Discrete phase switchable interconnection reconfigurable intelligent surface unit structure based on tree connection

Abstract

The invention discloses a discrete phase switchable interconnection reconfigurable intelligent surface unit structure based on tree connection. The unit structure comprises a plurality of radio frequency units and interconnection links, each radio frequency unit is provided with a port main line, the port main line is provided with at least two reflection taps used for grounding in the electromagnetic wave transmission direction, the interconnection links are connected with the radio frequency units to form a tree connection topology, and each interconnection link comprises at least two transmission branches with different electrical lengths. Preferably, the number of the radio frequency units is three, the radio frequency units are connected step by step through two interconnection links, radio frequency switches are arranged at the two ends of each interconnection link, the radio frequency switches and link switches are switched synchronously, each reflection tap comprises a control switch and a direct current bias network, and the single-port main line only allows one tap to be conducted at the same moment. According to the method, the regulation degree of freedom and the topology complexity are effectively balanced, the non-diagonal scattering capability is enhanced, the scale of the discrete state is moderate, engineering screening and calibration are facilitated, the interconnection implementation cost and the loss risk are greatly reduced, and good engineering implementation friendliness is achieved.

Description

Technical Field

[0001] This invention relates to the field of wireless communication and electromagnetic wave manipulation technology. More specifically, this invention relates to a tree-connected discrete phase switchable interconnect reconfigurable smart surface unit structure. Background Technology

[0002] Reconfigurable Intelligent Surface (RIS) is an important research direction in the fields of wireless communication and electromagnetic wave manipulation. Its radio frequency interconnect network and discrete reconfigurable impedance implementation design directly determine its electromagnetic manipulation capability. Reconfigurable intelligent surfaces with off-diagonal scattering capability have become the focus of research in this field because they can improve the degree of freedom of manipulation. The key to realizing such reconfigurable intelligent surfaces lies in designing a reasonable unit interconnect topology to achieve controllable coupling between ports and joint phase manipulation.

[0003] The mainstream implementation of reconfigurable smart surfaces currently involves independent control of individual reflective units. Each reflective unit changes its reflection phase through switchable or tunable loads, without interconnection between units. This structure struggles to achieve off-diagonal scattering capabilities, significantly limiting the degree of freedom for joint amplitude and phase control of incident electromagnetic waves. To improve the degree of freedom, related research proposes introducing radio frequency (RF) interconnects between multiple reconfigurable smart surface units, enabling the system's equivalent scattering matrix to have off-diagonal terms, thus achieving off-diagonal scattering control. Existing interconnection schemes mainly fall into two categories: one is pairwise grouping (NG=2) interconnection, which is the simplest structure but only achieves limited degree of freedom and cannot meet complex electromagnetic control requirements. The other is fully pairwise interconnection within a group (NG=4), which achieves the highest degree of freedom, but its topology and control logic are extremely complex, significantly increasing the number of RF switches and bias circuits required, resulting in significant signal insertion loss and parasitic coupling accumulation, and high engineering implementation costs.

[0004] Therefore, in practical engineering applications, there is an urgent need for a compromise RIS interconnect unit structure to solve the problems of existing technologies, such as the inability to introduce off-diagonal scattering capability with a limited number of interconnect links, the difficulty in balancing the degree of freedom of control and topological complexity, the inability to jointly control the local reflection phase and the interconnect coupling phase in a discrete manner, as well as the high cost, high loss risk, and high wiring and bias complexity of interconnect implementation. Summary of the Invention

[0005] Based on existing technology, the objective of this invention is to provide a tree-connected discrete phase switchable interconnect reconfigurable smart surface unit structure, which can effectively balance the complexity and control performance of the reconfigurable smart surface unit structure, take into account the operability of discrete states and the convenience of engineering implementation, and significantly reduce the implementation cost and loss risk of the interconnect structure.

[0006] A first aspect of the present invention provides a tree-connected discrete phase switchable interconnect reconfigurable smart surface unit structure, comprising: Multiple radio frequency (RF) units, each RF unit including a port mainline, the port mainline having at least two grounding reflective taps along the electromagnetic wave propagation direction; and Interconnect links are configured to connect the plurality of radio frequency units to form a tree connection topology, the tree connection topology being constructed as a closed-loop hierarchical interconnect topology, wherein each of the interconnect links includes at least two transmission branches of different electrical lengths.

