JP2006352293A - Polarization diversity antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarization diversity antenna which can impart equivalent electric characteristics to each polarized wave while reducing the size and cost. <P>SOLUTION: First print dipole antenna portion (10) and second print dipole antenna portion (20) are constituted by intersecting them at an angle of 90° using cuts (16, 26) formed therein. Contact of feeding line conductors (14, 14) constituting a balun is avoided by the cuts (16, 26). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an antenna suitable as a base station antenna for a mobile communication system or the like, and more particularly to a polarization diversity antenna capable of independently transmitting and receiving two orthogonal polarizations.

  Conventionally, as a base station antenna for a mobile communication system or the like, a space diversity type antenna has been used for the purpose of improving radio wave reception efficiency. However, this space diversity antenna has a drawback in that the shape of the upper part of the steel tower where the antenna elements are installed becomes large due to its structure. Therefore, recently, there has been a shift to a polarization diversity antenna that can simplify the base station equipment provided in the upper part of the steel tower.

FIG. 12 shows a conventional example of this polarization diversity antenna. This polarization diversity antenna includes a pair of antenna elements 2 fed by a coaxial feed line 1 using a metal cylinder, and these antenna elements 2 are supported by the feed line 1 so as to intersect at an angle of 90 °. It has the structure made. Each antenna element 2 has a length at both ends set to about λ / 2 (λ is a wavelength of the used frequency), and a feeding point is connected by a pair of jumper wires 3 that are crossed so as not to contact each other. Reference numeral 4 denotes a reflector.
On the other hand, there has been proposed a cross dipole antenna having a configuration in which two dielectric substrates each having an antenna circuit pattern are crossed with each other (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 2001-168637

  The conventional polarization diversity antenna shown in FIG. 12 has a complicated structure, and the size of the coaxial feed line 1 is determined not by the operating frequency but by the feed impedance. The shape becomes relatively large due to the influence of the dimensions of the electric wire 1. Further, when the frequency used is increased and the length of the antenna element 2 (about λ / 2 as described above) is shortened, the coaxial feed line 1 becomes relatively non-negligible. As a result, the VSWR characteristics and The amount of coupling between polarization characteristics deteriorates.

On the other hand, in the cross dipole antenna using a dielectric substrate, in order for the antenna circuit pattern to function as a dipole antenna element, it is necessary to connect the pattern with a conductor, which leads to a complicated structure. In order to solve this problem, a cross dipole antenna having a structure in which the center of each dipole element is shifted has been devised. However, the antenna having such a structure has a problem that the characteristics of each polarization vary because the position of the feeding point of each dipole element is shifted.
An antenna used as a mobile communication base station antenna is required to be small and inexpensive, and to have the same electrical characteristics of each polarization.

  In view of such a situation, an object of the present invention is to provide a polarization diversity antenna that can be configured in a small size and at a low cost and that can have electrical characteristics equivalent to each polarization.

  In order to solve the above-described problems, a polarization diversity antenna according to the present invention includes a pair of element conductors constituting a dipole element and a feeding point portion of each element conductor on one surface of a dielectric substrate. And a pair of ground conductors extending in a direction perpendicular to the respective element conductors in a form in which a slit having a predetermined width is formed between the first and second printed dipole antenna portions. The first printed dipole antenna includes a notch having a predetermined length extending from the start side to the end side of the slit on the axis of the slit, and the notch to form a balun together with the ground conductors. A feed line conductor printed on the other surface of the dielectric substrate in a form that does not contact the second printed dipole antenna. A slit having a predetermined length extending from the end side of the slit toward the start side on the axis of the slit, and the balun together with the ground conductors, so that the other side of the dielectric substrate is not in contact with the notch. Cross-couple the first and second printed dipole antenna portions to form an angle of 90 ° with each other by using the cut portions formed in the first and second printed dipole antenna portions. ing.

