阅读说明：本技术 用于运行机动车中的雷达传感器的方法、雷达传感器和机动车 (Method for operating a radar sensor in a motor vehicle, radar sensor and motor vehicle ) 是由 N·科赫 于 2018-04-20 设计创作，主要内容包括：本发明涉及一种用于运行机动车(21)中的雷达传感器(1)的方法,其中,雷达传感器(1)具有用于发射和接收雷达信号的至少一个天线装置(3),还具有用于评估接收到的雷达信号的处理设备(8),其中,对天线装置(3)进行驱控以用于在远距离频率范围(17)和近距离频率范围(18)中同时发射和接收雷达信号,然后将近距离频率范围(18)的接收到的雷达信号评估成较高距离分辨率的雷达数据,将远距离频率范围(17)的接收到的雷达信号评估成较低距离分辨率的雷达数据,其中,近距离频率范围(18)的带宽大于远距离频率范围(17)的带宽。(The invention relates to a method for operating a radar sensor (1) in a motor vehicle (21), wherein the radar sensor (1) has at least one antenna arrangement (3) for transmitting and receiving radar signals and a processing device (8) for evaluating the received radar signals, wherein the antenna arrangement (3) is actuated for the simultaneous transmission and reception of radar signals in a long-range frequency range (17) and a short-range frequency range (18), and the received radar signals of the short-range frequency range (18) are evaluated as radar data of a higher range resolution, and the received radar signals of the long-range frequency range (17) are evaluated as radar data of a lower range resolution, wherein the bandwidth of the short-range frequency range (18) is greater than the bandwidth of the long-range frequency range (17).)

1. A method for operating a radar sensor (1) in a motor vehicle (21), wherein the radar sensor (1) has at least one antenna device (3) for transmitting and receiving radar signals and a processing device (8) for evaluating the received radar signals,

It is characterized in that the preparation method is characterized in that,

The antenna device (3) is controlled for the simultaneous transmission and reception of radar signals in a long-range frequency range (17) and a short-range frequency range (18), wherein the received radar signals of the short-range frequency range (18) are then evaluated into radar data of a higher range resolution and the received radar signals of the long-range frequency range (17) are evaluated into radar data of a lower range resolution, wherein the bandwidth of the short-range frequency range (18) is greater than the bandwidth of the long-range frequency range (17).

2. method according to claim 1, characterized in that the same number of grid points is applied in the fast fourier transform when evaluating the received radar signals of both frequency ranges (17, 18), and/or that the bandwidth of the short-range frequency range (18) is at least twice the bandwidth of the long-range frequency range (17).

3. Method according to claim 1 or 2, characterized in that in the case of at least partial overlap of the spatial detection regions (10, 10 ', 11) of the frequency ranges (17, 18), the received radar signals of a coherent total frequency range (19, 19') completely comprising the short-range frequency range (18) and the long-range frequency range (17) are jointly evaluated.

4. A method as claimed in claim 3, characterized in that the long-range frequency range (17) is completely encompassed by the short-range frequency range (18) forming the total frequency range (19, 19 ') at least in the case that the spatial detection region (11) of the long-range frequency range (17) is completely encompassed in the spatial detection region (10, 10') of the short-range frequency range (18) in terms of beam angle.

5. A method as claimed in claim 3, characterized in that in the case of a missing frequency range (20) between the short-range frequency range (18) and the long-range frequency range (18) which is not covered by radar signals, the signal level for evaluation in the missing frequency range is set to zero or interpolated.

6. Method according to any of the preceding claims, characterized in that radar signals of the short-range frequency range (18) and radar signals of the long-range frequency range (17) are transmitted in different directions.

7. Method according to any of the preceding claims, characterized in that the radar signals received in the long-range frequency range (17) and the short-range frequency range (18) are evaluated in parallel in time.

8. The method according to claim 7, characterized in that a radar sensor (1) is used which comprises at least two processing units of a processing device (8), in particular digital signal processors (9), which are each associated with a respective frequency range (17, 18, 19').

9. Method according to any of the preceding claims, characterized in that an antenna device (3) comprising one sub-antenna device (4, 5) each for a short-range frequency range (18) and a long-range frequency range (17) and/or having at least one antenna designed as a horn-shaped transmitting antenna is applied as the antenna device (3).

10. Method according to any of the preceding claims, characterized in that at least two transmission channels of the antenna device (3) are applied, wherein different transmission channels are applied for transmitting radar signals of different frequency ranges (17, 18).

