Modularized reconfigurable intelligent surface

Abstract

There is provided a modularized reconfigurable intelligent surface. The modularized reconfigurable intelligent surface comprises tiles. The tiles are arranged in an array. Each of the tiles comprises at least one receive antenna element, at least one transmit antenna element, and an integrated circuit for setting beam weights of the at least one receive antenna element and the at least one transmit antenna element and for connecting the at least one receive antenna element to the at least one transmit antenna element. The modularized reconfigurable intelligent surface further comprises a controller. The controller is common for all tiles. The controller is configured to control how the beam weights are set in each tile.

Description

[0001]MODULARIZED RECONFIGURABLE INTELLIGENT SURFACE TECHNICAL FIELD Embodiments presented herein relate to a modularized reconfigurable intelligent surface. BACKGROUND Reconfigurable intelligent surfaces (RISs) offer an opportunity for improved wireless communication. Specifically, significant gains are envisioned to be made for millimeter wave spectrum, which is the spectrum used in fifth generation and sixth generation telecommunication systems. This spectrum has serious challenges when it comes to propagation and coverage, e.g., due to its support for very high frequency ranges in tens of GHz. The challenges are larger compared to challenges for spectrum with lower frequencies e.g., for so-called sub-6GHz frequency bands. However, RISs also have uses in other types of wireless communication systems. Usage of RIS can vary, but in general an RIS can be configured to reflect wireless signals in a controlled manner, e.g., to steer transmitted signals in a certain direction. This could for example be used to improve overall system coverage, range, and efficiency, and thus enable communication with backscatter devices. RISs are commonly also referred to as large intelligent surfaces, smart reflect-arrays, intelligent reflecting surfaces, passive intelligent mirrors, artificial radio space, and meta-surfaces. In short, the RIS at its surface comprises an antenna array having multiple (e.g., hundreds or thousands) of antenna elements, or just elements for short. In some aspects, the antenna elements are referred to as atoms. Each element can be individually configured, or controlled, to dynamically adjust the reflecting properties of the surface. The elements are provided rather to modify the properties of a signal by its reflection. The RIS commonly comprises a controller that is configured to transmit control signals to tune the properties of each element in the RIS. One example of this is disclosed in A. Araghi et al., “Reconfigurable Intelligent Surface (RIS) in the Sub-6 GHz Band: Design, Implementation, and Real-World Demonstration,” in IEEE Access, vol.10, pp.2646-2655, 2022, doi: 10.1109 / ACCESS.2022.3140278. The RIS is thus not transmitting or receiving signals by itself but instead acts as a controllable reflector of signals transmitted and received by other nodes in the system. One example of using RIS in backscatter communication for short-range and low- power Internet-of-Things (IoT) backscatter devices is proposed in M. Nemati, J. Ding and J. Choi, "Short-Range Ambient Backscatter Communication Using Reconfigurable Intelligent Surfaces," 2020 IEEE Wireless Communications and Networking Conference (WCNC), 2020, pp.1-6, doi: 10.1109 / WCNC45663.2020.9120813. According to the proposed scheme, the RIS augments the quality of the backscattered signal by compensating the phase distortion effect of multipath propagation channels. There are some of the challenges that limit the mass-scale implementations of RIS. Current implementations for phase variation of the elements in the antenna array of the RIS is based on diodes, especially PIN diodes. PIN diodes are discrete components that tend to be expensive, at least for high frequency usages. Furthermore, each and every diode needs to have its own controllable bias, which needs to be controlled. This makes the architecture of a large scale RISs very complex costly to build. Additionally, the quantization of the phase is limited with a PIN diode. The larger the size of the RIS becomes, the higher the complexity and cost will be for power and control for phase the adjustments. Hence, there is a need for improved architectures for RISs. SUMMARY An object of embodiments herein is to provide architecture for RISs that do not suffer from the above issues, or where the above issues are at least mitigated or reduced. A particular object is to provide RISs with a modularized architecture. In accordance with the herein disclosed embodiments there is presented a modularized reconfigurable intelligent surface. The modularized reconfigurable intelligent surface comprises tiles. The tiles are arranged in an array. Each of the tiles comprises at least one receive antenna element, at least one transmit antenna element, and an integrated circuit for setting beam weights of the at least one receive antenna element and the at least one transmit antenna element and for connecting the at least one receive antenna element to the at least one transmit antenna element. The modularized reconfigurable