EP2262059B1 - Dielectric antenna - Google Patents

Description

The invention relates to a dielectric antenna having a dielectric feed section, a first transition section comprising a dielectric rod, a second transition section forming a dielectric horn and a dielectric emission section, the supply section being exposed to electromagnetic radiation, electromagnetic radiation with the first transition section and the second transition section is feasible and the electromagnetic radiation from the radiating portion can be emitted as a free space wave.

Dielectric antennas per se have long been known and are used in a variety of configurations and sizes for very different purposes, such as in industrial process monitoring to determine distances - for example, media surfaces in tanks - on the transit time of reflected electromagnetic waves (radar applications). The invention described herein is completely independent of the field in which the subsequently treated antennas are used; By way of example, reference will be made below to the use of the antennas in question in the field of fill level measuring technology.

XP 575262 discloses a prior art dielectric antenna

In the case of dielectric antennas known from the prior art, the emission section and the second transition section forming a dielectric horn coincide and are usually referred to as horn antennas, also referred to as horn radiators in the transmission case. Via a metallic waveguide, such a dielectric antenna with a TE-wave or a TM-wave is fed, such. B. with a TE ₁₁ wave (equivalent to H ₁₁ wave), the electric field strength thus has no share in the propagation direction of the electromagnetic wave. The electromagnetic wave guided by the waveguide propagates via the dielectric feed section into the first transition section comprising the dielectric rod and from there into the further second transition section forming a dielectric horn and becomes the aperture of the second transition section, ie in this case forms the radiating section, continued In contrast to the widespread horn antennas with a metallic wall, dielectric antennas, on the other hand, essentially consist of a body of dielectric material, electromagnetic waves also being guided in the material and being radiated over the material in the emission direction , By "emission direction" is here meant essentially the main emission direction of the dielectric antenna, ie the direction in which the directivity of the dielectric antenna is particularly pronounced.

Dielectric antennas are often used in industrial process measurement technology - as mentioned above - for level measurement. In such applications, it is of particular advantage if the antennas used have the smallest possible main emission direction and at the same time the most compact possible design. However, these requirements are contradictory with regard to the constructive measures that usually have to be taken for their technical implementation.

A narrow directional characteristic in the main emission direction can, as is known, only be achieved by a large aperture-that is, aperture area-of the emission section, which necessitates a large expansion of the antenna perpendicular to the main emission direction. In order for the aperture to also be used in the sense of a narrow main emission direction, the electromagnetic radiation emitted by the emission section must have as flat a phase front as possible, such a planar phase front usually only being able to be realized with increasing length of the antenna, which also counteracts the desired compact design. In the field of level measurement, an additional problem often is that the geometric aperture can only be increased within narrow limits, otherwise the antenna is no longer in the volume to be monitored -. B, over existing tank openings and nozzles - introduced and can not be mounted there. Furthermore, owing to the geometric conditions of the installation situation, electromagnetic waves must be conducted with low-emission through installation geometries in order to prevent parasitic tank installation reflections which lead to a distortion of the useful signal

It is therefore an object of the present invention to provide a dielectric antenna which is as low loss adaptable to different installation situations, which is also possible low reflection and at the same time hochbündelnd.

The above-derived and described object is according to the invention a dielectric antenna according to claim 1. In the dielectric antenna according to the invention, the second transition section thus acts as a "real" transitional section between physically separate regions of the dielectric antenna, namely between the first transition section comprising a dielectric rod radiation section. The continuation of the electromagnetic waves over the emission-side dielectric tube has the advantage that with optimal - ie modest-pure - excitation a considerable variability of the length of the dielectric antenna is achieved.

In an advantageous embodiment of the dielectric antenna according to the invention, it is provided that the wall thickness of the dielectric tube forming the emission section is selected to be such that only electromagnetic waves in the hybrid fundamental mode HE ₁₁ are propagated along the dielectric tube. In this case, it has been recognized that the rod geometry of the dielectric antenna in the first transition section and the tube geometry in the emission section of the dielectric antenna in the electromagnetic sense represent self-wave systems, along which each field distribution can be represented as a superposition of individual eigen waves. The fundamental mode is hybrid in the two systems and is referred to as the HE ₁₁ mode. With the inventively designed thin-walled dielectric tube, the highest directivity for a given maximum outer diameter of the tube can be achieved and at the same time a fashion-pure guidance of the electromagnetic waves is achieved.

