Method for operating radar network, interference detection and avoidance method, and radar network

Abstract

The invention relates to a method for operating a cooperative multiple-input multiple-output (MIMO) radar network having a plurality of analog radar sensors and at least one digital radar sensor. The method comprises determining deviations of transmission times and transmission frequencies of the at least a plurality of analog radar sensors relative to each other, and adapting the transmission times, reception times and transmission frequencies of signals of the at least a plurality of analog radar sensors to each other. In addition, the invention comprises a method for interference identification and interference avoidance. Furthermore, the invention comprises a cooperative multiple-input multiple-output (MIMO) radar network comprising a plurality of analog radar sensors and at least one digital radar sensor.

Description

Technical Field

[0001] The invention relates to a cooperative multiple-input multiple-output (MIMO) radar network and a method for operating such a cooperative multiple-input multiple-output radar network. In particular, the invention relates to a method for operating a cooperative radar network for environment detection in a driver assistance system of a motor vehicle and to such a cooperative radar network. Furthermore, the invention relates to a method for interference detection and interference avoidance during the operation of a cooperative radar network. Background Art

[0002] The following modulation method is usually used for radar networks as components of driver assistance systems in motor vehicles: the modulation method performs frequency modulation on the signal in the linear frequency modulation method. Modern radar networks are so-called multiple-input multiple-output (MIMO) radar networks, which have multiple transmitters and multiple receivers. In this case, for example, each radar sensor can be designed to be a transmitter and a receiver at the same time. In this case, linear frequency modulation signals (Chirps) are transmitted by means of multiple transmitters, and the reflected signals are received by means of multiple receivers. In this case, by corresponding modulation in the multiplexing method, the transmitter can be determined for each clearly unique signal, and therefore, depending on the multiplexing method used, the angle estimation can be performed by means of the apertures of different monostatic (monostatischen) or bistatic (bistatischen) signals or by means of the aperture of a virtual radar network formed by transmitters and receivers. Here, common modulation multiplexing methods are a Doppler-division-multiplex method (DDM), a time-division-multiplex method (TDM), or a code-division-multiplex method (CDM).

[0003] Frequency modulated continuous wave (FMCW) radar sensors are usually used in such radar networks, which are distinguished primarily by their high technological maturity and low cost. The necessary signals are generated with the aid of analog components, for example by voltage-controlled oscillators (VCOs). In addition, the received reflected signals are demodulated by analog mixing with the transmitted signal before the required analog-to-digital conversion is evaluated, and the bandwidth is reduced to several MHz in this way.

[0004] In addition, radar sensors with broadband digital signal generation (hereinafter referred to as digital radar sensors) are known, in which the signal is generated directly by a digital-analog converter with a sampling rate of at least several hundred MHz, for example greater than 200 MHz, using a predetermined local oscillator (LO). Similarly, the reflected signal is mixed with a predetermined local oscillator and provided for analysis by means of an analog-digital converter with a sampling rate of at least several hundred MHz, for example greater than 200 MHz, without the need for necessary analog demodulation. As a result, digital radar sensors can operate in a large number of modulation methods, which significantly increases the range of use of the digital radar sensors compared to analog radar sensors. The digital radar sensors can also receive the entire bandwidth or a large part of the bandwidth of the signal spectrum used in the radar network at a time point and have a very high time resolution. However, compared with common analog FMCW sensors, the digital radar sensors are significantly more complicated and expensive to produce.

[0005] In addition, radar networks for driver assistance systems of motor vehicles are increasingly being installed with a greater number of individual radar sensors, even of different designs. This results in a greater flexibility in terms of possible modulation methods. In this context, a common cooperative operating mode is advantageous, which can significantly increase the aperture and thus the angular resolution, for example, by means of a common data evaluation, or can reduce or avoid interference between the individual sensors. Such radar networks are also referred to as cooperative radars. Summary of the invention

[0006] The object of the present invention is to provide a method for efficiently operating different radar sensors and modulation types in a cooperative radar network. Another object of the present invention is to provide a radar network for operation as a cooperative radar network.

[0007] According to the invention, these objects are solved by means of a method for operating a cooperative MIMO radar network and a method for interference detection and interference avoidance in the method for operating a cooperative MIMO radar network and a radar network. Advantageous further developments are shown below.

[0008] The method for operating a multiple-input multiple-output (MIMO) radar network according to the present invention comprises the following steps:

[0009] Generate and transmit signals. Send signals with the aid of a plurality of analog radar sensors and at least one digital radar sensor, wherein the plurality of analog radar sensors and at least one digital radar sensor send in a first modulation method, or wherein the plurality of analog radar sensors send in a first modulation method and at least one digital radar sensor sends in a second modulation method, wherein the transmission spectra of the signals of the first and second modulation methods do not overlap. Receive and preprocess the reflected signals for digital processing, wherein at least one digital radar sensor receives the transmitted signals of all radar sensors. Determine the deviation of the transmission times and transmission frequencies of at least a plurality of analog radar sensors relative to one another with the aid of the signals received by the at least one digital radar sensor. Adapt the transmission times, reception times and transmission frequencies of the signals of at least a plurality of analog radar sensors to one another. Analyze the received signals in at least one of the following paths: a monostatic path of the corresponding radar sensor, at least one bistatic path from at least one analog radar sensor to the digital radar sensor, a corresponding bistatic path between the plurality of analog radar sensors, and - if the plurality of analog radar sensors and at least one digital radar sensor send in the first modulation method - a corresponding bistatic path from at least one digital radar sensor to the plurality of analog radar sensors.

