WO1997044857A1

WO1997044857A1 - Transmission structure with expanded absorption bands

Info

Publication number: WO1997044857A1
Application number: PCT/FR1997/000872
Authority: WO
Inventors: Ferdy Mayer
Original assignee: Ferdy Mayer
Priority date: 1996-05-17
Filing date: 1997-05-16
Publication date: 1997-11-27
Also published as: FR2748861B1; FR2748861A1

Abstract

RFI interference has for a long time posed problems to electronic engineers, for instance, and demands a serious approach to ensure the protection of apparatus against such interference and also to avoid interference radiation by such apparatus. In his patents of EUA 3.191.132 and 3.309.633, the applicant described the basic principles of such interference suppression by means of distributed structures represented by absorbing wires (in relation with open conductor structures) and of cables (in relation with closed conductor structures), essentially using magnetic and dielectric losses in the current transmission medium and magnetic fields associated with the current conduction in these wires and cables. The principle of losses spread over distributed lines has been published in detail in IEEE Transactions on Electromagnetic Compatibility, Vol. EMC-10, n°2, June 1968, p. 181 ff. These losses stem from interference attenuation by absorption, i.e. suppression along the transmission structure and, simultaneously, reduction of coupling and interference radiation of the structure.

Description

PROPAGATION STRUCTURES WITH ENLARGED ABSORPTION BANDS

In my French patent n ° 7833385, the ease of using absorbent composite materials has been described in propagation structures, in particular in wires, cables and integrated circuits.

The absorption spectra (as a function of frequency) of such structures were essentially linked to the spectra of the magnetic permeability of the composites, that is to say that of the ferri- or ferromagnetics used, of which the imaginary part (permeability of losses ) introduce absorption. From these facts, one can hardly obtain a magnetic absorption:

- for lower frequencies (for example below some 10 MHz), where the magnetic material has reduced losses (justifying its conventional use),

- for very high frequencies (for example above a few GHz), where the magnetic phenomena disappear (Snoek effect) or else, narrow in narrow band (magnetic resonance under anisotropy field or continuous polarization field) ,

- and for frequencies in the absorption range (some 10 MHz to some GHz), one can hardly obtain an absorption with a different shape than that of the intrinsic permeability spectrum of the material used (essentially linked to a relaxation phenomenon and / or magnetic resonances). This explains, at the start of this range, a slope loss of +1 to +1.5, i.e. increasing proportionally to the frequency or with the power 1.5 with the frequency (6 to 9 dB / octave) .

To widen the absorption frequency range, in my French patent n ° 2.550.657, ^a solution has been described, using wave reflections due to mismatches, by variation of characteristic impedance (cables), with a structure continuous, or even with a discontinuous structure, by the addition of localized components (inductances, capacitances). Still in the same direction of widening the absorption band, in my French patent No. 2,592,265, the production of a "synthetic" ferrite (mixture of several magnetic materials) _has been described, representing the drawback that the effects of each of the materials are obviously reduced: in other words, as for the above solution, the enlargement / modeling of the absorption spectrum is at the expense of absorption in the absorption frequency range clean of magnetic material.

Again in the same direction, another means of widening the absorption band has been described in my French patent n ° 83-255851 consisting in deriving part of the HF current from the basic absorbent structure ("simulated skin effect") the drawback of this solution being a limited attenuation towards the high frequencies.

In the present patent, I describe the use of one or more new absorption effects other than the dielectromagnetic losses of the structures mentioned above, each of these effects having one or more absorption spectra, complementary to 1 ' ferro- or ferrimagnetic absorption: The invention is thus charac¬ terized by an addition to the latter (therefore without dilution effect), in order to widen the frequency range and / or in order to modify the appearance of the variation of absorption as a function of frequency, as well as the selection of complementary absorption spectra, so as to widen / reshape the overall absorption spectrum of the structure.

The effects of dielectric losses, which occur automatically in a propagation structure, are considered in the context of the descriptive examples which follow.

A first object of the present invention therefore consists in describing the additional absorbent effects used, each of these additional absorbent effects possibly existing (and being used) alone, or even, being used together.

For reasons of ease of understanding, most of the examples will be chosen in the aspect of enlargement / reshaping of the electromagnetic absorption of a ferro- or ferrimagnetic material as described in my French patent No. 78.33385. A second object of the invention consists in producing global spectra (that is to say with the various additional effects), extending below some 10 MHz and / or above a few GHz, and / or the realization of the weakening slopes (both downwards and upwards) exceed the +1 to 1.5 slope intrinsic to magnetic materials.

