Radar apparatus and method for operating a radar apparatus

Abstract

In a method according to the invention for operating a radar apparatus of a vehicle, the radar apparatus initially transmits radar beams simultaneously via a plurality of transmission antenna channels (TX) in a first MIMO mode. The radar apparatus also receives radar beams simultaneously via a plurality of receiving antenna channels (RX) in each case, said radar beams having been reflected by the surroundings of the vehicle. According to the invention, when a multi-reflection scenario is detected or expected, a change is made to a second MIMO mode in which the number of simultaneously transmitting transmission antenna channels is reduced. After the multi-reflection scenario has ended, the radar apparatus is again operated in the first MIMO mode.

Description

[0001] 24-2007PIF 1 September 30, 2024

[0002] Radar device and method for operating a radar device

[0003] The present invention relates to methods for operating a radar device of a vehicle according to the preamble of claim 1.

[0004] The present invention further relates to a radar device according to the preamble of claim 10.

[0005] Modern vehicles include a radar device that detects objects in the vehicle's surroundings and can enable autonomous driving.

[0006] Autonomous driving includes a vehicle's ability to park itself, determine whether a lane change is possible, and provide features such as adaptive cruise control, where a vehicle maintains a constant distance from the vehicle ahead as well as matching its speed. Autonomous braking and collision avoidance are safety features that prevent accidents caused by driver inattention. These features monitor the area around the vehicle and alert the autonomous driving subsystems when obstacles are detected that are likely to collide with the vehicle.

[0007] Frequency-modulated continuous wave (FMCW) radars enable the precise measurement of distances and relative speeds of obstacles and other vehicles. Therefore, such radars are intended for autonomous vehicle applications (e.g., lane departure warning and cross-traffic alert) and safety applications (autonomous braking and collision avoidance).

[0008] In established radar systems, an increasing number of antenna channels (transmitter TX and receiver RX) are used to increase range and sensitivity and improve angular resolution. To fully exploit this potential, all transmission channels are operated simultaneously in a so-called "Full MIMO" mode. "MIMO" stands for "Multiple Input Multiple Output" and describes a method or transmission system for using multiple antennas.

[0009] Transmitting and receiving antennas for wireless communication. For this purpose, the individual TX channels are coded. "Full" means the full and simultaneous use of all channels.

[0010] Encoding in known radar devices is carried out using CDMA and DDMA methods.

[0011] A CDMA code division multiple access (CDM) method is a multiplexing technique that enables the simultaneous transmission of different user data streams on a shared frequency range. A key characteristic of this shared frequency range is its greater bandwidth than that of the user data stream. Special spreading codes are used to spread the frequency and differentiate the various data streams.

[0012] The problem with such spreading codes is that they are never 100% orthogonal; that is, the isolation from one (virtual) receive channel to the next is not infinite, but, for example, -15 dB. The more transmit channels are used, the more potentially disruptive cross-correlation occurs.

[0013] Doppler Division Multiple Access (DDMA) coding provides slightly higher orthogonality, but has disadvantages regarding velocity ambiguities, which is also a disadvantage when used in a vehicle.

[0014] Known methods and radar devices therefore exhibit serious disadvantages, particularly in scenarios where radar signals are reflected from many directions with high energy densities, i.e., in so-called multi-reflection scenarios.

[0015] Such multi-reflection scenarios can occur when using known methods, especially in tunnels, galleries and parking garages, as well as along buildings or walls running alongside a roadway, and lead to a situation where a clear assignment of the signals to the transmission channels is no longer possible.

[0016] This results in, for example, incorrect detected angles or Doppler velocities, which in turn leads to false positive detections of objects at positions 24-2007PIF 3 30 September 2024 where no objects actually exist. Relative velocities can also be detected incorrectly.

[0017] These misinterpretations of the environment can have drastically negative consequences in driving situations.

[0018] It is therefore the object of the present invention to provide a method for operating a radar device and a radar device in which these problems are solved.

[0019] This problem is solved by a method according to the characterization of claim 1 and by a radar device according to the characterization of claim 10.

[0020] In such a method for operating a vehicle's radar device, the radar device first transmits radar beams simultaneously via several transmit antenna channels (TX) in a first MIMO method.

[0021] The radar device also simultaneously receives radar beams reflected from the vehicle's surroundings via several receiving antenna channels (RX).

