JP4625514B2 - Horizontally polarized antenna and characteristic adjustment method thereof - Google Patents

Description

  The present invention relates to an antenna that transmits and receives horizontally polarized waves, and particularly relates to a technology for realizing a horizontally polarized antenna that can obtain the same beam width over a wide frequency band.

  In mobile communication, a plurality of users can be accommodated by using a plurality of frequency bands or by dividing a sector, thereby improving communication efficiency. For example, in the IMT-2000 system (third generation system), since the same frequency is repeatedly used in adjacent zones, interference is reduced by reducing the overlap portion between the radio zones, and the subscriber capacity is increased. Therefore, the horizontal beam width of the base station antenna (angle range where the gain is half the maximum gain) is the sector division angle of the service area (in the case of a three-sector wireless zone configuration, the division angle per sector is Narrower than 120 °). However, since an area where radio waves do not reach within the sector is generated if it is too narrow, it is desirable that the beam width is close to 120 ° (for example, about 100 ° ± 10 °). As an implementation technique related to this, a dipole antenna that realizes a beam width of about 120 ° by making the element non-directional in a horizontal plane by making the element into an arc shape in Patent Document 1 and further inserting a reflector behind it. Is disclosed.

In addition, in the base station antenna, it is desired that the number of antennas is as small as possible from the viewpoint of reducing installation space and introduction cost. In response to such a request, Patent Document 1 discloses that an arc-shaped parasitic element having a resonance frequency higher than that of the feeding element is disposed in the vicinity of the arc-shaped feeding element, thereby resonating in two frequency bands. A method of constructing a horizontally polarized antenna is disclosed.
Japanese Patent Laid-Open No. 11-68446 Shimura, Kanome, Ebine, "800 / 1500MHz band frequency / polarization shared 120 ° beam mobile communication base station antenna", IEICE General Conference, 2001, B-1-136

  The frequency bands used in IMT-2000 are three frequency bands of 800 MHz band, 1.7 GHz band, and 2 GHz band, and it is assumed that further different bands will be added in the future. A horizontally polarized antenna that resonates in a plurality of frequency bands can be realized by the technique disclosed in Patent Document 1 (an arc-shaped parasitic element is disposed close to an arc-shaped feeding element). However, the horizontally polarized antenna configured by the technique disclosed in Patent Document 1 shares a single reflector with a plurality of elements having different resonance frequencies. Since the distance to the device differs depending on each element, even if an antenna that resonates in a plurality of frequency bands can be configured, the beam width varies depending on the frequency band, and the effect of sector division cannot be fully enjoyed.

  1 and 2 are diagrams of a horizontally polarized antenna 100 in which an arc-shaped parasitic element having a resonance frequency higher than that of the feed element is arranged above and below the arc-shaped feed element based on the invention disclosed in Patent Document 1. It is a structural example. 1 (a) is a perspective view, FIG. 1 (b) is a plan view, and FIG. 2 is a plan view of FIG. 1 (b), omitting parasitic elements, and symbols corresponding to the parameters relating to the shape of the element. Is shown.

  The horizontally polarized antenna 100 includes a feeding element 110, a first parasitic element 120, a second parasitic element 130, and a reflector 150, and the feeding element 110 has a midpoint of a circular line segment formed by the feeding element 110 ( Power is supplied from a power supply point 111). The feeding element 110 is arranged in parallel with the ground, and the parasitic element 120 and the parasitic element 130 are arranged in parallel above and below the feeding element 110, and the arc line formed by the parasitic element 120 and the parasitic element 130. As shown in FIG. 1B, the midpoints of the minutes are arranged so as to be in a straight line with the midpoint of the arc segment formed by the feed element 110 in the z-axis direction (perpendicular to the ground). . Note that the spacing s between the feeding element 110 and the parasitic elements 120 and 130 in the z-axis direction is 5 mm. The reflection plate 150 is disposed on the outer peripheral portion at a predetermined distance d from the arc formed by the feeding element 110 and the parasitic elements 120 and 130 as shown in FIG.

  FIG. 3 illustrates the frequency characteristics of the beam width of the horizontally polarized antenna 100. Here, the values of the parameters in FIG. 1 are as follows: the radius Re of the arc formed by the feed element 110 is 40 mm, the center angle θe is 120 °, the radius Re of the arc formed by the parasitic element 120 is 25 mm, the center angle θe is 146 °, The radius Re of the arc formed by the parasitic element 130 is 20 mm, the center angle θe is 160 °, and the element lengths resonate in the 800 MHz, 1.5 GHz, and 2 GHz bands, respectively. The frequency of the VSWR as shown in FIG. Has characteristics. The radius Rr of the arc formed by the reflector 150 is 60 mm, the center angle θr of the arc formed by the reflector 150 is 160 °, the distance d between the radiating element 110 and the reflector 150 is 50 mm, and the z axis direction of the reflector 150 is The length h is 300 mm.

