CN113497322A

CN113497322A - Arrangement comprising a waveguide for radio frequency signals

Info

Publication number: CN113497322A
Application number: CN202110362929.9A
Authority: CN
Inventors: S·布尔加; W·泰普尔; D·维格纳; R·科普夫
Original assignee: Nokia Technologies Oy
Current assignee: Nokia Technologies Oy
Priority date: 2020-04-06
Filing date: 2021-04-02
Publication date: 2021-10-12
Anticipated expiration: 2041-04-02
Also published as: CN113497322B; EP3893326A1

Abstract

An apparatus includes a waveguide for a radio frequency signal and at least one active element including a transition metal oxide material and two electrodes for applying a control voltage to the transition metal oxide material.

Description

Arrangement comprising a waveguide for radio frequency signals

Technical Field

Example embodiments relate to an apparatus including a waveguide for a Radio Frequency (RF) signal.

Background

Devices of the aforementioned type may be used for transmitting RF signals, for example from a source to a sink.

Disclosure of Invention

The scope of protection sought for the various embodiments of the invention is set forth by the independent claims. The exemplary embodiments and features (if any) described in this specification, which are not included in the scope of the independent claims, should be construed as examples useful for understanding the various exemplary embodiments of the present invention.

Exemplary embodiments relate to an apparatus comprising a waveguide for a radio frequency signal and at least one active element comprising a transition metal oxide material (TMO) and two electrodes for applying a control voltage to the transition metal oxide material. This enables influencing the change of the electrical characteristics at the portion of the waveguide where the active element 120 is located, for example by altering the control voltage, so that the propagation of electromagnetic waves associated with the RF signal can be influenced.

According to further exemplary embodiments, the TMO material may comprise at least one of: tungsten trioxide (WO)₃) Titanium dioxide (TiO)₂) Vanadium dioxide (VO)₂) Nickel oxide (NiO), manganese dioxide (MnO)₂)。

According to a further exemplary embodiment, the at least one active element may be at least partially arranged within or at the waveguide, preferably such that the active element or at least a part of the TMO material of the active element may interact with at least a part of the RF signal propagating within the waveguide.

According to further exemplary embodiments, disposing the at least one active element at least partially within or at the waveguide may comprise disposing the at least one active element relative to the waveguide such that the active element or at least a portion of the TMO material of the active element may interact with at least a portion of the RF signal propagating outside the waveguide.

According to a further exemplary embodiment, the at least one active element is configured to change between a dielectric state, in which the at least one active element is not electrically conductive, and a conductive state, in which the at least one active element is electrically conductive, depending on the control voltage.

According to further exemplary embodiments, the at least one active element may be configured to perform a phase change and/or a metal-non-metal transition, such as a Mott-transition, depending on an electric field (e.g. in the form of a control voltage) applied to the TMO material. In this way, by applying a particular control voltage, the active element can be influenced to exhibit electrical properties similar to a metal conductor or to a dielectric material (i.e., spacer). According to further exemplary embodiments, this property may also be changed gradually or continuously by changing the control voltage gradually or continuously, which e.g. enables to selectively attenuate the RF signal(s) propagating within the waveguide.

According to a further exemplary embodiment, the at least one active element is arranged at least partially a) within the core of the waveguide and/or b) within the cladding (or each within at least one cladding) of the waveguide.

According to a further exemplary embodiment, the waveguide comprises in cross-section at least a) a circular cross-section or b) a non-circular cross-section, such as an elliptical cross-section or a polygonal cross-section, such as a rectangular cross-section.

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 a dielectric material.

According to further exemplary embodiments, the at least one cladding of the waveguide may comprise or consist of a dielectric material.

According to further exemplary embodiments, the dielectric material may comprise a polymer material which is cost effective and enables efficient production.

According to a further exemplary embodiment, the waveguide comprises or is at least one polymer fiber.

According to a further exemplary embodiment, the waveguide is a polymer fiber having a core of a polymer material and a cladding surrounding the core, wherein the cladding preferably further comprises a polymer material. According to further exemplary embodiments, an optional coating may be provided, which may for example surround the cladding.

According to a further exemplary embodiment, the at least one active element comprises a stack of layers stacked along the first axis, preferably on top of each other, wherein the stack comprises a first layer formed by a first electrode of the two electrodes, a second layer formed by a second electrode of the two electrodes, and a third layer formed by a Transition Metal Oxide (TMO) material, the third (e.g. TMO) layer being arranged between the first and second layers.

According to a further exemplary embodiment, the first axis of the stack extends substantially parallel to the longitudinal axis of the waveguide. According to a further exemplary embodiment, "substantially parallel" means that the angle between the longitudinal axis of the waveguide and the first axis of the stack may be in the range between 0 degrees and 20 degrees.

According to a further exemplary embodiment, at least one of the first electrode and the second electrode comprises a metal layer ("electrode layer").

According to a further exemplary embodiment, at least one of the first electrode and the second electrode comprises a thickness which is smaller than a skin depth of at least one frequency component of the radio frequency signal. This enables the RF signal(s) propagating within the waveguide to propagate (at least partially) through the at least one active element (and its electrode (s)), especially if the at least one active element or its TMO material is in its dielectric (i.e., non-metallic) state, which may also be considered an "OFF (OFF)" state according to further exemplary embodiments.

