WO2019063396A1

WO2019063396A1 - Method for suppressing flase detections, radar system and driver assistance system

Info

Publication number: WO2019063396A1
Application number: PCT/EP2018/075418
Authority: WO
Inventors: Serdal Ayhan; Gang Li
Original assignee: Valeo Schalter Und Sensoren Gmbh
Priority date: 2017-09-28
Filing date: 2018-09-20
Publication date: 2019-04-04
Also published as: DE102017122578A1

Abstract

The invention relates to a method for suppressing false detections (36b) in the determining of object information of an object, which is detected with a radar system, in particular of a vehicle. An original detection threshold (42) is carried out as an original window function (44), which has a maximum (46). From the result of a multi-dimensional discrete fourier transform of a receive signal of the radar system, a signal is determined as a target signal with an amplitude that is above a predefined limit value for target signals. The original window function (44) is scaled in relation to the amplitude of the target to form a scaled window function (54). The window function (54) is shifted in a doppler gate-range gate dimension of the result of the fourier transform, such that its maximum is at the target signal. An adapted detection threshold from the scaled and shifted adapted window function is compared with the original detection threshold (42) of the original window function (44), which was shifted with its maximum (46) to the maximum of the target signal. In the event that the adapted detection threshold is above the shifted original detection threshold (42), the adapted detection threshold is used for the result of the fourier transform in relation to the signals with the same doppler value and/or the same range value as the target signal. Otherwise, the original detection threshold (42) is used.

Description

Method for suppression of false detections, radar system and driver assistance system

Technical area

The invention relates to a method for suppressing false detections in the determination of object information of at least one object which is detected by a radar system, in particular of a vehicle,

in which at least part of a result of a multi-dimensional discrete Fourier transformation of at least one received signal of the radar system is compared with at least one adaptable detection threshold, and

- Those signals from the result of the Fourier transform are identified as false detections or discarded, whose amplitudes are below the at least one detection threshold.

Furthermore, the invention relates to a radar system, in particular of a vehicle, for determining at least one object information of at least one object,

with at least one transmitter for transmitting transmission signals in a monitoring area,

- With at least one receiver for receiving reflected at the at least one object echoes of the transmission signals as received signals and

- With at least one control and / or evaluation, wherein the at least one control and / or evaluation means comprises means

for carrying out at least one multi-dimensional discrete Fourier transformation of the received signals,

for comparing at least part of the result of the Fourier transformation with an adaptable detection threshold and - To identify or discard those signals from the result of the Fourier transformation as false detections whose amplitudes are below the detection threshold.

Moreover, the invention relates to a driver assistance system of a vehicle, comprising

at least one electronic control device for controlling functional devices of the vehicle depending on object information provided by at least one radar system, and

- At least one radar system for determining at least one object information of at least one object, wherein the at least one radar system comprises

at least one transmitter for transmitting transmission signals in a surveillance area,

at least one receiver for receiving echoes of the transmission signals reflected at the at least one object as received signals and

at least one control and / or evaluation device, wherein the at least one control and / or evaluation device has means

for comparing at least part of the result of the Fourier transformation with an adaptable detection threshold and

- To identify or discard those signals from the result of the Fourier transformation as false detections whose amplitudes are below the detection threshold. State of the art

From DE 10 2012 024 999 A1 a method for setting a detection threshold is known, with which a received signal of a frequency modulation continuous wave radar sensor of a motor vehicle with respect to the detection of a target object in the environment of the motor vehicle is compared. In each measurement cycle, the detection threshold is set individually for a subset of at least one frequency bin of a received signal.

The invention has for its object to design a method, a radar system and a driver assistance system of the type mentioned, in which Falschdetek- tions, especially due to side lobes of the radar transmission signals or reflections in the vicinity, can be better suppressed.

