Radar sensor

Abstract

The invention relates to a radar sensor comprising a high-frequency component (14) and an antenna assembly (12) which are arranged on opposite faces of a printed circuit board (10) and comprising a coupling structure for coupling the antenna assembly (12) to the high-frequency component (14) so as to transmit signals. The invention is characterized in that the printed circuit board (10) has an opening (28) which is dimensioned so as to be permeable to microwave radiation (32) and such that the high-frequency component (14) is connected to the printed circuit board (10) by means of a multilayer connection structure (18) which covers the opening (28), and the coupling structure has a resonator element (38) which is integrated into the connection structure (18) and is designed to emit microwave radiation into the antenna assembly (12) through the opening (28).

Description

[0001] R.399669 22.03.2022

[0002] Description

[0003] title

[0004] radar sensor

[0005] The invention relates to a radar sensor with a high-frequency component and an antenna arrangement arranged on opposite sides of a circuit board, and with a coupling structure for signal coupling of the antenna arrangement to the high-frequency component.

[0006] In particular, the invention relates to a radar sensor suitable for use in driver assistance systems or autonomous driving systems for motor vehicles.

[0007] State of the art

[0008] US 2020 365 971A1 discloses a radar sensor of the above-mentioned type, in which the antenna array is coupled to the radio-frequency component via electrically conductive vias in the circuit board. However, with this design principle, low-loss signal transmission is only possible if very tight tolerances are maintained during manufacturing.

[0009] US 11,031,681 B2 shows an example of a radar sensor in which the antenna and the radio-frequency component are located on the same side of the circuit board. However, this design principle limits the design freedom in arranging the radar sensor components on the circuit board. The prescribed geometric arrangement of the antenna elements on the circuit board generally requires relatively long and lossy signal paths.

[0010] Disclosure of the invention

[0011] The object of the invention is to provide a low-loss radar sensor of the type mentioned above which is easier to manufacture.

[0012] This object is achieved according to the invention in that the circuit board has an opening which is dimensioned such that it is permeable to microwave radiation, in that the radio-frequency component is connected to the circuit board by a multi-layer connecting structure which covers the opening, and in that the coupling structure has a resonator element embedded in the connecting structure which is designed to radiate microwave radiation through the opening into the antenna arrangement.

[0013] In this solution, the resonator element, which serves to couple the antenna array to the radio-frequency component, is embedded in a so-called interposer, which mechanically and electrically connects the radio-frequency component to the circuit board. Signal coupling in the direction perpendicular to the plane of the circuit board is achieved through electromagnetic radiation, eliminating the need for vias in either the circuit board or the interposer, which would otherwise only allow for tight manufacturing tolerances.

[0014] Advantageous embodiments of the invention are specified in the subclaims. Exemplary embodiments are explained in more detail below with reference to the drawings.

[0015] They show:

[0016] 5

[0017] Fig. 1 shows a section through part of a radar sensor according to an embodiment of the invention;

[0018] Fig. 2-4 partial sections through radar sensors according to further embodiments of the invention;

[0019] Fig. 5-7 sections through different layers of an interposer in the embodiment according to Fig. 2;

[0020] Fig. 8 a section analogous to Fig. 7 for a modified

[0021] Example of implementation;

[0022] Fig. 9 a plan view of a high-frequency component on an interposer with multiple coupling structures;0

[0023] Fig. 10 a plan view of waveguide elements, which

[0024] coupling structures according to Fig. 9 are assigned;

[0025] Fig. 11 a floor plan of a complete radar sensor; ^

[0026] Fig. 12 shows an example of a coupling structure with two feed points for microwave signals;

[0027] Fig. 13 shows a coupling structure with two resonance elements for different vibration modes; Figs. 14-16 show further examples of arrangements of resonance elements with different vibration modes; and Figs. 17(a)-(d) show examples of multi-channel feed systems for the coupling structures according to Figs. 15 and 16.