According to a further exemplary embodiment, in the off-state the TMO material layer of the active element exhibits dielectric properties (i.e. non-conductive properties), thus in principle enabling the propagation of RF signals and associated Electromagnetic (EM) waves through the TMO material layer (and according to a further preferred embodiment also through the electrode layer(s) if they are sufficiently thin).

According to further exemplary embodiments, in the "on" state, the TMO material of the active element exhibits metallic (i.e., conductive) properties, thus in principle preventing the RF signal and associated Electromagnetic (EM) waves from propagating through the TMO material layer, i.e., from a transmission perspective, attenuating the RF signal. According to further exemplary embodiments, however, the degree of attenuation may be controlled by selecting the layer thickness of the TMO material layer. In particular, similar to the electrode layer according to further exemplary embodiments, if the TMO material layer has a sub-skin depth thickness value, at least part of the RF signal(s) may propagate through the TMO material layer, even in the on-state.

According to a further exemplary embodiment, at least one of the first electrode and the second electrode comprises a thickness which is smaller than a skin depth of a highest frequency component of the radio frequency signal. This enables the highest frequency component of the radio frequency signal to be at least partially transmitted (i.e. propagated) through the at least one active element.

According to a further exemplary embodiment, at least one of the first electrode and the second electrode comprises a thickness smaller than 1 micrometer (μm), preferably smaller than 500 nanometers (nm).

According to a further exemplary embodiment, the third layer comprises a thickness larger than a skin depth of the at least one frequency component of the radio frequency signal, in some embodiments the thickness is larger than 300% of the skin depth, such as larger than 500% of the skin depth.

According to a further exemplary embodiment, the apparatus comprises at least one control device configured to provide at least one control voltage to the at least one active element, whereby the dielectric or electrical properties of the TMO material may be influenced as exemplarily explained above. Thus enabling control of the degree of attenuation or propagation of the radio frequency signal(s).

According to a further exemplary embodiment, the at least one control device is configured to provide, at least temporarily, to the at least one control voltage a) a plurality of discrete voltage values, or b) a continuous voltage value.

According to further exemplary embodiments, providing a plurality (e.g., two) different discrete voltage values may be used to switch the at least one active element 120 on and off, i.e., to switch the at least one active element between its conductive state of the TMO material and its dielectric state of the TMO material.

According to further exemplary embodiments, providing the active elements with a continuous voltage value may be used to continuously change at least one active element between its conductive state of the TMO material and its dielectric state of the TMO material, thus for example influencing the continuously changing degree of the attenuation.

According to a further exemplary embodiment, the apparatus comprises at least one impedance transformer, wherein preferably the at least one impedance transformer is arranged adjacent to the at least one active element. As an example, at least one impedance transformer may be used to perform impedance matching between the waveguide and the at least one active element. Especially in case the at least one active element is in the off-state, whereby reflections of the RF signal at the interface between the waveguide and the at least one active element can be avoided or at least reduced.

According to a further exemplary embodiment, an impedance transformer having an electrical length of a quarter wavelength at the operating frequency (i.e. the (center) frequency of the RF signal (s)) may be provided, the characteristic impedance Z of which_matchMay be characterized, for example, by:

wherein Z_{free space}Characterizing the impedance of free space, where_{r OFF}Characterizing the relative permittivity of at least one active element in the off-state, where ∈_{r PMF}The relative dielectric constant of the waveguide is characterized. As an example, the at least one active element may be in its off-state if the control voltage CV has a zero value.

According to a further exemplary embodiment, the at least one impedance transformer may comprise a segment of a waveguide having a predetermined length.

According to a further exemplary embodiment, the at least one impedance transformer is provided, for example based on [ equation 1], such that in an off-state of the at least one active element, there is (at least substantially) no undesired reflection at the waveguide/active element interface and propagation of the RF signal between the input and the output is not impeded.

According to further exemplary embodiments, the situation may change as soon as a non-zero control voltage is applied to the at least one active element or its TMO material, respectively. Now, the layer comprising the transition metal oxide becomes conductive (on-state), in particular highly conductive by indirect contact with a conductive electrode ("bias pad"), which according to a further exemplary embodiment is a sub-skin depth conductor.

According to a further exemplary embodiment, the composite electrical thickness of the at least one active element or its TMO material (layer) may now be significantly increased (compared to the off-state), e.g. in the on-state, thus generating a significant reflection of the RF signal at the boundary or interface between the waveguide and the at least one active element.

According to a further exemplary embodiment, it is assumed that the RF signal has been provided to the at least one active element on the "input" side of the at least one active element, which may result in a significantly attenuated RF signal at the "output" of the apparatus (i.e. on the output side of the at least one active element).

According to a further exemplary embodiment, the composite electrical thickness of the at least one active element or of its active (e.g. TMO) region may be, for example, in the range of several skin depths of the RF signal(s), such that the RF signal at the output may be (in particular completely) cancelled out.

According to further exemplary embodiments, the composite electrical thickness of the at least one active element may depend on the physical thickness of the transition metal oxide layer, and possibly also on the mode of operation of the at least one active element.

According to further exemplary embodiments, two modes may be distinguished:

1. according to an exemplary first mode, the active (e.g., TMO) layer thickness in the on state is several skin depths thick;

2. according to an exemplary second mode, the active layer thickness in the on state is sub-skin depth thick.

