Reflective beam steering metasurface

Abstract

An embodiment of the present invention may present a full-duplex non-reciprocal beam steering transmission type phase gradient metasurface. The metasurface may comprise a conductor layer interposed between two dielectric layers. Each of the dielectric layers may comprise a plurality of unit cells embedded therein. Each of the unit cells may comprise a phase shifter and an antenna element. The metasurface may function such that when an electromagnetic wave is received at the surface of the metasurface, the metasurface can transmit waves having a similar or identical frequency to the frequency of the received wave in different directions in space.

Description

Technical Field

[0001] Technical Field The following relates to the field of metasurfaces for non-reciprocal wave engineering and electromagnetic wave radiation control. Specifically, a general method for controlling electromagnetic waves for full-duplex and non-reciprocal beam steering by a reflective surface is presented.

Background Art

[0002] Background Modern wireless communication systems may require general-purpose devices capable of non-reciprocal wave processing, especially in the reflection state.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Non-reciprocal radiation means electromagnetic wave radiation in which a structure produces different responses under a change in the direction of the incident field. Ferrite-based magnetic materials have been used for the implementation of non-reciprocity. However, ferrite-based magnetic materials can be heavy, expensive, may not be compatible with printed circuit board technology, and may not be suitable for high-frequency applications that may include 5G, 6G, and future-generation communication systems.

[0004] An improved communication system is needed.

Means for Solving the Problems

[0005] Summary In one embodiment, a reflective metasurface is provided. The metasurface includes a dielectric layer sandwiched between two conductor layers. The lower conductor layer can function as a ground plane for patch antenna elements and may also include a direct current (DC) signal patch of a unidirectional circuit. The upper conductor layer may include patch antenna elements, transistors, and phase shifters. The dielectric layer can separate the two conductor layers from each other.

[0006] Each unit cell may be formed by a patch antenna element, a phase shifter, and a unidirectional circuit.

[0007] When electromagnetic waves are received by the surface of a metasurface, the metasurface reflects waves having the same frequency as the received waves in a desired direction in space.

[0008] In another embodiment, a metasurface system is provided. The metasurface system comprises a dielectric layer interposed between two conductive layers. Each conductive layer comprises a plurality of unit cells embedded therein. Each unit cell within the plurality of unit cells comprises a peripheral circuit. The peripheral circuit may consist of a unidirectional circuit, for example, at least one microstrip patch radiator electrically connected to a phase shifter electrically connected to a transistor. The transistor high-frequency (RF) circuit includes two decoupling capacitors, and the transistor's DC bias circuit includes an inductor, two capacitors, and one resistor.

[0009] In yet another embodiment, a beam steering method using a reflective metasurface is provided. This method includes biasing a unit cell with a DC signal, the DC signal undergoing at least one set of gradient phase shifts, and the DC signal then biasing at least one transistor to generate a non-reciprocal phase shift.

[0010] Brief explanation of the drawing Next, embodiments will be described with reference to the attached drawings. [Brief explanation of the drawing]

