CN207456563U - For the radar levelmeter of the high-frequency model and application of the level gauging high-frequency model - Google Patents

Abstract

The utility model provides a high-frequency module for level measurement and a radar level gauge using the high-frequency module. The high-frequency module includes: a transmitting device, a waveguide device and a PCB board, wherein the transmitting device includes: a radiating element and a non-conductive cover, the radiating element and the non-conductive cover are arranged on the same side of the PCB, and the non-conductive cover The radiation cavity is defined with the PCB board, so that the radiation element is placed in the radiation cavity, wherein the waveguide device and the emission device are installed on the same side of the PCB board, and a waveguide path corresponding to the radiation element is formed, and the non-conductive cover The cover part covering the radiating element is in contact with the bottom edge of the part of the waveguide device forming the waveguide path, and the height of the cover part is set so that the distance between the radiation surface of the radiating element and the starting point of the waveguide path is less than The wavelength of electromagnetic waves emitted by a radiating element. The high-frequency module seals the radiating element by means of a non-conductive module cover, so that unnecessary reflections caused by the seal do not occur.

Description

High-frequency module for level measurement and radar level gauge using the high-frequency module

technical field

The utility model relates to a material level measurement technology, in particular to a high frequency module for material level measurement and a radar level gauge using the high frequency module.

Background technique

The radar level gauge is a measuring instrument that measures the distance between the signal emission point of the level gauge and the measured material point by measuring the time interval between the radar emission signal and the reflection signal reception.

For a radar level gauge with a waveguide, the electromagnetic signal is usually generated by the signal generating device of the high frequency module of the radar level gauge, and then emitted by the radiation element of the high frequency module, and the transmitted signal is then transmitted by the waveguide.

For safety reasons of explosion protection, it is necessary to prevent explosive substances or gas mixtures from entering the interior of the radar level gauge from the inside of the container containing the measured material.

For example, Chinese Invention Patent Application Publication CN104428943A and Chinese Invention Patent Application Publication CN104428944A both disclose a waveguide coupling input device with a seal, a high-frequency module, a material level radar and its application, by setting the seal at the initial region of the waveguide To isolate the high-frequency module from the environment in an airtight manner. However, this special arrangement of seals needs to cooperate with the initial area of the waveguide, the transition area leading to the main area of the waveguide, and the mutual size relationship between the main areas of the waveguide (mutual size relationship between inner diameters), and it is also necessary to set the vents inside and outside the waveguide. Auxiliary components such as boards have complex structures and the deviation of the seal will result in loss of sealing effect or device failure. In addition, the connection between the seal and the waveguide will also generate unnecessary reflections on the signal emitted by the radiating element.

Utility model content

The utility model provides a new high-frequency module for level measurement, which seals the radiation element through a non-conductive module cover, avoids unnecessary reflection caused by the seal, and has a simpler structure and is easier to process. The process can be simplified and the cost can be reduced.

According to one aspect of the present utility model, a high-frequency module for level measurement is provided, which includes: a transmitting device, a waveguide device and a PCB board, wherein the transmitting device includes: a radiation element and a non-conductive cover , the radiation element and the non-conductive cover are arranged on the same side of the PCB board, and the non-conductive cover and the PCB board define a radiation cavity, so that the radiation element is placed in the radiation cavity, wherein the The waveguide device and the emitting device are installed on the same side of the PCB board, and form a waveguide path corresponding to the radiation element, and the non-conductive cover covers the cover part of the radiation element and the Bottom edges of the part of the waveguide device forming the waveguide are connected, and the height of the cover part is set so that the distance between the radiation surface of the radiating element and the starting point of the waveguide is smaller than the The wavelength of electromagnetic waves emitted by a radiating element.

According to the high-frequency module of the embodiment of the present invention, for example, the height of the cover part of the non-conductive cover covering the radiating element is half of the wavelength of the electromagnetic wave emitted by the radiating element.

According to the high-frequency module of the embodiment of the utility model, for example, the non-conductive cover is made of PTFE plastic or PP plastic to cover the cover part of the radiation element, and the height of the cover part is 1.34mm.

According to the high-frequency module of the embodiment of the present utility model, for example, the cover part of the non-conductive cover covering the radiation element is in contact with the bottom edge of the tube wall forming the wave guiding path of the wave guiding device.