According to further exemplary embodiments, in the first mode, the device may be operable, for example, by applying a continuous DC (direct current) control voltage (i.e. a control voltage that may vary from 0V (volts) to a maximum value Vmax, Vmax >0V), wherein, for example, the conductivity and thus the skin depth of the transition metal oxide layer may be a function of the voltage value of the applied control voltage. This (exemplary first) mode of operation may also be referred to as an "analog waveguide or transmission line attenuator".

According to further exemplary embodiments, in the second mode, even if the highest allowed control voltage (value Vmax) is applied to the at least one active element or its TMO material (layer), one active region or TMO layer may not be sufficient to completely eliminate the input RF signal. Thus, in order to provide full controllability of the amplitude of the output RF signal, according to further exemplary embodiments, several TMO material layers may be provided, for example in the form of a plurality of (preferably adjacent) active elements.

In other words, according to further exemplary embodiments, a plurality of active elements may be provided in the waveguide, wherein at least two active elements may be arranged adjacent to each other.

According to further exemplary embodiments, a plurality of active elements may be arranged in series along one axis or the longitudinal axis of the waveguide, wherein preferably adjacent active elements share one common electrode. As an example, the second electrode of the first active element may also form the first electrode of a second active element arranged adjacent to the first active element.

According to a further exemplary embodiment, the plurality of active elements may be provided in a length segment of the waveguide corresponding to 20% or less, preferably 10% or less, more preferably 5% or less of the total length of the waveguide. In other words, the region of the waveguide comprising one or more active elements according to embodiments may form a relatively small portion compared to the total length of the waveguide.

According to a further exemplary embodiment, the at least one active element or the plurality of active elements may be arranged at the first and/or second axial end of the waveguide.

According to a further exemplary embodiment, the apparatus may comprise a coupler, wherein the at least one active element is connected to at least one port of the coupler.

According to a further exemplary embodiment, at least a first active element or a first group of active elements is connected to a first port of the coupler and at least a second active element or a second group of active elements is connected to a second port of the coupler.

Further exemplary embodiments relate to a method of using a device comprising a waveguide for radio frequency signals and at least one active element comprising a transition metal oxide material and two electrodes for applying a control voltage to the transition metal oxide material, the method comprising at least one of the following steps: a) processing the radio frequency signal; b) influencing a radio frequency signal, in particular a radio frequency signal propagating within a waveguide; c) attenuating the radio frequency signal; d) reflecting the radio frequency signal; e) selecting one or more modes of a radio frequency signal; f) modulating the radio frequency signal.

Drawings

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 an exemplary embodiment;

2A, 2B each schematically depict a simplified side view of an apparatus according to further exemplary embodiments;

FIG. 3A schematically depicts a simplified cross-sectional elevation view of a waveguide according to further exemplary embodiments;

FIG. 3B schematically depicts a simplified cross-sectional elevation view of a waveguide according to further exemplary embodiments;

fig. 4 schematically depicts a simplified side view of an active element according to a further exemplary embodiment;

FIG. 5 schematically depicts a simplified side view of an apparatus according to a further exemplary embodiment;

FIG. 6 schematically depicts a simplified side view of an apparatus according to further exemplary embodiments;

FIG. 7 schematically depicts a simplified perspective view of an apparatus according to further exemplary embodiments;

FIG. 8 schematically depicts a simplified perspective view of an apparatus according to further exemplary embodiments; and

fig. 9 schematically depicts a block diagram of an apparatus according to a further exemplary embodiment.

Detailed Description

Fig. 1 schematically depicts a simplified block diagram of an apparatus 100 according to an exemplary embodiment. The apparatus 100 comprises a waveguide 110 for Radio Frequency (RF) signals RF1, RF1' and at least one active element 120, the active element 120 comprising a Transition Metal Oxide (TMO) material and two electrodes for applying a control voltage CV to the TMO material. This enables influencing the change of the electrical characteristics at the portion of the waveguide 110 where the active element 120 is located, for example by altering the control voltage CV, so that the propagation of electromagnetic waves associated with the RF signal can be influenced, with reference to the further RF signal RF'.

According to further exemplary embodiments, the at least one active element 120 may be arranged at least partially within the waveguide 110 or at the waveguide 110, preferably such that the active element 120 or at least a part of the TMO material of the active element 120 may interact with at least a part of the RF signal(s) RF1, RF1' propagating within the waveguide 110.

According to further exemplary embodiments, disposing at least one active element 120 at least partially within the waveguide 110 or at the waveguide 110 may include disposing the at least one active element 120 relative to the waveguide 110 such that at least a portion of the active element 120 or TMO material of the active element 120 may interact with at least a portion of the RF signals RF1, RF1' propagating outside the waveguide.

According to a further exemplary embodiment, the at least one active element 120 is configured to change, depending on the control voltage CV, between a dielectric state, in which the at least one active element 120 (or its respective TMO material) is non-conductive, and a conductive state, in which the at least one active element 120 (or its respective TMO material) is conductive.

According to further exemplary embodiments, the at least one active element 120 may be configured to perform a phase change and/or a metal-to-non-metal transition, such as a mott transition, depending on an electric field applied to the TMO material (e.g. in the form of a control voltage CV). In this way, by applying a specific control voltage CV, the active element 120 can be influenced to exhibit electrical properties similar to that of a metal conductor or to that of a dielectric material (i.e., spacer).

