Process setup for simulating a radar target

Abstract

The invention relates to a process arrangement for simulating a radar target at a relative velocity to a radar sensor (3), comprising at least one test unit (1) with a rotor (7) rotatably mounted about a rotor axis, the rotor having a number of test elements (11, 29, 31) distributed in the circumferential direction of the rotor, which reflect an electromagnetic wave (10) emitted by the radar sensor (3) back towards the radar sensor (3). According to the invention, for optimized radar reflection (12) towards the radar sensor (3), the test elements (11, 29, 31) are configured such that the test unit (1) provides a constant radar reflectance surface (RCS) during rotor rotation over at least one rotor rotation angle range (α).

Description

[0001] The invention relates to a process arrangement for simulating a radar target according to the preamble of claim 1.

[0002] The detection and speed measurement capabilities of a vehicle radar system can be tested using a specific process setup, such as those known from DE 10 2021 207 338 A1 or DE 10 2005 032 649 A1. According to these patents, the test unit is a Doppler generator that produces a Doppler frequency shift by rotating test elements (i.e., rotor blades). The vehicle radar system then tests its detection and speed measurement capabilities based on this shift. The process setup known from the prior art utilizes a simple radial compressor with metallic vanes that generate retroreflective surfaces through their rotation.

[0003] This leads to the following problem: In radar sensor testing, not only the Doppler shift for velocity simulation is of interest, but also the detection accuracy of the radar sensor as a function of the radar cross-sectional area (RCS) of the radar target (i.e., the test unit). However, with radar sensor testing methods known from the prior art, the radar cross-sectional area (RCS) of the radar target cannot be readily determined.

[0004] The object of the invention is to provide a process arrangement for simulating a radar target with relative velocity to a radar sensor, in which the significance of the test result is increased compared to the prior art.

[0005] The problem is solved by the features of claim 1. Preferred embodiments of the invention are disclosed in the dependent claims.

[0006] The invention relates to a process arrangement for simulating a radar target moving at a relative velocity to a radar sensor. The process arrangement comprises at least one test unit with a rotor mounted to rotate about a rotor axis. This rotor is equipped with a number of test elements distributed around its circumference, which reflect a radar signal emitted by the radar sensor back towards the radar sensor. According to the characterizing part of claim 1, the reliability of the radar sensor test is increased by the following measures: For optimized radar reflection towards the radar sensor, the test elements distributed around the rotor are designed such that the test unit can provide the radar sensor with a constant radar reflector area or radar cross-sectional area over at least a certain angular range during rotor rotation.

[0007] According to the invention, the test elements (for example, the rotor blades) are shaped such that they always present the same radar cross-sectional area (RCS) to the radar during rotation and are not obscured by other rotor blades. The radar signal is reflected back from the rotor blade to the transmitter of the radar sensor, similar to a corner reflector; simultaneously, the movement of the test element produces a Doppler effect. Furthermore, the number and arrangement of the test elements are designed so that they do not shadow each other or alter the radar cross-sectional area. The number of test elements is chosen so that, on the one hand, there are no detection gaps (i.e., objects detected and undetectable) and, on the other hand, no obscuration occurs.

[0008] The desired radar cross-sectional area can be uniquely calculated using mathematical formulas, for example, while the entire structure of the test element can be simulated and optimized using field simulation. The formula for the radar cross-sectional area of ​​a flat rotor blade surface oriented perpendicular to the beam direction is as follows: σ=4π⋅A2λ2 , where A = Rotor blade area λ = wavelength σ = Radar reflector

[0009] In a technical implementation, the rotor, as a test element, can have a number of circumferentially distributed rotor blades that project radially outwards from a rotor shaft axis. Each of the rotor blades can be designed with a number of back-reflective surface segments that are spatially oriented differently relative to each other.