According to the high-frequency module of the embodiment of the present utility model, for example, the waveguide path is a columnar cavity or has a variable-diameter cavity structure.

According to the high frequency module of the embodiment of the present utility model, for example, the part of the wave guiding device forming the wave guiding path is made of metal material.

According to the high-frequency module of the embodiment of the present invention, for example, the radiation element is installed on the insulating layer of the PCB, and the non-conductive cover is installed on the PCB.

According to the high-frequency module of the embodiment of the present utility model, for example, the high-frequency module further includes a radar signal transceiving device, the radar signal transceiving device includes one or more chips, and is electrically connected to the radiation element of the transmitting device, the The chip includes a microwave chip that generates electromagnetic waves emitted by the radiating element or has such a function.

According to the high-frequency module of the embodiment of the present invention, for example, a metal layer is coated on the surface of the insulating layer of the PCB board, and then circuit wiring is formed on the metal layer, and the radar signal transceiver and the radiation element are connected electrical connection.

According to the high-frequency module of the embodiment of the present invention, for example, the electromagnetic wave signal generated by the chip is transmitted to the radiation element through a microstrip line.

According to the high-frequency module of the embodiment of the present invention, for example, the chip and the microstrip line and the radiation element are arranged on the same side of the PCB board, and the chip or the chip and the microstrip The strip line is arranged in the space defined by the absorbing material.

According to the high-frequency module of the embodiment of the present invention, for example, the absorbing material is arranged in the space defined by the non-conductive cover.

According to the high-frequency module of the embodiment of the present utility model, for example, the radiation element is a sheet-shaped device with a small area.

According to the high-frequency module of the embodiment of the present invention, for example, the high-frequency module is suitable for 75-120 GHz radar level measurement application.

According to another aspect of the present invention, a radar level gauge is provided, which includes the aforementioned high-frequency module.

According to another aspect of the present utility model, a method of manufacturing a radar level gauge is provided, which includes: forming a part of the metal layer on the insulating layer of the PCB board; installing a radiation element on the insulating layer; Install the radar signal transceiver and non-conductive cover on the same side of the insulating layer as the radiating element; install the waveguide on the same side; install the high-frequency module on the shell part of the radar level gauge head; The space defined by the shell part of the radar level gauge head is filled with sealant.

According to still another aspect of the present utility model, a radar level gauge manufactured by the aforementioned method is provided.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description only relate to some embodiments of the present invention, rather than to the present invention. New types of restrictions.

Fig. 1 is an exploded view of a high-frequency module for a radar level gauge according to an embodiment of the present invention;

FIG. 2A is a perspective view of the assembled high-frequency module shown in FIG. 1;

Fig. 2B is a perspective view from another angle after the high-frequency module shown in Fig. 1 is assembled;

Fig. 3A is a partial frontal cross-sectional view of the assembled high-frequency module shown in Fig. 1;

Fig. 3B is a partial side sectional view of the assembled high-frequency module shown in Fig. 1;

Fig. 4A schematically shows a partial front sectional view of the radar level gauge with the high-frequency module shown in Fig. 1;

Fig. 4B schematically shows a partial side sectional view of the radar level gauge with the high-frequency module shown in Fig. 1;

Fig. 5A and Fig. 5B schematically show a front partial sectional view and a side partial sectional view of a high frequency module according to another embodiment of the present invention;

Fig. 6A and Fig. 6B schematically show a front partial sectional view and a side partial sectional view of a high frequency module according to yet another embodiment of the present invention.

Attached text

100 launchers

101 radiating elements

102 non-conductive cover

103 radiation cavity

200 wave guide device

201 waveguide channel

300 PCB boards

301 insulating layer

302 metal layer

303 substrate

400 radar signal transceiver device

401 chip

402 microstrip line

403 absorbing material

501 screw

502 tape

Detailed ways

In order to make the purpose, technical solution and advantages of the embodiment of the utility model clearer, the technical solution of the embodiment of the utility model will be clearly and completely described below in conjunction with the accompanying drawings of the embodiment of the utility model. Apparently, the described embodiments are some of the embodiments of the present invention, but not all of them. Based on the described embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

