Radar level gauge for measuring fill levels in containers

Abstract

Radar level measuring device for detecting fill levels in containers, comprising: a primary emitter for transmitting and receiving radar beams; a dielectric lens for transmitting and receiving the radar beams; a waveguide unit for guiding the radar beams between the primary emitter and the dielectric lens; wherein the dielectric lens and the waveguide unit are spaced apart from each other.

Description

Field of the InventionThe present invention relates to a radar fill level measuring device for detecting fill levels in containers and to a system for detecting fill levels.BackgroundRadar fill level measuring devices are fundamentally known in the prior art and are used, for example, in the process and chemical industry for monitoring fill levels in containers.In this context, it has now been found that there is a further need to provide a radar fill level measurement device for detecting fill levels; in particular, there is a need to provide an efficient, cost-effective and robust radar fill level measurement device for detecting fill levels.These and other objects, which will be mentioned or can be recognized by the skilled person upon reading the following description, are achieved by the subject matter of independent claims. The dependent claims further develop the central idea of the present invention in a particularly advantageous manner.SUMMARY OF THE INVENTIONAccording to a first aspect of the present invention, there is provided a radar level gauge for detecting levels in containers, comprising:a primary radiator for transmitting and receiving radar beams;a dielectric lens for transmitting and receiving the radar beams;a waveguide unit for guiding the radar beams between the primary radiator and the dielectric lens;wherein the dielectric lens and the waveguide unit are arranged at a distance from one another.The term primary radiator is to be understood broadly in the present case and means a structural element which is configured to emit electromagnetic waves, preferably radar beams, which are generated by a circuit, preferably a high-frequency circuit in the GHz range, and / or to receive reflected radar beams. The primary radiator can be embodied in one piece or in multiple pieces. The primary radiator can be arranged at least partially on the high-frequency circuit for generating the radar beams and for processing reflected radar beams.The term dielectric lens is to be understood broadly in the present case and preferably means a lens which is curved on both sides and is made of a dielectric material and receives radar beams emitted indirectly or directly by the primary radiator and forwards these in a directed manner or receives reflected radar beams and sends these in a directed manner directly or indirectly to the primary radiator. The dielectric lens can influence the shape or direction of the radiation. The dielectric lens preferably has a spherical shape. Depending on a radius or curvature, a distance is obtained in which the radiation emitted or emitted by the dielectric lens is focused. The dielectric lens preferably comprises a lossless dielectric material.The term waveguide unit is to be understood broadly in the present case and means a device which is configured to guide electromagnetic waves, preferably radar beams. The waveguide unit can be one-piece or multi-piece. The waveguide unit can be designed as a waveguide (e.g. metallic waveguide). The waveguide unit can be designed as a dielectric waveguide.The term spaced apart is to be understood broadly here and means that the waveguide unit and the dielectric lens are arranged with respect to one another such that there is a spatial distance or free space between an end of the waveguide unit which faces the dielectric lens and the dielectric lens. The length of this distance preferably depends on the geometry of the dielectric lens. The free space is preferably filled with air.The term radar fill level measuring device is to be understood broadly in the present case and preferably means a measuring device for detecting fill levels in containers, wherein the measuring device determines the fill level level on the basis of the principle of the transit time measurement of the radar beams. In this case, a fill level to be measured is determined in the container taking into account the position of the fill level measuring device and the measured transit time between transmitted radar beams and received radar beams, i.e. radar beams reflected from the surface of, for example, a bulk material in a container. Different methods can be used for determining the runtimes, for example. Pulsed radar or continuous wave frequency modulation radar.The invention is based on the finding that the sensor electronics of the radar fill level measuring device must not exceed a temperature of approximately 85° C., whereas the process temperature in the containers in which the fill level is measured can be up to 450° C. This leads to the need for thermal decoupling of sensor electronics and radar antenna. Furthermore, radar filling level measuring devices which operate in the range above 100 GHz are currently being used with increasing gain. The thermal decoupling in the range of radar fill level measuring devices which operate in the range below 100 GHz usually takes place by means of so-called waveguides. The waveguides are usually made of metal and have a bore diameter of 2.5 mm to 3.0 mm for radar fill level measurement devices in the working range of 80 GHz. The waveguides serve for the transmission of the radar beams from the primary radiator to the antenna. The length of the waveguide provides the thermal decoupling. However, as the frequency increases, the permissible