Radar sensor with waveguide structure

Abstract

The invention relates to a radar sensor having a plate-shaped substrate (12), which has at least one layer made of an electrically non-conductive material and has a waveguide structure on one side and a high-frequency source / sink on the opposite side, which is connected to the waveguide structure via a high-frequency feed-through (22) through the substrate, characterized in that the high-frequency feed-through (22) passes through the substrate and the high-frequency feed-through (22) passes through the substrate. The wall of the high-frequency feedthrough (22) is formed by a series of cylindrically curved face segments (30) having a uniform cross-section over at least a portion of the length of the high-frequency feedthrough.

Description

Technical Field

[0001] The invention relates to a radar sensor having a plate-shaped substrate, which has at least one layer composed of a non-conductive material and has a waveguide structure on one side and a high-frequency source / sink on the opposite side, which is connected to the waveguide structure via a high-frequency feedthrough through the substrate.

[0002] In particular, the present invention relates to radar sensors for motor vehicles. Background Art

[0003] Radar sensors are used in motor vehicles to implement comfort functions such as adaptive cruise control and safety functions such as emergency brake assist. The radar sensor emits a high-frequency radar beam via an antenna structure and receives the beam reflected on an object. The detected object can be stationary or moving. The distance and direction (angle) to the object can be calculated using the received radar beam. In addition, the speed of the object relative to the radar sensor can be calculated.

[0004] Radar sensors typically operate in the frequency range of 76 to 81 GHz.

[0005] Driver assistance functions with higher functionality in the area of ​​comfort or safety, such as the NCAP AEB emergency braking function for pedestrians or cyclists, as well as autonomous functions in the future in the range of Level 3 to Level 5, lead on the one hand to a plurality of sensors that have to be arranged at different positions around the vehicle in order to cover the necessary field of view and on the other hand to sensors with an ever-wider azimuth detection range.

[0006] Furthermore, a radar sensor with a wide azimuth detection range and a long range can be realized with the aid of a waveguide antenna. The waveguide antenna can be fed via a metallized opening through the circuit board, so that the waveguide antenna and the high-frequency source (or high-frequency sink, i.e., receiver) can be arranged on opposite sides of the circuit board. It is known to manufacture the opening of the circuit board used as the high-frequency feed-through by drilling or milling a notch with the desired cross section in the circuit board and then metalizing the circuit board (the surface containing the notch) according to standard methods. Summary of the invention

[0007] The object of the present invention is to provide a radar sensor having a high-frequency feedthrough which has a geometry optimized for the respective application and which can nevertheless be produced cost-effectively.

[0008] This object is achieved according to the invention in that the wall of the high-frequency passage is formed from a series of cylindrically curved surface segments which have a uniform cross section over at least a portion of the length of the high-frequency passage.

[0009] The high-frequency feedthrough can be produced cost-effectively in any desired cross-sectional shape, in that holes can be arranged one next to the other according to the course of the wall of the high-frequency feedthrough, the cross sections of the holes overlapping one another or at least almost touching one another. Although the wall of the high-frequency feedthrough formed in this way has a certain waviness, since each individual hole forms at least one cylindrically curved section of the wall, it can be realized with a relatively small number of holes and correspondingly little effort, so that the waviness does not have a negative effect on the transmission characteristics of the high-frequency feedthrough for microwaves, in particular when the wall unevenness is smoothed by subsequent metallization.

[0010] A significant advantage of this production method is that no complex milling methods are required to achieve the desired geometry of the high-frequency feedthrough that deviates from a circular shape. The holes can be produced in a reasonable manner using a single drill bit or a combination of a few drill bits and can be arranged in such a way that only low transverse forces act on the drill bit during the drilling process.

[0011] The invention also relates to a method for producing a radar sensor having the above-mentioned features, in which method the high-frequency feedthrough is formed by arranging a plurality of holes according to the course of a wall of the high-frequency feedthrough to be produced.

[0012] Advantageous embodiments and refinements are specified in the dependent claims.

[0013] The holes can be introduced into the substrate in such a way that their cross sections overlap one another, i.e. the distance between the axes of two adjacent holes is smaller than the diameter of the holes or, if these diameters are different, smaller than the sum of the radii of the two holes. The holes arranged one above the other then produce straight or curved slots in the substrate.