A third aim of the invention is to describe the application to propagation structures in general, such as:

- open structures (connecting wires, unshielded cables, multiple conductors, flat cables, printed circuits, MICetc circuits),

- semi-open structures (inverted coaxial cables, wires taken from the mass, printed and integrated circuits (MICPCetc), antireflective surfaces, etc.), and

- closed structures (coaxial cables, waveguides, enclosures, etc.).

A fourth object of the invention is to describe how the various additional effects are chosen above, in order to give a given spectrum to the overall absorption, with the essential point, that the additional effects are dissipative in themselves, in order that the effect of addition (rather than dilution) is actually present.

A fifth object of the invention is to describe continuous intrinsic structures (therefore easy to produce), in opposition to the concepts of ruptures of characteristic impedances, according to my patent π ° 2,550,657.

A sixth aim of the invention is to describe the addition of effects occurring in series (in the equivalent Kirchhoff scheme), where the di electromagnetic effects mentioned above, occur mainly in derivation. In other words, these effects occur whatever the parallel structure of the structure, ie independently of the insulators used (intervening in shunt). A seventh object of the invention is to describe combinations of the new "widened" absorbent structures (that is to say: widened and / or reshaped spectrum), represented essentially by structures with distributed constants, with localized components, to achieve assemblies.

An eighth object of the invention consists in obtaining absorption spectra of a particular shape, achievable by the choice and the dosage of additional effects. Thus, for example, parasitic effects due to the localized components of the above assemblies can be compensated. The application to complex systems follows the same order of idea.

A ninth object of the invention is to describe some typical embodiments according to the invention, as nonlimiting examples, chosen to be representative for specific industrial or military applications.

I will first describe in more detail three additional effects used according to the invention.

First the artificial calf effect, using the concentration of the current in a conductor, on the surface, at high frequencies: the normal skin effect is artificially increased, using a magnetic conductor with high permeability or even a simple layer of such a conductor on the surface of a non-magnetic conductor, such as copper. I described the application of this effect in detail in my French patents n ° 1.428.517 and 1.514.178.

This effect is linked to conduction (and not to dielectromagnetic effects): therefore, the spectrum of these magnetic losses spreads towards frequencies below a few MHz, and is added to the absorbing dielectromagnetic phenomena.

Then, a second additional effect is linked to the proximity effects in the conductors. I noticed it unexpectedly in a known structure used to reduce absorption: the LTTZ wire. In such a wire, insulated fine conductors are assembled in a strand, so that each wire crosses the section of the strand: then, it is known, that the current is distributed in the section, and the skin effect is thus canceled: the high-frequency resistance of such a strand being more reduced, the LITZ wire makes it possible to produce inductances with high overvoltage.

However, by reducing the diameter of the individual strands and increasing their number (for a given frequency) with possibly the introduction of the artificial skin effect (above), on each of the strands, I obtained a very strong increase in the resistance of the strand, that is to say an absorption proportional to the square root of the number of strands of the conductor (when the skin effect proposed on each strand plays to the full). The current of one of the strands introduces a "proximity effect" with the adjacent strands, and the corresponding couplings introduce losses, which increase the absorption.

Here again, the frequency domain of this effect (additional or used alone) can be placed as desired, in frequencies below 10 MHz, and even in the range of 10 έ 1 GHz, making it possible to increase and widen absorption.

This increase in the impedance of the conductor further acts on the "internal" impedance (and losses) of the conductor.

Then, a third additional effect is linked to coupling effects of resonant or anti-resonant lines, placed near the conductor (internal or external) of the structure or more generally in the path of the electromagnetic waves due to the incident electromagnetic field.

Such line elements will absorb electro-magnetic energy taken from the conductors, at the frequencies where they are resonant (or anti-resonant), and this all the more so since their coupling with the conductor (s) is important, and that they are themselves absorbent. I observed that such elements of coupled lines can take various forms (such as electrical and; or magnetic couplings) and various realizations, as I observed that their lengths of resonance (antiresonance) are directly proportional to the propagation constant of the medium in which they are inserted, and therefore correspond to physical lengths considerably shorter than half (or a quarter) of the wavelength in question. Again, the frequency domains of this effect (additional or used alone) can be placed as desired, in the frequency domain: at low frequencies (for example, below 10 MHz), but also at very low frequencies. high (for example above 1 GHz).

