A discrete phase-switchable, fully interconnected, reconfigurable smart surface unit structure based on group connections with a group size of 4

Abstract

This invention discloses a discrete-phase switchable fully interconnected reconfigurable smart surface (RIS) cell structure based on a group connection of size 4. The cell structure includes first to fourth radio frequency (RF) units and interconnecting links. The interconnecting links enable the four RF units to form a pairwise interconnected structure, and each interconnecting link has at least two transmission branches of different electrical lengths. Each RF unit is equipped with a port mainline, which has two ground reflection taps along the transmission direction. RF switches are located at both ends of the interconnecting links, and the RF switches at both ends of the same link are switched synchronously by the same control signal. Under the condition of a group size of 4, this invention constructs a fully interconnected RIS cell structure within a group using engineering-feasible discrete RF devices, achieving highly free energy coupling between ports, strong joint amplitude and phase modulation capability, enumerable and screenable discrete scattering states, good structural flexibility and engineering feasibility, and significantly reducing system-level control complexity.

Description

Technical Field

[0001] This invention relates to the field of wireless communication and electromagnetic wave manipulation technology. Specifically, this invention relates to a discrete phase switchable fully interconnected reconfigurable smart surface unit structure based on group connections with a group size of 4. Background Technology

[0002] Reconfigurable Intelligent Surfaces (RIS) are an important research direction in the fields of wireless communication and electromagnetic wave manipulation. They enable flexible control of electromagnetic wave propagation paths, phases, and other parameters by adjusting the reflection phase and amplitude characteristics of external control units, showing broad application prospects in next-generation wireless communication systems. The RF interconnection and impedance reconstruction structure design of RIS directly determines its electromagnetic manipulation capability. Discrete-phase switchable off-diagonal scattering RIS with grouped connections has become a research focus in this field due to its higher degree of control freedom.

[0003] Existing RIS cells mostly employ independent reflection control, with each cell adjusting its reflection phase solely through its own load. Their equivalent scattering matrix is ​​approximately diagonal, lacking controllable coupling between ports, thus limiting the joint amplitude and phase control capability of incident electromagnetic waves. To improve the degree of freedom in control, related research has proposed introducing RF interconnects between multiple reconfigurable smart surface cells, giving the system's equivalent scattering matrix off-diagonal terms and enabling off-diagonal scattering control. However, as the interconnect scale increases, the complexity of the interconnect structure, the number of RF switches used, the size of the bias network, and the insertion loss of the signal all increase rapidly, significantly increasing the difficulty of engineering implementation. For a group-wide fully interconnected structure with a group size of 4, current research only includes theoretical studies; no concrete scheme for engineering implementation of this structure has yet emerged. It is impossible to construct an effective group-wide fully interconnected reconfigurable smart surface cell structure using discrete RF devices, and it is also difficult to achieve deterministic control of the interconnect state and effective suppression of parasitic leakage while maximizing the number of interconnect links. Furthermore, it is impossible to organize the discrete state space of this structure into a finite codebook that meets the requirements of system-level applications, making it difficult to experimentally realize and verify this theoretically optimal control structure in engineering.

[0004] Therefore, there is an urgent need for a discrete phase switchable fully interconnected RIS cell structure with a group size of 4 to solve the problem that the intra-group fully interconnected RIS cell structure with a group size of 4 is difficult to implement in engineering. Summary of the Invention

[0005] Based on existing technologies, the objective of this invention is to provide a discrete phase-switchable fully interconnected RIS cell structure with a group size of 4. This structure can be constructed using engineering-featured discrete RF devices to achieve an effective intra-group fully interconnected structure, enabling highly flexible energy coupling between ports while ensuring the determinism of interconnected states and suppressing parasitic leakage. The discrete state space is organized into an enumerable, filterable, and calibrable finite codebook. While achieving maximum off-diagonal control capability, the structure is ensured to be feasible for experimental implementation and engineering verification, thus solving the problem that existing intra-group fully interconnected RIS cell structures with a group size of 4 are difficult to implement in engineering.

[0006] A first aspect of the present invention provides a discrete phase-switchable, fully interconnected, reconfigurable smart surface unit structure based on group connections of size 4, comprising: Radio frequency unit, including first to fourth radio frequency units; and An interconnecting link is configured to connect the radio frequency units such that the first to fourth radio frequency units form a structure in which they are interconnected in pairs, wherein each of the interconnecting links includes at least two transmission branches of different electrical lengths.