[0011] [Figure 1] A schematic diagram of the metasurface system and non-reciprocal beam steering operation is provided. [Figure 2] A schematic diagram is provided showing a chain of interconnected reflective non-reciprocal phase-shift unit cells and their operation under forward and reverse incident electromagnetic fields. [Figure 3]A diagram of a metasurface system formed by non-reciprocal phase-shift radiation unit cells is provided. [Figure 4] We provide an energy harvesting version of the metasurface shown in Figure 3, using fewer unidirectional transistors. [Figure 5] This invention provides a circuit for a non-reciprocal phase-shift unit cell that can be used to further improve metasurface behavior for advanced non-reciprocal beam steering. [Figure 6] This provides an overview of the two layers of the fabricated metasurface. [Figure 7] Provides a photograph of the manufactured metasurface. [Figure 8] A schematic diagram of an experimental setup for a non-reciprocal radiation beam-reflecting metasurface is provided. [Figure 9a] This provides experimental results demonstrating the non-reciprocal full-duplex beam steering function for wave incidence from an incidence angle of 80 degrees. [Figure 9b] This paper provides experimental results demonstrating the frequency response of the non-reciprocal full-duplex beam steering function to wave incidence from an incidence angle of 80 degrees. [Figure 10a] This provides experimental results demonstrating the non-reciprocal full-duplex beam steering function for wave incidence from an incidence angle of 70 degrees. [Figure 10b] This paper provides experimental results demonstrating the frequency response of the non-reciprocal full-duplex beam steering function to wave incidence from an incidence angle of 70 degrees. [Figure 11a] This provides experimental results demonstrating the non-reciprocal full-duplex beam steering function for wave incidence from an incidence angle of 60 degrees. [Figure 11b] This paper provides experimental results demonstrating the frequency response of the non-reciprocal full-duplex beam steering function to wave incidence from an incidence angle of 60 degrees. [Figure 12a] This provides experimental results demonstrating the non-reciprocal full-duplex beam steering function for wave incidence from an incidence angle of 50 degrees. [Figure 12b] This paper provides experimental results demonstrating the frequency response of the non-reciprocal full-duplex beam steering function to wave incidence from an incidence angle of 50 degrees. [Figure 13a]Provide experimental results demonstrating a non-reciprocal full-duplex beam steering function for wave incidence from an incident angle of 45 degrees. [Figure 13b] Provide experimental results demonstrating a non-reciprocal full-duplex beam steering function for wave incidence from an incident angle of 40 degrees. [Figure 14a] Provide experimental results demonstrating a beam steering function by varying the phase shift of a non-reciprocal phase shifter for wave incidence from an incident angle of 60 degrees. [Figure 14b] Provide experimental results demonstrating a beam steering function by varying the phase shift of a non-reciprocal phase shifter for wave incidence from an incident angle of 30 degrees. [Figure 15a] Provide a schematic diagram of a near-field experimental apparatus for a non-reciprocal radiation beam reflection type metasurface. [Figure 15b] Provide experimental results demonstrating the near-field performance of the metasurface for wave incidence from an incident angle of 40 degrees.

Mode for Carrying Out the Invention

[0012] Detailed Description Embodiments of the present invention can present a non-reciprocal beam steering phase gradient reflection type metasurface that can assist in efficient full-duplex communication. The metasurface can be arranged in front of a wall or an antenna to amplify waves and / or manipulate the beam in a desired direction, i.e., convert the radiation pattern and introduce different radiation patterns for wave incidence from its left and right sides. The metasurface has a directional, diverse, and asymmetric transmit and receive radiation beam and has an adjustable beam shape. Furthermore, these beams can be operated by changing the DC bias of the non-reciprocal phase shifter. There are no unwanted harmonics, resulting in a high conversion efficiency with significant wave amplification, which is most important for practical applications such as point-to-point full-duplex communication.

[0013] Referring to the drawings, Figure 1 shows the structure of the reflective metasurface 112 and the operating principle of the non-reciprocal beam function of the metasurface. The thickness of the metasurface is sub-wavelength. In the forward problem indicated by "F", the incident wave 100 from the upper right side 104 at an incident angle 108 collides with the top of the metasurface 112, and the desired reflection At corner 109, it is amplified and reflected to the upper left side 102 of the metasurface. reflection Amplification of wave 109 105 and reflection The angle can be adjusted by the DC bias supplied to the non-reciprocal phase shifter.

[0014] In the reverse problem indicated by "B", the incident wave 101 from the upper left side at an incident angle 110 collides with the top of the metasurface 112 and is reflected to the upper right side 107 of the metasurface 103 at a desired transmission angle 111, which is different from the transmission angle 109 in the forward problem. The amplification levels and transmission angles for the forward and reverse problems are completely different and can be adjusted by the DC bias supplied to the non-reciprocal phase shifter.

[0015] Figure 2 shows a schematic of a chain of interconnected unit cells. Each unit cell consists of a patch antenna element 107 and a non-reciprocal phase shifter 113. The non-reciprocal phase shifter 113 can be either unidirectional or bidirectional. A unidirectional non-reciprocal phase shifter consists of a unidirectional device incorporating a fixed phase shifter 106, such as a transistor-based amplifier. The patch antenna element 107 can be a double-fed microstrip patch antenna to allow the transmission flow of power in a desired direction within the metasurface. However, the first patch antenna element 107a and the last patch antenna element 107n may be single-fed patches. The chain of interconnected patches 107 and non-reciprocal phase shifters 113 behaves differently from the left 101 and 103 with respect to incident waves from the right 100 and 102.

