METHOD FOR EVALUATING OVERLAPPING TARGETS

Abstract

A method for evaluating overlapping targets in a two-dimensional radar spectrum, wherein the following steps are carried out: providing the two-dimensional radar spectrum, selecting at least one region of interest as an input signal from the spectrum, and performing an evaluation of the input signal to determine an information about the overlapping targets, wherein the evaluation is specific for a model order selection method.

Claims

1. A method for evaluating overlapping targets in a two-dimensional radar spectrum, the method comprising: providing the two-dimensional radar spectrum; selecting at least one region of interest as an input signal from the spectrum; performing an evaluation of the input signal to determine an information about the overlapping targets, the evaluation being specific for a model order selection method.

2. The method according to claim 1, wherein the evaluation is performed by using a two-dimensional model order selection method or an ESTER or SAMOS method, wherein the model order selection method is specifically adapted or exclusively to a two-dimensional form of the input signal.

3. The method according to claim 1, wherein the determined information about the overlapping targets is an estimated number of the overlapping targets, and after the step of performing the evaluation, the following step is carried out: performing a high-resolution algorithm using the estimated number of the overlapping targets and the input signal to estimate a parameter of the overlapping targets, particularly a range and/or a relative radial velocity and/or a complex amplitude of the overlapping targets.

4. The method according to claim 1, wherein after the step of providing and before the step of selecting, at least the following is performed: detecting of peaks in the provided spectrum; wherein the step of selecting comprises selecting the at least one region of interest depending on at least one of the detected peaks, wherein each of the at least one region of interest is being selected around one different of the detected peaks each providing one input signal, wherein for every of the provided at least one input signal the evaluation is performed to determine the information about the overlapping targets for each of the at least one input signal, and wherein the overlapping targets for one respective input signal correspond to the one peak of this input signal.

5. The method according to claim 4, wherein, for providing each of the at least one input signal, a two-dimensional spectrum processing or a transform or a two-dimensional inverse finite Fourier transform is applied to each of the at least one region of interest to determine at least one respective transformed region of interest.

6. The method according to claim 5, wherein after the two-dimensional spectrum processing for each of the at least one respective transformed region of interest, a windowing compensation is performed for a determination of each of the at least one input signal.

7. The method according to claim 1, wherein the evaluation comprises the determination of a Hankel block matrix and/or the determination of a singular value decomposition of the Hankel block matrix from the input signal.

8. A radar system for evaluating overlapping targets in a two-dimensional radar spectrum, the radar system comprising an evaluation unit adapted to perform the steps of: providing the two-dimensional radar spectrum; selecting at least one region of interest as an input signal from the spectrum; and performing an evaluation of the input signal to determine an information about the overlapping targets, wherein the evaluation is specific for a model order selection method.

9. A computer program comprising instructions, which, when the computer program is executed by a computer, causes the computer to carry out the steps of the method according to claim 1.

10. A computer readable medium having stored thereon the computer program according to claim 9.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0074] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

[0075] FIG. 1 is a schematic visualisation of a method according to the invention and a radar system according to the invention,

[0076] FIG. 2 is a further schematic visualisation of a method according to the invention,

[0077] FIG. 3 is a further schematic visualisation of a method according to the invention.

DETAILED DESCRIPTION

[0078] FIG. 1 shows a radar system 1 for a visualisation of a method according to the invention. The system 1 can comprise an evaluation unit 2, which can be embodied as a computer 2 or processor 2 or the like. Furthermore, a data storage unit 3 of the system 1 can be provided, particularly integrated into the evaluation unit 2. The data storage unit 3 can be embodied as a computer readable medium according to the invention so that a computer program according to the invention is stored thereon. This allows the evaluation unit 2 to read the computer program from the data storage unit 3 for executing the computer program and thereby performing the method according to the invention. Therefore, the evaluation unit 2 can be connected to another component of the radar system 1, like an analog-to-digital converter or another processor of the system 1, for receiving a signal specific for a detection of the radar system 1. Afterwards, this signal can be processed for providing a two-dimensional radar spectrum 100.

[0079] With reference to FIGS. 2 and 3, a method according to the invention is further illustrated. The method according to the invention can serve for evaluating overlapping targets 110 in a two-dimensional radar spectrum 100. Therefore, at first a providing 10 the two-dimensional radar spectrum 100 can be performed. This is exemplarily described in more detail in the following.

