Patent Publication Number: US-11380972-B2

Title: Microwave waveguide comprising a cavity formed by layers having conductive surfaces and a dielectric strip disposed in the cavity

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. national stage application under 35 U.S.C. § 371 of International Application No. PCT/EP2018/083625, filed Dec. 5, 2018 which claims priority to French patent application no. 1761661, filed Dec. 5, 2017, the entireties of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a microwave component including a wave guide comprising at least one upper layer having at least one electrically conductive surface, a lower layer having at least one electrically conductive surface, and a central layer intermediate between the upper layer and the lower layer, the layers defining a zone of propagation for an electromagnetic wave, the propagation zone extending along a propagation axis, and comprising a cavity, the cavity being bounded by the upper layer, the lower layer, and, laterally, by two opposite lateral edges of the central layer. 
     BACKGROUND OF THE INVENTION 
     At this time, one major issue in the telecom industry, in particular for 5G base stations, the millimetric radar industry for drones, autonomous cars, and more generally for any type of robot, is reducing losses in the systems drastically, at a time where energy savings are essential for future applications. These loss levels are indeed prohibitive for equipment items such as upstream equipment of a transceiver antenna (equipment of the “front-end RF” type). 
     To reduce losses, it is known to design passive electronic structures by using air-filled substrate integrated waveguide or empty substrate integrated waveguide (AFSIW or ESIW) technology. The passive structure then forms a microwave transmission line. 
     However, for some applications, the bandwidth offered by such structures is not fully satisfactory. 
     One aim of the invention is therefore to manufacture and provide, at low costs, a microwave component suitable for working in the millimetric wavelength domain, the component having a good bandwidth and low losses. 
     To that end, the invention relates to a microwave component of the aforementioned type, wherein the waveguide comprises at least one dielectric strip placed in the propagation zone, the dielectric strip being defined in one of the upper layer and the lower layer or being placed in the cavity away from the lateral edges of the cavity. 
     SUMMARY OF THE INVENTION 
     The component according to the invention may comprise one or more of the following features, considered alone or according to any technically possible combination(s):
         the dielectric strip extends along a longitudinal direction parallel to the propagation axis, and is centered on a median plane of the two lateral edges or is laterally offset from the median plane of the two lateral edges;   the dielectric strip is placed in the cavity separated from the lateral edges of the cavity, the waveguide comprising a functional attachment component, the functional attachment component being formed by a plurality of dielectric fasteners integral with the dielectric strip, each dielectric fastener extending from one of the lateral edges, the dielectric fasteners being configured to perform a filter function for an electromagnetic wave propagating in the propagation zone;   each dielectric fastener is in the form of a rectilinear bar and extends from one of the lateral edges;   the dielectric strip is placed in the cavity separated from the lateral edges of the cavity, the central layer comprising at least one dielectric sublayer, the cavity being defined along the propagation axis between a front end and a rear end of the central layer, the dielectric strip extending from the front end to the rear end and being integral with the dielectric sublayer of the central layer;   the dielectric strip is placed in the cavity separated from the lateral edges of the cavity, the dielectric strip being a first dielectric strip, the waveguide further comprising a second dielectric strip, the second dielectric strip being placed in the cavity, separated from the first dielectric strip, and separated from the lateral edges of the cavity;   the dielectric strip is defined in one of the upper layer and the lower layer, the dielectric strip having a surface defining the cavity;   the dielectric strip is a first dielectric strip, the waveguide further comprising a second dielectric strip placed in the propagation zone, the second dielectric strip being delimited in one of the upper layer and the lower layer, separated from the first dielectric strip, and having a surface defining the cavity;   the waveguide further comprises another dielectric strip, the other dielectric strip being positioned in the cavity, separated from the lateral edges of the cavity;   the dielectric strip is formed in a dielectric sublayer of one of the upper layer and the lower layer, and is defined by a part of an electrically conductive sublayer of the layer, and laterally between two lateral borders; and   the cavity is filled with a fluid having a dielectric constant, or defines a sealed closed volume and is empty of fluid.       

     The invention also relates to a process for manufacturing a microwave component comprising the following steps:
         providing an upper layer and a lower layer respectively having at least one electrically conductive surface;   providing a central layer having one or several recess(es), the recess or the plurality of recesses being intended to form a cavity defined laterally by opposite lateral edges formed by the central layer; then   assembling the layers such that the central layer is intermediate between the upper layer and the lower layer, the layers defining a zone of propagation for an electromagnetic wave, the propagation zone extending along a propagation axis, and comprising a cavity, the cavity being formed by the recess or the plurality of recesses while being bounded by the upper layer, the lower layer, and, laterally, by the lateral edges of the central layer;       

     the step for providing at least one of the layers comprising producing a dielectric strip, the dielectric strip being placed in the layer, such that after the assembly step, the dielectric strip is placed in the propagation zone and is defined in one of the upper layer and the lower layer, or such that after the assembly step, the dielectric strip is placed in the propagation zone and in the cavity separated from the lateral edges of the cavity. 
     The manufacturing process according to the invention may comprise one or more of the following features, considered alone or according to any technically possible combination(s):
         the step for providing the central layer comprises producing the dielectric strip, the dielectric strip being placed in the central layer, such that after the assembly step, the dielectric strip is placed in the propagation zone and in the cavity separated from the lateral edges of the cavity, the dielectric strip being placed between a plane defined by an upper surface of the central layer and a plane defined by a lower surface of the central layer;   the step for providing the central layer comprises:
           providing an initial layer, the initial layer being intended to form the central layer, comprising at least one initial dielectric sublayer and being devoid of recess,   cutting, in the initial layer, the plurality of recesses intended to form the cavity,   the step for producing the dielectric strip being carried out during the cutting of the plurality of recesses, the plurality of cut recesses defining the dielectric strip, the dielectric strip having a length, taken along the propagation axis, equal to the length of the cavity, taken along the propagation axis;   
           the step for providing the central layer comprises:
           providing an initial layer, the initial layer being intended to form the central layer, comprising at least one initial dielectric sublayer and being devoid of recess,   cutting, in the initial layer, the plurality of recesses intended to form the cavity,   the step for producing the dielectric strip being carried out during the cutting of the plurality of recesses, the plurality of cut recesses being intended to define the cavity, and defining the dielectric strip and attachment means of the dielectric strip, the attachment means comprising a plurality of dielectric fasteners coupling the dielectric strip to at least one of the lateral edges;   
           the step for producing the dielectric strip comprises providing a dielectric strip and attachment means of the dielectric strip, the attachment means comprising a plurality of dielectric fasteners secured to the dielectric strip, the dielectric strip and the attachment means being provided separated from the central layer;   the assembly step of the layers comprises attaching the central layer to the lower layer, then removing the attachment means, by cutting the attached means, once the central layer is attached to the lower layer;   the step for providing one of the upper layer and the lower layer comprising producing the dielectric strip, the dielectric strip being placed in the layer, such that after the assembly step, the dielectric strip is placed in the propagation zone and is defined in the layer;   the median plane of the lateral edges of the cavity forms a plane of symmetry of the assembly formed by the dielectric fasteners;   the dielectric fasteners only extend from a single one of the lateral edges;   each dielectric fastener is in the form of a rectilinear bar and extends from one of the lateral edges;   at least part of the attachment means is not removed during the assembly step of the layers, the part of the attachment means then forming a functional attachment component, the dielectric fasteners that are not removed being configured to perform a filter function for an electromagnetic wave propagating in the propagation zone;   the process comprises a step for supplying the microwave component with an electromagnetic wave propagating in the propagation zone, the electromagnetic wave having at least one propagation mode having two electric field maximums, the or each dielectric strip being located in the cavity at one of the maximums;   the dielectric strip is a first dielectric strip, the manufacturing step being a step for manufacturing the first dielectric strip and a second dielectric strip, the step for manufacturing the first dielectric strip and the second dielectric strip being carried out during the cutting of the plurality of recesses; the plurality of cut recesses defining the first dielectric strip, the second dielectric strip and attachment means of the first dielectric strip and the second dielectric strip; the attachment means comprising a plurality of first dielectric fasteners coupling the first dielectric strip to one of the lateral edges and a plurality of second dielectric fasteners coupling the second dielectric strip to the other of the lateral edges;   after assembly, the dielectric strip has a surface defining the cavity;   the step for providing one of the upper layer and the lower layer comprises providing an initial layer, the initial layer being intended to form the layer and comprising at least one dielectric sublayer, an electrically conductive upper sublayer, and an electrically conductive lower sublayer; the manufacture of the dielectric strip comprising the implementation of lateral borders in the initial layer and the elimination of at least part of one of the electrically conductive sublayers of the initial layer extending between the two lateral borders;   the dielectric strip is a first dielectric strip, a step for providing the upper layer or the lower layer comprising producing a second dielectric strip; and   after assembly, the cavity is filled with a fluid having a dielectric constant, or defines a sealed closed volume and is empty of fluid.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood upon reading the following description, provided solely as an example, and in reference to the appended drawings, in which: 
         FIG. 1  is a top schematic sectional view of a first microwave component according to the invention, the section passing through the dielectric strip; 
         FIG. 2  is a schematic cross-sectional view of the first component of  FIG. 1 ; 
         FIG. 3  is a schematic cross-sectional view of the first component during the first manufacturing process; 
         FIG. 4  is a top schematic sectional view of the first component during a first embodiment of a manufacturing process according to the invention, the section passing through the dielectric strip; 
         FIG. 5  is a top schematic sectional view of the first component during a variant of the manufacturing process of the first component according to the invention, the section passing through the dielectric strip; 
         FIG. 6  is a schematic cross-sectional view of a second microwave component according to the invention; 
         FIG. 7  is a top schematic sectional view of a third microwave component according to the invention, the section passing through the dielectric strip; 
         FIG. 8  is a top schematic sectional view of a fourth component according to the invention, the section passing through the dielectric strip; 
         FIG. 9  is a top schematic sectional view of a fifth microwave component according to the invention, the section passing through the dielectric strip, with representation of lower attached layers in phantom; 
         FIG. 10  is a schematic cross-sectional view of the fifth component of  FIG. 9 , with representation of lower attached layers and upper attached layers in phantom; 
         FIGS. 11 to 17  are respective schematic sectional views of sixth, seventh, eighth, ninth, tenth, eleventh and twelfth components according to the invention. 
