JP6767041B2 - Tapered TEM horn antenna - Google Patents

Description

In the present invention, the maximum radiation direction and the front direction of the antenna are matched in a wide band, and the taper is suitable as an EMC test antenna (for example, an antenna for applying an electric field in a proximity radiation immunity test method, an antenna for measuring an electric field in radiation emission measurement, etc.). Regarding TEM horn antenna.

Conventionally, a TEM horn antenna having a tapered antenna element has been known. The TEM horn antenna has a tapered structure up to the antenna feeding portion and the opening of the horn. At that time, in order to minimize the influence of reflection, it is necessary to match the characteristic impedance of the feeding part and the opening surface. For this reason, a resistance-loaded TEM antenna in which a resistor is loaded on the tapered antenna element is used (see, for example, Non-Patent Document 1 and Non-Patent Document 2).

Further, the resistance-loaded TEM horn antenna described in Non-Patent Documents 1 and 2 is being studied for use as an electric field application antenna in the proximity radiation immunity test method among EMC tests (for example, Non-Patent Document 3). reference). However, the resistance-loaded TEM horn antenna has a problem that the radiation efficiency is lowered due to the resistance on the tapered antenna element. Due to this drawback of reduced radiation efficiency, the resistance-loaded TEM horn antenna is not suitable as an antenna for electric field measurement in radiation emission measurement.

On the other hand, an exponential taper TEM horn antenna having an exponential taper structure that does not require resistance loading has been proposed (see, for example, Non-Patent Document 4). According to the exponential taper TEM horn antenna described in Non-Patent Document 4, there is no problem that the radiation efficiency is lowered unlike the resistance-loaded TEM horn antenna.

M. Kanda, "The Effects of Resistive Loading of" TEM "Horns", IEEE TRANSACTIONS ON ELECTROMAGNETIC COMPATIBILITY, MAY 1982. VOL. EMC-24, NO. 2, p. 245-255 C. A. Grosvenor, R.M. T. Johnk, D.M. R. Novotny, D.I. R. Canles, S.A. Canales, B. Davis, and J. et al. Veneman, "TEM Horn Antenna Design Principles", NIST Technical Note 1544, Jan. 2007. IEC CDV 61000-4-39-ELECTROMAGNETIC COMPATIBILITY (EMC) -Part 4-39: Testing and measurement techniques-Radiated fields in cross-immunity. H. Choi and S. Lee, "DESIGN OF AN EXPONENTIALLY TAPERED TEM HORN ANTENNA FOR THE WIDE BROADBAND COMMUNICATION", MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, M Vol. 40, No. 6, pp. 531-534

However, the invention described in Non-Patent Document 4 has a problem that the maximum radiation direction does not match the front direction of the antenna in a specific frequency band. As described above, if there is a frequency band in which the radiation directivity deteriorates, it is not possible to properly apply a wide band electric field or measure the electric field with one exponential taper TEM horn antenna. Therefore, the exponential taper TEM horn antenna is not suitable for the electric field application antenna in the proximity radiation immunity test method of the EMC test or the electric field measurement antenna in the radiation emission measurement.

Therefore, in the present invention, the maximum radiation direction and the front direction of the antenna are matched in a wide band, and the taper is suitable as an EMC test antenna (antenna for applying an electric field in the proximity radiation immunity test method, an antenna for measuring an electric field in radiation emission measurement, etc.). An object of the present invention is to provide a TEM horn antenna.

In order to solve the above problems, the tapered TEM horn antenna according to claim 1 has an antenna length based on a target minimum frequency so that a continuous impedance change occurs from the input impedance of the feeding portion to the characteristic impedance of the opening surface. For an exponentially tapered TEM horn antenna in which a pair of antenna elements are designed with L, the antenna is cut evenly from the opening surface side of both antenna elements by the cutting length Lc determined from the range of 0.06L to 0.11L. It is characterized in that it is provided with a pair of shortened antenna elements having a length Ls (Ls = L-Lc).

