FREQUENCY-DEPENDENT MICROWAVE FILTER, ARRANGEMENT COMPRISING THE SAME, AND METHOD OF FREQUENCY-DEPENDENT MICROWAVE FILTERING

Abstract

Disclosed is a frequency-dependent microwave filter (1). The filter (1) comprises an enclosure (11) comprising a filter medium including at least one constituent of: atoms, molecules, ions, and point defects in an optically pumpable solid. The at least one constituent is excitable to an initial energy state. The filter (1) further comprises a field generator (12) configured to generate an inhomogeneous electric and/or magnetic field (12A) within the enclosure (11). The filter (1) further comprises means (13) for feedthrough of a microwave signal through the enclosure (11) and an optical pump (14) configured to periodically excite the at least one constituent of the filter medium to the initial energy state in alternation with the feedthrough of the microwave signal through the enclosure (11). Thereby, intensity-dependent filtering is achieved.

Claims

1. A frequency-dependent microwave filter, comprising an enclosure comprising a filter medium including at least one constituent of: atoms, molecules, ions, and point defects in an optically pumpable solid, the at least one constituent being excitable to an initial energy state; a field generator configured to generate an inhomogeneous electric and/or magnetic field within the enclosure; means for feedthrough of a microwave signal through the enclosure; and an optical pump configured to periodically excite the at least one constituent of the filter medium to the initial energy state in alternation with the feedthrough of the microwave signal through the enclosure.

3. The filter of claim 1, the enclosure comprising at least one of: a gas cell, and a diamond.

4. The filter of claim 3, the gas comprising at least one chemical element; the at least one chemical element preferably being from a first main group; the at least one chemical element preferably comprising rubidium.

5. The filter of claim 4, the at least one chemical element further comprising at least one of: nitrogen, neon, and radon.

6. The filter of claim 1, further comprising an optical cavity comprising the enclosure.

7. The filter of claim 1, the means for feedthrough comprising a waveguide; the waveguide preferably comprising a wire.

8. The filter of claim 1, further comprising a power splitter or power switch configured to split up the microwave signal into a plurality of partial microwave signals on respective waveguides configured to guide the plurality of partial microwave signals through the filter medium at respective lateral positions relative to a propagation direction of the plurality of partial microwave signals.

9. The filter of claim 8, the filter further comprising a number of phase shifters interposed in the respective waveguides configured to shift a relative phase of the plurality of partial microwave signals in accordance with a Rabi frequency of the periodic excitation of the comprised filter medium.

10. The filter of claim 1, the field generator comprising a permanent magnet or electromagnet.

11. The filter of claim 1, the optical pump comprising a coherent light source being resonant to at least one energy transition in the at least one constituent of the filter medium; the optical pump preferably configured to excite the filter medium in a continuous wave, CW, mode or in a pulsed mode; the optical pump preferably configured to excite the filter medium from a lateral direction perpendicular to the propagation direction of the microwave signal.

12. An arrangement, comprising a microwave amplifier; and a filter of any one of the claim 1 arranged upstream of the microwave amplifier.

13. A method of frequency-dependent microwave filtering, comprising generating an inhomogeneous electric and/or magnetic field within an enclosure, the enclosure comprising a filter medium including at least one constituent of: atoms, molecules, ions, and point defects in an optically pumpable solid, the at least one constituent being excitable to an initial energy state; periodically exciting the at least one constituent of the filter medium to the initial energy state in alternation with a feedthrough of the microwave signal through the enclosure.

14. The method of claim 13, wherein a respective absorption rate of frequency components of the microwave signal increases with a respective energy of its frequency components.

15. The method of claim 13, being performed by a frequency-dependent microwave filter comprising: an enclosure comprising a filter medium including at least one constituent of: atoms, molecules, ions, and point defects in an optically pumpable solid, the at least one constituent being excitable to an initial energy state; a field generator configured to generate an inhomogeneous electric and/or magnetic field within the enclosure; means for feedthrough of a microwave signal through the enclosure; and an optical pump configured to periodically excite the at least one constituent of the filter medium to the initial energy state in alternation with the feedthrough of the microwave signal through the enclosure.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0038] The above-described aspects and implementations will now be explained with reference to the accompanying drawings, in which the same or similar reference numerals designate the same or similar elements.

[0039] The features of these aspects and implementations may be combined with each other unless specifically stated otherwise.

[0040] The drawings are to be regarded as being schematic representations, and elements illustrated in the drawings are not necessarily shown to scale. Rather, the various elements are represented such that their function and general purpose become apparent to those skilled in the art.