[0007] Furthermore, the radio frequency unit includes a reflection unit or an equivalent radio frequency port.

[0008] Furthermore, each of the radio frequency units also includes a corresponding port mainline, wherein: Each of the port mainlines is configured to have two reflective taps along the transmission direction, and the reflective taps are configured to be grounded.

[0009] Furthermore, the reflective tap includes: A control switch configured to control the grounding of the reflective tap, wherein the control switch is an radio frequency switching device; and The radio frequency blocking inductor is configured to introduce DC bias.

[0010] Furthermore, the port mainlines corresponding to the first to fourth radio frequency units have the same or similar characteristic impedances.

[0011] Furthermore, the interconnection link includes: A first interconnect link connects the first radio frequency unit and the second radio frequency unit; The second interconnection link connects the first radio frequency unit and the third radio frequency unit; A third interconnect link connects the first radio frequency unit and the fourth radio frequency unit; The fourth interconnect link connects the second radio frequency unit and the third radio frequency unit; The fifth interconnect link connects the second RF unit and the fourth RF unit; and The sixth interconnect link connects the third radio frequency unit and the fourth radio frequency unit.

[0012] Furthermore, each of the interconnecting links includes a short electrical length branch and a long electrical length branch, which are configured to correspond to different discrete transmission phases by means of differences in electrical length.

[0013] Furthermore, each of the interconnecting links is provided with radio frequency switches at both ends, wherein the common terminal of the radio frequency switch is connected to the corresponding port main line, and the throw terminal of the radio frequency switch is connected to the short electrical length branch and the long electrical length branch respectively.

[0014] Furthermore, the radio frequency switches at both ends of each interconnection link are synchronously switched between the short electrical length branch and the long electrical length branch via the same control signal.

[0015] A second aspect of the present invention provides a reconfigurable smart surface array, comprising the unit structure described in the first aspect of the present invention, wherein: The unit structures are repeatedly arranged in the array as basic blocks, and the basic blocks are not interconnected.

[0016] The present invention has at least the following beneficial effects: (1) Under the condition of a group size of 4, this invention constructs a fully interconnected RIS unit structure within the group using discrete RF devices that are feasible in engineering, thereby achieving highly free energy coupling between ports. This invention balances high controllability and engineering feasibility. Through the selection of mature RF devices, clear topology layout design, and standardized control methods, it transforms the theoretically highly free group size of 4 fully interconnected structure into a physically feasible hardware architecture, clarifying the hardware requirements, wiring requirements, and isolation design points of the structure.

[0017] (2) The RIS unit structure provided by the present invention has a strong joint amplitude and phase control capability. Through the coordinated control of the local discrete reflection phase of the port and the interconnection coupling phase between the ports, the equivalent response of each radio frequency unit is determined by its own reflection state and the coupling state of other radio frequency units. A large number of off-diagonal scattering states can be formed, breaking through the limitation of traditional reconfigurable smart surfaces that can only achieve single reflection phase control, and realizing the joint precise control of the amplitude and phase of the incident electromagnetic wave.

[0018] (3) The discrete scattering states of the present invention are enumerable and screenable. Under reasonable constraints, the discrete states of the local reflection phase of the port and the discrete states of the coupling phase of the interconnection link can be combined to form a standardized finite set of discrete states, which constitutes a discrete codebook that can be directly called. It can screen out the preferred states with low loss and high phase separation through offline simulation or experiment, eliminate invalid or low-performance states, and greatly reduce the complexity of system-level control.

[0019] (4) The present invention has good structural flexibility and scalability. Without departing from the core concept, the number of transmission branches of the interconnection link, the type of radio frequency switching device, and the number of port reflection taps can be adjusted. It can also achieve flexible switching between full interconnection and partial interconnection modes. Furthermore, the unit structure can be repeatedly arranged as a basic block in a large-scale reconfigurable smart surface array. It can adapt to application scenarios with different frequency bands, different response speeds, and different complexity requirements, which greatly enhances the practical application value of the present invention.

