Radar system, and method for operating the radar system

Abstract

The radar system has a global reference oscillator configured to generate a global reference signal, and a number of radar devices linked to the global reference oscillator. At least one of the radar devices has a local reference oscillator configured to generate a local reference signal. At least one of the radar devices has a synchronization device configured to control the local reference oscillator to synchronize it with the global reference oscillator using the global reference signal.

Description

Technical Field

[0001] The present invention relates to a radar system and a method for operating a radar system.

Background Art

[0002] A radar sensor transmits a signal that is reflected by an object in a radar channel. The reflected signal is received and evaluated by the same radar sensor in the monostatic case to detect the distance, speed, and angle of a radar target relative to the radar sensor. In the bistatic case, the reflected radar signal can also be received by a second radar sensor spatially separated.

[0003] The actual distance or angle to a radar target can be calculated by referring to the known distance between the respective radar sensors. If the system is coherent, i.e., if the work should be done with a fixed phase relationship between both radar sensors, the synchronization of the respective transmission signals must be performed. This can be done by physically distributing a common local oscillator (LO) signal.

[0004] When such a kind of LO signal distribution is not made, the transmission signals of the respective radar sensors are not correlated in time or in phase. In the case of signal generation using a variable oscillator and a phase-locked loop (PLL), for example, the start point of the ramp in a frequency-modulated continuous-wave radar (FMCW) is not strictly unique either.

[0005] Thus, timing errors between the frequency ramp and the scanning time of the analog-to-digital converter in the receiver, and uncorrelated phase noise in bistatic measurements limit the performance of the system, for example, with respect to the reach.

[0006] A method for restoring phase relationships from bistatic radar signals by signal processing is known from International Publication No. 2017 / 118621. Phased array radar is known from U.S. Patent Application Publication No. 2014 / 292561. Distributed radar systems are known from U.S. Patent Application Publication No. 2022 / 196826. [Overview of the project] [Means for solving the problem]

[0007] The present invention provides a radar system and a method for operating the radar system having the features of an independent claim.

[0008] Preferred embodiments are the subject of each dependent claim.

[0009] In a first aspect, the present invention relates to a radar system having a global reference oscillator configured to generate a global reference signal, and a number of radar devices linked to the global reference oscillator. At least one of the radar devices has a local reference oscillator configured to generate a local reference signal. At least one of the radar devices has a synchronization device configured to control the local reference oscillator in order to synchronize the local reference oscillator with the global reference oscillator using the global reference signal.

[0010] In a second aspect, the present invention relates to a method for operating a radar system having a number of radar devices, wherein at least one of the radar devices has a local reference oscillator configured to generate a local reference signal. A global reference signal is generated by a global reference oscillator. The local reference oscillator of at least one radar device is synchronized with the global reference oscillator using the global reference signal.

[0011] Advantages of the invention For a cooperative radar system, that is, a network of multiple radar devices, to function, the radar devices must be linked or synchronized with each other.

[0012] To avoid synchronization by deterministic circuits for transmitting clock, trigger, and local oscillator (LO) signals, and to simultaneously achieve good performance despite uncorrelated phase noise, the local reference oscillator is synchronized with a global reference oscillator using a global reference signal.

[0013] Individual radar units are designed to facilitate synchronization of radar units when used in a cooperative radar system, without the need for additional synchronization and LO lines or additional algorithmic LO signal distribution.

[0014] To synchronize radar equipment as simply as possible, the clocks of all local components of the radar equipment that generate or process signals, such as transmitters, receivers, analog-to-digital converters, or digital signal processors, can be derived from a local reference signal. This allows for the synchronization of the local reference signal with a global reference signal.

[0015] Within the framework of this invention, "synchronization" can be understood as tuning with respect to phase and / or amplitude.

[0016] In one embodiment of the radar system, the global reference oscillator is located externally to the radar devices of the radar system. In this embodiment, each radar device may have a local reference oscillator synchronized with the external global reference oscillator. Therefore, there is an advantage that all radar devices may be configured identically.

