Time-of-flight transmission measurement for calibration and diagnosis of photonic radar systems

Abstract

The invention relates to a photonic radar system (100) comprising a central station (200) and at least one radar head device (300, 300-n) designed as a transmitter and / or receiver module, wherein the at least one radar head device (300, 300-n) is connected to at least one transmission medium (400, 400-n) for transmitting an optical signal to the radar head device (300, 300-n), and is connected to at least one return transmission medium (500, 500-n), wherein a monitoring unit (600) comprises: a test-signal generation unit for generating an optical test signal for transmission via the at least one transmission medium to the at least one radar head device (300, 300-n) and for return transmission via the at least one return transmission medium (500, 500-n); a detection unit (630) for detecting the returned test signal; and an evaluation unit which is designed to determine at least one transmission characteristic and to output at least one calibration information item derived from the at least one transmission characteristic to a computation unit (270) of the central station (200). The invention also relates to a method for operating a photonic radar system comprising a monitoring device (600).

Description

[0001] Description

[0002] Time-of-flight transmission measurement for the calibration and diagnosis of photonic radar systems

[0003] The invention relates to the calibration and diagnosis of photonic radar systems, in particular multiple-input-multiple-output (MIMO) radar systems of vehicles for environmental and / or interior monitoring.

[0004] Radar systems are defined as environmental detection systems that determine the distance and speed of objects in the environment, and preferably also their angular orientation relative to the radar system, by emitting electromagnetic radiation in the frequency range of 3 GHz to 300 GHz and detecting the backscattered radiation. Radar systems, particularly historical ones, operating in the lower frequency range are also known.

[0005] To achieve good angular resolution, the largest possible aperture is desirable. In a radar system, this can be increased by combining multiple transmitting and receiving antennas in an antenna array. The area covered by the antenna array determines the aperture size. It has proven advantageous to centralize signal generation and processing in a central station. Radar radiation is emitted via radar head units coupled to the antennas. These units simply amplify the radar signal information transmitted by the central station and, if necessary, multiply its frequency beforehand. The reflected or backscattered radar radiation is detected by the radar head units, and the corresponding echo signal information is transmitted back to the central station for processing.

[0006] If the transmission of radar signal information and echo signal information between the central station and the radar head units is optical, such a radar system is called a photonic radar system. The use of a central station to generate the radar signal information to be transmitted, and the use of optical transmission, furthermore makes it possible to achieve coherence between the radar signals emitted by the various transmitting antennas and the detected echo signal information transmitted back. For correct evaluation, among other things, precise knowledge of the travel time of the optical signals between the central station and the individual radar head units, which operate as transmit and receive modules, is necessary.

[0007] The radar head units, functioning as transmit and receive modules, are preferably implemented in an electronically-photonically cointegrated chip, a so-called EPIC. This enables the monolithic integration of photonic components, high-frequency electronics, and digital electronics on a single chip. The advantage lies in the fact that signal transmission can occur using optical signals in the terahertz (THz) range, onto which the radar and echo signal information, typically in the sub-gigahertz (GHz) range, is modulated. The information to be transmitted is modulated onto an optical carrier signal generated in the central station. In principle, configurations with multiple microchips are also possible, in which photonic and electronic components are implemented on separate chips.

[0008] Optical transmission links typically utilize fiber optics as their optical transmission medium. These fibers can change under unfavorable environmental conditions, such as temperature or humidity fluctuations, and / or be mechanically damaged or impaired. Furthermore, typical manufacturing tolerances must be considered. If such changes are ignored, they can impair and distort the data analysis.

[0009] WO 2020 / 084408 A1 describes a device for testing for faults and deviations in an electrical waveguide, such as a coaxial cable or coaxial line, as used in radio and television towers or mobile phone masts. The device is designed to inject a signal into the waveguide and to receive a backscattered signal, from which mismatches or faults can be detected.

[0010] EP 2 026 094 A1 describes a time-of-flight calibration system for a radar-based measuring device, comprising a target antenna and a waveguide, e.g., a coaxial cable coupled to the target antenna at one end and terminated at the other end with a wave-reflecting impedance. WO 2018 / 134617 A1 describes a device for locating a measurement anomaly, such as a hot spot, along an optical waveguide, comprising: an optical waveguide, a light source configured to transmit light along the waveguide, and a plurality of sensors positioned along the waveguide. Each sensor is configured to reflect a portion of the light propagating along the waveguide at a corresponding sensor wavelength representing a measurement.The multiple sensors are configured in one or more sets according to their sensor wavelengths, each set comprising multiple sensors with corresponding sensor wavelengths, the sensors being configured such that the sensor wavelength is substantially the same for each sensor in a corresponding set when the measured quantity detected by each of the sensors in that set is the same.The device further comprises a detector configured to monitor the light reflected by the sensors, and a control system configured to cause the following steps to be carried out: transmitting light along the optical waveguide using the light source; monitoring the light reflected by the sensors to obtain a measured spectrum representing a measurement experienced by each of the sensors; detecting an anomalous signal in the measured spectrum, having a characteristic wavelength and emanating from an anomalous sensor of the plurality of sensors, the anomalous sensor experiencing the measurement anomaly; and locating at least the group containing the anomalous sensor.

[0011] All these systems are based on the reflection of signals that have only a limited intensity.

[0012] The invention is based on the objective of creating an improved device and an improved method, respectively, for calibrating and diagnosing photonic radar systems, and a radar system with diagnostic and calibration capabilities.

