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

<CIT> discloses an apparatus comprising a first layer of electrically conductive material and a second layer of electrically conductive material.

<CIT> discloses infrared emission devices comprising an array of polaritonic infrared emitters arranged on a substrate.

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 according to claim <NUM>. 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.

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 LiNbO<NUM>, lithium niobate), c) an electrochromic (EC) layer or film (e.g. comprising WO<NUM>, 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 <NUM> degrees and <NUM> degrees, preferably between <NUM> degrees and <NUM> 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 <NUM> degrees and <NUM> degrees, preferably between <NUM> degrees and <NUM> 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 <NUM>° degrees, or completely, i.e. comprising <NUM>° 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 according to claim <NUM>.

Further exemplary embodiments relate to a method of using according to claim <NUM>.

Further examples 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 examples, 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.

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

<FIG> schematically depicts a simplified block diagram of an apparatus <NUM> according to exemplary embodiments. The apparatus <NUM> comprises a waveguide <NUM> for radio frequency, RF, signals, RF1, RF1', and at least one electrochromic, EC, element <NUM> a permittivity of which can be controlled by applying a control voltage CV to the EC element <NUM>, wherein the at least one EC element <NUM> is at least partly arranged within or at the waveguide <NUM>. This enables to effect a change of electric characteristics of the portion of the waveguide <NUM> where the EC element <NUM> 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> by the different reference signs RF1, RF1', wherein reference sign RF1 is e.g. associated with an RF signal input to the waveguide <NUM>, and wherein reference sign RF1' represents the influenced RF signal, i.e. after passing the EC element <NUM>.

According to further exemplary embodiments, arranging the at least one EC element <NUM> at least partly within or at the waveguide <NUM> may comprise arranging the at least one EC element <NUM> relative to the waveguide <NUM> such that the EC element <NUM> or at least a portion of EC material (cf. e.g. <FIG> explained further below) of the EC element <NUM> may interact with at least a portion of the RF signal(s) RF1, RF1' propagating within the waveguide <NUM>.

According to further exemplary embodiments, cf. the apparatus 100a of <FIG>, the at least one EC element <NUM> is at least partly (presently fully) arranged within a core <NUM> of the waveguide <NUM>.

According to further exemplary embodiments, cf. the apparatus 100b of <FIG>, the at least one EC element <NUM> is at least partly arranged within a cladding <NUM> of the waveguide <NUM>, and partly within the core <NUM>.

According to further exemplary embodiments, cf. the apparatus 100c of <FIG>, the at least one EC element <NUM> is fully arranged within the cladding <NUM>.

According to further exemplary embodiments, cf. the apparatus 100d of <FIG>, the at least one EC element <NUM> is fully arranged within the core <NUM> and the cladding <NUM>.

According to further exemplary embodiments, arranging the at least one EC element <NUM> at least partly within or at the waveguide <NUM> may comprise arranging the at least one EC element <NUM> relative to the waveguide <NUM> such that the EC element <NUM> or at least a portion of EC material of the EC element <NUM> may at least interact with a portion of RF signal(s) propagating outside of the waveguide <NUM>.

In this regard, according to further exemplary embodiments, cf. the apparatus 100e of <FIG>, the at least one EC element <NUM> is partly arranged within the cladding <NUM>, which still enables to influence the RF signal RF1, e.g. under control of the EC element <NUM> by means of the control voltage CV (<FIG>).

According to further exemplary embodiments, cf. reference sign <NUM>' of <FIG>, the at least one EC element <NUM>' may be arranged at an outside of the waveguide <NUM>, i.e. placed onto an outer surface <NUM>' of the waveguide <NUM>.

According to further exemplary embodiments, cf. reference sign <NUM>'' of <FIG>, the at least one EC element <NUM>'' may be arranged at an outside of the waveguide <NUM>, particularly spaced apart from, i.e. not in direct surface contact with, the outer surface <NUM>' of the waveguide <NUM>. 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 <NUM> and the at least one EC element <NUM>''. Nevertheless, the propagation of the RF signal RF1 (<FIG>) guided by the waveguide <NUM> may be influenced using the at least one EC element <NUM>'' (<FIG>), 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 <NUM>''.

