Use of photonic microring resonators for up-down-chirp generation in photonically-electronically cointegrated radar systems

Abstract

The invention relates to a computing device (4) for a radar system (2), comprising - an optical unit (65) for providing an optical transmission signal (7); - a first optical ring resonator (27) of a synthesis unit (19), which optical ring resonator is designed to couple the optical transmission signal (7) into the first optical ring resonator (27) and to modulate a first optical signal (29), - a second ring resonator (28) of the synthesis unit (19), which ring resonator is designed to couple the optical transmission signal (7) into the second optical ring resonator (28) and to modulate a second optical signal (28), wherein the two optical signals (29, 30) have different pulse sequence frequencies (freq1, freq2); - the synthesis unit (19), which is designed to generate a first chirp signal (41) and a second chirp signal (42) on the basis of the two optical signals (29, 30). The invention also relates to a radar system (2), to a vehicle (1) and to a method.

Description

[0001] Description

[0002] Use of photonic microring resonators for up-down chip generation in photonic-electronic cointegrated radar systems

[0003] The invention relates to a computing device for a radar system.

[0004] Furthermore, the invention relates to a radar system with a corresponding computing device and at least one transmitting-receiving unit.

[0005] Furthermore, the invention relates to a vehicle with a corresponding radar system. The invention also relates to a method for operating a radar system.

[0006] A dynamically reconfigurable sensor array is known from US Pat. No. 8,761,693 B1. The sensor array can comprise several distributed sensors, each of which is adjustable or reconfigurable. Each of the sensors contains a transmitter, and each of the sensors is connected to the other sensors of the sensor array via wireless communication channels. The sensors are designed to be operable in a compatible manner with the other sensors.

[0007] Furthermore, WO 2022 / 157191 A1 discloses a radar sensor device for a motor vehicle, wherein the motor vehicle can be configured to be at least partially autonomous, in particular fully autonomous. The radar sensor device has a central electronic computing device configured to generate an electrical control signal for a transmitting device of the radar sensor device. Furthermore, the radar sensor device comprises a laser device that, depending on the electrical control signal, generates an optical transmission signal for transmission to the transmitting device.

[0008] Furthermore, US 2016 / 0291131 A discloses methods for characterizing an FM (frequency modulator) chirp signal generated by a device under test (DUT). Standardized and automated measurement equipment can be used for this purpose to test radar systems in the automotive industry.

[0009] One object of the present invention is to improve the signal-to-noise ratio in a radar sensor and to enable more stable signal generation in a radar sensor. This object is achieved by a computing device, a radar system, a vehicle, and a method according to the independent patent claims. Useful further developments are disclosed in the dependent patent claims.

[0010] One aspect of the invention or a first aspect of the invention relates to a computing device for a radar system, with

[0011] - an optical unit for providing an optical transmission signal;

[0012] - a first optical ring resonator of a synthesis unit, which is designed to couple the optical transmission signal into the first optical ring resonator and to modulate a first optical signal in dependence on the coupled optical transmission signal,

[0013] - a second ring resonator of the synthesis unit, which is different from the first ring resonator and is designed to couple the optical transmission signal into the second optical ring resonator and to modulate a second optical signal, which is different from the first optical signal, as a function of the coupled-in optical transmission signal, wherein the two optical signals have different pulse repetition frequencies;

[0014] - the synthesis unit, which is designed to generate, on the basis of the two optical signals, a first chirp signal which has a temporally increasing frequency and a second chirp signal which has a temporally decreasing frequency;

[0015] - a first optical output of the synthesis unit for providing the first chirp signal; and

[0016] - a second optical output of the synthesis unit for providing the second chirp signal.

[0017] The proposed computing device enables more stable signal generation for the radar system, and in particular the transmit-receive unit, with a high signal-to-noise ratio (“SNR”). This is achieved in particular by the two chirp signals provided, which can be made available, for example, to a transmit-receive unit, i.e., a radar sensor of the radar system.

[0018] The proposed computing device, which can be used in a radar system, can reduce phase noise; in particular, it can provide low, stable phase noise in the radar system. With the help of the computing device, optical up-down chirp ramp generation can be performed. This can be done in a particularly flexible manner. Furthermore, the computing device offers the advantage that, especially when used in a radar system, the radar system requires a smaller number of optical fibers.

[0019] In particular, the computing device can be designed as a cointegrated circuit or chip. Cointegration can be achieved using the "EPIC" process in SiGe, SiM, CMOS, or hybrid bi-CMOS processes. In particular, the proposed computing device enables cost savings, particularly for the radar system. Furthermore, the advantages of the signals provided by the computing device for the radar system offer the possibility of providing or creating a radar system with increased resolution. The two ring resonators enable optical signal generation for gigahertz signals.

[0020] Using the two ring resonators, up-down chirp generation for a radar system can be carried out.

[0021] In signal processing, a chirp is a signal whose frequency changes over time. A distinction is made between positive chirps, in which the frequency increases over time, and negative chirps, in which the frequency decreases. For example, strong, short laser pulses can be "chirped" to amplify them by increasing the pulse duration.

[0022] For example, the optical unit can be a laser device or a laser for generating the optical transmission signal or an optical carrier signal. This optical transmission signal can be made available to the two optical ring resonators, in particular as an input signal. It is also conceivable for a second transmission signal to be made available to the first optical ring resonator and a second transmission signal to be made available to the second optical ring resonator. The ring resonators are designed such that the respective optical transmission signal is coupled into the respective ring resonator in order to be able to generate the two optical signals. The two optical signals can also be referred to as frequency combs. In particular, the two optical signals have different or various pulse repetition frequencies.In other words, the two optical ring resonators can be used to generate two mutually detuned frequency combs, i.e. two mutually detuned signals. The two different optical signals can be made available or transmitted to the synthesis unit, in particular combined. The synthesis unit can be referred to, for example, as a frequency synthesis unit, in particular as a gigahertz frequency synthesis unit. With the help of the synthesis unit, the two optical signals can be changed or adapted. This means that the first chirp signal can be generated as a positive chirp signal. This results in up-chirp generation of the first optical signal. The second chirp signal, i.e. a negative chirp signal, can therefore be generated by down-chirp generation of the second optical signal.Thus, the first chirp signal has a rising frequency ramp, and the second chirp signal has a falling frequency ramp. The two chirp signals can be provided using the first and second optical outputs. In particular, these two chirp signals can be provided to the radar system, and in particular to a transceiver unit of the radar system, and can be transmitted, in particular, via optical transmission paths.

[0023] For example, the computing device can be referred to as an electronic computing device or electronic computing system. In particular, the computing device is a central unit for a radar system or radar sensor system. With the help of the computing device, which serves, for example, as the backend for a radar system's transmitting / receiving unit, signal processing, signal conditioning from environmental detection, signal processing, data digitization, and / or data fusion of environmental data or radar data can be performed. In particular, the computing device serves to control or actuate transmitting and / or receiving units or radar sensors of the radar system.

