Waveguide antenna with polarization means and radar sensor

Abstract

The invention relates to a waveguide antenna (10) for a radar sensor (46), comprising a waveguide substrate (12) having cavity structures (14) for transmitting radar waves within the waveguide antenna (10), an antenna surface (18) facing surroundings (16) of the waveguide antenna (10), at least one emission element (20) for emitting radar waves into the surroundings (16) of the waveguide antenna (10), said radar waves being polarized in a first direction (22) perpendicular to a normal direction (24) of the antenna surface (18), wherein at least regions of the antenna surface (18) comprise polarization means (34) for rotating the polarization of radar waves that were reflected in the surroundings (16) and are incident on the polarization means (34). The invention also relates to a radar sensor (46).

Description

[0001] R. 413965

[0002] - 1 -

[0003] Description

[0004] title

[0005] Waveguide antenna with polarizing agent and radar sensor

[0006] The invention relates to a waveguide antenna according to claim 1. The invention further relates to a radar sensor.

[0007] State of the art

[0008] In radar technology, waveguide antennas are increasingly used as a high-frequency interface to the environment. A typical waveguide antenna in a radar sensor is a flat, rectangular block with a large metallic surface on its top. If this waveguide antenna is installed behind a protective cover that partially reflects the radar waves, undesirable secondary wave paths arise due to reflections from the surfaces of the waveguide antenna and the protective cover, interfering with the primary path. When the primary path is affected by a secondary wave path, the radiation characteristics of the waveguide antenna are altered at a given angle. Depending on the properties of the protective cover and its distance from the waveguide antenna, the secondary wave path can cause constructive or destructive interference with the primary path, which can impair the detection performance of the radar sensor.

[0009] Furthermore, the secondary path typically varies for each radiating element of the waveguide antenna. This occurs, for example, if the protective cover is not perfectly parallel to the antenna surface. Consequently, the respective phases of the radar waves from the radiating elements are modified differently by the secondary wave paths. This can ultimately reduce the angle determination performance of the radar sensor.

[0010] Disclosure of the invention R. 413965

[0011] - 2 -

[0012] According to the present invention, a waveguide antenna with the features of claim 1 is proposed. This reduces the influence of secondary wave paths on the detection performance and measurement accuracy of a radar sensor. The radar sensor can thus exhibit increased detection performance and measurement accuracy. The reflectivity and relative orientation of a protective cover with respect to the waveguide antenna have less of an impact on the detection performance and measurement accuracy of the radar sensor.

[0013] The radar sensor can be mounted in a vehicle, a robot, or a device. The radar sensor can enable environmental sensing.

[0014] The radar sensor can be located behind a protective cover. This cover can be a body component of the vehicle, such as a bumper. The cover can be at least partially transparent to radar waves. In addition to the main path of the radar waves, which leads from the waveguide antenna through the cover to the surroundings, secondary wave paths with at least one reflection between the cover and the radar sensor can occur.

[0015] The waveguide substrate can be made of metal, plastic, in particular metal-coated plastic, a composite material or a combination of at least two of these materials.

[0016] The polarizing elements can be made of metal, plastic, a composite material, or a combination of at least two of these materials. The polarizing elements can be integrated with or separate from the waveguide substrate. The polarizing elements can be positively bonded, materially bonded, and / or frictionally bonded to the waveguide substrate.

[0017] The emitting element can have at least one opening for transmitting the radar waves. The opening can be connected to at least one of the cavity structures for transmitting the radar waves.

[0018] The radar sensor has at least one receiving element for receiving the R. 413965 emitted by the emitting element and reflected in the environment.

[0019] - 3 -

[0020] Radar waves are received. The receiving element is preferably configured to receive only radar waves with the polarization of the radar waves emitted by the transmitting element.

[0021] Polarization is the orientation of the electric field component of radar waves.

[0022] In a preferred embodiment of the invention, it is advantageous if the rotation is a rotation about the normal direction of the antenna surface as the axis of rotation. The rotation can be performed at an angle greater than 45°.

[0023] In a specific embodiment of the invention, it is advantageous if the rotation is a 90° rotation. This allows the secondary wave paths to be filtered as efficiently as possible.

[0024] A preferred embodiment of the invention is advantageous in which the polarization means have recessed structures extending at an angle of 45° to the first direction along a direction of extension. The waveguide antenna can be rectangular. The direction of extension can be angled at 45° to an edge of the waveguide antenna. The first direction can be parallel to at least one edge of the waveguide antenna.

