Patent Application
20250105520
The present disclosure relates to a planar antenna.
This application claims priority on Japanese Patent Application No. 2022-004158 filed on Jan. 14, 2022, the entire content of which is incorporated herein by reference.
In a planar antenna provided on a surface of a dielectric substrate, a surface current that is propagated on the substrate surface due to a radio wave radiated from the planar antenna may occur. This surface current is propagated from the planar antenna to the edge of the dielectric substrate, to cause a radiant wave from the edge. This radiant wave causes deterioration of the directivity of the planar antenna.
PATENT LITERATURE 1 discloses a technology that suppresses the surface current on the substrate surface by using an electromagnetic band gap structure.
A planar antenna as an embodiment includes: a dielectric substrate; a feed line provided on a first surface of the dielectric substrate and having a first lateral side extending along a first direction and a second lateral side opposed to the first lateral side; three or more radiation elements arrayed on the first surface along the first direction and provided at the first lateral side and the second lateral side so as to alternately protrude; and an electromagnetic band gap structure having an arrangement region on the first surface. The first surface includes a first adjacent region adjacent to the first lateral side and a second adjacent region adjacent to the second lateral side. The arrangement region includes a first arrangement region included in the first adjacent region, and a second arrangement region included in the second adjacent region. The three or more radiation elements include a plurality of first radiation elements protruding from the first lateral side toward the first adjacent region, and one or a plurality of second radiation elements protruding from the second lateral side toward the second adjacent region. At least a part of the first arrangement region is positioned closer to the feed line with respect to a first imaginary line below. At least a part of the second arrangement region is positioned closer to the feed line with respect to a second imaginary line below.
The first imaginary line: a straight line parallel to the first direction and passing through the first adjacent region, an interval between the straight line and an imaginary center line below being twice w1 below.
The second imaginary line: a straight line parallel to the first direction and passing through the second adjacent region, an interval between the straight line and the imaginary center line being twice w2 below.
The imaginary center line: a straight line parallel to the first direction and passing through a center, in a second direction orthogonal to the first direction, of the feed line.
The w1: an interval between the imaginary center line and a leading edge of the plurality of first radiation elements.
The w2: an interval between the imaginary center line and a leading edge of the one or the plurality of second radiation elements.
The above conventional example indicates that influence of the surface current can be suppressed by the electromagnetic band gap structure, but does not mention influence of the positional relationship between the antenna and the electromagnetic band gap structure on the directivity of the antenna and the surface current.
The inventors of the present application conducted a thorough study with respect to the influence of the positional relationship between an antenna and an electromagnetic band gap structure on the directivity of the antenna.
In the study, the inventors found that the positional relationship between an antenna and an electromagnetic band gap structure has a large influence on a ripple appearing as an aspect of deterioration in the directivity of the antenna, and arrived at the present disclosure.
That is, an object of the present disclosure is to provide a technology that can effectively suppress the ripple appearing in the directivity of an antenna.
According to the present disclosure, the ripple appearing in the directivity of an antenna can be effectively suppressed.
First, contents of the embodiments will be listed and described.
(1) A planar antenna as an embodiment includes: a dielectric substrate; a feed line provided on a first surface of the dielectric substrate and having a first lateral side extending along a first direction and a second lateral side opposed to the first lateral side; three or more radiation elements arrayed on the first surface along the first direction and provided at the first lateral side and the second lateral side so as to alternately protrude; and an electromagnetic band gap structure having an arrangement region on the first surface. The first surface includes a first adjacent region adjacent to the first lateral side and a second adjacent region adjacent to the second lateral side. The arrangement region includes a first arrangement region included in the first adjacent region, and a second arrangement region included in the second adjacent region. The three or more radiation elements include a plurality of first radiation elements protruding from the first lateral side toward the first adjacent region, and one or a plurality of second radiation elements protruding from the second lateral side toward the second adjacent region. At least a part of the first arrangement region is positioned closer to the feed line with respect to a first imaginary line below. At least a part of the second arrangement region is positioned closer to the feed line with respect to a second imaginary line below.
The first imaginary line: a straight line parallel to the first direction and passing through the first adjacent region, an interval between the straight line and an imaginary center line below being twice w1 below.
The second imaginary line: a straight line parallel to the first direction and passing through the second adjacent region, an interval between the straight line and the imaginary center line being twice w2 below.