According to the tapered TEM horn antenna according to the present invention, the maximum radiation direction and the front direction of the antenna can be matched in a wide band, and the EMC test antenna (antenna for applying an electric field in the proximity radiation immunity test method, electric field in radiation emission measurement). It is suitable as a measurement antenna, etc.).

(A) is a block diagram which shows the embodiment of the taper TEM horn antenna which concerns on this invention. (B) is a block diagram showing an exponential taper TEM horn antenna which is a base of the taper TEM horn antenna according to the present embodiment. (A) is an explanatory diagram of an exponential taper transmission line, which is a basic concept of an exponential taper TEM horn antenna. (B) is a side view of an exponential taper TEM horn antenna. (C) is a plan view (bottom surface) of an exponential taper TEM horn antenna. FIG. 5 is a gain-frequency characteristic diagram showing a gain in the front direction of the antenna and a maximum radiation gain in an exponential taper TEM horn antenna (cut length Lc = L × 0%). FIG. 5 is a gain-frequency characteristic diagram showing a gain in the front direction of the antenna and a maximum radiation gain in a tapered TEM horn antenna provided with a shortened antenna element having a cut length Lc = L × 2%. FIG. 5 is a gain-frequency characteristic diagram showing a gain in the front direction of the antenna and a maximum radiation gain in a tapered TEM horn antenna provided with a shortened antenna element having a cut length Lc = L × 4%. FIG. 5 is a gain-frequency characteristic diagram showing a gain in the front direction of the antenna and a maximum radiation gain in a tapered TEM horn antenna provided with a shortened antenna element having a cut length Lc = L × 6%. FIG. 5 is a gain-frequency characteristic diagram showing a gain in the front direction of the antenna and a maximum radiation gain in a tapered TEM horn antenna provided with a shortened antenna element having a cut length Lc = L × 8%. FIG. 5 is a gain-frequency characteristic diagram showing a gain in the front direction of the antenna and a maximum radiation gain in a tapered TEM horn antenna provided with a shortened antenna element having a cut length Lc = L × 10%. FIG. 5 is a gain-frequency characteristic diagram showing a gain in the front direction of the antenna and a maximum radiation gain in a tapered TEM horn antenna provided with a shortened antenna element having a cut length Lc = L × 15%. FIG. 5 is a gain-frequency characteristic diagram showing a gain in the front direction of the antenna and a maximum radiation gain in a tapered TEM horn antenna provided with a shortened antenna element having a cut length Lc = L × 20%. Gain-frequency characteristic diagram showing the gain in the front direction of the antenna in a tapered TEM horn antenna provided with a shortened antenna element with a cut length Lc = L × 6% and the gain in the front direction of the antenna in an exponential function tapered TEM horn antenna with an antenna length L. Is. Gain-frequency characteristic diagram showing the gain in the front direction of the antenna in a tapered TEM horn antenna provided with a shortened antenna element with a cut length Lc = L × 8% and the gain in the front direction of the antenna in an exponential function tapered TEM horn antenna with an antenna length L. Is. Gain-frequency characteristic diagram showing the gain in the front direction of the antenna in a tapered TEM horn antenna provided with a shortened antenna element with a cut length Lc = L × 10% and the gain in the front direction of the antenna in an exponential function tapered TEM horn antenna with an antenna length L. Is. Gain-frequency characteristic diagram showing the gain in the front direction of the antenna in the tapered TEM horn antenna provided with the shortened antenna element with the cut length Lc = L × 11% and the gain in the front direction of the antenna in the exponential function tapered TEM horn antenna of the antenna length L. Is. Gain-frequency characteristic diagram showing the gain in the front direction of the antenna in a tapered TEM horn antenna provided with a shortened antenna element with a cut length Lc = L × 12% and the gain in the front direction of the antenna in an exponential function tapered TEM horn antenna with an antenna length L. Is. Gain-frequency characteristic diagram showing the gain in the front direction of the antenna in a tapered TEM horn antenna provided with a shortened antenna element with a cut length Lc = L × 15% and the gain in the front direction of the antenna in an exponential function tapered TEM horn antenna with an antenna length L. Is.