[0025] In an advantageous embodiment of the invention, the groove structures have several grooves spaced at least one distance apart in a lateral direction perpendicular to the direction of extension. At least two of the grooves can have parallel directions of extension. Preferably, the main part of the grooves, and in particular all grooves, have parallel directions of extension. The grooves can extend continuously over the entire antenna surface and be interrupted only by the radiating and receiving elements. A bottom region of the grooves can be parallel to the surface of the antenna.

[0026] In a particular embodiment of the invention, it is advantageous if the distance is less than half the wavelength of the radar waves in air. Preferably, the distance is at most one-quarter of the wavelength of the radar waves in air. R. 413965

[0027] - 4 -

[0028] In a preferred embodiment of the invention, the width of the grooves along the lateral direction is less than half the wavelength of the radar waves in air. Preferably, the width is at most one-quarter of the wavelength of the radar waves in air.

[0029] The distance can be equal to the width. The distance and the width can be different.

[0030] In a particular embodiment of the invention, it is advantageous if the grooves have a depth with respect to the normal direction that is between 0.8 and 1.2 times a quarter of the wavelength of the radar waves in air. The depth can be between 0.9 and 1.1 times, and in particular between 0.95 and 1.05 times, a quarter of the wavelength of the radar waves in air.

[0031] In a preferred embodiment of the invention, the grooves extend into the depth by forming side walls along the normal direction, the side walls being spanned by the normal direction and the direction of extension. An angled embodiment, for example with an angle between 0 degrees and 10 degrees, of at least one of the side walls with respect to the normal direction is also possible. The angled side wall can be spanned by a direction angled to the normal direction and the direction of extension. At least one of the grooves can have only angled side walls or at least one angled side wall and one perpendicular side wall.

[0032] According to the present invention, a radar sensor with the features according to claim 10 is further proposed.

[0033] Further advantages and advantageous embodiments of the invention will become apparent from the description of the figures and the illustrations.

[0034] Character description

[0035] The invention is described in detail below with reference to the illustrations. Specifically, the illustrations shown are: R. 413965

[0036] - 5 -

[0037] Figure 1: A spatial view of a waveguide antenna in a special embodiment of the invention.

[0038] Figure 2: A functional diagram of a radar sensor in a special embodiment of the invention.

[0039] Figure 3: A section of a spatial cross-section of a waveguide antenna in a further special embodiment of the invention.

[0040] Figure 4: A spatial view of a waveguide antenna in a further special embodiment of the invention.

[0041] Figure 1 shows a three-dimensional view of a waveguide antenna in a specific embodiment of the invention. The waveguide antenna 10 for a radar sensor, for example for use in a vehicle, comprises a waveguide substrate 12 with cavity structures 14 for transmitting radar waves within the waveguide antenna 10 and an antenna surface 18 facing the surroundings 16 of the waveguide antenna 10, several emitting elements 20 for emitting radar waves polarized along a first direction 22 perpendicular to a normal direction 24 of the antenna surface 18 into the surroundings 16 of the waveguide antenna 10, and several receiving elements 26 for receiving the emitted radar waves reflected in the surroundings 16. The emitting elements 20 each have several openings 28 for emitting the radar waves, and the receiving elements 26 also have several openings 30 for receiving the radar waves.In an area 32 surrounding the openings 28, 30, the antenna surface 18 is designed to be flat.

[0042] Outside the emitting elements 20 and the receiving elements 26, the antenna surface 18 has, in certain areas, and here over the entire antenna surface 18 except for the emitting elements 20 and the receiving elements 26, polarization means 34 for rotating the polarization of the radar waves incident on the polarization means 34 from the environment 16. The polarization means 34 comprise depression structures 38 extending at an angle of 45° to the first direction 22 along a direction of extension 36. The depression structures 38 have a distance of at least one unit R in a lateral direction 40 perpendicular to the direction of extension 36.

[0043] - 6 - several grooves 42. The grooves 42 cover the entire antenna surface 18 outside the radiating elements 20 and the receiving elements 26.

[0044] The waveguide antenna 10 is rectangular and the extension direction 36 runs at an angle of 45° to an edge 44 of the waveguide antenna 10. The first direction 22 is parallel to the edge 44 of the waveguide antenna 10.

[0045] Figure 2 shows a functional diagram of a radar sensor in a specific embodiment of the invention. The radar sensor 46 comprises a high-frequency unit 48 and the associated waveguide antenna 10. The radar sensor 46 is mounted behind a protective cover 50 and emits radar waves from the waveguide antenna 10 into the environment via a main path 52. These waves penetrate the protective cover 50, are partially reflected by the protective cover 50, and strike the antenna surface 18, where they are again reflected and penetrate the protective cover 50, thus forming secondary wave paths 54 parallel to the main path 52.

