EP3879623A1

EP3879623A1 - Apparatus comprising a waveguide for radio frequency signals

Info

Publication number: EP3879623A1
Application number: EP20162303.0A
Authority: EP
Inventors: Wolfgang Templ; Dirk Wiegner; Senad Bulja; Rose Kopf
Original assignee: Nokia Technologies Oy
Current assignee: Nokia Technologies Oy
Priority date: 2020-03-11
Filing date: 2020-03-11
Publication date: 2021-09-15
Also published as: CN113394532A; CN113394532B

Abstract

Apparatus comprising a waveguide for radio frequency signals, and at least one electrochromic element a permittivity of which can be controlled by applying a control voltage to the electrochromic element, wherein the at least one electrochromic element is at least partly arranged within or at the waveguide.

Description

Field of the Disclosure

Exemplary embodiments relate to an apparatus comprising a waveguide for radio frequency, RF, signals.

Background

Apparatus of the aforementioned type can be used to transmit RF signals, e.g. from a source to a sink.

Summary

The scope of protection sought for various embodiments of the invention is set out by the independent claims. The exemplary embodiments and features, if any, described in this specification, that do not fall under the scope of the independent claims, are to be interpreted as examples useful for understanding various exemplary embodiments of the invention.
Exemplary embodiments relate to an apparatus comprising a waveguide for radio frequency, RF, signals, and at least one electrochromic, EC, element a permittivity of which can be controlled by applying a control voltage to the EC element, wherein the at least one EC element is at least partly arranged within or at the waveguide. This enables to effect a change of electric characteristics of the portion of the waveguide where the EC element is located, e.g. by altering the control voltage, so that a propagation of electromagnetic waves associated with the RF signal may be influenced.
According to further exemplary embodiments, arranging the at least one EC element at least partly within or at the waveguide may comprise arranging the at least one EC element relative to the waveguide such that the EC element or at least a portion of EC material of the EC element may interact with at least a portion of the RF signal(s) propagating within the waveguide.
According to further exemplary embodiments, arranging the at least one EC element at least partly within or at the waveguide may comprise arranging the at least one EC element relative to the waveguide such that the EC element or at least a portion of EC material of the EC element may at least interact with a portion of RF signals propagating outside of the waveguide.
According to further exemplary embodiments, the at least one EC element may be arranged at an outside of the waveguide, i.e. placed onto an outer surface of the waveguide.
According to further exemplary embodiments, the at least one EC element may be arranged at an outside of the waveguide, particularly spaced apart from, i.e. not in direct surface contact with, the outer surface of the waveguide. In other words, according to further exemplary embodiments, there may be a gap, e.g. being filled with a surrounding medium such as air or a protective gas or the like, between the waveguide and the at least one EC element. Nevertheless, the propagation of the RF signal guided by the waveguide may be influenced using the at least one EC element, particularly as long as the Poynting vector associated with the RF signal has at least one non-vanishing component in the region of the at least one EC element.
According to further exemplary embodiments, the at least one EC element is at least partly arranged within a) a core of the waveguide, and/or within b) a cladding (or at least one cladding, respectively) of the waveguide.
According to further exemplary embodiments, the waveguide may comprise or consist of one or more dielectric materials. According to further exemplary embodiments, the core of the waveguide may comprise or consist of dielectric material. According to further exemplary embodiments, at least one cladding of the waveguide may comprise or consist of dielectric material. According to further exemplary embodiments, the dielectric material may comprise polymer material, which is cost-effective and enables efficient manufacturing.
According to further exemplary embodiments, the EC element may feature an (electrically tunable) permittivity which may differ significantly, e.g. from the permittivity of the cladding.
According to further exemplary embodiments, the waveguide comprises at least in sections a) a circular cross-section or b) a non-circular cross-section, e.g. elliptical or polygonal, e.g. rectangular, cross-section.
According to further exemplary embodiments, the waveguide comprises or is at least one polymer fiber, wherein preferably at least one component of the fiber comprises polymer material.
According to further exemplary embodiments, the waveguide is a polymer fiber having a core of polymer material and a cladding, which surrounds the core, wherein the cladding preferably also comprises a polymer material. According to further exemplary embodiments, an optional coating may be provided, which may e.g. surround the cladding.
According to further exemplary embodiments, the at least one EC element comprises a stack of layers stacked, preferably upon each other, along a first axis (which may also be denoted as "stack coordinate"), wherein the stack comprises a first electrically conductive element or layer, a second electrically conductive element or layer, and an EC layer arranged between the first electrically conductive layer and the second electrically conductive layer.
According to further exemplary embodiments, the EC layer, too, may comprise a stack of layers ("EC layer stack"), stacked, preferably upon each other, along the first axis, wherein the EC layer stack may comprise at least one of: a) an ion storage layer (e.g. comprising NiO, nickel oxide), b) an electrolyte layer (e.g. comprising LiNbO₃, lithium niobate), c) an electrochromic (EC) layer or film (e.g. comprising WO₃, tungsten trioxide).
According to further exemplary embodiments, the first axis of the stack extends substantially parallel to a longitudinal axis of the waveguide. In other words, according to further exemplary embodiments, the at least one EC element is arranged at least partly within or at the waveguide such that the first axis of its stack, i.e. the stack coordinate, is substantially parallel or collinear with the longitudinal axis of the waveguide.
According to further exemplary embodiments, "extending substantially parallel to the longitudinal axis of the waveguide" means that an angle between the longitudinal axis of the waveguide and the first axis of the stack ranges between 0 degrees and 30 degrees, preferably between 0 degrees and 10 degrees.
According to further exemplary embodiments, the first axis of the stack extends substantially perpendicular to a longitudinal axis of the waveguide, which e.g. means that an angle between the longitudinal axis of the waveguide and the first axis of the stack ranges between 60 degrees and 90 degrees, preferably between 80 degrees and 90 degrees.
According to further exemplary embodiments, the first axis of the stack extends, particularly at least in sections, circumferentially around the longitudinal axis of the waveguide. In these exemplary embodiments, the stack coordinate may be curved, and the sequence of the layers of the EC stack may extend in a circumferential direction.
According to further exemplary embodiments, the first axis of the stack (and thus also the sequence of the layers of the (EC) stack) extends radially with respect to the longitudinal axis of the waveguide.
According to further exemplary embodiments, the stack comprises a circular ring segment cross-section extending at least partly (i.e., less than 360° degrees, or completely, i.e. comprising 360° degrees) circumferentially around the longitudinal axis of the waveguide.
According to further exemplary embodiments, the first axis of the stack comprising a circular ring segment cross-section may be (at least substantially) parallel to the longitudinal axis of the waveguide.
According to further exemplary embodiments, the first axis of the stack comprising a circular ring segment cross-section may be (at least substantially) perpendicular to the longitudinal axis of the waveguide.
According to further exemplary embodiments, two or more EC elements are provided, wherein preferably each of the two or more EC elements is at least partly arranged within or at the waveguide.
According to further exemplary embodiments, in the case of two or more EC elements within and/or at the waveguide, at least two EC elements may comprise an identical or similar structure (particularly also with parallel or collinear first axes or stack coordinates), as exemplarily explained above.
According to further exemplary embodiments, in the case of two or more EC elements within and/or at the waveguide, at least two EC elements may comprise a different structure (particularly also with perpendicular first axes or stack coordinates).
According to further exemplary embodiments, the two or more EC elements are arranged along a or the longitudinal axis of the waveguide.
According to further exemplary embodiments, a plurality of EC elements are periodically arranged along the longitudinal axis of the waveguide, i.e. with identical distance between neighboring EC elements. This enables to at least temporarily provide a periodic variation of a refractive index or permittivity thus providing a spatially distributed, frequency-specific reflective configuration ("mirror").
According to further exemplary embodiments, a plurality of EC elements are arranged along the longitudinal axis of the waveguide in a chirped fashion, i.e. with gradually changing distance between neighboring EC elements along the longitudinal axis.
According to further exemplary embodiments, different spacings and/or arrangements of EC elements with smaller and/or larger distance spacing may be provided, e.g. for addressing different frequencies either in parallel or sequentially.
According to further exemplary embodiments, one or more groups of EC elements may be provided, wherein EC elements of at least one of the groups may comprise at least one of: identical spacings between neighboring EC elements, varying spacings between neighboring EC elements, or any combination thereof.
According to further exemplary embodiments, at least one of the first electrically conductive element and the second electrically conductive element or layer comprises at least one of: a) a film, b) a mesh (e.g., a mesh of wires or other electrical conductors), c) a wire. This enables to apply the control voltage to the EC element while at the same time offering mechanical flexibility facilitating e.g. bending of the waveguide or the apparatus.
According to further exemplary embodiments, at least one of the first electrically conductive element or layer and the second electrically conductive element or layer is implemented such that the conductive elements do not (substantially) affect propagating waves or the transmission characteristic.
According to further exemplary embodiments, at least one RF blocking element such as e.g. an inductive element may be provided to supply a reference potential associated e.g. with the control voltage to the first and/or second electrically conductive element, thus preventing RF leakage from e.g. an interior of the waveguide to the outside (or vice versa, e.g. preventing injection of RF signals from an outside into the interior of the waveguide or the EC element, respectively).
According to further exemplary embodiments, the at least one RF blocking element may be chosen depending on e.g. an intended application and/or target system: a) EC control without modulation -> the EC control voltage path may be very wideband RF blocked, b) e.g., in order to support potential applications using wanted modulation effect induced via EC-control/permittivity variation, the EC control voltage path may not be completely RF blocked but may e.g. be "open", i.e. transmissive, for the modulation bandwidth while blocking the RF bandwidth of the RF signal propagating within the waveguide.
Further exemplary embodiments relate to a device for processing radio frequency, RF, signals comprising at least one apparatus according to the embodiments.
Further exemplary embodiments relate to a use of the apparatus according to the embodiments and/or of the device according to the embodiments for at least one of: a) processing an RF signal, b) influencing an RF signal, particularly an RF signal propagating within the waveguide, wherein the RF signal may e.g. be a single signal (or single band signal), a multiband signal, a wideband signal, contiguous or non-contiguous multi-carrier signal, c) filtering an RF signal, d) attenuating an RF signal, e) reflecting an RF signal, f) selecting one or more modes of an RF signal, g) computing, particularly analog computing, based on an RF signal and one or more control signals (e.g., control voltages) for the at least one EC element.
Further exemplary embodiments relate to a method of manufacturing an apparatus comprising a waveguide for radio frequency, RF, signals, and at least one electrochromic, EC, element a permittivity of which can be controlled by applying a control voltage to the EC element, the method comprising: providing the waveguide, arranging the at least one EC element at least partly within or at the waveguide.
According to further exemplary embodiments, the step of arranging the at least one EC element at least partly within or at the waveguide may also be performed simultaneously or in an at least partially temporally overlapping fashion with respect to the step of providing the waveguide.