[0014] In one embodiment, the high-frequency through-hole is formed directly through the gap. In another embodiment, the curved or multi-bent gap forms a closed line. Within this line, the remaining material of the circuit board then forms an island that is not connected to the surrounding material and thus falls off, so that a high-frequency through-hole with a width greater than the gap width is obtained.

[0015] Each individual hole produces a cylindrically curved wall section in the wall of the high-frequency passage, and the wall sections adjoining one another form a series of edges along the wall of the high-frequency passage, which protrude into the interior of the passage. The smaller the distance between the axes of the individual holes, the flatter and more blunt these edges are. If the distance between the axis of the holes increases, the edges become higher and sharper, but the following advantage results: during the drilling of the individual holes, less transverse forces act on the drill bit, because the surface of the drill bit acting on the substrate wall is more evenly distributed.

[0016] If the distance between the axes of the final holes is increased to such an extent that it is equal to the diameter of the holes, the cylindrical wall segments form a series of semicircles. If the distance between the axes is increased still further, narrow webs remain between the individual holes. However, if the gaps formed by the holes form a closed line, the islands surrounded by this line (which are then connected to the surrounding material via the narrow webs) can be destroyed with very little force, so that a high-frequency feedthrough with a relatively large cross section is obtained with a relatively small number of holes (in which, moreover, virtually no transverse forces occur).

[0017] The substrate is generally a multilayer circuit board having at least two conductive layers on its two opposing surfaces. However, additional conductive layers can be selectively arranged inside the circuit board. After one or more high-frequency feedthroughs have been produced by the method described above, metallization layers can be produced on both surfaces of the circuit board and on the inner surface of the high-frequency feedthrough in a single working process by means of known chemical or electrochemical metallization methods. Preferably, the metallization layer on the inner surface of the high-frequency feedthrough should have a thickness of 1 μm or more, because then the above-mentioned edges are reliably covered and the high-frequency characteristics are no longer related to the metallization thickness.

[0018] Since the method according to the invention allows a high degree of flexibility in the configuration of the cross-sectional geometry of the high-frequency feedthrough, the bandwidth can be optimized in a simple manner and the desired filter or damping characteristics can be achieved by suitable selection of the geometry, optionally also for a specific polarization direction. In a known manner, the damping characteristics and the dielectric constant of the high-frequency feedthrough can also be influenced by filling the gaps forming these high-frequency feedthroughs with a suitable material. Then, as required, further conductor structures can be mounted on the filling material at the opposite ends of the high-frequency feedthrough.

[0019] It is also not mandatory that the holes that create the walls of the high-frequency feedthrough run from one side of the circuit board to the other. For example, a first contour can be formed by a series of holes with a small depth, and then a further contour can be formed inside it by a series of deeper holes, the geometry of which is independent of the geometry of the first contour within certain limits. In this way, a stepped structure can also be achieved in the high-frequency feedthrough. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Exemplary embodiments are explained in more detail below with reference to the drawings.

[0021] The accompanying drawings show:

[0022] Figure 1 : A partial cross section of a radar sensor according to an embodiment of the present invention;

[0023] Figure 2 :according to Figure 1 A cross section of a substrate of a radar sensor and a high-frequency through-hole formed therein;

[0024] Figure 3 and 4 : Examples of high frequency vias with different geometries; and

[0025] Figure 5 : A cross section of a substrate having a high-frequency through-portion according to another embodiment. DETAILED DESCRIPTION

[0026] exist Figure 1 The radar sensor 10 shown in FIG. 1 in partial section has a substrate 12 which consists of a plurality of layers 14 of non-conductive material and alternating layers 16 of conductive material. The top and bottom of the substrate 12 are metallized and thus also form layers 16 of conductive material.

[0027] A waveguide structure 18 is arranged on the upper side of the substrate 12, which waveguide structure can be, for example, a waveguide antenna or a connecting structure leading to a waveguide antenna (not shown). Figure 1 Below, on the opposite side of the substrate 12, a high-frequency source / sink 20 is arranged, which is formed, for example, by an integrated high-frequency module (MMIC) and is used to generate microwave signals and feed them into the waveguide structure 18 and / or detect and evaluate microwave signals received by the waveguide antenna.

