Broadband reconfigurable metamaterial surface for spectral sensing and beamforming

Abstract

Embodiments of the present disclosure relate to wideband reconfigurable metamaterial surfaces for spectral sensing and beamforming. Systems and methods for performing frequency conversion using RF metamaterials are provided. An RF metasurface element includes a first antenna and a second antenna on first and second surfaces, respectively, the first and second surfaces being opposite each other. A modulation signal input is configured to receive a modulation signal. The RF metasurface element is configured to receive a first signal having a first frequency at the first antenna. The RF metasurface element is further configured to transmit a second signal from the second antenna at a different second frequency, where the second frequency depends on the first frequency and a frequency of the modulation signal. A plurality of RF metasurface elements can be assembled as an array of elements.

Description

Cross-reference to related applications

[0001] This application claims the rights and priorities of U.S. Provisional Patent Application No. 63 / 747,781, filed January 21, 2025, and U.S. Patent Application No. 19 / 202,487, filed May 8, 2025, the entire contents of which are incorporated herein by reference. Background Technology

[0002] Reflective radio frequency (RF) metamaterial surfaces are designed to manipulate electromagnetic waves in unique ways. For example, such materials can alter the reflectivity characteristics of incident signals to control aspects such as phase, amplitude, and polarization, and in some cases, control the direction of the reflected signal. Some RF metamaterials can have tunable resonant frequencies based on various structures realized on them.

[0003] RF metamaterials can be used in many different applications. For example, in wireless networks, RF metamaterials can be used to optimize the indoor signal coverage of indoor wireless networks, and also to reduce radar cross-section, etc. Attached Figure Description

[0004] This disclosure is described in detail with reference to the following figures, based on one or more various examples. These figures are provided for illustrative purposes only and depict only typical, non-limiting aspects of such examples.

[0005] Figure 1 The illustration shows an example of a network configuration that can implement the disclosed technology.

[0006] Figure 2A This is a schematic diagram illustrating an example of a system comprising an RF metamaterial capable of performing frequency conversion of a received signal.

[0007] Figure 2B The diagram illustrates operations such as Figure 2A The flowchart shows an example method of the system.

[0008] Figure 3A This is a perspective view of an example RF metamaterial unit used to realize an RF metasurface.

[0009] Figure 3B This is an exploded view of an example RF metamaterial unit used to realize an RF metasurface.

[0010] Figure 4 This is a top view of an example RF metamaterial unit.

[0011] Figure 5 This is a bottom view of an example RF metamaterial unit.

[0012] Figures 6A to 6DThis is a schematic diagram illustrating different possible operating modes of an example RF metamaterial unit.

[0013] Figure 7 This is a perspective view illustrating an example system that includes an RF metamaterial and a modulation signal generator.

[0014] Figures 8A to 8C This is a diagram illustrating an example use case of an RF metamaterial system based on this disclosure.

[0015] The accompanying drawings are not exhaustive and do not limit this disclosure to the precise form disclosed. Detailed Implementation

[0016] Wireless networks are often sensitive to real-world environments where communication links are limited by RF propagation characteristics and interference. This can be especially true for indoor environments such as Wi-Fi networks, but may also apply to other wireless networks. Problem areas in various wireless networks can include those related to spectrum occupancy detection (to minimize signal interference), as well as the need to improve coverage and signal quality given a mix of radio types.

[0017] One mechanism for addressing the various problems discussed above is the use of metamaterials, such as RF metasurfaces in wireless networks. Such surfaces can be used to reflect and thus redirect the propagation of wireless signals within a given area. This, in turn, allows the wireless signal to be directed to the intended receiver. Furthermore, some RF metasurfaces can have the ability to perform beamforming to further narrow the beam of the RF signal, which can improve the signal-to-noise ratio at the intended receiver. However, such RF metasurfaces may be limited to transmitting signals at the same frequency as the received signal.

[0018] This disclosure relates to an RF metasurface and RF metasurface units capable of performing frequency conversion (e.g., frequency conversion performed by a mixer similar to that of an RF transmitter / receiver). This frequency conversion can be performed using a technique known as space-time modulation. The frequency conversion can also depend on controlling parameters (e.g., resonant frequency) of a receiving antenna on a first surface of the RF metasurface unit and parameters of a transmitting antenna on a second surface (opposite to the first surface). The units of the RF metasurface can receive a modulated signal from a modulated signal source. The modulated signal is combined with the received signal to generate an electromagnetic signal (e.g., an RF signal) that is transmitted from the transmitting antenna at a frequency different from the received signal. These units are also tunable relative to the resonant frequency of the receiving antenna.

[0019] Additionally, the RF metasurface can be used for beamforming and beamdirection to control the directionality of transmitted signals. Beamforming and beamdirection can be performed concurrently with frequency conversion. Therefore, the RF metasurface of this disclosure can allow for more efficient use of available spectrum resources and can reduce network congestion when a large number of devices compete for network bandwidth.

