Radar Sensor

Abstract

1. A radar sensor comprising: a high frequency component (14) and an antenna arrangement (12) arranged on opposite sides of a circuit board (10); and a coupling structure for signal coupling the antenna arrangement (12) to the high frequency component (14), wherein the circuit board (10) comprises an opening (28), the opening (28) is dimensioned to be transparent to microwave radiation (32), the high frequency component (14) is connected to the circuit board (10) by a multi-layer connection structure (18), the multi-layer connection structure (18) covers the opening (28), and the coupling structure comprises a resonator element (38) embedded in the connection structure (18), the resonator element (38) is configured to radiate microwave radiation to the antenna arrangement (12) through the opening (28).

Description

[Technical field]

[0001] The present invention relates to a radar sensor that includes a radio frequency component and an antenna arrangement disposed on opposite sides of a circuit board, and a coupling structure for signal coupling the antenna arrangement to the radio frequency component.

[0002] In particular, the present invention relates to a radar sensor suitable for use in driver assistance or autonomous driving systems for automobiles. [Background technology]

[0003] From US 2020 / 365971 A1 a radar sensor of the above type is known in which the antenna arrangement is coupled to the high-frequency component via a conductive via in the circuit board, but this design principle only allows for low-loss signal transmission if very strict tolerances are observed during manufacturing.

[0004] US Pat. No. 1,103,1681 shows an example of a radar sensor in which the antenna and high frequency components are 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: a given geometric arrangement of antenna elements on a circuit board typically requires relatively long and lossy signal paths. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] US Patent Application Publication No. 2020 / 365971 [Patent Document 2] U.S. Pat. No. 1,103,1681 Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the invention is to provide a low-loss radar sensor of the type mentioned at the outset which can be manufactured more easily. [Means for solving the problem]

[0007] This problem is solved according to the invention by the fact that the circuit board comprises an opening, the opening is dimensioned to be transparent for microwave radiation, the high-frequency component is connected to the circuit board by a multi-layer connection structure, the multi-layer connection structure covers the opening, and the coupling structure comprises a resonator element embedded in the connection structure, the resonator element being configured to radiate microwave radiation through the opening to the antenna arrangement.

[0008] In this solution, the resonator elements, which serve to couple the antenna arrangement to the high-frequency component, are embedded in a so-called interposer, which mechanically and electrically connects the high-frequency component with the circuit board. The signal coupling in the direction perpendicular to the plane of the circuit board is achieved by electromagnetic radiation, so that no vias, which are permitted with smaller manufacturing tolerances, are required in either the circuit board or the interposer.

[0009] Advantageous embodiments of the invention are defined in the dependent claims. Exemplary embodiments are explained in more detail below with reference to the drawings. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view through a portion of a radar sensor according to one exemplary embodiment of the present invention. [Diagram 2] FIG. 4 is a partial cross-sectional view of a radar sensor according to a further exemplary embodiment of the present invention. [Diagram 3] FIG. 4 is a partial cross-sectional view of a radar sensor according to a further exemplary embodiment of the present invention. [Figure 4] FIG. 4 is a partial cross-sectional view of a radar sensor according to a further exemplary embodiment of the present invention. [Diagram 5]3A-3C are cross-sectional views through different layers of the interposer in the exemplary embodiment of FIG. 2. [Figure 6] 3A-3C are cross-sectional views through different layers of the interposer in the exemplary embodiment of FIG. 2. [Figure 7] 3A-3C are cross-sectional views through different layers of the interposer in the exemplary embodiment of FIG. 2. [Figure 8] FIG. 8 is a cross-sectional view similar to FIG. 7 for a modified exemplary embodiment. [Figure 9] FIG. 1 is a plan view of a high frequency component on an interposer having multiple bonding structures. [Figure 10] FIG. 10 is a plan view of a waveguide element allocated to the coupling structure according to FIG. [Figure 11] FIG. 2 is a plan view of the completed radar sensor. [Figure 12] FIG. 1 shows an example of a coupling structure with two feed points for microwave signals. [Figure 13] FIG. 1 shows a coupling structure with two resonator elements for different vibration modes. [Figure 14] 4A-4D show further examples of arrangements of resonator elements with different vibration modes. [Figure 15] 4A-4D show further examples of arrangements of resonator elements with different vibration modes. [Figure 16] 4A-4D show further examples of arrangements of resonator elements with different vibration modes. [Figure 17(a)] FIG. 17(a) shows an example of a multi-channel power supply system for the coupling structures according to FIGS. [Figure 17(b)] FIG. 17(b) is a diagram showing an example of a multi-channel power supply system for the coupling structure according to FIGS. [Figure 17(c)] FIG. 17(c) shows an example of a multi-channel power supply system for the coupling structure according to FIGS. [Figure 17(d)] FIG. 17(d) is a diagram showing an example of a multi-channel power supply system for the coupling structure according to FIGS. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] 1 shows a partial cross section through a radar sensor comprising a circuit board 10 having an antenna arrangement 12 formed on one side thereof (the upper side in the illustrated example) and a high frequency component 14 on the lower side, which may for example be an MMIC (Monolithic Microwave Integrated Circuit).