Disclosure of the invention

This object is achieved in the method in that

at least one primary detection threshold is realized as a primary window function, which has a maximum,

directly or indirectly from the result of the Fourier transformation at least one signal is determined as a target signal whose amplitude is above a predetermined limit value for target signals,

the original window function is normalized with respect to the amplitude of the at least one target signal to a normalized window function,

the window function is shifted before or after normalization in a Doppler-gate distance-gate dimension of the result of the Fourier transformation such that its maximum lies on the at least one target signal,

an adapted detection threshold from the normalized and shifted, adapted window function with the original detection threshold of the original window function, which has been shifted with its maximum to the maximum of the at least one target signal, and optionally with a previously adapted detection threshold of one previous matched window function, which was determined during a previous run of the method,

and if the adjusted detection threshold is above the shifted original detection threshold and possibly above the previous adjusted detection threshold, the adjusted detection threshold for the result of the Fourier transformation with respect to the signals having the same Doppler value and / or the same distance value as the at least one Target signal is used

otherwise the original detection threshold or, if appropriate, the previously adapted detection threshold is used.

According to the invention, based on at least one target signal, a primal window function is adapted such that further signals having the same distance value or the same Doppler value as the at least one target signal lie below the adjusted detection threshold and are identified or suppressed as a false signal. A target signal is detected by its amplitude being above a predetermined limit. The limit value is selected to be high enough that only amplitudes of signals which are most likely to originate from a real object lie above it.

The further signals which have the same distance value or the same Doppler value as the at least one target signal may be so-called side lobes of the echo signal. These can be caused in particular by strong reflections. According to the invention, when strong reflections occur, all signals with the same distance value or the same Doppler value as the at least one target signal are eliminated or marked in order to exclude such false detections, so-called ghost signals, from being erroneously used as target signals be recorded.

In addition, false detections due to reflections in the near range, so-called near range leakage (NRL), can also be eliminated with the invention. Such reflections in the near range can be caused, in particular, by a bumper of the vehicle on which the radar transmission signals are reflected. you can.

Advantageously, a known method for determining a constant false alarm rate (CFAR) can be used to determine the original window function. The CFAR method can be optimized according to the invention in order to better suppress false detections. By improving the CFAR method, a computing speed can be improved. Furthermore, the suppression of false detections can be performed more efficiently.

Advantageously, in the course of determining at least one object information, at least one multi-dimensional fast Fourier transformation can be carried out as a discrete Fourier transformation. In this way, the at least one Fourier transformation can be calculated faster.

The method can advantageously be realized with at least one means by software and / or hardware. The method can be realized in software and / or hardware in combination with the control and / or evaluation device. The means for carrying out the method can be contained in an already required control and / or evaluation device of the radar system.

Individual steps of the method can also be performed in a different order. Individual process steps can also be conveniently combined.

The radar system can detect stationary or moving objects, in particular vehicles, persons, obstacles, road bumps, in particular potholes or stones, roadway boundaries, free spaces, in particular parking spaces, or the like.

The invention can be used in a vehicle, in particular a motor vehicle. Advantageously, the invention can be used in a land vehicle, in particular a passenger car, truck, a bus, a motorcycle or the like, an aircraft and / or a watercraft. The invention can also be used in autonomous or at least partially autonomous vehicles. The radar system may advantageously be connected to or part of a driver assistance system of the vehicle, in particular a parking assistance system, a chassis control and / or a driver information device or the like. In this way, the detected with the radar system object information, in particular distances, directions and / or speeds of an object relative to the vehicle, transmitted to a control of the driver assistance system and for influencing driving functions, in particular the speed, a brake function, a steering function, a chassis control and / or an output of a warning and / or warning signal, in particular for the driver or the like.

In an advantageous embodiment of the method, at least one signal whose amplitude is above the predetermined limit value for target signals can be recorded in a detection list from the result of the Fourier transformation and the at least one target signal can be indirectly determined therefrom. In this way, the elimination of false detections on the detection level, in particular after a detector module, take place.

In a further advantageous embodiment of the method, the original window function can be realized as a cardinal sinus function. A cardinal sine function provides a primal window function with a maximum. Furthermore, such a primal window function may be a priori relatively close to a profile of main lobes and sidelobes of the result of the Fourier transform. In this way, an effort in the standardization and displacement according to the invention can be reduced.

Advantageously, the original window function can be realized as a Hamming window, Blackman window or the like.

