Broadband nonreciprocal coupling between asymmetric transmission lines

Abstract

The present disclosure relates to transmission lines, in particular to the coupling of electromagnetic waves between two transmission lines. An apparatus and method are presented that enable broadband non-reciprocal coupling of electromagnetic waves between two asymmetric transmission lines. This is achieved by individually controlling a set of adjustable impedance elements that are distributed along at least one of the transmission lines to generate a set of impedance modulations in that transmission line, and with each impedance modulation, a new tone in the electromagnetic wave propagating in that transmission line. Depending on the direction of propagation of the electromagnetic wave, the new tones can constructively or destructively interfere with the modes of the other transmission line, resulting in non-reciprocal coupling.

Description

Technical Field

[0001] This disclosure relates to transmission lines and communication via transmission lines. It relates to optical transmission via waveguides serving as transmission lines and RF transmission via radio frequency (RF) transmission lines. Particularly, this disclosure relates to the coupling of electromagnetic waves between two transmission lines. Therefore, this disclosure aims to achieve broadband non-reciprocal coupling of electromagnetic waves between two asymmetric transmission lines. Background Technology

[0002] Non-reciprocal devices are prevalent in many technological applications, such as microwave circuits for antenna multiplexing, reflection-based amplifiers, or sources that shield backscattered signals. Traditionally, such non-reciprocal devices, like those used in microwave circuits, rely on ferrite biased by a strong magnetic field to break reciprocity. Due to the ferrite and the magnet that generates the magnetic field, these irreversible devices are bulky, typically measuring in the tens of millimeters and cannot be integrated onto a chip. Furthermore, the considerable magnetic field interferes with superconductivity, thus degrading the performance of superconducting circuits (such as those used in quantum computers or other ultra-low noise applications).

[0003] Therefore, alternative solutions based on ferrites have been proposed and can be categorized into three types. The first type relies on transistors, which, when properly biased, are inherently irreversible due to their unidirectional gain. However, the bias current leads to resistive dissipation, Joule heating, and increased thermal noise. The second type relies on nonlinear media and asymmetric magnetic field distributions. However, this method is only effective for non-simultaneous electromagnetic signals above a certain amplitude, which can trigger a nonlinear response in the medium. The third type relies on parametric modulation to divide the electromagnetic signal into multiple modes and generate direction-dependent interference between these modes. However, this interference-based non-reciprocal method is only effective within a fairly limited frequency range. Summary of the Invention

[0004] In view of the above, the object of this disclosure is to provide an improved solution for non-reciprocal devices that allows for the avoidance of the aforementioned disadvantages. For example, one object is to avoid strong magnetic fields. Another object is to avoid dissipation, heat generation, and noise, which are inherent in transistor-based methods. Another object is to avoid dependence on electromagnetic wave amplitude, which is inherent in methods using nonlinear media. Another object is to avoid reciprocal behavior when nonlinear media are simultaneously input at opposite ports. Another object is to avoid the limited operating bandwidth of methods based on modulation and interference modes.

[0005] In summary, there is a need for a compact device for efficient broadband non-reciprocal electromagnetic signal transmission.

[0006] The above and other objectives are achieved by the solutions proposed in this disclosure, as described in the independent claims. Advantageous embodiments are described in the dependent claims.

[0007] A first aspect of this disclosure provides an apparatus for non-reciprocal signal transmission, the apparatus comprising: a first transmission line having a first set of electromagnetic modes supporting the propagation of electromagnetic waves at a first phase velocity; a second transmission line having a second set of electromagnetic modes supporting the propagation of electromagnetic waves at a second phase velocity different from the first phase velocity; and a set of first adjustable impedance elements distributed along the first transmission line; and a controller configured to control the set of first adjustable impedance elements to generate an impedance modulation set in the first transmission line, each impedance modulation in the set generating a new frequency modulation in the electromagnetic waves propagating in the first transmission line; wherein the controller is configured to individually control each first adjustable impedance element to generate an impedance modulation set having a specific associated phase set such that: for a first propagation direction of the electromagnetic waves in the first transmission line, the new frequency modulation in the electromagnetic waves in the first transmission line constructively interferes with and couples with the modes of the second transmission line, and for an opposite second propagation direction of the electromagnetic waves in the first transmission line, the new frequency modulation in the electromagnetic waves in the first transmission line destructively interferes with and does not couple with the modes of the second transmission line.

[0008] The device of the first aspect can be constructed in a compact manner, without being as bulky as ferrite-based methods. Furthermore, it enables broadband non-reciprocal electromagnetic signal transmission. No magnetic field is required, nor are bias transistors needed, as bias current would lead to resistive dissipation, Joule heating, and thermal noise.

[0009] When the controller does not apply interference modulation through an impedance modulation element, the unequal phase velocities of the two transmission lines prevent the coupling of electromagnetic waves between them. In this case, the unequal phase velocities lead to destructive interference between the electromagnetic waves propagating in the two transmission lines, thus preventing coupling despite the presence of passive electromagnetic coupling.

