Radarsensor

Abstract

The invention relates to a radar sensor (10) having at least one antenna element (20-22, 25-27) and a radar converging lens (30), the focal point (40) of which for radar radiation has a predetermined focal distance (FA) from the lens side (31) of the radar converging lens (30) facing the focal point (40). According to the invention, the at least one antenna element (20-22, 25-27) is arranged spatially between the focal point (40) and the lens side (31) of the radar converging lens (30) facing the focal point (40).

Description

[0001] The invention relates to a radar sensor with at least one antenna element and a radar collecting lens, the focal point of which for radar radiation has a predetermined focal distance from the lens side of the radar collecting lens facing the focal point.

[0002] Such radar sensors are well known and are sold, for example, by Pepperl+Fuchs SE.

[0003] Lenses are disclosed, for example, in US publications US 2020 / 0 243 983 A1 and US 2021 / 0 143 546 A1.

[0004] A radar sensor having the features according to the preamble of claim 1 is described in British publication GB 2 458 723 A.

[0005] The invention is based on the object of providing a radar sensor which has particularly good transmission and reception characteristics.

[0006] This object is achieved according to the invention by a radar sensor having the features according to claim 1. Advantageous embodiments of the radar sensor according to the invention are specified in subclaims.

[0007] A significant advantage of the radar sensor according to the invention is that the offset arrangement of the at least one antenna element with respect to the focal point, as provided according to the invention, allows for a particularly favorable shape of the transmission and reception characteristics, hereinafter referred to as the antenna directional characteristic. Specifically, compared to a conventional arrangement of the antenna element(s), i.e., compared to an arrangement in the region of the focal point, a particularly bulbous configuration of the main lobe of the antenna directional characteristic can be achieved.

[0008] For example, depending on the offset of the antenna element(s) relative to the focal point, it is possible to avoid the formation of side lobes next to the main lobe, or to merge the neighboring sections adjacent to the main lobe with the main lobe in such a way that at the interface between the main lobe and the respective neighboring section, the antenna directional characteristic does not have an indentation directed inwards towards the antenna element, or at most has a plateau. In other words, it is possible, for example, to ensure that the antenna directional characteristic decreases continuously from the maximum value in the area of the main lobe towards the neighboring sections, as well as in the neighboring sections, i.e., no intermediate region is formed at the interface in which the antenna directional characteristic is smaller than in the adjacent neighboring section and smaller than in the adjacent area of the main lobe.

[0009] In a preferred embodiment, the radar collecting lens is concave on the lens side facing the at least one antenna element and convex on the lens side facing away from the at least one antenna element.

[0010] In another preferred embodiment, the radar collecting lens is flat on the lens side facing the at least one antenna element and convex on the lens side facing away from the at least one antenna element.

[0011] For radar operation, it is advantageous if the radar sensor has at least two antenna elements, a first of which is electrically connected to a radar transmitting device and a second of which is electrically connected to a radar receiving device.

[0012] The distance between the focal point and the first antenna element is preferably at least 10% of the focal distance and the distance between the focal point and the second antenna element is preferably also at least 10% of the focal distance, wherein the distance between at least one of the antenna elements and the lens side of the radar collecting lens facing it is preferably between 0.7 and 0.8 times the focal distance.

[0013] In the latter embodiment, it is advantageous if the distance between the first antenna element and the lens side of the radar collecting lens facing it is between 0.7 times and 0.8 times the focal distance, and the distance between the second antenna element and the lens side of the radar collecting lens facing it is between 0.7 times and 0.8 times the focal distance.

[0014] With regard to direction determination, it is considered advantageous if the radar receiving device is additionally electrically connected to a third antenna element of the radar sensor and the radar receiving device is designed to detect the direction of received radar radiation by evaluating the received signals of the second and third antenna element.

[0015] In the latter embodiment, it is advantageous if the distance between the focal point and the third antenna element is at least 10% of the focal distance.