[0024] With the help of the computing device, the signals received by radar sensors can be evaluated for environmental detection.

[0025] In one embodiment, it is further provided that the synthesis unit has a dispersive element, wherein the dispersive element is designed to change a respective frequency spectrum of the two optical signals such that the two chirp signals can be generated or are generated. The dispersive element can be a prism or other scattering element, for example. In particular, a respective spectrum of the two optical signals can be changed and / or adapted using the dispersive element. Optionally, dispersion takes place using the dispersive element so that a time-variable signal can be impressed on the respective individual pulses of the optical signals. Thus, with the help of the dispersive element, the synthesis unit can be designed or become designed such that a synthesis or pulse synthesis can be carried out.For this purpose, the two optical signals, and in particular the two mutually detuned frequency combs relating to the two optical signals, can be combined and transmitted together through the dispersive element or a dispersive medium.

[0026] In one embodiment, it is further provided that the two optical ring resonators are designed as micro-ring resonators.

[0027] In particular, the invention utilizes the coupling of radiation from the laser device, which can in particular also be embodied as a CW laser, into a photonic semiconductor via an optical interface. The radiation propagates within a linear waveguide structure located in the semiconductor. Another, ring-shaped waveguide structure is arranged on the semiconductor at a very short distance from the linear waveguide structure. If the distance between the two waveguides is so small that the evanescent field of the electromagnetic radiation extends from the linear waveguide into the ring guide, radiation from the linear waveguide is coupled into the ring guide, where it propagates.If the optical path length of the ring is chosen so that it is an integer multiple of the wavelength, the light propagating in the ring guide constructively interferes with the coupled evanescent field after one cycle, resulting in amplification. Since the interaction zone between the linear and ring-shaped waveguide is in the wavelength range, the interaction between the two fields is only short-lived, resulting in only constructive interference. This creates an optical ring resonator. More laser radiation is coupled into the ring guide than losses occur, up to and including saturation of the internal resonator power. A portion of the light propagating within the ring waveguide is coupled out again in the linear waveguide after the completion of each cycle and can be used as a signal.With a suitable choice of waveguide diameter and coupling ratio, the light is amplitude-modulated through the ring resonator, generating a pulse with high peak intensity from a CW input signal. In semiconductors, the diameter of optical ring resonators ranges from a few hundred micrometers to a few micrometers. The round-trip time of the light determines a repetition rate f. rep of the output signal or pulse train. Ring resonators designed in this way have high quality factors of Q greater than 10 6 which lead to peak intensities within the resonator that can drive nonlinear optical processes, so-called multiphoton processes. These occur during the interaction of high-intensity light and matter. The evolution of the electric polarization P is an established model for describing multiphoton processes in light-matter interactions. where P describes the electrical pulsation, X the sensitivity, E the electric field and E0 the electrical constant.

[0028] While the linear term with electrical sensitivity X (1) scaled linearly with the electric field, higher order thermals X (n) with n greater than 1, a non-linear proportionality to the electric field strength is observed. These processes are called multiphoton processes. The number of photons required scales with the order n of X. (n)Effects such as frequency doubling or sum and difference frequency generation require two photons, generating photons corresponding to the fundamental frequency of light and thus inducing second-order nonlinearity in the material. Third-order effects, such as frequency tripling or similar, require three photons for third-order frequency conversion, and so on. These effects of nonlinear light-matter interaction offer the possibility of nonlinearly modulating an incident light source.

[0029] In the optical ring resonator, the nonlinear refractive index cannot be neglected if the coupling into the ring is sufficient. For example, due to the Kerr effect, especially at a sensitivity of X< 2Four-wave mixing processes occur during the interaction of high-intensity light with the waveguide. Due to the steady increase in intensity in the resonator ring, a degenerative four-wave mixing process initially occurs. In this process, two photons Y Pof the CW laser is absorbed, which is specifically referred to as optical pumping, and an electron is raised to a virtual or real, energetically higher level. After a short time, especially when stimulated, the electron returns to its ground state. In doing so, it emits the absorbed energy in the form of a signal and an idler sideband photon (Ys and Yi, respectively), which only match the sum of the photon energy of the two photons from the CW laser. This creates new spectral components within the ring resonator. The signal and idler sideband photons are correlated in phase, amplitude, and frequency due to the coherent generation process. Due to the increasing frequency conversion from YP to Ys or Yi, the ring resonator becomes bistable, resulting in slight variations in phase and frequency, which in turn create new sidebands.A non-degenerative four-wave mixing process begins, and the generation of new frequencies cascades. The newly generated frequencies are in a fixed phase and frequency relationship to each other, meaning the spectral modes are coupled. This resulting mode coupling causes a fundamental soliton to develop, forming a pulse with a high spectral bandwidth that propagates dispersion-free in the ring resonator and oscillates at the resonator frequency f. rep This transforms a CW laser signal into a pulsed signal, which is characterized by an extremely high signal-to-noise ratio and low temporal variances.

[0030] To generate the pulse state, additional, complex waveguide structures can be used. For example, a second waveguide on the opposite side of the ring resonator can be used to couple out the pulse train. Furthermore, additional resonator rings with coupling points can be used for further coupling between the ring resonators, allowing the corresponding frequency ranges from f rep For example, these ring arrangements can produce pulses with f rep = 100 megahertz.

[0031] A further aspect of the invention relates to a radar system with a computing device according to the previous aspect or an advantageous development thereof and at least one transmitting-receiving unit, wherein the computing device is coupled to the transmitting-receiving device.

[0032] With the aid of the computing device, the chirp signals generated by the synthesis unit can be transmitted to the transmit-receive unit, i.e., a combined transmit and receive unit, via optical transmission paths. These two chirp signals can then be used to transmit signals, particularly radar signals.

[0033] In particular, the transmit-receive unit m is a single semiconductor chip for T x - and R x-Channel. For example, this unit can be manufactured based on a CMOS, SiN-CMOS, Bi-CMOS, or a hybrid Bi-CMOS process. In particular, the computing device and / or the transceiver unit is a photonic-electronic co-integrated chip or semiconductor chip. With the aid of the radar system according to the invention, a reduction in the data transmission load in radar systems in which the radar sensor device is used as intended with distributed antennas can be achieved. For example, the radar system can be used for motor vehicles. The radar system can also be used in a wide variety of technical applications. For example, the radar system can be used in aeronautical engineering, marine engineering, automation technology, or communications technology.

[0034] In particular, such a radar system can be used in, for example, at least partially autonomous vehicles, but especially also in fully autonomous vehicles. However, to enable such automated driving, reliable environmental perception is essential. The environment is recorded using sensors such as radar, lidar, and cameras. A holistic, 360-degree three-dimensional recording of the environment is particularly important so that all static and dynamic objects can be detected. Redundant, robust environmental detection plays a key role, particularly with lidar, as this type of sensor can precisely measure distances in environmental detection and can also be used for classification. However, these lidar sensors are cost-intensive and complex to construct.360-degree three-dimensional environment detection is particularly problematic, as it requires either many smaller individual sensors, which typically operate with many individual light sources and detector elements, or large lidar sensors. Furthermore, lidar sensors are susceptible to weather influences such as rain, fog, or direct sunlight. A radar system according to the invention can remedy this.