[0010] Such a differentiated orientation of the retroreflecting surface segments ensures optimal retroreflectivity across various rotation angles. Each rotor blade can be designed so that, when illuminated by radar at the 0° position of the rotor's rotation, it exhibits a constant radar cross-sectional area (RCS) and generates a Doppler frequency through its rotation. As one rotor blade rotates out of the effective range (i.e., the irradiation area), a subsequent rotor blade enters the effective range, ensuring that the radar cross-sectional area remains constant throughout a full rotor revolution.

[0011] At least a subset, and in particular all, of the retroreflective surface segments of the test elements can preferably be designed with a flat surface. Test elements with such flat retroreflective surface segments are easier to produce, for example by cutting or injection molding. Furthermore, the flat retroreflective surface segments minimize unwanted scattering and reflection losses.

[0012] Each rotor blade, viewed along the rotor's circumference, can be shaped like an arc, with a hollow inner surface facing in the direction of rotation and a negative-shaped outer surface facing in the opposite direction. This arc shape minimizes air resistance and ensures smooth rotor operation. Furthermore, the arc shape promotes uniform and focused reflection of the radar signal.

[0013] The reflector segments of the rotor blade can transition angularly into one another at the edges, forming a fold pattern. The arc shape of the rotor blade can be superimposed on this fold pattern, which is particularly advantageous. The combination of the arc shape and the fold pattern offers the following benefits: The arc shape ensures directional reflectivity within a defined area. The fold pattern complements this arc shape by creating additional reflection points that compensate for varying angular orientations of the rotor blades. This keeps the radar cross-sectional area constant over a wider range of rotation angles.

[0014] The folded pattern also provides additional reflective surfaces in multiple directions. This leads to improved adaptation to different angles of incidence of the radar signal and ensures that the reflected radar signal remains stable even with small variations in the angle of incidence. Furthermore, the combination of the folded pattern and the curved shape allows the reflection properties to be better adapted to those of a real object that does not have perfectly smooth surfaces. Particularly in simulations of pedestrians, vehicles, or irregular surfaces, this structure contributes to the replication of realistic conditions.

[0015] In the combination of an arc shape and a pleated pattern, the rotor blade is designed in a zigzag shape similar to a triple mirror (i.e., a corner reflector). The width and height of the rotor blade are simply calculated using the area (width x height) in relation to the wavelength used (e.g., 4 mm or 12 mm) or frequency range (e.g., 77 GHz or 24 GHz), which corresponds to the radar cross-sectional area (RCS). In one embodiment, for example, 0 dBsm = 1 square meter can be achieved at 77 GHz (4 mm wavelength). A field simulation aids in the design and verification of the desired result. A triple reflection arrangement per blade allows for almost half a rotation from -85° to +85° with a constant RCS, thus requiring only two blades.

[0016] The transition edges between the retroreflective surface segments can run straight or parallel to the rotor axis. Straight transition edges simplify the manufacturing process and assembly. Furthermore, such an axis-parallel alignment optimizes reflections to the radar sensor.

[0017] The rotor blade can be made of plastic, particularly a polyamide (PA6 or PA66). An additive to increase radar reflectivity can be mixed into the plastic. Alternatively, the reflective surface segments of the rotor blade can be coated with a radar-reflective layer, such as a paint or film. Such a plastic rotor can be manufactured using a 3D printing process. In one design variant, a polyamide (PA6, PA66) with additional additives to increase radar reflectivity can be selected as the plastic. In principle, bent, shaped sheet metal is also possible as a rotor blade; however, this has the disadvantage of generating multiple reflections and diffraction effects at the metallic parts.The preferred design using plastic enables more precise control of the radar reflecting surface, the reflection point and the reflecting orientation, without necessarily causing parasitic diffraction effects on the other fan components.

[0018] In an alternative embodiment, the rotor can have not the rotor blades as test elements, but rather a number of circumferentially distributed parabolic structures, such as a parabolic concave mirror or a hollow conical reflector that opens or expands radially outwards in the rotor's radial direction, with an inner surface of the parabolic structure forming the back-reflecting segment. The parabolic structure focuses the transmitted signal and improves the signal quality.

