Patent Publication Number: US-2010109963-A1

Title: Sealing an Antenna System

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of the filing date of U.S. Provisional Patent Application Ser. No. 61/051,402 filed on May 8, 2008 and EP Patent Application Serial No. EP 08 155 923.9 filed on May 8, 2008, the disclosures of which are hereby incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of measuring technology, in particular fill-level measuring technology, pressure measuring technology and limit-level measuring technology. In particular, the present invention relates to an adaptation apparatus, an antenna arrangement, a measuring device and a method for closing off respectively sealing a waveguide (Wellenleiter). 
     TECHNOLOGICAL BACKGROUND 
     Waveguides can be implemented as hollow conductors and wave ducts, respectively. In a hollow conductor that is stimulated in a mode an electromagnetic wave can arise which makes it possible to transmit information. 
     Document U.S. Pat. No. 5,872,494 may describe a waveguide assembly comprising a first waveguide portion with a first waveguide bore, and a second waveguide portion, attached to the first waveguide portion and comprising a second waveguide bore that is axially aligned with the first waveguide bore. Furthermore, the waveguide assembly comprises a mechanical barrier with a first shaft section, arranged in the first waveguide section, a second shaft section, arranged in the second waveguide section, and a raised annular shoulder, arranged in a process sealing cavity, wherein the raised annular shoulder has a width, which extends radially outward from an outside diameter of the shaft section to approximately λ G /2, and has a height, which extends axially between the first and second waveguide sections, of approximately ¼ λ G . 
     Furthermore, antenna systems with an adaptation apparatus that is radially sealed may be known. 
     There may be a need to provide for an efficiently closing off of a waveguide. 
     SUMMARY OF THE INVENTION 
     According to an exemplary embodiment of the present invention an adaptation apparatus, an antenna arrangement, a measuring device and a method for closing off a waveguide may be created. 
     An adaptation apparatus may comprise an adaptation cone. The adaptation cone can also be referred to as a closing-off apparatus or closing-off body. The adaptation cone may, for example, be made from PTFE (polytetrafluoroethylene), on which a radial enlargement and expanded section, respectively may be attached. If the adaptation cone may not comprise an enlargement, the adaptation cone on its own may be referred to as the adaptation apparatus. It may also be possible to form this radial enlargement such that essentially by forming the radial enlargement a sealing effect can be achieved. By this forming the use of an additional sealing element or an additional sealing device, such as an O-ring, can thus be avoided. A groove or a plurality of grooves or at least fluting may be provided on the radial enlargement as a form and formation, respectively by which a sealing effect may be achievable. 
     The adaptation apparatus or the adaptation element may be used to essentially close off an opening or bore of a waveguide, and at the same time to adapt a frequency response or a frequency characteristic of an arrangement of waveguides with an adaptation apparatus in such a way that for a predetermined frequency the arrangement may have a low attenuation, and for this wavelength may reflect essentially only a portion of the wave, which portion may be as small as possible. 
     An additional sealing element that may be axially affixed to the radial enlargement of the adaptation cone may increase the sealing effect. This sealing element can also be designated a sealing ring or sealing device. Imaginable sealing elements may be an O-ring, a flat seal, a wave seal or a combined seal (metal-plastic). 
     “Radial sealing” may refer to a sealing which may be arranged on the outside, i.e. on the generated surface, the superficies surface and lateral surface (Mantelfläche), respectively of a cylinder or a cone along the radius of the part to be sealed off. As an alternative, a radial sealing may be arranged in a deepening groove of the part to be sealed. Radial sealing may thus refer to sealing that may take place on the outside of a cylinder or a cone along the radius of the part to be sealed. 
     “Axial sealing” may refer to a sealing that may be arranged on a radial enlargement. In other words, axial sealing may refer to sealing that may take place on a radial enlargement. On the radial enlargement the seal then may be affixed in axial direction on one side or both sides. Axial sealing may take place along a direction of propagation of an electromagnetic wave, i.e. an axial sealing may be positioned in a direction of propagation of the electromagnetic wave in front of or behind the radial enlargement. 
     Or in other words, an axially arranged sealing may prevent a material flow that would move in radial direction of an adaptation apparatus, i.e. in perpendicular direction to the longitudinal axis of the adaptation apparatus. 
     A radially arranged sealing may prevent a material flow that would move parallel to a longitudinal axis of the adaptation apparatus. 
     With an axial arrangement of a sealing ring, i.e. an axial sealing, a waveguide may be able to be provided, in particular an antenna system for a fill level radar may be able to be provided, in which waveguide or in which antenna system the sealing ring features a small design and wherein the sealing ring may be suitable for sealing the waveguide. Furthermore, the sealing ring may comprise little influencing of electrical signals, in particular electromagnetic waves. In other words, the sealing ring may have low attenuation to electromagnetic waves. 
     A radial enlargement, shoulder or collar of the adaptation apparatus may be referred to as an “HF choke” (high frequency choke). The adaptation apparatus can comprise an angular, edged or oval form. 
