Distributed radar system with signal processing on the basis of SIMO and MIMO structures

Abstract

The invention relates to a radar system comprising a central unit (C), a plurality of radar transmission units (TX1, TX2,., TXn) and a plurality of radar reception units (RX1, RX2, RX3,., RXn), the radar system having both a MIMO radar structure and a SIMO radar structure, wherein, in the case of the MIMO radar structure, a plurality of radar transmission signals are transmitted by a plurality of radar transmission units and a plurality of radar reception signals are received by a plurality of radar reception units and, in the case of the SIMO radar structure, one radar transmission signal is transmitted by one radar transmission unit and a plurality of radar reception signals are received by a plurality of radar reception units. The central unit (C) is designed to determine first radar information from the radar reception signals of the SIMO radar structure and to determine second radar information by jointly processing the first radar information with the radar reception signals of the MIMO radar structure.

Description

[0001] Description

[0002] Distributed radar system with signal processing based on SIMO and MIMO structures

[0003] The present invention relates to a distributed radar system that can be operated, for example, in a vehicle. The present invention further relates to a method for operating such a radar system.

[0004] For driver assistance 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 capture the environment. Based on the collected sensor data, an environmental model can then be created. While cameras provide detailed visual information and enable the recognition of traffic signs, lane markings, and colors, for example, they deliver poor results in unfavorable lighting conditions, fog, or glare, and provide only inadequate distance information. Lidar-based systems, while capable of precise distance measurement, are expensive and susceptible to weather conditions. Radar sensors, on the other hand, deliver reliable and fail-safe data in all weather conditions.However, the resolution of radar sensors currently in series production in the automotive sector is limited.

[0005] Current developments in distributed radar systems rely on the arrangement of transmit and / or receive modules in a spatially distributed aperture, which leads to a significant increase in resolution. A special case of distributed radar systems are photonic radar systems, in which driver signals in the GHz range can be distributed to a multitude of radar sensors via one or more optical fibers using an optical carrier signal in the THz frequency range. Here, electronic and photonic components can be co-integrated on a single semiconductor chip, enabling compact form factors for the individual radar sensors and, consequently, arrays with a multitude of such radar sensors integrated into the vehicle. German patent DE 102017221 257 A1 discloses a radar system in which signal transmission between a central unit and a radar transmitting unit or a radar receiving unit is implemented optically.For this purpose, a radar driver signal is optically generated in the central processing 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 processing unit. In the central processing unit, the modulated optical signal is received, evaluated, and then made available as radar information.

[0006] In distributed radar systems, signal processing is based on a so-called MIMO (Multiple-Input Multiple-Output) structure, in which each transmitting antenna independently emits a signal, and the resulting received signals are picked up by a multitude of receiving antennas and fed into a common radar signal processing system. In contrast to a radar device with a SIMO (Single-Input Multi-Output) structure using a single transmitting antenna, the signals from the individual transmitting antennas must be distinguished. This can be achieved, in particular, by ensuring that only one transmitting antenna emits at any given time during MIMO operation. Signal processing based on MIMO or SIMO structures in vehicle radar systems is disclosed, for example, in DE 102020107 222 A1, DE 102024104927 A1, and DE 102024202475 A1.

[0007] In contrast to this prior art, one object of the invention is to provide an improved distributed radar system and a method for operating such a radar system.

[0008] This problem is solved by the independent claims. Preferred embodiments of the invention are the subject of the dependent claims.

[0009] A radar system according to the invention, comprising a central unit, multiple radar transmitters, and multiple radar receivers, has both an M1 MO radar structure and an S1 MO radar structure. In the M1 MO radar structure, multiple radar signals are transmitted by multiple radar transmitters and multiple radar receivers are received by multiple radar receivers. In the S1 MO radar structure, one radar signal is transmitted by one radar transmitter and multiple radar receivers are received by multiple radar receivers. The central unit is configured to determine first radar information from the radar receivers of the S1 MO radar structure and to determine second radar information by jointly processing the first radar information with the radar receivers of the M1 MO radar structure.

[0010] Preferably, an Sl MO data set is generated based on the radar echo signals of the radar receiving units that are sensitive to the radar transmitting units of the Sl MO radar structure, and a MIMO data set is generated based on the radar echo signals of the radar receiving units that are sensitive to the radar transmitting units of the MIMO unit.

[0011] In particular, radar target information can be determined by processing the SIMO data set, and this radar target information can be added to the MIMO data set for MIMO signal processing.

[0012] According to one embodiment of the invention, the central unit comprises a common signal generation unit for generating SIMO and MIMO radar ramp signals.

