JP5473737B2 - Planar antenna - Google Patents

Description

  The present invention relates to a planar antenna, and more particularly, to a planar antenna that can realize a wide band narrow beam and high gain and can easily realize a beam tilt with a periodic structure and a small number of excitation elements.

For example, to increase the gain in a planar aperture antenna composed of a plurality of radiating elements arranged in a plane, increase the number of radiating elements such as dipole antenna elements and increase the area that is equiphased on the aperture plane. It is necessary to let
However, increasing the number of radiating elements inevitably complicates the power supply circuit for supplying power to each radiating element, and the wider the aperture, the longer the line length to the end, which increases transmission loss. Can not escape.
For example, in the case of the conventional six-element corner reflector antenna shown in FIG. 26, the gain is increased by forming a fan-shaped beam in the horizontal plane, exciting the radiating elements stacked in the vertical direction, and narrowing the beam. In this case, the number and spacing of the radiating elements are determined by the specifications of the gain and directivity required for the antenna. When the radiating element is a half-wave dipole antenna, as shown in FIG. Is separated by 1.3λo (λo is a free space wavelength of the used frequency fo) or more, the sidelobe level increases and the gain decreases. In FIG. 29, A indicates the gain, and B indicates the 1st side lobe level.
In order to solve these problems, Patent Document 1 below discloses an antenna device that realizes a high gain by one-element excitation using a periodic structure made of a rectangular patch conductor.

JP 2007-235460 A

However, although the antenna described in Patent Document 1 described above is useful for reducing the loss of the feed system, there is a problem that it is difficult to widen the band and it is difficult to obtain a wide band narrow beam / high gain characteristic.
The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to provide a planar antenna that can obtain a narrow beam and high gain with a periodic structure and a small number of excitation elements. There is.
The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.
(1) A reflective surface, a periodic structure disposed on the reflective surface and having a plurality of conductor patterns disposed in a line or matrix, and disposed between the reflective surface and the periodic structure. possess at least two excitation elements, each conductor pattern of the periodic structure has a rectangular shape, when the free space wavelength of the used frequency fo the .lamda.o, of each of the at least two excitation elements The interval between the excitation elements is 1.3λo or more. Here, an interval between the reflecting surface and the periodic structure is 0.45λo or more. When a dielectric layer having a relative dielectric constant εr is provided in a space between the reflective surface and the periodic structure, the distance between the reflective surface and the periodic structure is 0.45λo / √ ( εr) or more.
(2) In (1), excitation power having different phases is supplied to the at least two excitation elements.

(3) A reflection surface, a periodic structure disposed on the reflection surface, and a plurality of conductor patterns arranged in a line or matrix, and a matrix between the reflection surface and the periodic structure. possess at least four excitation element are arranged, the conductor pattern of the periodic structure has a rectangular shape, when the free space wavelength of the used frequency fo of .lamda.o, at least four excitation element The interval between the respective excitation elements is 1.3λo or more. Here, an interval between the reflecting surface and the periodic structure is 0.45λo or more. When a dielectric layer having a relative dielectric constant εr is provided in a space between the reflective surface and the periodic structure, the distance between the reflective surface and the periodic structure is 0.45λo / √ ( εr) or more.
(4) In (3), the at least four excitation elements are divided into a plurality of groups in the vertical direction or the horizontal direction, and excitation power having different phases is supplied to each group.
(5) In any one of (1) to (4), the reflecting surface is an EBG (Electromagnetic Band Gap) plate.
(6) In any one of (1) to (5), the conductor pattern is a strip-like pattern that is long in a direction orthogonal to the electric field surface of the excitation element.

The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.
According to the present invention, it is possible to provide a planar antenna that can obtain a narrow beam and a high gain with a periodic structure plate and a small number of excitation elements.

