JP2013183204A - Antenna device and array antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an antenna device that can reduce mutual interference by decreasing the area of a ground conductor on a dielectric substrate; and an array antenna including a plurality of the antenna devices.SOLUTION: An antenna device 2 includes: a dielectric substrate 2; a ground conductor 3 disposed on a rear surface 20b of the dielectric substrate 2 and connected to a reflection board 10; a first conductor part 41 and a second conductor part 42 that are disposed on a surface 20a of the dielectric substrate 20 with the dielectric substrate 20 interposed between themselves and the ground conductor 3, and are disposed so as to be parallel to each other; a feeding conductor 4 having a third conductor part 43 for connecting the first conductor part 41 and the second conductor part 42; and an antenna element 5 that resonates in a predetermined frequency band. The antenna element 5 includes: a first element 51 disposed on the surface 20a with one end of the first element 51 connected to the first conductor part 41; and a second element 52 disposed on the surface 20a with one end of the second element 52 connected to the second conductor part 42.

Description

  The present invention relates to an antenna device and an array antenna including a plurality of antenna devices.

  2. Description of the Related Art Conventionally, there is known a dipole antenna with a reflector in which a dipole antenna element is provided on a dielectric substrate that is erected on a reflector (see, for example, Patent Document 1). Also, an array antenna is known in which a plurality of dipole antennas of this type are erected on a single reflector (see, for example, Patent Document 2).

  In the dipole antenna with a reflector described in Patent Document 1, a folded conductor that forms a feeding circuit is provided on the surface of a dielectric substrate. In addition, a ground conductor and a dipole antenna element that form a feed circuit are provided on the back surface of the dielectric substrate.

  The dipole antenna element on the back surface of the dielectric substrate is divided into two parts by a triangular cut. In addition, the ground conductor forming the feeder circuit has a partial area on the dipole antenna element side divided into two by a notch formed in the longitudinal direction. The notch of the dipole antenna element communicates with the notch of the ground conductor forming the feed circuit, and the dipole antenna element and the ground conductor are respectively connected on both sides of the notch and have a T shape as a whole. That is, the dipole antenna element is configured as a part of the ground conductor.

Japanese Patent Laid-Open No. 10-150319 JP 2011-87241 A

  As described in Patent Document 2, when an array antenna is configured by arranging a plurality of dielectric substrates on which a grounding conductor forming a dipole antenna element and a feeding circuit is formed in parallel with a reflector, The ground conductors may interfere with each other and a desired radiation characteristic may not be obtained. The influence on the radiation characteristics due to the mutual interference appears as a phenomenon such as a decrease in gain, a decrease in VSWR (Voltage Standing Wave Ratio), or a beam width that is not as designed.

  It has been confirmed by the present inventors that the influence on the radiation characteristics due to this mutual interference increases according to the area of the ground conductor on the dielectric substrate.

  Accordingly, an object of the present invention is to provide an antenna device that can reduce mutual interference by reducing the area of the ground conductor on the dielectric substrate, and an array antenna including a plurality of the antenna devices. To do.

  In order to solve the above problems, the present invention provides a dielectric substrate having first and second main surfaces, and is provided on the first main surface of the dielectric substrate and is electrically grounded. A first conductor portion and a second conductor portion provided on the second main surface and sandwiching the dielectric substrate between the ground conductor and the ground conductor, and provided in parallel to each other; and A power supply conductor having a third conductor portion that connects one conductor portion and the second conductor portion, and an antenna element that resonates in a predetermined frequency band, and one end of the antenna element is connected to the first conductor portion There is provided an antenna apparatus having a first element provided on the second main surface and a second element provided on the second main surface with one end connected to the second conductor portion.

  The ground conductor is provided on the first main surface corresponding to the first conductor portion, the second conductor portion, and the third conductor portion of the feeding conductor, and the other end of the first element and the first conductor portion. It is preferable that the first main surface corresponding to the other end of the two elements is not provided.

  The dielectric substrate may be erected on a reflecting plate, and the first element and the second element may be provided on the reflecting plate side with respect to the third conductor portion of the feeding conductor.

  The present invention also provides an array antenna in which the above antenna device is erected on a common reflector in order to solve the above-described problems.