To better describe the different aspects of the invention, I will choose some typical examples of simple propagation structures, as described in the description, starting from wires and cables comprising a dielectromagnetic absorbent envelope, as described in detail in my French patent. no.7833385.

In a first example, described by FIG. 1 a, a central conductor (l) is surrounded by a layer of absorbent composite (2) 1 and a layer of internal and / or external insulation Q), and of a external display

(^: this is the classic low pass coaxial structure.

In Figure 2, the absorption of such a cable follows the path

(T), exclusively reflecting the absorption of the absorbent ferrite composite: Above 250 MHz, the absorption exceeds 100 dB / m, a value which extends to around 18 GHz, with the absorbent mixtures described in my patent cited.

The two embodiments according to FIGS. 1a and 1b use a central copper conductor, 1 mm in diameter, and a thickness of 1 mm from the absorbent layer. The latter consists of a composite comprising a volume concentration of 68% ferrite, in a PVC or silicone type matrix, giving this composite a low frequency permeability around 20. The insulating layer 3 consists of 2 gimped polyester tapes, 0.05 mm thick.

In FIG. 1b, the same central conductor Hj is surrounded by a thin ferromagnetic layer ζ5J, as described in my Patents Artificial Skin France n ° 1.428.517 and 1.514.178, produced for example, by an external layer of wires has high permeability, or a covering in thin ferromagnetic strip with high permeability. The layer (T) is composed of the same absorbent ferrimagnetic composite as before, and the layer (F) still represents a wrapping or garmenting of ferromagnetic material with high permeability, placed under _a shielding braid {4 even even replacing this one- this. The dimensions are identical to those of FIG. La: the thickness of the ferromagnetic layers and of 20 μ.

In Figure 2, the combined absorption is represented by plot B, where the absorption at 10 MHz has increased from around 0.8 dB / m to 6.5 dB / m.

In both embodiments, the shielding braid (4) representing the mass, can be constituted by an adjacent ground surface, or else other conductors at the average potential of the mass, thus producing open structures according to the invention.

Here, I observed the remarkable fact, that for a larger signal (such as nuclear pulse (EMP), or a lightning bolt), the attenuation in the MHz range is multiplied by a factor of

5 to 10: it is the choice of the rectangularity of the hysterisis cycle of the ferromagnetic (s), which thus makes it possible to obtain, if desired, a bandwidth cable self-controlled by the disturbing signal: in a way, the cable cuts the transmission of the EMP signal, while representing, at weak signals, only a reduced attenuation for low frequencies. The same phenomenon can be obtained with special ferrites (in the dielectromagnetic composition or in the components described below).

The superposition effects of the absorptions specific to the dielectromagnetic composite mixture and to the artificial skin effect, are clear in this example: the magnetic spectrum of ferromagnetic at low frequencies, and the dielectromagnetic spectrum of ferrimagnetic at high frequencies are added.

In a second example, I will describe the application of the second additional effect, based on the absorption of a Litz wire, by proximity effect, at frequencies beyond those where the skin effect takes place, in each strand of the driver.

By definition, this is, as for the effect of absorption by artificial skin effect, of a broadband effect, occurring at high frequencies, and linked to the conductor (s) the serial element of the Kirchhoff scheme. From these facts, this effect can be applied in addition to, or even as a replacement for, the absorption of the dielectromagnetic composite with ferrites. In FIG. 3a, the conductor Qj is produced according to the Litz technique (total diameter 1mm), that is to say, the various conductive strands are isolated from each other, and assembled in a strand, each strand passing through the section in its whole.

The dielectric ^ (2 layers of polyester 0.05 "^ thick) insulates the central conductor from the braid (or ground surface); if necessary, it may be absent, insofar as the insulation of the strands of the read is enough.

In FIG. 4, I have reproduced the low-pass absorption effect of an embodiment according to FIG. 3 a: In curve A, we indeed see that the losses by proximity effect make it possible to obtain an effect of broadband low pass absorption: This effect increases only with the root of the frequency, where the absorption effect by the ferrite component increases with the power -h 1 to 1.5 of the frequency. In frequencies below 100 MHz, the attenuation is more reduced than with the artificial skin effect, to approach zero below 1 MHz, where the litz wire (used in its primary capacity) , represents negligible losses.