intelligent surface further comprises a controller. The controller is common for all tiles. The controller is configured to control how the beam weights are set in each tile. Advantageously, this modularized reconfigurable intelligent surface is scalable. Advantageously, this modularized reconfigurable intelligent surface has a low cost for implementation. Advantageously, this modularized reconfigurable intelligent surface can be used for both single-polarization antennas and dual-polarization antennas. Advantageously, this modularized reconfigurable intelligent surface can be composed of a plurality of identical tiles (i.e., where the transmit antenna elements and the receive antenna elements have the same location in each tile), as well as of different types of tiles (i.e., where the transmit antenna elements and the receive antenna elements do not have the same location in each tile). Advantageously, this modularized reconfigurable intelligent surface can be used for both passive reconfigurable intelligent surfaces and active reconfigurable intelligent surfaces. Advantageously, this modularized reconfigurable intelligent surface enables active probing of a signal received by the receive antenna elements. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following detailed disclosure, from the attached dependent claims as well as from the drawings. Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, module, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, module, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated. BRIEF DESCRIPTION OF THE DRAWINGS The inventive concept is now described, by way of example, with reference to the accompanying drawings, in which: Fig.1 is a schematic diagram illustrating a communication network according to embodiments; Fig.2 is a schematic diagram illustrating a tile according to ab embodiment; Fig.3 is a schematic diagram illustrating a modularized reconfigurable intelligent surface according to an embodiment; Fig.4 is a schematic diagram illustrating a substrate according to an embodiment; and Figs.5, 6, 7, and 8 are schematic diagrams illustrating a tile according to embodiments. DETAILED DESCRIPTION The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the inventive concept are shown. This inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like numbers refer to like elements throughout the description. Any step or feature illustrated by dashed lines should be regarded as optional. Fig.1 schematically illustrates a communication network 100 where a network node 110 and a user equipment 150 are communicating with each other via a reconfigurable intelligent surface 120. The reconfigurable intelligent surface 120 comprises a reflective array 140 and a controller 130. A signal as transmitted by the network node 110 can thereby be reflected by the reflective array 140 towards the user equipment 150, as illustrated by arrows 160, 170, where settings of the reflective array 140 are configured by the controller 130. As noted above there is a need for improved architectures for RISs. Assume a passive RIS with a linear antenna array where the separation between two elements is ^^ and where the wavelength for the central frequency be ^^. Then, for an incident angle ^^^^, the required phase adjustment ^^^^for an incident beam between a reference element and a neighboring element becomes: Similarly, for a reflection direction ^^^^the required phase adjustment ^^^^for a reflection beam between a reference element and a neighboring element becomes: In other words, for a two-dimensional (2D) antenna array, for the azimuth direction the total phase adjustment ^^^^to create a pencil beam becomes: 2^^ ^^^^=^^ ∙ (sin(^^^ ) + sin(^^ ))^^^ ^^Similarly, in the elevation direction, total phase adjustment ^^^^to create a pencil beam becomes: 2^^ ^^^^= ^^^^ ∙ (sin(^^^^) + sin(^^^^))The total phase adjustment to create a pencil beam for element of the 2Dantenna array with element(1,1)as the reference thus becomes: Therefore, as long as the distance from the reference element is uniform (multiplication of ^^) or at least known, phase adjustment can be added to get the correct beam link for the RIS. This means that the phase adjustment is a localized requirement. Based on this, the elements can be distributed to individual tiles where the tiles can be cascaded to form a big RIS. Assume further that the gain of each receiving antenna element is ^^^^and the gain of each transmitting antenna element is ^^^^. Assume further that these two gains areequal to each other. That is, ^^^^ = ^^^^ = ^^^^. Further, assume that the gain (or actually,the loss) of each phase shifter is ^^^^^^^^. Then, the total gain of an element in the RIS is equal to ^^^^^^^^^^^^^^^^. For a RIS with ^^ elements in total, the total gain ^^^^_^^^^^^(assuming phase aligned, and time synchronized elements) thus becomes: ^^^^_^^^^^^ = ^^^^^^^^^^^^^^^^^^ = ^^^^^^2^^^^^^^^Expressed in the decibel scale the total gain ^^^^_^^^^^^can be expressed as: ^^^^_^^^^^^ = 10log10(^^) + 2^^^^ + ^^^^^^^^Here ^^^^ = 10log10(^^^^), and ^^^^^^^^ = 10log10(^^^^^^^^).Thus, the gain is limited to the number of elements and the phase alignment between the elements. Some of the herein disclosed embodiments are based on a modularized