Radar sensor device and method for operating a radar sensor device

Abstract

The invention relates to a radar sensor device (10) comprising at least one radar sensor (RS1) and a controller (SE) which is connected to the at least one radar sensor (RS1) and is designed to control the process of generating a transmission signal and the process of scanning a received signal of the radar sensor, wherein the transmission signal is a periodically repeated and linearly frequency-modulated signal, the center frequency and / or ramp gradient and / or pulse repetition rate of the transmission signal and / or the number of frequency ramps per measurement cycle and / or pauses between measurement cycles can be adjusted, and the controller is designed to detect pulse interference occurring in the scanned received signal and to calculate the frequencies of the transmission causing the interference.

Description

[0001] Description

[0002] title

[0003] Radar sensor device and method for operating a radar sensor device

[0004] The present invention relates to a radar sensor device and a method for operating a radar sensor device.

[0005] State of the art

[0006] Radar sensors can play an important role in the increasing degree of vehicle automation, and the number of radar sensors per vehicle is expected to continue to rise. In typical applications, a large number of vehicles can already be equipped with driver assistance functions implemented using radar sensors. A radar sensor emits a modulated electromagnetic wave and uses the received reflection, which is delayed and Doppler-shifted, to determine the distances and relative velocities of various reflection points in the vicinity of the moving vehicle.

[0007] The current series sensors of different vehicles use independent modulations and are generally not coordinated with each other, which simultaneously increases the probability that the signals of the radar sensors will interfere due to an overlap of the electromagnetic waves and the reduction of the signal quality.

[0008] Due to the increasing number of radar sensors within a vehicle, the radar sensors are operated in a coordinated manner to reduce interference between the radar sensors from one vehicle. For this purpose, the radar sensors are synchronized on the hardware side.

[0009] In MB Alabd, B. Nuss, C. Winkler and T. Zwick, "Partial Chirp Modulation Technique for Chirp Sequence based Radar Communications," 2019 16th European Radar Conference (EuRAD), 2019, pp. 173-176. An application of a modulation technique is called a modulation technique.

[0010] EP 3 572 828 A1 describes a combined radar and communications system.

[0011] Disclosure of the invention

[0012] The present invention provides a radar sensor device according to claim 1 and a method for operating a radar sensor device according to claim 6.

[0013] Preferred further training is the subject of the subclaims.

[0014] Advantages of the invention

[0015] The idea underlying the present invention is to provide a radar sensor device and a method for operating a radar sensor device, wherein the scanning of a radar sensor can be better selected at specific times and signal waveforms. Sampling here refers to the reception of the high-frequency signals emitted by the radar sensor, which are characterized as linear frequency modulation, i.e., frequency ramps over time. In the receiver, the signal received by the antenna system is mixed down to the baseband with the transmitted signal and then sampled with an analog-to-digital converter.

[0016] According to the invention, the radar sensor device comprises at least one radar sensor; and a control device which is connected to the at least one radar sensor and is configured to apply a transmission signal to the radar sensor and to perform a scanning sequence on the radar sensor, wherein a specific time period of the transmission signal and / or a reception signal at the radar sensor is selectable for applying the scanning sequence.

[0017] According to the invention, the radar sensor device comprises at least one radar sensor; and a control device which is connected to the at least one radar sensor and is configured to control the generation of a transmission signal and the sampling of a reception signal of the radar sensor, wherein the transmission signal is a periodically repeated and linearly frequency-modulated signal, and wherein a center frequency and / or a ramp gradient and / or a pulse repetition rate of the transmission signal and / or a number of frequency ramps per measuring cycle and / or pauses between measuring cycles can be set, and the control device is configured to detect pulse-like interference occurring in the sampled reception signal and to calculate the frequencies of the emission causing it.

[0018] According to a preferred embodiment of the radar sensor device, the causing transmission concerns another radar sensor and is emitted by this.

[0019] According to a preferred embodiment of the radar sensor device, it comprises a reference control unit and a reference sensor which is configured to transmit a reference transmission signal and the control device is connected to the radar sensor and with which the transmission signal of the radar sensor can be synchronized with the reference transmission signal of the reference sensor with regard to transmission and scanning by the control device.

[0020] According to a preferred embodiment of the radar sensor device, the transmission signal comprises a triangular signal.