[0013] Preferably, the MIMO radar structure and the SIMO radar structure comprise separate, independent radar transmitting units, whereas at least some of the radar receiving units are shared by the SIMO radar structure and the MIMO radar structure.

[0014] Advantageously, several radar receiving units used by the SIMO radar structure can be arranged at uniform intervals along a line in space.

[0015] According to one embodiment of the invention, only one of the radar transmitting units emits a radar signal at any given time.

[0016] According to a further embodiment of the invention, at least one radar transmitter of the SIMO radar structure emits a radar signal at the same time as one of the radar transmitters used by the MIMO radar structure. According to one embodiment of the invention, the SIMO and MIMO radar ramp signals represent signal components that are shifted in time relative to each other.

[0017] Preferably, the central unit for this purpose comprises a signal generation unit for generating the SIMO radar ramp signals and a separate signal generation unit for generating the MIMO radar ramp signals.

[0018] Likewise, the central unit can include a signal generation unit for generating a radar ramp signal, wherein a part of the generated radar ramp signal is fed to a delay element, and wherein one of the SIMO and MIMO radar ramp signals is formed by the time-delayed signal part and the other of the SIMO and MIMO radar ramp signals is formed by the undelayed signal part.

[0019] According to a further embodiment of the invention, the SIMO and MIMO radar ramp signals represent signal components that are shifted relative to each other in frequency.

[0020] Preferably, the central unit also includes a signal generation unit for generating the SIMO radar ramp signals and a separate signal generation unit for generating the MIMO radar ramp signals.

[0021] Likewise, the central unit can preferably include a signal generation unit for generating a radar ramp signal, wherein a part of the generated radar ramp signal is fed to a mixing unit and wherein one of the SIMO and MIMO radar ramp signals is formed by the frequency-shifted signal part due to the mixing and the other of the SIMO and MIMO radar ramp signals is formed by the non-frequency-shifted signal part.

[0022] Furthermore, the invention also includes a method for operating a radar system according to the invention.

[0023] Finally, the invention also includes a vehicle that has a radar system according to the invention.

[0024] Further features of the present invention will become apparent from the following description and the claims in conjunction with the figures. Figure 1 shows a schematic representation of an embodiment of a radar system according to the invention;

[0025] Fig. 2 shows a flowchart of the signal processing of an S1 MO structure in combination with a MIMO structure;

[0026] Fig. 3 shows an exemplary temporal arrangement of SIMO and MIMO radar ramp signals in time-delayed operation;

[0027] Fig. 4 shows a schematic representation of a central station with signal generation of time-delayed SIMO and MIMO radar ramp signals via (a) separate signal generation units and (b) a shared signal generation unit with a downstream delay element;

[0028] Fig. 5 shows an exemplary temporal arrangement of SIMO and MIMO radar ramp signals during frequency-shifted operation;

[0029] Fig. 6 shows a schematic representation of a central station with signal generation of frequency-shifted SIMO and MIMO radar ramp signals via (a) separate signal generation units and (b) a shared signal generation unit with a downstream mixing element;

[0030] Fig. 7 shows a schematic representation of a central unit (a) and a SIMO-MIMO transmit and SIMO-MIMO receive unit (b) of a photonic radar system;

[0031] Fig. 8 shows a schematic representation of a central unit (a) and a SIMO-MIMO transmit and SIMO-MIMO receive unit (b) of a photonic radar system with wavelength division multiplexing; and

[0032] Fig. 9 shows a schematic representation of a central unit (a) and a SIMO-MIMO transmit and SIMO-MIMO receive unit (b) of a photonic radar system with electrical multiplexing in the front end.

[0033] 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.

[0034] Figure 1 shows a schematic representation of a radar system according to the invention. The radar system comprises a central unit C, several radar transmitters TXi, TX2,..., TX n , as well as several radar receiver units RX1, RX2, RX3,..., RX nAlthough the figure shows only a few radar transmitter and receiver units as examples, a large-area integration of a multitude of antenna chips, each comprising radar transmitters and / or radar receivers, is possible, particularly in a photonic radar system. However, the radar system according to the invention is not limited to photonic radar systems.

[0035] When implemented in a passenger car, the radar system can be integrated into various surfaces, such as the windshield, rear window, and bumper. The underbody, roof, and B-pillar can be used for integration along the sides of the vehicle. The central unit, for example, can be a radar control unit located in the passenger compartment or engine compartment. The central unit is referred to as the backend, while the radar transmitters and receivers are referred to as the frontend.

[0036] 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.

[0037] 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 integration of the RF circuits for the radar antennas, including the frequency multiplier, with the photonic circuit can be achieved in a monolithic design without additional wire or flip-chip bonding. Furthermore, chips can be optically and electrically tested directly 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.

