Radar fill-level measuring device for detecting fill levels in containers

Abstract

The invention relates to a radar fill-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 one another.

Description

[0001] Radar level gauge for measuring fill levels in containers

[0002] Reference to related applications

[0003] This application claims priority from German patent application No. 10 2023 206 192.9, filed on June 30, 2023, which is incorporated in its entirety by reference into this document.

[0004] Field of the invention

[0005] The present invention relates to a radar level measuring device for detecting fill levels in containers and a system for detecting fill levels.

[0006] background

[0007] Radar level measuring devices are generally known in the state of the art and are used, for example, in the process and chemical industries to monitor fill levels in containers.

[0008] In this context, it has now become apparent that there is a further need to provide a radar level measuring device for detecting fill levels, in particular there is a need to provide an efficient, cost-effective and robust radar level measuring device for detecting fill levels.

[0009] These and other objects, which will be mentioned upon reading the following description or which may be recognized by a person skilled in the art, are achieved by the subject matter of the independent claims. The dependent claims develop the central idea of ​​the present invention in a particularly advantageous manner.

[0010] Summary of the Invention According to a first aspect of the present invention, a radar level gauge for detecting fill levels in containers is provided, 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.

[0011] The term "primary radiator" is to be understood broadly in this context and refers to a structural element configured to emit electromagnetic waves, preferably radar beams, 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 designed as a single-piece or multi-piece unit. 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.

[0012] The term "dielectric lens" is to be understood broadly here and preferably refers to a lens made of a dielectric material that is curved on both sides and receives radar beams emitted directly or indirectly by the primary radiator and transmits them in a directed manner, or receives reflected radar beams and transmits them directly or indirectly to the primary radiator. The dielectric lens can influence the shape or direction of the radiation. The dielectric lens is preferably spherical. Depending on a radius or curvature, a distance results at which the radiation emitted or transmitted by the dielectric lens is focused. The dielectric lens preferably comprises a loss-free dielectric material.

[0013] The term "waveguide unit" is to be understood broadly in this context and refers to a device designed to guide electromagnetic waves, preferably radar beams. The waveguide unit can be a single-piece or multi-piece unit. The waveguide unit can be designed as a hollow guide (e.g., a metallic hollow guide). The waveguide unit can be designed as a dielectric waveguide.

[0014] The term "spaced apart" is to be understood broadly here and means that the waveguide unit and the dielectric lens are arranged relative to one another such that a spatial distance or a free space exists between an end of the waveguide unit facing 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.

[0015] The term "radar level gauge" is to be understood broadly in this context and preferably refers to a measuring device for detecting fill levels in containers. The measuring device determines the fill level based on the principle of measuring the time of flight of the radar beams. The fill level to be measured in the container is determined taking into account the position of the level gauge and the measured time of flight between the transmitted and received radar beams—i.e., the radar beams reflected from the surface of, for example, a bulk material in a container. Different methods can be used to determine the time of flight, e.g., pulse radar or frequency modulation continuous-wave radar.

[0016] The invention is based on the finding that the sensor electronics of the radar level measuring device must not exceed a temperature of approximately 85 °C, whereas the process temperature in the containers in which the level is measured can reach up to 450 °C. This leads to the need for thermal decoupling of the sensor electronics and the radar antenna. Furthermore, radar level measuring devices that operate in the range above 100 GHz are currently being used more and more. Thermal decoupling in radar level measuring devices that operate in the range below 100 GHz is usually achieved using 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 level measuring devices in the operating range of 80 GHz. The waveguides serve to transmit the radar beams from the primary radiator to the antenna. The length of the waveguide provides the thermal decoupling.However, with increasing frequency, the permissible bore diameter of the waveguide decreases. For example, an operating frequency of 250 GHz requires a bore diameter of 0.87 mm. This is complex to implement and thus leads to increased costs. For example, the waveguide can only be manufactured using special EDM processes, which are uneconomical. Within the scope of the present invention, the problem of thermal decoupling is solved by using a dielectric lens as the antenna and spacing the dielectric lens from the waveguide unit. This makes it possible, for example, to continue using metallic waveguides as the waveguide unit, since they do not have to reach the antenna, which is designed here as a dielectric lens. Thus, the length of the metallic waveguide can be shorter even at high frequencies.Furthermore, there is air between the end of the waveguide unit and the dielectric lens, which additionally acts as an insulator. Thus, thermal decoupling is achieved by the arrangement according to the invention. This can have a beneficial effect on the measurement accuracy and the robustness of the radar level gauge. Furthermore, the use of a dielectric waveguide, preferably made of plastic, as a component of the waveguide unit can advantageously enable galvanic decoupling or potential separation between the sensor electronics and the container or container potential.