According to further exemplary embodiments, this property may also be changed gradually or continuously by changing the control voltage CV gradually or continuously, which e.g. enables to selectively attenuate the RF signal(s) RF1, RF1' propagating within the waveguide 110.

According to a further exemplary embodiment, referring to the schematic side view of the apparatus 100a of fig. 2A, the at least one active element 120 is arranged at least partially a) within the core 112 of the waveguide 110, and/or b) within the cladding 114 (or each within at least one cladding) of the waveguide 110.

According to the example of fig. 2A, the cross-section of the at least one active element 120 substantially corresponds to the cross-section of the waveguide 110 (i.e. comprising the core 12 and the cladding 114).

According to a further exemplary embodiment, referring to the schematic side view of the apparatus 100B of fig. 2B, the at least one active element 120 is arranged at least partially within the core 112 of the waveguide 110, instead of within the cladding 114 of the waveguide 110.

According to a further exemplary embodiment, referring to the cross-sectional elevation view of fig. 3A, the waveguide 110a comprises at least a section of a) circular cross-section with a core 112a and a cladding 114 a.

According to further exemplary embodiments, referring to the cross-sectional elevation view of fig. 3B, the waveguide 110B includes a non-circular cross-section, such as an elliptical cross-section, or, as depicted in fig. 3B, a polygonal cross-section, such as a rectangular cross-section. Presently, the waveguide 110B of fig. 3B includes a core 112B having a rectangular cross-section, the core 112B illustratively being embedded (e.g., "sandwiched") between two claddings 114a, 114B (a top cladding and a bottom cladding).

According to further exemplary embodiments, waveguide configurations with non-circular cross-sections, wherein the core is completely circumferentially surrounded by cladding(s) (not shown) are also possible.

According to further exemplary embodiments, similar to the

waveguides

110, 110a, 110b, the at least one active element 120 may have a) a circular cross-section or b) a non-circular cross-section, e.g. an elliptical or polygonal cross-section, e.g. a rectangular cross-section.

According to further exemplary embodiments, the at least one active element 120 may be completely embedded within the at least one cladding layer, or may be partially embedded within the at least one cladding layer, e.g. sandwiched between a top cladding layer and a bottom cladding layer.

According to further exemplary embodiments, the

waveguides

110, 110a, 110b may comprise or consist of one or more dielectric materials.

According to further exemplary embodiments, the

cores

112, 112a, 112b of the

waveguides

110, 110a, 110b may comprise or consist of a dielectric material.

According to further exemplary embodiments, the at least one

cladding layer

114, 114a, 114b of the

waveguide

110, 110a, 110b may comprise or consist of a dielectric material.

According to further exemplary embodiments, the

waveguide

110, 110a, 110b comprises or is at least one polymer fiber.

According to a further exemplary embodiment, the

waveguide

110, 110a, 110b is a polymer fiber having a

core

112, 112a, 112b of a polymer material and a

cladding

114, 114a, 114b surrounding the core, wherein the cladding preferably further comprises a polymer material. According to further exemplary embodiments, an optional coating (not shown) may be provided, which may for example surround the

cladding

114, 114a, 114 b.

According to a further exemplary embodiment, referring to fig. 4, the at least one active element 120a comprises a stack S of layers stacked along a first axis a1, preferably on top of each other, wherein the stack S comprises a first layer 122 formed by a first electrode 122 of the two

electrodes

122, 123, a second layer 123 formed by a second electrode 123 of the two electrodes, and a third layer 121 formed by a Transition Metal Oxide (TMO) material, the third (e.g. TMO) layer 121 being arranged between the first layer 122 and the second layer 123.

According to a further exemplary embodiment, referring to the apparatus 100c of fig. 5, the first axis a1 of the stack S extends substantially parallel to the longitudinal axis LA (see also fig. 1) of the waveguide 110. According to further exemplary embodiments, "substantially parallel" means that an angle between the longitudinal axis LA of the waveguide 110 and the first axis a1 (fig. 4) of the stack S may be in a range between 0 degrees and 20 degrees.

According to further exemplary embodiments, at least one of the first electrode 122 and the second electrode 123 comprises a metal layer ("electrode layer").

According to a further exemplary embodiment, at least one of the first electrode 122 and the second electrode 123 comprises a thickness t1 that is smaller than a skin depth of at least one frequency component of the radio frequency signals RF1, RF1' (fig. 1). This enables an RF signal propagating within the waveguide 110 to propagate (at least partially) through the at least one active element 120 (and its electrode (s)), particularly if the at least one active element 120 or its TMO material 121 is in its dielectric (i.e., non-metallic) state, which may also be considered an "OFF state" according to further exemplary embodiments.

According to a further exemplary embodiment, in the off-state the TMO material 121 (fig. 4) of the active element 120 exhibits dielectric properties (i.e. non-conductive properties), thus in principle enabling the RF signals RF1, RF1' and the associated Electromagnetic (EM) waves to propagate through the TMO material layer 121 (and according to a further preferred embodiment also through the electrode layer(s) 122, 123 if they are sufficiently thin).

According to further exemplary embodiments, in the "on" state, the TMO material 121 of the active element 120 exhibits metallic (i.e., conductive) properties, thus in principle preventing the RF signals RF1, RF1 'and associated Electromagnetic (EM) waves from propagating through the TMO material layer 121, i.e., attenuating the RF signals RF1, RF1' from a transmission perspective. According to further exemplary embodiments, however, the degree of attenuation may be controlled by selecting the layer thickness t2 (fig. 4) of the TMO material layer 121. In particular, similar to the electrode layers 122, 123 according to further exemplary embodiments, if the TMO material layer 121 has a sub-skin depth thickness value, at least a portion of the RF signal(s) may propagate through the TMO material layer 121 even in the on-state.

