Reflective structure in a wireless communications network

Abstract

A structure (301, 501) for reflecting radio signals in a wireless communications network (100) is provided. The structure comprises a first conductive layer (310) providing phase-shifting antennas (311) to a front (312) of the structure (301, 501). The structure also comprises a second conductive layer (320), arranged behind the front (312) of the structure (301, 501), providing one or more energy-harvesting antennas (321) having an operational frequency range that is lower than the operational frequency range of the phase-shifting antennas (311).

Description

[0001] REFLECTIVE STRUCTURE IN A WIRELESS COMMUNICATIONS NETWORK

[0002] TECHNICAL FIELD

[0003] Embodiments herein relate to a structure for reflecting radio signals in a wireless communications network.

[0004] BACKGROUND

[0005] In today’s wireless communications networks a number of different technologies are used, such as, 6G / New Radio (NR), Long Term Evolution (LTE), LTE-Advanced, Wideband Code Division Multiple Access (WCDMA), Global System for Mobile communications / Enhanced Data rate for GSM Evolution (GSM / EDGE), Worldwide Interoperability for Microwave Access (WiMax), or Ultra Mobile Broadband (UMB), just to mention a few possible technologies for wireless communication. A wireless communications network commonly comprises Radio Base Stations, RBSs, providing radio coverage over at least one respective geographical area forming a cell. This is commonly referred to as a Radio Access Network, RAN. The RAN is in turn connected to the core network in the wireless communications network via a so-called backhaul network. Wireless devices, also referred to as User Equipments or UEs, mobile stations, and / or wireless terminals, are served in the cells by the respective radio base station and are communicating with respective radio base station in the RAN over an air / radio interface. Commonly, the wireless devices transmit data over the air / radio interface to the radio base stations in uplink, UL, transmissions and the radio base stations transmit data over the air / radio interface to the wireless devices in downlink, DL, transmissions.

[0006] In recent developments, so-called Reconfigurable Reflective Surfaces, RRSs, or Reconfigurable Intelligent Surfaces, RISs, has emerged as a promising RAN technology. These RRSs / RISs are tuneable reflective surfaces that may be constructed from metamaterials and comprises a number of phase-shifting antennas that controls part of the propagation channel between a transmitter and a receiver, e.g. between a network node and wireless devices. The phase-shifting antennas may also be referred to, for example, as reflection / reflective elements or antennas, and comprise e.g. micro-strip patches or patch antennas. The phase-shifting antennas of a reflective surface have the potential to reflect the incoming signal towards a target direction by applying a different phase shift at each phase-shifting antenna, i.e. each phase-shifting antenna having a different or individual reflection state. By adjusting phase shift values, a beam gain of up to N2may be obtained at the surface, where N is the total number of antennas. This beam gain may be further increased by amplifying the incoming signal at the reflective surface. However, due to their low energy requirements and less hardware costs, passive reflective structures or surfaces without any amplifiers are commonly accepted in the prior art and prototyped by many wireless technology manufacturers.

[0007] Fig. 1 illustrates a typical scenario or use case for a reflective surface, RIS 300. In the example shown in Fig. 1, a direct radio link 141 between the network node 110 and the wireless device 121 in the wireless communications network 100 is blocked, e.g. due to physical objects located between them. In this case, a reconfigurable reflective surface 300 may be useful to reflect the incoming signal 142 from the network node 110 towards the wireless device 121, i.e. the reflected signal 143, to enable a good radio access link between the network node 110 and the wireless device 121. Here, the Angle-of-Arrival, AoA, and Angle-of-Departure, AoD, of the radio signals is exemplified as AoA = 10° and AoD = -60°. This scenario or use case for the reconfigurable reflective surface 300 may commonly be referred to as blind-spot coverage.

