Radar sensor

Abstract

The invention relates to a radar sensor (10) comprising at least one antenna element (20-22, 25-27) and a radar converging lens (30), the focal point (40) of which for radar radiation is at a predefined focal distance (FA) from the lens side (31) of the radar converging lens (30) facing the focal point (40). The invention provides for the at least one antenna element (20-22, 25-27) to be 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] Description Radar Sensor The invention relates to a radar sensor with at least one antenna element and a radar converging lens, the focal point of which for radar radiation has a predetermined focal distance from the side of the radar converging lens facing the focal point. Such radar sensors are generally known and are marketed, for example, by Pepperl+Fuchs SE. The invention is based on the object of specifying a radar sensor that has particularly good transmission and reception characteristics. This object is achieved according to the invention by a radar sensor with the features according to claim 1. Advantageous embodiments of the radar sensor according to the invention are specified in the subclaims. Accordingly, the invention providesthat the at least one antenna element is arranged spatially between the focal point and the lens side of the radar collector lens facing the focal point. 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 a particularly favorable shape design of the transmission or reception characteristic, 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 design of the main lobe of the antenna directional characteristic can be achieved. For example, depending on the offset of the antenna element(s) relative to the focal point,that the formation of side lobes next to the main lobe is avoided, or the neighboring sections adjacent to the main lobe merge 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 inward toward 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 toward the neighboring sections, as well as in the neighboring sections, i.e., that 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. It is considered advantageous ifif the distance between the focal point and the at least one antenna element is at least 10% of the focal distance. It is particularly advantageous if the distance between the at least one antenna element and the lens side of the radar converging lens facing it is between 0.5 and 0.9 times the focal distance, particularly preferably between 0.65 and 0.85 times the focal distance, in particular between 0.7 and 0.8 times the focal distance. In a preferred embodiment, the radar converging 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. In another preferred embodiment, the radar converging 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. For radar operation it is advantageousif 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. 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. In the latter embodiment, it is advantageous if the distance between the first antenna element and the lens side of the radar converging lens facing it is between 0.5 and 0.9 times the focal distance, particularly preferably between 0.65 and 0.85 times the focal distance, in particular between 0.7 and 0.8 times the focal distance.and the distance between the second antenna element and the lens side of the radar collector lens facing it is between 0.5 and 0.9 times the focal distance, particularly preferably between 0.65 and 0.85 times the focal distance, in particular between 0.7 and 0.8 times the focal distance. 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 elements. In the latter embodiment, it is advantageousif the distance between the focal point and the third antenna element is at least 10% of the focal distance. The distance between the third antenna element and the lens side of the radar collector lens facing it is preferably between 0.5 and 0.9 times the focal distance, particularly preferably between 0.65 and 0.85 times the focal distance, in particular between 0.7 and 0.8 times the focal distance. More than three antenna elements can also be present, i.e., a fourth and further antenna elements. The following also preferably applies to the latter antenna elements:that the antenna elements are spatially arranged between the focal point and the lens 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% of the focal distance, or the distance between the respective antenna element and the lens side of the radar collector lens facing it is preferably between 0.5 and 0.9 times the focal distance, particularly preferably between 0.65 and 0.85 times the focal distance, in particular between 0.7 and 0.8 times the focal distance. For radar sensor operation, it is advantageous, for example, if seven antenna elements are present, of which three are operated as transmitting antennas and four as receiving antennas. In terms of material, it is considered advantageousif the radar collector lens consists of a one-piece element made of Teflon or polycarbonate. The antenna elements are preferably each formed by a conductor track element (also called a conductor track pad in technical terms). It is advantageous if the conductor track elements are mounted on the same circuit board. The plane of the circuit board is preferably arranged perpendicular to the center axis of the radar lens, at least in the area of ​​the conductor track elements. The term "distance" between two objects is to be understood here in the usual sense, namely as the shortest distance between the respective objects. Since in conventional radar sensor designs, the antenna element(s), particularly in the case of a design as a flat conductor track pad, as well as the lens side of the radar collector lens facing them, always have a spatial extension,The term "distance" between the antenna element and the lens side facing it is always to be understood as the shortest distance between the respective antenna element and the lens side, and the term "distance" between the antenna element and the focal point is always to be understood as the shortest distance between the respective antenna element and the focal point. The invention is explained in more detail below using exemplary embodiments. by way of example: Figure 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 collector lens, Figure 2 shows the directional characteristic of the antenna element according to Figure 1 in more detail, Figure 3 shows the directional characteristic of the antenna element according to Figure 1 in the form of a diagram that represents the antenna directivity over the radiation angle, Figure 4 shows the directional characteristic of the antenna element according to Figure 1 for comparison,if this were arranged at the focal point, Figure 5 shows the directional characteristic in an exemplary 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, Figure 6 shows, for comparison, the directional characteristic of a radar sensor in which two antenna elements are arranged at the focal point, Figure 7 shows antenna elements arranged on a circuit board in an exemplary embodiment of a radar sensor according to the invention, which is equipped with three antenna elements,and Figure 8 shows the arrangement of the antenna elements between the focal point and the radar converging lens in the embodiment according to Figure 7 in a cross-sectional view. For the sake of clarity, the same reference numerals are used throughout the figures for identical or comparable components. Figure 1 shows