KR20180003515A - Compact, wideband log-periodic dipole array antenna - Google Patents

Abstract

The present invention relates to a log periodic antenna and, more specifically, to a compact broadband log periodic dipole array antenna which includes dipole radiator elements having an enhanced top-loading structure to form the log periodic dipole array antenna, thereby effectively reducing the size and enhancing frequency characteristics in a low frequency band. The log periodic dipole array antenna including the plurality of dipole radiator elements comprises one or more dipole radiator elements having a first top-loading structure, wherein the first top-loading structure includes a first branch line branched from one end of a first dipole radiator element to both sides and a second branch line bending from both ends of the first branch line to the other end of the first dipole radiator element.

Description

A compact wideband log-periodic dipole array antenna

The present invention relates to an algebraic periodic antenna. Specifically, by constructing an algebraic periodic dipole array antenna including a dipole radiating element having an improved upper load structure, it is possible to effectively reduce the size and further improve the frequency characteristics in a low frequency band To a small wideband algebraic dipole array antenna.

Generally, a logarithmic periodic antenna is a broadband antenna in which the length and interval of adjacent radiating elements are constant and the frequency characteristics are almost constant within the frequency band of use.

Such log periodic antennas are frequently used where a plurality of frequency bands are required for one usage purpose, such as digital broadcasting signal reception and mobile communication base stations, due to their advantages such as broadband characteristics.

In particular, a log-periodic dipole array (LPDA) antenna has a relatively uniform input impedance, VSWR, and radiation characteristics over a wide frequency band, making it easy to apply to various wireless communication systems.

Typically, flat LDPA antennas are widely used in EMC systems because of their low height, compact size, light weight, low cost, high gain, etc. Various techniques have been attempted to improve the characteristics of flat LDPA antennas Has come. Particularly, a planar LDPA antenna can be enlarged due to a structure in which a plurality of dipoles are periodically arranged, and various studies have been made to improve the size.

For example, in an article entitled "Miniaturized LPDA Antenna for Portable Direction Finding Applications" by J. Yeo et al. (ETRI Journal, vol. 34, 2102), an LDPA antenna is constructed by applying a bow- To reduce the size of the system. However, in this case, the lateral size (width) of the LPDA antenna can be reduced, but the boom size (length) of the antenna greatly increases due to the characteristics of the bow-tie radiating element.

Further, when the structure of the LPDA antenna is changed to reduce the size of the antenna, the antenna characteristics such as the frequency bandwidth of the antenna may be deteriorated. Therefore, it is desirable to reduce the size of the antenna and to suppress deterioration of antenna characteristics.

Accordingly, there is a need for a method that can effectively reduce the size of the logarithmic periodic dipole array (LPDA) antenna, while suppressing the deterioration of the antenna characteristics such as the bandwidth. However, a proper solution has not yet been proposed.

Korean Patent Publication No. 10-2012-0138916

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems of the related art as described above, and it is an object of the present invention to provide an LPGA antenna capable of effectively reducing the size of a logarithmic periodic dipole array (LPDA) antenna, (LPDA).

According to an aspect of the present invention, there is provided an algebraic periodic dipole array antenna including a plurality of dipole array elements, wherein the algebraic periodic dipole array antenna includes a plurality of dipole array elements each having a branch from one end to the other end of the first dipole radiating element, And a second branch line bending from both ends of the first branch line toward the other end of the first dipole radiating element. And at least one dipole radiating element.

At this time, the first upper load structure may further include a third branch line bending from the end of the second branch line toward the first dipole radiating element.

The first dipole radiating element includes a first monopole radiating element that branches off from a first feed line on an upper surface of a substrate and a second monopole radiating element that branches from a second feed line on a lower surface of the substrate, May be symmetrically provided at both ends of the first monopole radiation element and the second monopole radiation element.

Here, a trapezoidal resistive stub may be provided at a connection site of the first monopole radiating element to the first feeder line and a connection site of the second monopole radiating element to the second feeder line.

The apparatus may further include at least one dipole radiating element having a second top load structure including branch lines branching at one end of the second dipole radiating element.

In addition, the feeder lines feeding the at least one dipole radiating element may include a meander structure.

