DE102019217735A1 - Radar chip with a waveguide coupling - Google Patents

Abstract

Radar chip with a waveguide coupling, which has a high-frequency substrate with a first line, a second line and a substrate-integrated waveguide arranged in between, for coupling the radar signal into the antenna or the waveguide of the radar measuring device.

Description

Field of the invention

The invention relates to radar measurement technology. In particular, the invention relates to a radar chip with a waveguide coupling, the use of such a radar chip in a radar measuring device, and a method for producing such a radar chip.

background

Radar measuring devices can be used in automation technology in an industrial environment. For example, they are designed in the form of radar level measuring devices, which are very often equipped with horn antennas that are fed via waveguides. Especially in the frequency range between 40 and 300 GHz, the mechanical dimensions of the waveguide components are in a range that they can be easily integrated into the radar device.

The coupling of the radar signals generated by the high-frequency circuit of the measuring device into the horn antenna can take place via a so-called stripline, which is also referred to as a microstrip line, which protrudes into a waveguide of the horn antenna.

In order to protect the high-frequency circuit, which can be designed as a radar chip, from mechanical stress, it can be cast in a potting compound.

Summary

It is an object of the present invention to provide a radar chip with a waveguide coupling that can be protected by potting compound.

This object is achieved by the features of the independent patent claims. Further developments of the invention emerge from the subclaims and the following description of embodiments.

A first aspect of the present disclosure relates to a radar chip with a waveguide coupling, set up to couple a radar signal of the radar chip into an antenna or a waveguide of a radar measuring device. This waveguide can in particular be a part of the antenna that introduces the coupled radar signal into the antenna horn.

The waveguide coupling has a high-frequency substrate, for example in the form of a circuit board, with a first line, a second line and a waveguide which is arranged between these two lines and which is integrated into the substrate. This arrangement is set up for transmitting the radar signal from the radar chip to an antenna or a waveguide of the radar measuring device, as well as for coupling the radar signal into the antenna or the waveguide of the radar measuring device. The radar signals reflected on the medium to be measured are also transmitted from the antenna to the radar chip via this arrangement.

The substrate-integrated waveguide can be viewed as a filled waveguide. According to one embodiment, it has a flat top side and a flat bottom side, between which there is substrate material and which are electrically conductively connected to one another by means of plated-through holes or vias that form the “side walls” of the “waveguide”.

According to one embodiment, the first line, the second line and the upper side of the substrate-integrated waveguide arranged therebetween are arranged in the same plane of the high-frequency substrate. This plane can be an outer plane, but it can also be a plane inside the high-frequency substrate.

According to one embodiment, the first line, the second line and the upper side of the substrate-integrated waveguide arranged therebetween are arranged on the surface of the high-frequency substrate.

According to one embodiment, the first line is connected to or connected to an initial region of the upper side of the waveguide integrated into the substrate. This starting area is, for example, the “front edge” of the metallic top side of the substrate-integrated waveguide. The second line is correspondingly connected to or connected to an end region (the rear edge) of the upper side of the substrate-integrated waveguide.

According to a further embodiment, the substrate-integrated waveguide of the waveguide coupling has a width which is many times greater than the widths of the first line and the second line. The width runs parallel to the surface of the substrate and perpendicular to the direction of propagation of the radar signal. In general, it can be said that the width, as in 1 shown, is not necessarily the width of the conductor track. The edge and thus the width of the substrate-integrated waveguide is defined by the vias. The surface 102a but can also expand over a large area and be connected to ground (circuit ground) from the "direct current point of view". The again offers advantages in terms of Ex approval. This is because no voltage can build up on the unpotted microstrip line that feeds the waveguide, since it is short-circuited from a direct current perspective via the waveguide integrated into the substrate. This in turn means that a potentially flammable atmosphere cannot ignite via this line.

According to one embodiment, the width of the first line is less than the width of the second line.

According to a further embodiment, the radar chip with the waveguide coupling has a potting compound in which the radar chip, the first line and a portion of the top of the substrate-integrated waveguide are embedded, set up to protect the radar chip from mechanical loads.

This potting compound can be, for example, a relatively hard potting compound, for example a two-component resin, for example GlobTop.

This potting compound also embeds the bond wires or soldered connections.

A further potting compound can also be provided, which is applied to the first potting compound after the first potting compound and, for example, completely embeds it. This can be a softer potting compound, for example a gelatinous one. This should in particular provide explosion protection for the entire arrangement.