[0012] The high-frequency components 14 are embedded in a plastic molding 16 and are mechanically and electrically connected to conductor tracks 22 of the circuit board 10 by means of a connection structure, hereinafter referred to as an interposer 18, and a so-called BGA 20 (Ball Grid Array; i.e. an array of solder balls).

[0013] The circuit board 10 comprises, as is customary, alternating dielectric layers 24 and conductive layers 26, some of which (not shown in the simplified diagram) 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 illustrated example, the walls of the opening 28 are metallized and are grounded via conductive layers above and below the circuit board 10. The dimensions of the opening 28 are large enough to allow an electromagnetic wave 32, whose wavelength is determined by the frequency band of the radar sensor, to propagate through the opening to the waveguide element 30.

[0014] The interposer 18 also comprises alternating dielectric layers 34 and 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 inside the opening 28 in plan view and is formed by a patch in the conductive layer L2 in the example shown. The resonator element 38 is surrounded by a cage 40 formed by ground vias that extend to the surface of the interposer adjacent to the BGA 20. Within the cage 40, the conductive layers L2 and L3 are interrupted, so that the resonator element 38 is completely embedded in a non-conductive material. A microwave signal generated in the high frequency component 14 can be electromagnetically coupled to the resonator element 38 via the feed line 36. The distance between the "grid bars" of cage 40 is small compared to the wavelength of microwave radiation, and therefore the cage acts like a waveguide through which resonator element 38 can radiate microwave power towards aperture 28 and ultimately to waveguide element 30. It should be appreciated that BGA 20 is also interrupted at the location of aperture 28.

[0015] FIG. 2 shows a modified exemplary embodiment which differs from the exemplary embodiment of FIG. 1 only in that contact of the interposer 18 is made via an LGA 42 (Land Grid Array; an array of contact surfaces) rather than via a BGA.

[0016] 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 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.

[0017] In this example, contact to the interposer 18 is made via a BGA, but alternatively an LGA is also possible, this being the case for all exemplary embodiments described in this application. 4 shows a schematic representation of an exemplary embodiment in which the interposer 18 comprises a number of conductive layers L1 to LN. The number of layers on which the resonator elements 38 are formed may be one, two or more layers.

[0018] Figure 4 further shows an example of a configuration in which two or more separately fed resonator elements 38 are arranged in the same layer L2. Although not visible in Figure 4, the associated feed lines 36 are connected to different outputs of the high frequency component 14. In this example, the coupling to the resonator elements 38 is done electromagnetically.

[0019] Figure 5 shows a cross section through the cage 40 at the level of the top surface of layer L1 in Figure 2. Here, the individual grid bars of the cage 40 can be seen in cross section. Additionally, one end of the feed line 36 can be seen (coplanar waveguide), which is separated by a gap 44 from a grounded metallization layer 46. The grid 40 is also grounded via the metallization layer, and has a passage 48 formed in the grid 40 for the feed line 36.

[0020] FIG. 6 shows a cross section through the cage 40 at the level of the dielectric layer 38 which separates the conductive layers L1 and L2 from each other. 7 shows a cross section at the level of the top surface of a resonator element 38, configured in this case as a rectangular patch, which generates linearly polarized vibration modes inside the cage 40, whose polarization direction depends on the orientation of the rectangle.

[0021] Alternatively, the patch may have a rectangular shape with two diagonal corners "cut off", as shown in Fig. 8. As is known, a patch with this geometry will generate a circularly polarized vibration mode. If necessary, the geometry of the cage 40 can be adapted to the vibration mode that can be primarily excited.

[0022] In Fig. 9, a semiconductor component 14 and an associated interposer 18 are shown in a schematic plan view. In this example, eight coupling structures 50 are embedded in the interposer 18, each of which couples to a waveguide element (not shown here) corresponding 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 connected to the output of the semiconductor component 14 via respective feed lines 36. Directly above the feed lines 36, each cage 40 has a passage 48 (Fig. 5). The grid bars of this passage lead to a number of vias 52 on either side of the feed line 36, which are configured as coplanar waveguides.

[0023] Figure 10 shows a cross section through a waveguide element 30 which is located on the upper side of the circuit board 10 and which is assigned to the coupling structure 50 shown in Figure 9. Here, the openings 28 of the circuit board 10 are visible through the waveguide element 30. These openings are formed, for example, by a series of holes whose circular cross sections overlap, so that in plan view the openings have a shape which approximates an oval.

[0024] The completed radar sensor is shown in plan view in Fig. 11. The antenna arrangement 12 comprises a housing 52 which is held on a circuit board 10 beyond which the housing 52 projects in plan view. The housing 52 accommodates eight waveguide antennas 54 arranged in two parallel rows. Each of these waveguide antennas 54 is connected to one of the waveguide elements 30 on the circuit board 10 via a connecting element 56 (shown in dashed lines) also configured as a waveguide, which in turn is coupled to a resonator element 38 (not shown in Fig. 11) via an opening 28 in the circuit board.

