Photonic radar system with operating point adjustment of the optical and / or electrical components

Abstract

The invention relates to a radar system comprising a central unit (Z), at least one radar transmitting unit (S-1, S-2, S-3, S-n) and at least one radar receiving unit (E-1, E-2, E-3, E-n), which each comprise optical and electrical components. A control unit (14, 49, 50) is provided in the central unit (Z), at least one radar transmitting unit (S-1, S-2, S-3, S-n) and / or at least one radar receiving unit and is designed to adjust the operating point of the optical and / or electrical components.

Description

[0001] Description

[0002] Photonic radar system with operating point adjustment of the optical and / or electrical components

[0003] The present invention relates to a radar system that can be operated, for example, in a vehicle. The present invention further relates to a central unit, a radar transmitter unit, and a radar receiver unit of such a radar system. The invention also relates to a method for operating such a radar system.

[0004] For driver assistance systems and safety systems in fully automated driving, the safest possible perception of the surroundings is essential. This is achieved by using sensors such as radar, lidar, and camera sensors integrated into the vehicle to detect the environment.

[0005] For example, an environmental model can be created based on the acquired sensor data using a suitable machine learning model. This can involve perception modules that can recognize learned objects in the environment and forward this information to a planning module. The planning module can then take the recognized objects into account for trajectory planning and safe vehicle control. Of particular importance here is a comprehensive 360° 3D capture, enabling complete 360-degree recording of all static and dynamic objects and the creation of the highest possible resolution 3D models of the environment.

[0006] While lidar-based systems are capable of providing precise distance measurements and can also be used for classification, they are expensive and complex to build. Furthermore, lidar systems are susceptible to weather conditions such as rain, fog, or direct sunlight. Radar sensors, on the other hand, deliver reliable and fail-safe data in all weather conditions. Even poor visibility conditions such as rain, fog, snow, dust, and darkness hardly affect their accuracy.

[0007] However, their resolution is currently limited. For example, radar sensors currently used in series production in the automotive sector have a resolution of approximately 2°. This is insufficient to meet the requirements for Levels 4 and 5 of automated driving with safe driving functions, as these require radar sensors to deliver three-dimensional images with a high resolution of 0.1° and below, with high insensitivity to interference from their surroundings. This cannot be achieved with conventional radar technology because the resolution of such systems is too low.

[0008] Currently under development are so-called photonic radar systems, in which driver signals in the GHz range can be distributed to a large number of radar sensors using an optical carrier signal in the THz frequency range. This allows for the co-integration of electronic and photonic components on a single semiconductor substrate, enabling extremely compact form factors for the individual radar sensors and, consequently, arrays with a large number of such radar sensors integrated into the vehicle.

[0009] German patent application DE 10 2017221 257 A1 discloses a radar system in which signal transmission between a central unit and a radar transmitter or radar receiver is implemented optically. For this purpose, a radar driver signal is optically generated in the central unit and transmitted via at least one optical fiber to at least one radar receiver and / or at least one radar transmitter. In the radar transmitter, the radar driver signal is then converted into an electrical radar driver signal and used to drive a radar transmitter. A radar echo signal received by a radar receiver is mixed with the electrical radar driver signal in a mixer of the radar receiver. The mixed signal is then modulated onto the optical driver signal by means of a modulation unit, coupled into the optical fiber, and transmitted back to the central unit.The central unit receives the modulated optical signal and evaluates it using an evaluation unit. The result is then provided as radar information.

[0010] In contrast to this prior art, one object of the invention is to provide an improved radar system and an improved method for operating a radar system.

[0011] This problem is solved by the independent claims. Preferred embodiments of the invention are the subject of the dependent claims.

[0012] The radar system according to the invention comprises a central unit, at least one radar transmitter unit and at least one radar receiver unit, each comprising optical and electrical components, wherein a control unit is provided in the central unit, and / or at least one radar transmitter unit, and / or at least one radar receiver unit, which is designed for setting the operating point of the optical and / or electrical components.

[0013] This enables a fully integrated solution for setting the operating point. Compared to conventional photonic radar systems, where the operating point must be set via external control units, this reduces costs and installation space requirements.

