Fill level measuring device

Abstract

The invention relates to a radar-based filling level measuring device (1), comprising the following parts: a semiconductor component (10) for generating a high-frequency electrical signal (s HF , e HF ) or for receiving a high frequency signal (e HF ) determines a filling level value (L); a dielectric waveguide (11a, b) which is placed in contact with the semiconductor component (10) so as to transmit a high frequency signal (s HF ) as the radar signal (S HF ) is coupled into the antenna and / or the radar signal (E) received from the antenna (12) HF ) as an electrical signal (e HF ) is coupled to the semiconductor component (10); a potting package (13) which radially encapsulates at least the waveguide (11a, b) so that a defined cavity (14) is formed between the waveguide (11a, b) and the potting package (13). The advantage of this design is that, especially at high radar frequencies, the radar signal (S HF 、E HF ) is efficiently coupled in and out of the radar signal (S). The fill-level measuring device (1) can thus be operated in an energy-efficient manner. Due to the implementation of semiconductor components and high radar frequencies, the fill-level measuring device (1) can also be designed compactly without reducing the radar signal (S HF , E HF )’s gathering.

Description

Technical Field

[0001] The invention relates to a fill level measuring device for measuring the fill level of a filling material located in a container. Background Art

[0002] In process automation technology, field devices are often used for capturing or modifying process variables. To this end, the functionality of the field devices is based in each case on a suitable measuring principle in order to capture the corresponding process variable, such as fill level, flow rate, pressure, temperature, pH value, redox potential or conductivity. A wide variety of such field devices are manufactured and distributed by Endress+Hauser.

[0003] For measuring the fill level of filling material in a container, radar-based measuring methods have been established because they are robust and require minimal maintenance. Within the scope of the present invention, the term "container" also refers to an unclosed container, such as a basin, a lake or a flowing body of water. The key advantage of radar-based measuring methods is its ability to measure the fill level quasi-continuously. In the context of this patent application, the term "radar" refers to a microwave signal with a frequency between 0.03 GHz and 300 GHz.

[0004] In the case of radar-based fill level measurement, the pulsed time-of-flight principle is the established measuring principle. Here, a pulse-shaped microwave signal is cyclically emitted in the direction of the filler and the flight time until the corresponding pulse-shaped reception signal is received is measured. Based on this measuring principle, fill level measuring devices can be implemented with relatively low circuit complexity. If more complex circuit technology is acceptable, FMCW (frequency-modulated continuous wave) is a possible measuring principle for radar-based fill level measurement. The operating principle of a fill level measuring device based on FMCW and pulse radar is described, for example, in "Radar Level Measurement" Peter Devine, 2000.

[0005] In the field of fill level measurement, the measurements are mainly carried out at radar frequencies of 6 GHz, 26 GHz or 79 GHz. In general, the higher the selected frequency band, the narrower the beam cone of the radar signal. Moreover, at least in the case of FMCW, higher frequency bands are preferred because a larger absolute frequency bandwidth can be used. For example, at 79 GHz, a bandwidth of 4 GHz is used, that is to say from 76 GHz to 80 GHz. With a larger bandwidth, a higher resolution of the distance measurement can in turn be achieved. Especially in the case of fill level measurement, this represents an important requirement, because, depending on the application, it is necessary to know the fill level as accurately as possible. Another advantage of using higher frequencies is that radar-based distance measuring devices can be equipped with more compact antennas without reducing the beam effect of the antenna. For example, in fill level measurement, this makes it possible to have a connection flange of reduced size for attachment to the container. Therefore, it is also desirable to operate the fill level or distance measurement generally at a frequency higher than 79 GHz (up to 300 GHz radar frequency).