[0021] According to a preferred embodiment of the radar sensor device, a reference unit comprising the reference control unit and the reference sensor, as well as a further sensor unit comprising the control device and the radar sensor, are located in different vehicles.

[0022] Using the (specific) sampling sequence, a received signal from the radar sensor can be evaluated, and the distance and movement of an object can be deduced. The sampling points and / or transmission points can be advantageously selected in terms of frequency and time, for example, at a specific time and frequency of the signal, as well as in terms of number and duration, and / or similar. The change in frequency can involve a specific type of frequency response at the selected sampling points, such as a section where a signal ramp increases in frequency (linearly or nonlinearly) or decreases, or both.

[0023] This allows the sign of the ramp slope (ramp direction) to be changed during sampling, or sampling to occur when the signal gradient is at the desired level. This allows sampling to be selected for signal sections within a "chirp sequence" measurement cycle. A particular advantage lies in the simplicity of the method, which allows it to be applied immediately without affecting subsequent signal processing. The desired signal can be specified, and the sections to be sampled can be selected.

[0024] The ramp direction within a measurement cycle can be selected arbitrarily, which can offer various potentials for radar sensors. For example, the use of triangular modulation with almost identical signal processing can be achieved, which eliminates the need for stepbacks in the phase-locked loop and allows the ramp repetition rate to be increased. By omitting the stepback, interference is reduced and it is possible to dispense with switching off the transmit amplifier. Furthermore, synchronization of cooperative sensors can be achieved, whereby transmissions can also be coordinated wirelessly to avoid interference. Furthermore, by selecting the ramp direction depending on an information data stream (e.g., a sequence of 0 and 1 symbols), communication between radar sensors can be enabled. This can be used to coordinate the communicating radar sensors and exchange information.

[0025] According to a preferred embodiment of the radar sensor device, it comprises a reference sensor, which transmits a reference transmission signal and / or uses a reference sampling signal; and the control device, which controls the reference transmission and reference sampling signals with regard to time, frequency, and ramp direction.

[0026] Furthermore, coordination of the operation of several radar sensors or synchronization of the operation or scanning of the radar sensors can be improved.

[0027] According to a preferred embodiment of the radar sensor device, the predetermined transmission signal comprises a triangular signal, advantageously as a function of the frequency of the transmission signal over time.

[0028] The transmission signal can advantageously be variable and therefore adapted / synchronized to the reference signal and / or the reference sampling rate.

[0029] According to a preferred embodiment of the radar sensor device, sampling can be carried out during a frequency-increasing signal ramp of the transmitted signal and / or the received signal and / or during a frequency-decreasing signal ramp of the transmitted signal and / or the received signal and / or the gradient of the signal ramp can be selected by means of the control device.

[0030] According to a preferred embodiment of the radar sensor device, it comprises a plurality of radar sensors which can be installed in the same vehicle or in particular in different vehicles and by means of which the transmission signal and the scanning sequence at the radar sensors can be synchronized with the reference scanning signal and with the reference transmission signal.

[0031] In addition to synchronization, communication between the radar sensors can take place via the air interface. According to the invention, the method for operating a radar sensor device comprises providing a radar sensor device according to the invention comprising at least one radar sensor and one reference sensor; detecting the pulse interference generated by the transmission of the reference sensor in the received signal of the radar sensor and calculating the transmission frequencies of the transmission of the reference sensor; and controlling the radar sensor by means of the control device such that, by appropriately setting the modulation parameters, in particular center frequency, ramp gradient, and time of transmission, the detected frequency of the frequency generated by the reference sensor in the received signal of the radar sensor is constant.

[0032] According to a preferred embodiment of the method, transmissions from the radar sensor are further synchronized with the transmissions from the reference sensor; the radar sensor is controlled by the control device with a sequence of ramp gradients suitable for minimizing the duration of the amplitude-pulse disturbances and thus the interference.

[0033] According to a preferred embodiment of the method, the radar sensor is further controlled by means of the control device with a sequence of ramp gradients which is suitable for generating a sequence of amplitude pulse disturbances in the received signal of the reference sensor, which transmits a message based on a defined code book.

