Assembly for high-frequency field devices, high-frequency field devices, and measuring location

Abstract

The invention relates to an assembly comprising: a coaxial plug connector (21) comprising an inner conductor (22), a surrounding outer conductor (23), a socket (24) which has an end face (25) and multiple spacers (26); and a printed circuit board (11) with a galvanically isolated conductor path (12) and conductor structure (13), multiple connection surfaces (14, 15), and shielding elements (32); wherein the inner conductor (22) and the conductor path (12) are electrically connected, the outer conductor (23) and the conductor structure (13) are electrically connected, the socket (24) is integrally bonded to the outer conductor (23), each spacer (26) protrudes from the end face (25) and is molded onto the socket (24), the coaxial plug connector (21) is arranged on the printed circuit board (11), each spacer (26) is integrally bonded to a first joint location (14), and a gap (31) is formed between the end face (25) of the socket (24) and the printed circuit board (11). Each shielding element (32) is positioned with a space between two adjacent spacers (26) and is integrally bonded to both the socket (24) as well as to one of the second connection surfaces (15).

Description

[0001] Assembly for high-frequency field devices, high-frequency field devices and measuring point

[0002] The invention relates to an assembly comprising a coaxial connector arranged on a circuit board and transmitting a high-frequency electromagnetic signal from a conductor to a conductor track. The invention further relates to high-frequency field devices and measuring points comprising said assembly and configured to detect various measured variables using suitable sensors.

[0003] High-frequency field devices are used in process and automation technology, particularly to detect fill levels and / or to determine the dielectric properties of a medium. For this purpose, the applicant manufactures and markets a variety of different field device types. Examples of field devices for determining dielectric properties using an electromagnetic signal in the microwave range are known from DE102017130728A1, in which a field device is taught that determines a dielectric value of a medium by measuring a phase shift of an electromagnetic signal that occurs when electromagnetic waves with different frequencies propagate in a medium. Furthermore, the field device for measuring a dielectric value, known from

[0004] DE102020134320A1 , the permittivity of a fluid conveyed in a pipe is measured, whereby a change in the amplitude and phase of a microwave signal that has passed through a container is measured and is closely related to the dielectric value of the medium. Examples of field devices for determining a fill level are known from DE102012104858A1 and DE102013108490A1 , which teach field devices that determine a distance to a surface of a medium or to another radar target in a pipe by generating frequency-modulated radar transmission signals that are reflected at the surface of a medium and received again. Properties such as the distance to the surface of the medium are determined from the properties of the received signal.Furthermore, the level gauge, known from DE102020134061 A1, measures the fill level of filling materials in containers by emitting a radar signal in the high-frequency range and receiving the radar signal reflected by the filling material according to the time-of-flight principle. The radar signal has frequencies between 0.03 GHz and 300 GHz, with typical frequency bands for this type of measurement being 2, 26, 79, or 120 GHz. All of the above-mentioned types of high-frequency field devices are based on the fact that a signal to be transmitted is generated by measuring electronics, routed to a transmitting antenna and radiated there, and a measurement signal is received by a receiving antenna. The signal to be transmitted and the measurement signal are transmitted via coaxial conductors between the antenna arrangement and the respective electronic components.

[0005] In this case, the coaxial conductors are connected to the respective electronic components using coaxial connectors. This can lead to the problem that high-frequency interference signals can escape laterally at the junctions between the inner conductor of a coaxial connector and a conductor track. These interference signals can then interfere with the electronic components of a device, thereby affecting measurements. In particular, these interference signals can make measurements of material properties impossible if the amplitude of a measurement signal is comparable to the amplitude of the interference signal.

[0006] The problem is solved by US2003052755A1 , which teaches a coaxial connector having an electromagnetic protective sheath with an annular mounting surface that can be integrally bonded to a printed circuit board by means of full-surface adhesive or soldering, thus preventing the escape of interference. The prior art is plagued by the problem that, when connected to the printed circuit board, air is trapped inside the annular structure, where there is a hole for the inner conductor. This air expands and contracts when a solder connection is made, thereby impairing the integral connection and, in particular, creating the risk of a short circuit between the inner and outer conductors due to running solder.

