Apparatus of inductively coupled multi-frequency electromagnetic resonators forming an array of resonators or a metamaterial, and method of implementing same

Abstract

The invention relates to an array device (RR1, RR2, RR3) composed of individual multi-frequency passive resonators (MR1) that are not electrically connected. These resonators are formed by transmission lines (M11-M14) that are interrupted self-closed circuits nested within each other, each formed by a group of two or more parallel tracks, paired with each other in a non-contact manner around one or more dielectric layers (d1) of a substrate. Such an array is used in particular to modulate an incident magnetic or electromagnetic field (Ci) and / or to perform impedance matching by being placed between the incident magnetic field (Ci) and a body (9) or object to be treated or observed. It is also used to improve a method for the non-contact characterization of a medium under investigation (91, 928) by inductively coupling one or more resonators of said array to a probe (S1) connected (102) to a reader (S0).

Description

[Technical field]

[0001] The invention relates to an array device composed of individual, non-electrically connected, multi-frequency passive resonators. These resonators are formed by transmission lines that are interrupted self-closed circuits nested within each other, each formed by a group of two or more parallel tracks, paired with each other in a non-contact manner around one or more dielectric layers of a substrate. Such arrays are used in particular to modulate incident magnetic or electromagnetic fields and / or to perform impedance matching by being placed between an incident magnetic field and a body or object to be treated or observed. They are also used to improve methods for the non-contact characterization of a medium under investigation by inductively coupling one or more resonators of said array to a probe connected to a reader. [Background technology]

[0002] It is known to group electromagnetic resonators into arrays to obtain a "metamaterial" effect that gives an overall effect on electromagnetic fields different from the effect obtained by the one or more materials that make up the "metamaterial."

[0003] Such metamaterials are often fabricated using regularly spaced resonators that are connected to each other by electrical connections or electrically coupled transmission lines, and interact primarily with electric fields.

[0004] For example, US Pat. No. 5,999,333 relates to an antenna and microwave tomography system, used for detection and diagnosis of the human body. This document proposes placing a metamaterial between the antenna and the skin, which is used for impedance matching with the human tissue and facilitating penetration. The metamaterial is formed by an array of single-frequency copper elements on a dielectric support. The resonant frequency can be static, or tuned by means such as voltage-controlled MEMS or microfluidic flows that change the dielectric properties of the metamaterial, or optically tuned using a photosensitive material whose dielectric properties change when illuminated with light.

[0005] The following non-patent documents propose metamaterials formed by regularly repeating SRRs (split-ring resonators), which are single-frequency resonators, to improve the performance of microwave monitoring or imaging systems (Non-Patent Document 1, Non-Patent Document 2).

[0006] However, such metamaterials remain difficult to fabricate and tune and would benefit from development in different directions, particularly in terms of robustness and versatility of applications. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] US2019 / 0021626 [Non-patent literature]

[0008] [Non-Patent Document 1] Razzicchia, E., Koutsoupidou, M., Cano Garcia, H., Sotiriou, I., Kallos, E., Palikaras, G., & Kosmas, P. (2019): "Metamaterial designs to enhance microwave imaging applications". In Proceedings of the 2019 21st International Conference on Electromagnetics in Advanced Applications, ICEAA 2019 (pp. 147-150). [Non-Patent Document 2] Vincenza Portosi, Antonella Maria Loconsole and Francesco Prudenzano: "A Split Ring Resonator-Based Metamaterial for Microwave Impedance Matching with Biological Tissue". In Applied Sciences 2020, 10, 6740. Summary of the Invention [Problem to be solved by the invention]

[0009] The object of the present invention is to overcome all or part of the drawbacks of the prior art, in particular to provide devices and methods based on electromagnetic resonators that are more effective, flexible, versatile, easy to manufacture and use, and flexible. [Means for solving the problem]