     
    
    
     It is noted that like reference numbers and designations in the various drawings and in the specification descriptions indicate like elements. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first microwave component  10 A according to the invention is illustrated in  FIGS. 1 and 2 . 
     The first component  10 A is for example a filter, in particular a bandpass, low-pass, high-pass or notch filter. In a variant, the first microwave component  10 A is for example a transmission line, a multiplexer, a coupler, a divider, a combiner, an antenna, an oscillator, an amplifier, a circulator, a resonator, a phase shifter or an isolator. 
     The first component  10 A here is of the type “with guide integrated into the substrate”. 
     The first component  10 A includes a waveguide  12  capable of guiding an electromagnetic wave along a propagation axis X-X illustrated in  FIG. 1 , the electromagnetic wave in particular having a wavelength greater than or equal to a predetermined minimum wavelength. 
     The waveguide  12  comprises an upper layer  14 , a lower layer  16 , and a central layer  18  intermediate between the upper layer  14  and the lower layer  16 , the layers  14 ,  16 ,  18  defining a propagation zone  19  of the electromagnetic wave, the propagation zone  19  extending along the propagation axis X-X illustrated in  FIG. 1 . 
     The waveguide  12  further comprises at least one dielectric strip  28  placed in the propagation zone  19 . 
     Hereinafter, “dielectric element” means that the element has a relative dielectric permittivity greater than or equal to 1. 
     The dielectric material can have absorbent properties, that is to say, a loss tangent coefficient greater than 0.004, to perform an attenuating function. 
     Each of the upper layer  14 , lower layer  16  and central layer  18  extends parallel to a plane XY, defined by the propagation axis X-X illustrated in  FIG. 1  and by a transverse axis Y-Y illustrated in  FIG. 1  orthogonal to the propagation axis X-X. 
     Each of the upper layer  14 , lower layer  16  and central layer  18  has an upper surface  20 A,  20 B,  20 C and a lower surface  21 A,  21 B,  21 C. 
     In the first component  10 A, each of the upper surfaces  20 A,  20 B,  20 C and each of the lower surfaces  21 A,  21 B,  21 C are electrically conductive. 
     Hereinafter, “electrically conductive element” means that the element has an electrical conductivity greater than 1*10 6  S·m −1 , preferably equivalent to that of a metal of the copper, silver, aluminum or gold type. 
     The lower layer  16  and the upper layer  14  are placed at a distance from one another, on either side of the central layer  18 , in contact with the central layer  18 . 
     In particular, the lower surface  21 A of the upper layer  14  is in contact with the upper surface  20 C of the central layer  18 . Likewise, the lower surface  21 C of the central layer  18  is in contact with the upper surface  20 B of the lower layer  16 . 
     Thus, the upper layer  14 , the lower layer  16  and the central layer  18  form a stack. 
     The lower surface  21 A of the upper layer  14  is electrically coupled to the upper surface  20 C of the central layer  18 . Likewise, the lower surface  21 C of the central layer  18  is electrically coupled to the upper surface  20 B of the lower layer  16 . 
     In the remainder of the disclosure, the “transverse direction” Y-Y refers to a direction parallel to the transverse axis Y-Y illustrated in  FIG. 1 . 
     A transverse direction is therefore a direction orthogonal to the propagation axis X-X illustrated in  FIG. 1  and parallel to the lower surface  21 A of the upper layer  14 . 
     In one preferred embodiment, each of the upper layer  14 , lower layer  16  and central layer  18  forms a substrate. 
     Each of the upper layer  14 , lower layer  16  and central layer  18  thus comprises an electrically conductive upper sublayer  22 A,  22 B,  22 C, an electrically conductive lower sublayer  24 A,  24 B,  24 C and a dielectric central sublayer  26 A,  26 B,  26 C, having a first dielectric constant, intermediate between the upper sublayer  22 A,  22 B,  22 C and the lower sublayer  24 A,  24 B,  24 C. 
     Furthermore, the lower sublayer  24 A of the upper layer  14  is electrically connected to the upper sublayer  22 C of the central layer  18 . Likewise, the lower sublayer  24 C of the central layer  18  is electrically connected to the upper sublayer  22 B of the lower layer  16 . 
     The upper sublayers  22 A,  22 B,  22 C and the lower sublayers  24 A,  24 B,  24 C are for example made from copper. 
     The central sublayers  26 A,  26 B,  26 C are for example made from epoxide resin or Teflon. 
     The propagation zone  19  corresponds to a zone in which the electromagnetic wave is combined during its propagation in the waveguide  12 . 
     In the first component  10 A of  FIGS. 1 and 2 , the propagation zone  19  is defined by the electrically conductive lower sublayer  24 A of the upper layer  14 , the electrically conductive upper sublayer  22 B of the lower layer  16  and two central lateral borders  30  each arranged in the central layer  18  and spaced apart from one another. 
     Furthermore, the propagation zone  19  comprises a cavity  32  delimited by the upper layer  14 , the lower layer  16  and, laterally, by the central layer  18 . 
     The central lateral borders  30  of the propagation zone  19  are able to prevent the passage of an electromagnetic wave having a wavelength greater than or equal to the minimum predetermined wavelength. 
     Each central lateral border  30  electrically connects the lower sublayer  24 A of the upper layer  14  and the upper sublayer  22 B of the upper layer  14  to one another. 
     The central lateral borders  30  extend parallel to the propagation axis X-X and here are parallel to one another. 
     The central lateral borders  30  in particular extend along the direction Z-Z orthogonal to the propagation axis X-X and the transverse axis Y-Y. 
     Hereinafter, the terms “above” and “below” will be understood with respect to the direction Z-Z as illustrated in  FIG. 1 . 
     The central lateral borders  30  in particular extend over the entire thickness of the central layer  18 . 
     The central lateral borders  30  are in particular placed laterally on either side of the cavity  32 , for example here outside the cavity  32 . 
     In the embodiment of  FIGS. 1 and 2 , each central lateral border  30  comprises a row of electrically conductive vias  34 , arranged at least through the central cavity  18 . A “via” refers to a hole, arranged at least through the central layer  18 , having walls covered with an electrically conductive coating, for example metallized. 
     More specifically, each via  34  extends along the direction Z-Z orthogonal to the propagation axis X-X and through the transverse axis Y-Y, while passing through at least the central layer  18 . 
     Each via  34  electrically connects the lower sublayer  24 A of the upper layer  14  and the upper sublayer  22 B of the upper layer  14  to one another. 
     The separation between two successive vias  34  of a central lateral border  30  is smaller than the predetermined minimum wavelength, in particular smaller than one tenth of the predetermined minimum wavelength, preferably smaller than one twentieth of the predetermined minimum wavelength. 
     In the example illustrated in  FIGS. 1 and 2 , the cavity  32  is delimited by the lower surface  21 A of the upper layer  14 , the upper surface  20 B of the lower layer  16  and lateral edges  36  of the central layer  18 . 