[0017] Modern radar level measuring devices for the process industry and automation technology are gradually tapping into the frequency range above 100 GHz. Due to the emergence of new frequency regulations, ever-improving semiconductor processes, and more precise manufacturing techniques, radar-based level measuring devices can be developed, produced, and marketed up to 250 GHz. Higher frequency ranges offer the advantage of allowing a narrower beam angle with the same antenna size. The agitators or heating coils installed in vessels often generate interference in the radar signal, which, however, decreases or even disappears with a smaller antenna beam angle.

[0018] From a regulatory perspective, a larger signal bandwidth is also permitted in higher frequency ranges, which allows for better discrimination between two adjacent radar targets.

[0019] A fundamental difference between sensors operating at frequencies below 100 GHz and above 100 GHz is that, above 100 GHz, the generated radar signal is fed directly from the signal-generating semiconductors into the waveguide. For this purpose, a radiator element is located on the semiconductor material containing the high-frequency circuit. This element, combined with a coupling element and resonator element arrangement, can form a primary radiator. Such a primary radiator can either be coupled into a dielectric waveguide or directly illuminate a dielectric lens. The semiconductor material can be bonded to a circuit board using an adhesive layer.

[0020] The advantage of such an arrangement, particularly at frequencies above 100 GHz, is that the radar signal experiences the lowest possible signal attenuation. In radar devices below 100 GHz, the radar signal is typically first routed via a circuit board that has at least one layer of high-frequency 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 circular waveguides, have a diameter of between 2.5 and 3.0 mm in this frequency range and can be manufactured relatively inexpensively in sufficient lengths using deep-hole drilling techniques. The length of the waveguide is fundamentally important with regard to 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 can reach up to 450°C. Temperature decoupling is achieved using appropriately long waveguides.

[0021] With increasing frequencies, waveguide diameters become increasingly smaller, as the cutoff frequency of the fundamental mode depends on the waveguide diameter. For a 250 GHz radar signal, the waveguide diameter is only 0.87 mm. With such a small diameter, it becomes considerably more complex to manufacture a waveguide of the same length than with a waveguide diameter at 80 GHz.

[0022] The present invention can have the advantage that metallic waveguides can be used as thermal decoupling elements even at higher frequencies.

[0023] In one embodiment, the waveguide unit comprises a dielectric waveguide. The dielectric waveguide can be made of plastic. Examples include HDPE, PVDF, FEP, and PFA. The dielectric waveguide can have any cross-sectional geometry. The dielectric waveguide preferably has a round or rectangular cross-section. The plastic preferably has a low relative permittivity and a low loss factor. This has an overall positive effect on signal attenuation (i.e., low signal attenuation). For example, long dielectric waveguides can be manufactured easily and cost-effectively using micro-injection molding or extrusion, and they also exhibit lower signal attenuation than a metallic waveguide.The combination of air volume between the dielectric lens and the waveguide as well as the manufacture of the waveguide from a plastic bring further advantages in terms of thermal decoupling.

[0024] In one embodiment, the waveguide unit comprises a metallic waveguide. The metallic waveguide can be made of metal and / or metal-coated plastic. By arranging the metallic waveguide and dielectric lens at a distance from each other, a reduced length of the metallic waveguide can advantageously be achieved, while the spacing still ensures thermal decoupling. The metallic waveguide is suitable for operating frequencies below 100 GHz, but can also advantageously be used for operating frequencies above 100 GHz with the present arrangement. The metallic waveguide is ideally positioned so that one end of the metallic waveguide is at the focal point / focus of the dielectric lens.

[0025] 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.

[0026] In a preferred embodiment, the metallic waveguide has a matching element for coupling 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 that has a geometry that corresponds to a geometry of another structural element (e.g., primary radiator or dielectric waveguide) such that the radar beams can be transmitted. The matching element is preferably part of the waveguide, preferably the metallic waveguide or 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 that has a geometry that is configured to transmit and receive radar waves, e.g.an inner cone. The radiating element is preferably part of the waveguide, preferably the metallic waveguide or the dielectric waveguide. In other words, the radiating element is configured to illuminate the dielectric lens. The radiating element is preferably located at the focus of the dielectric lens. Overall, the matching element and the radiating element have a beneficial effect on signal transmission.

[0027] In a preferred embodiment, the dielectric waveguide has a matching 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 its geometry. The geometry of the matching element corresponds, for example, to the geometry of the primary radiator, so that they can achieve surface contact. This advantageously enables 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 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 a beneficial effect on signal transmission.

[0028] In a preferred embodiment, air is located between the waveguide unit and the dielectric lens for thermal insulation. This has a beneficial effect on the thermal decoupling of the measurement electronics from the process. Air is a better insulator than metal. This can result in the metallic waveguide being shorter, even at higher frequencies, and therefore being easier and cheaper to manufacture, while still maintaining sufficient thermal decoupling.