Next, an embodiment of the tapered TEM horn antenna according to the present invention will be described with reference to the accompanying drawings.

FIG. 1A shows a schematic configuration of the tapered TEM horn antenna 10, in which the tapered first shortened antenna element 11 has the same shape as the first shortened antenna element 11 and is symmetrically arranged on the XZ plane. It is composed of a second shortened antenna element 12, a first coaxial feeding unit 13a connected to a power receiving end 11a of the first shortened antenna element 11, and a second coaxial feeding unit 13b connected to a power receiving end 12a of the second shortened antenna element 12. .. In the following description, the horizontal direction is X, the vertical direction is Y, and the opening surface of the tapered TEM horn antenna 10 (including the open end 11b of the first shortened antenna element 11 and the open end 12b of the second shortened antenna element 12). Let Z be the direction orthogonal to the virtual surface of the substantially quadrangle.

The taper TEM horn antenna 10 described above is based on the exponential taper TEM horn antenna 110 shown in FIG. 1 (b), and is the open surface of the first antenna element 111 and the second antenna element 112 (the open end of the first antenna element 111). The first and second shortened antenna elements 11 and 12 are obtained by cutting the required amount (detailed later) evenly from the side (a substantially square virtual surface including the open end 112b of the second antenna element 112) and the 111b. is there.

The exponential function taper TEM horn antenna 110 causes a continuous impedance change from the input impedance (for example, 50Ω) of the first and second coaxial feeding portions 113a and 113b to the characteristic impedance of the opening surface (for example, 377Ω). The first and second antenna elements 111 and 112 are designed with an antenna length L (for example, 1/2 of a wavelength λ of 400 MHz) based on a target minimum frequency (for example, 400 MHz).

FIG. 2A is an explanatory diagram of an exponential taper transmission line, which is a basic concept of an exponential taper TEM horn antenna. The characteristic impedance Z (z) at an arbitrary position z of the transmission line is given by the following equation (1).

Further, if Z (0) = Z ₀ and Z (L) = Z _L , the following equation (2) can be obtained.

The structure of the exponential taper TEM horn antenna 110 is shown in the side view of FIG. 2B and the plan view (or bottom view) of FIG. 2C, and the first and second antenna elements 111 and 112 are respectively shown. The input impedance corresponds to Z ₀ in the equation (2), and the characteristic impedance at each opening surface of the first and second antenna elements 111 and 112 corresponds to Z _L in the equation (2). The height h (z) of the exponential taper TEM horn antenna 110 at an arbitrary position z is given by the following equation (3).

Here, the plate spacing between the first and second coaxial feeding portions 113a and 113b is h ₀ (= h (0)), and the separation between the open end 111b of the first antenna element 111 and the open end 112b of the second antenna element 112. Assuming that the aperture length H, which is the distance, is L (= h (L)), which is the same as the antenna length, the following equations (4) and (5) are obtained.

Further, the widths W (z) of the first and second antenna elements 111 and 112 at the position z are given by the following equation (6) which is an approximate equation of the characteristic impedance of the parallel plate.

The plate spacing h ₀ (= h (0)) and width (W ₀ ) of the first and second coaxial feeding portions 113a and 113b are the input impedance of the coaxial feeding and the first and second antenna elements 111 and 112. It is given so that the characteristic impedances at the feeding ends 111a and 112a are matched.

The characteristics of the exponential taper TEM horn antenna 110 to which the taper transmission line described above was applied were evaluated using MW-Studio (manufactured by CST, Germany), which is an electromagnetic field analysis solver based on the finite integral method (FIM). The analysis model of the exponential taper TEM horn antenna 110 is set to the dimension of H = W = L = 375 [mm] with the minimum frequency set to 400 MHz, and the materials of the first and second antenna elements 111 and 112 are assumed to be perfect conductors. Then, it was modeled with a non-uniform mesh with a maximum of λ / 20. An 8-layer PML (Perfectly Matched Layer) was used as an absorbing boundary on the outer periphery of the analysis region.

