JP4223448B2 - antenna - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a horizontal omnidirectional antenna that can be used for mobile communication devices, small information terminals, and other wireless devices, and more particularly to a horizontal omnidirectional antenna that achieves a wider bandwidth and is smaller and lighter. .

Monopole antennas and discone antennas are known as omnidirectional antennas in a horizontal plane composed of a ground plane and a radiating element. For example, FIG. 20 shows a configuration of a conventional monopole antenna. In FIG. 20, reference numeral 101 denotes a disk-shaped conductor, and a coaxial connector 102 is attached to the disk-shaped conductor 101 from below, and a central conductor that extends upward from the coaxial connector 102 and penetrates the disk-shaped conductor 101. 103 is insulated from the disk-shaped conductor 101. The length h of the radiation element 103 of the monopole antenna needs to be about ¼ of the wavelength of the electromagnetic wave having the lowest resonance frequency. At this time, the detailed dimensions of the radiating element are determined depending on the impedance characteristics.
FIG. 21 shows a configuration of a conventional discone antenna. The discone antenna has a structure 104 in which the shape of the central conductor 103 of the monopole antenna is an inverted conical shape, and this shape can also be considered as one of the biconical antennas having a disk shape. An ideal discone antenna has an infinite size and is not frequency dependent, but with a discone antenna with a finite size, the upper limit of the operating wavelength is limited to about four times the length h of the radiating element. Is done. An example in which a broad band is achieved in the omnidirectional antenna in the horizontal plane constituted by the ground plane and the radiating element as described above will be shown below.

FIG. 22 shows an antenna disclosed in Patent Document 1, for example. The antenna includes a skirt portion 110 in which spiral conductive elements 112 a and 112 b are formed along the circumferential surface of the conical base 111, and a meander on the plane of a circular flat base body 121 disposed near the top of the skirt portion 110. And a top load portion 120 on which a conductive element 122 is formed. In the antenna, the band is widened based on the reason that the meandering conductive element 122 formed on the planar substrate 121 has a relatively wide band shape, and can have multiple resonances due to the presence of a plurality of meander lines. Is planned.
In addition, the spiral conductive elements 112a and 112b formed in the skirt portion can realize an electrical length longer than the apparent length, and thus can be formed smaller than a conventional discone antenna. However, in the antenna, it is necessary to form a meander-like or spiral conductor pattern on the substrate, and the conductor pattern needs to be densified as the bandwidth becomes wider, so the structure becomes complicated.
FIG. 23 shows an antenna disclosed in Patent Document 2, for example. The antenna is composed of a conductor 142 whose outer peripheral surface of the radiating element is a semi-elliptical rotor and a flat ground plane 143. In the antenna, the radiating element 142 is formed in a semi-elliptical rotator shape or a hemispherical shape, thereby reducing the size and increasing the bandwidth. However, in such an antenna using a flat ground plane, the dimensional element of the radiating element is dominant in the usable frequency band, so that the antenna is not enlarged in order to be usable at a lower frequency. must not.
JP 09-083238 A JP 09-153727 A

In the conventional monopole antenna and discone antenna, the antenna structure becomes complicated when attempting to increase the bandwidth, and the antenna must be enlarged in order to be usable in a lower frequency band.
The present invention has been made in view of the above points, and it is intended to provide a small and lightweight antenna device having a simple structure, capable of transmitting and receiving in a wide band, usable in a lower frequency band, and the like. It is aimed.
Specifically, it is an object of the invention of claim 1 to reduce the size of the antenna by widening the usable frequency band of the antenna to the low frequency side.
Further, in the invention of claim 2, as well as low profile of the antenna radiating element, and its object is the frequency band available antennas by broadened to the low frequency side to allow miniaturization of the antenna.
Furthermore, an object of the invention of claim 3 is to further reduce the position of the radiating element in the antenna of claim 2 and to reduce the size of an information communication device equipped with the antenna.
According to a fourth or fifth aspect of the present invention, the antenna according to any one of the first to fourth aspects is intended to reduce the weight of the antenna.