reconfigurable intelligent surface with a passive architecture (i.e., without any additional gain elements between the receiving antenna elements and the transmitting antenna elements), whilst other embodiments are based on a modularized reconfigurable intelligent surface with an active architecture (i.e., with one or more additional gain elements, such as one or more low noise amplifiers (LNAs), between the receiving antenna elements and the transmitting antenna elements) to achieve some amplification gain for the RIS. Let the gain (loss) of each phase shifter be ^^^^ℎ, the number of transmitting antennaelements be ^^^^ and the number of receiving antenna elements be ^^^^. Thus, ^^ = ^^^^ + ^^^^. Further, let the gain (loss) of each transmitting antenna element due to splitting be Further, let the gain of each additional gain element, such as per LNA, be ^^^^^^^^. The expected total gain of the RIS (assuming phase aligned, and time synchronized elements) becomes: In the decibel scale this can be expressed as Here, ^^^^^^^^ = 10log10(^^^^^^^^), and ^^^^ℎ = 10log10(^^^^ℎ). The expected additional gain incomparison to a passive RIS for the same number of elements ^^ becomes: ^^^^_^^^^^^ = ^^^^_^^^^^^ + ^^^^ where ^^^^^^^^is the loss in case PIN diodes are used. It then follows that the expected gain due to the additional gain elements would be: That is: This equation can be further simplified considering the losses to be equal, i.e., that This equation demonstrates that the higher the number of receiving antenna elements is, the lower the additional gain needs to be. The herein disclosed modularized reconfigurable intelligent surface 120 comprises tiles 200. Reference is here made to Fig.2 in which is illustrated one such tile 200 of the modularized reconfigurable intelligent surface 120. The tiles 200 are arranged in an array 210 of antenna elements 230, 240. In Fig.2 is illustrated an example wherethe array 210 is a 3 × 3 array, and hence where the total number of antenna elementsis 9. However, this is just an example and the array 210 could also be of other sizes. In general terms, the number of antenna elements 230, 240 cold be based on a design practice which gives maximum yield, according to some design criterion, and whist still enabling a practical implementation. Further, in Fig.2 is illustrated an example where the array 210 comprises dual-polarized antenna elements 230, 240, where the dual-polarization is illustrated by there being two circles inside the antenna elements. However, the antenna elements 230, 240 could also be single-polarized. Further, although the illustrated array 210 is a 2D array, the array 210 could alternatively be a one-dimensional array. Particularly, each of the tiles 200 comprises at least one receive antenna element 230, at least one transmit antenna element 240, and an integrated circuit 220. The integrated circuit 220 is configured to set beam weights of the at least one receive antenna element 230 and the at least one transmit antenna element 240 and to connect the at least one receive antenna element 230 to the at least one transmit antenna element 240. The modularized reconfigurable intelligent surface 120 further comprises a controller 130. The controller 130 is common for all tiles 200 and is configured to control how the beam weights are set in each tile 200. Embodiments relating to further details of the modularized reconfigurable intelligent surface 120 will now be disclosed. In Fig.3 is schematically illustrated a modularized reconfigurable intelligent surface 300 composed of three cascaded tiles 310a, 310b, 310c. However, this is just an example and the modularized reconfigurable intelligent surface 300 in general is composed of at least two tiles 310a:310c, where each tile 310a:310c is configured as in Fig.2. In the examples of Fig.3 the modularized reconfigurable intelligent surface 300 further comprises a power bus 330 for providing power to the integrated circuits 220 of all the tiles 200, 310a:310c. Additionally, the modularized reconfigurable intelligent surface 300 further comprises an input / output bus 340. The integrated circuits 220 of all the tiles 310a:310c could then be connected to the controller 130, 320 via the input / output bus 340. Phase adjustments (and gain adjustments) is (are) set by the integrated circuit 220. The integrated circuit 220 can be interfaced to the controller 130, 320 via the input / output bus 340. In this way, the complexity of the bus routing and control could be reduced. Furthermore, since all the tiles 310a:310c could share a common power bus, no dedicated power bus for each tile 310a:310c is needed. This will reduce the cost and complexity of the reconfigurable intelligent surface 120, 300. By means of each integrated circuit 220 being interfaced to the controller 130, 320, each tile 310a:310c can have a shared, and thus common, knowledge of the desired beam direction and corresponding adjustments. There can be different types of distributions of transmit antenna elements 240 and receive antenna elements 230 in each tile 310a:310c. In some examples, there are as many receive antenna elements 230 as transmit antenna elements 240 in each tile 310a:310c. In some examples there are unequally many receive antenna elements 230 