[0025] The number, shape and arrangement of the coupling structures 50 can be varied in order to provide a broadband and flexibly configurable radar sensor. FIG. 12 shows an example of a coupling structure with two resonator elements 38 arranged on the same layer of an interposer. Both resonator elements 38 are configured as rectangular patches oriented 90° apart. FIG. 13 shows the associated feed lines 36, which are also oriented at right angles to each other. The two patches can generate a linearly polarized radiation field with the polarization directions rotated 90° from each other. This arrangement can be used, for example, to switch between two polarization directions at right angles to each other by feeding one or the other of the resonator elements 38. Alternatively, both resonator elements can be fed simultaneously, which results in diagonal or circular polarization depending on the phase relationship of the feed signals.

[0026] In Figures 14 to 16 different configurations of the resonator elements 38 and the feed lines 36 are shown. In the arrangement of Figure 15, two vibration modes with mutually orthogonal polarizations can be generated, similar to Figures 12 and 13. In Figure 16, only one rectangular resonator element is provided per interposer layer, but it can be fed via feed lines 36 oriented at right angles to each other. In this case too, two vibration modes with mutually orthogonal polarizations can be generated.

[0027] In Fig. 15 and Fig. 16, one of the two feed lines 36 is shown hatched and the other one is shown without hatching to allow a better distinction. Fig. 17 shows examples of different systems for feeding these feed lines with microwave signals. In Fig. 17(a), the two feed lines 36 are directly connected to two different outputs of the high frequency component 14. In Fig. 17(b), the two feed lines are connected to two outputs of a transformer or amplifier 58, which is further connected to the output of the high frequency component 14. This arrangement makes it possible to feed the two resonator elements synchronously with a common-phase signal.

[0028] In FIG. 17(c), a ring coupler 60 is connected to the output of the high-frequency component 14, and the feed line 16 is connected to the ring coupler 60 at a position where signals having different phase positions are extracted.

[0029] In Fig. 17(d) two feed lines 36 are connected to the output 62 of the high frequency component 14. One of the two feed lines is directly connected to the output 62, while the other feed line has a bypass line 64, the length of which determines the phase position of the signal fed to the resonator element 38.

[0030] In addition to layer L1 of interposer 18 forming the feed line 36, at least one further conductive layer of the interposer can form resonator elements 38, each having the same shape and arrangement as the resonator elements in Figures 14-16, but without their own feed line, and which are excited to vibrate by electromagnetic coupling to layer L1.

[0031] In the exemplary embodiments described so far, the feed lines 36 are configured as coplanar waveguides, but for all the above mentioned embodiments, variants are also conceivable in which the feed lines are configured as SIW (Substrate Integrated Waveguides). These SIW waveguides are bounded above and below by the grounded conductive layers of the interposer, and in the horizontal direction by a number of vias, similar to the cage 40.

Claims

1. A radar sensor comprising: a high frequency component (14) and an antenna arrangement (12) disposed on opposite sides of a circuit board (10); and a coupling structure (50) for signal coupling the antenna arrangement (12) to the high frequency component (14), the circuit board (10) includes an opening (28), the opening (28) being dimensioned to be transparent to microwave radiation (32); The high-frequency component (14) is connected to the circuit board (10) by a multi-layer connection structure (18), and the multi-layer connection structure (18) covers the opening (28); The coupling structure (50) comprises a resonator element (38) embedded in the connecting structure (18), the resonator element (38) being configured to radiate microwave radiation through the opening (28) to the antenna arrangement (12). A radar sensor comprising:

2. 2. The laser sensor of claim 1, wherein the antenna arrangement (12) comprises at least one waveguide element (30) aligned with the opening (28) to receive and further transmit microwave radiation (32) generated by the resonator element (38).

3. 3. The radar sensor according to claim 1, wherein the resonator element (38) is arranged in a cage (40) acting as a waveguide, the walls of the cage (40) being formed by vias of the multi-layer connection structure (18).

4. The radar sensor according to any one of claims 1 to 3, wherein at least two conductive layers of the connection structure (18) each include at least one resonator element (38), and corresponding resonator elements (38) in different layers are congruent with each other.

5. The radar sensor according to any one of the preceding claims, wherein at least two resonator elements (38) are arranged in the same layer of the connection structure (18).

6. 6. The radar sensor according to claim 1, wherein at least two feed lines (36) connecting the high frequency component (14) with one or more of the resonator elements (38) are configured to excite different vibration modes of the microwave radiation (32) by differently supplying microwave power to the feed lines.

7. 7. The radar sensor of claim 6, wherein each of a plurality of resonator elements (38) located in the same layer of the connection structure (18) has its own feed line (36).

8. 7. The radar sensor of claim 6, wherein two feed lines (36) are connected to the same resonator element (38) and, depending on the selection of the feed lines, are capable of exciting vibration modes having different polarizations.

9. A radar sensor according to any one of claims 6 to 8, wherein one or more of the resonator elements (38) are electromagnetically coupled to a respective feed line (36).

10. A radar sensor according to any one of claims 6 to 8, wherein one or more of the resonator elements (38) are galvanically coupled to a respective feed line (36).

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

12. The radar sensor according to any one of claims 6 to 10, wherein the at least one feed line (36) is a SIW waveguide.

Images