Brief description of the figures

Some exemplary embodiments will now be described with reference to the accompanying drawings in which:

Fig. 1: schematically depicts a simplified block diagram of an apparatus according to exemplary embodiments,
Fig. 2A, 2B, 2C, 2D, 2E, 2F: each schematically depict a simplified side view of an apparatus according to further exemplary embodiments,
Fig. 3A: schematically depicts a simplified cross-sectional view of a waveguide according to further exemplary embodiments,
Fig. 3B: schematically depicts a simplified front view of a waveguide according to further exemplary embodiments,
Fig. 3C: schematically depicts a simplified cross-sectional view of a waveguide according to further exemplary embodiments,
Fig. 4A: schematically depicts a simplified side view of an electrochromic element according to further exemplary embodiments,
Fig. 4B: schematically depicts a simplified side view of an electrochromic element according to further exemplary embodiments,
Fig. 5A: schematically depicts a simplified side view of an apparatus according to further exemplary embodiments,
Fig. 5B: schematically depicts a simplified side view of an apparatus according to further exemplary embodiments,
Fig. 6A, 6B, 6C, 6D, 6E, 6F: each schematically depict a simplified partial cross-sectional front view of an apparatus according to further exemplary embodiments,
Fig. 7: schematically depicts a simplified side view of an apparatus according to further exemplary embodiments,
Fig. 8: schematically depicts a perspective view of an apparatus according to further exemplary embodiments,
Fig. 9: schematically depicts a perspective view of an apparatus according to further exemplary embodiments,
Fig. 10: schematically depicts an exemplary topology according to further exemplary embodiments,
Fig. 11: schematically depicts a simplified side view of an apparatus according to further exemplary embodiments,
Fig. 12: schematically depicts a perspective view of a device according to further exemplary embodiments,
Fig. 13A: schematically depicts a simplified side view of an apparatus according to further exemplary embodiments, and
Fig. 13B: schematically depicts a table according to further exemplary embodiments.