[0008] In Fig. 1 , the reconfigurable reflective surface 300 is composed by several phaseshifting antennas 311. To apply or tune the different phase-shifts at each phase-shifting antenna 311, each phase-shifting antenna 311 may comprise a phase-shifting circuit. For these phase-shifting circuits applying the phase-shifts at each phase-shifting antenna 311 , different discrete electrical components may be used, such as, e.g. pin diodes, varactor diodes, liquid crystals, etc. The state of the phase-shifting circuits of the phase shifting antennas 311 may be controlled by control circuitry (not shown), which thus may control the phase-shift of each phase-shifting antenna 311. In some cases, state of the phaseshifting circuits of the phase shifting antennas 311 may also be network-controlled or be controlled by other wireless devices in a wireless communications network 100. In other words, the control circuitry may operate on its own, or via communication with one or more network nodes or via communication with or more wireless devices, or combinations thereof. This provides the reconfigurable reflective surface 300 in the wireless communications network 100 with one of its main advantages, that is, it does not perform any baseband operation to apply the phase shifts to the incoming signal 142 and hence the energy consumption is potentially very low.

[0009] Fig. 2 illustrates an example of a gain of a reflective surface as a function of the azimuth AoD. In Fig. 2, a beam-pattern of a 32 x 32 reflective surface (N = 1024) is shown, where N is the number of phase-shifting antennas 311. Here, it is assumed that the azimuth AoA is fixed at 10° and that the phase-shifting antennas 311 of the reconfigurable reflective surface 300 have been tuned for an azimuth AoD of -60°, as shown in Fig 1. Hence, it may be seen in Fig. 2 that the gain of the reconfigurable reflective surface 300 has a peak when the azimuth AoD equals -60°, which is the target AoD. At the peak, we have a gain 10 log10( V2) = 10 log10((32 x 32)2) « 60.2 dB.

[0010] Although the reflective surface has low energy requirements today, there is a constant need to reduce the energy consumption of all deployments with a wireless communications network.

[0011] SUMMARY

[0012] It is an object of the present disclosure to mitigate, alleviate or eliminate one or more of the above-identified deficiencies and disadvantages and reduce the energy consumption in wireless communications networks. This object is achieved by means of a structure as described in the appended claims.

[0013] According to one aspect of embodiments herein, the object is achieved by a structure for reflecting radio signals in a wireless communications network. The structure comprises a first conductive layer providing phase-shifting antennas to a front of the structure. The structure also comprises a second conductive layer, arranged behind the front of the structure, providing one or more energy-harvesting antennas having an operational frequency range that is lower than the operational frequency range of the phase-shifting antennas. By having a structure as described above, a combined system is enabled wherein an RF signal based energy harvesting functionality is jointly integrated as a layered design into a reflective surface. Hence, the structure is able to harvest radio frequency, RF, energy at one frequency range, and be designed for radio signal reflections in another frequency range. By being able to harvest RF energy, the structure may not require an external energy source, such as, e.g. cabling, solar panel, batteries requiring regular exchange, etc., and hence will reduce the energy consumption in wireless communications networks.

[0014] In some embodiments, all or a subset of the phase-shifting antennas provided by the first conductive layer is combined with a corresponding energy-harvesting antenna provided by the second conductive layer. In some embodiments, the second conductive layer is formed by a metal sheet serving as an antenna for a circuit adapted to harvest energy from radio signals received by the energy-harvesting antenna. In some embodiments, the second conductive layer serves as a Radio Frequency, RF, ground plane for the first conductive layer. In some embodiments, the phase-shifting antennas provided by the first conductive layer are designed to be transparent to radio signals transmitted in the operational frequency range of the one or more energy-harvesting antennas provided by the second conductive layer. In some embodiments, the second conductive layer is arranged to the back of the first conductive layer via a dielectric layer.

[0015] In some embodiments, the structure comprises one or more intermediate conductive layers sandwiched, via dielectric layers, between the first conductive layer and the second conductive layer. Each intermediate conductive layer provides additional phase-shifting antennas having progressively lower operational frequency ranges than the operational frequency range of the phase-shifting antennas provided by the first conductive layer and additional phase-shifting antennas of any preceding intermediate conductive layer, and wherein all additional phase-shifting antennas provided by each intermediate conductive layer has a higher operational frequency range than the operational frequency range of the one or more energy harvesting antennas provided by the second conductive layer.

[0016] In some embodiments, the structure further comprises one or more additional conductive layers arranged, via dielectric layers, behind the second conductive layer, wherein each additional conductive layer provides additional energy-harvesting antennas having, progressively for each additional conductive layer, a lower operational frequency range than the operational frequency range of the energy-harvesting antennas provided by any preceding conductive layer. In some embodiments, the structure is implemented as a multi-layered Printed Circuit Board, PCB.

