Radar sensor with waveguide structure

Abstract

This invention provides a radar sensor equipped with a high-frequency feedthrough that has a shape optimized for each application and can be manufactured cost-effectively, as well as a method for manufacturing the same. [Solution] A radar sensor comprising a plate-shaped substrate 12 having at least one layer made of a non-conductive material, a waveguide structure on one side, and a high-frequency source / sink connected to the waveguide structure on the opposite side via a high-frequency feedthrough 22 penetrating the substrate, wherein the wall surface of the high-frequency feedthrough 22 is formed by a series of cylindrically curved surface segments 30 having a uniform cross-section in at least a portion of the length of the high-frequency feedthrough.

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 particularly relates to a radar sensor for automobiles.

Background Art

[0003] Radar sensors are used in automobiles 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 through 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 to cover the required field of view, and on the other hand, lead to sensors having a wider azimuth detection range.

[0005] Radar sensors with a wide azimuth detection range and a large range can be realized, in particular, using waveguide antennas. Since the waveguide antenna can be fed through a metal-clad opening that penetrates the circuit board, the waveguide antenna and the high-frequency source (or high-frequency sink, i.e., receiver) can be placed on opposite sides of the circuit board. It is known that such an opening that functions as a high-frequency feedthrough can be formed in a circuit board by drilling or milling a perforation with a desired cross-section into the circuit board, and then metal-clading the circuit board, including the surface of the perforation, by a standard method. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The objective of this invention is to manufacture a radar sensor equipped with a high-frequency feedthrough that has a shape optimized for each application and can be manufactured cost-effectively. [Means for solving the problem]

[0007] This problem is solved, according to the present invention, by forming the wall surface of the high-frequency feedthrough with a series of cylindrically curved surface segments having a uniform cross-section in at least a portion of the length of the high-frequency feedthrough.

[0008] Such high-frequency feedthroughs can be cost-effectively manufactured in the desired cross-sectional shape by arranging holes whose cross-sections overlap or at least substantially contact each other along the course of the high-frequency feedthrough wall. The wall of the high-frequency feedthrough thus formed has a certain undulation because each individual hole forms at least one cylindrically curved wall segment, but this undulation affects the transmission characteristics of the microwave high-frequency feedthrough, especially when the wall irregularities are smoothed by subsequent metal coating. It is possible to avoid adverse effects with a relatively small number of pores and the resulting minimal complexity.

[0009] A major advantage of this manufacturing method is that it eliminates the need for complex milling processes to achieve the desired shape of the high-frequency feedthrough that deviates from a circular shape. Holes can be efficiently manufactured with a single drill or a combination of several drills, and the drills can be positioned to minimize the lateral forces acting on them during the drilling process.

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

[0011] Advantageous embodiments and further improvements are described in the cited claims. The holes can be mounted on the substrate such that their cross-sections overlap, i.e., the distance between the axes of two adjacent holes is less than the diameter of the holes, and if their diameters are different, it is less than the sum of the radii of the two holes. The aligned holes form slots in the substrate that extend either linearly or in a curved manner.

[0012] In one embodiment, the high-frequency feedthrough is directly formed by this slot. In another embodiment, the curved or multi-angled slot forms a closed line. Within this line, the remaining material of the circuit board forms islands that are not connected to the surrounding material and are therefore missing, resulting in the formation of a high-frequency feedthrough that is wider than the width of the slot.

[0013] Each individual hole forms a cylindrically curved wall segment on the wall of the high-frequency feedthrough, and adjacent wall segments form a series of projections along the wall of the high-frequency feedthrough, which protrude into the interior of the feedthrough. The smaller the distance between the axes of the individual holes, the flatter and blunter these projections become. Increasing the distance between the axes of the holes results in higher and sharper projections, but has the advantage of reducing the lateral force applied to the drill when drilling each hole, as the surface area that the drill engages with the substrate wall is more evenly distributed.

[0014] Finally, if the distance between the axial ends of the holes is increased to equal the diameter of the holes, the cylindrical wall segments form a series of semicircles. If the distance between the axial ends is increased further, a narrow web remains between the individual holes. However, if the slots formed by the holes form closed lines, the islands enclosed by the lines are connected to the surrounding material via narrow webs and can be fractured with minimal force, thus allowing for high-frequency feedthroughs with a relatively large cross-sectional area with a relatively small number of holes, where virtually no lateral forces are generated.