  In a preferred embodiment, each of the dipole elements of the first printed dipole antenna unit and the dipole elements of the second printed dipole antenna unit is not configured in such a manner that a predetermined distance can be formed in the beam projection direction from these dipole elements. A power feeding element is provided. The parasitic elements for the dipole elements may be integrally formed so as to form a cross shape.

In another preferred embodiment, the dipole element of the first printed dipole antenna portion and the dipole element of the second printed dipole antenna portion are each formed by being bent into an umbrella shape.
Each of the polarization diversity antennas can be provided with a reflector if necessary.

  An array antenna can be configured by arranging a plurality of any of the above-mentioned polarization diversity antennas at a predetermined interval. A reflector may be provided in the arrayed polarization diversity antenna.

The polarization diversity antenna according to the present invention is configured by cross-coupling the first and second printed dipole antenna portions so as to form an angle of 90 ° with each other using a cut portion formed in them. Therefore, as compared with the conventional polarization diversity antenna, it is possible to reduce the size, the cost, and the assembly.
In addition, since the dipole elements in the first and second printed dipole antenna sections are fed at the center, there is no bias in directivity, and each dipole element is symmetrically arranged, so that the electrical characteristics equivalent to each polarization are obtained. Can be given.

Furthermore, since the feeder line conductor is formed on the dielectric substrate, the structure of the feeder part is reduced in size. Therefore, even when the operating frequency is high, that is, even when the length of the dipole element is small, the influence of the power feeding portion on the electrical characteristics can be reduced.
In addition, if parasitic elements are provided at appropriate intervals in the beam direction of each dipole element, the band characteristics can be improved, and as a result, the posture can be lowered. If the parasitic elements for the dipole elements are integrated in a cross shape, the structure is simplified.
Furthermore, if each dipole element is bent and formed in an umbrella shape, the beam width by each dipole element itself is widened, so that it is possible to realize a polarization diversity antenna having a large beam width in a horizontal plane.

FIG. 1 is a perspective view showing an embodiment of a polarization diversity antenna according to the present invention.
This polarization diversity antenna A1 is configured by combining the first printed dipole antenna unit 10 shown in FIG. 2 and the second printed dipole antenna unit 20 shown in FIG.
The first printed dipole antenna unit 10 includes a rectangular dielectric substrate 11, a dipole element 12 and ground conductors 13 a and 13 b printed on one surface of the dielectric substrate 11, and the other of the dielectric substrate 11. And a feeder line conductor 14 printed on the surface.

  The dipole element 12 is formed of element conductors 12a and 12b extending along one end (hereinafter, referred to as an upper end) of the dielectric substrate 11, and has a length of about λ / 2 (λ is a wavelength of a use frequency). The ground conductors 13a and 13b extend in a direction perpendicular to the element conductors 12a and 12b, respectively, starting from the feeding point of the element conductors 12a and 12b. That is, the ground conductors 13a and 13b extend to the other end (hereinafter referred to as the lower end) of the dielectric substrate 11 so that a slit 15 having a length of about λ / 4 is formed therebetween.

  The dielectric substrate 11 is formed with a notch 16 having a predetermined length extending from the upper end to the lower end side (from the start side to the end side of the slit 15) of the dielectric substrate 11 in a form located on the axis of the slit 15. Has been. The cut portion 16 in this embodiment extends to a portion where the tip reaches the longitudinal axis of the dipole element 12.

The feed line conductor 14 extends from one end of the dielectric substrate 11 to the other end side so as to face the back surface of the ground conductor 13a, and then bends to the element conductor 12b side behind the feed point portion of the element conductor 12a. The bent upper half extends along the back surface of the element conductor 12b. The upper half is set to have a length of about λ / 4, and is offset slightly downward in the drawing from the longitudinal axis of the dipole element 12 so as not to contact the tip of the notch 16.
Note that the bent upper half may be bent again downward behind the feeding point portion of the element conductor 12b, as indicated by a one-dotted line. That is, the feed line conductor 14 can be formed in an L shape or a U shape.