as transmit antenna elements 240 in each tile 310a:310c. In some embodiments, at least one of the tiles 200, 310a, 310b, 310c comprises more receive antenna elements 230 than transmit antenna elements 240. There can be different types of tiles 310a:310c in the modularized reconfigurable intelligent surface 120, 300. Fig.3 further shows an example where modularized reconfigurable intelligent surface 120, 300 comprises at least two tiles 200, 310a, 310b, 310c with mutually different number of receive antenna elements 230 and transmit antenna elements 240. In other words, there can be different types of tiles (with respect to the number of receive antenna elements 230 and transmit antenna elements 240 per tile) in the modularized reconfigurable intelligent surface 120, 300. However, in other embodiments, all tiles 310a:310c in the modularized reconfigurable intelligent surface 120, 300 are identical to each other. Reference is next made to Fig.4 which schematically illustrates a side view of a substrate 400. This substrate can be used for implementing all antenna elements 230, 240 as well as the integrated circuit 220. Therefore, the substrate 400 can be referred to as a common substrate 400. In other words, the at least one receive antenna element 230, the at least one transmit antenna element 240, and the integrated circuit 220 in each of the tiles 200, 310a, 310b, 310c, can be provided in a common substrate 400. Further, also the input / output bus 340 and the power bus 330, for example as imposed on a circuit board 420, can be implemented in the common substrate 400. All elements are coupled to the integrated circuit 220 via a ball grid array 410. Reference is next made to Fig.5 which schematically illustrates a tile 500 of a modularized reconfigurable intelligent surface according to an embodiment, showing one array 510 of the tile 500. It is thus understood that a modularized reconfigurable intelligent surface might comprises a plurality of such tiles 500, as in Fig.3. The modularized reconfigurable intelligent surface with tiles 500 is an example of a passive modularized reconfigurable intelligent surface where the signal received in each receive antenna is fed to each transmit antenna. Further, Fig.5 further schematically illustrates a controller 540 (corresponding to the controller 320), a power bus 550 (corresponding to the power bus 330), and an input / output bus 560 (corresponding to the input / output bus 340). Variable loads 530 for reflection and individual phase tuning elements 520 might be implemented in the integrated circuit 220. That is, in some embodiments, the integrated circuit 220 in each of the tiles 500 comprises individual phase tuning elements 520 for the at least one receive antenna element 230 and the at least one transmit antenna element 240. The controller 540 might control the variable loads 530 as well as individual phase tuning elements 520, as being part of a phase shifter network. The phase tuning elements 520 can be digitally controlled by the controller 130, 320. In the integrated circuit 220 the phase control can be implemented using a tunable transmission line, dedicated phase-shifters, and vector modulation phase shifters. The gain can be set with any known possible techniques. In some examples the gain setting with the variable load can be set where the corresponding reflection ^^ is where ^^^^is the load impedance and where ^^0is the system impedance (such as the impedance of the antenna elements and / or transmission lines) Further, the phase (and the gain) can be set according to a digital block based on real-time calculations or by utilizing lookup tables. An advantage of using lookup tables is the scalability when using identical tiles. When the required phase offset is communicated by the controller 540 or otherwise made known to the integrated circuit 220, the tiles can be phase aligned, where the phase offset (and gain) for the elements in each tile can be set using corresponding entries from the lookup table such that there is a linear offset in reference to other tiles. In an active modularized reconfigurable intelligent surface, the signal received in each receive antenna is fed to each transmit antenna via gain elements, for example as provided in a signal amplification stage. An example of a tile 600 of such an active modularized reconfigurable intelligent surface is illustrated in Fig.6, showing an array 610 of such a tile 600. The array 610 comprises four receive antenna elements (marked by “Rx”) and twelve transmit antenna elements (marked by “Tx”). It is understood that a modularized reconfigurable intelligent surface might comprises a plurality of such tiles 600, as in Fig.3. In Fig.6 the controller, the power bus, and the input / output bus have been intentionally left out to avoid clutter in the figure. Further, in Fig.6, each of the at least one receive antenna element in a given tile 600 is coupled to each of the at least one transmit antenna element in this given tile 600 via a phase shifter network, a power combiner network, a power splitter network, and a signal amplification stage 640. The signals as received at the receive antenna elements are combined in a signal combiner 620 before being fed to the signal amplification stage 640 and split