bore diameter of the waveguides decreases. Thus, at an operating frequency of 250 GHz, a bore diameter of 0.87 mm is required. This is complicated to implement and thus leads to increased costs. For example, the waveguide can only be produced by means of special erosion processes, which are uneconomical, however. Within the scope of the present invention, the problem of thermal decoupling is realized by using a dielectric lens as antenna, as well as the spacing of the dielectric lens from the waveguide unit. As a result, it is possible, for example, to continue using metallic waveguides as the waveguide unit, since these do not have to extend as far as the antenna, which is designed here as a dielectric lens. Thus, the length of the metallic waveguide can be shorter even at high frequency. Furthermore, air is present between the end of the waveguide unit and the dielectric lens, which additionally functions as an insulator. Thus, a thermal decoupling is effected by the arrangement according to the invention. This can have an advantageous effect on the accuracy of the measurement and the robustness of the radar fill level measurement device. Furthermore, through the use of a dielectric waveguide, which is preferably made of plastic, as a component of the waveguide unit, galvanic decoupling or potential separation between the sensor electronics and the container or container potential can additionally advantageously be made possible.Modern radar fill level measurement devices for the process industry and automation technology have in the meantime gradually become open to the frequency range above 100 GHz. Due to the development of new frequency regulations, ever better semiconductor processes and more accurate manufacturing methods, radar-based fill level measurement devices up to 250 GHz can be developed, produced and marketed. Higher frequency ranges have advantages in that a narrower aperture angle can be realized with the same antenna size. Frequently, the stirrers or heating coils installed in containers generate disturbing reflections in the radar signal, which however become smaller or even disappear with a smaller opening angle of the antenna.A larger signal bandwidth is likewise permissible from a regulatory point of view in higher frequency ranges, as a result of which a better separation of two adjacent radar targets can be achieved.A fundamental difference between sensors below 100 GHz and above 100 GHz is that the generated radar signal above 100 GHz is fed directly from the signal-generating semiconductors into the waveguide. For this purpose, the semiconductor material on which the high-frequency circuit is located is simultaneously also provided with a radiator element which, in combination with an arrangement of coupling element and resonator element, can form a primary radiator. With such a primary radiator, either a dielectric waveguide can be coupled in or a dielectric lens can be directly illuminated. The semiconductor material can be bonded to a circuit board by means of an adhesive layer.The advantage of such an arrangement, in particular at frequencies above 100 GHz, is that the radar signal thus experiences as little signal attenuation as possible. In radar devices below 100 GHz, the radar signal is typically only guided over a printed circuit board which has at least one layer of high-frequency printed circuit board material, before the signal is fed into a waveguide or a coaxial conductor. The waveguides, which are predominantly used in 80 GHz sensors, have the task of transmitting the radar signal from the radar module to the antenna. The waveguides, which in this case are predominantly designed as round waveguides, have a diameter in this frequency range between 2.5 and 3.0 mm and can be produced comparatively favorably by deep hole drilling methods in a sufficient length. The length of the waveguide is of fundamental importance with regard to the temperature decoupling between the process to be monitored and the sensor electronics. The sensor electronics must not exceed a temperature of 85° C., whereas the process temperature may be up to 450° C. The temperature decoupling is carried out via waveguides of corresponding length.As the frequencies become higher, the waveguide diameters become increasingly smaller, since the cutoff frequency of the fundamental mode depends on the waveguide diameter. In the case of a 250 GHz radar signal, the waveguide diameter is only 0.87 mm. With such a small diameter, it becomes considerably more complicated to produce a waveguide of the same length than with the waveguide diameter at 80 GHz.The present invention can have the advantage that metallic waveguides can be used as thermal decoupling elements even at higher frequencies.In an embodiment, the waveguide unit comprises a dielectric waveguide. The dielectric waveguide can be made of plastic. Examples thereof are HDPE, PVDF, FEP and PFA. The dielectric waveguide can have any desired geometries as a cross section. Preferably, the dielectric waveguide has a round cross section or a rectangular cross section. The plastic preferably has a lower relative permittivity and a low loss factor. This has a positive effect on the signal attenuation (i.e. low signal attenuation). For example, long dielectric waveguides can be manufactured simply and economically by means of microinjection molding or extrusion and also have a lower signal attenuation compared to a metallic waveguide. The combination of air volume between dielectric lens and waveguide and the production of the waveguide from a plastic bring with it further advantages with regard to thermal decoupling.In one embodiment, the waveguide unit comprises a metallic waveguide. The metallic waveguide can consist of metal and / or