FIG. 3 shows the calculation results of the gain-frequency characteristics of the exponential taper TEM horn antenna 110. As can be seen from this figure, a relatively flat gain characteristic of 4 [dBi] or more can be obtained in a wide band of 0.4 to 6 [GHz]. However, in the exponential taper TEM horn antenna 110, two frequency bands (2 to 3 [GHz] band, 4.5 to 5.5 [GHz]] in which the maximum value of the antenna gain does not match the bore sight direction in front of the antenna. There is a band). Therefore, the exponential taper TEM horn antenna 110 is not suitable for an EMC test antenna (an antenna for applying an electric field in the proximity radiation immunity test method, an antenna for measuring an electric field in radiation emission measurement, etc.).

Thus, the tapered TEM horn antenna 10 according to the present invention has a structure using the above-mentioned exponential tapered TEM horn antenna 110 as a base, whereby the radiation characteristics can be improved.

As shown in FIG. 1 (a), the exponential function taper TEM horn antenna 110 (indicated by the broken line in FIG. 1 (a)) in which the first and second antenna elements 111 and 112 are designed with the antenna length L is 0. Only the cutting length Lc determined from the range of 06L to 0.11L is evenly cut from the opening surface side of the first and second antenna elements 111 and 112, respectively, only the first element removing portion 14a and the second element removing portion 14b. As a result, the tapered TEM horn antenna 10 including the first and second shortened antenna elements 11.12 having an antenna length Ls (Ls = L-Lc) is obtained.

The tapered TEM horn antenna 10 according to the present embodiment also has a part of the exponential taper shape to which the tapered transmission line is applied in the first and second shortened antenna elements 11 and 12. However, since the exponential taper shapes of the first and second shortened antenna elements 11 and 12 do not apply the exponential taper structure to the antenna length Ls, the exponential taper having the original exponential taper structure is provided. In order not to be confused with the TEM horn antenna 110, the present invention is simply referred to as a "tapered TEM horn antenna".

Then, in the tapered TEM horn antenna 10, the antenna length becomes Ls by cutting the first and second element removing portions 14a and 14b from the first and second antenna elements 111 and 112, respectively, and the antenna opening The opening width (the length of each open end 11b, 12b of the first and second shortened antenna elements 11 and 12) on the surface is Ws, and the opening height (open end 11b of the first shortened antenna element 11 and the second shortened antenna) Since the (separation distance) of the element 12 from the open end 12b is Hs, there is an advantage that the tapered TEM horn antenna 10 itself can be miniaturized according to the sizes of the first and second element removing portions 14a and 14b.

Further, the tapered TEM horn antenna 10 according to the present embodiment has an advantage that the radiation directivity can be enhanced by matching the maximum value of the antenna gain with the front surface of the antenna (boresite direction), but the first and second The causal relationship between the sizes of the element removing portions 14a and 14b (cutting length Lc) and the improvement of the radiation characteristics in the tapered TEM horn antenna 10 has not been clarified. However, by confirming the radiation characteristics of the tapered TEM horn antenna 10 modeled by changing the cut length Lc, the cut length Lc effective for improving the radiation characteristics of the taper TEM horn antenna 10 is 0.06 L (L × 6). %) It was confirmed that more than that was required. The MW-Studio was also used to calculate the gain-frequency characteristics shown below.

FIG. 4 is a gain-frequency characteristic diagram of the taper TEM horn antenna 10 to which 2% of the antenna length L of the exponential taper TEM horn antenna 110 is applied as the cutoff amount (Cutoff lens) Lc. When the cutting amount Lc = 0.02L, the antenna gain is increased in the 2.5 to 3.5 [GHz] band and the 5 to 6 [GHz] band, probably because the sizes of the first and second element removing portions 14a and 14b are small. The maximum value deviates from the front direction of the antenna. Therefore, the tapered TEM horn antenna 10 having an antenna length Ls = 0.98L with a cutting length Lc = 0.02L cannot achieve the intended purpose.