Since the second printed dipole antenna unit 20 shown in FIG. 3 has a configuration similar to that of the first printed dipole antenna unit 10, reference numerals corresponding to elements corresponding to the components of the antenna unit 10 are attached. It is. Only the components different from the first printed dipole antenna unit 10 will be described below.
The dielectric substrate 21 of the second printed dipole antenna unit 20 is positioned on the axis of the slit 25 from the lower end to the upper end side (from the end side to the start end side of the slit 25) of the dielectric substrate 21. A cut portion 26 having a predetermined length is formed. The cut portion 26 in this embodiment extends to a portion where the tip reaches the longitudinal axis of the dipole element 12.

  Further, the feeder line conductor 24 of the printed dipole antenna unit 20 is slightly longer than the longitudinal axis of the dipole element 22 so that the bent upper half (about λ / 4) does not come into contact with the tip of the notch 26. It is offset upward. The feed line conductor 24 may be formed in a U shape as indicated by a chain line in FIG.

  The polarization diversity antenna A1 shown in FIG. 1 can be formed by cross-coupling the first printed dipole antenna unit 10 and the second printed dipole antenna unit 20. This cross coupling can be easily achieved by pushing the antenna unit 20 from above the antenna unit 10 using the cut unit 16 of the antenna unit 10 and the cut unit 26 of the antenna unit 20.

In the first printed dipole antenna section 10, since the ground conductors 13a and 13b and the feed line conductor 14 form a balun, the center conductor and the external conductor of the coaxial feed line (not shown) are respectively connected to the feed line conductor 14 and the ground conductor. The dipole element 12 can be excited by connecting and supplying power to the bases of 13a and 13b.
Similarly, in the second printed dipole antenna section 20, since the ground conductors 23a and 23b and the feed line conductor 24 form a balun, the center conductor and the external conductor of another coaxial feed line (not shown) are respectively connected to the feed line. The dipole element 22 can be excited by connecting and supplying power to the bases of the conductor 24 and the ground conductors 23a and 23b.
Therefore, the polarization diversity antenna A1 according to this embodiment can transmit and receive horizontal polarization to one of the antenna units 10 and 20, and can transmit and receive vertical polarization to the other.

FIG. 4 shows a polarization diversity antenna A2 according to the second embodiment of the present invention in which a cross-shaped parasitic element 30 is combined with the polarization diversity antenna shown in FIG.
The cross-shaped parasitic element 30 is juxtaposed at a predetermined distance from the dipole element 12 of the first printed dipole antenna unit 10 and the dipole element 22 of the second printed dipole antenna unit 20, and the dipole element 12 and the dipole element The length of the portion along 22 is set to about λ / 2.

  According to the polarization diversity antenna A2 including the cross-shaped parasitic element 30, it is possible to reduce the return loss and obtain a wider band characteristic. Thus, the parasitic element 30 improves the band characteristics. Therefore, even when the length of the slits 15 and 25 shown in FIGS. 2 and 3 is set to be smaller than about λ / 4 and the posture is lowered, the slits 15 and 26 can be obtained by using the parasitic element 30 together. It is possible to obtain band characteristics substantially equivalent to the case where the length of is set to about λ / 4.

FIG. 5 shows a third embodiment of the polarization diversity antenna according to the present invention in which the first printed dipole antenna unit 100 shown in FIG. 6 and the second printed dipole antenna unit 200 shown in FIG. 7 are cross-coupled. .
5-7, the code | symbol corresponding to the element corresponding to each element shown in FIGS. 1-3 is attached | subjected. Hereinafter, only components different from the configurations shown in FIGS. 1 to 3 will be described.

In the polarization diversity antenna A3 according to the third embodiment, the element conductors 120a and 120b are obliquely downward at the feeding point site or in the middle so that the dipole element 120 of the first printed dipole antenna unit 100 has an umbrella shape. Similarly, the element conductors 220a and 220b are formed by being bent obliquely downward at the feeding point portion or in the middle so that the dipole element 220 of the second printed dipole antenna unit 200 has an umbrella shape. is there.
The dielectric substrates 110 and 210 of the antenna units 100 and 200 have both shoulders formed in a tapered shape, and the edge portions of the both shoulders are aligned with the dipole elements 120 and 220.

