Method and apparatus for transmitting electromagnetic radiation and receiving a portion of the radiation reflected by an object

Abstract

A method and apparatus for emitting electromagnetic radiation and receiving a portion of the radiation reflected on an object are provided. The apparatus is capable of determining the current performance capabilities of its system detection. The method and apparatus have means for emitting a frequency-modulated transmission signal, the transmission signal having at least two signal sequences that each have ramps with successive gaps during the frequency change and are interleaved with each other with a predetermined time offset. A mixer for mixing the frequency-modulated transmission signal with the received signal, an analog-to-digital converter for digitizing the mixed product of the mixer, means for transforming the digitized signal into a two-dimensional spectrum, means for identifying phase noise in each of the two-dimensional spectra, a setting means that, in a first step, compares the phase change of the received signal on all two-dimensional spectra with a pre-calculated model, and in a second step, determines the cause of the phase noise by means of one or more predetermined criteria.

Description

Field of the Invention

[0001] The present invention relates to a method and a device for transmitting electromagnetic radiation and receiving a part of the radiation reflected at an object, which can determine the current performance capabilities of its system detection In such a way that there is provided a device for transmitting a frequency-modulated signal having at least two signal sequences, each of the at least two signal sequences having successively following ramps during the frequency change, with a gap existing between the ramps, wherein the at least two signal sequences are interleaved with a pre-given time offset such that the first ramp of each of the at least two signal sequences is output before the second ramp of at least one of the at least two signal sequences is output. The device further has a mixer for mixing the frequency-modulated transmitted signal with the signal received by at least one antenna, an analog / digital converter for digitizing the mixing product of the mixer, a device for transforming the digitized signal of each of the at least two signal sequences into a two-dimensional spectrum, and a device for identifying the phase noise in each of the two-dimensional spectra. Therein, a device is provided in which, in a first step, the phase change of the received signal on all two-dimensional spectra is compared with a pre-calculated model and, in a second step, the cause of the phase noise is determined by means of one or more pre-determined criteria Background Art

[0002] A method for determining the distance and relative speed of a plurality of simultaneously located objects from an FMCW radar is known from DE 10 2012 220 879 A1. In this method, the frequency of the transmitted signal is modulated in the form of periodically repeated ramps. The transmitted signal is mixed with the received signal to form an intermediate frequency signal, and the phase change of the intermediate frequency signal is analyzed ramp by ramp to determine the distance and / or relative speed of the object. The modulation pattern includes at least two ramps, the at least two ramps differing only in a fixed frequency offset and following each other at a determined time interval, and a more precise approximation of the object distance is calculated for these two ramps based on the phase difference of the intermediate frequency signal Summary of the Invention

[0003] The core of the present invention lies in explaining a method and a device by means of which it can be recognized whether there is excessive phase noise in a determined spectral region, such that within a determined distance limit, the measurement accuracy of the system is affected, or the detection capability of the system is reduced due to a radome coating. According to the present invention, this is achieved by the features according to the present invention. Advantageous extensions and configurations result from the preferred embodiments

[0004] According to the present invention, strong phase noise should be recognized in a radar sensor by means of the present invention. The radar sensor uses a transmission signal composed of at least two signal sequences. According to the received signal generated by the ramp-shaped transmission signal, the distance and relative speed of the detected object can be obtained through the phase difference of at least two ramp sequences. If more than two (for example, three) signal sequences are used, in addition, the speed quality can be obtained, that is, a measure of the probability that the obtained values actually correspond to the true distance and the true relative speed and are not distorted due to phase noise. The transfer of the present invention from two signal sequences to three signal sequences is not a problem for those skilled in the art and can be within the technical scope of those skilled in the art. In addition, two ramp sequences are shown within the scope of the described embodiment, but they should be considered as examples. As shown in the figure, the time offset between the individual ramp sequences is usually not equidistant, so that the start time of the first ramp of the second ramp sequence usually does not exactly fall on the end point of the first ramp of the first ramp sequence. It is also possible to set a time gap between the end of a ramp and the start of the subsequent ramp, which results in a certain dead time (Totzeit) of the transmission signal.