  As can be seen from FIGS. 3 and 4, even if good VSWR characteristics are obtained in three frequency bands of 800 MHz, 1.5 GHz, and 2 GHz, the beam width varies greatly depending on the frequency band.

  The present invention provides a characteristic adjustment method in which a horizontal polarization antenna that resonates in a plurality of frequency bands has a beam width that is approximately the same (eg, about 100 ° ± 10 °) over a wide band, and can further resonate in a desired band. The purpose is to do.

  In a horizontally polarized antenna with an arc-shaped radiating element arranged parallel to the ground, the beam width in the horizontal plane can be changed by changing the length of the radiating element by changing the center angle of the arc while keeping the radius of the arc constant. Adjust the frequency characteristics. Further, the resonance frequency shifted by changing the length of the radiating element is adjusted to resonate in a desired band by connecting linear conductors to both ends of the radiating element.

  With the characteristic adjustment method of the present invention, in a horizontally polarized antenna that resonates in a plurality of frequency bands, the beam width can be made equal over a wide band, and resonance can be achieved in a desired band.

[First Embodiment]
First, a method for adjusting the beam width in the case of a single feeding element will be clarified.
5 is an external view of the horizontally polarized antenna 200 in which the parasitic elements 120 and 130 are removed from the horizontally polarized antenna 100 shown in FIG. 1, FIG. 5 (a) is a perspective view, and FIG. 5 (b) is a perspective view. It is a top view. The symbols corresponding to the parameters related to the element shape are the same as those in FIG.

  FIG. 6 shows the frequency characteristics of the beam width when the radius Re of the arc formed by the feed element 110 of the horizontally polarized antenna 200 is constant at 35 mm and the center angle θe is changed in three ways of 80 °, 200 °, and 246 °. Is illustrated. Since the radius Re of the arc is constant, the length of the feed element is also changed by changing the central angle θe. The central angle θe = 80 ° corresponds to the resonance length in the 800 MHz band, and the central angle θe = 200 ° is 1 The center angle θe = 246 ° corresponds to the resonance length in the 2 GHz band when the resonance length is in the 0.5 GHz band. The other parameter values are as follows: the radius Rr of the arc formed by the reflector 150 is 60 mm, the center angle θr is 160 °, the distance d between the radiating element 110 and the reflector 150 is 45 mm, and the length of the reflector 150 in the z-axis direction. The length h is 300 mm.

  As can be seen from FIG. 6, the frequency characteristic of the beam width varies greatly depending on the value of θe. Conversely, it can be said that the frequency characteristic of the beam width can be adjusted by appropriately changing θe. However, in such a single element, it is practically difficult to make the beam width comparable (for example, about 100 ° ± 10 °) over a wide band.

[Second Embodiment]
Next, a method for adjusting the beam width when a parasitic element is provided in addition to the feeding element will be clarified. The configuration is the same as that shown in FIGS. 1 and 2, and the parameter values are the same as those described in “Problems to be Solved by the Invention” except for the central angle of the feed element.

  When the radius Re of the circular arc formed by the feed element 110 in the horizontally polarized antenna 100 is fixed to 40 mm, the frequency characteristics of the beam width when the central angle θe is changed in three ways of 120 °, 180 °, and 240 °, This is illustrated in FIG. Here, the characteristic curve when θe is 120 ° (corresponding to the resonant element length in the 800 MHz band) is the same as that shown in FIG. As can be seen from FIG. 7, even when there is a parasitic element, the frequency characteristics of the beam width vary greatly depending on the value of the central angle θe. In particular, when the center angle θe is 180 ° in this configuration, the beam width is 100 ° ± 10 ° in the range of 500 MHz to 2.1 GHz, except for the vicinity of 1.7 GHz, and the beam width is almost the same over a wide band. You can see that you can.

  In the above description, the center angle θe is adjusted with respect to the feed element. However, the frequency characteristic of the beam width can be adjusted also with respect to the parasitic element.

  In the above description, the element length of the feed element 110 is changed by fixing the arc radius Re at 40 mm and changing the center angle θe. However, the center angle θe is changed by keeping the element length of the feed element 110 constant. FIG. 8 shows the frequency characteristics of the beam width when the radius Re of the arc formed by the feeding element 110 is changed to 35 mm, 40 mm, and 45 mm. FIG. 8 shows that the frequency characteristics of the beam width hardly change by changing the central angle θe while keeping the element length of the feed element 110 constant.