It is a perspective view which shows the structure of the planar antenna of Example 1 and Example 2 of this invention. It is sectional drawing of the planar antenna of Example 1 and Example 2 of this invention. It is a perspective view which shows the structure of the planar antenna of Example 3 of this invention. It is a graph which shows an example of the directional characteristic in the electric field surface (XZ surface shown in FIG. 1) of an example of the planar antenna of Example 1 of this invention. It is a graph which shows an example of the directional characteristic in the magnetic field plane (YZ surface shown in FIG. 1) of an example of the planar antenna of Example 1 of this invention. It is a graph which shows the other example of the directional characteristic in the electric field plane (XZ surface shown in FIG. 1) of the other example of the planar antenna of Example 1 of this invention. It is a graph which shows the other example of the directional characteristic in the magnetic field surface (YZ surface shown in FIG. 1) of the other example of the planar antenna of Example 1 of this invention. It is a graph which shows an example of the directional characteristic in the electric field surface (XZ surface shown in FIG. 1) of an example of the planar antenna of Example 2 of this invention. It is a graph which shows the other example of the directional characteristic in the electric field plane (XZ surface shown in FIG. 1) of the other example of the planar antenna of Example 2 of this invention. It is a graph which shows the gain characteristic of the planar antenna of Example 1 and Example 2 of this invention, and the planar antenna of the prior art shown in FIG. It is a graph which shows an example of the directional characteristic in the electric field surface (XZ surface shown in FIG. 1) of an example of the planar antenna of Example 3 of this invention. It is a graph which shows an example of the directional characteristic in the magnetic field surface (XY plane shown in FIG. 1) of an example of the planar antenna of Example 3 of this invention. It is a perspective view which shows the structure of the planar antenna of Example 4 of this invention. It is a perspective view which shows arrangement | positioning of the excitation element of the planar antenna of Example 4 of this invention. It is a perspective view which shows arrangement | positioning of the excitation element of the planar antenna of the prior art corresponding to the planar antenna of Example 4 of this invention. It is an example of the graph of the gain change by the patch dimension of the planar antenna of Example 4 of this invention, and a patch gap | interval. It is the graph which compared the frequency characteristic of the gain of the planar antenna of Example 4 of this invention, and the planar antenna by a prior art corresponding to this. It is a perspective view which shows the structure of the planar antenna of Example 5 of this invention. It is a graph which shows an example of the relative directional characteristic in the electric field plane (XZ surface shown in FIG. 18) of an example of the planar antenna of Example 5 of this invention. It is a graph which shows an example of the relative directional characteristic in the magnetic field plane (YZ surface shown in FIG. 18) of an example of the planar antenna of Example 5 of this invention. Relative directional characteristics in the electric field plane (XZ plane shown in FIG. 18) of an example of the conventional planar antenna having the arrangement of the excitation elements shown in FIG. 15 corresponding to an example of the planar antenna of the fifth embodiment of the present invention. It is a graph which shows an example. Relative directional characteristics in the magnetic field plane (YZ plane shown in FIG. 18) of an example of the conventional planar antenna having the arrangement of the excitation elements shown in FIG. 15 corresponding to an example of the planar antenna of Example 5 of the present invention. It is a graph which shows an example. It is a figure which shows the planar antenna of the prior art corresponding to Example 1 of this invention. 24 is a graph showing an example of directivity characteristics in the electric field plane (XZ plane shown in FIG. 23) of the planar antenna shown in FIG. 24 is a graph showing an example of directivity characteristics in the magnetic field plane (YZ plane shown in FIG. 23) of the planar antenna shown in FIG. It is a perspective view which shows the conventional 6 element corner reflector antenna. It is a graph which shows an example of the directional characteristic in the electric field surface (XZ surface shown in FIG. 26) of the conventional 6 element corner reflector antenna. It is a graph which shows an example of the directional characteristic in the magnetic field surface (YZ surface shown in FIG. 26) of the conventional 6 element corner reflector antenna. It is a graph which shows the side lobe level with respect to the radiation | emission element space | interval, and a gain characteristic in the conventional 6 element corner reflector antenna.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In all the drawings for explaining the embodiments, parts having the same functions are given the same reference numerals, and repeated explanation thereof is omitted. Also, the following examples are not intended to limit the interpretation of the scope of the claims of the present invention.
[Example 1]
1 is a perspective view showing a configuration of a planar antenna according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view of the planar antenna according to the first embodiment of the present invention.
As shown in FIGS. 1 and 2, the planar antenna of this embodiment includes a reflector 1, two excitation elements (dipole antenna elements in this embodiment) disposed on the reflector 1, and two pieces. And the periodic structure 3 disposed on the excitation elements (2 ₁ , 2 ₂ ). The reflection plate 1 is made of a metal plate, and includes a side surface formed on both sides and a bottom surface that is inclined so as to become deeper toward the center.
In this embodiment, the _{2 1, 2 2} spacing of the two excitation elements (Sd in Fig. 1) is, 1.3λo (λo is the free space wavelength of the used frequency fo) are higher. Further, the distance (Hd in FIG. 2) between the central portion of the bottom surface of the reflector 1 and the two excitation elements (2 ₁ , 2 ₂ ) may be set at a position where the input impedance becomes an appropriate value.
The periodic structure 3 is configured by a plurality of conductor patterns 5 that are arranged so as to be orthogonal to the side surface of the reflector 1 and arranged in a 19 × 2 matrix. Here, the plurality of conductor patterns 5 arranged in a 19 × 2 matrix are constituted by, for example, a plurality of conductor patterns printed on a synthetic resin.
Moreover, the space | interval (He) of the center part of the bottom face of the reflecting plate 1 and the periodic structure 3 shall be 0.45 (lambda) o or more. When a dielectric layer is provided in the space between the bottom surface of the reflecting plate 1 and the periodic structure 3, He is a value obtained by dividing by the square root √ (εr) of the relative dielectric constant εr of the dielectric, 0.45λo / √ (εr) or more.

