WO2021192823A1

WO2021192823A1 - Tapered tem horn antenna

Info

Publication number: WO2021192823A1
Application number: PCT/JP2021/007641
Authority: WO
Inventors: 勝茂張間
Original assignee: 国立研究開発法人情報通信研究機構
Priority date: 2020-03-26
Filing date: 2021-03-01
Publication date: 2021-09-30
Also published as: JP2021158467A

Abstract

Provided is a tapered TEM horn antenna which has high radiation efficiency across a wide frequency band, which has favorable reflection characteristics and radiation characteristics, and which is small.　A tapered TEM horn antenna (1) is provided with a pair of antenna elements （１０_１，１０_２）that expand, from an end section (11) to an opening section (12), in the height direction in a curved tapered shape expressed by an exponential function.

Description

Tapered TEM horn antenna

The present invention relates to a tapered TEM horn antenna used for EMC tests such as proximity radiation immunity test.

The international standard proximity radiation immunity test stipulates the use of a TEM horn antenna (Non-Patent Document 1). This TEM horn antenna is composed of a pair of metal plates arranged so as to face each other, and it is necessary to consider matching of the characteristic impedances of the feeding portion and the opening in order to reduce the influence of reflection.

Conventionally, a linear taper TEM horn antenna that is resistance-loaded on a plate having a linear spread is known (Non-Patent Documents 2 and 3). Further, an exponential taper TEM horn antenna that does not require resistance loading by applying an exponential taper transmission line to a plate structure is also known (Non-Patent Documents 4 and 5).

However, the conventional linear taper TEM horn antenna has a problem that the radiation efficiency is lowered due to the resistance loaded on the plate. Further, the conventional exponential taper TEM horn antenna has a problem due to the structure that there is a frequency band in which the maximum gain direction and the front direction of the antenna do not match. Further, the conventional linear taper TEM horn antenna and the exponential taper TEM horn antenna have an antenna length of half a wavelength or more of the lower limit frequency, and therefore become large in the 300 MHz band or less.

Therefore, an object of the present invention is to provide a tapered TEM horn antenna having high radiation efficiency over a wide frequency band, good reflection characteristics and radiation characteristics, and a small size.

In order to solve the above problems, the tapered TEM horn antenna according to the present invention is a tapered TEM horn antenna including a pair of antenna elements arranged to face each other and a feeding portion connected to one end of the pair of antenna elements. Therefore, the antenna element is a narrowing portion that expands in the width direction in a linear taper shape from one end to the opening formed on the opposite side of the one end, and narrows in the width direction from both ends of the opening toward the center. Was formed, and the pair of antenna elements had a curved taper shape represented by an exponential function and spread in the height direction from one end to the opening.

According to such a tapered TEM horn antenna, a hybrid structure having a linear taper shape and a curved taper shape that matches the characteristic impedance of the taper transmission line so that the characteristic impedance changes continuously is adopted, and predetermined from both ends of the opening. Removed the size area. As a result, according to the tapered TEM horn antenna, impedance matching due to resistance loading is not required, and the maximum gain direction and the front direction of the antenna can be matched. Therefore, the tapered TEM horn antenna has high radiation efficiency over a wide frequency band, has good reflection characteristics and radiation characteristics, and can be miniaturized.

According to the present invention, it is possible to realize a compact tapered TEM horn antenna having high radiation efficiency over a wide frequency band, good reflection characteristics and radiation characteristics.

It is a schematic block diagram of the taper TEM horn antenna which concerns on embodiment, (a) shows after removing a region, (b) shows before removing a region. (A) is a plan view of the tapered TEM horn antenna according to the embodiment, and (b) is a side view of the tapered TEM horn antenna. It is explanatory drawing explaining the region to remove from the antenna element in embodiment. (A) to (c) are plan views which show another example of a taper TEM horn antenna. (A) is a graph showing the gain characteristics in the examples, and (b) is a graph showing the gain characteristics in the comparative examples. (A) is a graph showing the reflection characteristics in the examples, and (b) is a graph showing the reflection characteristics in the comparative examples. (A) to (f) are graphs showing the electric field distribution at a typical test frequency at a location 10 cm away from the opening surface of the antenna in the embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiments described below are for embodying the technical idea of the present invention, and the present invention is not limited to the following unless otherwise specified. Further, in the embodiment, the same means may be designated by the same reference numerals and the description thereof may be omitted.

[Configuration of taper TEM horn antenna]
Hereinafter, the configuration of the tapered TEM horn antenna 1 according to the embodiment will be described.
As shown in FIG. 1 (a), tapered TEM horn antenna 1, the opposed pair of antenna elements which are arranged 10 ₍₁₀ 1, 10 _2), which is connected to one end of the pair of antenna elements 10 feed A unit 20 is provided.

