Transmission-type metasurface loading antenna and transmission-type metasurface plate

Abstract

[Problem] To provide a transmission-type metasurface plate and a variable directivity antenna that make it possible to reduce loss in a transmission line and reduce costs by standardizing components compared to the prior art. [Solution] This transmission-type metasurface loading antenna comprises a transmission-type metasurface plate and an antenna section arranged parallel to the transmission-type metasurface plate. The transmission-type metasurface plate has a plurality of transmission elements, and near-plane waves incident from one surface are converted in one plane by the transmission-type metasurface plate into directional electromagnetic waves having directivity in a predetermined direction. The transmission elements transmit the incident near-plane waves with a predetermined phase difference. The transmission-type metasurface plate has transmission elements with different predetermined phase differences. The antenna section is a plane wave antenna that emits near-plane waves.

Description

Transparent metasurface-loaded antenna and transparent metasurface plate

[0001] The present invention relates to a transmission type metasurface-loaded antenna and a transmission type metasurface plate, and more particularly to a variable directivity antenna and a spatial phase shifter that use a transmission type metasurface plate and a plane wave excitation element.

[0002] The directivity of an array antenna is shaped by arraying it using a divider circuit and generating phase and amplitude differences. Conventional sector antennas use a reflector on the backside to obtain sector directivity, and a divider circuit and amplitude ratio control are used to narrow the vertical directivity and increase gain, resulting in vertical directivity with suppressed side lobes. Prior art 1 directly converts the excitation wave from a spherical wave source or horn into a plane wave with a phase gradient.

[0003] Naser Ojaroudi Parchin, et. al., “Recent Developments of Reconfigurable Antennas for Current and Future Wireless Communication Systems” MDPI, Electronics 8(2), 128, January 2019

[0004] The structure is large due to the transmission loss of the divider circuit, the complexity of the design, and the need for a reflector to achieve sector directivity. A phase difference circuit is required to generate tilt, but phase shifters in the millimeter-wave band consume power. Direct control from spherical waves is difficult because the phase difference within the same plane is too large. To achieve high gain, the divider circuits must be stacked, requiring antenna design that takes into account the circuit routing method and transmission loss due to circuit length. The larger the array size, the greater the loss, resulting in a decrease in radiation efficiency. For example, in conventional configurations where phase difference feed and excitation amplitude are controlled by a divider to generate directivity, the directivity must be adjusted by adjusting the circuit length when generating phase difference and amplitude ratio in the transmission line. This causes losses, resulting in a transmission line loss of approximately 4 dB. Furthermore, the stacked structure and feed circuit are complex. In directivity shaping using a transmit array, taking into account the spherical wave nature of the wave source, the phase of the wave source and the transmission phase of the transmit array are shaped as the directivity. Because the wave source is a spherical wave, it is necessary to design it taking into account the positional relationship with the excitation source and the path length difference, and in the millimeter wave band, sensitive phase design is required, which requires design flexibility. In Prior Art 1, the excitation wave from a spherical wave source or horn is directly converted into a plane wave with a phase gradient, so a design that takes into account the phase distribution of the spherical wave is necessary. Therefore, the present invention aims to provide a transparent metasurface plate and a steerable antenna that can reduce losses in the transmission line and reduce costs by standardizing components compared to conventional methods.