[0010] Each impedance modulation distorts the electromagnetic field in the first transmission line, thus generating a new frequency modulation. It is worth noting that the electromagnetic field can be decomposed into a series of electromagnetic waves, each of which can be considered as the excitation of a mode. Whether the electromagnetic field carries information is irrelevant; therefore, the electromagnetic waves can be signals and / or noise.

[0011] In the implementation of this device, the first set of adjustable impedance elements includes one of the following: a superconducting quantum interference device configured to be modulated by an external flux, a voltage-controlled capacitor configured to be controlled by an external voltage, a Josephson junction, a dynamic inductor, a material having second- or third-order nonlinearity, or any other nonlinear element configured to be impedance modulated by a pump signal.

[0012] For the first two alternatives, the external flux or external voltage can be considered as a pump signal. Generally, pump signals can carry information such as a specific frequency and phase.

[0013] In the implementation of this device, the controller is configured to control the group of first adjustable impedance elements to generate an impedance modulation set with an associated phase set at a first frequency, so as to achieve non-reciprocal coupling between an electromagnetic wave supported by the electromagnetic mode of the first transmission line and propagating in the first propagation direction and an electromagnetic wave supported by the electromagnetic mode of the second transmission line and propagating in the same first propagation direction.

[0014] Therefore, in the device of the first aspect, non-reciprocal coupling can be achieved between electromagnetic waves propagating in the same direction. Non-reciprocal coupling between electromagnetic waves propagating in the same direction, supported by modes on the same transmission line, can also be achieved.

[0015] In the implementation of this device, the controller is configured to control the group of first adjustable impedance elements to generate an impedance modulation set with associated phase set at a first frequency, so as to achieve non-reciprocal coupling between an electromagnetic wave supported by the electromagnetic mode of the first transmission line and propagating in the first propagation direction and an electromagnetic wave supported by the electromagnetic mode of the second transmission line and propagating in the second propagation direction.

[0016] Therefore, in the device of the first aspect, non-reciprocal coupling can be achieved between electromagnetic waves propagating in opposite directions. Non-reciprocal coupling between counter-propagating electromagnetic waves supported by modes on the same transmission line can also be achieved.

[0017] In the implementation of this device, the controller is configured to control the set of first adjustable impedance elements to generate an impedance modulation set with associated phase sets at multiple frequencies to achieve a set of non-reciprocal couplings between electromagnetic waves supported by the electromagnetic modes of one of the two transmission lines and electromagnetic waves supported by the electromagnetic modes of the other transmission line.

[0018] Therefore, in the device of the first aspect, multi-frequency modulation can generate multiple non-reciprocal couplings.

[0019] In the implementation of this device, a modulation frequency and associated phase set are configured to achieve non-reciprocal coupling and directional energy exchange between electromagnetic waves supported by the electromagnetic modes of the first transmission line and electromagnetic waves supported by the electromagnetic modes of the second transmission line.

[0020] Therefore, non-reciprocal coupling between electromagnetic waves supported by two modes leads to energy exchange between the modes. It is worth noting that other modulation frequencies may exist, causing other simultaneous non-reciprocal coupling between different mode sets. The term "directional exchange" indicates that energy typically flows back and forth between the two coupled modes along the direction of their coupling. In the opposite direction, the two modes are decoupled, and therefore no energy exchange occurs.

[0021] In the implementation of this device, a modulation frequency and associated phase set are configured to achieve non-reciprocal coupling and directional amplification of electromagnetic waves propagating in the first transmission line and electromagnetic waves propagating in the second transmission line.

[0022] Therefore, non-reciprocal coupling can also be used to achieve "parametric" amplification and / or parametric "conversion". The only difference lies in the frequency and phase of the impedance modulation, which is used to obtain this non-reciprocal coupling scheme.

[0023] In the implementation of this device, the non-reciprocal coupling between an electromagnetic wave supported by an electromagnetic mode of one of two transmission lines designed to have low loss and an electromagnetic wave supported by an electromagnetic mode of the other transmission line designed to have high loss is configured to produce non-reciprocal electromagnetic field attenuation.

[0024] In this implementation, the device further includes: a set of second adjustable impedance elements distributed along the second transmission line; wherein the controller is configured to control the set of second adjustable impedance elements to generate a second set of impedance modulations in the second transmission line, each impedance modulation in the second set generating a new frequency modulation in an electromagnetic wave propagating in the second transmission line; wherein the controller is configured to individually control each second adjustable impedance element to generate a second set of impedance modulations having a specific associated phase set, such that: for a first propagation direction of the electromagnetic wave in the second transmission line, the new frequency modulation in the electromagnetic wave in the second transmission line constructively interferes with and couples with the mode of the first transmission line, and for the opposite second propagation direction of the electromagnetic wave in the second transmission line, the new frequency modulation in the electromagnetic wave in the second transmission line destructively interferes with and does not couple with the mode of the first transmission line.