[0020] We will now discuss in more detail the various implementations of RF metasurfaces, the cells used in RF metasurfaces, and their applications, starting with networks that can utilize such metasurfaces. Further references will follow. Figure 2A and Figure 2B The use of RF metasurfaces for frequency conversion is described. (Reference) Figure 3A and Figure 3B The construction of an example unit cell for an RF metasurface is described. Figure 4 and Figure 5 The descriptions address both the receiving and transmitting antennas, and explain how frequency conversion can be implemented according to this disclosure. (See references.) Figures 6A to 6D Different operating modes of the unit cell relative to the RF metasurface are discussed. See below for reference. Figure 7 This section briefly discusses the components of a system used in one implementation of RF metasurfaces. (References) Figures 8A to 8C An example application utilizing an RF metasurface with frequency conversion is described.

[0021] It should be noted that the terms “optimized,” “optimal,” etc., used in this document can be used to describe manufacturing or achieving the most efficient or perfect performance possible. However, as a person skilled in the art will recognize upon reading this document, perfection is never achievable. Therefore, these terms can also encompass manufacturing or achieving the best possible, most efficient, or most practical performance under given conditions, or manufacturing or achieving performance that is better than that achievable using other settings or parameters.

[0022] Before describing in detail examples of the disclosed systems and methods, it is useful to describe an example network installation in which these systems and methods can be implemented in various applications. Figure 1 The illustration shows an example of a network configuration 100 that can be implemented for organizations such as businesses, educational institutions, government entities, healthcare facilities, or other organizations. Figure 1 An example of the implemented configuration is illustrated, in which an organization has multiple users (or at least multiple client devices or workstations (STAs) 110, such as 110A, 110B, 110C, etc.) and possibly multiple physical or geographic sites 102, 132, 142. Network configuration 100 may include a master site 102 communicating with network 120. Network configuration 100 may also include one or more remote sites 132, 142 communicating with network 120.

[0023] Main site 102 may include a main network, which can be, for example, an office network, a home network, or other network installation. The main network may be a private network, such as a network that may include security and access controls to restrict authorized users' access to the private network. Authorized users may include, for example, employees of a company located at main site 102, residents of a residence, or customers of a business.

[0024] exist Figure 1 In the example, master site 102 includes controller 104 that communicates with network 120. Controller 104 facilitates communication between master site 102 and network 120. Besides controller 104, other points may exist for master site 102 to communicate with network 120. Although a single controller 104 is illustrated, master site 102 may include multiple controllers or multiple communication points within network 120. In some examples, controller 104 may communicate with network 120 via a router (not shown). In other examples, controller 104 provides router functionality to devices within master site 102.

[0025] Controller 104 is operable to configure and manage network devices (such as at the main site 102) and can also manage network devices at remote sites 132 and 134. Controller 104 is operable to configure and / or manage switches, routers, access points, and / or client devices connected to the network. Controller 104 itself may be an access point or provide access point functionality.

[0026] Controller 104 can communicate with one or more switches 108 or wireless access points (APs) 106A-106C. Switches 108 and wireless APs 106A-C provide network connectivity to various client devices or workstations (STAs) 110A-J. Using the connection to switches 108 or APs 106A-C, STAs 110A-J can access network resources, including the (main site 102) network and other devices on network 120.

[0027] Examples of client devices may include: desktop computers, laptop computers, servers, web servers, authentication servers, Authentication, Authorization and Accounting (AAA) servers, Domain Name System (DNS) servers, Dynamic Host Configuration Protocol (DHCP) servers, Internet Protocol (IP) servers, Virtual Private Network (VPN) servers, network policy servers, mainframes, tablet computers, e-readers, netbook computers, televisions and similar monitors (e.g., smart TVs), content receivers, set-top boxes, personal digital assistants (PDAs), mobile phones, smartphones, smart terminals, dumb terminals, virtual terminals, video game consoles, virtual assistants, Internet of Things (IoT) devices, etc.

[0028] Within the main site 102, switch 108 is included as an example of an access point for STA 110I-J to access the network established in the main site 102. STA 110I-J can connect to switch 108 and access other devices within network configuration 100 through switch 108. STA 110I-J can also access network 120 through switch 108. STA 110I-J can communicate with switch 108 via a wired or wireless connection 112. In the illustrated example, switch 108 communicates with controller 104 via a wired or wireless connection 112.

[0029] Wireless AP 106A-C is another example of an access point included for STA 110A-H to access the network established in main site 102. Each AP in AP 106A-C can be a combination of hardware, software, and / or firmware configured to provide wireless network connectivity to wireless STA 110A-H. Figure 1 In the example, AP 106A-C can be managed and configured by controller 104. AP 106A-C communicates with controller 104 and the network via connection 112, which can be a wired or wireless interface.