metal-coated plastic. Due to the spaced-apart arrangement of metallic hollow conductor and dielectric lens, a reduced length of the metallic hollow conductor can be advantageously realized, wherein thermal decoupling is still ensured due to the spacing. The metallic waveguide is suitable for operating frequencies below 100 GHz, but can also be used advantageously for operating frequencies above 100 GHz in the present arrangement. In this case, the metallic waveguide is ideally placed in such a way that one end of the metallic waveguide is located at the focal point / focus of the dielectric lens.In a preferred embodiment, the waveguide unit comprises a dielectric waveguide and a metallic waveguide. The dielectric waveguide is preferably arranged between the primary radiator and the metallic waveguide. The metallic waveguide is preferably arranged between the dielectric waveguide and the dielectric lens.In a preferred embodiment, the metallic waveguide has an adaptation element for coupling in the radar beams and a beam element for emitting the radar beams. The term matching element is to be understood broadly in the present case and preferably means a structural element which has a geometry which corresponds to a geometry of another structural element (e.g. primary radiator or dielectric waveguide) in such a way that the radar beams can be transmitted. The matching element is preferably part of the waveguide, preferably of the metallic waveguide or of the dielectric waveguide. For example, the matching element has an inner cone and the corresponding geometry of the dielectric waveguide of the common interface has an outer cone. The term beam element is to be understood broadly in the present case and means a structural element which has a geometry which is configured to transmit and receive radar waves, for example an inner cone. The beam element is preferably part of the waveguide, preferably of the metallic waveguide or of the dielectric waveguide. In other words, the beam element is configured to illuminate the dielectric lens. The beam element is preferably located at the focus of the dielectric lens. Overall, the matching element and the beam element have an advantageous effect on the signal transmission.In a preferred embodiment, the dielectric waveguide has an adaptation element for coupling the radar beams and a beam element for emitting the radar beams. The matching element is preferably part of the dielectric waveguide and differs from the rest of the dielectric waveguide in terms of the geometry. The geometry of the matching element corresponds, for example, to the geometry of the primary radiator, so that these can realize a flat contact. This advantageously allows a good coupling of the radar beams. The beam element is preferably part of the dielectric waveguide and differs from the rest of the dielectric waveguide in terms of the geometry of the beam element. The beam element preferably has a geometry suitable for transmitting and receiving radar beams, for example a spherical shape or a conical shape. Overall, the matching element and the radiating element have an advantageous effect on the signal transmission.In a preferred embodiment, air for thermal isolation is located between the waveguide unit and the dielectric lens. This has an advantageous effect on the thermal decoupling of the measurement electronics from the process. Air is a better insulator than metal. This can have the consequence that the metallic waveguide can be made shorter even at higher frequencies and therefore also simpler and more cost-effective and nevertheless sufficient thermal decoupling can take place.In a preferred embodiment, the primary radiator comprises a radiator element, a coupling element and a resonator element. The radiator element is preferably connected directly to the high-frequency electronics which generate the radar radiation. The resonator element is preferably arranged between the radiator element and the coupling element. The coupling element is made of PEEK, for example. This can have a positive effect on the quality of the measurement.In a preferred embodiment, the dielectric waveguide comprises a plastic. The plastic can be, for example, one of the following: HDPE, PVDF, FEP or PFA. This can advantageously implement a galvanic decoupling between the measuring electronics and the container.In a preferred embodiment, a radar level gauge is provided wherein a distance between the dielectric lens and the waveguide unit is derived from a geometry of the dielectric lens. The dielectric lens has, for example, a spherical shape. This spherical shape results in focusing of radar radiation emitted from the lens at a certain point outside or spaced apart from the lens. The arrangement of the waveguide unit, waveguide or dielectric conductor, at this point, brings about an advantageous increase in the signal quality or transmission quality.In a preferred embodiment, a radar fill level measurement device is provided which is configured to measure at a frequency above 100 GHz. With increasing measurement frequency, the radiation cone of the emitted radiation of the radar fill level measuring device is advantageously reduced. This can have a positive effect on the measurement accuracy, since interfering contours such as, for example, stirrers or heating coils in a container do not contribute to the reflection of the radar radiation.In a preferred embodiment, the waveguide unit comprises a beam element, wherein the beam element is arranged in the focus of the dielectric lens. The term focus here means the point at which the radar beams emitted from the dielectric lens are converged. This can have a positive effect on the quality of the measurement.A further aspect of the present invention