[0005] In addition, the time offset of the individual ramp sequences may be so large that ambiguity (Mehrdeutigkeit) occurs when determining the relative speed or detecting an object. The ambiguity is resolved by means of the phase relationship of a single sequence. Here, it is necessary to study and track multiple speed hypotheses within the scope of object analysis and then discard several of these speed hypotheses in further methods. Therefore, the comparison with the model mentioned in the present invention consists of multiple individual comparisons or correlations and subsequent maximum value search for different correlation values.

[0006] Advantageously, it is provided that the current performance capabilities of the radar system include recognizing sensor blindness (especially due to an absorptive radar dome coating), and / or recognizing the weaker detection ability for weak targets when detecting stronger targets simultaneously. In the context of the present invention, the terms "weak target" and "strong target" are used for radar reflections on an object, where in the case of a "weak target", only less signal power is reflected, while in the case of a "strong target", a lot of signal power is reflected back to the receiving antenna. Depending on the amount of signal power reflected back, phase noise can have a stronger or weaker impact on object detection. In the case of simultaneous strong and weak detections, the ratio of the phase noise measured especially in the area of weak detection to the received power is much larger than the phase noise in the area of strong target detection, because in the area of strong target detection, the phase noise can even be ignored due to the higher received power.

[0007] Furthermore, it is advantageous that the pre-computed model pre-gives an expected phase difference for each point in the two-dimensional spectrum and compares the measured phase difference with the expected value. For example, by using the discrete two-dimensional Fourier transform, a two-dimensional spectrum of its own is generated for each received ramp of the transmitted ramp-shaped signal, where object detection can be obtained through the phase difference. Here, the pre-computed model obtains the value of the expected phase difference (which can be expected according to known object detection) for each point in the two-dimensional spectrum. These expected phase differences obtained using the model are compared with the measured phase differences to obtain phase noise and infer system degradation.

[0008] Furthermore, it is advantageously that the comparison of the phase difference between the measured value and the expected value is obtained by correlation. For this purpose, for each expected phase value of the model in the two-dimensional spectrum, correlation is performed with the corresponding point of the measured two-dimensional spectrum, and it is inferred according to the magnitude of the correlation value whether the measured value is roughly consistent with the value calculated using the model or deviates too far.

[0009] Furthermore, it is advantageously that there is phase noise when the deviation between the measured phase difference value and the expected value is greater than the allowed threshold. Here, it is particularly advantageous that the allowed threshold can be determined for each point in the two-dimensional spectrum, and this threshold depends on the signal-to-noise ratio of each point in the two-dimensional spectrum. Therefore, its own threshold can be determined for each point in the two-dimensional spectrum, and this threshold is derived from the corresponding signal-to-noise ratio of each point in the two-dimensional spectrum.

[0010] Furthermore, it is advantageous that the comparison of the phase difference is only performed in the following region in the two-dimensional spectrum: the region where an object is detected. This is advantageous because computing performance can be saved thereby, because it is not necessary to perform analysis processing on the following region: the region where no object is detected and no object is expected in the current measurement period.

[0011] Advantageously, one or more criteria (based on which the cause of the phase noise is determined) are the number of detections with low velocity quality, or the total number of detections, or the maximum signal-to-noise ratio of all valid targets, or the relative positions of detections with low velocity quality with respect to each other and with respect to the strongest valid target, or any combination of these possibilities. For this purpose, one or more of these criteria can be analyzed and processed during a measurement cycle, and thus the cause of the phase noise can be inferred, and thus the cause of system degradation can be inferred. Here, the number of detections with low velocity quality is the number of radar reflections on one or more objects, where the radar reflections only use detections with low velocity quality (i.e., the probability that the measured velocity value is not very accurate). Additionally, the total number of detections can be analyzed and processed, i.e., the number of radar reflection points on one or more objects. The criterion of the maximum signal-to-noise ratio of all valid targets is another criterion, where objects that can be considered as actually existing targets are evaluated as valid targets because they meet certain quality criteria, such as detections in a previous measurement cycle, having high velocity quality, or sufficiently high backscatter power.