FIG. 5 is a gain-frequency characteristic diagram of the tapered TEM horn antenna 10 to which 4% of the antenna length L of the exponential taper TEM horn antenna 110 is applied as the cutout amount Lc. Even if the cutting amount Lc = 0.04L, the maximum antenna gain is in the 3-4 [GHz] band and the 5.5-6 [GHz] band, probably because the sizes of the first and second element removing portions 14a and 14b are still small. The value deviates from the front direction of the antenna. Therefore, the tapered TEM horn antenna 10 having an antenna length Ls = 0.96L with a cutting length Lc = 0.04L cannot achieve the intended purpose.

FIG. 6 is a gain-frequency characteristic diagram of the tapered TEM horn antenna 10 to which 6% of the antenna length L of the exponential taper TEM horn antenna 110 is applied as the cutout amount Lc. When the cutting amount Lc = 0.06L, it is recognized that the maximum value of the antenna gain is slightly deviated from the front direction of the antenna in the 3 to 4 [GHz] band. However, the gain difference is extremely small, and it is considered that there is no practical problem even if it is used as an EMC test antenna. Therefore, since the radiation directivity of the tapered TEM horn antenna 10 having an antenna length Ls = 0.94L with a cutting length Lc = 0.06L is improved, this 0.06L is the lower limit value of the cutting amount Lc.

FIG. 7 is a gain-frequency characteristic diagram of the tapered TEM horn antenna 10 to which 8% of the antenna length L of the exponential taper TEM horn antenna 110 is applied as the cutout amount Lc. If the cutting amount Lc = 0.08L, the maximum value of the antenna gain in a wide band of 0.4 [GHz] to 6 [GHz] coincides with the front direction of the antenna, and the cutting length Lc = 0.08L. The tapered TEM horn antenna 10 having a length Ls = 0.92 L is suitable as an antenna for EMC testing. Therefore, 0.06L ≦ Lc ≦ 0.8L is assumed as the range of the cutting length Lc in which the radiation directivity of the tapered TEM horn antenna 10 can be improved.

FIG. 8 is a gain-frequency characteristic diagram of the tapered TEM horn antenna 10 to which 10% of the antenna length L of the exponential taper TEM horn antenna 110 is applied as the cutout amount Lc. Even when the cutting amount Lc = 0.1L, the maximum value of the antenna gain in a wide band of 0.4 [GHz] to 6 [GHz] coincides with the front direction of the antenna, and the cutting length Lc = 0.1L is the antenna length. The tapered TEM horn antenna 10 having Ls = 0.9L is suitable as an EMC test antenna. Therefore, 0.06L ≦ Lc ≦ 1.0L is assumed as the range of the cutting length Lc in which the radiation directivity of the tapered TEM horn antenna 10 can be improved.

FIG. 9 is a gain-frequency characteristic diagram of the tapered TEM horn antenna 10 to which 15% of the antenna length L of the exponential taper TEM horn antenna 110 is applied as the cutout amount Lc. Even when the cutting amount Lc = 0.15L, the maximum value of the antenna gain in the wide band of 0.4 [GHz] to 6 [GHz] coincides with the front direction of the antenna, and the cutting length Lc = 0.15L is the antenna length. The tapered TEM horn antenna 10 having Ls = 0.85 L is suitable as an EMC test antenna. Therefore, 0.06L ≦ Lc ≦ 1.5L is assumed as the range of the cutting length Lc in which the radiation directivity of the tapered TEM horn antenna 10 can be improved.

FIG. 10 is a gain-frequency characteristic diagram of the tapered TEM horn antenna 10 to which 20% of the antenna length L of the exponential taper TEM horn antenna 110 is applied as the cutout amount Lc. Even when the cutting amount Lc = 0.2L, the maximum value of the antenna gain in a wide band of 0.4 [GHz] to 6 [GHz] coincides with the front direction of the antenna, and the cutting length Lc = 0.2L is the antenna length. The tapered TEM horn antenna 10 having Ls = 0.8 L is suitable as an EMC test antenna. Therefore, 0.06L ≦ Lc ≦ 2.0L is assumed as the range of the cutting length Lc in which the radiation directivity of the tapered TEM horn antenna 10 can be improved.