     The cavity  32  is filled with a fluid  38  having a second dielectric constant for example lower than the first dielectric constant. 
     The fluid  38  is for example air. In a variant, in the case where the cavity  32  defines a sealed closed volume, the cavity  32  is filled with air, nitrogen or is empty of fluid. 
     As illustrated in  FIG. 1 , the lateral edges  36  of the central layer  18  extend parallel to the propagation axis X-X. 
     The lateral edges  36  of the central layer  18  in particular extend orthogonally to the transverse axis Y-Y. 
     The lateral borders  36  of the central layer  18  run alongside the central lateral borders  30 . “Run alongside” means that the lateral edges  36  are in contact with the central lateral borders  30  or placed at a distance, for example constant, from the central lateral borders  30 , this distance preferably being less than 100 μm. 
     In the first component  10 A illustrated in  FIGS. 1 and 2 , the dielectric strip  28  is placed in the cavity  32 , separated from the lateral edges  36  of the cavity  32 . 
     In particular, the dielectric strip  28  is placed in the propagation zone  19  such that, projected on the upper surface  20 B of the lower layer  16 , the dielectric strip  28  is separated from the lateral edges  36  of the cavity  32 . 
     The dielectric strip  28  is placed between the lateral edges  36  of the cavity  32 . 
     The dielectric strip  28  here has an elongated shape and extends in a longitudinal direction parallel to the propagation axis. Furthermore, the dielectric strip  28  here extends orthogonally to the transverse axis Y-Y. 
     In the example illustrated in  FIG. 1 , the dielectric strip  28  has a width in particular between 1% and 90% of the width of the cavity  32 . 
     “Width of an element” refers to the edge-to-edge distance of the element, taken along the transverse axis Y-Y. 
     The width of the dielectric strip  28  is for example constant along the propagation axis X-X, as illustrated in  FIG. 1 . 
     The dielectric strip  28  here is centered on a median plane of the two lateral edges  36 . 
     In this example, the dielectric strip  28  has a thickness smaller than the height of the cavity  32 . “Thickness of an element” or “height of an element” refers to the edge-to-edge distance of the element, taken along the direction Z-Z orthogonal to the propagation axis X-X and the transverse axis Y-Y. 
     Here, the dielectric strip  28  is placed separated from the lower surface  21 A of the upper layer  14  and the upper surface  20 B of the lower layer  16 . 
     The dielectric strip  28  is fastened to the upper surface  20 B of the lower layer  16  by means of a lower contact sublayer  40 . More specifically, the dielectric strip  28  is fastened to the lower contact sublayer  40 , the lower contact sublayer  40  being fastened to the upper surface  20 B of the lower layer  16 . The lower contact sublayer  40  is electrically conductive. 
     The dielectric strip  28  is further fastened to the lower surface  21 A of the upper layer  14  by means of an upper contact sublayer  42 . More specifically, the dielectric strip  28  is fastened to the upper contact sublayer  42 , the upper contact sublayer  42  being fastened to the lower surface  21 A of the upper layer  14 . The upper contact sublayer  42  is electrically conductive. 
     A first manufacturing process relative to the manufacturing of the first component  10 A according to the invention will now be described, in reference to  FIGS. 3 and 4 . 
     The first process comprises providing the upper layer  14  and the lower layer  16 . 
     The first process also comprises providing the central layer  18 , the central layer  18  being provided here by providing a plurality of recesses  44 , the plurality of recesses  44  being intended to form the cavity  32  of the first component  10 A. 
     The upper layer  14 , the lower layer  16  and the central layer  18  are provided separated from one another. 
     In the first process, the step for providing the central layer  18  comprises providing an initial layer  46 , the initial layer  46  being intended to form the central layer  18 . 
     The initial layer  46  thus comprises at least one initial dielectric sublayer  48 , having the first dielectric constant, which is in particular intended to form the central sublayer  26 C of the central layer  18 . 
     In particular, the initial layer  46  also comprises an electrically conductive initial upper sublayer  50  intended to form the upper sublayer  22 C of the central layer  18 , and an electrically conductive initial lower sublayer  52  intended to form the lower sublayer  24 C of the central layer  18 . 
     The initial layer  46  is provided while being devoid of recess. 
     The step for providing the central layer  18  then comprises cutting, in the initial layer  46 , the plurality of recesses  44  intended to form the cavity  32 . 
     The cutting is carried out in the entire thickness of the initial layer  46 . 
     Before or after the cutting step, the first process comprises a step for implementing central lateral borders  30 . 
     For example, the implementation of the central lateral borders  30  comprises producing the row of vias  34 . 
     In the first process, the step for providing the central layer  18  further comprises producing the dielectric strip  28 . 
     The production of the dielectric strip  28  here is carried out during the cutting of the plurality of recesses  44 , as illustrated in  FIG. 3 . The plurality of recesses  44  is then intended to define the cavity  32 , the dielectric strip  28  and attachment means  54  of the dielectric strip  28 . 
     During the cutting, the dielectric strip  28  is more specifically formed by part of the initial dielectric sublayer  48  of the initial layer  46 . 
     The dielectric strip  28  is thus placed in the initial layer  46 . In line with the dielectric strip  28 , the electrically conductive initial upper and lower sublayers  50 ,  52  of the initial layer  46  respectively above and below the dielectric strip  28  respectively form the upper contact sublayer  42  and the lower contact sublayer  40  of the first component  10 A. 
     As illustrated in  FIG. 4 , the attachment means  54  comprise a plurality of dielectric fasteners  56  coupling the dielectric strip  28  to at least one of the lateral edges  36  of the cavity  32 . 
     Thus, the dielectric strip  28 , the dielectric fasteners  56  and the lateral edges  36  of the cavity  32  are integral. 
     As illustrated in  FIG. 4 , each dielectric fastener  56  is in the form of a rectilinear bar, and here extends perpendicularly from one of the lateral edges  36 . 
     In the example illustrated in  FIG. 4 , at least one dielectric fastener  56  extends from each of the lateral edges  36 . 
     The dielectric fasteners  56  are separated from one another. 
     In the first process, as illustrated in  FIG. 4 , the distance between two adjacent dielectric fasteners  56  is equal for all of the dielectric fasteners  56 . 
     Projected on the propagation axis X-X, each dielectric fastener  56  extending from one of the lateral edges  36  is positioned substantially in the middle of two adjacent dielectric fasteners  56  extending from the opposite lateral edge  36 . 
     The production of the dielectric strip  28  for example comprises eliminating the electrically conductive initial upper and lower sublayers  50 ,  52  in line with the dielectric fasteners  56 , in particular above and below the dielectric fasteners  56 . 
     In this example, the dielectric fasteners  56  have a thickness smaller than the height of the cavity  32 . 
     At the end of the step for producing the dielectric strip  28  and the cutting step, the initial layer  46  forms the central layer  18 . 
     At the end of the production step, the dielectric strip  28  is placed between a plane defined by the upper surface  20 C of the central layer  18  and a plane defined by a lower surface  21 C of the central layer  18 . 
     The dielectric strip  28  is thus intended to be placed in the cavity  32 , between the lateral edges  36 . 
     Hereinafter, the first process comprises the assembly of the upper layer  14 , the lower layer  16  and the central layer  18 , such that the central layer  18  is intermediate between the upper layer  14  and the lower layer  16 . 
     Throughout the entire manufacturing process, the layers  14 ,  16 ,  18  are aligned with one another by means of centering studs or by a camera with test charts. 
     As illustrated in  FIG. 3 , the assembly first comprises attaching the central layer  18  to the lower layer  16 . This attachment is for example done by gluing. 
     During this attachment step, the dielectric strip  28  is likewise attached to the lower layer  16 . 
     Throughout the entire duration of this attachment, the dielectric strip  28  is kept in position relative to the central layer  18  and the lower layer  16  by the dielectric fasteners  56 . The positioning of the dielectric strip  28  is therefore relatively imprecise and chosen during the cutting step. 
     In the first process, the assembly next comprises the removal of the attachment means  54 , once the central layer  18  is fastened to the lower layer  16 , in particular once the dielectric strip  28  is fastened to the lower layer  16 . 
     This removal is carried out by the cutting of the attachment means  54 , in particular by the cutting of the dielectric fasteners  56 . The preceding step for eliminating the electrically conductive initial upper and lower sublayers  50 ,  52  makes it possible to facilitate this step for cutting of the dielectric fasteners  56 . 
     This cutting is for example done manually with a scalpel, a digital milling machine or a laser. 
     Each dielectric fastener  56  is preferably cut while being flush with the lateral edge  36  from which the dielectric fastener  56  extends. 
     Furthermore, each dielectric fastener  56  is advantageously cut while being flush with the dielectric strip  28 . 
