JP3870902B2 - Bowtie antenna device and bowtie array antenna device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an antenna device for obtaining a highly efficient and smooth frequency characteristic over a wide band in a broadband antenna device.
[0002]
[Prior art]
In the conventional bow tie antenna device, since a ferrite is provided as a radio wave absorber inside the cylindrical conductor provided in the antenna conductor, and a resistance element connecting the antenna conductor and the cylindrical conductor is provided, the traveling wave type It has a smooth frequency characteristic over a wide band. (For example, refer nonpatent literature 1.)
[0003]
[Non-Patent Document 1]
Yasuhiro Nishioka "Effective Radiation Efficiency of Resistor-Loaded Bow-Tie Antenna Covered with Ferrite-Coated Conducting Cavity LoC. E83-B, NO. 2, FEBRUARY 2000.
[0004]
[Problems to be solved by the invention]
In the conventional bow tie antenna device, since the ferrite is provided inside the cylindrical conductor as a radio wave absorber, the resonance phenomenon determined by the dimension of the cylindrical conductor is suppressed, and further, the resistance element connected to the antenna conductor and the cylindrical conductor Since it operates as a traveling wave antenna having a broadband characteristic, it has a configuration having a smooth frequency characteristic over a wide band. However, there is a problem that the antenna efficiency is lowered due to heat loss due to the radio wave absorber and the resistance element. In addition, there is a problem that it is difficult to manufacture the resistor element when it is actually provided.
[0005]
The present invention has been made to solve the above-mentioned problems, and a bow-tie antenna device having a smooth frequency characteristic over a wide band without reducing antenna gain by not using a radio wave absorber and a resistance element. The purpose is to obtain.
[0006]
[Means for Solving the Problems]
The bow tie antenna device according to the present invention assumes a first conductor having a triangular shape and an axis provided with a gap from one apex of the first conductor, and the axis is symmetrical with respect to the axis. A second conductor in which the first conductor is arranged symmetrically is provided, an antenna conductor composed of the first conductor and the second conductor, one bottom surface is opened, and a connector is provided on the other bottom surface. A balun circuit having means for converting the coaxial-mode electromagnetic field supplied from the connector into a balanced mode is provided inside the cylindrical conductor so that the antenna conductor is provided so as not to contact the cylindrical conductor. In the bow tie antenna device further comprising the balun circuit connected to two apexes of the first conductor and the second conductor that are close to each other, the first conductor and the second conductor. Each of the conductors has a cutting portion formed substantially in parallel with the base of the triangle whose apex is a connection point with the balun circuit, and each of the first conductor and the second conductor is the cutting The structure is divided into conductor patterns having no electrical connection by the portion.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
FIG. 1 shows a bow tie antenna apparatus according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view of the first embodiment shown in FIG. In FIG. 1, the inner conductor 1 of the connector protrudes into the cylindrical conductor 2, and the outer conductor 3 of the connector is connected to the bottom surface 4 of the cylindrical conductor. The inner conductor 1 of the connector is connected to the signal line 6 of the balun circuit 5 provided inside the cylindrical conductor 2, and the ground line 7 of the balun circuit 5 is connected to the bottom surface 4 of the cylindrical conductor. Further, the balun circuit 5 is provided with a balanced two-wire line 10 for supplying power to the first conductor 8 having a cut portion and the second conductor 9 having the cut portion, and the first conductor having the cut portion. Are connected to the vertex 11 of the second conductor and the vertex 12 of the second conductor having the cut portion.
[0008]
The operation when used as a transmitting antenna in the above configuration will be described. The same operation can be explained at the time of reception using the reversibility of the antenna. Input unbalanced signal microwave from the connector. The unbalanced signal microwave input to the connector is input to the balun circuit 5 and converted into a balanced signal microwave by the balun circuit 5, and the first conductor 8 having a cut portion and the second conductor having the cut portion. 9 outputs a microwave signal having a phase difference of 180 °. The first conductor 8 having a cut portion to which the microwave signal is input and the second conductor 9 having the cut portion create an electric field 13 of the first embodiment as shown in FIG. 3 to excite the cylindrical conductor 2. , Electromagnetic waves radiate into space. The radiation pattern at this time is shown in FIG.
[0009]
According to non-patent literature, the antenna efficiency decrease 14 due to the radio wave absorber and the resistance element in the conventional bow tie antenna device is as shown in FIG. 5, and the antenna efficiency is decreased by 35% or more over a wide band.