[0017] In another embodiment of the radar system, the global reference oscillator is the local reference oscillator of one of the radar devices. This particular radar device does not require a synchronization device. All other radar devices may have synchronization devices to synchronize their own local reference oscillators with the global reference oscillator, i.e., the local reference oscillator of the particular radar device. This embodiment has the advantage of not requiring a separate global reference oscillator.

[0018] In another embodiment of the radar system, at least one of the radar devices includes a transceiver and a high-frequency local oscillator. The high-frequency local oscillator generates a high-frequency local oscillator signal using a local reference signal and outputs the high-frequency local oscillator signal to the transceiver and the local device. The transceiver and the local device of the radar system are synchronized by linking the high-frequency local oscillator with the local reference oscillator.

[0019] In another embodiment of the radar system, the high-frequency local oscillator operates using a carrier wave of a constant frequency, i.e., a fixed frequency, for example, by utilizing a phase control loop. In this case, the high-frequency local oscillator signal of the reference oscillator can also be subdivided into temporal segments, each having a different but constant frequency within its temporal segment. This allows for the realization of even smaller, or at least partially coherent, phase noise.

[0020] In another embodiment of the radar system, the transmitting and receiving device has an IQ mixer. A high-frequency local oscillator is configured to output the high-frequency local oscillator signal to the IQ mixer.

[0021] In another embodiment of the radar system, the transmitting and receiving device has a chirp generator for generating a chirp signal, and the chirp generator has an IQ mixer and a digital-to-analog converter or direct digital synthesis (DDS) device. A high-frequency local oscillator outputs the high-frequency local oscillator signal to the IQ mixer. The digital-to-analog converter or DDS device controls the IQ mixer using a local reference signal. For this purpose, the DDS device or digital-to-analog converter has two channels, one for the I path and one for the Q path. This allows the chirp to be modulated to match the HF carrier, including frequency offset and phase offset.

[0022] In another embodiment of the radar system, the high-frequency local oscillator includes a phase control loop device and an IQ mixer. The IQ mixer is located in the feedback path of the phase control loop device. A local reference oscillator outputs a local reference signal to the phase control loop device. The IQ mixer is controlled depending on the local reference signal. To this end, a digital-to-analog converter or DDS device may be provided that uses a reference signal as a clock source to control the IQ mixer. This allows for the application of frequency detuning.

[0023] In embodiments not covered by the radar system patent application, a local reference oscillator generates a comparison time signal. A synchronization device compares the comparison time signal with the reference time signal generated by referencing the global reference signal in order to synchronize the local reference oscillator with the global reference oscillator. The comparison time signal can be derived from the local reference oscillator, for example, by a counter unit or a time-to-digital converter (TDC).

[0024] The local reference oscillator generates a comparison frequency signal. The synchronization device compares the reference frequency signal generated by referring to the global reference signal with the comparison frequency signal in order to synchronize the local reference oscillator with the global reference oscillator. The comparison frequency signal can be obtained, for example, by frequency division.

[0025] By synchronizing the frequency of the local reference signal to a constant frequency by the synchronization device, it is possible to achieve that the phase noise is very small or at least partially coherent. The oscillator is only affected within a narrow range by the synchronization device. This enables the design of a local reference oscillator with high stability and small phase noise. The modulation of the radar signal is generated digitally in a subsequent step.

[0026] Other advantages, components, and specific matters of the present invention will become clear from the following description in which various embodiments are specifically described with reference to the drawings. The drawings show the following.

Brief Description of the Drawings

[0027] [Figure 1] A radar system according to one embodiment of the present invention is shown. [Figure 2] The reception path of the radar system illustrated in FIG. 1 is shown. [Figure 3] A radar system according to another embodiment of the present invention is shown. [Figure 4] A radar system according to another embodiment of the present invention is shown. [Figure 5] A radar system according to another embodiment of the present invention is shown. [Figure 6] A flowchart of a method for operating a radar system according to one embodiment of the present invention is shown.