Unless otherwise defined, the technical terms or scientific terms used herein shall have the usual meanings understood by those skilled in the art to which the present invention belongs. "First", "second" and similar words used in the utility model patent application specification and claims do not indicate any order, quantity or importance, but are only used to distinguish different components. Likewise, "a" or "a" and the like do not necessarily imply a numerical limitation. "Comprising" or "comprising" and similar words mean that the elements or items appearing before the word include the elements or items listed after the word and their equivalents, without excluding other elements or items. Words such as "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "Down", "Left", "Right" and so on are only used to indicate the relative positional relationship. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

Fig. 1 is an exploded view of a high frequency module for a radar level gauge according to an embodiment of the present invention. As shown in FIG. 1 , the emitting device 100 includes a radiation element 101 , a non-conductive cover 102 , and a radiation cavity 103 formed between the radiation element 101 and the non-conductive cover 102 . Wherein, the radiation element 101 and the non-conductive cover 102 are arranged on the same side of the PCB board 300, specifically, the radiation element 101 is installed on the insulating layer of the PCB (printed circuit board) 300, and the non-conductive cover 102 is also installed on the On the PCB, a radiation cavity 103 is formed, so that the radiation element 101 is placed in the radiation cavity 103 . The non-conductive cover 102 can be pasted on the PCB board 300 by, for example, double-sided tape.

The waveguide device 200 and the transmitting device 100 are installed on the same side of the PCB board 300, and form a waveguide path 201 corresponding to the position and area of the radiating element 101. The channel through which emitted electromagnetic signals are transmitted. Optionally, the columnar cavity is a cylindrical cavity (as shown in Figures 5A and 5B). The waveguide 201 may also have a variable-diameter cavity structure (as shown in FIG. 6A and FIG. 6B ). Generally speaking, the waveguide device 200, at least the part of the waveguide device 200 constituting the waveguide channel 201, is made of metal material, which can shield electromagnetic waves, thus guiding the electromagnetic waves emitted from the radiating element 101 to pass through the waveguide. The channel 201 is output to the outside of the waveguide device 200 . The outward side of the waveguide device 200 may also be connected to an external waveguide or antenna.

In Fig. 1, the non-conductive cover 102 includes two parts, the part 1021 with a smaller area, lower height and semicircular top corresponds to the radiating element 101, and is used to cover the radiating element 101; the other part 1022 has an area and height It is larger and has a rectangular shape for covering other circuit parts on the PCB board 300 . The non-conductive cover 102 is made of a non-conductive material such as plastic, which itself cannot shield electromagnetic signals, but mainly plays a role of sealing the circuit part including the radiation element 101, preventing explosive substances or gas mixtures from The interior of the container containing the measured material enters the circuit part of the radar level gauge.

The above two parts 1021 and 1022 of the non-conductive cover 102 may be integrally formed to form a connected cavity, as shown in FIG. 1 , and this design is convenient for processing. Since the non-conductive cover 102 itself does not have an electromagnetic shielding function, its shape and structure have a large design space. Different shapes, etc., are optional solutions.

For the parameter design of the non-conductive cover 102 , an important point is the height of the cover part 1021 covering the radiating element 101 , that is, the height relative to the PCB board 300 . Because the non-conductive cover 102 covers the cover part 1021 of the radiating element 101 and is arranged between the surface of the PCB 300 on which the radiating element 101 is mounted and the lower edge of the annular tube wall where the waveguide device 200 forms the waveguide 201, as shown in FIG. 1, therefore the cover part covering the radiating element 101 actually determines the distance between the radiation surface of the radiating element and the starting point of the waveguide 201, if the height of the cover part 1021 covering the radiating element 101 is set such that the radiating element The distance between the radiating surface of the radiating surface and the starting point of the waveguide 201 is less than the wavelength (λ) of the electromagnetic wave emitted by the radiating element 101, then only a small part of the electromagnetic wave emitted from the radiating element 101 and entering the waveguide 201 is transmitted from the The edge (corresponding to the height direction) of the cover portion 1021 leaks out. If the height of the cover part 1021 covering the radiation element 101 is set so that the distance between the radiation surface of the radiation element and the starting point of the waveguide path 201 is smaller than the wavelength (λ) of the electromagnetic wave emitted by the radiation element 101, then the cover part 1021 can be provided The height is half of the wavelength of the electromagnetic wave to be emitted, that is, λ/2. The height parameter of the cover part 1021 is related to the dielectric constant of the material of the cover part 1021 itself and the thickness of the material. For the cover part 1021 with a thinner material thickness (the thickness of the solid part of the cover without the cavity) and plastic material In terms of height, it is appropriate to use a height of about λ/2. For example, for electromagnetic waves with a frequency of 75-120 GHz or slightly higher than 120 GHz, the wavelength is about 3 mm to 2 mm. If the cover is made of PTFE plastic or PP plastic, its height can be 1.34mm for a 78G signal. In addition, other plastics (such as PEEK) or other non-conductive materials can also be used to manufacture the whole or part of the non-conductive cover.