The second transition section, which forms a dielectric horn, thus represents a waveguide transition between two different self-wave systems, the transitions from the rod-shaped first transition section into the second transition section and from the second transition section in the dielectric emission section for the guided electromagnetic waves represent discontinuities which are sources of higher order field distributions. If the higher modes excited by the discontinuities are below the cut-off frequency of the self-wave systems of the dielectric antenna, the higher modes can not be guided along the dielectric structures, but the associated electromagnetic radiation radiates directly into the discontinuity at the location of the discontinuities Free space, which leads to a curvature of the phase fronts and thus to a reduction in the directivity of the antenna.

The above-mentioned phenomenon is counteracted by a further advantageous embodiment of the dielectric antenna according to the invention, characterized in that the dielectric horn comprising second transition portion has a non-linear, increasingly in the emission direction inner contour, said inner contour usually the interface of the dielectric horn to a forms cavity enclosed by the dielectric horn. As a result of the non-linear inner contour of the second transition section comprising the dielectric horn, a mode purity with a comparatively short second transition section in the axial direction-main emission direction-can be achieved compared to linear second transition sections which are otherwise relatively long in the axial direction. By means of the aforementioned measure, shortening of the second transition section forming a dielectric horn can be achieved by more than a third of the length otherwise necessary for a linear horn.

Such inner contours have been found to be particularly suitable, which can be described by a power function with fractional exponent greater than one, these power functions having as an independent variable the spatial coordinate of the antenna extending in the main emission direction. Preferably, the exponent chosen is a value in the range between 1.09 and 1.13, more preferably a fractional exponent in the range of 1.10 to 1.12, preferably an exponent of substantially 1.11. In this case, the zero point of the aforementioned spatial coordinate can also be displaced into the first transitional section, which comprises a dielectric rod. In this context, it is particularly advantageous if the inner contour of the dielectric horn of the second transition section in the first Transition-forming dielectric rod continues, in particular, namely steplessly continued in the first transition portion forming dielectric rod. This means that, in particular, a cavity within the dielectric antenna continues into the dielectric bar of the first transition section.

The inner contour of the dielectric rod is preferably also described by a power function with fractional exponent greater than one, the power function again having as independent variable the spatial coordinate pointing in the main emission direction of the antenna, and the fractional exponent being preferably in the range from 1.09 to 1.13, in particular in the range 1.10 to 1.12 and very particularly preferably substantially has the value 1.11. The discontinuity between the first transition section and the second transition section is least when the inner contour of the first transition section comprising the dielectric rod and the inner contour of the second transition section comprising the dielectric horn are described by the same power function.

The teaching of the invention in connection with the inner contour of the first transition section and the inner contour of the second transition section also achieved detached from the teachings of the invention described above, the desired effect of increased directivity in a more compact design, ie not only in such dielectric antennas, the one as a dielectric Having tube configured radiating portion, however, both aspects can be advantageously realized together.

In the course of development of the above-described dielectric antennas, it has been recognized that optimizing the antenna design with respect to the radiation characteristic results in excellent bundling characteristics, but internal reflections of electromagnetic radiation can cause spurious signals and the resulting "antenna ringing" can lead to measurement errors. In order to prevent unwanted antenna-inherent reflections, it is therefore provided in a particularly advantageous embodiment of the dielectric antenna according to the invention that the inner contour of the first transition section comprising the dielectric rod has a stepped impedance converter in the transition to the feed-side full-bar region forms according to the principle of a quarter-wave transformer, in particular namely a single-stage impedance converter. It has been found that this wideband suppression of reflections can be significantly increased without affecting the desired field distribution negative.