[0035] Radar sensors and radar systems are also well-established in automotive engineering and deliver reliable and fail-safe data in all weather conditions. Even poor visibility conditions such as rain, fog, snow, dust, and darkness barely affect their detection reliability. However, their resolution is currently limited, particularly since the series-produced radars currently in use only have a resolution of around 7°. To meet the requirements for increased automation in automotive engineering with safe driving functions, the radar system is designed to deliver three-dimensional images with a high resolution in the range of 0.1° and below, with a high degree of immunity to interference from their surroundings. This cannot be achieved with conventional radar technology, as the resolution of such systems is too low.The radar system according to the invention can be used to significantly increase the resolution. By cointegrating electronic and photonic components on a single-chip system, i.e., on a single semiconductor chip, the resolution of photonic radar systems can be increased.

[0036] For example, silicon photonics technology can be used to cointegrate photonic and electronic components on a single-chip system. This enables the monolithic integration of photonic components, radio-frequency electronics, and digital electronics on a single integrated circuit or chip. Such a system offers the advantage of enabling GHz signal transmission using an optical carrier signal in the THz frequency range.

[0037] The generation of the FMCW signal, as well as the entire signal processing and evaluation, are carried out by a central station, for example, the computer. Each transmit and receive module consists of an electronic-photonic cointegrated chip (so-called "EPIC chip"). Silicon photonics technology is used for cointegration. This enables the monolithic integration of photonic components, radio-frequency electronics, and digital electronics together on a single chip ("electronic-photonic cointegration"). The technical innovation of such a system lies in the signal transmission of GHz signals using an optical carrier signal in the THz frequency range. A central station generates an optical carrier frequency (THz). The signal to be transmitted is modulated onto this frequency at 1 / 8 of the radar frequency and sent to the antenna chips via optical fiber.The frequency is multiplied eightfold on these, allowing radar radiation to be emitted by the antenna chips. Signal detection occurs in the opposite direction. All data is processed at the central station.

[0038] The principle of electronic-photonic cointegration in a single chip, with silicon-on-insulator regions for the photonic components and bulk silicon regions for the electronic circuits, is a globally unique technology. Especially at high data rates, it enables high signal quality with low parasitic interference. The connection of the RF circuits for the radar antennas, including the frequency multiplier, to the optical transceiver can be implemented without additional wire or flip-chip bonding. Furthermore, chips can be optically and electrically tested at the wafer level, enabling a high yield in the subsequent module design. This technology enables extremely compact form factors and is therefore highly relevant for the application of optical technologies based on silicon photonics in the automotive industry.The hurdle to the productive use of optical fibers lies in the lack of scalability of currently available technologies. This scalability to large volumes is made possible by the technology for highly integrated manufacturing of electronic photonic integrated circuits. The result is a significant reduction in assembly costs and a more efficient cost structure. The development of data center solutions has resulted in comprehensive libraries of electronic and photonic components for data transmission at high bandwidths, which will be utilized in this project.

[0039] However, the design described above requires extensive effort in the implementation of GHz electronics at the chip level. In particular, the frequency quadrupling that takes place on the chip after detection by a photodiode is technically challenging and represents a significant effort in terms of GHz signal generation with a high signal-to-noise ratio and the lowest possible jitter. The GHz signal must be stabilized in further steps, which is complex. Furthermore, GHz electronics are cost-intensive. Furthermore, high performance requirements are placed on the optical carrier (laser), as a high level of optical power is needed to generate a high-precision GHz signal, making a ring line with a single fiber difficult to implement for a radar array with many distributed RADAR semiconductor chips. Above all, two different photonic-electronic semiconductor chips are required for the transmit and receive channels (T x and R x), which leads to additional costs.

[0040] The central electronic unit can be coupled to an optical input and an optical output of the transmitting-receiving unit via at least one optical fiber.

[0041] Such a radar system can be used in particular in motor vehicles or automated systems, or in aeronautical or aerospace engineering. Further embodiments of the radar system and / or radar sensor device according to the invention could be used for polarization-sensitive detection by shaping the antenna geometry.

[0042] Likewise, an application could be in data transmission in the 5G frequency band or beyond. Using an optical ring resonator as a receiving antenna could also enable data transmission for Car-2-X applications, such as software updates, map updates, and infrastructure signals. The radar sensor device could also be used as a passive detector element for environmental perception. It is also conceivable that it could be used to detect emitted radiation for communication, such as radio, telecommunications, satellite communications, or similar camera systems.

[0043] The radar system is particularly advantageous for use in motor vehicles, as sensor systems distributed throughout the vehicle are required to enable efficient environmental perception. Thus, multiple radar sensor devices can be distributed throughout the vehicle, and these can be communicatively networked via the central electronic computing device. Thus, the radar system requires one, in particular a single, central electronic computing device, in particular a central station. With the help of the central electronic computing device, the various transceiver units can be supplied with the optical transmission signal, and the central electronic computing device can receive the optical output signals or other signals at the respective optical outputs of the transceiver units.

[0044] In particular, the central electronic computing device is a physically separate unit from the transmitting / receiving unit. In particular, the central electronic computing device is not part of the transmitting / receiving unit. The central electronic computing device can be a different semiconductor chip or integrated circuit from the transmitting / receiving unit.

[0045] For example, the central electronic processing unit can be used to track an FMCW (frequency modulated continuous wave) signal, as well as perform all signal processing and evaluation. The transmit / receive unit, in turn, can perform the transmit and receive operations.

[0046] In particular, the central electronic computing device can generate an optical carrier frequency, in particular the optical transmission signal, in the terahertz frequency range. The signal to be transmitted, in particular the optical transmission signal, is modulated onto this frequency at one-eighth of the radar system's radar frequency, and the optical phase, amplitude, or frequency modulation is sent or transmitted to the transceiver unit. In this way, the frequency is multiplied eightfold, so that the radar radiation, in particular the radar transmission signal, can be transmitted. Signal detection occurs in the reverse direction. All data is processed at the central station, in particular the central electronic computing device. The central electronic computing device is coupled to the optical input and output of the transceiver unit via one or more optical fibers.Consequently, the optical transmission signal generated by the central electronic processing unit is coupled into the optical fiber and transmitted via optical signal transmission to the optical input of the transceiver unit. Thus, the carrier signal or radar driver signal is transmitted via optical transmission paths. In particular, the optical fiber can be a fiber optic cable. The central electronic processing unit is also coupled to the optical output via a fiber optic cable. Consequently, the transceiver unit can couple the optical reception signal into the fiber optic cable and transmit it to the central electronic processing unit for evaluation of the received radar radiation.