Also, the feed line feeding the at least one dipole radiating element may comprise an arrow-shaped balun structure.

According to the present invention, by constructing the logarithmic periodic dipole array (LPDA) antenna including the dipole radiating element having the improved upper load structure, it is possible to effectively reduce the size of the antenna and further improve the frequency characteristics in the low frequency band (LPDA) antennas having a small-bandwidth algebraic periodic dipole array.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
1 is an exemplary view showing a basic structure of a logarithmic periodic dipole array antenna.
2 is a structural view of an algebraic periodic dipole array antenna according to an embodiment of the present invention.
3 is a view for explaining a first upper load structure according to an embodiment of the present invention.
4 is a cross-sectional view of a logarithmic periodic dipole array antenna according to an embodiment of the present invention.
5 is a reflection coefficient simulation graph of a dipole having an upper load structure according to an embodiment of the present invention.
6 is an equivalent circuit diagram of a meander structure of a feed line according to an embodiment of the present invention.
FIG. 7 is a graph of input impedance and reflection coefficient simulation according to modification of dimensions of a meander structure according to an embodiment of the present invention.
FIG. 8 is a simulation graph of impedance and reflection coefficient according to a dimension change of a trapezoidal stub according to an embodiment of the present invention. FIG.
9 is a photograph of a fabricated sample of an logarithmic periodic dipole array antenna according to an embodiment of the present invention.
10 is a graph showing simulation results and measured values of input reflection coefficient and gain of a logarithmic periodic dipole array antenna according to an embodiment of the present invention.
FIGS. 11A and 11B are graphs of simulation results and measured values of a radiation pattern for each frequency of an logarithmic periodic dipole array antenna according to an exemplary embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments will be described in detail below with reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The terms first, second, etc. may be used to describe various components, but the components are not limited by the terms, and the terms are used only for the purpose of distinguishing one component from another Is used.

Hereinafter, exemplary embodiments of a Log-Periodic Dipole Array (LPDA) antenna with improved low-frequency characteristics according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

First, FIG. 1 illustrates a general structure of a logarithmic periodic dipole array (LPDA) antenna used in the field of EMC and the like. The above antenna structure can be regarded as a frequency-free structure, because the entire structure can be defined by a scaling factor τ that is independent of frequency. The scaling factor? Can be defined as the ratio of the length of one radiating element to the longest radiating element of the neighboring radiating elements, from which various design parameters can be calculated. As can be seen in FIG. 1, the radiating element having the longest length l ₁ resonates at a half-wavelength of the lower frequency limit of the logarithmic periodic dipole array (LPDA) antenna, The short radiating element determines the upper frequency limit. The distance between the radiating elements, the width of each radiating element, the distance between the poles at the dipoles, and the apex angle of the radiating element are abbreviated as S _n , W _n , g _n and α, respectively, as shown in FIG.

FIG. 2 illustrates a structure of an algebraic periodic dipole array (LPDA) antenna 10 according to an embodiment of the present invention.

2, an algebraic periodic dipole array (LPDA) antenna 10 according to an embodiment of the present invention may include one or more (or more) of a first top- Dipole radiating element 100 may be included.

2, the first top-loading structure 200 includes a first dipole radiating element 100 and a second dipole antenna 200. The first top-loading structure 200 includes a first dipole radiating element 100, And a second branch line 210 bending from both ends of the first branch line 210 toward the other end of the first dipole radiating element 100, (220).

Furthermore, the first upper load structure 200 further includes a third branch line 230 bending from the end of the second branch line 220 toward the first dipole radiating element 100 .

FIG. 3 is a view for explaining a first upper load structure 200 according to an embodiment of the present invention.

3 (a), the first upper load structure 200 includes a first branch line 210 branching from one end of the first dipole radiating element 100 to the other, And a second branch line 220 bending from both ends of the first branch line 210 toward the other end of the first dipole radiating element 100 to form a ' Lt; / RTI >

3A, the first upper load structure 200 has a length of the first branch line 210, a length of the second branch line 210, By controlling the separation distance between the first dipole radiating element 100 and the first branch line 210 and controlling the equivalent resistance R ₁ , inductance L ₁ and capacitance C ₁ , resonance Thereby inducing the phenomenon.