     According to an aspect of the present invention, an adaptation apparatus may be created that may comprise a closing-off body and an enlargement, wherein the closing-off body may comprise a generated surface that may be adapted to establish contact with an external conductor of a waveguide. The enlargement may be arranged on the generated surface and may form a predetermined space between a short circuit and the generated surface of the closing-off body. 
     According to a further aspect of the present invention, an antenna arrangement may be created that may comprise a hollow conductor, an antenna horn and an adaptation apparatus according to the invention. The adaptation apparatus may be arranged between the hollow conductor and the antenna horn. 
     The arrangement of the adaptation apparatus between the hollow conductor and the antenna horn may mean that the adaptation apparatus may be arranged in such a way that part of the adaptation apparatus may project into the antenna horn while another part of the adaptation apparatus may project into the hollow conductor. 
     According to a further aspect of the present invention, a measuring device may be provided which may comprise an antenna arrangement according to the invention. 
     According to a further aspect of the present invention, a method for closing off a waveguide may be created. In this method a closing-off body may be arranged in the waveguide in such a way that a generated surface of the closing-off body may establish contact with the external conductor of the waveguide. Furthermore, an enlargement may be arranged on the generated surface of the closing-off body. By this enlargement an electrical short circuit may be spaced apart at a distance from the generated surface, i.e. the short circuit may be kept at a distance of the generated surface. 
     The short circuit, which may be transformed from the enlargement to the generated surface, may be formed by an external conductor of the hollow conductor, which may encompass the enlargement continuously, i.e. without interruption or without a gap. 
     The short circuit may be in contact with the enlargement. Since the short circuit may be to be spaced apart by the enlargement, the enlargement may be designed in such a way that the enlargement may essentially space apart the short circuit without any mechanical pressure being exerted on the enlargement. 
     The short circuit may be formed respectively built in the external conductor of the hollow conductor, and in the case of a particular selection of a space, for example in the case of a multiple of half the wavelength of a wave that may be transmitted respectively conducted in the waveguide, the short circuit may be transformed to a short circuit on the generated surface of the closing-off body. The short circuit may also be spaced apart at a distance of λ/2 from the generated surface. This may mean that the enlargement may keep the short circuit at a distance of λ/2 or a multiple of λ/2 from the generated surface. 
     In other words, the short circuit may be formed in the external conductor of the hollow conductor. The short circuit may be an apparent short circuit to the HF. In the case of a particular selection of a space, for example in the case of a multiple of half the wavelength of a wave that may be transmitted in the waveguide, the short circuit may be transformed to an apparent short circuit on the generated surface of the closing-off body. 
     The closing-off body may be conically formed or cylindrically formed and may make possible mechanical separation between two spaces. For example, the closing-off body may mechanically separate an internal space of a container from an external space of a container. In this way, for example, diffusion of a substance and material, respectively between two spaces may be prevented. 
     The short circuit may encompass the closing-off body, in particular the enlargement, in a continuous manner. In other words, this may mean that the waveguide near the enlargement essentially does not comprise a gap, and in particular, that the waveguide is made in one piece. For example, the waveguide may be a block of a conductive material such as metal. 
     Waveguides can be designed as hollow conductors or wave ducts. Waveguides can also comprise an antenna horn. By means of the waveguide an electromagnetic wave may be fed respectively led to an internal space of a reservoir or a container. If the conditions in the internal space of the container may differ from those in the external space, separation of the conditions can be maintained by means of an adaptation apparatus. 
     For example, a concentration difference of a material between an internal space of a container and an external space of a container may essentially be maintained. Corrosive liquids or gases may be able to be separated from the external space, or different pressures in the internal space and the external space of the container may be able to be maintained. Furthermore, ex-protection (explosion-proofness) specifications or guidelines may be complied with. 
     The enlargement may be designed as a radial enlargement, i.e. the enlargement may extend essentially at a right angle to the longitudinal axis of the adaptation apparatus. As a result of the small dimensions of the adaptation apparatus the space on the radial enlargement may not be adequate for accommodating one, two or a plurality of seals at a position in the waveguide, which position is to be sealed accordingly. 
     The adaptation apparatus may be in place in a waveguide. The enlargement may make it possible to increase the area and surface, respectively to which a seal, such as an O-ring, can be affixed, without the adaptation apparatus significantly interfering with the wave propagation in the hollow conductor. 
     To this effect the adaptation apparatus may transform a short circuit that is apparent to the HF at the end of the enlargement to a short circuit at the generated surface of the adaptation apparatus. Thus the electromagnetic wave may not “see” the enlargement to which the seal has been affixed. In order to keep the reflections at the transition locations as low as possible, an impedance converter may be arranged on the adaptation apparatus. A tip of a cone and a peak of a cone, respectively may be one embodiment of an impedance converter. In an example the impedance converter may be realized as a tip of a cone. The realisation as a tip of a cone may reduce the reflections at the transition from the material in the hollow conductor, e.g. air, to the material of the adaptation apparatus, e.g. PTFE. 