[0017] In some embodiments, the structure further comprises a control layer, wherein the control layer is arranged behind the second conductive layer, wherein the control layer comprises an energy harvesting circuitry that is connected to the energy-harvesting antennas and / or a control circuit that is connected to the phase-shifting antennas.

[0018] BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Features and advantages of the embodiments will become readily apparent to those skilled in the art by the following detailed description of exemplary embodiments thereof with reference to the accompanying drawings, wherein:

[0020] Fig. 1 is a schematic illustration of a typical scenario or use case for a reflective surface, Fig. 2 is a schematic illustration of a gain of a reflective surface as a function of the azimuth AoD of a reflected signal,

[0021] Fig. 3 is an example implementation of a structure for reflecting radio signals according to some embodiments,

[0022] Fig. 4 is another example implementation of a structure for reflecting radio signals according to some embodiments, and

[0023] Fig. 5 is a further example implementation of a structure for reflecting radio signals according to some embodiments.

[0024] DETAILED DESCRIPTION

[0025] Aspects of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings. The structure disclosed herein can, however, be realized in many different forms and should not be construed as being limited to the aspects set forth herein. Like numbers in the drawings refer to like elements throughout.

[0026] The terminology used herein is for the purpose of describing particular aspects of the disclosure only, and is not intended to limit the invention. It should be emphasized that the term “comprises / comprising” when used in this specification is taken to specify the presence of stated features, integers, steps, or components, but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term exemplary is in the present context to be understood as serving as an instance, example or illustration. The figures are schematic and simplified for clarity, and they merely show details which are essential to the understanding of the embodiments presented herein, while other details have been left out. Throughout, the same reference numerals are used for identical or corresponding parts or steps. The embodiments herein are not limited to the above described preferred embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be construed as limiting.

[0027] As part of the developing of the embodiments described herein, it has been realized that despite many advantages offered by reconfigurable reflective surfaces, e.g. RISs, they also have their own limitations. For example, a RIS do consume some energy and may need a power supply to support its operation. Since the RIS are expected to be deployed for long periods of time, it is not very practical, nor environmentally friendly to assume that battery replacements may be done to support the on-time operation of the RIS. In addition, such battery replacements in the RIS also comes with additional maintenance costs. Thus, there is a problem in that deployment of the RIS may be limited to locations where electricity is easily available or where solar panels, wind mills or other energy sources may be used at the site of the deployment. Such a continuous power requirement towards the deployment of the RIS may become a critical issue in many situations, e.g. on whether or not the deployment of the RIS may be considered as a low cost, low complexity solution.

[0028] Furthermore, the deployment of the RIS may also require manual intervention, for example, hiring an electrician to handle electricity cabling etc., and thus making the process of the deploying the RIS a complex one. In addition, in many locations it may not even be practical to get electricity cabling to a candidate deployment location. Further, considering the size of the RIS and above discussed complexities in deployment thereof, it would also be preferred to avoid applying a separate stand-alone energy source, such as, e.g. a solar panel or similar, at the location of the deployment of the RIS.

[0029] The above issues are addressed by the embodiments described herein by providing a structure enabling RF signal based energy harvesting functionality in a layered design of a RIS. One advantage of some embodiments of the structure described herein is that reflective surface deployment possibilities are improved since the structure may operate without any external energy sources and without excess equipment, such as, e.g. electric cabling, solar panels, batteries requiring regular exchange, etc. Another advantage of some embodiments described herein is that they provide a maintenance free reflective surface deployment, since no external energy sources are required to be maintained for the structure. In general, the structure further provides an advantage where both energy harvesting as well as radio channel adaptation may be conducted.

[0030] Additionally, the physical area and volume of the structure, and thus the reflective surface, may advantageously also be reduced or minimized by stacking the plurality of phase shifting antennas and energy harvesting antennas in the same structure. Hence, the structure enables a very compact and simple reflective surface deployment. For example, the structure may be implemented as one single RIS panel design.