The impedance between the feed line 300 and the first dipole radiating element 100 due to an impedance change (in particular, an imaginary resistance) generated when the shape of the first dipole radiating element 100 is artificially deformed, It can have an advantage that the matching can be easily achieved.

3 (b), the first upper load structure 200 according to an embodiment of the present invention includes the first dipole radiating element 100 at the end of the second branch line 220 And a third branch line 230 bending in the direction of the second branch line 230. [

As can be seen in FIG. 3 (b), the first upper load structure 200 has a third branch line 230, as compared to the case of FIG. 3 (a) An additional capacitance (C ₃ ) component may be further generated between the termination and the first dipole radiating element 100, thereby facilitating the impedance matching between the feeder line 300 and the first dipole radiating element 100 Can be advantageous.

In the first upper load structure 200 shown in FIG. 3 and FIG. 3, a general equivalent circuit structure that can be applied when the terminal structure of a general dipole radiating element is modified is applied. The equivalent circuit of 3 may be further modified.

As the first upper load structure 200 is applied, the length of the first dipole radiating element 100 can be greatly reduced with respect to the same resonance frequency, and in particular, the length of the long dipole radiating element corresponding to the low- The LPDA antenna 10 can be effectively reduced in size.

That is, by adding the first upper load structure 200 to one or more dipole radiating elements having the longest length among the plurality of dipole radiating elements, the LPDA antenna 10 can be effectively miniaturized have.

Also, the impedance matching between the feed line 300 and the first dipole radiating element 100 can be made easier by applying the first upper load structure 200.

2, the first dipole radiating element 100 includes a first monopole radiating element 110 branched from the first feed line 310 on the upper surface of the substrate 400, And a second monopole radiating element 120 branched from a lower second feeder line 320. The first upper load structure 200 may include a first monopole radiating element 110 and a second monopole radiating element 120, 2 monopole radiating element 120. [0052] In addition, as shown in FIG.

Further comprising at least one dipole radiating element having a second top load structure including a branch line branching at one end of one end of the second dipole radiating element different from the first dipole radiating element 100, The periodic dipole array (LPDA) antenna 10 may be further downsized.

However, when the first upper load structure 200 is applied for minimizing the LPDA antenna 10, as described above, the quality factor (Q-factor) increases in the low frequency band and decreases in the low frequency band There may be a problem that the impedance bandwidth is reduced.

On the contrary, as an embodiment of the present invention, a meander structure 600 may be added to the feed line, or a connecting portion of the first monopole radiating element 110 to the first feed line 310 and a connecting portion of the second monopole The trapezoidal resistive stub 500 is applied to the connecting portion of the radiating element 120 with respect to the second feed line 320 to improve the impedance matching characteristic so that the logarithmic periodic dipole array (LPDA) It is possible to improve the bandwidth characteristic in the low frequency band of FIG.

In addition, an arrow-shaped balun 700 may be added to the feed portion of the logarithmic periodic dipole array (LPDA) antenna 10 to implement a balanced transmission line structure as an embodiment of the present invention.

Hereinafter, the detailed design, implementation and measurement of the logarithmic periodic dipole array (LPDA) antenna 10 according to an embodiment of the present invention will be described in order.

First, a logarithmic periodic dipole array (LPDA) antenna 10 for a frequency band of 0.55 to 9 GHz is designed. A portion indicated by a solid line in FIG. 2 is located on an upper surface of the substrate 400, and a portion indicated by a dotted line is located on a lower surface of the substrate 400. In addition, the circular hole in the longest dipole radiating element in Fig. 2 is a screw hole for fixing the radome.

The design procedure of the logarithmic periodic dipole array (LPDA) antenna 10 according to an embodiment of the present invention is first described in Table 1, considering the theoretical target performance for the logarithmic periodic dipole array (LPDA) antenna 10 in free space. Can be started by selecting a scaling factor τ and a spacing factor σ that are listed in FIG.