[0080] The radar system 1 can particularly have at least one sensor (e. g. either 24 GHz or 77 GHz) that utilize the concept of fast chirp sequences as transmit signal modulation schema to determine the parameters of targets, i. e. range, relative velocity and angle. It can be provided that in every measurement cycle, this modulation schema sequentially transmits N frequency chirps within the duration T.sub.1, and the duration of a chirp is then T.sub.1/N. The current transmit frequency of the chirp is linearly changed within the transmit bandwidth B (linear frequency modulation). The processing of receive signal data can be carried out adjacently after T.sub.1 in a period of T.sub.2-T.sub.1, such that the whole measurement cycle duration comes up to T.sub.2.

[0081] Furthermore, the radar system 1 can advantageously provide at least one transmit antenna and up to three receive antenna with which a quadrature demodulator is applied to at least one receive antenna. The receive antennas can be arranged equidistantly with a distance d.sub.R in x-direction. The transmit signal will be backscattered to a radar sensor of the radar system 1 if it reaches an object. This reflected signal can firstly be demodulated into baseband at the receiver and subsequently be sampled by an analog-to-digital converter (ADC). Till the time point these data of all receive antennas is stored e. g. in 3 blocks, each of which is an ADC data matrix with M times N (M samples per chirp, and N chirps). The ADC data matrix obtained by the quadrature demodulator contains complex valued data. Afterwards, these 2D-baseband ADC signals are transformed into the 2D frequency domain by 2D discrete Fourier transform. The resulting signals form a two-dimensional spectrum 100 that represents a superposition of the reflection of relevant targets and unexpected signals, which are for instance termed as noise. FIG. 2 shows a respective two-dimensional spectrum 100 resulting from the 2D Fourier transform with two frequencies f1 and f2. As shown by way of example, two relevant targets are detected, and each is highlighted as a peak 130.

[0082] The peak parameters, i. e., two basic frequencies f1 (1st dimension) and f2 (2nd dimension), can be particularly extracted through a peak detection algorithm. The number of targets can be estimated as the number peaks 130 in the 2D spectrum 100. The frequency f1 can be exclusively dependent on the distance R of a target and the frequency f2 can be dependent on the relative speed v of this target corresponding to the peak 130.

[0083] Due to the constraints on available bandwidth and memory size of the embedded systems in the radar sensor of the radar system 1, it is possible that the Fourier-based estimation cannot provide the necessary fine range and Doppler resolutions for a specific use cases. As mentioned before, each peak 130 in the 2-D spectrum 100 is assumed to be a single point target. Whereas, in many critical use cases, this assumption could be violated while multiple targets could share similar range and relative velocities and partially overlap with each other in the 2D spectrum 100. After performing a peak detection 15, this can result in multiple overlapping targets 110 represented all by a single peak 130. Therefore, conventional peak detection algorithms are not able to resolve the multiple targets and therefore interpret a single peak 130 only as a single target. However, for a correct interpretation of the spectrum 100 more than one target must be evaluated for this peak 130. A method according to the invention can preferably be used to overcome this issue.

[0084] For this purpose, according to FIG. 2, firstly a region of interest 120 is selected around a single detected peak 130. At this stage, it is not known if this peak 130 comprise more than one single target. In other words, the following steps of the method according to the invention serve to determine if this specific peak 130 within the region of interest 120 comprises overlapping targets 110. More specifically, also the number of overlapping targets 110 can be determined.

[0085] After the selecting 20 of the at least one region of interest 120 as an input signal 105 from the spectrum 100 has been performed, particularly with a predefined pixel region around the peak 130, an evaluation 200 of the input signal 105 can be performed to determine an information about the overlapping targets 110 (like the number of overlapping targets 110). This evaluation 200 can be specific for a model order selection method.

[0086] According to FIG. 3, after performing the peak detection 15 and the selecting 20 of the at least one region of interest 120, for providing one input signal 105 for each region of interest 120 a two-dimensional spectrum processing 50, particularly a transform, preferably a two-dimensional inverse finite Fourier transform, can be applied to each region of interest 120 to determine at least one respective transformed region of interest 120. Furthermore, after the two-dimensional spectrum processing 50 for each of the at least one respective transformed region of interest 120 a windowing compensation 60 can be performed for a determination of each of the at least one input signal 105. The evaluation 200 can then be carried out using the input signal 105, to determine the parameter about the overlapping targets 110, like a number of overlapping targets 110 represented by the single peak 130. This result of the evaluation 200 can further be used as input for high-resolution algorithm which allows to determine further parameters of each of the overlapping targets 110.

[0087] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.