11. method according to one of the preceding claims, characterized in that radar signals of a far-range frequency range (17) with a higher transmission power than radar signals of a near-range frequency range (18) are transmitted, in particular by using a greater number of transmission channels, and/or in that radar signals of a far-range frequency range (17) are transmitted in focus, in particular by means of an associated sub-antenna arrangement (4, 5).

12. Method according to one of the preceding claims, characterized in that in the case of at least partial overlap of the spatial detection regions (10, 10', 11), the evaluation results for the short-range frequency range (18) and the long-range frequency range (17) are jointly further evaluated, in particular for determining an object probability and/or for tracking at least one detected object described by the evaluation results.

13. A radar sensor (1) for a motor vehicle (21), having at least one antenna arrangement (3) for transmitting and receiving radar signals, a processing device (8) for evaluating the received radar signals, and a control device (7) which is designed for carrying out the method according to one of the preceding claims.

14. A motor vehicle (21) having at least one radar sensor (1) according to claim 13.

Technical Field

The invention relates to a method for operating a radar sensor in a motor vehicle, wherein the radar sensor has at least one antenna device for transmitting and receiving radar signals and a processing device for evaluating the received radar signals, and also to a radar sensor and a motor vehicle.

Background

Radar sensors play an important role in modern motor vehicles with regard to environmental detection. A number of proposed and also actually implemented driver assistance systems and/or safety systems use radar sensors to obtain information about the environment of the motor vehicle. A prominent example of such a driver assistance system is a longitudinal control system, such as an ACC system, which at least partially automates the longitudinal control. The basic principle of radar sensors is to emit electromagnetic waves of radar signals, which are reflected and re-received on an object. The received radar signals can then be evaluated, in particular with regard to object spacing, direction and relative speed.

In the evaluation of the received radar signals, a fast fourier transformation is also carried out, which converts the received spectrum back into time of flight and the expenditure in terms of time and thus distance grids increases rapidly. However, the number of control points/grid points applied in the applied frequency range (frequency band) determines the range resolution. Different operating modes of radar sensors have been provided in terms of range resolution and radius of action/range of action. If the radar sensor is used for remote area detection, a narrow frequency bandwidth is usually used, for example in the known 76-GHz radar sensor, which applies a 250MHz birdsong signal. If, for example, 512 control points are applied in the range of a Fast Fourier Transform (FFT), an action radius of 84m is covered, wherein the size of each distance grid is about 30 cm. This grid size is also referred to as distance resolution. At shorter operating radii, i.e. more accurate detection in the short-range operating mode of the radar sensor, a higher frequency bandwidth is used, for example twice as high, so that the frequency bandwidth is 500MHz for the example described above. With the same number of FFT control points, the grid size is reduced to 15cm, and therefore the range resolution is increased, but this is disadvantageous for the maximum appreciable action radius at this time, since the range resolution is now only 42 m.

For very fine distance resolutions, which are to be used, for example, during parking, etc., the grid size is therefore in the range of approximately 3cm to 5cm, the maximum appreciable distance being only 10m to 15m, with the number of FFT control points remaining unchanged. The operating mode of such a radar sensor may also be referred to as a parking operating mode.

The parking operating mode of the radar sensor is expediently activated only for parking processes, while the determination of the operating mode in the short range operating mode ("short-range observation") and the long range operating mode ("long-range observation") is difficult. On the one hand, approaching objects should be recognized early, i.e., with a large radius of action, and on the other hand, approaching objects, in particular traffic participants, are significantly closer to the motor vehicle and are very important for the operation of the motor vehicle itself, so that it is desirable to detect and track (Tracking) approaching objects with a sufficiently high distance resolution.

It has therefore been proposed for radar sensors in motor vehicles to regularly switch between two operating modes, namely a short-range operating mode and a long-range operating mode ("interleave"). For example, a ratio of 1:1 or 1:2 can be switched between the long-range operating mode and the short-range operating mode, wherein the ratio can be selected, for example, as a function of the vehicle speed. In this case, however, when the radar sensor is in the short-range operating mode, the detection does not cover a large area of the radius of action, but only takes place at least one cycle later, so that in the case of a typical time window duration of 40ms to 50ms, the update rate is defined as: detection is only performed in the region of the distant radius of action every approximately 100 ms. It is therefore undesirable for a motor vehicle or other object which approaches very quickly to be identified only very late.