[Third Embodiment]
As shown in the second embodiment, by adjusting the central angle θe, it is possible to make the beam width approximately the same over a wide band, but the central angle θe is changed with the radius Re of the feeder element being constant. Therefore, there arises a new problem that the element frequency changes and the resonance frequency also changes. Specifically, when the central angle θe is 120 °, the feeding element 110 resonates in the 800 MHz band as shown in FIG. 9, but the element length is shortened by widening the central angle θe to 180 °, and 800 MHz. The resonance point in the band moves to the high frequency side. Therefore, in the present invention, for example, a linear conductor 140 is connected to both ends of the shortened element as shown in FIG.

  FIG. 11 shows the frequency characteristics of the beam width when the linear conductor 140 is not connected and when it is connected, and FIG. 12 shows the frequency characteristics of the VSWR when the linear conductor 140 is not connected and when it is connected. To do. For the case where the linear conductor 140 is connected, “when connected at a right angle to the element as shown in FIG. 10A and the total length L = 35 mm”, “when connected at a right angle with the element as shown in FIG. 10A. L = 40 mm ”,“ when tilted inside the arc formed by the element as shown in FIG. 10B and L = 40 mm connected ”,“ when outside the arc formed by the element as shown in FIG. 10C ” The simulation was performed for the four cases of “inclined connection and L = 40 mm”. Here, the linear conductor 140 is connected to the element at the positions of lengths L1 and L2 from both ends, and the length of L1: the length of L2 = 3: 1.

  In any case from FIG. 11, except for the vicinity of 1.7 GHz, the beam width is generally in the range of 100 ° ± 10 ° at 500 MHz to 2.1 GHz. Even if the linear conductor 140 is connected, the beam width is It turns out that there is almost no influence. On the other hand, it can be seen from FIG. 12 that, except for the case of “L = 35 mm in FIG.

  Thus, by connecting the linear conductor 140, it is possible to resonate in a desired band while maintaining the frequency characteristics of the beam width. Note that the connection form of the linear conductor 140 is not limited to the above, and a linear conductor is shown in FIG. 10. However, for example, the linear conductor 140 can be adjusted by bending it into a square shape at the connection portion with the element. is there.

  The present invention is not limited to the embodiments described above. In addition, it can change suitably in the range which does not deviate from the meaning of this invention.

  The present invention is particularly effective when a base station that transmits and receives horizontally polarized waves uses a plurality of frequency bands with a small number of antennas and wants to perform sector division.

The perspective view and top view which showed the structural example of the horizontal polarization antenna 100. FIG. The top view which described the code | symbol corresponding to each parameter which concerns on the shape of the element of the horizontal polarization antenna. The figure which showed the example of the frequency characteristic of the beam width of the horizontal polarization antenna. The figure which showed the example of the frequency characteristic of VSWR of the horizontal polarization antenna. The perspective view and top view which showed the structural example of the horizontal polarization antenna 200. FIG. The figure which showed the example of the difference in the frequency characteristic of the beam width for every center angle (theta) e of the horizontally polarized wave antenna 200. FIG. The figure which showed the example of the difference in the frequency characteristic of the beam width for every center angle (theta) e of the horizontal polarization antenna. The figure which showed the example of the difference in the frequency characteristic of the beam width for every radius Re of the feed element 110 of the horizontal polarization antenna 100. The figure which showed the example of the difference in the frequency characteristic of VSWR for every center angle (theta) e of the horizontal polarization antenna. The figure which shows the connection image to the element of the linear conductor 140. FIG. The figure which showed the example of the frequency characteristic of the beam width at the time of connecting the linear conductor 140 to the horizontal polarization antenna 100. FIG. The figure which showed the example of the frequency characteristic of VSWR at the time of connecting the linear conductor 140 to the horizontal polarization antenna 100. FIG.

Claims (5)

  A method of adjusting characteristics of a horizontally polarized antenna having an arc-shaped radiating element arranged in parallel with the ground, and changing the length of the radiating element by changing the center angle of the arc while keeping the radius of the arc constant The method of adjusting the characteristics of a horizontally polarized antenna that adjusts the frequency characteristics of the beam width in a horizontal plane In the horizontal polarization antenna characteristic adjustment method according to claim 1,
Furthermore, the resonance frequency is adjusted by connecting linear conductors to both ends of the radiating element to adjust the characteristic of the horizontally polarized antenna.   A horizontal polarization antenna comprising an arc-shaped radiating element arranged in parallel with the ground, wherein linear conductors are connected to both ends of the radiating element, respectively. The horizontally polarized antenna according to claim 3,
The radiating element is a feeding element,
The horizontal polarization antenna further comprising at least one arc-shaped parasitic element that is arranged in parallel with the radiating element and resonates at a higher resonance frequency than the radiating element. The horizontally polarized antenna according to claim 3 or 4,
The horizontal polarization antenna according to claim 1, further comprising a reflector on an outer peripheral portion spaced a predetermined distance from the radiating element.

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