A further stepped impedance converter, in particular simply stepped, is preferably provided in the transition of the emitting section designed as a dielectric tube into the free space. According to a particularly preferred embodiment, it is provided that the dielectric feed section is formed as a stepped impedance converter according to the principle of a quarter-wave transformer, in particular as a two-stage impedance converter, which achieves better results in the transition region of a metal waveguide usually used on the dielectric feed section as a single-stepped impedance converter , The stepped impedance converter provided in the dielectric feed section preferably has an inner contour with a cross-section which tapers in the emission direction, wherein preferably at least one step with an inner hexagonal profile is provided as the inner contour. The hexagon socket profile is particularly advantageous for mounting purposes, but it is also superior to other shapes from the electromagnetic point of view since it has the greatest possible robustness with respect to unknown angles of rotation.

A significant improvement of the transient reflection behavior can be achieved by a further design measure, namely, when the outer diameter of the feed section is selected such that in the assembled state of the antenna, a radial gap between the feed section and a feeding waveguide is formed, in which protrudes the feed section, in particular wherein the gap extends in the emission direction substantially over the axial extent - extension in the main emission direction - of the stepped impedance converter formed in the dielectric feed section. In conventional antenna dimensions with, for example, a solid rod diameter in the range of 22 mm, a gap width of about 1 mm has been reinforced.

The stepped impedance converters provided in the food area and in the first transition section also lead to reflection reductions in the case of dielectric Antennas which do not have a dielectric tube as the emission section are therefore to be understood as being independent of the feature of the emission section designed as a dielectric tube.

A further increase in directivity can be achieved in a preferred embodiment of the dielectric antenna according to the invention in that the dielectric rod is surrounded in the first transition section by a metallic horn projection opening in the emission direction of the antenna, wherein the metallic horn projection in particular neither into the region of in the dielectric feed section formed stepped impedance converter still extends into the region of the stepped impedance converter in the first transition section. By such a metallic Horn approach the directivity of the dielectric antenna according to the invention is further increased, since the fundamental mode of the electromagnetic radiation at the end of the metallic Horn approach coupled with causing minimal leakage in the desired HE ₁₁ -Stabmode. The opening inner contour of the metallic horn approach can be configured differently, is preferably designed linear, since with non-linear inner contours hardly improve the radiation characteristics can be achieved and linear inner contours are easier to produce.

Fig. 1

einen Querschnitt durch ein erstes Ausführungsbeispiel einer erfindungsgemäßen dielektrischen Antenne,

Fig. 2

einen Querschnitt durch ein zweites Ausfürungsbeispiel einer erfindungsgemäßen dielektrischen Antenne,

Fig. 3

schematisch eine erfindungsgemäße dielektrische Antenne mit dem gesamten erzeugten elektrischen Feld der abgestrahlten elektromagnetischen Strahlung in der E-Ebene, Modenfeld mit parasitärem Leckfeld,

Fig. 4a, 4b

die mit Ausführungsbeispielen erfindungsgemäßer dielektrischer Antennen erzielbare Direktivität gegenüber der Direktivität herkömmlicher Antennen und

Fig. 5

einen Querschnitt durch eine erfindungsgemäße dielektrische Antenne in Detailansicht.

In particular, there are now various possibilities for designing and developing the dielectric antennas according to the invention. Reference is made to the claims subordinate to claim 1 and to the description of preferred embodiments in conjunction with the drawings. In the drawing show

Fig. 1

a cross section through a first embodiment of a dielectric antenna according to the invention,

Fig. 2

a cross section through a second Ausfürungsbeispiel of a dielectric antenna according to the invention,

Fig. 3

schematically a dielectric antenna according to the invention with the entire generated electric field of the radiated electromagnetic Radiation in the E-plane, mode field with parasitic leakage field,

Fig. 4a, 4b

the achievable with embodiments of the invention of the dielectric antenna directivity over the directivity of conventional antennas and

Fig. 5

a cross section through a dielectric antenna according to the invention in detail view.

In the Fig. 1 and 2 FIG. 2 shows cross-sections of complete dielectric antennas 1, which have a dielectric feed section 2, a first transition section 3 comprising a dielectric rod, a second transition section 4 forming a dielectric horn, and a dielectric emission section 5, the dielectric feed section 2 being exposed to electromagnetic radiation 6, electromagnetic radiation 6 can be guided with the first transition section 3 and the second transition section 4, and the electromagnetic radiation 6 can be emitted by the emission section 5 as a free-space wave.