The cover part 1021 for sealing is butted or glued to the bottom edge of the tube wall forming the waveguide passage 201 of the waveguide device 200. Therefore, the cover part 1021 is covered on the radiation element 101 on one side and on the bottom edge It is sealed and connected with the surface of the PCB board 300, so as to seal the radiation element 101; on the other side, it is sealed and connected with the corresponding contact surface of the waveguide device 200, so as to seal one end of the waveguide channel 201 to prevent external gases, etc. It enters the inside of the radar level gauge from the waveguide 201 . Since the part of the waveguide device 200 forming the waveguide 201 is made of metal, and the non-conductive cover 102 is made of a non-conductive material, the materials of the two are usually different, and the two can be hermetically connected by bonding or the like. In order to achieve the explosion-proof effect, it is also possible to seal the high-frequency module by filling glue as a whole. If the glue filling method is used, the bonding between the cover part 1021 and the surface of the PCB board 300 and the bonding between the cover part 1021 and the surface of the PCB board 300 may not be necessary. The butt joint or bonding of the bottom edge of the waveguide 201 imposes higher sealing requirements.

According to the radar level gauge of the embodiment of the present invention, the high-frequency module further includes a radar signal transceiving device 400 in addition to the transmitting device 100 , the wave guiding device 200 and the PCB board 300 . The radar signal transceiving device 400 may include one or more chips 401 and be electrically connected to the radiation element 101 of the transmitting device 100 . For example, as shown in Figure 1 and Figure 3B, one or more chips 401 are arranged on the surface of the PCB board 300, and the chip 401, as a part of the radar signal transceiving device 400, includes a microwave chip that generates electromagnetic waves emitted by the radiation element 101 Or have such a function, the chips 401 can also process the received electromagnetic wave signal. The chip 401 may also include other chips of the radar level gauge, for example, a control chip of the radar level gauge, other chips of the high-frequency module, and the like.

In order to realize the electrical connection between the radar signal transceiving device 400 and the radiation element 101 of the transmitting device 100, a metal layer can be coated on the surface of the insulating layer of the PCB board 300, and then circuit wiring is formed on the metal layer to transmit and receive radar signals. The device 400 is connected to the radiating element 101 . In the solution shown in FIG. 1 , the electromagnetic wave signal generated by the chip is transmitted to the radiation element 101 through the microstrip line 402 , and other signal transmission methods may also be used.

The chip 401, the microstrip line 402 and the radiation element 101 can be arranged on the same side of the PCB board 300, which is convenient for processing. The circuit connection line part of the radar level gauge can be realized by making the PCB board 300 .

In addition, a wave-absorbing material 403 can be provided above the chip 401. As shown in FIG. The chip 401 is shielded from electromagnetic waves; the space defined by the wave-absorbing material 403 itself can accommodate not only multiple chips 401 but also microstrip lines 402, and is used to absorb electromagnetic waves generated by electronic devices such as microstrip lines.

FIG. 2A is a perspective view of the assembled high-frequency module shown in FIG. 1 , and FIG. 2B is a perspective view of the assembled high-frequency module shown in FIG. 1 from another angle. The relative positional relationship among the transmitting device 100 , the wave guiding device 200 and the PCB board 300 can be seen more clearly with reference to FIG. 2A , FIG. 2B and FIG. 1 . Wherein, the portion 1021 of the non-conductive cover 102 of the transmitting device 100 used to seal the radiating element 101 is disposed between the bottom edge of the wave guiding device 200 and the corresponding portion of the PCB board 300 . The transmitting device 100 can be fixedly connected to the surface of the PCB board 300 by, for example, bonding, and the waveguide device 200 can also be fixedly connected to the surface of the same side of the PCB board 300 by, for example, screw fixing.