[0006] At frequencies above 100 GHz, the high-frequency electrical signals with which radar signals are generated can no longer be guided via hybrid connection technology between the semiconductor components with which the corresponding high-frequency electrical signals are generated and the printed circuit board on which the semiconductor components are placed. Since the size of the connection structures to the various electronic components, such as bonding wires or soldering points, is in the order of magnitude of the wavelength of the radar signal, these connection structures interfere with the transmission behavior as parasitic elements. In addition, many materials commonly used in electronic devices lead to losses that increase with frequency, since high-frequency electrical signals are significantly attenuated even within a very short line distance. This is why, as the frequency increases, it is difficult to achieve high performance and reliable contact of semiconductor components with the help of standard hybrid technology. For this reason, in order to generate or receive radar signals, especially above 100 GHz, semiconductor components are used, and high-frequency electrical signals can be directly coupled out of the semiconductor components as radar signals, or the incoming radar signals can be directly converted into corresponding high-frequency electrical signals with the semiconductor components. Therefore, hybrid signal routing is no longer required. In this case, the radar signal is coupled out or coupled in with the help of a corresponding primary transmitter. This is, for example, a planar antenna, which is attached to the semiconductor component with the help of a micromechanical method. Such a semiconductor component is described in particular in publication DE 10 2015119 690 A1. This therefore prevents high-frequency electrical signals from having to be routed via external printed circuit boards, solder connections or bonding wires. This reduces the performance of the distance measuring device precisely at higher frequencies and the sensitivity to interference.

[0007] A further advantage of the monolithic construction is that signal generation and signal evaluation can be implemented in the same semiconductor component, so that the fill-level measuring device can have a more compact overall design. Depending on the measuring method, known circuit elements can be implemented in the semiconductor component in order to create a signal generation unit or a signal evaluation unit: In the case of FMCW, the high-frequency signal for the radar signal to be transmitted can be generated by a PLL (phase-locked loop); the received radar signal can be mixed with the high-frequency signal to be transmitted by a mixer, so that the distance or the fill level can be determined from the so-called difference frequency of the mixed signal. A correspondingly designed evaluation block can determine the difference frequency, for example, by means of an FFT (fast Fourier transform) of the mixed signal.

[0008] However, direct emission of radar signals from semiconductor components is not possible, at least in the case of fill level measurement, since the radiation from the primary radiator is mostly non-directional. Obviously, the radiation is focused via a dielectric lens. However, such a lens can only be adequately illuminated if the primary radiator has sufficient beam focusing or the lens is placed directly on the semiconductor component. However, strongly focused primary radiators have the disadvantage that a correspondingly sized chip surface must be retained on the semiconductor component for this purpose. Lenses mounted directly on the primary radiator then have the disadvantage that the semiconductor component is therefore also indirectly exposed to the fill or the environment associated with mechanical and thermal loads. Protective packaging, for example in the form of a pressure-resistant window, can only be implemented close to the semiconductor component with great difficulty.

[0009] It is therefore an object of the present invention to provide a radar-based fill-level measuring device which is designed for high radar frequencies and can be used under harsh ambient conditions. Summary of the invention

[0010] The invention achieves this object by a radar-based fill-level measuring device comprising at least the following items:

[0011] - A semiconductor component, the semiconductor component being constructed as follows:

[0012] o generating a high frequency electrical signal, preferably having a frequency of at least 100 GHz; and / or receiving a corresponding high frequency electrical signal, and

[0013] o determining a fill level value based at least on the received high-frequency signal,

[0014] a dielectric waveguide, preferably made of an insulating material with a dielectric value greater than 1 (especially HDPE or PTFE), wherein the waveguide is in contact with the semiconductor component so that the high-frequency signal is coupled as a radar signal to the semiconductor component.

[0015] - an antenna, and / or causing a received radar signal from the antenna to be coupled as an electrical signal into the semiconductor component,

[0016] - a potting package which radially encapsulates at least the waveguide such that a defined cavity is formed between the waveguide and the potting package.

[0017] It is advantageous for the fill-level measuring device according to the invention that the sealing and pressure-resistant encapsulation can be implemented spaced apart away from the sensitive semiconductor components towards the filling material, in particular by means of partial guidance of the radar signal in a waveguide. This simplifies the manufacturability of the fill-level measuring device. On the other hand, the fill-level measuring device according to the invention offers the advantage that effective coupling in and out of the radar signal is possible, in particular by means of the potting encapsulation spaced apart from the waveguide, without reducing the protection of the semiconductor components from thermal loads. As a result, the fill-level measuring device can be operated energy-efficiently on the one hand. On the other hand, by means of the implementation of the semiconductor components, the fill-level measuring device can be designed compactly, without reducing the focusing effect of the antenna. The fill-level measuring device can be designed flexibly depending on the field of application.