In the above description, the periodic structure 3 is composed of a plurality of conductor patterns 5 arranged in a 19 × 2 matrix, but is not limited to this value, and depends on the required directivity. Matrix values can be increased or decreased.
In this embodiment, the radio waves excited and radiated by the excitation elements (2 ₁ , 2 ₂ ) are repeatedly reflected between the reflecting surface of the reflecting plate 1 and the periodic structure 3, but the reflecting surface of the reflecting plate 1 When the interval between the periodic structures 3 is about (n / 2) λo (n is an integer), the radio waves radiated from the gap are radiated in the same phase.
Since the periodic structure 3 forms a capacitance between the inductance of the conductor pattern 5 serving as a nucleus and the adjacent conductor pattern 5, a unique impedance surface is created. An appropriate impedance surface can be realized by appropriately selecting the size and interval of the conductor pattern 5 of the periodic structure 3, and a large gain can be obtained.
Therefore, when the pattern of the conductor pattern 5 serving as a nucleus is small, the interval between the adjacent conductor patterns 5 is narrowed, and when the pattern of the conductor pattern 5 serving as a nucleus is large, the adjacent conductor pattern 5 It is necessary to widen the interval with 5.
2 ₁ and 2 ₂ spacing of the two excitation elements (Sd) is 1.3 wavelength or more, it can be extended further while considering the size of the opening surface. When the distance (Sd) between the two excitation elements 2 ₁ and 2 ₂ is 1.3λo, the power at the center of the aperture is stronger than that at the periphery of the aperture, and the power distribution in the aperture has a tapered distribution. Tends to have a low side lobe, but it is desirable to further widen the interval in order to further increase the gain.