In Figure 3b, I combined the above effect (conductor read 1), with the additional layer (2) of the ferrite composite absorbent (1mm thick). The line (S) in FIG. 4 indicates the increased attenuation according to the invention: the effects of proximity of conduction and of the absorption effect of a layer of ferrite composite are added, with essentially an increase in the absorption in the high and very high frequencies: indeed, a remarkable fact according to the invention, consists in the non-limitation of the attenuation towards the very high frequencies, contrary to the previous cases (Figures 2), where l absorption stopped with the disappearance of the magnetic effects.

It is also obvious that this proximity loss effect can still be used with other open, semi-open or closed structures, as indicated in the preamble. Among the many examples ^I and mention the use of a mass made of litz Proximity effect, _or inversely to the example of Figures 3, the proximity effect is achieved by the outer conductor. In a third example, I will describe the application of the third additional effect, due to the effects of ^' couplings between conductors with resonant (and / or anti-resonant) lines.

By definition, I have already said, it is a question of coupling to the fields (electric and / or magnetic) of a propagation structure, elements of isolated lines, of given length: this coupling will take energy (therefore introduce an absorption, seen from the hot conductor) at frequencies corresponding to n λ / 2 (for an open coupled line, half-wave) or at frequencies corresponding to (2n- 1).-φ- (for a coupled line, terminated in quarter-wave).

The "resonances" can be widened (in the frequency domain) insofar as the line elements are themselves absorbent (for example resistive, or with skin effect) or even insofar as they are placed near or emerged in an absorbent dielectromagnetic medium (such as the absorbent compounds mentioned).

To the extent, where I can therefore define the frequency location of such resonant absorptions, to fix their intensity by the degree of coupling to the excitation conductor, I first add an existing absorption effect to any absorption elsewhere , and this (s) addition (s) can be formed and placed at will, according to the invention.

In Figure 5, I indicate the general diagram of such a coupled line, with the example of a coaxial structure, using as other absorbent a layer of ferrimagnetic composite.

In this figure, (P represents the conductor, @ the layer of ferrimagnetic absorbent composite, ^} the insulator and © the ground braid of the cable. The resonant element (J) is represented as a thin conductive layer (or resistive, or skin effect): it only spreads over a certain geometric length α, of the structure, isolated from the other conductors (half-wave line), (Figure 5b). Its "electric" length -i, will be reduced by the ratio of the propagation constant of the place, and it is this reduced length which will have to present the _n.j -of the coupling effect. Of course, the appropriate choice of sections of length iy _n , P „- etc. will allow absorption resonances to be placed at the desired locations of the SDectrum.

His course, a nomore ae such sections coupled perme _t be déoosée along the structure, to multiply the effects have _D Sorbonne Bants.

Of course, the influence of each section will depend on the intensity of its coupling with the hot conductor (s): where, for example, the conductive layer 7 can be placed differently with respect to the successive layers of the structure, and fill only one by _¬ tie of the circumference ^; in other words conductive strips (or resistive or water effect) can be used, or alternatively conductive strips (or resistive or skin effect) along the genera¬ tion αe the structure prooogation. With such realizations (partial remolding) coupled lines of different lengths (<., - C _n , ^} \) can be placed in the same places of the structure.

A particular embodiment thus uses conductive wires

(resistive or skin effect) in the form of an open braid; another, with its conductive wires (resistive or with skin effect) integrated into the absorbent como-sita (and possibly coextruated with the aosorbent mixture).

A particularly simulated embodiment, will thus use one or more wires or braids of elbowed conductors accompanied by a loss insulator, or one or more wires or braids (or resistive and / or skin effect) bent, representing a conductor (s) free or additional in a cable (such as the 2nd conductor of a "twm-ax" coaxial or even a shielding braid). The simplicity and the very low cost price of such an embodiment are obvious.

FIGS. 5c and 5d indicate the typical embodiments quar _t of wave (2n-1) -Ç-; the power of the excitation element is coupled réa¬ Lisé by connecting one side, between the latter and the conduc _t eur cnaud or mass. Interest ae this embodiment lies in the faci lity _¬ placing αes "resonances" USID at low frequencies; the inconvé¬ deny (due to connection) does not exist when the connection fai es _t _t e at the time of use from one end of the structure, where we met _t just two ends electrically conductive, at a connection socket.

Some practical examples demonstrate these aspects of the invention: In Figure 6, curve A, are reproduced the low-pass performance of the embodiment according to Figure 5a, (with the geometry and absorbent layer of Figure 1b): with a conductive coupling layer 7, length 1 ≈ 11 cm , not connected to the two ends (ie realization "A / 2,). This layer was carried out in the form of closed circumferential conductive paint.