Description of exemplary embodiments

Figure 1 schematically depicts a simplified block diagram of an apparatus 100 according to exemplary embodiments. The apparatus 100 comprises a waveguide 110 for radio frequency, RF, signals, RF1, RF1', and at least one electrochromic, EC, element 120 a permittivity of which can be controlled by applying a control voltage CV to the EC element 120, wherein the at least one EC element 120 is at least partly arranged within or at the waveguide 110. This enables to effect a change of electric characteristics of the portion of the waveguide 110 where the EC element 120 is located, e.g. by altering the control voltage CV, so that a propagation of electromagnetic waves associated with the RF signal(s) RF1, RF1' may be influenced. This is exemplarily symbolized in Fig. 1 by the different reference signs RF1, RF1', wherein reference sign RF1 is e.g. associated with an RF signal input to the waveguide 110, and wherein reference sign RF1' represents the influenced RF signal, i.e. after passing the EC element 120.
According to further exemplary embodiments, arranging the at least one EC element 120 at least partly within or at the waveguide 110 may comprise arranging the at least one EC element 120 relative to the waveguide 110 such that the EC element 120 or at least a portion of EC material (cf. e.g. Fig. 4A, 4B explained further below) of the EC element 120 may interact with at least a portion of the RF signal(s) RF1, RF1' propagating within the waveguide 110.
According to further exemplary embodiments, cf. the apparatus 100a of Figure 2A, the at least one EC element 120 is at least partly (presently fully) arranged within a core 112 of the waveguide 110.
According to further exemplary embodiments, cf. the apparatus 100b of Figure 2B, the at least one EC element 120 is at least partly arranged within a cladding 114 of the waveguide 110, and partly within the core 112.
According to further exemplary embodiments, cf. the apparatus 100c of Figure 2C, the at least one EC element 120 is fully arranged within the cladding 114.
According to further exemplary embodiments, cf. the apparatus 100d of Figure 2D, the at least one EC element 120 is fully arranged within the core 112 and the cladding 114.
According to further exemplary embodiments, arranging the at least one EC element 120 at least partly within or at the waveguide 110 may comprise arranging the at least one EC element 120 relative to the waveguide 110 such that the EC element 120 or at least a portion of EC material of the EC element 120 may at least interact with a portion of RF signal(s) propagating outside of the waveguide 110.
In this regard, according to further exemplary embodiments, cf. the apparatus 100e of Figure 2E, the at least one EC element 120 is partly arranged within the cladding 114, which still enables to influence the RF signal RF1, e.g. under control of the EC element 120 by means of the control voltage CV (Fig. 1).
According to further exemplary embodiments, cf. reference sign 120' of Fig. 2E, the at least one EC element 120' may be arranged at an outside of the waveguide 110, i.e. placed onto an outer surface 110' of the waveguide 110.
According to further exemplary embodiments, cf. reference sign 120" of Fig. 2E, the at least one EC element 120" may be arranged at an outside of the waveguide 110, particularly spaced apart from, i.e. not in direct surface contact with, the outer surface 110' of the waveguide 110. In other words, according to further exemplary embodiments, there may be a gap, e.g. being filled with a surrounding medium such as air or a protective gas or the like, between the waveguide 110 and the at least one EC element 120". Nevertheless, the propagation of the RF signal RF1 (Fig. 1) guided by the waveguide 110 may be influenced using the at least one EC element 120" (Fig. 2E), particularly as long as the Poynting vector associated with the RF signal RF1 has at least one non-vanishing component in the region of the at least one EC element 120".
Figure 2F schematically depicts a further exemplary embodiment, wherein the apparatus 100f comprises an EC element 120 that is partly arranged within the core 112, the cladding 114, and which also partly protrudes from the surface of the cladding 114 or the waveguide 110.
According to further exemplary embodiments, the waveguide 110 (Fig. 1) may comprise or consist of one or more dielectric materials. According to further exemplary embodiments, the core 112 of the waveguide 110 may comprise or consist of dielectric material. According to further exemplary embodiments, at least one cladding 114 of the waveguide 110 may comprise or consist of dielectric material. According to further exemplary embodiments, the dielectric material may comprise polymer material, which is cost-effective and enables efficient manufacturing.
According to further exemplary embodiments, cf. Figure 3A, the waveguide 110a comprises at least in sections a circular cross-section.
According to further exemplary embodiments, cf. Figure 3B, the waveguide 110b comprises at least in sections a non-circular cross-section, e.g. elliptical (not shown) or polygonal, e.g. rectangular, cross-section.
According to further exemplary embodiments, cf. e.g. Figure 3C, the waveguide 110c comprises two claddings 114a, 114b with rectangular cross-sections, and a core 112, which may also comprise a rectangular cross-section.
According to further exemplary embodiments, the waveguide comprises or is at least one polymer fiber, wherein preferably at least one component 112, 114, 114a, 114b of the fiber comprises polymer material.
According to further exemplary embodiments, the waveguide 110a (Fig. 3A) is a polymer fiber having a core 112 of polymer material and a cladding 114, which surrounds the core, wherein the cladding 114 preferably also comprises a polymer material. According to further exemplary embodiments, an optional coating (not shown) may be provided, which may e.g. surround the cladding 114.
According to further exemplary embodiments, cf. Figure 4A, the at least one EC element 120a comprises a stack S of layers 121, 122, 123 stacked, preferably upon each other, along a first axis a1 (which may also be denoted as "stack coordinate"), wherein the stack S comprises a first electrically conductive element or layer 121, a second electrically conductive element or layer 122, and an EC layer 123 arranged between the first electrically conductive layer 121 and the second electrically conductive layer 122.
According to further exemplary embodiments, the control voltage CV may at least temporarily be applied to the electrically conductive layers 121, 122.
According to further exemplary embodiments, cf. the EC element 120b of Figure 4B, the EC layer 123, too, may comprise a stack of layers 123a, 123b, 123c ("EC layer stack"), stacked, preferably upon each other, along the first axis a1, wherein the EC layer stack 123 may comprise at least one of: a) an ion storage layer 123a (e.g. comprising NiO, nickel oxide), b) an electrolyte layer 123b (e.g. comprising LiNbO₃, lithium niobate), c) an electrochromic (EC) layer or film 123c (e.g. comprising WO₃, tungsten trioxide).
According to further exemplary embodiments (not shown), the EC element may comprise a stack structure as follows: a first conductive layer, a first electrolyte layer (e.g. comprising LiNbO₃), an electrochromic (EC) layer or film (e.g. comprising WO₃), an (optional) ion storage layer or film (e.g. comprising NiO), a second electrolyte layer (e.g. comprising LiNbO₃), a second conductive layer.
According to further exemplary embodiments, one or more of the EC elements 120, 120', 120" explained above with reference to Fig. 1 to 2F may e.g. comprise a configuration identical or at least similar to the configuration 120a of Fig. 4A or the configuration 120b of Fig. 4B or the further stack structures exemplarily mentioned above.
According to further exemplary embodiments, cf. the apparatus 100g of Figure 5A, the first axis a1 of the stack S extends substantially parallel to a longitudinal axis LA of the waveguide. In other words, according to further exemplary embodiments, the at least one EC element is arranged at least partly within or at the waveguide 110 such that the first axis a1 of its stack S, i.e. the stack coordinate a1, is substantially parallel or collinear with the longitudinal axis LA of the waveguide 110.