Document DE 102006049879 a1 relates to a radar system for a motor vehicle, in which a plurality of radar sensors, of which at least two LRR sensors, i.e. remote radar sensors, are intended to be used for monitoring the area ahead of the vehicle. It is proposed that in one embodiment the sensors are operated alternately with different frequency modulation patterns, wherein the modulation pattern of the sensors should be optimized for the short-range region in each cycle, and the modulation pattern should be optimized for the long-range region in the other sensors. In this way, signals with good distance resolution are obtained for the left-hand and right-hand sensors in each two cycles, while at the same time, by combining the data of the two sensors, an optimal remote-zone positioning in each cycle should be possible.

Here, two radar sensors are therefore required, which transmit time-staggered in each case, thus leading to increased expenditure and increased processing time.

Disclosure of Invention

It is therefore an object of the invention to reduce the delay time/latency until the presence of short-range area data and long-range area data in as little a way as possible.

In order to achieve this object, according to the invention in a method of the type mentioned at the outset, the antenna arrangement is controlled for the simultaneous transmission and reception of radar signals in a long-range frequency range and a short-range frequency range, wherein the bandwidth of the short-range frequency range is greater than the bandwidth of the long-range frequency range, as a result of which the received radar signals of the short-range frequency range are evaluated as radar data of a higher range resolution and the received radar signals of the long-range frequency range are evaluated as radar data of a lower range resolution.

The invention is based on the following idea: instead of separating the short-range operating mode from the long-range operating mode by using different time windows, the measurements are carried out simultaneously, i.e. at least in a common transmission time window and reception time window, by separating the frequency ranges. In other words, the radar signals are transmitted simultaneously in both the long-range and the short-range frequency ranges in a common transmission time window. During the subsequent reception time window, the reflected radar signals of the two frequency ranges are also received simultaneously. By means of this time-parallelization and simultaneous frequency separation of the radar signals, the detection is carried out with reduced delay times in the two effective radius regions and in the two range resolutions.

The operating mode, which was originally implemented alternately in time ("interleaved"), now takes place simultaneously, so that far and near fields are detected at the same time, wherein near fields are detected redundantly in overlapping detection fields, i.e. once in a coarse grid with a lower range resolution ("long look") and once in a finer grid with a higher range resolution ("short look"). In the case of temporally separate detection processes, the detected object can move and therefore the movement can only be detected roughly and with a temporally double duration, whereas the invention makes it possible to detect the movement more stably and more finely.

in summary, it has turned out that the entire region of the radius of action is detected simultaneously in both range resolutions, so that the delay is reduced and can even be completely eliminated in the case of simultaneous evaluation, as will be discussed in more detail below. A reduction in the delay is achieved even when evaluated sequentially in two frequency ranges, wherein experiments have shown that this reduction in delay is in the range of 60% to 75%. The reduced delay time results in particular in an advantage when tracking objects, since no jumps occur in the scanning time point, which increases the stability of the kalman filter in the tracking algorithm. The object can thus be better tracked.

In this case, it can be provided that, when evaluating the received radar signals of the two frequency ranges, the same number of control points/grid points is used in the fast fourier transformation, and/or that the bandwidth of the short-range frequency range is at least twice the bandwidth of the long-range frequency range. For example, 512 control points may be set; as the bandwidth, a bandwidth of 500MHz is applied to the short-distance frequency range, and a bandwidth of 250MHz is applied to the long-distance frequency range.

In a particularly preferred embodiment of the invention, it can be provided that, in the case of at least partial overlap of the spatial detection regions of the frequency ranges, the received radar signals of a consecutive/continuous total frequency range, which completely encompasses the short-range frequency range and the long-range frequency range, are jointly evaluated. The total frequency range thus starts with the lowest boundary frequency of the two frequency ranges and ends with the highest boundary frequency of the frequency ranges. The surprising side effect of using this approach in this way improves the accuracy of object detection in the proximity region. Not only does the detection of objects at different resolution grids contribute to an improved recognition, for example by confidence testing between each other, but the scanning of close objects is performed with a again increased bandwidth if the detection areas overlap properly and the far frequency range does not lie completely within the near frequency range.