According to the polarization diversity antenna A3 according to this embodiment, since the beam width by each dipole element 120, 220 itself is expanded, the beam width in the horizontal plane can be increased.
FIG. 9 is a graph illustrating the relationship between the bending angle of the element conductors 120a and 120b and the beam width in the horizontal plane. As shown in this graph, the beam width in the horizontal plane is enlarged as the bending angle increases.

In this embodiment, the feed line conductors 140 and 240 are both formed in a U-shape for the purpose of facilitating manufacturing. However, the upper half portions of the feed line conductors 140 and 240 are respectively element conductors. It is also possible to form so as to be located behind 120b and 220b.
In addition, a part of the upper half of the feed line conductors 140 and 240 protrudes above the ground conductors 130a and 130b. This is because the feed line conductors 140 and 240 are arranged in such a form. This is because the feeding impedance for the element conductors 120a and 120b is optimally adjusted. Therefore, depending on the shape and bending angle of the element conductors 120a and 120b, the feed line conductors 140 and 240 may be arranged in a form that does not protrude from the ground conductors 130a and 130b, or may protrude more greatly. Of course, the lengths of the cut portions 160 and 260 are appropriately adjusted according to the amount of protrusion of the feed line conductors 140 and 240.

FIG. 8 shows a polarization diversity antenna having an array configuration in which a plurality (two in this example) of the polarization diversity antennas A1 shown in FIG. 1 are arranged at a predetermined interval.
The arrayed polarization diversity antenna includes a dielectric substrate 40 and a reflecting plate 50 disposed on the back side of the dielectric substrate 40, and is disposed on a ground conductor 41 provided over the entire surface of the dielectric substrate 40. Each antenna A1 is arranged.

In each antenna A1, the bases of the ground conductors 13a, 13b, 23a, and 23b are electrically connected to the ground conductor 41 by means such as soldering, and the feed line conductors 14 and 24 are connected to the lower surface of the dielectric substrate 40. The printed line conductors 42 and 43 are connected to the printed lines, respectively.
The reflecting plate 50 is bent on both sides along the longitudinal direction to the dielectric substrate 40 side. Both antennas A1 are oriented so that the dielectric substrates 11 and 21 form an angle of 45 ° with respect to a plane that includes the longitudinal axis of the dielectric substrate 40 and is perpendicular to the dielectric substrate 40.

In the polarization diversity antenna having this array configuration, the center conductors of special coaxial feed lines (not shown) are connected to the terminal portions 42a and 43a of the feed line conductors 42 and 43, respectively, and the outer conductors of these feed lines are ground conductors. 41.
In the polarization diversity antenna having this array configuration, each antenna A1 is arranged on a common dielectric substrate 40, but each antenna A1 may be arranged in a state of being attached to an individual dielectric substrate. .
Further, in place of the antennas A1, the polarization diversity antenna A2 shown in FIG. 4 or the polarization diversity antenna A3 shown in FIG. 5 can be arranged on the dielectric substrate 40. A polarization diversity antenna having an array configuration that makes use of the characteristics of the antennas A2 and A3 can be configured.

  According to the polarization diversity antenna A1 shown in FIG. 1 and the polarization diversity antenna A2 shown in FIG. 4, VSWR characteristics C1 and C2 as shown in FIG. 10 can be obtained, respectively. That is, in the antenna A1, a specific band of about 17% is obtained with VSWR 1.5, and in the antenna A1 whose band is widened by the cruciform parasitic element 30, the same band of about 20% is obtained.

  11 shows the directivity in the horizontal plane of the polarization diversity antenna A1 shown in FIG. 1 by a solid line, and shows the same directivity of the polarization diversity antenna A3 shown in FIG. 5 by a dotted line. As apparent from FIG. 11, the antenna A3 can expand the beam width in the horizontal plane.