Modes for Carrying Out the Invention

[0028] In all drawings, the same components or components and devices with the same function are denoted by the same reference numeral. The numbering of the method steps is for illustrative purposes only and does not generally imply a specific chronological order. In particular, multiple method steps can be performed simultaneously.

[0029] Figure 1 shows radar system 1a. Radar system 1a has a global reference oscillator 2 that generates a global reference signal. The global reference signal may include a reference time or a reference frequency.

[0030] A global reference signal is provided to a number of radar devices 3a-1 through 3a-n. However, the present invention is not limited to a specific number of radar devices 3a-1 through 3a-n.

[0031] Each of the radar devices 3a-1 through 3a-n is linked to a global reference oscillator 2 for receiving a global reference signal via its respective synchronization interface 6.

[0032] The control device 5 controls the local reference oscillators 4 of the corresponding radar devices 3a-1 to 3a-n, and plays a role in synchronizing the local reference oscillators 4 with the global reference oscillator 2. In this way, the control device 5 and the synchronization interface 6 constitute a synchronization device.

[0033] The reference oscillator 4 generates a local reference signal. The control device 5 generates a control signal for the local reference oscillator 4 by comparing the local reference signal with a global reference signal.

[0034] The local reference oscillator 4 is thus affected and begins to operate in synchronization with the global reference oscillator 2. In this way, all radar devices 3a-1 through 3a-n can access the global reference oscillator 2, and consequently their local reference signals are synchronized.

[0035] The local reference oscillator 4 can generate a reference signal having a substantially constant frequency, for example, within a predetermined time range.

[0036] In the following description, only one radar device 3a-1 will be described, but the other radar devices 3a-2 through 3a-n may be configured identically or substantially identically.

[0037] The radar system 3a-1 includes a transmitting / receiving device 9a and a high-frequency local oscillator 7a.

[0038] The high-frequency local oscillator 7a has a high-frequency source 8 that generates a high-frequency local oscillator signal using a local reference signal. The high-frequency source 8 may be a high-frequency source of a fixed frequency, or a temporarily fixed frequency (for example, in the case of a stepped signal), for example, 20 GHz.

[0039] The high-frequency local oscillator 7a outputs a high-frequency local oscillator signal to the transmitting and receiving device 9a. Optionally, the radar system 3a-1 may be intended to have a number of transmitting and receiving devices 9a, and the high-frequency local oscillator 7a provides the high-frequency local oscillator signal to these transmitting and receiving devices via the line 16.

[0040] In the following, an example of a transmitting / receiving device 9a will be described. The transmitting / receiving device 9a includes a frequency multiplier 10 to convert a high-frequency local oscillator signal to a desired frequency band, for example, 80 GHz.

[0041] Furthermore, the transmitting / receiving device 9a includes a transmission path 20a and a reception path 19a. The transmission path 20a includes a splitter 11 that divides the converted high-frequency local oscillator signal, and the resulting signals are phase-shifted by 90 degrees from each other. In addition, the transmission path 20a includes an IQ mixer 12. The signal generated by the IQ mixer 12 is amplified by an amplifier 13 and transmitted via an antenna member (not shown).

[0042] In another embodiment, a conventional mixer is used instead of the IQ mixer 12.

[0043] Furthermore, the transmitting / receiving device 9a includes a first digital-to-analog converter 14 and a second digital-to-analog converter 15 that receive a local reference signal provided by the local reference oscillator 4 and use the local reference signal or a signal derived therefrom as a sampling clock to appropriately control the I path or Q path of the IQ mixer 12. Since the local reference oscillator 4 is linked with the global reference oscillator 2, the transmitted signals are also synchronized.

[0044] Figure 2 shows the receiving path 19a of the radar system 1a shown in Figure 1. The receiving path 19a also includes a splitter 21, an IQ mixer 22, and an amplifier 23. Furthermore, the receiving path includes analog-to-digital converters 51 or 52 linked to the I path or the Q path.

