JP4444845B2 - Dipole antenna - Google Patents

Description

  The present invention relates to a printed dipole antenna having a wide band castle property, and more particularly to a printed dipole antenna suitable as a base station antenna of a mobile communication system.

  A dipole antenna having a configuration incorporating a balun (balanced-unbalanced converter) is known (for example, Patent Document 1). In this dipole antenna, a balun made of a coaxial conductor is incorporated. A dipole antenna in which this balun is printed has also been proposed.

JP-A-6-188610

However, the conventional dipole antenna has a problem that the band characteristics are not good because there is one feeding line including a balun.
An object of the present invention is to provide a dipole antenna capable of improving the band characteristics in view of such conventional problems.

  In order to achieve the above object, a dipole antenna according to the present invention includes a first dielectric substrate in which a dipole is printed on one surface and a first feed line including a balun is printed on the other surface, A second dielectric substrate printed with a second feed line including a balun on the surface thereof, and the dipole via the balun in which the first feed line and the second feed line are included. The other surface of the second dielectric substrate is bonded to one surface of the first dielectric substrate so as to be coupled to the first dielectric substrate.

A plurality of the dipoles may be arranged along the longitudinal direction of the dipole so as to have an array antenna configuration.
The first dipole has a length that resonates at a _first frequency f ₁ and the second dipole has a length that resonates at a second frequency f ₂ (f ₂ > f ₁ ). A second dipole formed by a cut in one dipole and a cut in the second dipole so as to have a length resonating at a _third frequency f ₃ (f ₃ > f ₂ ). a third dipole was similarly below, so as to have a length which resonates with the frequency f _n of the n (f _n> f _n-1), the formed by cuts in the (n-1) of the dipole You may give the structure which combined the dipole element of n.
Further, a plurality of the first, second, third,..., Nth dipoles may be arranged along the longitudinal direction to provide an array antenna configuration.

  The first, second, third,..., N-th dipole has a contour that gradually increases in width as the distance from the feeding point increases, for example, an isosceles trapezoid or two isosceles trapezoids. It can be formed to have a combined hexagonal profile.

  According to the dipole antenna of the present invention, the first dielectric substrate on which the dipole and the first feed line including the balun are printed, and the second dielectric on which the second feed line including the balun is printed. Since the first and second power supply lines are joined to the dipole via the balun provided to the substrate, the first and second power supply lines are connected to each other. The band characteristics can be improved by resonating at different frequencies.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows the appearance of a dipole antenna according to an embodiment of the present invention. This dipole antenna is configured by superposing and joining the dielectric substrates 1 and 3 shown in FIG.

As shown in FIG. 2, a dipole 5 made of metal foil, feed lines 7 a and 7 b and a ground conductor portion 9 are printed on the surface of the dielectric substrate 1, and on the back surface of the dielectric substrate 1. A feeding line 11 made of metal foil is printed.
The dipole 5 includes left and right antenna elements 5a and 5b, and the length between both ends thereof is about ½ of the wavelength of the center frequency so as to resonate at the center frequency (for example, 0.8 GHz) of the applicable frequency band. Is set to
The antenna elements 5a and 5b are formed so as to gradually increase in width as they move away from the central feeding point P, but may be formed in a rectangular shape.
The left and right feed lines 7a and 7b are formed so as to connect the inner ends of the antenna elements 5a and 5b to the ground conductor 9, respectively, and a central line C1 perpendicular to the longitudinal axis C2 of the dipole 5 is interposed between them. The slit 13 formed along is interposed.

  The feed line 11 formed on the back surface of the dielectric substrate 1 extends laterally from the input / output point, and then, as shown in FIG. 3, passes the back side of the feed line 7a so as to pass to the left side of the slit 13. Standing up along the edge. The feed line 11 is formed so as to be reversed along the right side edge of the slit 13 in the “U” shape in the vicinity of the central feed point P, and is formed by a balun ( A balanced-unbalanced converter) 11a.

