Radar sensor having a waveguide structure

Abstract

A radar sensor comprising a plate-shaped substrate (12) having at least one layer (14) made of a non-conductive material, having a waveguide structure (18) on one surface, and having a high-frequency source / sink (20) connected to the waveguide structure (18) via a high-frequency feed-through (22; 22a-c) penetrating the substrate on the opposite surface, wherein the wall surface of the high-frequency feed-through (22; 22a-c) is formed by a series of cylindrically curved surface segments (30; 30c) having a uniform cross-section at least in a part of the length of the high-frequency feed-through.

Description

Technical Field

[0001] The present invention relates to a radar sensor comprising a plate-shaped substrate having at least one layer made of a non-conductive material, a waveguide structure on one surface, and a high-frequency source / sink connected to the waveguide structure via a high-frequency feed-through penetrating the substrate on the opposite surface.

[0002] The present invention relates in particular to a radar sensor 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 transmits a high-frequency radar beam via an antenna structure and receives the beam reflected by an object. At this time, the detected object may be stationary or moving. Using the received radar beam, the distance and direction (angle) to the object can be calculated. Furthermore, the relative speed of the object with respect to the radar sensor can also be calculated.

[0004] Normally, radar sensors operate in a frequency band of 76 to 81 GHz. For example, driving assistance functions with higher functionality in the areas of comfort and safety, such as the AEB (Autonomous Emergency Braking) emergency braking function of NCAP (New Car Assessment Program) for pedestrians and bicycles, and future autonomous functions in the range from level 3 to level 5, on the one hand, lead to a large number of sensors that must be arranged at various positions around the vehicle in order to cover the necessary field of view, and on the other hand, lead to sensors with a wider azimuth detection range.

[0005] A radar sensor having a wide azimuth detection range and a large reach range can be realized particularly by using a waveguide antenna. Since the power supply of the waveguide antenna can be performed through a metal-coated opening penetrating the circuit board, the waveguide antenna and the high-frequency source (or high-frequency sink, i.e., the receiver) can be arranged on the opposite side of the circuit board. It is known to form such an opening functioning as a high-frequency feed-through on the circuit board by drilling or milling a perforation having a desired cross section in the circuit board and subsequently metallizing the circuit board including the surface of the perforation by a standard method.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] The problem of the present invention is to fabricate a radar sensor provided with a high-frequency feed-through having a shape optimized for each application and capable of being manufactured cost-effectively.

MEANS FOR SOLVING THE PROBLEMS

[0007] According to the present invention, this problem is solved in that the wall surface of the high-frequency feed-through is formed by a series of cylindrically curved surface segments having a uniform cross section at least in a part of the length of the high-frequency feed-through.

[0008] Such a high-frequency feed-through can be manufactured cost-effectively in a desired cross-sectional shape respectively by arranging holes whose cross sections overlap or at least substantially contact according to the course of the wall surface of the high-frequency feed-through. The wall surface of the high-frequency feed-through formed in this way has a certain undulation because each individual hole forms at least one cylindrically curved wall surface segment. In particular, when the unevenness of the wall surface is smoothed by subsequent metallization, it is possible to achieve that this undulation does not adversely affect the transmission characteristics of the high-frequency feed-through for microwaves with a relatively small number of holes and the associated low complexity.

[0009] A major advantage of this manufacturing method is that it does not require a complex milling method to achieve the desired shape of the off - circular high - frequency feed - through. The holes can be efficiently manufactured with a single drill or a combination of several drills and can be arranged so that the lateral forces acting on the drill during the drilling process are small.

[0010] The subject of the present invention is a method for manufacturing a radar sensor having the above - mentioned features, wherein the high - frequency feed - through is formed by arranging a plurality of holes according to the course of the wall of the high - frequency feed - through to be manufactured.

[0011] Advantageous embodiments and further improvements are described in the dependent claims. The holes can be attached to the substrate such that their cross - sections overlap, i.e., the distance between the axes of two adjacent holes is smaller than the diameter of the holes, and if these diameters are different, it is smaller than the sum of the radii of the two holes. The aligned holes form a straight or curved slot on the substrate.