[0029] In a preferred embodiment, the primary radiator comprises a radiator element, a coupling element, and a resonator element. The radiator element is preferably directly connected to the high-frequency electronics that generates 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.

[0030] In a preferred embodiment, the dielectric waveguide comprises a plastic. The plastic can be one of the following, for example: HDPE, PVDF, FEP, or PFA. This can advantageously provide galvanic isolation between the measurement electronics and the container.

[0031] In a preferred embodiment, a radar level gauge is provided in which a distance between the dielectric lens and the waveguide unit is derived from the geometry of the dielectric lens. The dielectric lens has, for example, a spherical shape. This spherical shape results in a focusing of radar radiation emitted by the lens at a specific point outside or spaced from the lens. The arrangement of the waveguide unit, hollow guide, or dielectric guide at this point advantageously increases the signal quality or transmission efficiency.

[0032] In a preferred embodiment, a radar level gauge is provided that is configured to measure at a frequency above 100 GHz. As the measurement frequency increases, the radiation cone of the radar level gauge's emitted radiation advantageously decreases. This can have a positive effect on measurement accuracy, since interfering contours such as agitators or heating coils in a container do not contribute to the reflection of the radar radiation.

[0033] In a preferred embodiment, the waveguide unit comprises a beam element, wherein the beam element is arranged at the focus of the dielectric lens. The term "focus" here refers to the point at which the radar beams emitted by the dielectric lens are focused. This can have a positive effect on the quality of the measurement.

[0034] A further aspect of the present invention encompasses a system for detecting fill levels, comprising at least one radar level gauge as described above and a container for storing a material. The material can be liquid or solid, or a combination thereof.

[0035] In a preferred embodiment, the container has an agitator for stirring the material.

[0036] In a preferred embodiment, the container has a heating coil for heating the material.

[0037] Description of the preferred embodiments

[0038] Below is a detailed description of the figures, showing

[0039] Figure 1 is a schematic view of a system according to the invention for detecting fill levels;

[0040] Figure 2 shows a schematic section of a radar level measuring device according to the invention; Figure 3 shows a schematic section of a radar level measuring device according to the invention;

[0041] Figure 4 shows a schematic section of a radar level measuring device according to the invention of a first embodiment;

[0042] Figure 5 shows a schematic section of a radar level measuring device according to the invention of a second embodiment;

[0043] Figure 6 shows a schematic section of an inventive

[0044] Radar level gauge of a first embodiment;

[0045] Figure 7 shows a schematic section of an inventive

[0046] Radar level gauge of a second embodiment;

[0047] Figure 1 shows a schematic view of a system 100 according to the invention for detecting fill levels.

[0048] The system 100 comprises a radar driver's cab measuring device 101, described in more detail below. The radar level measuring device 101 has a dielectric lens 102 in its lower area for transmitting and receiving radar beams. Depending on the measurement frequency, an aperture angle 103 of the emitted 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. The drawing shows that the radiation cone resulting from the aperture angle 103 does not overlap with the agitator. This has a beneficial effect on the measurement accuracy, as no interfering reflections occur. Furthermore, the system 100 can also comprise a heating coil (not shown).

[0049] Figure 2 shows a schematic section of a radar level gauge 200 according to the invention. The radar level gauge comprises at least one carrier plate (i.e., a circuit board) 207. A semiconductor material 201 is attached to the carrier plate 207 via an adhesive layer 204. A high-frequency circuit (not shown) and a radiator element (not shown) are located on the semiconductor material. A resonator element 202 is located above the radiator element. A coupling element 203 made of PEEK is arranged above the resonator element 202. The coupling element 203, the resonator element 202, and the radiator element form the primary radiator 206 in this case. The semiconductor material 201 is electrically connected to the carrier plate 207 via bonding wires 208. A dielectric waveguide 205 is arranged above the primary radiator 206. The primary radiator 206 transmits the radar radiation generated by the frequency switching to the dielectric waveguide 205 orreceives the radar radiation guided by the dielectric waveguide 205 and reflected by the surface of the material.

[0050] Figure 3 shows a schematic section of a radar level gauge 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 circuit 302 is transmitted to the radiator element 301, from where it is amplified by the resonator element 306. The radar radiation reflected from the surface of the material and the radiation received by the radar level gauge travel the same path, only in opposite directions.

[0051] Figure 4 shows a schematic section of an embodiment of a radar level gauge 400 according to the invention. The radar level gauge 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 level gauge 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. The dielectric waveguide 408 transmits the radar beams from the primary radiator 405 to the metallic waveguide 401 and vice versa. The metallic waveguide 401 has a matching element 402, wherein the matching element 402 has an inner cone that corresponds to the outer cone of the dielectric waveguide 408.In this case, the matching element 402 and the dielectric waveguide 408 rest on one another. The matching element 402 is part of the metallic waveguide 401. The metallic waveguide 401 further comprises a radiating element 403, which in this case is designed as an inner cone. The radiating element 403 is configured to transmit and receive the radar beams 410. The radar level gauge 400 further comprises a dielectric lens 404 for transmitting and receiving the radar beams. The dielectric lens 404 and the waveguide unit 407, in particular the radiating 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 includes 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.