[0013] The invention is solved by a radar system with the features of claim 1 and a method with the features of claim 9. Advantageous embodiments are described in the dependent claims.

[0014] Basic idea of ​​the invention The invention is based on the idea of ​​further developing a photonic radar system with a central station and at least one radar head assembly designed as a transmitting and / or receiving module, preferably a plurality of radar head assemblies designed as transmitting and / or receiving modules, wherein the at least one or the plurality of radar head assemblies is each connected to at least one transmission medium for transmitting an optical signal to the respective radar head assembly and to at least one return transmission medium for transmitting an optical signal back, wherein an optically transmissive transmission path from the transmission medium to the return transmission medium is provided in the radar head assembly or the respective radar head assembly.The radar head devices are configured such that at least a portion of the optical signal transmitted to the respective radar head device via the at least one transmission medium is transmitted back via the return transmission medium. A monitoring device for diagnosing and / or calibrating the individual radar head devices optically connected to a central station is provided, such that an optical test signal is generated in or spatially adjacent to the central station and optically transmitted to the corresponding radar head device. The test signal transmitted by the radar head device and transmitted back is detected, and at least one transmission parameter is determined based on this detected test signal. For example, the propagation time of an optical signal, i.e., the total transmission time for the transmission to the radar head device and back, is determined.This can be used by the central station to improve radar signal generation and analysis. In addition to the transmission duration, the signal intensity of the back-transmitted test signal can also be recorded and analyzed. This allows for the detection of changes or impairments to the transmission medium and the back-transmission medium, such as local deformation, which can lead to signal loss. Numerous environmental factors can affect the transmission of optical signals via the transmission medium and / or the back-transmission medium. Furthermore, a failure of a radar head for environmental sensing can also be detected if no back-transmitted test signal is detected.

[0015] Preferred embodiments

[0016] A photonic radar system is proposed, comprising a central station and at least one radar head assembly configured as a transmitting and / or receiving module, wherein the at least one radar head assembly is connected to at least one transmission medium for transmitting an optical signal to the radar head assembly and to at least one return transmission medium for transmitting an optical signal back, wherein an optically transmissive transmission path from the transmission medium to the return transmission medium is formed in the at least one radar head assembly, such that at least part of the optical signal transmitted to the at least one radar head assembly via the at least one transmission medium is transmitted back via the return transmission medium.wherein a monitoring device comprises a test signal generation unit for generating an optical test signal for transmission via the at least one transmission medium to the at least one radar head device and back transmission via the at least one return transmission medium, and a detection unit for detecting the back-transmitted test signal, as well as an evaluation device configured to determine at least one transmission characteristic on the basis of the detected back-transmitted test signal and to output at least one calibration information derived on the basis of the at least one transmission characteristic to a calculation unit of the central station.

[0017] Furthermore, a method for diagnosing and / or calibrating a photonic radar system is provided, comprising a central station and at least one radar head unit optically connected thereto via a transmission medium and a return transmission medium, the radar head unit being configured as a transmitting and / or receiving module, wherein the at least one radar head unit is connected to the at least one transmission medium for transmitting an optical signal to the radar head unit and to the at least one return transmission medium for transmitting an optical signal back, wherein an optically transmissive transmission path is formed in the radar head unit from the transmission medium to the return transmission medium, such that at least a part of the optical signal transmitted to the at least one radar head unit via the at least one transmission medium is transmitted back via the return transmission medium, wherein the method comprises the steps:

[0018] Generating a test signal and transmitting the test signal via the at least one transmission medium, the at least one radar head device and the at least one return transmission medium to a detection unit;

[0019] Capturing the transmitted test signal;

[0020] Determine at least one transmission parameter based on the captured, back-transmitted test signal,

[0021] Deriving at least one calibration piece of information from the determined transmission parameter and outputting the control information. The proposed preferred embodiments make it possible to improve and reliably ensure the evaluation of the photonic radar system. Changes occurring in the transmission medium, the feedback medium, and / or the radar head units can thus be detected promptly, and, for example, a failure of a radar head unit can be addressed immediately during the generation and evaluation of the radar signals. Furthermore, a defective radar head unit and / or the associated transmission or feedback medium can be easily identified.

[0022] If the radar system comprises several radar head units, each radar head unit is connected to at least one transmission medium and a separate return transmission medium, between which a transmissive (transparent) optical connection exists in the radar head unit.

[0023] Compared to diagnostic methods based on light scattering or light reflection, the proposed method and device offer the advantage that the evaluated test signal exhibits a significantly higher intensity, thus achieving a better signal-to-noise ratio.

[0024] It should be clearly emphasized once again that the radar head unit does not actively intervene in the transmission of the test signal. Rather, the transmission and return transmission are based on a transmissive optical connection within the radar head unit between an input port, to which the transmission medium is connected, and an output port, to which the return transmission medium is connected.

[0025] In a simple embodiment, the test signal generation unit is designed to generate the test signal as a short, time-limited pulse. Short laser pulses can be generated easily. The propagation time of the signal via the transmission medium, the radar head assembly, and the return transmission medium can be determined by a simple time measurement between the transmission of the test signal and the reception of the returned test signal.

[0026] One embodiment of the method therefore provides that the test signal is generated as a short, time-limited pulse and that the time difference between the generation of the test signal and the detection of the transmitted test signal is determined via a timing device in order to derive a transit time of optical signals.