[0007] Furthermore, the radio frequency unit includes a first to a third radio frequency unit, and the interconnection link includes a first interconnection link connecting the first radio frequency unit and the second radio frequency unit, and a second interconnection link connecting the second radio frequency unit and the third radio frequency unit.

[0008] Furthermore, the first to third radio frequency units each include corresponding first to third port mainlines, wherein: The first port mainline has a first connection point, the second port mainline has a second connection point and a third connection point, and the third port mainline has a fourth connection point.

[0009] Furthermore, the first interconnecting link connects the first connection point and the second connection point, and the second interconnecting link connects the third connection point and the fourth connection point.

[0010] Furthermore, each of the first interconnection link and the second interconnection link includes a short electrical length branch and a long electrical length branch, which are configured to correspond to different discrete transmission phases through differences in electrical length.

[0011] Furthermore, the unit structure also includes: A first radio frequency switch, the common terminal of which is connected to a first connection point, and the throw terminal of which is connected to the short electrical length branch and the long electrical length branch of the first interconnection link respectively; The second radio frequency switch has its common terminal connected to the second connection point, and its throw terminal connected to the short electrical length branch and the long electrical length branch of the first interconnection link, respectively. A third radio frequency switch, its common terminal connected to a third connection point, and its throw terminal connected to the short electrical length branch and the long electrical length branch of the second interconnection link, respectively; and The fourth radio frequency switch has its common terminal connected to the fourth connection point, and its throw terminal connected to the short electrical length branch and the long electrical length branch of the second interconnection link, respectively.

[0012] Furthermore, the first RF switch and the second RF switch are switched synchronously via a first control signal, and the third RF switch and the fourth RF switch are switched synchronously via a second control signal.

[0013] Furthermore, the reflective tap includes: A control switch configured to control the grounding of the reflective tap; and A DC bias network is configured to introduce a DC bias voltage to the control switch to achieve on / off control of the control switch and to block the leakage of radio frequency signals to the bias line via the reflection tap.

[0014] Furthermore, for any port mainline, only one control switch corresponding to the reflection tap is allowed to be in the ON state at any given time.

[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) The RIS unit structure provided by the present invention has fewer interconnect links than the full interconnect structure within the group and more than the pair-group interconnect structure. It can achieve a better balance between the degree of freedom of regulation and topological complexity, the risk of signal insertion loss and the scale of control. It not only breaks through the limitation of insufficient degree of freedom of regulation of the pair-group interconnect structure, but also avoids the problem of overly complex topology and control of the full interconnect structure within the group.

[0017] (2) The present invention enables controllable coupling between the ports of the radio frequency unit through the combined effect of tree connection interconnection topology and port local discrete reflection phase, effectively enhancing the off-diagonal scattering capability of the reconfigurable smart surface, breaking through the limitation that the traditional unit independent control structure can only achieve diagonal scattering, and significantly improving the overall control freedom of the reconfigurable smart surface.

[0018] (3) The discrete state scale design of the present invention is moderate, which can provide a richer joint amplitude and phase state compared with the paired group interconnection structure. At the same time, it will not generate an excessive control burden due to the large state space. It is convenient to conduct offline screening and experimental calibration of all discrete states, and can quickly screen out the state set that is suitable for system operation, reducing the control difficulty at the system level.

[0019] (4) The present invention significantly reduces the number of interconnect links, correspondingly reduces the number of RF switches used, reduces the need for bias line routing, alleviates the problem of wiring congestion, effectively reduces the risk of parasitic coupling, reduces signal loss during transmission, and the overall structure is more suitable for prototype verification and large-scale implementation, with good engineering implementation friendliness.

[0020] (5) The present invention realizes the joint control of the local reflection phase of the port and the interconnection coupling phase between the ports in a discrete manner. This control method is compatible with the technical requirements of hardware implementation, and does not require complex real-time control logic. It not only ensures the accuracy and repeatability of phase control, but also facilitates the enumeration and calibration of the overall phase control state, thereby improving the practical application value of the reconfigurable smart surface.