According to further exemplary embodiments, "extending substantially parallel to the longitudinal axis LA of the waveguide 110" means that an angle between the longitudinal axis LA of the waveguide 110 and the first axis a1 of the stack S ranges between 0 degrees and 30 degrees, preferably between 0 degrees and 10 degrees.
According to further exemplary embodiments, cf. the apparatus 100h of Figure 5B, the first axis a1 of the stack S extends substantially perpendicular to the longitudinal axis LA of the waveguide 110, which e.g. means that an angle between the longitudinal axis LA of the waveguide 110 and the first axis a1 of the stack S ranges between 60 degrees and 90 degrees, preferably between 80 degrees and 90 degrees.
Figure 6A schematically depicts a simplified partial cross-sectional front view (i.e., along the longitudinal axis LA, cf. Fig. 1) of an apparatus 100i according to further exemplary embodiments. Depicted is an outer front surface 121a of the first electrically conductive layer 121 of the EC stack, wherein the further layers 123, 122 (also cf. Fig. 4A) are not visible in the exemplary depiction of Fig. 6A as the stack coordinate a1 extends collinearly with the longitudinal axis LA into the drawing plane of Fig. 6A.
According to further exemplary embodiments, the conductive layer 121 may be slotted, cf. the apparatus 100j of Fig. 6B, wherein two electrode sections 121a_1, 121a_2 are defined, separated by slots SL, which may reduce RF radiation emanating from the conductive layer 121, i.e. preventing it to operate as an "antenna" for the RF signal(s) RF1.
According to further exemplary embodiments, cf. the apparatus 100k of Figure 6C, the first axis a1 of the stack S extends, particularly at least in sections, circumferentially around the longitudinal axis of the waveguide 110. In these exemplary embodiments, the stack coordinate a1 may be curved, and the sequence of the layers 121, 123, 122 of the EC stack may extend in a circumferential direction a1, as exemplarily depicted for one EC element 120_1 of the apparatus 100k.
According to further exemplary embodiments, the apparatus 100k may comprise (presently three) further EC elements 120_2, 120_3, 120_4, which may have a similar or identical structure with respect to the EC element 120_1.
According to further exemplary embodiments, cf. the apparatus 1001 of Figure 6D, the first axis a1 of the stack S (and thus also the sequence of the layers of the (EC) stack) extends radially with respect to the longitudinal axis of the waveguide 110.
According to further exemplary embodiments, the stack S (Fig. 4A, 4B) comprises a circular ring segment cross-section extending at least partly (i.e., less than 360° degrees, or completely, i.e. comprising 360° degrees) circumferentially around the longitudinal axis of the waveguide, which may e.g. apply to the EC element(s) of Fig. 6A, 6B, 6C, 6D.
According to further exemplary embodiments, the first axis a1 of the stack comprising a circular ring segment cross-section may be (at least substantially) parallel to the longitudinal axis LA of the waveguide 110, cf. e.g. Fig. 6A, 6B.
According to further exemplary embodiments, the first axis a1 of the stack comprising a circular ring segment cross-section may be (at least substantially) perpendicular to the longitudinal axis LA of the waveguide 110, cf. e.g. Fig. 6C (first axis a1 curved, but also perpendicular to longitudinal axis LA), 6B.
Figure 6E schematically depicts a simplified partial cross-sectional front view (i.e., along the longitudinal axis LA, cf. Fig. 1) of an apparatus 100m according to further exemplary embodiments, wherein the electrodes 121', 122' are configured as a mesh, i.e. mesh of wires.
According to further exemplary embodiments, the core 112 is not shielded by the inner mesh 121' from the influence of the EC element, because the skin depth in a considered frequency range may be considerably greater than the thickness of the conductor layer (which may e.g. be a few µm).
According to further exemplary embodiments, at least one electrode 121', 122' may also comprise or consist of a wrapped foil, e.g. instead of the mesh.
Figure 6F schematically depicts a simplified partial cross-sectional front view (i.e., along the longitudinal axis LA, cf. Fig. 1) of an apparatus 100n according to further exemplary embodiments, wherein the electrode 121" comprises a plurality (presently for example four) wires, and wherein the radially outer electrode 122' is configured as a mesh, i.e. mesh of wires.
According to further exemplary embodiments, cf. the apparatus 100o of Figure 7, two or more EC elements 120_5, 120_6, 120_7 are provided, wherein preferably each of the two or more EC elements 120_5, 120_6, 120_7 is at least partly arranged within or at the waveguide 110.
According to further exemplary embodiments, in the case of two or more EC elements 120_5, 120_6, 120_7 within and/or at the waveguide 110, at least two EC 120_5, 120_6, 120_7 elements may comprise an identical or similar structure (particularly also with parallel or collinear first axes a1 or stack coordinates), as exemplarily explained above.
According to further exemplary embodiments, in the case of two or more EC elements 120_5, 120_6, 120_7 within and/or at the waveguide, at least two EC elements 120_5, 120_6, 120_7 may comprise a different structure (particularly also with perpendicular first axes a1 or stack coordinates).
According to further exemplary embodiments, the two or more EC elements are arranged along the longitudinal axis LA of the waveguide, cf. Fig. 6C, and may e.g. be arranged at a same or similar coordinate of the longitudinal axis LA, e.g. in the drawing plane of Fig. 6C.
According to further exemplary embodiments, cf. Figure 7, a plurality of EC elements 120_5, 120_6, 120_7 are periodically arranged along the longitudinal axis LA of the waveguide, i.e. with identical distance(s) d1, d2 between neighboring EC elements 120_5, 120_6 and 120_6, 120_7. This enables to at least temporarily provide a periodic variation of a refractive index or permittivity thus providing a spatially distributed, frequency-specific reflective configuration ("mirror").
According to further exemplary embodiments, a plurality of EC elements are arranged along the longitudinal axis of the waveguide in a chirped fashion (not shown), i.e. with gradually changing distance between neighboring EC elements along the longitudinal axis LA.
In further exemplary embodiments, the distances between the EC elements or EC segments may differ also more than only gradually, e.g. in case of controlling RF signals of different RF carrier frequencies (contiguous, non-contiguous, simultaneously transmitted, only one transmitted at a time, etc.). Also, in further exemplary embodiments, e.g. in case of waveguide input and/or output filtering, respective EC elements or EC segments may be clearly separated from each other.
According to further exemplary embodiments, at least one of the first electrically conductive element or layer 121 (Fig. 4A, 4B) and the second electrically conductive element or layer 122 comprises at least one of: a) a film, b) a mesh (e.g., a mesh of wires or other electrical conductors, cf. e.g. Fig. 6E, 6F), c) a wire (Fig. 6F). This enables to apply the control voltage CV (Fig. 1, 4A) to the EC element while at the same time offering mechanical flexibility facilitating e.g. bending of the waveguide or the apparatus.
Figure 8 schematically depicts a perspective view of an apparatus lOOp according to further exemplary embodiments. The apparatus lOOp comprise two EC elements 120_8, 120_9 arranged along the longitudinal axis of the waveguide 110, each of which e.g. comprise a structure similar to the configuration 100j of Fig. 6B. The slotted electrodes 121a_1, 121a_2 (Fig. 6B) are supplied with respective control voltages V_ECbias1, V_ECbias2 via RF blocking elements such as e.g. inductive elements, thus preventing RF leakage from e.g. an interior of the waveguide 110 to the outside (or vice versa, e.g. preventing injection of RF signals from an outside into the interior of the waveguide or the EC element, respectively). According to further exemplary embodiments, as a consequence of the applied control voltages VECbias1, VECbias2 , the EC elements 120_8, 120_9 may change their permittivity along the longitudinal axis LA, which may e.g. favor a modification of transmission modes with the E (field)-vector along the longitudinal axis LA.