<FIG> schematically depicts a further exemplary embodiment, wherein the apparatus 100f comprises an EC element <NUM> that is partly arranged within the core <NUM>, the cladding <NUM>, and which also partly protrudes from the surface of the cladding <NUM> or the waveguide <NUM>.

According to further exemplary embodiments, the waveguide <NUM> (<FIG>) may comprise or consist of one or more dielectric materials. According to further exemplary embodiments, the core <NUM> of the waveguide <NUM> may comprise or consist of dielectric material. According to further exemplary embodiments, at least one cladding <NUM> of the waveguide <NUM> 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. <FIG>, the waveguide 110a comprises at least in sections a circular cross-section.

According to further exemplary embodiments, cf. <FIG>, 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. <FIG>, the waveguide 110c comprises two claddings 114a, 114b with rectangular cross-sections, and a core <NUM>, 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 <NUM>, <NUM>, 114a, 114b of the fiber comprises polymer material.

According to further exemplary embodiments, the waveguide 110a (<FIG>) is a polymer fiber having a core <NUM> of polymer material and a cladding <NUM>, which surrounds the core, wherein the cladding <NUM> 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 <NUM>.

According to further exemplary embodiments, cf. <FIG>, the at least one EC element 120a comprises a stack S of layers <NUM>, <NUM>, <NUM> 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 <NUM>, a second electrically conductive element or layer <NUM>, and an EC layer <NUM> arranged between the first electrically conductive layer <NUM> and the second electrically conductive layer <NUM>.

According to further exemplary embodiments, the control voltage CV may at least temporarily be applied to the electrically conductive layers <NUM>, <NUM>.

According to further exemplary embodiments, cf. the EC element 120b of <FIG>, the EC layer <NUM>, 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 <NUM> 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 LiNbO<NUM>, lithium niobate), c) an electrochromic (EC) layer or film 123c (e.g. comprising WO<NUM>, 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 LiNbO<NUM>), an electrochromic (EC) layer or film (e.g. comprising WO<NUM>), an (optional) ion storage layer or film (e.g. comprising NiO), a second electrolyte layer (e.g. comprising LiNbO<NUM>), a second conductive layer.

According to further exemplary embodiments, one or more of the EC elements <NUM>, <NUM>', <NUM>'' explained above with reference to <FIG> may e.g. comprise a configuration identical or at least similar to the configuration 120a of <FIG> or the configuration 120b of <FIG> or the further stack structures exemplarily mentioned above.

According to further exemplary embodiments, cf. the apparatus <NUM> of <FIG>, 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 <NUM> 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 <NUM>.

According to further exemplary embodiments, "extending substantially parallel to the longitudinal axis LA of the waveguide <NUM>" means that an angle between the longitudinal axis LA of the waveguide <NUM> and the first axis a1 of the stack S ranges between <NUM> degrees and <NUM> degrees, preferably between <NUM> degrees and <NUM> degrees.

According to further exemplary embodiments, cf. the apparatus <NUM> of <FIG>, the first axis a1 of the stack S extends substantially perpendicular to the longitudinal axis LA of the waveguide <NUM>, which e.g. means that an angle between the longitudinal axis LA of the waveguide <NUM> and the first axis a1 of the stack S ranges between <NUM> degrees and <NUM> degrees, preferably between <NUM> degrees and <NUM> degrees.

<FIG> schematically depicts a simplified partial cross-sectional front view (i.e., along the longitudinal axis LA, cf. <FIG>) of an apparatus 100i according to further exemplary embodiments. Depicted is an outer front surface 121a of the first electrically conductive layer <NUM> of the EC stack, wherein the further layers <NUM>, <NUM> (also cf. <FIG>) are not visible in the exemplary depiction of <FIG> as the stack coordinate a1 extends collinearly with the longitudinal axis LA into the drawing plane of <FIG>.

According to further exemplary embodiments, the conductive layer <NUM> may be slotted, cf. the apparatus 100j of <FIG>, wherein two electrode sections 121a_1, 121a_2 are defined, separated by slots SL, which may reduce RF radiation emanating from the conductive layer <NUM>, i.e. preventing it to operate as an "antenna" for the RF signal(s) RF1.