[0025] Therefore, in the apparatus of the first aspect, impedance modulation can be generated in one or both of the two transmission lines. As described above with respect to the first transmission line, impedance modulation in the second transmission line distorts the electromagnetic field of the electromagnetic wave propagating on the transmission line and generates a new frequency modulation.

[0026] In the implementation of this device, the first transmission line and the second transmission line are configured to have their own electromagnetic modes, which have dispersion curves that are parallel to each other within a predetermined frequency range.

[0027] In other words, the dispersion of the first and second transmission lines is engineered such that any two electromagnetic modes separated by a given frequency shift will exhibit the same phase shift / phase velocity difference within a predetermined frequency range.

[0028] Although non-reciprocal coupling between transmission lines can be achieved without dispersion curve engineering, dispersion curve engineering provides the possibility of achieving non-reciprocal coupling within a predetermined frequency range using a single modulation frequency and associated phase set.

[0029] In the implementation of this device, the electromagnetic wave is an RF wave or RF noise, or the electromagnetic wave is an optical wave or optical noise and the transmission line is a waveguide.

[0030] The device in the first aspect can therefore be implemented and used in RF and optical communication applications.

[0031] A second aspect of this disclosure provides a method of operating an apparatus for non-reciprocal signal transmission, the method comprising: propagating an electromagnetic wave supported by a first set of electromagnetic modes of a first transmission line at a first phase velocity in a first direction or a second direction opposite to it; propagating an electromagnetic wave supported by a second set of electromagnetic modes of a second transmission line at a second phase velocity in the first direction or the second direction; and controlling a set of first adjustable impedance elements distributed along the first transmission line to generate an impedance modulation set in the first transmission line, each impedance modulation in the set generating a new frequency modulation in the electromagnetic wave propagating in the first transmission line; wherein each first adjustable impedance element is individually controlled to generate an impedance modulation set having a specific associated phase set such that: for a first propagation direction of the electromagnetic wave in the first transmission line, the new frequency modulation in the electromagnetic wave in the first transmission line constructively interferes with and couples to the modes of the second transmission line, and for a second propagation direction opposite to it in the first transmission line, the new frequency modulation in the electromagnetic wave in the first transmission line destructively interferes with and does not couple to the modes of the second transmission line.

[0032] The second method can have an implementation corresponding to the implementation of the apparatus of the first aspect. The second method and its implementation achieve the effects and advantages of the apparatus and its implementation of the first aspect described above.

[0033] The apparatus and method of this disclosure solve all the problems of the aforementioned different methods. Specifically, the solution of this disclosure achieves non-reciprocal transmission while avoiding all of the following problems: (i) bulky magnets and strong magnetic fields that hinder the integration of conventional non-reciprocal devices on-chip and / or with superconducting circuits; (ii) the inherent dissipation, heating, and noise of transistor-based solutions; (iii) the inherent amplitude dependence of devices using nonlinear media; (iv) the reciprocal behavior of nonlinear media with simultaneous input at opposite ports; and (v) the limited operating bandwidth of devices based on modulation and interference modes. Attached Figure Description

[0034] The above aspects and implementations are explained in the following description of embodiments with reference to the accompanying drawings: Figure 1 An apparatus for non-reciprocal transmission is shown according to an exemplary embodiment of the present disclosure.

[0035] Figure 2 An apparatus for non-reciprocal transmission is shown according to an exemplary embodiment of the present disclosure.

[0036] Figure 3 An example of an asymmetric coupled transmission line in an apparatus according to an exemplary embodiment of the present disclosure is shown.

[0037] Figure 4 A modulated asymmetric coupled transmission line in an apparatus according to an exemplary embodiment of the present disclosure is shown.

[0038] Figure 5 Non-reciprocal parametric coupling in an apparatus according to an exemplary embodiment of the present disclosure is illustrated.

[0039] Figure 6 Directional energy exchange and amplification via non-reciprocal parametric coupling in an apparatus according to an exemplary embodiment of this disclosure is illustrated.

[0040] Figure 7 Non-reciprocal parametric coupling between arbitrary electromagnetic waves propagating in an apparatus according to an exemplary embodiment of the present disclosure is shown.

[0041] Figure 8 Multi-frequency parametric modulation via multiple non-reciprocal couplings is illustrated in an apparatus according to an exemplary embodiment of the present disclosure.

[0042] Figure 9 The dispersion engineering design of the transmission line of an apparatus according to an exemplary embodiment of the present disclosure is shown.

[0043] Figure 10 An exemplary implementation of an impedance modulation element of a device according to an exemplary embodiment of the present disclosure is shown.

[0044] Figure 11 An implementation of an impedance modulation element as a varactor diode in an apparatus according to an exemplary embodiment of the present disclosure is shown.

[0045] Figure 12 An implementation of an impedance modulation element as a superconducting quantum interference device (SQUID) in an apparatus according to an exemplary embodiment of the present disclosure is shown.

[0046] Figure 13 A flowchart illustrating a method of operating an apparatus according to an exemplary embodiment of the present disclosure is shown. Detailed Implementation

[0047] Figure 1 A device 10 according to the present disclosure is schematically illustrated. Device 10 is configured to implement non-reciprocal signal transmission, wherein the signal is provided by electromagnetic waves. Non-reciprocal transmission can mean that signal transmission between any two ports of device 10 depends on the direction of signal propagation.

