JPH0856112A - Isometric spiral antenna - Google Patents

Abstract

PURPOSE:To provide a broad band antenna with a high gain and less gain fluctuation over a wide frequency range. CONSTITUTION:A reflector body structure 3 is provided in the inside of a cylindrical case 5 and a radiator in which equiangular spiral shaped conductors 22, 23 are formed on the front side of a printed circuit board 21 is fitted to the end face of a case 5 and the radiator body structure 2 of the case 5 is threaded to a wave director body structure 1 in which a circular wave director 12 is formed in the middle of a cylindrical cover 11. Thus, a broad band characteristic is obtained by adopting the antenna of equiangular spiral shape, a high gain characteristic is obtained by providing the reflector and a flat gain characteristic with less gain fluctuation is obtained by providing the wave director.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spiral antenna having a wide band circular polarization characteristic, and more particularly to a structure for improving an operating gain in a high frequency band.

[0002]

2. Description of the Related Art The inventor of the present invention has previously described a spiral antenna corresponding to a circularly polarized wave in a wide band in Japanese Patent Application No. 5-52469.
Proposed in the issue. The outline of the invention of this Japanese Patent Application No. 5-52469 (hereinafter referred to as prior invention) will be described below.

According to the prior invention, two equiangular spiral conductors surrounded by two equiangular spiral curves are rotated by π radians on a surface of a printed circuit board having a plane circular shape, and a printed pattern is formed. The printed circuit board is fitted into a tubular body with its printed pattern surface facing outward, and the inside of the tubular body is a radio wave absorber whose inner surface is a conical surface, and the hem side of the conical surface is the above-mentioned print. Inside the antenna, which has a structure that is fitted so that it is on the side of the board, or inside the tubular body,
An antenna having a structure in which a reflector made of a conical surface-shaped conductor is fitted so that the apex of the conical surface is on the printed circuit board side, and any structure antenna is formed on the printed circuit board, etc. The end point at the center of the rectangular spiral conductor is used as the feeding point, and the feeding structure is connected to the equiangular spiral conductor and the connector using a microstrip line with a narrow width on the feeding point side and a wide width on the connector side for feeding. It has a structure for impedance matching with the coaxial cable.

[0004]

FIG. 7 shows the frequency vs. operating gain characteristics of the antenna according to the invention of the prior application. In this figure, the characteristic indicated by the solid line is an antenna in which a reflector is provided inside the tubular body (hereinafter referred to as the first antenna in this section).
The characteristics indicated by the dotted line indicate the characteristics of the antenna (hereinafter referred to as the second antenna in this section) in which the electromagnetic wave absorber is provided inside the tubular body.

As is clear from the characteristics shown in FIG. 7,
The first antenna can obtain a higher operating gain on average than the second antenna, but there is a problem that the operating gain fluctuates drastically in the frequency region higher than around 9.5 GHz and the stability of the characteristic is lacking. , And the second antenna is the first
Compared with the antenna of (1), the variation of the operating gain is small and a stable gain can be obtained, but there is a problem that the operating gain is low.

The present invention solves the above-mentioned problems of the invention of the prior application, and a novel antenna having both the high operation gain of the first antenna and the stability of the operation gain of the second antenna is provided. The challenge is to obtain the structure.

[0007]

In order to solve the above problems, the present invention provides an antenna having a structure having a reflector, in which the circular waveguide is provided in front of the spiral conductor. It was done.

Further, as the structure of the above-mentioned reflector, in addition to the conical reflector, in addition to the conical reflector, two disc-shaped reflectors having different diameters are newly formed in a two-tiered structure. is there.

[0009]

A high operating gain is obtained due to the structure having a reflector, and the operating gain is flattened in the high frequency region by the action of the director, and stable high operation is achieved over the entire intended frequency band. It has a gain characteristic.

[0010]

1 to 6 show an embodiment of the present invention.
FIG. 1 is a perspective view of the main constituent members of the first embodiment, and FIG.
5 is a central longitudinal sectional view of the embodiment, FIG. 3 is a perspective view of a reflector structure according to the second embodiment, and FIG. 4 is a central longitudinal sectional view of the second embodiment.
Is a diagram showing the frequency vs. operating gain characteristic of the first embodiment, and FIG. 6 is a diagram showing the frequency vs. operating gain characteristic of the second embodiment.