     Subsequently, the assembly comprises the attachment of the upper layer  14  to the central layer  18 , as illustrated in  FIG. 2 . This attachment is for example done by gluing. 
     During this attachment, the cavity  32  is then formed by the plurality of recesses  44  while being delimited by the upper layer  14 , the lower layer  16 , and laterally, by the opposite lateral edges  36  of the central layer  18 . 
     After assembly, the first component  10 A is formed, as illustrated in  FIG. 2 . In particular, the layers  14 ,  16 ,  18  define the propagation zone  19  of an electromagnetic wave. 
     The propagation zone  19  is then defined by the electrically conductive lower sublayer  24 A of the upper layer  14 , the electrically conductive upper sublayer  22 B of the lower layer  16  and the central lateral borders  30 . 
     This propagation zone  19  comprises the cavity  32 . 
     After the assembly step, the dielectric strip  28  is placed in the cavity  32 , separated from the lateral edges  36  of the cavity  32 . 
     In particular, after the assembly step, the dielectric strip  28 , placed in the central layer  18 , is placed in the propagation zone  19  and, projected on the upper surface  20 B of the lower layer  16 , separated from the lateral edges  36  of the cavity  32 . 
     During use, the first process comprises a step for supplying the first microwave component  10 A with an electromagnetic wave propagating in the propagation zone  19 . The electromagnetic wave has at least one propagation mode having an electric field maximum. 
     The dielectric strip  28  is positioned in the cavity  32  in a predetermined position such that, during this supply step of the first component  10 A, the predetermined position corresponds to the level of the electric field maximum. 
     More specifically, during the step for producing the dielectric strip  28 , the dimensions of the dielectric fasteners  56  are predetermined such that, after assembly, the dielectric strip  28  is located in the cavity  32  in the predetermined position. 
     The dielectric strip  28  thus has an effect on the propagation mode. In particular, the dielectric strip  28  charges the waveguide  12  so as to broaden the monomodal bandwidth. 
     Additionally, after use, the structure comprising three layers  14 ,  16 ,  18  makes it possible to make the first component  10 A compact and flexible. 
     In a variant, not shown, of the first component  10 A, the waveguide  12  comprises a first electrically insulating layer between the lower sublayer  24 A of the upper layer  14  and the upper sublayer  22 C of the central layer  18 , and/or a second electrically insulating layer between the lower sublayer  24 C of the central layer  18  and the upper sublayer  22 B of the lower layer  16 . 
     The insulating layer(s) are for example made from prepreg. 
     Each central lateral border  30 , and in particular each via  34 , passes through the insulating layer(s). 
     In a variant, not shown, of the first component  10 A, the dielectric strip  28  is not centered on a median plane of the two lateral edges  36 , but is laterally offset from the median plane. Such a lateral offset makes it possible to provide control of the desired propagation modes of the electromagnetic waves propagating in the waveguide  12 . 
     In a variant, not shown, of the first component  10 A, the width of the dielectric strip  28  varies along the propagation axis. 
     In a variant, not shown, of the first component  10 A, the waveguide  12  comprises electrically conductive wires passing all the way through the cavity  32 , and electrically connecting the lower sublayer  24 A of the upper layer  14  to the upper layer  22 B of the lower layer  16 . These wires make it possible to perform an impedance adaptation to another circuit. 
     In a variant, not shown, of the first component  10 A, the waveguide  12  comprises electrically conductive wires passing through the cavity  32 , electrically connected to the lower sublayer  24 A of the upper layer  14 , and having a free end separated from the upper layer  22 B of the lower layer  16 . These wires make it possible to produce capacitive studs making it possible to adjust filtering properties of the component. 
       FIG. 5  shows a variant of the manufacturing process of the first component  10 A. 
     This variant differs from the first described process in that the median plane of the two lateral edges  36  is a plane of symmetry of the dielectric fasteners  56 . 
     Furthermore, each dielectric fastener  56  does not extend perpendicularly from one of the lateral edges  36 . 
     At least two dielectric fasteners  56  extend from a same lateral edge  36 , coming together at the dielectric strip  28 . As illustrated in  FIG. 5 , these two dielectric fasteners  56  form a pattern that repeats along the propagation axis. 
     More generally, for each dielectric fastener  56 , another dielectric fastener  56  extends from the same lateral edge  36 , coming together at the dielectric strip  28 . 
     In a variant, not shown, of the first manufacturing process, the production of the dielectric strip  28  does not comprise eliminating the electrically conductive initial upper and lower sublayers  50 ,  52  in line with the dielectric fasteners  56 . These sublayers  50 ,  52  are eliminated during the removal of the attachment means  54 . 
     In a variant, not shown, of the first manufacturing process, the dielectric fasteners  56  extend from only one of the lateral edges  36 . 
     A second microwave component  10 B will now be described in reference to  FIG. 6 . 
     This second component  10 B differs from the first component  10 A in that the dielectric strip  28  and the lower surface  21 A of the upper layer  14  define a free space between them. 
     The dielectric strip  28  is thus not fastened to the lower surface  21 A of the upper layer  14  by means of the upper contact sublayer  42 . 
     The waveguide  12  is then devoid of the upper contact sublayer  42 . 
     A second manufacturing process relative to the manufacturing of the second component  10 B differs from the first process in that the production of the dielectric strip  28  comprises eliminating the electrically conductive initial upper sublayer  50  above the dielectric strip  28 . 
     A third microwave component  10 C will now be described in reference to  FIG. 7 . 
     This third component  10 C differs from the first component  10 A in that the waveguide  12  further comprises a functional attachment component  58 . 
     The functional attachment component  58  is formed by a plurality of dielectric fasteners  56  that are integral with the dielectric strip  28 , each dielectric fastener  56  extending from one of the lateral edges  36 . 
     The dielectric fasteners  56  have characteristics identical to the dielectric fasteners described in the first process. 
     In the third component  10 C illustrated in  FIG. 7 , the dielectric fasteners  56  extend from only one of the lateral edges  36 . 
     The dielectric strip  28  is therefore separated from the lateral edges  36  in at least one region of the dielectric strip  28 . 
     Furthermore, the dielectric fasteners  56  are configured to perform a filter function for an electromagnetic wave propagating in the propagation zone  19 . 
     In particular, the separation between two adjacent dielectric fasteners  56 , and their dimensions, are predetermined to perform the filter function. 
     A third manufacturing process relative to the manufacturing of the third component  10 C differs from the first process in that at least part of the attachment means  54  is not removed during the assembly step. 
     The upper layer  14  is fastened to the central layer  18  without removing all of the dielectric fasteners  56 . 
     The part of the attachment means  54  then forms the functional attachment component  58 , the dielectric fasteners  56  not removed being configured to perform the filter function for an electromagnetic wave propagating in the propagation zone  19 . 
     In particular, during the step for producing the dielectric strip  28 , the separation between two adjacent dielectric fasteners  56 , and their dimensions, are predetermined to perform the filter function. 
     In a variant, not shown, of the third component  10 C, the width of the dielectric strip  28  varies along the propagation axis. 
     In a variant, not shown, of the third component  10 C, the width of the dielectric strip  28  is constant between two adjacent dielectric fasteners  56 , and the width of the dielectric strip  28  between a pair of adjacent dielectric fasteners  56  is different for at least two pairs of adjacent dielectric fasteners  56 . 
     In another variant, not shown, of the third component  10 C, the width of the dielectric strip  28  taken at a dielectric fastener  56  is different from the width of the dielectric strip  28  taken at an adjacent dielectric fastener  56 . The side of the dielectric strip  28  joining the two adjacent dielectric fasteners  56  then has, in top view, a predetermined profile chosen from among: a straight line or a curve. 
     A fourth component  10 D according to the invention is illustrated in  FIG. 8 . 
     This fourth component  10 D differs from the first component  10 A in that the dielectric strip  28  is made from a dielectric material different from the material from which the central sublayer  26 C of the central layer  18  is made. 
     The dielectric strip  28  is in contact with the upper surface  20 B of the lower layer  16 . 
     In particular, the dielectric strip  28  is fastened to the upper surface  20 B of the lower layer  16 , for example by gluing. 
     In this example, the dielectric strip  28  is in contact with the lower surface  21 A of the upper layer  14 . In other words, the dielectric strip  28  has a thickness equal to the height of the cavity  32 . 
     In particular, the dielectric strip  28  is fastened to the lower surface  21 A of the upper layer  14 , for example by gluing. 
     In a variant, not shown, of the fourth component  10 D, the dielectric strip  28  and the lower surface  21 A of the upper layer  14  define a free space there between. In other words, the dielectric strip  28  is devoid of contact with the lower surface  21 A of the upper layer  14 . The thickness of the dielectric strip  28  is therefore smaller than the thickness of the central layer  18 . 