     For example, the wavelength which may have to be transmitted by the waveguide may be 2.62 mm in the W-band at 79 GHz in PTFE (polytetrafluoroethylene). An enlargement or a collar whose radial extent may be a multiple of λ/2 may be wider than 1.31 mm on the cone, i.e. on the generated surface of a conical or cylindrical adaptation apparatus. The radial extent may essentially be at a right angle to the longitudinal axis of the adaptation apparatus. An O-ring, which for sealing in axial direction of the waveguide may be arranged in front of or behind the collar, may be easily affixable and may according to the rules of high-frequency technology (i.e. in a HF technical way) reduce the interference influences on the propagation of a high-frequency wave. 
     In order to achieve a predetermined sealing effect, the cord thickness (Schnurstaerke) of an O-ring can be varied. “Cord thickness” may refer to the diameter of the part of an O-ring that is filled with substance and material, respectively. 
     The axial arrangement of an O-ring on the enlargement may simplify installation of the O-ring when compared to a radial arrangement of the O-ring. By the axial arrangement or the axial installation of the O-ring, it may be prevented that the O-ring may be stretched open too far or too wide, respectively until the O-ring may be installed. 
     Furthermore, the axial arrangement of the O-ring may prevent the O-ring having to be selected so as to be large in relation to the hollow conductor. This may prevent the signal path of the HF wave from being interfered with by the sealing, and may prevent the occurrence of interfering reflections. 
     The W-band may be the range of the electromagnetic spectrum that extends from 75 to 110 GHz (gigahertz). 
     A frequency at which an electromagnetic wave may be transmitted may be interpreted as being a frequency band. For example, a transmission frequency of 79 GHz may mean that an electromagnetic wave may be transmitted at a centre frequency of 79 GHz, and may comprise a bandwidth of, for example, ±2 GHz around the centre frequency. A frequency band may be a range of frequencies. 
     Information in this document that may refer to λ, λ/2 or λ/4 may assume to be related to a centre frequency of a frequency band, and in particular to a wavelength that may be associated with this centre frequency. 
     It would also be imaginable that the adaptation apparatus may be suitable for use in the K-band, i.e. from 23 GHz-27 GHz. 
     According to a further aspect of the present invention, an adaptation apparatus may be created, wherein the space at which the short circuit may be kept by the adaptation apparatus may exceed λ/2. In other words, the space or distance may be greater than λ/2. 
     At small wavelengths the adaptation apparatus may be able to be dimensioned in such a way that a sealing, for example an O-ring, can be arranged on the enlargement. In the case where small wavelengths are used, the adaptation apparatus may be dimensioned such that the sealing can be arranged at the enlargement. 
     According to a further aspect of the present invention, the space may be an integral multiple of λ/2. 
     A short circuit that may be kept spaced apart from the generated surface, which space corresponds to an integral multiple of λ/2, may also be transformed to an apparent short circuit on the generated surface, like a short circuit at a space, which space essentially may correspond to λ/2. The effect of a space of λ/2 may essentially correspond to the effect of a space of an integral multiple of λ/2. 
     According to another exemplary embodiment of the present invention, an angle of 90° may be formed between the generated surface of the closing-off body and the enlargement. 
     The form of the closing-off body may thus be a cylinder form or a rectangular form that can be arranged in a round hollow conductor and in a rectangular hollow conductor, respectively. 
     According to yet another exemplary embodiment of the present invention, an obtuse angle may be formed between the generated surface of the closing-off body and the enlargement. 
     The shape of the closing-off body may thus be a conical shape which can be arranged in a hollow conductor of any desired cross section. 
     According to a further aspect of the present invention, an adaptation apparatus may be created that comprises a seal, a sealing or a sealing arrangement, wherein the seal is arranged in front of and/or behind the enlargement when viewed in the direction of propagation of an electromagnetic wave. 
     The enlargement may represent an attachment option for the seal. 
     According to another aspect of the present invention, the seal may rest against the enlargement. 
     The seal, sealing arrangement or the O-ring may rest against the enlargement. The seal may thus be in contact with the enlargement. As a result of this contact the sealing effect may be increased. A flow of substance and a flow of material, respectively along the enlargement in the direction of the longitudinal axis of the adaptation apparatus may essentially be suppressible. 
     According to yet another aspect of the present invention, the seal may rest against the generated surface. 
     The seal resting against the generated surface may essentially suppress a material stream along the generated surface in a direction parallel to the longitudinal axis of the adaptation apparatus. 
     According to yet another aspect of the present invention, the generated surface of the closing-off body may be selected from the group of generated surfaces consisting of a cone surface, a cylinder surface, a rectangle surface and a pyramid surface. 
     Any combination of the generated surfaces may be imaginable, too. The various shapes may allow adapting the closing off body to the shape of the waveguide. Furthermore, the shapes may essentially reduce reflections of electromagnetic waves. 
     According to another aspect of the present invention, the adaptation apparatus in a non-compressed state or in a relaxed state comprises a radial enlargement whose length may essentially be λ/2. 
     When the enlargement may have a length of λ/2 the enlargement may keep the short circuit at a space of λ/2 and at a distance of λ/2, respectively even if the space of the short circuit were to be enlarged or reduced by an external force without the presence of the enlargement. The enlargement may thus also serve as a support that maintains the space of λ/2. The length of the enlargement may be λ/2 also in the installed state. As a result of these measures the space of λ2 may be able to be set more precisely. 