[0010] Here, the plurality of analog radar sensors are, for example, frequency modulated continuous wave radar sensors (FMCW sensors). Here, at least one digital radar sensor refers to a radar sensor with broadband digital signal generation (hereinafter referred to as a digital radar sensor for short), which processes signals by means of a digital analog-to-digital converter and an analog-to-digital converter, the sampling rate of which is at least several hundred MHz, for example greater than 200 MHz. Since the at least one digital radar sensor receives the signals of all radar sensors, the corresponding deviations of the transmission time and the transmission frequency relative to other radar sensors and / or relative to predetermined transmission time and transmission frequency can be determined by processing the signals received by the digital radar sensor from each of the analog radar sensors. By corresponding adaptation by means of correction values ​​for each radar sensor compared to other radar sensors and / or correction values ​​for corresponding predetermined transmission time and transmission frequency and by outputting the correction values ​​to the corresponding radar sensors, the efficiency and accuracy of the radar network can be significantly increased. Here, the adaptation can also be realized by adapting the transmission signal generated for each radar sensor.

[0011] Thus, for example, it is possible, depending on the deviations present before the adaptation, to adapt the analog radar sensors to one another in such a way that an evaluation in the corresponding bistatic path between the analog radar sensors becomes possible or is significantly simplified. If an evaluation in the corresponding bistatic path between the analog radar sensors is not possible due to the existing deviations, the evaluation can be performed only after the signal has been adapted and the adapted signal has been retransmitted and received. In this case, a bistatic path or a bistatic signal describes the reception of a reflected signal by means of a radar sensor as a receiver, which radar sensor does not correspond to the radar sensor that transmits the reflected signal, i.e., the receiver does not correspond to the transmitter. In contrast, a monostatic path or a monostatic signal describes the reception of a reflected signal by means of a radar sensor as a receiver, which radar sensor corresponds to the radar sensor that transmits the reflected signal, i.e., the receiver corresponds to the transmitter. In this case, the determination of the deviation is limited by the time resolution and the frequency-dependent resolution of at least one digital radar sensor, which for conventional digital radar sensors is, for example, in the sub-nanosecond range. In this case, for example, at least the maximum determinable deviation of the analog radar sensor may be a few microseconds (μs) in its transmission time and several tens of MHz in its transmission frequency. In this case, the transmission time, the reception time and the transmission frequency of the signal may be adapted, for example, with an accuracy of a few nanoseconds (<1 μs) and in the sub-MHz range (<1 MHz). In this case, residual deviations that cannot be corrected, for example due to the limitations of the time resolution and frequency-specific resolution of the analog radar sensor, may be detected by at least one digital radar sensor and taken into account in the evaluation. In this case, the evaluation is performed in at least one of the possible paths, preferably in any combination of the paths and more preferably in all the paths.

[0012] The method according to the invention is particularly advantageous because the possible determination and correction of deviations enables a robust operation of a radar network operated by means of the method and the radar network can be operated as a cooperative radar network comprising a plurality of analog radar sensors and at least one digital radar sensor. This ensures high precision and robustness, while the costs for such a radar network remain low. Here too, analog radar sensors and digital radar sensors can be operated cooperatively, thereby significantly increasing the possible angular resolution, for example.

[0013] In this case, the method may also include a plurality of digital radar sensors. In this case, at least one digital radar sensor may transmit in the second modulation method, while the other digital radar sensors transmit in the first modulation method, or all digital radar sensors may transmit in the first or second modulation method. In this case, the steps described for the at least one digital radar sensor may also be performed by a plurality or all of the plurality of digital radar sensors. Alternatively, the steps may be performed by one of the plurality of digital radar sensors, wherein the determination of the deviation may also be performed for a plurality of digital radar sensors.

[0014] According to a preferred embodiment of the method, the method can further include a prior step for time synchronization of the radar sensor, wherein the synchronization includes sending a separate radar signal at a predetermined time point for determining the deviation and adapting on this basis; or wherein the synchronization is implemented by a trigger signal of at least one radar sensor and / or by a synchronization protocol and / or by a clock signal.

[0015] By means of time synchronization, the deviations of the radar sensors, in particular the analog radar sensors, with respect to one another can already be reduced before the deviations are determined and the adaptation is carried out with the aid of data measured by at least one digital radar sensor. This has the advantage that the time expenditure for determining the deviations is small and the signal adaptation can therefore be carried out correspondingly more quickly. Even in the case of deviations of the analog radar sensors which would not allow an evaluation in a corresponding bistatic path between the analog radar sensors, the synchronization can make the evaluation possible already in the first method run.