[0005] A transmission metasurface-loaded antenna in one embodiment of the present invention comprises a transmission metasurface plate and an antenna unit arranged parallel to the transmission metasurface plate, the transmission metasurface plate having a plurality of transmission elements for converting a substantially plane wave incident from one surface into a directional electromagnetic wave having directivity in a predetermined direction within one plane, the transmission elements transmitting the incident substantially plane wave with a predetermined phase difference, the transmission metasurface plate having transmission elements with different predetermined phase differences, and the antenna unit being a plane wave antenna that emits a substantially plane wave. Here, the substantially plane wave includes a quasi-plane wave. While a plane wave has equiphase surfaces that are in phase, a quasi-plane wave is not a perfect plane wave but is a wave with a phase difference of several tens of degrees. While a plane wave has equiphase surfaces that appear at a predetermined period, a quasi-plane wave that has an error of several tens of degrees at a predetermined period is also included in the definition of a transmission metasurface-loaded antenna. A transmission type metasurface-loaded antenna in one embodiment of the present invention is any of the above transmission type metasurface-loaded antennas, characterized in that the transmission type metasurface plate converts, within a single plane, two mutually different polarized waves incident from one surface into directional electromagnetic waves each having directivity in a predetermined direction. A transmission type metasurface-loaded antenna in one embodiment of the present invention is any of the above transmission type metasurface-loaded antennas, characterized in that the antenna unit has a single excitation element. A transmission type metasurface-loaded antenna in one embodiment of the present invention is any of the above transmission type metasurface-loaded antennas, characterized in that the antenna unit is a Fabry-Perot antenna. A transmission type metasurface-loaded antenna in one embodiment of the present invention is any of the above transmission type metasurface-loaded antennas, characterized in that it has a movable part, and the movable part changes the directivity by moving the transmission type metasurface plate. A transmission type metasurface-loaded antenna in one embodiment of the present invention is any of the above transmission type metasurface-loaded antennas, characterized in that the antenna unit has a plurality of excitation elements, and a plurality of transmission type metasurface plates are arranged at positions corresponding to the respective excitation elements.A transmission metasurface-loaded antenna in one embodiment of the present invention is any of the above-mentioned transmission metasurface-loaded antennas, characterized in that the antenna unit includes a switching unit that switches between multiple excitation elements.A transmission metasurface plate in one embodiment of the present invention is a transmission metasurface plate used in any of the above-mentioned transmission metasurface-loaded antennas, having multiple transmission elements that transmit incident plane waves with a predetermined phase difference, and the transmission metasurface plate has transmission elements with different predetermined phase differences, and is characterized in that it converts a substantially plane wave incident from one side into a directional electromagnetic wave having directivity in a predetermined direction within one plane.A transmission metasurface plate in one embodiment of the present invention is any of the above-mentioned transmission metasurface plates, characterized in that the transmission elements have a first substrate portion and a second substrate portion, the first substrate portion and the second substrate portion are formed from dielectric substrates and arranged parallel to each other, and have metal portions, the metal portions forming a magnetic loop with an electric dipole. In one embodiment of the present invention, the transmission metasurface plate is any of the above transmission metasurface plates, characterized in that it has a fixing portion that fixes its position relative to the plane wave antenna.In one embodiment of the present invention, the transmission metasurface plate is any of the above transmission metasurface plates, characterized in that the metal portions of at least some of the transmission elements have straight portions that are parallel to each other.In one embodiment of the present invention, the transmission metasurface plate is any of the above transmission metasurface plates, characterized in that the metal portions of at least some of the transmission elements have a first bent portion at the end of the straight portion that is turned approximately 90 degrees in the same direction, and are approximately U-shaped.In one embodiment of the present invention, the transmission metasurface plate is any of the above transmission metasurface plates, characterized in that the metal portions of at least some of the transmission elements have a second bent portion that is turned another approximately 90 degrees from the first bent portion, and are approximately C-shaped.

[0006] The present invention, with the above configuration, makes it possible to eliminate the complex feed circuit of a phased array antenna and reduce transmission loss. Furthermore, by replacing the transmission metasurface plate, i.e., the transmit array, it is possible to change the directivity, making it possible to standardize and simplify the design even when different directivities are required. Other advantages of the present invention are also described in the detailed description of the invention.

[0007] 1 shows an example of the configuration of a transmission metasurface-loaded antenna in an embodiment of the present invention. 2 shows an example of the configuration of a transmission metasurface-loaded antenna in an embodiment of the present invention. 3 shows an example of the configuration of a transmission metasurface-loaded antenna in an embodiment of the present invention. 4 shows an example of the configuration of a transmission metasurface-loaded antenna in an embodiment of the present invention. 5 shows an example of the configuration of a transmission metasurface-loaded antenna in an embodiment of the present invention. 6 shows an example of the configuration of a transmission metasurface-loaded antenna in an embodiment of the present invention. 7 shows an example of the configuration of a transmission metasurface-loaded antenna in an embodiment of the present invention. 8 shows an example of the configuration of a transmission metasurface-loaded antenna in an embodiment of the present invention. 9 shows an example of the configuration of a transmission metasurface plate in an embodiment of the present invention. 10 shows an example of the configuration of a transmission metasurface plate in an embodiment of the present invention. 11 shows an example of the configuration of a transmission metasurface plate in an embodiment of the present invention. 12 shows an example of the configuration of a transmission metasurface plate in an embodiment of the present invention. 13 shows an example of the configuration of a transmission metasurface plate in an embodiment of the present invention. 14 shows an example of the configuration of a transmission metasurface plate in an embodiment of the present invention.