  According to the antenna device and the array antenna according to the present invention, it is possible to reduce mutual interference by reducing the area of the ground conductor on the dielectric substrate.

It is a perspective view which shows the structural example of the array antenna which concerns on the 1st Embodiment of this invention. The antenna apparatus which comprises an array antenna is shown, (a) is a top view on the surface side, (b) is a top view on the back side. It is a Smith chart which shows an example of the complex impedance for every frequency of an antenna apparatus. The antenna apparatus which concerns on the 2nd Embodiment of this invention is shown, (a) is a top view on the surface side, (b) is a top view on the back side. It is a perspective view which shows the structural example of the array antenna which concerns on the 3rd Embodiment of this invention.

[First Embodiment]
FIG. 1 is a perspective view showing a configuration example of an array antenna according to the first embodiment of the present invention. 2A and 2B show an antenna device constituting an array antenna, where FIG. 2A is a plan view of the front surface, and FIG. 2B is a plan view of the back surface.

  The array antenna 1 includes a reflective plate 10 connected to a ground wire (not shown) and electrically grounded, and a plurality of antenna devices 2 erected on the reflective surface 10 a side of the reflective plate 10. That is, the plurality of antenna devices 2 are erected on the common reflector 10. The array antenna 1 is installed in the antenna base station so that a plurality of antenna devices 2 are arranged along the vertical direction. In the example shown in FIG. 1, only the antenna device 2 for horizontal polarization is shown, but an antenna element for vertical polarization may be provided.

  The reflector 10 is made of a plate-like metal conductor and is installed so that its longitudinal direction is the vertical direction. A plurality of L-shaped fixtures 12 are fastened to the reflector 10 by bolts 11. Each antenna device 2 is fixed to the reflecting plate 10 by the fixing bracket 12. In the present embodiment, each antenna device 2 is fixed by two conductive fixing members 12 so as to be parallel to each other.

  The antenna device 2 is provided between the grounding conductor 3 and the grounding conductor 3, which is provided on the dielectric substrate 20 and the back surface 20 b (first main surface) of the dielectric substrate 20 and connected to the reflector 10. A power supply conductor 4 provided on the front surface 20a (second main surface) of the dielectric substrate 20 with the substrate 20 interposed therebetween, and an antenna element 5 that resonates in a predetermined frequency band are provided. The grounding conductor 3, the feeding conductor 4, and the antenna element 5 are highly conductive metal foils, for example, a copper (Cu) layer and a solder plating layer or a gold (Au) plating layer formed on the surface of the copper layer. Consists of.

  The dielectric substrate 20 is made of a flat dielectric such as a liquid crystal polymer or glass epoxy. In the present embodiment, dielectric substrate 20 is formed in a rectangular shape having a long side in a direction parallel to reflecting surface 10a of reflecting plate 10 and a short side in a direction perpendicular to reflecting surface 10a. . The dielectric substrate 20 is fixed to the reflecting plate 10 by two fixing brackets on the front surface 20a side and the back surface 20b side. Hereinafter, the direction parallel to the long side of the dielectric substrate 20 is referred to as “longitudinal direction of the dielectric substrate 20”, and the direction parallel to the short side of the dielectric substrate 20 is referred to as “short direction of the dielectric substrate 20”.

  The ground conductor 3 is connected to the reflecting plate 10 by a fixing metal 12 and is electrically grounded. The ground conductor 3 includes a first base end portion 31 connected to the fixing bracket 12 on the back surface 20b side of the dielectric substrate 20, a second base end portion 32 connected to the fixing bracket 12 on the front surface 20a side, A first ground conductor portion 33 extending in the short direction of the dielectric substrate 20 continuously to the base end portion 31 and a second ground conductor extending in the short direction of the dielectric substrate 20 continuously to the second base end portion 32. Part 34, and a third ground conductor part 35 that connects the first ground conductor part 33 and the second ground conductor part 34.

  The first ground conductor portion 33 and the second ground conductor portion 34 are parallel to each other, and a slit portion 30 where no conductor is provided is formed between the first ground conductor portion 33 and the second ground conductor portion 34. Has been. One end of the first ground conductor portion 33 and the second ground conductor portion 34 is connected to the first base end portion 31 and the second base end portion 32, and the other end on the opposite side is connected to the third ground conductor portion 35. ing.