in a signal splitter 630 before being fed to the transmit antenna elements. Hence, Fig.6 shows an example were a network of phase control and power combiner / splitter help to have an amplification stage between the receiving and transmitting side. Hence, for each of the tiles 600 that comprise at least two transmit antenna elements, the signal amplification stage 640 comprises a power splitter network 630 for splitting an output of the signal amplification stage 640 to each of the at least two transmit antenna elements. The phase shifters at the receiving sides help to align the receiving signal at the receive antenna elements to have constructively interfering signal at the input of the signal amplification stage 640. The phase shifters for the transmit antenna elements are set create the beam to the transmitting direction. Further, phase shifters at the receiving sides might be used to help to align the receiving signal at the receive antenna elements to have constructively interfering signal at the input. The phase shifters for the transmit antenna elements can be set to create a beam in the transmitting direction. That is, for each of the tiles 600 that comprises at least two receive antenna elements and at least two transmit antenna elements, the phase tuning elements of the at least two receive antenna elements are configured to align a signal received in the at least two receive antenna elements. The phase tuning elements of the at least two transmit antenna elements are configured to beamform a signal transmitted in the at least two transmit antenna elements. Another example of a tile 700 of an active modularized reconfigurable intelligent surface is illustrated in Fig.7. The array 710 comprises one receive antenna element (marked by “Rx”) and eight transmit antenna elements (marked by “Tx”). It is understood that a modularized reconfigurable intelligent surface might comprises a plurality of such tiles 700, as in Fig.3. In Fig.7 the controller, the power bus, and the input / output bus have been intentionally left out to avoid clutter in the figure. The active modularized reconfigurable intelligent surface 700 is an example of a modularized reconfigurable intelligent surface configured for dual-polarization. Therefore, the signal amplification stage comprises one signal amplifier 720, 730 for each polarization. Further, the signal amplification stage comprises one power splitter network 740, 750 for each polarization for splitting an output of the signal amplification stage to each of the at least two transmit antenna elements. That is, when the modularized reconfigurable intelligent surface is configured for dual polarization, there could be one power splitter network 740, 750 per polarization. In some examples, such as for the tile 800 illustrated in Fig.8, at least one of the tiles 800 in the modularized reconfigurable intelligent surface has measurement capabilities for at least on antenna element. The array 810 comprises eight receive antenna elements (marked by “Rx”) and one transmit antenna element (marked by “Tx”). Each of the receive antenna elements are coupled to the transmit antenna element in via a phase shifter network and a power combiner network. Further, Fig.8 further schematically illustrates a controller 870 (corresponding to the controller 320), a power bus 890 (corresponding to the power bus 330), and an input / output bus 880 (corresponding to the input / output bus 340). In some embodiments, at least one of the tiles 800 comprises a measurement probe 850. The measurement probe 850 is generally coupled to at least one of the receive antenna elements 820. This antenna element could either be dedicated for measurements, or be coupled to the transmitter antenna elements. That is, for each of the tiles 800 that comprise at least two receive antenna elements 230, the receive antenna element 230 that the measurement probe 850 is coupled to is either just coupled to the measurement probe 850 or is also coupled to the at least one transmit antenna element. In the example of Fig.8, the measurement probe 850 is coupled to all the receive antenna element 820 In order to have probing capabilities to achieve maximum intelligent at least one full receiver is needed per tile 800. In Fig.8 one receive antenna element 820 is directly connect to a digital receiver with corresponding analog processing and down conversion. A filter 830 can be designed to limit the signal bandwidth of the received signal, to minimize coupling effect between transmitting and receive antenna elements, and to suppress unwanted signal and corresponding intermodulation. The probing can be used for the controller to obtain phase and amplitude information of the received signal. Amplifiers 840a, 840b (and a single phase shifter) are provided to amplify (and phase shift) the signal of the received signal so as to facilitate digital signal processing. Converter 860 is configured to convert the received signal to digital domain for further digital signal processing. The tile 800 otherwise comprises the same elements as the tile 500. However, the tile 800 could likewise comprise the same elements as any of the tiles 600, 700. The inventive concept has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended patent claims.