[0012] In one embodiment, the high - frequency feed - through is directly formed by this slot. In another embodiment, the curved or multi - angled slot forms a closed line. Inside this line, the remaining material of the circuit board forms islands that fall out because they are not connected to the surrounding material, resulting in the formation of a high - frequency feed - through with a width larger than the width of the slot.

[0013] Each individual hole forms a cylindrically curved wall segment on the wall of the high - frequency feed - through, and adjacent wall segments form a series of protrusions along the wall of the high - frequency feed - through, and these protrusions project into the feed - through. The smaller the distance between the axes of the individual holes, the flatter and blunter these protrusions become. Increasing the distance between the axes of the holes makes the protrusions higher and sharper, but has the advantage that the surfaces where the drill engages the wall of the substrate are more evenly distributed, resulting in a smaller lateral force on the drill when opening the individual holes.

[0014] Finally, when the distance between the axes of the holes is increased until it equals the diameter of the holes, the cylindrical wall segments form a series of semi - circles. When the distance between the axes is further increased, thin webs remain between the individual holes. However, if the slots formed by the holes form a closed line, the islands surrounded by the line are connected to the surrounding material via the narrow webs and can be broken with little force, so that a high - frequency feed - through with a relatively large cross - sectional area can be obtained with a relatively small number of holes that do not generate substantially lateral forces.

[0015] The substrate is generally a multilayer circuit board having at least two conductive layers on two opposing surfaces. However, optionally, additional conductive layers may be provided inside the circuit board. After one or more high - frequency feed - throughs are manufactured using the method described above, the metal coating layers on the two surfaces of the circuit board and the metal coating layer on the inner surface of the high - frequency feed - through can be manufactured in one step using known chemical or electrochemical metal coating methods. Since the above - mentioned protrusions are reliably covered and the high - frequency characteristics do not depend on the thickness of the metal coating, the metal coating layer on the inner surface of the high - frequency feed - through preferably has a thickness of 1 μm or more.

[0016] The method according to the present invention allows high flexibility in forming the cross - sectional shape of the high - frequency feed - through, so that the bandwidth can be easily optimized, and the desired filter characteristics or attenuation characteristics can be selectively realized, in some cases even for a specific polarization direction, by an appropriate selection of the shape. By filling the five perforations forming these high - frequency feed - throughs with an appropriate material in a known method, the attenuation characteristics and the dielectric constant of the high - frequency feed - through may be affected. Then, if necessary, an additional conductor structure may be attached to the filling material at the opposite end of the high - frequency feed - through.

[0017] Also, it is not essential that the holes used to generate the walls of the high-frequency feed-through penetrate from one side of the circuit board to the other. For example, a first outer shape may be formed by a series of shallow holes, and within them, a further outer shape may be formed by a series of deeper holes whose shape within a specific range does not depend on the shape of the first outer shape. In this way, a stepped structure may be realized for the high-frequency feed-through.

[0018] Hereinafter, embodiments will be described in more detail with reference to the drawings.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0020] The radar sensor 10 shown in a partial cross-sectional view in FIG. 1 has a substrate 12 formed by a plurality of layers 14 made of a non-conductive material and alternating layers 16 made of a conductive material. The upper and lower surfaces of the substrate 12 are metallized, and thus, the layers 16 made of a conductive material are also formed.

[0021] On the upper surface of the substrate 12, a waveguide structure 18 is arranged, which may be, for example, a waveguide antenna or a connection structure connected to a waveguide antenna (not shown). On the opposite side of the substrate 12, the lower side in FIG. 1, a high-frequency source / sink 20 is arranged, which is formed, for example, by a monolithic microwave integrated circuit (MMIC), generates a microwave signal and supplies it to the waveguide structure 18, and / or functions to detect and evaluate the microwave signal received by the waveguide antenna.

[0022] The waveguide structure 18 and the high-frequency source / sink 20 are signal-technologically connected to each other by a high-frequency feed-through 22. In the illustrated example, this high-frequency feed-through 22 extends with a uniform cross-section from the upper surface to the lower surface of the substrate 12, and its wall is formed by a perforation having a metal coating 24.