[0016] Figure 3 provides a schematic of a reflective beam steering metasurface 112. The metasurface is formed by a series of interconnected patches 107 (a, b, c, ... n) via gradient non-reciprocal phase shifters 113, 106.

[0017] The proposed concepts and non-reciprocal techniques can be used in various frequency bands ranging from acoustic and microwave to terahertz and optical. For example, by adjusting the dimensions of patch antenna elements and using transistor-based non-reciprocal phase shifters, similar metasurfaces can be fabricated at millimeter-wave and terahertz frequencies. In one embodiment, patch antenna elements for millimeter waves can be smaller and unidirectionally power amplified. Millimeter waves may be useful in optical and optics applications.

[0018] To increase bandwidth, other microstrip patch antennas, such as Vivaldi antennas, can be used. These can convert to terahertz frequencies (10-12 Hz) and can be used for high frequencies such as 6G, 7G, and 8G.

[0019] The array size can be changed as needed. For example, a larger array can be used to improve angular selectivity. Typically, at least two unit cells may be required.

[0020] Figure 4 provides schematic diagrams of energy harvesting and low-cost versions of the reflective metasurface 112b. In this embodiment, the metasurface 112b has fewer or fewer non-reciprocal phase shifters 106, 113 and therefore requires lower power. In this embodiment, only one pair of gradient non-reciprocal phase shifters per row of patch 107 is used. This embodiment can be implemented in parallel or series circuit configurations.

[0021] Figure 5 shows the structure of a bidirectional non-reciprocal phase shifter 113. The non-reciprocal phase shifter is formed by two power dividers 115a and 115b, two unidirectional transistor-based amplifiers 116a and 116b, two fixed-phase shifters 114a and 114b, and four decoupling capacitors 104, 105, 106, and 107. The upper and lower phase shifters provide different phase shifts. The upper and lower amplifiers can provide equal amplification and isolation in the forward and reverse directions, respectively. A signal entering the structure from the left side 118 passes through the upper arm, is amplified by the upper amplifier, and then passes through the upper phase shifter. However, a signal entering the structure from the right side 119 passes through the lower arm, is amplified by the lower amplifier, and then passes through the lower phase shifter.

[0022] Figure 6 shows the layout of the fabricated reflective beam steering metasurface. The upper layer includes a chain of patches 107 interconnected via a unidirectional transistor base gradient non-reciprocal phase shifter 113. The lower conductor layer includes two metals: a first metal 118 acts as the background ground for the patch antenna 107, and a second metal 119 provides the DC bias for the transistors 118. The DC bias for the transistors is supplied to the lower right side of the upper layer 120, transferred to the lower layer via via holes, and then supplied to each transistor via via holes. In some embodiments, the two metals are not connected.

[0023] Figure 7 provides a photograph of a fabricated reflective metasurface. In this embodiment, the metasurface is formed by 30 patch antenna elements 107 (i.e., 20 dual-fed patch antenna elements and 10 single-fed patch antenna elements) and 25 non-reciprocal phase shifters 113. Each non-reciprocal phase shifter 113 includes a cross-transmission line base phase shifter, a Gali-2+ transistor base amplifier, two decoupling capacitors, an inductor, and a bypass capacitor.

[0024] In one embodiment, a total of 25 Gali-2+ amplifiers and 25 Lchk =15nH inductor, 25 100pF bypass capacitors, and 50 C cpl A decoupling capacitance of 3pF is used. The metasurface is fabricated as a two-layer circuit, i.e., two conductive layers and one dielectric layer, and is made from Rogers RO 4350 with a height of 30 mils. Each unit cell contains one amplifier, one inductor, one bypass capacitor, and two decoupling capacitors per unit cell. Layers of any thickness can be used.

[0025] Other amplifiers may be used. For example, in high-frequency applications, it may be desirable to use an alternative amplifier.

[0026] Figure 8 provides a schematic diagram illustrating the experimental proof of a non-reciprocal radiation beam-reflecting metasurface. The measurement apparatus consists of a fabricated reflective metasurface 112, an absorber 122 for holding the metasurface 112, a vector network analyzer, a DC power supply, and two horn antennas 121.