[0038] The central unit is connected to the radar transmitters TXi, TX2,..., TX via one or more transmission media. n and the radar receiver units RX1, RX2, RX3,..., RX nconnected, whereby the transmission media can be, in particular, one or more optical fibers. In the case of an integrated unit on which circuits for both sending and receiving are located, the signal only needs to be sent to this common unit.

[0039] The central processing unit is responsible for generating a frequency-modulated continuous wave (FMCW) signal, as well as processing and evaluating the signals generated by the radar receivers. For clarity, the components required for this are not shown. This centralized processing and evaluation of the signals allows the individual radar sensors to be designed as small and cost-effectively as possible.

[0040] In the central station, a control unit P, which can be designed, for example, as an IC, microcontroller, or digital signal processor, controls a signal generation unit SG, which is specifically designed as a ramp generator. In the embodiment shown in Figure 1, a single, shared signal generation unit is depicted for generating SIMO and MIMO radar ramp signals; however, separate signal generation units for generating the SIMO and MIMO radar ramp signals can also be used. Ramp modulation involves a repetitive linear modulation of the frequency between a start and a stop frequency, with each of these frequency phases being called a chirp. Depending on whether the frequency increases or decreases over time, this is referred to as an up or down chirp. The radar ramp signals are then modulated onto a radar driver 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 or 1 / 4 of the radar carrier frequency commonly used in road vehicles. An optical carrier signal modulated with this radar driver signal is then coupled into the transmission medium, for example, an optical fiber.

[0041] The optical carrier signal, modulated by the radar driver signal, is coupled out of the transmission medium by each individual radar transmitter unit using a coupling unit (not shown), and the radar driver signal is separated in each unit. If this radar driver signal is only a fraction of the radar frequency used, for example, 1 / 8 or 1 / 4 of the stated radar frequency, it is first multiplied eightfold or fourfold, respectively, in the individual radar transmitter units. The resulting signal then drives the respective radar transmitters in the radar transmitter units. The individual radar transmitters include, in particular, radar antennas, each of which then emits a radar signal.

[0042] According to the invention, a SIMO structure is provided in combination with the M1 MO structure, which simplifies signal processing. The SIMO structure can be integrated into the distributed radar system independently of the MIMO structure, so that in such a case a SIMO unit and a MIMO unit are separate. In a preferred embodiment, as shown by way of example in Figure 1, elements of both the SIMO unit and the MIMO unit are shared. Here, separate, independent radar transmitters are used for the SIMO and MIMO methods; in the illustrated example, TX1 is part of the SIMO structure and TX2 and TX3 are separate components. n as part of the MIMO structure. In contrast, the radar receivers RX1, RX2, and RX are supplied by the SIMO unit and the MIMO unit from the receiving antennas. nshared, only the radar receiver unit RX3 is exclusively part of the MIMO structure.

[0043] In a further preferred embodiment, the radar receiving units of the SIMO unit can form a Uniform Linear Array (ULA) in which several identical SIMO elements are arranged at uniform intervals along a line in space. This enables particularly precise and robust signal processing. For example, phase differences between the incoming signals can be measured very easily for direction determination due to the uniform arrangement of the SIMO elements, and signals from a desired direction can be amplified while interference from other directions is suppressed. Furthermore, the regular, linear arrangement allows the use of efficient mathematical methods, such as a Fourier transform, in signal processing.

[0044] In a radar system according to the invention with combined SIMO and MIMO elements, it can be provided that only one transmitting unit transmits at any given time. Likewise, in a further preferred embodiment, it can be provided that at least one transmitting unit of the SIMO unit transmits at the same time as one of the MIMO transmitting units.

[0045] By using the SIMO unit, some of the computational work of the MIMO unit can be pre-calculated with less computational effort. A flowchart describing the signal processing is shown in Figure 2. This assumes that the SIMO and MIMO units operate simultaneously, i.e., synchronously.

[0046] The basis for the signal processing operations is SIMO or MIMO data sets, where a data set (or frame) is understood to be a data structure in which a temporally defined block of measurement data, based on the radar echo signals of several radar ramp signals transmitted in quick succession, is combined. Specifically, two different received data sets are generated: a SIMO data set 20 based on the radar echo signals of the receiving antennas, which are sensitive to the transmitting antennas of the SIMO unit, and a MIMO data set 21 based on the radar echo signals of the receiving antennas, which are sensitive to the transmitting antennas of the MIMO unit.

