JP3460031B2 - Spiral antenna - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises an antenna substrate on which an antenna element having a conductor spiral pattern is formed, and a reflector arranged at a distance of nλ / 4 (n: odd number, λ: wavelength) from the antenna substrate. The present invention relates to a spiral antenna provided, and particularly to improvement of a circular polarization axial ratio of this spiral antenna.

[0002]

2. Description of the Related Art As a spiral antenna, for example, one having a structure shown in FIG. 3 is known. This spiral antenna has a configuration in which an antenna substrate 110 and a reflecting plate 112 are arranged at intervals of nλ / 4 (n: odd number, λ: wavelength). In the illustrated spiral antenna, n is 1, and the antenna substrate 110 and the reflector 112 are separated by λ / 4. The antenna substrate 110 is formed of a dielectric substrate, and an antenna element including two spiral conductor patterns 114 and 116 is formed on the surface of the dielectric substrate 110. The antenna element is directly fed from the back surface of the antenna element via the coaxial line 118. However, in the spiral antenna having such a configuration, the coaxial line 11 for feeding the antenna element is used.
Since 8 also defines the distance between the reflector 112 and the antenna substrate, this distance must be maintained not only when the antenna is actually used but also when it is transported, which causes a problem that the antenna becomes large. was there.

The applicant of the present application has already made a proposal (Japanese Patent Application No. 5-21354) shown in FIG. 4 in order to solve such a problem. FIG. 5 shows the antenna substrate 110 of FIG. 4 as seen through from the right side of the drawing. 4 and 5, 228 is a peripheral conductor pattern , 230 is a connector, 2
Reference numeral 34 is a through hole, and 232 is a feed line formed on the back side of the antenna substrate 110.

[0004]

However, in this case, the frequency band in which a good circular polarization with a circular polarization axis ratio of 2 dB or less is obtained is about 10%, and for example, in a system such as a telephone line, the frequency band is 10% or more. Difficulties have arisen in application to systems that require frequency bands.

An object of the present invention is to provide a spiral antenna capable of obtaining a good circular polarization axial ratio over a wide frequency band.

[0006]

According to the present invention, an antenna substrate made of a dielectric material and having a main surface and a facing surface facing the main surface, and a first substrate formed on the main surface of the antenna substrate are provided. An antenna element having first and second spiral conductor patterns, and nλ from the facing surface of the antenna substrate.
Placed at a distance of / 4 (n: odd number, λ: wavelength),
A reflection plate that reflects radiation from the antenna element and an inner end formed on the facing surface of the antenna substrate and connected to one inner end of the first and second spiral conductor patterns of the antenna element. And a feed line which is a line for feeding power to the antenna element, and the first and the second lines formed on the main surface of the antenna substrate and apart from the first and second spiral conductor patterns. A first peripheral conductor pattern surrounding the second spiral conductor pattern and a first peripheral conductor pattern formed on the main surface of the antenna substrate and connecting the respective outer ends of the first and second spiral conductor patterns to the peripheral conductor pattern. And a second connection conductor pattern, and the first and second connection conductor patterns are provided.
A spiral antenna is obtained in which each of the connection conductor patterns has a fan shape that extends outward of the main surface of the antenna substrate.

Further, according to the present invention, the peripheral conductor pattern has a circular inner edge portion, and the circular inner edge portion is separated from the first and second spiral conductor patterns. A spiral antenna is obtained which is characterized by surrounding 1 and the second spiral conductor pattern.

Further, according to the present invention, the feed line is formed on the facing surface of the antenna substrate, and the inner end of the feed line is one of the first and second spiral conductor patterns of the antenna element . A spiral conductor pattern for power supply, which is connected to a terminal and serves as a line when power is supplied to the antenna element, and the spiral conductor pattern for power supply and the other of the first and second spiral conductor patterns of the antenna element. A spiral antenna is obtained in which a portion from the outer end to the inner end constitutes a parallel conductor line.

[0009]

In the spiral antenna of the present invention, the feed line to the antenna element is formed on the back side of the antenna substrate. That is, when the spiral antenna of the present invention is used, power may be fed to the antenna element via the feed line formed on the back side of the antenna substrate. Therefore, it is not necessary to use a member that is interposed between the antenna substrate and the reflection plate and holds the distance between the two, and the size of the antenna during transportation (when the spiral antenna is not used) becomes small.

