Patent Application
20210021051
The disclosures herein relate to a slot array antenna.
In recent years, services using high-speed and high-capacity wireless communication systems using microwave and millimeter-wave frequency bands have been expanding, such as the transition from 4G LTE to 5G (sub6). As an antenna used in such a frequency band, there is known a slot array antenna that feeds power to a plurality of slots by using a coplanar waveguide (for example, refer to Non-Patent Literature 1).
However, since slot array antennas, such as disclosed in Non-Patent Literature 1, feed power to a plurality of slots arranged in one direction with a common coplanar waveguide, the direction of directivity is limited to the direction of the arranged slots.
In this regard, it may be preferable to provide a slot array antenna with an improved design degree of freedom in the direction of directivity.
Non-Patent Literature 1: J. McKnight et al., A Series-Fed Coplanar Waveguide Slot Antenna Array, 2010 IEEE 11th Annual Wireless and Microwave Technology Conference
According to an embodiment, a slot array antenna includes a dielectric layer, a power feeding unit, a first coplanar waveguide formed in a conductor layer provided on one surface of the dielectric layer, and a second coplanar waveguide formed in the conductor layer, wherein each of the first coplanar waveguide and the second coplanar waveguide includes a first end part connected to a point to which the power feeding unit is connected or situated in proximity and at least one second end part connected to at least one slot formed in the conductor layer.
According at least one embodiment, the design degree of freedom of direction of directivity is improved.
Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings. Furthermore, in each of the embodiments, deviation in a direction such as parallel, right-angle, orthogonal, horizontal, vertical, top and bottom, left and right, or the like is allowed to the extent that the effect of the present invention is not impaired. Furthermore, the X-axis direction, the Y-axis direction, and the Z-axis direction respectively represent a direction parallel to the X-axis, a direction parallel to the Y-axis, and a direction parallel to the Z-axis. The X-axis direction, the Y-axis direction, and the Z-axis direction are orthogonal to each other. The XY plane, the YZ plane, and the ZX plane respectively represent a virtual plane parallel to the X-axis direction and the Y-axis direction, a virtual plane parallel to the Y-axis direction and the Z-axis direction, and a virtual plane parallel to the Z-axis direction and the X-axis direction.
A slot array antenna according to an embodiment of the present disclosure is a coplanar feeding type planar array antenna that feeds power to a plurality of slots by using a plurality of coplanar waveguides, and is suitable for transmitting/receiving electromagnetic waves in a high frequency band such as microwaves or millimeter waves (for example, 0.3 GHz to 300 GHz). For example, a slot array antenna according to an embodiment of the present disclosure is applicable to, but is not limited to, a fifth-generation mobile communication system (so-called 5G), an on-vehicle radar system, and the like.
A slot array antenna 101 shown in
A dielectric layer 40 is a plate-shaped or sheet-shaped base material including a dielectric material as the main component. A dielectric layer 40 includes a first surface 41 and a second surface 42 opposite to the first surface 41. A first surface 41 is parallel to the XY plane. A second surface 42 may be parallel to the XY plane or non-parallel. In other words, in the cross-sectional schematic diagram (YZ plane) of
A conductor layer 43 is a planar layer whose surface is parallel to the XY plane. For example, the conductor layer 43 may be a conductor sheet, a conductor substrate, and the conductor layer 43 may have a non-uniform thickness and a distribution. Examples of the material of the conductor used for the conductor layer 43 may include, but are not limited to, silver and copper. Furthermore, the conductor layer 43 may be arranged in a mesh pattern so that a part of the dielectric layer can be seen. This allows, for example, the slot array antenna 101 including the mesh pattern to be made transparent or translucent when glass or resin having high transparency to visible light is used as the dielectric layer 40. The term “transparent” means, for example, a state in which a transmittance of 90% or more is obtained in visible light. Furthermore, various shapes can be applied to the mesh as long as the coplanar waveguides can be electrically connected, and the shapes are not particularly limited. The mesh part of the conductor layer 43 may be a part or all of the layer.
A coplanar waveguide 30 is an example of a power feeding unit and is a plane transmission line formed in a conductor layer 43. A coplanar waveguide 30 includes a pair of slots 34, 35 running parallel in the Y-axis direction, and a center conductor 31 extending in the Y-axis direction sandwiched between the pair of slots 34, 35. A conductor area outside the pair of slots 34, 35 in the conductor layer 43 functions as a ground conductor 45. A coplanar waveguide 30 includes one end part 32 connected to a point to be a junction (branching point 36) for coplanar waveguides 10, 20, and the other end part 33 connected to an external device not shown in the figure such as an amplifier. The other end part 33 serving as a feeding end is positioned at the edge of the dielectric layer 40 and the conductor layer 43.