An example of the parameters of the first embodiment is shown below.
(1) The width of the reflector 1 (W in FIG. 2) is 50 mm.
(2) The height from the center of the bottom surface of the reflector 1 to the side surface (Hr in FIG. 2) is 5 mm, and the height of the side surface of the reflector 1 (He-Hr in FIG. 2) is 30 mm.
(3) The distance (He in FIG. 2) between the center of the bottom surface of the reflector 1 and the periodic structure 3 is 35 mm.
(4) The size of the conductor pattern 5 of the periodic structure 3 is 15 mm × 15 mm.
(5) The gap between the conductor patterns 5 of the periodic structure 3 is 4 mm both vertically and horizontally.
(6) The distance (Hd in FIG. 2) between the central portion of the bottom surface of the reflector 1 and the excitation elements (2 ₁ , 2 ₂ ) is 15 mm.
(7) The total length of the reflector 1 is 380 mm.
(8) The center frequency is 5.6 GHz
4 and 5, in Example 1 of the present invention, other conditions of the above parameters, two intervals of the excitation element _{2 1} and _{2 2} of FIG. 1, when 100mm of (Sd ≒ 1.87λo) 4 is an example of directivity, FIG. 4 is a graph showing an example of directivity in the electric field plane (XZ plane shown in FIG. 1), and FIG. 5 is a graph in the magnetic field plane (YZ shown in FIG. 1). It is a graph which shows an example of the directional characteristic of a surface. In the graphs shown in FIGS. 4 and 5, the center is −25 dBi, and the outer circle is 20 dBi.
6 and 7, in the first embodiment of the present invention, in addition to the above parameters, the directivity characteristics in the case of two intervals of the excitation element _{2 1} and _{2 2} of FIG. 1, 200mm (Sd ≒ 3.73λo) FIG. 6 is a graph of the directivity in the electric field plane (XZ plane shown in FIG. 1), and FIG. 7 is the directivity in the magnetic field plane (YZ plane shown in FIG. 1). It is a graph which shows. In the graphs shown in FIGS. 6 and 7, the center is −25 dBi, and the outer circle is 20 dBi.

FIG. 23 is a diagram illustrating an example of a planar antenna according to the prior art. In FIG. 23, the number of the excitation elements 2 is one. Other related parameters are the same as those in the first embodiment.
24 is a graph showing an example of directivity characteristics in the electric field plane (XZ plane shown in FIG. 24) of the planar antenna according to the conventional technique shown in FIG. 23, and FIG. 25 is a plane according to the conventional technique shown in FIG. It is a graph which shows an example of the directional characteristic in the magnetic field surface of an antenna (YZ surface shown in FIG. 23). In the graphs shown in FIGS. 24 and 25, the center is −25 dBi, and the outer circle is 20 dBi.
As can be seen from the directivity graphs shown in FIGS. 4 and 6 and the directivity graph shown in FIG. 24, the planar antenna of this embodiment shown in FIGS. 4 and 6 is a planar antenna according to the prior art shown in FIG. It can be seen that the beam is narrowed.
FIG. 26 is a perspective view showing a conventional 6-element corner reflector antenna. In FIG. 26, 10 is a corner reflector, and 12 _{1 to} 12 ₆ are radiating elements (in FIG. 26, dipole antenna elements). The total length of the corner reflector is 380 mm, which is the same as the total length of the reflector 1 of the first embodiment.
FIG. 27 is a graph showing an example of directivity characteristics in the electric field plane (XZ plane shown in FIG. 26) of the conventional 6-element corner reflector antenna, and FIG. 28 is a graph of the conventional 6-element corner reflector antenna. It is a graph which shows an example of the directional characteristic in a magnetic field surface (YZ surface shown in FIG. 26).
27 and 28 are graphs showing directivity when the frequency is 5.6 GHz. In the graphs shown in FIGS. 27 and 28, the center is −25 dBi, and the outer circle is 20 dBi.
As can be seen from the directivity graphs shown in FIGS. 4 and 6 and the directivity graph shown in FIG. 27, the planar antenna of the present embodiment shown in FIGS. 1 and 2 has the conventional six-element corner shown in FIG. It can be seen that the characteristic is almost the same as that of the reflector antenna.

[Example 2]
1 and 2, the phase of the excitation power supplied to the two excitation elements (dipole antenna elements in this embodiment) (2 ₁ , 2 ₂ ) is expressed by, for example, a single differential phase shifter. It is possible to adjust the radiation direction (so-called tilt angle) of the radio wave by using and making different. Note that the radiation direction (so-called tilt angle) of radio waves can be adjusted by setting the number of excitation elements to three and changing the phase of the excitation power supplied to each.
The configuration of the second embodiment is the same as that of the first embodiment, but differs from the first embodiment in that the feeding phase to the excitation element is not the same. The parameters are the same as those in the first embodiment.
8, in the second embodiment of the present invention, the distance between the two excitation elements _{2 1} and _{2 2} of FIG. 1, with 100mm (Sd ≒ 1.87λo), and the excitation element _{2 1,} the excitation element _{2 2} 2 is a graph showing the directivity characteristics in the electric field plane (XZ plane shown in FIG. 1) when excitation power having a phase difference of 60 ° is supplied.
9, in the second embodiment of the present invention, the distance between the two excitation elements _{2 1} and _{2 2} of FIG. 1, with 200mm (Sd ≒ 3.73λo), and the excitation element _{2 1,} the excitation element _{2 2} 2 is a graph showing the directivity characteristics in the electric field plane (XZ plane shown in FIG. 1) when excitation power having a phase difference of 60 ° is supplied. In the graphs shown in FIGS. 8 and 9, the center is −25 dBi, and the outer circle is 20 dBi.