According to a further exemplary embodiment, at least one of the first electrode 122 and the second electrode 123 comprises a thickness t1 which is smaller than a skin depth of the highest frequency component of the radio frequency signals RF1, RF 1'. This enables the highest frequency component of the radio frequency signals RF1, RF1' to be at least partially transmitted (i.e., propagated) through the at least one active element 120.

According to a further exemplary embodiment, at least one of the first electrode 122 and the second electrode 123 comprises a thickness t1, the thickness t1 being less than 1 micrometer (μm), preferably less than 500 nanometers (nm).

According to further exemplary embodiments, the third layer 121 comprises a thickness t2 that is greater than a skin depth of at least one frequency component of the radio frequency signal, which in some embodiments, the thickness t2 is greater than 300% of the skin depth, such as greater than 500% of the skin depth.

According to a further exemplary embodiment, referring to fig. 1, the apparatus 100 comprises at least one control device 130, the at least one control device 130 being configured to provide at least one control voltage CV to the at least one active element 120, whereby the dielectric or electrical properties of the TMO material 121 may be influenced as exemplarily explained above. Thus enabling control of the degree of attenuation or propagation of the radio frequency signal(s) RF1, RF 1'.

According to a further exemplary embodiment, the at least one control device 130 is configured to provide, at least temporarily, to the at least one control voltage CV a) a plurality of discrete voltage values, or b) a continuous voltage value.

According to further exemplary embodiments, providing a plurality (e.g. two) different discrete voltage values may be used to switch the at least one active element 120 on and off, i.e. to switch the at least one active element 120 between its conductive state of the TMO material 121 and its dielectric state of the TMO material 121.

According to further exemplary embodiments, providing the active elements 120 with a continuous voltage value may be used to continuously change at least one active element 120 between its conductive state of the TMO material 121 and its dielectric state of the TMO material 121, thus for example influencing the continuously changing degree of the attenuation.

Fig. 6 schematically depicts a simplified side view of an apparatus 100d according to a further exemplary embodiment. The device 100d comprises a plurality of active elements, two of which are exemplarily depicted by fig. 6 and denoted by reference numerals 120_1, 120_ 2.

According to a further exemplary embodiment, a plurality of active elements 120_1, 120_2,. can be provided in the waveguide 110, wherein at least two active elements can be arranged adjacent to each other, see fig. 6.

According to a further exemplary embodiment, each of the plurality of active elements 120_1, 120_ 2.. may be controlled by a separate control voltage CV _1, CV _ 2.. which may be provided, for example, by the control device 130 (fig. 1).

According to a further exemplary embodiment (not shown), each of the plurality of active elements 120_1, 120_2,. may be controlled with the same (i.e., common) control voltage, which may also be provided by the control device 130 (fig. 1).

According to a further exemplary embodiment, referring to the perspective view of fig. 7, the apparatus 100e comprises at least one (presently illustratively two) impedance transformers 140_1, 140_ 2.

According to a further exemplary embodiment, the at least one impedance transformer is arranged adjacent to the at least one active element. As exemplarily depicted by fig. 7, both impedance transformers 140_1, 140_2 are arranged adjacent to the at least one active element 120, thus enabling impedance transformation, in particular impedance matching, for example from both sides of the active element 120.

As an example, at least one impedance transformer 140_1, 140_2 may be used to perform impedance matching between the waveguide 110 (fig. 1) (or each section 110_1, 110_2 of the waveguide) and the at least one active element 120. Especially in case the at least one active element 120 is in the off-state, whereby reflections of the RF signal RF1 at the interface between the waveguide 110, 110_1 and the at least one active element 120 may be avoided or at least reduced.

According to a further exemplary embodiment, the apparatus 100e of fig. 7 may be considered an attenuator for an RF signal RF1 propagating within a waveguide 110, wherein the waveguide has a first waveguide section 110_1 followed by a first impedance transformer 140_1, at least one active element 120, a second impedance transformer 140_2 and a second waveguide section 110_ 2. The attenuation of the RF signal RF1 is controllable by the control voltage CV, where the RF signal RF1' represents the attenuated RF signal.

According to further exemplary embodiments, signal transmission through the waveguide segments 110_1, 110_2 may be described roughly as being achieved by different dielectric properties (i.e., different relative permittivities) of the core 112 and the cladding, the core 112 and the cladding creating a kind of mirror that reflects the RF signal RF1 into the core 112 for a specific frequency (in particular total reflection). This also applies to the further exemplary waveguides described above with reference to fig. 1 to 6.