components of an embodiment of a radar sensor 10 according to the invention in a cross-section. An antenna element 20 and a radar converging lens 30 can be seen.which is suitable for focusing radar radiation. In the exemplary embodiment according to Figure 1, the radar converging lens 30 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. With a view to low absorption of the radar radiation, the radar converging lens 30 preferably consists of a one-piece element made of Teflon or polycarbonate. The focal point 40 of the radar converging lens 30 has a focal distance FA from the lens side 31 facing the focal point 40. The antenna element 20 is spatially arranged between the focal point 40 and the radar converging lens 30. The distance A between the antenna element 20 and the radar collecting lens 30 is preferably between 0.75 and 0.79 times the focal distance FA in the case of a convex-concave radar collecting lens 30 and preferably between 0.74 and 0.78 times the focal distance FA in the case of a plano-convex radar collecting lens 30.The following therefore preferably applies: 0.75 * FA < A < 0.79 * FA in the case of a convex-concave radar converging lens 30 and 0.74 * FA < A < 0.78 * FA in the case of a plano-convex radar converging lens 30. The focal distance FA is preferably in a range between 22 mm and 26 mm in the case of a convex-concave radar converging lens 30 and in a range between 16 mm and 20 mm in the case of a plano-convex radar converging lens 30. In the case of a convex-concave radar converging lens 30, the focal distance FA is, for example, 24 mm, with a distance A between the antenna element 20 and the radar converging lens 30 of 18.496 mm, i.e. 0.7707 times the focal distance FA, being regarded as optimal. In the case of a plano-convex radar lens 30, the focal distance FA is, for example, 18 mm, with a distance A between the antenna element 20 and the radar lens 30 of 13.6215 mm, i.e. 0.75675 times the focal distance FA,is considered optimal. Figure 2 shows an example of the antenna directional characteristic, i.e., the transmission and reception characteristics, of the antenna element 20 according to Figure 1. It can be seen that due to the axially offset arrangement of the antenna element 20 in the direction of the radar collector 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 at the focal point 40. 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 thatthat at the interface SS between the main beam lobe 50 and the respective neighboring section 50a or 50b, the antenna directional characteristic does not exhibit any indentation or constriction directed inward toward the antenna element 20. Figure 3 shows the course of the antenna directional characteristic in the form of an antenna directional value R plotted against the radiation angle ^. The radiation angle in Figures 2 and 3 is chosen, by way of example, such that its value ^=0 lies at the greatest transmission or reception strength or at the greatest antenna directivity, i.e., in the center of the main beam lobe 50. It can be seen in Figure 3 that the antenna directional value R continuously increases for values ​​^ below zero with increasing values ​​of ^, albeit at variable rates of increase, and continuously decreases for values ​​^ above zero with increasing values ​​of ^.albeit with variable decay rates. 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 ^ does exhibit a certain plateau, on which the antenna directivity R is relatively constant over the radiation angle ^; 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. In other words, in the embodiment according to Figures 2 and 3, the antenna directivity, starting from the maximum value that the antenna directivity R reaches in the area of ​​the center of the main beam lobe 50,in the direction of the neighboring sections 50a and 50b as well as in the neighboring sections 50a and 50b themselves, or at most is constant in certain sections. Therefore, no intermediate region is formed at the SS interfaces in which the antenna directivity R would be smaller than in the adjacent regions. For better understanding, Figure 4 shows the formation of side lobes 51 and 52 that occurs when the antenna element 20 is arranged at the focal point 40 of the radar collector lens 30. It can be seen in Figure 4 that - in contrast to Figure 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 directivity pattern exhibits clear indentations EB or constrictions in the direction of the antenna element 20. These indentations EB can cause an object,which is located angularly between the main beam lobe 50 and one of the adjacent side lobes 51 or 52, may not be detected under certain circumstances, depending on the sensitivity of the radar sensor 10. Figures 1 and 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, a first of which is electrically connected to a radar transmitting device and functions as a transmitting antenna element 21, and a second of which is electrically connected to a radar receiving device and functions as a receiving antenna element 22; such an embodiment of the invention is shown in a simplified representation in Figure 5. It can be seen in Figure 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, resulting in a bulbous antenna directional characteristic without indentations EB between the main beam lobe 60 and the neighboring sections 60a and 60b; the same applies to the main beam lobe 70 of the receiving antenna element 22 and its neighboring sections hidden in Figure 5. Furthermore, it can be seen that, due to the bulbous shape of the antenna directional characteristic, only a very small indentation EB is present 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. Figure 6 shows the antenna directional characteristics of two antenna elements 23 and 24 for comparison,which are arranged in the region 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 Figure 5. Figure 7 shows components of a further exemplary embodiment of the invention as well as a particularly preferred design and arrangement of antenna elements. Shown in plan view is a circuit board 100 with three conductor track elements, each forming an antenna element. One of the conductor track elements forms a transmitting antenna element 25, which is connected to a radar transmitter device 110 arranged on the circuit board 100 via a conductor track 101 of the circuit board 100. 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. 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. 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. Figure 8 shows the circuit board 100 according to Figure 7 in a cross-section, as well as the radar converging lens 30 and its focal point 40, also in cross-section. It can be seenthat 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 converging lens 30. 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 converging lens 30 facing the focal point 40. The antenna elements are preferably formed by conductor track elements of the same circuit board. Three of the antenna elements can, for example, be operated as transmitting antenna elements and the remaining four as receiving antenna elements. Finally, it should be mentioned that the features of all the embodiments described above can be combined with one another in any desired manner to form further embodiments of the invention. All features of subclaims can also be combined individually with any other claim.in each case alone or in any combination with one or more other subclaims in order to obtain further embodiments.