[0016] The distance between the third antenna element and the lens side of the radar collecting lens facing it is preferably between 0.5 and 0.9 times the focal distance, particularly preferably between 0.7 and 0.8 times the focal distance.

[0017] More than three antenna elements can also be present, i.e., a fourth and further antenna elements. For the latter antenna elements, too, it is preferable that the antenna elements are spatially arranged between the focal point and the side of the radar collector lens facing the focal point. The distance between the focal point and the respective antenna element is preferably at least 10%. For radar sensor operation, for example, it is advantageous if seven antenna elements are present, three of which are operated as transmitting antennas and four as receiving antennas.

[0018] In terms of material, it is considered advantageous if the radar collecting lens consists of a one-piece element made of Teflon or polycarbonate.

[0019] The antenna elements are preferably each formed by a conductor track element (also called a conductor track pad in technical terms).

[0020] It is advantageous if the conductor track elements are mounted on the same circuit board.

[0021] The plane of the circuit board is preferably arranged perpendicular to the central axis of the radar lens, at least in the area of the conductor track elements.

[0022] The invention is explained in more detail below using exemplary embodiments, which show, for example: Fig. 1 shows an embodiment of a radar sensor according to the invention, in which an antenna element is arranged between the focal point and the radar collecting lens, Fig. 2 the directional characteristic of the antenna element according to Fig. 1 in more detail, Fig. 3 the directional characteristic of the antenna element according to Fig. 1 in the form of a diagram showing the antenna directivity over the radiation angle, Fig. 4 for comparison the directional characteristic of the antenna element according to Fig. 1, if this were located at the focal point, Fig. 5 shows the directional characteristic in an embodiment of a radar sensor according to the invention, in which two antenna elements are arranged between the focal point and the radar collecting lens, Fig. 6 For comparison, the directional characteristic of a radar sensor in which two antenna elements are arranged at the focal point, Fig. 7 shows antenna elements arranged on a printed circuit board of an embodiment of a radar sensor according to the invention, which is equipped with three antenna elements, and Fig. 8 the arrangement of the antenna elements between the focal point and the radar collecting lens in the embodiment according to Fig. 7 in a cross-sectional view.

[0023] For the sake of clarity, the same reference symbols are always used in the figures for identical or comparable components.

[0024] The Fig. 1 shows components of an embodiment of a radar sensor 10 according to the invention in a cross section.

[0025] One can see an antenna element 20 and a radar collector lens 30, which is suitable for focusing radar radiation. The radar collector lens 30 is in the embodiment according to Fig. 1 is concave on the lens side 31 facing the antenna element 20 and convex on the lens side 32 facing away from the antenna element 20. The radar collector lens 30 preferably consists of a one-piece element made of Teflon or polycarbonate to minimize radar radiation absorption.

[0026] The focal point 40 of the radar collecting lens 30 has a focal distance FA to the lens side 31 facing the focal point 40.

[0027] The antenna element 20 is spatially arranged between the focal point 40 and the radar lens 30. The distance A between the antenna element 20 and the radar lens 30 is preferably between 0.75 and 0.79 times the focal distance FA in the case of a convex-concave radar lens 30, and preferably between 0.74 and 0.78 times the focal distance FA in the case of a plano-convex radar lens 30, thus preferably: 0.75 * FA < A < 0.79* FA in the case of a convex-concave radar lens 30 and 0.74 * FA < A < 0.78 * FA in the case of a plano-convex radar lens 30.

[0028] The focal distance FA is preferably in a range between 22 mm and 26 mm in the case of a convex-concave radar collecting lens 30 and in a range between 16 mm and 20 mm in the case of a plano-convex radar collecting lens 30.

[0029] In the case of a convex-concave radar collecting lens 30, the focal distance FA is, for example, 24 mm, whereby a distance A between the antenna element 20 and the radar collecting lens 30 of 18.496 mm, i.e. 0.7707 times the focal distance FA, is considered optimal.