According to a further exemplary embodiment, if the control voltage CV is not applied to the active element 120, which corresponds to the off-state of the active element 120, the active element 120 or an active (i.e. TMO) region 121 thereof behaves as a dielectric, e.g. with a value defined by ∈_{r OFF}Given a dielectric constant that is generally substantially different from the composite dielectric constant of the waveguides 110_1, 110_2, which is denoted ε_{r PMF}. These different dielectric constants can cause the characteristic impedance of the waveguide

And characteristic impedance of active region

According to further exemplary embodiments, impedance transformers 140_1, 140_2 having an electrical length of a quarter wavelength at the operating frequency (i.e. the (center) frequency of the RF signal(s) RF1, RF 1') may be provided, whose characteristic impedance Zmatch may be characterized, for example, by:

wherein Z_{free space}Characterizing the impedance of free space, where_{r OFF}Characterizing the relative permittivity of the at least one active element 120 in the off-state, where ∈_{r PMF}The relative permittivity of the waveguide 110 or its segments 110_1, 110_2 is characterized. As an example, if the control voltage CV has a zero value, i.e. 0V, the at least one active element 120 may be in its off-state.

According to further exemplary embodiments, the at least one impedance transformer 140_1, 140_2 may comprise a segment of a waveguide having a predetermined length. In other words, the at least one impedance transformer 140_1, 140_2 may be formed by a segment of a waveguide of a predetermined length.

According to a further exemplary embodiment, the at least one impedance transformer is provided, for example based on [ equation 1], such that in the off-state of the at least one active element 120 there is (at least substantially) no undesired reflection at the waveguide/active element interface and the propagation of the RF signal between the input and the output is not impeded.

According to further exemplary embodiments, the situation may change once a non-zero control voltage CV is applied to the at least one active element 120 or its TMO material 121, respectively. Now, the layer 121 comprising transition metal oxide becomes conductive (on-state), in particular highly conductive by indirect contact with a conductive electrode ("bias pad"), which according to a further exemplary embodiment is a sub-skin depth conductor.

According to a further exemplary embodiment, the composite electrical thickness of the at least one active element 120 or its TMO material (layer) 121 may now be significantly increased (compared to the off-state), e.g. in the on-state, thus generating a significant reflection of the RF signal RF1, RF1' at the boundary or interface between the waveguide 110, 110_1, 110_2 and the at least one active element 120.

According to further exemplary embodiments, assuming that the RF signal RF1 has been provided to the at least one active element on the "input" side of the at least one active element, this may result in a significantly attenuated RF signal RF1' at the "output" of the apparatus 100e (fig. 7), i.e. on the output side of the at least one active element 120.

According to a further exemplary embodiment, the devices may exhibit reciprocity, i.e. may behave (preferably at least substantially) the same as regards the direction of signal transmission. In other words, according to further exemplary embodiments, the input signal may be provided individually at either side of the device or waveguide.

According to a further exemplary embodiment, the composite electrical thickness of the at least one active element 120 or of its active (e.g. TMO) region 121 may be, for example, in the range of several skin depths of the frequency of the RF signal(s), such that the RF signal RF' at the output may be (in particular completely) cancelled out.

According to further exemplary embodiments, the composite electrical thickness of the at least one active element 120 may depend on the physical thickness t2 (fig. 4) of the transition metal oxide layer 121, and possibly also on the operating mode of the at least one active element 120.

According to further exemplary embodiments, two operating modes may be distinguished:

according to an exemplary first mode, the active layer thickness in the on state is several skin depths thick;

according to an exemplary second mode, the active layer thickness in the on state is sub-skin depth thick.

According to further exemplary embodiments, in the first mode, the device may be operable, for example, by applying a continuous DC (direct current) control voltage CV (i.e. a control voltage that may vary from 0V (volts) to a maximum value Vmax, Vmax >0V), wherein, for example, the conductivity and thus the skin depth of the transition metal oxide layer 121 may be a function of the voltage value of the applied control voltage CV. This (exemplary first) mode of operation may also be referred to as an "analog waveguide or transmission line attenuator".

According to further exemplary embodiments, in the second mode, even if the highest allowed control voltage (value Vmax) is applied to the at least one active element 120 or its TMO material (layer) 121, one active area or TMO layer may not be sufficient to completely eliminate the input RF signal. Thus, in order to provide full controllability of the amplitude of the output RF signal RF1', according to further exemplary embodiments, several layers of TMO material may be provided, for example in the form of a plurality of (preferably adjacent) active elements 120', see for example the simplified perspective view of the apparatus 100f of fig. 8.

In other words, according to further exemplary embodiments, a plurality of active elements 120' of the active elements 120_1, 120_ 2.

According to further exemplary embodiments, a plurality of active elements 120' may be arranged in series along one axis or longitudinal axis LA (fig. 1) of the waveguide, wherein preferably adjacent active elements 120_1, 120_2 share one common electrode. As an example, the second electrode 123_1 of the first active element 120_1 may also form the first (common) electrode CE of the second active element 120_2 disposed adjacent to the first active element 120_ 1. In fig. 8, the first electrode of the first active element 120_1 is denoted by reference numeral 122_1, and the TMO layer of the first active element 120_1 is denoted by reference numeral 121_ 1.

As exemplarily depicted in fig. 8, n active elements 120' may be provided, wherein n >2 (in particular n >10) is possible according to further embodiments.

According to further exemplary embodiments, the n active elements may be provided with respective independent control voltages CV (not shown).

According to a further exemplary embodiment, the n active elements may be provided with a common control voltage CV in common (not shown).

According to a further exemplary embodiment, at least one of the n active elements may be provided with a control voltage CV (see also fig. 1) according to at least one of the following aspects:

(a) gradually (a continuous control voltage, e.g. dc bias), e.g. an analogue attenuation of the partitions can be generated; or

(b) The control voltage CV may be made to have, for example, two states, e.g., b1) off (e.g., 0V) and b2) on (e.g., Vmax), for example, in order to switch the respective active element(s) on or off, e.g., to produce a "digitally controlled" attenuation — an attenuation controlled by discrete attenuation values; or

(c) The combination of (a) and (b) results in, for example, a coarse "digital" attenuation setting, assisted by an "analog" fine tuning of the attenuation.