[0014] According to one embodiment of the invention, the central unit is configured to provide an optical carrier signal, modulate a radar driver signal onto the optical carrier signal, and send the optical carrier signal modulated with the radar driver signal to the at least one radar transmitter and the at least one radar receiver. The at least one radar transmitter is configured to receive the optical carrier signal modulated with the radar driver signal, separate the radar driver signal, and transmit a radar signal based on the radar driver signal. The at least one radar receiver is configured to receive the optical carrier signal modulated with the radar driver signal, separate the radar driver signal, mix a radar echo signal with the radar driver signal, modulate the mixed signal onto the optical carrier signal, and send the modulated optical carrier signal to the central unit.The central unit is further designed to receive the optical carrier signal modulated with the mixed signal, to derive radar information from it, and to output the derived radar information.

[0015] Preferably, the at least one radar transmitter unit and the at least one radar receiver unit are connected to the central unit via at least one optical fiber.

[0016] Likewise, the radar transmitting units and the radar receiving units are preferably each integrated into a common unit.

[0017] It is particularly advantageous if the control unit includes a control loop in which at least one of the following operations is used to adjust the operating point of at least one optical and / or electrical component: amplitude or gain control, phase control, filtering, power, peak or envelope detection, and / or a comparator or difference / addition function.

[0018] According to a further embodiment of the invention, a central unit for use in the aforementioned radar system comprises a light source for providing the optical carrier signal and an optical modulation unit for modulating the radar driver signal onto the optical carrier signal, wherein the control unit is configured for setting the operating point of the light source and / or the optical modulation unit.

[0019] Advantageously, a partial beam is split off from the light of the optical carrier signal provided by the light source, and the light of the split partial beam is supplied to the control unit to generate a control signal for setting the operating point of the light source and / or the optical modulation unit.

[0020] It is particularly advantageous if the light source includes a laser diode, the optical modulation unit a Mach-Zehnder modulator, and the control unit a photodiode for converting the split partial beam into an electrical signal.

[0021] According to a further embodiment of the invention, the central unit comprises a receiving and processing unit and a control unit, wherein the receiving and processing unit is configured to receive the optical carrier signal modulated with the mixed signal, to separate the mixed signal and to derive radar information from it and to output the derived radar information, and wherein the control unit is configured for setting the operating point of the receiving and processing unit.

[0022] According to a further embodiment of the invention, a radar transmitting unit for use in the aforementioned radar system comprises a receiving unit, a radar transmitter and a control unit, wherein the receiving unit is configured to receive the optical carrier signal modulated with the radar driver signal, to separate the radar driver signal and to transmit a radar signal based on the radar driver signal, and wherein the control unit is configured for setting the operating point of the receiving unit.According to a further embodiment of the invention, a radar receiving unit for use in the aforementioned radar system comprises a mixer, an optical modulation unit and a control unit, wherein the mixer is configured to mix a received radar echo signal with the radar driver signal, wherein the modulation unit is configured to modulate the mixed signal onto the optical carrier signal, wherein the control unit is configured for setting the operating point of the optical modulation unit and wherein a partial beam is split off from the output signal of the optical modulation unit and supplied to the control unit for setting the operating point of the optical modulation unit.

[0023] Similarly, the radar receiving unit and / or the radar transmitting unit may include several electrical components for generating the radar signal and for processing the received radar echo signal, as well as a further control unit for adjusting the operating point of the electrical components.

[0024] Furthermore, in a method according to the invention for operating a radar system, in which a central unit, at least one radar transmitter unit and / or at least one radar receiver unit each comprise optical and electrical components, an operating point adjustment of the optical and / or electrical components in the central unit, at least one radar transmitter unit, and / or at least one radar receiver unit is carried out.

[0025] Finally, the invention also includes a vehicle that has a radar system according to the invention.

[0026] Further features of the present invention will become apparent from the following description and the claims in conjunction with the figures. These show:

[0027] Fig. 1 shows a schematic representation of one embodiment of the radar system;

[0028] Fig. 2 shows a schematic representation of an embodiment of a central processing unit of the

[0029] Radar system with automatic operating point setting;

[0030] Fig. 3 shows a control loop as it can be implemented in an automatic operating point setting unit; Fig. 4 shows a schematic representation of an embodiment of a radar receiver unit of the radar system with automatic operating point setting; and

[0031] Fig. 5 shows an exemplary integration of the radar system on the vehicle surface of a passenger car.