In order to solve the above problems, a first aspect of the present invention, a conductor surface comprising a ground plane, an antenna composed of the radiating element, the radiating elements are opposed to the top to the conductor surface A cone-shaped portion having a half apex angle θ1, and a truncated cone-shaped portion having a side surface with an angle of θ2 with the central axis of the cone-shaped portion from a predetermined height of the cone-shaped portion. There, the relationship between the angle .theta.1 and .theta.2 is the antenna Do that the .theta.1> .theta.2, the most important feature frustoconical portion antennas where the structure joining the bottom surface of the hemispherical portion in the bottom surface of the radiating element.
The invention described in 請 Motomeko 2, in the antenna according to claim 1 Symbol placement, wherein the conductive surface has a center and the conical recess the top of the conical portion of the radiating element .
According to a third aspect of the invention, in the antenna according to claim 2 Symbol mounting, wherein the depth of the conical recess is high and comparable the radiating element.
The invention according to claim 4 is the antenna according to any one of claims 1 to 3 , wherein the conductor surface or the radiating element has a structure in which a conductive metal film is formed on an outer peripheral surface of a dielectric. It is characterized by.
The invention according to claim 5 is the antenna according to any one of claims 1 to 4 , wherein the conductor surface or the radiating element has a structure in which a conductive metal film is formed on an outer peripheral surface of a dielectric, The dielectric structure is hollow.

According to the first aspect of the present invention, in the antenna constituted by the conductor surface serving as the ground plane and the radiating element, the radiating element has a conical portion having a half apex angle θ1 with the apex facing the conductor surface. And a shape having a truncated cone-shaped portion having a side surface with an angle of θ2 with respect to the central axis of the cone-shaped portion from a predetermined height of the cone-shaped portion, and the relationship between the angles θ1 and θ2 is θ1 > Θ2, and the bottom surface of the frustoconical portion of the radiating element is joined to the bottom surface of the hemispherical portion, so that the usable frequency band can be widened to the low frequency side and the antenna can be downsized. It becomes.
According to the invention 請 Motomeko 2 wherein, by the conductor surface has centered the conical recess the top of the conical portion of the radiating element, a portion of the radiating element protrudes from the base plate low In addition to the attitude, the usable frequency band is widened to the low frequency side, and the antenna can be downsized.
According to the third aspect of the present invention, in the antenna he is according to claim 2 Symbol placement, by the height about the same radiating element the depth of the conical recess, eliminating projections radiating element to the ground plane on The usable frequency band can be widened to the lower frequency side.
According to the invention described in claim 4, in the antenna according to any one of claims 1 to 3, the structure of the ground plane or the radiating element is a structure in which a conductive metal film is formed on the outer peripheral surface of the dielectric. Thus, the weight of the antenna can be reduced.
According to a fifth aspect of the present invention, in the antenna according to any one of the first to fourth aspects, the structure of the ground plane or the radiating element is a structure in which a conductive metal film is formed on the outer peripheral surface of the dielectric, By making the body structure hollow, the weight of the antenna can be reduced.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a configuration diagram of an antenna according to an embodiment of the present invention. This antenna is an antenna composed of a conductor surface serving as a ground plane 1 and a radiating element 3 that is electrically connected to a coaxial line 2. The radiating element 3 has a conical shape with a half apex angle θ 1 with the top facing the conductor surface 1. A portion 3a, and a shape having a truncated cone shape portion 3b having a side face with an angle θ2 with respect to the central axis of the cone shape portion 3a from a predetermined height position (upper bottom surface) of the cone shape portion, The relationship between the angles θ1 and θ2 is θ1> θ2.
FIG. 2 is a graph showing the correlation between θ1-θ2 and F-Fdc of the antenna of FIG. The vertical axis represents frequency deviation (F-Fdc), and the horizontal axis represents antenna angle (θ1-θ2). Note that F is a lower limit frequency of the operating band of the antenna (a band where the return loss is −10 dB or less), and Fdc is a lower limit frequency of the discone antenna in which the maximum diameter of the radiating element is equal to that of the antenna.
As is apparent from this figure, it can be seen that the frequency deviation increases in the region of θ1 <θ2, decreases from 0 to θ2 at the boundary, and has the minimum frequency deviation in the region of θ1> θ2.
FIG. 3 is a graph showing a correlation between D / H of the antenna of FIG. 1 and (θ1−θ2) max. The vertical axis represents the Max value of θ1-θ2, and the horizontal axis represents the ratio D / H between the width D and the height H of the antenna. As is clear from this figure, it is understood that D / H and (θ1−θ2) max have a positive correlation.