[0027] In addition to the transit time, a preferred embodiment also detects and evaluates the signal intensity of the transmitted test signal. This allows signal losses and attenuation, for example due to mechanical damage to the at least one transmission medium or the at least one feedback medium, to be detected early. If no transmitted test signal is detected at all, this indicates a failure of the radar head assembly or an interruption of the transmission medium or the feedback medium. In any case, it is necessary for the central unit to adjust the radar signal generation and evaluation accordingly. For this purpose, a signal is sent from the monitoring device to the central unit, in particular to a processing unit of the central unit.

[0028] Otherwise, the determined transmission parameters are preferably stored in a calibration file so that changes to at least one radar head can be easily detected during subsequent diagnostic or calibration steps and signaled to the central station's processing unit. Furthermore, the calibration file is preferably stored in such a way that the central station can access it and use the parameters it contains for evaluating and calibrating the radar system.

[0029] As an alternative to generating the test signal as a short, limited pulse, the test signal can also be generated with a frequency ramp or several frequency ramps whose ramp duration(s) is greater than a maximum total propagation time of an optical signal across the transmission medium, the radar head assembly, and the return transmission medium.

[0030] With a test signal generated in this way, part of the signal is routed directly to the detection unit, while another part is transmitted to the radar head and back. The portion of the test signal transmitted directly to the detection unit is optically superimposed on the portion transmitted back to the detection unit. This results in the detection of a beat signal during conversion, the frequency of which correlates with the propagation time of the test signal, i.e., the transmission duration. The signal transmission duration can thus be determined from the frequency of the electronically converted signal, which is referred to as the electronically converted back-transmitted test signal. Alternatively, it is possible to first electronically convert the back-transmitted test signal portion and then electronically superimpose it on a reference signal that represents the currently transmitted test signal., represents the test signal transmitted at the time of receipt of the returned test signal.

[0031] In one embodiment, the same structural components of the central station used to generate the signal for transmitting the radar signal information can also be used to generate the test signal. The radar signal information is used by the at least one radar head assembly, designed as a transmitter module, to generate the transmitted radar signal.

[0032] A frequency analysis of the beat signal and determination of the frequency correlated with the propagation delay is preferably performed using a Fourier transform, especially preferably using a Fast Fourier Transform (FFT).

[0033] Similarly, the acquisition unit can be integrated into a detection device of the central station and use the same converter component, i.e., the same converter, in particular a photodiode, to convert the optically acquired, transmitted test signal into an electrically transmitted test signal, which is also used to convert the transmitted echo radar signal information into electrical radar echo signal information. This minimizes the additional structural effort required for the monitoring equipment, i.e., for diagnostics and calibration.

[0034] Depending on the design of the central station's detection system for detecting and converting the echo radar signal information, it may be necessary to superimpose the untransmitted test signal component onto the transmitted test signal component at the converter using an optically controlled component. For detection systems that also incorporate optical superimposition during echo radar signal conversion, no additional structural modifications are required.

[0035] The use of structural components of the central facility already designed for radar operation is particularly possible in time-shifted operation, also known as time multiplexing. Especially precise evaluation of the radar signals is possible if changes to the transmission media, such as changes in length and / or attenuation losses due to environmental conditions, can be taken into account immediately. For this purpose, it is desirable to be able to perform the diagnostics continuously or quasi-continuously iteratively.

[0036] A diagnosis at the same time as environmental detection is particularly possible if the test signal is transmitted together with the other transmitted signals in a frequency division multiplexing method over the transmission medium or...

[0037] The data is transmitted via a return transmission medium. In this case, the components that generate the radar signal information to be transmitted are generally not usable. Instead, the monitoring device preferably comprises an independent pulse generation unit, which, according to one embodiment, is structurally separate from the central station.

[0038] One advantage of the physical separation is that the test signal generation unit is thermally isolated from the central station. This avoids further thermal stress on the central station, which is already very high due to the demanding computational workload in the processing unit. Physical separation of the pulse generation unit is therefore advantageous and facilitates cooling of the test signal generation unit.

[0039] The test signal generated by the test signal generation device is preferably routed to the central station and coupled there to the at least one transmission medium via an optical distribution device. Additionally, if the test signal is generated not as a short pulse signal but with frequency ramps, it is also routed to the detection unit.

[0040] If wavelength or frequency multiplexing is used, wavelength-selective or frequency-selective components, preferably optical components, are preferably provided in the beam path. These components separate the test signal from the optical signal used to transmit the radar signal information in the detection device and preferably also in the radar head assembly, so that the test signal does not interfere with environmental detection. In other embodiments, electronic frequency-dependent components may alternatively or additionally be provided to separate the test signal in the radar head assembly.

[0041] In the detection unit of the central station, in addition to the converter provided for converting the transmitted test signal, one or more further converters must be provided for converting the echo radar signal information. An additional converter is provided for each radar head assembly to convert the radar echo signal information.

[0042] If the test signal is transmitted with a time delay to only one of several radar head units using a switch, the back-transmitted test signal can be separated in the detection unit of the central station via frequency-selective beam splitters before the further transducers and directed to the transducer where the back-transmitted test signal is optically superimposed on the untransmitted test signal and detected.

[0043] The diagnosis and calibration can therefore be performed iteratively and cyclically.