Figure 9 schematically depicts a perspective view of an apparatus 100q according to further exemplary embodiments, comprising two EC elements 120_10, 120_11, e.g. of the type as exemplarily depicted by Fig. 6C. Figure 10 exemplarily depicts a schematic topology for supplying the control voltage V_ECbias1 to the EC elements 120_10. 120_11.
Figure 11 schematically depicts a simplified side view of an apparatus 100v according to further exemplary embodiments, wherein a plurality of (presently for example four) EC elements 120_12 is provided which are supplied with a common control voltage V_C+, V_C-. This embodiment may work with propagation modes having E-field components along the propagation-direction (i.e., along the longitudinal axis LA).
According to further exemplary embodiments, individual EC elements may also be connected to and/or controlled by individual supply voltages, e.g. allowing to control them individually and independently from each other.
According to further exemplary embodiments, the EC elements may either be limited to the core 112 only (not shown in Fig. 11), or can extend radially also to the cladding 114, which may have a different impact on an overall RF characteristic of the apparatus 100v, and which thus can be a further design parameter.
Further exemplary embodiments, cf. Figure 12, relate to a device 200 for processing radio frequency, RF, signals comprising at least one apparatus 100 according to the embodiments. As an example, presently, the device 200 is a 3dB-coupler having four ports 201, 202, 203, 204, wherein two apparatus 100 according to the embodiments are respectively coupled to the ports 203, 204. By modifying the control voltage CV (Fig. 1) each apparatus 100 can alter the reflective properties regarding RF signals output at the ports 203, 204 to the apparatus 100, thus effecting a modification of RF signals provided to at least one of the further ports 201, 202.
The configuration 200 of Fig. 12 may e.g. be employed for a variation of a phase of an RF signal RF1 (Fig. 1) travelling on the waveguide. The EC elements 120 of the apparatus 100 may be considered as reflective loads for the 3dB-coupler 200. The structure 200 obviates a need for impedance transformers as may be the case with transmission line realizations.
According to further exemplary embodiments, the principle of operation of the device 200 is as follows: An incoming RF signal is split into two quadrature components - direct and coupled "arms" of the coupler 200. Both direct and coupled arms are terminated into the EC elements of the apparatus 100 without impedance transformers. The signal on both the coupled and direct arms is reflected and passed to the output port (e.g., port 202) with its phase changed. According to further exemplary embodiments, the amount of phase shift is: $Δφ = 2 [\arctan (\frac{Z_{EC max}}{Z_{pmf}}) - \arctan (\frac{Z_{EC min}}{Z_{pmf}})]$
Here, Z_EC stands for the variable reactance of the region comprising the EC elements. According to further exemplary embodiments, the amount of phase shift can be increased by resonating the EC formed capacitor with an inductor. According to further exemplary embodiments, the inductor may be a length of a waveguide.
According to further exemplary embodiments, for pure phase shifting applications, a (spatial) separation between a plurality of EC elements of an apparatus 100 (also cf. Fig. 7) need not be proportional to the guided wavelength. However, for applications related to filtering (e.g., bandstop and bandpass), a spatial separation between several EC elements of the apparatus 100 of Fig. 12 may be proportional to the guided wavelength.
Figure 13A schematically depicts a simplified side view of an apparatus 100w according to further exemplary embodiments, which comprises two EC elements 120_13 that may e.g. be used as a computer, e.g. analog computer, by modifying the control voltages V_EC1, V_EC2. Figure 13B schematically depicts a table characterizing operating states "00", "01", "10", "11" of the apparatus 100w of Fig. 13A according to further exemplary embodiments. With each operating state, a specific overall relative permittivity of the waveguide section comprising the EC elements 120_13 is associated, which can be "selected" by applying the respective control voltages.
According to further exemplary embodiments, at the example shown in Fig. 13A, four discrete signal states (affected by four different εr,total values) can be adjusted, e.g. relevantly influencing the RF input signal RFin and being detectable at the measurable RF output signal RFout. In this exemplarily embodiment, two EC elements have been chosen, allowing to adjust εr,total values with larger difference making detectability easier. However, according to further exemplary embodiments, also a single EC element may support the application by adjusting four εr values but in this case with less difference in values. By increasing the number of EC elements according to further exemplary embodiments, the number of different states can be increased, leading to a possibility of more complex signal conditioning and processing.
By Figure 7 we described the concept of analogue computer achieved by combination of PMF with EC material by the example of implementing EC cells as slice segments, however the principle can also be realized by implementing EC cells as cladding rings with different kind of potential biasing concepts as e.g. indicated by exemplarily embodiments shown in Fig. 1 to Fig. 4.
Further exemplary embodiments relate to a use of the apparatus according to the embodiments and/or of the device according to the embodiments for at least one of: a) processing an RF signal RF1, b) influencing an RF signal RF1, particularly an RF signal propagating within the waveguide 110, 110a, 110b, 110c, c) filtering an RF signal RF1, d) attenuating an RF signal RF1, e) reflecting an RF signal RF1, f) selecting one or more modes of an RF signal RF1 (e.g., by arranging at least one EC element 120 in the cladding 114 and by controlling the EC element 120 accordingly), g) computing, particularly analog computing (cf. Fig. 13A, 13B), based on an RF signal and one or more control signals (e.g., control voltages) for the at least one EC element, h) inducing a modulation on an RF signal transmitted by the waveguide.
Further exemplary embodiments relate to a method of manufacturing an apparatus 100, 100a, 100b, 100w comprising a waveguide 110 for radio frequency, RF, signals, RF1, RF1' and at least one electrochromic, EC, element 120 a permittivity of which can be controlled by applying a control voltage CV to the EC element 120, the method comprising: providing the waveguide 110, arranging the at least one EC element 120 at least partly within or at the waveguide 110.
According to further exemplary embodiments, the step of arranging the at least one EC element at least partly within or at the waveguide may also be performed simultaneously or in an at least partially temporally overlapping fashion with respect to the step of providing the waveguide.
In the following, further aspects and exemplary embodiments are disclosed which may be - either alone or in combination with each other - combined with any of the above explained exemplary embodiments or any combination thereof.
The apparatus according to the embodiments may e.g. be used for current 4G and 5G (or future 6G) mobile radio systems, which may have to cope with very high data rates e.g. caused by immense number of portables, IoT (Internet of Things) devices, V2V (vehicle-to-vehicle) communication, etc. and content like 4K video, on the one hand within mobile radio units (e.g. frontend, baseband), on the other hand from system unit to system unit (e.g. backhauling, fronthauling).