[0041] FIG. 1 illustrates a frequency-dependent microwave filter in accordance with the present disclosure;

[0042] FIG. 2 illustrates a power-dependent absorption rate in accordance with the present disclosure;

[0043] FIG. 3 illustrates splitting up the microwave signal into a plurality of partial microwave signals on respective waveguides in accordance with the present disclosure;

[0044] FIG. 4 illustrates a first mode of operation in accordance with the present disclosure of the frequency-dependent microwave filter;

[0045] FIG. 5 illustrates a second mode of operation in accordance with the present disclosure of the frequency-dependent microwave filter;

[0046] FIG. 6 illustrates an arrangement in accordance with the present disclosure comprising a frequency-dependent microwave filter; and

[0047] FIG. 7 illustrates a flow diagram of a method in accordance with the present disclosure of frequency-dependent microwave filtering.

DETAILED DESCRIPTIONS OF DRAWINGS

[0048] FIG. 1 illustrates a frequency-dependent microwave filter 1 in accordance with the present disclosure.

[0049] The filter 1 comprises an enclosure 11. The enclosure 11 comprises a filter medium including at least one constituent of: atoms, molecules, ions, and point defects in an optically pumpable solid, such as nitrogen-vacancy (NV) center point defects. The at least one constituent is excitable to an initial energy (i.e., ground) state. In particular, the enclosure 11 may comprise at least one of: a gas cell, and a diamond.

[0050] The gas may comprise at least one chemical element. Preferably, the at least one chemical element is from a first main group (i.e., is a group 1 element). In particular, the at least one chemical element may comprise rubidium (Rb), and may further comprise at least one of nitrogen (N.sub.2), neon (Ne), and radon (Rn).

[0051] The filter 1 further comprises a field generator 12. The field generator 12 is configured to generate an inhomogeneous electric and/or magnetic field 12A within the enclosure 11.

[0052] In particular, the field generator 12 may comprise a permanent magnet or electromagnet configured to generate the inhomogeneous magnetic field 12A. Alternatively, the field generator 12 may comprise an arrangement configured to generate the inhomogeneous electric field 12A, such as an electrical capacitor.

[0053] The filter 1 further comprises means 13 for feedthrough of a microwave signal 13A through the enclosure 11. In particular, the means 13 for feedthrough may comprise a waveguide. The waveguide may preferably comprise a wire. The microwave signal may refer to an electromagnetic field forming and extending in an “antenna region” around said wire.

[0054] The filter 1 further comprises an optical pump 14 configured to periodically excite the at least one constituent of the filter medium to the initial energy state using a laser beam 14A in alternation with the feedthrough of the microwave signal through the enclosure 11.

[0055] Optical pumping may refer to a process of stimulating quantum systems having at least two energy levels/states, such as atoms, molecules, ions and/or point defects in an optically pumpable solid, through resonant absorption of photons of adequate frequency.

[0056] The optical pump 14 may comprise a coherent light source being resonant to at least one energy transition in the at least one constituent of the filter medium, such as a laser or a frequency comb.

[0057] A laser may refer to a device configured to emit light based on stimulated emission of electromagnetic radiation.

[0058] A frequency comb may refer to a laser source whose spectrum includes of a series of discrete, equally spaced frequency lines.

[0059] The optical pump 14 may preferably be configured to excite the filter medium in a continuous wave, (CW) mode or in a pulsed mode.

[0060] The optical pump 14 may preferably be configured to excite the filter medium from a lateral direction L which is substantially perpendicular to a propagation direction P of the microwave signal 13A, as shown in FIG. 1.

[0061] The filter 1 may further comprise an optical cavity 15 comprising the enclosure 11.

[0062] FIG. 2 illustrates a power-dependent absorption rate in accordance with the present disclosure.

[0063] As can be seen, a respective absorption rate of frequency components of the microwave signal increases with a respective energy of its frequency components.

[0064] As such, for a given duration Δt of the RF / microwave radiation, high-energy frequency components achieve a more exhaustive population inversion of the gas particles or point defects from the ground state to the excited state than low-energy frequency components, resulting in an intensity-dependent filtering of the microwave radiation in a particular interaction region of the enclosure 11.

[0065] FIG. 3 illustrates splitting up the microwave signal into a plurality of partial microwave signals 13A, 13B on respective waveguides 13, 13′ in accordance with the present disclosure.

[0066] To this end, the filter 1 may further comprise a power splitter or power switch 16. The power splitter or power switch 16 is configured to split up the microwave signal into a plurality of partial microwave signals 13A, 13B on respective waveguides 13, 13ʹ. Without limitation, the exemplary 3 dB power splitter 16 of FIG. 3 is configured to split up the microwave signal into two partial microwave signals 13A, 13B.