[0044] One embodiment therefore provides that the detection unit is integrated into the detection device of the central station and that a wavelength-selective beam splitter is arranged in the optical beam path, which separates the optical test signal transmitted back via the at least one return transmission medium from the transmitted optical radar echo signal and, in addition to a converter for converting the transmitted optical test signal into an electrically transmitted test signal of the optical radar echo signal, a further converter for converting radar echo signal information of the optical radar echo signal into an electrical radar echo signal is provided in the detection device.

[0045] As an alternative to optical separation of the test signal when using a different optical frequency for the test signal than for radar signal information transmission, it is also possible to signal the individual radar head units via an electronic channel not to amplify and transmit the incoming optical signal while a diagnosis is being performed.

[0046] If frequency division multiplexing is performed simultaneously for several radar head units, the detection unit of the monitoring device comprises several transducers, at each of which the untransmitted test signal is optically superimposed on the transmitted test signal. Further transducers are integrated into the detection unit of the central station for converting the echo radar signal information.

[0047] Depending on the design of the central station's optical distribution system, the test signal can also be transmitted simultaneously to several radar head units and back to the central station's detection unit via the corresponding return transmission media. In such a case, multiple converter components are necessary to individually capture and evaluate the test signal components transmitted back via the various return transmission media for each radar head unit and its associated transmission and return transmission media.If, however, an optical switch is used in the central station that sequentially couples the test signal to the various transmission media for the different radar head units with a time delay, wavelength-selective coupling elements, such as beam splitters, can be introduced into the beam paths of the return transmission media for multiplexing during environmental detection in the detection unit. These elements direct the test signal to the same converter component, where the respective returned test signal, optionally superimposed with the untransmitted test signal, is converted and evaluated. With such an embodiment, the individual radar head units and their associated transmission and return transmission media can thus be monitored iteratively and cyclically.Any changes in length and / or transmission losses that occur can thus be detected promptly and taken into account when evaluating the radar system. This significantly increases its reliability and accuracy.

[0048] A further development of the procedure therefore provides that the test signal is generated with a different frequency than a signal for transmitting the radar signal information and is coupled together via the transmission medium using frequency division multiplexing and is separated from the radar echo signal transmitted back together via the return transmission medium (500, 500-n) in the detection unit of the central device by means of a frequency-dependent optical unit and is converted into an electrically detected test signal transmitted back.

[0049] In yet another embodiment, not only the test signal generation device, but also the detection device and other components are structurally separated from the central station and, in addition to the at least one transmission medium and the at least one return transmission medium, which are used to transmit the test signal to the at least one radar head device and back from the at least one radar head device to the detection unit, at least one further transmission medium and one further return transmission medium are connected to the at least one radar head device in order to transmit the radar signal information generated by the central station to the radar head device and to transmit the radar echo information detected by the radar head device back to the central station via the further return transmission medium.In this embodiment, each radar head assembly is connected to four transmission media, allowing monitoring and testing using the test signal to be performed completely independently of its operation as a transmit and receive module. For this to work, the transmission and return transmission media used for transmitting the test signal must be calibrated during the radar system's production, relative to the other transmission and return transmission media used for radar signal information and radar echo signal information. This means that length and transit time differences are determined once during manufacturing and stored in a calibration file.Furthermore, the transmission media are laid as close together as possible, parallel to each other, so that changes due to environmental influences affecting the transmission medium and the feedback medium can be transmitted to the next transmission medium and the next feedback medium. If the transmission media are laid in a media tree, it is preferred that the transmission and feedback media belonging to the monitoring system are located on the outside and the additional transmission and feedback media used for environmental sensing are located inside the media tree or media strand. This ensures that external damage first affects the transmission and feedback media belonging to the monitoring system and that their damage is thus reliably detected before it impairs the actual radar operation.However, any changes in length that occur can be transmitted to the other transmission and return transmission media. This improves the modularity of the monitoring system, allowing individual components of the monitoring system to be renewed and replaced separately from the components required for radar operation.

[0050] The invention is explained in more detail below with reference to a drawing. Figure 1 shows a schematic view of a photonic M1 MO radar system with a

[0051] Monitoring device;

[0052] Fig. 2a - 2c shows a schematic front, rear and side view of a motor vehicle with the positions of radar antennas shown;

[0053] Fig. 3 shows a schematic representation of a photonic M1 MO radar system in which the test signal generation device is structurally separate from the central station;

[0054] Fig. 4 shows a schematic representation of a photonic MIMO radar system in which the monitoring device is completely structurally separate from the central unit;

[0055] Fig. 5 shows a schematic flowchart of a method for operating a photonic radar system.

[0056] Figure 1 schematically depicts a photonic radar system 100. This system comprises a central station 200 and a plurality of radar head units 300, 300-n, configured as transmit and / or receive modules. The central station 200 and radar head units 300, 300-n are each individually coupled via two optical fibers 401, 401-n, 501, 501-n. The optical fibers 401, 401-n serve as transmission media 400 for transmitting optical signals from the central station to the radar head unit 300, 300-n. The optical fibers 501, 501-n serve as return transmission media 500. Additionally, the radar head units 300, 300-n are preferably connected to the central station 200 via an electronic control line 460 and an electronic return line 550. The electronic control line 460 and the electronic return line 560 can be configured as a bus system.Alternatively or additionally, the individual radar head units 300, 300-n can each be equipped with an individual control line and individual electronic return line.

[0057] Lowercase letters -n ... stand for natural numbers to indicate countability and distinguishability of the corresponding objects.