[0016] In this case, the trigger signal of at least one radar sensor can be a signal emitted at a predetermined time point, which is received by at least a plurality of analog radar sensors and these radar sensors are time-synchronized with the aid of the received signal. In this case, such synchronization can be an approximate time synchronization, which can also include a deviation of a few microseconds. In this case, the synchronization protocol can be, for example, the Precision Time Protocol (PTP). In this case, the clock signal can be a signal output to each radar sensor.

[0017] According to a preferred embodiment of the method, the first modulation method may be an FMCW method using a Doppler multiplexing method (DDM) or a time division multiplexing method (TDM) or a code division multiplexing method (CDM); and / or the second modulation method may be an orthogonal frequency division multiplexing method (OFDM) or a phase modulation continuous wave (PMCW) method. In particular, the second modulation method may be a broadband digital modulation method that can only be performed by at least one digital radar sensor.

[0018] According to another preferred embodiment of the method, the evaluation of the signals received by the plurality of analog radar sensors can include demodulation of the corresponding received signals. This is achieved, for example, by demodulation of the transmitted signal, whereby the bandwidth of the demodulated signal is reduced to a few megahertz (MHz). Preferably, the demodulation is performed in a demodulation method corresponding to the type of the modulation method.

[0019] According to another preferred embodiment of the method, if a plurality of analog radar sensors and at least one digital radar sensor transmit in a first modulation method, the evaluation of the signal received by the at least one digital radar sensor includes separating the monostatic signal of the at least one digital radar sensor from the bistatic signals of the plurality of analog radar sensors by means of an optimal filter. Such an optimal filter (matched filter) converts the received signal into a baseband signal, which can then be demodulated by means of a conventional demodulation method. Different optimal filters can be used for the signals of the monostatic path and the bistatic path, whereby the signals of the analog radar sensors can then also be demodulated and evaluated.

[0020] If the at least one digital radar sensor transmits using the second modulation method, the evaluation of the signal received by the at least one digital radar sensor includes separating the monostatic signal of the at least one digital radar sensor from the bistatic signals of the plurality of analog radar sensors by means of a frequency mask. Such a frequency mask can be, for example, a time-frequency mask, which can be generated from the transmission signal of the at least one digital radar sensor. Thus, signals corresponding to the monostatic path of the at least one digital radar sensor can be filtered out and evaluated. The unfiltered signal corresponds to the signal in the bistatic path to the at least one digital radar sensor and, as described above, can be demodulated and evaluated in a conventional manner.

[0021] In addition, the present invention includes a method for interference recognition and interference avoidance. The method is applied in a method for operating a radar network according to one of the above-mentioned embodiments and can constitute an independently implemented method or can also constitute an advantageous extension of the method as a step of the method for operating a radar network. Such a method for interference recognition and interference avoidance includes the following steps: determining a frequency band with no and / or very little interference from a signal received by at least one digital radar sensor; and adapting the transmission frequency of the signals of at least a plurality of analog radar sensors to the frequency band.

[0022] Since at least one digital radar sensor receives the transmitted signals of all radar sensors, i.e. the complete bandwidth or a large part of the complete bandwidth of the utilized radar band, interference-free bands can be determined from the signals received by the at least one digital radar sensor. Likewise, bands with as little interference as possible can be determined. Next, the transmission frequency of at least the analog radar sensor is moved to these bands. Preferably, the transmission frequency is moved to the interference-free band. If there are more transmission frequencies than the interference-free band, the excess transmission frequencies are moved to the low-interference band as much as possible. Next, the method is re-executed and adapted accordingly. By repeatedly or continuously executing the method, an ideal frequency band adapted to the corresponding situation can be selected. As a result, interference can be completely avoided or strongly reduced.

[0023] According to a preferred embodiment of the method, the step of determining a frequency band with no and / or very little interference from the signal received by at least one digital radar sensor is performed together with the step of determining the deviation of the transmission time points and the transmission frequency of at least a plurality of analog radar sensors relative to one another by means of the signal received by at least one digital radar sensor; and / or the step of adapting the transmission frequency of the signals of at least a plurality of analog radar sensors to a frequency band with no and / or very little interference is performed together with the step of adapting the transmission time points, the reception time points and the transmission frequency of the signals of at least a plurality of analog radar sensors to one another. For example, the corresponding steps are performed simultaneously or in one step. This is particularly advantageous for the method according to the invention because such an embodiment requires only increased computing power and otherwise does not affect the operation of the radar network in a disruptive manner or delay the execution of the method for operating the radar network.

[0024] Furthermore, the present invention includes a multiple-input multiple-output (MIMO) radar network, which includes a plurality of analog radar sensors, wherein the plurality of analog radar sensors are designed to transmit and receive signals in a first modulation method; at least one digital radar sensor, wherein the at least one digital radar sensor is designed to transmit and receive signals in a first modulation method or in a second modulation method, wherein the transmission spectra of the signals of the first and second modulation methods do not overlap, wherein the at least one digital radar sensor is designed to receive the transmitted signals of all radar sensors; wherein the at least one digital radar sensor and the plurality of analog radar sensors are designed to exchange data directly or via a switching unit; a computing unit, wherein the computing unit is designed to determine a deviation of transmission times and transmission frequencies of at least a plurality of analog radar sensors relative to one another from the signals received by the at least one digital radar sensor, wherein the at least one computing unit is further designed to adapt the transmission times, reception times and transmission frequencies of at least a plurality of analog radar sensors to one another. In this case, the switching unit can be the computing unit.