FIG. 4 is a cross-sectional view showing the configuration of the antenna according to Embodiment 1 of the present invention. The antenna according to this embodiment is fed by a coaxial line 2 and includes a ground plane 1 having a diameter of 24 mm and a radiating element 3 having a height of 15 mm. The radiating element 3 has a conical shape portion 3a having a half apex angle θ1 = 22 ° with the top portion facing the top surface of the ground plane, and further has a conical shape from the upper end portion (position of height 9 mm) of the conical shape portion 3a. This is a shape in which a truncated cone-shaped portion 3b having a side surface with an angle θ2 formed with the central axis of the portion 3a is continuously formed. Angle θ1 and θ2 is, Ru Tei has a relationship of θ1> θ2. The ground plane 1 and the radiating element 3 are mainly composed of a good conductor such as copper. Since the angle θ2 = 0 °, the truncated cone shape portion 3b is a cylindrical shape portion.
The operation of the antenna having such a configuration will be described. FIG. 5 shows the return loss vs. frequency characteristics of the antenna of this embodiment with a solid line. For comparison, the return loss vs. frequency characteristics of a conventional discone antenna whose maximum diameter and height of the radiating element are equal to the present antenna are also shown by broken lines. The lower limit frequency at which the return loss is -10 dB or less is 10.8 GHz in the case of the conventional discone antenna, but is reduced to 9.4 GHz in the case of this antenna.
As is apparent from this embodiment, by applying the present invention, the usable frequency band can be widened to the low frequency side, so that the antenna can be downsized.

FIG. 6 is a cross-sectional view showing a configuration of an antenna according to Embodiment 2 of the present invention. The antenna of the present embodiment is fed by a coaxial line, and includes a ground plane 1 having a diameter of 24 mm and a radiating element 3 having a height of 15 mm. The radiating element 3 has a configuration in which the bottom surface of the hemispherical portion 3d having a diameter of 9.6 mm is joined to the bottom surface (upper surface in the drawing) of the conical portion 3c having a half apex angle of 22 °. The ground plane and the radiating element are made of copper as a main material.
The operation of the antenna having such a configuration will be described. FIG. 7 shows the return loss vs. frequency characteristics of the antenna of this embodiment with a solid line. For comparison, the return loss vs. frequency characteristics of a conventional discone antenna whose maximum diameter and height of the radiating element are equal to the present antenna are also shown by broken lines. The lower limit frequency at which the return loss is -10 dB or less is 10.4 GHz in the case of the conventional discone antenna, but is reduced to 9.9 GHz in the case of this antenna.
As is apparent from this embodiment, by applying the present invention, the usable frequency band can be widened to the low frequency side, so that the antenna can be downsized.