According to a further embodiment, the first line has a first matching structure in the area of the connection to the substrate-integrated waveguide. As an alternative or in addition to this, the second line can have a second matching structure in the area of its connection to the substrate-integrated waveguide.

According to a further embodiment, the substrate-integrated waveguide has vias from its upper side to its lower side.

Another aspect of the present disclosure relates to a waveguide coupling with the features described above and / or below.

Another aspect of the present disclosure relates to the use of a radar chip with waveguide coupling described above and below in a radar measuring device, in particular in a radar level measuring device. For example, the radar measuring device has an antenna or a waveguide which rests on the upper side of the substrate-integrated waveguide so that a potting compound can flow into the interior of the antenna or the waveguide.

Another aspect relates to a method for producing a radar chip with a waveguide coupling described above and below, in which a radar chip with a waveguide coupling is first provided, which is set up to couple a radar signal from the radar chip into an antenna or a waveguide, followed by potting of the radar chip, the first line and a portion of the top of the substrate-integrated waveguide with a first potting compound to protect the radar chip from mechanical loads.

In a possible further method step, the radar chip is potted with a further potting compound, which is applied to the first potting compound. The planar structure of the upper metal layer of the substrate-integrated waveguide makes it possible to create a seal between the potting compound and the waveguide, since penetration of the second potting compound into the waveguide would mean that it no longer fulfills its task.

In addition to mechanical protection, the second encapsulation can provide efficient explosion protection.

Embodiments are described below with reference to the figures. If the same reference numerals are used in the following description of the figures, they denote the same or similar elements. The representations in the figures are schematic and not to scale.

Figure list

• 1 shows a waveguide coupling according to an embodiment.
• 2 shows an alternative waveguide coupling.
• 3 shows the side view of a radar measuring device with a hollow conductor coupling.
• 4th shows a side sectional view of a radar measuring device with a waveguide coupling according to an embodiment.
• 5 shows the top view of the in the 3 Waveguide coupling shown.
• 6th shows a top view of the in 4th Waveguide coupling shown.
• 7th shows a top view of the in 4th Waveguide coupling shown, compared to 6th but with the antenna installed.
• 8th shows a flow diagram of a method according to an embodiment.

Detailed description of embodiments

Radar level gauges are very often equipped with horn antennas that are fed via waveguides. Especially in the frequency range between 40 and 300 GHz, the mechanical dimensions of the waveguide components are in a range that they can be easily integrated into the radar device.

3 shows the side view of a radar measuring device with a waveguide coupling. A high-frequency measurement signal is used in the electronics unit of a radar module for radar-based level measurement 300 on a radar chip 301 generated.

The unhoused radar chip sits on a special circuit board substrate 302 that has good high-frequency properties, such as low signal attenuation. There it is glued on, for example, and is made with bond connections 303 contacted. The high-frequency radar signal is then transmitted via the bond 303 on a stripline 304 (Microstrip line). As an alternative to this, the chip can also be soldered onto the substrate. The radar signal is then soldered to a stripline 304 (Microstrip line). The microstrip line in turn leads directly into a waveguide 305 which is perpendicular to the high frequency substrate. The waveguide has a small gate 306 through which the microstrip line is passed.

The waveguide is with the antenna 307 connected. The radar signal can be sent and received via this arrangement. A resonator integrated in the substrate can be used to increase the bandwidth of the transition between the microstrip line and the waveguide 308 be used. To protect the radar chip from mechanical loads, dust or other impurities, it is covered with an epoxy resin together with the bonded connections or soldered connections 309 (GlobTop) potted. The resin is applied to the chip and the substrate in liquid form. The resin flows over the microstrip line to an undefined point.

However, this arrangement has some disadvantages which are remedied by the arrangement described below.

One disadvantage is that the GlobTop 309 only covers the microstrip line up to an undefined area. Since the GlobTop 309 differs from air in its dielectric properties, the microstrip line has a different impedance in the area in which it is covered by the GlobTop material than in the area in which the line is surrounded by air.

Furthermore, under certain conditions, radar devices can receive approval for use in potentially explosive areas. A prerequisite for this can be that the entire electronics unit is under a potting compound 401 is potted so that no ignitable mixture can accumulate in the electronics. In order to be able to encapsulate such an electronic unit, it must be sealed from the outside. However, this can present a problem with the high frequency signal. The waveguide should not be filled with potting compound, otherwise its high-frequency properties could be impaired. However, since the microstrip line leads through a gate into the waveguide, this would inevitably happen with the structure described above.