     In a variant, not shown, of the fourth component  10 D, the waveguide  12  includes a functional attachment component  58  similar to the functional attachment component  58  of the third component  10 C. 
     A fourth manufacturing process relative to the manufacturing of the fourth component  10 D will now be described. 
     The fourth process differs from the first process in that the dielectric strip  28  and the attachment means  54  are not cut in the central layer  18 , and in that the step for producing the dielectric strip  28  comprises providing the dielectric strip  28  and attachment means  54  of the dielectric strip  28 , the dielectric strip  28  and the attachment means  54  being provided separated from the central layer  18 . 
     The central layer  18  is provided while having a recess  44  intended by itself to form the cavity  32 . 
     The attachment means  54  have characteristics identical to the attachment means of the first process, but differ from the latter in that the dielectric fasteners  56  are not integral with the lateral edges  36  of the cavity  32 . 
     The attachment means  54  thus comprise the plurality of dielectric fasteners  56  secured to the dielectric strip  28 , the dielectric fasteners  56  being secured to the dielectric strip  28 , for example integral with the dielectric strip  28 . 
     The dielectric strip  28  and the dielectric fasteners  56  are preferably made from a dielectric material different from the material from which the central sublayer  26 C of the central layer  18  is made. In a variant, the dielectric strip  28  and the dielectric fasteners  56  are made from the same material as that of the central sublayer  26 C of the central layer  18 . 
     During the assembly, the dielectric strip  28  is fastened to the lower layer  16 . 
     The dielectric strip  28  is kept in position relative to the lower layer  16 , by the dielectric fasteners  56  throughout the entire duration necessary for its attachment to the lower layer  16 . 
     Hereinafter, the central layer  18  is fastened to the lower layer  16 , the dielectric strip  28  then being placed in the recess  44 . 
     A fifth component  10 E according to the invention is illustrated in  FIGS. 9 and 10 . 
     This fifth component  10 E differs from the first component  10 A in that the cavity  32  is defined along the propagation axis between a front end  60  and a rear end  62  of the central layer  18 , the dielectric strip  28  extending from the front end  60  to the rear end  62 . 
     The cavity  32  has, projected on the upper surface  20 B of the lower layer  16 , a closed outer contour. 
     As illustrated in  FIG. 9 , the fifth component  10 E further comprises two attached transmission lines  64 , placed longitudinally on either side of the cavity  32 , the propagation zone  19 , and the central lateral borders  30 , extending in each of these two attached transmission lines  64 . 
     Each attached transmission line  64  comprises an electrically conductive upper attached layer  66 , identical to the upper layer  14  and integral with the upper layer  14 , an electrically conductive lower attached layer  67 , identical to the lower layer  16  and integral with the lower layer  16 , and a dielectric central attached layer  68 , identical to the central layer  18  and integral with the central layer  18 . 
     The attached transmission lines  64  are devoid of cavity  32 . 
     The separation, taken along the transverse axis Y-Y, between the central lateral borders  30 , is larger in the cavity  32  at their separation in the attached transmission lines  64 . 
     The dielectric strip  28  is secured with the central sublayer  26 C of the central layer  18 . In particular, the dielectric strip  28  here is secured with the central sublayer  26 C of the central layer  18 . 
     The dielectric strip  28  is thus in particular secured with the attached central layer  68  of each of the attached transmission lines  64 . 
     The dielectric strip  28  has a length equal to the length of the cavity  32 . “Length of an element” refers to the edge-to-edge distance of the element, taken along the propagation axis. 
     Furthermore, the embodiment of the fifth component  10 E illustrated in  FIG. 10  differs from the first component  10 A in that, in at least one segment of the cavity  32 , taken along the transverse axis Y-Y, the dielectric strip  28  respectively defines, with the lower surface  21 A of the upper layer  14  and the upper surface  20 B of the lower layer  16 , a free space. 
     More specifically, the upper attached layers  66  and the lower attached layers  67  protrude in the cavity  32  respectively above and below the dielectric strip  28 . 
     Projected on the upper surface  20 B of the lower layer  16 , the projections in the cavity  32  of the upper attached layers  66  and the lower attached layers  67  have a pointed shape. 
     A fifth manufacturing process relative to the manufacturing of the fifth component  10 E will now be described. 
     The fifth process differs from the first process in that during the cutting of the plurality of recesses  44 , the plurality of recesses  44  is intended to define the cavity  32 , along the propagation axis, between a front end  60  and a rear end  62  of the central layer  18 . 
     During the cutting, the plurality of recesses  44  is intended to define the cavity  32  such that the cavity  32  has, projected on the upper surface  20 B of the lower layer  16 , a closed outer contour. 
     The cut plurality of recesses  44  defines the dielectric strip  28 , the dielectric strip  28  extending from the front end  60  to the rear end  62 , and in particular having a length equal to the length of the cavity  32 . 
     For example, the plurality of recesses  44  defines the dielectric strip  28  without defining dielectric fasteners  56  coupling the dielectric strip  28  to the rest of the central layer  18 . 
     Furthermore, the implementation of central lateral borders  30  is done such that, after assembly, the propagation zone  19  extends longitudinally on either side of the cavity  32 . The upper layer  14 , the lower layer  16  and the central layer  18  then define the two attached transmission lines  64  on either side of the cavity  32 . 
     During use, during the step for supplying the fifth microwave component  10 E with an electromagnetic wave, the wave propagates in the propagation zone  19  in one of the attached transmission lines  64 . 
     The projections of the upper attached layers  66  and lower attached layers  67  make it possible to ensure a good electromagnetic transition for the waves propagating in the propagation zone  19  between the attached transmission lines  64  and the cavity  32 . 
     A sixth microwave component  10 F will now be described in reference to  FIG. 11 . 
     This sixth component  10 F differs from the previous embodiments in that the central lateral borders  30  do not comprise rows of vias  34 . 
     Each central lateral border  30  comprises an electrically conductive continuous lateral wall  70 . 
     The continuous lateral wall  70  is in particular formed by an electrically conductive coating, for example metallic. The coating here is applied on the lateral edges  36  of the cavity  32 . 
     “Continuous lateral wall” means that the metallic coating is applied on the entire height and length of the lateral edges  36 . 
     The central lateral borders  30  are in particular devoid of vias. 
     A sixth manufacturing process relative to the manufacturing of the sixth component  10 F will now be described. 
     The sixth process differs from the first process in that the step for implementing central lateral borders  30  is carried out after the step for cutting the plurality of recesses  44 . 
     This step for implementing central lateral borders  30  comprises producing an electrically conductive continuous lateral wall  70 , by applying an electrically conductive coating, for example metallic, on edges of the plurality of recesses  44 , these edges being intended to form the lateral edges  36  of the cavity  32 . 
     A seventh component  10 G according to the invention will now be described in light of  FIG. 12 . 
     This seventh component  10 G differs from the first component  10 A in that the dielectric strip  28  is a first dielectric strip  28 , and in that the waveguide  12  further comprises a second dielectric strip  72 . 
     The second dielectric strip  72  is placed in the cavity  32 , separated from the first dielectric strip  28 , and separated from the lateral edges  36  of the cavity  32 . 
     In particular, the second dielectric strip  72  is placed in the propagation zone  19  such that, projected on the upper surface  20 B of the lower layer  16 , the second dielectric strip  72  is separated from the lateral edges  36  of the cavity  32 . 
     The second dielectric strip  72  is placed between the lateral edges  36  of the cavity  32 . 
     The first dielectric strip  28  and the second dielectric strip  72  respectively extend along a longitudinal direction parallel to the propagation axis X-X. Furthermore, the first dielectric strip  28  and the second dielectric strip  72  extend here orthogonally to the transverse axis Y-Y. 
     The first dielectric strip  28  and the second dielectric strip  72  are laterally offset from the median plane of the two lateral edges  36 . 
     In the example illustrated in  FIG. 12 , the second dielectric strip  72  is at least partially positioned between the first dielectric strip  28  and one of the lateral edges  36 . 
     The second dielectric strip  72  is substantially similar to the first dielectric strip  28 . 
     The second dielectric strip  72  has a width in particular between 1% and 90% of the width of the cavity  32 . 
     The width of the second dielectric strip  72  is for example constant along the propagation axis X-X. In a variant, the width of the second dielectric strip  72  varies along the propagation axis. 
     In this example, the second dielectric strip  72  has a thickness smaller than the height of the cavity  32 . 
     Here, the second dielectric strip  72  is placed separated from the lower surface  21 A of the upper layer  14  and the upper surface  20 B of the lower layer  16 . 