A coplanar waveguide 10 is an example of a first coplanar waveguide and is a plane transmission line formed in a T-shape in the plan view of the conductor layer 43. A coplanar waveguide 10 includes a first waveguide extending in the X-axis direction and a second waveguide extending in the Y-axis direction. A coplanar waveguide 10 includes a pair of slots 16, 17 running parallel in the X-axis direction, a pair of slots 18, 19 running parallel in the Y-axis direction, and a center conductor 11 extending in a T-shape sandwiched between the slots 16-19.
In the slot array antenna 101 shown in
A conductor area outside the slots 16-19 in the conductor layer 43 functions as a ground conductor 45. A coplanar waveguide 10 includes an end part 12 connected to the branching point 36, an end part 13 connected to the slot 51, and an end part 14 connected to the slot 52. The end part 12 is an example of a first end part, and the end parts 13, 14 are an example of a second end part. A coplanar waveguide 10 includes a point to be a junction for slots 51, 52 (branching point 15) between the end part 12 and the end parts 13, 14.
A coplanar waveguide 20 is an example of a second coplanar waveguide and is a plane transmission line formed in a T-shape in the plan view of the conductor layer 43. A coplanar waveguide 20 includes a third waveguide extending in the X-axis direction and a fourth waveguide extending in the Y-axis direction. A coplanar waveguide 20 includes a pair of slots 26, 27 running parallel in the X-axis direction, a pair of slots 28, 29 running parallel in the Y-axis direction, and a center conductor 21 extending in a T-shape sandwiched between the slots 26-29.
A conductor area outside the slots 26-29 in the conductor layer 43 functions as a ground conductor 45. A coplanar waveguide 20 includes an end part 22 connected to the branching point 36, an end part 23 connected to the slot 53, and an end part 24 connected to the slot 54. The end part 22 is an example of a first end part, and the end parts 23, 24 are an example of a second end part. A coplanar waveguide 20 includes a point to be a junction for slots 53, 54 (branching point 25) between the end part 22 and the end parts 23, 24.
Each of the slots 51-54 is a slot-shaped antenna element formed in the conductor layer 43. Each of the slots 51-54 functions as a half-wavelength dipole antenna, and for example, when the wavelength at the operating frequency of the slots 51-54 is λg, length d of each slot 51-54 in the longitudinal direction is set to about λg/2. This allows the antenna gain of the slot array antenna 101 to be improved.
In this manner, the coplanar waveguides 10, 20 include end parts commonly connected to the branching point 36 connected to the coplanar waveguide 30 which is the third coplanar waveguide. In other words, the coplanar waveguides 10, 20 are respectively branched from the branching point 36 connected to the coplanar waveguide 30 which is a power feeding unit. Accordingly, since the direction that the coplanar waveguides 10, 20 extend can be designed separately, the design degree of freedom of the respective directions of the slots 51-54 connected to the respective end parts of the coplanar waveguides 10, 20 can be increased. Accordingly, the slot array antenna 101 can be provided with an improved degree of freedom for designing the direction of directivity.
Furthermore, it is preferable to adjust the position of the coplanar waveguide 30 which is the power feeding unit so that all phases of the high frequency currents flowing in each slot 51-54 are aligned (so that the slots 51-54 are fed in the same phase). In the case of
In
It is preferable that a part or all of the slots 51-54 are parallel to each other in terms of improving the antenna gain of the slot array antenna 101. In the case of
It is preferable that a part or all of the slots 51-54 are symmetrically positioned with respect to a symmetry axis in terms of improving the antenna gain of the slot array antenna 101. In the case of
It is preferable that each of the end parts of coplanar waveguides 10, 20 is connected at right angles to (longitudinal direction of) at least one slot connected to its end part in terms of improving the antenna gain of the slot array antenna 101. In the case of
If the slots 51-54 are positioned in each of four areas from dividing by two virtual straight lines orthogonal to each other at the branching point 36, it is possible to increase the direction of directivity at which the antenna gain becomes maximum. For example, in
As shown in
As previously described, a parasitic element (parasitic conductor) such as the conductor layer 44 may be provided on a part of the second surface 42 of the dielectric layer 40. In this case, the parasitic conductor may be provided in a predetermined area so that the antenna gain with the desired directivity can be obtained, for example, by aligning with the position of at least one slot out of a plurality of slots 51-54, preferably all the slots, when viewed from the normal direction (the Z-axis direction) of the first surface 41. For example, when the parasitic conductor is provided on a part of the second surface 42 of the dielectric layer 40, it is preferable to overlap with at least one of the slots 51-54 when viewed from the normal direction (the Z-axis direction) of the first surface 41. With this arrangement, the directivity to the negative side in the Z-axis direction with respect to the dielectric layer 40 is enhanced, and the parasitic conductor can function as a waveguide. Furthermore, when the parasitic conductor is provided on a part of the second surface 42 of the dielectric layer 40, the planar shape of the parasitic conductor may not be limited to the shape of a square, rectangle, polygon, circle, ellipse or the like, but may also be a shape forming an area having any outer edge. In this case, the free space wavelength of the electromagnetic wave to be transmitted and received is set to λ0, the wavelength shortening rate of the dielectric layer 40 at the wavelength λ0 is set to k, and the wavelength λd=k×λ0. For example, when the planar shape of the parasitic conductor is a polygon including a square, the diagonal line of the polygon is set to λd/2 or less, when the planar shape is a circle, the diameter of the circle is set to λd/2 or less, and when the planar shape is an ellipse, the major axis of the ellipse is set to λd/2 or less.