[0010] [Disclosure of the Invention] The invention provides a device comprising a plurality of passive multi-frequency electromagnetic resonators (i.e. each resonator has a plurality of predefined resonant frequencies). In particular, these resonators share at least one resonant frequency, referred to as a common resonant frequency, although this need not necessarily be the case. Each of said resonators comprises a plurality of transmission lines, galvanically isolated (with respect to each other and to the outside of the resonator), each having a resonant frequency different from each other and each forming a path that is self-closing and interrupted by one or more divisions. The transmission lines are spatially arranged with respect to each other such that, when the device is exposed to what is referred to as an incident magnetic field, they share between them a common interaction region where the magnetic flux lines of the incident magnetic field interact with the plurality of transmission lines. It is understood that this incident magnetic field can be an electric, magnetic or electromagnetic field. According to the invention, the resonators themselves are arranged in the array in such a way that they are sufficiently close to each other to form an array of resonators that have no electrical contact between them and can interact with each other via inductive coupling.

[0011] In this way, one obtains an array of resonators that are separated from one another (spatially and electrically), distributed to cover an area or even a certain volume, and that inductively interact with one another to produce a collective response.

[0012] These resonators are for example multi-frequency resonators as described in French patent application FR 2 112 292 by the same inventors, the specific features of which are also applicable to the present invention.

[0013] According to one particular feature of the invention, the resonators of this array (all or at least some of them) each include one or more transmission lines formed by a group of at least two interrupted tracks, in each group these tracks are arranged parallel to one another but without electrical contact between them and following the same common path, in such a group one or more interruptions of each track of said group are respectively arranged facing a solid part of the other tracks of said group, in particular facing a solid part of all other tracks of said group.

[0014] In this way, an array of resonators is obtained which particularly facilitates inductive and magnetic interactions.

[0015] Typically, all or part of the multi-frequency resonator comprises multiple transmission lines each nested within one another, and in particular contained within a two-dimensional surface (which may be planar or non-planar, e.g. cylindrical or conical, tuned, or of other shape).

[0016] The multiple multi-frequency resonators of the device of the invention may each comprise multiple transmission lines formed by at least two tracks arranged on two opposite faces of a two-dimensional dielectric substrate on the same substrate, in particular common to all or some transmission lines of the same multi-frequency resonator.

[0017] The various tracks of the same track group are, for example, three or more tracks deposited on both sides of an insulating substrate layer or located between insulating substrate layers.

[0018] If desired, the one or more substrates are arranged such that their dielectric properties can be modified, thereby changing the resonant frequency of each group of tracks, and therefore each resonator, for example by using a layer of piezoelectric material that is electrically controlled to vary its thickness, or by incorporating microfluidic channels in the substrate and varying the overall dielectric properties of the substrate by injecting or removing fluids into or from these channels, or by using any known means for altering and / or controlling (or "activating") such changes in dielectric properties.

[0019] Such an array can be used in a variety of ways, in particular according to one group of embodiments, within an incident magnetic field surrounding or passing through said array.

[0020] [Metamaterials] Thus, according to one particular feature, multi-frequency resonators are arranged in a spatially periodic structure arranged to form an electromagnetic metamaterial capable of interacting with an external electromagnetic field (called an incident magnetic field) such that there is no electrical contact between them.

[0021] According to another aspect of the invention there is provided a method of modulating the interaction of a living organism or object with an incident electromagnetic field, the method comprising placing, holding or activating a device as disclosed herein around said organism or object, or between a source of said incident magnetic field and said organism or object.

[0022] The use of this type of metamaterial enables a variety of applications according to various specific, not mutually exclusive, characteristics.

[0023] According to one particular feature, the resonator is designed and arranged to interact with an incident electromagnetic field in a manner that filters or attenuates all or some frequencies other than the resonant frequency of said resonator.

[0024] Thus, for example, a filtering effect is obtained, for example by absorbing and re-emitting especially resonant frequencies. For example, a screen can be created between the incident magnetic field and the target object to protect it from, for example, resonant frequencies. Also, a screening effect can be created, for example by passing only resonant frequencies over a very small frequency band, for example around 100 kHz. In this way, a very high quality factor is obtained.

[0025] According to another particular feature, the resonators are designed and arranged to interact with electromagnetic fields passing through the device so as to amplify their strength at the resonant frequencies of the resonators, by magnetic induction at these frequencies.

[0026] In this way it is possible to amplify the effect of certain frequencies, thereby improving, for example, detection, imaging or processing-based methods.