We can clearly see the addition of the half-wave resonances, to the background attenuation of the absorbent composite mixture.

In the case of non-circumferential bands, or simple wires along the generator, we have exactly the same effects, with reduced amplitudes of resonances, due to the weaker coupling of the coupled line or lines. Conversely, in the case of lines more strongly coupled to the central conductor (or external conductor), the amplitude of the resonances increases.

The same sample cable, when I connect the section coupled to one end of the central conductor (or the braid) gives the reso¬ nances in Xi 4, as shown in trace B in Figure 6. In this case, I the advantage of an important inductive coupling, even when the coupled line is one or more simple wire (s) along the generator.

I easily verify that the multiples of the resonances A / 2 or X / 4 are not placed exactly at the multiples of the frequencies: as already said these resonances are linked to the constant of internal propulsion of the cable, or of the structure with propagation in general, itself dispersive, when a dispersive medium (such as a layer of absorbent composite, for example) is present.

According to the invention, I can superimpose such resonances (A / 2 and / or X / 4) on selected frequencies, and give them the desired importance, with an ad hoc coupling. According to the invention also, differen¬ your resonances can coexist on the same cable length, as will be demonstrated with the following example.

In Figure 7, in an embodiment using only coupled lines type A / 2. I used the implementation of Figure 5a (curve Figure 6 A) with the coupled segment of Ion- length of 1 = 11 cm, but covering only half the circumference. The other half of the circumference, comprising two metallizations twice the length of 5.1 cm, separated by 8 mm.

If the resonance at A / 2 (1 = 11 cm) is now or slightly less marked, (around 240 MHz), around 500 MHz we find the resonance 3λ / 2 (1 = 1 lcm) plus the resonances A / 2 of two sections of 1 ^ = 5.1 cm, therefore very marked resonance. The resonances in 3/2 (1 „= 5.1 cm) are also apparent.

According to the invention, it therefore appears clearly that I can "model" at will, in frequency, in bandwidth and in amplitude these additional absorption effects and in particular, to place them in the low frequencies (for example ^ .100 MHz) and very high frequencies (> i GHz for example) to complete the fixed absorption spectra linked to ferro- and ferrimagnetic absorptions.

Obviously, the invention includes a wide variety of implementations, apart from the coaxial structures described above, as will be seen below.

The few examples which follow show some industrial applications of the principles of coupled resonant lines, in connection with other uses of losses.

In a first example, I consider the low-pass cable according to the MIL-C-85485 standard, with its essential characteristic of attenuation above 100 dB / m, beyond 1 GHz (and up to a few 18 GHz) according to the embodiment of Figure la. (The absorbent layer © ⁱⁿ ferrimagnetic composite, can be placed against the conductor φ, or even be placed under the braid (4) (insulator (T) on conductor), or finally be placed between two insulating layers 3).

To obtain a "cut-off" frequency of 100 dB / m at 1 GHz, a thin absorbent layer (for example 0.1 mm) is sufficient, the insulator (s) has / have thicknesses of the same order. In FIG. 8, trace A indicates the absorption of the typical cable according to the standard (reaching 100 dB / m for some 500 MHz); this cable has an (unwanted) weakening of some 2 dB / m at 10 MHz, thus defining a "passband" (at low losses) of some 10 MHz. The introduction of coupling segments (in 1/2) of 16 cm and 10 cm, with possibly a third intermediate length, achieves absorption resonances in the frequency range of the attenuation slope (around 120 to 200 MHz). In other words, I have increased the natural slope of absorption, linked to ferrimagnetism. .4ussï ιe pevx realize, according to the invention, a much steeper filter "slope" (for example 60 dB / octave), as well as a bandwidth, at 2 dB, which will increase to around 30 MHz. In addition, the absorption is greater than 100 dB from 230 MHz.

The addition of conductive fibers (resistive, skin effect, etc.) of a few cm to mm (for example, in the mass of the composite), also makes it possible to introduce absorptions by resonances up to frequencies of 50 GHz. and more, replacing the magnetic absorption of the composite, which disappears beyond some 10 GHz: here, the effect of the resonant fibers is superimposed, on the residual dielectric losses of the dielectromagnetic composite.

Identical results can be obtained, if I replace the more or less concentric cast sections, by fibers of suitable lengths, thus using the principle of "tangled" operation. The use of chiral particles, instead of fibers, represents a typical case, with both electrical and magnetic couplings to the electromagnetic fields of the structure.