     Many improvements and further developments, respectively of the invention may have been described with reference to the adaptation apparatus. These embodiments may also apply to the antenna arrangement, the measuring device and the method for closing off a waveguide. 
     It should be noted that different aspects of the invention have been described with reference to different subject-matters. In particular, some aspects have been described with reference to apparatus type claims, whereas other aspects have been described with reference to method-type claims. However, the skilled person can see from the above description and from the description below that, unless otherwise described, additional to each combination of features which belong to a category of subject-matters, any combination of features that relate to different categories of objects should be considered to be disclosed. In particular, combinations of features of apparatus type claims with features of method type claims are also disclosed. 
     According to a further aspect of the present invention, the measuring device may be selected from the group of measuring devices consisting of a fill-level measuring device, flow-through measuring device, pressure measuring device, a radar measuring device, a measuring device based on the principle of the guided microwave, a fill-level radar which operates in pulse mode or as an FMCW (frequency-modulated continuous wave) device, a delay measuring device and a transit-time measuring device (Laufzeitmessgerät). 
     By means of an axial arrangement of a sealing ring, antenna systems or antenna arrangements for a fill-level radar may be built that in spite of their compact design and small dimensions, respectively combine good sealing characteristics with good electrical characteristics. 
     The small design may be caused by the high frequency of an electromagnetic wave that is used. 
     As far as the electrical characteristics are concerned, lower performance losses of the echo amplitude when compared to those with radially affixed O-rings may be achieved. Furthermore, any tendency to “antenna ringing” (Antennenklingeln) or “ringing” may be low because the sealing ring may be arranged outside the direct signal path of the electromagnetic wave, and thus the influence of the material characteristics and of the material properties, respectively of the sealing ring may be reduced. “Ringing” may essentially be caused by undesired reflections on the sealing ring, but it can, for example, already arise at transition locations within the antenna (for example between the PTFE tip and the air-HL (air-hollow conductor)). Antenna ringing may be interference caused by reflections at an end of the antenna. 
     It may not be necessary to use special materials for hollow conductor and adaptation cones, but instead, for example, commonly used materials such as steel and PTFE can be used. Hollow conductors and adaptation cones may thus be producible simply and economically as turned parts. Thanks to the applied construction of the adaptation cone, commercially available sealing rings of any materials may be usable. Installation of an antenna arrangement according to the invention may be easy and may be able to be carried out without a special tool (e.g. a press tool). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Below, advantageous exemplary embodiments of the present invention are described with reference to the figures: 
         FIG. 1  shows a lateral view of an adaptation apparatus according to an exemplary embodiment of the present invention. 
         FIG. 2  shows a lateral view of a further adaptation apparatus according to an exemplary embodiment of the present invention. 
         FIG. 3  shows a longitudinal section of an antenna arrangement with the adaptation apparatus of  FIG. 2 , according to an exemplary embodiment of the present invention. 
         FIG. 4  shows a longitudinal section of an antenna arrangement with the adaptation apparatus of  FIG. 1 , according to an exemplary embodiment of the present invention. 
         FIG. 5  shows a perspective view of the antenna arrangement of  FIG. 4 , according to an exemplary embodiment of the present invention. 
         FIG. 6  shows a longitudinal section of a further antenna apparatus with the adaptation apparatus of  FIG. 2 , according to an exemplary embodiment of the present invention. 
         FIG. 7  shows an antenna arrangement in which the collar of an adaptation element has been pressed onto (verpresst) the flange of an antenna horn, according to an exemplary embodiment of the present invention. 
         FIG. 8  shows the antenna arrangement of  FIG. 7 , wherein between the collar of the adaptation element and the flange of the antenna horn a disc is arranged according to an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The drawings in the figures are schematic respectively diagrammatic and not-to-scale. In the following description of  FIGS. 1 to 8  the same reference numerals are used for identical or corresponding elements. 
       FIG. 1  shows a lateral view of an adaptation apparatus  100 . The adaptation apparatus  100  is not only adapted for separating two spaces, e.g. an internal space and an external space of a container; but the adaptation apparatus  100  is also adapted to effect little influence on an electromagnetic wave. Since little influencing of an electromagnetic wave, in particular of a high-frequency electromagnetic wave (HF-wave), is achievable if the adaptation apparatus  100  comprises conical ends or tapering ends, the adaptation apparatus  100  is also referred to as an adaptation cone  100 . 
     The adaptation apparatus  100  can be a rotationally-symmetrical turned part that is, for example, made of PTFE. In the case of rotational symmetry, the rotational axis may be parallel to the longitudinal axis of the adaptation apparatus  100 . The adaptation apparatus  100  further comprises a first conical end  103  and a second conical end  104 . The two conical ends are arranged on the circular collar  101 , on the ring-shaped enlargement  101  or on the circular flange  101  with their bases or with their base areas, wherein in the case of single-piece production the bases are no longer recognisable. 
     The first conical end  103  and the second conical end  104  form, for example, a closing-off body. 