4, the directional characteristics shown in FIG. 6, FIG. 8, when comparing the directivity characteristics shown in FIG. 9, the excitation element 2 _1, to the excitation element 2 _2, the 60 ° phase respectively provide different excitation power Thus, it can be seen that the beam is tilted.
For example, in the conventional 6-element corner reflector antenna shown in FIG. 26, in order to realize beam tilt without causing significant deterioration of the side lobes, the excitation phases of the radiating elements (12 _{1 to} 12 ₆ ) are sequentially changed. If the number of radiating elements (12 _{1 to} 12 ₆ ) is equal to the number of radiating elements (12 _{1 to} 12 ₆ ), and branch terminals for branching them are prepared, or the tilt angle is variable It is necessary to prepare at least three differential type phase shifters and a feeding line and branch terminals associated therewith.
On the other hand, in the present embodiment, it is only necessary to provide an excitation phase difference between the two excitation elements (2 ₁ , 2 ₂ ), so two feeding lines with different electrical lengths and one branch terminal are prepared. When the tilt angle is variable, it is only necessary to prepare one variable phase shifter, two feed lines, and one branch terminal, and the beam tilt can be realized very easily.

FIG. 10 is a graph showing gain characteristics of the planar antennas according to the first and second embodiments of the present invention and the related art.
10, A is the gain characteristic of the planar antenna according to the prior art shown in FIG. 23, and B is the distance between the two excitation elements 2 ₁ and 2 _{2 in} FIG. the gain characteristic when the 100 mm, C, in the first embodiment of the present invention, the distance between the two excitation elements _{2 1} and _{2 2} of FIG. 1, the gain characteristics when the 200 mm, D is the invention in example 2, the spacing of the two excitation elements _{2 1} and _{2 2} of FIG. 1, the gain characteristics when the 100 mm, E is the second embodiment of the present invention, ₂ of Figure 1 ₁ and 2 ₂ shows the gain characteristics when the distance between the two excitation elements is 200 mm.
From the graph of FIG. 10, the planar antennas of Example 1 and Example 2 can obtain a gain of 18 dBi or more at a frequency of about 5.6 GHz, except when the spacing between the excitation elements of Example 2 is 100 mm. In Example 1, it can be seen that the gain increases at 5 GHz or more by widening the interval between the excitation elements (2 ₁ , 2 ₂ ). In Example 2, it can be seen that the gain is increased as a whole by widening the interval between the excitation elements (2 ₁ , 2 ₂ ).
Although the aperture area is the same, the characteristic A of the planar antenna according to the prior art only realizes a gain of less than 18 dBi at a single frequency in the vicinity of 5.6 GHz, whereas the characteristic B of Example 1 Is 18 dBi or more over the 0.1 GHz band, characteristic C is 18 dBi or more over the 0.22 GHz band, and characteristic E of the second embodiment achieves a gain of 18 dBi or more over the 0.18 GHz band. It can be seen that the planar antenna of this embodiment achieves higher gain in a much wider frequency band than the planar antenna according to the prior art.
In the frequency range higher than the center frequency, the slope of the frequency characteristic of the gain is not greatly different in A, B, C, and D. However, when the gain characteristics in the frequency range lower than the center frequency are compared, the planar antenna according to the prior art In contrast to the characteristic A according to the above, the characteristics B, C, D and E in Examples 1 and 2 are descending with a remarkably gentle slope. The wide bandwidth of the planar antenna is obvious.