[0052] Figure 5 shows a schematic section of a radar level gauge 500 according to the invention in a second embodiment. In contrast to the embodiment shown in Figure 4, the waveguide unit 506 in this case has only one dielectric waveguide 501. The dielectric waveguide 501 is arranged between the primary radiator 505 and the dielectric lens 504. The dielectric waveguide 501 in this case has a radiating element 503 and a matching element 502. The radiating 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. This spacing advantageously achieves thermal and galvanic decoupling.

[0053] Figure 6 shows a schematic section of a radar level measuring device 600 according to the invention in a first embodiment of the invention. In contrast to Figure 4, a metallic housing 601 of the radar level measuring device 600 is also shown here. Furthermore, the radar level measuring device 600 has an interface 603 for power supply and data exchange, for example, implemented with an M12 connector. The radar level measuring device 600 has a plurality of carrier plates 604, 605, and 606, which are used for the power supply, the control, and the high-frequency circuit for generating and processing radar beams. These are electrically connected to one another via connectors 607. The radar level measuring device 600 has a metallic process connection 602 in the lower region of the housing 601.The dielectric lens 608, 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 achieved, for example, via a material-to-material or mechanical joining process. For example, the metallic waveguide 609 is screwed into the metallic process connection 602 via a thread. For example, the dielectric lens 608 is sealed into the metallic process connection 602 by adhesive bonding.

[0054] Figure 7 shows a schematic section of a radar level gauge 700 according to the invention in a second embodiment. The radar level gauge 700 again has a housing 701 and a process connection 702. In contrast to the radar level gauge 600 shown in Figure 6, the radar level gauge 700 only has a dielectric waveguide 703, which is arranged in the process connection 702 via a holder 704. The dielectric lens 705 is again arranged sealingly in the process connection 702.

[0055] Reference list

[0056] 100 systems

[0057] 101 , 200, 300, 400, 500, 600, 700 Radar level gauge

[0058] 102, 404, 504, 608, 705 dielectric lens

[0059] 103 opening angle

[0060] 104 Materials

[0061] 105 containers

[0062] 106 agitator

[0063] 201 , 304, 406 Semiconductor material

[0064] 202, 306 Resonator element

[0065] 203 coupling element

[0066] 204 Adhesive layer

[0067] 205, 408, 501 , 610, 703 dielectric waveguides

[0068] 206, 405, 505 primary radiators

[0069] 207, 303, 604, 605, 606 carrier plate

[0070] 208, 305 bond wires

[0071] 301 radiator element

[0072] 302 high-frequency circuit

[0073] 401 , 609 waveguide

[0074] 402, 502 adjustment element

[0075] 403, 503 beam element

[0076] 407, 506 waveguide unit

[0077] 409 distance

[0078] 410 radar beams

[0079] 601 , 701 housing

[0080] 602, 702 process connection

[0081] 603 Interface

[0082] 607 connectors

[0083] 704 bracket

Claims

Claims:

1. 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.

2. Radar level gauge according to claim 1, wherein the waveguide unit comprises a dielectric waveguide.

3. Radar level gauge according to claim 1 or 2, wherein the waveguide unit comprises a metallic waveguide.

4. Radar level gauge according to claim 3, wherein the metallic waveguide has a matching element for coupling the radar beams and a beam element for emitting the radar beams.

5. Radar level gauge according to claim 2, wherein the dielectric waveguide has a matching element for coupling the radar beams and a beam element for emitting the radar beams.

6. Radar level gauge according to one of the preceding claims, wherein air is located between the waveguide unit and the dielectric lens for thermal insulation.

7. Radar level gauge according to one of the preceding claims, wherein the primary radiator comprises a radiation element, a coupling element and a resonator element.

8. Radar level gauge according to one of the preceding claims, wherein the dielectric waveguide comprises a plastic.

9. Radar level gauge according to one of the preceding claims, wherein a distance between the dielectric lens and the waveguide unit is derived from a geometry of the dielectric lens.

10. Radar level gauge according to one of the preceding claims, wherein the radar level gauge is configured to measure at a frequency above 100 GHz.

11. Radar level gauge according to one 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.

12. System for detecting fill levels, comprising at least one radar level measuring device according to one of claims 1 to 11 and a container for storing a material.

13. The system of claim 12, wherein the container comprises an agitator.

14. The system of claim 12 or 13, wherein the container comprises a heating coil.

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