     The enlargement  101  is an HF choke  101  and the enlargement  101  is used in order to affix respectively to mount a seal in axial direction. By means of the axial seal a small sealing effect that the enlargement  101  may achieve on its own may be increased. 
     In other words, the enlargement  101  essentially blocks a flow of a fluid along the generated surface  102 ,  107  of the two conical ends  103 ,  104 . In order to prevent a fluid from being able to spread around the enlargement, a seal is arranged in axial direction on the enlargement  101 . In particular, for sealing on the enlargement  101  a seal, for example an O-ring, is arranged. However, in  FIG. 1  the seal is not shown. 
     The enlargement  101  may increase the area to which a seal can be affixed. In an installed state the seal may come to rest between the enlargement and a waveguide or the external conductor of a waveguide. If the seal is jammed by pressure between the enlargement  101  and the waveguide, the sealing effect of the seal may be increased. 
     The bases of the two conically shaped ends  103 ,  104  follow on directly from the enlargement  101 . I.e. the bases of the two conical ends  103 ,  104  are directly joined to the enlargement  101 . The enlargement is arranged at a right angle to the longitudinal axis of the adaptation apparatus  100 . Thus respective angles  105 ,  106  result between the conical ends  103 ,  104  and the enlargement  101 , which angles  105 ,  106  exceed 90°, i.e. are obtuse angles. 
     In order to increase the sealing effect, in axial direction in front of or behind the collar  101  a sealing ring, for example an O-ring, can be arranged firmly fitting to the collar  101 . In other words, the sealing can be arranged so as to rest firmly against the collar  101 . 
     The enlargement  101  has a space w, a distance w or a length w from the outermost generated surface of the base of the first conical end  103  of more than λ/2. Thereby, λ denotes the wavelength of an electromagnetic wave which also, like the fluid, propagates essentially parallel to the symmetry axis of the adaptation apparatus. The length w can be any multiple of λ/2. Depending on the direction of view from which the enlargement  101  is viewed, the extent w of the enlargement can be designated the width w or length w. In a direction perpendicular to the longitudinal axis of the adaptation apparatus  100 , the enlargement  101  may have the length w. When viewed in longitudinal direction, the enlargement  101  may have the width w. 
     In this arrangement the width w, the length w or the radius w may be selected such that an apparent short circuit to the HF, which apparent short circuit is located at the end of the enlargement  101 , which end is furthest away from the longitudinal axis of the adaptation apparatus, is transformed to an apparent short circuit on the outermost generated surface of the first conically shaped end  103  or generally on the outermost generated surface of the closing-off body. As a result of this transformation, essentially interference-free propagation of an electromagnetic wave may take place because the HF choke  101  in the corresponding frequency band or at a corresponding centre frequency is practically essentially not visible respectively invisible to HF and therefore essentially causes no interference, or at least only little interference as a result of reflections. 
     The thickness h of the enlargement  101  in axial direction relative to the longitudinal axis of the adaptation apparatus is λ/4 or a value very close to λ/4 (λ/4 plus/minus 10%, i.e. from 0.9 λ/4 to 1.1 λ/4). Other values, e.g. 3 λ/4 or still other values are imaginable, however, certain interference can then occur in the form of reflections and/or attenuation. The shape of the enlargement  101  can be ring-shaped, rectangular, polygonal or oval. 
     As an alternative, the first conically shaped end  103  or the second conically shaped end  104  can be pyramid-shaped. If the adaptation apparatus  100  is used for a rectangular hollow conductor, the base area of the first conically shaped end and of the second conically shaped end can correspond to the shape of the rectangular hollow conductor. The dimensions can depend on the wavelength λ. In the case of a round hollow conductor the base area or the closing-off body  102 ,  107  can be round. 
     In the arrangement according to  FIG. 1 , the adaptation apparatus  100  is shaped in such a way that the adaptation apparatus  100  essentially does not interfere from a HF-technical view, and that the antenna system can nevertheless efficiently be sealed. As a result of the enlargement  101  of the adaptation apparatus in the form of a collar  101 , sealing takes place at said collar  101  so that the seal essentially does not interfere in the actual signal path. In other words, the S-parameter S 11 , i.e. reflection attenuation or return-flow attenuation, may have a low value. 
     The space from the tip or from the peak of the first conically shaped end  103  to the base of the first conically shaped end  103  is smaller than the space from the tip or from the peak of the second conically shaped end  104  and the base of the second conically shaped end  104 . Consequently the angle at the tip of the first conically shaped end  103  is more obtuse than the angle at the tip of the second conically shaped end  104 . 
     The adaptation apparatus  100  according to the present invention also makes it possible for an antenna system to be sealed efficiently even in the W-band, without significantly influencing the HF. 
     The enlargement  101  is not limited to λ/2; instead it can also exceed λ/2. The enlargement can, for example, also be a multiple of λ/2. 
       FIG. 2  shows a further adaptation apparatus  200 . As far as the adaptation cone  200  or the adaptation apparatus  200  is concerned, the description of the adaptation cone  100  of  FIG. 1  essentially applies. The adaptation cone  200 , too, comprises a first conically shaped end  203  and a second conically shaped end  204 . Likewise the flange  201 , the enlargement  201 , the shoulder  201  or the collar  201  can be recognized, which is arranged between the two conically shaped ends  203 ,  204 . 