In a further advantageous embodiment of the method, the normalized window function can be subjected to an amplitude offset. In this way, the detection threshold can be set correspondingly higher. Thus false detections with higher amplitudes can be marked and / or suppressed. In a further advantageous embodiment of the method, at least part of the method can be repeated for at least one further target signal. In this way, a plurality of target signals can be analyzed accordingly and optionally suppressed with these associated false signals.

Advantageously, the number of target signals to be examined can be specified. In this way, the number of repetitions of the process can be limited. Thus, a time required can be reduced accordingly.

In a further advantageous embodiment of the method, the original window function can be taken from a lookup table. In this way, the original window function can be calculated in advance and stored in the lookup table. Thus, a corresponding amount of computation when performing the actual process during operation of the radar system can be reduced. Lookup tables are known to be translation tables available at the computational level. The look-up table can be recorded before commissioning of the radar system, in particular during a constitution.

Furthermore, the object is achieved according to the invention in the radar system in that the control and / or evaluation has means for carrying out the method according to the invention.

In addition, the object according to the invention in the driver assistance system is achieved in that the control and / or evaluation has means for carrying out the method according to the invention.

Incidentally, the features and advantages shown in connection with the method according to the invention, the radar system according to the invention and the driver assistance system according to the invention and their respective advantageous embodiments apply mutatis mutandis and vice versa. The individual features and advantages can, of course, be combined with one another, whereby further advantageous effects can be achieved that go beyond the sum of the individual effects. Brief description of the drawings

Further advantages, features and details of the invention will become apparent from the following description, are explained in more detail in the embodiments of the invention with reference to the drawing. The person skilled in the art will expediently also individually consider the features disclosed in the drawing, the description and the claims in combination and combine these into meaningful further combinations. It show schematically

1 shows a motor vehicle with a driver assistance system and a radar system for monitoring a monitoring area in the direction of travel in front of the motor vehicle;

FIG. 2 shows a functional representation of the motor vehicle with the driver assistance system and the radar system from FIG. 1;

FIG. 3 shows a range gate Doppler gate diagram of a primary window function for suppressing false detections of the radar system;

Figure 4 is a range gate-Doppler tern diagram of signals from echo signals of the radar system after application of the original window function of Figure 3, which is shifted to a maximum target signal;

Figure 5 is a range gate-Dopplertor diagram of the signals corresponding to

FIG. 4, wherein here an adapted window function has been applied starting from the original window function for the suppression of false detections;

FIG. 6 shows a flow chart of a method for suppressing false detections by means of a matched window function;

Figure 7 is a detailed flow diagram of a method step of the method of Figure 6;

FIG. 8 shows a Doppler-Gate amplitude diagram in which the original window function, the normalized primal window function and the adapted window function are shown by way of example for a distance value;

FIG. 9 shows a Doppler-Gate amplitude diagram in which a radar measurement signal waveform, the original window function, the normalized window function and the adjusted window function are shown by way of example for a distance value;

FIG. 10 shows a distance-gate-amplitude diagram in which a signal curve of FIG Radar measurement of Figure 9, the original window function, the normalized window function and the adjusted window function are shown by way of example for a Doppler value;

Figure 1 1 is a range gate amplitude diagram in which a waveform of a

Radar measurement in a close range, the original window function, the adjusted window function and a constant matched window function determined therefrom are shown, the method was applied in accordance with Figures 6 and 7.

In the figures, the same components are provided with the same reference numerals.

Embodiment (s) of the invention

FIG. 1 shows a motor vehicle 10 in the form of a passenger car in front view. The motor vehicle 10 has a radar system 12. The radar system 12 is arranged by way of example in the front bumper of the motor vehicle 10. With the radar system 12, a monitored area 14 indicated in FIG. 2 in the direction of travel 16 in front of the motor vehicle 10 can be monitored for objects 18. The radar system 12 can also be arranged elsewhere on the motor vehicle 10 and aligned differently. The objects 18 may, for example, be other vehicles, persons, obstacles, road bumps, for example potholes or stones, roadway boundaries or the like. In FIG. 2, an object 18 is indicated by way of example as a checkered rectangle. FIG. 2 is otherwise merely a functional diagram of some components of the motor vehicle 10 and of the radar system 12, which does not serve the spatial orientation.