[0019] The parabolic structure is particularly advantageous for providing a precise reflection center. Maintaining a constant radar cross-sectional area of ​​the test unit is only possible up to a certain angle of rotation with a rotor featuring parabolic structures. As soon as one parabolic structure leaves a radar coverage area, a neighboring parabolic structure enters the radar coverage area, thus largely keeping the radar cross-sectional area of ​​the test unit constant.

[0020] In a specific embodiment, the process arrangement can include a set of test units. Each of these test units provides the radar sensor with a predefined radar cross-sectional area (RCS). This allows the test size of the radar target to be adjusted as needed by selecting at least one of the test units. To further adjust the test size of the radar target, the process arrangement can also have a modular design in which several individual test units can be combined into a single overall test unit. In the overall test unit, the individual test units with their rotors are arranged coaxially one behind the other in the axial direction. Each of the individual test units can have a coupling element by means of which the rotors of adjacent test units can be drivenly coupled to one another. Such a design enables flexible scaling of the radar cross-sectional area by adding or removing test units.Each test unit delivers specific retroreflectivity values ​​that can be adapted to different test scenarios.

[0021] The radar cross-sectional area can therefore be increased additively or logarithmically. In principle, any radar cross-sectional area can be generated, but -10 dBm, 0 dBm, and +10 dBm have proven to be good test values ​​in radar testing. This can be taken into account by having each test unit have a radar cross-sectional area of ​​-10 dBm, which represents a pedestrian or small object. When using two test units, the radar cross-sectional area can be 0 dBm or one square meter, which represents a motorcycle or medium-sized object. Consequently, when three units are combined, a +10 dBm cross-sectional area is generated, which corresponds to a vehicle.

[0022] Alternatively, other increments are possible, such as 6 dBsm or 3 dBsm, which corresponds to a doubling of the radar cross-sectional area when the test units are connected, thus enabling even small increases in the radar cross-sectional area. In a particularly advantageous embodiment, each radar cross-sectional area can be represented in 1 dBsm increments using logarithmic increments. With increments of 0 dBsm, ±1, ±2, ±5, ±10, this works particularly well in a range of ±20 dBsm in increments of 1.

[0023] The individual test units combined to form the overall test unit can – with appropriate dimensioning – preferably be operated with only one common drive motor. However, separate drives in each unit, synchronized by coupling the drive shafts (gear, toothed belt, chain, etc.), offer greater flexibility.

[0024] In a specific embodiment, the test unit can have a housing that encloses the rotor and is made of radar-absorbing material. The housing can be designed with a window-like recess through which the energy emitted by the radar sensor and the radar reflections reflected by the rotor are guided. A radar-absorbing, adjustable aperture can be associated with the housing recess, by means of which a portion of the rotor can be shaded. This allows only the retroreflective surface segments moving towards the radar sensor to be exposed for detection during rotor rotation, while the retroreflective surface segments moving away from the radar sensor are shaded, or vice versa.

[0025] The rotor speed is adjustable by regulating the voltage / current of the rotor drive motor, which affects the Doppler shift. Reversing the motor's polarity allows for the simulation of forward and reverse motion. In a preferred embodiment, a potentiometer with a scale in m / s and / or km / h for the represented Doppler shift is used to adjust the speed, and a switch for reversing the fan wheel's direction of rotation is implemented. The formula for the Doppler shift used to adjust the rotor's rotational speed is as follows: fD=2vλ where f D = Doppler frequency [Hz] λ = wavelength of the transmitted frequency v = target speed [m / s]

[0026] A potentiometer regulates the operating voltage of the drive motor and thus its rotational speed. A scale for the radar's measured Doppler velocity allows the correct rotational speed to be set without delay. Good test values ​​have proven to be 1 m / s (3.6 km / h = pedestrian), 5 m / s = cyclist at approximately 18 km / h, 10 m / s (36 km / h = slow vehicle), and 20 m / s (72 km / h = medium-speed vehicle).