Directivity [dBi] Scaling factor
(Scaling factor)? Spacing factor σ 7 0.782 0.138 7.5 0.824 0.146 8 0.865 0.157 8.5 0.892 0.165 9 0.918 0.169 9.5 0.935 0.174 10 0.943 0.179 10.5 0.957 0.182 11 0.964 0.185

For example, the scaling factor τ = 0.935 and the spacing factor σ = 0.174 were selected for the case where the directivity as the initial antenna design value is 9.5 dBi. Thus, the number N of dipole radiating elements can be calculated to be 48 for the logarithmic periodic dipole array (LPDA) antenna 10 (e.g., CA Balanis, "Frequency Independent Antennas," in Antenna Theory analysis and design, 2005, pp. 631-633). Next, the length l ₁ of the longest dipole radiating element that resonates at a half-wavelength length of the lower frequency limit of 0.55 GHz can be determined. Then, the length l _n , the width W _n , and the spacing S _n of the remaining radiating elements can be obtained by using the following equation 1, whereby l / w is 27.5.

[Equation 1]

In addition, in order to improve the radiation efficiency in the high frequency band, two dipole radiation elements are added in the direction of the feeding part of the logarithmic periodic dipole array (LPDA) antenna 10 (accordingly, the total number of dipole radiation elements is 50 ).

In the following step, the size of the logarithmic periodic dipole array (LPDA) antenna 10 is miniaturized. 2, a logarithmic periodic dipole array (LPDA) antenna 10 according to the present invention includes radiating elements printed on top and bottom of a substrate 400 to form a coplanar array, do. When the length of the longest radiating element in the free space il l _fs, the length l ₁ of the long radiation elements in the log-periodic dipole array (LPDA) antenna 10 according to the present invention is adjusted by the following equation (2) ( scaling.

&Quot; (2) "

In this case, ε _eff is the effective dielectric constant (effective permittivity) of the substrate, which may be represented by Equation 3 below.

&Quot; (3) "

Here, W and h indicate the width of the feeder line 300 and the thickness of the substrate 400, respectively, as shown in FIG.

The spacing between the radiating elements was optimized when the spacing factor sigma was 0.06. The spacing factor sigma value selected for the logarithmic periodic dipole array (LPDA) antenna 10 is a somewhat unusual, but very practical value, and is the boom size of the antenna, as compared to the conventional logarithmic periodic dipole array (LPDA) (Length) can be reduced by nearly 20%.

Further, as one embodiment of the present invention, two types of deformed top-loading structures in the form of a hat and a tee (T) as shown in Fig. 2 are applied to the dipole radiating element, The length of the longest dipole radiating element resonating at 0.55 GHz is shortened to 193.5 mm so that the lateral size (width) of the antenna is about 27% as compared to the conventional log periodic dipole array (LPDA) . The longest top-loaded dipole element forms a resonant frequency at about 0.5 GHz, resulting in a wider active region.

However, when the physical length of the longest radiating element is reduced by using the first upper load structure 200, the impedance bandwidth tends to narrow in the low frequency band of the operating frequency band of the antenna. This can be confirmed by looking at the simulation results of the reflection coefficient of the radiating element to which the upper load operating at 0.6 GHz is applied and the typical radiating element, with reference to FIG. In other words, the impedance bandwidth of the conventional dipole (S ₁₁ <-10dB), and this shows that spacious than that of the dipole of the first upper loading structure 200 is applied, wherein the reduction of bandwidth as can be seen in Figure 5 About 3%.

Accordingly, the dipole to which the first upper load structure 200 is applied may have a higher quality factor (Q-factor) while the bandwidth may be reduced, which is considered to be due to the impedance mismatch in the low frequency band.

As shown in FIG. 2, in order to improve the impedance bandwidth in the low frequency band of the antenna operating frequency range, the feeder line between the radiating elements to which the upper load is applied may be intermittently twisted as meander ) Structure (600) was applied.

The meander structure 600 of the feed line can be represented by the equivalent circuit shown in Fig. In FIG. 6, the capacitor C ₁ mainly represents an effective capacitance due to the self-capacitance due to the winding structure of the meander region, and the inductor L ₁ has a meander region Inductance due to the self-inductance of the radiating element, and r ₁ represents the radiation resistance in the radiating element. In this case, the input impedance Z _in viewed from the input port of the feed line in FIG. 6 can be expressed by Equation (4) below.