[0032] To better understand the principles of the present invention, embodiments of the invention are explained in more detail below with reference to the figures. It is understood that the invention is not limited to these embodiments and that the described features can also be combined or modified without departing from the scope of protection of the invention as defined in the claims.

[0033] In the following figures, electrical connections are represented by solid lines and optical connections by dashed lines for differentiation.

[0034] Figure 1 shows a schematic representation of a radar system according to the invention. The radar system comprises a central unit Z, several radar transmitters S-1, S-2, S-3,..., S-n, and several radar receivers E-1, E-2, E-3,..., En. The central unit is hereinafter also referred to as the backend, and the radar transmitters and radar receivers as the frontend. Although the radar transmitters and radar receivers are shown here as separate units, they can also be implemented using combined units, each of which integrates both a transmitter and a receiver.

[0035] The central unit Z is connected via one or more transmission media G to the radar transmitting units S-1, S-2, S-3,..., Sn and the radar receiving units E-1, E-2, E-3,..., En, wherein the transmission media can in particular be one or more optical fibers. In the case of an integrated unit on which circuits for transmitting and receiving are located, the signal can only be sent to this common unit.

[0036] According to the invention, a continuous adjustment of the various operating points (automatic bias control, ABC) of the optical and / or electrical components is integrated into the central unit, the radar transmitter units, and / or the radar receiver units. For the sake of clarity, the operating point adjustment units provided for this purpose are not shown in this figure but will be explained in detail in connection with the subsequent figures.

[0037] The central processing unit Z generates a frequency-modulated continuous wave (FMCW) signal and processes and evaluates the signals generated by the radar receiver units E-1, E-2, E-3, ..., En. Instead of a frequency-modulated continuous wave signal, a signal with a different waveform can also be generated. This centralized processing and evaluation of the signals allows the individual radar sensors to be designed as small and cost-effectively as possible.

[0038] At the central station, a radar driver signal is generated, which consists of a radar carrier signal with frequency fcarrier and a radar ramp signal with frequency fr. ra m PThe radar driver signal is modulated onto an optical carrier signal. The frequency of the radar driver signal is preferably only a fraction of the carrier frequency required to drive the individual radar transmitters. For example, the signal to be transmitted can be modulated with 1 / 8 of the radar frequency. With a carrier frequency of 77 GHz currently common for road vehicles, this results in a frequency of 9.625 GHz. The optical carrier signal modulated with the radar driver signal is then coupled into the transmission medium G.

[0039] The optical carrier signal modulated by the radar driver signal is coupled out of the transmission medium G by each of the individual radar transmitter units S-1, S-2, S-3,..., Sn by means of a coupling unit (not shown), and the radar driver signal is separated in each case. If this radar driver signal is only a fraction of the radar frequency used, for example, 1 / 8 of the radar frequency, it is first amplified eightfold in each of the individual radar transmitter units S-1, S-2, S-3,..., Sn. The resulting signal then drives the respective radar transmitters in the radar transmitter units S-1, S-2, S-3,..., Sn. The individual radar transmitters include, in particular, radar antennas, each of which then transmits a radar signal.

[0040] In addition, the optical carrier signal modulated with the radar driver signal is also transmitted to the individual radar receiver units E-1, E-2, E-3,..., En and likewise coupled out of the transmission medium G by means of a coupling unit. Radar echo signals are received by the individual radar receiver units E-1, E-2, E-3,..., En and then mixed with the radar driver signal. The mixed signal is modulated onto the optical carrier signal, and the resulting signal is coupled into the transmission medium G by means of further coupling units and sent back to the central unit.

[0041] The central unit Z then receives the signals from the radar receivers E-1, E-2, E-3,..., E-n, evaluates them, and provides derived radar information. This radar information can then be further processed, for example, to create or update an environmental model.