[0027] Exemplary embodiments of the invention are described below with reference to the accompanying figures.

[0028] They show: Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6 to Fig. 7 different views, which illustrate the structure and operation of the process arrangement according to the invention.

[0029] In Fig. Figure 1 illustrates a process setup with a test unit 1 and a radar sensor 3 to be tested. Using the test unit 1, a radar target with a relative velocity to the radar sensor 3 is simulated in a test situation. This calibrates / adjusts the radar sensor 3, which may be installed in a vehicle. The radar sensor 3 is, for example, a component of a driver assistance system that informs the vehicle about the distance to an object in front of the vehicle in the direction of travel, as well as its size / dimensions.

[0030] The test unit 1 has a housing 5 made of radar-absorbing material in which the rotor 7 is rotatably mounted. The rotor 7 consists of a rotor shaft 9, which defines the rotor axis, and a total of three rotor blades 11 projecting radially outwards from the rotor shaft and arranged with uniform spacing. The housing 5 also has a window-like recess 13 through which a radar signal 10 emitted by the radar sensor 3 is directed onto the rotor blades 11 of the rotor 7, as well as a radar reflection 12 reflected back towards the radar sensor 3.

[0031] The Doppler effect is used in radar sensor testing, since a rotating rotor 7 results in a frequency shift between the radar signal 10 and the radar reflection 12 reflected by the rotor, which can be evaluated by an evaluation electronics of the radar sensor 3.

[0032] A key aspect of the invention is that the geometry of the rotor blades 11 is designed such that the rotor 7 as a whole provides a constant radar cross-section (RCS) over at least a certain range of rotation angles during rotor rotation. The radar cross-section (RCS) is a parameter that describes how strongly an object (i.e., test unit 1) reflects an incident electromagnetic wave 10 and returns it to the radar sensor 3. The radar cross-section (RCS) is measured in square meters or decibel-meters. 2The provision of such a substantially constant radar reflectance surface (RCS) ensures stable and repeatable test conditions. Many objects in road traffic (e.g., pedestrians or vehicles) also exhibit a stable radar reflectance surface (RCS), thus enabling a more precise simulation of real-world conditions in the process setup. Furthermore, any RCS measurement that deviates from the constant radar reflectance surface (RCS) may indicate a faulty radar measurement.

[0033] As from the Fig. As can be seen from Figure 1, each of the rotor blades 11, viewed in the direction of rotor rotation, has an arc shape, with a hollow inner surface 13 facing against the direction of rotation D and a negative outer surface 15 facing in the direction of rotation D. The arc shape of the rotor blade 11 is superimposed by a pleated pattern 17, in which individual, flat retroreflective surface segments 19 merge into one another at transition edges 21 in an angled or zigzag pattern. The transition edges 21 between the retroreflective surface segments 19 run in straight lines and parallel to the rotor axis.

[0034] In the Fig. In Figure 1, the rotor blades 11 are, by way of example, made of a plastic in which an additive for increasing radar reflectivity is mixed. Preferably, each of the rotor blades can be produced in a 3D printing process in which a large number of degrees of freedom are provided with regard to the rotor blade geometry.

[0035] In the Fig. In 1, a vertically adjustable aperture 23 is assigned to the housing cutout 13, by means of which a lower rotor section is shaded from the radar signal 10 emitted by the radar sensor 3. In this way, in the Fig. 1. During a counterclockwise rotation of the rotor D, only the retroreflective surface segments 19 moving away from the radar sensor 3 are exposed. Alternatively, in the Fig. 2 the aperture 23 is moved vertically upwards, so that an upper rotor section is shaded from the radar signal 10 emitted by the radar sensor 3. This results in the Fig. 2. During a counterclockwise rotation of the rotor D, only the retroreflective surface segments 19 are exposed, which move towards the radar sensor 3. As soon as one of the rotor blades 11 moves out of the irradiation area, a subsequent rotor blade 11 enters the irradiation area, so that the RCS remains largely constant here as well during the rotor rotation.