[0028] Fig. 1 shows a partial section through a radar sensor. The radar sensor comprises a circuit board 10, on one side of which, in the example shown, an antenna array 12 is formed, and on the underside of which a radio-frequency component 14 is mounted, which may be, for example, an MMIC (Monolithic Microwave Integrated Circuit).

[0029] The high-frequency component 14 is embedded in a molded body 16 made of plastic and is mechanically and electrically connected to conductor tracks 22 of the circuit board 10 by a connecting structure, referred to below as an interposer 18, and a so-called BGA 20 (ball grid array; i.e., an arrangement of solder balls). The circuit board 10, as usual, has an alternating sequence of dielectric layers 24 and electrically conductive layers 26, some of which (not shown in the simplified illustration) form the conductor tracks 22. An opening 28 is formed in the circuit board, which is aligned with a waveguide element 30 of the antenna arrangement 12. In the example shown, the walls of the opening 28 are metallized and grounded via electrically conductive layers on the top and bottom of the circuit board 10.The dimensions of the aperture 28 are large enough that electromagnetic waves 32, whose wavelength is determined by the frequency band of the radar sensor, can propagate through the aperture into the waveguide element 30. The interposer 18 also has an alternating sequence of dielectric layers 34 and electrically conductive layers L1, L2, L3. The lower layer L1, directly adjacent to the high-frequency component 14, forms, among other things, a feed line 36 for a resonator element 38 embedded in the interposer 18. The resonator element 38 is located within the footprint of the.

[0030] breakthrough 28 and, in the example shown, is formed by a patch in the electrically conductive layer L2. The resonator element 38 is surrounded by a cage 40 formed by grounded vias that extend to the surface of the interposer adjacent to the BGA 20. Within the cage 40, the electrically conductive layers L2 and L3 are interrupted, so that the resonator element 38 is completely embedded in non-conductive material. A microwave signal generated in the radio-frequency component 14 can be electromagnetically coupled into the resonator element 38 via the feed line 36. The distances between the "lattice bars" of the cage 40 are small in relation to the wavelength of the microwave radiation, so that the cage acts like a waveguide through which the resonator element 38 can radiate the microwave power into the breakthrough 28 and then finally into the waveguide element 30.It is understood that the BGA 20 is also interrupted at the location of the breakthrough 28. 0.

[0031] Fig. 2 shows a modified embodiment which differs from the embodiment according to Fig. 1 only in that the contacting of the interposer 18 is not carried out via a BGA, but via an LGA 42 (Land Grid Array; arrangement of contact surfaces). ^

[0032] Fig. 3 shows an embodiment that differs from the embodiments of Figs. 1 and 2 in that the resonator element 38 is galvanically connected to the feed line 36. Furthermore, in this example, a second resonator element 38 is formed in the electrically conductive layer L3. The distance between the two resonator elements is adapted to the wavelength so that a greater directivity is achieved when coupling the microwave power into the waveguide element 30.

[0033] In this example, contacting of the interposer 18 is made via a BGA, but an LGA would also be conceivable. This applies to all embodiments described in this application.

[0034] Fig. 4 schematically shows an embodiment in which the interposer 18 has a larger number of electrically conductive layers L1 -LN. The number of layers in which resonator elements 38 are formed can be 1, 2, or more.

[0035] Fig. 4 further illustrates an example of a configuration in which two or more separately fed resonator elements 38 are arranged in the same layer L2. The associated feed lines 36 are connected to different outputs of the radio-frequency component 14, although this is not visible in Fig. 4. The coupling to the resonator elements 38 is electromagnetic in this example. Fig. 5 shows a section through the cage 40 at the level of the top side of layer L1 in Fig. 2. The individual grid bars of the cage 40 can be seen in section here. Also visible is one end of the feed line 36, which is separated from a grounded metallization layer 46 by a gap 44 (coplanar waveguide). The grid 40, in which a passage 48 for the feed line 36 is formed, is also grounded via the metallization layer.