In the planar antennas of Example 1 and Example 2 described above, the reflector 1 may be a planar reflector. Moreover, although the metal plate was used as the reflecting plate 1, any plate may be used as long as it reflects electrically, such as a plate of any conductive material, a lattice, a mesh, and a perforated plate. An EBG (Electromagnetic Band Gap) plate may be used as the reflecting plate 1. In this case, the distance between the excitation element (2 ₁ , 2 ₂ ) and the reflecting plate 1 can be narrowed, so that the antenna can be thinned. Furthermore, the front-back characteristics are also improved.
Further, in the planar antennas of Example 1 and Example 2 described above, the shape of the conductor pattern 5 constituting the periodic structure 3 is not limited to a square, and may be a circle, a triangle, a rectangle, or a polygon. Furthermore, it may be a loop instead of a plate.
Further, in the planar antenna of Example 1 and this Example 2 above, the excitation element (2 _{1, 2 2)} Although the electric field is oriented in the longitudinal direction of the reflector 1, the excitation element (2 _1, 2 ₂₎ The polarization plane may be changed by directing the electric field in the width direction of the reflector 1.

[Example 3]
FIG. 3 is a perspective view showing the configuration of the planar antenna according to the third embodiment of the present invention. The conductor pattern 6 is different from the first embodiment shown in FIG. 1 in that a strip-like pattern that is long in the direction perpendicular to the electric field of the excitation element (2 ₁ , 2 ₂ ) is used. That is, the gap between the conductor patterns 5 arranged two by two in FIG. 1 is filled with the conductor to form one band-like conductor pattern (6 in FIG. 3), which is formed in parallel with the excitation element (2 ₁ , 2 ₂ ).
In the case of such a configuration, the obtained radiation directivity and gain are substantially the same as those in the first embodiment shown in FIG.
FIG. 11 is a graph showing an example of directivity characteristics in the electric field plane (XZ plane shown in FIG. 3) of the planar antenna of the third embodiment. FIG. 12 is a magnetic field plane (FIG. 12) of the planar antenna of the third embodiment. 3 is a graph showing an example of directivity characteristics of the YZ plane shown in FIG. In both cases, the center is −25 dBi and the outer circle is 20 dBi.
That is, in the planar antenna according to the first embodiment, when the polarization of the antenna is linearly polarized and the plane of polarization is fixed, each conductor pattern is composed of a long band in a direction perpendicular to the electric field plane. Design and production becomes simple.

[Example 4]
FIG. 13 is a perspective view showing the configuration of the planar antenna according to the fourth embodiment of the present invention, and FIG. 14 is a perspective view showing the arrangement of the excitation elements of the planar antenna according to the fourth embodiment of the present invention.
As shown in FIG. 13 and FIG. 14, the planar antenna of this embodiment includes a planar reflector 1 and four excitation elements (dipole antenna elements in this embodiment) disposed on the reflector 1 ( 2 _{1 to} 2 ₄ ) and the periodic structure 3 disposed on the _four excitation elements (2 ₁ to 2 ₄ ).
In the planar antenna of this embodiment, four excitation elements (2 ₁ to 2 ₄ ) are arranged in a matrix at intervals of 1.3λo or more, and in accordance therewith, the periodic structure 3 However, it is different from the planar antenna of Example 1 described above in that it is composed of a plurality of conductor patterns 5 arranged in an 8 × 8 matrix.
Also in this _embodiment, 21 to ₂₄ intervals of the four excitation elements (Sd) is greater than or equal to 1.3Ramudao. Moreover, what is necessary is just to set the space | interval of the reflecting plate 1 and the four excitation elements (2 ₁ to 2 ₄ ) to a position where the input impedance becomes an appropriate value.
In addition, the periodic structure 3 is configured by conductor patterns 5 that are arranged in parallel with the reflector 1 and arranged in an 8 × 8 matrix. Here, the conductor pattern 5 arranged in an 8 × 8 matrix is configured by a conductor pattern printed on a synthetic resin, for example.
Moreover, the space | interval of the reflecting plate 1 and the periodic structure 3 is 0.45 (lambda) o or more. When a dielectric layer is provided in the space between the reflector 1 and the periodic structure 3, the distance between the reflector 1 and the periodic structure 3 is the square root √ (εr of the relative dielectric constant εr of the dielectric. ), Which is 0.45λo / √ (εr) or more.
In the present embodiment shown in FIGS. 13 and 14, the conductor patterns are arranged in an 8 × 8 matrix, but the present invention is not limited to this value, and the matrix is not limited to the required directivity. Depending on the required directivity, the number of conductor patterns arranged in rows and columns may be different, and the interval between metal patterns is different between rows and columns. You can also.