In a particularly advantageous development of the above-described method, it can be provided that, at least with regard to the beam angle, the long-range frequency range is completely included in the short-range frequency range forming the total frequency range, if the spatial detection region of the long-range frequency range is completely contained in the spatial detection region of the short-range frequency range. In this embodiment, the total frequency range is thus the close-range frequency range, so that the evaluation in the total frequency range corresponds to the evaluation in the close-range frequency range. In this way, it is also advantageous to require only one bandwidth of the transmitted signal, which is sufficient for sufficient range resolution in the short-range region, so that no correction is necessary either. Based on the received signals, the long-range frequency range is simply cut out of the short-range frequency range and fed to the corresponding evaluation device.

Alternatively, however, the total frequency range is greater than the close-range frequency range, wherein preferably the close-range frequency range is separated from the far-range frequency range, except for possible contact frequencies, and thus is disjoint, so that the total frequency range is additively produced if the frequency ranges are directly adjacent to one another. Thus, if the frequency separation is set such that, for example, the long-range frequency range ends at the beginning of the short-range frequency range, a total detection bandwidth of 750MHz results with a detection bandwidth of 500MHz for the short-range frequency range and a detection bandwidth of 250MHz for the long-range frequency range. With the same number of FFT control points, for example 512 control points, it is thus possible to achieve a significant reduction of the distance grid, for example to below 3cm, which is suitable for the evaluation of the total frequency range.

In this case, an advantageous development provides that, if a missing frequency range not covered by the radar signal is present between the short-range frequency range and the long-range frequency range, the signal level there for evaluation is set to zero or interpolation is carried out in the missing frequency range. If a certain frequency range, in this case a missing frequency range, is missed, an evaluation in the overall frequency range, which involves the bandwidth of the overall frequency range and thus enables an excellent distance resolution in the ultra-short range, can still be achieved. If the missing frequency range has a frequency bandwidth of 250MHz in the example described above, a frequency bandwidth of the total frequency range of 1000MHz to 1GHz results, wherein advantageously also the total frequency bandwidth of the total frequency range does not have to be occupied. Since the signal level in the missing frequency range can simply be set to zero, as may eventually occur if attenuation may occur in this region, or interpolation may be carried out between the short-range frequency range and the long-range frequency range. It is thus conceivable, for example, to increase the resolution of the total frequency range by: the long range frequency range starts at the lowest end of the total frequency range and the short range frequency range ends at the highest end of the total frequency range, wherein values are interpolated or set to zero in the missing range. The solution for closing bandwidth gaps has been derived by: most of the objects present in practice move linearly and exhibit linear behavior, resulting overall in improved quasi-resolution in the super-short range, without the radius of action having to be limited here.

A suitable embodiment of the invention provides that the radar signals of the short-range frequency range and the radar signals of the long-range frequency range are emitted in different directions. Thus, for example, forward and sideways or even opposite sides can be detected by means of a single radar sensor, in the case of a corresponding presence of an antenna arrangement, without the need for a strong delay loss being taken into account as a result. It is thus possible to scan different directions with the radar sensor without delays being formed here. For example, radar sensors have been provided which, in a long-range operating mode, emit in the longitudinal direction of the vehicle and, in a short-range operating mode, measure with a widened visibility range toward the side of the vehicle. With such radar sensors according to the prior art, it is now not possible to identify objects on the side during detection in the longitudinal direction of the motor vehicle in the remote range operating mode and vice versa. If it is set to operate alternately in the two operation modes, the update rate effective for both the long range area and the short range area is 100ms although the update rate is 50 ms. If the invention now allows radar signals to be transmitted and received in parallel for a plurality of directions, wherein resolution can be easily achieved with frequency separation, the delay is significantly reduced for these cases as well and the current measurement data are provided more frequently.

As mentioned above, in principle one can consider: the received radar signals of the short-range frequency range and radar signals of the long-range frequency range are evaluated sequentially, in particular using the same evaluation unit/processing unit. Subsequently, although the processing time needs to be increased, in practice the delay is reduced, for example in the range of 60% to 75% as already described above.