[0030] Network configuration 100 may include one or more remote sites 132. Remote sites 132 may be located in a different physical or geographical location than the main site 102. In some cases, remote sites 132 may be located in the same geographical location as the main site 102, or may be located in the same building, but may lack a direct connection to the network within the main site 102. Instead, remote sites 132 may utilize connections through a different network (e.g., network 120). For example, remote site 132 may be a satellite office, another floor or suite in a building, etc. Remote site 132 may include a gateway device 134 for communicating with network 120. Gateway device 134 may be a router, a digital-to-analog modem, a cable modem, a digital subscriber line (DSL) modem, or some other network device configured to communicate with network 120. Remote site 132 may also include a switch 138 or an access point (AP) 136 communicating with gateway device 134 via a wired or wireless connection. Switch 138 and AP 136 provide connectivity to the network for various STAs 140A-D.

[0031] In various examples, remote station 132 can communicate directly with master station 102, enabling STAs 140A-D at remote station 132 to access network resources at master station 102 as if they were located at master station 102. In this example, remote station 132 is managed by controller 104 at master station 102, and controller 104 provides the necessary connectivity, security, and accessibility for communication between remote station 132 and master station 102. Once connected to master station 102, remote station 132 can be used as part of a private network provided by master station 102.

[0032] In various examples, network configuration 100 may include one or more smaller remote sites 142, which consist only of a gateway device 144 and a wireless access point 146 for communicating with network 120, through which STAs 150A-B access network 120. Such a remote site 142 may represent, for example, an employee's home or a temporary remote office. Remote site 142 may also communicate with master site 102, enabling STAs 150A-B at remote site 142 to access network resources at master site 102 as if they were located at master site 102. Remote site 142 may be managed by controller 104 at master site 102 to enable this transparency. Once connected to master site 102, remote site 142 can be used as part of a private network provided by master site 102.

[0033] Network 120 may be a public or private network (such as the Internet) or other communication network to allow connectivity between various sites 102, 130 to 142 and access to servers 160A-B. Network 120 may include third-party telecommunications lines, such as telephone lines, broadcast coaxial cables, fiber optic cables, satellite communications, cellular communications, etc. Network 120 may include any number of intermediate network devices, such as switches, routers, gateways, servers, and / or controllers, which are not directly part of network configuration 100 but facilitate communication between the various parts of network configuration 100 and between network configuration 100 and other network-connected entities. Servers 160A-B may be, for example, content servers. That is, servers 160A-B may include various providers of downloadable and / or streaming multimedia content (including audio, video, graphics, and / or text content or any combination thereof), examples of which include web servers, streaming broadcast and video providers, and cable and satellite television providers. STA 110A-J, 140A-D, and 150A-B can request and access multimedia content provided by server 160A-B.

[0034] In various examples, systems using RF metamaterials can be implemented in conjunction with other network hardware, such as various wireless access points 106A, 106B, and 106C of geosite 102 (similar implementations can be performed in geosites 132 and 142). RF metamaterial systems can use RF metamaterials to receive, transmit, and / or reflect wireless signals for propagation. As will be discussed in further detail below, this can include using RF metamaterials to perform frequency conversion, by which RF signals received on the metasurface at a first frequency are retransmitted from the metasurface at a second frequency. Additionally, beamforming and beam shaping can also be performed to control the propagation direction of RF signals, for example, guiding them to improve the signal-to-noise ratio at the endpoint receiver. It should be noted that various operations performed using RF metamaterials in this disclosure can be combined.

[0035] Figure 2 is an example diagram illustrating a system comprising an RF metamaterial capable of performing frequency conversion of a received signal. The RF metamaterial system 200 shown in Figure 2 includes an RF metasurface 201 comprising a plurality of cells 202. In this particular example, the cells are arranged in a grid pattern, but other arrangements are possible and contemplated in this disclosure.

[0036] The RF metasurface 201 includes a receive / reflection side 204 and a transmit side 205. RF signals received on the receive / reflection side can be retransmitted from the transmit side in at least one operating mode and can be reflected without retransmission in at least another operating mode. As will be discussed in further detail below, each element 202 includes a first (receive) antenna located on a first surface corresponding to the receive / reflection side of the RF metasurface 201 and a second (transmit) antenna located on a second surface corresponding to the transmit side. Using components coupled to these antennas, their respective resonant frequencies can be adjusted to tune their respective frequency responses.

[0037] In various implementations, the RF metasurface 201 can perform frequency conversion. As shown in the example of Figure 2, the incident wave of the incident RF signal 251 can be received by the receiving / reflecting side 204 of the RF metasurface at a frequency f0 (or angular frequency ω0). Each element 202 of the RF metasurface 201 can receive a modulated signal 252 having a frequency f0. m (angular frequency ω) m These two signals can be combined such that the incident RF signal 251 is modulated by the modulation signal 252 to generate a signal with frequency f. t (angular frequency ω) t , where ω t =ω0+ω mThe emitted RF signal 253 is the input RF signal. Therefore, the information initially carried by the input RF signal 251 can be carried by the output RF signal 253 during modulation and retransmission. The RF metasurface 201 can perform the same or similar functions as a nonlinear mixer circuit, but with lower power consumption.