Further, the first and second connection conductor patterns for connecting the outer ends of the first and second spiral conductor patterns to the peripheral conductor pattern are respectively directed to the outside of the main surface of the antenna substrate. By expanding the fan shape, the impedance of the spiral antenna element seen from the outer edge of the surrounding conductor pattern becomes constant over a wide band, so a frequency that produces better circular polarization than the conventional method is generated. It becomes possible to widen the band.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

Referring to FIG. 1, there is shown a structure of a two-wire spiral antenna according to an embodiment of the present invention. 2 is a perspective view of the antenna substrate 110 of FIG. 1 seen from the right side of the drawing.

With reference to FIGS. 1 and 2, this spiral antenna has an antenna substrate 110 made of a dielectric material and having a main surface and a facing surface facing the main surface. The antenna element has spiral conductor patterns 114 and 116 formed on the main surface of the antenna substrate 110. The reflector 112 is nλ / 4 (n:
They are placed at a distance of an odd number, λ: wavelength, and reflect the radiation from the antenna element. In the illustrated spiral antenna, n is 1, and the antenna substrate 110 and the reflector 112 are separated by λ / 4.

The feed line 232 is formed on the opposite surface of the antenna substrate 110, and one end thereof is connected to the inner end of one of the spiral conductor patterns 114 and 116 (the spiral conductor pattern 114 in the illustrated example) of the antenna element and the through hole 234. Is connected to the other end through the connector 230.
And serves as a line for feeding power to the antenna element via the connector 230. Specifically, the power supply line 232 is
It is formed from a power supply spiral conductor pattern, and the inner end of this power supply spiral conductor pattern is connected to the inner end of one of the spiral conductor patterns 114 and 116 (spiral conductor pattern 114 in the illustrated example) of the antenna element.
The power supply spiral conductor pattern is connected to the connector 230 via the through hole 234, and the outer end of the power supply spiral conductor pattern is connected to the connector 230. The power supply spiral conductor pattern serves as a line when power is supplied to the antenna element via the connector 230. The feeding spiral conductor pattern and the other of the spiral conductor patterns 114 and 116 (the spiral conductor pattern 116 in the illustrated example) of the antenna element sandwich the antenna substrate 110 to form a parallel conductor line. That is, this feeding spiral conductor pattern is the other of the spiral conductor patterns 114 and 116 of the antenna element (that is, the spiral conductor pattern 116).
From the outer end to the inner end of the antenna substrate 110
A parallel conductor line is formed by sandwiching.

The peripheral conductor pattern 228 is formed on the main surface of the antenna substrate 110, and the spiral conductor pattern 11 is formed.
The spiral conductor patterns 114 and 116 are separated from the spiral conductor patterns 114 and 116. In detail, the peripheral conductor pattern 228 has a circular inner edge portion, and the circular inner edge portion surrounds the spiral conductor patterns 114 and 116 in a state of being separated from the spiral conductor patterns 114 and 116.

Connection conductor patterns 221 'and 222'
Are formed on the main surface of the antenna substrate and connect the outer ends of the spiral conductor patterns 114 and 116 to the inner edge of the peripheral conductor pattern 228. The connection conductor patterns 221 ′ and 222 ′ are respectively the antenna substrate 1
It has a fan shape that spreads outward from the main surface of 10.

As described above, in this embodiment, no member such as the coaxial line 118 or the microstrip line shown in FIG. 3 is interposed between the antenna substrate 110 and the reflector 112. In this embodiment, a connecting conductor pattern 22 arranged to feed power from an outer peripheral portion to an antenna element formed in the same plane as the two-wire spiral antenna.
The shapes of 1'and 222 'are fan-shaped. Further, power feeding to the antenna element composed of the spiral conductor patterns 114 and 116 is performed through the power supply line 232 composed of the spiral conductor pattern formed on the back surface of the connector 230 and the antenna substrate 110.

The feed line 232 composed of this spiral conductor pattern is arranged so as to form a parallel conductor line with the spiral conductor pattern 116, and the tip of the feed line 232 is arranged through the through hole 234.
Connected to 6. That is, the parallel conductor line composed of the spiral conductor patterns 116 and 232 is a parallel feed line in which the spiral conductor pattern 116 serves as a ground conductor, and the spiral conductor pattern 114 is fed from the central portion.

The width of the power supply line 232 formed of the power supply spiral conductor pattern is set so as to become continuously narrower as it approaches the through hole 234 (that is, as it approaches the inner end of the power supply spiral conductor pattern). . This is because the input impedance of the antenna element composed of the spiral conductor patterns 116 and 114 is 17
It is based on the fact that it is as high as 0Ω and the input impedance of the connector 30 is as low as 50Ω. That is, the width setting of the feed line 232 composed of the spiral conductor pattern is
This is for impedance matching between the connector 30 and a cable (not shown) connected to the connector 30 and the antenna element.