[0031] Fig. 3 is an example implementation of a structure 301 for reflecting radio signals. The structure 301 is suitably used to provide a reconfigurable reflective surface 300 for reflecting radio signals 142 in a wireless communications network 100 as exemplified in Fig. 1. The reconfigurable reflective surface 300 may also be referred to as a Reconfigurable Reflective Surface, RRS, or Reconfigurable Intelligent Surface, RIS, device.

[0032] The structure 301 comprises a first conductive layer 310 providing phaseshifting antennas 311 to a front 312 of the structure 301 , as denoted by the waved lined parts in Fig. 3. The first conductive layer 310 may be provided or implemented on a dielectric layer 313, such as, a Printed Circuit Board, PCB or some other suitable carrier. The phase-shifting antennas 311 of the first conductive layer 310 may also be referred to as phase-shifting or reflective reconfigurable antennas / elements. The phase-shifting antennas 311 of the first conductive layer 310 may be tuned or tunable to an operational frequency range of the radio signals 142 in the wireless communications network 100. The phase-shifting antennas 311 of the first conductive layer 310 may also be connected to bias lines 314, e.g. electrical connections or wires, running through first dielectric layer 313 electrically connecting the phase-shifting antennas 311 of the first conductive layer 310 to discrete electrical components behind or beneath the first dielectric layer 313.

[0033] The structure 301 also comprises a second conductive layer 320 arranged behind the front 312 of the structure 301 providing one or more energy-harvesting antennas 321, as denoted by the straight lined parts in Fig. 3. This means that the second conductive layer 320 may be located behind or beneath the dielectric layer 313, thus effectively spatially separating it, and electrically insulating it, from the first conductive layer 310 at the front 312 of the structure 301. In some embodiments, the second conductive layer 320 may be arranged to the back of the first conductive layer 310 via the dielectric layer 313. The one or more energy-harvesting antennas 321 of the second conductive layer 320 may also be referred to as rectifier antennas or antennas connected to an energy-harvesting rectifier circuit.

[0034] The second conductive layer 320 may also be provided or implemented on a second dielectric layer 323, such as, a Printed Circuit Board, PCB or some other suitable carrier. The one or more energy-harvesting antennas 321 of the second conductive layer 320 may also be connected to bias lines 325, e.g. electrical connections or wires, running through the second dielectric layer 323 electrically connecting the one or more energy-harvesting antennas 321 of the second conductive layer 320 with discrete electrical components behind or beneath the second dielectric layer 323. In some embodiments, the second conductive layer 320 may also be formed by a metal sheet serving as a single energy-harvesting antenna 321. In some embodiments, the metal sheet may be selected as a single metal sheet forming the second conductive layer 320. As shown in the example implementation in Fig. 3, the second conductive layer 320 may, for example, comprise one or more vias 324 for guiding the bias lines 314 of the phaseshifting antennas 311 of the first conductive layer 310 to discrete electrical components behind or beneath the second dielectric layer 323.

[0035] The one or more energy-harvesting antennas 321 of the second conductive layer 320 have an operational frequency range that is lower than the operational frequency range of the phase-shifting antennas 311 of the first conductive layer 310. In this way, the phase-shifting antennas 311 may be designed or adjusted to target one frequency range, and the one or more energy-harvesting antennas 321 may be configured for another frequency range. Thus, the structure 301 when deployed in a reconfigurable reflective surface 300 within the wireless communication network 100 may harvest energy from lower frequency RF signals, while reflecting higher frequency RF signals. For example, the structure 301 may harvest energy from RF signals transmitted from a wide area coverage network such as at frequency of 800 MHz, 2 GHz, or 3.5 GHz wireless network deployment, and the structure 301 may enhance high-frequency radio conditions via the phase-shifting antennas 311 at frequency for example, 5 GHz, or 28 GHz frequency.