  A through hole 21 that penetrates the dielectric substrate 20 in the thickness direction is opened in the first base end portion 31. A center conductor of an unillustrated coaxial cable is inserted into the through hole 21 from the back surface 20b toward the front surface 20a. The outer conductor of the coaxial cable is not inserted into the through hole 21 but is soldered to the first base end portion 31 in the periphery of the opening of the through hole 21.

  The power supply conductor 4 includes a first conductor portion 41 and a second conductor portion 42 provided so as to be parallel to each other, and a third conductor portion 43 that connects the first conductor portion 41 and the second conductor portion 42. ing. The first conductor portion 41 and the second conductor portion 42 are formed to extend in parallel to each other along the short direction of the dielectric substrate 20. That is, the first conductor portion 41 and the second conductor portion 42 are arranged in parallel along the longitudinal direction of the dielectric substrate 20 with a predetermined interval. The third conductor portion 43 is formed so as to extend along the longitudinal direction of the dielectric substrate 20, the first conductor portion 41 is connected to one end thereof, and the second conductor portion 42 is connected to the other end thereof.

  The first conductor portion 41 is provided on the surface 20 a side of the first ground conductor portion 33. That is, the first conductor portion 41 is provided at a position where the dielectric substrate 20 is sandwiched between the first conductor portion 41 and the first ground conductor portion 33 provided on the back surface 20b. Similarly, the second conductor portion 42 is provided on the surface 20 a side of the second ground conductor portion 34. The third conductor portion 43 is provided on the surface 20 a side of the third ground conductor portion 35. That is, the ground conductor 3 is provided on the back surface 20 b corresponding to the first conductor portion 41, the second conductor portion 42, and the third conductor portion 43 of the power supply conductor 4 to form a microstrip line. In the present embodiment, the first ground conductor portion 33, the second ground conductor portion 34, and the third ground conductor portion 35 are wider than the first conductor portion 41, the second conductor portion 42, and the third conductor portion 43, respectively. Is formed.

  The length of the first conductor portion 41 in the extending direction is longer than the length of the second conductor portion 42 in the extending direction. The length of the second conductor portion 42 in the extending direction is, for example, half or less of the length of the first conductor portion 41 in the extending direction. The through hole 21 is opened at one end of the first conductor portion 41, and the central conductor of the coaxial cable is soldered to the periphery of the opening.

  The antenna element 5 has one end connected to the first conductor portion 41 and provided on the surface 20 a of the dielectric substrate 20, and one end connected to the second conductor portion 42 and the surface of the dielectric substrate 20. And a second element 52 provided at 20a.

  The first element 51 and the second element 52 are formed so as to extend in parallel to the reflecting surface 10a while maintaining a predetermined distance between the reflecting surface 10a and the reflecting surface 10a. Further, the first element 51 and the second element 52 are provided closer to the reflector 10 than the third conductor portion 43. In the present embodiment, the first element 51 and the second element 52 have a common length (length in the longitudinal direction of the dielectric substrate 20) and width (width in the short direction of the dielectric substrate 20).

  The first element 51 is not provided with the ground conductor 3 on the back surface 20b side except for one end connected to the first conductor portion 41. Similarly, the grounding conductor 3 is not provided on the back surface 20b side of the second element 52 except for one end connected to the second conductor portion. That is, the ground conductor 3 is not provided on the back surface 20 b corresponding to the other end of the first element 51 and the other end of the second element 52. The widths of the first conductor portion 41 and the second conductor portion 42 are made the same as the widths of the first ground conductor portion 33 and the second ground conductor portion 34, and the back surfaces of the first element 51 and the second element 52 are the back side. You may comprise so that the grounding conductor 3 may not be provided in the 20b side.

The length of the antenna element 5 in the longitudinal direction of the dielectric substrate 20 L ₁ (the length from the other end to the other end of the second element 52 of the first element 51), the center frequency of the frequency band the antenna element 5 resonates the wavelength of _{f 0 λ 0 (λ 0 (} m) = v / f 0 (Hz); v = radio wave propagation velocity (m / sec)) When equal to λ _0/2 (1-half wavelength) _{(L 1 = λ 0/2} ).