[0058] In the illustrated embodiment, the central station 200 is configured to generate radar signal information for transmission, whereby, in the illustrated example, this occurs at a frequency eight times lower than the transmission of a radar signal via an antenna 350, 350-n of one of the radar head units 300, 300-n configured as transmitter modules. For this purpose, the central station 200 comprises a control unit 210, which controls a coherent light source 220, preferably configured as a laser. In an environment detection operating state, radar signal information is modulated onto the optical carrier signal generated by the laser 220 via a modulation unit 230. The radar signal information is, for example, a frequency-modulated continuous wave (FMCW) signal intended for transmission, divided by a factor of eight.The modulation device is, for example, designed as a Mach-Zehnder modulator (MZM). The optical signal is routed via an optical control unit 240 to a 1:N switch 250. The 1:N switch 250 (or 1:N splitter) is also controlled by a control unit 210 and selectively switches the optical signal to one of the fiber outputs. The optical signal is thus switched to one of the transmission media 400 or 400n and transmitted to one of the radar head units 300 or 300n.

[0059] The fiber output is coupled to one of the optical waveguides 401, 401-n, i.e., one of the fibers 402, 402-n. The optical fibers 402, 402-n are connected at their other end to one of the radar head devices 300, 300-n.

[0060] The radar head units 300, 300-n each have a fiber input 305, 305-n, to which the fiber 402-n coming from the central station 200 is connected. The optical carrier signal with the modulated and transmitted radar signal information is coupled via a photoreceiver coupler 310 into an electronic photonic integrated circuit (EPIC) 315. The photonic components are preferably formed in a region where silicon is located on an insulator, whereas the electronic components are formed on so-called bulk silicon. Embodiments are also possible that are based on other materials or use separate photonic integrated circuits and electronic integrated circuits.In the radar head assembly 300, 300-n, the fiber input 305, 305-n is optically coupled to a fiber output 395, 395-n, such that at least part of the optical signal transmitted to the radar head assembly 300, 300-n via the fiber 402, 402-n serving as the transmission medium 400, 400-n is transmitted back to the central station 200 via the fiber 502, 502-n serving as the return transmission medium 500, 500-n. The fiber 502, 502-n serving as the return transmission medium 500 is connected to the corresponding fiber output 395, 395-n.

[0061] The transmitted optical signal can be converted into an electronic signal in the radar head unit 300, 300-n, whereby the radar signal information is separated from the carrier signal. The radar signal information is typically amplified in the radar head unit, and its frequency is often also multiplied. It is then emitted as electromagnetic radiation from the corresponding antenna 350 of the radar head unit 300, 300-n as a radar signal.

[0062] The electromagnetic radiation reflected from an object in the vicinity is also received as a radar echo signal by an antenna 350, 350-n of one or more radar head units 300, 300-n. In a mixing process, radar echo signal information is typically derived from the radar echo signal and generated and processed as an intermediate frequency signal. This intermediate frequency signal is then optically modulated onto the carrier signal transmitted by the radar head unit and transmitted back to the central station 200 via the corresponding return transmission medium 500, 500-n. The radar head unit 300, 300-n does not actively generate a carrier signal, but it can be modified by modulation.

[0063] In the central station 200, a detection unit 260 separates the radar echo information from the optical carrier signal and converts it into an electrical signal during conversion into an electronic signal. The radar echo information received via the various transmission media is evaluated together in a processing unit 270 of the central station to determine the distance, relative velocity, and relative angular position of individual objects in the surrounding area. Upon transmission to the processing unit 270, electrical signals can be digitized in a digitizing unit 280 and pre-processed in a processing unit 290, for example, by undergoing a Fourier transform, which can be implemented in special modules.

[0064] Figures 2a to 2c schematically illustrate a possible distribution of the radar head units 300, 300-n with their antennas 350, 350-n on a motor vehicle 1000. This enables almost 360° surround detection with high angular resolution.

[0065] In Fig. 2a, vehicle 1000 is shown schematically from its front 1002 (Fig. 2a), in Fig. 2b from its left side 1004, and in Fig. 2c from its rear 1006. The right side of the vehicle is not shown here, but is preferably designed analogously to the left side 1004.

[0066] The diagram shows schematic small antenna symbols 1100, which indicate the positions of radar head units. On the front 1002 of the vehicle 1000, these are arranged, for example, at intervals between them, on a lower edge 1012 of a windshield 1010 and, viewed from the front, on a left side edge 1014 of the windshield, essentially vertically spaced apart from each other. Additionally, radar head units 1100 are also arranged horizontally spaced apart from each other along a front bumper 1020.

[0067] On the left side 1004 of the vehicle 1000, shown in Fig. 2b, radar head units 1100 are arranged horizontally spaced apart from one another along a sill 1050, and radar head units 1100 are also arranged horizontally spaced apart from one another along a roof edge 1030. Additionally, radar head units are arranged substantially vertically spaced apart from one another along a B-pillar 1040.

[0068] On the rear side 1006, shown in Fig. 2c, the antenna symbols 1100, representing the radar head devices, are arranged horizontally spaced apart from each other along the rear bumper 1070 and horizontally and vertically spaced apart from each other along a lower side edge 1064 of the rear window 1060 along the left side edge 1066 of the rear window 1060 as seen from the rear.

[0069] The operating state of the environmental detection system is only simplified and briefly presented here and is known to those skilled in the art for a photonic radar system with a plurality of radar head devices designed as transmitting and / or receiving modules.

