JP3662465B2 - Square spiral antenna - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rectangular spiral antenna, and more particularly to a rectangular spiral antenna that is used for mobile radio communication, satellite communication, and the like and that supports circular polarization in a wide band.
[0002]
[Background Art and Problems to be Solved by the Invention]
In communication fields such as mobile communication, satellite broadcasting, and radar, circularly polarized radio waves are used so that signals can be received regardless of the inclination of the polarization plane. In these communications, in order to perform transmission and reception simultaneously, it is necessary to use a plurality of frequencies, and broadband radio waves are required. Therefore, the antenna to be used is required to be able to transmit and receive circularly polarized waves over a wide band. In addition, an antenna for mounting on a mobile body is required that can be configured to be small and thin.
[0003]
Therefore, a main object of the present invention is to provide a small and thin rectangular spiral antenna capable of obtaining a good axial ratio over a wide frequency band.
[0004]
[Means for Solving the Problems]
The present invention is a rectangular spiral antenna corresponding to circularly polarized waves, which is a rectangular dielectric, a ground conductor provided on one surface of the dielectric, and eight microstrips provided on the other surface of the dielectric. A single-wire spiral formed by connecting lines and a coaxial line inserted from the ground conductor side, and the total length of the microstrip line of the single-wire spiral is 1λa or less when the effective wavelength of the frequency used is λa. The outermost peripheral length is selected to be 1λa or more and 2λa or less, the coaxial wire is connected to one end of the microstrip line, and the coaxial wire is connected to the ground conductor. , Where x is the length of the eighth microstrip line from the center of the single wire spiral toward the end of the single wire spiral, x is a length in the range of 0.015λa ≦ x ≦ 0.3λa Characterized in that it chosen.
[0005]
Preferably, x has a length of 0.15λa.
[0006]
More preferably, the operating frequency of the rectangular spiral antenna is 5.8 GHz, the dielectric has a shape of 16.5 mm in length and width, and a height of 6.0 mm, and its dielectric constant is selected to be 4.4. It is characterized by being.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic view of a rectangular spiral antenna according to an embodiment of the present invention, FIG. 2 is a side view of the same, and FIG. 3 is a top view of a spiral microstrip line of the rectangular spiral antenna.
[0011]
In FIG. 1, the square spiral antenna includes a ground conductor 1, a dielectric layer 2, and a square spiral microstrip line 3.
[0012]
The ground conductor 1 is not particularly limited, but a conductor such as copper having high conductivity is desirable. As the dielectric layer 2, a dielectric material having a small dielectric loss in the operating frequency region such as glass epoxy resin, Teflon, alumina, or the like is used. In this embodiment, the dielectric layer 2 has a dielectric constant of 4.4, and the outer diameter is 16.5 mm in length and width and 6.0 mm in height.
[0013]
The rectangular spiral microstrip line 3 uses a conductor material that has a small conductor loss in the operating frequency region and is easy to process. In this embodiment, the square spiral microstrip line 3 is formed by a printing method, and the line width is selected to be 0.6 mm. The square spiral microstrip line 3 is composed of eight lines. The square spiral microstrip line 3 is connected to the core wire of the coaxial wire 4 inserted from the ground conductor 1 side and fed with a high frequency signal. The ground portion of the coaxial line 4 is connected to the ground conductor 1.
[0014]
The total length A of the square spiral microstrip line 3 is λa as the effective wavelength of the frequency used.
A <λa
Where λ0 is the wavelength in the vacuum of the frequency used, and εeff is the effective dielectric constant for the stripline,
λa = λ0 / √εeff
It is represented by
[0015]
Here, 5.8 GHz is adopted as a use frequency. At this time, the effective wavelength λa = 30 mm, and the total length of the spiral microstrip line 3 is within λa. Further, in the eight microstrip lines constituting the square spiral microstrip line 3 at this time, the length of the eighth microstrip line from the spiral center toward the spiral end is defined as x.
[0016]
In FIG. 3, the broken line L indicates the outermost peripheral length of the square spiral microstrip line 3. At this time, L exceeds 1λa and is within 2λa.
[0017]
FIG. 4 is a graph showing the antenna axial ratio when the length x of the microstrip line of the embodiment shown in FIG. 1 is changed. As can be seen from the graph of FIG. 4, when the length of x is changed in the range of 0.015λa ≦ x ≦ 0.3λa, an axial ratio of 3 dB or less can be realized. From the graph results, the value of x that can realize the best axial ratio is x = 0.15λa, and the antenna axial ratio at this time is 0.41 dB at 5.8 GHz.