The imaginary center line: a straight line parallel to the first direction and passing through a center, in a second direction orthogonal to the first direction, of the feed line.
The w1: an interval between the imaginary center line and a leading edge of the plurality of first radiation elements.
The w2: an interval between the imaginary center line and a leading edge of the one or the plurality of second radiation elements.
According to the above configuration, at least a part of the electromagnetic band gap structure can be provided closer to the feed line with respect to the first imaginary line and the second imaginary line. Therefore, the electromagnetic band gap structure and the plurality of radiation elements can be made moderately close to each other.
As a result, the ripple appearing in the directivity of the antenna can be effectively suppressed.
(2) In the planar antenna (1) above, preferably, at least a part of the first arrangement region is positioned closer to the feed line with respect to a third imaginary line below, and at least a part of the second arrangement region is positioned closer to the feed line with respect to a fourth imaginary line below.
The third imaginary line: a straight line parallel to the first direction and passing through a leading edge of the plurality of first radiation elements.
The fourth imaginary line: a straight line parallel to the first direction and passing through a leading edge of the one or the plurality of second radiation elements.
In this case, the electromagnetic band gap structure and the plurality of radiation elements can be made closer to each other.
As a result, the ripple appearing in the directivity of the antenna can be further effectively suppressed.
(3) In the planar antenna of (2) above, preferably, a part of the first arrangement region is positioned between the plurality of first radiation elements.
In this case, the electromagnetic band gap structure and the plurality of first radiation elements can be made closer to each other.
(4) In the planar antenna of (2) or (3) above, a maximum value of a width dimension along the second direction of the first arrangement region may be larger than a maximum value of a width dimension along the second direction of the plurality of first radiation elements, and a maximum value of a width dimension along the second direction of the second arrangement region may be larger than a maximum value of a width dimension along the second direction of the one or the plurality of second radiation elements.
In this case, the surface current occurring from the side of the lateral side of the feed line can be effectively suppressed from being propagated to the periphery.
(5) In the planar antenna of any one of (1) to (4) above, the arrangement region may further include a third arrangement region connecting the first arrangement region and the second arrangement region so as to surround the feed line.
In this case, the surface current occurring from the leading end side of the feed line can be suppressed from being propagated to the periphery.
(6) In the planar antenna of any one of (2) to (4) above, a part of the second arrangement region may be positioned between the plurality of second radiation elements.
In this case, the electromagnetic band gap structure and the plurality of second radiation elements can be made closer to each other.
(7) In the planar antenna of any one of (2) to (4) and (6) above, the third imaginary line may be a straight line parallel to the first direction and passing through a leading edge farthest from the imaginary center line out of leading edges of the plurality of first radiation elements.
In this case, the area of the region between the first lateral side and the third imaginary line can be ensured to be as large as possible. As a result, setting the first arrangement region 31 so as to be closer to the feed line with respect to the third imaginary line I3 can be facilitated.
(8) In the planar antenna of any one of (2) to (4), (6), and (7) above, the fourth imaginary line may be a straight line parallel to the first direction and passing through a leading edge farthest from the imaginary center line out of leading edges of the plurality of second radiation elements.
In this case, the area of the region between the second lateral side and the fourth imaginary line can be ensured to be as large as possible. As a result, setting the second arrangement region so as to be closer to the feed line with respect to the fourth imaginary line can be facilitated.
(9) In the planar antenna of any one of (1) to (8) above, the w1 may be an interval between the imaginary center line and a leading edge farthest from the imaginary center line out of leading edges of the plurality of first radiation elements.
In this case, the area of the region between the first lateral side and the first imaginary line can be ensured to be as large as possible. As a result, setting the first arrangement region so as to be closer to the feed line 12 with respect to the first imaginary line can be facilitated.
(10) In the planar antenna of any one of (1) to (9) above, the w2 may be an interval between the imaginary center line and a leading edge farthest from the imaginary center line out of leading edges of the plurality of second radiation elements.
In this case, the area of the region between the second lateral side and the second imaginary line can be ensured to be as large as possible. As a result, setting the second arrangement region so as to be closer to the feed line with respect to the second imaginary line can be facilitated.
(11) In the planar antenna of any one of (1) to (10) above, preferably, each radiation element has a rectangular shape.