Although not shown when the cutout amount Lc is larger than 20%, the tendency that the maximum value of the antenna gain matches the antenna front direction in a wide band continues to some extent even if the cutout amount Lc is larger than 20%. Is assumed. However, it can be seen that the taper TEM horn antenna 10 having an antenna length Ls = 0.8L with a cutting length Lc = 0.2L has a very deteriorated gain in a low frequency band. As described above, if the antenna gain is significantly deteriorated, even if the radiation directivity is improved, it cannot be said that the antenna is suitable for the EMC test antenna.

Therefore, for the tapered TEM horn antenna 10 of the present embodiment, the upper limit of the cutting amount Lc is determined from the decrease in gain in the low frequency band. As a criterion for determining the gain decrease, in the present embodiment, the amount of decrease is suppressed within about 3 [dBi] with respect to the gain in the exponential taper TEM horn antenna 110 around 1.0 [GHz]. The amount Lc was set to the upper limit value.

FIG. 11 is a gain-frequency characteristic diagram of the tapered TEM horn antenna 10 to which 6% of the antenna length L of the exponential taper TEM horn antenna 110 is applied as the cutout amount Lc. Compared with the characteristics (gain in the boresight direction) of the exponential taper TEM horn antenna 110 shown by the broken line in the figure, in the taper TEM horn antenna 10 with a cutout amount Lc = 0.06 L, it is around 1 [GHz]. It is recognized that the exponential function is lower than that of the tapered TEM horn antenna 110 by about 1.5 [dBi]. However, since the gain reduction amount is suppressed within 3 [dBi], it is considered that there is no practical problem even if it is used as an EMC test antenna. Therefore, the tapered TEM horn antenna 10 having an antenna length Ls = 0.94L with a cutting length Lc = 0.06L satisfies the condition for determining the gain decrease, and this 0.06L is the lower limit value of the cutting amount Lc.

FIG. 12 is a gain-frequency characteristic diagram of the tapered TEM horn antenna 10 to which 8% of the antenna length L of the exponential taper TEM horn antenna 110 is applied as the cutout amount Lc. Compared with the characteristics (gain in the boresight direction) of the exponential taper TEM horn antenna 110 shown by the broken line in the figure, the taper TEM horn antenna 10 with a cutout amount Lc = 0.08 L is around 1 [GHz]. It is recognized that the exponential function is lower than that of the tapered TEM horn antenna 110 by about 2 [dBi]. However, since the gain reduction amount is suppressed within 3 [dBi], it is considered that there is no practical problem even if it is used as an EMC test antenna. Therefore, the tapered TEM horn antenna 10 having an antenna length Ls = 0.92L with a cutting length Lc = 0.08L satisfies the condition for determining the gain decrease, and the cutting length Lc is 0.06L ≦ Lc ≦ 0. .08L is assumed.

FIG. 13 is a gain-frequency characteristic diagram of the tapered TEM horn antenna 10 to which 10% of the antenna length L of the exponential taper TEM horn antenna 110 is applied as the cutout amount Lc. Compared with the characteristics (gain in the boresight direction) of the exponential taper TEM horn antenna 110 shown by the broken line in the figure, the taper TEM horn antenna 10 with a cutout amount Lc = 0.10 L is around 1 [GHz]. It is recognized that the exponential function is lower than that of the tapered TEM horn antenna 110 by about 2.8 [dBi]. However, since the gain reduction amount is suppressed within 3 [dBi], it is considered that there is no practical problem even if it is used as an EMC test antenna. Therefore, the tapered TEM horn antenna 10 having an antenna length Ls = 0.9L with a cutting length Lc = 0.10L satisfies the condition for determining the gain decrease, and the cutting length Lc is 0.06L ≦ Lc ≦ 0. .10L is assumed.

