RADAR DEVICE AND METHOD FOR PRODUCING A RADAR DEVICE

A radar device. The radar device includes a printed circuit board; a signal generation circuit, which is arranged at least indirectly on the printed circuit board, is electrically coupled to the printed circuit board and is designed to generate a radar signal; a waveguide antenna device, which is arranged at least indirectly on the printed circuit board; and a waveguide coupling device, wherein the signal generation circuit is arranged on or in the waveguide coupling device, and wherein the waveguide coupling device is designed to couple the radar signal generated by the signal generation circuit, into the waveguide antenna device.

FIELD

The present invention relates to a radar device and to a method for producing a radar device. In particular, the present invention relates to a radar device for use in a motor vehicle.

BACKGROUND INFORMATION

Networked vehicles as well as assisted and autonomous driving will play an increasingly greater role. In this respect, the detection of the vehicle environment is of particular importance. In addition to camera systems, sensors that provide more accurate speed estimates and, even in low light conditions, deliver good measurement results are increasingly used with increasing degree of autonomy. Radar is one such technology that works reliably even in complete darkness or against the sun.

Initially, radar devices were used for comfort functions, such as the adaptive cruise control. Since then, sensor technology has evolved greatly and, today, safety aspects are in the foreground. Most notably, the safety classification of the New Car Assessment Program (NCAP) organizations requires, for a good rating, not only safety in the crash test but also systems that prevent accidents from happening in the first place. For example, assistants for recognizing objects in the blind spot are part of the standard equipment in new vehicles, as are lane-change assistants. Emergency brake assist systems are also required, not only for simple scenarios between vehicles but also for scenarios in which so-called vulnerable road users are involved, e.g., pedestrians or cyclists.

For radar sensor technology, this means constantly increasing requirements with respect to sensitivity and selectivity, which imposes high requirements on the antenna field of the radar sensor. At the same time, costs are to be kept low. In this case, costs can be reduced by integration, e.g., by integrating electrical signal generation, transmission, reception, and processing into a single system on a chip (SoC).

In such single-chip approaches, there are no high-frequency connections between the chips on the circuit board. The conventionally used patch antenna is therefore the only remaining element that the printed circuit board requires for high frequencies. The sensor size is primarily determined by the patch antennas, which occupy a significant portion of the space on the high-frequency printed circuit board.

Besides form factor and size, a further limitation of today's patch antennas is their limited operational frequency bandwidth. Newer automotive radar sensors have increased spatial resolution requirements, which are reflected in operational bandwidths of 4 GHz to 5 GHz. While conventional patch antenna arrays typically have a narrower band, waveguide antennas can cover bandwidths of up to approx. 10 GHz. In addition, waveguide antennas promise better efficiency, lower losses, and a greater field of view in comparison to today's patch antennas. An exemplary waveguide interface is described in U.S. Patent Application Publication No. US 2020/0365971 A1.

Transitioning to such antenna technology could therefore significantly reduce the printed circuit board size and the sensor size and, at the same time, improve the performance of the radar sensor. If the radar chip could additionally be directly coupled into such a waveguide antenna, this would allow the use of cheap printed circuit boards and thus pave the way for more cost-effective and better radar sensors.

A direct coupling between the radar chip and a waveguide antenna is realized by waveguide coupling devices, which are also referred to as waveguide launchers. These waveguide coupling devices must be integrated into the radar chip package so that no millimeter wave signal is transmitted on the printed circuit board.

The waveguide antenna and radar chip may be mounted on opposite sides of the printed circuit board so that a transition via the printed circuit board is required. In this case, the transitions must be precisely, smoothly and evenly metallized in order to achieve good millimeter wave transmission performance. Furthermore, the cooling system is located on the top surface of the housing, which is generally less efficient than a cooling system on the rear side.