[0038] As shown in Figure 2, the ability of system 200 to perform frequency conversion can allow signal relay between different frequency bands in, for example, a WiFi network. This can further reduce network congestion within a WiFi network, especially when a large number of users consume a portion of a specific frequency band.

[0039] Now for reference Figure 2B This describes a method for operating a system such as system 200. Method 280 can be performed by any of the various system implementations disclosed herein. Furthermore, systems capable of performing method 280 but not otherwise discussed herein are also considered to fall within the scope of this disclosure.

[0040] Method 280 includes receiving information encoded in a first signal at one of a plurality of elements of an RF metasurface, wherein the first signal is a radio frequency (RF) signal having a first frequency (box 282). The element of the RF metasurface can be one of a plurality of elements, for example, as described above. Figure 2A As shown in the other figures discussed below, when receiving the first signal, a first antenna having a resonant frequency on the first surface of a given element can be tuned using, for example, a PIN diode.

[0041] Method 280 further includes modulating a first signal and generating a second signal using the modulated signal received by one of a plurality of elements. The second signal may have a second frequency different from the first frequency, wherein the second signal is an RF signal encoded with information (block 284). The modulated signal can be generated using any suitable type of modulation signal generation circuitry and can be provided to a cell of the RF metasurface by, for example, a diode or other suitable circuitry. When the modulated signal is received at a given cell of the RF metasurface, it is combined with the first signal to generate a second signal at a second frequency, wherein the second frequency depends on the first frequency and the frequency of the modulated signal.

[0042] This operation is similar to that of an RF mixer in a transmitter and receiver circuit, which can perform upconversion on the signal to be transmitted or downconversion on the signal to be received, respectively. However, the power consumed may be much lower than that of an active mixer that utilizes multiple active circuit components (e.g., transistors) biased in the nonlinear operating region.

[0043] Method 280 also includes transmitting information from one of the plurality of elements using a second signal (box 286). In various implementations, where the first signal is received on an antenna on a first side of a given element on an RF metasurface, the second signal can be transmitted from a second antenna on a second side of that element, where the second side is opposite to the first side.

[0044] In addition to transmitting signals after frequency conversion, the elements of the RF metasurface according to this disclosure can also perform beamforming and beamdirection. Beamforming can be used to improve signal strength, signal-to-noise ratio, and signal quality at the receiver. It can also improve signal range and spectral efficiency. Beamdirection allows these improvements to be maintained as the receiver moves through a specific area of ​​the transmitted signal.

[0045] Figure 3A This is a perspective view of an example RF metamaterial unit for realizing an RF metasurface. In the illustrated example, metamaterial unit 302 includes a receiving antenna 304 located on a first surface and a transmitting antenna 305 located on a second surface opposite to the first surface. A frequency control diode 315 integrated into the first antenna can be used to control the resonant frequency of the first antenna. At least one modulation signal diode 316 is present on the first surface and coupled to the receiving antenna 304 to provide a signal path to the modulation signal.

[0046] In the example shown, the receiving antenna 304 is electrically coupled to the transmitting antenna 305 via an interconnect provided by the central conductor 311. Other conductors may be present in some implementations. A mode switch 317 is integrated into the transmitting antenna 305 and can be used to select the operating mode for the RF metasurface, of which the metamaterial unit is part.

[0047] exist Figure 3B The diagram further illustrates the construction of an example of a unit cell. Figure 3B This is an exploded view of an example RF metamaterial unit used to realize an RF metasurface. In the illustrated example, the RF metamaterial unit 302 is implemented using different materials in various layers. Figure 3B As shown, the illustrated unit cell design includes multiple metal layers and a multilayer glass fiber reinforced laminate (FR4 in this particular implementation). A diode control conductor 334 extends vertically through the structure to enable the application of a bias voltage to the diode, while a center conductor 311 connects the receiving antenna 304 to the transmitting antenna 305.

[0048] The first surface (the top shown here) includes a receiving antenna 304 and a PIN diode 315 integrated therein. The receiving antenna 304 includes different metal portions that can be electrically connected to each other via the PIN diode 315. The respective dimensions and shapes of the metal portions of the receiving antenna 304 and the operation of the PIN diode 315 can be used to control the resonant frequency of the antenna (refer to below). Figure 4 (To be explained in further detail). The modulation signal diode 316 is also coupled to the receiving antenna 304 to enable the input of the modulation signal and thus frequency conversion.

[0049] A ground plane 325 is implemented beneath FR4 layer 327 to isolate electromagnetic radiation between the receiving antenna and the transmitting antenna 305, which is located on the second (bottom) surface of unit 302. The ground plane 325 is connected to the transmitting antenna 305 using at least one through-hole 336. FR4 layer 328 is disposed below the ground plane 325 and is the thickest layer in the glass fiber reinforced laminate layers. Below FR4 layer 328 (and above FR4 layer 329) are multiple instances of bias lines 321 with short stubs, which can be used to apply a bias voltage to the corresponding PIN diode 315 via the corresponding diode control conductor 334 (only one is labeled here for illustration).