[0018] For example, for high temperature applications, the waveguide can be dimensioned to have a length of at least 3 cm, in particular greater than 8 cm, in order to thermally decouple the semiconductor component and any other electronics from the antenna. The coupling-in and coupling-out of radar signals can be further optimized if the potting package is designed such that the cavity between the waveguide and the potting package has a distance of at least twice the wavelength of the radar signal.

[0019] If the semiconductor component is arranged on a printed circuit board, the waveguide can be fixed to the Hall effect conductor component by attaching the electromagnetic shielding of the semiconductor component to the printed circuit board inside the potting package. In this case, the shielding fixes the waveguide toward the semiconductor component so that the radar signal can be coupled into the waveguide or into the semiconductor component in a loss-minimizing manner. Therefore, the fixing of the shielding of the semiconductor component and the waveguide is achieved by the same element. If the semiconductor component is arranged on a printed circuit board, the potting package can additionally be designed so that the surface of the printed circuit board facing away from the semiconductor component is additionally encapsulated. Therefore, any electronic components arranged on the back side of the printed circuit board are also covered by the potting package.

[0020] When the fill-level measuring device is designed with the above-described shielding, the manufacturability of the fill-level measuring device can be simplified by designing the waveguide in two parts, so that the waveguide is subdivided in the region of the shielding into a first section and a second section.

[0021] A possible housing of the fill-level measuring device can be designed so that at least the semiconductor component, the waveguide and the potting package are surrounded by the housing, wherein the antenna must be fastened outside the housing. Therefore, a grommet can be provided in the housing for coupling the radar signal in and out between the inside and the outside of the housing. Such a grommet can preferably be designed so that the waveguide is fixed to the antenna so that the radar signal is coupled to the antenna or into the waveguide in a lossless manner. In order to simplify the production of the fill-level measuring device, the grommet can also be designed to be self-centering relative to the waveguide. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention is explained in more detail with reference to the following drawings. Shown below is:

[0023] Figure 1 is a typical arrangement of a radar-based fill level measuring device on a container; and

[0024] Figure 2 is a sectional view of a fill-level measuring device according to the invention. DETAILED DESCRIPTION

[0025] In order to understand the present invention in a basic way, Figure 1 A typical arrangement of a radar-based fill level measuring device 1 on a container 2 is shown. In the container 2 is a filling material 3, whose fill level L is to be determined by the fill level measuring device 1. For this purpose, the fill level measuring device 1 is mounted on the container 2 above the maximum permitted fill level L. Depending on the field of application, the installation height h of the fill level measuring device 1 above the container bottom can be greater than 100 m.

[0026] Typically, the fill-level measuring device 1 is connected to a superordinated unit 4, such as a process control system or a decentralized database, via a bus system, such as "Ethernet", "PROFIBUS", "HART" or "WirelessHART". On the one hand, information about the operating state of the fill-level measuring device 1 can thus be communicated. On the other hand, information about the fill level L can also be transmitted via the bus system in order to control any inflow or outflow that may be present at the container 2.

[0027] Assumptions Figure 1The fill level measuring device 1 shown in FIG. 1 is designed as a free-radiating device, which comprises a corresponding antenna 12. As indicated, the antenna 12 is designed as a horn antenna, especially at radar frequencies below 60 GHz. Here, the antenna 12 is oriented so that the radar signal S HF Emitted in the direction of the filling material 3.

[0028] Radar signal S HF is reflected at the surface of the filling material 3 and, after a corresponding signal flight time, is received by the antenna 12 of the fill level measuring device 1 as a reflected radar signal E HF Assuming that the signal propagation time depends on the distance d=h−L of the fill-level measuring device 1 relative to the filling surface, the fill level can be determined based on the signal propagation time.

[0029] The aperture angle of the beam cone depends not only on the size of the horn antenna 12 but also on the radar signal S HF 、E HF The frequency at which the radar signal S is transmitted HF , or receiving the reflected radar signal E below the aperture angle HF The higher the frequency, the narrower the aperture angle. The narrow aperture angle reduces the risk of generating interfering reflections inside the container which could be incorrectly interpreted as fill level echoes. The potentially achievable resolution of the fill level depends on the frequency, at least in the case of fill level measuring devices operated by means of the FMCW method. Here too, the higher the frequency, the higher the potentially achievable resolution of the fill level value.