[0047] Initially, signal processing is performed using the SIMO unit, which, due to its simpler structure, can be calculated more easily. This simplification must be viewed in the context of the complex signal processing of the data set acquired from a MIMO structure. The structural arrangement of all MIMO elements results in significant differences in propagation time due to their wide distribution along a radar aperture. These propagation time differences must be compensated for using complex methods within the signal processing to make the information contained in the radar signal accessible.The structural design of the SIMO structure, in the exemplary form of a ULA, instead efficiently utilizes occurring time differences to allow an initial angle estimation over a possible solid angle of a target, whereby a preceding two-dimensional Fourier transformation over the data set of a receiving antenna is not subject to any time differences.

[0048] In process step 22, the sub-array spanned by SIMO transmit and receive units is determined. Then, in process step 23, radar information, e.g., frequency-based analyses based on FFTs (Fast Fourier Transforms), is determined for each channel to calculate radar target information. The acquired data are combined in process step 24 and compiled into a common target list 25. This common target list, in addition to the MIMO data set 21, is then fed to the MIMO signal processing 26. The target list includes indicators in the range / Doppler spectrum whose power values ​​exceed a threshold. These indicators, which represent a spectral peak, are assigned a distance- or speed-dependent frequency.From this frequency, a distance or speed can be derived for this indicator, which in turn attributes to the target associated with the indicator.

[0049] The prior SIMO signal processing allows for particularly efficient MIMO signal processing 26, since the frequency components present in the range / Doppler information for targets are also present in the same form in the received signals of the MIMO structure. The result of the MIMO signal processing is the acquisition of radar targets and corresponding radar target information, such as range, relative angle, and relative velocity. Further radar targets can then be queried and calculated via a feedback path to the target list obtained from the SIMO signal processing.

[0050] Overall, this allows for efficient distance and position determination, and the velocity of the respective target object can be determined by detecting frequency shifts caused by the Doppler effect. The efficiency gain is explained by the elimination of compensation for propagation delay differences in the received signals of the MIMO structure, since these propagation delay differences do not exist within a data set of the MIMO structure, and distance information, or rather the velocity, is directly proportional.

[0051] Doppler velocities can be determined by simple Fourier transformation. In preferred embodiments, the SIMO and MIMO radar ramp signals represent different signal components. In a preferred variant, the SIMO and MIMO radar ramp signals can represent signal components that are shifted relative to each other in time, as exemplified by the time course of the frequency of the radar ramp signals in Figure 3. The solid lines represent the transmitted Tx radar ramp signals, and the dashed lines correspond to the received Rx radar echo signals with a time delay T. (r ) of the radar echo signal in relation to the transmitted radar ramp signals. In the example shown, a transmitted MIMO radar ramp signal 31 is followed by a transmitted SIMO radar ramp signal 33 with a time offset TD; accordingly, the received MIMO radar ramp signals 32 are offset by TD relative to the received SIMO radar ramp signals 34.

[0052] The time offset TD between the transmitted MIMO and SIMO radar ramp signals can be achieved by an additional, dedicated signal generation unit within the central unit, as schematically illustrated in Figure 4a. In this case, a control unit P controls a signal generation unit SGs for generating the SIMO radar ramp signals and a separate signal generation unit SGM for generating the MIMO radar ramp signals. The generated MIMO and SIMO radar ramp signals are then transmitted to the radar transmitting antennas via the transmission medium as described above. In an alternative embodiment schematically illustrated in Figure 4b, a single, shared signal generation unit SG for generating SIMO and MIMO radar ramp signals can be used in combination with a downstream physical delay unit D to create a time offset.If a time offset between the two ramp signals is known beforehand, a corresponding delay can be incorporated into the design of the circuits / circuit board of the central unit by appropriately selecting the length of the signal paths. SIMO and MIMO radar ramp signals can be multiplexed and routed to the SIMO and MIMO transmit and receive units via a single line. For the sake of clarity, the illustration of further components, such as couplers, dividers, or combiners, has been omitted from Figures 4a and 4b.

[0053] Unlike the representation shown in Figures 4a and 4b, in another embodiment the SIMO and MIMO radar ramp signals can also be routed to the SIMO and MIMO transmit and receive units via several parallel lines. In a further embodiment not shown, it is also possible to transmit only a single radar ramp signal from the central unit, with the time delay of SIMO and MIMO radar ramp signals then being implemented in the front end.

[0054] In another embodiment, the SIMO and MIMO radar ramp signals represent signal components shifted in frequency relative to each other, as shown by way of example in Figure 5. As in Figure 3, the solid lines represent the transmitted Tx radar ramp signals and the dashed lines represent the received Rx radar echo signals. In the illustrated example, there is a frequency offset fs between the transmitted MIMO radar ramp signal 33 and the transmitted SIMO radar ramp signal 31, and correspondingly between the received MIMO radar ramp signal 34 and the received SIMO radar ramp signal 32.