[0036] In the Fig. Figure 3 shows a further embodiment of the test unit 1, whose basic structure and function are essentially identical to those of test unit 1 of the Fig. 1 and Fig. 2 is. Therefore, reference is made to the preliminary description. Unlike the Fig. 1 and Fig. 2 is in the Fig. 3 of rotor 7 is equipped with only two rotor blades 11. Each of the two rotor blades 11 has an identical rotor blade geometry, as can be seen from the Fig. 1 is described. In the Fig. Figure 3 shows, for example, the upper half of the rotor exposed to radar sensor 3, while the lower half of the rotor is shaded by radar sensor 3.

[0037] In the Fig. Figure 4 indicates a diagram determined by an evaluation electronics unit of the radar sensor 3, in which the radar reflectance area RCS of the Fig. The test unit 1 is plotted against the rotor rotation angle as shown in diagram 3. The test unit radar reflector surface RCS is composed of the individual radar reflector surfaces of the rotor blades 11. From the diagram of the Fig. 4. The evaluation electronics can derive a quasi-constant test unit radar reflector surface RCS within the rotation angle range α between approximately 120° and approximately 250°. From this, the evaluation electronics of the radar sensor 3 can determine the size of the radar target. For example, in the Fig. 4 the radar reflectance area RCS of test unit 1 read from the diagram by the evaluation electronics at approximately 0dBsm, which represents a pedestrian or a similarly small object.

[0038] In the Fig. Figure 5a shows a process arrangement comprising a set of 24 test units 1a, 1b, 1c, each of which provides a predefined radar cross-sectional area (RCS). This allows for a modular design of the process arrangement, in which the test size of the radar target can be adjusted as needed by selecting at least one of the test units 1a, 1b, or 1c. To adjust the test size of the radar target, the following are provided in the Fig. Figure 5b shows, by way of example, the individual test units 1a, 1b combined into a total test unit 25. In the total test unit 25, the individual test units 1a, 1b with their rotors 7 are arranged one behind the other in the axial direction. Each of the individual test units 1a, 1b is assigned an implicit coupling element 27 by means of which the rotors 7 of the two adjacent test units 1a, 1b can be coupled to each other. Thus, the two individual test units 1a, 1b can be driven by only one drive motor.

[0039] In the Fig. 6 and Fig. Figure 7 shows a rotor 7 according to a further embodiment, in which the rotor 7 has a number of circumferentially distributed parabolic structures 29, 31 instead of rotor blades 11. The parabolic structures are arranged in the Fig.7. This is exemplified by parabolic concave mirrors 29 or, alternatively, by hollow conical reflectors 31. The parabolic structures 29, 31 are radially open or widened in the rotor radial direction, with the inner surfaces of the parabolic structures 29, 31 each forming the backreflecting surface segments 19. Each of these parabolic structures 29, 31 generates a reflection center and supports precise radar backreflection 12 towards the radar sensor 3. During the rotor rotation, one of the parabolic structures 29, 31 is continuously moved into or out of an irradiation area, thus keeping the radar backreflecting surface RCS largely constant, at least over rotational angle ranges. REFERENCE MARK LIST: 1 test unit 2 Rotor sensor 5 cases 7 Rotor 9 Rotor shaft 10 Radar signal 11 Rotor blade 12 Radar reflection 13 Housing recess 14 Rotor inside 15 Rotor outer side 17 pleat patterns 19 Retroreflective surface segment 21 Transition edge 23 aperture 24 sets of test units 25 Total test units 27 coupling element 29, 31 Parabolic structure RCS radar reflector α Rotor rotation angle range Direction of rotation QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2021 207 338 A1

[0002] DE 10 2005 032 649 A1

[0002]