[0030] exist Figure 2 , a schematic construction of a fill-level measuring device according to the invention is shown, which can be operated at radar frequencies of more than 100 GHz and utilizes the advantages associated therewith:

[0031] The core of the fill-level measuring device 1 according to the invention is a semiconductor component 10 which, depending on the implemented measuring principle (FMCW or pulse propagation principle), can generate or process corresponding high-frequency signals s-1 with a frequency of up to 160 GHz or more. HF 、e HF When implementing the FMCW principle, the high-frequency signal s to be transmitted is generated, for example, by means of an oscillator (for example in the form of a “voltage-controlled oscillator”). HF , which is controlled by a PLL (Phase Locked Loop). For signal processing, the semiconductor component 10 may include a mixer on the receiving side for converting the high frequency signal s currently to be transmitted HF The high frequency signal currently received HFThis is used to be able to determine the distance d to the filling material 3 or the filling level L from the mixed signal in the corresponding circuit block of the semiconductor component 10 , for example by means of FFT (Fast Fourier Transformation) using the frequency of the mixed signal.

[0032] In the high-frequency component 1 according to the present invention Figure 2 In the design variant shown in FIG. 1 , the semiconductor component 10 is arranged on a printed circuit board 15 . The semiconductor component 10 and also any data transmission to the superordinated unit 4 are supplied via the printed circuit board 15 . Assuming that the high-frequency signal s HF 、e HF The generation and processing of the high frequency signals takes place completely on the semiconductor component 10, and the high frequency signals do not have to be conducted to the printed circuit board 15. This eliminates the loss-causing hybrid connection lines.

[0033] High frequency signals HF From the semiconductor component 10, for example via the primary transmitter ( Figure 2 (not explicitly shown) as the radar signal S HF is coupled into the waveguides 11a, b. Similarly, the radar signal E reflected in the container 2 HF The primary radiator is coupled into the semiconductor component 10 via the waveguides 11a, b. For this purpose, the primary radiator can be designed, for example, as a rectangular planar structure, which is arranged on the side of the semiconductor component 10 facing away from the printed circuit board 15. In this case, it is advantageous if the waveguides 11a, b are in direct contact with the semiconductor component 10, for example by corresponding bonding or statically-dominated contact pressure.

[0034] The cross-sectional shape (e.g. circular or rectangular) and the cross-sectional dimensions of the waveguides 11a, b will be adapted to the radar signal S to be emitted / coupled. HF , R HF frequency or desired mode. For a rectangular design, the two sides of the rectangle can be designed, for example, so that they have a side length ratio of 2:1. In this case, the first side length can be dimensioned in each case to have a high-frequency signal S HF , R HF Therefore, the second side length can be designed to be at 2 / 3 of the wavelength. In order to conduct the radar signal S in the waveguides 11a, b in a lossless manner HF 、E HF , the material of the waveguide must be selected accordingly with regard to the dielectric constant. Assuming that a dielectric constant of at least approximately 1.5 is advantageous for the waveguide, HDPE or PTFE are particularly suitable as materials for the waveguides 11a, b.

[0035] If the semiconductor component 10 is not arranged as a "bare die" on the printed circuit board 15, the package of the semiconductor component 10 must be suitable in such a way that a corresponding waveguide contact is possible between the waveguides 11a, b and the primary radiator. For example, a potting package can be used, with which the surface of the primary radiator is recessed. Thus, the semiconductor component 10 can be designed, for example, as a correspondingly modified DIP (dual in-line package) or QFN (quad flat no-lead package) component. In order to simplify the mounting of the waveguides 11a, b on the Hall effect conductor element 10, it is also conceivable to design the package in such a way that the waveguides 11a, b are self-centering with respect to the primary radiator.

[0036] exist Figure 2 In the exemplary embodiment of the filling level measuring device 1 according to the invention shown in , the waveguides 11a, b are fixed relative to the semiconductor component 10 by means of a shielding 16. The shielding 16 is designed as a cap and is mounted on the printed circuit board 15 so that it covers the semiconductor component 10 on the printed circuit board 15. In order to achieve a shielding effect, it is necessary to design at least the surface of the shielding 16 in an electrically conductive manner. Thus, for example, the shielding 16 can be made completely of metal. However, a coated plastic substrate to which a metal coating is applied, for example by PVD (physical vapor deposition), can also be used as a cap. Assuming that the shielding 16 includes corresponding grommets on the axis of the waveguides 11a, b, it is responsible for fixing the waveguides 11a, b relative to the semiconductor component 10 in addition to providing shielding.