Alternatively, the millimeter wave signal may not be transmitted through the printed circuit board but may be directly coupled into the waveguide antenna. The printed circuit board material can therefore be cost-optimized without any millimeter wave requirements or constraints. The heat dissipation can also be optimized by attaching heat sinks to both the top side and the underside of the chip. However, since the millimeter wave is conducted via the mold compound, any change in the electrical properties, e.g., during the production process, due to a changing temperature or due to age, can change or degrade the attenuation in the millimeter wave signal path. In addition, the production of such housings is complex, resulting not only in difficulty in meeting the required tolerances for low high-frequency losses and leakages but also in high producing costs.

SUMMARY

The present invention provides a radar device and a method for producing a radar device.

Preferred embodiments of the present invention are disclosed herein.

According to a first aspect, the present invention accordingly relates to a radar device. According to an example embodiment of the present invention, the radar device includes a printed circuit board; a signal generation circuit, which is arranged at least indirectly on the printed circuit board, is electrically coupled to the printed circuit board and is designed to generate a radar signal; a waveguide antenna device, which is arranged at least indirectly on the printed circuit board; and a waveguide coupling device, wherein the signal generation circuit is arranged on or in the waveguide coupling device, and wherein the waveguide coupling device is designed to couple the radar signal generated by the signal generation circuit, into the waveguide antenna device.

According to a second aspect, the present invention relates to a method for producing a radar device. According to an example embodiment of the present invention, the method comprises the steps of: providing a printed circuit board; arranging a signal generation circuit at least indirectly on the printed circuit board, wherein the signal generation circuit is electrically coupled to the printed circuit board and is designed to generate a radar signal; forming a waveguide coupling device at least indirectly on the printed circuit board, wherein the signal generation circuit is arranged on or in the waveguide coupling device; and arranging a waveguide antenna device at least indirectly on the printed circuit board, wherein the waveguide coupling device is designed to couple the radar signal generated by the signal generation circuit, into the waveguide antenna device.

The radar device of the present invention can be produced simply and cost-effectively while the millimeter wave losses can be kept low. Furthermore, the radar device can have good properties in terms of bandwidth, system costs, mechanical stability, and reliability.

According to an example embodiment of the present invention, the printed circuit board can be provided for transmitting low-frequency signals only. Furthermore, the printed circuit board provides a common mechanical base for the signal generation circuit (radar chip) and the waveguide antenna device. It is not used for the transmission or conduction of millimeter wave signals and can therefore be implemented in a cost-effective standard process.

According to a preferred embodiment of the radar device of the present invention, the waveguide coupling device comprises a mold compound, which at least partially surrounds the signal generation circuit. The mold compound can be applied by means of transfer molding. The mold compound protects the signal generation circuit from ambient stresses and impacts, such as during assembly of the radar device. However, according to other embodiments, the radar device may also not have any mold compound.

According to a preferred embodiment of the radar device of the present invention, the waveguide coupling device comprises an interposer designed to conduct the radar signal generated by the signal generation circuit, to the waveguide antenna device.

According to a preferred embodiment of the radar device of the present invention, the interposer comprises an integrated waveguide portion in order to conduct the radar signal generated by the signal generation circuit, to the waveguide antenna device.

According to a preferred embodiment of the radar device of the present invention, the interposer comprises an impedance adjustment portion in order to conduct the radar signal generated by the signal generation circuit, to the waveguide antenna device.

According to a preferred embodiment of the radar device of the present invention, an air gap is formed at least in sections between the waveguide coupling device and the waveguide antenna device. Depending on the choice of materials for the different components of the radar device and their mechanical properties (in particular their relative expansion), the air gap enables the compensation of the stresses in the radar device during small movements of the various components relative to one another. The coupling between the printed circuit board and the waveguide antenna device can be designed in such a way that stress compensation and small movements are possible.

According to a preferred embodiment of the radar device of the present invention, the waveguide antenna device is movably or displaceably disposed on the printed circuit board directly or via small pins. As a result, the friction between the waveguide and the printed circuit board can be reduced.