In this case, the radiation element can be easily made close to the electromagnetic band gap structure.
Hereinafter, preferable embodiments will be described with reference to the drawings.
At least some parts of the embodiments described below may be combined as desired.
This planar antenna 1 is, for example, a planar antenna that is mounted to a traffic infrastructure or the like and that is used in transmission of a radio wave (radar wave) in a radar for detecting vehicles and pedestrians.
In the description below, in each drawing, three directions orthogonal to each other are defined as an X-direction (first direction), a Y-direction (second direction), and a Z-direction. In the X-direction, the direction in which an arrow X is oriented will be referred to as an X1-direction, the direction in which an arrow Y is oriented will be referred to as a Y1-direction, and the direction in which an arrow Z is oriented will be referred to as a Z1-direction. The opposite direction of the arrow X will be referred to as an X2-direction, the opposite direction of the arrow Y will be referred to as a Y2-direction, and the opposite direction of the arrow Z will be referred to as a Z2-direction.
The planar antenna 1 includes: a dielectric substrate 2 having a rectangular shape; a first ground plate 4 provided on a first surface 2a of the dielectric substrate 2; an array antenna 6 provided on the first surface 2a; and a second ground plate 8 provided on a second surface 2b of the dielectric substrate 2. The second surface 2b of the dielectric substrate 2 is the opposite surface of the first surface 2a. The second ground plate 8 is a plate-shaped member composed of a conductor such as copper. The second ground plate 8 is provided over approximately the entire region of the second surface 2b.
The planar antenna 1 is formed by using a rigid substrate or a flexible substrate. Examples of the material of the dielectric substrate 2 include polyimide, liquid crystal polymer, PPE resin, and fluorocarbon resin.
The first ground plate 4 is a plate-shaped member composed of a conductor such as copper. The first ground plate 4 includes a base part 4a having a rectangular shape and extending along the Y-direction, and a pair of L-shaped parts 4b extending from both ends in the longitudinal direction of the base part 4a into the X1-direction.
At the center in the Y-direction at one lateral side 4a1 of the base part 4a, the array antenna 6 is connected.
At the center in the Y-direction at the other lateral side 4a2 of the base part 4a, a feeding point 10 is provided. A signal wave radiated by the array antenna 6 is provided to the feeding point 10.
The first ground plate 4 is connected to the second ground plate 8 through a plurality of vias 4c. The plurality of vias 4c are each a columnar member composed of a conductor such as copper. The plurality of vias 4c penetrate the portion between the first surface 2a and the second surface 2b of the dielectric substrate 2. The plurality of vias 4c may be provided as through-holes.
The plurality of vias 4c include a plurality of outer peripheral vias 4c1 provided along the peripheral edge of the first ground plate 4, and a plurality of inner vias 4c2 provided in a center portion of the base part 4a.
The plurality of inner vias 4c2 are provided so as to cross the base part 4a along the X-direction, on both sides of a band-shaped region B where no vias are provided in a center portion in the Y-direction of the base part 4a.
Both sides in the Y-direction of the band-shaped region B are sectioned by the plurality of inner vias 4c2. The feeding point 10 is connected to the end, facing the X2-direction, of the band-shaped region B. The array antenna 6 is connected to the end, facing the X1-direction, of the band-shaped region B.
The plurality of vias 4c2 and the band-shaped region B form a so-called substrate integrated waveguide (SIW). Therefore, a signal wave provided to the feeding point 10 passes through the band-shaped region B, to be provided to the array antenna 6.
The array antenna 6 is composed of a conductor such as copper provided on the first surface 2a.
As shown in
A base end 12a, which is one end of the feed line 12, is connected to the base part 4a. A leading end 12b, which is the other end of the feed line 12, is positioned closer to the base part 4a than an edge 4b1 of each L-shaped part 4b.
The feed line 12 has a first lateral side 12c extending along the X-direction, and a second lateral side 12d opposed to the first lateral side 12c. The first lateral side 12c faces the Y1-direction. The second lateral side 12d faces the Y2-direction.
The plurality of radiation elements 14 each have a rectangular shape. The plurality of radiation elements 14 are provided at the first lateral side 12c and the second lateral side 12d of the feed line 12 so as to alternately protrude.
The plurality of radiation elements 14 are connected integrally with the feed line 12. Therefore, the signal wave provided to the array antenna 6 is provided to the plurality of radiation elements 14 through the feed line 12.