[0022] According to the invention, in the event of a detected or expected multireflection scenario, a switch is made to a second MIMO method in which the number of simultaneously transmitting antenna channels is reduced.

[0023] After the multireflection scenario has ended (or after the end of the multireflection scenario has been detected), the radar device is operated again in the first MIMO procedure.

[0024] The present invention offers the advantage that although a degradation measure is initiated, this significantly reduces the probability of generating false positive objects.

[0025] This does result in a loss of sensitivity, which can be communicated to downstream functions. Consequently, for example, the maximum range for an emergency braking assistant may be reduced, but this can be functionally compensated for by limiting the maximum permissible driving speed. Reducing the number of actively transmitting antenna channels decreases the signal-to-noise ratio (SNR) and resolution, both of which contribute to a reduced range of functions, which is actively communicated. According to the invention, however, this avoids the far greater problems of false detections.

[0026] Once the critical sections with potential or actual multi-reflection scenarios have been traversed, the invention switches back to the first MIMO method, in which radar beams are again transmitted via more or more transmit antenna channels (TX). Then the full range of functions is available again.

[0027] Preferred embodiments of the invention are set forth in the dependent claims.

[0028] Preferably, the first MIMO method is a CDMA or a DDMA method.

[0029] A particularly preferred embodiment of the present invention is one in which the second MIMO method is a TDMA method. In such a time-division multiplexing method (TDMA stands for Time Division Multiple Access), the various transmit antenna channels (TX) transmit in different time slices or time intervals. This is easy to implement and offers almost ideal orthogonality. On the receive side, preferably all receive antenna channels (RX) can remain active. This ensures that at least all installed RX resources are utilized.

[0030] In a further or alternative embodiment of the present invention, the second MIMO method involves temporarily terminating the transmission of radar beams from some of the multiple transmit antenna channels (TX). Thus, only a portion of the installed TX resources is used at any given time, while the rest are switched off. This also reduces the negative effects of a multi-reflection method.

[0031] Preferably, a multi-reflection scenario is detected by an increase in false-positive detections. Such an increase can be assumed, for example, if the detection count suddenly jumps. An increase in false-positive detections can also be assumed if, with an increase in the detection count, other sensors, such as lidar sensors or camera systems, do not confirm that the number of actually present objects has increased.

[0032] The presence of a multireflection scenario can also be detected by a drop in the signal-to-noise ratio (SNR).

[0033] In a further preferred embodiment of a method according to the invention, an anticipated multireflection scenario can be detected based on localization. If access to other vehicle sensors, in particular camera or lidar sensors, indicates that a tunnel is being traversed or a parking garage is being entered, an anticipated multireflection scenario can be assumed. Map data from a navigation system installed in the vehicle can also be used to identify an anticipated multireflection scenario that will be encountered in the near future.

[0034] Similarly, a multi-reflection scenario can be assumed to be imminent if a vehicle ahead reports its presence via Car2X communication. Car2X, also known as C2X, is the name for a communication technology that allows information exchange between vehicles and thus contributes to increased road safety.

[0035] Preferably, the switch from the first MIMO method to the second MIMO method or back is only made when a currently running radar cycle has ended.

[0036] A radar cycle is complete when all raw data (received chirps) have been acquired and the detections transmitted to a vehicle bus. A typical duration of a radar cycle is 50 ms. At the end of a radar cycle, a detection list is generated, which is a list of detected objects resulting from subsequent processing. A radar cycle is therefore preferably always completed using the same method in which it was initiated. A radar cycle with, for example, 256 chirps will thus preferably be carried out entirely in a single MIMO method, and there will not be a switch, for example, from a TDMA method to a DDMA method after the first 128 chirps. The latter would be too complex in resolving ambiguities.

[0037] A radar device according to the invention for a vehicle has several transmitting antennas (TX) for simultaneously emitting radar beams and several receiving antennas (RX) for simultaneously receiving radar beams that have been reflected from the vehicle's surroundings.

[0038] According to the invention, the radar device is designed to temporarily reduce the number of simultaneously transmitting antenna channels in the event of a detected or expected multireflection scenario.

[0039] The present invention will be explained in more detail below with reference to the accompanying figure.

[0040] This shows:

[0041] Fig. 1 shows a schematic of a method according to the invention.