Further, when the end face of the dielectric substrate 20 facing the reflector 10 is an end face 20c and the end face opposite to the end face 20c is an end face 20d, the edge of the third conductor 43 on the end face 20d side and the antenna element 5 The distance L ₂ between the edge on the end face 20 d side is common to the first element 51 and the second element 52. The distance L ₃ between the end face 20 c and the edge of the antenna element 5 on the end face 20 c side is common to the first element 51 and the second element 52.

  When the antenna device 2 configured as described above radiates radio waves, a high-frequency signal transmitted by a coaxial cable is supplied to the antenna element 5 via the ground conductor 3 and the feed conductor 4. That is, the first to third ground conductor portions 33 to 35 and the first to third conductor portions 41 to 43 function as a feeding line that feeds power to the antenna element 5, and the first to third conductor portions 41 to 43 are balanced. -Also functions as a balun that performs unbalanced conversion. The antenna element 5 functions as a dipole antenna element and radiates radio waves in a predetermined frequency band according to the supplied high frequency signal.

  When the antenna device 2 absorbs radio waves, an electrical signal corresponding to the radio waves absorbed by the antenna element 5 is output to the coaxial cable via the ground conductor 3 and the feed conductor 4.

  FIG. 3 is a Smith chart showing an example of the complex impedance for each frequency of the antenna device 2. In this Smith chart, the complex impedance at the lower limit frequency of the frequency band of the radio wave radiated (transmitted) or absorbed (received) by the antenna element 5 is ▽ 1, the complex impedance at the upper limit frequency is ▽ 3, and the complex impedance at the center frequency is The impedance is indicated by ▽ 2.

As shown in FIG. 3, it can be understood that the impedance matching is appropriately performed by drawing a trajectory in which the curve indicating the complex impedance in the frequency band goes around the center coordinate (1, 0) of the Smith chart. In the antenna device 2, the impedance adjustment, the distance L ₂ may be performed by (see FIG. 2 (a)). That is, the antenna device 2, the impedance matching is done by adjusting the distance L _2.

More specifically, the curve showing the complex impedance moves downward of the Smith chart when the distance L ₂ is shortened, increasing the distance L ₂ this curve moves upward of the Smith chart. Therefore, by the curve showing the complex impedance at a desired frequency band to adjust the distance L ₂ to come to a position that will involve the center coordinates of the Smith chart (1,0), can be appropriately impedance matching .

Further, the directivity beam width of the antenna device 2 can be adjusted by the distance L ₃ (see FIG. 2A). That is, the distance L ₃ is short (the closer the antenna element 5 to the reflecting plate 10), the beam width becomes wider, the distance L ₃ is long (when away antenna element 5 from the reflecting plate 10), the beam width is narrow Become. Thus, by adjusting the distance L _3, it is possible to obtain an antenna device 2 of the desired beam width.

(Operation and effect of the first embodiment)
According to the first embodiment described above, the following effects can be obtained.

(1) The antenna element 5 is provided not on the back surface 20b on which the ground conductor 3 is provided, but on the surface 20a on the opposite side. For example, in the conventional dipole antenna shown in Patent Document 1, since the dipole antenna element is connected to the ground conductor forming the feeder circuit, the dipole antenna element is substantially grounded. The antenna element 5 is not connected to the ground conductor 3. Thereby, the area of the metal foil electrically grounded among the metal foils formed on the front surface 20a and the back surface 20b of the dielectric substrate 20 is reduced. That is, since the area of the ground conductor is reduced, it is possible to reduce mutual interference between the antenna devices 2 when the plurality of antenna devices 2 are arranged on the reflection plate 10.

(2) The ground conductor 3 on the back surface 20b of the dielectric substrate 20 is on the back surface 20b corresponding to the other ends of the first element 51 and the second element 52 (both ends of the antenna element 5 in the longitudinal direction of the dielectric substrate 20). Since it is not provided, for example, the area of the ground conductor 3 can be reduced compared with the case where the ground conductor 3 is provided on the entire back surface 20b side of the first element 51 and the second element 52, and the antenna device It becomes possible to further reduce the mutual interference between the two.