[0048] Non-reciprocal transmission means that electromagnetic waves propagating on two lines in device 10 can couple to the other line when propagating in one direction, but decouple from the other line when propagating in the opposite direction.

[0049] The device 10 includes a first transmission line 11 having a first set of electromagnetic modes supporting the propagation of electromagnetic wave 13 at a first phase velocity. The device 10 also includes a second transmission line 12 having a second set of electromagnetic modes supporting the propagation of electromagnetic wave 13 at a second phase velocity different from the first phase velocity. In principle, the two transmission lines 11, 12 can be arranged for electromagnetic coupling, for example, they can be close enough together and not shielded from each other to allow passive electromagnetic coupling. However, the electromagnetic coupling of electromagnetic wave 13 between the transmission lines is adjustable, as will become apparent in the further description.

[0050] The device 10 also includes a set of first adjustable impedance elements 14 arranged or distributed along the first transmission line 11. For example, the first adjustable impedance elements 14 may be arranged one after another and / or at regular intervals along the extension direction of the first transmission line 11. The adjustable impedance elements 14 may all be of the same type.

[0051] Furthermore, the device 10 includes a controller 15 configured to control the group of first adjustable impedance elements 14. The controller 15 is configured to control each adjustable impedance element individually. For example, the controller 15 can be any unit capable of providing a control signal or pump signal to each first impedance element 14. The controller can be a processor, but it can also be a voltage source or a current source. The controller 15 is specifically configured to control the adjustable impedance elements 14 such that they generate an impedance modulation set in the first transmission line 11. Each impedance modulation in this impedance modulation set generates a new frequency modulation, i.e., a new frequency, in the electromagnetic wave 13 propagating in the first transmission line 11. The electromagnetic wave 13 in the transmission line can be a signal and / or noise.

[0052] The controller 15 is configured to control each of the first adjustable impedance elements 14 to generate a set of impedance modulations with a specific set of associated phases. These associated phases (e.g., selected by the controller 15) are thus chosen such that the coupling between the two transmission lines differs for different propagation directions of the electromagnetic wave 13. Specifically, for a first propagation direction of the electromagnetic wave 13 in the first transmission line 11, the new frequency modulation of the electromagnetic wave 13 in the first transmission line 11 constructively interferes with and couples with the mode of the second transmission line 12. For the opposite second propagation direction of the electromagnetic wave 13 in the first transmission line 11, the new frequency modulation of the electromagnetic wave 13 in the first transmission line 11 destructively interferes with and does not couple with the mode of the second transmission line 12. In this way, non-reciprocal transmission of the electromagnetic wave 13 (e.g., a signal) through the transmission lines 11, 12 of the device can be achieved, because the coupling depends on the propagation direction.

[0053] Figure 2 An apparatus 10 is shown according to an exemplary embodiment of the present disclosure, which is constructed in Figure 1 Based on the device 10 shown. Figure 1 and Figure 2 The same elements in the figure are marked with the same reference numerals, can be implemented similarly, and will not be described again.

[0054] In addition to a set of adjustable impedance elements 14 Figure 2 The device 10 also includes a set of second adjustable impedance elements 21 arranged or distributed along the second transmission line 12. In an exemplary configuration, no adjustable impedance elements are arranged between the two transmission lines 11, 12; however, this is also possible. For example, the second adjustable impedance elements 21 may be arranged one after another and / or at regular intervals along the extension direction of the second transmission line 12. The adjustable impedance elements 21 may all be of the same type.

[0055] Figure 1 or Figure 2 The first adjustable impedance element 14 and / or the second impedance element 21 shown can be, respectively, a superconducting quantum interference device configured to be modulated by an external flux, or a voltage-controlled capacitor, or a Josephson junction, or a dynamic inductor, or a material having second- or third-order nonlinearity, or any other nonlinear element configured to be impedance-modulated by a pump signal (e.g., provided by controller 15). This will be explained in more detail later.

[0056] Figure 2 The controller 15 of the illustrated device 10 is further configured to also control the group of second adjustable impedance elements 21. The controller 15 is configured to control each adjustable impedance element individually. Specifically, the controller 15 is configured to control the second adjustable impedance elements 21 such that they generate a second impedance modulation set in the second transmission line 12. Each impedance modulation in the second impedance modulation set produces a new frequency modulation in the electromagnetic wave 13 propagating in the second transmission line 12.

[0057] The controller 15 is configured to control each of the second adjustable impedance elements 21 to generate a set of impedance modulations with a specific set of associated phases. These associated phases (e.g., selected by the controller 15) are thus chosen such that the coupling between the two transmission lines is different for different propagation directions of the electromagnetic wave 13. Specifically, for a first propagation direction of the electromagnetic wave 13 in the second transmission line 12, the new frequency modulation of the electromagnetic wave 13 in the second transmission line 12 constructively interferes with and couples with the mode of the first transmission line 11. For the opposite second propagation direction of the electromagnetic wave 13 in the second transmission line 12, the new frequency modulation of the electromagnetic wave 13 in the second transmission line 12 destructively interferes with and does not couple with the mode of the first transmission line 11. In this way, non-reciprocal propagation of the electromagnetic wave 13 (e.g., the electromagnetic wave of a signal) can be achieved.