[0008] 1 and 2 show an example of the configuration of a transmission-type metasurface-loaded antenna 1 according to an embodiment of the present invention. The transmission-type metasurface-loaded antenna 1 according to this embodiment includes a transmission-type metasurface plate 100 and an antenna unit 200 arranged parallel to the transmission-type metasurface plate 100. In this description, the transmission-type metasurface plate 100 may be referred to as a transmit array. The transmission-type metasurface plate 100 has multiple transmission elements 110 and converts a substantially plane wave incident from one side into a directional electromagnetic wave with directivity in a predetermined direction within a single plane. In other words, the transmission-type metasurface plate 100 converts a substantially plane wave represented by a vertically elongated circle in the figure into a directional electromagnetic wave represented by a horizontally elongated circle in the figure. The transmission elements 110 transmit the incident substantially plane wave with a predetermined phase difference. The transmission-type metasurface plate 100 has transmission elements 110 with different predetermined phase differences.

[0009] The antenna unit 200 is a plane wave antenna that emits approximately plane waves. A plane wave or plane wave-like antenna is used as the radiation source, and a transmit array with a phase distribution set according to the required directivity is arranged relative to the radiation source, allowing for a phase difference during transmission. The phase difference set can be the same as when the transmitting element 110 is treated as an antenna element. Since the decrease in radiation efficiency is smaller than the loss in the transmission line, transmission line loss can also be reduced. Furthermore, costs can be reduced by eliminating the complex feed circuit of a phased array antenna and standardizing components such as antennas. By standardizing the radiating elements to a thin antenna capable of plane wave excitation and configuring the radiation directivity in the vertical and horizontal planes using a transmit array, transmission loss due to the distribution and phase difference circuit can be reduced, while also enabling standardization and simplification of the design, thereby improving the designability of sector antennas.

[0010] In one embodiment of the present invention, the transmissive metasurface plate 100 converts two different polarized waves incident on one surface into directional electromagnetic waves each having a directivity in a predetermined direction within a single plane. This allows it to be used as a dual-polarized antenna by controlling the directivity of the horizontally polarized wave and the vertically polarized wave, for example.

[0011] 3 shows an example of the configuration of a transmission type metasurface-loaded antenna 1 according to one embodiment of the present invention. In this embodiment, the antenna unit 200 has a single driven element 201. This configuration makes it possible to achieve a small size and shape the directivity of the driven element 201 with a single element.

[0012] In this embodiment, the antenna unit 200 is a Fabry-Perot antenna. However, other structures, such as an array antenna, can be used as long as they are plane-wave antennas that emit approximately plane waves. In this embodiment, a high-gain antenna, such as a Fabry-Perot antenna, is used as the radiating element. An excitation wave similar to a plane wave is generated very close to the antenna, i.e., at a distance of less than the wavelength, and then the excitation wave is incident on a transmit array tuned to the desired directivity. Furthermore, by adjusting the transmission phase distribution of the transmit array and its positional relationship with the radiating element to match the desired vertical and horizontal directivity, it is possible to shape the directivity using a metasurface with the high-gain antenna as a wave source. In this embodiment, the directivity of the Fabry-Perot antenna is shaped using a metasurface, achieving a horizontal beamwidth of 10° to 60°, vertical tilt angles of 10°, 20°, and 30°, and a voltage standing wave ratio (VSWR) of 2.0 or less, for a center frequency of approximately 30 GHz.

[0013] When a point-like radiation source is used, the phase inversion occurs over a very small area in the transmit array, making electromagnetic control difficult. In contrast, in this embodiment, the area where the phase is close to equal is large, making it easier to control. Furthermore, since the wave is close to a plane wave, phase control near the driven element 201 is easier. When designing the aperture phase distribution, a two-dimensional phase distribution is required for directivity shaping, but a phase difference for beam tilt can be set only in the vertical or horizontal direction. To widen the beam, i.e., to reduce the gain, a phase difference can be set to adjust the conical surface beam width in the horizontal direction. Conversely, to narrow the beam, i.e., to increase the gain, a phase difference can be set to focus the light in both the horizontal and vertical directions. Setting the focus at the distance to the receiving area enables efficient communication.