[0010]
Next, a decrease in antenna efficiency when the absorber and the resistance element are not used will be described. In the conventional bow tie antenna device, when the radio wave absorber and the resistance element are not provided, the reflected power loss in the reflection characteristics of the antenna, that is, the lost power obtained by dividing the reflected power returning to the connector by the input power is the radio wave absorption in FIG. The actual measurement data 15 is obtained when the body and the resistance element are not provided, and the reflected power loss exceeds 60% at a low frequency. As described in the non-patent document, the resistance element that reduces the resonance of the antenna is removed, so that it does not operate as a traveling wave antenna. As a result, the dimension obtained by adding the first conductor and the second conductor is In the vicinity of the frequency that is approximately λ / 2 or in the frequency band below that frequency, the radiation length is insufficient, so that the radiation resistance is reduced, and it is not possible to match the spatial impedance of about 377 ohms. Energy is returned to the connector, the antenna efficiency in the low band is lowered, and a smooth frequency characteristic over a wide band cannot be obtained. Therefore, the resistance element in the conventional bow tie antenna device is indispensable for obtaining smooth frequency characteristics. The traveling wave antenna is an antenna composed of an excitation unit, a waveguide unit, and a termination unit, and electromagnetic wave energy flows from the excitation unit to the termination unit only in one direction. In the conventional bow tie antenna device, the excitation portion corresponds to the balun circuit 5, the waveguide portion corresponds to the antenna conductor, and the termination portion corresponds to the resistance element.
[0011]
On the other hand, in the bow tie antenna device of the first embodiment in which the antenna conductor is provided with a cut surface, the measured data 16 of the first embodiment shown in FIG. 6 is obtained, and the reflected power loss is 15% or less. At this time, since the radio wave absorber and the resistance element are not provided in the first embodiment, there is no reduction in antenna efficiency due to the radio wave absorber and the resistance element. Therefore, when a cut surface is provided in the antenna conductor, a bow-tie antenna device can be obtained which can obtain a high-efficiency and smooth broadband frequency characteristic even without a radio wave absorber and a resistance element.
[0012]
In addition, although the explanatory drawing of Embodiment 1 is a cylindrical conductor, the same effect is acquired also in the cylindrical conductor of arbitrary shapes.
[0013]
Embodiment 2
FIG. 7 shows a bow tie antenna device according to Embodiment 2 of the present invention. In FIG. 7, the inner conductor 1 of the connector protrudes into the rectangular tubular conductor 17, and the outer conductor 3 of the connector is connected to the bottom surface 18 of the rectangular tubular conductor. The inner conductor 1 of the connector is connected to the signal line 6 of the balun circuit 5 provided inside the rectangular tubular conductor 17, and the ground line 7 of the balun circuit 5 is connected to the bottom surface 18 of the rectangular tubular conductor. Further, the balun circuit 5 is provided with a balanced two-wire line 10 for supplying power to the first conductor 8 having a cut portion and the second conductor 9 having the cut portion, and the first conductor having the cut portion. Are connected to the vertex 11 of the second conductor and the vertex 12 of the second conductor having the cut portion.
[0014]
The operation when used as a transmitting antenna in the above configuration will be described. The same operation can be explained at the time of reception using the reversibility of the antenna. Input unbalanced signal microwave from the connector. The unbalanced signal microwave input to the connector is input to the balun circuit 5 and converted into a balanced signal microwave by the balun circuit 5, and the first conductor 8 having a cut portion and the second conductor having the cut portion. 9 outputs a microwave signal having a phase difference of 180 °. The first conductor 8 having a cut portion to which the microwave signal is input and the second conductor 9 having a cut portion create the electric field 20 of the second embodiment as shown in FIG. 8 and excite the rectangular tubular conductor 18. And radiate electromagnetic waves into space. The radiation pattern at this time is also a pattern equivalent to the first embodiment.
[0015]
When a bow tie antenna device that is a phased array antenna and is not provided with a radio wave absorber and a resistance element is arranged with a certain regularity, the dimensions of the cylindrical conductor are determined by the arrangement interval. When exciting a cylindrical conductor in a bow tie antenna device without a wave absorber and a resistive element, the fundamental mode of the waveguide is excited, so the cutoff frequency determined by the shape of the cylindrical conductor has an effect, and the frequency below the cutoff. In the band, radiation resistance becomes low and radiation becomes difficult.