Hereinafter, the horizontal direction (width direction) is defined as the X axis, the vertical direction (height direction) is defined as the Y axis, and the depth direction is defined as the D axis. That is, it is a three-dimensional coordinate system in which the horizontal direction, the vertical direction, and the depth direction are orthogonal to each other.
Further, the antenna element before forming the narrowing portion 14 described later is described as "antenna element 90", and the antenna element after forming the narrowing portion 14 is described as "antenna element 10". Hereinafter, the antenna element 10 and the antenna element 90 will be described separately as needed. Further, in FIGS. 1 (a) and 2 (a), the antenna element 90 is shown by a broken line.
Further, when the two antenna elements are described together, it is simply described as "antenna element 10".

The pair of antenna elements 10 are _{arranged so that the two} _{antenna elements 10 1} and 102 face each other and emit electromagnetic waves. That is, _{the flat surfaces of the two} _{antenna elements 10 1} and 102 are arranged so as to face each other. Further, the two

antenna elements

10 ₁ and 10 ₂ have the same shape and the same size. For example, the antenna element 10 can be formed of a metal plate such as aluminum, copper, or brass, and its thickness is 0.7 mm.

In the antenna element 10, the feeding portion 20 is connected to one end portion 11, and the opening 12 is formed on the opposite side of the one end portion 11 in the depth direction. Hereinafter, the XY plane in the opening 12 will be referred to as an “opening surface”.

Here, the antenna element 10 has a hybrid structure having a linear taper shape and a curved taper shape so that the characteristic impedance continuously changes from the feeding portion 20 to the opening portion 12. Specifically, as shown in FIG. 2A, when the tapered TEM horn antenna 1 is viewed from the vertical direction, the antenna element 10 has a linear taper shape from one end 11 toward the opening 12 in the horizontal direction. It has spread to. That is, the closer the one end portion 11 to the opening portion 12 in the depth direction, the wider the width of the antenna element 90 becomes linearly. Further, as shown in FIG. 2 (b), when viewed tapered TEM horn antenna 1 from the horizontal spacing of the

antenna elements

₁₀ 1, 10 _2, from one end 11 to the opening 12 is represented by an exponential function Curve taper and widen in the vertical direction. That is, from one end 11 in the depth direction closer to the opening 12, the spacing of the

antenna elements

₁₀ 1, 10 ₂ is widely curved.

Further, as shown in FIGS. 1A and 2A, the antenna element 10 is formed with a narrowing portion 14 narrowing in the width direction from both end sides to the center side of the opening 12. That is, in the antenna element 10, the width reduction portion 14 is formed so that the width of the antenna element 10 becomes narrower from the vicinity of the center to the opening 12 in the depth direction. Here, the width reduction portion 14 can be formed on the antenna element 10 by removing the region 13 having a predetermined size from both ends of the antenna element 90. In this embodiment, each of the

antenna elements

₁₀ 1, 10 ₂ in total from both ends four locations, triangular regions ₁₃ 1-13 ₄ is removed. Incidentally, the entire region ₁₃ 1-13 ₄ are the same shape and the same size.

The power feeding unit 20 is connected to one end 11 of the antenna element 10 and supplies electric power of electromagnetic waves radiated by the antenna element 10. For example, the power supply unit 20, the coaxial feeding section and the like which are connected to the

respective antenna elements

₁₀ 1, 10 _2.

[Antenna element structure]
Hereinafter, the structure of the antenna element 10 will be described in detail.
Hereinafter, the overall length, width, and height of the antenna element 10 will be described as L, W, and H, respectively. The total length L of the antenna element 10 represents the length from one end 11 to the opening 12 in the depth direction. Further, the total width W of the antenna element 10 before removing the region 13 is equivalent to the total width of the antenna element 90, and represents the width of the opening 12 in the horizontal direction. Further, the total height H of the antenna element 10 represents the height of the opening 12 in the vertical direction.

As shown in FIG. 2A, at an arbitrary distance d, the width w (d) of the antenna element 10 before removing the region 13 is equivalent to the width of the antenna element 90, and the following equation (1) And expressed by equation (2). _{The width w 0} = w (0) of the one end portion 11 _{and the width W = w L} = w (L) of the opening 12. Further, the distance d represents the distance from one end portion 11 to an arbitrary position in the depth direction.

As shown in FIG. 2 (b), at any distance d, the

antenna elements

₁₀ 1, 10 ₂ of the spacing h (d) is an exponential function (exactly as shown in the following equation (3) to (5) Is the product of the exponential function and the linear function). _{The input impedance Z 0} = Z (0) at the one end portion 11 _{and the characteristic impedance Z L} = Z (L) at the opening 12.