[0012] Furthermore, other criteria for the relative positions of detections with low velocity quality with respect to each other and with respect to the strongest valid target are the analysis and processing of detections, i.e., radar reflections on objects strongly caused by their weak received power, where the detections in the two-dimensional spectrum are analyzed and processed in terms of the distribution of positions and the following is analyzed and processed: whether there are strong targets near these positions of the detections in the two-dimensional spectrum that have an adverse effect on weak targets.

[0013] Advantageously, the following regions of the spectral region are marked as unreliable for identifying absorptive blindness: in which regions an increase in phase noise is determined. Advantageously, when a decrease in detection performance, especially for weaker targets, is identified, driver assistance functions subordinate to these determined interval regions of the sensor are provided in the determined interval regions of the sensor. If spectral regions in the two-dimensional spectrum are determined to be unreliable, the interval regions of the sensor are inferred from the positions of these spectral regions in the two-dimensional spectrum, and these interval regions of the sensor are also marked as unreliable regions. Driver assistance functions subordinate to such unreliable interval regions can be provided - such as ACC regulation, automatic emergency braking function, automatic emergency avoidance function, or a fusion function, where the fusion function fuses objects identified by different sensors - to improve the performance and reliability of the functions.

[0014] Furthermore, it is advantageous to distinguish between detections with micro-Doppler effects and true phase noise in such a way that the detections with low velocity quality are distinguished according to their relative positions with respect to one another and according to their relative positions with respect to the strongest valid target. Objects with micro-Doppler effects are those objects in which object parts (e.g., rotating wheels on a moving car or rotating pedals on a bicycle) move with a relative velocity with respect to the total velocity of the object, broadening the width of the detections in their spectra, however not due to phase noise, but due to the measured micro-Doppler effect.

[0015] Furthermore, it is advantageously provided that the two-dimensional spectrum is a velocity-bin spectrum.

[0016] Furthermore, it is provided that device features are similarly generated corresponding to the described method features. The method can be implemented, for example, in the form of software, hardware, or a combination of software and hardware, e.g., in a control device. The solution proposed here also implements driver assistance functions, such as distance regulation, emergency braking functions, or emergency avoidance functions, which are configured to execute, control, or implement the steps of a variant of the method proposed here in a corresponding device.

[0017] The driver assistance function can be an electrical device that has at least one computing unit for processing signals or data, at least one storage unit for storing signals or data, and at least one interface and / or communication interface for reading or outputting data embedded in a communication protocol. The computing unit can be, for example, a signal processor, a so-called system ASIC, or a microcontrol device, which is used to process sensor signals and output data signals according to the sensor signals. The storage unit can be, for example, a flash memory, an EPROM, or a magnetic storage unit.

[0018] Also advantageous is a computer program product or computer program with program code that can be stored on a machine-readable carrier or storage medium (e.g., semiconductor memory, hard disk memory, or optical memory) and is used to execute, implement, and / or control the steps of the method according to one of the above-described embodiments, especially when the program product or program is implemented on a computer or a programmable control device or a similar device. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Embodiments of the present invention are described below with reference to the drawings. The drawings show:

[0020] Figure 1 A schematic block diagram showing a device or a method according to the present invention;

[0021] Figure 2 A three-part diagram exemplarily showing a frequency-modulated transmission signal composed of at least two signal sequences;

[0022] Figure 3 An exemplary diagram showing a noise spectrum;

[0023] Figure 4 An exemplary representation of a two-dimensional spectrum is shown with a representation of unreliable regions in the two-dimensional spectrum. DETAILED DESCRIPTION

[0024] Figure 1 A schematic block diagram of a device according to the invention or a method according to the invention for transmitting electromagnetic radiation and receiving a portion of the radiation reflected by an object is shown. An antenna 1 can be seen, which in the example shown is operated as a monostatic antenna, i.e. can both transmit and receive. Alternatively, the invention can also be implemented in a bistatic system by providing separate antennas for transmitting and receiving electromagnetic radiation.