[0007] The invention is based on the object of providing an assembly that, on the one hand, reduces the interference signals emerging laterally from the interface between the inner conductor of a coaxial connector and a conductor track, and, on the other hand, enables an unaffected solder connection, reducing the risk of a short circuit between the inner and outer conductors of the coaxial connector. The invention solves this problem by an assembly according to independent claim 1.

[0008] The assembly according to the invention comprises a coaxial connector with an inner conductor, with an outer conductor surrounding the inner conductor, and with a base having an end face and a plurality of spacers; a printed circuit board with a conductor track and with a conductor structure having a plurality of first connecting surfaces, a plurality of second connecting surfaces, and a plurality of shielding elements; wherein the conductor track is galvanically isolated from the conductor structure; wherein the inner conductor is electrically connected to the conductor track; wherein the outer conductor is electrically connected to the conductor structure; wherein the base is integrally connected to the outer conductor or is molded onto the outer conductor; wherein each spacer from the plurality of spacers is molded onto the base and protrudes relative to the end face.wherein the coaxial connector is configured to be connected to a coaxial conductor and is arranged on the circuit board; wherein each of the spacers is integrally connected to a first joint of the conductor structure, in particular by means of a soldered connection; wherein a gap is formed between the end face of the base and the circuit board; wherein the shielding elements are each positioned between two adjacent spacers at a distance from these and are integrally connected both to the base and to one of the second connecting surfaces.

[0009] In one embodiment of the invention, the end face of the base has a substantially polygonal shape with at least three corners; wherein the plurality of spacers each has one spacer per corner of the polygon.

[0010] In one embodiment of the invention, the polygon is a rectangle, in particular a square.

[0011] In one embodiment of the invention, shielding elements are mounted spaced apart between each two adjacent spacers; the respective distances between one shielding element and the two adjacent spacers are essentially equal. In one embodiment of the invention, the shielding elements have a dimension of 100 micrometers or more in a direction parallel to the circuit board.

[0012] An assembly arrangement according to the invention comprises two assemblies according to the invention, wherein the two sockets of the two coaxial connectors have a distance of less than 1 cm.

[0013] A field device according to the invention for determining a measured variable of a medium, in particular the fill level or a dielectric property, comprises one or more assemblies or assembly arrangements according to at least one of the preceding claims.

[0014] One embodiment of the field device comprises electronics connected to an assembly, configured to generate an electrical transmission signal to be transmitted, in particular with a carrier frequency between 0.03 GHz and 300 GHz, and to determine a defined characteristic value based on a received reception signal.

[0015] One embodiment of the field device comprises one or more antennas for transmitting and / or receiving high-frequency electromagnetic signals; one or more coaxial conductors for conducting the transmitted signal to one of the one or more antennas, and for conducting the received signal received by one of the one or more antennas to one of the modules connected to the electronics.

[0016] A measuring point according to the invention comprises a field device according to the invention and a container for containing a medium, wherein the field device is arranged on or at the container and is connected to an antenna via a coaxial conductor, and wherein the measured variable to be determined is the fill level of the medium.

[0017] A field device according to the invention comprises: a container for containing, in particular a tube for guiding, a medium; wherein the electronics are arranged on or at the container; wherein the electronics are connected to two antennas via two coaxial conductors; wherein the measured variable to be determined is a dielectric property of the medium or one or more measured variables derivable therefrom; wherein the signal frequency is at least 0.1 GHz and less than 40 GHz, in particular less than 20 GHz.

[0018] The invention has the advantage of allowing the use of commercially available coaxial connectors with a base and molded-on spacers. In these coaxial connectors, the spacers have a square footprint with an edge length of approximately 25% to 35% of the side length of the square base. These coaxial connectors with spacers enable a manufacturing process using solder connections without impairing the solder structure and / or causing short circuits. The amplitudes of the escaping interference signals can then be significantly reduced by attaching shielding elements, which can be manufactured cost-effectively from preformed solder.Another advantage is that a normal assembly process with high manufacturing precision can be carried out when assembling the circuit board. First, the solder paste is applied to the circuit board, then the solder preforms are mechanically assembled, and finally the coaxial connector is assembled. During the subsequent reflow soldering of the circuit board, the solder preforms melt and form a bond between the coaxial connectors and the circuit board. Another advantage is that very little additional space is required for the assembly.