According to further exemplary embodiments, and in particular regardless of the exemplary operating mode, e.g. depending on the desired attenuation level of a particular field of application, the number of active elements n may be varied.

According to further exemplary embodiments, further degrees of freedom for the device according to embodiments are provided by the thickness (and thus the attenuation granularity) of the active (i.e. TMO) region 121, the conductivity of the corresponding active region 121, and the operating frequency (i.e. the operating frequency of the RF signals RF1, RF 1').

For example, according to another exemplary embodiment, using equation 2 described below, if the composite conductivity of the active region 121 in the on-state at the control voltage CV of Vmax is σ ═ 10⁷S/m (west per meter), the thickness t2 (fig. 4) of the active region 121 is about 500nm, and the skin depth is 500nm at an operating frequency f0 of 100 GHz.

Wherein mu₀Is magnetic permeability of free space, and in which_rIs the relative permeability of active region 121 in the on state. The skin depth is defined as the thickness of the conductor at about 37% (1/e, e is the euler constant) of the value that the signal has at the surface of the conductor. Thus, in this example, t₂A single active region thickness of 500nm may produce a signal that is attenuated by-20 log (0.37) to 8.6dB compared to its input. Increasing the number of stages (i.e., n >1, see fig. 8) according to further exemplary embodiments may increase the overall level of attenuation of the RF signal(s) RF 1. For example, according to further exemplary embodiments, two stages 120_1, 120_2 (fig. 8) may produce an attenuation level of-20 log (0.37 x 0.37) to 17.2dB, three stages (n-3) may produce-20 log (0.37 x 0.37) to 25.9dB, and so on.

According to further exemplary embodiments, in some cases, aspect (a) as described above may also be referred to as an "analog sub-skin depth waveguide or transmission line attenuator", aspect (b) may also be referred to as a "digital sub-skin depth waveguide or transmission line attenuator", and aspect (c) may also be referred to as an "analog-to-digital sub-skin depth waveguide or transmission line attenuator".

According to further exemplary embodiments, the plurality of active elements 120' may be provided in a length segment (not shown) of the waveguide corresponding to 20% or less, preferably to 10% or less, more preferably to 5% or less, more preferably even less than 1% of the total length of the waveguide. In other words, the region of the waveguide comprising one or more active elements according to embodiments may form a relatively small part of the total length of the waveguide, which may be e.g. a few meters or e.g. at most 50m, compared to the total length of the waveguide.

According to a further exemplary embodiment, the regions of the waveguide comprising one or more active elements according to an embodiment may not be adjacent, i.e. may be separated by waveguide segments without active elements.

According to further exemplary embodiments, the at least one active element 120 or the plurality of active elements 120' may be arranged, in particular concentrated, at the first and/or second axial end of the waveguide.

According to a further exemplary embodiment, referring to fig. 9, the apparatus 100g may comprise a coupler 150, wherein the at least one active element 120_1, 120_2 is connected to at least one port of the coupler 150.

Currently, at least a first active component 120_1 or a first set of active components is connected to the first port 151 of the coupler 150 and at least a second active component 120_2 or a second set of active components is connected to the second port 152 of the coupler 150.

According to a further exemplary embodiment, at least one of the

further ports

153, 154 of the coupler 150 may for example be used as an input port and/or an output port for the radio frequency signal RF1 (see fig. 1).

According to a further exemplary embodiment, each of the active elements 120_1, 120_2 may be provided with a respective control voltage CV _1, CV _ 2.

According to further exemplary embodiments, the active elements 120_1, 120_2 may alternatively be provided with a common control voltage (not shown) that supports or facilitates a symmetric biasing of the active elements 120_1, 120_2, which may be preferred for some reflective configurations.

The configuration 100g of fig. 9 enables reflection-type attenuation of RF signals, while the configurations of fig. 1-8 may be considered transmission-type attenuators according to further exemplary embodiments.

According to further exemplary embodiments, coupler 150 (fig. 9) may be a 3-dB hybrid coupler that splits an input signal (e.g., provided at port 154) into two equal magnitude signals whose phases are in quadrature in the coupled and direct arms. . The coupler 150 may comprise waveguide segments s1, s2, s3, s4, s5, s6, s7, s8, wherein preferably the segments s1, s3, s84. s6, s7, s8 have a characteristic impedance ZPMF, and wherein segments s2, s5 have a characteristic impedance

Assuming that the active elements 120_1, 120_2, which can be considered as reflective loads for the coupler 150, are identical, the scattering (S) parameter of this structure is: s₁₁0 and S₂₁J Γ ═ equation 3]Where Γ characterizes the reflection coefficient at the load 120_1, 120_ 2. As can be seen from equation 3, the "reflection" attenuator of FIG. 9 is at the input (S), as opposed to the "transmission line" attenuator (see, e.g., FIG. 7)₁₁0), in particular regardless of the control voltage(s) CV _1, CV _2 applied to the active region(s) 121 of the loads 120_1, 120_ 2.