[0020] In summary, this invention, through core designs such as a group-size (4-group) fully interconnected topology, dual-dimensional discrete phase modulation, and dual-end synchronous gating, significantly improves the degree of freedom of control and the joint amplitude and phase modulation capability. It also solves the problems of difficult state management and engineering implementation of high-degree-of-freedom reconfigurable intelligent surface unit structures. Furthermore, it possesses advantages such as state selectability, clear structural costs, and strong scalability and adaptability, achieving a good balance between performance and engineering feasibility. This invention can be applied to various scenarios in the fields of wireless communication and electromagnetic wave modulation technology, especially suitable for scenarios in next-generation wireless communication systems with high requirements for the degree of freedom and precision of electromagnetic wave modulation. It can also serve as a performance benchmark in RIS technology development, providing a reference for the design and optimization of related structures, and possesses broad application prospects and technical reference value. Attached Figure Description

[0021] To further illustrate the advantages and other features of the various embodiments of the present invention, a more specific description of the embodiments of the present invention will be presented with reference to the accompanying drawings. It is understood that these drawings depict only typical embodiments of the invention and are therefore not intended to limit its scope. In the drawings, identical or corresponding parts will be indicated by the same or similar reference numerals for clarity.

[0022] Figure 1 A schematic diagram of the RIS unit structure in one embodiment of the present invention is shown.

[0023] Figure 2 A schematic diagram of the structure of the radio frequency unit in one embodiment of the present invention is shown.

[0024] Figure 3 A schematic diagram of the interconnection link structure is shown in one embodiment of the present invention.

[0025] List of reference numerals 100 RIS unit structure 110 Radio Frequency Unit 110-1 First Radio Frequency Unit 110-2 Second Radio Frequency Unit 110-3 Third Radio Frequency Unit 110-4 Fourth Radio Frequency Unit 111 port mainline 112 Reflective Tap 120 interconnect links 120-1 First Interconnection Link 120-2 Second Interconnect Link 120-3 Third Interconnect Link 120-4 Fourth Interconnection Link 120-5 Fifth Interconnection Link 120-6 Sixth Interconnection Link 121 Transmission Branch 121-1 Short electrical length branch 121-2 Long electrical length branch 122 Multi-throw RF switch Detailed Implementation It should be noted that the components in the various figures may be shown exaggeratedly for illustrative purposes and are not necessarily to scale. In each figure, the same reference numerals are used for components that are identical or have the same function.

[0026] In this invention, the various embodiments are merely intended to illustrate the solutions of the invention and should not be construed as limiting.

[0027] It should also be noted that, in the embodiments of the present invention, only a portion of the components or parts may be shown for clarity and simplicity. However, those skilled in the art will understand that, under the teachings of the present invention, necessary components or parts can be added as needed for specific scenarios. Furthermore, unless otherwise stated, features in different embodiments of the present invention can be combined with each other. For example, a feature in the second embodiment can replace a corresponding or functionally identical or similar feature in the first embodiment, and the resulting embodiment will also fall within the scope of disclosure or description of this application.

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0029] Figure 1 A schematic diagram of the RIS unit structure in one embodiment of the present invention is shown.

[0030] In one embodiment of the present invention, a discrete-phase switchable fully interconnected reconfigurable smart surface unit structure (hereinafter referred to as "RIS unit structure") 100 based on a group connection of group size 4 is provided. This structure includes first to fourth radio frequency (RF) units 110-1, 110-2, 110-3, and 110-4, and interconnect links 120 connecting each RF unit. The components work together to achieve the construction of a fully interconnected topology within the group and the switchable control of the discrete phase, providing hardware support for the high-degree-of-freedom off-diagonal scattering of the reconfigurable smart surface. In one embodiment of the present invention, the interconnect link 120 is the core interconnect structure connecting the first to fourth RF units and is configured to construct a fully interconnected topology in which each of the four RF units is interconnected with the others.

[0031] In one embodiment of the present invention, the interconnection link 120 includes a first interconnection link 120-1, a second interconnection link 120-2, a third interconnection link 120-3, a fourth interconnection link 120-4, a fifth interconnection link 120-5, and a sixth interconnection link 120-6.

[0032] In a specific embodiment of the present invention, the first interconnect link 120-1 connects the first radio frequency unit 110-1 and the second radio frequency unit 110-2, the second interconnect link 120-2 connects the first radio frequency unit 110-1 and the third radio frequency unit 110-3, the third interconnect link 120-3 connects the first radio frequency unit 110-1 and the fourth radio frequency unit 110-4, the fourth interconnect link 120-4 connects the second radio frequency unit 110-2 and the third radio frequency unit 110-3, the fifth interconnect link 120-5 connects the second radio frequency unit 110-2 and the fourth radio frequency unit 110-4, and the sixth interconnect link 120-6 connects the third radio frequency unit 110-3 and the fourth radio frequency unit 110-4. The six interconnect links completely cover all pairwise combinations of the four radio frequency units, realizing a topology architecture with a group size of 4 and full interconnection within the group.