In a second example, js considers a shielded multi-conductor cable: by using one or more conductors (or even an additional braid, in a multi-shielded cable) in coupled lines, I arrive at solutions which are very easy to implement, by especially if I want to introduce absorption (s) at lower frequencies. For example, I start from a shielded cable, comprising three phase conductors (copper strand diameter 1.20 mm: thickness of absorbent composite layer 0.5 mm; thickness of insulating extruded PVC 0.45 mm) under screen.

For the common mode, (the three conductors together, in relation to the screen) in Figure 9, trace A, shows the attenuation due to the absorbent composite. By connecting one of the conductors in Segmen _t s resonant A / 4 (thus cutting this conductor in places, and réu¬ ning one of both sides, the hot conductors), with lengths 1 = 0.60 m, 1. = 1.05 m and 1 = 1.81 m, I get a "filter-extension cable", with a total length of 3.50 m ~.

I obtain the weakening of trace B, where I have therefore "optimized" the choices of resonance frequencies to obtain a wider band effect. Thus the frequencies of 6.6 MHz and 20.3 MHz correspond to the resonances A / 4 and 3 XI 4 of the section 1. = 1.81 m, 11.5 MHz and 34.8 MHz correspond to the resonances of the length 1 „ = 1.05 m and 20.3 MHz and 64 MHz at resonances of length 1, = 0.60 m).

In a third example in the extension of the example above, I will indicate the overall synthesis of a given attenuation spectrum, by the addition of the various effects according to the invention, by a structure manufactured continuously.

The attenuation sought (for a total length of 3.50 m) is 0.9 dB at 1 MHz, 3.8 dB at 3 MHz, 10 dB at 10 MHz, 18.4 dB at 10 MHz and greater than 20 dB beyond.

~ ^s easily verifies that:

the solution with the absorbent mixture (described) alone is not possible: Indeed, it would require a volume concentration of some 76% and which is no longer easily extrudable.

Then: the desired characteristics can be obtained according to the invention:

- by adding to the absorbent composite structure (according to Figure 1b) (with a slight increase in the ferrite concentration to 73%, extrudable) of the effect of the resonant couples segments (according to Figure 9).

- By adding to the standard absorbent composite structure (according to Figure 1b) the artificial skin effect (according to Figure 3b) on the conductor under the braid. by adding to the absorbent composite structure (according to FIG. 1b) the artificial skin effect (on one side only) (according to FIG. 3b) with the effect of resonant couples segments (according to FIG. 9 ).

This is easily verified by modeling according to the principles described in my publication "Absorptive Low-Pass Cables: State of the Art and an Outlook to the Future", IEEE EMC Washington, 23-25 August 1983.

Now, it is obvious that it is easier to obtain absorptions at lower frequencies, by using conventional helical structures or even "reverse coaxial" (French patent n ° 2,593,329), with the use of the various "additional" techniques described:

In a fourth example, I indicate a helical embodiment (2 insulated copper conductors of diameter 0.75 mm, in parallel, wound in steps of 3 mm on a composite absorbent core of diameter 2.5 mm t resistive metallization (open circumferentially) resistance 10 / m; outer layer with the composite absorbent described, diameter 5.5 mm; mass braid).

In figure 10, curve A indicates the attenuation of a cable with a length of 2.20 m in the absence of the resistive braid; curve B in the presence of this braid, connected on one side to the central conductor (coupling X / 4). This example clearly shows the possibility of extending the low-pass attenuation to MHz frequencies: around 1.7 MHz is the A / 4 resonance, around 6 MHz is the 3A / 4 resonance.

This example also shows, the use of resistive elements, for the reasons mentioned above: indeed, the reduced weakening of the composite at these frequencies, would give rise to very narrow band resonances at the above frequencies, without l introduction of "damping of resonant effects. The ignition wire, - described in the France patent cited in the introduction, is another example of a helical structure, using a dielectromagnetic absorber, but this time open: the principle of adding the effect of coupled sections, of the effect of proximity losses, and of the artificial skin effect is applied according to the invention.

In a fifth example, I used the artificial water effect, instead of using an absorbent composite: in this example therefore, in the sense of the invention, I will graft segments of coupled lines.

