavelength), as shown by the broken line in FIG. The diameter d of the ring-shaped conductor 63 was inevitably 50 mm.

  In other words, the dimension a needs to be about 83 mm, which is a quarter wavelength.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP 2000-059129 A

  As described above, the conventional monopole antenna has a problem that it is difficult to make the dimension a shorter than ¼ wavelength.

  SUMMARY OF THE INVENTION The present invention solves such a conventional problem, and an object thereof is to provide a small monopole antenna that operates at a plurality of frequencies and can make the a dimension shorter than a quarter wavelength. .

  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 a flat conductor formed of an inner conductor and an outer conductor, and the inner conductor and the outer conductor are connected within a predetermined range. By providing, it is possible to obtain a monopole antenna in which the inner conductor operates at the first frequency and the outer conductor operates at the second frequency.

  The invention according to claim 2 is the invention according to claim 1, wherein the sum h + d of the dimension h of the distance between the ground conductor and the flat conductor and the dimension d of the outer conductor's outer shape is given by the operating frequency of the outer conductor. The wavelength is set to ¼ wavelength or less, and has an effect that a small monopole antenna can be obtained.

  The invention according to claim 3 is the invention according to claim 1, in which the inner conductor, the outer conductor, and the connecting conductor of the flat conductor are integrally formed, and has an effect that the manufacture is easy.

  The invention according to claim 4 is the invention according to claim 1, wherein the inner conductor, the outer conductor and the connecting conductor of the flat conductor are formed integrally and on the same plane, and are configured on the same plane. It has the effect of being easy to manufacture.

  According to a fifth aspect of the present invention, in the first aspect of the invention, the ground conductor and the inner conductor are short-circuited, and the short-circuit conductor is juxtaposed with the straight conductor, and the short-circuit conductor and the straight conductor are excited. Therefore, the impedance of the antenna becomes high and the excitation band can be widened.

  As described above, according to the present invention, there is an advantageous effect that a small monopole antenna can be obtained while operating at a plurality of frequencies.

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

(Embodiment)
FIG. 1 is a schematic perspective view showing a monopole antenna according to an embodiment of the present invention. In FIG. 1, 1 is a disk-shaped ground conductor made of a conductive material such as copper, and 10 is a single copper plate or a wiring board. It is a disk-shaped flat conductor formed using copper foil or the like.

  The flat conductor 10 is disposed opposite to the ground conductor 1 with an interval h, and the inner conductor 11, the middle conductor 12, and the outer conductor 13 having the maximum diameter d are integrally formed concentrically from the inside. And in the same plane.

  Here, forming each inner / middle / outer conductor integrally means that the outer edge portion of the inner conductor 11 and the inner edge portion of the inner conductor 12 are formed by the connecting conductor 31 having an angle θ within a predetermined range, and the outer edge of the inner conductor 12. 2 and the inner edge of the outer conductor 13 are connected by connecting conductors 32 having an angle θ.

  In addition, a metal rod-shaped linear conductor 3 such as copper extending from the power feeding portion 2 insulated from the ground conductor 1 and a metal rod-shaped short-circuit conductor 5 connected to the ground conductor 1 are juxtaposed at the approximate center of the inner conductor 11. Connected.

  The antenna element 4 is formed by the straight conductor 3, the short-circuit conductor 5, and the flat conductor 10.

  Further, the monopole antenna 40 is composed of the antenna element 4 and the ground conductor 1.

  In the above configuration, the antenna element 4 transmits the second highest frequency f2 and the lowest third frequency f3 from the highest first frequency f1 to the inner conductor 11 from the power feeding unit 2 via the straight conductor 3. The power supply operates as follows.

  First, the operation of the antenna element 4 at the first frequency f1 is such that the connecting conductor 31 that resonates at the first frequency f1 has a high impedance with respect to the first frequency f1, and therefore the inner conductor 11 and the middle conductor. 12 is electrically insulated, and the straight conductor 3 and the short-circuit conductor 5 to the inner conductor 11 are excited.