[0067] The respective waveguides 13, 13′ are configured to guide the plurality of partial microwave signals 13A, 13B through the filter medium within the enclosure 11 at respective lateral positions L relative to a propagation direction P of the plurality of partial microwave signals 13A, 13B.

[0068] The filter 1 may further comprise a number of phase shifters 17 interposed in the respective waveguides 13, 13′. Without limitation, the single exemplary phase shifter 17 of FIG. 3 interposed in waveguide 13 downstream of the power splitter 16 is configured to shift a relative phase of the plurality of partial microwave signals 13A, 13B in accordance with (i.e. in relation to) a Rabi frequency f.sub.Rabi of the periodic excitation of the comprised filter medium. That is to say, despite the periodic excitation of the comprised filter medium a continuous operation of the filter may be achieved in at least one portion of the filter at any time, while the gas particles or point defects in other portions of the filter revert to a ground state in accordance with the Rabi cycle.

[0069] The filter 1 may further comprise a power splitter or power switch 16′ to re-combine the filtered plurality of partial microwave signals 13A, 13B.

[0070] FIG. 4 illustrates a first mode of operation in accordance with the present disclosure of the frequency-dependent microwave filter 1.

[0071] The filter 1 corresponds to the exemplary implementation of FIG. 3, wherein two partial microwave signals 13A, 13B are guided through the filter medium within the enclosure 11 at respective lateral positions L corresponding to respective waveguides 13, 13′.

[0072] The two partial microwave signals 13A, 13B are not phase shifted with respect to one another (Δt = 0) and therefore represent different time intervals of the incident microwave signal.

[0073] The at least one constituent of the filter medium is periodically excited / initialized to the initial energy (i.e., ground) state at respective lateral positions corresponding to the waveguides 13, 13′ using the laser beam 14A in accordance with the Rabi frequency f.sub.Rabi. A feedthrough of the respective microwave signal 13A, 13B through the enclosure 11 takes place in alternation with said periodic optical pumping, in support of a continuous operation wherein one of the respective microwave signals 13A, 13B at a time undergoes filtering despite the periodic initialization.

[0074] FIG. 5 illustrates a second mode of operation in accordance with the present disclosure of the frequency-dependent microwave filter 1.

[0075] In this implementation, the filter 1 comprises a power splitter 16 configured to split up the microwave signal into a plurality of partial microwave signals 13A, 13B on respective waveguides 13, 13′, a number of phase shifters 17 interposed in the respective waveguides 13, 13′, and a power splitter 16′ to re-combine the phase-shifted plurality of partial microwave signals 13A, 13B. The re-combined microwave signal is then passed on towards the enclosure 11 using waveguide 13.

[0076] The at least one constituent of the filter medium is periodically excited / initialized to the initial energy state using the laser beam 14A in accordance with the Rabi frequency f.sub.Rabi.

[0077] As the two partial microwave signals 13A, 13B are phase shifted with respect to one another (Δt > 0), the same portion of the incident microwave signal is used multiple times to excite the at least one constituent of the filter medium from the ground state to the excited state, resulting in a different filter response.

[0078] A feedthrough of the re-combined microwave signal through the enclosure 11 takes place in alternation with said periodic optical pumping, in support of a discontinuous operation. A plurality of branches carrying respective re-combined microwave signals may be needed for a continuous operation.

[0079] FIG. 6 illustrates an arrangement 2 in accordance with the present disclosure.

[0080] The arrangement 2 comprises a microwave amplifier 21 and a frequency-dependent microwave filter 1 of the first aspect or any of its implementations as previously described, arranged upstream (with respect to the propagation direction P of the microwave signal) of the microwave amplifier 21.

[0081] In said arrangement the frequency-dependent microwave filter 1 is configured to operate as a power limiter for the microwave amplifier 21 as well as subsequent receiver components arranged downstream of the microwave amplifier 21.

[0082] FIG. 7 illustrates a flow diagram of a method 3 in accordance with the present disclosure of frequency-dependent microwave filtering.

[0083] The method 3 comprises generating 32 an inhomogeneous electric and/or magnetic field 12A within an enclosure 11. The enclosure 11 comprises a filter medium including at least one constituent of: atoms, molecules, ions, and point defects in an optically pumpable solid. The at least one constituent is excitable to an initial energy state.

[0084] The method 3 further comprises periodically exciting 34 the at least one constituent of the filter medium to the initial energy state in alternation with a feedthrough of the microwave signal through the enclosure 11.

[0085] The method 3 may be performed by a frequency-dependent microwave filter 1 of the first aspect or any of its implementations as previously described.