[0025] For operation, the oscillator 7 is operated in such a way that a signal is provided at the carrier frequency of the device. For this purpose, a signal of the oscillator control device 6 can be provided to the oscillator 7. Figure 2 As shown, the oscillator control device 6 can generate the generated frequency in this way, for example. Since the phase differences between the ramps of different signal sequences are evaluated according to the invention to determine the distance and / or relative speed of the detected object, it is necessary that the oscillator control device 6 outputs corresponding control signals to an oscillator 7 or to a plurality of oscillators 7 so that a frequency corresponding to the detected object is provided. Figure 2 The transmission signal generated by means of the oscillator 7 is fed to the mixer 8, which also serves as a transmit and receive duplexer and passes the transmission signal on to the antenna 1.

[0026] The antenna 1 emits an electromagnetic transmission signal 3, which in normal operation penetrates the radome 2 and has the task of detecting objects in the sensor's surroundings. Objects in the sensor's surroundings reflect the transmission radiation 3 back to the transmitter, which, after passing through the radome 2 again, is received by the transmission and reception antenna 1 as reception radiation 5. The reception signal received by the antenna 1 is fed to a mixer 8, in which it is mixed with the transmission signal and demodulated. The mixer 8 generates an intermediate frequency signal, which is output to an analog / digital converter 9 connected downstream.

[0027] After the intermediate frequency signal is digitized in the analog / digital converter 9, it is subjected to a device 10 for Fourier transformation (especially discrete and two-dimensional Fourier transformation), which then outputs a spectrum or multiple two-dimensional spectra, which are further processed. In this case, a dedicated two-dimensional spectrum is generated for each signal sequence 20, 23.

[0028] The radome 2 can for example be the covering device of the device according to the invention, which covering device protects the components from weather influences and mechanical influences. It can also be envisaged that the radome 2 is configured in a lens shape and thus additionally has the property of focusing for the transmitted and received electromagnetic radiations 3, 5 as well.