All in the Fig. 1 to 3 - Dielectric antennas 1 shown more or less faithfully - are characterized in that the emission section 5 is designed as a dielectric tube adjoining the second transition section 4. It is thereby achieved that the length of the dielectric antenna 1 can be varied within wide ranges, namely by different choice of the length of the first transition section 3 comprising the dielectric rod and by selecting the length of the radiating section 5 embodied as a dielectric tube. Both areas 3 and 5 are In the electromagnetic sense, self-wave systems with the second transition section 4 forming a dielectric horn as a waveguide transition between these different self-wave systems.

In all the exemplary embodiments illustrated, the wall thickness of the emission section 5 designed as a dielectric tube is selected such that only electromagnetic radiation 6 in the hybrid fundamental mode HE ₁₁ runs along the guided dielectric capable of propagation, so that the electromagnetic radiation 6 is basically pure state passed over the dielectric rod first transition section 3 and designed as a dielectric tube radiating section 5. The higher modes occurring at the discontinuity points are radiated directly into the free space at the location of the discontinuities, ie in particular in the region of the second transition section 4 forming a dielectric horn. The release of the parasitic electromagnetic leakage field is shown in FIG Fig. 3 can be seen, in which the maximum amplitude of the electric field distribution in the E-plane at 9.5 GHz is shown at a length of the radiation section 5 of 1500 mm. This tube length has been chosen so long only for purposes of illustration (about 50 λ), in order to detect a separation between guided and parasitically radiated field at all, since the wavenumbers of guided mode and free space field differ only very little.

In the in the Fig. 1 and 2 illustrated embodiments, the wall thickness of the dielectric tube of the Abstrahlabschnitts 5 is less than 5% of the outer diameter of the tube. In the present case, the outer diameter of the tube is 43 mm with a wall thickness of 2.0 mm, which, when using polypropylene (PP, Fig. 1 ) and polytetrafluoroethylene (PTFE, Fig. 2 ) and at an excitation frequency of 9.5 GHz leads to the desired selective transmission behavior.

The transmission behavior of the first, comprising the dielectric rod transition section 3 to the designed as a dielectric tube radiating section 5 is in the illustrated embodiments according to Fig. 1 and 2 in that the second transition section 4 comprising the dielectric horn has a nonlinear inner contour 8 which increasingly opens in the emission direction 7, the inner contour 8 being described by a power function with fractional exponent> 1 as a function of the spatial coordinate in the main emission direction 7 of the antenna 1 ; in the present case, the exponent has the value of essentially 1.1.

It has been found that in such a way as a dielectric horn configured second transition sections 4 to achieve a certain directivity of the dielectric antenna 1 can be formed considerably shorter than dielectric Antennas with a dielectric horn as a second transition section, which has a linear inner contour.

The antennas according to Fig. 1 and 2 is also common that the dielectric horn comprehensive second transition section 4 has a linear, opening in the emission direction 7 outer contour 9. It has been found that the shaping of the outer contour 9 is not decisive to the same extent for the transmission behavior of the second transition section 4 as the configuration of the inner contour 8; In that regard, the easiest to produce outer contour 9 has been chosen here.