     In contrast to  FIG. 1 , from  FIG. 2  additionally it can be recognized that between the flange  201  and the first conically shaped end  201  the first cylinder region  207  of the closing-off body is arranged. Furthermore it can be recognized that between the second conically shaped end  204  and the flange  201  the second cylinder region  208  of the closing-off body is arranged. In other words this means that in each case the closing-off body comprises a cylinder region  207 ,  208  and a conically shaped end  201 ,  204 . 
     The closing-off body is designed as a solid body. 
     Between the generated surface  211  of the first cylinder region  207  and the enlargement  201  a first right angle  205  can be recognized. Between the generated surface  212  of the second cylinder region  208  and the enlargement  201  the second right angle  206  can be recognized. 
     The enlargement  201  extends along the length w or across the width w, which is λ/2 or a multiple of λ/2. 
     The shape  211  of the generated surface of the first cylinder region  207  and the shape of the generated surface  212  of the second cylinder region  208  can be adapted to the shape of a hollow conductor. Furthermore, the shape of the generated surface  211  of the first cylinder region  207  and the shape of the generated surface  212  of the second cylinder region  208  can be adapted to the shape of the base of the first conically shaped end  203 . Thus an essentially continuous transition between the generated surface  209  of the first conically shaped end  203  and the generated surface of the first cylinder region  207 , as well as between the generated surface  210  of the second conically shaped end  204  and the generated surface of the second cylinder region  208  is possible. 
     The first cylinder region  207  and the second cylinder region  208 , respectively can, independently of each other, be a regular cylinder respectively a circular cylinder or a rectangular cylinder. 
     The first cylinder region  207  is longer than the second cylinder region  208 . 
     The adaptation apparatus  100  as well as the adaptation apparatus  200  can be configured in one part, in a single part or in several parts. In the case of a single-part construction the adaptation apparatus  100 ,  200  is, for example, produced as a turned part or an injection part. 
     In the case of a two-part construction, the two halves are separated or cut apart along a perpendicular separation plane to the longitudinal axis of the adaptation apparatus  100 ,  200 . In this arrangement the separation plane can extend through the enlargement  101 ,  201 , can be situated between the enlargement  101 ,  201  and the first conically shaped end  103 ,  203 , or can be situated between the enlargement  101 ,  201  and the second conically shaped end  103 ,  203 . 
       FIG. 3  shows a longitudinal cut through an antenna arrangement  302  with the adaptation apparatus  200  of  FIG. 2 .  FIG. 3  shows the way the adaptation cone  200  is built into an antenna system  302 . 
     The antenna system  302  or the antenna arrangement  302  comprises the hollow conductor  300  and the antenna horn  301 . The antenna horn  301  comprises a funnel-shaped enlargement. The antenna horn  301  can comprise a rectangular or round cross section. The hollow conductor  300 , in particular the external conductor  300  of the hollow conductor, the antenna horn  301  and the adaptation apparatus  200  can be rotationally symmetrically built. The associated symmetry axes extend parallel to the longitudinal axis of the adaptation apparatus  200  and essentially determine the direction of propagation of an electromagnetic wave. 
     Generally speaking, in this document the term “direction of propagation” may refer to the direction of a wave, which direction is directed towards a material and a good, respectively, wherein the distance from the good is to be measured. In the direction that is opposite this direction a reflected wave may travel. In  FIG. 3  the direction of propagation is designated by the arrow  305 . 
     Both the antenna horn  301  and the hollow conductor  300  are filled with air. However, any desired material, in particular any desired dielectric material, can be used for filling. 
     The adaptation device  200  and adaptation apparatus  200 , respectively, in particular by means of the enlargement  201  and by means of the closing-off body, essentially blocks the connection between the antenna horn  301  and the hollow conductor  300  to penetration by a fluid. The first conically shaped end  203  projects into the hollow conductor  300  and the second conically shaped end  204  projects into the antenna horn  301 . The shape of the adaptation apparatus  200  is adapted such that in the case of an arrangement of the adaptation device  200  in the antenna arrangement  302  reflection arises as low as possible, i.e. that the S 11  value or S 11  wave parameter is as low as possible, while the width w of the collar  201  or the width w of the collar measured from the generated surface  211 ,  212  of the closing-off body has a multiple of λ/2. One example of a value of the S-parameter S 11  is −20 dB. At this value, essentially only a hundredth of the fed-in power may be reflected back. 
     Expressed as an equation this means that 
         w=nλ/ 2; n=2, 3, 4, 5, 6, . . . or  w=nλ/ 2; n=1, 2, 3, 4, 5, 6, . . . . 
     The collar width w, i.e. the radial expansion of the enlargement  101 ,  201  can exceed λ/2. In particular, the collar width w can also be a multiple of λ/2. The enlargement  201 ,  101  can also be referred to as a radial enlargement. In axial direction the radial enlargement has a thickness h. The thickness h of the radial enlargement can be in the range of λ/4. 