[0014] 4 and 5 show an example of the configuration of a transmission type metasurface-loaded antenna 1 in one embodiment of the present invention. The transmission type metasurface-loaded antenna 1 in this embodiment has a movable part 300. The movable part 300 moves the transmission type metasurface plate 100 to change the directivity. By making the transmit array a movable structure, the directivity can be changed depending on the irradiation position.

[0015] 6 and 7 show an example of the configuration of a transmission type metasurface-loaded antenna 1 according to one embodiment of the present invention. In the transmission type metasurface-loaded antenna 1 according to this embodiment, an antenna section 200 includes a plurality of excitation elements 201. A plurality of transmission type metasurface plates 100 are arranged at positions corresponding to the respective excitation elements 2019.

[0016] A multi-beam configuration can be realized by arranging a plurality of transmit arrays and switching the drive elements 201. The antenna unit 200 can also be configured to include a switching unit 210 that switches between the plurality of drive elements 201, thereby switching the directivity and intensity.

[0017] 8 and 9 show an example of the configuration of a transmission-type metasurface-loaded antenna 1 according to an embodiment of the present invention. In this embodiment, antennas loaded with transmit arrays are arranged in a circular pattern, and the transmit arrays can be used to form a sector antenna with beam tilt and horizontal plane directivity.

[0018] The transmission metasurface plate 100 in one embodiment of the present invention is a transmission metasurface plate 100 used in any of the above-mentioned transmission metasurface-loaded antennas 1, and has a plurality of transmission elements 110 as shown in Figure 2. The transmission elements 110 transmit incident plane waves with a predetermined phase difference. The transmission metasurface plate 100 has transmission elements 110 with different predetermined phase differences, and converts a substantially plane wave incident from one surface into a directional electromagnetic wave with directivity in a predetermined direction within one plane.

[0019] 10 shows an example of the configuration of a transmission type metasurface plate 100 in one embodiment of the present invention. In the transmission type metasurface plate 100 in this embodiment, the transmission element 110 has a first substrate portion 111 and a second substrate portion 112. The first substrate portion 111 and the second substrate portion 112 are formed from dielectric substrates, are arranged parallel to each other, and have a metal portion 113. The metal portion 113 forms a magnetic loop with an electric dipole.

[0020] In the transmission metasurface, the transmission element 110 forms an electric dipole and a magnetic loop. The resonant frequency is expressed as f = 1 / 2πsqrt(LC), and the resonant frequency decreases as the value of C increases. Since the mode changes to an electric dipole mode or a magnetic loop mode every time the phase changes by 90°, in this embodiment, low reflection characteristics can be achieved over a wide bandwidth by appropriately controlling the electric and magnetic resonant frequencies.

[0021] 11 shows an example of the configuration of a transmission type metasurface plate 100 according to one embodiment of the present invention. In the transmission type metasurface plate 100 according to this embodiment, the metal parts 113 of at least some of the transmission elements 110 have linear parts 114 that are parallel to each other.

[0022] 12 shows an example of the configuration of a transmission type metasurface plate 100 according to one embodiment of the present invention. In the transmission type metasurface plate 100 according to this embodiment, the metal part 113 of at least some of the transmission elements 110 has a first bent part 115 at the end of the straight part 114, which is turned approximately 90 degrees in the same direction, and is approximately U-shaped.

[0023] 13 shows an example of the configuration of a transmission type metasurface plate 100 according to one embodiment of the present invention. In the transmission type metasurface plate 100 according to this embodiment, the metal part 113 of at least some of the transmission elements 110 has a second bend 116 that is further turned approximately 90 degrees from the first bend 115, and is approximately C-shaped.

[0024] FIG. 14 shows an example configuration of a transmission metasurface plate 100 according to one embodiment of the present invention. In this embodiment, the transmission metasurface plate 100 has metal portions 113 of at least some of the transmission elements 110, each of which has a linear portion 114 that is parallel to one another. With this configuration, the transmission metasurface plate 100 converts two different polarized waves incident from one side into directional electromagnetic waves, each of which has directivity in a predetermined direction, within a single plane. This allows the transmission metasurface plate 100 to be used as a dual-polarized antenna by controlling the directivity of the horizontally polarized wave and the vertically polarized wave. In one embodiment of the present invention, the transmission metasurface plate 100 has metal portions 113 of at least some of the transmission elements 110, each of which has a first bend 115 at the end of the linear portion 114, which is turned approximately 90 degrees in the same direction, in two orthogonal directions, forming an approximately U-shape.