[0027] Figure 9a provides experimental results demonstrating the non-reciprocal full-duplex beam steering function for wave incidence from an incidence angle of 80 degrees. In the forward problem, where the incident wave strikes the metasurface from the right, i.e., at an incidence angle of +80 degrees, the wave is instantaneously amplified by approximately 16.5 dB by the metasurface and reflected at the desired reflection angle of -5 degrees. However, in the reverse problem, where the incident wave strikes the metasurface from the left, i.e., at incidence angles of -5 degrees and -80 degrees, the wave is not amplified significantly.

[0028] Figure 9b provides experimental results demonstrating the frequency response of the non-reciprocal full-duplex beam steering function for wave incidence from an incidence angle of 80 degrees. The separation between wave reflections at different angles indicates that adequate wave amplification and separation are achieved at a frequency of 5.81 GHz.

[0029] Figure 10a provides experimental results demonstrating the non-reciprocal full-duplex beam steering function for wave incidence from an incidence angle of 70 degrees. In the forward problem, where the incident wave strikes the metasurface from the right, i.e., at an incidence angle of +70 degrees, the wave is instantaneously amplified by approximately 19 dB by the metasurface and reflected at the desired reflection angle of -20 degrees. However, in the reverse problem, where the incident wave strikes the metasurface from the left, i.e., at incidence angles of -20 and -70 degrees, the wave is amplified by less than 13 dB below the reflection angle corresponding to the opposite incidence angle.

[0030] Non-reciprocal full-duplex operation is as follows: The main ports for receiving and transmitting are positioned at -20 degrees. As a result, a transmit gain of +12 dB is obtained from -20 to +20 degrees. However, a receive gain of 18.5 dB is obtained from +70 to -20 degrees. Therefore, the metasurface allows for simultaneous transmission and reception, but with different transmission and reception angles (transmission angels), namely +20 degrees for transmission and +70 degrees for reception.

[0031] Figure 10b provides experimental results demonstrating the frequency response of the non-reciprocal full-duplex beam steering function for wave incidence from an incidence angle of 70 degrees. The separation between wave reflections at different angles indicates that adequate wave amplification and separation are achieved at a frequency of 5.81 GHz.

[0032] Figure 11a provides experimental results demonstrating the non-reciprocal full-duplex beam steering function for wave incidence from an incidence angle of 60 degrees. In the forward problem, where the incident wave strikes the metasurface from the right, i.e., at an incidence angle of +60 degrees, the wave is instantaneously amplified by more than 21.2 dB by the metasurface and reflected at the desired reflection angle of -28.5 degrees. However, in the reverse problem, where the incident wave strikes the metasurface from the left, i.e., at incidence angles of -28.5 degrees and -60 degrees, the wave is not amplified significantly.

[0033] The non-reciprocal operation of the metasurface is present not only in the amplification of different waves for forward and reverse wave incidence, but also in beam steering. The non-reciprocal beam steering operation of the metasurface is as follows: For a forward problem corresponding to an incidence angle of +60 degrees, the normal reflection reads -60 degrees, but the wave is steered toward -28.5 degrees according to the metasurface's phase gradient profile. However, for a reverse wave incidence corresponding to an incidence angle of -28.5 degrees, the wave is reflected at the normal reflection angle, i.e., +28 degrees. This is due to the fact that the metasurface's non-reciprocal phase gradient profile primarily affects forward waves arriving from the right.

[0034] Figure 11b provides experimental results demonstrating the frequency response of the non-reciprocal full-duplex beam steering function for wave incidence from an incidence angle of 60 degrees. The separation between wave reflections at different angles indicates that adequate wave amplification and separation are achieved at a frequency of 5.81 GHz.

[0035] Figure 12a provides experimental results demonstrating the non-reciprocal full-duplex beam steering function for wave incidence from an incidence angle of 50 degrees. In the forward problem, where the incident wave strikes the metasurface from the right, i.e., at an incidence angle of +50 degrees, the wave is instantaneously amplified by more than 21.7 dB by the metasurface and reflected at the desired reflection angle of -20 degrees. However, in the reverse problem, where the incident wave strikes the metasurface from the left, i.e., at incidence angles of -20 and -50 degrees, the wave is reflected with much less power amplification at nearly normal reflection angles.