Claims

CLAIMS 1. A modularized reconfigurable intelligent surface (120, 300), comprising: tiles (200, 310a, 310b, 310c, 500, 600, 700, 800), wherein the tiles (200, 310a, 310b, 310c, 500, 600, 700, 800) are arranged in an array (210, 510, 610, 710, 810), and wherein each of the tiles (200, 310a, 310b, 310c, 500, 600, 700, 800) comprises at least one receive antenna element (230), at least one transmit antenna element (240), and an integrated circuit (220) for setting beam weights of the at least one receive antenna element (230) and the at least one transmit antenna element (240) and for connecting the at least one receive antenna element (230) to the at least one transmit antenna element (240); and a controller (130, 320), wherein the controller (130, 320) is common for all tiles (200, 310a, 310b, 310c, 500, 600, 700, 800) and configured to control how the beam weights are set in each tile (200, 310a, 310b, 310c, 500, 600, 700, 800).

2. The modularized reconfigurable intelligent surface (120, 300) according to claim 1, wherein the modularized reconfigurable intelligent surface (120, 300) further comprises: a power bus (330) for providing power to the integrated circuits (220) of all the tiles (200, 310a, 310b, 310c, 500, 600, 700, 800).

3. The modularized reconfigurable intelligent surface (120, 300) according to claim 1 or 2, wherein the modularized reconfigurable intelligent surface (120, 300) further comprises: an input / output bus (340), wherein the integrated circuits (220) of all the tiles (200, 310a, 310b, 310c, 500, 600, 700, 800) are connected to the controller (130, 320) via the input / output bus (340).