The cable considered is a twinax, made as follows:

2 0.78mm copper diameter conductors; 1.20 mm Tefzel insulated and twisted together; covered with a tight braid made of 0.04 mm permallov flat (longitudinal resistance 2.5 SLlm), insulating material 0.2 mm thick, external copper braid.

Figure 11 shows the attenuations obtained with such a structure: trace A indicates the attenuation when the external braid is connected to the external braid, all along: it is the attenuation due only to the 'artificial skin effect (patent cited). The attenuation values are typical for another use of low-pass cables according to Standard MIL-C-85485 (manufactured by the company Gore).

When ηe disconnects the internal magnetic braid, to reconnect it in one end, I make a coupled segment X / 4, = t I obtain the attenuation of the trace B, showing the effects of the line coupled ^¬ A 14 In this example, the end of the resonant braid is connected (at the end of the line) to the copper braid, according to FIG. 5d, giving better coupling for this type of multicore cable.

This example is interesting, since the attenuation for the common mode (figure 10) is important; the attenuation of the differential mode (weakening of the line represented by the two internal conductors) is negligible, typical implementation therefore according to the principles of French patent n ° 2,593,329. Finally, the large width of the absorption peaks, in the frequency domains, are here the result of a resisting and skin effect coupled segment.

It is evident, moreover, that the addition of resonant coupled segments at higher frequencies, analogous to the principle of the realization of trace B of FIG. 8 allows the reproduction of the attenuation requested by standard MIL-C-85485 according to line A of this same figure.

In a sixth example, I consider a bundle of conductors, a flat cable or stripline, microstripline etc: I can realize the principle of resonant couplings by using free conductors, next to hot conductors (the whole surrounded by example of two ground conductors or of a ground surface). Additional attenuation can be introduced by an absorbent composite surface, by artificial skin effect conductors etc.

The application of the effects of losses by proximity, artificial skin and segments coupled to other open structures is obvious: I can cite for example an absorbent cable, with an outer layer of absorbent composite (on the shield), to which I only apply coupled segments and / or the artificial skin effect, according to the invention. I can cite, as another example of an open structure, the simple absorbent wiring wire, composed by the structural elements 1, 2, 3 in FIG. La, this wire being placed near a ground. This is an embodiment - type of wiring, the wire being close to a metal wall, or placed in a wiring harness.

The additional action of the artificial skin effect, of the effect of coupled lines, of the proximity effect, in addition to that of influencing the overall absorption curve, according to the invention, will reduce the influence. of a variation of the distance from the mass, by the privileged action on the series elements of the line. In a seventh example, I consider another open electromagnetic structure, subjected to an unguided electromagnetic cross wave. The example of an absorbent surface, to cover the conductive walls of an anechoic chamber is typical: in such an embodiment, ie can use compact ferrite, but of which we also know the performance limitations at low and very high frequencies . According to the invention, the intrinsic ferri- and ferromagné¬ absorption of this ferrite can be supplemented by one or more layers with half-wave absorbent coupling effects described. For example, metallic fibers or bands are included / inserted in the ferrite, or on its surface between the plates to provide the additional attenuation sought. According to the invention also, an artificial skin effect layer can complete this embodiment: quite simply the ferrite tiles are placed on a ferrimagnetic conductive surface, achieving, at the frequency considered, the skin effect in its thickness.

In an eighth example, compact ferrite beads / tubes are used to make low-pass filters for common-mode inductors or even cross-over filters. The use of artificial skin effects and / or resonant coupled segments allows improvement of the weakening, in particular at low frequencies and at very high frequencies.

In the same vein, the absorption additions according to the invention apply to hyper frequency joints: in particular the addition of line elements coupled to a dielectromagnetic composite is advantageous for oven joints microwaves, where the resonance effect makes it possible to favor particular qualities, such as the suppression of harmonics, the reduction of leaks when the door is opened, etc.

In a final example, _I e consider the application of my inven¬ tion to the structures of my patent France 2 ^{~ τ} ^ .657, with parti¬ ticular application to absorbent son and cables in conjunction with localized components , such as for example a filter-extender, comprising a determined length of electric wire / cable with connection, and one or more components located at the point, such as inductances and capacitances: the effects of additional losses written in this invention apply here to improve performance.

For example, such an extension filter can be produced with the Litz wire, according to the invention, and / or with the artificial skin effect, and / or the resonances by coupled segments: I will use, advantageously the fact that the determined length of the cord provides specific coupling effects, which will set the _jth / resonances in the frequency range, wherein the components located introduce disruptive effects (such as self-resonances of compo¬ nents resonances due to the cascade of components and / or facial mter resonances).