The plurality of radiation elements 14 radiate the provided signal wave, as a radio wave, into the air.
The array antenna 6 of the present embodiment includes three radiation elements 14. Out of the three radiation elements 14, radiation elements 14a, 14b protruding from the first lateral side 12c into the Y1-direction are also referred to as first radiation elements 14a, 14b, and a radiation element 14h protruding from the second lateral side 12d into the Y2-direction is also referred to as a second radiation element 14h. The first radiation element 14b is provided at the leading end 12b of the feed line 12.
When the set wavelength is defined as λ, the pitch in the X-direction of the plurality of radiation elements 14 is set to λ/2. The set wavelength λ is a wavelength set based on the wavelength when the signal wave transmitted by the array antenna 6 is propagated through the feed line.
The pitch is the interval between the centers in the X-direction of the radiation elements 14 adjacent to each other in the X-direction.
Therefore, the interval between the center in the X-direction of the first radiation element 14a and the center in the X-direction of the first radiation element 14b is λ.
An interval w1 between an imaginary center line C of the feed line 12 and a leading edge 14a1 of the first radiation element 14a facing the Y1-direction is set to λ/2. The imaginary center line C is a straight line parallel to the X-direction and passing through the center in the Y-direction of the feed line 12.
An interval w2 between the imaginary center line C and a leading edge 14h1 of the second radiation element 14h facing the Y2-direction is also set to λ/2.
The dimension in the X-direction and the dimension in the Y-direction of the first radiation element 14b are slightly smaller than the dimension in the X-direction and the dimension in the Y-direction of the first radiation element 14a in consideration of a reflected wave when the signal wave is reflected at the leading end 12b of the feed line 12.
Therefore, in the present embodiment, w1 is the interval between the imaginary center line C and the leading edge farthest from the imaginary center line C out of the leading edges of the plurality of first radiation elements 14a, 14b.
The planar antenna 1 of the present embodiment further includes an electromagnetic band gap structure 20.
As shown in
The EBG structure 20 includes a plurality of unit cells 22 and a plurality of vias 24.
The plurality of unit cells 22 are provided on the first surface 2a of the dielectric substrate 2. The plurality of unit cells 22 are each a plate-shaped member composed of a conductor such as copper. The outer shape of each unit cell 22 is a regular hexagon in an X-Y plane.
As shown in
The outer shape of the unit cell 22 is preferably a regular hexagon, but may be a square or may be another polygon. When the outer shape of the unit cell 22 is a regular hexagon, the unit cells 22 can be arrayed at a higher density than in the case of a square. Further, the outer shape of the unit cell 22 may include a curve portion or uneven shapes.
The plurality of vias 24 are each a columnar member composed of a conductor such as copper. Each of the plurality of vias 24 connects a unit cell 22 and the second ground plate 8. Thus, the via 24 penetrates the portion between the first surface 2a and the second surface 2b of the dielectric substrate 2. The via 24 may be provided as a through-hole.
The EBG structure 20 is a type of an EBG structure having a mushroom structure. The EBG structure 20 has a characteristic of shielding a radio wave in a certain frequency band. That is, the EBG structure has a frequency band (shielding band) in which a radio wave can be shielded.
The shielding band of the EBG structure 20 of the present embodiment is set so as to include the frequency of the radio wave radiated from the array antenna 6.
The arrangement region 30 of the EBG structure 20 of the present embodiment includes a first arrangement region 31, a second arrangement region 32, and a third arrangement region 33.
The first arrangement region 31 is a region, in the range in the X-direction from the base end 12a to the leading end 12b of the feed line 12, that is arranged so as to be adjacent, with an interval, to the first lateral side 12c of the feed line 12.
Here, the range in the X-direction from the base end 12a to the leading end 12b is a range, on the first surface 2a, sandwiched by a straight line (a straight line matching the one lateral side 4a1 of the first ground plate 4) passing through the base end 12a and a straight line L1 passing through the leading end 12b of the feed line 12.
The outer edge on the X1-direction side of the first arrangement region 31 extends along the straight line L1. Therefore, the first arrangement region 31 is included in a first adjacent region 41. The first adjacent region 41 is a region surrounded by the straight line L1, the first lateral side 12c of the feed line 12, the base part 4a, and the L-shaped part 4b connected to the end in the Y1-direction of the base part 4a. That is, the first adjacent region 41 is a region adjacent to the first lateral side 12c.