[0033] In one embodiment of the present invention, the first to fourth radio frequency units 110-1 to 110-4 are the core functional units of the RIS unit structure 100, serving as the basic carrier for realizing electromagnetic wave reflection, local phase modulation, and inter-port coupling. Specifically, each radio frequency unit is a reflection unit or an equivalent radio frequency port; both are physical entities of the same functional unit or abstract forms of radio frequency networks, each possessing independent electromagnetic signal reception, reflection, and coupling capabilities, collectively forming the core block of a RIS unit structure with a group size of 4.

[0034] Figure 2 A schematic diagram of the structure of the radio frequency unit in one embodiment of the present invention is shown.

[0035] In one embodiment of the present invention, the first to fourth radio frequency units 110-1 to 110-4 are each configured with a corresponding port main line 111. The port main line 111 is the core channel for radio frequency signal transmission and undertakes three core functions: as the main propagation path of the reflected signal, it carries the bidirectional transmission of incident electromagnetic waves and reflected electromagnetic waves; as the connection node of the interconnection link 120, it realizes electrical interconnection with other radio frequency units; and as the carrier of local discrete reflection phase modulation, it provides a physical basis for the layout of reflection taps.

[0036] In one embodiment of the present invention, the port main line 111 corresponding to the first to fourth radio frequency units 110-1 to 110-4 is designed to have the same or similar characteristic impedance. For example, in a specific embodiment of the present invention, the characteristic impedance of the port main line 111 is set to 50Ω.

[0037] In one embodiment of the present invention, by unifying wiring specifications such as line width, line spacing, and dielectric substrate parameters, the electromagnetic characteristics of the first to fourth radio frequency units 110-1 to 110-4 are ensured to be consistent, avoiding signal reflection and coupling distortion caused by impedance differences, and laying the hardware foundation for uniform signal interaction of full interconnection within the group.

[0038] In one embodiment of the present invention, two reflection taps 112 are sequentially arranged on each port main line 111 along the electromagnetic wave transmission direction. The two reflection taps 112 maintain different electrical distances from the feed point of the port main line 111, and their arrangement avoids the connection node between the interconnection link 120 and the port main line 111, so as to realize the independence of local reflection phase control and inter-port coupling control, and avoid electromagnetic interference between the two.

[0039] In one embodiment of the present invention, each reflection tap 112 includes an RF switch and an RF blocking inductor, which work together to control the grounding on / off state and introduce DC bias of the reflection tap. The RF switch is connected in series between the reflection tap 112 and system ground, and is configured to control the grounding on / off state of the reflection tap 112. The RF blocking inductor is connected in series between the RF switch and the DC bias circuit, and is configured to introduce a DC bias voltage to the RF switch while blocking RF signal leakage through the bias line, thus achieving isolation between DC and RF signals.

[0040] In one specific embodiment of the present invention, the RF switching device is a PIN diode, which possesses the characteristics of high-speed switching in the RF band, low insertion loss, and high isolation, adapting to the planar integration requirements of the RIS unit structure 100. When the PIN diode receives a forward DC bias, it is in a low-impedance conducting state, and the corresponding reflection tap 112 is equivalent to an RF short-circuit termination; when the PIN diode receives a reverse DC bias or no bias, it is in a high-impedance cutoff state, and the corresponding reflection tap 112 has no significant impact on the RF signal. In other embodiments, the RF switching device can also be replaced with a MEMS RF switch, GaAs RF switch, or other equivalent devices, all of which can realize the on / off control function of the reflection tap.

[0041] In a preferred embodiment of the present invention, on the main port line 111 of each RF unit, only one RF switch device corresponding to a reflection tap 112 is allowed to be turned on at any given time. This constraint is achieved through the logic control of the DC bias circuit, which can avoid the superposition and interference of multiple reflection signals generated by two short-circuit terminals, ensure the determinism and repeatability of the reflection phase at the feed point, and at the same time minimize the insertion loss of the RF signal and improve the reflection efficiency of the RIS unit structure 100.