[0058] The solutions disclosed herein, for example, are in Figure 1 and Figure 2 The aforementioned apparatus 10, based on integrated asymmetric coupled transmission lines 11 and 12, and an impedance modulation set generated in at least one of transmission lines 11 and 12, introduces non-reciprocal coupling between the transmission lines. This impedance modulation set can be equivalent to a propagation impedance modulation generated in at least one of transmission lines 11 and 12. A more detailed explanation is provided in the following description of examples and exemplary embodiments.

[0059] like Figure 3 As shown in (a), the two transmission lines 11 and 12 can be designed asymmetrically, i.e., they propagate electromagnetic waves 13 at different phase velocities. Without impedance modulation, these transmission lines 11 and 12 effectively couple electromagnetic waves from one transmission line to the other. Specifically, a portion of the electromagnetic waves 13 propagating in the first transmission line 11 and coupled to the second transmission line 12 (and vice versa) will acquire a certain phase shift compared to the remaining electromagnetic waves 13 in the first transmission line 11. When electromagnetic wave 13 propagates at different points in space and couples to the second transmission line 12, interference at each point in the second transmission line is generally destructive due to phase mismatch. That is, the unequal phase velocities of transmission lines 11 and 12 lead to destructive interference, which prevents the propagated electromagnetic wave 13 from effectively coupling between the two transmission lines 11 and 12, despite the presence of passive electromagnetic coupling. This can be achieved... Figure 3 As seen in the dispersion diagram shown in (b), there are unequal phase velocities for propagation length Δz. v A / B = f 0 / λ 0,A / B Converted to phase difference Δ .

[0060] However, this phase mismatch can be compensated by using impedance modulation elements 14 and / or 21 (e.g., flux-modulated SQUID, Josephson junction, varactor diode, etc.) in at least one of the two transmission lines 11, 12 to generate an impedance modulation set.

[0061] In a linear time-invariant system, where the parameters are constant over time (unmodulated), electromagnetic wave 13 propagates and accumulates a certain delay and phase difference, but its spectrum remains unchanged. Conversely, in a linear time-varying system, where the parameters change over time—in this case, due to impedance modulation—electromagnetic field distortion occurs, and new frequency modulations appear in the spectrum of electromagnetic wave 13. These new frequency modulations are intermodulation products. For example, a three-wave mixing process can produce frequency up / down conversions by modulating the impedance of one of the transmission lines at a specific frequency, accompanied by a phase shift depending on the impedance modulation phase. Based on the emergence of these intermodulation products, impedance modulation (or other wave mixing processes) produce new frequency modulations, which involves the coupling of the input power of electromagnetic wave 13, which is supported by one mode, to another mode. This is called parametric coupling. Notably, these parametric conversions do not consume any power on the chip and are noiseless processes.

[0062] Figure 4 This explains how this can be used for non-reciprocal transfers in device 10. For example, as... Figure 4 As shown in (a), the impedance modulation element 14 can generate multiple impedance modulations that distort the electromagnetic field in the first transmission line 11 and produce a series of new frequency moduli in the electromagnetic wave 13 propagating in the first transmission line 11. By controlling the phase of these impedance modulations of the individually controlled impedance modulation element 14, the phase of the new frequency moduli can be controlled, and the new frequency moduli can be coupled and constructively interfered on the second transmission line 12. Figure 4 In the dispersion diagram of (b), impedance modulation is indicated by arrows. If the impedance modulation has an appropriate frequency... f p and associated phase { p ( z If these impedance modulations can be coupled from another transmission line, then these impedance modulations can be coupled to the other transmission line. f 0 and f i = f 0 ±n f p The mode supports the propagation of two electromagnetic waves 13.

[0063] In other words, by controlling the impedance modulation element 14 through the controller 15, impedance modulation can be engineered to cancel the phase shift Δ that occurs when the electromagnetic wave 13 propagates on different transmission lines 11 and 12 without modulation. It is worth noting that for impedance modulation with a fixed phase set, this phase matching condition may not be satisfied simultaneously in both propagation directions. Therefore, non-reciprocal coupling is achieved between the two transmission lines 11 and 12, i.e., coupling dependent on the propagation direction of the electromagnetic wave 13. Note that this non-reciprocal behavior holds regardless of the signal amplitude and also holds when the opposite ports are excited simultaneously.

[0064] Figure 5 (a) and (b) illustrate non-reciprocal parametric coupling in a modulated asymmetric coupled transmission line. Impedance modulation of the phase produces a new frequency modulation in the first transmission line 11, which constructively interferes in one propagation direction (forward) and destructively interferes in the opposite direction (reverse) on the second transmission line 12, thus achieving non-reciprocal coupling between the two transmission lines 11 and 12. Figure 5 In the dispersion diagram shown in (c), the same modulation, i.e., the arrows, cannot couple two modes in opposite directions. f 0 and f i .