[0030] In the case of a plano-convex radar collecting lens 30, the focal distance FA is, for example, 18 mm, whereby a distance A between the antenna element 20 and the radar collecting lens 30 of 13.6215 mm, i.e. 0.75675 times the focal distance FA, is considered optimal.

[0031] The Fig. 2 shows an example of the antenna directional characteristic, i.e. the transmission and reception characteristics, of the antenna element 20 according to Fig. 1. It can be seen that due to the axially offset arrangement of the antenna element 20 in the direction of the radar collecting lens 30, a very bulbous configuration of the main beam lobe 50 of the antenna directional characteristic occurs - compared to an arrangement of the antenna element 20 in the focal point 40.

[0032] The formation of side lobes immediately adjacent to the main beam lobe 50 is avoided because the neighboring sections 50a and 50b adjacent to the main beam lobe 50 merge with the main beam lobe 50 in such a way that at the interface SS between the main beam lobe 50 and the respective neighboring section 50a or 50b, the antenna directional characteristic does not have any indentation or constriction directed inwards towards the antenna element 20.

[0033] The Fig. 3 shows the course of the antenna directivity in the form of an antenna directivity R over the radiation angle ϕ.

[0034] The beam angle is in the Fig. 2 and Fig. 3 is chosen, for example, so that its value ϕ=0 is at the highest transmission or reception strength or at the highest antenna directivity, i.e. in the center of the main beam lobe 50.

[0035] It can be found in the Fig. 3 that the antenna directivity R for values ϕ below zero increases continuously with increasing value of ϕ, albeit at variable rates of increase, and for values ϕ above zero decreases continuously with increasing value of ϕ, albeit at variable rates of decrease.

[0036] In the area of the interfaces SS between the main beam lobe 50 and the two immediately adjacent neighboring sections 50a and 50b, the course of the antenna directivity over the radiation angle ϕ does indeed exhibit a certain plateau, on which the antenna directivity R is relatively constant over the radiation angle ϕ; however, no local maxima or local minima are formed, neither in the area of the main beam lobe 50 nor in the area of the two immediately adjacent neighboring sections 50a and 50b; there is only one maximum, namely an absolute one in the central area of the main beam lobe 50.

[0037] In the embodiment according to the Fig. 2 and Fig. 3 In other words, the antenna directional characteristic, starting from the maximum value reached by the antenna directional value R in the region of the center of the main beam lobe 50, decreases continuously toward the neighboring sections 50a and 50b, as well as in the neighboring sections 50a and 50b themselves, or at most remains constant in certain sections. Thus, no intermediate region is formed at the SS interfaces in which the antenna directional values R would be smaller than in the adjacent areas.

[0038] For a better understanding, the Fig. 4 shows the formation of side lobes 51 and 52, which occurs when the antenna element 20 is arranged in the focal point 40 of the radar lens 30. Fig. 4, that - in contrast to Fig. 2 - there is a clear separation of the side lobes 51 and 52 and no merging of the main beam lobe 50 with the neighboring sections; the antenna directional characteristic exhibits clear indentations EB or constrictions in the direction of the antenna element 20. These indentations EB can lead to an object located angularly between the main beam lobe 50 and one of the neighboring side lobes 51 or 52 possibly not being detected, depending on the sensitivity of the radar sensor 10.

[0039] The Fig. 1 and Fig. 2 show an embodiment of the invention with only a single antenna element 20. It is advantageous if the radar sensor 10 has at least two antenna elements, of which a first is electrically connected to a radar transmitting device and functions as a transmitting antenna element 21 and a second is electrically connected to a radar receiving device and functions as a receiving antenna element 22; such an embodiment of the invention shows in a simplified representation the Fig. 5.