Furthermore, a parasitic element (parasitic conductor) such as the conductor layer 44 may be disposed on the second surface 42 side of the dielectric layer 40 apart from the second surface 42 (in the −Z-axis direction), and may be disposed on the first surface 41 side of the dielectric layer 40 apart from the conductor layer 43 (in the +Z-axis direction). Furthermore, when a parasitic conductor such as the conductor layer 44 is disposed on the second surface 42 side of the dielectric layer 40 apart from the second surface 42, the parasitic conductor, as previously described, may be disposed to overlap with at least one slot, preferably all slots. When disposing a conductor layer 44 functioning as a reflector (reflecting conductor) on the second surface 42 side of the dielectric layer 40 apart from the second surface 42, the directivity to the positive side in the Z-axis direction on the basis of the dielectric layer 40 is increased. By disposing the conductor layer 44 on the second surface 42 side of the dielectric layer 40 apart from the second surface 42, the conductor layer 44 can function as a reflecting conductor. Furthermore, with regard to the dielectric layer 40, when the first surface 41, the second surface 42 and the conductor layer 44 are disposed in parallel, it is preferable that the conductor layer 44 is disposed apart from the second surface 42 at a distance greater than 0 and not more than λ0/4. Furthermore, in order to separate the dielectric layer 40 from the conductor layer 44 to a predetermined distance, for example, a spacer may be provided at the end part of the slot array antenna 101, or the slot array antenna 101 may be fixed by a bracket or the like to hold the distance.
In
In
D1,D2=λ/4=2.7 mm (FIG. 18)
D1,D2=2λ/4=5.4 mm (FIG. 19)
D1,D2=3λ/4=8.1 mm (FIG. 20)
D1,D2=4λ/4=10.8 mm (FIG. 21).
In
In
Furthermore, it is preferable to adjust the position of the coplanar waveguide 30 so that all phases of the high frequency currents flowing in the slots 51-54 are aligned (so that the slots 51-54 are fed in the same phase). In the case of
Furthermore, not all of the slots 51-54 may extend in the same direction, and a part of the slots and the remaining slots may extend in different directions. For example, a part of the slots may extend in the X-axis direction and the remaining slots may extend in the Y-axis direction to correspond to both vertical polarization and horizontal polarization. However, it is preferable that all the slots 51-54 extend in the same direction because the transmitting and receiving sensitivity of a predetermined polarized wave can be enhanced.
Furthermore, the coplanar waveguide 30 may be linear, but also may include a bent part for sufficiently securing a distance from the slot in order to suppress deterioration of the characteristics such as directivity due to a coupling caused by proximity to the slot functioning as the antenna element. In the case of
In
The LC filter 60 is, for example, a bandpass filter that passes a high frequency signal of a predetermined frequency band passing through the power feeding unit or the coplanar waveguide and blocks a high frequency signal of a frequency band other than the predetermined frequency band.
The LC filter 60 is a circuit including at least one inductance unit (L) and at least one capacitance unit (C) and, in the case of shown in the figure, is formed with a planar pattern. By forming the LC filter with a planar pattern, it is possible to prevent the external dimensions of the slot array antenna in the Z-axis direction from increasing due to the addition of the LC filter.
In the case of
Furthermore, the LC filter may not be limited to the case where its shape is formed with a planar pattern, for example, a filter circuit may be formed with a plurality of discrete elements. However, the LC filter is preferably formed with a planar pattern, because loss due to a connecting point with discrete elements and the like can be reduced.
In other words, the number of slots connected to each end part of the first coplanar waveguide and the second coplanar waveguide may be at least one or more, and may be odd or even.