  On the other hand, a feed line 17 is formed on the surface of the other dielectric substrate 3 shown in FIG. The feed line 17 has a shape similar to that of the feed line 11 except that the inversion direction of the tip portion is reversed. That is, the feed line 17 extends laterally from the input / output point and then rises along the right side edge of the slit 13 so as to pass through the back side of the feed line 7b, and the central feed point P (see FIG. 3). ) In the vicinity, the direction is reversed to a “U” shape, and has a shape that falls along the left side edge of the slit 13. The feed line 17 also constitutes a balun (balance-unbalance converter) 17a by the inverted tip portion. It is also possible to provide the feed line 17 so as to overlap the feed line 11.

As is clear from the above description, the dipole antenna according to this embodiment includes the feed line 11 including the balun 11a and the feed line 17 including the balun 17a.
The lengths of the baluns 11a and 17a are set so that the feed lines 11 and 17 resonate at different frequencies. That is, in this embodiment, when the center frequency of the applicable frequency band of the dipole 5 is f, the length of the balun 11a is set so that the feed line 11 resonates at _a frequency f + Δfa higher than the center frequency f. Further, the length of the balun 17a is set so that the feed line 17 resonates at a frequency f−Δf _b lower than the center frequency f. Therefore, the length of the balun 11a is shorter than the length of the balun 17a.
When the center frequency f is, for example, 0.8 GHz, the frequencies f + Δf and f−Δf _b are, for example, 0.9 GHz and 0.7 GHz, respectively.
Incidentally, contrary to the above, the length of the balun 11a set to be longer than the length of the balun 17a, be configured to resonate in the feed line 11 and 17 respectively frequency f-Delta] f _b and f + Delta] f _a Is also possible.

According to a dipole antenna according to this embodiment, since it is possible to two frequencies f + Delta] f _a and f-Delta] f _b resonate in application frequency band feed lines 11 and 17 as described above, a band characteristic Can be improved. In this case, _a high frequency signal of frequency f + Δfa is input / output at the input / output point of the feed line 11, and _a high frequency signal of frequency f−Δf _b is input / output at the input / output point of the feed line 17.

FIG. 4 shows a dipole antenna having an array configuration according to the present invention, which is constructed by overlapping and joining the long dielectric substrates 10 and 30 shown in FIG.
A dielectric substrate 10 shown in FIG. 5 has a configuration in which substantially four dielectric substrates 1 shown in FIG. 1 are joined along the longitudinal direction of the dipole 5. Therefore, dipoles 5-1 to 5-4 corresponding to the dipole 5 shown in FIG. 2 are printed on the surface of the dielectric substrate 10 at a predetermined interval, and the ground conductor portion 9 shown in FIG. A ground conductor 90 having a shape in which four conductors are joined, and a feed line (corresponding to the feed lines 7a and 7b in FIG. 2) connecting the ground conductor 90 and the dipoles 5-1 to 5-4 are printed. .

As shown in FIG. 6, on the back of the dielectric substrate 10, feed line 11-1 to 11-4 corresponding to feed line 11 shown in FIG. 2 is printed form, further, a branch from the input-output point P _IO The feeder lines 19 and 21 to be printed are printed. The feed lines 11-1 to 11-4 are respectively provided with baluns 11-1a to 11-4a corresponding to the balun 11a of the feed line 11 shown in FIG. The feed lines 11-1 and 11-2 are branched from the feed line 19, and the feed lines 11-3 and 11-4 are branched from the feed line 21.

On the other hand, as shown in FIG. 7, on the surface of the dielectric substrate 30, the feed lines 17-1 to 17-4 corresponding to the feed line 17 shown in FIG. 2 and the feed line branched from the output point P _IO ′. 23 and 25 are printed. The feed lines 17-1 to 17-4 are respectively provided with baluns 17-1a to 17-4a corresponding to the balun 17a of the feed line 17 shown in FIG. The feed lines 17-1 and 17-2 are branched from the feed line 23, and the feed lines 17-3 and 17-4 are branched from the feed line 25.

The dipole antenna having this array configuration also includes a feed line on the dielectric substrate 10 side and a feed line on the dielectric substrate 30 side. Therefore, in order to resonate these feed lines at different frequencies, the baluns 11-1a to 11- By setting the lengths of 4a and baluns 17-1a to 17-4a, it is possible to increase the bandwidth.
It should be noted that the number of dipoles 5 arranged in the array-structured dipole antenna is not limited to four, and can be set to an arbitrary number of two or more.

