METHOD FOR DETERMINING ANGLE INFORMATION

Abstract

A method for determining angle information about a direction of a target object in a radar system for a vehicle, wherein the following steps are performed: providing a first item of sensing information for a first modulation mode of the radar system, providing at least one second item of sensing information for at least a second modulation mode of the radar system, and combining the sensing information for the different modulation modes in order to perform the determination of the angle information on the basis of the combined sensing information.

Claims

1. A method for determining angle information about a direction of a target object in a radar system for a vehicle, the method comprising: providing a first item of sensing information for a first modulation mode of the radar system; providing at least one second item of sensing information for at least a second modulation mode of the radar system; and combining the first item and second item sensing information for the different modulation modes to perform a determination of the angle information on the basis of the combined sensing information.

2. The method according to claim 1, wherein the first and the at least one second sensing information items each have at least two component signals, wherein the at least two component signals are specific to at least two radar signals that are emitted in accordance with an identical modulation mode and are reflected at the same target object and whose signal transit times differ as a function of the direction of the target object.

3. The method according to claim 2, wherein the at least two radar signals are emitted or received by different antennas of a radar sensor of the radar system so that the different transit times are a function of the direction of the target object and so that a first component signal of the at least two component signals is specific to a first antenna of the different antennas and a second component signal of the at least two component signals is specific to a second antenna of the different antennas.

4. The method according to claim 2, wherein a radar sensor of the radar system has at least two transmitting antennas that are spaced apart from one another and at least one receiving antenna so that the radar signals for an identical modulation mode are emitted through the at least two transmitting antennas and/or wherein the radar sensor has at least two receiving antennas that are spaced apart from one another and at least one transmitting antenna so that the radar signals for an identical modulation mode are received by the at least two receiving antennas in order to obtain different transit times of the radar signals to determine the angle information as a function of the direction of the target object.

5. The method according to claim 4, wherein the following steps are performed by the radar sensor of the radar system: emitting, by the at least one transmitting antenna of the radar sensor, at least one first radar signal in accordance with the first modulation mode; emitting, by the at least one transmitting antenna, at least one second radar signal in accordance with the second modulation mode; receiving, by the at least one receiving antenna of the radar sensor, the first radar signal for the first modulation mode reflected at the target object and delayed by the transit time; and receiving, by the at least one receiving antenna of the radar sensor, the second radar signal for the second modulation mode reflected at the target object and delayed by the transit time.

6. The method according to claim 5, wherein the first sensing information is specific to the at least one received first radar signal and the second sensing information is specific to the at least one received second radar signal.

7. The method according to claim 2, wherein the following step is performed before the combining: recognizing the target object in the items of sensing information in order to select, from the sensing information items for the different modulation modes, those component signals in each case that have information about the same target object.

8. The method according to claim 7, wherein the information about the same target object includes at least one of the following items of information, which are provided by the sensing information through at least one frequency analysis: a speed of the target object; or a distance of the target object.

9. The method according to claim 7, wherein the selected component signals have different phase information items about the transit times of the radar signals, wherein the following step is performed before the combining: performing a normalization of the selected component signals, in particular of the phase information items, in order to make component signals for different modulation modes comparable.

10. The method according to claim 9, wherein the following steps are performed for each item of sensing information in order to perform the normalization: providing a first component signal for a first antenna of the radar sensor; providing at least one second component signal for at least one second antenna of the radar sensor; and processing or dividing the at least one second component signal by the first component signal.

11. The method according to claim 7, wherein the combining is performed in that the selected, and in particular normalized, component signals of the same antennas and different sensing information items, and thus for different modulation modes, are summed, in particular added.

12. The method according to claim 7, wherein the determination of the angle information on the basis of the combined sensing information is performed in that, after the combining, the direction of the target object is determined as additional information by a processing of the summed component signals of different antennas with one another, in particular by an additional frequency analysis.