[0042] In one embodiment of the present invention, each interconnect link 120 includes at least two transmission branches 121, and the electrical lengths of the multiple transmission branches 121 are different. The difference in electrical length enables discrete transmission phase switching of the coupled signals between ports. The electrical length of the transmission branch is determined by the physical length, the propagation speed of electromagnetic waves in the transmission line, and the operating frequency. Branches with different electrical lengths will cause different phase shifts in the coupled signals, providing a basis for discrete phase modulation.

[0043] Figure 3 A schematic diagram of the interconnection link structure is shown in one embodiment of the present invention.

[0044] In one specific embodiment of the present invention, each interconnecting link 120 includes a short electrical length branch 121-1 and a long electrical length branch 121-2, which are transmission line structures arranged in parallel. By using a preset electrical length difference, the coupled signal generates a discrete transmission phase with significant separation when it is transmitted on the two branches, thereby meeting the precision requirements of engineering control.

[0045] In one specific embodiment of the present invention, when a signal propagates in the transmission branch 121 of the interconnect link 120, the resulting inter-port coupling phase θ s The electrical length ℓ of the transmission branch s It is determined that when the coupled signal propagates along the short electrical length branch 121-1, the coupling phase formed between the ports is θ. s =βℓ sWhen the coupled signal propagates along the long electrical branch 121-2, the coupling phase formed between the ports is θ. ℓ =βℓ ℓ Where β is the phase constant of the electromagnetic wave in the transmission line of the transmission branch, ℓ s For the electrical length of short electrical length branch 121-1, ℓ ℓ For the electrical length of the long electrical branch 121-2, in this embodiment, it is determined by adjusting the ℓ s With ℓ ℓ By making reasonable designs and selections, sufficient phase separation is achieved between the two discrete coupling phases corresponding to the short electrical length branch 121-1 and the long electrical length branch 121-2. This effectively avoids overlap or ambiguity between different coupling phases, thereby significantly enhancing the distinguishability of the coupled signals between ports in different gating states of the interconnect link 120. This ensures the accuracy and effectiveness of coupling phase control, laying the foundation for the entire RIS unit structure 100 to achieve high-degree-of-freedom discrete phase switching.

[0046] In one embodiment of the present invention, each interconnecting link 120 is provided with a multiple-throw radio frequency switch 122 at both ends. The multiple-throw radio frequency switch 122 is the core control component for enabling transmission branch selection. The common terminal of the multiple-throw radio frequency switch 122 is electrically connected to the port main line 111 of the corresponding radio frequency unit. Each throw terminal of the multiple-throw radio frequency switch 122 is connected to at least two transmission branches 121 of the interconnecting link 120 respectively. By switching the switch state, the selection of different transmission branches is realized.

[0047] In one specific embodiment of the present invention, the multi-throw radio frequency switch 122 is a single-pole double-throw radio frequency switch (SPDT), whose two throw terminals are respectively connected to the short electrical length branch 121-1 and the long electrical length branch 121-2, which can realize the fast selection and switching of the two branches and adapt to the real-time response speed requirements of discrete phase modulation.

[0048] In one embodiment of the present invention, the multiple-throw RF switches 122 at both ends of the same interconnect link 120 are driven by the same control signal to achieve synchronous switching between the short electrical length branch 121-1 and the long electrical length branch 121-2. This dual-end synchronous gating method can ensure that the conduction path of the interconnect link 120 is always consistent, avoid parasitic leakage and state uncertainty caused by single-end conduction, ensure the determinism and reproducibility of the coupling phase between ports, and effectively reduce the insertion loss of RF signals.