[0036] In some embodiments, the phase-shifting antennas 311 of the first conductive layer 310 are designed to be transparent to radio signals transmitted in the operational frequency range of the one or more energy-harvesting antennas 321 of the second conductive layer 320. This means that the phase-shifting antennas 311 of the first conductive layer 310 may be designed to be transparent to the lower frequencies for which the one or more energy-harvesting antennas 321 of the second conductive layer 320 may be tuned, which then allows the incident RF signals to pass the first conductive layer 310 onto lower layers, i.e. the one or more energy-harvesting antennas 321 at the second conductive layer 320. The term transparent should here be interpreted as the phase-shifting antennas 311 being configured to not reflect or absorb at least a significant portion of the lower frequency RF signals. Hence, behind or beneath the phase-shifting antennas 311 of the first conductive layer 310, the one or more energy-harvesting antennas 321 of the second conductive layer 320 that are tuned to the lower frequency RF signals may harvest energy from the lower frequency RF signals.

[0037] Optionally, as shown in the example implementation in Fig. 3, a separate Radio Frequency, RF, ground plane or layer 330 may also be layered in structure 301. The RF ground plane or layer 330 may, for example, be located behind or beneath the dielectric layer 323. The dielectric layer 323 thus effectively spatially separating it, and electrically insulating RF ground plane or layer 330 from the first conductive layer 310 and the second conductive layer 320. In some examples, the second conductive layer 320 may also serve as a Radio Frequency, RF, ground plane or layer for the first conductive layer 310.

[0038] Furthermore, the structure 301 may comprise a control plane or layer 340. The control plane 340 may, e.g. in addition to having a conductive layer with connections and a dielectric layer for insulation, comprise discrete electrical components used to control the reflection of the radio signals by the phase-shifting antennas 311 of the first conductive layer 310. The control plane 340 may also comprise discrete electrical components used to harvest and store energy via the one or more energy-harvesting antennas 321 of the second conductive layer 320, which may be used to power the control of the phase-shifting antennas 311. Here, it should be noted that the discrete electrical components may, for example, be placed on top of a PCB or carrier, at the bottom, or inside in cavities in dielectric layers, etc. In some carriers, it may also be possible to create some integrated components.

[0039] As shown in the example implementation in Fig. 3, the control plane or layer 340 may comprise control circuitry 341. The control circuitry 341 may comprise discrete electrical components, e.g. radio frequency and digital parts. The control circuitry 341 may be connected to and arranged to control the phase-shifting antennas 311 via the bias lines 314. The control circuitry 341 may, for example, control an angle of reflection of an incident beam of the radio signals 142 reflected by the phase-shifting antennas 311 of the first conductive layer 310. The control over the angle of reflection enables the structure 301 to function as a reconfigurable reflective surface 300 in a wireless communications network 100. The control circuitry 341 may be arranged to tune the phase-shifting antennas 311 to an operational frequency range of the radio signals 142 in the wireless communications network 100. In some embodiments, the control circuitry 341 may also comprise antenna impedance tuning mechanism. This mechanism may be used in case some detuning of the antenna impedance occurs due to the layered or stacked design of the structure 301.

[0040] Also, the control plane or layer 340 may comprise energy-harvesting circuitry 342. The energy-harvesting circuitry 342 may comprise discrete electrical components, e.g. radio frequency and digital parts, such as, energy-harvesting rectifiers or rectifier circuits. The energy-harvesting circuitry 342 may be connected to the one or more energy-harvesting antennas 321 via the bias lines 325 and arranged to harvest energy from the radio signals received by the one or more energy-harvesting antennas 321 of the second conductive layer 320. In some embodiments, the energy-harvesting circuitry 342 may be used to power the control circuitry 341 and / or other discrete electrical components comprised in the control layer 340.

[0041] Also, in some embodiments, the energy-harvesting antennas 321 may receive information that may be further used by the control circuitry 341 and / or other discrete electrical components comprised in the control layer 340. For example, the energyharvesting antennas 321 may receive information to enabling the beam steering of the phase-shifting antennas 311 to be controlled remotely. Since the energy-harvesting antennas 321 may operate at low frequencies, the range of such low frequency RF signals in the wireless communications network 100 may be significant.

[0042] As shown in the example implementation in Fig. 3, the energy-harvesting circuitry 342 may be electrically connected to the control circuitry 341 , e.g. via one or more bias lines 326 in the control plane or layer 340. Hence, the energy-harvesting circuitry 342 may provide harvested energy to the control circuitry 341 and / or exchange information with the control circuitry 341. Hence, the structure 301 may comprise a control layer 340 arranged behind the second conductive layer 320. The control layer 340 comprising an energy harvesting circuitry 341 that is connected to the energy-harvesting antennas 321 and / or a control circuitry 342 that is connected to the phase-shifting antennas 311.