FIG. 3A is a partial front sectional view of the assembled high-frequency module shown in FIG. 1 , and FIG. 3B is a partial side sectional view of the assembled high-frequency module shown in FIG. 1 .

As shown in FIG. 3A and FIG. 3B , the PCB board 300 has an insulating layer 301 , a metal layer (ie copper clad layer) 302 and a substrate (substrate) 303 arranged in sequence, which form a multilayer composite structure. Optionally, the substrate 303 itself may also be a multi-layer PCB board. According to an embodiment of the present invention, as shown in FIG. 3A and FIG. 3B , the radiation element 101 is attached to the insulating layer 301 of the PCB 300 , and a metal layer 302 can be formed on the insulating layer 301 to form a circuit.

A non-conductive cover 102 is provided on the side of the PCB 300 where the radiation element 101 is disposed, and the non-conductive cover 102 forms a radiation cavity 103 for accommodating the radiation element 101 . The radiating cavity 103 provides a space for signal transmission from the microstrip line 402 to the radiating element 101 .

In addition, as shown in FIG. 3A and FIG. 3B , on the side where the radiating element 101 and the non-conductive cover 102 are provided, the surface of the insulating layer of the PCB board corresponding to the radiating cavity 103 is not covered or not fully coated with a metal layer, specifically, The part in contact with the radiating element 101 and its surrounding parts (together the part corresponding to the projected area of the radiating cavity 103) does not have a metal layer (except for the electronic circuit (microstrip line) connecting the radiating element 101 and the radar signal transceiving device 400 )).

The radiating element 101 may be a thin sheet-like device with a small area and have, for example, a square or rectangular shape.

For example, for a cylindrical (as shown in FIG. 5A and FIG. 5B ) or bell-shaped (as shown in FIG. 3A and FIG. 3B ) waveguide, the size of the inner hole of the waveguide (ie, the formed waveguide 201 diameter) or the size of the inner hole near the end of the non-conductive cover 102 may match the size of the radiation cavity 103 . Optionally, the waveguide 201 may also adopt other variable diameter structures (as shown in FIG. 6A and FIG. 6B ).

Fig. 5A and Fig. 5B schematically show the front partial sectional view and the side partial sectional view of the high frequency module according to another embodiment of the present invention; Fig. 6A and Fig. 6B schematically show another embodiment according to the present utility model The front partial sectional view and the side partial sectional view of the high-frequency module of the example. Compared with the structure of the high frequency module shown in FIGS. 3A and 3B , the difference between the high frequency modules shown in FIGS. 5A and 5B and FIGS. 6A and 6B is only the shape of the waveguide 201 .

Fig. 4A schematically shows a partial front sectional view of the radar level gauge with the high frequency module shown in Fig. 1, and Fig. 4B schematically shows the radar level gauge with the high frequency module shown in Fig. 1 Partial side cutaway view. As shown in Fig. 4A and Fig. 4B, after the high-frequency module according to the embodiment of the present invention is installed on the head part of the radar level meter, the sealant can be filled in the space mainly limited by the shell of the head part of the level meter, Seal all the parts except the opening of the waveguide, so that a better sealing effect can be obtained.

When processing the waveguide device according to the embodiment of the present invention, the high-frequency module including the waveguide device, and the radar level timer using the high-frequency module, first process the printed circuit board in the high-frequency module, specifically, in Before coating the metal layer, process through holes such as bolt holes on the substrate of the PCB board, then print the metal layer, and then process on the metal layer to form an insulating layer; then form a part of the metal layer on the insulating layer, and a part of the metal layer is used for Realize the electrical connection between the radar signal transceiving device of the high-frequency module and the radiating element; install the radiating element, install the radar signal transceiving device and non-conductive cover on the same side of the insulating layer as the radiating element, and on this side Install wave guides for high-frequency modules. As mentioned above, the waveguide device can be fixed on the printed circuit board by means of bolts, etc., and the high-frequency module can be installed on the shell part of the radar level meter head, and can also be connected to the shell of the radar level meter head. The space defined by the part is filled with sealant, so that the head part can meet the explosion-proof requirements as a whole.