According to a preferred embodiment of the present invention, the radar device comprises a connection layer, which connects the waveguide coupling device at least in sections to the waveguide antenna device. In this embodiment, no air gap or only a partial air gap is thus formed between the waveguide coupling device and the waveguide antenna device. As a result, the mechanical stability can be increased. The materials used can be selected according to their material properties. In particular, the expansion properties of the waveguide coupling device, waveguide antenna device and printed circuit board are coordinated with one another. As a result of the connection of the structures, the radar device has low HF losses that occur at the transition between the interposer of the waveguide coupling device and the transition structure to the waveguide antenna device.

According to a preferred embodiment of the present invention, the connection layer only extends between the waveguide coupling device and the waveguide antenna device. However, there is no fixed connection layer between the waveguide antenna device and the printed circuit board. On the one hand, this enables efficient transmission of the HF signal from the waveguide coupling device to the waveguide antenna device with low losses. On the other hand, small movements of the components relative to one another are still made possible.

According to a preferred embodiment of the radar device of the present invention, the waveguide antenna device comprises a substrate and a cover arranged on the substrate, wherein at least one waveguide is formed at least in sections between the substrate and the cover. As a result, the radar device can be produced cost-effectively.

According to a preferred embodiment of the present invention, the radar device comprises at least one heat sink, which is at least indirectly connected to the signal generation circuit and/or the printed circuit board in order to dissipate heat.

According to a preferred embodiment of the radar device of the present invention, the signal generation circuit is a system-on-a-chip circuit or a monolithic microwave integrated circuit (MMIC).

According to a preferred embodiment of the radar device of the present invention, a heat sink is arranged on the printed circuit board on a side opposite the signal generation circuit. As a result, efficient heat transfer can be enabled.

In all figures, identical or functionally identical elements and devices are provided with the same reference signs.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG.1shows a schematic cross-sectional view of a radar device100. The radar device100comprises a printed circuit board109(PCB) with one or more metallization layers106. The metallization layer106is coupled to a signal generation circuit108, wherein the latter is integrated into a waveguide coupling device.

The waveguide coupling device has a mold compound103, which surrounds the signal generation circuit108on a side facing away from the printed circuit board109. The waveguide coupling device furthermore comprises an interposer104with one or more metallization layers105. The metallization layers105,106can consist at least partially of copper. In deviation, more or fewer metallization layers may also be provided.

The interposer104is not surrounded by the mold compound103in the outer regions in order to enable low-loss coupling from the waveguide coupling device into a waveguide antenna device102. For example, the interposer104may have a size of between 11×11 mm2and 20×20 mm2.

The signal generation circuit108is arranged on the interposer104and the interposer104is connected to the printed circuit board109via solder balls or pads107so that a ball-grid-array (BGA)- or land-grid-array (LGA)-like housing is formed. The signal generation circuit108is a monolithic microwave integrated circuit (MMIC). According to further embodiments, the signal generation circuit108can also be a system-on-a-chip circuit. The signal generation circuit108is designed to generate and receive a radar signal (HF signal).

The waveguide antenna device102is arranged on the printed circuit board and surrounds the waveguide coupling device and the signal generation circuit108integrated therein. An air gap110is formed between the waveguide antenna device102and the waveguide coupling device. This air gap extends between the waveguide antenna device102and the mold compound103or the interposer104with the metallization layer105. The air gap110can be reduced in size in order to enable physical contact between the waveguide antenna device102and the waveguide coupling device. The waveguide antenna device102can be or can comprise a metallized injection-molded part.

The waveguide coupling device is designed to couple the radar signal generated by the signal generation circuit108, into the waveguide antenna device102. The transition to the waveguide antenna device102is advantageously realized on a portion of the interposer104that is not surrounded by the mold compound103, which reduces HF losses and ensures high bandwidth.