13. The method according to claim 1, wherein the radar system emits at least three different radar signals in accordance with a multi-mode operation in order to ascertain the first and the second and a third sensing information item on the basis of the received radar signals for three different modulation modes, wherein the radar signals of the radar system are modulated differently in the different modulation modes.

14. A radar system for a vehicle for determining angle information about a direction of a target object, the system comprising a processing device to perform the method according to claim 1.

15. The radar system according to claim 14, wherein the radar system is a continuous wave radar.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] 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:

[0044] FIG. 1 is a schematic representation of a vehicle with a radar system according to the invention in a side view;

[0045] FIG. 2 is a schematic top view of a vehicle with a radar system according to the invention;

[0046] FIGS. 3-6 are additional schematic representations of parts of a radar system according to the invention;

[0047] FIG. 7 is a schematic representation of steps of a method according to the invention; and

[0048] FIG. 8 is a schematic representation of radar signals with different modulation modes.

DETAILED DESCRIPTION

[0049] In FIG. 1, a vehicle 1 with a radar system 2 according to the invention is shown schematically in a side view. The vehicle 1 can employ the radar system 2 according to the invention for use with a driver assistance system, for example. In this case, the radar system 2 can also serve to determine angle information 200 about a direction of a target object 5 in addition to determining a distance and a speed. In order to perform the requisite signal processing, the radar system 2 can have an electronic processing device 3 for carrying out a method according to the invention. The processing device 3 is electrically connected to a radar sensor 4, which has multiple antennas 20, 21.

[0050] In FIGS. 3 to 6, the arrangement of the antennas 20, 21 is shown with additional details. According to FIG. 3, the radar sensor 4 of the radar system 2 has, for example, at least two receiving antennas 20 that are spaced apart from one another and only one transmitting antenna 21. In FIG. 4, in contrast, at least two transmitting antennas 21 that are spaced apart from one another and only one receiving antenna 20 are provided for the radar sensor 4. In FIG. 5, an MIMO (multiple-input multiple-output) transmitting and receiving scheme is used for the radar system 2. The use of more than two antennas 20, 21 can make it possible to ascertain the angle 240 (angle of emergence and/or incidence) of the radar signals through a comparison of the different transit times on the basis of the phases of the radar signals 230. This consequently permits the determination of the angle information 200 as information about this angle 240 and thus about the direction of the target object 5.

[0051] The option for determining the angle information 200 is illustrated in FIG. 6 with additional details. It can be seen there that the transit times, and thus phases, of the radar signals 230 vary with respect to the first receiving antenna 20′ on account of the distances d of the receiving antennas 20 from one another and on account of the angle of incidence of the radar signals 230 and thus the direction of the target object 5. A first radar signal 231 and a second radar signal 232 are shown by way of example for purposes of illustration.

[0052] In FIG. 7, a method according to the invention for determining the angle information 200 about the direction of the target object 5 in the radar system 2 for the vehicle 1 is visualized schematically. According to a first method step 101, provision of a first item of sensing information 201 for a first modulation mode 251 of the radar system 2 can be accomplished here. According to a second method step 102, furthermore, provision of at least one second item of sensing information 202 for at least a second modulation mode 252 of the radar system 2 is performed. The sensing information items here represent the “measured values” of the radar system 2, which can be ascertained by the emitting and receiving of the radar signals and, if applicable, a subsequent signal processing. The first sensing information 201 here results from an emitting and receiving of such radar signals, which were modulated in accordance with a first modulation mode 251. The second sensing information 202 results from an emitting and receiving of such radar signals 230, which were modulated in accordance with a second modulation mode 252. A third item of sensing information 203 of a third modulation mode 253 can also be provided, if applicable. According to a third method step 103, a combining of the sensing information items 201, 202, 203 for the different modulation modes 251, 252, 253 takes place. In this way, the determination of the angle information 200 can be performed on the basis of the combined sensing information 201, 202, 203.