[0042] Figure 1 schematically shows an example of a method according to the invention for operating a radar device of a vehicle.

[0043] The starting point is a radar device operating in full MIMO mode, which uses CDMA or alternatively DDMA for channel separation and reconstruction. The overall system can be exemplified as an automated driving system with a maximum permissible speed (Vmax) of 130 km / h and an automated parking system with a maximum permissible parking speed (Vpark) of 15 km / h.

[0044] Scenario detection is used, which monitors for sudden jumps in the number of detections as well as a widespread reduction in the signal-to-noise ratio (SNR) of the detections. Such a sudden SNR reduction is indicated schematically. 24-2007PIF 7 30 September 2024

[0045] Additionally, the map data of an integrated navigation system contains information (not shown in detail) on the location of tunnels, parking garages and other potentially disruptive environments.

[0046] If either the radar-based multi-reflection scenario detection recognizes a multi-reflection scenario or the navigation system / map data reports that such a scenario will occur, a switch to TDMA takes place after completion of the currently running radar cycle (50 ms).

[0047] Radar-based object detection (tracking) continues. A signal is sent to the automated driving function indicating that a new, reduced maximum speed (Vmax) of 100 km / h applies to driving functions and a new, reduced maximum parking speed (Vpark) of 10 km / h applies to parking functions. These maximum speeds are implemented fully automatically (or after user confirmation).

[0048] When the conditions for the restriction (e.g., tunnel, parking garage) no longer exist (due to map-based reasons, reduced detection rates, or an improvement in the signal-to-noise ratio of the remaining detections), the multi-reflection scenario is recognized as terminated. After the current radar cycle is completed, the system switches back to CDMA or DDMA. Subsequently, the driving and parking functions are informed that the higher limits of 130 km / h and 15 km / h apply again, or that the restrictions have been lifted.

[0049] Such a measure should preferably always be implemented at the same points where a similar switch occurred during data generation (testing, endurance run) for implementing the procedure. This ensures consistent data quality, which advantageously serves to demonstrate the functionality.

Claims

24-2007PIF 8 September 30, 2024 Claims:

1. A method for operating a radar device of a vehicle, wherein in the course of the method: the radar device first transmits radar beams simultaneously via several transmit antenna channels (TX) in a first MIMO method, and also simultaneously receives radar beams reflected from the vehicle's environment via several receive antenna channels (RX), characterized in that: in the event of a detected or expected multireflection scenario, the device switches to a second MIMO method in which the number of simultaneously transmitting antenna channels is reduced, and after the multireflection scenario has ended, the radar device is operated again in the first MIMO method.

2. The method according to claim 1, characterized in that the first MIMO method is a CDMA or a DDMA method.

3. Method according to one of the preceding claims, characterized in that the second MIMO method is a TDMA method.

4. Method according to one of the preceding claims, characterized in that the second MIMO method includes that a portion of the multiple transmit antenna channels (TX) terminates the emission of radar beams.

5. Method according to one of the preceding claims, characterized in that the multireflection scenario is recognized by an increase in false-positive detected objects.

6. Method according to one of the preceding claims, characterized in that the multireflection scenario is detected by a drop in the SNR. 24-2007PIF 9 September 30, 2024 7. Method according to one of the preceding claims, characterized in that an expected multireflection scenario is detected based on localization and preferably an expected multireflection scenario is assumed when at least one of the following scenarios is present: driving through a tunnel, driving into a parking garage, or when a preceding vehicle reports the presence of a multireflection scenario via Car2X communication.

8. Method according to one of the preceding claims, characterized in that the switch from the first MIMO method to the second MIMO method or back only occurs when a currently running radar cycle has ended.

9. Method according to one of the preceding claims, characterized in that an expected multireflection scenario is detected by using other sensors of the vehicle, in particular camera or lidar sensors of the vehicle, or map material of a navigation system installed in the vehicle.

10. Radar device for a vehicle, wherein the radar device has several transmitting antennas (TX) for simultaneously emitting radar beams and several receiving antennas (RX) for simultaneously receiving the radar beams reflected from the vehicle's surroundings, characterized in that: the radar device is designed to temporarily reduce the number of simultaneously transmitting antenna channels in the event of a detected or expected multireflection scenario.

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