[0070] The embodiment shown in Fig. 1 also includes a monitoring device 600, which is distributed across various components of the central station 200. A monitoring control device 610 is also integrated into the control unit 210. This controls the alternative, preferably alternating, operation in the environmental detection operating state and the monitoring operating state.

[0071] In a monitoring operating state, the monitoring control unit 610 integrated into the control unit 210 ensures that a test signal generation unit 620 is formed by means of the laser 220 and the modulation unit 230. In monitoring operating mode, an optical test signal is generated and provided.

[0072] In one embodiment, the optical test signal is generated as an optical signal with a short, time-limited pulse. Analogous to the environmental sensing operating state, the test signal is selectively transmitted via the 1:N switch 250 or 1:NT splitter (multi-splitter) to one of the radar head units 300, 300-n via the corresponding transmission medium 400, 400-n. Due to the transmission characteristics of the radar head units 300, 300-n, the test signal is transmitted back to the central station 200 via the corresponding return transmission medium 500, 500-n. There, the test signal is converted into an electronic signal. The detection unit 260 thus serves as the acquisition unit 630 of the monitoring unit 600. The processing unit 270 of the central station serves as the evaluation unit 640. This receives signals from the control unit 210, 610, which are correlated with the generation and transmission of the test signal.The processing unit 270, which has an internal oscillator (not shown), is capable of determining the transit time of the test signal as a transmission parameter. Additionally or alternatively, the intensity of the transmitted test signal can also be evaluated. If no signal intensity is detected, an interruption of the corresponding transmission medium 400-n or return transmission medium 500, 500-n, or a failure of the radar head assembly 300, 300-n, can be identified. If the transmission medium 400, 400-n and the return transmission medium 500, 500-n are of the same length, their lengths can be determined based on the transit time of the test signal and thus used for calibration purposes.Otherwise, only the total length can be determined; a division into the lengths or transit times, into the sections associated with the transmission of the radar signal information or the radar echo signal information, can be done using calibration data obtained during the manufacture of the radar system using other methods.

[0073] Preferably, the transmission parameters are stored in a calibration file, where they are available for further monitoring cycles to enable rapid detection of changes. Furthermore, the processing unit can access the calibration file to use the data it contains for evaluation during environmental monitoring operation.

[0074] The calibration file may also contain additional information, such as the calibration data mentioned above, which may be obtained during the manufacture of the radar system using other calibration procedures. This could include, for example, values ​​indicating the ratio of the lengths of the transmission medium and the associated return transmission medium.

[0075] In another embodiment, the test signal can also be generated as a signal whose frequency changes monotonically and continuously over time in segments. The carrier signal generated by the laser can, for example, be modified accordingly in the modulator. In other embodiments, the carrier frequency of the laser can be changed directly. In this embodiment, the corresponding frequency ramps of the test signal are selected to be longer than the maximum total transmission time of the test signal via the transmission medium through the radar head assembly and the return transmission medium. In this embodiment, a portion of the test signal is coupled out to the detection unit 260 or acquisition unit 630 via an optical control device 240 located in the beam path between the modulation device 230 and the 1:N switch 250 or 1:N splitter (multiple splitter). In the detection unit 260 or 630, the test signal is then processed by the modulation device 230.The currently generated test signal in the detection unit 630 is optically superimposed and interfered upon with the test signal transmitted back via the transmission medium 400, 400-n, the radar head unit 300, 300-n, and the return transmission medium 500, 500-n. This creates a beat signal on the converter for converting the optical signal into an electrical signal. The frequency of this beat signal is correlated with a transmission duration via the time-dependent frequency ramp function of the test signal. If the propagation speed in the transmission media and in the section of the radar head unit 300, 300-n is known, the total transmission time can be converted into a length. The frequency thus directly indicates the duration that the test signal required for transmission through the transmission medium to the radar head unit, through the radar head unit, and back via the return transmission medium to the central station.Calibration can also be performed using this method. The second variant with the frequency-varying ramp signal is preferred because it results in a better signal-to-noise ratio.

[0076] Figure 3 schematically illustrates another embodiment of a radar system with a monitoring device 600. Identical technical features are designated with the same reference numerals in all figures. The embodiment according to Figure 3 has its own test signal generation unit. One advantage is that such an embodiment enables frequency division multiplexing, which allows simultaneous diagnostics and environmental sensing. For this purpose, the test signal is generated with an optical frequency that differs from the optical frequency of the carrier signal used by the radar system in the environmental sensing operating state. Again, the test signal is preferably generated as a continuous wave signal with frequency ramps. Part of the control unit 610, which controls the test signal generation and beam splitting in an optical control unit 650, is located in an external monitoring device 600'.The external monitoring device 600' also includes the test signal generation unit 620, which comprises several optical components, for example a laser, a modulator, a signal generator for generating the ramp signal, etc., which are not shown separately here for the sake of simplicity. Furthermore, the optical control unit 650 is integrated into the external monitoring device 600'.

[0077] In alternating operation in monitoring mode and environmental detection mode, this embodiment according to Fig. 3 works analogously to the one according to Fig. 1.