FIG. 8 shows an exploded perspective view of a dipole antenna according to another embodiment of the present invention. This dipole antenna has the same configuration as that of the dipole antenna shown in FIG. 2 except that a composite dipole 50 is formed instead of the dipole 5 shown in FIG. Therefore, in FIG. 8, the same reference numbers are given to elements common to the elements shown in FIG.
The dipole 50 includes a dipole 51 composed of a pair of elements 51a and 51b, a dipole 52 composed of a pair of elements 52a and 52b, a dipole 53 composed of a pair of elements 53a and 53b, and a dipole 54 composed of a pair of elements 54a and 54b. It has the structure formed coaxially.

  That is, the contours of the elements 52a and 52b constituting the dipole element 52 are formed by notches provided inside the elements 51a and 51b constituting the dipole element 51, respectively. Similarly, the elements 53 a and 53 b constituting the third dipole element 53 are contoured by notches provided inside the elements 52 a and 52 b, respectively, and further the elements constituting the fourth dipole element 54. The contours of 54a and 54b are formed by notches provided inside the elements 53a and 53b, respectively.

  The elements 51a, 51b, 52a, 52b, 53a, 53b, 54a, and 54b have a contour that gradually increases in width as they move away from the central feeding point P, for example, an isosceles trapezoidal contour, It has a hexagonal outline combined with a leg trapezoid. However, it is also possible to form each of the elements so as to have a rectangular outline.

The lengths of the dipoles 51, 52, 53, and 54 are set so as to resonate at different frequencies f ₁ , f ₂ , f ₃ , and f ₄ (f ₁ <f ₂ <f ₃ <f ₄ ). ing.
That is, the length of the dipole 51 is about ½ of the wavelength λ ₁ of the frequency f ₁ (for example, 0.8 GHz), and the length of the dipole 52 is the wavelength λ _{2 of the} frequency f ₂ (for example, 1.5 GHz). The length of the dipole 53 is about 1/2 of the wavelength λ _{3 at} the frequency f ₃ (eg, 1.7 GHz), and the length of the dipole 54 is about the frequency f ₄ (eg, 2 GHz) is set to about ½ of the wavelength λ ₁ .

The dipole antenna according to this embodiment (having the same external shape as the antenna of FIG. 1) configured by superposing and joining the dielectric substrates 10 and 20 of FIG. 8 includes the first dipole 51 to the fourth dipole. 54 resonates at the first to fourth frequencies, respectively, so that it can be applied to a very wide band despite having a compact configuration.
Moreover, similarly to the antenna shown in FIG. 1 and FIG. 2, the power supply line 11 including the balun 11a and the power supply line 17 including the balun 17a are included. Therefore, for example, the first power supply line has the frequency f. ₃ and adjust the length of the balun 11a so as to resonate in the middle of the frequency of the frequency f _4, the length of the balun 17a such that the second feed line resonates in the middle of the frequency of the frequency f ₁ and frequency f ₂ By adjusting the thickness, the broadband property is further improved.
The dipole 50 has a configuration in which four dipoles 51, 52, 53, and 54 are combined, but the combined number can be set to an arbitrary number n of 2 or more.

9 shows a dielectric substrate 100 having a structure in which the dielectric substrate 1 shown in FIG. 8 is joined along the longitudinal direction of the dipole 5 and the dielectric substrate 3 shown in FIG. 8 along the same direction. FIG. 2 is an exploded perspective view of a dipole antenna having an array configuration according to the present invention including a dielectric substrate 300 having a configuration in which four are joined.
Dipoles 50-1 to 50-4 corresponding to the dipole 50 shown in FIG. 8 are printed on the surface of the dielectric substrate 100 at a predetermined interval, and four ground conductor portions 9 shown in FIG. 8 are provided. The ground conductor portion 900 in the shape of the joint and the feed line connecting the ground conductor portion 900 and the dipoles 50-1 to 50-4 (corresponding to the feed lines 7a and 7b in FIG. 8) are printed.