Incidentally, in FIG. 1, the case, the cable and the connector are omitted, and in FIG. 3, only the reflector structure different from that of the first embodiment is shown in the second embodiment, and FIGS. 6 shows the characteristics of the antenna having the electromagnetic wave absorber of the prior invention and the characteristics of the antenna having only the reflector (antenna having no director) for comparison of characteristics.

The structure of the first embodiment will be described with reference to FIGS.

Reference numeral 1 denotes a waveguide structure having an upper surface 111 having a circular planar shape, a side surface 112 having a cylindrical shape, and a lower surface 1.
A cylindrical lid body 11 having an opening 13 and an upper surface 11 thereof
1 and a circular waveguide 12 attached to the center of the side surface 1, and the inside of the side surface 112 has a threaded structure.
The lid 11 is entirely made of an insulator, and the director 12 is made of a conductor. The easiest form to make is a circular insulating frame with internal threading (side 1
Equivalent to 12. 2), a circular printed circuit board (corresponding to the upper surface 111) on which the waveguide 12 is formed at the center by a printed pattern is attached to one end surface.

Reference numeral 2 denotes a radiator assembly, which is formed on a surface of a circular printed circuit board 21 by two conformal spiral conductors 22, 2 made of a conductor surrounded by two conformal spiral curves.
3 are formed in a positional relationship of being rotated by π radians with respect to each other, and are printed in a state of being surrounded by the end points 221 and 231 of the equilateral spiral conductors 22 and 23 on the center side of the printed circuit board 21. Holes 21 penetrating the front and back of the substrate 21
1 is provided.

Reference numeral 3 denotes a reflector structure, which is composed of a conical cylindrical body 31 having an upper surface 311 having a conical shape, a side surface 312 having a cylindrical shape, and a lower surface 313 having an open shape.
11 has a hole 314 penetrating through the inside and outside of the conical cylinder 31.
Is provided. Further, the conical cylindrical body 31 is entirely formed of a conductor.

In the reflector structure 3 having the above-described structure, the main portion functioning as a reflector is the conical upper surface 311.

Reference numeral 4 denotes a feeder structure, which comprises a slender printed circuit board 41 having a tapered shape, a microstrip line 42 made of a tapered conductor is formed on the surface thereof, and a conductor is attached to the entire back surface thereof to form a ground conductor. Four
3 is formed.

Reference numeral 5 denotes a case, which is formed in a cylindrical shape having a bottom, and the inner diameter of which is the same as the outer diameter of the reflector structure 3,
The upper surface side is opened with the same size as the outer diameter of the radiator structure 2, and the outer side surface 51 has a threaded structure for fitting the waveguide structure 1 by screwing. Further, the bottom surface 52 of the case 5 is provided with a hole 521 for introducing the feeder line 6 into the inside. The case 5 is made of a conductor to prevent unnecessary radio waves from being radiated from the back side of the radiator assembly 2.

Further, 6 is a power supply line made of a coaxial cable, and 7 is a connector for connecting to the outside.

The above-described components are assembled together as shown in FIG. That is, the reflector assembly 3 is housed inside the case 5 with its conical surface (upper surface 311) facing upward, and the radiator assembly 2 is installed on the upper surface of the case 5.
The radiating conductor surface (the surface on which the equiangular spiral conductors 22 and 23 are formed) faces upward and is fitted.

The feeder structure 4 is inserted into the hole 314 of the reflector structure 3 with the side of the narrow end 411 formed in a narrow width being the side of the radiator structure 2, and the narrow end 411 is the hole of the radiator structure 2. It is inserted in 211, here, microstrip line 4
2 and the ground conductor 43 are the end points 221 and 23 on the center side of the conformal spiral conductors 22 and 23 of the radiator assembly 2, respectively.
1 are electrically connected to each. In addition, the wide end portion 412 formed to have a wide width is electrically connected to the power supply line 6 near the inner bottom surface of the case 5 (the microstrip line 4).
2 is connected to the center conductor of the power supply line 6, and the ground conductor 43 is connected to the peripheral conductor (ground conductor) of the power supply line 6. In this way, the conformal spiral conductors 22 and 23 of the radiator assembly 2 are electrically led to the connector 7 attached to the bottom surface 52 of the case 5.