[0078] If frequency division multiplexing is used, monitoring can be performed simultaneously with environmental detection. However, in addition to the converter in the detection unit where the transmitted test signal (possibly superimposed with the currently generated test signal) is converted into an electronic signal, it is necessary to provide a further converter for converting the radar echo signal into an electronic signal. Frequency-selective, i.e., wavelength-selective, optical components can separate the test signal from the radar echo signal in the detection unit for this purpose. Wavelength-selective or optical frequency-dependent optical components can also be used in the radar head units to prevent the test signal from interfering with the conversion of the radar transmission information and / or the modulation of the radar echo information onto the carrier signal for transmission back to the central station 200.

[0079] Figure 4 shows a further embodiment in which the monitoring device 600" is completely separate from the central station 200. In addition to the at least one or more transmission media 400, 400-n and the at least one or more return transmission media 500, 500-n, via which the test signals are transmitted, at least one further transmission media 450, 450-n and at least one further return transmission media 550, 550-n are provided between the central station 200 and the at least one radar head unit or the several radar head units 300, 300-n, via which the radar signal information and the radar echo signal information are transmitted and returned.

[0080] To distribute the test signal to the transmission media 400 and 400-n, the testing device includes an optical distribution device 660, which can be a multi-splitter, a 1:N switch, or similar. In this embodiment, the necessary calibration information is transmitted directly from the monitoring device 600 to the processing unit 270 of the central station 200 as control information. The advantage of this embodiment is that parallel operation in a monitoring mode and an environmental sensing mode is possible, eliminating the need for multiplexing. Deviations between the transmission media 400-n and corresponding additional transmission media 450-n, as well as between the return transmission media 500-n and the additional return transmission media 550-n, can be measured and taken into account during the assembly of the respective fibers.

[0081] Figure 5 shows a schematic flowchart 2000 for operating a photonic radar system.

[0082] The radar system can be operated in an environmental detection state, corresponding to radar operation, and in a monitoring state. In some embodiments that use frequency division multiplexing or have a structurally separate design of the monitoring device from the central station, both operating states can be assumed simultaneously. Here, an embodiment is described in which the operating states are assumed alternatively, possibly interleaved in time.

[0083] When the photonic radar system is activated, it first switches to the monitoring operating state 2100. Other embodiments may begin with the environment sensing operating state.

[0084] Next, a calibration file 2200 is loaded, containing information about the radar system and previously performed diagnostic steps, in particular monitoring parameters for the individual radar head units of the radar system.

[0085] A time-of-flight measurement is then performed for one, several, preferably all radar head devices of the radar system, and the corresponding transmission parameters are determined and the calibration information is derived from them 2300.

[0086] The derived transmission parameters and calibration information are then evaluated for anomalies and / or deviations from the known information in the calibration file, and the functionality of the radar system is checked (2400). If this is not the case, the processing unit and / or the control unit of the central station is notified, so that the radar system is adjusted. This may involve, for example, controlling the radar signal information generation, the optical 1:N switch, changes in signal processing, etc. (2500). Furthermore, the calibration file is adjusted accordingly, and the procedure continues with the loading of the calibration file (2200).

[0087] If, however, it is determined in process step 2400 that no anomalies or deviations are present, then in step 2600 it is checked whether the calibration of the radar system is up to date.

[0088] If the calibration is not up-to-date, a calibration of the radar system is initiated (2700) and the calibration file is adjusted accordingly, and the procedure continues with the loading of the calibration file (2200).

[0089] If, however, it is determined in process step 2600 that the calibration is up to date, the system switches to the environmental sensing operating state 2800. The radar system's control unit then preferably re-initiates the monitoring operating state at intervals.

[0090] It will be understood by those skilled in the art that only exemplary embodiments are described here. The features shown in the different embodiments can be used in any combination to implement the invention.

[0091] Reference symbol list for photonic radar system

[0092] Central station

[0093] Control unit

[0094] Laser

[0095] Modulation device optical control device 1 :N switch

[0096] Detection device

[0097] Unit of calculation

[0098] Digitization facility

[0099] Processing unit, 300-n radar head unit, 305-n fiber input

[0100] Photoreceiver electronic-photonic integrated circuit (EPIC) antenna, 395-n fiber output, 400n transmission medium, 401-n optical fiber, 402-n fiber, 450-n further transmission medium electronic control line, 500-n return transmission medium, 501-n optical fiber, 502-n fiber, 550-n further return transmission medium electronic return line monitoring device monitoring control device test signal generation device acquisition unit 640 evaluation device

[0101] 650 optical control unit

[0102] 660 optical distribution device

[0103] 1000 motor vehicles

[0104] 1002 Front

[0105] 1004 Left side

[0106] 1006 reverse

[0107] 1100 Antenna symbol

[0108] 1010 Windscreen

[0109] 1012 bottom edge

[0110] 1014 left side edge

[0111] 1020 front bumper

[0112] 1030 Roof edge

[0113] 1040 B-pillar

[0114] 1050 sills

[0115] 1060 Rear window

[0116] 1064 lower side edge

[0117] 1070 rear bumper

[0118] 1100 Antenna symbol

[0119] 2000 Flowchart

[0120] 2100 Switch to monitoring operating mode

[0121] 2200 Loading calibration file

[0122] 2300 Runtime measurement

[0123] 2400 Functionality test

[0124] 2500 Radar system adjustment

[0125] 2600 Is calibration up to date?