FIG. 16 shows the gap (patch gap) of the conductor pattern 5 and the patch when the dimensions of the conductor pattern (patch) 5 are 10 mm × 10 mm, 15 mm × 15 mm, and 20 mm × 20 mm in Example 4 of the present invention. When the patch is arranged so that the size of the antenna is approximately 150 mm square by changing the ratio with the side length (patch width) of the antenna, the frequency characteristic of the antenna gain is calculated, and the frequency at which the maximum gain is obtained. 5 is a graph of conversion gain obtained by obtaining the aperture efficiency of the antenna and applying the obtained aperture efficiency to a 150 mm square antenna aperture.
In FIG. 16, A is the case where the patch size is 20 mm × 20 mm, B is the case where the patch size is 15 mm × 15 mm, and C is the case where the patch size is 10 mm × 10 mm. From FIG. 16, it can be seen that when the patch size is 20 mm × 20 mm shown in FIG. 16A, a relatively high gain is obtained and the degree of freedom with respect to the patch gap is large. The excitation element interval (Sd in FIG. 14) was 80 mm both vertically and horizontally, and the interval between the reflector 1 and the periodic structure 3 was 32 mm. The frequency with the highest gain was in the range of 5.0 GHz to 5.4 GHz.
FIG. 15 is a perspective view showing the arrangement of the excitation elements 2 of the conventional planar antenna corresponding to an example of the planar antenna according to the fourth embodiment of the present invention.
In FIG. 17, the structure of the periodic structure is 8 × 8, the size of the reflecting plate 1 is 150 mm × 150 mm, the distance between the reflecting plate 1 and the periodic structure 3 is 32 mm, and the size of the conductor pattern (patch) 5 is 15 mm. 15 × 15 mm, the gap between the conductor patterns (patch) 5 is 3 mm, the number of excitation elements is 2 × 2, and the excitation element interval (Sd in FIG. 14) is 82 mm (A in FIG. 17). When the excitation element which is a planar antenna of the prior art shown in FIG. 1 is one element (B in FIG. 17), the periodic structure plate 3 is not provided, the number of radiating elements is 2 × 2, and the spacing between radiating elements is 82 mm (FIG. It is a graph of the frequency characteristic of the gain of C).
In FIG. 17, the gain of the periodic structure 3 is higher over a wide band, and the present embodiment of 2 × 2 achieves a gain of 2 dB or more higher than the conventional planar antenna having one excitation element. The -1 dB bandwidth is 0.5 GHz or more with respect to a little less than 0.4 GHz, and it can be seen that this example is excellent.