[0019] The invention is explained using the following figures.

[0020] It shows:

[0021] Fig. 1a: an embodiment of a printed circuit board 11 with first connecting surfaces 14 and second connecting surfaces 15;

[0022] Fig. 1 b: an embodiment of the printed circuit board 11 ' with connecting surfaces 14 according to the prior art;

[0023] Fig. 2: a schematic representation of an embodiment of the coaxial connector 21;

[0024] Fig. 3: a schematic side view of an embodiment of the invention with two adjacent coaxial connectors 21 and 2T; Fig. 4: a schematic cross-section of an embodiment of a (radar-based) level measuring device; and

[0025] Fig. 5: a schematic representation of a design of a (microwave based) dielectric measuring device.

[0026] The printed circuit board 11' shown in Fig. 1a corresponds to the prior art and comprises four connecting surfaces 14, via which four corresponding spacers 26 of a coaxial connector 21 are connected to the conductor structure 13, and furthermore the conductor track 12 which is connected to the inner conductor 22 of the coaxial connector 21.

[0027] The printed circuit board 11 shown in Fig. 1b is used for an embodiment of the invention, wherein four additional connecting surfaces 15 are provided, via which an electrically conductive connection is established between the outer conductor 23 of the coaxial connector and the conductor structure 13 by the shielding elements 32. On both sides, the conductor structure 13 is represented by vertical hatching, which connects the first connecting surfaces 14 and the second connecting surfaces 15.

[0028] The embodiment of a coaxial connector 21 shown in Fig. 2 comprises an inner conductor 22. In one embodiment, the inner conductor 22 runs inside the hollow, cylindrical outer conductor 23, with both conductors connected by an insulator. The outer conductor 23 is integrally connected to the polygonal base 24, which has an end face 25 with spacers 26 formed on its corners and a hole in the center through which the inner conductor is passed to connect to the conductor track 12 on the circuit board 11. Each of the shielding elements 32 is positioned between two spacers 26 at the edge of the end face.

[0029] The embodiment of the invention shown in Fig. 3 comprises two coaxial connectors 21 and 2T, which are spaced apart by a distance d. In this embodiment, the outer conductor 23 is molded onto the polygonal base 24 and electrically connected to the circuit board 11 by its spacers 26. Furthermore, a gap is formed between the base 24 and the circuit board 11. Shielding elements 32, consisting of preformed solder parts, are integrally formed on the side of the base 24 between two adjacent spacers 26, both on the base 24 and on a connecting surface 15, and serve to reduce the amplitude of the interference signal emerging laterally from the interface between the inner conductor 22 and the conductor track 12.

[0030] The embodiment of a measuring point shown in Fig. 4 consists of a field device and a container 44. In one embodiment of the invention, the field device is designed as a (radar-based) level measuring device. Accordingly, the level measuring device can, for example, be arranged on a container 44 containing a medium 45 whose fill level is the quantity to be measured. In this embodiment, the field device comprises electronics 41 for generating and evaluating electrical signals. A generated electrical signal is transmitted via a coaxial conductor 43 from the electronics 41 to the antenna 42 and emitted by the antenna 42 in the form of a radar signal, which is reflected off the surface of the medium 45. This creates a reflected radar signal, which is received by the antenna 42 and transmitted as a received signal back to the electronics 41 via the coaxial conductor 43.

[0031] The embodiment of the invention shown in Fig. 5 is a (microwave-based) field device for measuring the dielectric properties of a medium 45. Accordingly, the field device can, for example, be arranged on a pipe through which the medium 45 flows. In one embodiment, the field device comprises electronics 41, which includes a unit that generates a transmit signal and a unit that evaluates a receive signal, wherein the two units are each connected to a separate assembly according to the invention. A signal generated by the transmit signal generating unit is transmitted via a coaxial conductor 43 to a first antenna 42, which radiates the signal as an electromagnetic (microwave) signal into the medium 45. A second antenna 42' receives the (microwave) signal and transmits it as a receive signal via a coaxial conductor 43' to the unit that evaluates the receive signal. List of Reference Symbols