[0045] Optionally, the transmitting and receiving device 9a may include other transmitting paths 20a and receiving paths 19a, which may be identical or differently manufactured. The high-frequency local oscillator signal converted by the frequency multiplier 10 is provided to the other transmitting paths 20a and receiving paths 19a via the corresponding lines 17.

[0046] In Figure 1, both the transmission path 20a and the reception path 19a are shown, whereas in the following embodiment, only either the transmission path 20a or the reception path 19a may exist.

[0047] Furthermore, the radar device 3a-1 may also have other digital components 18, such as an analog-to-digital converter, which are provided with a local reference signal generated by the local reference oscillator 4 and utilize the local reference signal or a signal derived therefrom as a clock.

[0048] In the embodiment of radar system 1a shown in Figure 1, the local reference oscillator 4 generates a comparison time signal, for example, by a counter unit or a time-to-digital converter (TDC). The control device 5 of the synchronization devices 5 and 6 compares the generated reference time signal and the comparison time signal with the global reference signal to synchronize the local reference oscillator 4 with the global reference oscillator 2.

[0049] The local reference oscillator 4 generates a comparison frequency signal. The control device 5 of the synchronization devices 5 and 6 compares the generated reference frequency signal with the comparison frequency signal by referencing the global reference signal and synchronizes the local reference oscillator 4 with the global reference oscillator 2.

[0050] In the embodiment of radar system 1a shown in Figure 1, the global reference oscillator 2 is located externally to the radar devices 3a-1 to 3a-n of radar system 1a. However, the global reference oscillator 2 may be intended to be a local reference oscillator 4 of one of the radar devices 3a-1 to 3a-n. In that case, these radar devices 3a-1 to 3a-n do not require synchronization devices 5,6.

[0051] The starting phase is static because the carrier wave has a fixed frequency linked to the global reference oscillator 2 via the local reference oscillator 4. Since modulation is generated by the digital-to-analog converters 14, 15 or the DDS device 31, the starting phase of the modulation can be defined, and this is also static.

[0052] A fixed-frequency HF carrier architecture allows signal generation to be optimized for low phase noise.

[0053] Figure 3 shows another radar system 1b. This radar system 1b differs from the radar system 1a shown in Figures 1 and 2 in that a direct digital synthesis (DDS) device 31 is provided instead of the first digital-to-analog converter 14 and the second digital-to-analog converter 15. The DDS device has two channels for the I path and the Q path. In other respects, radar system 1b corresponds to radar system 1a shown in Figures 1 and 2, so there is no need to repeat the description of the other components here.

[0054] Figure 4 shows another radar system 1c, which is distinguished from radar systems 1a and 1b shown in Figures 1 to 3 by the structure of the transmitting and receiving device 9c.

[0055] Accordingly, the transmitting and receiving device 9c has a chirp generator 41 for generating a chirp signal, which has a splitter 42 that splits the received signal into two signals that are shifted by 90° in phase with respect to each other, as described above.

[0056] Furthermore, the chirp generator 41 includes an IQ mixer 43 and a DDS device 45. The DDS device 45 receives a local reference signal from a local reference oscillator 4 and uses the local reference signal to control the IQ mixer 43.

[0057] Optionally, the chirp generator 41 may also include a high-pass filter or a band-pass filter 44 to filter the signal output from the IQ mixer 43.

[0058] The transmission path 20c includes a modulator 46 and an amplifier 13. The modulator 46 modulates the signal received from the chirp generator 41, and the amplifier 13 amplifies the signal output from the modulator 46 and outputs it to an antenna member (not shown) for the transmission of radar radiation.

[0059] The modulator 46 may be, for example, a digital phase shifter and / or a variable gain amplifier (VGA). The modulators 46 in the transmission path 20c may enable additional relative phase modulation and / or amplitude modulation of each transmission path 20c and may also be linked to a local reference oscillator 4.