[0065] Figure 6 The diagram illustrates energy exchange and amplification achieved through non-reciprocal parametric coupling in apparatus 10 according to an exemplary embodiment. Modulated asymmetric coupled transmission lines 11 and 12 with non-reciprocal coupling are shown in… Figure 6 (a) illustrates and demonstrates two different phenomena. With appropriate modulation frequency and associated phase, non-reciprocal coupling can be used to achieve both modes initially. f 0 and f i Directed energy exchange between the two modes allows electromagnetic wave 13 to propagate on separate transmission lines 11 and 12, such as Figure 6 As shown in (b). Secondly, by selecting appropriate frequencies and associated phases for impedance modulation, two modes supporting the propagation of electromagnetic wave 13 on separate transmission lines 11 and 12 can be achieved. f 0 and f i Directional amplification, such as Figure 6 As shown in (c).

[0066] Figure 7 This illustrates non-reciprocal parametric coupling between arbitrary electromagnetic waves 13 propagating in apparatus 10 according to an exemplary embodiment of the present disclosure. As described above, Figure 7 (a) The modulated asymmetric coupled transmission lines 11 and 12 shown can be used in two modes by means of appropriate modulation frequency and associated phase. f 0 and f iNon-reciprocal coupling occurs between them, and these two modes allow electromagnetic wave 13 to propagate in the same direction on separate transmission lines 11 and 12, such as... Figure 7 As shown in (b). Alternatively, by selecting appropriate frequencies and associated phases, the same device 10 can couple electromagnetic waves 13 supported by modes on separate transmission lines 11, 12 and propagating in opposite directions, such as... Figure 7 As shown in (c). Similarly, with the correct modulation frequency and phase, electromagnetic waves 13 supported by modes within modulation transmission lines 11 and / or 12 can also be non-reciprocally coupled, regardless of whether they are in Figure 7 (d) shows propagation in the same direction or in Figure 7 It propagates in the opposite direction as shown in (e).

[0067] Figure 8 Multi-frequency parametric modulation via multiple non-reciprocal couplings is illustrated in apparatus 10 according to an exemplary embodiment of the present disclosure. Consider... Figure 8 (a) shows modulated asymmetric coupled transmission lines 11 and 12, wherein the modulation includes multiple frequencies { f p} and its associated phases { p ( z )}, with appropriate phase p Each frequency component f p This results in non-reciprocal coupling between electromagnetic waves 13 propagating on transmission lines 11 and 12. For example, consider dual-frequency modulation, i.e. Figure 8 The two arrows in (b) indicate that one frequency modulation provides positive amplification, while the second frequency modulation converts electromagnetic wave 13 to the second transmission line 12 in the reverse direction, as shown in the diagram. Figure 8 As shown in (c).

[0068] Figure 9 The dispersion engineering design of transmission lines 11, 12 of a broadband device 10 according to an exemplary embodiment is shown. The two asymmetric coupled transmission lines 11, 12 can be engineered to have dispersion curves such that, within a predetermined frequency range, they belong to separate curves and are affected by a given frequency shift n. f p Any two separated electromagnetic modes exhibit the same phase shift n p In this way, for a single impedance modulation frequency and associated phase set, non-reciprocal coupling between the two transmission lines 11 and 12 can be obtained over the entire desired frequency range. One possible embodiment is... Figure 9 The device 10 shown in (a) generates Figure 9 The dispersion curves described in (b) are shown. The results are as follows: Figure 9As shown in (c), for any signal in the 6-12 GHz range, through a single modulation frequency f p and associated phase set { p This allows for directional energy exchange between two lines.

[0069] Figure 10 Exemplary implementations of impedance modulation elements 14 and / or 21 are shown and can be used in any device 10 described in this disclosure. Multiple impedance modulation elements 14 can be used to achieve impedance modulation using the controller 15. For example, such as Figure 10 As shown in (a), a superconducting quantum interference device (SQUID) configured to be modulated by an external flux can be used. Alternatively, as... Figure 10 As shown in (b), a varactor diode can be used, wherein the capacitance of the varactor diode is controlled by an external voltage. Alternatively, a varactor diode can be used. Figure 10 (d) shows a Josephson junction, or an inductor modulated by a pump current (provided by controller 15). Similarly, a dynamic inductor, or a material with second- or third-order nonlinearity, or any other nonlinear element with impedance modulated by a pump signal, such as... Figure 10 As shown in (c), or any other process that can achieve a phase-preserving mixing process that generates a new frequency modulus.

[0070] Figure 11 It is shown as such Figure 11 The specific implementation of the impedance modulation element of the varactor diode in (b). Figure 11 (c) shown with Figure 11 The pump signal propagating on the adjacent additional line 111 of transmission line 11 in (A) can modulate the voltage seen (across the varactor diode) by the varactor diode, thereby changing its capacitance. If the adjacent pump line 111 has the correct phase velocity, the pump will generate impedance modulation with a sufficient phase set in transmission line 11.