[0016]
For example, in a regular triangle arrangement, a bow tie antenna device configured with a cylindrical conductor has a cylindrical shape in which the length 20 of one side of the regular triangle arrangement and the diameter 21 of the cylindrical conductor are the same as shown in FIG. A bow tie antenna device with the maximum conductor diameter 21 can be arranged. Therefore, the fundamental mode at the maximum diameter of the cylindrical conductor when arranged in an equilateral triangle, that is, the cut-off frequency of the TE11 mode is expressed by Equation 1 using the length 20 of one side of the equilateral triangle arrangement. Here, f1 in Equation 1 is the cutoff frequency of the TE11 mode, which is the fundamental mode of the cylindrical conductor, π is the circumference, d is the length 20 of one side of the equilateral triangle array, ε is the dielectric constant in the cylindrical conductor, μ Is the magnetic permeability in the cylindrical conductor.
f1 = 1.842 / {π × d × √ (ε × μ)} (1)
[0017]
Next, a description will be given of a bow tie antenna device configured with a rectangular tubular conductor in an equilateral triangular arrangement. In the equilateral triangle arrangement, the bow tie antenna device constituted by the rectangular tubular conductor has the same length 20 on one side of the equilateral triangle arrangement and the dimension 22 in the direction perpendicular to the electric field of the rectangular tubular conductor as shown in FIG. In this case, it is possible to arrange a bow tie antenna device in which the dimension 22 in the direction perpendicular to the electric field of the rectangular tubular conductor is maximized. Therefore, the fundamental mode in the rectangular tubular conductors arranged in an equilateral triangle, that is, the cut-off frequency of the TE01 mode is expressed by using the length 20 of one side of the equilateral triangle arrangement. Here, f2 in Equation 2 is the cutoff frequency of the TE01 mode, which is the fundamental mode of the rectangular tubular conductor, π is the circumference, d is the length of one side of the equilateral triangle array, and ε is the dielectric constant in the rectangular tubular conductor. , Μ is the magnetic permeability in the rectangular tubular conductor.
f2 = 1 / {2 × d × √ (ε × μ)} (2)
[0018]
The cutoff frequency f1 of the TE11 mode that is the fundamental mode of the cylindrical conductor of Equation 1 is compared with the cutoff frequency f2 of the TE01 mode that is the fundamental mode of the rectangular tubular conductor of Equation 2. When the ratio of f1 in Equation 1 and f2 in Equation 2 is calculated, Equation 3 is obtained. Here, f1 in Equation 3 is the cutoff frequency of the TM11 mode, which is the fundamental mode of the cylindrical conductor, f2 is the cutoff frequency of the TE01 mode, which is the fundamental mode of the rectangular tubular conductor, and f1: f2 is the frequency of f1 and f2. Indicates the ratio.
f1: f2 = 3.682: π≈3.682: 3.14 (3)
[0019]
As a result, since the cutoff frequency is lower in the case of f2, the frequency band radiated by the rectangular tubular conductor is widened at a lower frequency. Although only the regular triangle array has been described above, the same description can be applied to an array having regularity such as a regular square array. When a bow tie antenna device is used for an array antenna having regularity, a bow tie antenna device having the widest frequency characteristic can be achieved by reducing the cutoff frequency of the cylindrical conductor of the bow tie antenna device having a rectangular tubular conductor to a low frequency range. It becomes. This is the same effect even when the bow tie antenna having no cut surface is used for the antenna conductor shown in the first embodiment, and the same effect is obtained when an array arrangement is used for a broadband antenna using a cylindrical conductor. Is obtained.
[0020]
Embodiment 3 FIG.
FIG. 11 shows a bow-tie antenna device according to Embodiment 3 of the present invention. Here, a case where a flat conductor portion is provided will be described. In FIG. 11, the inner conductor 1 of the connector protrudes into the cylindrical conductor 23 when the flat conductor portion is provided, and the outer conductor 3 of the connector is connected to the bottom surface 24 of the cylindrical conductor when the flat conductor portion is provided. . The inner conductor 1 of the connector is connected to the signal line 6 of the balun circuit 5 provided inside the cylindrical conductor 23 when the flat conductor portion is provided, and the electric field direction is narrowed to the ground line 7 of the balun circuit 5. The flat conductor portion is connected to the bottom surface 24 of the cylindrical conductor when provided. Further, the balun circuit 5 is provided with a balanced two-wire line 10 for supplying power to the first conductor 8 having a cut portion and the second conductor 9 having the cut portion, and the first conductor having the cut portion. Are connected to the vertex 11 of the second conductor and the vertex 12 of the second conductor having the cut portion.