19 is a graph showing an example of relative directivity characteristics in the electric field plane (XZ plane shown in FIG. 13) of Example 4 of the present invention, and FIG. 20 is in the magnetic field plane of Example 4 of the present invention. It is a graph which shows an example of the relative directivity characteristic of (YZ plane shown in FIG. 13).
19, FIG. 20 is a center frequency 5.3 _GHz, distance of the four parasitic elements 21 to ₂₄ is indicative of the relative directivity when the 82mm (Sd ≒ 1.45λo in Figure 14), respectively It is a graph.
FIG. 21 shows an electric field plane (XZ plane shown in FIG. 15) of a conventional planar antenna corresponding to an example of the planar antenna according to the fourth embodiment of the present invention (in the case of one excitation element 2 shown in FIG. 14). 22) is a graph showing an example of the relative directivity characteristic, and FIG. 22 is a graph showing a conventional planar antenna corresponding to an example of the planar antenna according to the fourth embodiment of the present invention (in the case of one excitation element 2 shown in FIG. 14). 16 is a graph showing an example of relative directivity characteristics in a magnetic field plane (YZ plane shown in FIG. 15). 21 and 22 are graphs showing the relative directivity when the center frequency is 5.3 GHz.
Comparing each graph of FIGS. 19-22, it turns out that the planar antenna of a present Example is narrower than the planar antenna by a prior art.
19, 20, 21, and 22 are graphs showing directivity characteristics for the following parameters.
(1) The distance between the reflector 1 and the periodic structure 3 is 32 mm.
(2) The size of the conductor pattern 5 of the periodic structure 3 is 15 mm × 15 mm
(3) The gap between the conductor patterns 5 of the periodic structure 3 is 3 mm both vertically and horizontally.
(4) The distance between the reflector 1 and the excitation elements (2 ₁ to 2 ₄ ) is 10 mm.
In the planar antenna of this embodiment, a metal plate is used as the reflecting plate 1. However, any material can be used as long as it reflects electrically, such as a plate of any conductive material, a lattice, a mesh, or a perforated plate. . An EBG (Electromagnetic Band Gap) plate may be used as the reflection plate 1. In this case, the distance between the excitation element (2 ₁ to 2 ₄ ) and the reflection plate 1 can be narrowed, so that the antenna can be thinned. Furthermore, the front-back characteristics are also improved.
Also in the planar antenna of this embodiment, the shape of the conductor pattern 5 constituting the periodic structure 3 is not limited to a square, and may be a circle, a triangle, a rectangle, a polygon, and a loop instead of a plate. It may be a shape.

[Example 5]
FIG. 18 is a perspective view showing the configuration of the planar antenna according to the fifth embodiment of the present invention. The conductor pattern 6 is different from the above-described fourth embodiment shown in FIG. 13 in that the conductor pattern 6 is formed of a strip-like pattern that is long in a direction orthogonal to the electric field of the excitation elements (2 ₁ to 2 ₄ ). The obtained characteristics are not substantially different from the planar antenna of Example 4. The design and manufacture are simplified as in the third embodiment.
As described above, according to the planar antenna of each embodiment of the present invention, a narrow beam and high gain can be obtained over a wide frequency band with a small number of excitation elements.
In each of the above-described embodiments, the excitation element is not limited to the dipole antenna element, and a patch element or the like can be used. In the first, second, and fourth embodiments, the circularly polarized wave is used. A radiating element can also be used.
As mentioned above, the invention made by the present inventor has been specifically described based on the above embodiments. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Of course.

1 reflector 2, 2 _{1 to} 2 ₆ excitation element (dipole antenna element)
3 periodic structure 5,6 conductive pattern 10 corner reflector 12 ₁ to 12 ₆ radiating element

Claims (6)

A reflective surface;
A periodic structure disposed on the reflecting surface and having a plurality of conductor patterns disposed in a line or matrix;
Having at least two excitation elements disposed between the reflective surface and the periodic structure;
Each conductor pattern of the periodic structure has a rectangular shape,
A planar antenna characterized in that, when λo is a free space wavelength of a use frequency fo, the interval between the at least two excitation elements is 1.3λo or more.   2. The planar antenna according to claim 1, wherein excitation power having different phases is supplied to each of the at least two excitation elements. A reflective surface;
A periodic structure disposed on the reflecting surface and having a plurality of conductor patterns disposed in a line or matrix;
Having at least four excitation elements arranged in a matrix between the reflective surface and the periodic structure;
Each conductor pattern of the periodic structure has a rectangular shape,
A planar antenna characterized in that, when λo is a free space wavelength of a use frequency fo, the interval between the at least four excitation elements is 1.3λo or more.   The planar antenna according to claim 3, wherein the at least four excitation elements are divided into a plurality of groups in the vertical direction or the horizontal direction, and excitation power having different phases is supplied to each group.   The planar antenna according to any one of claims 1 to 4, wherein at least a bottom surface of the reflecting surface is formed of an EBG plate.   6. The planar antenna according to claim 1, wherein the conductor pattern is a strip-like pattern that is long in a direction perpendicular to the electric field surface of the excitation element.

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