[0034] According to a preferred embodiment of the method, interference of the message at the radar sensor is further minimized in conjunction with controlling the radar sensor by means of the control device with a sequence of ramp gradients that has a suitable time offset from the transmissions from the radar sensor in order to avoid or reduce interference generated by the reference sensor in the received signal of the radar sensor. According to a preferred embodiment of the method, interference of the message at the radar sensor is further minimized, in particular in conjunction with controlling the radar sensor by means of the control device with a sequence of ramp gradients that has a suitable frequency offset from the transmissions from the reference sensor in order to avoid or reduce interference generated by the reference sensor in the received signal from the radar sensor.

[0035] According to a preferred embodiment of the method, after synchronization and transmission of the messages from several radar sensors, the reference sensor transmits messages for coordinating the transmissions of the various radar sensors by transmitting a suitable ramp sequence, wherein the control devices of the radar sensors interpret the message according to a previously defined code book.

[0036] According to the invention, the method for operating a radar sensor device comprises providing a radar sensor device according to the invention; controlling the radar sensor with the transmission signal and performing the scanning sequence on the radar sensor, wherein a specific time period of the transmission signal and / or the reception signal is selected for applying the scanning sequence.

[0037] According to a preferred embodiment of the method, the sign of a ramp gradient of the transmitted signal and / or the received signal and / or the sampling sequence is selected according to a specification.

[0038] According to a preferred embodiment of the method, the reference sensor transmits the reference transmission signal to which the second (or a further) radar sensor synchronizes its own transmission signal with the aid of the control device.

[0039] According to a preferred embodiment of the method, the reference sensor generates a reference transmission signal and / or a reference scanning signal; which, from a second sensor with its control device, synchronizes the transmission signal of the second sensor with the reference transmission signal of the reference sensor with respect to transmission and scanning.

[0040] The presented method is easy to implement and can be directly applied to current radar sensors. However, due to the existing separation between radiolocation services and communications in the regulation of current radar frequency bands, the method also appears particularly suitable for future sensors in new frequency bands, for example, above 100 GHz. Due to the expanded speed evaluation range, it offers advantages for the sensor itself, and due to reduced interference, it also offers advantages for all radar sensors in use in the field.

[0041] The radar sensor device can also be characterized by the features and advantages mentioned in connection with the method and vice versa.

[0042] Further features and advantages of embodiments of the invention will become apparent from the following description with reference to the accompanying drawings.

[0043] Short description of the drawings

[0044] The present invention is explained in more detail below with reference to the exemplary embodiments shown in the schematic figures of the drawing.

[0045] They show:

[0046] Fig. 1 is a schematic representation of a signal curve of frequency over time for operating a radar sensor device according to a comparative example and according to two embodiments of the present invention;

[0047] Fig. 2 is a block diagram of method steps of the method for operating a radar sensor device according to a further embodiment of the present invention.

[0048] Fig. 3 shows an interference signal from fully synchronized radar sensors and a deviation from it

[0049] In the figures, the same reference symbols denote the same or functionally identical elements.

[0050] Fig. 1 shows a schematic representation of a signal curve for operating a radar sensor device according to a comparative example and according to two embodiments of the present invention.

[0051] Figure 1a shows a ramp signal (transmitted or received signal) of frequency f as a function of time t, which corresponds to a conventional chirp signal. Sampling can usually only be performed on the frequency-descending branch via the sampling points di.

[0052] The state of the art is a sawtooth-shaped "chirp sequence" modulation scheme, as shown in Fig. 1a. Fig. 1a shows the modulation scheme and the indicated sampling times di on the rising ramp of the signal frequency at the radar sensor. After two-dimensional scanning in the time and frequency directions, the distance (via time delay) and speed (via Doppler frequency shift) of radar targets can be determined (e.g., by superimposing the transmitted and received signals).

[0053] Figures 1b and 1c, on the other hand, pursue an inventive approach according to which the "chirp sequence" modulation method can be used in an adapted form without affecting the radar signal processing. Instead, the application of the modulation can be improved, resulting in even further application possibilities, e.g., for the synchronization or communication of cooperatively operating radar sensors. A typical chirp sequence radar uses the generated transmission signal (frequency ramps with frequency dependence f(t)) simultaneously as the input signal of the mixer in the receive path (homodyne principle). After the mixer, the received signal is low-pass filtered by an anti-aliasing filter (AAF) with a cutoff frequency fAAF. Sampling then takes place through the A / D converter. Due to the homodyne principle, the frequency range sensitive for receiving signals is effectively shifted by f(t).