The frequency range of the current frequency-modulated continuous wave radar (FMCW) level gauge is 4-27GHz. With the development of radar applications in the automotive field, the frequency of radar has been applied to 75-120GHz. The use of high-frequency signals for level measurement has more advantages, such as good directionality and smaller instrument size.

According to the high-frequency module of the embodiment of the utility model and the radar level gauge using the high-frequency module, explosive gas can be prevented from entering the electronic cavity, and can be applied to the radar level measurement application of 75-120 GHz.

The above descriptions are only exemplary implementations of the present utility model, and are not intended to limit the protection scope of the present utility model, which is determined by the appended claims.

Claims (15)

1. A high-frequency module for level measurement,

it is characterized in that the preparation method is characterized in that,

the method comprises the following steps: a launch device (100), a guided wave device (200) and a PCB board (300),

wherein,

the transmitting device (100) comprises: a radiating element (101) and a non-conductive cover (102), the radiating element (101) and the non-conductive cover (102) being arranged on the same side of the PCB board (300), and the non-conductive cover (102) and the PCB board (300) defining a radiating cavity (103) such that the radiating element (101) is placed inside the radiating cavity (103),

wherein,

the wave guide device (200) is installed on the same side of the PCB (300) as the transmission device (100) and forms a wave guide path (201) corresponding to the radiation element (101),

the cover portion (1021) of the non-conductive cover (102) covering the radiation element (101) is in contact with the bottom edge of the portion of the waveguide (200) where the waveguide (201) is formed, and the height of the cover portion (1021) is set so that the distance from the radiation surface of the radiation element (101) to the start of the waveguide (201) is smaller than the wavelength of the electromagnetic wave emitted from the radiation element (101).

2. The high-frequency module according to claim 1, characterized in that the height of the cover portion (1021) of the non-conductive cover (102) covering the radiating element (101) is half the wavelength of the electromagnetic waves emitted by the radiating element (101).

3. A high-frequency module according to claim 1, characterized in that the cover part (1021) of the radiating element (101) is covered by the non-conductive cover (102) made of PTFE plastic or PP plastic, the height of the cover part (1021) being 1.34 mm.

4. The high frequency module according to claim 1, characterized in that the cover part (1021) of the non-conductive cover (102) covering the radiating element (101) meets the bottom edge of the tube wall of the wave guide (200) forming a wave guide path (201).

5. The high frequency module according to claim 1, characterized in that the waveguide (201) is a cylindrical cavity or has a variable diameter cavity structure.

6. The high frequency module according to claim 1, characterized in that the portion of the guided wave device (200) forming the guided wave path (201) is made of a metallic material.

7. The high-frequency module according to claim 1, characterized in that the radiating element (101) is mounted on an insulating layer of the PCB board (300) and the non-conductive cover (102) is mounted on the PCB board (300).

8. The high-frequency module according to claim 1, characterized in that it further comprises radar signaling means (400), the radar signaling means (400) comprising one or more chips (401) and being electrically connected to the radiating element (101) of the emitting means (100), the chips (401) generating electromagnetic waves emitted by the radiating element (101).

9. The high-frequency module according to claim 8, wherein a metal layer is coated on a surface of the insulating layer of the PCB board (300), and then a circuit wiring is formed on the metal layer to electrically connect the radar signal transceiving means (400) and the radiating element (101).

10. The high-frequency module according to claim 8 or 9, characterized in that the electromagnetic wave signal generated by the chip (401) is transmitted to the radiating element (101) by means of a microstrip line (402).

11. The high-frequency module according to claim 10, characterized in that the chip (401) and the microstrip line (402) are arranged on the same side of the PCB board (300) as the radiating element (101), and the chip (401) or the chip (401) and the microstrip line (402) are arranged in a space defined by a wave-absorbing material (403).

12. The high-frequency module according to claim 11, characterized in that the wave-absorbing material (403) is arranged in a space defined by the non-conductive cover (102).

13. A high-frequency module according to claim 1, characterized in that the radiating element (101) is a thin sheet-like device with a small area.

14. The high frequency module according to claim 1, characterized in that the high frequency module is suitable for radar level gauging applications at 75-120 GHz.

15. A radar level gauge, characterized in that it comprises a high frequency module as claimed in any one of claims 1 to 14.