[0043] According to some embodiments, the structure 301 may be configured as a stacked or layered implementation of the phase-shifting antennas 311 and the one or more energy-harvesting antennas 321 within the same structure 301. This is advantageous since the physical area and volume of the structure 301 , and thus the physical area and volume of a reconfigurable reflective surface 300 comprising the structure 301 , may be reduced by stacking the plurality of phase shifting antennas 311 and the energy harvesting antennas 321 in the same structure 301. In some embodiments, the structure 301 may be implemented as a multi-layered Printed Circuit Board, PCB or some other suitable carrier.

[0044] Fig. 4 is another example implementation of the structure 301 for reflecting radio signals. The example implementation of the structure 301 in Fig. 4 is identical to the example implementation of the structure 301 in Fig. 3, except that the bias lines 314 of the phase-shifting antennas 311 of the first conductive layer 310 running through first dielectric layer 313 is routed differently and through alternative vias 424 to electrically connect the phase-shifting antennas 311 of the first conductive layer 310 to discrete electrical components behind or beneath the first dielectric layer 313. In other words, the bias lines may be routed in the first conductive layer 310, whereby electrical connections may be made between different conductive layers using vias 424.

[0045] Fig. 5 is another example implementation of a structure 501 for reflecting radio signals in a wireless communications network 100. The structure 301 may be implemented in two layers, e.g. the first conductive layer 310 and the second conductive layer 320 as shown in the example implementations in Figs. 3-4. However, according to some embodiments, the first conductive layer 310 may also comprise multiple layers of the phase-shifting antennas 311 and the second conductive layer 320 may also comprise multiple layers of the energy-harvesting antennas 321. In this case, the frequency range for each phase shifting antenna 311 in the multiple layer of the phase-shifting antennas 311 increases with an increment in the layers of the phase-shifting antennas 311 , with a highest frequency in an uppermost layer of the phase-shifting antenna 311. Similarly, the frequency range for each energy-harvesting antennas 321 in the multiple layer of the energy-harvesting antennas 321 increases with an increment in the layers of the energyharvesting antennas 321, with a highest frequency in an uppermost layer of the energyharvesting antenna 321. This is illustrated in the example implementation of the structure 501 in Fig. 5.

[0046] In other words, the structure 501 may comprises one or more intermediate conductive layers 510 sandwiched, via dielectric layers 313, 520, between the first conductive layer 310 and the second conductive layer 320. Each intermediate conductive layer 510 provides additional phase-shifting antennas 511 having progressively lower operational frequency ranges than the operational frequency range of the phase-shifting antennas 311 provided by the first conductive layer 310 at the front 312 of the structure 501, and additional phase-shifting antennas 511 of any preceding intermediate conductive layer 510. All additional phase-shifting antennas 511 provided by each intermediate conductive layer 510 has a higher operational frequency range than the operational frequency range of the one or more energy harvesting antennas 321 provided by the second conductive layer 320.

[0047] In some embodiments, the structure 501 further comprises one or more additional conductive layers 610 arranged, via dielectric layers 323, 620, behind the second conductive layer 320. Each additional conductive layer 610 provides additional energy-harvesting antennas 621 having a lower operational frequency range, progressively for each additional conductive layer 610 than the operational frequency range of the energy-harvesting antennas 321 provided by any preceding conductive layer 610.

[0048] Furthermore, as illustrated in the example implementation of the structure 501 in Fig. 5, all or a subset of the phase-shifting antennas 311 , 511 of the first or intermediate conductive layers 310, 510 may be combined with a corresponding energy-harvesting antenna 321 , 621 of the second or additional conductive layers 320, 610. In some embodiments, the phase-shifting antennas 311 , 511 and the energy-harvesting antenna 321 , 621 may be arranged to be progressively increasing in size for each lower layer, e.g. a doubling of size for each layer. As shown above in Figs. 3-5, it should be noted that the structure 501 may be configured as a stacked or layered implementation of the phaseshifting antennas 311 , the additional phase-shifting antennas 511 , the one or more energy-harvesting antennas 321 , and the additional energy-harvesting antennas 621 within the same structure 501. This is advantageous since the physical area and volume of the structure 501 , and thus the physical area and volume of a reconfigurable reflective surface 300 comprising the structure 501 , may be reduced.