[0060] The receiving path 19c may be configured in accordance with the transmitting path 20c. The receiving path 19c may correspond to a conventional receiving path. The receiving path may be selectively constructed as a real receiving path or an IQ receiving path.

[0061] In this embodiment, the chirp generator 41 can be used to modulate the chirp, including the frequency offset, in accordance with the HF carrier wave.

[0062] Figure 5 shows another radar system 1d. This radar system 1d is distinguished from radar systems 1a to 1c shown in Figures 1 to 4 by the structure of the high-frequency local oscillator 7d.

[0063] The high-frequency local oscillator 7d includes a phase control loop device 51 and an IQ mixer 54. The phase control loop device 51 generates an output signal dependent on a local reference signal, which is supplied to the high-frequency source 52 to generate the high-frequency local oscillator signal.

[0064] The IQ mixer 54 is located in the feedback path of the phase control loop device 51. For this purpose, the high-frequency local oscillator signal generated by the high-frequency source 52 is first converted to a desired frequency band by the frequency divider 56, and then split by the splitter 55, resulting in signals that are phase-shifted by 90 degrees. Both of these signals are supplied to the IQ mixer 54. The output signal of the IQ mixer 54 is supplied to the phase control loop device 51.

[0065] The local reference oscillator 4 provides a local reference signal to the digital-to-analog converter or DDS device 53, and the output signal is provided to the IQ mixer 54.

[0066] Frequency detuning can be applied by a digital-to-analog converter or DDS device 53 via an IQ mixer 54 in the feedback path of the phase control loop device 51. Since the digital-to-analog converter or DDS device 53 is also linked to the local reference oscillator 4, these sources are also synchronized with the other components.

[0067] In the radar systems 1a to 1d described above, the respective structures allow for low or (partially) coherent phase noise in the high-frequency local oscillator signal (e.g., by using a fixed-frequency oscillator), and a stable relative phase state between different radar devices can be achieved, especially during measurements, even when frequency jumps occur. This is particularly preferable for bistatic measurements using a distributed radar system.

[0068] The various embodiments shown in the illustrations can also be combined. In particular, the high-frequency local oscillator 7d shown in Figure 5 can also be applied to one of the radar systems 1a to 1c shown in Figures 1 to 4. In this case, the high-frequency local oscillator 7d can replace the ramp generator, which includes a frequency multiplier 10, a splitter 42, an IQ mixer 43, a band-pass filter 44, and a DDS device 45.

[0069] Figure 6 shows a flowchart illustrating how to operate a radar system having multiple radar devices. In particular, this radar system may be one of the radar systems 1a to 1d described above. At least one of the radar devices has a local reference oscillator configured to generate a local reference signal.

[0070] In the first step S1, a global reference signal is generated by a global reference oscillator. The global reference oscillator may be located externally to the radar equipment of the radar system. The global reference oscillator may also be a local reference oscillator of one of the radar equipment.

[0071] In the second step S2, the local reference oscillator of at least one radar device is synchronized with the global reference oscillator using a global reference signal.

[0072] In this case, at least one of the radar devices may have a transmitting / receiving device and a high-frequency local oscillator. The high-frequency local oscillator generates a high-frequency local oscillator signal using a local reference signal and outputs the high-frequency local oscillator signal to the transmitting / receiving device. In this case, the high-frequency local oscillator may be an oscillator that operates at a constant frequency (at least regionally).

[0073] Furthermore, the transmitting and receiving devices may have an IQ mixer linked to a high-frequency local oscillator for each transmit channel / receive channel.

[0074] Furthermore, the transmitting and receiving devices may be intended to have a chirp generator for generating a chirp signal, and the chirp generator may have an IQ mixer and a DDS device. A high-frequency local oscillator outputs a high-frequency local oscillator signal to the IQ mixer. The DDS device controls the IQ mixer using a local reference signal.