By the way, the prior application (Japanese Patent Application No. 5-21354)
No.), a peripheral conductor pattern 228 in which two spiral antenna elements are formed in the same plane is connected to the spiral antenna element in a circular shape by parallel lines between the slots. However, in this configuration, a balanced-unbalanced conversion circuit (balun) composed of a normal Lecher line and a ground conductor arranged orthogonal to it cannot be sufficiently configured,
For this reason, the characteristics of the spiral antenna having wide band characteristics cannot be fully utilized.

On the other hand, in the case of the peripheral conductor pattern 228 of this structure, by making the shape of the line between the spiral antenna element and the surrounding slots fan-shaped, a current as if it is orthogonal to the Lecher line is slotted. It flows to the end, and as a result, it performs the same operation as an ideal balanced-unbalanced conversion circuit and enables wide band operation. Specifically, 2
A good circular polarization axis ratio of dB or less can be obtained over a frequency band of 10% or more.

[0022]

As described above, according to the present invention, the first and second connecting conductor patterns for connecting the outer end of each of the first and second spiral conductor patterns and the surrounding conductor pattern are respectively provided. , By adopting a fan shape that spreads outwards from the main surface of the antenna substrate, the impedance seen by the spiral antenna element from the outer edge of the peripheral conductor pattern becomes constant over a wide band. It is possible to widen the frequency band that produces good circular polarization compared to That is, according to the present invention, the ground conductor (first
Also, by simply changing the shape of the second connection conductor pattern), the broadband operation of the original spiral antenna can be performed, and as a result, an excellent antenna that can be used as a telephone line antenna and the like can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view of a spiral antenna according to an exemplary embodiment of the present invention.

2 is an antenna substrate 11 of the spiral antenna of FIG.
It is the figure which looked through 0 from the right side in the figure.

FIG. 3 is a perspective view of a conventional spiral antenna.

FIG. 4 is a perspective view of another conventional spiral antenna.

5 is an antenna substrate 11 of the spiral antenna of FIG.
It is the figure which looked through 0 from the right side in the figure.

[Explanation of symbols]

110 antenna board 112 reflector 114 spiral conductor pattern 116 spiral conductor pattern 118 coaxial line 221 'connection conductor pattern 222 'connection conductor pattern 228 Surrounding conductor pattern 230 connector 232 feeder line

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-181408 (JP, A) JP-A-5-14043 (JP, A) JP-A-5-37226 (JP, A) Actual Kaihei 2- 100308 (JP, U) US Patent 5491490 (US, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01Q 9/26 H01Q 1/36 H01Q 11/04 H01Q 19/10 H01Q 21/24

Claims (3)

(57) [Claims] 1. An antenna substrate, which is made of a dielectric material and has a main surface and a facing surface facing the main surface, and first and second antenna substrates formed on the main surface.
An antenna element having a spiral conductor pattern, and a reflector plate placed at a distance of nλ / 4 (n: odd number, λ: wavelength) from the facing surface of the antenna substrate and reflecting radiation from the antenna element. , are formed on the facing surface of the antenna substrate, is contacted connected inner end to one of the inner end of said first and second spiral conductor patterns of the antenna elements, and the line at the time of power feeding to the antenna element And a peripheral conductor pattern formed on the main surface of the antenna substrate and surrounding the first and second spiral conductor patterns in a state of being separated from the first and second spiral conductor patterns, Outer ends of the first and second spiral conductor patterns formed on the main surface of the antenna substrate and the peripheral conductor pattern, respectively. A first connecting conductor pattern and a second connecting conductor pattern which are connected to each other, wherein the first and second connecting conductor patterns each have a fan shape that spreads outward of the main surface of the antenna substrate. Spiral antenna featuring. 2. The peripheral conductor pattern has a circular inner edge portion, and the circular inner edge portion is separated from the first and second spiral conductor patterns by the first and second conductor patterns. The spiral antenna according to claim 1, which surrounds the spiral conductor pattern. 3. The feed line is formed on the facing surface of the antenna substrate, and the inner end is one of the first and second spiral conductor patterns of the antenna element.
A spiral conductor pattern for feeding, which is connected to an inner terminal of the antenna element and serves as a line when feeding power to the antenna element, the spiral conductor pattern for feeding, and the first and second spiral conductor patterns of the antenna element. The part from the other outer end to the inner end of the above constitutes a parallel conductor line, and the spiral antenna according to claim 1 or 2.