[0036] Non-reciprocal full-duplex operation is as follows: The main ports for receiving and transmitting are positioned at -20 degrees. As a result, a transmit gain of +12 dB is obtained from -20 to +24 degrees. However, a receive gain of 21.6 dB is obtained from +50 to -20 degrees. Therefore, the metasurface allows simultaneous transmission and reception, but at different transmit and receive angles, namely +24 degrees for transmitting and +50 degrees for receiving.

[0037] Figure 12b provides experimental results demonstrating the frequency response of the non-reciprocal full-duplex beam steering function for wave incidence from an incidence angle of 50 degrees. The separation between wave reflections at different angles shows that wave amplification and separation exceeding 21.7 dB is achieved at a frequency of 5.81 GHz.

[0038] Figure 13a provides experimental results demonstrating the non-reciprocal full-duplex beam steering function for wave incidence from an incidence angle of 45 degrees. In the forward problem, where the incident wave strikes the metasurface from the right, i.e., at an incidence angle of +45 degrees, the wave is instantaneously amplified by more than 25 dB by the metasurface and reflected at the desired reflection angle of -18 degrees. However, in the reverse problem, where the incident wave strikes the metasurface from the left, i.e., under an incidence angle of -45 degrees, the wave is not amplified significantly and is not beam-steered.

[0039] Figure 13b provides experimental results demonstrating the non-reciprocal full-duplex beam steering function for wave incidence from an incidence angle of 40 degrees. In the forward problem, where the incident wave strikes the metasurface from the right, i.e., at an incidence angle of +40 degrees, the wave is instantaneously amplified by approximately 21.6 dB by the metasurface and reflected at the desired reflection angle of 0 degrees. However, in the reverse problem, where the incident wave strikes the metasurface from the left, i.e., under an incidence angle of -40 degrees, the wave is not amplified significantly.

[0040] Figure 14a provides experimental results demonstrating the beam steering function by changing the phase shift of a non-reciprocal phase shifter with a DC bias for wave incidence from an incidence angle of +60 degrees at 5.8 GHz. In the forward problem where the incident wave collides with the metasurface from the right side, i.e., at an incidence angle of +60 degrees, the wave is instantaneously amplified by more than 10 dB by the metasurface and reflected to different desired reflection angles for DC biases of 3.6 V, 3.84 V, and 4 V.

[0041] Figure 14b provides experimental results demonstrating the beam steering function by varying the phase shift of a non-reciprocal phase shifter for wave incidence from an incidence angle of +30 degrees at a frequency of 5.8 GHz. In the forward problem where the incident wave collides with the metasurface from the right side, i.e., at an incidence angle of +60 degrees, the wave is instantaneously amplified by more than 10 dB by the metasurface and reflected to different desired reflection angles for DC biases of 3.7 V and 3.84 V.

[0042] Figure 15a provides a schematic diagram of a near-field experimental setup for a non-reciprocal radiation beam-reflecting metasurface. In this experiment, two source-horn antennas are positioned very close to the metasurface within the near-field zone of the metasurface.

[0043] Figure 15b provides experimental results demonstrating the near-field performance of the metasurface for wave incidence at an incidence angle of +40 degrees. This figure shows that the metasurface provides very similar results for both far-field and near-field experiments. This demonstrates the excellent performance of the metasurface in the near field.

[0044] Reflective metasurfaces offer an opportunity to achieve full-double reflection beam steering with wave amplification. Mechanisms have been proposed to achieve non-reciprocal beam operation in the reflective state, and as a result, the structure can be used as a radome for antennas or mounted on a wall. Incident wave and reflection Waves share the same frequency. Non-reciprocal phase and amplitude transitions in the unit cell are used to realize a radiated non-reciprocal phase shifter, and the structure is not affected by undesirable frequency harmonics.

[0045] It should be noted that there are no inherent limitations on the bandwidth expansion of the proposed metasurface. The frequency bandwidth of the proposed unit cell can be expanded by using engineering techniques for bandwidth expansion of microstrip patch elements and non-reciprocal phase shifters.

[0046] Table 1 provides an overview of one embodiment of the disclosed non-reciprocal beam-operable reflective metasurface performance. Other operating frequency ranges are available from 5 GHz to 8 GHz. Higher and lower frequency values ​​can be used as needed.