  The present invention is not limited to the embodiment described above, and includes various modifications. For example, in the antennas A1, A2 and A3 shown in FIGS. 1, 4 and 5, a reflector similar to the reflector 50 shown in FIG. 8 can be used in combination as necessary.

1 is a perspective view showing a first embodiment of a polarization diversity antenna according to the present invention. FIG. 2 is an elevational view illustrating a configuration of a first printed dipole antenna unit in the antenna of FIG. 1. FIG. 3 is an elevation view illustrating a configuration of a second printed dipole antenna unit in the antenna of FIG. 1. It is a perspective view which shows 2nd Embodiment of the polarization diversity antenna which concerns on this invention. It is a perspective view which shows 3rd Embodiment of the polarization diversity antenna which concerns on this invention. FIG. 6 is an elevational view showing a configuration of a first printed dipole antenna part in the antenna of FIG. 5. FIG. 6 is an elevational view showing a configuration of a second printed dipole antenna part in the antenna of FIG. 5. FIG. 2 is a perspective view showing a polarization diversity antenna having an array configuration in which a plurality of polarization diversity antennas shown in FIG. 1 are arranged at predetermined intervals. 6 is a graph showing a relationship between a bending angle of an element conductor and a beam width in a horizontal plane in the antenna of FIG. 5. 5 is a graph showing VSWR characteristics of the antenna of FIG. 1 and the antenna of FIG. 4. It is a graph which shows the directivity in the horizontal surface of the antenna of FIG. 1 and the antenna of FIG. It is a perspective view which shows an example of the conventional polarization diversity antenna.

Explanation of symbols

10,100 First printed dipole antenna unit 11,110 Dielectric substrate 12,120 Dipole element 13a, 13b, 130a, 130b Ground conductor 14,140 Feed line conductor 20,200 Second printed dipole antenna unit 21,210 Dielectric Body substrate 22, 220 Dipole element 23a, 23b, 230a, 230b Ground conductor 24, 240 Feed line conductor 30 Cross-shaped parasitic element 40 Dielectric substrate 41 Ground conductor 42, 43 Feed line conductor 50 Reflector

Claims (7)

Each element in a form in which a pair of element conductors constituting a dipole element and a slit having a predetermined width are formed between each element conductor, starting from a feeding point portion of each element conductor, on one surface of the dielectric substrate A pair of ground conductors extending in a direction perpendicular to the conductors, and first and second printed dipole antenna portions each formed by printing,
The first printed dipole antenna is in contact with the notch portion to form a balun together with a notch portion having a predetermined length extending on the slit axis from the start end side to the end end side of the slit. A feed line conductor printed on the other surface of the dielectric substrate in a form that does not,
The second printed dipole antenna is in contact with the notch to form a balun together with a notch of a predetermined length extending from the end of the slit toward the start side on the axis of the slit and the ground conductor. A feed line conductor printed on the other surface of the dielectric substrate in a form that does not,
A polarization diversity antenna characterized in that the first and second printed dipole antenna portions are cross-coupled so as to form an angle of 90 ° with each other by using the cut portions formed in them.   A parasitic element is provided for each of the dipole element of the first printed dipole antenna unit and the dipole element of the second printed dipole antenna unit in such a manner that a predetermined distance is formed in the beam projection direction from these dipole elements. The polarization diversity antenna according to claim 1.   3. The polarization diversity antenna according to claim 2, wherein the parasitic elements for the dipole elements are integrally formed so as to form a cross shape.   2. The polarization diversity antenna according to claim 1, wherein the dipole element of the first printed dipole antenna portion and the dipole element of the second printed dipole antenna portion are each formed by being bent into an umbrella shape.   The polarization diversity antenna according to claim 1, further comprising a reflector.   A polarization diversity antenna comprising a plurality of polarization diversity antennas according to claim 1, 2 and 4 arranged at a predetermined interval in order to constitute an array antenna. The polarization diversity antenna according to claim 6, further comprising a reflector.

Images