wobei x die Ortskoordinate in Abstrahlrichtung 7 der Antenne und angebbar in Millimetern ist, und r(x) die Höhe der Innenkonturen 8, 10 über der Achse der unabhängigen Ortskoordinate x bezeichnet. Der Nullpunkt der Ortskoordinate x liegt hier 80 mm innerhalb des Übergangs des ersten Übergangsabschnitts 3 zum zweiten Übergangsabschnitt 4, wobei der als dielektrisches Horn ausgebildete zweite Übergangsabschnitt 4 eine Erstreckung von insgesamt 150 mm in Abstrahlrichtung 7 aufweist. Der sich daran anschließende, als dielektrisches Rohr ausgestaltete Abstrahlabschnitt 5 hat in Abstrahlrichtung 7 der dielektrischen Antenne 1 eine Erstreckung von lediglich 15 mm.Of very particular importance for the transmission behavior of the illustrated dielectric antennas 1, however, is that the inner contour 8 of the dielectric horn of the second transition section 4 continues in an inner contour 10 of the first transition section 3 forming the dielectric rod, namely in this case continuously in the first transition section 3 forming dielectric rod continues. In the illustrated embodiments, the inner contour 10 of the dielectric first connecting portion 3 and the inner contour 8 of the dielectric horn comprehensive second transition portion 4 is described by the same power function, whereby any discontinuities in the transition region between the first transition section 3 and the second transition section 4 are avoided , In the present case, the inner contours 8, 10 are described by the following equation: $$\mathrm{r}\left(\mathrm{x}\right)\mathrm{=}\mathrm{16}\mathrm{.}\mathrm{5}\mathrm{mm}\mathrm{*}{\left(\mathrm{x}\mathrm{/}\mathrm{230}\mathrm{mm}\right)}^{\mathrm{1}\mathrm{/}\mathrm{0}\mathrm{.}\mathrm{9}}\mathrm{+}\mathrm{3}\mathrm{mm}\mathrm{.}$$

where x is the spatial coordinate in the emission direction 7 of the antenna and is given in millimeters, and r (x) denotes the height of the inner contours 8, 10 above the axis of the independent spatial coordinate x. The zero point of the spatial coordinate x is here 80 mm within the transition of the first transition section 3 to the second transition section 4, wherein the formed as a dielectric horn second transition section 4 has an extension of 150 mm in total in the emission 7. The adjoining, designed as a dielectric tube radiating section 5 has in the direction of radiation 7 of the dielectric antenna 1 an extension of only 15 mm.

Table 1 below shows the transmission behavior and characteristic radiation parameters upon excitation of short emission sections 5 designed as a dielectric tube with different transition sections 4 designed as a dielectric horn when excited at 9.5 GHz. Tab. 1: Transmittance behavior with different linear inner contours and a nonlinear inner contour of a dielectric antenna at 9.5 GHz. Contour length / mm Transmission in the Nutzmode Dir / dBi H-plane E-plane linear dB SLS / dB HPBW / ° SLS / dB EPBW / ° linear 150 0.883 -1.081 18.5 27.5 22.5 39.4 25.1 350 0.936 -0.574 19.7 30.4 19.4 40.5 21.3 550 0.957 -0.382 20.0 30.4 18.3 40.5 19.8 nonlinear 230 0.935 -0.584 20.3 28.3 19.2 21.1 19.9

In Table 1 are for three different inner contours 8,10 within the dielectric rod of the first transition section 3 and within the dielectric horn forming second transition section 4 for a linear inner contour (150 mm, 350 mm and 550 mm) and for an optimized non-linear inner contour (230 mm as the sum of an 80 mm long first transition section 3 and a 150 mm long second transition section 4) the transmission behavior and characteristic radiation characteristics (dir = directivity, SLS = half power beamwidth) with excitation of one as a short tube (50 mm) designed Abstrahlabschnitts 5 at a excitation of 9.5 GHz. It can readily be seen that with a nonlinear inner contour 8, 10 of a length of 230 mm, approximately the same transmission and directivity can be achieved as with a linear inner contour, which, however, is considerably longer (350 mm). In the case of the nonlinear inner contour, a higher directivity (here about 0.5 dB) compared to a longer linear transition (350 mm) at comparable HE ₁₁ mode purity achieved. In the present case, this is possible by deliberately avoiding a particularly significant side lobe suppression (SLS) of more than 20 dB in the E plane. This is acceptable, since a lower level of suppression will no longer allow a significant gain in measurement accuracy.