[0047] [Table 1]

[0048] As can be understood, those skilled in the art can easily adapt the technology to use higher and lower frequency values ​​without inventiveness, especially as telecommunications technology develops to use a variety of frequencies.

[0049] Although embodiments of the present invention have been described with reference to specific embodiments, various modifications can be adopted without departing from the spirit and scope of the invention.

Claims

1. Metasurface for reflective beam steering, A dielectric layer sandwiched between two conductive layers, At least one unit cell embedded in the two conductive layers, Equipped with, Each of the at least one unit cell comprises at least one antenna element and at least one non-reciprocal phase shifter. The meta-surface is a meta-surface that, when an incident electromagnetic wave having a frequency collides with the meta-surface, amplifies the incident electromagnetic wave and radiates the amplified incident electromagnetic wave, which has the same frequency as the original incident electromagnetic wave, as a reflected wave in a desired direction in space.

2. The metasurface according to claim 1, wherein the at least one antenna element comprises at least one of a patch antenna element, a microstrip patch radiator, and a patch.

3. The metasurface according to claim 1, wherein the DC bias circuit is embedded in the lower conductor layer of the two conductor layers.

4. The metasurface according to claim 1, wherein the non-reciprocal phase shifter adjusts at least one characteristic of the reflected wave by a DC bias generated by a DC bias circuit.

5. The metasurface according to claim 4, wherein the at least one characteristic includes a reflection angle.

6. The metasurface according to claim 5, wherein the at least one characteristic includes the amplitude of the reflected wave.

7. The metasurface according to claim 6, wherein the peripheral circuit comprises at least one reciprocal phase shifter, at least one transistor-based amplifier, at least one choke inductor, at least two decoupling capacitors included in the RF circuit, and at least one bypass capacitor.

8. The at least one unit cell comprises two or more unit cells, The at least one choke inductor prevents leakage of the incident electromagnetic wave into the DC bias circuit. The metasurface according to claim 7, wherein at least one decoupling capacitor of one of the two or more unit cells prevents leakage of the DC bias to the RF circuit of the next unit cell among the two or more unit cells.

9. A metasurface system for reflective beam steering, Multiple dielectric layers interposed between two conductive layers, A chain of unit cells embedded in the two aforementioned conductive layers, Equipped with, Each unit cell in the chain of unit cells comprises at least one non-reciprocal phase shifter and at least one antenna element, and the dielectric layer and the chain of unit cells are combined to form a metasurface. The metasurface system is such that when an incident electromagnetic wave having a frequency collides with the metasurface, the incident electromagnetic wave is amplified, and the amplified incident electromagnetic wave having the same frequency as the original incident electromagnetic wave is radiated as a reflected wave in a desired direction in space.

10. The metasurface system according to claim 9, wherein the at least one antenna element comprises at least one of a patch antenna element, a microstrip patch radiator, and a patch.

11. The metasurface system according to claim 9, wherein the DC bias circuit is embedded in the lower conductor layer of the two conductor layers.

12. The metasurface system according to claim 9, wherein the non-reciprocal phase shifter adjusts at least one characteristic of the reflected wave by a DC bias generated by a DC bias circuit.

13. The metasurface system according to claim 12, wherein the at least one characteristic includes a reflection angle.

14. The metasurface system according to claim 13, wherein the at least one characteristic includes the amplitude of the reflected wave.

15. The metasurface system according to claim 14, wherein the peripheral circuit comprises at least one reciprocal phase shifter, at least one unidirectional transistor-based amplifier, at least one choke inductor, at least one bypass capacitor, and at least two decoupling capacitors included in the RF circuit.

16. The metasurface system according to claim 15, wherein the at least one choke inductor and the at least one decoupling capacitor isolate the DC bias circuit from the RF circuit of the metasurface.

17. A reflective beam steering method using a metasurface, The metasurface comprises a dielectric layer sandwiched between two conductive layers and at least one unit cell embedded in the two conductive layers. The aforementioned method, The at least one unit cell is biased by a DC bias circuit, Following the DC bias circuit, the process involves causing a non-reciprocal phase shift of the incident electromagnetic wave having a frequency, amplification of the incident electromagnetic wave, and radiation of the amplified incident electromagnetic wave having the same frequency as the incident electromagnetic wave as a reflected wave in a desired direction in space. A reflective beam steering method that uses a metasurface, including

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