[0047] In an embodiment of the further aspect, it is provided that the transmit-receive unit has a first detection unit for generating a first electrical signal based on the first chirp signal and a second detection unit for generating a second electrical signal based on the second chirp signal.

[0048] Heterodyne detection can be performed using the two detection units. Thus, the two detector units can be referred to as heterodyne detector units. In particular, the two detection units can belong to a higher-level heterodyne detection unit.

[0049] The detection units can be used to measure or select the chirp signals, their frequency combs, or frequency comb modes. Furthermore, a conversion from an optical signal to an electrical or electronic signal can be performed. The two electrical signals can then be used for transmission. For example, the first electrical signal can have an increasing frequency ramp. The second electrical signal can have a decreasing frequency ramp.

[0050] In one embodiment, the transceiver unit is configured to generate an electrical transmission signal or radar signal depending on the first and second electrical signals, wherein the transmission signal has a frequency formed from a difference between a frequency of the first signal and a frequency of the second signal. In particular, heterodyne detection can be used to determine the difference or the difference frequency of the two chirp signals or their frequency combs. The difference frequency can, in particular, be in the gigahertz frequency range. Thus, a gigahertz frequency signal is available for transmission.

[0051] In an embodiment of the further aspect, it is provided that the transmitting / receiving unit has an antenna configured to transmit the electrical transmitted signal and to receive an electrical received signal based on the electrical transmitted signal. Consequently, the transmitting / receiving unit or transmitting and receiving unit can have an antenna or an antenna element. This antenna serves both for transmitting signals and for receiving signals, in particular radar signals. Above all, the transmitting / receiving unit can be designed more compactly, which is particularly advantageous for use in the automotive sector, since the transmitting / receiving unit can be mounted and used on and / or in the vehicle in a space-saving, flexible, and versatile manner.

[0052] Using chirp signals and their subsequent conversion or detection, a highly stable, low-noise signal can be emitted in the gigahertz frequency range. This enables improved, particularly three-dimensional, image plane detection, environmental detection, and radar detection.

[0053] The transmitted signal can be an electronic gigahertz signal. The transmitted signal can be transmitted into the vicinity of the radar system. If the transmitted signal is reflected, for example, by an object in the surrounding area and is reradiated or reflected as a quasi-radar signal, this can be received by the antenna as an electrical or electronic received signal.

[0054] In an embodiment of the further aspect, it is provided that the transmitting / receiving unit has a control unit with which the transmitting / receiving unit can be controlled depending on an electrical control signal that is transmitted via an electrical transmission path from the computing device to the transmitting / receiving unit. Furthermore, the control unit is designed to switch the transmitting / receiving unit between a transmission mode for transmitting the electrical transmission signal and a reception mode for receiving the electrical reception signal. In particular, the antenna and the corresponding electrical or electronic components of the transmitting / receiving unit can be controlled or actuated via the electronic or electrical transmission path with which the computing device is electrically connected to the transmitting / receiving unit.Consequently, a space-saving transceiver unit can be designed, since the actual computing power or contact line steps take place in the computing unit. Using the control signal, the antenna and, in particular, all components required for mode switching can be controlled. The antenna can be switched between transmitting and receiving. Furthermore, the necessary components and / or units are also controlled, so that the antenna can either transmit using the transmitted signal, or the received signal can be processed accordingly and then made available to the computing unit, for example, for environmental detection or radar analysis.

[0055] In a further embodiment, it is provided that the transmitting-receiving unit has an electrical-optical wall unit, wherein the electrical-optical wall unit is designed to convert the received electrical reception signal into an optical reception signal.

[0056] With the help of the electrical-optical conversion unit or electrical-optical conversion device, the reception of an electrical signal can be converted. This can be done, for example, in the receive mode of the transceiver unit. This conversion, in turn, allows the received signal, such as a radar signal, to be provided or transmitted optically to the computing device via optical transmission paths or an optical transmission link.

[0057] In one embodiment, it is further provided that the radar system has an optical back channel for transmitting the optical reception signal from the transmitting / receiving unit to the computing device. The computing device has an electrical-optical conversion unit for converting the optical reception signal into an electrical signal, and the electrical signal can be evaluated with respect to radar information or environmental information using an evaluation unit of the computing device. Thus, the received signal from the antenna can first be optically transmitted to the computing device via optical transmission paths and then returned or converted in the computing device into an electrical or electronic signal.In this case, the electrical signal can further be processed, compressed and / or digitized accordingly in order to subsequently be able to evaluate at least one piece of radar information, in particular environmental information, with the aid of the evaluation unit, in particular an electronic evaluation unit.

[0058] In an embodiment of the further aspect, it is provided that the radar system or the transceiver unit and the computing device are physically and spatially separate units. Consequently, the radar system consists of a computing device, which is designed as an independent unit, such as a single-chip system, EPIC chip, or as an integrated circuit, and of at least one transceiver unit, which is different or separate from the computing device. This case has the advantage that the radar system can operate multiple transceiver units or radar sensors with the aid of a single central unit, such as the computing device. This is said to be a flexible and universally applicable option for the radar system.

[0059] A further aspect of the invention relates to a vehicle with a radar system according to one of the preceding aspects and an advantageous development. In particular, the radar system described above can be advantageously used in the vehicle. For example, the computing device can be centrally integrated in the vehicle, and several distributed transceiver units can be arranged in and / or on the vehicle for environmental detection.

[0060] In particular, the transmit / receive units can be integrated over a large area in or on the vehicle as miniaturized, photonic co-integrated radar chips in a coherently distributed, thinned array. These, in turn, can be connected or coupled to the computing device for control and signal processing or evaluation.

[0061] The radar system according to the invention makes it possible to create an ultra-stable, extremely low-noise 3D imaging radar sensor system that can also be used at the electronic-photonic co-integrated chip level as a cost-effective, redundant information source for secure data fusion. This is particularly advantageous in the automotive sector and in highly automated or autonomous vehicles.

[0062] Furthermore, the radar system offers the advantage of reliably detecting an environment by achieving a high signal-to-noise ratio and stable signal generation in the sensor. This is particularly advantageous for large devices with sparse antenna arrays, enabling the reliable detection and acquisition of targets, especially in the vicinity of a vehicle. In vehicle systems, the angular resolution is limited by the size of the antennas (in radar technology, devices refer to the area over which the antennas are distributed). Radar systems, for example, are modules with a size of approximately 10 by 10 cm. 2limited by the integration of vehicles. The angular resolution is accordingly limited to approximately 2 degrees, for example. The resolution improves proportionally with the size of the equipment. If two objects are to be resolved in angle (azimuth and elevation), an equipment extending in two directions is required. This can be achieved by the proposed radar system, and in particular by using the radar system in the vehicle.