[0029] If the vehicle is contaminated during its driving operation or the vehicle operates in rainy or snowy weather, the absorbent coating 4 or the coating 4 that performs absorption can adhere to the sensor radome 2, thereby absorbing the transmitted transmission radiation and the received reception radiation and converting them into loss heat within the coating. Since almost no reflected signal is generated by the absorbent coating 4, it is difficult to identify the absorbent coating 4 on the radome surface 2, such that in further operation, the sensor may become blind without noticing this. Similarly, depending on the constellation of the detected objects, the so-called weak objects detected in the spectrum near the so-called strong objects may also have strong noise, and these phase noises make it difficult to accurately determine the distance and relative speed of the objects. Here, a strong object is a reflecting object that reflects a high received power back to the receiving antenna, and a weak object is a reflecting object that reflects only a small amount of received power back to the receiving antenna. This means that although there are objects in the surrounding environment and the functional mode of the sensor conforms to expectations, the device does not receive or hardly receives a reception signal. In order to still be able to identify the absorbent radome coating 4 or the objects covered by phase noise, the two-dimensional velocity-distance spectrum output by the device 10 is further analyzed. For this purpose, correlation is performed in the first step 112. In order to perform correlation in the correlator 11, the data of a pre-calculated model is provided to the correlator 11. Such a two-dimensional pre-calculated model is used to calculate the phase noise for each point of the distance-velocity spectrum for the expected (which can be expected according to the signal-to-noise ratio of the currently detected objects and the respective positions of the two-dimensional spectrum). The velocity quality is also taken into account in these pre-calculated models, where the velocity quality indicates the probability that the measured phase difference is consistent with the phase difference from the model and thus corresponds to the actual target. These values pre-calculated according to the noise model 12 are correlated with the measured two-dimensional spectrum by means of the correlator 11 and correlation values are formed, which indicate whether the measured phase noise is consistent with the expected phase noise. These correlation values are further transmitted to another device 13 for determining the cause of the noise, in which the cause of the phase noise is determined for the regions where unexpectedly high phase noise is determined by means of different criteria. For this purpose, various criteria 14 are analyzed in the device, such as the number of detections with low velocity quality or the total number of detections in the current or previous measurement cycles. Other criteria 14 for determining the cause of the phase noise can be the maximum signal-to-noise ratio of all valid targets, i.e., all objects detected and verified as real targets in the previous measurement cycle. Other criteria 14 for determining the cause of the phase noise are the positions of the detections with low velocity quality in the two-dimensional spectrum, where the positions of these detections relative to each other and the positions of the detections with low velocity quality relative to the strongest valid target are analyzed. Here, the distances of the detections in the spectrum are analyzed in the distance dimension, or analyzed in the relative velocity dimension, or analyzed in a combination of both.If a criterion 14 for the cause of phase noise is determined in the device 13, the determined interval regions can be identified as unreliable measurement regions, and for example, the analysis of the object detection to be processed can be prevented in these regions or carried out by other methods. Thus, the device for determining the cause of the noise can provide an output signal 15, which is provided to the subordinate driver assistance functions, such as interval adjustment, adaptive speed adjustment, automatic emergency braking function, automatic avoidance function or other safety functions and assistance functions, or for the fusion of objects identified by different sensors. Thereby, the objects in the following regions can be evaluated accordingly: the measured detection of the region is severely affected by phase noise.

[0030] In Figure 2 FIG. shows an exemplary transmission sequence of the transmission signal according to the invention. Thus, in the attached Figure 2 FIG. a shows a first ramp 20 of at least two signal sequences. The time axis 21 can be seen, on which the frequency axis 22 of the first ramp is plotted. Exemplarily, the instants t1, t2 to t5 are plotted on the time axis, which are shown equidistantly. However, within the scope of the present invention, these instants do not have to be equidistant, and these regions do not have to be directly connected to each other, such that there may also be a dead time during the transition from one ramp to the next ramp, during which no transmission signal is transmitted. The first ramp 27 can be seen, which shows a linearly increasing frequency f1(t). In the following time period, there is no first ramp signal between t2 and t3. In the interval immediately following between t3 and t4, a ramp 28 is linearly generated, which is shown in the same way as the ramp 27. According to the invention, the ramp 28 can have a different slope, a different length or different frame values. In the attached Figure 2 FIG. b of the drawing, a second ramp signal 23 of at least two signal sequences is plotted. The time axis 21 is shown again, which represents the instants t1 to t5. The frequency axis 24 of the second ramp is plotted on the time axis 21 as the signal f2(t). In the time interval between t1 and t2 (during which the first ramp 27 generates a signal), no signal is generated by the second signal sequence 23. In the subsequent section between t2 and t3 (during which the first transmission sequence 20 does not output a signal), a linearly increasing frequency ramp 30 is generated. The frequency ramp 30 can have the same start and end frequencies f2(t) as the Figure 2 ramp 27 or 28 in FIG. a, but other frequency values can also be used for this.

[0031] In Figure 2 FIG. c shows Figure 2a common signal 25 of at least two signal sequences 20 and 23 of a and 2b, in such a way that: the first ramps 27, 28, 29 and the second ramps 30, 31 are combined with each other. As already described, the first ramps 27, 28, 29 and the second ramps 30, 31 do not have to have equidistant times t1 to t5, nor do they have to have the same start frequency and end frequency, so that the two ramps can also be significantly different from each other. When using two sequences, the object, its interval and relative velocity are obtained by changing the phase difference between the two received signals. The velocity quality cannot be obtained here. If an additional third transmission sequence is used instead of the two shown transmission sequences 20, 23, the phase difference system will be overdetermined, and the velocity quality can be calculated, which describes the probability that the measured value may be consistent with the actual value.