     The second dielectric strip  72  is fastened to the upper surface  20 B of the lower layer  16  by means of a second lower contact sublayer  74 . More specifically, the second dielectric strip  72  is fastened to the second lower contact sublayer  74 , the second lower contact sublayer  74  being fastened to the upper surface  20 B of the lower layer  16 . The second lower contact sublayer  74  is electrically conductive. 
     The second dielectric strip  72  is further fastened to the lower surface  21 A of the upper layer  14  by means of a second upper contact sublayer  76 . More specifically, the second dielectric strip  72  is fastened to the second upper contact sublayer  76 , the second upper contact sublayer  76  being fastened to the lower surface  21 A of the upper layer  14 . The second upper contact sublayer  76  is electrically conductive. 
     A seventh manufacturing process relative to the manufacturing of the seventh component  10 G will now be described. 
     The seventh process differs from the first process in that the step for providing the central layer  18  comprises a step for producing the first dielectric strip  28  and the second dielectric strip  72 . 
     The production of the first dielectric strip  28  and the second dielectric strip  72  here is carried out during the cutting of the plurality of recesses  44 . 
     During the cutting of the plurality of recesses  44 , the plurality of recesses  44  is intended to define the first dielectric strip  28 , the second dielectric strip  72  and attachment means  54  of the first dielectric strip  28  and the second dielectric strip  72 . 
     During the cutting, the first dielectric strip  28  and the second dielectric strip  72  are more specifically formed by part of the initial dielectric sublayer  48  of the initial layer  46 . 
     In line with the second dielectric strip  72 , the electrically conductive initial upper and lower sublayers  50 ,  52  of the initial layer  46  respectively above and below the second dielectric strip  72  respectively form the second upper contact sublayer  76  and the second lower contact sublayer  74  of the seventh component  10 G. 
     The attachment means  54  comprise a plurality of first dielectric fasteners coupling the first dielectric strip  28  to one of the lateral edges  36  of the cavity  32 . The attachment means  54  further comprise a plurality of second dielectric fasteners coupling the second dielectric strip  72  to the other of the lateral edges  36  of the cavity  32 . 
     For example, the attachment means  54  comprise a plurality of intermediate dielectric fasteners coupling the first dielectric strip  28  to the second dielectric strip  72 . 
     The first dielectric fasteners, the second dielectric fasteners and the intermediate dielectric fasteners have characteristics substantially identical to the dielectric fasteners  56  described in the first process. 
     Like in the first process, during use, the seventh process comprises a step for supplying the seventh microwave component  10 G with an electromagnetic wave propagating in the propagation zone  19 . 
     The electromagnetic wave here has at least first and second propagation modes, the second propagation mode having two electric field maximums. 
     The first dielectric strip  28  and the second dielectric strip  72  are respectively positioned in the cavity  32  in a first predetermined position and a second predetermined position such that, during this supply step of the seventh component  10 G, the first predetermined position and the second predetermined position respectively correspond to the levels of the electric field maximums. 
     More specifically, during the step for producing the dielectric strip  28 , the dimensions of the first fasteners and second fasteners are predetermined such that, after assembly, the first dielectric strip  28  and the second dielectric strip  72  are respectively located in the cavity  32  at the electric field maximums. 
     The first dielectric strip  28  and the second dielectric strip  72  thus have an effect on the second propagation mode. In particular, the first dielectric strip  28  and the second dielectric strip  72  decrease the monomodal band of the seventh component  10 G in order to obtain a controlled bimodal structure. 
     An eighth component  10 H will now be described in reference to  FIG. 13 . 
     This eighth component  10 H differs from the fourth component  10 D in that the dielectric strip  28  is a first dielectric strip  28 , and in that the waveguide  12  comprises at least one other dielectric strip  72 . 
     In the example illustrated in  FIG. 13 , the waveguide  12  comprises at least three other dielectric strips  72 . 
     Each other dielectric strip  72  is placed in the cavity  32 , separated from the first dielectric strip  28 , separated from each other dielectric strip  72  and separated from the lateral edges  36  of the cavity  32 . 
     In particular, each other dielectric strip  72  is placed in the propagation zone  19  such that, projected on the upper surface  20 B of the lower layer  16 , the other dielectric strip  72  is separated from the lateral edges  36  of the cavity  32 . 
     Each other dielectric strip  72  is placed between the lateral edges  36  of the cavity  32 . 
     The first dielectric strip  28  and each other dielectric strip  72  respectively extend along a longitudinal direction parallel to the propagation axis X-X. Furthermore, the first dielectric strip  28  and each other dielectric strip  72  extend here orthogonally to the transverse axis Y-Y. 
     The first dielectric strip  28  and each other dielectric strip  72  are laterally offset from the median plane of the two lateral edges  36 . 
     Projected on the upper surface  20 B of the lower layer  16 , the first dielectric strip  28  and each other dielectric strip  72  respectively define a circular outer contour. The term “strip” here must therefore be understood broadly. 
     In the example illustrated in  FIG. 13 , each other dielectric strip  72  is substantially similar to the first dielectric strip  28 . In particular, here each other dielectric strip  72  and the first dielectric strip  28  have a substantially identical diameter. 
     The first dielectric strip  28  and each other dielectric strip  72  then respectively have a dielectric permittivity greater than 6. 
     An eighth manufacturing process relative to the manufacturing of the eighth component  10 H will now be described. 
     The eighth process differs from the fourth process in that the eighth process comprises a step for producing each other dielectric strip  72 . The step for producing each other dielectric strip  72  comprises providing the other dielectric strip  72  and means for attaching the other dielectric strip  72 , the other dielectric strip  72  and the attachment means being provided separated from the central layer  18 . 
     During the assembly, each other dielectric strip  72  is fastened to the lower layer  16 , in particular before the central layer  18  is fastened to the lower layer  16 . 
     In a variant of the eighth component  10 H, projected on the upper surface  20 B of the lower layer  16 , at least one of the first dielectric strip  28  and each other dielectric strip  72  defines an outer contour having a rectangular, square or oval shape. 
     In still another variant of the eighth component  10 H, projected on the upper surface  20 B of the lower layer  16 , at least one of the first dielectric strip  28  and each other dielectric strip  72  defines a ring shape, having an outer contour with a circular, rectangular, square or oval shape, and an inner contour with a circular, rectangular, square or oval shape. 
     In still another variant of the eighth component  10 H, at least two strips among the first dielectric strip  28  and the other dielectric strips  72  are made from different materials. 
     The described eighth manufacturing process allows the simultaneous assembly of several strips  28 ,  72  made from different materials. 
     In a variant of the eighth component  10 H, the waveguide  12  further comprises a functional attachment component formed by a plurality of dielectric fasteners that are integral with at least one of the strips  28 ,  72 , each dielectric fastener extending from one of the lateral edges  36 . In the manufacturing process associated with this variant, at least part of the attachment means is not removed during the assembly step. 
     A ninth component  10 I according to the invention will now be described in light of  FIG. 14 . 
     This ninth component  10 I differs from the first component  10 A in that the dielectric strip  28  is not placed in the cavity  32 . 
     The dielectric strip  28  is placed in the propagation zone  19  and is defined in the upper layer  14 . The dielectric strip  28  is thus formed in the upper layer  14 . 
     The dielectric strip  28  is formed in the central sublayer  26 A of the upper layer  14  and is defined by a part of the electrically conductive upper sublayer  22 A of the upper layer  14 , and laterally between two upper lateral borders  78 . 
     The dielectric strip  28  opens onto the cavity  32 . 
     As illustrated in  FIG. 14 , the dielectric strip  28  has a surface  80  defining the cavity  32 . 
     The dielectric strip  28  is placed between a plane defined by an upper surface  20 C of the central layer  18  and a plane defined by an upper surface  20 A of the upper layer  14 . 
     The upper layer  14  is devoid of lower sublayer  24 A, in at least a part of the upper layer  14  between the two upper lateral borders  78 . In particular, in the example illustrated in  FIG. 14 , the upper layer  14  is completely devoid of lower sublayer  24 A, between the two upper lateral borders  78 . 
     The dielectric strip  28  here is placed in the propagation zone  19  such that, projected on the upper surface  20 B of the lower layer  16 , the dielectric strip  28  is separated from the lateral edges  36  of the cavity  32 . 
     Like in the first component  10 A, the propagation zone  19  is defined by the electrically conductive upper sublayer  22 B of the lower layer  16  and the two central lateral borders  30  each arranged in the central layer and spaced apart from one another. Furthermore, in the ninth component  10 I, the propagation zone  19  is defined by the part of the upper sublayer  22 A of the upper layer  14  extending above the dielectric strip  28 , by a part of the electrically conductive lower sublayer  24 A of the upper layer  14 , and by the upper lateral borders  78 , the upper lateral borders  78  joining the parts. 