[0063] Furthermore, the distance between the elements or individual antennas is important for an antenna element. This determines the clearly measurable angular range. Larger antenna distances lead to ambiguities in the angle measurement. Radar systems in the automotive sector therefore use so-called virtual antenna elements. Such a virtual antenna element consists of the combination of a transmitting antenna with a receiving channel, precisely in the center of the connection vector. With n transmitting antennas and m receiving antennas, a virtual error consisting of mxn elements can be generated. This principle is known as "multiple-input-multiple-output" (MIMO). These problems and challenges can be solved by the proposed radar system, as these transmitting-receiving units or radar chips each require a single antenna and can be distributed throughout the vehicle, as these individual units are coupled to the computing device via optical connections.

[0064] A further aspect of the invention relates to a method for operating a radar system according to one of the preceding aspects or an advantageous embodiment thereof, wherein the following steps are carried out:

[0065] - Modulating the first optical signal by coupling the optical transmission signal into the first optical ring resonator;

[0066] - modulating the second optical signal by coupling the optical transmission signal into the first-second optical ring resonator, wherein the two optical signals are modulated such that they have different pulse repetition frequencies (freq1, freq2);

[0067] - generating the first chirp signal, which has a temporally increasing frequency, based on the first optical signal and the second chirp signal, which has a temporally decreasing frequency, based on the second optical signal;

[0068] - Transmitting the two chirp signals to the transmitter-receiver unit;

[0069] - generating the electrical transmission signal based on the two chirp signals; and

[0070] - Emitting the electrical transmission signal with the antenna. Using the proposed method, photonic microresonators for up-down chirp generation can be achieved or used in photonic-electronic cointegrated radar systems. In particular, the proposed method can be used to develop a corresponding radar system and / or computing device according to the previous aspects and in advantageous further developments thereof.

[0071] In particular, the computing device and / or the radar system have means to be able to carry out the method just described.

[0072] In an embodiment of the further aspect, it is provided that the electrical reception signal based on the electrical transmission signal is received by the antenna and converted into the optical reception signal, wherein the conversion is carried out on the basis of the electrical-optical reception signal, wherein the radar information is evaluated on the basis of the optical reception signal, so that environmental detection can be carried out with the radar system.

[0073] In an embodiment of the further aspect, it is provided that the two chirp signals are converted into the two electrical signals by means of heterodyne detection, and the electrical transmission signal is generated on the basis of the two electrical signals.

[0074] Advantageous embodiments of one aspect of the invention are to be regarded as advantageous embodiments of all other aspects and vice versa.

[0075] Specifically, the computing device, the radar system and / or the vehicle has means to be able to carry out the method according to the invention.

[0076] For use cases or application situations that may arise during the method and which are not explicitly described here, it may be provided that, in accordance with the method, an error message and / or a request to enter user feedback is issued and / or a default setting and / or a predetermined initial state is set.

[0077] The invention also includes further developments of the radar system according to the invention, the vehicle according to the invention, and the method according to the invention, which have features already described in connection with the further developments of the computing device according to the invention. For this reason, the corresponding further developments of the radar system according to the invention, the vehicle according to the invention, and the method according to the invention are not described again here.

[0078] The invention also includes combinations of the features of the described embodiments.

[0079] Exemplary embodiments of the invention are described below. Shown are:

[0080] Fig. 1 is a schematic representation of a vehicle with a radar system according to the invention;

[0081] Fig. 2 is a schematic representation of the radar system 2 from Fig. 1;

[0082] Fig. 3 is a schematic representation of the synthesis unit 19 and a transmitting-receiving unit of the radar system 2 from Fig. 2;

[0083] Fig. 4 is an exemplary representation of a diagram with two specific frequency combs;

[0084] Fig. 5 is an exemplary representation of a frequency spectrum relating to a first chirp signal;

[0085] Fig. 6 exemplary representation of a frequency of a frequency spectrum of a second or negative chirp signal;

[0086] Fig. 7 is an exemplary diagram of an electrical signal with an increasing frequency ramp;

[0087] Fig. 8 is an exemplary representation of a signal with a falling frequency ramp; and

[0088] Fig. 9 is a schematic representation of the transmission signal resulting from an up-down chirp method.

[0089] The exemplary embodiments explained below are preferred exemplary embodiments of the invention. In the exemplary embodiments, the described components each represent individual, independently considered features of the invention, which also further develop the invention independently of one another and are thus also to be considered as components of the invention, either individually or in a combination other than that shown. Furthermore, the described exemplary embodiments can also be supplemented by further features of the invention already described.

[0090] In the figures, functionally identical elements are provided with the same reference numerals.

[0091] Figure 1 shows a schematic view of a vehicle 1, which may be a motor vehicle. The vehicle 1 includes, for example, a radar system 2.

[0092] The radar system 2 can be, for example, a sensor system, an environmental sensor system, or a radar sensor system of the vehicle 1. For this purpose, the radar system 2 can be communicatively networked, for example, with one or more driver assistance systems or other vehicle systems. For example, the radar system can have at least one radar sensor or another type of sensor. In addition to the use of the radar system 2 in the vehicle 1, it can also be used or applied in systems external to the vehicle.

[0093] With the help of the radar system 2, in particular an environment 3 of the vehicle 1 can be detected so that an environment detection can be carried out.

[0094] For example, the radar system 2 can also be used in automated systems, in the shipping industry, in aeronautical engineering or in communications technology.

[0095] For illustrative purposes, the example shown here is how the radar system 2 is used in the automotive sector, in the vehicle 1.

[0096] Fig. 2 shows an exemplary view of the radar system 2. The radar system can have a computing device 4, in particular a central electronic one. Furthermore, the radar system 2 can have a plurality of transceiver units 5, which can be arranged, for example, distributed on the vehicle 1, in particular for environmental detection. The transceiver units 5 can be, for example, radar chips or radar sensor units. The transceiver units 5 can be used both for transmitting and for transmitting or receiving signals. The transceiver units are thus combined units for transmitting and receiving signals. In particular, such a transceiver unit 5 can be referred to as a transmit and receive module. This can be referred to or formed from an electronic-photonic co-integrated chip (so-called "EPIC chip").The computing device, which can be referred to as the central processing unit, can also be formed from an electronic-photonic co-integrated chip. In particular, the computing device 4 is a physically and / or spatially separate unit from the transmitting / receiving units 5.

[0097] For example, the computing device 4 can have an optical unit 65 or a laser device or a laser. In particular, the optical unit 65 can be designed as an optical source or as a CW laser. With the aid of the optical unit, an optical transmission signal 7 or a carrier signal can be generated and thus provided. The optical transmission signal 7 can in particular be designed as an optical carrier signal in the terahertz frequency range. The computing device 4 can, for example, generate the optical carrier frequency. The signal to be transmitted can be modulated onto this optical carrier frequency with one-eighth of a radar frequency and transmitted, for example, to the transceiver units 5. In this way, frequency multiplication can take place. In turn, with the aid of the transceiver units 5, signals in the gigahertz frequency range can be received.