[0037] The potting package 13 is arranged radially around the waveguides 11a, b outside the shield 16. According to the invention, the waveguides 11a, b are thus potted so that a defined cavity 14 is formed between the waveguides 11a, b and the potting package 13. The potting package 13 is constructed so that it has a radially extending cavity 14 from the waveguides 11a, b, at least the radar signal S HF 、E HF The distance r is twice the wavelength of the radar signal. The distance r decisively increases the HF 、E HF The potting package 13 can be constructed, for example, by means of corresponding potting cups surrounding the waveguides 11a, b, which define the structure of the potting package 13 during potting. In the design variant shown, the potting package 13 further surrounds the surface of the printed circuit board 15 facing away from the semiconductor component 10. Thus, any electronic components on the back side of the printed circuit board 15 are also encapsulated. Optionally, as Figure 2As shown, the outer surface 21 of the potting package 13 can be designed to be electromagnetically shielded in order to achieve improved electromagnetic compatibility. Here again, it is conceivable that the outer surface of the potting package 13 is metal-coated, for example by PVD (physical vapor deposition). Alternatively, a separate metal potting cup can also be used for this purpose.

[0038] To transmit the radar signal S HF Or to receive the reflected radar signal E HF , the waveguides 11a, b are extended in the horn antenna 12.

[0039] The horn antenna 12 is located on the outside of a housing 17 of the fill-level measuring device 1, in which a printed circuit board 15 with semiconductor components 10, waveguides 11a, b and a shield 16 are accommodated. In order to fix the waveguides 11a, b toward the horn antenna 12, the housing 17 comprises corresponding grommets 18 for the waveguides 11a, b. Figure 2 As shown, the grommet 18 may also be designed to make the waveguides 11a, b self-centering during assembly.

[0040] In order to isolate the interior of the housing 17 from the interior of the container 2 in a sealed and pressure-resistant manner, a window 19 is inserted between the waveguides 11a, b and the horn antenna 12 at the level of the grommet 18 and for the radar signal E HF , S HF is transparent. It can therefore be made of glass or ceramic and fixed, for example, by adhesive bonding, welding or some other melt-joining method. Preferably, the window 19 is made of a non-conductive material having a dielectric value greater than 1. In terms of thickness, the window 19 is ideally designed so that it can withstand an absolute pressure of at least 100 bar.

[0041] In order to prevent the enlargement of the horn antenna 12 and the associated reduction in performance, a filler 20 is introduced throughout the interior of the horn antenna 12. The filler 20 is made of an electrically insulating material. Since the filler 20 acts as a dielectric, the design of the horn antenna 12 must be adapted accordingly to the dielectric.

[0042] For guiding the radar signal S between the semiconductor component 10 and the horn antenna 13 by means of the waveguide 11 a, b according to the invention HF 、E HF Advantageously, the distance between the printed circuit board 15 and the horn antenna 12 can be dimensioned as required. In the case of measurement applications in which high temperatures above 100° C. prevail in the interior of the container, the waveguide can be dimensioned, for example, to have a length of, for example, up to 8 cm or more, so that the electronic components on the printed circuit board are accordingly thermally decoupled from the climate in the container 3.

[0043] like Figure 2As shown, in order to simplify the modular production of various variants of the fill-level measuring device 1 according to the invention, the waveguide 11a, b can be constructed in two parts. Figure 2 In the design variant of the fill-level measuring device 1 shown in FIG. 1 , the waveguide 11a, b is therefore divided at the level of the shielding layer 16 into a first section 11a facing the semiconductor 10 and a second section 11b facing the horn antenna 12 . HF 、E HF In order to achieve unimpeded transmission along the final contact point between the segments 11a, 11b, it is advantageous if the segments 11a, 11b are connected to one another at least by a static contact pressure. HF 、E HF It is also possible to bond this contact point with a transparent adhesive.