[0032] In Figure 3 the spectrum 35 of the phase noise is shown. These spectra show the frequency axis 36 on the abscissa, on which the noise power P is plotted with the help of the ordinate axis 37. In this exemplary graph, a first curve 38 is shown, which shows the thermal noise without phase noise. Another curve 39 is plotted above it, which shows the estimated noise level. In addition, a third curve 40 is plotted, which extends above the two curves 38 and 39. This other curve 40 presents the maximum noise that appears, which consists of phase noise and thermal noise. This curve 40 can be permanently stored in the system and depends on the equipment used. For example, considering additional tolerances, this curve 40 can be used as a decision threshold: whether the currently analyzed frequency region is an unreliable region or can be estimated as reliable. The difference between the curve 39 of the measured noise and the curve 40 of the estimated maximum noise can be used as a decision criterion here: whether the phase noise is very significant and thus there is a region 43. If the phase noise is very significant, it can be inferred that the measured value is unreliable. This region is marked by the lower limit frequency 41 and the upper limit frequency 42, and delimits the unreliable spectral region 43.

[0033] In Figure 4 a two-dimensional velocity-interval spectrum 44 is plotted in the graph, which shows discrete interval values k (also called frequency bins) in the horizontal dimension and discrete relative velocity values (so-called relative velocity bins) in the vertical dimension I. Such a two-dimensional velocity-interval spectrum 44 is generated for each of the two transmission sequences 20, 23 and is analyzed and processed according to the present invention. By Figure 3The area obtained can infer an area with reduced detection performance. The reduced detection performance may be due to unreliable detection and / or may also be caused by poor detection. In the case of unreliable detection, the measured values are mixed with strong noise, making the detection have increased uncertainty, and thus reducing the probability of correct detection compared to non-unreliable (nicht- ) detection.

[0034] In the case of poor detection, only a small amount of electromagnetic power is received as the received signal 5, which may be due to the low reflection characteristics of the reflection points on the object or to strong attenuation on the signal path. The received power may even be so low that it is below the estimated noise level. In this case, the reflection points of the object can no longer be detected.

[0035] In both cases, the unreliable area can be limited by interval values or interval bins, which describe the unreliable area in the interval direction k. For this purpose, the lower limit interval 47 and the upper limit interval 48 of the unreliable distance area 49 can be obtained from the unreliable area 43. In this way, the output signal 15 can be transmitted to these unreliable areas 49, and the object detections in these unreliable areas 49 can be analyzed and processed only cautiously in other driver assistance functions or vehicle safety functions, because these object detections have large measurement uncertainties, or it is difficult to detect weak targets there.

Claims

1. A method for determining the current performance capabilities of a radar system, the radar system having means for transmitting electromagnetic radiation and receiving a portion of the radiation reflected at an object, the method using a frequency-modulated transmission signal, the transmission signal having at least two signal sequences (20, 23), the at least two signal sequences each having successively following ramps (27, 28, 29, 30, 31) during the frequency variation, with gaps between the ramps, wherein, the at least two signal sequences (20, 23) are interleaved with a pre-given time offset such that a first ramp (27, 28, 29) of each of the at least two signal sequences (20, 23) is output before a second ramp (30, 31) of one of the at least two signal sequences (20, 23) is output, wherein a mixer (8) mixes the frequency-modulated transmission signal with the signal received by at least one antenna (1), wherein an analog / digital conversion (9) is performed on the mixing product of the mixer (8), the digitalized signal of each of the at least two signal sequences (20, 23) is transformed into a two-dimensional spectrum (44), and phase noise is identified in each of the two-dimensional spectra, characterized in that, in a first step (11), the phase change of the received signal over all two-dimensional spectra is compared with a pre-calculated model (12), and in a second step (13), the cause of the phase noise is determined by means of one or more pre-determined criteria (14).