[0055] The frequency offset between the transmitted MIMO and SIMO radar ramp signals can be achieved by an additional, dedicated signal generation unit within the central unit, as schematically illustrated in Figure 6a. In this case, a control unit P controls a signal generation unit SGs for generating the SIMO radar ramp signals with center frequency fi and a separate signal generation unit SGM for generating the MIMO radar ramp signals with center frequency fi+ fs.

[0056] In an alternative embodiment schematically illustrated in Figure 6b, a single, common signal generation unit SG can be used for generating SIMO and MIMO radar ramp signals in combination with a downstream mixing unit M (up / down conversion) for one of the two signal components to generate a frequency offset. For example, the signal generation unit SG can supply the mixing unit M with a local oscillator signal LO with a frequency offset f. s are supplied to generate a radar ramp signal with a center frequency fi+ fs by mixing the radar ramp signal of center frequency fi generated by the signal generation unit SG with the local oscillator signal LO.

[0057] Here too, the SIMO and MIMO radar ramp signals can be multiplexed to the SIMO and MIMO transmit and receive units via a single line or via several parallel lines. In another embodiment not shown, it is also possible to transmit only a single radar ramp signal from the central unit, with the frequency offset of the SIMO and MIMO radar ramp signals then being implemented by mixing in the front end.

[0058] According to another embodiment, a combination of a time offset of the emitted MIMO and SIMO radar ramp signals and a frequency offset of the emitted MIMO and SIMO radar ramp signals relative to each other is used.

[0059] Exemplary embodiments of the invention, integrating SIMO and MIMO units into a photonic radar system, are shown in the following figures. It is assumed that all transmit and receive units from Figure 1 can be used as SIMO and MIMO transmit and receive units, with selection occurring during operation via parameterization. Furthermore, it is assumed that SIMO and MIMO transmit units operate synchronously and in parallel. Implementation using separate solutions is also possible.

[0060] A first embodiment of a photonic radar system is illustrated by way of example in Figures 7a and 7b, where Figure 7a shows an exemplary implementation of a central unit and Figure 7b shows an exemplary implementation of a SIMO-MIMO transmitting unit (top) and SIMO-MIMO receiving unit (bottom). Only the components relevant to the invention are shown; for the sake of clarity, other components, e.g., couplers, dividers, amplifiers, or combiners, have been omitted.

[0061] To provide the optical output signals, the central processing unit C in the embodiment shown in Figure 7a comprises a light source 700. This can be 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. Alternatively, a so-called ASE light source (Amplified Spontaneous Emission) can be used, which emits light generated by spontaneous emission and subsequently optically amplified by stimulated emission.

[0062] The optical carrier signal generated by the light source 700 is fed to an electro-optic modulator 701, which modulates the SIMO and / or MIMO radar ramp signal generated by a ramp generator 702 onto the optical carrier signal as described above. For example, the electro-optic modulator can be a Mach-Zehnder modulator, in which the optical carrier signal is first split into two waveguides, in which 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, for example via directly modulated light sources, are also possible.

[0063] The optical carrier signal modulated by the electro-optical modulator 701 can then be fed to an optional optical control unit 703, which can, for example, control or regulate the amplitude, phase, or polarization of the modulated optical carrier signal. Subsequently, the modulated optical carrier signal TS is output by the central unit and transmitted to the front-end units.

[0064] In the transmitting units, one of which, Tx, is shown as an example in Figure 7b, the optical carrier signal TS received from the central unit is first converted optically to electrically by an optical detection unit 720. A photodiode can be used for this purpose. The electrical signal is then separated into the SIMO and MIMO ramp signals by a separation unit 721. An electrical switch 722 then determines which of the two ramp signals is to be fed to the respective antenna as the antenna signal AS.

[0065] All receiving units, one of which, Rx, is shown as an example in Figure 7b, receive both the SIMO and MIMO radar echo signals RE reflected from a target. The signals coming from the antenna are routed to two different mixers 741 and 742 by means of an electrical switch 740. The local oscillator LO required for downconversion is either the SIMO or the MIMO ramp signal, which, identical to the transmitting unit, is optically converted to electrical signals by an optical detection unit 743 and separated by a separation unit 744. Depending on the applied LO, either the SIMO or the MIMO radar echo signal is transformed to a lower intermediate frequency (IF), while the other radar echo signal is shifted to a higher intermediate frequency. This results in the separation of the two signals at the receiver.These signals can then be modulated on the receiving end via corresponding optical modulators 745, 746, which can also be Mach-Zehnder modulators, for example, onto a continuous wave (CW) signal provided by the central unit. The modulated signal IF is then sent back to the central unit. The unmodulated continuous wave signal received by the central unit can first be fed at the input of the radar receiving unit Rx to an optional optical control unit 747, which can, for example, control or regulate the amplitude, phase, or polarization of the unmodulated continuous wave signal. The processed signal is then subsequently fed to the optical modulators 745, 746 via an optical switch or beam splitter 748. It is also conceivable to place the switch 740 after the separation unit 744, or to use only one mixer, or...only one optical modulator 745, 746.