As shown in FIG. 10, the back surface of the dielectric substrate 100, a feed line 111-1～111-4 corresponding to the power supply line 11 shown in FIG. 8, the feed line 190 which branches from the input-output point P _IO, 210 is printed. The feed lines 111-1 to 111-4 are respectively provided with baluns 111-1a to 111-4a corresponding to the balun 11a of the feed line 11 shown in FIG. The feed lines 111-1 and 112-2 are branched from the feed line 190, and the feed lines 111-3 and 111-4 are branched from the feed line 210.

On the other hand, as shown in FIG. 11, on the surface of the dielectric substrate 300, a feed line 117-1～117-4 corresponding to the feed line 17 shown in FIG. 8, branches from the input-output point P _IO 'feed The electric wires 230 and 250 are printed. The feed lines 117-1 to 117-4 are respectively provided with baluns 117-1a to 117-4a corresponding to the balun 17a of the feed line 17 shown in FIG. The feed lines 117-1 and 117-2 are branched from the feed line 230, and the feed lines 117-3 and 117-4 are branched from the feed line 250.

This dipole array antenna (having the same external shape as the antenna of FIG. 4) constructed by superposing and joining the dielectric substrates 100 and 300 has four types of frequencies f ₁ as with the dipole antenna of FIG. , F ₂ , f ₃ , and f ₄ . In addition, since the power supply line on the dielectric substrate 100 side and the power supply line on the dielectric substrate 300 side are provided, for example, the power supply line on the dielectric substrate 100 side has the frequency f ₃ as shown in FIG. adjust the length of the balun 111a so as to resonate in the middle of the frequency of the frequency f _4, the dielectric substrate 300 side of the feed line is of the balun 17a so as to resonate in the middle of the frequency of the frequencies f ₁ and f ₂ By adjusting the length, the broadband property can be further improved.
The number of dipoles arranged in the dipole antenna having the array configuration is not limited to four, and can be set to an arbitrary number of two or more.

By the way, in mobile communications used for mobile phones, automobile phones, etc., a plurality of frequency bands are allocated, and in order to improve frequency utilization efficiency, an area covered by one base station is divided into sector sectors. However, in the near future, small cells are achieved by controlling the tilt angle of the beam in the vertical plane and setting the main beam to the ground side. However, since the difference in propagation characteristics for each frequency band is large, if each frequency band is configured in the same area, problems such as a drop in level due to propagation characteristics may occur in areas with high frequencies. Small cells are required.
Since the dipole antenna having the above array configuration can make the beam tilt angles for the frequencies f ₁ and f ₂ greatly different from the beam tilt angles for the frequencies f ₃ and f ₄ as described below, This is effective for the further miniaturization of cells.

That is, for example, the arrangement interval of the dipoles 50-1 to 50-4, that is, the interval between the feeding points P ₁ , P ₂ , P ₃ and P ₄ is about 0.67λ _c (λ _c is the frequency f _{1 to} f _4. central case of the frequency wavelength of f _c) of, by setting as follows mechanical length of each feed path from the input point P _IO to the feeding point P ₁ to P _4, the frequency frequency f _3, f ₄ About 15 beam tilt angle. Can be. Here, as the dielectric substrates 100 and 300, those having a relative dielectric constant of 2.6 are used.
_{P IO ~P 1: L a mm} ( standard length)
P _IO ~P _2: L _a + about 24mm
P _IO ~P _3: L _a + about 48mm
P _IO ~P _4: L _a + about 72mm

Further, by setting the mechanical length of each feeding path from the input / output point _PIO ′ to the feeding points P _{1 to} P ₄ as follows, the beam tilt angle for the frequencies f ₁ and f ₂ is about 5. Can be.
_{P IO ~P 1: L b mm} ( standard length)
P _IO ~P _2: L _b + about 8.5mm
P _IO ~P _3: L _b + about 17mm
P _IO ~P _4: L _b + about 25.5mm