However, a preferred embodiment of the invention provides that the radar signals received in the long-range frequency range and the short-range frequency range are evaluated in parallel in time. An optimized operation of the radar sensor can then be achieved in that the last received radar signal is always evaluated during the current transmission and measurement phase. For example, for the last received radar signal, a transmission and reception block of 50ms duration can be implemented in parallel to the evaluation block time of 50ms, so that new, current radar data can be determined every 50ms by evaluation. In this context, it is particularly preferred to use radar sensors which comprise at least two processing units of the processing device, in particular digital signal processors, which are each associated with a respective frequency range. In particular in a multi-core processor, the processing unit can be defined abstractly, for example as a plurality of cores of such a multi-core processor, however the radar sensor can preferably be provided, for example, with a further Digital Signal Processor (DSP), in order to evaluate the received radar signals of different frequency ranges, i.e. at least the near-range frequency range and the far-range frequency range, on separate processors. In an embodiment, it is also conceivable that a processing unit for evaluation in the total frequency range is additionally provided if the total frequency range would otherwise not correspond to the short-range frequency range. The "short-distance observation" and the "long-distance observation" can be processed in parallel without delay by applying separate processing units. The evaluation results of the two simultaneously used operating modes also exist simultaneously for further processing.

In particular, it is possible to combine the evaluation results of the short-range frequency range and the long-range frequency range without delay even in parallel evaluation, in particular for improving the object probability by a plausibility test between one another and/or for tracking based on the respective results. When tracking the object, there is no jump in the scanning time point, which is beneficial for a reliable operating mode of kalman filtering.

In an alternative embodiment, although less preferred, it is conceivable to evaluate the frequency ranges sequentially, wherein the received radar signals of the frequency range to be evaluated later are blocked by delays in the signal processing, in particular in the analog-digital converter, until the evaluation begins. If at least one second processing unit is not used, the received radar signals of the long-range frequency range can be evaluated first, for example, wherein the evaluation result can be temporarily stored for later evaluation in another frequency range, for example, the short-range frequency range. For this purpose, it is expedient to delay the signal processing in the analog-digital converter (a/D converter). The processing speed of a Digital Signal Processor (DSP) is very high, in particular when it is operated in a special ASIC, so that the delay caused in the sequential processing and thus the remaining delay is only a few milliseconds. In the case of sequential evaluation, it is of course also possible to convey the evaluation results for common further processing or evaluation, for example in order to enable object verification and/or to improve the tracking of the object by comparing the respective evaluation results. In the design described in this way, the delay is not completely eliminated, but is significantly reduced, but processing units, for example digital signal processors, can be saved.

Preferably, an antenna arrangement with one respective sub-antenna arrangement for the short-range frequency range and the long-range frequency range and/or an antenna arrangement with at least one antenna designed as a horn-shaped transmitting antenna can be used as the antenna arrangement. Depending on, for example, whether the antenna arrangement requires an increased bandwidth in a certain desired overall frequency range, and thus to what extent the range resolution is to be improved, it can be provided that the antenna arrangement of the existing radar sensor is modified. In the prior art, so-called patch antenna slots are known, for example, which have a usable bandwidth of approximately 700MHz to a maximum of 1000 MHz. The principle generally applies here that the smaller the relative bandwidth, for example approximately 1%, the higher the quality of the antenna arrangement, so that conversely the quality of the antenna arrangement also decreases with a larger relative bandwidth.

If the bandwidth of the antenna arrangement is to be designed wider, the quality is reduced for this purpose in order to obtain more available bandwidth for good frequency separation. An alternative embodiment of the invention, however, provides that separate sub-antenna arrangements are provided for the short-range frequency range and the long-range frequency range, since the sub-antenna arrangements can be designed with a high-quality narrow band. However, the radar sensor may be designed larger and more complex in the case of the use of sub-antenna devices, so that in other cases it is also possible to provide a single antenna device for the short-range frequency range and the long-range frequency range in a rational manner.

It is generally proposed to use horn antenna structures, so that antennas designed as horn transmitting antennas are used in the antenna arrangement. The horn transmitting antenna is characterized in its structural form by a metal surface which approximates the shape of an exponential-curve horn and which can be fed through a waveguide/hollow conductor. Such horn radiator antennas suitable for use in the context of the present invention are also disclosed, for example, in the following published patent document DE 102016007434.5. The horn transmit antenna described therein has a large usable frequency bandwidth of up to 30 GHz. Alternatively, a slot-coupled patch antenna can also be used for an antenna designed as a horn antenna, in order to improve the frequency bandwidth of the antenna arrangement. Other solutions known in principle from the prior art are of course also conceivable.