[0126] 2700 Bump Calibration

[0127] 2800 Change to environmental sensing operating state

Claims

Patent claims 1. Photonic radar system (100) comprising a central station (200) and at least one radar head assembly (300, 300-n) configured as a transmitting and / or receiving module, wherein the at least one radar head assembly (300, 300-n) is connected to at least one transmission medium (400, 400-n) for transmitting an optical signal to the radar head assembly (300, 300-n) and to at least one return transmission medium (500, 500-n) for transmitting an optical signal back, wherein an optically transparent transmission path from the transmission medium to the return transmission medium (500, 500-n) is formed in the radar head assembly (300, 300-n) such that at least a part of the optical signal transmitted via the at least one transmission medium to the at least one radar head assembly (300, 300-n) is transmitted via the return transmission medium (500, 500-n) is transferred back, characterized by,that a monitoring device (600) includes a test signal generation unit for generating an optical test signal for transmission via the at least one transmission medium to the at least one radar head device (300, 300-n) and back transmission via the at least one return transmission medium (500, 500-n), and a detection unit (630) for detecting the back-transmitted test signal, as well as an evaluation device (640) configured to determine at least one transmission characteristic and to output at least one calibration information derived from the at least one transmission characteristic to a calculation unit (270) of the central station (200). 2 Photonic radar system according to claim 1 , characterized in that the test signal generation unit (620) is configured to generate the test signal as a short, time-limited pulse.

3. Photonic radar system according to claim 1 or 2, characterized in that the test signal generation device is configured to generate a test signal provided with a frequency ramp and the monitoring device (600) is configured to either transmit a part of the generated test signal to the detection unit (630) with the optically superimpose the transmitted optical test signal or electronically superimpose a signal representing one part of the generated test signal with the detected transmitted electronic test signal, wherein the evaluation device (640) is configured to determine a transit time of the test signal based on a beat frequency of the superimposed signal.

4. Photonic radar system (100) according to one of claims 1 to 3, characterized in that the detection unit (630) is integrated into the detection device of the central station and is configured to use the same converter for converting the transmitted optical test signal into an electrically detected test signal as for converting the radar echo signal transmitted back by the radar head device (300, 300-n) into an electrical radar echo signal.

5. Photonic radar system (100) according to one of claims 1 to 3, characterized in that the detection unit (630) is integrated into the detection device of the central station and a wavelength-selective beam splitter is arranged in the optical beam path, which separates the optical test signal transmitted back via the at least one return transmission medium (500, 500-n) from the transmitted optical radar echo signal and, in addition to a converter for converting the transmitted optical test signal into an electrical signal, a further converter for converting radar echo signal information into electrical information is provided in the detection device.

6. Photonic radar system (100) according to one of the preceding claims, characterized in that the test signal generation unit (620) is structurally separate from the central station (200).

7. Photonic radar system (100) according to claim 4, characterized in that the detection unit (600) is structurally separate from the central station (200) and, in addition to the at least one transmission medium (400, 400-n) and the at least one return transmission medium (500, 500-n), which are used to transmit the test signal to the at least one radar head assembly (300, 300-n) and to transmit it back from the at least one radar head assembly (300, 300-n) to the detection unit (630) with the at least one radar head assembly (300, 300-n), at least one further transmission medium (450, 450-n) and a further The return transmission medium (550, 550-n) is connected to transmit the radar signal information generated by the central station (200) to the radar head device (300, 300-n) and the radar echo signal information to the detection device (260) of the central station (200).

8. Photonic radar system (100) according to one of claims 1 to 3, characterized in that the test signal generation unit (620) is configured to generate the test signal with a time delay to the optical signal for transmitting the radar signal information with components of the central station (200) with which the optical signal for transmitting the radar signal information is generated.

9. Method for diagnosing and / or calibrating a photonic radar system comprising a central station and at least one radar head assembly (300, 300-n) optically connected thereto via a transmission medium and a return transmission medium, the radar head assembly being configured as a transmit and / or receive module, wherein the at least one radar head assembly (300, 300-n) is connected to the at least one transmission medium for transmitting an optical signal to the radar head assembly (300, 300-n) and to the at least one return transmission medium (500, 500-n), wherein an optically transmissive transmission path from the transmission medium (400, 400-n) to the return transmission medium (500, 500-n) is formed in the radar head assembly (300, 300-n), such that at least part of the signal transmitted via the at least one transmission medium (400, 400-n) to the radar head assembly is transmitted to the radar head assembly (300, 300-n). (300, 300-n) transmitted optical signal via the return transmission medium (500,500-n) is transferred back, comprising the steps:, Generating a test signal and transmitting the test signal via the at least one transmission medium (400, 400-n), the at least one radar head device (300, 300-n) and the at least one return transmission medium (500, 500-n) to a detection unit (630); Capturing the transmitted test signal; Determine at least one transmission parameter based on the captured, transmitted test signal, derive at least one calibration information based on the determined transmission parameter, and output the calibration information.

0. Method according to claim 9, characterized in that a test signal is generated with a constant monotonic frequency ramp, wherein a ramp duration is longer than a maximum total transit time of an optical signal for transmission via the at least one transmission medium (400, 400-n), which is the at least one radar head device (300, 300-n) and the at least one return transmission medium (500, 500-n), and wherein the returned test signal is either optically superimposed with a portion of the test signal generated by the test signal generation device (620) and not transmitted in order to detect a beat signal with a beat frequency as an electrically returned test signal, or the returned test signal is detected and superimposed with an electronic signal representing the untransmitted test signal in order to generate the beat signal.and a propagation delay is derived as a transmission parameter based on the determined frequency of the beat signal.

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