Further, the microstrip line 42 of the feeder structure 4 and the ground conductor 43 should not be in electrical contact with the reflector structure 3, and therefore, the hole 3 of the reflector structure 3 is required.
14 is set to a size that the feeder structure 4 penetrates without contact.

Next, the director assembly 1 is screwed onto the radiator assembly 2 mounting surface side of the case 5. As a result, the director 12 is arranged in front of the central portions of the equiangular spiral conductors 22 and 23.

The positional relationship of the respective parts in the state where the respective components are assembled as described above will be described. The apex of the conical cylindrical body 31 of the reflector structure 3 (the formation point of the hole 314),
A line passing through the center of a circle (circumferential surface of the skirt) formed by being surrounded by the circumference of the skirt 315 of the conical upper surface 311 and the radiator assembly 2
So that the center line that intersects perpendicularly with the center (that is, the center of the equiangular spiral conductors 22 and 23) coincides, and the apex of the conical cylindrical body 31 is closer to the radiator structure 2 than the skirt circumferential surface. The reflector structure 3 is arranged, and the feeder structure 4 is arranged on the center line. In addition, the director 1
2 is arranged such that its plate surface is parallel to the formation surface of the equiangular spiral conductors 22 and 23 and in front of the center portion thereof (the center line of the equiangular spiral conductors 22 and 23 and the center line of the director 12). The distance between the director 12 and the conformal spiral conductors 22 and 23 can be arbitrarily adjusted depending on the degree to which the lid 11 is screwed into the case 5.

Next, referring to the dimensions of each part of the first embodiment, the diameter D of the radiator assembly 2 is about 21 mm, and the director 1
2 has a diameter d of about 6 mm, and the distance t between the radiating conductor surface of the radiator assembly 2 (the surface on which the equiangular spiral conductors 22 and 23 are formed) and the director 12 is about 2.0 to 3.5 mm (between the two). Adjust with)
And the frequency band in this specification is about 8 GHz to 20 GHz.
GHz.

The distance HA between the radiating conductor surface of the radiator assembly 2 and the apex (conical surface apex) of the conical cylinder 31 of the reflector assembly 3 is 4 of the wavelength of the radio wave at the upper limit frequency of use.
The distance H between the radiation conductor surface and the skirt circumferential surface formed by the skirt 315 of the conical cylinder 41.
B is set to 1/4 of the wavelength of the radio wave at the lower limit frequency of use. Therefore, in the case of using an antenna whose operating frequency is, for example, 9 GHz to 14 GHz, the spacing HA is about 5.4 mm and the spacing HB is about 8.3 mm.

Next, the structure of the second embodiment will be described with reference to FIGS. 3 and 4. The second embodiment is structurally different from the first embodiment only in the structure of the reflector structure 3, and therefore only the reflector structure 3 is shown in FIG.

As shown in FIG. 3, the reflector structure 3 of the second embodiment has a first shape in which the upper surface 321 has a circular planar shape, the side surface 322 has a cylindrical shape, and the lower surface 323 is open.
The cylindrical body 32 and the upper surface 331 have a circular planar shape, and the side surface 33
2 has a cylindrical shape, and the lower surface 333 has a first cylindrical body 32.
And a second cylindrical body 33 having an open shape (therefore, the upper surface 321 of the first cylindrical body 32 has a shape in which the central portion is open), and the second cylindrical body 33 is stacked in two stages. The diameter of the first tubular body 32 is larger than the diameter of the second tubular body 33, and the second tubular body 33 is stacked in the center of the first tubular body 32.