The radar system 12 is designed, for example, as a frequency-modulated continuous wave radar. Frequency-modulated continuous wave radars are also referred to in the art as FMCW (Frequency Modulated Continuous Wave) radars. With the radar system 12, for example, a distance, a direction and a speed of the object 18 relative to the motor vehicle 10 can be determined.

The radar system 12 is part of a driver assistance system 20 or may at least be connected to it. With the driver assistance system 20, for example, a driver of the motor vehicle 10 can be supported. For example, the motor vehicle 10 at least partially autonomously driving, on or off parking with the help of the driver assistance system 20. With the driver assistance system 20 driving functions of the motor vehicle 10, such as a motor control, a braking function or a steering function, influenced or hints or warning signals are issued. For this purpose, the driver assistance system 20 is connected to functional devices 22 in a regulating and / or controlling manner. FIG. 2 shows by way of example two functional devices 22. The functional devices 22 may be, for example, an engine control system, a brake system, a steering system, a chassis control or a signal output system.

The driver assistance system 20 has an electronic control device 24 with which corresponding electronic control and regulating signals can be transmitted to the functional devices 22 and / or received and processed by them.

The radar system 12 includes by way of example a transmitter 26, an electronic control and evaluation device 28 and a receiver 30.

The control and evaluation device 28 is signal-technically connected to the control device 24. With the control device 24, depending on object information of the radar system 12, driving functions of the motor vehicle 1 0 can be controlled / regulated.

For the invention, it is not essential whether electrical / electronic control and / or evaluation devices, such as the control device 24, the control and evaluation device 28, an engine control unit of the motor vehicle 10 or the like, integrated in one or more components or groups of components or at least partly realized as decentralized components or component groups.

With the transmitter 26 transmission signals 32 can be sent, for example, with constantly changing frequency in the monitoring area 14. The transmit signals 32 are reflected at the object 18 and sent back as corresponding receive signals 34 to the receiver 30 and received therewith. From the received signals 34, the distance, the direction and the speed of the object 18 relative to the motor vehicle 10 are determined with the control and evaluation device 28. The method for determining object information of objects 18 detected by the radar system 12 will be explained below by way of example.

With the control and evaluation device 28, the transmitter 26 is controlled so that transmission signals 32 are sent to the monitoring area 14. The transmission signals 32 are generated, for example, from frequency-modulated continuous-wave signals.

With the receiver 30, the echoes of the transmission signals 32 reflected at the object 18 are received as received signals 34 and, if necessary, brought into a form which can be utilized by the control / evaluation device 28.

The received signals 34 are subjected to appropriate means of the control / evaluation device 28 of a two-dimensional fast Fourier transform.

From the result of the two-dimensional discrete Fourier transformation, corresponding target signals 36a of physically present target objects and their respective amplitudes emerge from the transmission signals 32. A target object is an area of the object 18. Several target objects may originate from the same object 18 or from different objects. By reflection in the near range, which are referred to in English as "near rank leakage" (NRL), or due to side lobes of a window function explained below by strong reflections, so-called "high peaks", there is a risk that falsely so-called "ghost targets" as False detections are detected in the form of false signals 36b The essence of the invention is to suppress such false detections.

In FIGS. 4 and 5, by way of example, two target signals 36a in a range gate doppler gate matrix are indicated by a cross. Accordingly, some false signals 36b are indicated as black dots. Exemplary signal curves 39 of the result of the Fourier transformation with corresponding target signals 36a and false signals 36b are shown in FIG. 9 in a Doppler-Gate amplitude diagram and in FIG. 10 in a range-gate-amplitude diagram.

The range gate-doppler gate matrix shown in FIGS. 3 to 5 consists of cells. each characterized by a distance value and a Doppler value and having an amplitude. The amplitudes characterize the intensity of any signal 36a or 36b in the cell or, if no signal is received, the noise there. In the range gate Doppler gate matrix, the range gates correspond to so-called "range bins." The Doppler gates correspond to so-called relative speed gates or "Doppler bins." The range gate Doppler gate matrix includes, by way of example, 256 range gates and 128 Doppler gates.