[0027] According to yet another specific feature, the resonator is designed and arranged to interact with an incident electromagnetic field to deflect or reflect all or a portion of its intensity at one or more frequencies.

[0028] By inserting the array between an incident magnetic field and a body or object, it becomes possible to protect this object from the incident magnetic field in terms of its strength and / or in terms of modulating the signature or image produced by said incident magnetic field, or in terms of the response it produces in said body or object.

[0029] [Impedance matching] According to a group of embodiments not exclusive of the above group, the resonator is designed and arranged to interact with the electromagnetic field passing through it so as to modulate / match the impedance of an incident signal carried by said electromagnetic field or a response signal caused by said electromagnetic field passing through the device.

[0030] The invention thus makes it possible to produce impedance matching devices that modulate, tune or improve the performance of electromagnetic wave-based detection, imaging or processing methods, such as microwave tomography or MRI. Such modulation can be applied, for example, to the precision, penetration, depth of investigation or the nature of the tissue or material being observed or processed, and can be applied over a wider or more flexible frequency range. It can also minimize side effects on the tissue from such treatment or observation.

[0031] According to one particular feature, the device disclosed herein comprises a flexible or rigid film carrying all or part of the resonator of said device, which is placed to surround a living or non-living object, called the subject, in particular to protect said object or to modulate its interaction with the electromagnetic field in order to optimize the treatment or investigation carried out on said object by said field.

[0032] In this way, a flexible impedance matching device is produced that is easy to use, transport or store, e.g., comparable to a survival blanket, or the flexible portion can be produced, e.g., for localized masking purposes, or to be worn as a garment ("wearable") or dressing.

[0033] [Non-contact characteristic evaluation] According to yet another group of embodiments, not excluding the above group, the present invention provides a method for non-contact characterization of at least one area of ​​interest in a medium to be characterized, comprising the steps of: - simultaneous non-contact inductive coupling of the probe to one or more multi-frequency resonators, called probe resonators, which constitute part of the array of resonators formed by the device described herein. The array is positioned in the vicinity of the area under investigation, but does not necessarily contact the area under investigation, such that resonators of the array interact with the area under investigation. - measuring the impedance change of the probe resonator with a reader interacting with the probe. - processing said measurements of impedance change by including a spectral analysis as a function of frequency to determine a plurality of individual impedances measured for a plurality of measurement frequencies. - processing one or more of said individual impedances to extract one or more electrical properties of said area under investigation.

[0034] Due to coupling between the various resonators of the array, the impedance of one or more resonators probed by the probe changes according to the change in impedance of the other resonators, called unprobed resonators. The interaction of the unprobed resonators with the medium to be characterized propagates to some extent to one or more of the probed resonators. Thus, from a probe that is directly coupled only to some resonators, the reader can extract electrical properties also from areas interacting with other resonators further away from the probe.

[0035] This provides improvements over many known issues in non-contact interrogation, including, for example, increased robustness of the measurements with respect to positioning of the probe relative to the medium, since more resonators are examined with the same probe.

[0036] This characterization method is based on the same principle as the method using a single multi-frequency resonator described in French patent application FR 2 112 292 by the same inventors, in which the various variants described are also applicable to this method, for example in terms of the nature and structure of the resonator, or in terms of the control of the depth of the investigated area, or in terms of its various applications.

[0037] According to one particular feature, the array comprises different types of multi-frequency resonators having different frequency combinations, the resonators being spatially distributed in said array such that different regions have different frequency combinations, in particular with different resonators or different combinations of different resonators.

[0038] By coupling to one or more of the probe resonators, the reader can analyze the change in impedance at various frequencies or combinations of frequencies for a large portion of the array that includes multiple different regions, even if the probe resonator is not included. Thus, by using a probe coupled to a resonator that interacts with the medium in a first region, electrical properties can be extracted from the medium in a second region that interacts with an unprobed resonator.

[0039] As long as the spatial distribution of the resonators for the various frequency combinations is known, this method provides characterization information that is spatially distributed across multiple regions while probing only one region.