[0050] like Figure 3B As shown, the transmitting antenna 305 is implemented on the bottom surface of unit 302. In this non-limiting example, the transmitting antenna includes three distinct metal sections in which two mode-switching PIN diodes 317 are integrated. Control of the PIN diodes 317 can be used to select one of several operating modes for unit 302, thereby selecting the RF metasurface that is part of it. See below for reference. Figure 5 Additional discussion is provided regarding the structure and operation of the transmitting antenna 305 in transmitting signals and the operation of the PIN diode 317 in mode selection.

[0051] Figure 4 This is a top view of an example of a receiving antenna for an RF metamaterial unit. The receiving antenna 404 can be referenced above. Figure 3A and Figure 3B The example RF metamaterial unit 302 discussed is implemented. The shape and size of the metal portions 431, 432, and 433, as well as the operation of the PIN diode 415, can be used to control the resonant frequency of the receiving antenna 404 and the mixing operation. This mixing operation can be controlled using a modulation signal to generate a second signal for transmission at a different frequency based on the first signal received by the receiving antenna 404.

[0052] The metal portion 433 of the receiving antenna 404 can be referred to as the central metal portion, and has a first dimension W2 along a first axis and a second dimension L2 along a second axis perpendicular to the first axis. Two side metal portions (metal portion 431 and metal portion 432) form microstrip lines that can be used to control the tunability of the receiving antenna 404. Each of these microstrip lines has a dimension W1 on the first axis and a dimension L1 on the second axis. Metal portion 431 is separated from metal portion 433 by a first spacing distance S1. Metal portion 432 is separated from metal portion 433 by a second spacing distance S2 less than S1. The tunability of the receiver 404 depends on these dimensions, which will now be discussed in more detail.

[0053] The frequency tunability of the receiving antenna 404 (and its corresponding unit cells) can be achieved using PIN diodes 415. By applying a reverse bias voltage to a given PIN diode in the PIN diodes 415, the center patch (metal portion 433) of the antenna is effectively connected to a corresponding side microstrip line formed by metal portions 431 or 432 to form an H-shaped antenna structure. When a reverse bias voltage is applied to a given PIN diode in the PIN diodes 415, it can be considered to be turned on. When this occurs, the selected PIN diode 415 acts as a coupling capacitor at a specific frequency depending on the level of the reverse bias voltage applied to it. When no bias voltage is applied to it, a given PIN diode in the PIN diodes 415 can be considered to be off and thus can act as a resistor.

[0054] If only one of the PIN diodes 415 is turned on, the incident wave creates an unbalanced electric field, resulting in a non-uniform current. This causes a perturbation in the surface impedance at frequency. The H-shaped patch will couple to the other microstrip line where the diode is off, extending the effective size and lowering its resonant frequency. For example, if the PIN diode 415 coupled between metal portions 431 and 433 is turned on while the other PIN diode 415 is turned off, the H-shaped patch formed by metal portions 415 and 433 will couple to metal portion 432, thereby lowering the resonant frequency of the receiving antenna 404.

[0055] Therefore, when different PIN diodes are switched on, the frequency tunability of the receiving antenna 404 is achieved by controlling the effective dimensions of the microstrip line formed by metal portions 431 and 432 and the central metal portion 433. More simply, the resonant frequency of the receiving antenna 404 can be controlled by controlling the effective length and width of the antenna. In this way, the illustrated example implements 2-bit control to provide four different configurations to cover a specific bandwidth range. Table 1 below illustrates examples of the effective width, length, and center frequency achievable using 2-bit control in a non-limiting implementation: Table 1

[0056] To perform frequency conversion, the unit cell using the receiving antenna 404 implementation employs time as an additional degree of freedom. Specifically, the desired mixing of the received (incident) signal and the modulating signal is achieved using space-time modulation of the microstrip lines (metallic portions 431 and 432). Space-time modulation simultaneously alters the amplitude and phase of the signal within the cell by controlling a bias voltage at the modulating signal diode 416 (in this example, a grounded PIN diode) that varies in amplitude and frequency over time. An additional diode on the receiving antenna 404 mixes the incident signal with the input modulating signal. The mixing can be based on the frequency ω0 of the incident signal and the frequency ω of the modulating signal. m To generate a frequency of ω t The transmitted signal makes ω t =ω0+ω m The modulation signal can be provided by a voltage-controlled oscillator (VCO), which in some implementations can be digitally programmable and can use a power divider to provide equal modulation signal voltages to multiple cells of the RF metasurface.