[0025] According to a preferred embodiment of the present invention, at least one computing unit is further implemented to adapt the transmission time points, reception time points and transmission frequencies of at least multiple simulated radar sensors to each other in such a way that analysis and processing of received signals can be performed in corresponding bistatic paths between the multiple simulated radar sensors.

[0026] In this case, the computing unit can further be embodied to adapt the transmission time and the reception time to coincide in the nanosecond range and / or to adapt the transmission frequency to a predetermined transmission frequency with an accuracy in the sub-MHz range.

[0027] According to a preferred embodiment of the present invention, at least one digital radar sensor and a plurality of analog radar sensors are implemented to be synchronized in time. Further preferably, the radar network includes a synchronization protocol and / or a separate radar signal and / or a clock signal.

[0028] According to a preferred embodiment of the present invention, the first modulation method is an FMCW method using a Doppler multiplexing method (DDM) or a time division multiplexing method (TDM) or a code division multiplexing method (CDM); and / or the second modulation method is an orthogonal frequency division multiplexing method (OFDM) or a PMCW method. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In the following, preferred embodiments of the present invention are described in more detail according to the accompanying drawings. The accompanying drawings show:

[0030] Figure 1A schematic diagram showing an embodiment of a radar network according to the present invention;

[0031] Figure 2 A schematic diagram showing a transmission spectrum according to a first embodiment of the method of the present invention;

[0032] Figure 3 A schematic diagram showing a transmission spectrum according to a second embodiment of the method of the present invention;

[0033] Figure 4 A schematic diagram showing a transmission spectrum according to a third embodiment of the method of the present invention;

[0034] Figure 5 A schematic diagram showing a transmission spectrum according to a fourth embodiment of the method of the present invention;

[0035] Figure 6 A schematic diagram showing the method steps of the method according to the invention;

[0036] Figure 7 The schematic diagram shows the method steps of the method according to the invention with interference detection and adaptation. DETAILED DESCRIPTION

[0037] In the following, resolution refers to the frequency accuracy and time accuracy with which different radar sensors can send and receive signals. The radar sensor comprises at least one transmitter (Tx) and a receiver (Rx). Time terms such as before / after refer to the sequence of method steps. Spatial terms refer to the arrangements shown in the figures. The described embodiments can of course be combined with one another, as far as technically feasible.

[0038] Figure 1A schematic diagram of an embodiment of a radar network 10 according to the present invention is shown. The radar network is installed, for example, on one side of a vehicle 12, further, for example, on the front of the vehicle 12, and includes four analog radar sensors 14, 16, 18 and 20, which are arranged in a manner distributed along the front of the vehicle 12 and have a defined spacing between each other. In the current embodiment, each analog radar sensor 14-20 includes a transmitter (Tx) and a receiver (Rx). Here, the transmitter can be a receiver at the same time, but each radar sensor can also include a separate transmitter and receiver. In the current embodiment, the transmitter and the receiver are arranged together, respectively, but can be arranged separately from each other, for example, arranged along one side of the vehicle 12. Here, each analog radar sensor can also include multiple transmitters and receivers. In addition, the radar network 10 includes a digital radar sensor 22. In the illustrated embodiment, the digital radar sensor is arranged centrally between the analog radar sensors 14-20, but is certainly not limited to this arrangement. The digital radar sensor 22 includes at least one transmitter and a receiver.

[0039] Radar network 10 is designed to detect radial speed, distance, azimuth and elevation of targets as part of a driver assistance system of vehicle 12 and feed them into the driver assistance system. In this case, signals can be detected in monostatic paths of individual analog radar sensors 14-20 and / or monostatic paths of digital radar sensors 22. In this case, a monostatic path corresponds to a signal that is emitted by one radar sensor 14-22 and received again by the radar sensor. In this case, depending on the operating method of radar network 10, bistatic paths between individual analog radar sensors 14-20 and / or between respective analog radar sensors 14-20 and digital radar sensor 22 can also be detected. In this case, a bistatic path corresponds to a signal that is emitted by one radar sensor 14-22 and received again by another radar sensor 14-22.

[0040] The analog radar sensors 14-20 are implemented to operate in a multiplexing method. Depending on the type of operation, this may be, for example, a DDM multiplexing method, a TDM multiplexing method or a CDM multiplexing method. The digital radar sensor 22 is implemented to operate in a broadband digital modulation method (e.g., an OFDM method) or in an FMCW method with a DDM multiplexing method, a TDM multiplexing method or a CDM multiplexing method. If the digital radar sensor operates in a modulation method different from that of the analog radar sensor, only the bistatic path from the corresponding analog radar sensor to the digital radar sensor can be detected, i.e., the signal sent by the analog radar sensor can be received by the digital radar sensor. The digital radar sensor is implemented to detect the complete bandwidth or a large part of the bandwidth of the transmitted signal. If the digital radar sensor operates in the same modulation method as the analog radar sensor, the bistatic path from the digital radar sensor to the corresponding analog radar sensor can also be detected by these radar sensors.