FIG. 8 is a cross-sectional view showing a configuration of an antenna according to Embodiment 3 of the present invention. The antenna according to this embodiment is fed by a coaxial line 2 and includes a ground plane 1 having a diameter of 24 mm and a radiating element 3 having a height of 15 mm. The radiating element 3 has a cone-shaped portion 3e having a half apex angle θ1 = 22 ° with the top facing the surface of the ground plane 1, and further has a conical shape from the upper end (position of height 7 mm) of the cone-shaped portion 3e. It has a configuration in which a frustoconical portion (that is, a columnar portion) 3f having a side surface with an angle of θ2 = 0 ° with the central axis of the portion 3e is provided, and the bottom surface of the hemispherical portion 3g is joined to the upper bottom surface thereof. The ground plane 1 and the radiating element 3 are made of a copper film formed on the outer peripheral surface of the dielectric, and are lighter than when the entire antenna is made of copper.
The operation of the antenna having such a configuration will be described. FIG. 9 shows the return loss vs. frequency characteristics of the antenna of this embodiment with a solid line. For comparison, the return loss vs. frequency characteristics of a conventional discone antenna whose maximum diameter and height of the radiating element are equal to the present antenna are also shown by broken lines. The lower limit frequency at which the return loss is -10 dB or less is 11.2 GHz in the case of the conventional discone antenna, but is reduced to 9.8 GHz in the case of this antenna.
As is apparent from this embodiment, by applying the present invention, the usable frequency band can be widened to the low frequency side, so that the antenna can be downsized.

FIG. 10 is a cross-sectional view showing a configuration of an antenna according to Embodiment 4 of the present invention. The antenna according to this embodiment is fed by a coaxial line 2 and includes a ground plane 1 having a diameter of 24 mm and a radiating element 3 having a height of 15 mm. The radiating element 3 has a conical shape with a half apex angle of 22 ° with the top facing the surface of the ground plane 1. The ground plane 1 has a conical depression 1a centered on the top of the radiating element. Therefore, the portion where the radiating element 3 protrudes from the ground plane 1 is lowered. The depth of the recess 1a is 4.5 mm, and the angle formed by the inclined surface of the recess 1a with the horizontal direction is 28 °. The ground plane 1 and the radiating element 3 are made of a copper film formed on the outer peripheral surface of a hollow dielectric, and are lighter than when the entire antenna is made of copper.
The operation of the antenna having such a configuration will be described. FIG. 11 shows the return loss vs. frequency characteristics of the antenna of this embodiment with a solid line. For comparison, the return loss vs. frequency characteristics of a conventional discone antenna in which the shape of the radiating element is the same as that of the present antenna and the ground plane is a flat plate are also shown by broken lines. The lower limit frequency at which the return loss is -10 dB or less is 9.7 GHz in the case of the conventional discone antenna, but is reduced to 8.7 GHz in the case of this antenna.
As is apparent from this embodiment, by applying the present invention, the portion where the radiating element protrudes from the ground plane can be lowered, and the usable frequency band can be widened to the low frequency side. Can be miniaturized.

FIG. 12 is a cross-sectional view showing a configuration of an antenna according to Embodiment 5 of the present invention. The antenna according to this embodiment is fed by a coaxial line 2 and includes a ground plane 1 having a diameter of 24 mm and a radiating element 3 having a height of 15 mm. The radiating element 3 has the same shape as the radiating element of the antenna shown in the first embodiment. The ground plane 1 has a conical depression 1a centered on the top of the radiating element. Therefore, the portion where the radiating element protrudes from the ground plane is lowered. The depth of the recess 1a is 4.5 mm, and the angle formed by the slope of the recess with the horizontal direction is 28 °. The ground plane and the radiating element are made of copper as a main material.
The operation of the antenna having such a configuration will be described. FIG. 13 shows the return loss vs. frequency characteristics of the antenna of this embodiment with a solid line. For comparison, the return loss versus frequency characteristics of a conventional discone antenna in which the maximum diameter and height of the radiating element are equal to those of the present antenna and the ground plane is flat are also shown by broken lines. The lower limit frequency at which the return loss is -10 dB or less is 10.8 GHz in the case of the conventional discone antenna, but is reduced to 8.4 GHz in the case of this antenna.
As is apparent from this embodiment, by applying the present invention, the portion where the radiating element protrudes from the ground plane can be lowered, and the usable frequency band can be widened to the low frequency side. Can be miniaturized.