FIG.2shows a schematic cross-sectional view of a radar device200. The signal generation circuit108is applied to the interposer104by means of flip-chip technology and is connected to the interposer104by means of contactings213. The signal generation circuit108is not surrounded by a mold compound. It is thus a bare die structure. In the lateral regions of the printed circuit board, high-frequency (HF) structures211are realized in the conductive layers. They are designed to couple the radar signal generated by the signal generation circuit108, into an adjoining waveguide antenna device (not shown). A capillary underfill (CUF) or mold underfill (MUF)212is formed between the signal generation circuit108and the interposer104. In the radar device200, the waveguide coupling device is formed by the interposer104with CUF or MUF212, contactings213and HF structures211. The printed circuit board109is not shown.

FIG.3shows a schematic cross-sectional view of a radar device300. The structure substantially corresponds to the structure illustrated inFIG.2. Additionally, the signal generation circuit108is partially surrounded by a mold compound303. However, the lateral regions of the interposer104are not surrounded by mold compound303.

FIG.4shows a schematic cross-sectional view of a radar device400. In this case, the signal generation circuit408is arranged on an underside of the interposer104and surrounded by mold compound403. The relevant HF structures211are arranged on the top side of the interposer104, and the HF wave signals are emitted upward and coupled into the waveguide antenna device (not shown).

FIG.5shows a schematic plan view (top) and cross-sectional view (bottom) of a radar device500. The mold compound503is also formed in the outer regions on the interposer104, wherein the HF signals are coupled into the waveguide antenna device (not shown) by means of vias514,515. The vias514,515extend through the mold compound503and are produced by means of through mold via technology.

FIG.6shows a schematic cross-sectional view of a radar device600. In this case, a waveguide coupling device surrounded by a mold compound603is provided, wherein the HF structures211are exposed or at least partially covered by a thin mold compound layer, and the emitted HF signals are guided through a waveguide structure616within the mold compound603, wherein the waveguide structure616is preferably metallized toward the outside.

FIG.7shows a schematic cross-sectional view of a radar device600a. The latter differs from the radar device600shown inFIG.6in that the HF structures211are not exposed in the mold compound603a. Above the HF structures211, beamforming elements611are formed.

FIG.8shows a schematic cross-sectional view of a radar device700. Only the additions and changes in comparison to the radar device100shown inFIG.1are explained below.FIG.8thus illustrates the contactings718(such as copper pillars) extending through the interposer104, between the signal generation circuit108and the solder balls107. It furthermore illustrates that a region719of the metallization layer105formed on the interposer104is exposed in order to couple the HF signals, which are transmitted via the interposer104and have been generated by the signal generation circuit108, into waveguide channels720of the waveguide antenna device702. The waveguide antenna device702comprises a metallization layer716.

Furthermore, air-filled cavities717are formed in the lateral regions next to the waveguide channels720. For HF signals transmitted through the air gap110, the cavities serve as λ/4 trap so that there is a reduction in HF leakages and cross-couplings. Three air-filled cavities717are illustrated, one near the signal generation circuit108at the edge of the interposer104, one on the side of the interposer104, and one on the side of the printed circuit board109. However, according to further embodiments, there can also be more or fewer cavities717.

According to further embodiments, the cavities717can surround the region719in whole or in part.

According to further embodiments, the cavities717can be replaced by compensation structures in the interposer104up to or into the printed circuit board109.

The correct positioning of the waveguide antenna device702relative to the printed circuit board109and to the waveguide coupling device is improved with the aid of a centering721by pins. In further embodiments, self-centering structures can be provided. For this purpose, the underside of the waveguide antenna device702can be structured with a solder island, the total base area of which is adjusted to the printed circuit board top side, wherein a reflow soldering process serves to center the waveguide antenna device702. In order to reduce stress, the centering components, such as pins or the like, can be arranged near the waveguide coupling device.

FIG.9shows a schematic plan view of the radar device700shown inFIG.8.