[0041] In addition, radar network 10 includes at least one first computing unit (not shown here), which is designed to determine the corresponding deviations of the transmission time points and the transmission frequencies of analog radar sensors 14-20 relative to each other from the signals received by digital radar sensor 22. In addition, radar network 10 includes a second computing unit (not shown here), which is designed to adapt the transmission time points, reception time points and transmission frequencies of analog radar sensors 14-20 to each other. In this case, the first and second computing units can be the same computing unit. In addition, at least one computing unit is configured to jointly analyze the received signals of multiple analog radar sensors and digital radar sensors in terms of the distance, relative speed and azimuth / elevation angle of the reflection.

[0042] Radar sensors 14-22 are implemented to communicate with at least one computing unit and / or the first and / or second computing unit. In addition, radar sensors 14-22 are implemented to communicate directly with each other and can exchange data directly or via a switching unit. Here, at least one computing unit can constitute a switching unit.

[0043] Figure 2 A schematic diagram of a transmission spectrum of a first specific embodiment of a method according to the invention for operating a radar network is shown. In the method, a first modulation method is operated Figure 1In the first modulation method, the simultaneously transmitted signals can be separated by coding, for example by a DDM method. Each radar signal of the simulated radar sensors 14-20 is simultaneously emitted as a chirp with a frequency f that increases over time t. Radar sensor 14 emits signal 24, radar sensor 16 emits signal 26, radar sensor 18 emits signal 28, and radar sensor 20 emits signal 30.

[0044] Figure 1 Digital radar sensor 22 in the embodiment of the present invention emits signal 32 in a second modulation method, for example in a wideband modulation (for example an OFDM method). Radar sensors 14-22 are operated in such a way that signals 24-30 of radar sensors 14-20 do not overlap with signals 32 of digital radar sensor 22. For example, signal 32 is modulated in such a way that it is frequency-shifted and / or time-shifted relative to signals 24-30.

[0045] Figure 3 A schematic diagram of a transmission spectrum according to a second embodiment of the method according to the present invention is shown. In this method, a first modulation method is operated Figure 1 1 and 2. In the embodiment of the invention, analog radar sensors 14-20 of radar network 10 are shown in FIG. 1 , in which the transmitted signals can be separated by a time offset during transmission, for example by a TDM method. Each radar signal of analog radar sensors 14-20 is emitted in a single time range (time slot) as a linear frequency modulation with a frequency f that increases over time t. Radar sensor 14 transmits signal 34, radar sensor 16 transmits signal 36, radar sensor 18 transmits signal 38, and radar sensor 20 transmits signal 40. Figure 1 Digital radar sensor 22 in the embodiment of the present invention emits signal 42 in a second modulation method, for example in a wideband modulation (for example an OFDM method). Radar sensors 14-22 are operated in such a way that signals 34-40 of radar sensors 14-20 do not overlap with signal 42 of digital radar sensor 22. For example, signal 42 is modulated in such a way that it is frequency-shifted and / or time-shifted relative to signals 34-40.

[0046] Figure 4 A schematic diagram of a transmission spectrum according to a third embodiment of the method according to the present invention is shown. In this method, a first modulation method is run Figure 1In the case of a radar network 10 of analog radar sensors 14-20 and digital radar sensor 22, in the first modulation method, a separation of the simultaneously transmitted signals can be achieved by coding, for example by a DDM method. Each radar signal of radar sensors 14-22 is simultaneously emitted as a linear frequency modulation with a frequency f that increases over time t. Radar sensor 14 emits signal 44, radar sensor 16 emits signal 46, radar sensor 18 emits signal 48, radar sensor 20 emits signal 50, and digital radar sensor 22 emits signal 52.

[0047] Figure 5 A schematic diagram of a transmission spectrum according to a fourth embodiment of the method according to the present invention is shown. In this method, a first modulation method is run Figure 1 In the case of analog radar sensors 14-20 and digital radar sensor 22 of radar network 10 in the first modulation method, the transmitted signals can be separated by a time offset during transmission, for example by a TDM method. Each radar signal of radar sensors 14-22 is emitted in a single time range (time slot) as a linear frequency modulation with a frequency f that increases over time t. Radar sensor 14 transmits signal 54, radar sensor 16 transmits signal 56, radar sensor 18 transmits signal 58, radar sensor 20 transmits signal 60, and digital radar sensor 22 transmits signal 62.

[0048] Figure 6 Show according to Figures 2 to 5 A schematic diagram of the method steps of the method according to the present invention according to any one of the embodiments of the present invention. In this case, the method can be performed by means of Figure 1 The radar network 10 in FIG. 1 is implemented and described below accordingly. Figure 1 The implementation is performed on a radar network in FIG. , which reference is for illustration only and the method can also be implemented on other suitable radar networks.

[0049] The method comprises a step S1 of generating and transmitting a radar signal to a plurality of radar sensors, such as radar sensors 14 - 22 . The signal can be generated in two variants. Figure 6 In the first and second embodiments of the method, the signal is, for example, as Figure 2 and Figure 3 The transmission spectrum shown in is generated. In this case, the signals for analog radar sensors 14-20 are generated using a first modulation method, and the signals for at least one digital radar sensor 22 are generated using a second modulation method. In this case, the signals are generated in such a way that the signal determined for at least one digital radar sensor 22 does not overlap with the signals determined for multiple analog radar sensors 14-20.