&Quot; (4) &quot;

As shown in FIG. 7 (a), the impedance matching performance in the low frequency band can be improved by changing the input impedance while changing the length f _x and the width f _y of the meander line to various values. As the values of f _x and f _y of the meander line change, various capacitances and inductance values are generated and added to the radiation resistance of the radiating element, so that the impedance at the input terminal can be adjusted . Therefore, the impedance viewed from the input terminal of the logarithmic periodic dipole array (LPDA) antenna 10 coincides with the impedance viewed from the terminal of the radiating element, thereby minimizing signal reflection and achieving excellent impedance matching performance.

FIG. 7 shows simulation results of the reflection coefficient and the input impedance in the 0.5 GHz to 1.0 GHz band according to the change of the f _x and f _y values in the meander structure 600. Referring to FIG. 7 (b) it can be confirmed that when _{f x = 1.0mm, f y =} 0.5mm in the entire frequency band showed a value equal to or less than -10dB indicates the optimum impedance matching properties.

2, a trapezoidal resistive stub 500 is connected to the connection portion of the feed line 300 including the radiating element and the meander structure 600 to which the upper load is applied, And the input impedance was adjusted by changing the width r _w of the stub. As r _w changes, the radiation resistance r ₁ of the radiating element changes. As a result, as shown in FIG. 8, the input impedance can be adjusted and the bandwidth can be improved. In FIG. 8 (a), it can be seen that the input impedance has a value close to 50 ohms as r _w increases, so that the impedance matching performance in the low frequency band can be improved. However, it can be seen that as the r _w increases, the effect on the input reflection coefficient decreases, which means that improving the impedance performance of the trapezoidal resistive stub 500 may be somewhat limited. Particularly, in one embodiment of the present invention, by applying the meander structure 600 and the trapezoidal resistive stub 500 simultaneously to the logarithmic periodic dipole array (LPDA) antenna 10, It can be effectively improved.

2, an arrowhead-shaped balun 700 is added to the feeding portion of the logarithmic periodic dipole array (LPDA) antenna 10 to implement a balanced transmission line structure. The concept of the balun can be applied to an algebraic periodic dipole array (LPDA) antenna 10 based on a Klopfenstein microstrip tapered line that can be used for impedance matching in a microstrip transmission line. . In particular, the balun structure has been applied for progressive conversion from a coaxial transmission mode (quasi-TEM in a microstrip transmission line) to a full-line transmission mode (full TEM) in a transmission line so that the balanced transmission line is connected to an unbalanced coaxial line So that it can be easily connected.

FIG. 9 shows a photograph of a production sample of the logarithmic periodic dipole array (LPDA) antenna 10 according to an embodiment of the present invention. 9, a planar logarithmic periodic dipole array (LPDA) antenna 10 is fabricated using a Rogers RO4003 substrate (? _R = 3.55 and tan? = 0.0027) (400) of 282 mm x 194 mm x 0.508 mm (L x W x H) . The manufactured LPDA antenna 10 includes 50 radiating elements and a feeder line 300 connected thereto and a balun 700 acting as an input terminal. Respectively. (LPDA) antenna 10 through the coaxial line and the balun, as shown in FIG. 9, the coaxial line is soldered along the lower portion of the feeder line 300 And an inner conductor may be connected to the upper portion of the feeder line through a hole at the end of the feeder line 300.

The manufactured logarithmic periodic dipole array (LPDA) antenna 10 was measured with a radome mounted or removed. The optimal design parameters applied to manufacture the logarithmic periodic dipole array (LPDA) antenna 10 according to an embodiment of the present invention are as shown in Table 2 below.

D [dBi] τ σ α [°] N ㅣ ₁ [mm] 9.5 0.935 0.06 13.58 50 193.5

The radiation pattern, input reflection coefficient and gain were then measured and analyzed for the fabricated planar logarithmic periodic dipole array (LPDA) antenna 10.

In FIG. 10, simulation results and measured values of the input reflection coefficient and gain for the planar logarithmic periodic dipole array (LPDA) antenna 10 are compared and shown. As shown in Fig. 10 (a), the measured value of the input reflection coefficient shows a somewhat unexpectedly superior result to the simulation result. 10 (a), the simulation result of the input reflection coefficient shows a value of less than -10 dB in the frequency range of 0.55 to 8.5 GHz, while the measured value of the input reflection coefficient is -10 dB in the frequency range of 0.4 to 9.7 GHz The following values are shown.