In a further development of the invention, it can be provided that at least two transmission channels of the antenna arrangement are used, wherein different transmission channels are used for transmitting radar signals in different frequency ranges. For example, highly integrated radar sensors are known today, which provide three separate transmit channels and four independent receive channels. If a wideband antenna structure is used, for example, as described above, on four receive channels, a total licensed radar band of 76GHz to 81GHz may be detected, for example. However, the invention also makes it possible to assign the transmission channels to a short-range frequency range and a long-range frequency range, respectively. It can thus be provided, for example, that one transmission channel is used for a high-quality antenna in the short-range frequency range, while two further transmission channels are connected in parallel to at least one further high-quality antenna, so that radar signals can be transmitted for this purpose in the long-range frequency range. By using a larger number of transmit channels for a long range of frequencies, higher power is provided, which is advantageous for spanning large distances and thus for large effective radii. In the case of two transmit channels for the long-range frequency range and one transmit channel for the short-range frequency range, double the transmit power can thus be achieved for the long-range frequency range. The sub-antenna arrangement for the long-range frequency range can also be designed such that it focuses the main emission direction with high intensity onto a region of interest in the long range, so that, for example, an action radius of approximately 250m can be achieved without problems.

it is generally expedient to transmit radar signals of the long-range frequency range with a higher transmission power than radar signals of the short-range frequency range, in particular by using a greater number of transmission channels, and/or to transmit radar signals of the long-range frequency range in a focused manner, in particular by means of corresponding sub-antenna arrangements. Corresponding emission techniques are known in the prior art and need not be shown here in detail, in particular the beam optics need not be described here either.

As already explained, a particularly preferred embodiment of the invention provides that, in the case of at least partial overlap of the spatial detection regions, the evaluation results for the short-range frequency range and the long-range frequency range are jointly evaluated further, in particular for determining the object probability and/or for tracking at least one detected object described by the evaluation results. A plausibility test of the detected objects with respect to one another and thus object identification can thus be carried out at least in the overlapping region of action radius and beam angle; advantages in tracking, such as in kalman filtering, have been described.

In addition to the method, the invention also relates to a radar sensor for a motor vehicle, having at least one antenna device for transmitting and receiving radar signals, a processing device for evaluating the received radar signals, and a control device, which is designed to carry out the method according to the invention. All embodiments relating to the method according to the invention can be used analogously for the radar sensor according to the invention, so that the advantages already described can likewise be achieved by means of the radar sensor.

Finally, the invention also relates to a motor vehicle having a radar sensor according to the invention.

Drawings

Further advantages and details of the invention emerge from the exemplary embodiments described below and from the figures.

The figures show that:

Figure 1 shows a schematic sketch of a radar sensor according to the invention,

Figure 2 shows the detection area obtained by the radar sensor of figure 1,

figure 3 shows the detection regions radiating in different directions in an alternative design,

Figure 4 shows a time course in a radar sensor according to the invention,

Figure 5 shows a first design of band locations,

FIG. 6 shows a second embodiment of the band location, and

fig. 7 shows a motor vehicle according to the invention.

Detailed Description

Fig. 1 shows a schematic sketch of a radar sensor 1 according to the invention. The radar sensor 1 comprises first of all an antenna arrangement 3 arranged in a housing 2, which can optionally be divided, for example by means of a controller, into sub-antenna arrangements 4, 5 by means of different transmission channels. As a chip designed on the circuit board 6, the radar sensor 1 further comprises a control unit as a control device 7, which is designed for carrying out the method according to the invention, and at least two digital signal processors 9 (DSPs) as processing devices 8.

The antenna arrangement 3 may have a plurality of antennas designed as slot patch antennas/slotted patch antennas or horn transmit antennas. The sub-antenna device 4 is controlled by a first of the three transmit channels, and the sub-antenna device 5 is controlled by two of the transmit channels. The sub-antenna arrangements 4, 5 are designed here for realizing the different detection regions 10, 11 shown in detail in fig. 2. By means of the first sub-antenna arrangement 4, a short-range detection region 10 can be scanned, which has a larger beam angle than the long-range detection region 11. However, since only one transmit channel is used, the transmit power is smaller, which also shows a smaller effective radius. For the remote detection region 11, a larger effective radius is formed due to the doubled transmission power, wherein a narrower beam angle is obtained by focusing, in order to be able to reliably scan objects that are further away. Obviously, the detection areas 10, 11 have an overlap.