(3) The first element 51 and the second element 52 are provided closer to the reflector 10 than the third conductor portion 43. That is, since the distance L ₂ (see FIG. 2A) is a value larger than 0, the impedance adjustment of the antenna device 2 can be appropriately performed by the distance L ₂ .

[Second Embodiment]
Next, a second embodiment of the present invention will be described.

  4A and 4B show the antenna device 2A according to the present embodiment, where FIG. 4A is a plan view on the front surface 20a side, and FIG. 4B is a plan view on the back surface 20b side. In this antenna device 2A, the shapes of the ground conductor 3A and the feed conductor 4A are different from the shapes of the ground conductor 3 and the feed conductor 4 of the antenna device 2 according to the first embodiment, and the others are common to the antenna device 2. . Among the components of the antenna device 2A, the same components as those of the antenna device 2 are denoted by the same reference numerals, and redundant description is omitted.

  The power supply conductor 4A includes a first conductor portion 41A, a second conductor portion 42A, and a third conductor portion 43A, and the first conductor portion 41A and the second conductor portion 42A are parallel to each other. The first conductor portion 41A and the second conductor portion 42A are formed so as to extend in the short direction of the dielectric substrate 20, and the third conductor portion 43A is formed so as to extend in the longitudinal direction of the dielectric substrate 20. . The first conductor portion 41A is longer than the second conductor portion 42A, and the first conductor portion 41A and the second conductor portion 42A are connected by the third conductor portion 43A.

  The ground conductor 3A is provided on the back surface 20b of the dielectric substrate 20 corresponding to the first conductor portion 41A, the second conductor portion 42A, and the third conductor portion 43A of the power supply conductor 4A. In the present embodiment, the entire ground conductor 3 </ b> A is formed in a rectangular shape having long sides in the short direction of the dielectric substrate 20. In addition, an opening of the through hole 21 is formed in the ground conductor 3A. An outer conductor of a coaxial cable (not shown) is soldered to the periphery of the opening of the through hole 21, thereby electrically grounding the ground conductor 3 </ b> A.

The antenna element 5A including the first element 51A and the second element 52A is provided on the surface 20a of the dielectric substrate 20, and one end of the first element 51A is the first conductor portion 41A and one end of the second element 52A is the first. The two conductor portions 42A are connected to each other. In the present embodiment, the second element 52A is provided at the distal end portion (end portion on the end surface 20c side) of the second conductor portion 42A, and the first element 51A is spaced from the end surface 20c of the dielectric substrate 20 (distance). L ₃ ) is provided to be equal to the second element 52A.

  The length of the short side of the ground conductor 3A is a length corresponding to the width of the power supply conductor 4A in the longitudinal direction of the dielectric substrate 20, and corresponds to the other end of the first element 51A and the other end of the second element 52A. The ground conductor 3A is not provided on the back surface 20b.

Also in the antenna device 2A according to the present embodiment, the distance L ₂ (L ₂ > 0) between the edge on the end face 20d side of the third conductor portion 43A and the edge on the end face 20d side of the antenna element 5A is changed. Therefore, that is, impedance matching can be performed by changing the length of the second conductor portion 42A. Further, by changing the distance L ₃ between the end surface 20c side of the edge of the end face 20c and the antenna element 5A, it is possible to adjust the directivity of the beam width of the antenna device 2A. The length L ₁ in the longitudinal direction of the dielectric substrate 20 of the antenna element 5A is a length of about one-half of a wavelength of the antenna elements 5A corresponds to the center frequency of the frequency band resonating.

(Operation and effect of the second embodiment)
Also according to the present embodiment, the same operations and effects as those described for the first embodiment can be obtained.

[Third Embodiment]
Next, a third embodiment of the present invention will be described.

  FIG. 5 is a perspective view showing a configuration example of an array antenna 1A according to the third embodiment of the present invention. In the first embodiment, the array antenna 1 is configured by arranging a plurality of antenna devices 2 having common specifications on the common reflector 10, but the array antenna 1A according to the present embodiment is configured to emit or The array antenna 1 </ b> A is configured by a plurality of antenna devices and reflectors 10 having different frequency bands of radio waves to be absorbed.