[0018]
FIG. 5 is a graph showing a frequency band in which the axial ratio becomes 3 dB or less when the length x of the microstrip line is changed. When an axial ratio of 3 dB or less is defined as a good circular polarization characteristic, it can be seen that a good circular polarization characteristic is obtained over a wide frequency band.
[0019]
FIG. 6 is a graph showing the relationship between the axial ratio and the frequency when x = 0.15λa. From the graph of FIG. 6, when x = 0.15λa, the frequency at which the axial ratio is 3 dB or less is 5.58 to 6.09 GHz, and the band is 508 MHz.
[0020]
Further, FIG. 7 shows a graph of the standing wave ratio characteristic (VSWR) of the antenna when x = 0.15λa. If a frequency band satisfying VSWR ≦ 2 is defined as a band that can be used as an antenna, a frequency satisfying VSWR ≦ 2 is in a range from 5.11 GHz to 6.5 GHz or more. This sufficiently covers the frequency band that is circularly polarized, and it can be seen that it can be used as a circularly polarized antenna in the frequency band of 5.58 GHz to 6.09 GHz.
[0021]
FIG. 8 shows the YZ plane radiation pattern of the antenna with x = 0.15λa, and FIG. 9 also shows the XZ plane radiation pattern. 8 and 9, the antenna surface is the XY plane, and the vertical direction of the antenna surface is the Z axis. FIG. 8 and FIG. 9 show the radiation pattern of right-handed polarization, and it can be seen that the antenna of one embodiment of the present invention can realize right-handed polarization. When the gain was measured, it was 5.8 dBi at 5.8 GHz.
[0022]
FIG. 10 is a schematic view of a rectangular spiral antenna according to another embodiment of the present invention, and FIG. 11 is a view similarly seen from the ground conductor side. In this embodiment, a part of the ground conductor 1 on the back surface of the antenna is cut out, and a coplanar line 5 is provided here, and power is supplied to the square spiral microstrip line 3 from a coaxial line inserted from the side of the antenna. This is done via the line 5. Also in this embodiment, in the eight microstrip lines constituting the square spiral microstrip line, the length of the eighth microstrip line from the spiral center toward the end is assumed to be x.
[0023]
FIG. 12 is a graph showing the antenna axial ratio when the length x of the microstrip line is changed. As can be seen from the graph shown in FIG. 12, when the length of x is changed in the range of 0.015λa ≦ x ≦ 0.3λa, an axial ratio of 3 dB or less can be realized. From the result of this graph, the value of x that can realize the best axial ratio is x = 0.17λa, and the antenna axial ratio at this time is 0.45 dB at 5.5 GHz.
[0024]
FIG. 13 is a graph showing a frequency band in which the axial ratio becomes 3 dB or less when the length x of the microstrip line is changed. When an axial ratio of 3 dB or less is defined as a good circular polarization characteristic, it can be seen that a good circular polarization characteristic is obtained over a wide frequency band.
[0025]
FIG. 14 is a graph showing the relationship between the axial ratio and the frequency when x = 0.17λa. From the graph, when x = 0.17λa, the frequency at which the axial ratio is 3 dB or less is 5.29 GHz to 5.93 GHz, and the band is 640 MHz.
[0026]
FIG. 15 shows a graph of the standing wave ratio characteristic (VSWR) of the antenna when x = 0.17λa. If the frequency band satisfying VSWR ≦ 2 is a band that can be used as an antenna, the frequency satisfying VSWR ≦ 2 is in the range of 5.4 GHz to 6.5 GHz or more. Therefore, according to this embodiment, it can be seen that it can be used as a circularly polarized antenna in the band of 5.4 GHz to 5.93 GHz.
[0027]
FIG. 16 shows the radiation pattern on the YZ plane of the antenna with x = 0.17λa, and FIG. 17 shows the radiation pattern on the XZ plane. 16 and 17, the antenna surface is the XY plane, and the vertical direction of the antenna surface is the Z axis. FIGS. 16 and 17 show radiation patterns of right-handed polarization, and it can be seen that right-handed polarization can also be realized in the antenna of this embodiment. Further, when the gain was measured, it was 4.6 dBi at 5.5 GHz.