In the method according to the invention and therefore also in the radar sensor 1, it is provided that, when simultaneously transmitting radar signals in the short-range frequency range and the long-range frequency range and correspondingly simultaneously receiving reflected radar signals, the two detection regions 10, 11 are scanned simultaneously, so that a short-range operating mode and a long-range operating mode are simultaneously implemented. The received radar signals can be distinguished by different frequency ranges and are fed to a corresponding processing unit of the processing device 8, i.e. the digital signal processor 9, in which the received radar signals are evaluated in time parallel, so that no time delay exists between the evaluation results for the short-range detection area 10 and the long-range detection area 11. The evaluation is performed here with a coarser grid in terms of distance in the detection region 11, for example a distance resolution of 30cm, than in the short-range detection region 10, in which the distance resolution may be, for example, 15cm, whereas the same number of control points are respectively applied in the Fast Fourier Transformation (FFT). The different range resolutions result from the fact that currently a frequency bandwidth of 500MHz is used in the short-range frequency range and a frequency bandwidth of 250MHz is used in the long-range frequency range.

It is also to be noted that in alternative embodiments it is also possible to evaluate the received radar signals of the short-range frequency range and the received radar signals of the long-range frequency range sequentially, for example when there is only one processing unit, i.e. the digital signal processor 9.

Although in the embodiment of fig. 2 the radar signals for the short-range frequency range and the radar signals for the long-range frequency range are emitted in the same direction, this is not mandatory, as shown, for example, in particular the radar signals of the short-range frequency range are emitted sideways with differently oriented sub-antenna arrangements 4, 5 emitting radar signals in different directions, so that in this case a detection region 10' is obtained which does not overlap the detection region 11.

As shown in fig. 2, in the case of overlapping detection regions 10, 11, the evaluation results of the short-range frequency range and the long-range frequency range can also be jointly evaluated further, at least for the overlap region 12, for example in terms of inter-object plausibility tests/object confirmations for determining object probabilities and/or in the context of tracking objects, in particular in the case of kalman filtering, wherein it is to be noted that the stability of the reliability of the tracking algorithm also contributes to a reduced delay time.

Fig. 4 illustrates the time course of the process in the radar sensor more precisely. The time block 13 can be understood here as a transmit and receive block, which currently lasts 50ms each. The block 14 can be understood as an evaluation block in which the evaluation of the last received radar signal takes place in parallel with the transmission and reception block 13, to be precise, as is the case with transmission and reception, in parallel in time for the short-range frequency range and the long-range frequency range. If the arrow 15 represents the output of the evaluation result, an evaluation result for the short-range frequency range, i.e. the detection region 10 or 10', and a result for the long-range frequency range, i.e. the detection region 11, are thus produced at intervals 16 of 50 ms.

Fig. 5 shows a first possible embodiment of the position of the frequency ranges 17, 18 in the frequency domain. In this embodiment, the far-range frequency range 17 in the lower frequencies and the near-range frequency range 18 in the higher frequencies directly adjoin one another. The long-range frequency range and the short-range frequency range thus seamlessly form a total frequency range 19 which, with the above-mentioned bandwidth, has a frequency bandwidth of 750 MHz. It is now expedient in the context of the invention if a better range resolution is sought to jointly evaluate the received radar signals of the two frequency ranges 17, 18 as well, i.e. to carry out a joint evaluation on the basis of the total frequency range 19 having a larger frequency bandwidth. The performance of such an evaluation may be limited to a certain mode of operation in relation to the ultra-short range. It is furthermore stated that, of course, further processing units of the processing device 8 can also be provided for such additional evaluation processes.

fig. 6 shows an alternative, preferred embodiment, which comprises separate frequency ranges 17, 18. Here, the frequency ranges 17, 18 are separated by a missing frequency range 20 of 250 MHz. A reasonable evaluation is still obtained if the signal level is set to zero or interpolated in the missing frequency range 20 in the case of a common evaluation in the total frequency range 19 ', which also includes the missing frequency range 20, the total frequency range 19' having an increased frequency bandwidth than the total frequency range 19, which here is 1 GHz.

it should be noted here that in principle also designs with overlapping frequency ranges 17, 18 or even long-range frequency ranges 17 which are completely contained in the short-range frequency range 18 are conceivable.

Fig. 7 shows a schematic representation of a motor vehicle 21 according to the invention, in which two radar sensors 1 are currently installed, one of which is oriented toward the front zone of the motor vehicle 21 and the other of which is oriented toward the rear compartment of the motor vehicle 21.