  A plurality (two in the example shown in FIG. 5) of first to fourth antenna devices 2B to 2E are fixed to the reflecting plate 10 of the array antenna 1A. More specifically, the reflecting plate 10 has a first antenna device 2B, a second antenna device 2C, a third antenna device 2D, and a fourth antenna in order from one end in the longitudinal direction (the right side in FIG. 5). The device 2E, the second antenna device 2C, the third antenna device 2D, the first antenna device 2B, and the fourth antenna device 2E are fixed in this order.

  The first antenna device 2B is an 800 MHz band horizontally polarized antenna device. The second antenna device 2 </ b> C is a shared antenna device for horizontal polarization of 1.5 GHz band and horizontal and vertical polarization of 2 GHz band. The third antenna device 2D is a 1.5 GHz band vertically polarized antenna device. The fourth antenna device 2E is an 800 MHz band vertically polarized antenna device.

  The first to fourth antenna devices 2B to 2E have different shapes and sizes depending on the difference in frequency band, etc., but the power supply conductor and the antenna element are provided on the surface of the dielectric substrate, and the back surface. The ground conductor is provided in common with the antenna devices 2 and 2A according to the first and second embodiments. With this configuration, the area of the ground conductor provided in the first to fourth antenna devices 2B to 2E can be reduced, and the mutual interference between the first to fourth antenna devices 2B to 2E can be reduced. Is possible. That is, even when the array antenna is configured by combining a plurality of antenna devices having different frequency bands of radiated or absorbed radio waves, the same operations and effects as those described in the first embodiment can be obtained.

  While the embodiments of the present invention have been described above, the embodiments described above do not limit the invention according to the claims. In addition, it should be noted that not all the combinations of features described in the embodiments are essential to the means for solving the problems of the invention.

  The present invention is not limited to the first to third embodiments described above, and can be implemented in various modes without departing from the gist thereof. For example, a parasitic element for narrowing the beam width may be additionally provided in the antenna devices 2 and 2A according to the first and second embodiments. In addition, the dielectric substrate 20 is not limited to a rectangular shape, and for example, a region where the ground conductors 3 and 3A, the feed conductors 4 and 4A, and the antenna elements 5 and 5A are not provided may be cut out. In this case, the weight of the dielectric substrate 20 can be reduced.

DESCRIPTION OF SYMBOLS 1,1A ... Array antenna, 2, 2A ... Antenna apparatus, 2B-2E ... 1st-4th antenna apparatus, 3, 3A ... Ground conductor, 4, 4A ... Feeding conductor, 5, 5A ... Antenna element, 10 ... Reflector plate, 10a ... reflecting surface, 11 ... bolt, 12 ... fixing bracket, 20 ... dielectric substrate, 20a ... front surface, 20b ... back surface, 20c, 20d ... end face, 21 ... through hole, 30 ... slit part, 31st 1 base end portion, 32 ... second base end portion, 33 ... first ground conductor portion, 34 ... second ground conductor portion, 35 ... third ground conductor portion, 41, 41A ... first conductor portion, 42, 42A ... 2nd conductor part, 43, 43A ... 3rd conductor part, 51, 51A ... 1st element, 52, 52A ... 2nd element

Claims (4)

A dielectric substrate having first and second major surfaces;
A ground conductor provided on the first main surface of the dielectric substrate and electrically grounded;
A first conductor portion and a second conductor portion provided on the second main surface with the dielectric substrate sandwiched between the ground conductor and parallel to each other; and the first conductor portion; A feed conductor having a third conductor portion connecting the second conductor portion;
An antenna element that resonates in a predetermined frequency band,
The antenna element has one end connected to the first conductor portion and provided on the second main surface, and one end connected to the second conductor portion and provided on the second main surface. An antenna device. The ground conductor is provided on the first main surface corresponding to the first conductor portion, the second conductor portion, and the third conductor portion of the power supply conductor, and the other end of the first element and the second element. Is not provided on the first main surface corresponding to the other end of
The antenna device according to claim 1. The dielectric substrate is erected on a reflector,
The first element and the second element are provided closer to the reflector than the third conductor portion of the power supply conductor,
The antenna device according to claim 1 or 2. An array antenna comprising a plurality of antenna devices according to claim 1 or 2 erected on a common reflector.

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