[0054] The signs of individual ramps of a signal at the radar sensor can be changed within a measurement cycle; in other words, the ramp (or several ramps) can be selected at which the frequency response of the radar transmission signal can occur according to a specific sequence with a positive or a negative gradient, whereby pauses are also possible.

[0055] If the ramp direction is to be reversed without affecting the signal processing, the sampling of the frequency ramps must be adjusted so that the sample values ​​correspond to the same instantaneous frequency of the ramp, i.e. have the same time step size of the sample points, even with a frequency-falling ramp, as shown in Fig. lb.

[0056] In a system consisting of two radar sensors (reference sensor or first sensor and second sensor), the second sensor is operated with a sequence complementary to the first sensor. This means that where the reference sensor uses a signal that increases in frequency over time, the second sensor uses a signal that decreases over time.

[0057] Both the first and second sensors detect the sampled values ​​in the received signal that are affected by interference from other sensors. Interference occurs when high-frequency signals are received from other sensors. The interference manifests itself as amplitude pulse noise in the sampled received signal. This pulse noise is assigned to a specific frequency in the receiver (Fig.

[0058] 3)

[0059] In particular, the second sensor detects the sample values ​​that have been disturbed (interfered) by the signal from the first sensor as amplitude pulse noise. The sample values ​​of the interference of the signal from the first sensor in a fully synchronized second sensor (with a sequence complementary to the first sensor in terms of ramp gradients) in the "chirp sequence" method of Fig. 1a are advantageously located at the same frequency for each chirp in the middle of the frequency range covered by the frequency ramp. In this case, the start times of the frequency ramps of the first sensor and the second sensor are synchronous.

[0060] The radar channel, i.e., the signals reflected by the objects, can be assumed to be temporally constant with respect to their baseband frequency for the duration of the ramps (e.g., sections of an ascending or descending ramp). For ramps with a reverse direction, only the order of the sample values ​​needs to be reversed. This procedure has no influence on the subsequent signal processing.

[0061] Due to the absence of a return to the beginning of a rising ramp, as is the case in Fig. 1a (the new sampling series only starts again at the rising ramp, and the frequency sample values ​​return to the smallest value of the sample in known methods; however, in method steps according to the invention, such a return can be omitted), firstly, the ramp repetition rate can be increased, thereby increasing the clearly measurable speed. Secondly, this also reduces the interference potential, meaning that switching off the transmit amplifiers during the ramp return is no longer necessary.

[0062] Furthermore, according to Fig. lc, different sequences of rising, falling or resting areas of the signal can be used and follow one another, whereby this change in the ramp direction can be understood as a binary coding (e.g. a rising ramp corresponds to a 1, a falling ramp corresponds to a 0, cf. Fig. lc with the code 1101).

[0063] The meaning assigned to this code can be used to transmit specific information. It should be noted that the return time should take into account the fact that a constant ramp repetition rate is then present.

[0064] Coding the ramp direction in this way can also be used for data transmission between radar sensors. Thus, after synchronization between a first and a second sensor, the temporal position of the pulsed interference can be used to determine whether the received interference signal is a rising or falling ramp. Pulsed interference in the received signal arises when the transmitted signal of the first sensor, with frequency dependence fsi(t), crosses the frequency range of the second sensor sensitive to reception, with the cutoff frequencies fs2(t)±fAAF,2. This signal is then visible as pulsed interference in the sampled baseband signal.

[0065] The actual frequency of the interference can be calculated from the temporal position of the disturbed samples and fs2(t).

[0066] Subsequently, decoding can take place and correspond to a simple interference detection on the receiver side.

[0067] Pulse-shaped interference introduced by this communication can be limited to a few samples of the sampling sequence and can be corrected after decoding with conventional methods by suitable filtering or by replacing the disturbed samples with estimated values.

[0068] The assignment described above can be used to assign meaning to the coded sequence of rising and falling ramps used by the first sensor, allowing for the transmission of optional information that can be used to improve the coordination of the radar sensors. Examples include an ID (identification) for the function performed by the radar sensor or a prioritization of frequency bands. The transmission of a sensor type identifier, the center frequency and bandwidth used, etc., are also possible.