comprises a system for detecting fill levels, comprising at least one radar fill level measuring device described above and a container for storing a material. The material may be liquid or solid or a combination thereof.In a preferred embodiment, the container has an agitator for agitating the material.In a preferred embodiment, the container has a heating coil for heating the material.DESCRIPTION OF THE PREFERRED EMBODIMENTSA detailed description of the figures is given below, in which FIG. 1 shows a schematic view of a system according to the invention for detecting fill levels; FIG. 2 shows a schematic section of a radar fill level measuring device according to the invention; FIG. 3 shows a schematic section of a radar fill level measuring device according to the invention; FIG. 4 shows a schematic section of a radar fill level measuring device according to the invention of a first embodiment; FIG. 5 shows a schematic section of a radar fill level measuring device according to the invention of a second embodiment; FIG. 6 shows a schematic section of a radar fill level measuring device according to the invention of a first embodiment; FIG. 7 shows a schematic section of a radar fill level measuring device according to the invention of a second embodiment;FIG. 1 shows a schematic view of a system 100 according to the invention for detecting fill levels.The system 100 comprises a radar operator position measuring device 101 described in more detail below. the radar fill level measuring device 101 has a dielectric lens 102 in the lower region for emitting and receiving radar beams. Depending on the measurement frequency, an opening angle 103 of the transmitted radar radiation is established. The system further comprises a container 105 for storing a material 104, for example a liquid. The container further comprises an agitator 106. It can be seen from the drawing that the radiation cone, which results from the opening angle 103, does not overlap with the stirrer. This has an advantageous effect on the measurement accuracy, since no interference reflections thus occur. Furthermore, the system 100 can also comprise a heating coil (not shown).FIG. 2 shows a schematic section of a radar fill level measuring device 200 according to the invention. The radar fill level measuring device comprises at least one carrier plate (i.e. Circuit Board) 207. A semiconductor material 201 is attached to the carrier plate 207 via an adhesive layer 204. On the semiconductor material, a high-frequency circuit (not shown) and a radiating element (not shown) are provided. Above the radiator element is a resonator element 202. Above the resonator element 202, a coupling element 203 made of peek is arranged. The coupling element 203, the resonator element 202 and the radiator element form the primary radiator 206 in the present case. In the present case, the semiconductor material 201 is electrically connected to the carrier plate 207 via bonding wires 208. Above the primary radiator 206 a dielectric waveguide 205 is arranged. The primary radiator 206 transmits the radar radiation generated by the frequency circuit to the dielectric waveguide 205 or receives the radar radiation guided by the dielectric waveguide 205 and reflected by the surface of the material.FIG. 3 shows a schematic detail of a radar fill level measuring device 300 according to the invention in plan view. The semiconductor material 304 is arranged on the carrier plate 303 and electrically connected to the carrier plate 303 via the bonding wires 305. The high-frequency circuit 302 and the radiator element 301 are arranged on the semiconductor material 304. The resonator element 306 is arranged above the radiator element 301. The radar radiation generated in the high-frequency circuits 302 is passed on to the radiator element 301 in order to be amplified from there by the resonator element 306. The radar radiation reflected from the surface of the material and radiation received by the radar level gauge pass through the same path in only the opposite direction.FIG. 4 shows a schematic section of an embodiment of a radar fill level measuring device 400 according to the invention. The radar fill level measuring device 400 comprises a primary radiator 405 for transmitting and receiving radar beams. The primary radiator 405 is arranged on a semiconductor element 406 (as described above). The radar fill level measuring device 400 further comprises a waveguide unit 407 for guiding the radar beams between the primary radiator 405 and the dielectric lens 404. The waveguide unit 407 comprises a dielectric waveguide 408 and a metallic waveguide 401 in the present case. The dielectric waveguide 408 transfers the radar beams from the primary radiator 405 to the metallic waveguide 401, and vice versa. The metallic waveguide 401 in the present case has an adaptation element 402, wherein the adaptation element 402 has an inner cone, which corresponds to the outer cone of the dielectric waveguide 408. In the present case, the matching element 402 and the dielectric waveguide 408 lie on top of one another. The matching element 402 is part of the metallic waveguide 401. The metallic waveguide 401 furthermore has a radiating element 403, which is designed in the present case as an inner cone. The beam element 403 is configured in the present case for emitting and receiving the radar beams 410. The radar level gauge 400 further includes a dielectric lens 404 for transmitting and receiving the radar beams. The dielectric lens 404 and the waveguide unit 407, in particular the beam element 403 of the metallic waveguide 401, are arranged at a distance from one another. The distance 409 results from the geometry of the dielectric lens 404. The distance preferably comprises