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

[0016] The method according to the present invention allows for high flexibility in forming the cross-sectional shape of the high-frequency feedthrough, making it possible to easily optimize the bandwidth and selectively achieve desired filter characteristics or attenuation characteristics, in some cases even for specific polarization directions, by appropriately selecting the shape. By filling the five perforations forming these high-frequency feedthroughs with an appropriate material using a known method, the attenuation characteristics and dielectric constant of the high-frequency feedthrough can be improved. It may be affected. Subsequently, if necessary, an additional conductive structure may be attached to the filler material at the opposite end of the high-frequency feedthrough.

[0017] Furthermore, it is not necessary for the holes used to create the walls of the high-frequency feedthrough to penetrate from one side of the circuit board to the other. For example, a first outline may be formed by a series of shallow holes, and a further outline may be formed by a series of deeper holes within which the shape within a certain range does not depend on the shape of the first outline. In this way, a stepped structure may be realized in the high-frequency feedthrough.

[0018] The embodiments will be described in more detail below with reference to the drawings. [Brief explanation of the drawing]

[0019] [Figure 1] This is a partial cross-sectional view of a radar sensor according to one embodiment of the present invention. [Figure 2] Figure 1 shows a cross-sectional view of the substrate of the radar sensor and a diagram of the high-frequency feedthrough formed thereon. [Figure 3] These are examples of high-frequency feedthroughs with different shapes. [Figure 4] These are examples of high-frequency feedthroughs with different shapes. [Figure 5] This is a cross-sectional view of a substrate having a high-frequency feedthrough according to another embodiment. [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] A waveguide structure 18 is arranged on the upper surface of the substrate 12, 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-technically connected to each other by a high-frequency feed-through 22. In the example shown, 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 is formed by a perforation whose wall has a metallized portion 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] Figure 2 shows a cross-section of the high-frequency feedthrough 22. It can be seen that the high-frequency feedthrough 22 is formed by four aligned holes 28, the outline of which is shown by a dotted line in Figure 2. The four holes 28 have a uniform radius and are arranged at a uniform distance between their centers, and since this distance is slightly smaller than the diameter of the holes, the cross-sections of the holes overlap each other. Therefore, the upper and lower walls of the high-frequency feedthrough 22 in Figure 2 have an uneven cross-sectional shape and are formed by cylindrical wall segments 30, each corresponding to a part of the circumference of one of the holes 28, and adjacent to each other, forming projections 32.

[0025] Therefore, the high-frequency feedthrough 22 has an overall shape of an elongated straight slot, and its opposing wall surfaces are formed by opposing wall segments 30 on the same diameter of the hole.

[0026] A high-frequency feedthrough can be manufactured, for example, by clamping a substrate 12 to an XY table that can control and move the substrate in a two-dimensional XY plane, and continuously forming holes 28 with a drill clamped to a drill chuck fixed to the XY plane. Subsequently, a metal coating is applied to the substrate 12 to form a metal coating portion 24 on the wall surface of the high-frequency feedthrough 22, and simultaneously to form metal coating portions on the top and bottom surfaces of the substrate.

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

[0028] Figure 4 shows a high-frequency feedthrough 22b according to a further embodiment. In this case as well, the holes 28 have a uniform diameter, but their central axes are arranged on a curve, so the slots forming the high-frequency feedthrough have a curved shape as a whole.

[0029] Figure 5 shows a cross-section of the substrate 12c, where the longitudinal section of the high-frequency feedthrough 22c is stepped. This high-frequency feedthrough is manufactured by drilling holes of different diameters into the substrate from opposite sides.

[0030] Therefore, the wall surface of the high-frequency feedthrough 22c is defined by a cylindrically curved wall segment 30c, and the radius of curvature and width are smaller at the top of the feedthrough in Figure 5 than at the bottom. Consequently, the central axis of the hole drilled in the substrate from above is also smaller than the central axis of the hole drilled from below.

[0031] Therefore, a high-frequency feedthrough having a step 34 is formed overall. The outlines defined by the upper and lower wall segments 30c of 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, a waveguide structure (18) on one side, and a high-frequency source / sink (20) connected to the waveguide structure (18) on the opposite side via a high-frequency feedthrough (22; 22a-c) penetrating the substrate, The wall surface of the high-frequency feedthrough (22; 22a-c) is formed by a series of cylindrically curved surface segments (30; 30c) having a uniform cross-section in at least a portion of the length of the high-frequency feedthrough. A radar sensor characterized by the following features.

2. A method for manufacturing a radar sensor according to claim 1, characterized in that, in order to manufacture the high-frequency feedthrough (22; 22a-c), 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).

3. The method according to claim 2, wherein by arranging the holes (28), the high-frequency feedthrough (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 hole (28) is configured 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 the substrate is metal-coated after the manufacture of the hole (28) to form a metal coating (24) with a layer thickness of 1 μm or more on the wall surface of the high-frequency feedthrough.

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