[0046] The radar waves emanating from the emitting elements 20 are polarized along the first direction 22. The radar waves reflected by the protective cover 50 in the direction of the antenna surface 18 are also polarized along the first direction 22. However, upon reflection from the antenna surface 18, which has the polarizing means 34, the polarization of the radar waves is rotated by 90° around the normal direction 24, so that the radar waves reflected from the antenna surface 18 have a polarization perpendicular to the polarization of the radar waves emanating from the emitting elements 20 along a second direction 56 perpendicular to the first direction 22.

[0047] However, radar waves that are polarized in this way are no longer transmitted by the receiving elements and can therefore be filtered out.

[0048] Figure 3 shows a section of a spatial cross-section of a waveguide antenna in a further special embodiment of the invention. The waveguide antenna 10 has polarization means 34 with recess structures 38 on the antenna surface 18. The recess structures 38 comprise several grooves 42 spaced apart from each other by at least a distance 58 in a lateral direction 40 perpendicular to the extension direction 36. R. 413965

[0049] - 7 -

[0050] The distance 58 is in particular smaller than half the wavelength of the radar waves in air and preferably at most a quarter of the wavelength of the radar waves in air.

[0051] A width 60 of the grooves 42 along the lateral direction 40 is less than half the wavelength of the radar waves in air, preferably at most a quarter of the wavelength of the radar waves in air. Here, for example, the width 60 is greater than the spacing 58.

[0052] The grooves 42 have a depth 62 with respect to the normal direction 24, which corresponds approximately to one-quarter of the wavelength of radar waves in air. This allows for optimal polarization rotation when radar waves incident on the polarization means 34 from a normal direction 24. To optimize polarization rotation for radar waves incident on the polarization means 34 at an angle to the normal direction 24, the depth 62 can also be selected between 0.8 and 1.2 times one-quarter of the wavelength of radar waves in air.

[0053] The grooves 42 extend into the depth 62 by forming side walls 64 along the normal direction 24, the side walls 64 being spanned by the normal direction 24 and the extension direction 36.

[0054] Figure 4 shows a three-dimensional view of a waveguide antenna in a further specific embodiment of the invention. The waveguide antenna 10 has a waveguide substrate 12 in which the cavity structures 14 for transmitting the radar waves are located. The polarization means 34 are separate from the waveguide substrate 12 and connected to it, for example by a positive-locking connection. This allows the polarization means 34 to be made of a material different from that of the waveguide substrate 12.

Claims

R. 413965 - 8 - Patent claims 1. Waveguide antenna (10) for a radar sensor (46), comprising a waveguide substrate (12) with cavity structures (14) for transmitting radar waves within the waveguide antenna (10), an antenna surface (18) facing an environment (16) of the waveguide antenna (10), at least one emitting element (20) for emitting radar waves polarized along a first direction (22) perpendicular to a normal direction (24) of the antenna surface (18) into the environment (16) of the waveguide antenna (10), wherein the antenna surface (18) has at least partially polarizing means (34) for rotating the polarization of radar waves reflected from the environment (16) and incident on the polarizing means (34).

2. Waveguide antenna (10) according to claim 1 , characterized in that the rotation is a rotation about the normal direction (24) of the antenna surface (18) as the axis of rotation.

3. Waveguide antenna (10) according to claim 1 or 2, characterized in that the rotation is a rotation by 90°.

4. Waveguide antenna (10) according to one of the preceding claims, characterized in that the polarization means (34) have depression structures (38) extending at an angle of 45° to the first direction (22) along a direction of extension (36).

5. Waveguide antenna (10) according to claim 4, characterized in that the depression structures (38) have several grooves (42) spaced apart from each other by at least one distance (58) in a lateral direction (40) perpendicular to the extension direction (36). R. 413965 - 9 - 6. Waveguide antenna (10) according to claim 5, characterized in that the distance (58) is less than half the wavelength of the radar waves in air.

7. Waveguide antenna (10) according to claim 5 or 6, characterized in that a width (60) of the grooves (42) along the lateral direction (40) is smaller than half the wavelength of the radar waves in air.

8. Waveguide antenna (10) according to one of claims 5 to 7, characterized in that the grooves (42) have a depth (62) with respect to the normal direction (24) which is between 0.8 times and 1.2 times a quarter of the wavelength of the radar waves in air.

9. Waveguide antenna (10) according to one of claims 5 to 8, characterized in that the grooves (42) extend into the depth (62) by forming side walls (64) along the normal direction (24), wherein the side walls (64) are spanned by the normal direction (24) and the extension direction (36).

10. Radar sensor (46) with at least one high-frequency unit (48) at least for generating radar waves and a waveguide antenna (10) radiating the radar waves into an environment (16) according to one of the preceding claims.

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