[0098] For example, the computing device 4 can be connected to a respective transmitting / receiving unit 5 via a fiber optic cable 8, forming an optical transmission link. Signals, in particular optical signals, can be transmitted from the computing device 4 to the individual transmitting / receiving units 5 via the fiber optic cable 8. In order to be able to send received signals from the transmitting / receiving units 5 back to the computing device 4 for evaluation or signal processing, a respective transmitting / receiving unit 5 can be optically coupled to the computing device 4 via an optical return channel 9.

[0099] With at least one of the transmitting / receiving units 5, an electrical transmitted signal can be transmitted, in particular into the environment 3. Likewise, an electrical received signal 11 corresponding to the electrical transmitted signal 10 can be received by the transmitting / receiving unit 5. For example, the transmitted signal 10 can be reflected by an object in the environment 3 of the vehicle 1 and thus received as an electrical received signal 11. The received signal 11, which can be referred to as a radar signal, for example, can be transmitted or transferred to the computing device 4 for evaluation or signal processing. For this purpose, the electrical received signal 11 can be converted into an optical received signal 12 by means of the transmitting / receiving unit 5. For example, this can be transmitted via the return channel 9 of the computing device 4. By means of an optical-electrical converter unit 13 orThe detector unit of the computing device 4 can convert the optical received signal 12 into an electrical signal 14. Unit 13 can be used, for example, for optical detection. For this purpose, the conversion can be performed, for example, via homodyne detection or heterodyne detection. Furthermore, unit 13 can perform a phase measurement and / or a phase length measurement.

[0100] Digitization can then again take place via a digital interface 15. In this case, an analog-to-digital conversion can primarily take place. For this purpose, the digital interface 15 can have an analog-to-digital converter. A processing unit 16 can be arranged downstream. With this, for example, signal processing can be applied, in particular with a "low-level signal". For example, a Fast Fourier Transformation (FFT) can be used for this purpose. The digitized, processed electrical signal 14 can then be made available to an evaluation unit 17 of the computing device 4. In this case, radar information or environmental information contained in the electrical signal 14 can in particular be evaluated or processed.Furthermore, an electrical return channel 18 can be provided, which provides feedback from at least one of the transmitting-receiving units 5 to the computing device 4 and in particular to the digital interface 15.

[0101] In order to be able to carry out the most stable and low-noise environmental detection or detection of the radar system 2, the optical transmission signal 7 can be adapted by means of frequency synthesis or gigahertz frequency synthesis. For this purpose, the computing device 4 can have a synthesis unit 19. For this purpose, the optical transmission signal 7 can be fed to or transmitted to the synthesis unit 19. For example, modulation can be carried out before the optical transmission signal 7 is made available to the synthesis unit 19. For this purpose, a modulator or modulation unit 20 can be provided. This can be designed, for example, as an arbitrary generator or arbitrary function generator (AWG). After the synthesis unit 19, for example, an optical control unit 21 and an optical switch orA distributor 22 may be provided in the computing device 4 in order to make appropriately processed signals from the synthesis unit 19 available to the transmitting / receiving units 5 via the fiber optic cable 8. Furthermore, a control unit 23 may be controlled by the evaluation unit 17, in particular to monitor or control the generation of the optical transmission signal. Furthermore, a control unit or a feedback loop 24 may be provided.

[0102] Furthermore, the computing device 4 is electrically connected to the transmitting / receiving units 5 via an electrical transmission path 25. An electrical control signal 26 for controlling or activating the transmitting / receiving units 5 can be transmitted via this electrical transmission path 25.

[0103] In particular, the computing device 4 serves to generate an optical carrier signal, the optical transmission signal 7, and feed it into a gigahertz frequency synthesis unit, e.g., the synthesis unit 19. The synthesized gigahertz signal can be transmitted in the optical spectral range via fiber, i.e., the glass fiber 8, to the transceiver units 5, so that, for example, a 77 gigahertz signal can be emitted or transmitted by the transceiver units 5. Signal detection, in turn, can be performed in the reverse direction. All data can be processed or processed in the computing device 4.

[0104] Fig. 3 shows a detailed illustration of the synthesis 19 and an exemplary illustration of a transmitting / receiving unit 6 of the plurality of transmitting / receiving units 5. The optical transmission signal 7 can be made available to a first optical ring resonator 27 and a second ring resonator 28. Thus, in this example, one and the same optical transmission signal 7 can be made available to two different ring resonators 27, 28. The ring resonators 27, 28 can be, for example, micro-ring resonators. These can have an oval, in particular annular, shape. With the aid of the first ring resonator 27, a first optical signal 29 can be generated or modulated depending on the optical transmission signal 7 coupled into the optical ring resonators 27.

[0105] With the help of the second ring resonator 28, a second optical signal 30 can be modulated or generated by the transmission signal 7 coupled into the second optical ring resonator. The two optical signals have different pulse repetition frequencies F req1 and F req2.

[0106] The transmission signal 7 can be transmitted using an optical coupling element 31 or a linear waveguide for coupling into the ring resonator 27. The optical transmission signal can be made available at an input 32 in order to be able to make it available from there to the coupling element 31. The coupling element 31 can be arranged, in particular directly adjacent, to one side of the optical ring resonator 27. In particular, the coupling element 31 and the ring resonator 27 are arranged at a predetermined coupling distance from one another. Thus, the coupling element 31 and the ring resonator 27 have a gap or a distance from one another. In particular, the coupling element 31 and the ring resonator 27 do not touch one another. Depending on the coupling distance, a coupling ratio between the coupling element 31 and the ring resonator 27 can be predetermined, defined or set.For example, the transmission signal 7 can propagate within the coupling element 31. In an interaction zone, in which the distance is present in particular, the optical transmission signal 7 creates an evanescence field, whereby the transmission signal 7 is coupled into the optical ring resonator 27. For example, after one cycle within the ring resonator 27, newly coupled fields and fields already present in the ring resonator 27 can constructively interfere. An amplitude modulation can thus be generated. As the intensity increases in the ring resonator 27, a fundamental soliton builds up, which can be coupled out in the form of a pulse train 33 or the optical signal 29. The pulse train 33 can be generated in the ring resonator 27 by means of a 4-wave co-process depending on the coupled optical transmission signal 7.By means of a further optical coupling element 34, the first optical signal 29 can be coupled out from the ring resonator 27.

[0107] The situation is analogous with the second ring resonator 28. Here, the transmission signal 7 can again be coupled into the ring resonator 28 by means of a coupling element 35, and after appropriate modulation, the second optical signal 30 can be coupled out by means of a further coupling element 36. In this case, a pulse train 37 can again be generated or modulated. As already mentioned, the two optical signals 29, 30 differ in their respective pulse repetition frequency or pulse repetition rate. The respective pulse repetition frequency can be modulated depending on a respective diameter of the ring resonators 27, 28 and / or the respective coupling distance and / or a coupling ratio. As schematically shown in Fig. 3, the two ring resonators 27, 28 differ in their diameter.