[0032] 11 Circuit board

[0033] 12 conductor tracks

[0034] 13 Ladder structure

[0035] 14 First connecting surfaces

[0036] 15 Second connecting surfaces

[0037] 21 coaxial connectors

[0038] 22 inner conductors

[0039] 23 outer conductors

[0040] 24 bases

[0041] 25 frontal area

[0042] 26 spacers

[0043] 31 Gap between coaxial connector and circuit board

[0044] 32 Shielding element

[0045] 41 Electronics

[0046] 42 Antenna

[0047] 43 coaxial conductors

[0048] 44 Container

[0049] 45 Medium

Claims

Patent claims 1. An assembly comprising: a coaxial connector (21) having an inner conductor (22), an outer conductor (23) surrounding the inner conductor (22), and a base (24) having an end face (25) and a plurality of spacers (26); a printed circuit board (11) having a conductor track (12) and a conductor structure (13) having a plurality of first connecting surfaces (14), a plurality of second connecting surfaces (15), and a plurality of shielding elements (32); wherein the conductor track (12) is galvanically isolated from the conductor structure (13); wherein the inner conductor (22) is electrically connected to the conductor track (12); wherein the outer conductor (23) is electrically connected to the conductor structure (13); wherein the base (24) is integrally connected to the outer conductor (23) or is molded onto the outer conductor (23);wherein each spacer (26) from the plurality of spacers is formed on the base (24) and protrudes from the end face (25); wherein the coaxial connector (21) is designed to be connected to a coaxial conductor (43) and is arranged on the printed circuit board (11); wherein each of the spacers (26) is integrally connected to a first joint (14) of the conductor structure (13), in particular by means of a soldered connection; wherein a gap (31) is formed between the end face (25) of the base (24) and the printed circuit board (11); wherein the shielding elements (32) are each positioned between two adjacent spacers (26) at a distance from these and are integrally connected both to the base (24) and to one of the second connecting surfaces (15).

2. An assembly according to claim 1, wherein the end face (25) of the base (24) has a substantially polygonal shape with at least three corners; wherein the plurality of spacers each comprises one spacer (26) per corner of the polygon.

3. Assembly according to claim 2, wherein the polygon is a rectangle, in particular a square.

4. An assembly according to one of claims 1 to 3, wherein spaced-apart shielding elements (32) are mounted between each two adjacent spacers (26); wherein the respective distances between a shielding element (32) and the two adjacent spacers (26) are substantially equal.

5. An assembly according to any one of claims 1 to 4, wherein the shielding elements (32) have an extension of 100 micrometers or more in a direction parallel to the circuit board (11).

6. Assembly arrangement comprising at least two assemblies according to one of claims 1 to 5, wherein the at least two sockets (24 and 24') of the at least two coaxial connectors have a distance of less than 1 cm.

7. Field device for determining a measured variable of a medium, in particular the fill level or a dielectric property, comprising: one or more assemblies or assembly arrangements according to at least one of the preceding claims.

8. Field device according to claim 7, further comprising: an electronics unit (41) connected to an assembly, configured to generate an electrical transmission signal to be transmitted, in particular with a carrier frequency between 0.03 GHz and 300 GHz, and to determine a defined characteristic value based on a received reception signal.

9. Field device according to claim 8, further comprising: one or more antennas (42) for transmitting and / or receiving high-frequency electromagnetic signals; one or more coaxial conductors (43) for conducting the transmitted signal to one of the one or more antennas, and for conducting the received signal received by one of the one or more antennas into one of the assemblies connected to the electronics (41).

10. A measuring point comprising: a field device according to one of claims 7 to 9; a container (44) for containing a medium (45); wherein the field device is arranged on or at the container (44) and is connected to an antenna (42) via a coaxial conductor (43); wherein the measured variable to be determined is the fill level of the medium (45).

11. Field device according to one of claims 7 to 9, comprising: a container (44) for containing, in particular a tube for guiding, a medium (45); wherein the electronics (41) is arranged on or at the container (44); wherein the electronics (41) is connected to two antennas (42 and 42') via two coaxial conductors (43 and 43'); wherein the measured variable to be determined is a dielectric property of the medium (41) or one or more measured variables derivable therefrom; wherein the signal frequency is at least 0.1 GHz and less than 40 GHz, in particular less than 20 GHz.

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