[0050] exist Figure 6 In the third and fourth embodiments of the method, the signal is, for example, as Figure 4 The transmission spectrum shown in FIG. 5 is generated. In this case, the signals for multiple analog radar sensors 14-20 and for at least one digital radar sensor 22 are generated in a first modulation method.

[0051] In step S2.1, a signal generated using a first modulation method is transmitted by means of analog radar sensors 14-20. In a step S2.2, which is carried out simultaneously, a signal generated using a first or second modulation method is transmitted by means of at least one digital radar sensor 22. Depending on the modulation method, the signal can be transmitted by means of all radar sensors 14-22 simultaneously and / or in a predetermined time range.

[0052] The transmitted signal is reflected by a target that is in the visible range of the radar network 10, i.e., for example, in front of the vehicle 12. Next, in step S3, the reflected signal is received by at least one digital radar sensor 22 and preprocessed for digital signal processing. Here, the digital radar sensor receives the reflected signals of all radar sensors 14-22, i.e., the complete bandwidth of the utilized frequency. Here, the signal received by the digital radar sensor can be provided for analysis and processing with the aid of an analog-to-digital converter, which has a sampling rate of at least several hundred MHz, for example, greater than 200 MHz, without the need for necessary analog demodulation. This can, for example, be achieved by preventing bandwidth loss and providing detailed information about the signal frequency for signal processing. In addition, the digital radar sensor can provide accurate time information in addition to detailed frequency information due to its very good time resolution in the sub-nanosecond range.

[0053] This makes it possible to determine in step S4 the corresponding deviations of the transmission times and the transmission frequencies of the simulated radar sensor relative to one another. The deviations here respectively refer to the determined time deviations of the transmission times and / or the determined deviations of the frequency profiles. Figure 2 In a first embodiment of the method, for example, a deviation of the signals 24-30 relative to one another and thus of the radar sensors 14-20 relative to one another can be determined. For example, such a deviation can include a time deviation of the transmission time points. Figure 3 In a second specific embodiment of the method, for example, deviations of the frequency profiles of signals 24 - 30 with respect to one another and thus deviations of radar sensors 14 - 20 with respect to one another may be determined.

[0054] Such a determination is simplified in particular by the fact that signal 32 or 42 of digital radar sensor 22 can be filtered out of all received signals by means of an optimal filter and can be used to determine the deviation. Due to the high accuracy of digital radar sensor 22, the deviation of signal 24-30 or 34-40 can be determined in a simplified and accelerated manner by comparing the monostatic signal of digital radar sensor 22 with the bistatic signal of analog radar sensor 14-20 to digital radar sensor 22. In particular, flight time differences can be taken into account, which are caused by the distance of analog radar sensor 14-20 from digital radar sensor 22.

[0055] For example, according to Figure 4 In a third embodiment of the method, deviations of signals 44-52 relative to one another and thus of radar sensors 14-22 relative to one another can be determined. Since in such an embodiment the analog radar sensor and the digital radar sensor transmit in a common first modulation method, the deviations can be determined, for example, directly from a comparison of all received signals with one another and / or, for example, also from a comparison of a monostatic signal of a digital radar sensor with a bistatic signal of an analog radar sensor to a digital radar sensor.

[0056] For example, according to Figure 5 In a fourth embodiment of the method, deviations of signals 54-62 relative to one another and thus of radar sensors 14-22 relative to one another can be determined. Since in such an embodiment the analog radar sensor and the digital radar sensor are transmitted in a common first modulation method, the deviations can be determined, for example, directly from a comparison of all received signals with one another and / or further, for example, from a comparison of a monostatic signal of a digital radar sensor with a bistatic signal of an analog radar sensor to a digital radar sensor.

[0057] In step S4, the following deviation can be determined: the deviation is, for example, a few microseconds (μs) in terms of its transmission time point and tens of MHz in terms of its transmission frequency. Here, the limit of the deviation that can be determined or the deviation range that can be determined is determined by the modulation method used and the resolution of the digital radar sensor. If the deviation should be outside the limit that can be determined or if the determination of the deviation should be simplified, the method can also include a step S0 of time synchronization. By this step, at least the analog radar sensor is synchronized before the signal transmission so that the deviation of the analog radar sensor is within the deviation range that can be determined. This also reduces the computational workload required for determining the deviation in step S4, because the deviation only needs to be determined within the limit, which is determined by the synchronization performed in step S0. Here, the synchronization can be performed, for example, by a synchronization protocol, but is not limited to this.

[0058] Next, after the deviation is determined in step S4, an adaptation can be performed in step S5. Such an adaptation includes the following values ​​and data: the values ​​and data indicate the deviation of the corresponding analog radar sensor 14-20. In this case, the adaptation can be performed in such a way that the received signal can be corrected with the aid of the correction value and can then be evaluated in step S6. Alternatively or additionally, the adaptation can be performed in such a way that the transmission signal of the corresponding analog radar sensor 14-20 generated in step S1 is adapted with the aid of the correction value so that the signal subsequently transmitted no longer has a deviation. Likewise, the adaptation can be performed in such a way that the analog radar sensor 14-20 transmits its transmission signal in a corrected manner with the aid of the correction value. In this case, the adaptation can be performed with an accuracy of a few nanoseconds (<1 μs) and in the sub-megahertz (<1 MHz) range and is limited by the resolution of the analog radar sensor, which is usually smaller than the resolution of the digital radar sensor.