[0057] Figure 5 This is a bottom view of an example RF metamaterial unit. More specifically, Figure 5 An example of a transmitting antenna 505 is illustrated. The overall dimensions of the transmitting antenna are L3 along a first axis and W3 along a second axis perpendicular to the first axis. The transmitting antenna 505 includes three distinct metal portions: an outer metal portion 511, an outer metal portion 512, and a central metal portion 513. A first PIN diode 519 is coupled between the outer metal portion 511 and the central metal portion 513. A second PIN diode 519 is coupled between the outer metal portion 512 and the central metal portion 513. These first and second PIN diodes 519 can be used for both mode switching and phase control to achieve beamforming. The shapes of the various metal portions form what are known as O-rings or O-slot resonators.

[0058] Mode switching and phase control can be achieved through the structure described above by changing the direction of the current. A symmetrical pair of PIN diodes 519 can determine the phase and operating mode by blocking / allowing the corresponding receiving antenna to capture current into the O-slot resonator. If only one of the PIN diodes 519 is turned on (e.g., forward biased), there are two current distributions in opposite directions within the outer metal portions 511 and 512. This opposite current direction indicates a phase difference between the signals radiated from one outer metal portion of the antenna and the other. This characteristic can be used for beamforming of the radiated signal. If neither of the PIN diodes 519 is turned on, only a minimal amount of current leaks, so the signal power radiated by the transmitting antenna 505 may be very small. When both PIN diodes 519 are turned off, the corresponding unit operates in reflection mode, effectively suppressing the transmission of a second signal because the radiated signal power is very small. Otherwise, when at least one of the PIN diodes 519 is turned on, the corresponding unit operates in transmission mode.

[0059] The ability to control the phase difference between signals radiated from the outer portion of the transmitting antenna 505 using the corresponding states of various diodes enables beamforming and beamdirection control in an RF metasurface comprising multiple elements. The corresponding phases of the transmitted signals can be controlled among the multiple elements such that the signals emitted from them exhibit constructive interference (e.g., amplitude addition) in the desired direction, while the phase difference can cancel out or reduce the signal amplitude in other directions. The beam size may vary depending on the implementation and may be affected by the size of individual elements and the spacing between elements.

[0060] It is further possible and conceivable that during beamforming operations, only a subset of multiple cells (compared to all cells using the RF metasurface) may be active to perform beamforming operations. This could be used in various applications such as multipath / MIMO (multiple-input multiple-output) applications, partial beamdirection and sector-based control, adaptive beamforming, etc.

[0061] Figures 6A to 6D This is a schematic diagram illustrating different possible operating modes of an example RF metamaterial unit. RF metasurfaces using units of this disclosure can operate in either reflection or emission modes. Figure 6AThe diagram illustrates operation in reflection mode. In reflection mode, the receiving antenna 604 reflects the incident signal instead of transmitting a substantial signal from the transmitting antenna 605. While some signal may be radiated from the transmitting antenna 605, the power of this signal is likely so minimal that it may be difficult or impossible for a nearby receiver to detect. By turning off the PIN diode of the transmitting antenna (e.g., not forward biasing), so that the current from the central metal portion to the outer metal portion is only a very small leakage current, reflection mode can be entered. This, in turn, significantly reduces the power of any signal that would otherwise be radiated from the transmitting antenna 605.

[0062] Figure 6B The diagram illustrates the basic launch mode. In launch mode, refer to the above text. Figure 5 In the discussion, one of the PIN diodes 619 associated with the transmitting antenna 605 is turned on, thereby allowing current to flow from the central metal portion to one of the outer metal portions. Therefore, a signal can be transmitted from the transmitting antenna at a power level sufficient to be received by a receiver within the antenna's range. It should be noted that in this mode, the receiving antenna can still reflect at least a portion of the incident signal.

[0063] Figure 6C Further illustration shows the control of the resonant frequency of the receiving antenna 604, which can occur in either reflection or transmission mode. The selective control of the resonant frequency by the PIN diode 615 enables the connection or disconnection of metal portions 631 and 632 with metal portion 633, thereby altering the effective size of the receiving antenna 604. As shown in the examples in Table 1 above, both PIN diodes of the transmitting antenna 605 can be turned off, on, or one of the two PIN diodes can be turned on to achieve the desired resonant frequency. Further control of the resonant frequency can be achieved by applying a bias voltage to the bias stub shown in Figure 3. Since the resonant frequency depends on the effective size of the receiving antenna, this disclosure envisions various implementations of the unit cell, wherein the actual size and spacing of the various antenna portions are selected according to the desired frequency response.

[0064] Figure 6D The diagram further illustrates operation in a transmit mode with frequency switching. In this mode, a modulated signal is input to the receiving antenna and combined with the incident signal to generate the transmitted signal. The frequency of the transmitted signal depends on the corresponding frequencies of the modulated signal and the incident signal. Control of the frequency of the second signal can also be based on the states of various diodes in the unit cell and the amplitudes of various bias voltages that may be applied.

[0065] Figure 7This is a perspective view illustrating an example system including an RF metamaterial and a modulation signal generator. In the illustrated example, the RF metasurface 701 includes a plurality of elements 702. In this non-limiting implementation, the elements are arranged in a grid, but other arrangements are possible and contemplated in this disclosure.