The second arrangement region 32 is a region, in the range in the X-direction from the base end 12a to the leading end 12b, that is arranged so as to be adjacent, with an interval, to the second lateral side 12d of the feed line 12. Similar to the first arrangement region 31, the outer edge on the X1-direction side of the second arrangement region 32 also extends along the straight line L1. Therefore, the second arrangement region 32 is included in a second adjacent region 42. The second adjacent region 42 is a region surrounded by the straight line L1, the second lateral side 12d of the feed line 12, the base part 4a, and the L-shaped part 4b connected to the end in the Y2-direction of the base part 4a. That is, the second adjacent region 42 is a region adjacent to the second lateral side 12d.
The first adjacent region 41 and the second adjacent region 42 are included in the first surface 2a.
The first adjacent region 41 is adjacent to the first lateral side 12c. Therefore, the first radiation elements 14a, 14b protrude from the first lateral side 12c toward the first adjacent region 41.
The second adjacent region 42 is adjacent to the second lateral side 12d. Therefore, the second radiation element 14h protrudes from the second lateral side 12d toward the second adjacent region 42.
The third arrangement region 33 is a region adjacent in the X1-direction to the first adjacent region 41 and the second adjacent region 42. The third arrangement region 33 and the first arrangement region 31 are connected to each other with the straight line L1 as a boundary. The third arrangement region 33 and the second arrangement region 32 are connected to each other with the straight line L1 as a boundary.
Therefore, the third arrangement region 33 connects the first arrangement region 31 and the second arrangement region 32. Accordingly, in the array antenna 6, the region in the X1-direction of the array antenna 6, the region in the Y1-direction of the array antenna 6, and the region in the Y2-direction of the array antenna 6 are surrounded by the EBG structure 20.
The outer edge other than the portion of the straight line L1 of each arrangement region 31, 32, 33 is determined by the outer edges of unit cells 22 positioned at the outer edge of the arrangement region 31, 32, 33, out of the plurality of unit cells 22 forming the arrangement region 31, 32, 33.
In
A second imaginary line 12 is a straight line parallel to the X-direction and positioned between the second lateral side 12d of the feed line 12 and the L-shaped part 4b connected to the end in the Y2-direction of the base part 4a. In other words, the second imaginary line I2 is a straight line passing through the second adjacent region 42.
A third imaginary line I3 is a straight line parallel to the X-direction and passing through the leading edge 14a1 of the first radiation element 14a.
Therefore, in the present embodiment, the third imaginary line I3 is a straight line passing through the leading edge 14a1 farthest from the imaginary center line C out of the leading edges of the plurality of first radiation elements 14a, 14b.
A fourth imaginary line I4 is a straight line parallel to the X-direction and passing through the leading edge 14h1 of the second radiation element 14h.
The interval between the third imaginary line I3 and the imaginary center line C is w1 as described above. The interval between the fourth imaginary line I4 and the imaginary center line C is w2 as described above.
The interval between the first imaginary line I1 and the imaginary center line C is set to twice w1. Therefore, the interval between the first imaginary line I1 and the third imaginary line I3 is w1.
The interval between the second imaginary line I2 and the imaginary center line C is set to twice w2. Therefore, the interval between the second imaginary line I2 and the fourth imaginary line I4 is w2.
In the present embodiment, the first imaginary line I1 and the third imaginary line I3 cross the first arrangement region 31. Accordingly, a part of the first arrangement region 31 is positioned closer to the feed line 12 with respect to the third imaginary line I3.
As shown in
Accordingly, the part of the first arrangement region 31 positioned between the first radiation elements 14a, 14b can be made closer to the first radiation elements 14a, 14b than the other part of the first arrangement region 31.
Similarly, the second arrangement region 32 is positioned over the second imaginary line I2 and the fourth imaginary line I4. Accordingly, a part of the second arrangement region 32 is positioned closer to the feed line 12 with respect to the fourth imaginary line I4.
Therefore, as shown in
Thus, in the present embodiment, the EBG structure 20 can be provided closer to the feed line 12 with respect to the first imaginary line I1 and the second imaginary line I2, and thus, the EBG structure 20 and the radiation elements 14a, 14b, 14h can be made close to each other.