[0021] In summary, this invention, through core techniques such as tree-connected topology design and discrete phase joint control, effectively balances structural complexity and control performance while enhancing the off-diagonal scattering capability and increasing the degrees of freedom in control of reconfigurable smart surfaces. It also considers the operability of discrete states and the ease of engineering implementation, significantly reducing the implementation cost and loss risk of interconnect structures. This invention can be widely applied in the fields of wireless communication and electromagnetic wave control technology, especially suitable for application scenarios in next-generation wireless communication systems with practical requirements for electromagnetic wave control degrees of freedom and control precision. It can serve as the core unit structure of reconfigurable smart surfaces, adapting to the electromagnetic wave control needs of different frequency bands such as microwaves and millimeter waves. It provides a practical hardware implementation solution for applications such as intelligent electromagnetic environment construction, communication signal enhancement, and beamforming, exhibiting good scenario adaptability and technical feasibility. Attached Figure Description

[0022] 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.

[0023] Figure 1 A schematic diagram of a RIS unit structure according to one embodiment of the present invention is shown.

[0024] Figure 2 A schematic diagram of the structure of the radio frequency unit in one embodiment of the present invention is shown.

[0025] Figure 3 A schematic diagram of the interconnection link structure is shown in one embodiment of the present invention.

[0026] Figure 4 A schematic diagram of the configuration of the radio frequency switch in one embodiment of the present invention is shown.

[0027] 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 111 port mainline 111-1 First Port Mainline 111-2 Second Port Mainline 111-3 Third Port Mainline 112 Reflective Tap 113 Connection Point 113-1 First Connection Point 113-2 Second Connection Point 113-3 Third Connection Point 113-4 Fourth Connection Point 120 interconnect links 120-1 First Interconnection Link 120-2 Second Interconnect Link 121 Transmission Branch 121-1 Short electrical length branch 121-2 Long electrical length branch 122 Radio Frequency Switch 122-1 First Radio Frequency Switch 122-2 Second Radio Frequency Switch 122-3 Third Radio Frequency Switch 122-4 Fourth Radio Frequency 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.

[0028] In this invention, the various embodiments are merely intended to illustrate the solutions of the invention and should not be construed as limiting.

[0029] 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.

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0031] In one embodiment of the present invention, a tree-connected discrete phase switchable interconnect reconfigurable smart surface unit structure (hereinafter referred to as RIS unit structure 100) is provided, including multiple radio frequency units 110 and interconnect links 120. The interconnect links 120 connect the multiple radio frequency units 110 and form a tree connection topology. Each component works together to realize discrete switching of the local reflection phase of the port and the coupling phase between the ports, providing controllable off-diagonal scattering capability for the reconfigurable smart surface and improving the overall electromagnetic control degree of freedom.

[0032] Figure 1 A schematic diagram of a RIS unit structure according to one embodiment of the present invention is shown.

[0033] like Figure 1 As shown, in one embodiment of the present invention, the RIS unit structure 100 includes a first radio frequency (RF) unit 110-1, a second RF unit 110-2, and a third RF unit 110-3. Interconnection links 120 are correspondingly configured as the first interconnection link 120-1 and the second interconnection link 120-2. The first interconnection link 120-1 connects the first RF unit 110-1 and the second RF unit 110-2, and the second interconnection link 120-2 connects the second RF unit 110-2 and the third RF unit 110-3. This connection method enables the three RF units 110 to form a typical tree connection topology. There is no direct interconnection link between the first RF unit 110-1 and the third RF unit 110-3; their equivalent coupling requires relaying through the second RF unit 110-2. With the second RF unit 110-2 as the sole intermediate relay node, and the first and third RF units 110-1 and 110-3 as two terminal RF units, the simplest basic single-level tree connection structure is formed. In this embodiment, the number of interconnect links in the RIS unit structure 100 is 2, which is significantly smaller than the RIS unit structure with a group size of 4 (6) in the prior art, and larger than the pairwise group interconnect structure (1). Its complexity is moderate, and it can achieve a better balance between the degree of freedom of control and topological complexity, signal insertion loss risk and control scale.

[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, each RF unit 110 is configured with a corresponding port main line 111. The port main line 111 has at least two grounding reflection taps 112 along the electromagnetic wave transmission direction. The reflection taps 112 provide the hardware basis for the local discrete reflection phase adjustment of the port. The port main line 111 serves as the core channel for RF signal transmission and also functions as the node connection point of the interconnection link 120. In one embodiment of the present invention, the reflection tap 112 includes a control switch and a DC bias network. The control switch is configured to control the grounding on / off state of the reflection tap 112. When the control switch is on, the reflection tap 112 is grounded; when the control switch is off, the reflection tap 112 is disconnected from the ground. The DC bias network includes an RF blocking inductor and a decoupling capacitor. It is configured to introduce a DC bias voltage to the control switch to achieve on / off control of the control switch, and at the same time, it can block the leakage of RF signals through the bias line, achieving effective isolation between the DC control signal and the RF signal, ensuring the effectiveness of the grounding control of the reflection tap 112 and the integrity of the RF signal transmission. In one embodiment of the present invention, the control switch is a PIN diode or an equivalent radio frequency switch device.