Therefore, in some cases, mobile radio communication may expand from long time established e.g. sub-6 GHz frequency ranges (3G) via mm-wave frequency ranges (5G/NR (New Radio)) to future sub-THz and THz frequencies. There is a strong demand for suitable components for these frequency ranges, preferably at low cost, supporting future very high data rates and frequency ranges while still supporting flexibility. The apparatus according to exemplary embodiments may be used for the abovementioned frequency ranges and offers a cost-efficient and flexible way for tuning properties of a waveguide that can influence RF signal propagation.
Moreover, the principle according to the embodiments enables to provide fibers for RF signals, e.g. polymer fibers or polymer microwave fibers (PMF), which may e.g. comprise a length of up to some meters or even several 10 meters, e.g. 50m.
The principle according to the embodiments enables to provide e.g. PMF with tunable waveguide properties, e.g. based on the above described exemplary embodiments. By integrating one or more EC elements (either as cladding and/or as fibre segments), for example in regular mutual distances, into the polymer fibre 110, an electrically tunable "Bragg grating" structure may be provided within the fibre. According to further exemplary embodiments, this lends frequency-selective and phase-shifting properties (and optionally also inducing modulation on the (PMF) guided RF signal, e.g. by controlled variation of permittivity of the EC material) to the fibre reducing or eliminating the need for costly additional external components and complex transitions to such external components, which may introduce unwanted parasitic effects. According to further exemplary embodiments, this may be particularly beneficial for devices 200 or systems operating in the sub-THz and THz-range, where components are very costly or even not (yet) available, and where device transitions are complex.
The principle according to the embodiments may e.g. be used for realizing structures such as e.g., but not limited to, tunable devices like filters, phase shifters, chromatic dispersion compensators, add-drop multiplexers or analogue computing devices (cf. Fig. 13A), modulators, thus enabling a wide range of applications.
The principle according to the embodiments provides several degrees of freedom: a) during a design phase of the apparatus and/or device and b) during an operation of the apparatus and/or device.
According to further exemplary embodiments, RF signal or wave propagation conditions in the waveguide 110 can e.g. be defined/tuned by a) electrical properties of (polymer) core 112 and cladding 114, b) EC element position on/in the waveguide 110, c) and inter-distance d1, d2 (Fig. 7) of several EC elements, d) number of EC elements, e) length of EC elements along the longitudinal axis LA (Fig. 1) of the waveguide 110, f) radial distance between EC-element 120 and core 112, g) radial thickness of the EC element, etc.
According to further exemplary embodiments, a further design parameter may also be the EC material itself, e.g. characterized by at least one of: used material, type and/or sequence of stacking, thickness(es) of layers segments, etc..
According to further exemplary embodiments, one or more EC elements 120 may be placed quite flexibly into/at the waveguide 110, e.g. at an output (end section, and/or at an input section) of the waveguide, for example in case of associated output filtering embodiment. Thus, according to further exemplary embodiments, in many applications there is no need to implement EC elements 120 over a whole length of the waveguide 110, which reduces implementation effort and costs.
According to further exemplary embodiments, the apparatus may be used for processing RF signals in the GHz range, up to 100 GHz or more, i.e. even into the THz range.
According to further exemplary embodiments, and as already mentioned above, the permittivity of the EC element(s) 120 can be controlled by the tuning or control voltage CV, e.g. applied between two control electrodes 121, 122. Considering that the propagation properties of the electromagnetic waves associated with the RF signal RF1 inside the waveguide 110 depend e.g. on the ratio of core- and cladding-permittivity, a, modulation of this ratio e.g. by the embedded EC element(s) 120 may result in a frequency dependent modification of the propagation characteristics. As an example, in the case of regular distances d1 = d2 (Fig. 7), a notch-filter-type characteristic (in transmission) and a bandpass characteristic (in reflection) may be effected, with a center frequency given in first approximation by the Bragg condition λ_B = n_eff × 2d, with λ_B being the Bragg wave length (in vacuum), and n_eff the effective refraction index, which is a function of the refraction indices from core 112, cladding 114, EC element 120 (e.g., corresponding to the combination at each section of the waveguide), and the wave's propagation mode.
According to further exemplary embodiments, different filter structures can be realized within the waveguide by varying the Bragg-type structure of EC elements within the waveguide.
The principle according to exemplary embodiments enables to provide, e.g. in the form of the apparatus 100, a combined (single) device with tunable RF characteristic, which may be attained without complex individual building blocks (e.g. conventional waveguides and discrete filters) assembly which may result in unwanted parasitics, featuring inter alia design and/or tuning parameters listed in the following: Initial design parameters affecting RF-characteristic, which may however later, once device 200 is fabricated, not be variable any more: - EC element "cladding rings" (cf. e.g. Fig. 6A, 6B, 8) and EC element "slice segments" (cf. e.g. Fig. 11) -> may have different impact on wave modes, each ways for EC control voltage electrode implementation -> different implementation kinds can be beneficial for different wave modes, - number of EC elements implemented into waveguide -> affects e.g. intensity of wanted effect on RF-characteristic (e.g. selectivity of filtering, total phase shift, equalizer, etc.) or defines number of discrete adjustable states in case of analogue computing, - distance d1, d2 between individual EC elements 120 -> affects e.g. target frequency, may e.g. be used for frequency range pre-selection, - width of EC element-based cladding rings and/or EC elements -> also affecting phase shift and e.g. target frequency range; this may e.g. be used for frequency range pre-selection, - General value of dielectric constant around which the dielectric constant value can be tuned by applying control voltages CV (e.g. εr = 10 ... 20 or εr = 80 ... 100) -> e.g. affecting target frequency range.
According to further exemplary embodiments, if e.g. a permittivity of the cladding of the waveguide is in the range of the EC material's tunable permittivity range, a plurality of EC elements may be connected to each other, thus e.g. being implemented over a larger span or distance of the waveguide, i.e. PMF. Thus, if, according to further exemplary embodiments, e.g. the permittivity of the EC elements is chosen same as the permittivity of the cladding, then the EC elements (which may e.g. at least substantially comprise ring shape) may be "invisible" to the RF signal guided through the waveguide, i.e. PMF.
According to further exemplary embodiments, if some EC elements, for which the permittivity may be controlled differently from the permittivity of the cladding are visible to the RF signal guided through the PMF, these EC elements may thus affect the RF signal characteristic. By such an approach, even the effecting position of the EC elements can be "virtually" moved along the waveguide. By this, not only the effective position of the EC elements may be controlled after implementation, but also the effective width of the EC segments.
Parameters allowing for later tuning either in a fab, e.g. when putting device 200 into initial operation or even later when later deployed in the field (re-configuration, compensation of aging, etc.):