One solution to this problem is in 1 shown. The electromagnetic wave propagates along a stripline 103a between the conductor track on top and the ground layer in the dielectric of the PCB. This wave is converted into one of the PCB material, the two copper layers 102a 102b and vias 101 existing filled waveguide transferred. After that, it is turned back into a second stripline using the same principle 103b transferred back and coupled into the waveguide. Adaptation structures in the form of tapers have proven to be advantageous 104a 104b which, from a high-frequency point of view, create a transition between the respective line structures with less attenuation and reflection. The GlobTop material can now go down to the smooth surface 102a of the waveguide integrated in the substrate. Due to its nature, the substrate-integrated waveguide is largely independent of materials on its top and bottom, and in particular of the GlobTop material. It is therefore largely irrelevant at this point how far the GlobTop flows in its liquid form onto the substrate-integrated waveguide.

Since the entire microstrip line can now be encapsulated under GlobTop material on the side facing the radar chip, the impedance of the line can be adjusted across its width to a defined impedance of, for example, 50 ohms. In 1 it can be seen that the microstrip lines on the left-hand side have a different width than on the right-hand side of the board. Also the taper 104a is matched to the GlobTop material.

Furthermore, the metallic waveguide can now be designed so that its outer wall 402 touches down directly on the surface of the waveguide integrated in the substrate, see 4th . A sealing surface can thus be implemented so that the above-described sealing compound does not flow into the waveguide, but at the same time the high-frequency signal can be coupled into the waveguide.

The 5-7 each show the top view of the radar module. 5 describes a first embodiment. 6th shows the case in which the GlobTop material has a defined termination on the microstrip line due to the substrate-integrated waveguide.

7th shows a sectional view with the embodiment in which the antenna is designed so that it is also placed with a smooth sealing surface on the substrate-integrated waveguide in order to create a seal between the encapsulated electronics / radar module and the air-filled waveguide / radar antenna.

An important aspect is the provision of a sealing option between the encapsulated electronics and the air-filled waveguide by conducting the electromagnetic energy in the dielectric of the board with a continuous, uninterrupted ground plane.

Another aspect is the avoidance of an undefined point of the impedance jump between the microstrip line surrounded by GlobTop and the air-covered microstrip line.

The copper layer on top shows the stripline into which the radar chip is located on the left 301 feeds the transmission signal. In the middle is the area with the filled, substrate-integrated waveguide and the smooth copper surface. The transparent contour, which lies over the stripline for signal feed and half over the filled waveguide, represents the GlobTop material. On the right-hand side you can see the stripline in the unsealed area that carries the signal to the waveguide 305 the antenna 307 directs.

The bevels 104a , 104b at the transitions from the striplines 103a , 103b on the ground planes 102a , 102b of the filled waveguide serve to improve the transition between the stripline and the filled waveguide and improve the adaptation. The vias 101 form the two walls of the filled waveguide.

Another possibility is the use of 3 layers in the circuit board, as shown in 2 is shown. The electromagnetic wave is transferred via lambda / 4 striplines over the middle layer. The lowest layer is a closed mass layer.

8th shows a flow diagram of a method according to an embodiment. In step 801 an above-described radar chip with a waveguide coupling is provided. In step 802 the radar chip, its first line and part of the top of the substrate-integrated waveguide are encapsulated with a first potting compound to protect the radar chip from mechanical loads. In step 803 the radar chip is potted with another potting compound, which is applied to the first potting compound, for explosion protection.

During this process, it is not necessary to ensure that no potting compound flows into the waveguide or the antenna, since the interior of the antenna or the waveguide is sealed where the high-frequency signal is introduced into the waveguide or the antenna.

In addition, it should be noted that “comprising” and “having” do not exclude any other elements or steps and the indefinite articles “a” or “a” do not exclude a multiplicity. Furthermore, it should be pointed out that features or steps that have been described with reference to one of the above exemplary embodiments can also be used in combination with other features or steps of other exemplary embodiments described above. Reference signs in the claims are not to be regarded as restrictions.