Further, the inside of the first cylinder 32 and the inside of the second cylinder 33 are the lower surface 333 of the second cylinder 33 which is open.
Are in communication with each other through the upper surface 33 of the second tubular body 33.
1 is provided with a hole 334 for the same purpose as the hole 314 in the first embodiment.

The reflector structure 3 having the above structure is shown in FIG.
As shown in FIG. 5, as in the case of the first embodiment, the second cylinder 33 is housed inside the case 5 with the second cylinder 33 facing upward.

In the second embodiment, the components other than the reflector structure 3 and their assembled mutual positional relationship are the same as those in the first embodiment, and therefore the sectional structure is shown in FIG. Detailed description is omitted.

In the reflector structure 3 having the above-described structure, the main parts that function as a reflector are the upper surface 321 of the first cylindrical body 32 and the upper surface 331 of the second cylindrical body 33, which have a circular planar shape. The positional relationship after assembly shown in FIG.
Formed surfaces of the equiangular spiral conductors 22 and 23 (the printed circuit board 21), the upper surface 321 of the first cylindrical body 32, and the second cylindrical body 33.
Top surfaces 331 of the first cylinder 32 are parallel to each other, the center lines passing vertically through the respective centers coincide with each other, and the top surface 331 of the second cylinder body 33 having a small diameter is the top surface of the first cylinder body 32 having a large diameter. Three
The positional relationship is closer to the equiangular spiral conductors 22 and 23 than 21. The feeder structure 4 is arranged on the center line. Also, the fact that the center line of the director 12 coincides with the center line where the feeder assembly 4 is arranged is the same as in the first embodiment.

The dimensional relationship of each part of the second embodiment is the same as that of the first embodiment. However, HA is the distance between the radiation conductor surface of the radiator assembly 2 (the surface on which the equiangular spiral conductors 22 and 23 are formed) and the upper surface 331 of the second cylindrical body 33 of the reflector assembly 3, and HB Is the radiation conductor surface and the reflector structure 3
It is due to the distance between the first cylinder 32 and the upper surface 321 of the first cylinder 32. By doing so, the distances HA and HB have the same relationship as in the first embodiment. For example, use frequency 8
If the frequency is set to 20 GHz from GHz, the distance H
A is about 3.8 mm and the distance HB is about 9.4 mm.

The measured values of the operating gain characteristics of the first and second embodiments described above are shown in FIGS. 5 and 6, respectively. 5 and 6 show the results of measurement in the frequency band from 8 GHz to 16 GHz regardless of the frequency used in each example.

As can be seen in FIGS. 5 and 6, about 9.5.
In the frequency band of GHz or higher, any of the embodiments,
The operating gain (a) when the director 12 is provided is
Less variation than the operating gain (B) when not provided,
Flattening of operating gain has been achieved. It should be noted that the flattening of the operation gain is better in the second embodiment than in the first embodiment.

Further, comparing the operating gain (C) of the antenna provided with the conventional electromagnetic wave absorber with the operating gain (A) of the embodiment, both have a small fluctuation in the operating gain, but the value is
The operating gain (a) of the example is higher than the operating gain (c) of the conventional antenna by about 3 (dB) on average.

As described above, the present invention has an operational gain characteristic having both the high gain characteristic of the conventional reflector type antenna and the high stability characteristic of the conventional radio wave absorption type antenna.

In the above embodiments, one waveguide 12 is used as the disk 12, but the waveguide 1
2 may have various shapes, and may have a multi-stage structure in which a plurality of them are stacked in parallel with each other, and the difference in the shape and the number of the waveguides 12 does not change the gist of the present invention.

Further, in the above description of the embodiments, the matters concerning the dimensions (for example, setting the distance HA to be a quarter wavelength of the radio wave of the upper limit frequency of use, etc.) are the same as the predetermined values in practice. It may not be, but for this,
It should be understood as including a predetermined value and a range of values before and after the predetermined value as long as they are consistent with the spirit of the present invention. Further, the specific values of the dimensions illustrated in the examples are different due to the difference in operating frequency and the like, and the difference in the specific values does not change the gist of the present invention.