According to further exemplary embodiments, cf. the apparatus <NUM> of <FIG>, the first axis a1 of the stack S extends, particularly at least in sections, circumferentially around the longitudinal axis of the waveguide <NUM>. In these exemplary embodiments, the stack coordinate a1 may be curved, and the sequence of the layers <NUM>, <NUM>, <NUM> of the EC stack may extend in a circumferential direction a1, as exemplarily depicted for one EC element 120_1 of the apparatus <NUM>.

According to further exemplary embodiments, the apparatus <NUM> 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 <NUM> of <FIG>, 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 <NUM>.

According to further exemplary embodiments, the stack S (<FIG>) comprises a circular ring segment cross-section extending at least partly (i.e., less than <NUM>° degrees, or completely, i.e. comprising <NUM>° degrees) circumferentially around the longitudinal axis of the waveguide, which may e.g. apply to the EC element(s) of <FIG>.

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 <NUM>, cf. e.g. <FIG>.

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 <NUM>, cf. e.g. <FIG> (first axis a1 curved, but also perpendicular to longitudinal axis LA), 6B.

<FIG> schematically depicts a simplified partial cross-sectional front view (i.e., along the longitudinal axis LA, cf. <FIG>) of an apparatus <NUM> according to further exemplary embodiments, wherein the electrodes <NUM>', <NUM>' are configured as a mesh, i.e. mesh of wires.

According to further exemplary embodiments, the core <NUM> is not shielded by the inner mesh <NUM>' 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 <NUM>', <NUM>' may also comprise or consist of a wrapped foil, e.g. instead of the mesh.

<FIG> schematically depicts a simplified partial cross-sectional front view (i.e., along the longitudinal axis LA, cf. <FIG>) of an apparatus 100n according to further exemplary embodiments, wherein the electrode <NUM>'' comprises a plurality (presently for example four) wires, and wherein the radially outer electrode <NUM>' is configured as a mesh, i.e. mesh of wires.

According to further exemplary embodiments, cf. the apparatus 100o of <FIG>, 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 <NUM>.

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 <NUM>, 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>, 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>.

According to further exemplary embodiments, cf. <FIG>, 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 <NUM> (<FIG>) and the second electrically conductive element or layer <NUM> 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>), c) a wire (<FIG>). This enables to apply the control voltage CV (<FIG>, <FIG>) to the EC element while at the same time offering mechanical flexibility facilitating e.g. bending of the waveguide or the apparatus.

<FIG> schematically depicts a perspective view of an apparatus 100p according to further exemplary embodiments. The apparatus 100p comprise two EC elements 120_8, 120_9 arranged along the longitudinal axis of the waveguide <NUM>, each of which e.g. comprise a structure similar to the configuration 100j of <FIG>. The slotted electrodes 121a_1, 121a_2 (<FIG>) are supplied with respective control voltages VECbias1, VECbias2 via RF blocking elements such as e.g. inductive elements, thus preventing RF leakage from e.g. an interior of the waveguide <NUM> 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.

<FIG> 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>. <FIG> exemplarily depicts a schematic topology for supplying the control voltage VECbias1 to the EC elements 120_10.

<FIG> 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 VC+, VC-. 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 <NUM> only (not shown in <FIG>), or can extend radially also to the cladding <NUM>, 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. <FIG>, relate to a device <NUM> for processing radio frequency, RF, signals comprising at least one apparatus <NUM> according to the embodiments. As an example, presently, the device <NUM> is a 3dB-coupler having four ports <NUM>, <NUM>, <NUM>, <NUM>, wherein two apparatus <NUM> according to the embodiments are respectively coupled to the ports <NUM>, <NUM>. By modifying the control voltage CV (<FIG>) each apparatus <NUM> can alter the reflective properties regarding RF signals output at the ports <NUM>, <NUM> to the apparatus <NUM>, thus effecting a modification of RF signals provided to at least one of the further ports <NUM>, <NUM>.