[0036] In one embodiment of the present invention, each reflection tap 112 is configured with a corresponding PIN diode. When the PIN diode corresponding to any reflection tap 112 is turned on, the reflection tap 112 is grounded, thereby introducing an approximate short-circuit boundary at the location of the reflection tap 112 on the corresponding port main line 111. The reflection phase at the feed point of the port main line 111 is related to the electrical length between the short-circuit point and the feed point. Different electrical lengths result in different reflection phases at the feed point. Since two reflection taps 112 at different electrical positions are pre-set on each port main line 111 along the electromagnetic wave transmission direction, two discrete local reflection phase states can be obtained at the feed point of the port main line 111 by selectively turning one of the two reflection taps 112 on or off.

[0037] In a preferred embodiment of the present invention, in order to effectively reduce the transmission loss of radio frequency signals and simplify the combinational logic of the overall discrete state, a single tap conduction constraint is set for all port main lines 111. That is, each port main line 111 is only allowed to have one PIN diode or equivalent radio frequency switch device corresponding to one of its two reflection taps 112 in the conducting state at the same time, so as to ensure that only one short-circuit boundary is formed on the same port main line 111 and avoid the superposition and interference of multiple reflection signals.

[0038] Figure 3 A schematic diagram of the interconnection link structure is shown in one embodiment of the present invention.

[0039] In one embodiment of the present invention, the first radio frequency unit 110-1, the second radio frequency unit 110-2, and the third radio frequency unit 110-3 are respectively configured with a first port main line 111-1, a second port main line 111-2, and a third port main line 111-3. The first port main line 111-1 is provided with a first connection point 113-1, the second port main line 111-2 is provided with a second connection point 113-2 and a third connection point 113-3, and the third port main line 111-3 is provided with a fourth connection point 113-4. Each connection point 113 provides a physical node for the electrical connection between the interconnection link 120 and the port main line 111, ensuring effective conduction between the interconnection link 120 and the radio frequency unit 110.

[0040] In one embodiment of the present invention, the interconnect link 120 includes a short electrical length branch 121-1 and a long electrical length branch 121-2. The short electrical length branch 121-1 and the long electrical length branch 121-2 are parallel transmission branch structures with a preset electrical length difference. When electromagnetic waves are transmitted in different branches, different phase shifts will occur, thereby forming different discrete transmission phases. This provides a basis for the controllable switching of the coupling phase between ports. By selecting one of the two branches, the two discrete states of the coupling phase of the corresponding interconnect link can be switched.

[0041] In one embodiment of the present invention, the two ends of the first interconnection link 120-1 are electrically connected to the first connection point 113-1 and the second connection point 113-2, respectively, and the two ends of the second interconnection link 120-2 are electrically connected to the third connection point 113-3 and the fourth connection point 113-4, respectively. This connection method completes the physical construction of the tree connection topology, ensuring that the first radio frequency unit 110-1, the second radio frequency unit 110-2 and the third radio frequency unit 110-3 form a hierarchically coupled structure, while avoiding direct coupling between the first radio frequency unit 110-1 and the third radio frequency unit 110-3.

[0042] Figure 4 A schematic diagram of the configuration of the radio frequency switch in one embodiment of the present invention is shown.

[0043] like Figure 4As shown, in one embodiment of the present invention, the RIS unit structure 100 is further configured with a first RF switch 122-1, a second RF switch 122-2, a third RF switch 122-3, and a fourth RF switch 122-4. The common terminal of the first RF switch 122-1 is connected to the first connection point 113-1, and its throw terminal is connected to the short electrical length branch 121-1 and the long electrical length branch 121-2 of the first interconnect link 120-1, respectively. The common terminal of the second RF switch 122-2 is connected to the second connection point 113-2, and its throw terminal is also connected to the short electrical length branch 121-1 and the long electrical length branch 121-2 of the first interconnect link 120-1, respectively. The common terminal of the third RF switch 122-3 is connected to the third connection point 113-3, and its throw terminal is connected to the short electrical length branch 121-1 and the long electrical length branch 121-2 of the second interconnection link 120-2, respectively. The common terminal of the fourth RF switch 122-4 is connected to the fourth connection point 113-4, and its throw terminal is also connected to the short electrical length branch 121-1 and the long electrical length branch 121-2 of the second interconnection link 120-2, respectively. Each RF switch 122 provides a control basis for the gating of the transmission branch 121, realizing the active control of the coupling phase of the interconnection link.