     For reasons of diffusion density it can, for example, be necessary to select the thickness of the collar  101 ,  201  so that it is thicker than λ/4, wherein care is to be taken that the S 11  parameter is still below a predetermined maximum value. 
     The sealing ring  303 ,  304  or the sealing rings  303 ,  304  can be mounted either in front of or behind the collar  101 ,  102 , the enlargement  101 ,  102  or the HF choke  101 ,  102 . It is also imaginable to mount a single seal  303 ,  304  or several seals  303 ,  304  in front of or behind the expanded section  201 . 
     Any commonly used types of seals are imaginable for sealing, for example, one, a single, two or several O-rings. For example, an O-ring can also be arranged in a notch in one of the conical ends  102 ,  107 ,  209 ,  210 , on the first cylinder region  207  in a notch, and/or on the second cylinder region  208  in a notch. A notch can, for example, be designed as a groove, narrowing or recess. 
       FIG. 4  shows a longitudinal section of an antenna arrangement  402  with the adaptation apparatus  100  or the adaptation cone  100  from  FIG. 1 . 
     A wave propagation direction, or the direction of the longitudinal axis is indicated by the arrow  404 . 
     Similar to  FIG. 3 , in  FIG. 4  the adaptation apparatus  100  is arranged between the hollow conductor  400  and the antenna horn  401 . 
     The longer second conically shaped end  107  projects into the funnel-shaped antenna horn  401 , while the shorter first conical end  102  projects into the hollow conductor  400 . 
     The hollow conductor  400  and the antenna horn  401  are filled with air; however they can be filled with any desired dielectric material. Between the hollow conductor  400 , in particular the external conductor  400  of the hollow conductor and the antenna horn  401 , there may be formed a gap  405 . This gap may facilitate or may ease installation and de-installation of the antenna arrangement  402  for assembly and disassembly of the adaptation apparatus  100 . However, in the installed state the gap  405  may be so small that essentially a short circuit for an electromagnetic wave of a predetermined frequency can arise. 
     The antenna arrangement  302 ,  402  is arranged in an installed state on an external wall of the container in such a way that the funnel-shaped antenna horn  401  projects into the interior of the container, and the hollow conductor  300 ,  400  projects from the container so that a further conductor, in particular a further hollow conductor, can be connected to the hollow conductor  300 ,  400 . This further conductor can, for example, be used to feed waves to the hollow conductor, or it can be used as an HF injection (HF Einkopplung) and input coupling, respectively. 
     The HF-signal of the microwave module is coupled respectively injected into the hollow conductor. As a rule, the hollow conductor is stimulated in the base mode so that essentially only one mode is able to propagate. I.e. essentially only a single mode is able to propagate. In the case of the round hollow conductor this is the H 11  mode. 
     The cross-sectional area of the first cylinder region  207  or of the second cylinder region  208  or the base area or the base of the first conically shaped end  103 ,  203  or the base area and base surface, respectively of the second conically shaped end  104 ,  204  is aligned to the dimensions of the hollow conductor  300 ,  400 . The cross-sectional area or the base area thus depends on the wavelength λ that is to be transmitted in the hollow conductor  300 ,  400 . 
       FIG. 5  shows a perspective view of the antenna arrangement of  FIG. 4 , according to an exemplary embodiment of the present invention. The diagram shows the generated surface of the funnel-shaped antenna horn  401  can be recognized that forms the continuation of the hollow conductor  400 . 
     The antenna arrangement  402  can be regarded as a waveguide. The waveguide can comprise an antenna horn  401  and a hollow conductor  400 . 
       FIG. 5  also shows the axial arrangement of the sealing ring  403  on the enlargement  101  can be seen. The coordinate system  500  shows that the longitudinal axis of the adaptation apparatus  100  extends through the tips of the adaptation apparatus in the z-direction. In this diagram the z-axis also denotes the direction of the longitudinal axis of the adaptation apparatus. 
       FIG. 6  shows a longitudinal section of a further antenna arrangement  602  with the adaptation apparatus  200  of  FIG. 2 . Similar to  FIG. 3  the adaptation apparatus  200  is shown arranged in the hollow conductor  300  and in the antenna horn  301 . On the enlargement  201  on the same side the first sealing ring  600  and the second sealing ring  601  are arranged. 
     In order to arrange the first sealing ring  600 , in the external conductor  300  of the hollow conductor a rectangular recess or groove is installed which comprises smaller dimensions than the cord thickness of the first sealing ring  600  so that the first sealing ring  600  is compressed. Likewise, around the second sealing ring  601  a second rectangular recess is formed in the hollow conductor  300 , which recess accommodates the second sealing ring. 
     Antenna systems or antenna arrangements  302 ,  402  should be arranged in such a way that they comprise good impedance matching of electrical transitions, for example the transition between a connection line or HF feed and a hollow conductor  300 ,  400 ; between a hollow conductor  300 ,  400  and an antenna  301 ,  401 ; or between antenna  301 ,  401  and air, in order to obtain interference reflection as low as possible. 
     Furthermore, an antenna arrangement  302 ,  402  should be adapted in such a manner as to make possible essentially complete sealing of a container to the outside. 