Claims (15)

Radar chip (301) with a waveguide coupling (100), set up for coupling a radar signal from the radar chip into and out of an antenna (307) or a waveguide (305) of a radar measuring device (300), having the waveguide coupling: a high-frequency substrate (302) with a first line (103a), a second line (103b) and a substrate-integrated waveguide (102a, 102b, 101, 302) arranged between them, set up to transmit the radar signal from the radar chip to an antenna or a waveguide of the Radar measuring device and for and for coupling the radar signal into the antenna or the waveguide of the radar measuring device or for decoupling the radar signal from the antenna or the waveguide. Radar chip (301) with a waveguide coupling (100) according to Claim 1 , wherein the first line (103a), the second line (103b) and an upper side (102a) of the substrate-integrated waveguide (102a, 102b, 101, 302) arranged therebetween in the same plane of the high frequency substrate (302) are arranged. Radar chip (301) with a waveguide coupling (100) according to one of the preceding claims, wherein the first line (103a), the second line (103b) and the upper side (102a) of the substrate-integrated waveguide (102a, 102b, 101, 302) arranged therebetween are arranged on the surface of the high frequency substrate (302). Radar chip (301) with a waveguide coupling (100) according to one of the preceding claims, wherein the first line (103a) is connected to an initial region of the upper side (102a) of the substrate-integrated waveguide (102a, 102b, 101, 302); wherein the second line (103b) is connected to an end region of the upper side (102a) of the substrate-integrated waveguide (102a, 102b, 101, 302). Radar chip (301) with a waveguide coupling (100) according to one of the preceding claims, wherein the substrate-integrated waveguide (102a, 102b, 101, 302) of the waveguide coupling has a width which is many times greater than the width of the first line (103a) and the second line (103b). Radar chip (301) with a waveguide coupling (100) according to one of the preceding claims, wherein the width of the first line (103a) is smaller than the width of the second line (103b). Radar chip (301) with a waveguide coupling (100) according to one of the preceding claims, further comprising: a first potting compound (309), in which the radar chip (301), the first line (103a) and a portion of the upper side (102a) of the substrate-integrated waveguide (102a, 102b, 101, 302) are embedded, set up to protect the radar chip ( 301) from mechanical loads. Radar chip (301) with a waveguide coupling (100) according to Claim 7 , further comprising: a further potting compound (401) which is applied to the first potting compound after the first potting compound. Radar chip (301) with a waveguide coupling (100) according to one of the preceding claims, wherein the first line (103a) has a first matching structure (104a) in the region of the connection of the first line to the substrate-integrated waveguide (102a, 102b, 101, 302); and or wherein the second line (103b) has a second matching structure (104b) in the region of the connection of the second line to the substrate-integrated waveguide (102a, 102b, 101, 302). Radar chip (301) with a waveguide coupling (100) according to one of the preceding claims, wherein the substrate-integrated waveguide (102a, 102b, 101, 302) has vias (101) from its top (102a) to its bottom (102b). Waveguide coupling (100), set up for coupling and decoupling a radar signal from a radar chip into an antenna (307) or a waveguide (305) of a radar measuring device (300), having the waveguide coupling: a high-frequency substrate (302) with a first line (103a), a second line (103b) and a substrate-integrated waveguide (102a, 102b, 101, 302) arranged between them, set up to transmit the radar signal from a radar chip to an antenna or a waveguide of the Radar measuring device and for coupling the radar signal into the antenna or the waveguide of the radar measuring device. Use of a radar chip (301) with a waveguide coupling (100) according to one of the Claims 1 to 10 or a waveguide coupling Claim 11 in a radar measuring device (300), in particular in a radar level measuring device. Use after Claim 12 , wherein the radar measuring device (300) has an antenna (307) or a waveguide (305) which rests on the upper side (102a) of the waveguide (102a, 102b, 101, 302). Method for producing a radar chip (301) with a waveguide coupling (100) according to one of the Claims 1 to 9 , comprising the steps: providing a radar chip (301) with a waveguide coupling (100), set up for coupling a radar signal from the radar chip into an antenna (307) or a waveguide (305) of a radar measuring device (300), having the waveguide coupling: a high-frequency substrate ( 302) with a first line (103a), a second line (103b) and a substrate-integrated waveguide (102a, 102b, 101, 302) arranged between them, set up to transmit the radar signal from the radar chip to an antenna or a waveguide of a radar measuring device and to the Coupling the radar signal into the antenna (307) or the waveguide (305) of the radar measuring device; Potting the radar chip (301), the first line (103a) and a portion of the top side (102a) of the substrate-integrated waveguide (102a, 102b, 101, 302) with a first potting compound (309) to protect the radar chip (301) from mechanical damage Charges. Procedure according to Claim 14 , further comprising the step: Potting the radar chip (301) with a further potting compound (401) which is applied to the first potting compound (309).

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