Claims

Process arrangement for simulating a radar target with relative velocity to a radar sensor (3), with at least one test unit (1) having a rotor (7) rotatably mounted about a rotor axis, which has a number of test elements (11, 29, 31) distributed in the circumferential direction of the rotor, which reflect a radar signal (10) emitted by the radar sensor (3) back towards the radar sensor (3), characterized in that for optimized radar reflection (12) towards the radar sensor (3) the test elements (11, 29, 31) are designed such that the test unit (1) provides a constant radar reflectance area (RCS) during rotor rotation over at least one rotor rotation angle range (α). Process arrangement according to claim 1, characterized in that the rotor (7) has as test elements a number of circumferentially distributed rotor blades (11) which project radially outwards from a rotor shaft axis, and that each of the rotor blades (11) is formed with a number of retroreflective surface segments (19) which are spatially differently oriented to each other. Process arrangement according to claim 2, characterized in that the retroreflective surface segments (19) of at least a subset of, in particular all, rotor blades (11) are formed as flat surfaces. Process arrangement according to claim 2 or 3, characterized in that each of the rotor blades (11), viewed in the direction of rotation (D), is formed in an arc shape, with a hollow rotor blade inner side (14) pointing in the direction of rotation (D) and with a rotor blade outer side (15) pointing in the opposite direction in a negative shape, or vice versa. Process arrangement according to one of claims 2, 3 or 4, characterized in that the retroreflective surface segments (19) of the rotor blade (11) merge into one another at transition edges (21) in an angled or zigzag pattern, forming a fold pattern (17), and in particular that the arc shape of the rotor blade (11) is superimposed on the fold pattern (17). Process arrangement according to one of the preceding claims, characterized in that the transition edges (21) located between the retroreflective surface segments (19) run linearly straight and parallel to the rotor axis. Process arrangement according to one of claims 2 to 6, characterized in that the rotor blade (11) is made of plastic, in particular a polyamide (PA6 or PA66), and that an additive to increase radar reflectivity is added to the plastic, or that the retroreflective surface segments (19) of the rotor blade (11) are coated with a radar-reflecting layer, such as a paint layer or a film. Process arrangement according to claim 1, characterized in that the rotor (7) has a number of circumferentially distributed parabolic structures (29, 31) as test elements, and in particular that the parabolic structure (29, 31) is a parabolic concave mirror or a hollow conical reflector which opens or expands radially outwards in the rotor radial direction, and that an inner surface of the parabolic structure (29, 31) forms a retroreflective surface segment (19). Process arrangement according to claim 8, characterized in that the process arrangement comprises a set (24) of test units (1a, 1b, 1c), each of which provides a predefined radar cross-sectional area (RCS), such that, in particular, the test size of the radar target can be adjusted as required by selecting at least one of the test units (1a, 1b, 1c), and that, in particular for adjusting the test size of the radar target, the process arrangement has a modular structure in which several individual test units (1a, 1b, 1c) can be combined to form a total test unit (25), that, in particular, in the total test unit (25), the individual test units (1a, 1b, 1c) with their rotors (7) are arranged coaxially one behind the other in the axial direction, and that, in particular, each of the individual test units (1a, 1b, 1c) has a coupling element (27) by means of which the rotors (7) adjacent test units (1a, 1b, 1c) can be coupled to each other by means of a drive. Process arrangement according to one of the preceding claims, characterized in that the test unit (1) has a housing (5) that encloses the rotor (7) and is made of radar-absorbing material, that the housing (5) has a radar-transparent housing recess (13) through which the electromagnetic wave (10) emitted by the radar sensor (3) and the radar reflection (12) reflected by the rotor (7) are guided, and that, in particular, a radar-absorbing, adjustable aperture (23) is associated with the housing recess (13) by means of which a partial rotor area can be shaded, so that during rotor rotation only the test elements (11, 29, 31) moving towards the radar sensor (3) are exposed for radar detection, while the test elements (11, 29, 31) moving away from the radar sensor (3) are shaded from radar detection (10), or vice versa.

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