FIG.10shows a schematic plan view of a radar device800, wherein only the coupling of the radar signals by means of the waveguide coupling device are illustrated in more detail. The remaining components of the radar device800can correspond to one of the embodiments described above. The interposer here comprises a grounded coplanar portion805acoupled to the signal generation circuit108, an adjoining transition region805b, an integrated waveguide portion805c, and a portion805dnot surrounded by mold compound, in order to conduct the radar signal generated by the signal generation circuit108, to the waveguide antenna device (not shown).

FIG.11shows a schematic plan view of a radar device900. The structure is similar to the structure of the radar device800illustrated inFIG.10. The interposer here comprises a grounded coplanar portion905acoupled to the signal generation circuit108, an adjoining impedance adjustment portion905b, a transition region905c, and a portion905dnot surrounded by mold compound, in order to conduct the radar signal generated by the signal generation circuit108, to the waveguide antenna device (not shown).

The coupling mechanisms illustrated inFIGS.10and11can also be used in the other radar devices illustrated in the figures.

FIG.12shows a schematic cross-sectional view of a radar device1000. The structure substantially corresponds to the structure of the radar device700shown inFIG.8. The waveguide antenna device1002is manufactured from blocks, which, in the assembled state, form a three-dimensional structure. The waveguide antenna device1002is realized with only one block and a planar cover1018. The blocks can be produced from forged metal, metal sheets or molded composites, e.g., conductive plastics or composites, or plastics that are metallized in a post-molding process.

FIG.13shows a schematic cross-sectional view of a radar device1100. The structure of the radar device1100substantially corresponds to the structure of the radar device1000shown inFIG.12. Additionally, a thermal heat sink1122is arranged on the rear side of the printed circuit board109.

FIG.14shows a schematic cross-sectional view of a radar device1200that substantially corresponds to the radar device700shown inFIG.8. In contrast to the radar device700shown inFIG.8, the connection between waveguide coupling device, waveguide antenna device102and printed circuit board109is realized such that the waveguide antenna device102is fixedly attached to both the waveguide coupling device and the printed circuit board109. The fixed connection1223between the waveguide antenna device102and the waveguide coupling device is realized with a conductive and/or non-conductive adhesive or tape or a solder. Due to the continuous connection, the cavities717can be dispensed with.

FIG.15shows a schematic plan view of the radar device1200shown inFIG.14.

FIG.16shows a schematic cross-sectional view of a radar device1300that substantially corresponds to the radar device1000shown inFIG.12. In contrast to the radar device1000shown inFIG.12, the connection between waveguide coupling device, waveguide antenna device1302and printed circuit board109is realized such that the waveguide antenna device1302is fixedly attached to both the waveguide coupling device and the printed circuit board109.

FIG.17shows a schematic cross-sectional view of a radar device1400that substantially corresponds to the radar device1100shown inFIG.8. In contrast to the radar device1100shown inFIG.8, the connection between waveguide coupling device, waveguide antenna device1402and printed circuit board109is realized such that the waveguide antenna device1402is fixedly attached to both the waveguide coupling device and the printed circuit board109. A further difference is the additional heat sink1422formed on a top side of the waveguide coupling device. Additionally, or alternatively, a heat sink can be formed on the underside of the printed circuit board109.

Thermal cooling of the radar device1400can be further improved through the use of a heat-conducting adhesive or solder in that an efficient cooling path from the signal generation circuit108to the printed circuit board109along the mold compound103, the interposer104, and the metallization layer106is created. At the same time, the waveguide antenna device1402itself acts as a cooling element.

FIG.18shows a schematic cross-sectional view of a radar device1500that substantially corresponds to the radar device1200shown inFIG.14. In contrast to the radar device1200shown inFIG.14, the connection1523extends only between the waveguide coupling device and the waveguide antenna device1402. This enables efficient transmission of the HF signal from the waveguide coupling device to the waveguide antenna device102with low losses. However, there is no fixed connection layer between the waveguide antenna device1402and the printed circuit board109. The waveguide antenna device102can be arranged on the printed circuit board with or without pins so that small movements are possible. This is an advantage for the mechanical stability of the assembly over time and under stress, even if the mechanical properties of the different parts are not perfectly coordinated with one another. The fastening of the printed circuit board to the waveguide is designed such that small movements and corresponding stress compensation are possible.