  Next, at the second and third frequencies f2 and f3 lower than the first frequency f1, the connecting conductor 31 that resonates at the first frequency f1 has a low impedance, and the inner conductor 11 and the middle conductor 12 are in a substantially conductive state. Thus, the second and third frequencies f 2 and f 3 are transmitted to the middle conductor 12.

  The operation of the antenna element 4 at the second frequency f2 is that the connecting conductor 32 that resonates at the second frequency f2 has a high impedance with respect to the second frequency f2. 13 is electrically insulated, and the straight conductor 3 and the short-circuit conductor 5 to the middle conductor 12 are excited.

  Furthermore, the operation of the antenna element 4 at the third frequency f3 is such that the connecting conductor 32 resonating at the second frequency f2 has a low impedance at the third frequency f3 lower than the second frequency f2, and the middle conductor 12 And the outer conductor 13 become substantially conductive, and the third frequency f3 is transmitted to the outer conductor 13, and the straight conductor 3 and the short-circuit conductor 5 to the outer conductor 13 are excited.

  As described above, the monopole antenna 40 that operates at three frequencies can be realized.

  Next, FIG. 2 is a characteristic diagram showing the relationship between the angle θ of the connecting conductor and the operating frequency. Here, as an example, the angle θ of the connecting conductor 32 connecting the middle conductor 12 and the outer conductor 13 and the second, The characteristics of the third frequency f2 and f3 will be described.

  In the figure, first, when the angle θ of the connecting conductor 32 is 360 °, that is, the middle conductor 12 and the outer conductor 13 are one outer conductor, the operating frequency is naturally one.

  Next, when the angle θ is decreased from 360 °, the operating frequency becomes two when the angle θ is 180 °, the middle conductor 12 has the second frequency f2, and the outer conductor 13 has the third frequency. It operates at the frequency f3.

  Further, when the angle θ is reduced from 180 °, for example, the angle θ1 (about 45 °), the second frequency f2 is 1.9 GHz and the third frequency f3 is 0.9 GHz as two desired operating frequencies. Can be obtained.

  The first and second frequencies f1 and f2 can be obtained as two desired operating frequencies by appropriately selecting the angle θ of the connecting conductor 31 that connects the inner conductor 11 and the middle conductor 12.

  This indicates that by appropriately selecting the angle θ of the connecting conductor, a desired resonance frequency can be obtained by the connecting conductor, and it is possible to cope with an increase in operating frequency to three or more.

  Then, a resonance circuit constituted by a parallel circuit such as a coil and a capacitor, which is conventionally required, can be eliminated.

  Further, as explained in the background art, the conventional monopole antenna has a length (h + d size) that is a quarter wavelength of the operating frequency so that it is excited at a quarter wavelength of the operating frequency. However, in the monopole antenna 40 of the present invention, as shown in FIG. 3, the dimension “a” is set to a length equal to or less than a quarter wavelength of the operating frequency by providing a connecting conductor. it can.

  In FIG. 3, for example, when the third frequency f3 is 900 MHz, as shown by the solid line in FIG. 3, the height h of the straight conductor 3 and the short-circuit conductor 5 is 0 of h / λ (λ is the wavelength). .10, 33 mm, the diameter d of the outer conductor 13 can be 35 mm, and can be 68 mm, which is shorter than about 83 mm, which is a quarter wavelength of a constant value determined by the conventional third frequency f3.

  This is probably because the connecting conductor 32 that connects the middle conductor 12 and the outer conductor 13 contributes to excitation and the like at the second and third frequencies f2 and f3.

  Note that the dimension a (the sum of h and the diameter d of the middle conductor 12) determined by the connecting conductor 31 that connects the inner conductor 11 and the middle conductor 12 is also equal to or less than the length of a quarter wavelength of the second frequency f2. Can be set.

  Thus, according to the present embodiment, the flat conductor 10 is formed from the inner / middle / outer conductors 11, 12, and 13, and the conductors are connected by the predetermined connecting conductors 31 and 32. A monopole antenna 40 that operates at three frequencies can be obtained.

  Further, the dimension a (h + d) when the distance between the ground conductor 1 and the flat conductor 10 is h and the diameter of the outer conductor 13 is d can be made equal to or smaller than a quarter wavelength of the operating frequency of the outer conductor 13. For example, when the third frequency f3 at which the outer conductor 13 operates is 900 MHz, the dimension a is changed from about 83 mm to 68 mm, and the volume is reduced to about 80% to obtain the monopole antenna 40. Can do.