Such a wide impedance bandwidth characteristic (particularly including the low frequency band) is said to be due to the application of a meander structure 600 and a trapezoidal resistive stub 500 to the antenna structure for impedance matching .

More specifically, when the first upper load structure 200 is applied to reduce the length of the first dipole radiating element 100 in the low frequency band, the quality factor (Q-factor) increases in the low frequency band while the impedance bandwidth the meander structure 600 and the trapezoidal resistive stub 500 can be effectively used to improve the impedance matching characteristic including the low frequency band and to improve the bandwidth characteristic. .

11A and 11B show radiation pattern measurements at 0.55 GHz, 0.8 GHz, 0.95 GHz, 3.5 GHz, 5 GHz and 9 GHz for the E-plane and H-plane of the fabricated planar logarithmic periodic dipole array (LPDA) And simulation results, and it can be seen that the radiation pattern measurement is in good agreement with the simulation results for the entire frequency band. In addition, when the radiation pattern measurement of the logarithmic periodic dipole array (LPDA) antenna 10 is viewed, the radome has a gain in the range of 2.48 to 7.89 dBi when mounted with a radome, which is greater than -1.20 to 7.94 dBi And it has a high gain. The increase in the gain when the radome is mounted is mainly due to the increase in the directivity due to the radome. Therefore, the improvement of the radiation pattern performance is mainly due to the increase of the directionality by the radome, and this can be confirmed from the graph of the antenna gain of FIG. 10 (b).

As an embodiment of the present invention, a high gain small planar algebraic dipole array (LPDA) antenna 10 operating in the 0.55 GHz to 9 GHz frequency band, which can be used as a source antenna in a reverberation chamber, Respectively. When compared to a typical standard logarithmic periodic dipole array (LPDA) antenna 10, the length and width of the antenna could be reduced by about 27% and 20%, respectively. A top-loading structure and a very small spacing factor could be used to effectively reduce the size of the logarithmic periodic dipole array (LPDA) antenna 10. In addition, the meander structure 600 and the trapezoidal resistive stub 500 can be applied together to effectively improve the impedance matching characteristic in the low frequency band, The impedance bandwidth performance of the antenna 10 can be improved.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments described in the present invention are not intended to limit the technical spirit of the present invention but to illustrate the present invention. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents thereof should be construed as being included in the scope of the present invention.

10: Algebraic Cycle Dipole Array Antenna
100: first dipole radiating element
110: first monopole radiating element
120: second monopole radiating element
200: first upper load structure
210: first branch line
220: second branch line
230: third branch line
250: second upper load structure
300: Feeder
310: first feeder line
320: second feeder line
400: substrate
500: Trapezoidal resistance stub
600: Meander structure
700: Arrowhead - Shape balun

Claims (5)

1. A logarithmic periodic dipole array antenna comprising a plurality of dipole radiating elements,
A first branch line branching from one end of the first dipole radiating element to both sides,
A second branch line bending from both ends of the first branch line toward the other end of the first dipole radiating element,
A third branch that bends from the end of the second branch line toward the first dipole radiating element and forms an open capacitance with the first dipole radiating element to generate an additional capacitance component to improve the impedance matching characteristic, Wherein the antenna comprises at least one dipole radiating element having a first top-loading structure including a line. The method according to claim 1,
Wherein the first dipole radiating element comprises:
A first monopole radiating element that branches off from a first feed line on an upper surface of a substrate,
And a second monopole radiating element that branches off from a second feed line on the bottom surface of the substrate,
Wherein the first upper load structure is symmetrically provided at both ends of the first monopole radiating element and the second monopole radiating element. 3. The method of claim 2,
Wherein a trapezoidal resistive stub is provided at a connection site of the first monopole radiating element to the first feeder line and a connection site of the second monopole radiating element to the second feeder line. . The method according to claim 1,
Wherein the feed line feeding the at least one dipole radiating element comprises a meander structure. The method according to claim 1,
Wherein the feed line feeding the at least one dipole radiating element comprises an arrow-shaped balun structure.

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