[0021]
The operation when used as a transmitting antenna in the above configuration will be described. The same operation can be explained at the time of reception using the reversibility of the antenna. Input unbalanced signal microwave from the connector. The unbalanced signal microwave input to the connector is input to the balun circuit 5 and converted into a balanced signal microwave by the balun circuit 5, and the first conductor 8 having a cut portion and the second conductor having the cut portion. 9 outputs a microwave signal having a phase difference of 180 °. The first conductor 8 having the cut portion to which the microwave signal is input and the second conductor 9 having the cut portion create the electric field 25 of Embodiment 3 as shown in FIG. In this case, the cylindrical conductor 23 is excited to emit an electromagnetic wave to the space. The radiation pattern at this time is also the same radiation pattern as in the first embodiment.
[0022]
The basic mode for exciting the cylindrical conductor 23 in the case where the bow tie antenna device in the third embodiment is provided with the flat conductor portion is an electric field 26 similar to the basic mode of the rectangular waveguide shown in FIG. 13, and is substantially perpendicular to the electric field. When the directional dimension is extended in electrical length, the cut-off frequency shifts to a low frequency. Therefore, in the cylindrical conductor and the rectangular tubular conductor described in the second embodiment, the dimension 27 in the direction substantially perpendicular to the electric field has the same electrical length as that of the rectangular tubular conductor in the central portion of the cylindrical conductor, but is separated from the central portion. Accordingly, the electrical length of the entire cylindrical conductor is shorter for the cylindrical conductor. As a result, the cut-off frequency is higher for conductors such as circles.
[0023]
Furthermore, by forming the cylindrical conductor portion into a shape having a flat conductor portion, the electric field generated between the flat conductor and the first conductor 8 having the cut portion and the second conductor 9 having the cut portion is also implemented. Similarly to the second embodiment, the first conductor 8 having the cut portion, the second conductor 9 having the cut portion, and the flat portion are uniformly spaced, so that the electric field of the bow tie antenna device of the second embodiment Get closer.
[0024]
Based on this principle, in Embodiment 3, the dimension 27 in the direction substantially perpendicular to the electric field is longer in the entire cylindrical conductor than in the cylindrical conductor, and the cut-off frequency is lower than that in the cylindrical conductor. As a result, a low-frequency frequency is expanded as compared with a bow-tie antenna device configured with a cylindrical conductor, and a bow-tie antenna device with higher bandwidth is obtained. Thereby, it is possible to obtain a wide band simply by processing the inside of the cylindrical conductor, and to obtain a wide band even if a cylindrical conductor smaller than the cylindrical conductor is used, and the antenna can be downsized.
[0025]
When a convex conductor is provided instead of providing a flat conductor for the cylindrical conductor, the electrical length of dimension 27 in the direction substantially perpendicular to the electric field is extended due to inductivity, and a flat conductor is provided. The same effect as the case is obtained.
[0026]
Embodiment 4 FIG.
Note that even in the bow tie array antenna device in which a plurality of the first to third embodiments are arranged, a bow tie array antenna device having a high-efficiency and smooth frequency characteristic can be realized. In addition, since no resistive element is used, an active phased array having an antenna system that exceeds the power resistance of the resistive element, for example, a module 29 equipped with an amplifier that supplies large power to the back of each antenna element as shown in FIG. Application to a radar system or the like becomes possible.
[0027]
【The invention's effect】
In order to obtain a smooth frequency characteristic over a wide band without providing a radio wave absorber and a resistive element, the bow tie antenna element is cut to provide a smooth frequency characteristic over a wide band without providing a radio wave absorber and a resistive element. A bowtie antenna device is obtained.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a configuration diagram of a bowtie antenna device showing a first embodiment of the present invention.
FIG. 2 is a cross-sectional view of the bow tie antenna device showing Embodiment 1 of the present invention.