[0040] According to yet another aspect of the present invention, there is provided a system for non-contact characterization of at least one region, referred to as an area of ​​interest, in a medium to be characterized, the system comprising: - at least one of the devices described herein, forming an array of resonators which interact with each other via inductive coupling and whose transmission lines interact with the area under investigation, said device intended to be placed in the vicinity of said area under investigation, but which does not require contact with said area under investigation. - At least one probe arranged as follows: on the one hand, being inductively coupled to one or more resonators of said array of resonators (typically only a portion of the resonators of the array) by means of an inductive loop circuit; and on the other hand, interact with at least one leader; The reader is arranged to interact with the probe to implement the characterization methods disclosed herein. [Brief description of the drawings]

[0041] Other features and advantages will become apparent from the detailed description of entirely non-limiting embodiments and from the accompanying drawings, in which: [Figure 1a] FIG. 1a is a scaled top view of an example of a multi-frequency resonator that can be used in various embodiments of the present invention, showing a resonator with four nested single-turn circular meshes. [Figure 1b] FIG. 1b is a scaled top view of an example of a multi-frequency resonator that can be used in various embodiments of the present invention, showing a resonator with eight nested single-turn circular meshes. [Diagram 2] FIG. 2 is a scaled top view of an example of a multi-frequency resonator that can be used in various embodiments of the present invention, having four nested circular meshes, one of which is single turn and the others are multi-turn. [Diagram 3] FIG. 3 is a partial schematic top view, cross-sectional view, and exploded perspective view illustrating an example of a single-turn circular element transmission line (or TLR) that can be used in a multi-frequency resonator that can be used in various embodiments of the present invention. [Figure 4]4 is a partial schematic top and cross-sectional view of a multi-split-element transmission line (or TLR) that can be used in a multi-frequency resonator that can be used in various exemplary embodiments. In one example, the portion has six circular transmission lines of decreasing radius, which are concentric with each other and offset by 60°. Each is formed by two tracks disposed on each of the two faces of an insulating thin substrate, angularly offset from each other opposite each other. [Diagram 5] FIG. 5 is an equivalent circuit diagram of a resonator with “N” resonant frequencies, showing its interaction with the probe and the medium being characterized. [Figure 6] FIG. 6 shows curves of the real part of the impedance Zmes measured against frequency for the four resonators of FIG. 1a without load, and by simulation. [Figure 7] FIG. 7 shows simulated curves similar to those of FIG. 6 for the eight resonators of FIG. 1b. [Figure 8] FIG. 8 is a flow chart that illustrates a schematic of the operation of a characterization method used in some embodiments of the present invention. [Figure 9] FIG. 9 is a schematic plan view of an example of a multi-frequency resonator array having four frequency resonators that are all identical to one another, in accordance with an exemplary embodiment of the invention. [Figure 10] FIG. 10 illustrates the use of a multi-frequency resonator array of the same type as in FIG. 9 (or FIG. 11) as a non-contact sensor for characterizing a medium using a single channel inductive probe. [Figure 11] FIG. 11 is a schematic plan view illustrating an example of a multi-frequency resonator array having a plurality of different types of four-frequency resonators distributed in spatially distinct regions, according to an exemplary embodiment of the invention. [Figure 12] FIG. 12 is a cross-sectional view of an exemplary embodiment of the invention in which an array like that of FIG. 9 or FIG. 11 is embedded in the wall of a tank for non-contact characterization of the condition of the tank's interior surface with a single probe. [Figure 13]FIG. 13 illustrates the use of a multi-frequency resonator array arranged as a metamaterial to interact with an incident electromagnetic field. [Figure 14] FIG. 14 illustrates the use of a flexible film carrying a multi-frequency resonator array arranged as a metamaterial to perform impedance matching by being placed between an incident electromagnetic field and a body being investigated using said electromagnetic field. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] [Explanation with reference to drawings] [Individual multi-frequency resonators] 1a to 4 show examples of individual multi-frequency resonators that can be used to manufacture a resonator array according to the invention.

[0043] Figures 3 and 4 show the configuration of a transmission line M14, M1 that can be used to manufacture such a resonator. This transmission line is formed by two groups of interrupted tracks placed on either side of a planar dielectric substrate d1, with an angular offset between the divisions of the two tracks of each group.