In connection with the results from Table 1 are also the diagrams in the Fig. 4a and 4b to understand. In Fig. 4a is the directivity as a function of the length of designed as a dielectric tube second transition section 4 shown for the designed as a dielectric horn second transition sections 4 with a linear inner contour (150 mm, 350 mm, 550 mm) and for the excitation of a variable-length radiating section. 5 via a formed as a dielectric horn second transition section 4 with non-linear inner contour (230 mm). An increase of the HE ₁₁ mode purity leads to a reduction of the increase in directivity over the tube length and thus to a reduced length dependence of the radiation behavior. If the transmission in the payload mode is the same as in the case of the second transition section with a linear inner contour (350 mm) and in the case of the second transition section 4 with a nonlinear inner contour (230 mm), the directivity curves are nearly parallel to one another. On the other hand, the gradient is steeper at a lower transmission (150 mm) and flatter at a larger transmission (550 mm). In Fig. 4b are the far fields out of the picture Fig. 3 known arrangement with a tube length of the Abstrahlabschnitts 5 of 1500 mm and 750 mm and the ideal mode field. As Fig. 4b can be taken, it is in the described effect to a parasitic interference effect of two radiating cross-sections, since the increase in directivity arises only due to the constructive superposition of the HE ₁₁ mode field with the parasitic radiating in the region of the horn-shaped second transition section 4 leakage field. Since both field shares have almost the same wavenumber, the entire effect becomes visible only with longer lengths of the radiating section 5 in the form of a tube, that is to say when the directivity drops again, to which again the in Fig. 3 referenced field distribution is referenced.

In order to reduce internal reflections in the dielectric antenna 1, various stepped impedance transformers are formed inside the dielectric antenna 1, operating on the principle of a quarter-wave transformer. Thus, a first stepped impedance converter 11 is formed by the inner contour 10 of the dielectric rod comprising the first transition section 3 in the transition to the feed side full bar area, which is formed in the present case as a single-stage impedance converter. Single-stage impedance converters already lead to good results in purely dielectric transition regions with regard to the avoidance of internal reflections. Further, in the dielectric antennas 1 according to FIGS Fig. 1 and 2 provided that the dielectric feed section 2 is formed as a further stepped impedance converter 12, which also operates on the principle of a quarter-wave transformer. In this case, the stepped impedance converter 12 has an inner contour with a tapering in the emission direction 7 cross-section, wherein the smallest step is formed with a hexagon socket as the inner contour, which is in terms of mounting the dielectric antenna 1 is advantageous, but also - as already stated above - is a particularly preferred structure in terms of electromagnetic properties.

Of particular importance in the provided in the dielectric feed section 2 stepped impedance converter 12 is that the outer diameter of the dielectric feed section 2 is selected so that in the assembled state of the antenna, a radial gap 13 between the feed section 2 and a feeding waveguide 14 is formed in the In the present case, the radial gap 13 extends in the emission direction 7 substantially over the axial extent of the stepped impedance converter 12 formed in the dielectric feed section 2, which is particularly evident in FIG Fig. 5 can be seen.

A third stepped impedance converter 19, which operates on the principle of a quarter-wave transformer, is provided on the radiating section 2 designed as a tube.

Another measure to increase the directivity, which in the dielectric antenna according to Fig. 1 . 2 and 5 is implemented, is that the dielectric rod in the first transition section 3 of a metallic, Surrounding in the radiation direction 7 of the antenna 1 horn projection 15 is surrounded, wherein the metallic horn extension 15 extends neither in the region of the formed in the dielectric feed section 2 stepped impedance converter 12 into the region of the stepped impedance converter 11 in the first transition section 3 Experience shows that already Metallic horn sets 15, which exceed the outer diameter of the dielectric rod in the first transition section 3 at most by a factor of 2 already lead to a significant increase in directivity, such as the metallic Hornansätze 15 in the Fig. 1 . 2 and 5 having a maximum outer diameter of 40 mm with respect to an outer diameter of the dielectric rod formed in the first transition portion 3 of 22mm.

It is also advantageous in the embodiments according to the Fig. 1 and 5 in that the metallic horn lug 15 is surrounded by a dielectric sheath 16, the dielectric sheath 16 mechanically connecting the metallic horn lug 15 to the dielectric antenna 1 and fixing the metallic horn lug 15 to the dielectric antenna. In the present case, the dielectric sheath 16 is integral with Namely, it is formed on the other dielectric parts of the dielectric antenna 1, namely, it is molded on the dielectric antenna 1 in an injection process. The dielectric sheaths 16 according to the embodiments in FIGS Fig. 1 and 5 also have external thread 17 for mounting the dielectric antenna 1 in a process-side flange, wherein the process-side flange is not shown here. The wrapper 16 in Fig. 1 is configured adjacent to the external thread 17 as a nut, which facilitates the assembly of the antenna 1 as a whole.