[0066] The illustrated system also includes a modulation signal generator circuit 735 and a mode control circuit 740. The modulation signal generator circuit 735 may include, for example, a numerically controlled VCO, configured to distribute a modulated signal to each (or selected) unit in the unit 702 during operation. The modulation signal generator circuit 735 can control the frequency and amplitude of the generated modulated signal so that it is received by each unit 702 at the desired power and frequency.

[0067] The mode control circuit 740 in the illustrated example can generate bias voltages applied to the various diodes in each cell of cell 702, which may include bias voltages provided to bias stubs. In a given operating configuration, the mode control circuit 740 can apply the same voltage to all cells 702, while in another operating configuration, different voltages can be applied to selected cells. The mode control circuit 740 can also select operating modes (such as reflection and transmission modes discussed above) for the RF metasurface 701 and its cells 702, and select resonant frequencies for the receiving antennas of the various cells 702.

[0068] It should be noted that in some implementations, the modulation signal generator 735 and the mode control circuit 740 may be included in the same unit, for example, within a computer system communicatively coupled to the RF metasurface 701.

[0069] Figures 8A to 8C This is an illustration of an example use case of an RF metamaterial system based on this disclosure. Figure 8A In this example, an instance of the RF metasurface 801 is used for coverage extension to provide wireless coverage from wireless access point AP1 to user 1, where user 1's device might otherwise be blocked or restricted from receiving coverage from that access point. In this example, a different user (user 2) is receiving coverage from a second access point AP2. To avoid interference in the same frequency band, the RF metasurface 801 can perform frequency conversion according to this disclosure, allowing user 1 and user 2's devices to operate using different frequency bands. This can reduce or eliminate interference near user 1 and user 2's devices while enabling both to operate with good wireless connectivity.

[0070] exist Figure 8B In this example, an RF metasurface 801 is used for spectrum sensing applications. The narrowband sensor at the access point transmits a frequency of f to the RF metasurface 801. nThe signal, RF metasurface 801, then (using frequency conversion capability) generates a frequency of f1-f k Multiple signals. In this scenario, another access point uses frequency f2. Therefore, using spectrum sensing, the narrowband sensor can determine that the frequency band corresponding to f2 is occupied, while that corresponding to f1 and f3-f k The corresponding frequency band is not occupied. When a new device enters the area, it can be allocated one of the unoccupied frequency bands.

[0071] exist Figure 8C In this example, the system tracks the user's movement. A single access point AP1 transmits signals to RF metasurfaces 801A and 801B. In this example, RF metasurface 801A operates in transmit mode, thus relaying the signal to a mobile user moving through the area. The frequency of the signal relayed from RF metasurface 801A can be different from the frequency of the signal transmitted from access point AP1. In this example, RF metasurface 801B operates in reflect mode. The mobile user's device can also respond to the signal, relaying information back to the access point. As the user moves closer to RF metasurface 801B, the signal's time-of-flight changes. Using information about this change in time-of-flight, access point AP1 can track the movement of the mobile user's device through the area.

[0072] As used herein, the term “or” can be interpreted as inclusive or exclusive. Furthermore, descriptions of resources, operations, or structures in the singular form should not be construed as excluding the plural form. Unless otherwise expressly stated or clearly determined from the context, conditional language (such as “can,” “could,” “might,” or “may”) is generally intended to convey that certain examples include certain features, elements, and / or steps while others do not.

[0073] Unless otherwise expressly stated, the terms and phrases used in this document, and their variations thereof, should be interpreted as open-ended rather than restrictive. Adjectives such as “regular,” “traditional,” “normal,” “standard,” “known,” and similar terms should not be interpreted as limiting the described items to a given time period or to items available at a given time, but should be understood to encompass regular, traditional, normal, or standard techniques that may be available or known at any time now or in the future. In some instances, the presence of extended words and phrases (such as “one or more,” “at least,” “but not limited to,” or other similar phrases) should not be interpreted as implying a narrower meaning or requirement in instances where such extended phrases may not exist.

Claims

1. An apparatus comprising: Radio frequency (RF) metasurface elements, wherein the RF metasurface elements include: The first antenna on the first surface; A second antenna on a second surface, the second surface facing a direction opposite to that of the first surface; and Modulation signal input; The RF metasurface element is configured as follows: At the first antenna, a first electromagnetic signal having a first frequency is received; At the modulation signal input, a modulation signal is received; and A second electromagnetic signal corresponding to the first electromagnetic signal is emitted from the second antenna. The second electromagnetic signal has a second frequency that is different from the first frequency and depends on the first frequency and the frequency of the modulation signal.

2. The apparatus of claim 1, wherein the first antenna comprises a first metal portion, a second metal portion, and a third metal portion, wherein the first metal portion and the second metal portion are selectively connectable to the third metal portion.