[0049] In one embodiment of the present invention, the high degree of freedom discrete scattering characteristics of the RIS unit structure 100 are formed by the coordinated combination of two types of control quantities: port local reflection state and port interconnection state. The core source of its high degree of freedom is the combination of intra-group full interconnection topology design and two-dimensional discrete phase modulation. The specific implementation method and principle are as follows: Each radio frequency unit of the RIS unit structure 100 corresponds to two reflection taps 112 on the port main line 111. Under the preferred constraint that only one reflection tap 112 is allowed to be turned on at any given time, a single radio frequency unit can realize two discrete local reflection phase switching. The first to fourth radio frequency units 110-1 to 110-4 can form a total of 2 4 The various combinations of local reflection states provide the basic phase modulation degrees of freedom for the RIS unit structure 100. Simultaneously, each of the six interconnect links 120 of the RIS unit structure 100 has two transmission branches: a short electrical length branch 121-1 and a long electrical length branch 121-2. Under the optimal constraint that only one transmission branch can be selected at any given time, a single interconnect link 120 can achieve two discrete coupling phase switchings, and the six interconnect links 120 can form a total of 2 6 The various interconnection state combinations provide additional degrees of freedom for coupling control in the RIS cell structure 100. Based on the above two types of control variables, under the optimal constraints of only one tap being on per port and only one branch being selected per link, a RIS cell structure 100 with a single group size of 4 can achieve 2 4 ×2 6 =1024 discrete scattering states, forming a set of discrete states with high degrees of freedom. The core source of the high degree of freedom of this structure lies in the fully interconnected topology within the group, which enables direct electrical connection between each pair of the first to fourth radio frequency units 110-1 to 110-4. The equivalent electromagnetic response of any port is no longer determined solely by the conduction state of its own reflection tap 112, but is also affected by the transmission branch selection state of the multiple interconnection links 120 connected to it, as well as the combined coupling influence of the local reflection states of the other three radio frequency units. This interaction between multiple ports and multiple links enables the equivalent scattering matrix of the RIS unit structure 100 to generate the most off-diagonal terms, breaking through the degree of freedom limitation of independent control of traditional reconfigurable smart surface units, and ultimately achieving a high degree of control freedom in the field of discrete off-diagonal scattering reconfigurable smart surfaces.

[0050] In one embodiment of the present invention, to adapt to the complexity and controllability requirements of different application scenarios, while maintaining the core structure of the present invention with a group size of 4, that is, retaining the four RF units and the supporting port main line, local reflection taps and other basic structures, it is permissible to shut down some interconnect links according to actual needs. Specifically, this can be achieved by controlling the off state of the RF switches at both ends of the interconnect links, so that some interconnect links are in a non-conductive state, thereby reducing the number of interconnect links actually in operation, reducing the number of RF switches required for the entire unit structure and the design scale of the bias network, while effectively reducing the insertion loss of RF signals, and realizing flexible switching between full interconnection mode and partial interconnection mode. This implementation only makes adaptive adjustments to the working state of the interconnect links, without changing the basic structure and core working principle of the present invention, and can meet the needs of application scenarios with moderate controllability requirements and greater emphasis on the simplicity of engineering implementation.

[0051] In one embodiment of the present invention, to further improve the control level and precision of the coupling phase between ports, without departing from the core concept of the present invention, the transmission branch 121 of the interconnection link 120 is expanded and improved. The original dual-branch structure, which only includes a short electrical length branch 121-1 and a long electrical length branch 121-2, is expanded into a multi-branch structure with three or more transmission branches. Each transmission branch is designed with a different electrical length and is set in a gradient. By setting multiple levels of different electrical distances, more discrete local reflection phase switching is achieved, thereby improving the control level of the coupling phase and meeting the requirements of higher precision electromagnetic wave coupling phase control. This improvement only expands the number of transmission branches and the electrical length levels of the interconnection link, without changing the group size of 4 of the present invention's fully interconnected topology, nor changing the core control method of dual-end synchronous gating of the interconnection link. The basic working principle of the RIS unit structure 100 remains unchanged.

[0052] In one embodiment of the present invention, to further increase the number of local reflection states at the port and improve the flexibility of local discrete reflection phase control, without departing from the core concept of the present invention, the number of reflection taps 112 on each port mainline 111 is expanded and improved. The original two reflection taps set along the transmission direction are expanded to three or more. Each reflection tap maintains a different electrical distance from the port mainline feed point, and each reflection tap is still equipped with an RF switching device and an RF blocking inductor. More discrete local reflection phase switching is achieved through multiple electrical distance levels. This improvement only expands the number of reflection taps, does not change the control principle of local discrete reflection phase at the port, and does not affect the fully interconnected topology within the group or the control logic of the coupling phase between ports.