[0028]
In addition, the frequency demonstrated by the above-mentioned embodiment is an example of the use frequency in the square spiral antenna of this invention, and is not limited to this frequency.
[0029]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
[0030]
【The invention's effect】
As described above, according to the present invention, in the single wire spiral formed by connecting the eight microstrip lines, the length of the eighth microstrip line is changed from the center of the spiral toward the end of the spiral. Axial ratio, antenna frequency band, etc. can be controlled. Thereby, a favorable circular polarization axial ratio can be obtained over a wide frequency band. In addition, a small antenna can be realized by selecting the length of the square spiral microstrip line within a length of 1λa and the outermost peripheral length being 1λa or more and 2λa or less.
[0031]
Even if a coplanar line is provided on the ground conductor side of the antenna, good circular polarization characteristics can be realized over a wide frequency band. Also, by providing such a coplanar line, it is possible to feed from the side of the antenna surface compared to feeding from a coaxial line that feeds in the direction perpendicular to the antenna surface. The height of the entire structure can be reduced, and a reduction in thickness can be realized.
[Brief description of the drawings]
FIG. 1 is a schematic view of a rectangular spiral antenna according to an embodiment of the present invention.
FIG. 2 is a side view of a rectangular spiral antenna according to an embodiment of the present invention.
FIG. 3 is a top view of a spiral microstrip line of a square spiral antenna.
FIG. 4 is a graph showing the antenna axial ratio when the length x of the microstrip line is changed.
FIG. 5 is a graph showing a frequency band in which the axial ratio becomes 3 dB or less when the length x of the microstrip line is changed.
FIG. 6 is a graph showing a relationship between an axial ratio and a frequency when x = 0.15λa.
FIG. 7 is a graph showing a standing wave ratio characteristic of an antenna when x = 0.15λa.
FIG. 8 is a diagram showing a YZ plane radiation pattern of an antenna of x = 0.15λa.
FIG. 9 is a diagram showing an XZ plane radiation pattern of an antenna of x = 0.15λa.
FIG. 10 is a schematic view of a square spiral antenna according to another embodiment of the present invention.
FIG. 11 is a view of a square spiral antenna according to another embodiment of the present invention as viewed from the ground conductor side.
FIG. 12 is a graph showing the relationship between the axial ratio and the x length of a square spiral antenna according to another embodiment of the present invention.
FIG. 13 is a graph showing a frequency band in which circular polarization characteristics of a rectangular spiral antenna according to another embodiment of the present invention can be obtained.
FIG. 14 is a graph showing the relationship between the axial ratio and the frequency of a rectangular spiral antenna according to another embodiment of the present invention.
FIG. 15 is a graph showing a standing wave ratio characteristic of a square spiral antenna according to another embodiment of the present invention.
FIG. 16 is a diagram showing a YZ plane radiation pattern of a rectangular spiral antenna according to another embodiment of the present invention.
FIG. 17 is a diagram showing an XZ radiation pattern of a rectangular spiral antenna according to another embodiment of the present invention.
[Explanation of symbols]
1 ground conductor, 2 dielectric layer, 3 single wire spiral, 4 coaxial line, 5 coplanar line.

Claims (3)

A square spiral antenna that supports circular polarization,
A rectangular dielectric,
A ground conductor provided on one surface of the dielectric;
A single-wire spiral provided on the other surface of the dielectric and formed by coupling eight microstrip lines, and a coaxial line inserted from the ground conductor side;
When the effective wavelength of the frequency used is λa, the total length of the microstrip line of the single-wire spiral is within 1λa, the outermost peripheral length is 1λa or more, and is selected to be 2λa or less. And
The coaxial wire is connected to one end of the microstrip line, the coaxial wire is connected to the ground conductor ,
When the length of the eighth microstrip line from the center of the single wire spiral toward the end of the single wire spiral is x, x is selected to be in the range of 0.015λa ≦ x ≦ 0.3λa. Tei Rukoto and said, square-shaped spiral antenna. The square spiral antenna according to claim 1, wherein x is 0.15λa in length . The operating frequency of the square spiral antenna is 5.8 GHz,
The dielectric aspect is 16.5 mm, a shape of 6.0mm height, characterized in that the dielectric constant is selected to 4.4, square according to claim 1 or 2 Spiral antenna.

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