[0042] The radar transmitters and receivers can each be designed as separate electronically and photonically cointegrated chips (so-called "EPIC chips") or implemented on a single electronically and photonically cointegrated chip. Silicon photonics technology can be used for the cointegration of the electronic and photonic components, enabling the monolithic integration of photonic devices, high-frequency electronics, and digital electronics on a single chip. A hybrid implementation using separate electronic (EIC) and photonic (PIC) chips is also possible.

[0043] The integration of optical components into the chip can be achieved, for example, using so-called silicon-on-insulator (SOI) regions, while the integration of electronic components can be accomplished using bulk silicon regions. In SOI regions, a thin silicon layer is separated from the silicon substrate by an insulating layer, such as silicon dioxide. Since silicon is transparent at the near-infrared wavelengths common in optical communication technology, and the refractive indices of silicon and silicon dioxide differ significantly in this wavelength range, various optical components can be implemented using SOI structures. This allows for high signal quality with low parasitic interference, particularly at high data rates.The connection of the RF circuits for the radar antennas, including the frequency multiplier, to the photonic circuit can be implemented without additional wire or flip-chip bonding. Furthermore, chips can be tested optically and electrically at the wafer level. Additionally, the scalability to large volumes in the highly integrated manufacturing of electronically and photonically integrated circuits enables a significant reduction in assembly costs and a more efficient cost structure.

[0044] Figure 2 schematically illustrates an embodiment of a central unit of a photonic radar system with automatic operating point adjustment. For clarity, only the optical components are shown; however, automatic operating point adjustment can also be implemented for the electronic components.

[0045] To provide the optical carrier signal, the central unit Z comprises a light source 11. This can be, in particular, a laser diode that emits continuous laser light in the near-infrared range. Preferably, the wavelength of the laser diode is in a range where optical losses and dispersion are as low as possible, for example, 850 nm, 1310 nm, or 1550 nm. However, an ASE (Amplified Spontaneous Emission) light source can also be used, which emits light generated by spontaneous emission and subsequently optically amplified by stimulated emission.

[0046] The optical carrier signal generated by the light source is fed to an electro-optic modulator 12, which modulates the electrical radar driver signal, consisting of the radar carrier signal and the radar ramp signal, onto the optical carrier signal. For example, the electro-optic modulator 12 can be a Mach-Zehnder modulator, in which the optical carrier signal is first split into two waveguides where phase modulation is performed and then recombined, with the partial signals superimposing to form the modulated output signal depending on their relative phase. Alternative modulation principles, e.g., using directly modulated light sources, are also possible.

[0047] The optical carrier signal modulated by the electro-optic modulator 12 is then fed to an optical beam splitter or switch 13, which splits off a partial beam and feeds it to a control unit 14 for adjusting the operating point of the optical components, in the illustrated example the light source 11 and / or the electro-optic modulator 12. Based on this, the control unit 14 can generate an error signal to correct unintended changes in intensity, frequency, and / or phase in a control loop. For example, short-term intensity fluctuations caused by vibrations and frequency drifts caused by temperature changes can be compensated for. If the electro-optic modulator 12 is a Mach-Zehnder modulator, the optical beam splitter can also be part of the optical modulator.

[0048] The partial beam not split by the optical beam splitter or switch 13 is first fed to an optical control unit 15 and then to an optical 1 :N switch or beam splitter 16, which ensures that the radar driver signal can be provided on several channels for the individual radar transmitting units and / or radar receiving units.

[0049] To receive and evaluate the signals transmitted by the radar receiving units, the central unit Z first comprises an optical receiving and processing unit 17, in which the radar signal superimposed on the optical signal can be separated by means of an optical-electrical conversion. The optical receiving and processing unit 17 can, for example, include a unit for separating the signals from the different radar transmitting units and, for each of the separated signals, a photodiode, a transimpedance amplifier, and an IQ mixer.

[0050] The resulting signal can then first be fed to a digital interface 18, where it is digitized by analog-to-digital converters. Optionally, the digitized signals can also be preprocessed in a preprocessing unit 19, for example by an FFT to divide the signal into several frequency components.

[0051] The pre-processed signal is then fed to the evaluation unit 20, which derives radar information from the signal. This radar information can then be output and further processed, for example, for environmental detection.