[0049] In some embodiments, the structure 501 may be implemented as a multi-layered Printed Circuit Board, PCB or some other carrier. Here, it should also be noted that each of the dielectric layers 313, 520, 323, 620 may be configured to provide proper spacing that secures a suitable electrical insulation between each of the first conductive layers 310, the intermediate conductive layers 510, the second conductive layer 320, and / or the additional conductive layers 610, as well as a suitable antenna impedance.

[0050] In some examples, a separate Radio Frequency, RF, ground plane or layer 330 as shown in Figs. 3-4 may also be layered under all antennas in the structure 301 , 501 with vias for allowing electrical connections to / from the antennas to pass through.

[0051] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and / or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the scope of the disclosure.

Claims

CLAIMS1. A structure (301 , 501) for reflecting radio signals (142) in a wireless communications network (100), comprising a first conductive layer (310) providing phase-shifting antennas (311) to a front (312) of the structure (301 , 501), and a second conductive layer (320), arranged behind the front (312) of the structure (301 , 501), providing one or more energy-harvesting antennas (321) having an operational frequency range that is lower than the operational frequency range of the phase-shifting antennas (311).

2. The structure (301 , 501) according to claim 1 , wherein all or a subset of the phaseshifting antennas (311) provided by the first conductive layer (310) is combined with a corresponding energy-harvesting antenna (321) provided by the second conductive layer (320).

3. The structure (301 , 501) according to any of claims 1-2, wherein the second conductive layer (320) is formed by a metal sheet serving as an energy-harvesting antenna (321) for a circuit (342) adapted to harvest energy from radio signals (142) received by the energy-harvesting antenna (321).

4. The structure (301 , 501) according to any of claims 1-3, wherein the second conductive layer (320) serves as a Radio Frequency, RF, ground plane (330) for the first conductive layer (310).

5. The structure (301 , 501) according to any of claims 1-4, wherein the phase-shifting antennas (311) provided by the first conductive layer (310) are designed to be transparent to radio signals transmitted in the operational frequency range of the one or more energy-harvesting antennas (321) provided by the second conductive layer (320).

6. The structure (301 , 501) according to any of claims 1-5, wherein the second conductive layer (320) is arranged to the back of the first conductive layer (310) via a dielectric layer (313).

7. The structure (301 , 501) according to any of claims 1-5, further comprising one or more intermediate conductive layers (510) sandwiched, via dielectric layers (313; 520), between the first conductive layer (310) and the second conductive layer (320), wherein each intermediate conductive layer (510) provides additional phaseshifting antennas (511) having progressively lower operational frequency ranges than the operational frequency range of the phase-shifting antennas (311) provided by the first conductive layer (310) and additional phase-shifting antennas (511) of any preceding intermediate conductive layer (510), and wherein all additional phase-shifting antennas (511) provided by each intermediate conductive layer has a higher operational frequency range than the operational frequency range of the one or more energy harvesting antennas (321) provided by the second conductive layer (320).

8. The structure (301 , 501) according to any of claims 1-7, further comprising one or more additional conductive layers (610) arranged, via dielectric layers (323; 620), behind the second conductive layer (320), wherein each additional conductive layer (610) provides additional energyharvesting antennas (621) having, progressively for each additional conductive layer (610), a lower operational frequency range than the operational frequency range of the energy-harvesting antennas (321) provided by any preceding conductive layer.

9. The structure (301 , 501) according to any of claims 1-8, wherein the structure (301 , 501) implemented as a multi-layered Printed Circuit Board, PCB.

10. The structure (301 , 501) according to any of claims 1-9, further comprising a control layer (340), wherein the control layer (340) is arranged behind the second conductive layer (320), wherein the control layer (340) comprises an energy harvesting circuitry (342) that is connected to the energy-harvesting antennas (321) and / or a control circuitry (341) that is connected to the phase-shifting antennas (311).

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