[0028] The waveguide structure 18 and the high-frequency source / sink 20 are connected to each other for signal technology via a high-frequency through-hole 22. The high-frequency through-hole 22 is formed by a notch, which in the example shown runs from the upper side to the lower side of the substrate 12 with a uniform cross section and the walls of the notch have a metallization 24. The high-frequency through-hole 24 can therefore transmit microwave signals from the connection point of the waveguide structure 18 to the connection point of the high-frequency source / sink 20, and vice versa. The transmittance of the high-frequency through-hole 22 for microwave signals of different frequencies and polarizations depends on the geometry, in particular on the cross section of the notch forming the high-frequency through-hole 22.

[0029] exist Figure 2 The high-frequency passage 22 is shown in cross section in FIG. It can be seen that the high-frequency passage 22 is composed of four holes 28 arranged in parallel with each other, the outlines of which are in FIG. Figure 2 The four holes 28 have a uniform radius and are arranged at a uniform center distance, wherein the center distance is slightly smaller than the diameter of the hole, so that the cross sections of the holes overlap each other. Figure 2 The upper and lower walls of the high-frequency passage 22 in , have a corrugated cross-sectional shape and are formed by cylindrical wall sections 30 which each correspond to a part of the circumference of one of the holes 28 and adjoin one another forming edges 32 .

[0030] The high-frequency passage 22 therefore has overall the shape of an elongated straight slot, the opposite walls of which are formed by mutually facing wall sections 30 of the same hole.

[0031] For example, the high-frequency feedthrough can be produced by clamping the substrate 12 into an XY table, which enables controlled movement of the substrate in a two-dimensional XY plane and forming the holes 28 one after another by means of a drill bit clamped into a drill chuck fixed in position in the XY plane. Subsequently, the substrate 12 is metallized in order to form the metallization 24 on the wall of the high-frequency feedthrough 22 and simultaneously on the upper side and the lower side of the substrate.

[0032] Figure 3 The high frequency through portion 22a is shown. Figure 2 The embodiment of the embodiment of FIG. 2 differs in that the holes 28 have different diameters. In the example shown, the diameter is selected so that the slot forming the high-frequency passage has a waist in the middle and its width increases towards the two ends.

[0033] Figure 4 A high-frequency feedthrough 22b according to another embodiment is shown. In this case, the hole 28 again has a uniform diameter, but the central axis of the hole is arranged on a curved line, so that the slot forming the high-frequency feedthrough has a curved configuration overall.

[0034] Figure 5 The cross section of a substrate 12c with a high-frequency passage 22c which is stepped in longitudinal section is shown. The high-frequency passage is produced by introducing holes with different diameters into the substrate from opposite sides. The wall of the high-frequency passage 22c is therefore bounded by a cylindrically curved wall section 30c which is formed at Figure 5 In the upper part of the through-hole 30c, the radius of curvature and the width are smaller than in the lower part. Accordingly, the center axis of the hole introduced into the substrate from above is also at a smaller distance than the center axis of the hole introduced from below. Overall, a high-frequency through-hole is thus obtained with a step 34. The contours defined by the wall section 30c above and below the step can be different from each other.

Claims

1. A radar sensor having a plate-shaped substrate (12), the substrate having at least one layer (14) made of a non-conductive material and having a waveguide structure (18) on one side and a high-frequency source / sink (20) on the opposite side, the high-frequency source / sink being connected to the waveguide structure (18) via a high-frequency passage (22; 22a-c) passing through the substrate, characterized in that The wall of the high-frequency through-portion (22; 22a-c) is formed by a series of cylindrically curved face segments (30; 30c) having a uniform cross-section over at least a portion of the length of the high-frequency through-portion.

2. A method for manufacturing a radar sensor according to claim 1, characterized in that In order to produce the high-frequency passage (22; 22a-c), a plurality of holes (28) extending at right angles to the plane of the substrate are arranged one to another so that the peripheral walls of the holes (28) form wall sections (30; 30c).

3. The method according to claim 2, wherein the high-frequency passages (22; 22a-c) are formed in the form of slots by arranging the holes (28) relative to one another, the width of the slots corresponding to the diameter of the holes (28).

4. A method according to claim 2 or 3, in which the axes of the holes (28) produced successively lie in a straight line.

5. Method according to any one of claims 2 to 4, in which method the holes (28) have different diameters.

6. The method according to any one of the preceding claims, in which the hole (28) is configured to pass through the substrate (12) from one side to the other side.

7. The method according to any one of claims 2 to 6, in which the substrate is metallized after the production of the hole (28), wherein: A metallization (24) having a layer thickness of 1 μm or more is formed on the wall of the high-frequency feedthrough.

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