In order to suppress false detections, the method described below is used, which is explained with reference to an exemplary flowchart according to FIG.

In a step 40, a primal detection threshold 42 is realized as a primal windowing function 44. The original window function 44 can either be calculated or taken from a lookup table. The lookup table can be created, for example, before the first startup of the radar system 12. The primal window function 44 may be, for example, a so-called Hamming window, a Blackman window or the like.

In FIG. 3, the original window function 44 is shown by way of example. The Ur-detection threshold 42 has an extension in Doppler direction, for example in the range gate with the distance value 128, and an extension in the direction of distance, for example, with the distance value 64. Overall, the Ur-detection threshold 42 extends approximately cross-shaped, with a maximum 46 im Center of the cross has. The course of the original detection threshold 42 in the Doppler dimension is shown in FIG. 8 in a Doppler-Gate amplitude diagram. FIG. 8 shows, by way of example, the individual phases in the adaptation of the window function in the course of the method.

In a step 48, those signals which have an amplitude above a predetermined limit value 50 are determined as the target signal 36a from the result of the Fourier transformation. The limit value 50 is indicated, for example, in FIG. 9 in a Dopplertor amplitude diagram. The limit value 50 is chosen so that strong signa- With larger amplitudes, it is most likely that they originate from real object targets. For example, if the amplitudes of the signals are given in decibels, the threshold 50 may be 60 dB.

In a step 52, the original window function 44 is normalized to one of the determined target signals 36a. The thus normalized window function 54 is shown for example in FIGS. 8 and 9.

In an optional step 56, the normalized window function 54 is subjected to an amplitude offset 58. The normalized offset function of the window is referred to below as the "normalized offset window function 60" and is shown in FIG.

In a step 62, the normalized offset window function 60 is shifted in the distance direction and in the Doppler direction so that its maximum 46 lies on the target signal 36a, as shown in FIGS. 9 and 10. FIG. 9 shows the Doppler dimension and FIG. 10 shows the distance dimension. FIGS. 9 and 10 show the phases of the window function in the course of the method, wherein the displacement of the window function was carried out in the representation of FIGS. 9 and 10 before the normalization. Therefore, the respective phases of the window function and the waveform 39 of the result of the Fourier transform are shown together.

The shifted normalized offset window function 60 is referred to below as "adapted window function 64." The curve of the adapted window function 64 forms an adapted detection threshold 66 whose maximum lies at the maximum of the used target signal 36a.

In a step 68, the adapted detection threshold 66 is compared with a shifted original detection threshold 42 of the original window function 44, the original window function 44 also having its maximum 46 being shifted towards the corresponding target signal 36a.

If it is determined in a step 70 that the adjusted detection threshold 66 is higher in amplitude than the original detection threshold 42, in a step 72 customized window function 64 used as a new window function.

Subsequently, in a step 74, all signals from the result of the Fourier transformation with the same distance value or the same Doppler value as the target signal 36a used, which lie below the adapted detection threshold 66 of the new window function, are recognized as false signals 36b and discarded.

If the check in step 70 shows that the adjusted detection threshold 66 is below the original detection threshold 42 of the shifted original window function 44, then in a step 76 the shifted original window function 44 is used as a new window function and accordingly the suppression of the false signals 36b performed in step 74.

4 shows the application of the displaced primal window function 44 to the signal course 39. In comparison, FIG. 5 shows the application of the matched window function 64 to the signal course 39. In a comparison, it can be seen that the in FIG. 4, false signals 36b having the same Doppler value or the same distance value as the target signal 36a used are suppressed with the adapted window function 64 and are therefore no longer visible in FIG. The target signal 36a used is located in the center of the cross of the displaced primal window function 44 or the adapted window function 64. By way of example, a further target signal 36a, which lies above the adapted detection threshold 66, is also recognized when using the adapted window function 64.

In a step 78, it is checked whether there is still another strong target signal 36a for which a corresponding adaptation of the original window function 44 is to take place. If so, steps 52, 56, 62, 68, 70, 72, 74, 76 and 78 are repeated for this further target signal 36a.