Value of dielectric constant to be currently applied on individual EC element 120 -> frequency tuning at previously (initial design) defined frequency range (e.g. in case of filter application) or switching between different states in case of analogue computer application.

According to further exemplary embodiments, depending on a sensitivity for detectability of the permittivity related states, even a number of states can be later re-configured. E.g. at the beginning, an EC element may be responsible for one state, while later two permittivity values of an EC element may be defined, e.g. in order to increase to two represented states. The principle according to exemplary embodiments inter alia enables the following four major applications: RF tuning of a device 200 or system, e.g. when putting into initial operation in the fab -> reduced tuning effort, later RF tuning of device 200 or system, e.g. when deployed in the field, related to actually addressed application -> increased system flexibility and sustainability, compensation of aging and environmental parameter shifts, reducing variety of components to be hold available, waveguide integrated RF filtering, RF phase shifter, Signal equalization, Analogue computing, also enabling higher compactness and avoiding unwanted disturbing parasitic effects (e.g. at transitions) in case of combining PMF with separate filtering, etc. device(s).
The principle according to exemplary embodiments may also support multiband applications, e.g. in such way, that e.g. signals at different RF carriers/frequency bands can be independently controlled/processed, e.g. by implementing different EC elements and/or groups of EC elements related to different respective RF carriers/frequency bands.