[0040] It can be found in the Fig. 5 that in the antenna directional characteristic of the transmitting antenna element 21, the neighboring sections 60a and 60b merge with the main beam lobe 60 and a bulbous antenna directional characteristic without indentations EB between the main beam lobe 60 and the neighboring sections 60a and 60b is achieved; the same applies to the main beam lobe 70 of the receiving antenna element 22 and its Fig. 5 hidden neighboring sections.

[0041] It can also be seen that due to the bulbous shape of the antenna directional characteristic, there is only a very small indentation EB between the two main lobes 60 and 70, so that the antenna directional characteristic of the radar sensor 10 is virtually constant overall in the main direction.

[0042] The Fig. For comparison, Figure 6 shows the antenna directional characteristics of two antenna elements 23 and 24 arranged in the area of the focal point 40. For clarity, only the two main lobes 80 and 90 are shown. It can be seen that between the maxima of the two main lobes 80 and 90, a considerable indentation EB occurs, which is significantly larger and deeper than in Fig. 5 is.

[0043] The Fig. Figure 7 shows components of another embodiment of the invention, as well as a particularly preferred configuration and arrangement of antenna elements. A top view of a circuit board 100 with three conductor track elements, each forming an antenna element, is shown.

[0044] One of the conductor track elements forms a transmitting antenna element 25, which is connected to a radar transmitting device 110 arranged on the circuit board 100 via a conductor track 101 of the circuit board 100.

[0045] Another of the conductor track elements forms a first receiving antenna element 26, which is connected to a radar receiving device 120 arranged on the circuit board 100 via a conductor track 102 of the circuit board 100.

[0046] A third antenna element 20 forms a second receiving antenna element 27, which is connected to the radar receiving device 120 arranged on the circuit board 100 via a conductor track 103 of the circuit board 100.

[0047] The radar receiving device is designed to detect the direction of received radar radiation by evaluating the received signals of the second and third antenna elements 26 and 27, in particular by evaluating the phase shift between the two received signals.

[0048] The Fig. 8 shows the circuit board 100 according to Fig. 7 in a cross-section and also in cross-section the radar collecting lens 30 and its focal point 40. It can be seen that the plane E of the circuit board 100 is arranged perpendicular to the central axis M of the radar lens and between the focal point 40 and the radar collecting lens 30.

[0049] The number of antenna elements can also be greater than three. For example, seven antenna elements can be present, each arranged between the focal point 40 and the lens side 31 of the radar collector lens 30 facing the focal point 40. The antenna elements are preferably formed by conductor track elements of the same circuit board. For example, three of the antenna elements can be operated as transmitting antenna elements and the remaining four as receiving antenna elements.

[0050] Finally, it should be mentioned that the features of all embodiments described above can be combined with each other in any way to form further other embodiments of the invention.

[0051] All features of subclaims can also be combined with any other claim, either individually or in any combination with one or more other subclaims, in order to obtain further embodiments. List of reference symbols 10 radar sensor 20 antenna element 21 Transmitting antenna element 22 Receiving antenna element 23 Antenna element 24 antenna element 25 Transmitting antenna element 26 Receiving antenna element 27 Receiving antenna element 30 radar collecting lens 31 lens side 32 lens side 40 focus points 50 Main beam lobe 50a neighboring section 50b neighboring section 51 side lobe 52 side lobe 60 main beam 60a neighboring section 60b neighboring section 70 Main beam lobe 80 Main beam lobe 90 Main beam lobe 100 circuit boards 101 Conductor track 102 conductor track 103 Conductor track 110 Radar transmitter 120 radar receiving device A distance E Level EB indentations FA focus distance M central axis R Antenna directional value SS interface ϕ beam angle