As a result, the ripple appearing in the directivity of the array antenna 6 can be suppressed.
Further, in the present embodiment, a part of the first arrangement region 31 is positioned closer to the feed line 12 with respect to the third imaginary line I3, and a part of the second arrangement region 32 is positioned closer to the feed line 12 with respect to the fourth imaginary line I4. Therefore, the EBG structure 20 and the radiation elements 14a, 14b, 14h can be made closer to each other.
As a result, the ripple appearing in the directivity of the array antenna 6 can be more effectively suppressed.
In the present embodiment, the third arrangement region 33 connected to the first arrangement region 31 and the second arrangement region 32 on the leading end 12b side of the feed line 12 is provided. Therefore, the surface current occurring from the leading end 12b side of the feed line 12 can be suppressed from being propagated to the periphery.
In the present embodiment, the maximum value of the width dimension along the Y-direction of the first arrangement region 31 is larger than the maximum value of the width dimension along the Y-direction of the first radiation element 14a, 14b and the maximum value of the width dimension along the Y-direction of the second arrangement region 32 is larger than the maximum value of the width dimension along the Y-direction of the second radiation element 14h.
Accordingly, the surface current occurring from the first lateral side 12c side and the second lateral side 12d side of the feed line 12 can be effectively suppressed from being propagated to the periphery.
In the present embodiment, w1 is the interval between the imaginary center line C and the leading edge 14a1 farthest from the imaginary center line C out of the leading edges of the plurality of first radiation elements 14a, 14b.
Further, in the present embodiment, the third imaginary line I3 is the straight line passing through the leading edge 14a1 farthest from the imaginary center line C out of the leading edges of the plurality of first radiation elements 14a, 14b.
Accordingly, the first imaginary line I1 and the third imaginary line I3 can be separated from the imaginary center line C as much as possible, and the area of the region between: the first lateral side 12c; and the first imaginary line I1 and the third imaginary line I3 can be ensured to be large. As a result, setting the first arrangement region 31 so as to be closer to the feed line 12 with respect to the first imaginary line I1 and the third imaginary line I3 can be facilitated.
Here, a cause for the ripple appearing in the directivity of the array antenna 6 will be described.
As shown in
The desired wave and the radiant wave are radiated to the periphery around their wave sources, but in
In
λa is the wavelength in air of the desired wave.
When an interval D between the radiation element 14 as the desired wave source and the unit cell 22 as the radiant wave source shown in
The directivity of the antenna is represented by change in the gain corresponding to the angle Φ. Therefore, when the period of the angle Φ satisfying the above (1) increases, the period of the gain variation appearing in the directivity of the antenna increases, whereby the ripple is suppressed.
That is, when the interval D between the radiation element 14 and the unit cell 22 is made smaller, the ripple appearing in the directivity of the antenna can be effectively suppressed accordingly.
Therefore, as in the present embodiment, when the EBG structure 20 and the radiation elements 14a, 14b, 14h are made closer to each other, the ripple appearing in the directivity of the array antenna 6 can be effectively suppressed.
In the present modification, the arrangement region 30 is set such that the unit cells 22 adjacent to the radiation element 14 remain and the unit cells 22 away from the radiation element 14 are removed.
Therefore, the first arrangement region 31, the second arrangement region 32, and the third arrangement region 33 of the present modification are smaller than those in the first embodiment.
The outer edge in the Y2-direction of the first arrangement region 31 and the outer edge in the Y1-direction of the second arrangement region 32 are the same as those in the first embodiment. A part of the first arrangement region 31 is positioned closer to the feed line 12 with respect to the third imaginary line 13, and a part of the second arrangement region 32 is positioned closer to the feed line 12 with respect to the fourth imaginary line I4.
Therefore, the EBG structure 20 and the radiation elements 14a, 14b, 14h are very close to each other.
Thus, in the present modification as well, as in the first embodiment, the ripple appearing in the directivity of the array antenna 6 can be effectively suppressed.
In the present modification, the first arrangement region 31 is positioned over the first imaginary line I1, but is not positioned over the third imaginary line I3.
Similarly, the second arrangement region 32 is positioned over the second imaginary line I2, but is not positioned over the fourth imaginary line I4.
In the present modification, a part of the first arrangement region 31 is positioned closer to the feed line 12 with respect to the first imaginary line I1.