[0052] Additionally, the electrical and optical components of the central unit Z can be controlled via one or more optional control interfaces and units 21, 22. In particular, this includes switching the control unit 14 on / off, parameterizing, diagnosing, etc., for setting the operating point. Furthermore, communication with the radar transmitting and receiving units can also be established via the control interfaces and units 21, 22, and can be carried out electrically, optically, or electrically and optically. For clarity, the control interfaces and units 21, 22 are divided into several blocks in the figure; however, in one implementation, they can also be realized as a single component.

[0053] As already mentioned, an analogous implementation, not shown in Figure 2, can also be carried out for the receiving unit of the backend. In this case, the operating point of the optical receiving and processing unit 17 and / or the subsequent electrical components can be set in the central unit Z by means of a control unit for operating point setting, which can be designed separately from the control unit 14 or also be part of the control unit 14.

[0054] Figure 3 shows a control loop as it can be implemented in an automatic operating point setting unit. In the case of an optical input signal, an opto-electrical conversion 31 can first be performed, e.g. via a photodiode.

[0055] Subsequently, the following optional operations can be performed in any order: a. Amplitude / gain control 32, for example via a transimpedance amplifier (TIA) or variable gain amplifier. b. Phase control 33. c. Filtering 34, for example low-pass, high-pass, band-pass, etc. d. Power, peak, or envelope detection 35. e. Comparator or difference / addition functions 36, for example based on a reference signal.

[0056] The sequence of operations shown in Figure 3 is exemplary; the operations can also be performed in a different order. Furthermore, the operations are optional in that not all of the shown operations need to be performed.

[0057] The resulting signal is fed back to the component to be controlled in order to optimize its operating point. In this way, the operating point of the light source 11 and / or the electro-optical modulator 12, for example a Mach-Zehnder modulator, can be controlled to ensure stable operation even over extended periods and regardless of environmental conditions. Likewise, the control loop can also be used to regulate the operating point of one or more electrical components in the central processing unit, for example, for the amplification of an electrical amplifier.

[0058] Corresponding control units for setting the operating point can also be implemented in the front end of a photonic radar system, as shown in Figure 4 using the example of a radar receiver unit E-1 of the photonic radar system. The other radar receiver units E-2, E-3, and En are identically constructed. The modulated optical driver signal received by the central unit Z is first split into two partial beams at the input of the radar receiver unit E-1 by an optical beam splitter 41. In the upper branch, the modulated optical carrier signal is fed, as described above for the central unit, to an optical receiver and processing unit 42, in which the radar signal superimposed on the optical signal can be separated by means of an optical detection method.

[0059] The generated electrical output signal of the optical receiver and processing unit 42 is amplified in an electrical amplifier 43, for example, a transimpedance amplifier. In a multiplier unit 44, the frequency of the signal is multiplied to the frequency of the electrical radar driver signal. In the mixer 45, the received radar echo signal, which may be amplified by a low-noise amplifier 46 (LNA), is mixed with the electrical radar driver signal. The mixed signal can then be processed in a processing unit 47. The mixed and processed signal is then modulated by the modulation unit 48, which may be a Mach-Zehnder modulator, for example, onto the radar driver signal, which is supplied to the modulation unit 48 via a second branch from the optical beam splitter 41.The modulated signal can then first be fed to an optional additional optical control unit 55 and then coupled into a transmission medium (not shown) and transmitted to the central unit. Another embodiment includes providing a separate, unmodulated continuous wave signal, which can be used for transmission from the radar receiver to the central unit.

[0060] Figure 4 illustrates an optimization process for setting the operating point using multiple control units. This process involves a separation into a control unit 49 for optimizing the optical modulator and a control unit 50 for the electrical components. For clarity, a single control unit for the electrical components is shown, but separate control units are also possible. A control signal can be tapped at various points along the signal chain. In the illustrated example, a control signal for the electrical components is tapped via a first switch or splitter 51, which is located after the processing unit 47, and fed to the control unit 50 for setting the operating point of the electrical components.A second switch or splitter 52 is arranged downstream of the optical modulator 48 and supplies a partial optical signal to the control unit 49 for setting the operating point of the optical components. Alternatively, optimization of the entire signal chain is also possible via a tap at the end of the chain, e.g., only via the tap after the optical modulator.