     The upper lateral borders  78  are able to prevent the passage of an electromagnetic wave having a wavelength greater than or equal to the minimum predetermined wavelength. 
     The upper lateral borders  78  are each arranged in the upper layer  14 . 
     The upper lateral borders  78  extend parallel to the propagation axis X-X and here are parallel to one another. 
     The upper lateral borders  78  in particular extend over the entire thickness of the upper layer  14 . 
     The upper lateral borders  78  are spaced apart from one another. 
     Here, the upper lateral borders  78  are in particular symmetrical to one another relative to the median plane of the lateral edges  36 . The dielectric strip  28  here is thus centered on the median plane of the lateral edges  36 . 
     A cross-section of the propagation zone  19  is substantially in the shape of an upside-down T. 
     In the example illustrated in  FIG. 14 , projected on the upper surface  20 B of the lower layer  16 , the upper lateral borders  78  are positioned separated from and between the lateral edges  36 . 
     Each upper lateral border  78  electrically connects the lower sublayer  24 A of the upper layer  14  and the upper sublayer  22 A of the upper layer  14  to one another. 
     The upper lateral borders  78  and the central lateral borders  30  electrically connect the upper sublayer  22 B of the lower layer  16  to the upper sublayer  22 A of the upper layer  14 , respectively on either side of the cavity  32 . 
     In the embodiment of  FIG. 14 , each upper lateral border  78  comprises a row of electrically conductive vias  34 , arranged through the upper layer  14 . More specifically, each via  34  extends along the direction Z-Z, while passing through the upper layer  14 . 
     Each via  34  electrically connects the lower sublayer  24 A of the upper layer  14  and the upper sublayer  22 A of the upper layer  14  to one another. 
     The separation between two successive vias  34  of an upper lateral border  78  is smaller than the predetermined minimum wavelength, in particular smaller than one tenth of the predetermined minimum wavelength, preferably smaller than one twentieth of the predetermined minimum wavelength. 
     A ninth manufacturing process relative to the manufacturing of the ninth component  10 I will now be described. 
     The ninth process differs from the first process in that the dielectric strip  28  is not cut in the central layer  18  and is not placed in the cavity  32 . 
     Furthermore, no attachment means as described in the first process is cut in the central layer  18 . In this embodiment, no fastener is used compared to the embodiments making it possible to place the dielectric strip  28  in the cavity  32 . 
     The central layer  18  is provided while having a recess  44  intended by itself to form the cavity  32 . 
     The provision of the upper layer  14  comprises providing an initial upper layer, the initial upper layer being intended to form the upper layer  14 . 
     The initial upper layer thus comprises at least one initial dielectric sublayer, intended to form the central sublayer  26 A of the upper layer  14 , an electrically conductive upper sublayer, intended to form the upper sublayer  22 A of the upper layer  14 , and an electrically conductive lower sublayer, intended to form the lower sublayer  24 A of the upper layer  14 . 
     In the ninth process, the step for providing the upper layer  14  comprises producing the dielectric strip  28 . The production of the dielectric strip  28  comprises implementing upper lateral borders  78  and eliminating at least part, advantageously all, of the electrically conductive lower sublayer of the initial upper layer extending between the two upper lateral borders  78 . 
     The part of the central dielectric sublayer of the initial upper layer defined between the upper lateral borders  78  forms the dielectric strip  28 . 
     At the end of the step for producing the dielectric strip  28 , the initial upper layer forms the upper layer  14 . 
     During the assembly, the central layer  18  is fastened to the lower layer  16  and the upper layer  14  is fastened to the central layer  18  in order to form the ninth component  10 I. 
     Thus, after assembly, the propagation zone  19  comprises the dielectric strip  28  delimited in the upper layer  14 , the dielectric strip  28  having a surface defining the cavity  32 . 
     In a variant, not shown, of the ninth component  10 I, the dielectric strip  28  is defined in the lower layer  16 . In the associated manufacturing process, the step for providing the lower layer  16  comprises producing the dielectric strip  28 . 
     In a variant, not shown, of the ninth component  10 I, the dielectric strip  28  is not centered on the median plane of the lateral edges  36 . In particular, the dielectric strip  28  is laterally offset relative to the median plane of the lateral edges  36 . 
     The upper lateral borders  78  are then devoid of symmetry relative to the median plane of the lateral edges  36 . 
     A tenth component  10 J according to the invention will now be described in light of  FIG. 15 . 
     This tenth component  10 J differs from the ninth component  10 I in that the dielectric strip  28  is a first dielectric strip  28 . 
     The waveguide  12  further comprises a second dielectric strip  72  placed in the propagation zone  19  and defined in the lower layer  16 , separated from the first dielectric strip  28 . 
     The second dielectric strip  72  is thus formed in the lower layer  16 , in particular separated from the first dielectric strip  28 . 
     The second dielectric strip  72  is formed in the central sublayer  26 B of the lower layer  16  and is defined by a part of the electrically conductive lower sublayer  24 B of the lower layer  16 , and laterally between two lower lateral borders  82 . 
     The second dielectric strip  72  opens onto the cavity  32 . 
     As illustrated in  FIG. 15 , the second dielectric strip  72  has a surface  84  defining the cavity  32 . 
     The second dielectric strip  72  is placed between a plane defined by a lower surface  21 C of the central layer  18  and a plane defined by a lower surface  21 B of the lower layer  16 . 
     The lower layer  16  is devoid of upper sublayer  22 B, in at least a part of the lower layer  16  between the two lower lateral borders  82 . In particular, in the example illustrated in  FIG. 15 , the lower layer  16  is completely devoid of upper sublayer  22 B, between the two lower lateral borders  82 . 
     The second dielectric strip  72  is placed in the propagation zone  19 , such that, projected on the upper surface  20 B of the lower layer  16 , the second dielectric strip  72  is separated from the lateral edges  36  of the cavity  32 . 
     Like in the ninth component  10 I, the propagation zone  19  is defined by a part of the electrically conductive lower sublayer  24 A of the upper layer  14 , a part of the electrically conductive upper sublayer  22 A of the upper layer  14 , and the upper lateral borders  78  joining the parts. The propagation zone  19  is also laterally defined by the two central lateral borders  30  each arranged in the central layer  18  and spaced apart from one another. 
     Furthermore, in the tenth component  10 J, the propagation zone  19  is defined by the part of the electrically conductive lower sublayer  24 B of the lower layer  16  extending below the second dielectric strip  72 , by a part of the electrically conductive upper sublayer  22 B of the lower layer  16 , and by the lower lateral borders  82 , the lower lateral borders  82  joining the parts. 
     The lower lateral borders  82  of the propagation area  19  are able to prevent the passage of an electromagnetic wave having a wavelength greater than or equal to the minimum predetermined wavelength. 
     The lower lateral borders  82  are each arranged in the lower layer  16 . 
     The lower lateral borders  82  extend parallel to the propagation axis X-X and here are parallel to one another. 
     The lower lateral borders  82  in particular extend over the entire thickness of the lower layer  16 . 
     The lower lateral borders  82  are spaced apart from one another. 
     Here, the lower lateral borders  82  are in particular symmetrical to one another relative to the median plane of the lateral edges  36 . The second dielectric strip  72  here is thus centered on the median plane of the lateral edges  36 . 
     A cross-section of the propagation zone  19  is substantially in the shape of an upside-down cross. 
     In particular, the lower lateral borders  82  for example here extend respectively in the extension of the upper lateral borders  78 . 
     Furthermore, in the example illustrated in  FIG. 15 , projected on the upper surface  20 B of the lower layer  16 , the lower lateral borders  82  are positioned separated from and between the lateral edges  36 . 
     Each lower lateral border  82  electrically connects the upper sublayer  22 B of the lower layer  16  and the lower sublayer  24 B of the lower layer  16  to one another. 
     The lower lateral borders  82 , the upper lateral borders  78  and the central lateral borders  30  electrically connect the lower sublayer  24 B of the lower layer  16  to the upper sublayer  22 A of the upper layer  14 , respectively on either side of the cavity  32 . 
     In the embodiment of  FIG. 15 , each lower lateral border  82  comprises a row of electrically conductive vias  34 , arranged through the lower layer  16 . More specifically, each via  34  extends along the direction Z-Z, while passing through the lower layer  16 . 
     Each via  34  electrically connects the upper sublayer  22 B of the lower layer  16  and the lower sublayer  24 B of the lower layer  16  to one another. 