[0066] In the central station, the intermediate frequency (IF) signals for the SIMO and MIMO radar echo signals can be optically converted to electrical signals by optical detection units 704, 705 and subsequently converted analog to digital signals. A preferred embodiment provides for the use of an electrical switch 706 to select the signal to be converted, which is then fed to a fast analog-to-digital converter 707. The digitized signal is then fed to a control and processing unit 708, which can be designed, for example, as an integrated circuit (IC), microcontroller, or digital signal processor, for further processing.

[0067] Another preferred embodiment provides for the use of optical multiplexing methods, as exemplified in Figures 8a and 8b using wavelength division multiplexing. Here, two optical carrier signals with different wavelengths A1 and A2 are used, wherein either the SIMO or the MIMO radar ramp signal is modulated onto the optical carrier signals via appropriate optical modulators.

[0068] Figure 8a shows an exemplary realization of a central unit and Figure 8b shows an exemplary realization of a SIMO-MIMO transmitting unit (top) and SIMO-MIMO receiving unit (bottom), where again only the components relevant to the invention are shown.

[0069] To provide the optical output signals, the central processing unit C in this embodiment comprises two light sources 800 and 801, which may preferably be configured as laser diodes emitting laser light with different wavelengths A1 and A2. The optical carrier signal generated by the light source 800 is fed to an electro-optic modulator 802, which modulates the MIMO radar ramp signal generated by a ramp generator 803 onto an optical carrier signal. Similarly, the optical carrier signal generated by the light source 801 is fed to an electro-optic modulator 804, which modulates the SIMO radar ramp signal generated by a ramp generator 805 onto an optical carrier signal. Here, too, the electro-optic modulators may, for example, be Mach-Zehnder modulators.

[0070] The optical carrier signals modulated by the electro-optical modulators 802 and 804 are fed to an optical multiplexer 806, optionally after control or regulation of the amplitude, phase, or polarization, and combined by the latter. The two signals are then transmitted as a multiplexed optical carrier signal TS via an optical waveguide to the front-end units.

[0071] As shown in Figure 8b for a transmitting unit Tx, the multiplexed optical carrier signal TS is first fed to a demultiplexer 820 at the radar transmitter, where the radar ramp signals are separated again. The separated radar ramp signals are then converted optically to electrically by optical detection units 821, 822, for example photodiodes, and subsequently fed to the antenna as an antenna signal AS via an electrical switch 823.

[0072] On the radar receiving side, the radar ramp signals are also first separated by a demultiplexer 840 and converted optically to electrically by optical detection units 841, 842. The subsequent forwarding to the mixers 843, 844 is analogous to the embodiment described above in Figure 7. The SIMO and MIMO radar echo signals RE coming from the antenna are also fed to the mixers 843, 844 by means of an electrical switch 845.

[0073] In accordance with wavelength division multiplexing, the central unit also provides two continuous wave (CW) signals in this case. These signals are first optionally fed to an optical control unit 846 for monitoring and control of the amplitude, phase, or polarization, and then also pass through a demultiplexer 847. Using two optical modulators 848 and 849, the SIMO intermediate signal is modulated onto one of the two optical carrier signals, and the MIMO intermediate signal is modulated onto the other. The two optical radar echo signals are then combined via another multiplexer 850 and transmitted back to the central unit.

[0074] The two intermediate signals are separated again via a demultiplexer 807 located in the central unit. The subsequent processing is carried out analogously to the embodiment shown in Figure 7 by optical detection units 808, 809, an electrical switch 810 for selecting the signal to be converted, an analog-to-digital converter 811 and a control and processing unit 812.

[0075] In other preferred embodiments, other optical multiplexing methods can also be used, e.g. based on polarization or phase of the optical carrier signal.

[0076] Another preferred embodiment is based on an electrical multiplex in the front end, as illustrated by way of example in Figures 9a and 9b. For the sake of clarity, additional optical multiplexing methods are omitted, but a combination is possible.