[0053] The radar signals 230 with different modulation modes differ by the manner in which the radar signals 230 are modulated, in particular. It is shown in FIG. 8 that the bandwidths B0, B1, B2 can differ, for example. The radar signals 230 can also be modulated differently with regard to the frequency f. The different radar signals 251, 252, 253 can be output in chronological succession here, and can also have a different duration with regard to the time t. It is shown in FIG. 2 that different sensing regions can be covered by the different modulation modes 251, 252 in this way.

[0054] Furthermore, the first and the at least one second sensing information items 201, 202 can each have at least two component signals 210, wherein the at least two component signals 210 in each case are specific to at least two radar signals 230 that are emitted in accordance with an identical modulation mode 251, 252 and are reflected at the same target object 5 and whose signal transit times differ as a function of the direction of the target object 5. In other words, a first component signal 211 and at least one second component signal 212 can be provided for each sensing information item 201, 202. Because these signals result from the same sensing information items 201, 202, they are also specific to an identical (single) modulation mode 251, 252. Nevertheless, the component signals 251, 252 can be specific to different antennas 20, 21 of the radar system 2.

[0055] In FIG. 6 the radar sensor is shown with three receiving antennas 20 by way of example. It can be seen that a distance d, which influences the angle of incidence of the radar signals 230, is provided between the receiving antennas 20. A received signal can be electrically evaluated at each of the receiving antennas 20 as a function of the received radar signal 230. For the received signal s.sub.m at the m-th receiving antenna the following applies:

s.sub.m=a.sub.m exp(−l.Math.Δφ.sub.0m+φ.sub.0)

[0056] where designates the received amplitude, Δφ.sub.0m designates the phase difference between a first receiving antenna 20′ and an m-th receiving antenna 20, and φ.sub.0 designates the initial phase.

[0057] Thus, the following applies for the angle α:

[00003]$\alpha =a\sin \left(\frac{{\mathrm{\Delta \phi }}_{0m}}{k.Math.d_{0m}}\right).$

[0058] Now, if the received signal is distorted, the following relationship results for the estimated angle α:

[00004]$\alpha =a\sin \left(\frac{k.Math.d_{0m}}{}\right)\mathrm{with}={\mathrm{\Delta \phi }}_{0m}+n_{0m},$

[0059] where designates the measured phase difference and n.sub.0m designates the associated noise term.

[0060] It is immediately evident from these equations that an increase in the SNR (smaller n.sub.0m) and an increase in the aperture (larger d.sub.0m) result in a better angle estimate (smaller n at the output of the estimator).

[0061] As is shown in FIG. 8, the radar system 2 in multi-mode operation can emit different modulation schemes for each cycle in order to take into account the different requirements on measurement capability at close and long ranges. Emission can take place through the same or different transmitting antennas 21. For close range applications, nonfocused, omnidirectional antennas can be used, for example, and for long range applications sharply focusing antennas can be employed, for example. In this context, the different combinations of modulation mode 251, 252 & transmitting antenna 21 can have regions of overlap in which redundant information about a target object 5 is present (see FIG. 2).

[0062] The basic signal processing (which is to say data acquisition and frequency analysis and raw target determination) can take place separately for each modulation mode. Conventionally, a merging of the information can only take place at higher levels of abstraction (e.g., raw target level or object level). In this context, a raw target designates a reflection (local peak in the frequency range) with the associated attributes of distance, speed, angle, SNR, various qualities, etc.). According to the invention, multi-mode operation can be used to improve angle calculation. In general, L modulation modes can be merged at the raw signal level under the condition that the target object 5 is located within the FOV (Field Of View) of all modulation modes (see FIG. 2). Furthermore, all modulation modes can be transmitted within a measurement cycle of duration T using time-division multiplexing in accordance with FIG. 8.

[0063] The above explanation of the embodiments describes the present invention solely within the framework of examples. Individual features of the embodiments can of course be combined freely with one another, insofar as is technically appropriate, without departing from the scope of the present invention.

[0064] 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.