[0053] In one embodiment of the present invention, in order to adapt the unit structure of the present invention to the different operating frequency band requirements in the fields of wireless communication and electromagnetic wave modulation technology, the specific form of the transmission line in the unit structure can be flexibly adjusted according to the actual design frequency band, and the type of radio frequency device used can be adjusted accordingly. The form of the transmission line can be adaptively selected from microstrip lines, striplines, coplanar waveguides, etc., according to the frequency band characteristics. The radio frequency device can be replaced with equivalent devices with better high-frequency characteristics, such as MEMS radio frequency switches and GaAs radio frequency switches, according to the high-frequency characteristic requirements of the frequency band. In this embodiment, only the specific form of the transmission line and the specific type of the radio frequency device are specifically adjusted. The core topology of the present invention, which has a group size of 4 and is fully interconnected within the group, the dual-dimensional discrete phase modulation design of the port local and the port inter-port, and the dual-end synchronous gating control method of the interconnection link are not changed. The core working principle of the present invention remains unchanged and can be widely adapted to electromagnetic wave modulation application scenarios of different frequency bands from microwave to millimeter wave.

[0054] In one embodiment of the present invention, a reconfigurable smart surface (RIS) array is provided, including the RIS cell structure 100 provided in the foregoing embodiments of the present invention. The RIS cell structure 100 is repeatedly arranged as a basic block in the RIS array, and the blocks are not interconnected. Each block can independently complete its own local discrete reflection phase modulation, port-to-port discrete coupling phase modulation, and off-diagonal scattering electromagnetic modulation functions. This implementation retains the core advantage of the high degree of control freedom of the cell structure with a size of 4 per block through the standardized array arrangement of the blocks, and can realize intelligent modulation of a wider range of incident electromagnetic waves. At the same time, it avoids the exponential increase in overall structural complexity and control complexity caused by the interconnection between blocks, and greatly simplifies the wiring design and system control logic of large-scale RIS arrays.

[0055] Although various embodiments of the invention have been described above, it should be understood that they are presented by way of example only and not as limitations. It will be apparent to those skilled in the art that various combinations, modifications, and alterations can be made without departing from the spirit and scope of the invention. Therefore, the breadth and scope of the invention disclosed herein should not be limited by the exemplary embodiments disclosed above, but should be defined solely by the appended claims and their equivalents.

Claims

1. A discrete phase-switchable, fully interconnected, reconfigurable smart surface unit structure based on group connections with a group size of 4, characterized in that, include: The radio frequency unit includes the first to the fourth radio frequency units; as well as An interconnecting link is configured to connect the radio frequency units such that the first to fourth radio frequency units form a structure in which they are interconnected in pairs, wherein each of the interconnecting links includes at least two transmission branches of different electrical lengths.

2. The unit structure according to claim 1, characterized in that, The radio frequency unit includes a reflection unit or an equivalent radio frequency port.

3. The unit structure according to claim 1, characterized in that, Each of the radio frequency units also includes a corresponding port mainline, wherein: Each of the port mainlines is configured to have two reflective taps along the transmission direction, and the reflective taps are configured to be grounded.

4. The unit structure according to claim 3, characterized in that, The reflective tap includes: A control switch configured to control the grounding of the reflective tap, wherein the control switch is an radio frequency switching device; and The radio frequency blocking inductor is configured to introduce DC bias.

5. The unit structure according to claim 3, characterized in that, The main ports of the first to fourth radio frequency units have the same or similar characteristic impedances.

6. The unit structure according to claim 1, characterized in that, The interconnection link includes: A first interconnect link connects the first radio frequency unit and the second radio frequency unit; The second interconnection link connects the first radio frequency unit and the third radio frequency unit; A third interconnect link connects the first radio frequency unit and the fourth radio frequency unit; The fourth interconnect link connects the second radio frequency unit and the third radio frequency unit; The fifth interconnect link connects the second RF unit and the fourth RF unit; and The sixth interconnect link connects the third radio frequency unit and the fourth radio frequency unit.

7. The unit structure according to claim 6, characterized in that, Each of the interconnecting links includes a short electrical length branch and a long electrical length branch, which are configured to correspond to different discrete transmission phases by means of differences in electrical length.

8. The unit structure according to claim 7, characterized in that, Each of the interconnecting links is provided with radio frequency switches at both ends, wherein the common terminal of the radio frequency switch is connected to the corresponding port main line, and the throw terminal of the radio frequency switch is connected to the short electrical length branch and the long electrical length branch respectively.

9. The unit structure according to claim 8, characterized in that, The radio frequency switches at both ends of each interconnection link are switched synchronously between the short electrical length branch and the long electrical length branch via the same control signal.

10. A reconfigurable smart surface array, characterized in that, Includes the unit structure described in claims 1-9, wherein: The unit structures are repeatedly arranged in the array as basic blocks, and the basic blocks are not interconnected.

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