FIG.19shows a schematic cross-sectional view of a radar device1600. The coupling portion of the waveguide antenna device1602is integrally formed from a monolithic block, which represents a cost advantage. As a result, a waveguide channel1620is formed with an impedance adjustment portion1602a. The monolithic waveguide antenna block forms the three of four sides of the embedded waveguide channel1620. The metallization layer106of the printed circuit board109serves as the fourth wall of the wave guide channel1620. The printed circuit board109and the waveguide antenna device1602are connected by a conductive adhesive or solder1624, which is formed over the entire or part of the surface area.

As a result of the shown structure of the radar device1600, the radar device1600can be produced cost-effectively since the waveguide antenna device1602is realized with only one external block. In order to achieve a low-loss transition between the waveguide coupling device and the waveguide antenna device1602, the waveguide antenna device1602and the transition region of the waveguide coupling device are joined by means of a highly conductivity adhesive or solder1523and by means of an impedance adjustment portion1602ain the launcher region.

FIG.20shows a schematic plan view of the radar device1600shown inFIG.19. In the region1625, the waveguide antenna device102is connected to the metallization layer106of the printed circuit board109.

FIG.21shows a schematic cross-sectional view of a radar device1700. The waveguide antenna device702is glued or soldered to the printed circuit board109via a connection layer1701. However, there is no fixed or full connection layer between the waveguide antenna device702and the waveguide coupling device. Pins, conductive pastes, adhesives, or webs1702, which can be metallized or can be made of metal and are directly in contact with the waveguide coupling device, are formed or attached in the waveguide antenna device702. The pins, pastes, adhesives or webs1702can be applied onto the waveguide coupling device and are directly in contact with the waveguide antenna device702. In the region719from the signal transition between the interposer104and the waveguide antenna device702, the pins or bars are placed and shaped such that they form a channel for the HF signal and thus enable a good transition of the signal from the interposer104into the waveguide antenna device702. The radar device1700also allows for small movements of the waveguide antenna device702relative to the waveguide coupling device, which is a mechanical advantage.

FIG.22shows a schematic cross-sectional view of a radar device1800. The latter differs from the radar device1700shown inFIG.21in that no connection layer is formed between the waveguide antenna device702and the printed circuit board109.

Rather, pins or webs1801are also formed in this region. Furthermore, a centering721is provided.

FIG.23shows a schematic cross-sectional view of a radar device1900, which differs from the radar device1800shown inFIG.22in that the coupling of the HF signal into the waveguide channels720takes place by means of vias1902through the mold compound1903.

FIG.24shows a schematic cross-sectional view of a radar device2000, which differs from the radar device1900shown inFIG.23in that a connection layer1701as inFIG.21is provided.

FIG.25shows a schematic cross-sectional view of a radar device2100, which differs from the radar device1900shown inFIG.23in that air-filled cavities2117are provided.

FIG.26shows a schematic cross-sectional view of a radar device2200, which differs from the radar device2000shown inFIG.24in that a further connection layer2201is formed between the mold compound1903and the waveguide antenna device702.

In further embodiments, all radar devices shown above can have a planar cover (as inFIG.12) and/or at least one heat sink (as inFIG.17).

FIG.27shows a flow chart of a method for producing a radar device, in particular one of the radar devices described above.

In a first step S1, a printed circuit board is provided.

In a second step S2, a signal generation circuit is arranged at least indirectly on the printed circuit board, wherein the signal generation circuit is electrically coupled to the printed circuit board and is designed to generate a radar signal.

In a third step S3, a waveguide coupling device is formed, wherein the signal generation circuit is arranged on or in the waveguide coupling device.

In a fourth step S4, a waveguide antenna device is arranged at least indirectly on the printed circuit board.

The waveguide coupling device is designed to couple the radar signal generated by the signal generation circuit, into the waveguide antenna device.