If it results in step 78 that no further strong target signal 36a is to be used, the method is repeated, beginning with step 48, to determine another strong target signal 36a. FIG. 7 shows, by way of example, partial steps of method step 74 from FIG. 6. These sub-steps may be performed, for example, when the signals 36 are taken from a detection list. The detection list can be generated in a manner not of further interest following a radar measurement and contain corresponding distance values, Doppler values and amplitudes of the signals.

In a step 74a, signals 36 having the same distance value as the selected target signal 36a are searched. These further signals 36 may turn out to be false signals 36b, for example in the distance dimension. These false signals 36b may result, for example, from sidelobe effects of the target signal 36a used. These further signals 36 are identified below with "Det Range Det".

In a step 74b, a shift of the original window function 44 such that its maximum 46 lies in the same Doppler range gate as the maximum of the used target signal 36a is a relative distance to the signal marked "Det Range Det" 36 calculated.

In a step 74c, the amplitude of the signal 36 labeled Det-Range-Det is compared with the adjusted detection threshold 66.

If the amplitude of the signal marked with Det-Range-Det 36 is below the adjusted detection threshold 66, in a step 74d the signal marked Det-Range-Det 36 is discarded and recognized as a false signal 36b.

Then, the process steps 74a to 74d are performed instead of the distance values for the Doppler values corresponding to the selected target signal 36a.

Subsequently, the process continues from FIG. 6 to step 68.

FIG. 11 shows a distance-gate-amplitude diagram which illustrates the use of the method for suppressing false signals 36b in the near field. provides. For example, distance values smaller than 20 are referred to as a near field. In the near field dominated by a noise effect. The Ur-detection threshold 42 is there usually too low to suppress false signals 36b. This leads in particular to stationary targets, which may have the Doppler value 65 by way of example, to false detections. These false detections are caused by the so-called Near Range Leakage (NRL).

With the method according to the invention, this NRL can be compensated. For this purpose, the adjusted detection threshold 66 for a stationary target, for example with the Doppler value 65, is predefined. The fixed, adjusted detection threshold is designated in FIG. 11 with 66a.

The NRL may be compensated for the receiver 30 by using the strong target signal method 36a as described in FIGS. 6 and 7. In this case, the target signal 36a of a main reflection for compensation can be used, which may for example come from a bumper of the vehicle 10, for example with the Doppler value 0. For this purpose, the maximum amplitude of the signals in the range gates 0 to 5 is determined. These signals result from reflections on the bumper. As a rule, the amplitude value of these signals is constant. If the amplitude of the bumper reflection is given in decibels, the amplitude may vary between about 1 dB and 2 dB. The variation of the amplitude can vary in particular with long-term measurements with the measurement duration and, for example, temperature changes.

For example, when parking, it may be helpful to be able to recognize other actual target objects in the near field. For this purpose, the maximum amplitudes in the near-field range gates can be monitored over a corresponding period of time. By correspondingly large amplitude differences or fluctuations signals with these amplitudes can be distinguished from the determined bumper reflections.

For carrying out the method of FIGS. 6 and 7 for suppressing false detections in the near field, maximum amplitude signals 36 are obtained, for example, in the first five range gates at a Doppler value of 0, for example determined and used as corresponding target signals 36a. These target signals 36a themselves are discarded as invalid since they may result from reflections on the bumper.

Subsequently, analogously to the method according to FIGS. 6 and 7, the original window function 44 is normalized on the basis of one of these target signals 36a, subjected to an amplitude offset and shifted with its maximum 46 to the rejected target signal 36a.

Analogous to the method steps 74a to 74b from FIG. 7, for the Doppler values of, for example, 0 to 32, all signals with the same distance value as the used, rejected target signal 36a are sought, labeled "Det Range Det", with the adapted detection threshold 66 and correspondingly identified as false signals 36b or discarded.

The method steps explained in connection with FIGS. 6 and 7 can also be carried out in a different order. It is also possible to combine several process steps expediently. The flowcharts of FIGS. 6 and 7 serve essentially to explain the method according to the invention by way of example.