[0059] The adaptation in step S5 makes it possible to make the deviations of the signals of the simulated radar sensors relative to one another so small that a bistatic path between the simulated radar sensors can be evaluated. This means that a signal sent by any simulated radar sensor 14-20 can be received and evaluated by another simulated radar sensor 14-20. This makes it possible to perform an evaluation even with a lower resolution of the simulated radar sensors. This makes it possible, for example, to evaluate a larger virtual aperture that can be formed by different analyzable signal paths.

[0060] In this case, the determination (step S4) and adaptation (step S5) of the deviation can be performed only at the beginning of the operation of the radar network 10 according to one embodiment of the method according to the invention. Preferably, these steps are performed at regular intervals or continuously during operation. This improves the accuracy of the radar network and the method, because the deviations that occur are detected and corrected in a timely manner or without delay.

[0061] In step S6, depending on the embodiment, the different available signals are evaluated. This includes monostatic paths of the corresponding analog radar sensors and digital radar sensors, bistatic paths of the corresponding analog radar sensors to the digital radar sensors, and bistatic paths of the analog radar sensors between each other. Figure 4 and Figure 5 In the specific embodiment shown in FIG. 1 , in which all radar sensors transmit using the first modulation method, the bistatic path of the digital radar sensors to the corresponding analog radar sensors can also be evaluated.

[0062] In this case, deviations that still exist can be taken into account, which are less than the resolution limit of the accuracy of the analog radar sensor. This means that deviations that cannot be technically adapted can be detected by the higher resolution of the digital radar sensor and taken into account in the evaluation.

[0063] Figure 7 A schematic diagram shows the method steps of the method according to the invention with interference detection and subsequent adaptation. Figure 6 All the same steps are not repeated in the following. Figure 7 The method comprises step S7: determining an interference band from a signal received by at least one digital radar sensor, the interference band having no and / or very little interference. The digital radar sensor receives all signals sent (step S3). Thus, a frequency band having no interference or low interference can also be determined. Preferably, such a frequency band is determined in a frequency range utilized by an analog radar sensor. Here, step S7 is performed, for example, simultaneously with step S4. In this way, interference determination can be performed without affecting the operation of other methods and the radar network thus operated by means of the method. However, here, the determination of the interference band can also be performed, for example, before or after the determination of the deviation (step S4), which reduces the required computing power.

[0064] Furthermore, in step S5, the signal is adapted to the frequency band determined in step S7. For example, the signal frequency is shifted along the spectrum in such a way that it is located in a frequency band that has no and / or only very little interference. This adaptation can be performed simultaneously with the adaptation or correction of the deviation determined in step S4. Figure 7 With the method shown in , a cognitive radar can be operated that can detect and avoid interference that occurs. Since the determination of the frequency band in step S7 can be performed as an evaluation of the data digitally converted in step S3, the method according to the invention does not require any further adaptation of the radar network operated with the method, except for increased computing power.

[0065] Reference numerals

[0066] 10 Radar System

[0067] 12 Vehicles

[0068] 14 Simulating radar sensors

[0069] 16 Simulating radar sensors

[0070] 18 Simulating radar sensors

[0071] 20 Simulating radar sensors

[0072] 22 Digital radar sensors

[0073] 24; 34; 44; 54 Simulate the transmission signal of the radar sensor 14

[0074] 26; 36; 46; 56 Simulate the transmission signal of the radar sensor 14

[0075] 28; 38; 48; 58 Simulate the transmission signal of the radar sensor 14

[0076] 30; 40; 50; 60 Simulate the transmission signal of the radar sensor 14

[0077] 32; 42; 52; 62 Simulate the transmission signal of the radar sensor 14

Claims

1. A method for operating a multiple-input multiple-output (MIMO) radar network, the method comprising the steps of: Generate and transmit signals; transmitting the signal by means of a plurality of analog radar sensors and at least one digital radar sensor, in, The plurality of analog radar sensors and the at least one digital radar sensor are transmitted in a first modulation method, or wherein the plurality of analog radar sensors transmit in a first modulation method and the at least one digital radar sensor transmits in a second modulation method, wherein the transmission signals of the first modulation method and the second modulation method do not overlap in both the time range and the frequency range; Receive and pre-process the reflected signal for digital processing, wherein the at least one digital radar sensor receives the signals transmitted by all radar sensors; determining deviations of at least the transmission times and the transmission frequencies of the plurality of analog radar sensors relative to one another using signals received from the at least one digital radar sensor; Adapting at least the transmission time points, reception time points and transmission frequencies of the signals of the plurality of simulated radar sensors to one another; The received signal is analyzed and processed in at least one of the following paths: The corresponding monostatic path of the radar sensor, at least one bistatic path from the at least one analog radar sensor to the digital radar sensor, corresponding bistatic paths between the plurality of simulated radar sensors, and If the plurality of analog radar sensors and the at least one digital radar sensor are transmitted in the first modulation method, a corresponding bistatic path of the at least one digital radar sensor to the plurality of analog radar sensors.