[0044] These individual resonators are described in detail in French patent application FR2112292 by the same inventor.

[0045] [Method of evaluating characteristics using multi-frequency resonators] Figure 5 shows the interaction of a probe S1 with a resonator MR1 having "N" resonant frequencies including N transmission lines Z1-ZN in the context of a method for contactless characterization of a medium under investigation. Figures 6 and 7 show impedance measurements showing peaks corresponding to the resonant frequencies of the individual multi-frequency resonators of Figures 1a and 1b, respectively. Figure 8 shows the steps and application of such a characterization method.

[0046] This method is described in detail in French patent application FR2112292 by the same inventors.

[0047] FIG. 9 shows an example of a multi-frequency resonator array RR1 according to an embodiment of the present invention, having four identical frequency resonators MR1, similar to the one in FIG. 1a, fabricated on both sides of a planar dielectric substrate.

[0048] FIG. 10 shows the use of a multi-frequency resonator array of the same type as in FIG. 9 (or FIG. 11) as a non-contact sensor for characterizing a medium using an inductive probe S1 connected via a single channel 102 to a reader S0, e.g. a vector analyzer.

[0049] 11 shows an example of a multi-frequency resonator array RR2 having a number of four-frequency resonators of different types MR1a, MR1b, MR1c, MR1d, in this example similar to the resonators in FIG. 1a, but with different sizes and different combinations of resonant frequencies, according to an exemplary embodiment of the invention. In this array, the resonators of different types are distributed in four spatially distinct regions RR2a, RR2b, RR2c, RR2d.

[0050] Due to the inductive interactions that exist between resonators of the same array RR2, an inductive probe S1 coupled to one MR1a of the resonators of a certain area RR2a measures not only the impedance of the respective resonant frequency of the "probed" resonator, but also of other types of resonators and resonant frequencies from other areas of the array RR2.

[0051] FIG. 12 shows an exemplary implementation of a characterization method using an array such as that of FIG. 9 or FIG. 11 embedded in the wall of a tank 83 for non-contact characterization of the condition of the inner surface 928 of the tank 83 with a single probe S1.

[0052] Again, due to the inductive interactions present between the resonators of array RR1, probe S1 indirectly detects the impedance changes present in regions R7a-R7h covering the interface region between the tank wall and fuel 92 via individual inductively coupled multi-frequency resonators MR7e.

[0053] [Metamaterials] 13 shows the use of a multi-frequency resonator array RR1 arranged as a metamaterial to interact with an incident electromagnetic field Ci, in particular the magnetic or magnetic component of the electromagnetic field. Depending on the changes brought about by the metamaterial, this incident magnetic field Ci is changed, for example transmitted Cs1, refracted Cs2 or reflected Cs3, depending on the properties given to this metamaterial by the properties of its individual resonators.

[0054] FIG. 14 shows the use of a flexible film carrying a multi-frequency resonator array RR3 arranged as a metamaterial to perform impedance matching by being placed between the body of the patient 9 and the incident electromagnetic field Ci radiated by the probe S9 of the treatment device.

[0055] Of course, the invention is not limited to the examples given above and many adjustments can be made to these embodiments without going beyond the scope of the invention.

Claims

1. A device (RR1, RR2, RR3) including a plurality of passive multi-frequency electromagnetic resonators (MR1, MR2, MR3), each having a plurality of predetermined resonant frequencies, Each of the resonators has a different resonant frequency and includes a plurality of transmission lines (M11 to M14) that are galvanically insulated from one another and each of which forms a path that is self-closing and interrupted by one or more divisions (G14); the transmission lines are spatially positioned relative to one another such that, when the device is subjected to what is referred to as an incident magnetic field (Ci), the magnetic flux lines of the incident magnetic field share a common interaction region therebetween where they interact with the multiple transmission lines; A device in which the resonators are positioned sufficiently close to each other to form an array of resonators that have no electrical contact therebetween and can interact with each other via inductive coupling.

2. 2. A device according to claim 1, wherein all or some of said resonators (MR1, MR2, MR3) each comprise one or more transmission lines (M14) formed by a group of at least two interrupted tracks (C14a, C14b), said tracks being arranged parallel to one another but without electrical contact between them, tracing the same common path; A device in which one or more interruptions (G14, G14') of each of said tracks of said group are respectively arranged facing the substance of the other tracks of said group, in particular facing the substance of all other tracks of said group.