3. The apparatus of claim 2, further comprising a first PIN diode coupled between the first metal portion and the third metal portion, and a second PIN diode coupled between the second metal portion and the third metal portion, wherein the first PIN diode and the second PIN diode are configured to connect the first metal portion and the second metal portion to the third metal portion, respectively, in response to the application of a reverse bias voltage.

4. The apparatus of claim 3, wherein the resonant frequency of the first antenna is tunable based on which of the first PIN diode and the second PIN diode has a bias voltage applied thereto.

5. The apparatus of claim 3, wherein the second antenna comprises a central metal portion, a first outer metal portion, and a second outer metal portion, wherein the first outer metal portion and the second outer metal portion are coupled to the central metal portion via a third PIN diode and a fourth PIN diode, respectively.

6. The apparatus of claim 5, wherein the RF metasurface element is configured to transmit the second electromagnetic signal when operating in a transmission mode, wherein, When operating in the transmit mode, at least one of the third PIN diode and the fourth PIN diode is forward biased, and the RF metasurface is also configured to operate in a reflection mode in which neither the third PIN diode nor the fourth PIN diode is forward biased, and in which, when operating in the reflection mode, the second electromagnetic signal is prohibited from being transmitted from the second antenna.

7. The apparatus of claim 5, wherein the RF metasurface element is tunable relative to the first frequency and the second frequency, depending on the respective states of the first PIN diode, the second PIN diode, the third PIN diode, and the fourth PIN diode.

8. The apparatus of claim 2, wherein the RF metasurface element further comprises an interconnect via coupled between the third metal portion and the second antenna.

9. The apparatus of claim 1, wherein the RF metasurface element further comprises a modulation signal diode coupled between the modulation signal input and the first antenna.

10. The apparatus of claim 1, wherein the RF metasurface element further comprises a ground plane and a multilayer glass fiber reinforced laminate disposed between the first antenna and the second antenna.

11. A method comprising: At one of the multiple elements of the RF metasurface, information encoded in a first signal is received, wherein the first signal is a radio frequency (RF) signal having a first frequency; The first signal is modulated using a modulation signal received by one of the plurality of elements to generate a second signal having a second frequency different from the first frequency, wherein the second signal is an RF signal encoding the information; as well as The information is transmitted from one of the plurality of elements using the second signal.

12. The method of claim 11, further comprising receiving the first signal at a first antenna implemented on a first surface of one of the plurality of elements, and transmitting the second signal from a second antenna on a second surface of the one of the plurality of elements, wherein the second signal is opposite to the first surface.

13. The method of claim 12, further comprising: The first PIN diode and the second PIN diode of one of the plurality of elements are used to tune the first resonant frequency associated with the first antenna; as well as The third PIN diode and the fourth PIN diode of one of the plurality of elements are used to tune the second resonant frequency associated with the second antenna.

14. The method of claim 13, further comprising: A beam comprising the second signal is emitted from at least a subset of the plurality of elements; as well as The beam is controlled using PIN diodes of at least a subset of the plurality of elements.

15. The method of claim 11, further comprising: Operating one of the plurality of elements in a transmission mode, wherein operating in the transmission mode includes transmitting the second signal from the one of the plurality of elements; as well as Operating one of the plurality of elements in a reflection mode, wherein operating in the reflection mode includes disabling the transmission of the second signal from the one of the plurality of elements.

16. A system comprising: The signal generation circuit is configured to generate a modulated signal; as well as A radio frequency (RF) metasurface includes a plurality of elements, wherein an element among the plurality of elements includes a modulation signal input coupled to receive the modulation signal, and wherein a given element among the plurality of elements includes: The first antenna on the first surface; and A second antenna is on a second surface, the second surface facing a direction opposite to that of the first surface; The RF metasurface is configured to operate in transmit mode as follows: At the first antenna of one of the plurality of elements, a first RF signal having a first frequency is received; and A second RF signal having a second frequency different from the first frequency is transmitted from the second antenna of one of the plurality of elements, wherein the second frequency depends on the first frequency and the frequency of the modulation signal.

17. The system of claim 16, wherein the element among the plurality of elements comprises: The first PIN diode and the second PIN diode associated with the first antenna; as well as The third PIN diode and the fourth PIN diode associated with the second antenna; The corresponding resonant frequencies of the first antenna and the second antenna can be adjusted using the first PIN diode, the second PIN diode, the third PIN diode, and the fourth PIN diode.

18. The system of claim 17, wherein the RF metasurface is further configured to operate in a reflective mode based on the bias of the third PIN diode and the fourth PIN diode of the plurality of elements, wherein, During operation in the reflection mode, the second antenna of one of the plurality of elements is prohibited from transmitting the second RF signal.

19. The system of claim 17, wherein the RF metasurface is configured to manipulate the beam of the second RF signal based on the respective states of the first PIN diode, the second PIN diode, the third PIN diode, and the fourth PIN diode of the plurality of elements.

20. The system of claim 16, wherein the given element of the plurality of elements further comprises a conductor coupled between the first antenna and the second antenna.

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