[0069] During communication, i.e., the transmission of data between the radar sensors, the synchronization of the frequency ramp sequences of both sensors can be readjusted (corrected, improved, or adjusted) by comparing the time of the expected interference pulse with the actual time of the interference pulse. The difference can act as a controlled variable on a digital controller of the signal output for the ramp sequence. Fig. 2 shows a block diagram of method steps of the method for operating a radar sensor device according to another embodiment of the present invention.

[0070] In the method for operating a radar sensor device, a radar sensor device according to the invention is provided S1; the radar sensor is controlled S2 with the transmission signal and the scanning sequence is carried out on the radar sensor, wherein a specific time period of the transmission signal and / or reception signal is selected for applying the scanning sequence.

[0071] Fig. 3 shows a representation of an interference signal from fully synchronized radar sensors and a deviation from it.

[0072] The method can be used for the synchronization of cooperative radar sensors. "Cooperative" can mean that the radar sensors are connected to each other in some way and / or their functionality is coordinated. For this purpose, a reference sensor and a fixed bit sequence of the transmission and / or sampling signals can be determined in advance, with the reference sensor transmitting and measuring using this sequence, which is known to all other sensors. The radar sensor to be synchronized uses the inverted code, for example, 0100 in the case shown in Fig. 1c.

[0073] If the measurement cycles are perfectly synchronized, a pulse-shaped interference Int can occur in the middle of all ramps or baseband signals, as shown in Fig. 3a. The frequency-constant line Int shows that the pulse-shaped interference occurs at the same point (time or frequency connected by the ramp function) for all ramps of the second sensor. This "same point" is advantageously in the middle of the own ramps of the second signal. Then, complete synchronization in time and frequency is achieved. The ramps of the first sensor and the second transmitter, as increments to each other, intersect advantageously orthogonally, which corresponds to complete synchronization. In the event of a deviation (as can be seen in Fig. 3b, i.e., a slope of the ramps away from the orthogonal course to each other), the ramps can be corrected and thus synchronized.

[0074] If the interference is distributed towards the upper and lower edges (i.e., towards larger and smaller frequency values), then synchronization is no longer present, which is shown in Fig. 3b and can be detected using conventional interference detection methods. The length of the deviating pulses from the interference signal can symbolize arbitrary behavior depending on the error (shift in the time of the signal fS2(t) or stretching in the time of the signal fS2(t)) that modifies the synchronization. A shifted bar in the signal Int can represent the frequency position of the pulse-shaped interference that has occurred, which in this case is not synchronized. The width of the individual interference pulses can be a measure of the ramp slope of the interfering signal.This feature can also be used to classify the desired pulse sequence of the sensor to be synchronized, allowing the sequence of rising and falling ramps of the first sensor to be estimated from it. If the deviations of the interference maxima are detected as a control error (when the bars Int are shifted from the horizontal center), synchronization becomes a simple control task. If interference occurs only sporadically, the measurement cycles do not yet overlap, and rough synchronization must be restored, for example, by a delay.

[0075] For synchronization, the sensor to be synchronized switches to the original code (from the second sensor), i.e. the code that is optimal for its own function, and takes into account an additional delay, in particular a predetermined deviation from the determined reference signal. This allows the sensors to always transmit during mutual pauses and not interfere with each other. After synchronization, the second sensor (e.g. its control device) can know when the first sensor is not transmitting and deliberately sits in this pause. There it can select the sequence of rising and falling ramps so that it is optimal for its measuring task. For example, in the case of two sensors, sawtooth modulation can be used for synchronization (1111 and 0000).By allowing the temporal interference pulses (signal intersections in the time-frequency diagram when superimposed) to drift apart, deviations can be more easily detected when the ramp direction changes. The ramp timing between the reference sensor and the radar sensor can be adjusted by inserting additional pauses into the ramp sequence. Furthermore, different codes can be used for the sensors to be synchronized to synchronize multiple sensors.

[0076] The robustness of the described method can be increased by masking out interference signals that do not originate from the sensor to be synchronized.

[0077] The interference signals can be assigned to individual sensors by determining them and classifying them according to signal strength. For this purpose, only interference signals with sufficiently similar amplitudes are advantageously used.

[0078] For signal filtering, a correlation of the interference pulse sequence with the expected code (e.g. through prior knowledge from a so-called code book that prescribes the codes used by the communicating / cooperating sensors) can be used to filter out only the pulses desired for synchronization.