[0061] The radar receiver unit shown in Figure 4 also allows for the control of the electrical and optical components, and in particular the control units 49, 50 for setting the operating point, via one or more optional control interfaces and units 53, 54.

[0062] An analogous implementation is also possible in the front-end transmitter unit, i.e., the radar transmitter units, where each radar transmitter unit can comprise a receiver unit and a control unit for setting the receiver unit's operating point. The radar transmitter units can be configured to receive the optical carrier signal modulated by the radar driver signal via a transmission medium, separate the radar driver signal, and transmit a radar signal based on the radar driver signal. For this purpose, the respective receiver unit can include various electrical components, such as a photodiode, a transimpedance amplifier, a multiplier unit, an amplifier, and a radar transmitter.

[0063] Figure 5 schematically shows an exemplary large-area integration of a multitude of antenna chips A, each of which can comprise the described radar transmitting units and / or radar receiving units, onto the vehicle surface of a passenger car. For example, the windshield, rear window, and bumper can be used for integration into the front and rear, and the vehicle floor, roof, and B-pillar for integration along the sides. The central unit of the photonic radar system is not shown in this illustration and can, for example, be implemented as a radar control unit located in the vehicle's interior or engine compartment. Similarly, the figure omits the representation of the transmission media between the central unit and the antenna chips.

[0064] The radar system according to the invention, the method, the central unit, the radar transmitter unit and the radar receiver unit can be used, in particular, in any road vehicles, such as passenger cars, commercial vehicles, trucks or buses, in which radar-based environmental sensing is used, for example for driver assistance systems or for automatic or autonomous driving functions, but is not limited to this. Application in radar-based environmental sensing in other technical fields is also possible.

[0065] Reference symbol list

[0066] Central processing unit

[0067] S-1, S-2, S-3, Sn Radar transmitting units E-1, E-2, E-3, En Radar receiving units G Transmission medium 11 Light source 12 Electro-optical modulator 13 Switch or splitter 14 Control unit 15 Control unit 16 1 : N switch or divider 17 Receiver and processing unit 18 Digital interface 19 Preprocessing unit 20 Evaluation unit 21 Control interface and unit 21 Control interface and unit 31 Opto-electrical conversion 32 Amplitude / gain control 33 Phase control 34 Filtering 35 Power, peak, or envelope detection 36 Comparator or differential / addition function 41 Optical beam splitter 42 Optical receiver and processing unit 43 Electrical amplifier 44 Multiplier unit 45 Mixer 46 Low-noise amplifier 47 Processing unit 48 Modulation unit 49 Control unit 50 Control unit

[0068] 51 Switch or Splitter

[0069] 52-way switch or splitter

[0070] 53 Control interface and unit

[0071] 54 Control interface and unit

[0072] 55 Control unit

[0073] A antenna chip

Claims

Patent claims 1. Radar system comprising a central unit (Z), at least one radar transmitter (S-1 , S- 2, S-3, Sn) and at least one radar receiver (E-1, E-2, E-3, En), each comprising optical and electrical components, characterized in that a control unit (14, 49, 50) is provided in the central unit (Z) and / or at least one radar transmitter (S-1 , S-2, S-3, S- n), and / or at least one radar receiver, which is configured for adjusting the operating point of the optical and / or electrical components.

2. Radar system according to claim 1, wherein the central unit (Z) is configured to provide an optical carrier signal, to modulate a radar driver signal onto the optical carrier signal, and to transmit the optical carrier signal modulated with the radar driver signal to the at least one radar transmitting unit (S-1, S-2, S-3, Sn) and / or the at least one radar receiving unit (E-1, E-2, E-3, En), the at least one radar transmitting unit (S-1, S-2, S-3, Sn) is configured to receive the optical carrier signal modulated with the radar driver signal, to separate the radar driver signal, and to transmit a radar signal based on the radar driver signal, the at least one radar receiving unit (E-1, E-2, E-3, En) is configured to receive the optical carrier signal modulated with the radar driver signal, to separate the radar driver signal, and to mix a radar echo signal with the radar driver signal.to modulate the mixed signal onto an optical carrier signal and to send the modulated optical carrier signal to the central unit (Z), the central unit (Z) being further configured to receive the optical carrier signal modulated with the mixed signal, to derive radar information from it and to output the derived radar information.