     As the frequency increases (&gt;6 GHz) the requirements concerning antenna arrangements can possibly be met only with difficulty. Arrangements comprising radial sealing rings on the adaptation cone  100 ,  200  of the antenna feed-in and antenna input coupling, respectively can comprise performance losses in these frequency ranges. The performance losses and power losses, respectively can be caused in that the dimensions of the mechanical parts such as hollow conductor  300 ,  400 , adaptation cone  100 ,  200  etc. become progressively smaller when increasing the frequency. At the same time a sealing ring (O-ring)  304 ,  303 ,  403  should be adapted in such a way that it has a particular cord thickness and thus ensures a reliable sealing. 
     Despite the reduction in the wavelength in the region of higher frequencies, the size of a sealing ring and thus the size of the recess (Einstich) remains unchanged. As a result of the reduction in the wavelength in the region of higher frequencies, the recess or the groove in which a sealing ring  304 ,  303 ,  403  is arranged relative to the diameter of the cylinder  207 ,  208  of the adaptation cone  100 ,  200  already becomes such large that the recess can interfere with the propagation of the electromagnetic wave. Depending on the material characteristics and the material properties, respectively of the sealing ring, the echo amplitude of an electromagnetic wave can be attenuated. Furthermore, “ringing”, i.e. an undesirable reflection, can make itself felt. 
     A hollow conductor  300 ,  400  with an adaptation cone  100 ,  200  in which the sealing ring  303 ,  304 ,  600 ,  601  is axially attached can reduce attenuation of the echo amplitude or “ringing”. In an axially attached O-ring  303 ,  304 ,  600 ,  601  the O-ring with its partly negative electrical characteristics is essentially outside the direct signal path of an electromagnetic wave. 
     In order to implement an arrangement of the sealing ring  303 ,  304 ,  600 ,  601  outside the signal path, a thickened section  101 ,  201  or an enlargement  101 ,  201  at the adaptation cone  100 ,  200  can be used. The thickness h of this widened section should be in the range of λ/4. At the position of the thickened section  101 ,  201 , the radius of the adaptation cone  100 ,  200  is increased by w=λ/2 or by a multiple of λ/2. 
       FIG. 7  shows an antenna arrangement  706  in which the adaptation element  701 , in particular the collar  708  of the adaptation element  701 , or a seal  703  that is arranged on the collar  708  of the adaptation element, is pressed together with the flange  707  of the antenna horn  700 . The adaptation cone  701  comprises a rectangular end and a pointed end, wherein the rectangular end is adapted to accommodate the HF input coupling (high-frequency input coupling)  705 . 
     The adaptation cone  701  can be made from any material with dielectric properties. The sealing ring  703 , which is arranged in the ring-shaped groove  702 , can consist of any materials commonly used in sealing rings. For example, elastomers can be used in the production of the sealing rings  303 ,  304 ,  403 ,  600 ,  601 ,  703 . Elastomers are elastic materials. As a result of the axial arrangement of the sealing ring it is, however, possible to use non-elastic sealing rings  303 ,  304 ,  403 ,  600 ,  601 ,  703  or rigid sealing rings  303 ,  304 ,  403 ,  600 ,  601 ,  703 , e.g. made of metal or FEP (perfluoroethylene propylene copolymer) encased elastomers. 
     The recess  702  or the groove  702  for the sealing ring  703  is made in the hollow conductor in such a way that the O-ring  703  used is approximately situated in the middle of the thickened part  708 , in particular in the middle of the length w of the thickened part  708  (Verdickung), and rests against the inside of the hollow conductor  704  in such a way that the sealing ring  703  seals towards the rear (i.e. in the direction of the HF input coupling  705 ). 
     In the antenna arrangement  706  of  FIG. 7  the O-ring  703  is directly pressed together with the flange  707  of the antenna horn  700 . 
       FIG. 8  shows an antenna arrangement  801  in which a disc  800  is arranged between the hollow conductor  704  and the antenna horn  700 . In contrast to  FIG. 7 , in  FIG. 8  there is a disc  800  available. The disc  800  is arranged between the collar  708  of the adaptation element  701  and the flange  707  of the antenna horn  700 . 
     In the antenna arrangement  801  the O-ring  703  is pressed (verpresst) with the aid of an additional disc  800 , for example a metal ring  800 , which disc  800  is attached to the hollow conductor  704  by means of countersunk screws. In other words, the O-ring  703  is pressed into the groove  702  of the hollow conductor  704  by pressure that is exerted by the enlargement  708 . The pressure of the enlargement  708  is generated by a disc  800  that is pressed against the enlargement  708  by means of countersunk screws (not shown in  FIG. 8 ). In this way the adaptation cone  701  is secured against falling out. During a change of the antenna horn  700 , the danger of the adaptation cone  701  falling out of the hollow conductor  704  can be reduced. 
     In addition, it should be pointed out that “comprising” does not exclude other elements or steps, and “a” or “one” does not exclude a plurality. Furthermore, it should be pointed out that characteristics or steps which have been described with reference to one of the above exemplary embodiments can also be used in combination with other characteristics or steps of other exemplary embodiments described above. Reference numerals in the claims are not to be interpreted as limitations.