[0036] Fig. 6 shows a section through the cage 40 at the level of the dielectric layer 38, which separates the conductive layers L1 and L2. Fig. 7 shows a section at the level of the top of the resonator element 38, which in this case is formed as a rectangular patch. This patch generates a linearly polarized oscillation mode inside the cage 40, the polarization direction of which depends on the orientation of the rectangle.

[0037] Alternatively, the patch can also be rectangular in shape with two diagonally opposite corners "cut off," as shown in Fig. 8. A patch with this geometry is known to generate a circularly polarized oscillation mode. If necessary, the geometry of the cage 40 can be adapted to the predominantly excited oscillation mode.

[0038] Fig. 9 shows a schematic floor plan of the semiconductor component 14 and the associated interposer 18. In this example, eight coupling structures 50 are embedded in the interposer 18, each coupling to a waveguide element (not shown here) that corresponds to the waveguide element 30 in Fig. 1. Each coupling structure 50 is formed by a cage 40 containing at least one resonator element 38. The resonator elements 38 of each coupling structure 50 are each connected to an output of the semiconductor component 14 via a feed line 36. In the position immediately above the feed lines 36, each cage 40 has a passage 48 (Fig. 5). The grid bars of this passage merge into a gallery of vias 52 that flank the feed line 36, which is designed as a coplanar waveguide. Fig. 10 shows a section through the waveguide elements 30, which are located on the top side of the circuit board 10 and which correspond to the waveguide elements shown in Fig.9 are assigned to the coupling structures 50 shown. Looking through the waveguide elements 30, one sees the openings 28 of the circuit board 10. These openings are formed, for example, by a series of holes whose circular cross-sections overlap one another, so that the opening has an approximately oval shape in plan view.

[0039] Fig. 11 shows a complete radar sensor in plan view. The antenna arrangement 12 has a housing 52 that is mounted on the circuit board 10, but projects beyond it in plan view. The housing 52 accommodates eight waveguide antennas 54 arranged in two parallel rows. Each of these waveguide antennas 54 is connected via a connecting element 56 (shown in dashed lines), also designed as a waveguide, to one of the waveguide elements 30 on the circuit board 10. The waveguide elements couple to the resonator elements 38 (not shown in Fig. 11) via the openings 28 in the circuit board.

[0040] In order to create a broadband and flexibly configurable radar sensor, the number, shape, and arrangement of the coupling structures 50 can be varied in many ways. Fig. 12 shows, as an example, a coupling structure with two resonator elements 38 arranged in the same position of the interposer, both of which are designed as rectangular patches that differ in their orientation by ^. Fig. 13 shows the associated feed lines 36, which are also oriented at right angles to one another. The two patches can be used to generate linearly polarized radiation fields whose polarization directions are rotated by 90° relative to one another. This arrangement can be used, for example, to switch between two mutually perpendicular polarization directions by feeding either one or the other resonator element 38.Alternatively, both resonator elements can be fed simultaneously, resulting in diagonal or circular polarization depending on the phase relationship of the feed signals.

[0041] Figs. 14 to 16 show different configurations of resonator elements 38 and feed lines 36. Similar to Figs. 12 and 13, the arrangement shown in Fig. 15 allows two oscillation modes with mutually perpendicular polarization to be generated. In Fig. 16, only a single rectangular resonance element is provided per interposer layer, which, however, can be fed via feed lines 36 oriented at right angles to each other. In this case, too, two oscillation modes with mutually perpendicular polarization can be generated.

[0042] In Figs. 15 and 16, one of the two feed lines 36 is shown hatched and the other unhatched for better differentiation. Fig. 17 illustrates examples of different systems for feeding the microwave signal into these feed lines. In Fig. 17(a), the two feed lines 36 are connected directly to two different outputs of the radio-frequency module 14. In Fig. 17(b), the two feed lines are connected to two outputs of a transformer or amplifier 58, which in turn is connected to an output of the radio-frequency module 14. This arrangement allows the two resonator elements to be fed synchronously with in-phase signals.