That is, as shown in the above equation (4), the tapered TEM horn antenna 1 has the characteristic impedance Z (d) of the exponential taper transmission line at an arbitrary distance d. Here, consider a case where the antenna element 10 is composed of a large number of parallel flat plates having a minute width. In this case, _{the distance h (d) between the two} _{antenna elements 10 1} and 102 uses the characteristic impedance Z (d) of the exponential taper transmission line and the width w (d) represented by a linear taber shape. It is represented by the above equation (3).

In this way, in the tapered TEM horn antenna 1, the width w (d) and the interval h (d) of the antenna element 10 can be determined so that the characteristic impedance of the antenna maintains the characteristic impedance of the tapered transmission line.

Hereinafter, the region 13 to be removed from both ends of the antenna element 10 will be described with reference to FIG. In FIG. 3, the region 13 is removed from _{the left end 12 L} of the antenna element 10 in order to make the drawing easier to see. _{Needless to say, the right end 12 R} of the antenna element 10 is also removed in the same manner as the left end 12 _L (not shown in FIG. 3). Further, in FIG. 3, in order to make the drawing easier to see, the antenna element 10 is shown by a broken line, and the feeding unit 20 is not shown.

As shown in FIG. 3, the region 13 is a region having a minimum region R _min or more and a maximum region R _max or less. Here, the minimum region R _min _{is a region from the left end 12 L} of the antenna element 10 to the _{boundary line L min} where θ = 60 ° with respect to the opening surface at _{the position w min} at 20% of the opening width W. The maximum region R _max _{is a region from the left end 12 L} of the antenna element 10 to the _{boundary line L max} where θ = 60 ° with respect to the aperture surface at _{the position w max} of 50% of the aperture width W. _{That is, it may be removed from the left end 12 L} of the antenna element 10 within a range that is the difference between the maximum region R _max and the minimum region R _min (within the range shown by hatching in FIG. 3).

For example, the antenna element 10 of FIG. 2A has a boundary where θ = 50 ° with respect to the opening surface at _{a position w c} of 37% of the opening width W within the range shown by hatching in FIG. 3 from both ends thereof. The region 13 up to the line is removed. Further, as shown in FIG. 4A, the antenna element 10 removes the region 13 from both ends thereof to the boundary line where θ = 43 ° with respect to the opening surface at a position of 46% of the opening width W. May be good. In this way, the antenna element 10 can be linearly removed within the range illustrated by the hatching in FIG. The antenna element 10 is located w _c becomes scalene hexagonal shape in the case of less than 50% of the opening width W, the position w _c is the scalene pentagonal shape when 50% of the aperture width W.

Further, the antenna element 10 may be removed in a curved shape as long as it is within the range shown by the hatching in FIG. As shown in FIG. 4B, the concave curved region 13 may be removed from both ends of the antenna element 10. In this case, the antenna element 10 is formed with a width reduction portion 14 that swells in the horizontal direction. Further, as shown in FIG. 4C, the convex curved region 13 may be removed from both ends of the antenna element 10. In this case, the antenna element 10 is formed with a width reduction portion 14 that contracts in the horizontal direction.
The method of manufacturing the antenna element 10 is arbitrary. For example, the region 13 may be cut off from both ends of the antenna element 90 of FIG. 1 (b).

[Action / Effect]
According to the tapered TEM horn antenna 1 according to the embodiment, a hybrid structure having a linear tapered shape and a curved tapered shape is adopted, and regions 13 of a predetermined size are removed from both ends of the opening 12, so that the characteristic impedance matching can be performed. No resistance loading is required, and the maximum gain direction can be matched with the front direction of the antenna. As a result, the tapered TEM horn antenna 1 has high radiation efficiency over a wide frequency band, has good reflection characteristics and radiation characteristics, and can be miniaturized.

Hereinafter, as an example, the evaluation result of the tapered TEM horn antenna 1 of FIG. 1A will be described. In this embodiment, the characteristics of the tapered TEM horn antenna 1 are optimized under the condition that the total length L of the antenna element 10 = the total height H = the total width W = 24.5 cm. Specifically, in the tapered TEM horn antenna 1, the region 13 up to the boundary line where θ = 50 ° with respect to the opening surface at _{the position w c at 37% of the opening width W is removed from both ends of the antenna element 10.} .. Further, the input impedance of the feeding unit 20 is 50Ω, and the characteristic impedance of the opening 12 is 377Ω.

For example, in the conventional exponential taper TEM horn antenna, the total length of the antenna element is 56 cm. On the other hand, in the tapered TEM horn antenna 1, the total length L of the antenna element 10 is reduced to less than half, and the size can be significantly reduced as compared with the conventional case.

Here, as shown in FIG. 1 (b), the taper TEM horn antenna provided with the antenna element 90 will be described as a comparative example. The tapered TEM horn antenna according to the comparative example has the same configuration as that of the embodiment except that the region 13 is not removed from the antenna element 90.