[0071] Figure 12 It is shown as such Figure 12 The specific implementation of the impedance modulation element 14 of the SQUID in (b). The closed magnetic flux of the SQUID can also be modulated by a pump signal propagating on adjacent line 111, such as Figure 12 As shown in (c). If the adjacent line 111 has the correct phase velocity, the pump will generate impedance modulation with a sufficient phase set in the transmission line 11.

[0072] Figure 13 A flowchart of method 130 according to this disclosure, specifically method steps 131, 132, and 133, is shown. Method 130 can be performed to operate device 10 for non-reciprocal signal transmission, for example, as shown in the preceding figures.

[0073] Step 131 includes propagating an electromagnetic wave 13 supported by a first set of electromagnetic modes of the first transmission line 11 at a first phase velocity in a first direction or a second direction opposite to it. Step 132 includes propagating an electromagnetic wave 13 supported by a second set of electromagnetic modes of the second transmission line 12 at a second phase velocity in a first direction or a second direction.

[0074] Step 133 includes controlling a set of first adjustable impedance elements 14 distributed along the first transmission line 11 to generate an impedance modulation set in the first transmission line 11. Each impedance modulation in this set produces a new frequency modulation in the electromagnetic wave 13 propagating in the first transmission line. Step 133 can be individually controlled for each first adjustable impedance element 14 to generate an impedance modulation set with a specific associated phase set. Step 133 can thus be performed such that, for a first propagation direction of the electromagnetic wave 13 in the first transmission line 11, the new frequency modulation in the electromagnetic wave 13 of the first transmission line 11 constructively interferes with and couples to the mode of the second transmission line 12, and such that, for the opposite second propagation direction of the electromagnetic wave 13 in the first transmission line 11, the new frequency modulation in the electromagnetic wave 13 of the first transmission line 11 destructively interferes with and does not couple to the mode of the second transmission line 12.

[0075] In summary, this disclosure presents an apparatus 10 and a method 130 for asymmetric coupling of transmission lines 11 and 12, relying on non-reciprocal coupling of electromagnetic waves 13 propagating in transmission lines 11 and 12 induced by impedance modulation. The unequal phase velocities of the transmission lines 11 and 12 prevent strong coupling in the unmodulated case. However, this phase mismatch can be compensated for by controlling at least one set of impedance modulation elements 14 and 21 arranged along one or both of the transmission lines 11 and 12, resulting in stronger coupling between the two transmission lines 11 and 12. Furthermore, the impedance modulation set can be a controller with corresponding associated phases, such that phase matching of the propagating electromagnetic waves 13 occurs only in one propagation direction, rather than in the opposite direction, thereby making the coupling between the two transmission lines 11 and 12 non-reciprocal. Additionally, dispersion engineering can be used to ensure phase matching occurs over a wide frequency range, resulting in broadband non-reciprocity. The apparatus 10 of this disclosure, with minor relative adjustments, can be used as a gyrator, circulator, isolator, directional amplifier, or even a combination of these effects within the same apparatus 10.

[0076] In the claims and the description of this disclosure, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude multiple. A single element can perform the function of several entities or items described in the claims. The fact that certain measures are referenced in mutually different dependent claims does not indicate that a combination of these measures cannot be used in advantageous implementations.

Claims

1. An apparatus (10) for non-reciprocal signal transmission, the apparatus (10) comprising: The first transmission line (11) has a first set of electromagnetic modes that support the propagation of electromagnetic waves (13) at a first phase velocity; The second transmission line (12) has a second set of electromagnetic modes that support the propagation of electromagnetic waves (13) at a second phase velocity different from the first phase velocity; as well as A set of first adjustable impedance elements (14) distributed along the first transmission line (11). A controller (15) is configured to control the set of first adjustable impedance elements (14) to generate an impedance modulation set in the first transmission line (11), each impedance modulation in the set generating a new frequency modulation in the electromagnetic wave (13) propagating in the first transmission line (11). The controller (15) is configured to individually control each first adjustable impedance element (14) to generate an impedance modulation set with a specific associated phase set, such that: For the first propagation direction of the electromagnetic wave (13) in the first transmission line (11), the new frequency modulation of the electromagnetic wave (13) in the first transmission line (11) constructively interferes with and couples with the mode of the second transmission line (12), and For the electromagnetic wave (13) in the opposite second propagation direction in the first transmission line (11), the new frequency modulation in the electromagnetic wave (13) in the first transmission line (11) cancels the mode of the second transmission line (12) and is not coupled.

2. The device (10) according to claim 1, characterized in that: The first adjustable impedance element (14) of the group includes one of the following: a superconducting quantum interference device configured to be modulated by an external flux, a voltage-controlled capacitor configured to be controlled by an external voltage, a Josephson junction, a dynamic inductor, a material having second- or third-order nonlinearity, or any other nonlinear element configured to be impedance modulated by a pump signal.