[0108] In particular, the two optical signals 29, 30 can be modulated or generated, in particular with the aid of the ring resonators 27, 28, such that two different or two mutually determined frequency combs 38, 39 (see Fig. 4) can be generated. The frequency combs 38, 39 and in particular the signals 29, 30 can be transmitted, in particular in combination, through a dispersive element or dispersive medium 40. This allows, above all, a respective frequency spectrum of the two optical signals 29, 30 to be modified such that a first chirp signal 41 and a second chirp signal 42 can be generated. The two frequency combs 38, 39 are, in particular, slightly spectrally shifted. Thus, for example, with the aid of the first chirp signal 41, an up-chirp signal having a temporally increasing frequency can be provided. A down-chirp signal can be provided with the second chirp signal.For example, the frequency combs and spectra of the chirp signals 41, 42 are shown in Figs. 5 and 6.

[0109] The two chirp signals 41, 42 can, for example, be provided at a respective optical output 43, 44. In this case, either the outputs 43, 44 can be optically coupled directly to the transmitting / receiving unit 6 or, as shown in Fig. 2, the optical units 21, 22 can be connected after the synthesis 119.

[0110] Furthermore, elements 45, such as filters, frequency selectors, or switches, may be used to provide the first chirp signal 41. An element 46 may be provided for the second chirp signal 42; this element may, for example, comprise a filter, a frequency selector, and / or a switch. Furthermore, a delay line or delay element 47 (delay line) may be used to provide or generate the second chirp signal 42.

[0111] The two signals 41, 42 can thus be transmitted or provided either indirectly or directly by means of the optical outputs 43, 44 to a respective optical input 48, 49 of the transceiver unit 6. With the aid of a first detection unit 50, the first chirp signal 41 can be converted into a first electrical signal 52. The first electrical signal 52 can have an increasing frequency ramp (see Fig. 7). With the aid of a second detection unit 51, the second chirp signal 42 can in turn be converted into a second electrical signal 53. The second electrical signal 53 can, for example, have a decreasing frequency ramp (see Fig. 8). The two detection units 50, 51 can, for example, be referred to as a heterodyne detection unit. Thus, a heterodyne detection is carried out, so that, for example, by means of frequency selection, the measurement of the difference frequencies fdi3, fdi2, fdn (see Fig. 5) and f d23, fd22, fd2i (see Fig. 6) the comb of the frequency combs 38, 39 can be determined. The difference frequency lies primarily in the gigahertz frequency range and is "chirped" in time. Using heterodyne detection, the difference frequency can be measured by superimposing the two frequency combs 38, 39. A sequence of the difference frequencies of both combs 38, 39 thus provides the individual frequencies.

[0112] To convert signal 41 into signal 52, detector unit 50 may include elements such as beam splitters 54 and photodiodes or phototransistors 55. The second detector unit 51 may in turn include beam splitters and photodiodes 57. Furthermore, the second signal 53 may be temporally adjusted by a time delay 58.

[0113] The two electrical signals 52 and 53 can then be combined or unified to form the electrical transmission signal 10. An exemplary representation of this signal 10 is shown in Fig. 9. This is a resulting up-down chirp signal.

[0114] The two signals 52, 53 can, for example, be combined with a circulator to form the transmitted signal 10. The transmitted signal 10 can thus be transmitted as a gigahertz frequency signal for environmental detection. The transmitted signal 10 can, for example, be adjusted using a phase modulation unit and / or frequency modulation unit 59. Furthermore, an amplifier 60 can be provided to amplify the signal accordingly for transmission. Transmission can occur using an antenna 61 or an antenna element of the transmitting / receiving unit 6. Since the transmitting / receiving unit 6 provides only a single antenna 61 for both transmission and reception, a control unit 63 is provided. This control unit 63, which can be designed in particular as an electronic unit, can enable either transmission or reception using the control signal 26 of the computing device 4.For this purpose, electrical components 62, such as switches or RF drivers, and in particular the antenna 61, are controlled or operated in such a way that either the transmitted signal 10 can be transmitted or the received signal 11 can be received. For this purpose, in particular the control unit 63 can set or operate the transceiver unit 6 either in a transmit mode or in a receive mode. Furthermore, the transceiver unit 6 can have an electrical-optical converter unit 64, with which the received electrical signal can be converted into the optical signal 12 for feedback to the computing device 4 for signal processing. For example, the transceiver unit can be used as a TX-RX front end for detecting the surroundings of the vehicle 1. For this purpose, such a front end can be mounted in the area of ​​the vehicle windshield.

[0115] In particular, Fig. 3 shows a gigahertz frequency ramp synthesis with up- and down-chirp by means of two detuned microresonators 27, 28 and provision of a radar signal which is transmitted to the radar front end (transmitting-receiving unit 6) in order to be able to transform there from the terahertz spectral range into the gigahertz spectral range by means of frequency conversion using heterodyne detection.

[0116] In particular, specific frequency combs 38, 39 can be generated using the synthesis unit 19. To generate the gigahertz frequency ramps of a radar system, two frequency combs 38, 39 with different repetition rates freq1, freq2 can be used. For this purpose, the diameters of the microresonators 27, 28 can be designed differently so that the frequency combs are spectrally shifted from one another. With the aid of a dispersive element 40, all spectral components can propagate at the same time, so that the pulses or pulse trains 33, 37 theoretically have a minimal pulse duration. Thus, if a signal or frequency comb propagates through a normal disposable medium, such as air, the high-frequency spectral components experience a greater time delay than the low-frequency spectral components. In particular, the pulses 33, 37 can be positively and negatively chirped and thus stretched in time.The signals 41, 42 are measured using detector units 50, 51. The resulting frequencies form a ramp in the gigahertz spectral range.

[0117] For example, vehicle 1 can be a passenger car or a truck. For example, the vehicle can be a highly automated vehicle. In particular, multiple transceiver units 5 can be distributed over a large area in array arrangements in or on the vehicle 1. For this purpose, a sparse array configuration can be selected, for example.

[0118] For example, several individual transceiver units 5 can be arranged in the vehicle 1 and connected to the computing device 4. This can be used for an ADAS (Advanced Driver Assistant) system of the vehicle. For example, the transceiver units 5 can be arranged on windshields, rear windows, the vehicle roof, or bumpers. For example, a separate radiation source can be provided for the return channel 9.

[0119] In particular, both ring resonators 27, 28 can be fed with the same optical transmission signal 7. In another conceivable embodiment, both ring resonators 27, 28 can be fed with different optical transmission signals. Another possibility is that the optical signal 12 provided via the return channel 9 is made available to at least one of the two ring resonators 27, 28, so that it can be additionally coupled in or taken into account for the optical signals 29, 30.

[0120] In particular, the figures show the possibility of creating an ultra-stable, extremely space-saving radar system at the electronic photonic chip level.