FIG. 14 is a cross-sectional view showing a configuration of an antenna according to Embodiment 6 of the present invention. The antenna according to this embodiment is fed by a coaxial line 2 and includes a ground plane 1 having a diameter of 24 mm and a radiating element 3 having a height of 15 mm. The radiating element 3 has the same shape as the radiating element of the antenna shown in the second embodiment. The ground plane 1 has a conical depression 1 a centered on the top of the radiating element 3. Therefore, the part where the radiating element protrudes from the ground plane is lowered. The depth of the recess is 4.5 mm, and the angle between the slope of the recess and the horizontal direction is 28 °. The ground plane and the radiating element are made of copper as a main material.
The operation of the antenna having such a configuration will be described. FIG. 15 shows the return loss vs. frequency characteristics of the antenna of this embodiment with a solid line. For comparison, the return loss versus frequency characteristics of a conventional discone antenna in which the maximum diameter and height of the radiating element are equal to those of the present antenna and the ground plane is flat are also shown by broken lines. The lower limit frequency at which the return loss is -10 dB or less is 10.4 GHz in the case of the conventional discone antenna, but is reduced to 9.0 GHz in the case of this antenna.
As is apparent from this embodiment, by applying the present invention, the portion where the radiating element protrudes from the ground plane can be lowered, and the usable frequency band can be widened to the low frequency side. Can be miniaturized.

FIG. 16 is a cross-sectional view showing a configuration of an antenna according to Embodiment 7 of the present invention. The antenna according to this embodiment is fed by a coaxial line 2 and includes a ground plane 1 having a diameter of 24 mm and a radiating element 3 having a height of 15 mm. The radiating element 3 has the same shape as the radiating element of the antenna shown in the third embodiment. The ground plane 1 has a conical depression 1 a centered on the top of the radiating element 3. Therefore, the portion where the radiating element protrudes from the ground plane is lowered. The depth of the recess is 4.5 mm, and the angle between the slope of the recess and the horizontal direction is 28 °. The ground plane and the radiating element are made of copper as a main material.
The operation of the antenna having such a configuration will be described. FIG. 17 shows the return loss vs. frequency characteristics of the antenna of this embodiment with a solid line. For comparison, the return loss versus frequency characteristics of a conventional discone antenna in which the maximum diameter and height of the radiating element are equal to those of the present antenna and the ground plane is flat are also shown by broken lines. The lower limit frequency at which the return loss is -10 dB or less is 11.2 GHz in the case of the conventional discone antenna, but is reduced to 8.8 GHz in the case of this antenna.
As is clear from this embodiment, by applying the present invention, the portion where the radiating element protrudes from the ground plane can be lowered, and the usable frequency band can be widened to the low frequency side. Can be miniaturized.

FIG. 18 is a cross-sectional view showing a configuration of an antenna according to Embodiment 8 of the present invention. The antenna of the present embodiment is fed by a coaxial line 2 and includes a ground plane 1 having a diameter of 42 mm and a radiating element 3 having a height of 15 mm. The radiating element 3 has the same shape as the radiating element 3 of the antenna shown in the first embodiment. The ground plane 1 has a conical recess 1a centered on the top of the radiating element 3, the depth of the recess is 15 mm, and the angle between the inclined surface of the recess and the horizontal direction is 40 °. In the antenna of this embodiment, since the height of the radiating element is equal to the depth of the conical depression, the radiating element does not protrude above the ground plane. The ground plane and the radiating element are made of copper as a main material.
The operation of the antenna having such a configuration will be described. FIG. 19 shows the return loss vs. frequency characteristics of the antenna of this embodiment with a solid line. For comparison, the return loss versus frequency characteristics of a conventional discone antenna in which the maximum diameter and height of the radiating element are equal to those of the present antenna and the ground plane is flat are also shown by broken lines. The lower limit frequency at which the return loss is −10 dB or less is 10.8 GHz in the case of the conventional discone antenna, but is reduced to 8.2 GHz in the case of this antenna.
As is clear from this embodiment, by applying the present invention, the projecting portion of the radiating element on the ground plane can be eliminated, and the usable frequency band can be widened to the low frequency side. Miniaturization is possible.
When the antenna of the present embodiment is mounted on an information communication device, the device can be miniaturized by forming the antenna with a metal casing as a ground plane, and can be mounted without impairing the aesthetic appearance. In this case, since the antenna does not protrude from the housing, it is possible to avoid an increase in the size of the entire device even if the antenna is increased in size and widened.
Although the present invention has been described based on the embodiments, the present invention is by no means limited to the requirements shown here, such as the shapes raised in the above embodiments and combinations with other elements. With respect to these points, the present invention can be changed within a range that does not detract from the gist of the present invention, and can be appropriately determined according to the application form.