[0077] In the central processing unit, two optical SIMO and MIMO radar ramp signals are generated and sent to the front-end units. For this purpose, the central processing unit C, in this embodiment as well, comprises two light sources 900 and 901, preferably configured as laser diodes. The optical carrier signal generated by light source 900 is fed to an electro-optic modulator 902, which modulates the MIMO radar ramp signal generated by a ramp generator 903 onto an optical carrier signal. Similarly, the optical carrier signal generated by light source 901 is fed to an electro-optic modulator 904, which modulates the SIMO radar ramp signal generated by a ramp generator 905 onto an optical carrier signal. Here too, the electro-optic modulators can be Mach-Zehnder modulators. The optical carrier signals TS modulated by the electro-optic modulators 902 and 904 are then transmitted to the front-end units.

[0078] As shown in Figure 9b for a transmitting unit Tx, the modulated optical carrier signals TS are converted optically to electrically by optical detection units 921, 922, wherein the optical SIMO radar ramp signal is first delayed by an optical delay unit 920, so that it has a time offset AT relative to the optical MIMO radar ramp signal. The radar ramp signals are then subsequently routed to the antenna as an antenna signal AS via an electrical switch 923.

[0079] On the radar receiver side, the radar ramp signals are also first converted optically to electrically by optical detection units 941, 942. The subsequent forwarding of the radar ramp signals as well as the SIMO or MIMO radar echo signals RE to the mixers 943, 944 by means of an electrical switch 945 takes place analogously to the embodiments described above in Figures 7 and 8.

[0080] An unmodulated continuous wave signal received by the central unit can optionally be fed at the input of the radar receiver Rx to an optical control unit 946 for monitoring and control of the amplitude, phase, or polarization of the unmodulated continuous wave signal. The processed signal is then fed to the optical modulator 947, which modulates the SIMO intermediate signal and the MIMO intermediate signal onto the optical carrier signal. The delay of the optical SIMO radar ramp signal at the transmitter unit also delays the SIMO radar echo signal at the receiver unit. While the MIMO radar echo signal, as in the previously described embodiments, is transmitted at a specific intermediate frequency f| F The transformation of the emitted SIMO radar ramp signal leads to a higher intermediate frequency f| on the receiving side. F+s, which is preferably chosen such that the smallest frequency component of the SIMO intermediate signal lies above the largest frequency component of the MIMO intermediate signal. This is based on the fact that the frequency generated during downconversion is generally dependent on the spatial free-space distance between transmitter, target, and receiver. The additional time delay artificially "extends" this distance, resulting in the SIMO signal being generated at a higher center frequency. In other words, a target at a given distance will produce a higher frequency in the case of an emitted SIMO radar ramp signal than in the case of a MIMO radar ramp signal.

[0081] The two intermediate signals thus form two components of an electrical frequency multiplex signal, which can first be combined (not shown) and modulated via the common optical modulator 947 onto the optical radar carrier signal CW and sent to the central unit.

[0082] Once there, both frequency components are first converted optically to electrically by an optical detection unit 907 and then separated again by a separation unit 908, e.g., suitable filters. Optionally, the SIMO intermediate signal with the frequency offset can then be down-mixed to the lower intermediate frequency range by an electrical mixer 909. The subsequent processing is carried out analogously to the previous embodiments by means of an electrical switch 910 for selecting the signal to be converted, an analog-to-digital converter 911, and a control and processing unit 912. In another embodiment, the two signal components are not separated and are fed directly to an analog-to-digital converter 911.

[0083] The delay of the SIMO ramp signal is presented here as an example; an alternative delay of the MIMO radar ramp signal is also possible. Furthermore, an electrical delay is also possible instead of an optical delay.

[0084] The radar system according to the invention 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. Reference numerals

[0085] C Central processing unit

[0086] TXi, TX2,..., TX n Radar transmitters

[0087] RXi, RX2, RX3,..., RX n Radar receivers

[0088] SG Signal Generation Unit

[0089] SG's SIMO signal generation unit

[0090] SGM MIMO signal generation unit

[0091] D Delay unit

[0092] P control unit

[0093] M Mixing unit

[0094] 20 Sl MO data set

[0095] 21 MIMO data set

[0096] 22 Determining Sub-Array

[0097] 23 Sl MO processing

[0098] 24 Data Merging

[0099] 25 Target list

[0100] 26 MIMO signal processing

[0101] 31 Transmitted MIMO radar ramp signal 32 Received MIMO radar ramp signal 33 Transmitted SIMO radar ramp signal 34 Received SIMO radar ramp signal LO Local oscillator signal