In Figure 12, e _j considers the weakening in moae com¬ mon two cables filter Marketplace assemblies (EMC-CORD Eupen) using a 1.2 mH inductor component in the outlet; a length of absorbed composite shielded cable of 2 m, and open at the other end (line A) or comprising, at the other end a capacity to ground of 2.2 nF (line B).

The use of the proximity effects technique (according to the invention) makes it possible to obtain approximately the same attenuations, without the absorbent composite.

In addition, the use of the effect of coupled lines (with a resonant line in X / 4, using an additional conductive layer) over the length of 2 m, is of an immediate implementation: it would make it possible to realize the attenuation of the route B with the cord without capacity A: in other words, makes it possible to remove the capacities and to obtain a high-performance "original equipment" production, that is to say where the oranche user only 2 or 3 conductors when mounting his device.

Claims

Resell! it. tions:

1. Absorbing electromagnetic propagation structures, using losses intrinsic to the electromagnetic materials of the structure, in which the absorption in the frequency domain is widened / increased / shaped, by

the addition of equivalent series losses in the conductive part (s) of the structure, by the single or combined use of proximity effects (eddy current), of articular skin effect, and / or of coupled resonant conductive lines.

this / these additions being chosen, so that their absorption spectrum completes the absorption of the structure in the frequency domain, thus compensating for the insufficiencies of the absorption essentially in parallel, of the dielectromagnetic materials of the structure.

2. Structure according to the preceding claim and in which the series loss effect, alone or additional, consists of the "artificial" skin effect. that is to say the introduction of a thin layer with high permeability on the surface of the conductors of the structure.

3. Structure according to one of claims 1 or 2 in which the layer (s) with "artificial" skin effect and / or the absorbing dielectromagnetic layers are used, by one of the materials whose permeability increases with the amplitude of the signal electromagnetic (before decreasing towards saturation).

4. Structure according to one of claims 1 or 2 in which, the effect of series losses, alone or additional, consists of the proximity effect due to the eddy currents of the isolated conductors, assembled in "Litz" , by frequencies and geometries of wires where the skin effect plays for each strand of assembly.

5. Structure according to one or more of the preceding claims, in which the effect of electrically coupled resonant segments is implemented by line elements, placed along the structure, of half-wave length and multiples, these elements being isolated.

6. Structure according to one of claims 1 to 4, in which the effect of resonant segments magnetically coupled, is produced by the line elements, placed along the structure, of quarter-wavelength and multiples, these elements being connected to the conductors (internal or external) of the structure.

7. Structure according to one or more of the preceding claims in which the segments are produced in the form of good conductors, resistive conductors and / or with skin effect, and / or with proximity effect, more or less surrounding the main conductor (s) ; and arranged at the interface of the different layers of the structure, or placed on the surface of one of them.

8. Structure according to one or more of the preceding claims in which the segments are placed inside one of the layers of the structure, with the specific case of the insertion of fibers, or strips, of suitable length, mixed , on the surface or in ferrimagnetic materials or absorbent dielectromagnetic composite.

9. Structure according to one or more of the preceding claims, in which the dielectric losses, essentially in derivation (according to the Kirchhoff formalization) are due to absorbent composite materials, comprising ferro- / ferrimagnetic particles.

10. Structure according to one of claims 1 or 2, in which the dielectric losses, essentially in derivation, are due to compact magnetic materials, such as ferrites, etc.

11. Structure according to one of claims 1 or 2, in which the set of absorption spectra is placed so as to complement each other in a wide frequency domain, this in order to represent a given regular response curve.

22. Structure according to one of claims 1 or 2, in which the set of absorption spectra is placed so as to complement each other in one or more narrow frequency domains, this in order to represent a typical response curve " tape cutter ".

13. Structure according to one of claims 1 or 2, wherein the shaping of the absorption spectrum increases the slope of the absorption spectrum, and therefore increases the bandwidth of the structure.

14. Structure according to one of claims 1 or 2 in which is used a (or) conductor (ε) or shielding of the structure, available for connection in coupled lines.

15. Structure according to one of claims 1 or 2, in which the propagation structure is of picked size, representing an electronic component.

16. Structure according to one or more of the preceding claims, in which the structure used alone as a function or in a global system, with in particular the combination with localized components (inductance, capacitors, etc.) which are placed at the ends of the structure, these components possibly having their own absorption spectra.