A part of the second arrangement region 32 is positioned closer to the feed line 12 with respect to the second imaginary line I2.
Accordingly, the EBG structure 20 and the radiation elements 14a, 14b, 14h can be made moderately close to each other.
As a result, in the present modification as well, the ripple appearing in the directivity of the array antenna 6 can be suppressed.
The EBG structure 20 and the radiation elements 14a, 14b, 14h can be made closer to each other in the first embodiment and the first modification than in the present modification. Therefore, the ripple appearing in the directivity of the array antenna 6 can be more effectively suppressed in the first embodiment and the first modification.
The second embodiment is different from the first embodiment in that the array antenna 6 includes five radiation elements 14.
The width in the X-direction of each radiation element 14 of the present embodiment is smaller than the width of each radiation element 14 in the first embodiment.
The five radiation elements 14 are provided at the first lateral side 12c and the second lateral side 12d so as to alternately protrude, as in the first embodiment.
The five radiation elements 14 include first radiation elements 14a, 14b, 14c protruding from the first lateral side 12c into the Y1-direction, and second radiation elements 14h, 14i protruding from the second lateral side 12d into the Y2-direction.
Out of the first radiation elements 14a, 14b, 14c, the first radiation element 14b is longer in the Y-direction than the other first radiation elements.
The second radiation element 14i is longer in the Y-direction than the second radiation element 14h.
The interval w1 between the imaginary center line C of the feed line 12 and a leading edge 14b1 of the first radiation element 14b facing the Y1-direction is set to λ/2.
The interval w2 between the imaginary center line C and a leading edge 14i1 of the second radiation element 14i facing the Y2-direction is also set to λ/2.
The third imaginary line 13 of the present embodiment is a straight line parallel to the X-direction and passing through the leading edge 14b1 of the first radiation element 14b.
The fourth imaginary line I4 of the present embodiment is a straight line parallel to the X-direction and passing through the leading edge 1411 of the second radiation element 14i.
Thus, the third imaginary line I3 and the fourth imaginary line I4 are each set based on a radiation element 14 having the longest length in the Y-direction out of the radiation elements 14.
That is, the third imaginary line I3 is a straight line passing through the leading edge 14b1 farthest from the imaginary center line C out of the leading edges of the plurality of first radiation elements 14a, 14b, 14c.
The fourth imaginary line I4 is a straight line passing through the leading edge 14i1 farthest from the imaginary center line C out of the leading edges of the plurality of second radiation elements 14h, 14i.
The first arrangement region 31 of the present embodiment is positioned over the third imaginary line I3. Accordingly, a part of the first arrangement region 31 is positioned closer to the feed line 12 with respect to the third imaginary line 13.
As shown in
Accordingly, the part of the first arrangement region 31 positioned between the first radiation elements 14a, 14b and the part of the first arrangement region 31 positioned between the first radiation elements 14b, 14c can be made closer to the first radiation elements 14a, 14b than the other part of the first arrangement region 31.
Similarly, the second arrangement region 32 is positioned over the fourth imaginary line I4. Accordingly, a part of the second arrangement region 32 is positioned closer to the feed line 12 with respect to the fourth imaginary line I4.
As shown in
Accordingly, the part of the second arrangement region 32 positioned between the second radiation elements 14h, 14i can be made closer to the second radiation elements 14h, 14i than the other part of the second arrangement region 32.
Thus, in the present embodiment as well, a part of the first arrangement region 31 is positioned closer to the feed line 12 with respect to the third imaginary line 13, and a part of the second arrangement region 32 is positioned closer to the feed line 12 with respect to the fourth imaginary line I4. Therefore, the EBG structure 20 and the radiation elements 14 can be made closer to each other.
As a result, the ripple appearing in the directivity of the array antenna 6 can be effectively suppressed.
In the present embodiment, in all of the spaces between the plurality of first radiation elements 14a, 14b, 14c, a part of the first arrangement region 31 is provided, and a part of the second arrangement region 32 is provided between the plurality of second radiation elements 14h, 14i. Therefore, the arrangement region 30 can be provided along the contour of the array antenna 6, and thus, the ripple can be more appropriately suppressed.
As described above, the fourth imaginary line I4 is a straight line passing through the leading edge 1411 farthest from the imaginary center line C out of the leading edges of the plurality of second radiation elements 14h, 14i.