3. The device (10) according to claim 1, characterized in that: The controller (15) is configured to control the group of first adjustable impedance elements (14) to generate an impedance modulation set with associated phase set at a first frequency to achieve non-reciprocal coupling between an electromagnetic wave (13) supported by the electromagnetic mode of the first transmission line (11) and propagating in the first propagation direction and an electromagnetic wave (13) supported by the electromagnetic mode of the second transmission line (12) and propagating in the same first propagation direction.

4. The device (10) according to claim 1, characterized in that: The controller (15) is configured to control the group of first adjustable impedance elements (14) to generate an impedance modulation set with associated phase set at a first frequency to achieve non-reciprocal coupling between electromagnetic wave (13) supported by the electromagnetic mode of the first transmission line (11) and propagating in the first propagation direction and electromagnetic wave (13) supported by the electromagnetic mode of the second transmission line (12) and propagating in the second propagation direction.

5. The device (10) according to claim 1, characterized in that: The controller (15) is configured to control the first set of adjustable impedance elements (14) to generate an impedance modulation set with associated phase sets at multiple frequencies to achieve a set of non-reciprocal couplings between an electromagnetic wave (13) supported by the electromagnetic mode of one of the two transmission lines (11, 12) and an electromagnetic wave (13) supported by the electromagnetic mode of the other transmission line (11, 12).

6. The device (10) according to claim 1, characterized in that: A modulation frequency and the associated phase set are configured to achieve non-reciprocal coupling and directional energy exchange between electromagnetic waves (13) supported by the electromagnetic modes of the first transmission line (11) and electromagnetic waves (13) supported by the electromagnetic modes of the second transmission line (12).

7. The apparatus (10) according to claim 1, characterized in that: A modulation frequency and the associated phase set are configured to achieve non-reciprocal coupling and directional amplification of the electromagnetic wave (13) propagating in the first transmission line (11) and the electromagnetic wave (13) propagating in the second transmission line (12).

8. The apparatus (10) according to claim 6, characterized in that: The non-reciprocal coupling between an electromagnetic wave (13) supported by an electromagnetic mode of one of the two transmission lines (11, 12) designed to have lower loss and an electromagnetic wave (13) supported by an electromagnetic mode of the other transmission line (11, 12) designed to have higher loss is configured to produce non-reciprocal electromagnetic field attenuation.

9. The apparatus (10) according to claim 1, characterized in that, The device further includes: A set of second adjustable impedance elements (21) distributed along the second transmission line (12); The controller (15) is configured to control the set of second adjustable impedance elements (21) to generate a second set of impedance modulations in the second transmission line (12), each impedance modulation in the second set generating a new frequency modulation in the electromagnetic wave (13) propagating in the second transmission line (12); The controller (15) is configured to individually control each of the second adjustable impedance elements (21) to generate a second impedance modulation set with a specific associated phase set, such that: For the electromagnetic wave (13) in the first propagation direction in the first transmission line (12), the new frequency modulation of the electromagnetic wave (13) in the second transmission line (12) constructively interferes with and couples with the mode of the first transmission line (11), and For the electromagnetic wave (13) in the opposite second propagation direction in the second transmission line (12), the new frequency modulation of the electromagnetic wave (13) in the second transmission line (12) cancels the mode of the first transmission line (11) and is not coupled.

10. The apparatus (10) according to claim 1, characterized in that: The first transmission line (11) and the second transmission line (12) are configured to have their respective electromagnetic modes, which have dispersion curves that are parallel to each other within a predetermined frequency range.

11. The apparatus (10) according to claim 1, characterized in that: The electromagnetic wave (13) is radio frequency, RF, wave, or RF noise; or The electromagnetic wave (13) is a light wave or optical noise and the transmission lines (11, 12) are waveguides.

12. A method (130) for operating an apparatus (10) for non-reciprocal signal transmission, the method (130) comprising: Electromagnetic waves (13) supported by a first set of electromagnetic modes of a first transmission line (11) propagate at a first phase velocity (131) in a first direction or in the opposite second direction. An electromagnetic wave (13) supported by a second set of electromagnetic modes of the second transmission line (12) propagates at a second phase velocity (132) in the first or second direction; and A set of first adjustable impedance elements (14) distributed along the first transmission line (11) is controlled to generate an impedance modulation set in the first transmission line (11), each impedance modulation in the set generating a new frequency modulation in the electromagnetic wave (13) propagating in the first transmission line (11). Each of the first adjustable impedance elements (14) is individually controlled to generate an impedance modulation set with a specific associated phase set, such that: For the first propagation direction of the electromagnetic wave (13) in the first transmission line (11), the new frequency modulation of the electromagnetic wave (13) in the first transmission line (11) constructively interferes with and couples with the mode of the second transmission line (12), and For the electromagnetic wave (13) in the opposite second propagation direction in the first transmission line (11), the new frequency modulation in the electromagnetic wave (13) in the first transmission line (11) cancels the mode of the second transmission line (12) and is not coupled.

Images