[0023] Therefore, the high-frequency feed-through 24 can transmit a microwave signal from the connection point of the waveguide structure 18 to the connection point of the high-frequency source / sink 20, or vice versa. The transmittance of the high-frequency feed-through 22 for microwave signals with different frequencies and polarizations depends on the shape, particularly on the cross-section of the perforation forming the high-frequency feed-through 22.

[0024] FIG. 2 shows the cross-section of the high-frequency feed-through 22. It can be seen that the high-frequency feed-through 22 is formed by four holes 28 arranged side by side, and its outer shape is shown by a dotted line in FIG. 2. The four holes 28 have a uniform radius and are arranged with a uniform center-to-center distance, which is slightly smaller than the diameter of the holes, so that the cross-sections of the holes overlap each other. Therefore, the upper and lower wall surfaces of the high-frequency feed-through 22 in FIG. 2 have a wavy cross-sectional shape, each corresponding to a part of the circumference of one of the holes 28, and are formed by cylindrical wall segments 30 adjacent to each other to form protrusions 32.

[0025] Accordingly, the high-frequency feed-through 22 has an overall elongated straight slot shape, and its opposing wall surfaces are formed by wall segments 30 that oppose each other on the same hole diameter.

[0026] The high-frequency feed-through can be manufactured, for example, by clamping the substrate 12 to an X-Y table that can move while controlling the substrate in a two-dimensional X-Y plane, and continuously forming the holes 28 with a drill clamped to a drill chuck fixed to the X-Y plane. Thereafter, a metal coating 24 is formed on the wall surface of the high-frequency feed-through 22, and at the same time, the substrate 12 is metallized to form metal coatings on the upper and lower surfaces of the substrate.

[0027] FIG. 3 shows a high-frequency feed-through 22a, which is different from the embodiment described in FIG. 2 in that the diameter of the hole 28 is different. In the illustrated example, the slot forming the high-frequency feed-through has a body portion in the center, and the diameter is selected such that the width increases toward both ends.

[0028] FIG. 4 shows a high-frequency feed-through 22b according to a further embodiment. Also in this case, the holes 28 have a uniform diameter, but since their central axes are arranged on a curve, the slot forming the high-frequency feed-through has an overall curved shape.

[0029] FIG. 5 shows a cross-section of a stepped substrate 12c of a longitudinal section of a high-frequency feed-through 22c. This high-frequency feed-through is manufactured by drilling holes of different diameters from opposite sides of the substrate.

[0030] Accordingly, the wall surface of the high-frequency feed-through 22c is defined by a cylindrically curved wall segment 30c, and at the upper part of the feed-through in FIG. 5, the radius of curvature and the width are smaller than those at the lower part. Accordingly, the central axis of the hole drilled from above the substrate also has a smaller interval than the central axis of the hole drilled from below.

[0031] Thus, overall, a high-frequency feed-through having a step 34 is formed. The outer shapes defined by the wall surface segments 30c above and below this step may be different from each other.

Claims

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

2. A method for manufacturing the radar sensor according to claim 1, wherein a plurality of holes (28) extending perpendicular to the plane of the substrate are arranged such that the peripheral walls of the holes (28) form the wall segments (30; 30c) for manufacturing the high-frequency feed-through (22; 22a-c).

3. The method according to claim 2, wherein by arranging the holes (28), the high-frequency feed-through (22; 22a-c) is formed in the shape of a slot whose width corresponds to the diameter of the holes (28).

4. The method according to claim 2 or 3, wherein the axes of the continuously manufactured holes (28) are in a straight line.

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

6. The method according to any one of claims 1 to 5, wherein the holes (28) are formed to penetrate from one side to the other side of the substrate (12).

7. The method according to any one of claims 2 to 6, wherein after manufacturing the holes (28), the substrate is metallized to form a metal coating (24) with a layer thickness of 1 μm or more on the wall surface of the high-frequency feed-through.

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