3. 3. The device of claim 2, wherein each of said plurality of multi-frequency resonators comprises a plurality of transmission lines nested within one another, particularly within a two-dimensional surface.

4. 4. A device according to claim 3, wherein said plurality of multi-frequency resonators each comprise a plurality of transmission lines formed by at least two tracks arranged on two opposite faces of a two-dimensional dielectric substrate on the same substrate, in particular common to all or some of the transmission lines of the same multi-frequency resonator.

5. 5. The device of claim 4, wherein the multi-frequency resonators are arranged within a spatially periodic structure arranged to form an electromagnetic metamaterial capable of interacting with an external electromagnetic field (called an incident magnetic field) such that there is no electrical contact between them.

6. 3. A device according to claim 1 or claim 2, wherein the resonator is designed and arranged to interact with an incident electromagnetic field in a manner that filters or attenuates all or some of the frequencies other than the resonant frequency of the resonator.

7. 3. A device according to claim 1 or claim 2, wherein the resonator is designed and arranged to interact with an electromagnetic field passing through it so as to amplify the strength thereof at the resonant frequency of the resonator.

8. 3. The device of claim 1 or claim 2, wherein the resonator is designed and arranged to interact with an incident electromagnetic field to deflect, refract, or reflect all or a portion of its intensity at one or more frequencies.

9. 3. A device as claimed in claim 1 or claim 2, wherein the resonator is designed and arranged to interact with an electromagnetic field passing through it so as to modulate the impedance of an incident signal carried by the electromagnetic field or the impedance of a response signal caused by the electromagnetic field passing through the device.

10. 6. A device according to claim 4 or claim 5, comprising a flexible or rigid film carrying all or part of the resonator of the device, which film is arranged to surround a living or non-living object, referred to as an object, in order to modulate said interaction with said electromagnetic field, in particular to protect said object or to optimize a treatment or investigation carried out on said object by said electromagnetic field.

11. 10. A method for modulating the interaction of a living organism or object with an incident electromagnetic field, comprising placing, holding or operating a device as described in claim 1 or claim 2 around the living organism or object, or between a source of the incident magnetic field and the living organism or object.

12. A method for characterizing at least one region of interest in a medium to be characterized, comprising at least the following steps: - a step (102) of simultaneously and non-contactingly inductively coupling a probe to one or more multi-frequency resonators, called probe resonators, which constitute part of the array of resonators formed by the device according to claim 1, the array being positioned in the vicinity of the area under investigation but without needing to come into contact with the area under investigation such that the resonators of the array interact with the area under investigation; measuring (104) said change in impedance of said probe resonator using a reader interacting with said probe; - processing (103) said measurements of impedance variation by including a spectral analysis (103) as a function of frequency to determine a number of individual impedances (Zm1-Zm8) measured for a number of measurement frequencies (fm1-fm8 respectively); - processing (104) one or more of said individual impedances to extract one or more electrical properties of said area of ​​interest; The method includes:

13. 13. The method according to claim 12, wherein the array comprises different types of multi-frequency resonators with different frequency combinations, the resonators being spatially distributed in the array such that different regions (RR2a, RR2b) have different frequency combinations, in particular by different resonators or different combinations of different resonators.

14. A system for the contactless characterization of at least one region, called a region of interest (R1, R2, R3, R7, R8), in a medium to be characterized (91, 92, 93, 94), comprising: at least one device according to claim 1, forming an array (RR1, RR2) of resonators which interact with each other via inductive coupling and which transmission line interacts with the area under investigation, said device being intended to be placed in said vicinity of the area under investigation but which does not require contact with said area under investigation, on the one hand, it is inductively coupled to one or more resonators of the array of resonators (typically only a portion of the resonators of the array) by means of an inductive loop circuit (S1, S7, S8); and On the other hand, at least one probe arranged to interact with at least one reader (S0); The reader, arranged to interact with the probe to implement the characterization method of claim 12; Including, the system.

Images