[0102] 700, 800, 801, 900, 901 Light source

[0103] 701, 745, 746, 802, 804, electro-optical modulator

[0104] 848, 849, 902, 904, 947

[0105] 702 SIMO and MIMO signal generation unit 803, 903 MIMO signal generation unit

[0106] 805, 905 SIMO signal generation unit

[0107] 703, 747, 846, 946 optical control unit

[0108] 704, 705, 720, 743, 808, optical detection unit

[0109] 809, 821, 822, 841, 842,

[0110] 907, 921, 922, 941, 942, 722, 740, 810, 823, electric switch

[0111] , 910, 923, 945

[0112] , 811, 911 Analog-to-Digital Converter

[0113] , 812, 912 Control and processing unit , 744 Separation unit

[0114] , 742, 843, 844, 909, electric mixer

[0115] , 944

[0116] Optical switch or splitter, 850 Optical multiplexer

[0117] , 820, 840, 847 Optical Demultiplexer Separation Unit

[0118] optical delay unit

Claims

- 22 - Patent claims 1. Radar system with a central unit (C), several radar transmitters (TXi, TX2,..., TX) n ) and several radar receiver units (RXi, RX2, RX3,..., RX n), wherein the radar system has both a MIMO radar structure and a SIMO radar structure, wherein in the MIMO radar structure multiple radar transmit signals are sent by multiple radar transmitting units and multiple radar receive signals are received by multiple radar receive units, and in the SIMO radar structure one radar transmit signal is sent by one radar transmitting unit and multiple radar receive signals are received by multiple radar receive units, characterized in that the central unit (C) is configured to determine first radar information from the radar receive signals of the SIMO radar structure and to determine second radar information by jointly processing the first radar information with the radar receive signals of the MIMO radar structure.

2. Radar system according to claim 1, wherein a SIMO data set (20) is generated based on the radar echo signals of the radar receiving units which are sensitive to the radar transmitting units of the SIMO radar structure and an MIMO data set (21) is generated based on the radar echo signals of the radar receiving units which are sensitive to the radar transmitting units of the MIMO unit.

3. Radar system according to claim 2, wherein radar target information is determined by signal processing of the SIMO data set (20) and this radar target information is supplied to a MIMO signal processing (26) in addition to the MIMO data set (21).

4. Radar system according to one of the preceding claims, wherein the central unit (C) comprises a common signal generation unit (SG) for generating SIMO and MIMO radar ramp signals.

5. Radar system according to one of the preceding claims, wherein the MIMO radar structure and the SIMO radar structure comprise separate, independent radar transmitting units and at least some of the radar receiving units (RXi, RX2, RX) n ) are shared by the SIMO radar structure and the M1 MO radar structure.

6. Radar system according to one of the preceding claims, wherein several of the radar receiving units used by the SIMO radar structure are arranged at uniform intervals along a line in space.

7. Radar system according to one of the preceding claims, wherein at any one time only one of the radar transmitting units transmits a radar signal.

8. Radar system according to any one of claims 1 to 6, wherein at least one radar transmitter of the SIMO radar structure emits a radar signal at the same time as one of the radar transmitters used by the M1 MO radar structure.

9. Radar system according to one of claims 4 to 8, wherein the SIMO and MIMO radar ramp signals represent signal parts that are shifted in time relative to each other.

10. Radar system according to claim 9, wherein the central unit (C) comprises a signal generation unit (SGs) for generating the SIMO radar ramp signals and a separate signal generation unit (SGM) for generating the MIMO radar ramp signals.

11. Radar system according to claim 9, wherein the central unit (C) comprises a signal generation unit (SG) for generating a radar ramp signal and wherein a part of the generated radar ramp signal is fed to a delay element (D) and wherein one of the SIMO and MIMO radar ramp signals is formed by the time-delayed signal part and the other of the SIMO and MIMO radar ramp signals is formed by the non-delayed signal part.

12. Radar system according to one of claims 4 to 8, wherein the SIMO and MIMO radar ramp signals represent signal parts shifted relative to each other in frequency.

13. Radar system according to claim 12, wherein the central unit (C) comprises a signal generation unit (SGs) for generating the SIMO radar ramp signals and a separate signal generation unit (SGM) for generating the MIMO radar ramp signals.

14. Radar system according to claim 12, wherein the central unit (C) comprises a signal generation unit (SG) for generating a radar ramp signal and wherein a part of the generated radar ramp signal is fed to a mixing unit (M) and wherein one of the SIMO and MIMO radar ramp signals is formed by the frequency-shifted signal part due to the mixing and the other of the SIMO and MIMO radar ramp signals is formed by the non-frequency-shifted signal part.

15. Method for operating a radar system according to any one of claims 1 to 14.

Images