Configuration view of the antenna according to the onset Akira. The graph which shows the correlation of (theta) 1- (theta) 2 and F-Fdc of the antenna of FIG. The graph which shows the correlation of D / H of the antenna of FIG. 1, and ((theta) 1- (theta) 2) max. The block diagram of the antenna which concerns on Example 1 of this invention. The graph which shows the return loss vs. frequency characteristic of the antenna of Example 1. FIG. The block diagram of the antenna which concerns on Example 2 of this invention. The graph which shows the return loss vs. frequency characteristic of the antenna of Example 2. FIG. The block diagram of the antenna which concerns on Example 3 of this invention. The graph which shows the return loss vs. frequency characteristic of the antenna of Example 3. FIG. The block diagram of the antenna which concerns on Example 4 of this invention. The graph which shows the return loss vs. frequency characteristic of the antenna of Example 4. FIG. The block diagram of the antenna which concerns on Example 5 of this invention. The graph which shows the return loss vs. frequency characteristic of the antenna of Example 5. FIG. The block diagram of the antenna which concerns on Example 6 of this invention. The graph which shows the return loss vs. frequency characteristic of the antenna of Example 6. FIG. The block diagram of the antenna which concerns on Example 7 of this invention. The graph which shows the return loss vs. frequency characteristic of the antenna of Example 7. FIG. The block diagram of the antenna which concerns on Example 8 of this invention. The graph which shows the return loss vs. frequency characteristic of the antenna of Example 8. FIG. The block diagram of the conventional monopole antenna. The block diagram of the conventional discone antenna. The block diagram of the antenna disclosed by Unexamined-Japanese-Patent No. 09-083238. The block diagram of the antenna disclosed by Unexamined-Japanese-Patent No. 09-153727.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ground plane 2 Coaxial line 3 Radiating element 4 Conical shape part 5 Frustum shape part

Claims (5)

A conductor surface comprising a ground plane, an antenna composed of the radiating element, the radiating element has a conical portion of the semi-vertex angle θ1 made to face the top to the conductor surface, further wherein the conical portion from a predetermined height, the a shape having a truncated cone shaped portion having a central axis and the angle is .theta.2 side of the cone shaped portion, the antenna relationship .theta.1> .theta.2 and that Do of the angle .theta.1 and .theta.2 ,
An antenna characterized in that the bottom surface of the hemispherical portion is joined to the bottom surface of the frustoconical portion of the radiating element . 2. The antenna according to claim 1, wherein the conductor surface has a conical depression centered on a top of the conical portion of the radiating element . 3. The antenna according to claim 2 , wherein the depth of the conical depression is substantially the same as the height of the radiating element . 4. The antenna according to claim 1, wherein the conductor surface or the radiating element has a structure in which a conductive metal film is formed on an outer peripheral surface of a dielectric . The antenna according to any one of claims 1 to 4 , wherein the conductor surface or the radiating element has a structure in which a conductive metal film is formed on an outer peripheral surface of a dielectric, and the structure of the dielectric is hollow. An antenna characterized by that.

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