The characteristics (gain characteristics, reflection characteristics) of the tapered TEM horn antenna 1 according to the embodiment are shown in FIGS. 5 and 6. These gain characteristics and reflection characteristics are calculation results (simulation results) by the finite integration method.
FIG. 5A is a graph showing the gain characteristics in the examples, and FIG. 5B is a graph showing the gain characteristics in the comparative examples. Further, in FIG. 5, the horizontal axis is the frequency and the vertical axis is the gain. Further, in FIG. 5, the gain in the front direction of the antenna at each frequency is shown by a solid line, and the maximum gain at each frequency is shown by a broken line.

As shown in FIG. 5A, in the embodiment, the solid line and the broken line overlap in all frequency bands, and the maximum gain is obtained in the front direction. As described above, the tapered TEM horn antenna 1 according to the embodiment has directivity without beam cracking. On the other hand, as shown in FIG. 5B, in the comparative example, the solid line and the broken line are deviated in the frequency band of about 4 GHz to 6 GHz, and the maximum gain is not obtained in the front direction of the antenna.

FIG. 6A is a graph showing the reflection characteristics in the examples, and FIG. 6B is a graph showing the reflection characteristics in the comparative examples. Further, in FIG. 6, the horizontal axis is the frequency and the vertical axis is the voltage standing wave ratio (VSWR: Voltage Standing Wave Ratio). Further, in FIG. 6, the standard limit value for the antenna of the proximity radiation immunity test is shown by a broken line.

As shown in FIG. 6A, in the embodiment, VSWR is less than the standard limit value in all frequency bands, which completely satisfies the standard of the proximity radiation immunity test. On the other hand, as shown in FIG. 6B, in the comparative example, there is a frequency band in which VSWR exceeds the standard limit value. As described above, the tapered TEM horn antenna 1 according to the embodiment completely satisfies the standard of the proximity radiation immunity test.

In the proximity radiation immunity test, the uniform electric field region of the irradiation surface is defined as the range of 4 dB from the maximum electric field value. FIG. 7 is a graph showing the electric field distribution at a typical test frequency at a location 10 cm away from the opening surface of the antenna. In FIG. 7, the horizontal axis represents the horizontal position, the vertical axis represents the vertical position, and 0 cm represents the center of the opening 12 of the antenna element 10. This electrolytic distribution is a calculation example by simulation.

As shown in FIGS. 7A to 7F, in the embodiment, a good electric field irradiation region without failure can be formed in the vicinity of the antenna in the entire frequency band. As shown in FIG. 7 (f), a sufficiently wide electric field irradiation region is secured in the high frequency band, which is important in the proximity radiation immunity test.

As described above, the tapered TEM horn antenna 1 according to the embodiment has high radiation efficiency because it does not require resistance loading, and has reflection characteristics that satisfy the specifications of the proximity radiation immunity test at all test frequencies. Further, the tapered TEM horn antenna 1 according to the embodiment has directivity without beam cracking and has radiation characteristics capable of forming a good electric field irradiation region in the vicinity of the antenna. As described above, the tapered TEM horn antenna 1 according to the embodiment is considered to be most suitable as a small antenna for EMC testing.

1 Tapered

TEM horn antenna

10 _{, 10 1} , 10 ₂ Antenna element 11 One end 12 Opening 13 Removal area 14 Narrowing part 20

Feeding part

90, 90 ₁ _{, 90 2} Antenna element

Claims

A tapered TEM horn antenna including a pair of antenna elements arranged to face each other and a feeding portion connected to one end of the pair of antenna elements.
The antenna element has a linear taper shape that spreads in the width direction from one end to the opening formed on the opposite side of the one end, and narrows in the width direction from both ends of the opening toward the center. The part is formed,
The pair of antenna elements is a tapered TEM horn antenna characterized in that it extends from one end to the opening in a curved taper shape represented by an exponential function in the height direction.
The tapered TEM horn antenna according to claim 1, wherein the antenna element has a narrowed portion formed by removing a region having a predetermined size from both ends of the opening.
The region is equal to or greater than the minimum region from both ends of the opening to the boundary line at 60 ° with respect to the opening surface at a position of 20% of the opening width of the opening, and the opening width is 50 from both ends of the opening. The tapered TEM horn antenna according to claim 2, wherein the area is equal to or less than the maximum region up to the boundary line which is 60 ° with respect to the opening surface at the% position.
The distance d from the one end in the depth direction, the total length L from the one end to the opening, the width w 0 of the antenna element at the one end, and the total width of the antenna element before removing the region. Using equations (1) and (2) that include w L,

The tapered TEM horn antenna according to claim 2 or 3, wherein the width w (d) of the antenna element before removing the region is represented.
Using equations (3) to (5) including the input impedance Z 0 at one end and the characteristic impedance Z L at the opening,

The tapered TEM horn antenna according to claim 4, wherein the distance h (d) between the pair of antenna elements is represented.