3. Radar system according to claim 1 or 2, wherein the at least one radar transmitting unit (S-1, S-2, S-3, Sn) and the at least one radar receiving unit (E-1 , E-2, E-3, En) are connected to the central unit (Z) via at least one optical fiber (G).

4. Radar system according to one of the preceding claims, wherein the radar transmitting units and the radar receiving units are each integrated into a common unit.

5. Radar system according to one of the preceding claims, wherein the control unit (14, 49, 50) comprises a control loop in which at least one of the following operations is applied to adjust the operating point of at least one optical and / or electrical component: amplitude / gain control, phase control, filtering, power, peak or envelope detection, and / or a comparator or differential / addition function.

6. Central unit (Z) for use in a radar system according to one of the claims 1 to 4, wherein the central unit (Z) comprises a light source (11) for providing the optical carrier signal and an optical modulation unit (12) for modulating the radar driver signal onto the optical carrier signal, and the control unit (14) is configured for adjusting the operating point of the light source (11) and / or the optical modulation unit (12).

7. Central unit according to claim 6, wherein a partial beam is split off from the light of the optical carrier signal provided by the light source (11), the light of the split partial beam is supplied to the control unit (14) to generate a control signal for setting the operating point of the light source (11) and / or the optical modulation unit (12).

8. Central unit according to claim 5 or 6, wherein the light source (11) comprises a laser diode, the optical modulation unit (12) comprises a Mach-Zehnder modulator and the control unit (14) comprises a photodiode for converting the split partial beam into an electrical signal: - 19 - 9. Central unit according to one of claims 6 to 8, wherein the central unit comprises a receiving and processing unit (17) and a control unit, wherein the receiving and processing unit (17) is configured to receive the optical carrier signal modulated with the mixed signal, to separate the radar driver signal and to derive radar information from it and to output the derived radar information, and wherein the control unit is configured for setting the operating point of the receiving and processing unit (17).

10. Radar transmitting unit (S-1 , S-2, S-3, Sn) for use in a radar system according to any one of claims 1 to 4, wherein the radar transmitting unit (S-1, S-2, S-3, Sn) comprises a receiving unit, a radar transmitter and a control unit, wherein the receiving unit is configured to receive the optical carrier signal modulated with the radar driver signal, to separate the radar driver signal and to transmit a radar signal based on the radar driver signal, and wherein the control unit is configured for setting the operating point of the receiving unit.

11. Radar receiving unit (E-1, E-2, E-3, En) for use in a radar system according to any one of claims 1 to 4, wherein the radar receiving unit (E-1 , E-2, E-3, E- n) comprises a mixer (45), an optical modulation unit (48) and a control unit (49), wherein the mixer (45) is configured to mix a received radar echo signal with the radar driver signal, wherein the optical modulation unit (48) is configured to modulate the mixed signal onto an optical carrier signal, wherein the control unit is configured for setting the operating point of the optical modulation unit, and wherein a partial beam is split off from the output signal of the optical modulation unit (48) and supplied to the control unit (49) for setting the operating point of the optical modulation unit (48).

12. Radar receiving unit (E-1, E-2, E-3, En) according to claim 11, wherein the radar receiving unit (E-1, E-2, E-3, En) comprises several electrical components (43, 44, 45, 46, 47) for separating the radar driver signal and for processing the received radar echo signal, as well as a further control unit (50) for adjusting the operating point of the electrical components (43, 44, 45, 46, 47).

13. Method for operating a radar system comprising a central unit (Z), at least one radar transmitting unit (S-1 , S-2, S-3, Sn) and / or at least one radar receiving unit (E-1 , E-2, E-3, En) each optical and electrical - 20 - Components include a setting of the operating point of the optical and / or electrical components in the central unit (Z), at least one radar transmitting unit (S-1, S-2, S-3, Sn), and / or at least one radar receiving unit (E-1 , E-2, E-3, En).

14. Vehicle comprising a radar system according to any one of claims 1 to 5.

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