Claims

[1] Radar sensor (10) with at least one antenna element (20-22, 25-27) and a radar collecting lens (30), the focal point (40) of which for radar radiation has a predetermined focal distance (FA) from the lens side (31) of the radar collecting lens (30) facing the focal point (40), characterized by , that the at least one antenna element (20-22, 25-27) is arranged spatially between the focal point (40) and the lens side (31) of the radar collecting lens (30) facing the focal point (40), wherein the distance (A) between the focal point (40) and the at least one antenna element (20-22, 25-27) is at least 10% of the focal distance (FA) and wherein the distance (A) between the at least one antenna element (20-22, 25-27) and the lens side (31) of the radar collecting lens (30) facing it is between 0.7 and 0.8 times the focus distance (FA). [2] Radar sensor (10) according to claim 1, characterized bythat the radar collecting lens (30) is concave on the lens side (31) facing the at least one antenna element (20-22, 25-27) and convex on the lens side (32) facing away from the at least one antenna element (20-22, 25-27). [3] Radar sensor (10) according to claim 1, characterized by that the radar collecting lens (30) is planar on the lens side (31) facing the at least one antenna element (20-22, 25-27) and convex on the lens side (32) facing away from the at least one antenna element (20-22, 25-27). [4] Radar sensor (10) according to one of the preceding claims, characterized by that the radar sensor (10) has at least two antenna elements (21-22, 25-27), of which a first is electrically connected to a radar transmitting device (110) and a second is electrically connected to a radar receiving device (120). [5] Radar sensor (10) according to claim 4, characterized by , that - the distance (A) between the focal point (40) and the first antenna element (21, 25) is at least 10% of the focal distance (FA) and - the distance (A) between the focal point (40) and the second antenna element (22, 26) is also at least 10% of the focal distance (FA), - wherein the distance (A) between at least one of the antenna elements (20-22, 25-27) and the lens side (31) of the radar collecting lens (30) facing it is between 0.7 and 0.8 times the focus distance (FA). [6] Radar sensor (10) according to one of the preceding claims 4 to 5, characterized by , that - the distance (A) between the first antenna element (21, 25) and the lens side (31) of the radar collecting lens (30) facing it is between 0.7 and 0.8 times the focal distance (FA) and - the distance (A) between the second antenna element (22, 26) and the lens side (31) of the radar collecting lens (30) facing it is between 0.7 and 0.8 times the focus distance (FA). [7] Radar sensor (10) according to one of the preceding claims 4 to 6, characterized by , that - the radar receiving device is additionally electrically connected to a third antenna element (27) of the radar sensor (10) and - the radar receiving device is designed to detect the direction of received radar radiation by evaluating the received signals of the second and third antenna elements (26, 27). [8] Radar sensor (10) according to claim 7, characterized by that the distance (A) between the focal point (40) and the third antenna element (27) is at least 10% of the focal distance (FA). [9] Radar sensor (10) according to one of the preceding claims 7 to 8, characterized bythat the distance (A) between the third antenna element (27) and the lens side (31) of the radar collecting lens (30) facing it is between 0.7 and 0.8 times the focus distance (FA). [10] Radar sensor (10) according to one of the preceding claims, characterized by , that - the radar sensor (10) is equipped with four or more antenna elements, - the antenna elements are arranged spatially between the focal point (40) and the lens side (31) of the radar collecting lens (30) facing the focal point (40) and - the distance (A) between the focal point (40) and each of the antenna elements is at least 10% of the focal distance (FA). [11] Radar sensor (10) according to claim 10, characterized by that the distance (A) between each of the antenna elements and the lens side (31) of the radar collecting lens (30) facing them is between 0.7 and 0.8 times the focus distance (FA). [12] Radar sensor (10) according to one of the preceding claims, characterized by that the radar collecting lens (30) consists of a one-piece element made of Teflon or polycarbonate. [13] Radar sensor (10) according to one of the preceding claims, characterized by , that - the antenna elements (20-22, 25-27) are each formed by a conductor track element, - the conductor track elements are mounted on the same printed circuit board (100) and - the plane (E) of the printed circuit board (100) is arranged perpendicular to the central axis (M) of the radar collecting lens (30) at least in the region of the conductor track elements.

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