FIG. 14 is a gain-frequency characteristic diagram of the tapered TEM horn antenna 10 to which 11% of the antenna length L of the exponential taper TEM horn antenna 110 is applied as the cutout amount Lc. Compared with the characteristics (gain in the boresight direction) of the exponential taper TEM horn antenna 110 shown by the broken line in the figure, in the taper TEM horn antenna 10 with a cutout amount Lc = 0.11 L, it is around 1 [GHz]. It is recognized that the exponential function is lower than that of the tapered TEM horn antenna 110 by about 3.1 [dBi]. However, since the amount of gain reduction is suppressed to about 3 [dBi], it is considered that there is no practical problem even if it is used as an EMC test antenna. Therefore, the tapered TEM horn antenna 10 having an antenna length Ls = 0.89L with a cutting length Lc = 0.11L satisfies the condition for determining the gain decrease, and the cutting length Lc is 0.06L ≦ Lc ≦ 0. .11L is assumed.

FIG. 15 is a gain-frequency characteristic diagram of the tapered TEM horn antenna 10 to which 12% of the antenna length L of the exponential taper TEM horn antenna 110 is applied as the cutout amount Lc. Compared with the characteristics (gain in the boresight direction) of the exponential taper TEM horn antenna 110 shown by the broken line in the figure, in the taper TEM horn antenna 10 with a cutout amount Lc = 0.12 L, it is around 1 [GHz]. It is recognized that the exponential function is lower than that of the tapered TEM horn antenna 110 by about 3.4 [dBi]. Since it cannot be said that this gain reduction amount is suppressed to about 3 [dBi], it is considered that it is not appropriate to use it as an EMC test antenna. Therefore, the tapered TEM horn antenna 10 having an antenna length Ls = 0.88L with a cutting length Lc = 0.12L does not satisfy the condition for determining the gain decrease, and therefore 0.12L is not included in the cutting length Lc range and is 0. .06L ≦ Lc ≦ 0.11L is suitable.

FIG. 16 is a gain-frequency characteristic diagram of the tapered TEM horn antenna 10 to which 15% of the antenna length L of the exponential taper TEM horn antenna 110 is applied as the cutout amount Lc. Compared with the characteristics (gain in the boresight direction) of the exponential taper TEM horn antenna 110 shown by the broken line in the figure, the taper TEM horn antenna 10 with a cutout amount Lc = 0.15 L is around 1 [GHz]. It is recognized that the exponential function is lower than that of the tapered TEM horn antenna 110 by about 4.2 [dBi]. Since this gain reduction amount greatly exceeds 3 [dBi], it is not suitable for use as an EMC test antenna. Therefore, the tapered TEM horn antenna 10 having an antenna length Ls = 0.85L with a cutting length Lc = 0.15L does not satisfy the condition for determining the gain decrease, and therefore 0.15L is not included in the cutting length Lc range and is 0. .06L ≦ Lc ≦ 0.11L is suitable.

As described above, the tapered TEM horn antenna 10 of the present embodiment has 0 from the range of the cut amount Lc that can improve the radiation directivity and the range of the cut amount Lc based on the gain reduction suppression standard in the low frequency band. It was set to .06L ≦ Lc ≦ 0.11L. Therefore, if the tapered TEM horn antenna 10 having an antenna length of Ls is set according to the cutting amount Lc determined within this range, it is suitable for an EMC test antenna.

Although the tapered TEM horn antenna according to the present invention has been described above based on the embodiment, the present invention is not limited to this embodiment and can be realized as long as the configuration described in the claims is not changed. It includes all tapered TEM horn antennas as a claim.

10 Taper TEM horn antenna 11 1st shortened antenna element 11a Power receiving end 11b Open end 12 2nd shortened antenna element 12a Power receiving end 12b Open end 13a 1st coaxial feeding part 13b 2nd coaxial feeding part

Claims (1)

0 for an exponential taper TEM horn antenna in which a pair of antenna elements are designed with an antenna length L based on the target minimum frequency so that a continuous impedance change occurs from the input impedance of the feeding section to the characteristic impedance of the opening surface. A pair of shortened antenna elements having an antenna length Ls (Ls = L-Lc) are provided by evenly cutting the cut length Lc determined from the range of .06L to 0.11L from the opening surface side of both antenna elements. A tapered TEM horn antenna characterized by the fact that it is made.

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