[0121] List of reference symbols

[0122] vehicle

[0123] radar system

[0124] Vicinity

[0125] Computing device, 6 transmitting-receiving unit optical transmission signal

[0126] Fiber optic

[0127] Return channel 0 electrical transmission signal 1 electrical reception signal 2 optical reception signal 3 optical-electrical converter unit 4 electrical signal 5 digital interface 6 processing unit 7 evaluation unit 8 electrical return channel 9 synthesis unit 0 modulator 1 optical control unit 2 optical distributor 3 control unit 4 a feedback loop 5 electrical transmission path 6 electrical control signal 7, 28 ring resonators 9, 30 first and second chirp signal 1 optical coupling element 2 optical inputs 3 pulse train 4, 35, 36 optical coupling elements 7 pulse train 8, 39 mutually detuned frequency combs 0 dispersive element 41, 42 first and second chirp signal

[0128] 43, 44 first and second optical output

[0129] 45 elements

[0130] 46 elements

[0131] 47 Delay line

[0132] 48, 49 optical inputs

[0133] 50, 51 first and second detection unit

[0134] 52, 53 first and second electrical signal

[0135] 54 beam splitters

[0136] 55 photodiode

[0137] 56 beam splitters

[0138] 57 Photodiode

[0139] 58 Delay

[0140] 59 Phase modulator and / or frequency modulator

[0141] 60 amplifiers

[0142] 61 Antenna

[0143] 62 elements

[0144] 63 Control device

[0145] 64 electrical-optical conversion unit

[0146] 65 optical unit fREP1 , ffiEP2 pulse repetition frequencies fd1, fd12, fd13, fd21, fd22, fd23 difference frequencies

Claims

Patent claims 1. Computing device (4) for a radar system (2), with - an optical unit (65) for providing an optical transmission signal (7); - a first optical ring resonator (27) of a synthesis unit (19) which is designed to couple the optical transmission signal (7) into the first optical ring resonator (27) and to modulate a first optical signal (29) as a function of the coupled optical transmission signal (7), - a second ring resonator (28) of the synthesis unit (19), which is different from the first ring resonator (27), which is designed to couple the optical transmission signal (7) into the second optical ring resonator (28) and to modulate a second optical signal (28) different from the first optical signal (29) as a function of the coupled-in optical transmission signal (7), wherein the two optical signals (29, 30) have different pulse repetition frequencies (f req i, f req 2) have; - the synthesis unit (19) which is designed to generate, on the basis of the two optical signals (29, 30), a first chirp signal (41) which has a temporally increasing frequency and a second chirp signal (42) which has a temporally decreasing frequency; - a first optical output (43) of the synthesis unit (19) for providing the first chirp signal (41); and - a second optical output (44) of the synthesis unit (19) for providing the second chirp signal (42).

2. Computing device (4) according to claim 1, wherein the synthesis unit (19) has a dispersive element (40), wherein the dispersive element (4) is designed to change a respective frequency spectrum of the two optical signals (29, 30) such that the two chirp signals (41, 42) can be generated.

3. Computing device (4) according to one of the preceding claims, wherein the two optical ring resonators (27, 28) are designed as micro-ring resonators.

4. Radar system (2) with a computing device (4) according to one of the preceding claims 1 to 3 and at least one transmitting-receiving unit (5, 6), wherein the computing device is coupled to the at least one transmitting-receiving unit (5, 6).

5. Radar system (2) according to claim 4, wherein the transmitting-receiving unit (5, 6) comprises a first detection unit (50) for generating a first electrical signal (52) based on the first chirp signal (41) and a second detection unit (51) for generating a second electrical signal (53) based on the second chirp signal (42).

6. Radar system (2) according to claim 5, wherein the transmitting-receiving unit (5, 6) is designed to generate an electrical transmission signal (10) depending on the first and second electrical signals (52, 53), wherein the transmission signal (10) has a frequency which is formed from a difference between a frequency of the first signal (52) and a frequency of the second electrical signal (53).

7. Radar system (2) according to claim 6, wherein the transmitting-receiving unit (5, 6) has an antenna (61) which is configured to transmit the electrical transmission signal (10) and to receive an electrical reception signal (11) which is based on the electrical transmission signal (10).

8. Radar system (2) according to claim 7, wherein the transmitting-receiving unit (5, 6) has a control unit (63) with which the transmitting-receiving unit (5, 6) can be controlled depending on an electrical control signal (26) which is transmitted via an electrical transmission path (25) from the computing device (4) to the transmitting-receiving unit (5, 6), wherein the control unit (63) is designed to switch the transmitting-receiving unit (5, 6) between a transmission mode for transmitting the electrical transmission signal (10) and a reception mode for receiving the electrical reception signal (11).

9. Radar system (2) according to claim 7 or 8, wherein the transmitting-receiving unit (5, 6) comprises an electrical-optical converter unit (64), wherein the electrical-optical converter unit (64) is designed to to convert the received electrical reception signal (11) into an optical reception signal (12).

10. Radar system (2) according to one of the preceding claims 4 to 9, comprising: an optical return channel (9) for transmitting the optical reception signal (12) from the transmitting-receiving unit (5, 6) to the computing device (4), wherein the computing device (4) has an optical-electrical converter unit (13) for converting the optical reception signal (12) into an electrical signal (14), and wherein the electrical signal (14) can be evaluated with regard to radar information using an evaluation unit (17) of the computing device (4).

11. Radar system (2) according to one of the preceding claims 4 to 10, wherein the transmitting-receiving unit (5, 6) and the computing device (4) are physically and / or spatially separate units.

12. Vehicle (1) with a radar system (2) according to one of the preceding claims 4 to 11.

13. A method for operating a radar system (2) according to one of the preceding claims 4 to 11, wherein the following steps are carried out: - modulating the first optical signal (29) by coupling the optical transmission signal (7) into the first optical ring resonator (27); - Modulating the second optical signal (30) by coupling the optical transmission signal (7) into the first-second optical ring resonator (28), wherein the two optical signals (29, 30) are modulated such that they have different pulse repetition frequencies (f req i, f req 2) have; - generating the first chirp signal (41), which has a temporally increasing frequency, on the basis of the first optical signal (29) and the second chirp signal (42), which has a temporally decreasing frequency, on the basis of the second optical signal (30); - transmitting the two chirp signals (41, 42) to the transmitting-receiving unit (5, 6); - generating the electrical transmission signal (10) based on the two chirp signals (41, 42); and - Emitting the electrical transmission signal (10) with the antenna (61).

14. The method according to claim 13, wherein the electrical reception signal (11) based on the electrical transmission signal (10) is received by the antenna (61) and converted into the optical reception signal (12), wherein the radar information is evaluated on the basis of the optical reception signal (12) so that an environment detection can be carried out with the radar system (2).

15. The method according to claim 13 or 14, wherein the two chirp signals (41, 42) are converted into the two electrical signals (52, 53) by means of heterodyne detection, and the electrical transmission signal (10) is generated on the basis of the two electrical signals (52, 53).

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