[0044] In one embodiment of the present invention, the first RF switch 122-1 and the second RF switch 122-2 are driven by a first control signal and achieve synchronous switching, while the third RF switch 122-3 and the fourth RF switch 122-4 are driven by a second control signal and achieve synchronous switching. This synchronous switching method can ensure that the conduction path of each interconnect link 120 remains consistent, avoid parasitic coupling and state uncertainty caused by the switching of single-ended RF switches 122, ensure the determinism and reproducibility of the coupling phase between ports, and effectively reduce the insertion loss of RF signals during transmission.

[0045] The working principle of the RIS unit structure 100 is further explained below.

[0046] In one embodiment of the present invention, the tree connection topology of the RIS unit structure 100 exhibits a unique phase superposition mechanism and control freedom. Specifically, there is no direct interconnection link between the first RF unit 110-1 and the third RF unit 110-3. The equivalent coupling between the two needs to be completed through the second RF unit 110-2. The equivalent coupling phase is determined by the discrete coupling phase corresponding to the short electrical length branch 121-1 or the long electrical length branch 121-2 selected by the first interconnection link 120-1 and the second interconnection link 120-2, as well as the discrete phase introduced by the conduction state of the reflection tap 112 on the port main line 111. The joint control of multiple factors forms the unique phase superposition feature of the tree connection topology, and also makes the control freedom of this structure significantly higher than that of the paired group interconnection structure with only a single interconnection link.

[0047] In a preferred embodiment of the present invention, the overall discrete state scale of the RIS unit structure 100 is formed by the coordinated combination of the coupled phase discrete state of the interconnect link 120 and the local reflection phase discrete state of the port main line 111. Specifically, the first interconnect link 120-1 and the second interconnect link 120-2 can each be selected between the short electrical length branch 121-1 and the long electrical length branch 121-2. A single interconnect link corresponds to two discrete coupled phase states, and the coupled phase states of the two interconnect links are combined to form 2 2 In the discrete form, the first port mainline 111-1, the second port mainline 111-2, and the third port mainline 111-3 all have two reflection taps 112 and follow the single-tap conduction constraint. Each port mainline corresponds to two discrete local reflection phase states, and the combination of the local reflection phase states of the three port mainlines forms 2 3 In this discrete form, based on the coordinated control of the coupled phase and the local reflection phase, the total discrete state scale of the RIS unit structure 100 is 2. 2 With 2 3 The product of these 32 discrete states is moderately designed. Compared to interconnect structures with a group size of 2, it provides a richer set of joint amplitude and phase control states, meeting diverse electromagnetic wave control needs. At the same time, it avoids the excessively large discrete state space generated by a fully interconnected structure with a group size of 4, effectively preventing an overly heavy system control burden. It allows for convenient offline screening and experimental calibration of all discrete states, facilitating the rapid selection of low-loss, high-phase-separation preferred states for direct application in practical systems, significantly reducing the system-level control complexity of reconfigurable smart surfaces. In practical applications, the scattering matrix can be obtained through offline simulation or testing of the 32 discrete states of the RIS unit structure, allowing for the selection of a set of low-loss states with good mutual coupling and phase separation as the codebook.