FIG. 3 is an electric field diagram inside a cylindrical conductor made by the bow tie antenna device according to the first embodiment of the present invention;
4 is a radiation pattern diagram of the first embodiment. FIG.
FIG. 5 is a diagram showing an antenna efficiency decrease amount of a radio wave absorber and a resistance element calculated from a non-patent document.
FIG. 6 shows the reflected power loss obtained from the measurement data when the radio wave absorber and the resistance element are removed in the conventional bow tie antenna device, and the reflected power loss obtained from the measurement data of the bow tie antenna device of the first embodiment. FIG.
FIG. 7 is a configuration diagram of a bow tie antenna device according to a second embodiment of the present invention.
FIG. 8 is an electric field diagram inside a cylindrical conductor made by the bow tie antenna device according to Embodiment 2 of the present invention;
FIG. 9 is a diagram illustrating a bow tie antenna device using cylindrical conductors arranged in a regular triangular array for explaining the second embodiment of the present invention.
FIG. 10 is a view of a bow tie antenna device using rectangular tubular conductors arranged in a regular triangular array for explaining the second embodiment of the present invention;
FIG. 11 is a configuration diagram of a bow tie antenna device according to a third embodiment of the present invention.
FIG. 12 is an electric field diagram inside a cylindrical conductor made by the bow tie antenna device according to Embodiment 3 of the present invention;
FIG. 13 is an electric field diagram of a fundamental mode when a section of a cylindrical conductor according to the third embodiment is considered as a waveguide.
FIG. 14 is a view showing a configuration in the case of being used in an active phased array antenna system according to a fourth embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Inner conductor of connector, 2 Tube conductor, 3 Outer conductor of connector, 4 Bottom surface of tube conductor, 5 Balun circuit, 6 Signal line, 7 Ground line, 1st conductor which has 8 cut part, 9th which has cut part 2 conductors, 10 balanced two-wire line, 11 apex of the first conductor having a cut portion, 12 apex of the second conductor having a cut portion, 13 electric field of the first embodiment, and 14 radio wave absorber and resistance element 15 antenna measurement, 15 measured data when not configured to provide radio wave absorber and resistance element, 16 measured data of embodiment 1, 17 rectangular tubular conductor, 18 bottom surface of rectangular tubular conductor, 19 of embodiment 2 Electric field, 20 length of one side of regular triangular array, 21 diameter of cylindrical conductor, 22 dimension of rectangular tubular conductor in a direction perpendicular to electric field, 23 cylindrical conductor when flat conductor is provided, 24 flat conductor provided 25, the bottom surface of the cylindrical conductor, 25 the electric field of the third embodiment, the electric field similar to the fundamental mode of the rectangular waveguide, 27 the dimension in a direction substantially perpendicular to the electric field, and 28 the module on which the amplifier is mounted.

Claims (4)

Assuming a first conductor having a triangular shape and an axis provided with a gap from one vertex of the first conductor, the first conductor is arranged symmetrically with respect to the axis. The cylindrical conductor is provided inside the cylindrical conductor provided with the second conductor, the antenna conductor composed of the first conductor and the second conductor, and one bottom face opened and a connector provided on the other bottom face. A balun circuit provided with the antenna conductor so as not to contact the conductor and having means for converting the electromagnetic field of the coaxial mode supplied from the connector into a balanced mode is installed inside the cylindrical conductor, and further the first conductor In the bow tie antenna device formed by connecting the balun circuit to two apexes of the conductor and the second conductor that are close to each other.
Each of the first conductor and the second conductor has a cut portion formed substantially parallel to a base of the triangle having a vertex of a connection point with the balun circuit, and the first conductor and the second conductor Each of the second conductors is divided into conductor patterns having no electrical connection by the cutting portion . 2. The bow tie antenna device according to claim 1, wherein the cylindrical conductor is a rectangular tubular conductor. 2. The bow tie antenna device according to claim 1, further comprising a flat conductor portion or a convex conductor portion in which a part of two opposing side surfaces of the cylindrical conductor is narrowed so as to be axially symmetric with respect to the rotation center axis of the cylindrical conductor. A bow tie antenna device, wherein a tubular conductor is provided, and the antenna conductor is disposed so that both ends of the antenna conductor do not contact the flat conductor portion or the vicinity of the convex conductor portion, respectively. 4. A bow tie array antenna device comprising a plurality of the bow tie antenna devices according to claim 1 arranged in an array.

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