2. The method according to claim 1, characterized in that, the current performance capabilities of the radar system include identifying sensor blindness and / or identifying a weaker detection capability for weak targets when simultaneously detecting strong targets.

3. The method according to claim 1 or 2, characterized in that, the pre-calculated model (12) pre-gives an expected phase difference for each point of the two-dimensional spectrum (44), and the measured phase difference is compared with the expected value.

4. The method according to claim 3, characterized in that, the comparison of the phase difference formed by the measured value and the expected value is obtained by means of correlation.

5. The method according to claim 3, characterized in that, when the deviation of the value of the measured phase difference from the expected value is greater than an allowed threshold (39), there is phase noise.

6. The method according to claim 5, characterized in that, an allowed threshold (39) is determined for each point of the two-dimensional spectrum (44), and the threshold (39) depends on the signal-to-noise ratio of each point of the two-dimensional spectrum (44).

7. The method according to claim 3, characterized in that, the comparison of the phase difference is only performed in the following regions of the two-dimensional spectrum (44): regions in which an object is detected.

8. The method according to claim 1, characterized in that one or more of the following criteria (14), according to which the cause of the phase noise is determined: during one period - the number of detections with low velocity quality; - Total number of detections; - Maximum signal-to-noise ratio of all valid targets; - Relative positions of the detections with low velocity quality to each other and to the position of the strongest valid target, - Or any combination of the above.

9. The method according to claim 1 or 2, characterized in that the following regions (41, 42) of the spectral region (35) are marked as unreliable for identifying absorptive blindness: in which regions an increase in phase noise (40) is determined.

10. The method according to claim 1 or 2, characterized in that when a reduction in detection performance is identified, a driver assistance function subordinate to the determined interval regions (47, 48) of the sensor is provided in the determined interval regions (47, 48) of the sensor.

11. The method according to claim 1 or 2, characterized in that a distinction is made between detections with a micro-Doppler effect and "real" phase noise based on the relative positions of the detections with low velocity quality to each other and based on the relative position to the strongest valid target.

12. The method according to claim 1 or 2, characterized in that the two-dimensional spectrum (44) is a velocity-interval spectrum.

13. The method according to claim 2, characterized in that the sensor blindness is caused by an absorptive radome coating (4).

14. The method according to claim 10, characterized in that when a reduction in detection performance is identified for a weaker target, a driver assistance function subordinate to the determined interval regions (47, 48) of the sensor is provided in the determined interval regions (47, 48) of the sensor.

15. A computer program product, the computer program product being configured to implement, realize, and / or control the method according to any one of claims 1 to 14.

16. A machine-readable storage medium, on which the computer program according to claim 15 is stored.

17. A device for emitting electromagnetic radiation and receiving a portion of the radiation reflected on an object, the device being able to determine the current performance capabilities of the system detections of the device, the device having at least one antenna (1) for emitting a frequency-modulated transmission signal, the transmission signal having at least two signal sequences (20, 23), the at least two signal sequences each having successive ramps (27, 28, 29, 30, 31) during the frequency change, with gaps between the ramps, wherein the at least two signal sequences are interleaved with a pre-given time offset such that the first ramp (27, 28, 29) of each of the at least two signal sequences (20, 23) is output before the second ramp (30, 31) of one of the at least two signal sequences (20, 23) is output; a mixer (8) for mixing the frequency-modulated transmission signal with the signal received by the at least one antenna (1); an analog-to-digital converter (9) for digitizing the mixing product of the mixer (8); Apparatus for transforming a digitized signal of each of the at least two signal sequences (20, 23) into a two-dimensional spectrum (44); Apparatus for identifying phase noise in each of the two-dimensional spectra (44); Characterized in that there is provided the following apparatus: in the apparatus, in a first step (11), the phase change of the received signal on all the two-dimensional spectra (44) is compared with a pre-calculated model (12), and in a second step (13), the cause of the phase noise is determined by means of one or more predetermined criteria (14).

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