Accordingly, the fourth imaginary line I4 and the imaginary center line C can be separated from each other as much as possible, and the area of the region between the second lateral side 12d and the fourth imaginary line I4 can be ensured to be large. As a result, setting the second arrangement region 32 so as to be closer to the feed line 12 with respect to the fourth imaginary line I4 can be facilitated.
In the present modification, the first arrangement region 31 is positioned over the first imaginary line I1, but is not positioned over the third imaginary line I3.
Similarly, the second arrangement region 32 is positioned over the second imaginary line I2, but is not positioned over the fourth imaginary line I4.
In the present modification, a part of the first arrangement region 31 is positioned closer to the feed line 12 with respect to the first imaginary line I1.
A part of the second arrangement region 32 is positioned closer to the feed line 12 with respect to the second imaginary line I2.
Accordingly, the EBG structure 20 and the radiation elements 14a, 14b, 14h can be made moderately close to each other.
As a result, in the present modification as well, the ripple appearing in the directivity of the array antenna 6 can be suppressed.
In the present modification, w2 is the interval between the imaginary center line C and the leading edge 1411 farthest from the imaginary center line C out of the leading edges of the plurality of second radiation elements 14h, 14i.
Accordingly, the second imaginary line I2 and the imaginary center line C can be separated from each other as much as possible, and the area of the region between the second lateral side 12d and the second imaginary line I2 can be ensured to be large. As a result, setting the second arrangement region 32 so as to be closer to the feed line I2 with respect to the second imaginary line I2 can be facilitated.
In each embodiment above, an example case where the arrangement region 30 includes the third arrangement region 33 has been shown. However, the arrangement region 30 may be configured not to include the third arrangement region 33. In this case as well, the ripple appearing in the directivity of the array antenna 6 can be suppressed by the first arrangement region 31 and the second arrangement region 32.
In each embodiment above, an example case where w1 (w2) is the interval between the imaginary center line C and the leading edge farthest from the imaginary center line C out of the leading edges of the plurality of first radiation elements (second radiation elements) has been shown. However, w1 (w2) may the interval between the imaginary center line C and a leading edge other than the leading edge farthest from the imaginary center line C out of the leading edges of the plurality of first radiation elements (second radiation elements).
In each embodiment above, an example case where the third imaginary line I3 (the fourth imaginary line I4) is a straight line passing through the leading edge farthest from the imaginary center line C out of the leading edges of the plurality of first radiation elements (second radiation elements) has been shown. However, the third imaginary line I3 (the fourth imaginary line I4) may be a straight line passing through a leading edge other than the leading edge farthest from the imaginary center line C out of the leading edges of the plurality of first radiation elements (second radiation elements).
In each embodiment above, an example of a planar antenna used in transmission of a radio wave has been shown. However, the planar antenna of the present embodiment can also be used as a planar antenna for reception.
In the present embodiment, only the array antenna 6 of one system has been shown and described. However, a plurality of the array antennas 6 surrounded by the EBG structure 20 may be arranged on the same dielectric substrate, to be used as array antennas of a plurality of systems.
In the above second embodiment and modifications thereof, an example case where the array antenna 6 includes five radiation elements 14 has been shown. However, the array antenna 6 may include seven or more radiation elements 14.
The planar antenna shown in the present embodiment can be used not only as an antenna for radar but also as a transmission and reception antenna for wireless communication.
Next, a verification test performed with respect to the effects of the arrangement of the EBG structure 20 will be described.
As the test method, a model of a planar antenna was constructed and using the model, the directivity pattern on a Y-Z plane (
Through comparison of the obtained directivity patterns, verification of the effects of the arrangement of the EBG structure 20 was performed.
For the verification test, models were constructed for three Examples and one Comparative Example below.
In
With reference to
In contrast, with reference to
With reference to
From these results, it is seen that when the EBG structure 20 is appropriately arranged, the ripple occurring in the directivity pattern of the array antenna 6 can be effectively suppressed.
It should be noted that the embodiments disclosed herein are merely illustrative and not restrictive in all aspects.
The scope of the present disclosure is defined by the scope of the claims rather than the above description, and is intended to include meaning equivalent to the scope of the claims and all modifications within the scope.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-004158 | Jan 2022 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/035468 | 9/22/2022 | WO |