[0044] and Figure 2 In contrast to the illustration in FIG. 1 , the waveguides 11a, b can alternatively be designed with a curved course, preferably with a rectangular cross section. For this purpose, it is advantageous in the context of manufacturing if the waveguides 11a, b are made of a flexible material. In this regard, it is conceivable to bend the waveguides 11a, b along their course by 90° and to arrange the horn antenna 12 on the housing 12 accordingly at an angle, so that the overall structure of the fill level measuring device 1 can be designed as compactly as possible depending on the installation situation on the container 2.

[0045] Reference numerals list

[0046] 1 Fill level measuring device

[0047] 2 Container

[0048] 3 Filling materials

[0049] 4 Parent unit

[0050] 10 Semiconductor components

[0051] 11a, b Waveguide

[0052] 12 Antenna

[0053] 13 Casting package

[0054] 14 Cavity

[0055] 15. Printed Circuit Board

[0056] 16 Shielding

[0057] 17 Housing

[0058] 18 Grommet

[0059] 19 Window

[0060] 20 Filling

[0061] 21 Electromagnetic shielding outer surface of the package

[0062] d Distance

[0063] E HF Incoming radar signal

[0064] H Installation height

[0065] L Fill level

[0066] r distance

[0067] S HF Radar signal

[0068] s HF 、e HF High frequency signal

Claims

1. A fill level measuring device based on radar, comprising: - A semiconductor component (10) configured as ○ Generate and receive high frequency electrical signals, and o determining a fill level value based at least on the received high-frequency electrical signal, - a dielectric waveguide in contact with the semiconductor component (10) in order to couple the high-frequency electrical signal as a radar signal to - coupling a received radar signal from the antenna (12) into the semiconductor component (10) as a received high-frequency electrical signal, and - a potting package (13), the potting package (13) radially encapsulating at least the dielectric waveguide so that a defined cavity (14) is formed between the dielectric waveguide and the potting package (13); The potting package (13) is designed such that the cavity (14) between the dielectric waveguide and the potting package (13) has a distance (r) of at least twice the wavelength of the radar signal.

2. Fill level measuring device according to claim 1, wherein: The dielectric waveguide is dimensioned to have a length of at least 3 cm.

3. Fill level measuring device according to claim 2, wherein: The dielectric waveguide is dimensioned to have a length greater than 8 cm.

4. The filling level measuring device according to any one of claims 1 to 3, comprising: - a printed circuit board (15) on which the semiconductor component (10) is arranged, - an electromagnetic shield (16) for the semiconductor component (10), the electromagnetic shield (16) being mounted on the printed circuit board (15) inside the potting package (13), wherein the shield (16) fixes the dielectric waveguide toward the semiconductor component (10) so that the radar signal can be coupled into the dielectric waveguide or into the semiconductor component (10).

5. Fill level measuring device according to claim 4, wherein: The dielectric waveguide is designed in two parts, such that the dielectric waveguide is subdivided by the shielding member (16) into a first section (11a) and a second section (11b).

6. Fill level measuring device according to any one of claims 1 to 3, comprising: - a housing (17) which surrounds at least the semiconductor component (10), the dielectric waveguide and the potting package (13), wherein the antenna (12) is fixed to the outside of the housing (17), and - a grommet (18) in the housing (17), the grommet (18) fixing the dielectric waveguide towards the antenna (12) so that the radar signal can be coupled into the antenna (12) or into the dielectric waveguide.

7. Fill level measuring device according to any one of claims 1 to 3, wherein: The dielectric waveguide is made of an insulating material having a dielectric value greater than 1.

8. Fill level measuring device according to claim 7, wherein: The dielectric waveguide is made of HDPE or PTFE.

9. The filling level measuring device according to claim 4, wherein: The potting encapsulation (13) encapsulates a surface of the printed circuit board (15) facing away from the semiconductor component (10).

10. Fill level measuring device according to any one of claims 1 to 3, wherein: The outer surface (21) of the potting package (13) is designed to be electromagnetically shielded.

11. Fill level measuring device according to any one of claims 1 to 3, wherein The semiconductor component (10) is designed to generate a high-frequency electrical signal with a frequency of at least 100 GHz and to process the corresponding high-frequency electrical signal after receiving it.

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