Claims

claims

Method for suppressing false detections (36b) in the determination of object information of at least one object (18) which is detected by a radar system (12), in particular of a vehicle (10),

in which at least part of a result of a multi-dimensional discrete Fourier transformation of at least one received signal (34) of the radar system is compared with at least one adaptable detection threshold (66), and

- Those signals from the result of the Fourier transformation as false detections (36b) are marked or discarded, whose amplitudes are below the at least one detection threshold (66), characterized in that

at least one primary detection threshold (42) is realized as the original window function (44), which has a maximum (46),

directly or indirectly from the result of the Fourier transformation at least one signal is determined as the target signal (36a) whose amplitude is above a predetermined limit value (50) for target signals (36a),

the primal window function (44) is normalized with respect to the amplitude of the at least one target signal (36a) to a normalized window function (54),

the window function (54) is shifted before or after normalization in a Doppler-gate distance-gate dimension of the result of the Fourier transformation so that its maximum lies on the at least one target signal (36a),

- An adapted detection threshold (66) from the normalized and shifted, adapted window function (64) with the Ur-detection threshold (42) of the original window function (44), which with its maximum (46) to the maximum of the at least one target signal (36a). has been shifted, and possibly compared with a previous adjusted detection threshold of a previous adjusted window function, which was determined in a previous run of the method, and if the adjusted detection threshold (66) is above the shifted primary detection threshold (42) and optionally above the previous adjusted detection threshold, the adjusted detection threshold (66) for the result of the Fourier transformation with respect to the signals (36) same Doppler value and / or the same distance value as the at least one target signal (36a) is used,

otherwise the original detection threshold (42) or, if appropriate, the previous adjusted detection threshold is used.

2. The method according to claim 1, characterized in that from the result of the Fourier transform at least one signal whose amplitude is above the predetermined limit for target signals (36a) is recorded in a detection list and from this indirectly the at least one target signal (36a ) is determined.

3. The method according to claim 1 or 2, characterized in that the Ur-

Window function (44) is implemented as Cardinal sine function.

4. The method according to any one of the preceding claims, characterized in that the normalized window function (54) with an amplitude offset (58) is acted upon.

5. The method according to any one of the preceding claims, characterized in that at least part of the method for at least one further target signal (36a) is repeated.

6. The method according to any one of the preceding claims, characterized in that the

Ur window function (44) is taken from a lookup table.

7. Radar system (12), in particular of a vehicle (10) for determining at least one object information of at least one object (18),

- having at least one transmitter (26) for transmitting transmission signals (32) in a monitoring area (14),

- With at least one receiver (30) for receiving at the at least one object (18) reflected echoes of the transmission signals (32) as received signals (34) and

- With at least one control and / or evaluation device (28), wherein the at least one control and / or evaluation device (28) comprises means

for carrying out at least one multi-dimensional discrete Fourier Transformation of the received signals (34),

for comparing at least part of the result of the Fourier transformation with an adaptable detection threshold (66) and

- For identifying or discarding those signals from the result of the Fourier transformation as false detections (36b) whose amplitudes are below the detection threshold (66), characterized in that the control and / or evaluation device (28) means for carrying out the method according to the invention having.

8. Driver assistance system (20) of a vehicle (10), comprising

- At least one electronic control device (24) for controlling functional devices (22) of the vehicle (10) depending on object information, which are provided by at least one radar system (12), and

at least one radar system (12) for determining at least one object information of at least one object (18), the at least one radar system (12) having at least one transmitter (26) for transmitting transmission signals (32) into a monitoring area (14),

- At least one receiver (30) for receiving at the at least one object (18) reflected echoes of the transmission signals (32) as received signals (34) and

- At least one control and / or evaluation device (28), wherein the at least one control and / or evaluation device (28) comprises means

- For comparing at least a part of the result of the Fourier transformation with an adjustable detection threshold (66) and

for characterizing or discarding those signals from the result of the Fourier transformation as false detections (36b) whose amplitudes are below the detection threshold (66), characterized in that the control and / or evaluation device (28) has means for carrying out the invention. has the method according to the invention.