  Furthermore, by forming the flat conductor 10 with the inner, middle and outer conductors 11, 12, 13 and the connecting conductors 31, 32 in one and the same plane, the processing of the flat conductor 10 is simplified. At the same time, it can be manufactured easily.

  Further, since the excitation with the straight conductor 3 can be made in phase by the short-circuit conductor 5 provided further, the excitation can be strengthened and the profile can be lowered, the impedance of the antenna can be increased, and the excitation band can be widened. .

  In the above embodiment, the outer shape of the flat conductor 10 has been described as a disc shape, but the present invention is not limited to this, and for example, the same effect can be obtained even in a polygonal shape such as a square shape as shown in FIG. Can be obtained.

  In particular, when the flat conductor 10 has a quadrangular shape, when using a standard material such as a hoop-shaped copper plate having a certain width dimension or a square-shaped wiring board having a certain dimension, other external shapes (such as a disk shape) ) Can be used more efficiently than

  Moreover, although the space | interval of the ground conductor 1 and the flat conductor 10 was demonstrated as a space | gap, it is not restricted to this, For example, as shown in FIG. 5, the wiring which provided the copper foil on both surfaces of the resin material of phenol or an epoxy You may comprise using the board | substrate 6. FIG.

  In this case, the copper foil on one side of the wiring board 6 is used as the ground conductor 1 and the copper foil on the other side is used as the flat conductor 10, and this copper foil is etched to connect the inner / outer / outer conductors 11, 12, 13 and the connection. The conductors 31 and 32 can be formed integrally and on the same plane, the accuracy of each conductor can be improved, and the antenna characteristics can be stabilized.

  Further, the straight conductor 3 and the short-circuit conductor 5 may be formed by providing a through hole between the copper foils on both sides of the wiring board 6 and filling the through hole with a conductive material.

  Further, when the monopole antenna 40 of the present invention is attached to the inside or outside of the vehicle body, for example, as shown in FIG. 6, a recess is formed in the exterior chassis 111 of the vehicle body to be a ground conductor, and the antenna element 4 is arranged in this recess. Thus, the monopole antenna 40 in which the convex portion formed by the concave portion does not jump out of the interior cover 112 into the vehicle interior can be configured.

  The monopole antenna according to the present invention operates at a plurality of frequencies, and has the effect of making the dimension a shorter than a quarter wavelength of the operating frequency, and is useful for mobile communication such as in-vehicle use.

1 is a schematic perspective view of a monopole antenna according to an embodiment of the present invention. Characteristics chart Other characteristics Plan view according to another embodiment of the same embodiment Plan view of a monopole antenna according to another embodiment of the same embodiment Installation drawing on the vehicle Schematic perspective view of a conventional monopole antenna

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Grounding conductor 2 Feeding part 3 Straight conductor 4 Antenna element 5 Short-circuit conductor 6 Wiring board 10 Flat conductor 11, 12, 13 Conductor 31, 32 Connection conductor

Claims (5)

A ground conductor, a flat conductor disposed opposite to the ground conductor at a predetermined interval, and a linear conductor that feeds the flat conductor,
The flat conductor is formed from an inner conductor and an outer conductor,
A monopole antenna in which a predetermined range between an outer edge portion of the inner conductor and an inner edge portion of the outer conductor is connected by a connecting conductor. The monopole antenna according to claim 1, wherein the sum of the distance between the ground conductor and the flat conductor and the outer dimension of the outer conductor is a dimension equal to or less than ¼ wavelength of the operating frequency of the outer conductor. The monopole antenna according to claim 1, wherein the inner conductor, the outer conductor, and the connecting conductor of the flat conductor are integrally formed. 2. The monopole antenna according to claim 1, wherein the inner conductor, the outer conductor, and the connecting conductor of the flat conductor are integrally formed on the same plane. 2. The monopole antenna according to claim 1, wherein the ground conductor and the inner conductor are short-circuited, and the short-circuit conductor is juxtaposed with the straight conductor.

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