According to further exemplary embodiments, the apparatus 100g may particularly significantly reflect the input RF signal from its reflective loads 120_1, 120_2 for the case when the active region(s) is (are) turned on (i.e. has a conductive state).

According to further exemplary embodiments, similar to the exemplary embodiments described above with "transmission lines" or waveguide attenuators, see e.g. fig. 7, the exact amount of reflected signal may depend on the physical thickness t2 (fig. 4) of the transition metal oxide layer 121 of the load 120_1, 120_ 2. This exemplary case corresponds to the case where the device 100g (fig. 9) is in a low loss state.

According to further exemplary embodiments, the conductivity of the active region 121 of the load 120_1, 120_ may be reduced by, for example, reducing the control voltage CV _1, CV _ 2. The resistance at the active region 121 becomes equal to the resistance Z of the waveguide_PMF(or respective characteristic impedance), the entire RF signal may be absorbed and dissipated as heat in the resistor formed using the active region 121 of the loads 120_1, 120_ 2.

According to further exemplary embodiments, a resistor (not shown) may be added at the coupler and through the port. The resistance of the resistor may for example be chosen as Z_PMF-Z_{TMO_ON}. In this case, once the TMO layers are fully activated, they represent the resistance Z_{PMF_ON}This resistance, together with the termination resistor, may provide a condition for high signal attenuation.

According to further exemplary embodiments, to ensure low loss performance, and to have an incident signal that is fully reflected, it may be beneficial for the active region 121 to be at least several skin depths thick. This may be achieved, for example, by providing multiple active elements (e.g., similar to element 120' of fig. 8) as the loads 120_1, 120_2 instead of a single active element. In other words, a set of multiple active elements 120 may be connected to each

port

151, 152 of the coupler 150 to increase the reflective properties in case of the conductive state of the TMO layer.

Further exemplary embodiments relate to a method of using an apparatus according to an embodiment, the method comprising at least one of the following steps: a) processing radio frequency signals RF1, RF 1'; b) affecting a radio frequency signal RF1, in particular a radio frequency signal propagating within the waveguide; c) attenuating the radio frequency signal RF 1; d) reflected radio frequency signal RF 1; e) selecting one or more modes of a radio frequency signal; f) modulating the radio frequency signal.

According to further exemplary embodiments, the apparatus according to embodiments may be used for processing RF signals RF1, RF1' in the GHz range, up to 100GHz or higher (i.e. even in the THz range).

Claims

1. An electronic device, comprising:

a waveguide for radio frequency signals, wherein the waveguide comprises or is at least one polymer fiber; and

at least one active element, wherein a plurality of active elements are provided in the waveguide, the at least one active element comprising a transition metal oxide material and two electrodes for applying a control voltage to the transition metal oxide material.

2. The electronic device of claim 1, wherein the at least one active element is configured to change between a dielectric state in which the at least one active element is non-conductive and a conductive state in which the at least one active element is conductive, depending on the control voltage.

3. The electronic device according to any of claims 1-2, wherein the at least one active element is at least partially arranged a) within a core of the waveguide, and/or b) within a cladding of the waveguide.

4. The electronic device of any one of claims 1-2, wherein the waveguide comprises in cross-section at least: a) a circular cross-section, or b) a non-circular cross-section, such as an elliptical cross-section or a polygonal cross-section, such as a rectangular cross-section.

5. The electronic device according to any of claims 1-2, wherein the waveguide comprises or is at least one polymer fiber.

6. The electronic device according to any of claims 1 to 2, wherein the at least one active element comprises a stack of layers stacked along a first axis, preferably on top of each other, wherein the stack comprises a first layer formed by a first electrode of the two electrodes, a second layer formed by a second electrode of the two electrodes, and a third layer formed by the transition metal oxide material, the third layer being arranged between the first and second layers.

7. The electronic device of claim 6, wherein the first axis of the stack extends substantially parallel to a longitudinal axis of the waveguide.

8. The electronic device of claim 6, wherein at least one of the first electrode and the second electrode comprises a thickness that is less than a skin depth of at least one frequency component of the radio frequency signal.

9. The electronic device of claim 6, wherein the third layer comprises a thickness greater than a skin depth of at least one frequency component of the radio frequency signal.

10. The electronic device of claim 6, wherein at least one of the first and second electrodes comprises a thickness of less than 1 micron, preferably less than 500 nanometers.

11. The electronic apparatus according to any of claims 1 to 2, comprising at least one control device configured to provide at least one control voltage to the at least one active element.

12. The electronic apparatus of claim 11, wherein the at least one control device is configured to provide, at least temporarily, to the at least one control voltage a) a plurality of discrete voltage values, or b) a continuous voltage value.

13. The electronic device according to any of claims 1-2, comprising at least one impedance transformer, wherein preferably the at least one impedance transformer is arranged adjacent to the at least one active element.

14. The electronic device of claim 13, wherein the at least one impedance transformer comprises a segment of the waveguide having a predetermined length.

15. A method of using a device comprising a waveguide for radio frequency signals and at least one active element comprising a transition metal oxide material and two electrodes for applying a control voltage to the transition metal oxide material, the method comprising at least one of the following steps: a) processing the radio frequency signal; b) influencing a radio frequency signal, in particular a radio frequency signal propagating within the waveguide; c) attenuating the radio frequency signal; d) reflecting the radio frequency signal; e) selecting one or more modes of a radio frequency signal; f) modulating the radio frequency signal.