[0043] In Fig. 17(c), a ring coupler 60 is connected to an output of the high-frequency component 14, and the feed lines 16 are connected to the ring coupler 60 in such positions that they pick up signals with different phase positions.

[0044] In Fig. 17(d), the two feed lines 36 are connected to an output 62 of the high-frequency component 14. While one of the two feed lines is connected directly to the output 62, the other feed line has a bypass line 64, the length of which determines the phase position of the signals fed into the resonance elements 38.

[0045] It is understood that in addition to the layer L1 of the interposer 18, which forms the feed lines 36, at least one further electrically conductive layer of the interposer can form resonance elements 38, each of which has the same shape and arrangement as the resonance elements in Figs. 14 to 16, but which do not have their own feed lines, but are excited to oscillate by electromagnetic coupling to the layer L1.

[0046] While in the previously described embodiments, the feed lines 36 are designed as coplanar waveguides, variants are also conceivable for all described embodiments in which the feed line is designed as a SIW (Substrate Integrated Waveguide). These SIW waveguides are delimited on the top and bottom by grounded electrically conductive layers of the interposer, and the horizontal delimitation is achieved by galleries of vias, similar to the cages 40.

Claims

Claims 1. Radar sensor with a high-frequency component (14) and an antenna arrangement (12) arranged on opposite sides of a circuit board (10) 5 net are, and with a coupling structure (50) for signal coupling of the antenna arrangement (12) to the high-frequency component (14), characterized in that the circuit board (10) has a penetration (28) which is dimensioned to be transparent to microwave radiation (32), that the high-frequency component (14) is connected to the circuit board (10) by a multilayer interconnect structure (18) which covers the penetration (28), and that the coupling structure (50) has a resonator element (38) embedded in the interconnect structure (18) which is configured to radiate microwave radiation through the penetration (28) into the antenna arrangement (12). 5 2. Radar sensor according to claim 1, wherein the antenna arrangement (12) comprises at least one waveguide element (30) which is aligned with the opening (28) and receives and transmits the microwave radiation (32) generated by the resonator element (38).

3. Radar sensor according to claim 1 or 2, wherein the resonator element (38) is arranged in a cage (40) serving as a waveguide, the walls of which are formed by vias in the multilayer interconnect structure (18).

4. Radar sensor according to one of the preceding claims, wherein at least two electrically conductive layers of the connection structure (18) each contain at least one resonator element (38), wherein the corresponding resonator elements (38) are congruent to each other in the different layers.

5. Radar sensor according to one of the preceding claims, wherein at least two resonator elements (38) are arranged in the same position of the connecting structure (18). 5 6. Radar sensor according to one of the preceding claims, in which at least two feed lines (36) connecting the high-frequency component (14) to the resonator element (38) or resonator elements (38) are configured such that different modes of vibration of the microwave radiation (32) can be excited by different ways of feeding the microwave power into these feed lines.

7. Radar sensor according to claim 6, wherein each of several resonator elements (38) located in the same position of the connecting structure (18) has its own feed line (36).

8. Radar sensor according to claim 6, in which two feed lines (36) are connected to the same resonator element (38) such that vibration modes with different polarization can be excited depending on the choice of feed line.

9. Radar sensor according to one of claims 6 to 8, wherein the resonator element (38) or resonator elements (38) are electromagnetically coupled to their respective feed line (36).

10. Radar sensor according to one of claims 6 to 8, wherein the resonator element (38) or the resonator elements (38) are galvanically coupled to their respective feed line (36).

11. Radar sensor according to one of claims 6 to 10, wherein at least one feed line (36) is a coplanar waveguide.

12. Radar sensor according to one of claims 6 to 10, wherein at least one feed line (36) is an S IW waveguide.

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