The dielectric sheath 16 according to FIG Fig. 2 is additionally configured as extending vertically to the emission direction 7 of the antenna 1 extension, which serves as a sealing plate between mounting flanges, not shown; Such is in a simple manner - assuming a sufficient thickness of the gasket - also an explosion and / or flame protection achievable.

The dielectric sheath 16 brings for all shown embodiments, Fig. 1 . 2 and 5 , several advantages, which are practically significant Meaning may be such. As the encapsulation of all metal parts to the process and the ability to dispense with otherwise conventional sealing elements within the rod geometry or the waveguide, since the sealing elements can bring electromagnetically considerable disadvantages.

Further stability and improved electromagnetic transmission behavior is achieved in that - as in the Fig. 1 . 2 and 5 shown, the metallic horn extension 15 in the direction of the feed section 2, a cylindrical metal sleeve 18 is formed, which serves as a transition to a feeding metallic waveguide 14, or, even in this section, the feeding waveguide 14 represents. In Fig. 2 Furthermore, in the feed section 2 of the antenna 1, a thread formed between the feed section 2 and the metallic horn projection 15 or the surrounding metal sleeve 18 is indicated, with which the dielectric part of the antenna is secured in the metallic horn projection 15 or the surrounding metal sleeve 18.

Claims (6)

1. Dielectric antenna comprising a dielectric feeding section (2), a first transition section (3) comprising a dielectric rod, another, second transition section (4) forming a dielectric horn and a dielectric emitting section (5), wherein the feeding section (2) can be subjected to electromagnetic radiation (6), electromagnetic radiation (6) can be guided with the first transition section (3) and the second transition section (4), and the electromagnetic radiation can be emitted from the emitting section (5) as airborne waves, wherein the second transition section (4) comprising the dielectric horn has an inner contour opening increasingly in the direction of radiation and this inner contour forms the interface of the dielectric horn to a cavity surrounded by the dielectric horn and wherein the electromagnetic radiation (6) fed into the feeding section (2) is transmitted through the dielectric supply section (2) into the dielectric rod forming said first transition section (3) and from there into the further, second transition section (4) forming a dielectric horn and then is emitted via the emitting section (5) and the second transition section (4) forming a dielectric horn has a linear outer contour opening in the direction of radiation (7)
   characterized in
   that the inner contour (8) of the dielectric horn of the second transition section (4) continues in an inner contour (10) of the dielectric rod forming the first transition section (3), and that the emitting section (5) is designed as a dielectric tube with an outer diameter continuing from the second transition section (4).
2. Dielectric antenna according to claim 1, characterized in that the wall thickness of the dielectric tube is chosen at a maximum so that only electromagnetic radiation (6) in the hybrid basis mode HE₁₁ guided along the dielectric tube can be propagated, in particular wherein the wall thickness of the dielectric tube amounts at the most to 5% of the outer diameter of the dielectric tube.
3. Dielectric antenna according to claim 1 or 2, characterized in that the inner contour (8) of the dielectric horn of the second transition section (4) proceeds continuously with an inner contour (10) in the dielectric rod forming the first transition section (3).
4. Dielectric antenna according to one of claims 1 to 3, characterized in that the dielectric rod in the first transition section (3) is surrounded by a metallic horn hub (15) opening in the direction of emission (7) of the antenna (1), in particular wherein metallic horn hub (15) extends neither into the range of the non-continuous impendance converter (12) formed in the dielectric feeding section (2) nor into the range of the staged impedance converter (11) in the first transition section (3).
5. Dielectric antenna according to claim 4, characterized in that the maximum outer diameter of the metallic horn hub (15) exceeds the outer diameter of the dielectric rod in the first transition section (3) at the most by a factor of 2.5, preferably by a factor of 2.3 and most preferably by a factor of 2.
6. Dielectric antenna according to claim 4 or 5, characterized in that a cylindrical metal sleeve (18) is formed on the metallic horn hub (15) in the direction of the feeding section (2), in particular as a transition to a feeding, metallic waveguide.

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