[0040]

As described above, according to the present invention, a director is provided in front of the radiation surface of an equiangular spiral antenna having a reflector behind a conformal spiral conductor forming a radiation surface. There is a remarkable effect that it is possible to provide an antenna having high gain and stable operation gain characteristics with little fluctuation over the entire frequency range used.

[Brief description of drawings]

FIG. 1 is a perspective view of main constituent members of a first embodiment of the present invention,

FIG. 2 is a central longitudinal sectional view of the first embodiment of the present invention,

FIG. 3 is a perspective view of a reflector structure according to a second embodiment of the present invention,

FIG. 4 is a central longitudinal sectional view of a second embodiment of the present invention,

FIG. 5 is an operational gain characteristic diagram of the first embodiment of the present invention,

FIG. 6 is an operational gain characteristic diagram of the second embodiment of the present invention,

FIG. 7 is an operational gain characteristic diagram of a conventional example.

[Explanation of symbols]

1 ... Waveguide structure 2 ... Radiator structure 3 ... Reflector structure 4 ... Feeder structure 5 ... Case 6 ... Feed line 7 ... Connector 11 ... Lid body 12 ... Waveguide 21 ... Printed circuit board 22, 23 ... Equiangular spiral Conductor 31 ... Conical cylinder 32 ... First cylinder 33 ... Second cylinder 41 ... Printed circuit board 42 ... Microstrip line 43 ... Ground conductor

Claims (7)

[Claims] 1. A flat, equiangular spiral conductor is formed,
In an equiangular spiral antenna whose feeding point is the center end point of the equiangular spiral conductor, a reflector made of a conductor is provided behind the radio wave emitting surface of the equiangular spiral conductor, and a conductor is provided in front of the radio wave emitting surface of the equiangular spiral conductor. An equiangular spiral antenna with a body-made director. 2. A reflector is formed on a conical surface, a line connecting the apex of the conical surface and the center of the skirt circumferential surface coincides with a center line that passes vertically through the center of the equiangular spiral conductor surface, and The equiangular spiral antenna according to claim 1, wherein the positional relationship is set so that the apex is closer to the equiangular spiral conductor than the circumferential surface of the skirt portion. 3. The distance between the apex of the conical surface of the reflector and the equiangular spiral conductor is set to a length corresponding to a quarter wavelength of the radio wave of the upper limit frequency of use, and the circumferential surface of the hem of the conical surface is set. The conformal spiral antenna according to claim 2, wherein the distance from the conformal spiral conductor is set to a length corresponding to a quarter wavelength of a radio wave having a lower limit frequency of use. 4. A reflector is formed by stacking two structures having circular planes having different diameters so that the circular planes are parallel to each other and the center lines passing through the respective centers perpendicularly coincide with each other. The center lines of the two circular planes that are formed in a shape coincide with the center line that passes vertically through the center of the equiangular spiral conductor surface, and the circular plane having the smaller diameter is the equiangular spiral conductor than the circular plane having the larger diameter. The conformal spiral antenna according to claim 1, wherein the positional relationship is set so as to be closer to each other. 5. The distance between the circular flat surface of the reflector having a small diameter and the equiangular spiral conductor is 1 / of the radio wave of the upper limit frequency of use.
The length corresponding to four wavelengths is set, and the distance between the circular flat surface having a large diameter and the conformal spiral conductor is set to a length corresponding to ¼ wavelength of a radio wave having a lower limit frequency of use. The conformal spiral antenna according to 4. 6. A reflector is provided inside the cylindrical case, an equiangular spiral conductor is formed on the circular end surface of the cylindrical case, and a cylindrical lid body made of an insulator is formed on the circular end surface of the cylindrical case. The conformal spiral antenna according to any one of claims 1 to 5, wherein the cylindrical lid is covered with a director at the center of the upper circular surface. 7. A screw having a male and female relationship is provided on each of the inside of the side surface of the cylindrical lid and the outside of the side surface of the cylindrical case. The cylindrical lid is attached to the cylindrical case by screwing, and the degree of screwing is performed. The conformal spiral antenna according to claim 6, wherein the distance between the conformal spiral conductor and the director is adjustable by.