The slot array antenna 104 shown in
A coplanar waveguide 110 is an example of a first coplanar waveguide and is a plane transmission line formed in an L-shape in the conductor layer 43. A coplanar waveguide 110 includes a first waveguide extending in the X-axis direction and a second waveguide extending in the Y-axis direction. A coplanar waveguide 110 includes a pair of slots bent in an L-shape and a center conductor 111 extending in an L-shape sandwiched between the pair of slots. A coplanar waveguide 110 includes an end part 112 connected to the branching point 36 and an end part 113 connected to the slot 151. The end part 112 is an example of a first end part, and the end part 113 is an example of a second end part. There is no branching point between the end part 112 and the end part 113 of the coplanar waveguide 110.
A coplanar waveguide 120 is an example of a second coplanar waveguide and is a plane transmission line formed in an L-shape in the conductor layer 43. A coplanar waveguide 120 includes a first waveguide extending in the X-axis direction and a second waveguide extending in the Y-axis direction. A coplanar waveguide 120 includes a pair of slots bent in an L-shape and a center conductor 121 extending in an L-shape sandwiched between the pair of slots. A coplanar waveguide 120 includes an end part 122 connected to the branching point 36 and an end part 123 connected to the slot 153. The end part 122 is an example of a first end part, and the end part 123 is an example of a second end part. There is no branching point between the end part 122 and the end part 123 of the coplanar waveguide 120.
The slot array antenna 105 shown in
A coplanar waveguide 70 is an example of a first coplanar waveguide and is a plane transmission line formed so as to include an H-shape in the conductor layer 43. A coplanar waveguide 70 includes a pair of slots formed so as to include an H-shape and a center conductor 71 extending between the pair of slots. A coplanar waveguide 70 includes an end part 79 connected to the branching point 36, an end part 72 connected to the slot 91, an end part 73 connected to the slot 92, an end part 74 connected to the slot 93, and an end part 75 connected to the slot 94. The end part 79 is an example of a first end part, and the end parts 72-75 are examples of a second end part. A coplanar waveguide 70 includes three points to be junctions (branching point 76, 77, 78) for the slots 91-94 between the end part 79 and the end parts 72-75.
A coplanar waveguide 80 is an example of a second coplanar waveguide and is a plane transmission line formed so as to include an H-shape in the conductor layer 43. A coplanar waveguide 80 includes a pair of slots formed so as to include an H-shape and a center conductor 81 extending between the pair of slots. A coplanar waveguide 80 includes an end part 89 connected to the branching point 36, an end part 82 connected to the slot 95, an end part 83 connected to the slot 96, an end part 84 connected to the slot 97, and an end part 85 connected to the slot 98. The end part 89 is an example of a first end part, and the end parts 82-85 are examples of a second end part. A coplanar waveguide 80 includes three points to be junctions (branching point 86, 87, 88) for the slots 95-98 between the end part 89 and the end parts 82-85.
Furthermore, the coplanar waveguide 30 may be linear, but also may be bent for sufficiently securing a distance from the slot in order to suppress deterioration of the characteristics such as directivity due to a coupling caused by proximity to the slot functioning as the antenna element. In the case of
Furthermore, although the slot array antenna of the first to sixth embodiments all include the branching points 36, 136 branching into two coplanar waveguides, there is no limitation to this configuration. For example, based on the slot array antenna 101 of the first embodiment, the coplanar waveguide 30 may not only be divided into two coplanar waveguides from the branching point 36 but also include an extended coplanar waveguide 37 which passes through the branching point 36 and goes straight as shown in
As previously described, the line shape of the branching points 36, 136 is T-shaped. However, in order to satisfy the specifications of antenna transmitting/receiving sensitivity and directivity, the branching point of the slot array antenna may not only be T-shaped but also include one or more cross-shaped lines in accordance with the number of (linear) slots. In this case, the slot array antenna typically includes N cross-shaped branching points, and one T-shaped branching point. If coplanar waveguides branching from each branching point include M (linear) slots respectively, the slot array antenna includes (N+1)×M (linear) slots.
The slot array antenna has been described with reference to the embodiments, but the present invention is not limited to the above embodiments. Various modifications and improvements, such as combination with part or all of the other embodiments and substitution, are possible within the scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-077333 | Apr 2018 | JP | national |
| 2018-229768 | Dec 2018 | JP | national |
This application is a continuation of International Application PCT/JP2019/015478, filed on Apr. 9, 2019 and designated the U.S., which is based on and claims priority to Japanese patent application No. 2018-077333 filed on Apr. 13, 2018, and Japanese patent application No. 2018-229768 filed on Dec. 7, 2018. The entire contents of these applications are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2019/015478 | Apr 2019 | US |
| Child | 17064313 | US |