2. The method according to claim 1, further comprising a prior step for time synchronization of the radar sensor, in, The synchronization comprises sending out a separate radar signal at a predetermined time for determining the deviation and adapting on this basis; or In this case, the synchronization is carried out via a trigger signal of the at least one radar sensor and / or via a synchronization protocol and / or via a clock signal.

3. The method according to any one of claims 1 or 2, in, The first modulation method is an FMCW method using a Doppler multiplexing method (DDM) or a time division multiplexing method (TDM) or a code division multiplexing (CDM); and / or The second modulation method is an orthogonal frequency division multiplexing method (OFDM) or a phase modulation continuous wave (PMCW) method.

4. The method according to any one of the preceding claims, in, The evaluation of the signals received by the plurality of simulated radar sensors includes demodulation of the respective received signals.

5. The method according to any one of claims 1 to 4, in, If the plurality of analog radar sensors and the at least one digital radar sensor transmit in the first modulation method, the evaluation of the signal received by the at least one digital radar sensor comprises separating the monostatic signal of the at least one digital radar sensor from the bistatic signals of the plurality of analog radar sensors by means of an optimal filter; or If the at least one digital radar sensor transmits using the second modulation method, evaluating the signal received by the at least one digital radar sensor includes separating the monostatic signals of the at least one digital radar sensor from the bistatic signals of the plurality of analog radar sensors by means of a frequency mask.

6. A method for interference identification and interference avoidance in the method according to any one of claims 1 to 5, the method comprising the following steps: determining frequency bands having no and / or very little interference from the signals received by the at least one digital radar sensor; and At least a transmission frequency of the signals of the plurality of simulated radar sensors is adapted to the frequency band.

7. The method according to claim 6, in, The step of determining a frequency band having no and / or very little interference from the signal received by the at least one digital radar sensor is performed together with the step of determining deviations of at least the transmission times and transmission frequencies of the plurality of analog radar sensors relative to one another by means of the signal received by the at least one digital radar sensor; and / or Therein, the step of adapting the transmission frequency of at least the signals of the multiple simulated radar sensors to a frequency band with no and / or very little interference is performed together with the step of adapting the transmission time points, reception time points and transmission frequency of the signals of at least the multiple simulated radar sensors to each other.

8. A multiple-input multiple-output (MIMO) radar network comprising: Multiple simulated radar sensors, wherein the plurality of analog radar sensors are implemented for transmitting and receiving signals in a first modulation method; at least one digital radar sensor, wherein the at least one digital radar sensor is designed to transmit and receive signals using the first modulation method or using the second modulation method, The transmission signals of the first modulation method and the second modulation method do not overlap in both the time range and the frequency range. wherein the at least one digital radar sensor is designed to receive the transmitted signals of all radar sensors, The at least one digital radar sensor and the plurality of analog radar sensors are designed to exchange data directly or via a switching unit. a computing unit, wherein the computing unit is designed to determine deviations of at least the transmission times and the transmission frequencies of the plurality of analog radar sensors relative to one another from the signals received by the at least one digital radar sensor, Therein, the at least one computing unit is further implemented to adapt at least the transmission times, the reception times and the transmission frequencies of the plurality of simulated radar sensors to one another.

9. The radar network according to claim 8, in, The at least one computing unit is further designed to adapt at least the transmission times, reception times and transmission frequencies of the plurality of simulated radar sensors to one another such that an evaluation of received signals is possible in corresponding bistatic paths between the plurality of simulated radar sensors.

10. A radar network according to any one of claims 8 to 9, in, The at least one digital radar sensor and the plurality of analog radar sensors are embodied in a time-synchronized manner.

11. A radar network according to any one of claims 8 to 10, in, The radar network includes a synchronization protocol and / or individual radar signals and / or clock signals.

12. A radar network according to any one of claims 8 to 11, in, The first modulation method is an FMCW method using a Doppler multiplexing method (DDM) or a time division multiplexing method (TDM) or a code division multiplexing method (CDM); and / or wherein the second modulation method is an orthogonal frequency division multiplexing method (OFDM) or a phase modulation continuous wave (PMCW) method.

13. A radar network according to any one of claims 8 to 12, in, The computing unit is further designed to evaluate the adapted received signal in at least one of the following paths: The corresponding monostatic path of the radar sensor; at least one bistatic path from at least one analog radar sensor to said digital radar sensor; respective bistatic paths between the plurality of simulated radar sensors; if the plurality of analog radar sensors and the at least one digital radar sensor are transmitted in the first modulation method, a corresponding bistatic path of the at least one digital radar sensor to the plurality of analog radar sensors; and / or Therein, the computing unit is further designed to determine a frequency band having no and / or very little interference from the signal received by the at least one digital radar sensor and to adapt at least the transmission frequency of the signals of the plurality of analog radar sensors to the frequency band. 14 . The radar network according to claim 8 , which is used to implement the method according to claim 1 .

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