the focal length of the dielectric lens 404. In other words, the beam element 403 is located approximately in the focus of the dielectric lens 404. The space between dielectric lens 404 and beam element 403 is filled with air in the present case.FIG. 5 shows a schematic section of a radar fill level measuring device 500 according to the invention of a second embodiment. In contrast to the embodiment illustrated in FIG. 4, the waveguide unit 506 in the present case comprises only one dielectric waveguide 501. The dielectric waveguide 501 is disposed between the primary radiator 505 and the dielectric lens 504. The dielectric waveguide 501 in the present case has a beam element 503 and a matching element 502. The beam element 503 of the dielectric waveguide 501 is arranged at a distance from the dielectric lens 504. The spacing in turn results from the geometry of the dielectric lens 504. By virtue of the spacing, thermal and galvanic decoupling is advantageously effected.FIG. 6 shows a schematic section of a radar fill level measuring device 600 according to the invention of a first embodiment according to the invention. In contrast to FIG. 4, a metallic housing 601 of the radar fill level measuring device 600 is also shown in the present case. Furthermore, the radar fill level measuring device 600 has an interface 603 for energy supply and data exchange, for example realized with an M12 connection. The radar fill level measuring device 600 has a plurality of carrier plates 604, 605 and 606 which are used for the energy supply, the control and the high-frequency circuit for generating and processing radar beams. These are electrically connected to one another via plug connectors 607. The radar fill level measuring device 600 has a metallic process connection 602 in the lower region of the housing 601. Both the dielectric lens 608 and the metallic waveguide 609 and at least partially the dielectric waveguide 610 are arranged in the metallic process connection 602. The connection or arrangement can be effected, for example, via a cohesive or mechanical joining method. For example, the metallic waveguide 609 is screwed via a thread into the metallic process connection 602. For example, the dielectric lens 608 is sealingly bonded into the metallic process port 602.FIG. 7 shows a schematic section of a radar fill level measuring device 700 according to the invention of a second embodiment. The radar fill level measuring device 700 in turn has a housing 701 and a process connection 702. In contrast to the radar fill level measurement device 600 shown in FIG. 6, the radar fill level measurement device 700 only comprises a dielectric waveguide 703 which is arranged in the process connection 702 via a holder 704. The dielectric lens 705 is again arranged in a sealing manner in the process connection 702.Reference list100 System 101, 200, 300, 400, 500, 600, 700 radar fill level measuring device 102, 404, 504, 608, 705 dielectric lens 103 aperture angle 104 material 105 container 106 stirrer 201, 304, 406 semiconductor material 202, 306 resonator element 203 coupling element 204 adhesive layer 205, 408, 501, 610, 703 dielectric waveguides 206, 405, 505 primary radiator 207, 303, 604, 605, 606 carrier plate 208, 305 bonding wires 301 radiator element 302 high-frequency circuit 401, 609 waveguide 402, 502 matching element 403, 503 beam element 407, 506 waveguide unit 409 distance 410 radar beams 601, 701 housing 602, 702 process terminal 603 interface 607 plug connector 704 holder

Claims

A radar level gauge for detecting levels in containers, comprising: a primary radiator for transmitting and receiving radar beams; a dielectric lens for transmitting and receiving the radar beams; a waveguide unit for guiding the radar beams between the primary radiator and the dielectric lens; wherein the dielectric lens and the waveguide unit are spaced apart from each other.The radar level gauge of claim 1, wherein the waveguide unit comprises a dielectric waveguide.The radar level gauge according to claim 1 or 2, wherein the waveguide unit comprises a metallic waveguide.Radar fill level measuring device according to Claim 3, wherein the metallic waveguide has an adaptation element for coupling in the radar beams and a beam element for emitting the radar beams.Radar fill level measuring device according to Claim 2, wherein the dielectric waveguide has an adaptation element for coupling in the radar beams and a beam element for emitting the radar beams.The radar level gauge of any preceding claim, wherein air for thermal isolation is located between the waveguide unit and the dielectric lens.Radar fill level measuring device according to one of the preceding claims, wherein the primary radiator comprises a beam element, a coupling element and a resonator element.The radar level gauge of any preceding claim, wherein the dielectric waveguide comprises a plastic.The radar level gauge of any preceding claim, wherein a distance between the dielectric lens and the waveguide unit is derived from a geometry of the dielectric lens.The radar level gauge according to any of the preceding claims, wherein the radar level gauge is configured to measure at a frequency above 100GHz.The radar level gauge according to any of the preceding claims, wherein the waveguide unit comprises a beam element and wherein the beam element is arranged in the focus of the dielectric lens.System for detecting fill levels, comprising at least one radar fill level measuring device according to one of Claims 1 to 11 and a container for storing a material.The system of claim 12, wherein the container comprises an agitator.The system of claim 12 or 13, wherein the container comprises a heating coil.

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