[0025] 15 shows an example of the configuration of a transmission type metasurface plate 100 according to one embodiment of the present invention. In the transmission type metasurface plate 100 according to this embodiment, the metal part 113 of at least some of the transmission elements 110 has a second bend 116 that is further turned approximately 90 degrees from the first bend 115 in two orthogonal directions, and is approximately C-shaped.

[0026] 16 shows an example of the configuration of a transmission type metasurface plate 100 in one embodiment of the present invention. The transmission type metasurface plate 100 in this embodiment has a fixing part 400 that fixes its position relative to the plane wave antenna. With this configuration, the directivity can be changed by changing the attached elements, and flexible directivity design is possible by replacing the transmit array with one with a different transmission phase distribution.

[0027] The present invention is not limited to the above-described embodiments, and may include various embodiments within the scope of the present invention. For example, the configurations of the respective embodiments may be freely combined within the scope of no contradiction.

[0028] REFERENCE SIGNS LIST 1 Transmission type metasurface loaded antenna 100 Transmission type metasurface plate 110, 120, 130, 140 Transmission element 111 First substrate portion 112 Second substrate portion 113 Metal portion 114 Straight portion 115 First bent portion 116 Second bent portion 200 Antenna portion 201 Excitation element 210 Switching portion 300 Movable portion 400 Fixed portion

Claims

1. A transparent metasurface-loaded antenna comprising a transparent metasurface plate and an antenna section arranged parallel to the transparent metasurface plate, the transparent metasurface plate having a plurality of transparent elements and converting an approximately plane wave incident from one side into a directional electromagnetic wave having directivity in a predetermined direction within one plane, the transparent elements transmitting the incident approximately plane wave with a predetermined phase difference, the transparent metasurface plate having the transparent elements differing by a predetermined phase difference, and the antenna section being a plane wave antenna that emits approximately plane waves.

2. The transparent metasurface-loaded antenna of claim 1, characterized in that the transparent metasurface plate converts two different polarized waves incident from one side into directional electromagnetic waves each having a directivity in a predetermined direction within a single plane.

3. The transparent metasurface-loaded antenna according to claim 1, characterized in that the antenna section has a single excitation element.

4. The transmission type metasurface-loaded antenna according to claim 1, characterized in that the antenna portion is a Fabry-Perot antenna.

5. A transparent metasurface-loaded antenna as described in claim 1, further comprising a movable part, the movable part moving the transparent metasurface plate to change the directivity.

6. A transmission type metasurface-loaded antenna as described in claim 1, characterized in that the antenna section has a plurality of excitation elements, and a plurality of the transmission type metasurface plates are arranged at positions corresponding to each of the excitation elements.

7. The transparent metasurface-loaded antenna according to claim 7, characterized in that the antenna section is provided with a switching section for switching between a plurality of excitation elements.

8. A transmission type metasurface plate used in the transmission type metasurface-loaded antenna described in claim 1, comprising a plurality of transmission elements, each of which transmits an incident plane wave with a predetermined phase difference, the transmission type metasurface plate having transmission elements differing in a predetermined phase difference, and characterized in that the transmission type metasurface plate converts an approximately plane wave incident from one surface into a directional electromagnetic wave having directionality in a predetermined direction within one plane.

9. The transmission element has a first substrate portion and a second substrate portion, the first substrate portion and the second substrate portion being formed from a dielectric substrate, arranged parallel to each other, and having a metal portion, the metal portion forming an electric dipole and a magnetic loop. The transmission type metasurface plate described in claim 8.

10. The transmission type metasurface plate according to claim 8, characterized in that it has a fixing portion for fixing its position relative to the plane wave antenna.

11. The transmission type metasurface plate according to claim 8, characterized in that the metal portions of at least some of the transmission elements have straight portions that are parallel to each other.

12. A transmission type metasurface plate as described in claim 11, characterized in that the metal portion of at least a portion of the transmission elements has a first bend at the end of the straight portion that is turned approximately 90 degrees in the same direction, and is approximately U-shaped.

13. A transmission type metasurface plate as described in claim 12, characterized in that the metal portion of at least a portion of the transmission elements has a second bend portion that is further turned approximately 90 degrees from the first bend portion and is approximately C-shaped.

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