Claims

Apparatus (100) comprising a waveguide (110) for radio frequency signals (RF1, RF1'), and at least one electrochromic element (120) a permittivity of which can be controlled by applying a control voltage (CV) to the electrochromic element (120), wherein the at least one electrochromic element (120) is at least partly arranged within or at the waveguide (110).
Apparatus (100) according to claim 1, wherein the at least one electrochromic element (120) is at least partly arranged within a) a core (112) of the waveguide (110; 110a; 110b; 110c), and/or within b) a cladding (114; 114a, 114b) of the waveguide (110; 110a; 110b; 110c).
Apparatus (100) according to at least one of the preceding claims, wherein the waveguide (110; 110a; 110b; 110c) comprises at least in sections a) a circular cross-section or b) a non-circular cross-section, e.g. elliptical or polygonal, e.g. rectangular, cross-section.
Apparatus (100) according to at least one of the preceding claims, wherein the waveguide (110) comprises or is at least one polymer fiber.
Apparatus (100) according to at least one of the preceding claims, wherein the at least one electrochromic element (120; 120a; 120b) comprises a stack (S) of layers stacked, preferably upon each other, along a first axis (a1), wherein the stack (S) comprises a first electrically conductive element or layer (121), a second electrically conductive element or layer (122), and an electrochromic layer (123) arranged between the first electrically conductive layer (121) and the second electrically conductive layer (122).
Apparatus (100) according to claim 5, wherein the first axis (a1) of the stack (S) extends substantially parallel to a longitudinal axis (LA) of the waveguide (110) .
Apparatus (100) according to claim 5, wherein the first axis (a1) of the stack (S) extends substantially perpendicular to a longitudinal axis (LA) of the waveguide (110).
Apparatus (100) according to claim 7, wherein the first axis (a1) of the stack (S) extends, particularly at least in sections, circumferentially around the longitudinal axis (LA) of the waveguide (110).
Apparatus (100) according to claim 7, wherein the first axis (a1) of the stack (S) extends radially with respect to the longitudinal axis (LA) of the waveguide (110).
Apparatus (100) according to at least one of the claims 5 to 9, wherein the stack (S) comprises a circular ring segment cross-section extending at least partly circumferentially around the longitudinal axis (LA) of the waveguide (110).
Apparatus (100) according to at least one of the preceding claims, wherein two or more electrochromic elements (120; 120_1, 120_2, 120_3, 120_4; 120_5, 120_6) are provided.
Apparatus (100) according to claim 11, wherein the two or more electrochromic elements (120; 120_1, 120_2, 120_3, 120_4; 120_5, 120_6) are arranged along a or the longitudinal axis (LA) of the waveguide (110).
Apparatus (100) according to at least one of the claims 5 to 12, wherein at least one of the first electrically conductive element or layer (121) and the second electrically conductive element or layer (122) comprises at least one of: a) a film, b) a mesh, c) a wire.
Device (200) for processing radio frequency signals (RF1, RF1') comprising at least one apparatus (100) which comprises a waveguide (110) for radio frequency signals (RF1, RF1'), and at least one electrochromic element (120) a permittivity of which can be controlled by applying a control voltage (CV) to the electrochromic element (120), wherein the at least one electrochromic element (120) is at least partly arranged within or at the waveguide (110).
Device (200) according to claim 14, wherein the at least one electrochromic element (120) is at least partly arranged within a) a core (112) of the waveguide (110; 110a; 110b; 110c), and/or within b) a cladding (114; 114a, 114b) of the waveguide (110; 110a; 110b; 110c).
Device (200) according to at least one of the claims 14 to 15, wherein the waveguide (110) comprises or is at least one polymer fiber.
Device (200) according to at least one of the claims 14 to 16, wherein the at least one electrochromic element (120; 120a; 120b) comprises a stack (S) of layers stacked, preferably upon each other, along a first axis (a1), wherein the stack (S) comprises a first electrically conductive element or layer (121), a second electrically conductive element or layer (122), and an electrochromic layer (123) arranged between the first electrically conductive layer (121) and the second electrically conductive layer (122).
Device (200) according to claim 17, wherein the first axis (a1) of the stack (S) extends substantially parallel to a longitudinal axis (LA) of the waveguide (110) or substantially perpendicular to the longitudinal axis (LA) of the waveguide (110).
Device (200) according to at least one of the claims 14 to 18, wherein two or more electrochromic elements (120; 120_1, 120_2, 120_3, 120_4; 120_5, 120_6) are provided, wherein preferably the two or more electrochromic elements (120; 120_1, 120_2, 120_3, 120_4; 120_5, 120_6) are arranged along a or the longitudinal axis (LA) of the waveguide (110).
Method of using an apparatus (100) which comprises a waveguide (110) for radio frequency signals (RF1, RF1'), and at least one electrochromic element (120) a permittivity of which can be controlled by applying a control voltage (CV) to the electrochromic element (120), wherein the at least one electrochromic element (120) is at least partly arranged within or at the waveguide (110), the method comprising at least one of the following steps: a) processing a radio frequency signal, b) influencing a radio frequency signal, particularly a radio frequency signal propagating within the waveguide, c) filtering a radio frequency signal, d) attenuating a radio frequency signal, e) reflecting a radio frequency signal, f) selecting one or more modes of a radio frequency signal, g) computing, particularly analog computing, based on a radio frequency signal and one or more control signals for the at least one electrochromic element (120), h) modulating, particularly by controlled variation of permittivity of the at least one electrochromic element, i) frequency selective radio frequency signal processing, particularly conditioning, e.g. in case of multiband applications.