[0048] In a specific embodiment of the present invention, the electromagnetic control mechanism of the RIS unit structure 100 is realized by the local discrete reflection and stepwise coupling superposition of the incident electromagnetic wave. Taking the electromagnetic wave incident from the first radio frequency unit 110-1 as an example, the specific working process is as follows: When the electromagnetic wave enters the RIS unit structure 100 from the first radio frequency unit 110-1, part of the electromagnetic wave will be locally reflected at the reflection tap 112 on the first port main line 111-1 corresponding to the first radio frequency unit 110-1. The discrete reflection phase of the reflected wave is determined by the electrical position of the conducting reflection tap 112 on the first port main line 111-1. Another part of the electromagnetic wave will be coupled and transmitted to the second radio frequency unit 110-2 through the first interconnection link 120-1. The coupling phase generated in this process is determined by the short electrical length branch 121-1 or the long electrical length branch 121-2 selected by the first interconnection link 120-1. Different transmission branches form different discrete coupling phases due to differences in electrical length. The coupled electromagnetic wave entering the second radio frequency unit 110-2 will first be affected by the conduction state of the reflection tap 112 on the second port main line 111-2 corresponding to the second radio frequency unit 110-2, and superimposed with the discrete local reflection phase of the second radio frequency unit 110-2. Subsequently, the electromagnetic wave will be further coupled and transmitted to the third radio frequency unit 110-3 through the second interconnection link 120-2. The coupling phase in this process is determined by the short electrical length branch 121-1 or the long electrical length branch 121-2 selected by the second interconnection link 120-2. Thus, the equivalent coupling process from the first RF unit 110-1 to the third RF unit 110-3 reflects the unique phase modulation characteristics of the tree connection topology. That is, the link coupling phase superposition brought about by the first interconnect link 120-1 and the second interconnect link 120-2, together with the local reflection phase of the second RF unit 110-2, enables the RIS unit structure 100 to achieve rich off-diagonal scattering response with only a low number of interconnect links, effectively improving the electromagnetic control degree of freedom of the reconfigurable smart surface.

[0049] In one embodiment of the present invention, the transmission branches of the interconnection links can be extended to expand the original dual-branch structure of short electrical length branch 121-1 and long electrical length branch 121-2 into a multi-electrical length branch structure including short electrical length branch, medium electrical length branch and long electrical length branch. Each branch has a preset electrical length difference, so that each interconnection link 120 can form a multi-level discrete coupling phase. Compared with the dual-branch structure, it can achieve more precise inter-port coupling phase control and improve the electromagnetic control accuracy of the RIS unit structure 100.

[0050] In one embodiment of the present invention, a disconnected state can be added to the transmission branch selection state of the interconnection link, so that the first interconnection link 120-1 and the second interconnection link 120-2 both have three selectable states: short electrical length branch 121-1, long electrical length branch 121-2, and disconnected state. The switching of the three states is achieved by the operation of the RF switch 122. When the interconnection link is switched to the disconnected state, there is no electromagnetic coupling between the corresponding RF units. At this time, the RIS unit structure 100 can switch from the interconnection mode to the near diagonal RIS mode, which can adapt to the requirements of reconfigurable intelligent surface scattering mode in different application scenarios. This design is compatible with the original short and long branch selection control and does not require significant adjustments to the connection structure of the RF switch 122.

[0051] In one embodiment of the present invention, the reflection taps on the port main line can be expanded and modified. The original two reflection taps 112 on the port main line 111 can be expanded to three or more, with each reflection tap 112 set at a different electrical position along the electromagnetic wave transmission direction. This allows a single port main line 111 to form more discrete local reflection phases, improving the freedom of phase adjustment at the port. Alternatively, the original ground short-circuit type reflection tap 112 can be modified into a switchable impedance tap. This impedance tap can switch between resistor, inductor, and capacitor impedance forms as needed, forming diverse local reflection phases through the reflection characteristics of different impedances. Moreover, the above expansion and modification designs can all use the single tap conduction constraint to ensure the determinism and repeatability of the reflection phase at the feed point of the port main line 111.

[0052] In one embodiment of the present invention, the single-level tree connection topology of the RIS unit structure 100 can be extended into a multi-level tree structure to adapt to the deployment requirements of more radio frequency units. For example, with the second radio frequency unit 110-2 as the core root node, multiple levels of relay radio frequency units are added, and the newly added terminal radio frequency units are respectively connected to relay radio frequency units at different levels. All newly added radio frequency units are connected to the directly superior relay radio frequency unit or terminal radio frequency unit through only one interconnection link 120. There are no cross-level or same-level direct interconnection links, so that the number of interconnection links 120 increases approximately linearly with the increase of the number of radio frequency unit ports, avoiding the exponential increase in structural complexity. Moreover, the extended multi-level tree structure still follows the phase superposition mechanism of tree connection. The equivalent coupling of non-directly connected radio frequency units is realized step by step through each level of relay radio frequency unit. The coupling phase is formed by the superposition of the discrete coupling phase of each interconnection link and the local reflection phase of each relay radio frequency unit.