     The separation between two successive vias  34  of a lower lateral border  82  is smaller than the predetermined minimum wavelength, in particular smaller than one tenth of the predetermined minimum wavelength, preferably smaller than one twentieth of the predetermined minimum wavelength. 
     A tenth process relative to the manufacturing of the tenth component  10 J will now be described. 
     The tenth process differs from the ninth process in that the described step for producing the dielectric strip  28  corresponds to the production of the first dielectric strip  28 . 
     In the tenth process, the step for providing the lower layer  16  comprises producing the second dielectric strip  72 . 
     The provision of the lower layer  16  comprises providing an initial lower layer, the initial lower layer being intended to form the lower layer  16 . 
     The initial lower layer thus comprises at least one initial dielectric sublayer, intended to form the central sublayer  26 B of the lower layer  16 , an electrically conductive upper sublayer, intended to form the lower sublayer  22 B of the upper layer  16 , and an electrically conductive lower sublayer, intended to form the lower sublayer  24 B of the lower layer  16 . 
     The production of the second dielectric strip  72  comprises implementing lower lateral borders  82  and eliminating at least part, advantageously all, of the electrically conductive upper sublayer of the initial lower layer extending between the two lower lateral borders  82 . 
     The part of the central dielectric sublayer of the initial lower layer defined between the lower lateral borders  82  forms the second dielectric strip  72 . 
     At the end of the step for producing the second dielectric strip  72 , the initial lower layer forms the lower layer  16 . 
     During the assembly, the central layer  18  is fastened to the lower layer  16  and the upper layer  14  is fastened to the central layer  18  in order to form the tenth component  10 J. 
     Thus, after assembly, the propagation zone  19  comprises a second dielectric strip  72  defined in the lower layer  16 , the second dielectric strip  72  being separated from the first dielectric strip  28 . 
     In a variant of the tenth component  10 J, the second dielectric strip  72  is not centered on the median plane of the lateral edges  36 . In particular, the second dielectric strip  72  is laterally offset relative to the median plane of the lateral edges  36 . 
     The lower lateral borders  82  are then devoid of symmetry relative to the median plane of the lateral edges  36 . 
     A eleventh component  10 K according to the invention will now be described in light of  FIG. 16 . 
     The eleventh component  10 K differs from the ninth component  10 I in that the dielectric strip  28  is a first dielectric strip  28 . 
     The waveguide  12  further comprises a second dielectric strip  72  placed in the propagation zone  19  and defined in the upper layer  14 , separated from the first dielectric strip  28 . 
     The second dielectric strip  72  is thus formed in the upper layer  14 , in particular separated from the first dielectric strip  28 . 
     The first dielectric strip  28  and the second dielectric strip  72  are each formed in the central sublayer  26 A of the upper layer  14  and are respectively defined by a part of the electrically conductive upper sublayer  22 A of the upper layer  14 , and laterally between an inner upper lateral border  86  and an outer upper lateral border  88 . 
     The first dielectric strip  28  and the second dielectric strip  72  each open at least partially onto the cavity  32 . 
     As illustrated in  FIG. 16 , the first dielectric strip  28  and the second dielectric strip  72  each have a surface  90 A,  90 B defining the cavity  32 . 
     Between an inner upper lateral border  86  and the outer upper lateral border  88  that is adjacent thereto, the upper layer  14  is devoid of lower sublayer  24 A, in at least part of the upper layer  14 . “An inner upper lateral border and the outer upper lateral border that is adjacent thereto” means that no inner upper lateral border  86  is intermediate between the borders. 
     Like in the first component  10 A, the propagation zone  19  is defined by the electrically conductive upper sublayer  22 B of the lower layer  16  and the two central lateral borders  30  each arranged in the central layer  18  and spaced apart from one another. 
     Furthermore, in the eleventh component  10 K, the propagation zone  19  is defined by the part of the upper sublayer  22 A of the upper layer  14  extending above the first dielectric strip  28  and the second dielectric strip  72 , by a part of the electrically conductive lower sublayer  24 A of the upper layer  14 , and by the inner upper lateral borders  86  and by the outer upper lateral borders  88 , the inner upper lateral borders  86  and outer upper lateral borders  88  joining the parts. 
     The inner upper lateral borders  86  and outer upper lateral borders  88  are able to prevent the passage of an electromagnetic wave having a wavelength greater than or equal to the minimum predetermined wavelength. 
     The inner upper lateral borders  86  and outer upper lateral borders  88  are each arranged in the upper layer  14 . 
     The inner upper lateral borders  86  and outer upper lateral borders  88  extend parallel to the propagation axis X-X and here are parallel to one another. 
     The inner upper lateral borders  86  and the outer upper lateral borders  88  in particular extend over the entire thickness of the upper layer  14 . 
     The inner upper lateral borders  86  and outer upper lateral borders  88  are spaced apart from one another. 
     The inner upper lateral borders  86  and outer upper lateral borders  88  respectively electrically connect the lower sublayer  24 A of the upper layer  14  and the upper sublayer  22 A of the upper layer  14  to one another. 
     The outer upper lateral borders  88  and the central lateral borders  30  electrically connect the upper sublayer  22 B of the lower layer  16  to the upper sublayer  22 A of the upper layer  14 , respectively on either side of the cavity  32 . 
     In the example illustrated in  FIG. 16 , the outer upper lateral borders  88  are respectively placed in the extension of the central lateral borders  30 . In a variant, the outer upper lateral borders  88  are laterally offset relative to the central lateral borders  30 . 
     Here, the outer upper lateral borders  88  are symmetrical to one another relative to the median plane of the lateral edges  36 . 
     The inner upper lateral borders  86  are placed between the outer upper lateral borders  88 . 
     Here, the inner upper lateral borders  86  are symmetrical to one another relative to the median plane of the lateral edges  36 . 
     The first dielectric strip  28  and the second dielectric strip  72  are each laterally offset relative to the median plane of the lateral edges  36 . 
     In the example illustrated in  FIG. 16 , projected on the upper surface  20 B of the lower layer  16 , the inner upper lateral borders  86  are positioned separated from and between the lateral edges  36 . 
     The lower sublayer  24 A of the upper layer  14  electrically connects the inner upper lateral borders  86  to one another. 
     Between the inner upper lateral borders  86 , the lower sublayer  24 A of the upper layer  14  is continuous. “Continuous” means that the lower sublayer  24 A of the upper layer  14  is devoid of through opening. 
     In the embodiment of  FIG. 16 , each of the inner upper lateral borders  86  and outer upper lateral borders  88  comprises a row of electrically conductive vias  34 , arranged through the upper layer  14 . More specifically, each via extends along the direction Z-Z, while passing through the upper layer  14 . 
     Each via electrically connects the lower sublayer  24 A of the upper layer  14  and the upper sublayer  22 A of the upper layer  14  to one another. 
     The separation between two successive vias  34  of an inner  86  or outer  88  upper lateral border is smaller than the predetermined minimum wavelength, in particular smaller than one tenth of the predetermined minimum wavelength, preferably smaller than one twentieth of the predetermined minimum wavelength. 
     An eleventh process relative to the manufacturing of the eleventh component  10 K will now be described. 
     The eleventh process differs from the ninth process in that the step for providing the upper layer  14  comprises producing the first dielectric strip  28  and producing the second dielectric strip  72 . 
     The production step comprises implementing the inner upper lateral borders  86  and outer upper lateral borders  88  in the upper layer  14 , and eliminating at least part of the electrically conductive lower sublayer of the initial upper layer extending between the inner upper lateral borders  86  and outer upper lateral borders  88  adjacent to one another. 
     The parts of the central dielectric sublayer of the initial upper layer defined between the adjacent inner upper lateral borders  86  and outer upper lateral borders  88  form the first dielectric strip  28  and the second dielectric strip  72 . 
     A twelfth component  10 L according to the invention will now be described in light of  FIG. 17 . 
     The twelfth component  10 L differs from the eleventh component  10 K in that the waveguide  12  further comprises another dielectric strip  28 , the other dielectric strip  28 B being positioned in the cavity  32 , separated from the lateral edges  36  of the cavity  32 . 
     The other dielectric strip  28 B is similar to the dielectric strip of the first component  10 A. 
     The twelfth component  10 L makes it possible to broaden the monomodal band and also to obtain interesting propagation characteristics for the radiofrequency field of application. 
     A twelfth process relative to the manufacturing of the twelfth component  10 L will now be described. 
     The twelfth process differs from the eleventh process in that the twelfth process further comprises a step for producing the other dielectric strip  28 B. 
     This step for producing the other dielectric strip  28 B is substantially similar to the step for producing the dielectric strip of the first process. 
     The embodiments described above can be combined according to all technically possible combinations.