4. The modularized reconfigurable intelligent surface (120, 300) according to any preceding claim, wherein the integrated circuit (220) in each of the tiles (200, 310a, 310b, 310c, 500, 600, 700, 800) comprises individual phase tuning elements (520) for the at least one receive antenna element (230) and the at least one transmit antenna element (240).

5. The modularized reconfigurable intelligent surface (120, 300) according to claim 4, wherein the phase tuning elements (520) are digitally controlled by the controller (130, 320).

6. The modularized reconfigurable intelligent surface (120, 300) according to claim 4 or 5, wherein for each of the tiles (200, 310a, 310b, 310c, 500, 600, 700, 800) that comprises at least two receive antenna elements (230) and at least two transmit antenna elements (240), the phase tuning elements (520) of the at least two receive antenna elements (230) are configured to align a signal received in the at least two receive antenna elements (230), and wherein the phase tuning elements (520) of the at least two transmit antenna elements (240) are configured to beamform a signal transmitted in the at least two transmit antenna elements (240).

7. The modularized reconfigurable intelligent surface (120, 300) according to any preceding claim, wherein the at least one receive antenna element (230), the at least one transmit antenna element (240), and the integrated circuit (220) in each of the tiles (200, 310a, 310b, 310c, 500, 600, 700, 800) are provided in a common substrate (400).

8. The modularized reconfigurable intelligent surface (120, 300) according to any preceding claim, wherein each of the at least one receive antenna element (230) in a given tile (200, 310a, 310b, 310c, 500, 600, 700, 800) is coupled to each of the at least one transmit antenna element (240) in said given tile (200, 310a, 310b, 310c, 500, 600, 700, 800).

9. The modularized reconfigurable intelligent surface (120, 300) according to any preceding claim, wherein each of the at least one receive antenna element (230) in said given tile (200, 310a, 310b, 310c, 500, 600, 700, 800) is coupled to each of the at least one transmit antenna element (240) in said given tile (200, 310a, 310b, 310c, 500, 600, 700, 800) via a signal amplification stage (640, 720, 730).

10. The modularized reconfigurable intelligent surface (120, 300) according to claim 9, wherein for each of the tiles (200, 310a, 310b, 310c, 500, 600, 700, 800) that comprise at least two transmit antenna elements (240), the signal amplification stage (640, 720, 730) comprises a power splitter network (630, 740, 750) for splitting anoutput of the signal amplification stage (640, 720, 730) to each of the at least two transmit antenna elements (240).

11. The modularized reconfigurable intelligent surface (120, 300) according to claim 10, wherein the modularized reconfigurable intelligent surface (120, 300) is configured for dual polarization, and wherein there is one power splitter network (630, 740, 750) per polarization.

12. The modularized reconfigurable intelligent surface (120, 300) according to any preceding claim, wherein at least one of the tiles (200, 310a, 310b, 310c, 500, 600, 700, 800) comprises a measurement probe (850), wherein the measurement probe (850) is coupled to one of the at least one receive antenna element (230), and wherein, for each of the tiles (200, 310a, 310b, 310c, 500, 600, 700, 800) that comprise at least two receive antenna elements (230), the receive antenna element (230) the measurement probe (850) is coupled to is either just coupled to the measurement probe (850) or also coupled to the at least one transmit antenna element (240).

13. The modularized reconfigurable intelligent surface (120, 300) according to any preceding claim, wherein at least one of the tiles (200, 310a, 310b, 310c, 500, 600, 700, 800) comprises more receive antenna elements (230) than transmit antenna elements (240).

14. The modularized reconfigurable intelligent surface (120, 300) according to any preceding claim, wherein the modularized reconfigurable intelligent surface (120, 300) comprises at least two tiles (200, 310a, 310b, 310c, 500, 600, 700, 800) with mutually different number of receive antenna elements (230) and transmit antenna elements (240).

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