9 are arranged in a plurality of stages in the longitudinal direction of the dielectric substrates 100 and 300 to form an array, and variable values (not shown) at the input / output points _PIO and _PIO ′ of the individual antennas. By connecting each phase shifter and performing variable tilt, it becomes possible to change the beam tilt angle with respect to the frequencies f _{1 to} f _{4 in the} following range.
f ₁ 0 ° to 10 °
f ₂ 0 ° -10 °
f ₃ 10 ° ~ 20 °
f ₄ 10 ° ~ 20 °

As is apparent from the above description, according to the dipole antenna having this array configuration, by using the variable phase shifter in combination, for example, the vertical in-plane directivity with respect to the frequencies f ₁ and f ₂ is set to the 0 ° direction. The vertical in-plane directivity for f ₃ and f ₄ can be set to 20 ° on the ground side. Therefore, if the dipole antenna having the array configuration is applied to a base station antenna for mobile communication, it is possible to further reduce the number of cells.

It is a perspective view which shows the external appearance of the dipole antenna which concerns on this invention. It is a disassembled perspective view of the antenna shown in FIG. It is the elements on larger scale which show the shape of a balun. It is a perspective view which shows the external appearance of the dipole antenna of the array structure based on this invention which arranged multiple dipoles shown in FIG. It is a disassembled perspective view of the antenna shown in FIG. It is a front view which shows the structure of the feed line provided in one dielectric substrate of the antenna shown in FIG. FIG. 5 is a front view showing a configuration of a feed line provided on the other dielectric substrate of the antenna shown in FIG. 4. It is a disassembled perspective view which shows other embodiment of the dipole antenna which concerns on this invention. FIG. 9 is a perspective view showing an appearance of a dipole antenna having an array configuration according to the present invention in which a plurality of dipoles shown in FIG. 8 are arranged. FIG. 10 is a front view showing a configuration of a feed line provided on one dielectric substrate of the antenna shown in FIG. 9. FIG. 10 is a front view showing a configuration of a feed line provided on the other dielectric substrate of the antenna shown in FIG. 9.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,3 Dielectric board | substrate 5,50,51a-54a, 50-1-50-50 Dipole 5a, 5b Antenna element 7a, 7b, Feeding line 9,90,900 Ground conductor 10,30,100,300 Dielectric board 11, 17 Feed lines 11a, 17a Baluns 11-1 to 11-4, 17-1 to 17-4 Feed lines 11-1a to 11-4a, 17-1a to 17-4a Baluns 111-1 to 111-4, 117-1～117-4 feed line P, P1~P4 the feeding point P _IO, P _IO 'input and output points

Claims (6)

A first dielectric substrate having a dipole printed on one side and a first feed line including a balun printed on the other side;
A second dielectric substrate printed with a second feed line including a balun on one side,
The first dielectric substrate is coupled to the dipole via the balun included in the first feeder line and the second feeder line on one surface of the first dielectric substrate. A dipole antenna characterized by joining the other surfaces.   2. The dipole antenna according to claim 1, wherein a plurality of the dipoles are arranged along the longitudinal direction of the dipole so as to have an array antenna configuration. The dipole is
A first dipole having a length that resonates at a _first frequency f ₁ ;
A second dipole formed by a cut in the first dipole so as to have a length that resonates at a _second frequency f ₂ (f ₂ > f ₁ );
A third dipole formed by a cut in the second dipole so as to have a length that resonates at a _third frequency f ₃ (f ₃ > f ₂ );
Similarly, so as to have a length which resonates with the frequency f _n of the n (f _n> f _n-1), and the dipole elements of the n formed by cuts in the (n-1) of the dipole,
The dipole antenna according to claim 1, wherein the dipole antenna has a configuration in which the two are combined.   The dipole antenna according to claim 3, wherein a plurality of the dipoles are arrayed along the longitudinal direction of the dipole so as to have an array antenna configuration.   5. The dipole antenna according to claim 3, wherein the first, second, third,..., N th dipole has a contour such that the width gradually increases as the distance from the feeding point increases. .   6. The first, second, third,..., Nth dipole has an isosceles trapezoidal shape or a hexagonal outline in which two isosceles trapezoids are combined. The described antenna.

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