[0053] In one embodiment of the present invention, the RF switch 122 used in the RIS unit structure 100 can be replaced by an equivalent RF switch device such as a MEMS RF switch or a GaAs RF switch according to the frequency band and response speed requirements of the actual application scenario. The connection method and control logic of the various equivalent devices are consistent with the original RF switch 122.

[0054] In one embodiment of the present invention, the transmission line type in the system can be flexibly replaced according to the actual operating frequency band requirements of the RIS unit structure 100. The transmission line type of the port main line 111, as well as the transmission line type of the short electrical length branch 121-1 and the long electrical length branch 121-2 of the interconnection link 120, can be adaptively selected from microstrip lines, striplines, and coplanar waveguides. By adjusting the wiring specifications such as the line width, line spacing, and dielectric substrate parameters of the transmission line, the characteristic impedance matching of each component under different transmission line types can be ensured, and signal reflection and coupling distortion caused by changes in transmission line type can be avoided.

[0055] In one embodiment of the present invention, a reconfigurable smart surface array is provided. This array includes multiple RIS unit structures 100 provided in the foregoing embodiments of the present invention. The RIS unit structures 100 are repeatedly arranged as basic blocks in the array. These basic blocks are not interconnected and independently perform their own local discrete reflection phase modulation, port-to-port discrete coupling phase modulation, and off-diagonal scattering electromagnetic modulation functions. This arrangement retains the core advantage of the high degree of control freedom of a single RIS unit structure 100 while enabling intelligent reconfiguration of a wider range of incident electromagnetic waves, meeting the spatial range requirements for electromagnetic wave modulation in different application scenarios. Simultaneously, it simplifies the wiring design and system control logic of large-scale reconfigurable smart surface arrays.

[0056] 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 tree-connected discrete phase switchable interconnect reconfigurable smart surface unit structure, characterized in that, include: Multiple radio frequency units, each of the radio frequency units including a port main line, wherein the port main line is provided with at least two reflective taps for grounding along the electromagnetic wave propagation direction; as well as Interconnect links are configured to connect the plurality of radio frequency units to form a tree connection topology, the tree connection topology being constructed as a closed-loop hierarchical interconnect topology, wherein each of the interconnect 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 first to a third radio frequency unit, and the interconnection link includes a first interconnection link connecting the first radio frequency unit and the second radio frequency unit, and a second interconnection link connecting the second radio frequency unit and the third radio frequency unit.

3. The unit structure according to claim 2, characterized in that, The first to third radio frequency units each include corresponding first to third port main lines, wherein: The first port mainline has a first connection point, the second port mainline has a second connection point and a third connection point, and the third port mainline has a fourth connection point.

4. The unit structure according to claim 3, characterized in that, The first interconnect link connects the first connection point and the second connection point, and the second interconnect link connects the third connection point and the fourth connection point.

5. The unit structure according to claim 2, characterized in that, Each of the first interconnect link and the second interconnect link 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.

6. The unit structure according to any one of claims 1-5, characterized in that, The unit structure also includes: A first radio frequency switch, the common terminal of which is connected to a first connection point, and the throw terminal of which is connected to the short electrical length branch and the long electrical length branch of the first interconnection link respectively; The second radio frequency switch has its common terminal connected to the second connection point, and its throw terminal connected to the short electrical length branch and the long electrical length branch of the first interconnection link, respectively. A third radio frequency switch, its common terminal connected to a third connection point, and its throw terminal connected to the short electrical length branch and the long electrical length branch of the second interconnection link, respectively; and The fourth radio frequency switch has its common terminal connected to the fourth connection point, and its throw terminal connected to the short electrical length branch and the long electrical length branch of the second interconnection link, respectively.

7. The unit structure according to claim 6, characterized in that, The first radio frequency switch and the second radio frequency switch are switched synchronously by a first control signal, and the third radio frequency switch and the fourth radio frequency switch are switched synchronously by a second control signal.

8. The unit structure according to claim 1, characterized in that, The reflective tap includes: A control switch configured to control the grounding of the reflective tap; and A DC bias network is configured to introduce a DC bias voltage to the control switch to achieve on / off control of the control switch and to block the leakage of radio frequency signals to the bias line via the reflection tap.

9. The unit structure according to claim 7, characterized in that, For any port mainline, only one control switch corresponding to the reflection tap is allowed to be in the ON state at any given time.

10. A reconfigurable smart surface array, characterized in that, Includes the unit structure according to any one of 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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