[0079] The width of the individual interference pulses can be a measure of the ramp slope of the interfering signal due to the homodyne principle, since a frequency ramp of the first sensor generates wider interference pulses in the second sensor the more similar its ramp slope is to that of the first sensor. This feature can advantageously be used to classify the desired pulse sequence of the sensor to be synchronized. Although the present invention has been fully described above using the preferred embodiment, it is not limited to this but can be modified in a variety of ways.

Claims

Claims radar sensor device (10) comprising: - at least one radar sensor (RS1); and - a control device (SE) connected to the at least one radar sensor (RS1) and configured to control the generation of a transmission signal and the sampling of a reception signal of the radar sensor, wherein the transmission signal is a periodically repeated and linearly frequency-modulated signal, and wherein a center frequency and / or a ramp gradient and / or a pulse repetition rate of the transmission signal and / or a number of frequency ramps per measurement cycle and / or pauses between measurement cycles are adjustable, and the control device is configured to detect pulse-like disturbances occurring in the sampled reception signal and to calculate the frequencies of the causing transmission. Radar sensor device (10) according to claim 1, wherein the causing transmission relates to another radar sensor and is emitted by the latter. Radar sensor device (10) according to claim 1 or 2, which comprises a reference control unit (SE ref) and a reference sensor (Ref) which is configured to transmit a reference transmission signal and the control device (SEI) is connected to the radar sensor (RS1) and with which the transmission signal of the radar sensor (RS1) can be synchronized with the reference transmission signal of the reference sensor with regard to transmission and scanning by the control device (SEI). Radar sensor device (10) according to claim 1, 2 or 3, wherein the transmission signal comprises a triangular signal. Radar sensor device (10) according to claim 3, wherein a reference unit which comprises the reference control unit (SE re f) and the reference sensor (Ref) (SE re f and Ref), and a further sensor unit comprising the control device (SE) and the radar sensor (RS1) are located in different vehicles. A method for operating a radar sensor device (10), comprising the steps: - Providing (S1) a radar sensor device (10) according to one of claims 1 to 5 comprising at least one radar sensor (RS1) and one reference sensor (Ref); - detecting (S2) the pulse interference generated by the transmission of the reference sensor (Ref) in the received signal of the radar sensor (RS1) and calculating the transmission frequencies of the transmission of the reference sensor (Ref); - Controlling (S3) the radar sensor (RS1) by means of the control device (SEI) such that, by appropriately adjusting the modulation parameters, in particular center frequency, ramp slope, and time of transmission, the detected frequency of the frequency generated by the reference sensor (Ref) in the received signal of the radar sensor (RS1) is constant. Method according to claim 6, further comprising the steps of: - Synchronizing transmissions from the radar sensor (RS1) with the transmissions from the reference sensor (Ref); - Controlling the radar sensor (RS1) by means of the control device (SEI) with a sequence of ramp gradients suitable for minimizing the duration of the amplitude-pulse disturbances and thus the interference. Method according to claim 6 or 7, further comprising the steps of: - Controlling the radar sensor (RS1) by means of the control device (SEI) with a sequence of ramp gradients suitable for generating a sequence of amplitude pulse disturbances in the received signal of the reference sensor, which transmits a message based on a defined codebook. Method according to claim 8, further comprising the steps of: - minimizing interference of the message at the radar sensor (RS1) in conjunction with controlling the radar sensor (RS1) by means of the control device (SEI) with a sequence of ramp gradients having a suitable time offset to the transmissions from the radar sensor (Ref) in order to avoid interference generated in the received signal of the radar sensor (RS1) by the reference sensor (Ref) or reduce. Method according to claim 8 or 9, further comprising the steps of: - Minimizing the interference of the message at the radar sensor (RS1), in particular in conjunction with controlling the radar sensor (RS1) by means of the control device (SEI) with a sequence of ramp gradients that has a suitable frequency offset from the transmissions from the reference sensor (Ref) in order to avoid or reduce the interference generated by the reference sensor (Ref) in the received signal from the radar sensor (RS1). Method according to one of claims 8 to 10, wherein, after synchronization and transmission of the messages from several radar sensors (RS1, RS2, RS3), the reference sensor transmits messages for coordinating the transmissions of the various radar sensors by transmitting a suitable ramp sequence, wherein the control devices of the radar sensors interpret the message according to a previously defined codebook.

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