The configuration <NUM> of <FIG> may e.g. be employed for a variation of a phase of an RF signal RF1 (<FIG>) travelling on the waveguide. The EC elements <NUM> of the apparatus <NUM> may be considered as reflective loads for the 3dB-coupler <NUM>. The structure <NUM> 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 <NUM> is as follows: An incoming RF signal is split into two quadrature components - direct and coupled "arms" of the coupler <NUM>. Both direct and coupled arms are terminated into the EC elements of the apparatus <NUM> without impedance transformers. The signal on both the coupled and direct arms is reflected and passed to the output port (e.g., port <NUM>) with its phase changed. According to further exemplary embodiments, the amount of phase shift is: <MAT>.

Here, zEC 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 <NUM> (also cf. <FIG>) 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 <NUM> of <FIG> may be proportional to the guided wavelength.

<FIG> 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 VEC1, VEC2. <FIG> schematically depicts a table characterizing operating states "<NUM>", "<NUM>", "<NUM>", "<NUM>" of the apparatus 100w of <FIG> 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>, 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 <FIG> 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>.

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 <NUM>, 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 <NUM> in the cladding <NUM> and by controlling the EC element <NUM> accordingly), g) computing, particularly analog computing (cf. <FIG>), 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 <NUM>, 100a, 100b, 100w comprising a waveguide <NUM> for radio frequency, RF, signals, RF1, RF1' and at least one electrochromic, EC, element <NUM> a permittivity of which can be controlled by applying a control voltage CV to the EC element <NUM>, the method comprising: providing the waveguide <NUM>, arranging the at least one EC element <NUM> at least partly within or at the waveguide <NUM>.

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 <NUM> and <NUM> (or future <NUM>) 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 <NUM> 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-<NUM> frequency ranges (<NUM>) via mm-wave frequency ranges (<NUM>/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 <NUM> meters, e.g. <NUM>.

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 <NUM>, 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 <NUM> 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>), 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 <NUM> can e.g. be defined/tuned by a) electrical properties of (polymer) core <NUM> and cladding <NUM>, b) EC element position on/in the waveguide <NUM>, c) and inter-distance d1, d2 (<FIG>) of several EC elements, d) number of EC elements, e) length of EC elements along the longitudinal axis LA (<FIG>) of the waveguide <NUM>, f) radial distance between EC-element <NUM> and core <NUM>, 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 <NUM> may be placed quite flexibly into/at the waveguide <NUM>, 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 <NUM> over a whole length of the waveguide <NUM>, 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 <NUM> 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) <NUM> can be controlled by the tuning or control voltage CV, e.g. applied between two control electrodes <NUM>, <NUM>. Considering that the propagation properties of the electromagnetic waves associated with the RF signal RF1 inside the waveguide <NUM> depend e.g. on the ratio of core- and cladding-permittivity, a, modulation of this ratio e.g. by the embedded EC element(s) <NUM> may result in a frequency dependent modification of the propagation characteristics. As an example, in the case of regular distances d1 = d2 (<FIG>), 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 λB = neff × 2d, with λB being the Bragg wave length (in vacuum), and neff the effective refraction index, which is a function of the refraction indices from core <NUM>, cladding <NUM>, EC element <NUM> (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 <NUM>, 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 <NUM> is fabricated, not be variable any more: - EC element "cladding rings" (cf. e.g. <FIG>, <FIG>) and EC element "slice segments" (cf. e.g. <FIG>) -> 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 <NUM> -> 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 = <NUM>. <NUM> or εr = <NUM>. <NUM>) -> 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 <NUM> into initial operation or even later when later deployed in the field (re-configuration, compensation of aging, etc.):.

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. 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 <NUM> or system, e.g. when putting into initial operation in the fab -> reduced tuning effort, later RF tuning of device <NUM> 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).

Claim 1:
Apparatus (<NUM>) comprising a waveguide (<NUM>) for radio frequency signals (RF1, RF1'), wherein the waveguide (<NUM>) comprises or is at least one polymer fiber, and at least one electrochromic element (<NUM>) a permittivity of which can be controlled by applying a control voltage (CV) to the electrochromic element (<NUM>), wherein the at least one electrochromic element (<NUM>) is at least partly arranged within or at the waveguide (<NUM>).