[0002] 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 collector lens 31 Lens side 32 Lens side 40 Focus point 50 Main beam lobe 50a Neighboring section 50b Neighboring section 51 Side lobe 52 Side lobe 60 Main beam lobe 60a Neighboring section 60b Neighboring section 70 Main beam lobe 80 Main beam lobe 90 Main beam lobe 100 Printed circuit board 101 Conductor track 102 Conductor track 103 Conductor track 110 Radar transmitting device 120 Radar receiving device A Distance E Plane EB Indentations FA Focus distance M Central axis R Antenna directivity SS Interface ^ Beam angle

Claims

Patent claims 1. Radar sensor (10) with 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), characterized in 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 converging lens (30) facing the focal point (40).

2. Radar sensor (10) according to claim 1, characterized in that 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). 3.Radar sensor (10) according to one of the preceding claims, characterized in that the distance (A) between the at least one antenna element (20-22, 25-27) and the lens side (31) of the radar converging lens (30) facing it is between 0.5 and 0.9 times the focal distance (FA).

4. Radar sensor (10) according to one of the preceding claims, characterized in that the distance (A) between the at least one antenna element (20-22, 25-27) and the lens side (31) of the radar converging lens (30) facing it is between 0.65 and 0.85 times the focal distance (FA).

5. Radar sensor (10) according to one of the preceding claims, characterized in that the radar converging 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).

6. Radar sensor (10) according to one of the preceding claims 1 to 4, characterized in that the radar converging lens (30) is flat 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).

7. Radar sensor (10) according to one of the preceding claims, characterized in that the radar sensor (10) has at least two antenna elements (21-22, 25-27), a first of which is electrically connected to a radar transmitting device (110) and a second of which is electrically connected to a radar receiving device (120).Radar sensor (10) according to claim 7, characterized in 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).

9. Radar sensor (10) according to one of the preceding claims 7 to 8, characterized in that ^ the distance (A) between the first antenna element (21, 25) and the lens side (31) of the radar converging lens (30) facing it is between 0.5 and 0.9 times the focal distance (FA) and ^ the distance (A) between the second antenna element (22, 26) and the lens side (31) of the radar converging lens (30) facing it is between 0.5 and 0.9 times the focal distance (FA). 10.Radar sensor (10) according to one of the preceding claims 7 to 9, characterized in that ^ the distance (A) between the first antenna element (21, 25) and the lens side (31) of the radar converging lens (30) facing it is between 0.65 and 0.85 times the focal distance (FA) and ^ the distance (A) between the second antenna element (22, 26) and the lens side (31) of the radar converging lens (30) facing it is between 0.65 and 0.85 times the focal distance (FA).

11. Radar sensor (10) according to one of the preceding claims 7 to 10, characterized in 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 for detecting the direction of received radar radiation by evaluating the reception signals. nals of the second and third antenna elements (26, 27).

12. Radar sensor (10) according to claim 11, characterized in that the distance (A) between the focal point (40) and the third antenna element (27) is at least 10% of the focal distance (FA).

13. Radar sensor (10) according to one of the preceding claims 11 to 12, characterized in that the distance (A) between the third antenna element (27) and the lens side (31) of the radar converging lens (30) facing it is between 0.5 and 0.9 times the focal distance (FA).

14. Radar sensor (10) according to one of the preceding claims 11 to 13, characterized in that the distance (A) between the third antenna element (27) and the lens side (31) of the radar converging lens (30) facing it is between 0.65 and 0.85 times the focal distance (FA).Radar sensor (10) according to one of the preceding claims, characterized in 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).

16. Radar sensor (10) according to claim 15, characterized in that the distance (A) between each of the antenna elements and the lens side (31) of the radar converging lens (30) facing them is in each case between 0.5 and 0.9 times the focal distance (FA).

17. Radar sensor (10) according to one of the preceding claims, characterized in that ^ the distance (A) between each of the antenna elements and the lens side (31) of the radar converging lens (30) facing them is in each case between 0.65 and 0.85 times the focal distance (FA).

18. Radar sensor (10) according to one of the preceding claims, characterized in that the radar collector lens (30) consists of a one-piece element made of Teflon or polycarbonate. 19.Radar sensor (10) according to one of the preceding claims, characterized in 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 at least in the region of the conductor track elements perpendicular to the central axis (M) of the radar collecting lens (30).

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