[0075] A high-frequency local oscillator may also have a phase control loop device and an IQ mixer. The IQ mixer is placed in the feedback path of the phase control loop device. A local reference oscillator outputs a local reference signal to the phase control loop device and to a digital-to-analog converter or DDS device, which control the IQ mixer.

[0076] A local reference oscillator can generate a comparison time signal or a comparison frequency signal. A synchronization device compares the comparison time signal or comparison frequency signal with a reference time signal or reference frequency signal generated using a global reference signal to synchronize the local reference oscillator with the global reference oscillator.

Claims

1. In the radar system (1a to 1d), A global reference oscillator (2) configured to generate a global reference signal, It has a number of radar devices (3a-1 to 3a-n; 3b-1 to 3b-n; 3c-1 to 3c-n; 3d-1 to 3d-n) linked to the global reference oscillator (2), At least one of the radar devices (3a-1 to 3a-n; 3b-1 to 3b-n; 3c-1 to 3c-n; 3d-1 to 3d-n) has a local reference oscillator (4) configured to generate a local reference signal, A radar system (1a to 1d) wherein at least one of the radar devices (3a-1 to 3a-n; 3b-1 to 3b-n; 3c-1 to 3c-n; 3d-1 to 3d-n) has synchronization devices (5, 6) configured to control the local reference oscillator (4) in order to synchronize the local reference oscillator (4) with the global reference oscillator (2) using the global reference signal.

2. At least one of the radar devices (3a-1 to 3a-n; 3b-1 to 3b-n; 3c-1 to 3c-n; 3d-1 to 3d-n) has a transmitting / receiving device (9a to 9c) and a high-frequency local oscillator (7a; 7d), The radar system (1a to 1d) according to claim 1, wherein the high-frequency local oscillators (7a; 7d) are configured to generate high-frequency local oscillator signals using the local reference signals and output them to the transmitting and receiving devices (9a to 9c).

3. The radar system (1a to 1d) according to claim 2, wherein the high-frequency local oscillator (7a; 7d) is an oscillator that operates at least locally at a constant frequency.

4. The radar system (1a; 1b) according to claim 2 or 3, wherein the transmitting and receiving device (9a; 9b) has an IQ mixer (12), and the high-frequency local oscillator (7a; 7d) is configured to output a high-frequency local oscillator signal to the IQ mixer (12).

5. The transmitting / receiving device (9c) has a chirp generator (41) for generating a chirp signal, and the chirp generator (41) has an IQ mixer (43) and a digital-to-analog converter or direct digital synthesis DDS device (45). The high-frequency local oscillators (7a; 7d) are configured to output the high-frequency local oscillator signals to the IQ mixer (43), The radar system (1c) according to claim 2 or 3, wherein the digital-to-analog converter or the DDS device (45) is configured to control the IQ mixer (43) using the local reference signal.

6. The aforementioned high-frequency local oscillator (7d) includes a phase control loop device (51) and an IQ mixer (54). The transmitting / receiving device (9c) has a digital-to-analog converter or a direct digital synthesis (DDS) device (45), The IQ mixer (54) is placed in the feedback path of the phase control loop device (51). The radar system (1d) according to any one of the prior claims, wherein the local reference oscillator (4) is configured to output a local reference signal to the phase control loop device (51) and the digital-to-analog converter or the DDS device (45), and the output signal of the digital-to-analog converter or the DDS device (45) controls the IQ mixer (54).

7. The local reference oscillator (4) is configured to generate a comparison time signal, The radar system (1a to 1d) according to any one of the prior claims, wherein the synchronization devices (5, 6) are configured to synchronize the local reference oscillator (4) with the global reference oscillator (2) by comparing the comparison time signal with a reference time signal generated with reference to the global reference signal.

8. The aforementioned local reference oscillator (4) is configured to generate a comparison frequency signal, The radar system (1a to 1d) according to any one of the prior claims, wherein the synchronization devices (5, 6) are configured to synchronize the local reference oscillator (4) with the global reference oscillator (2) by comparing the comparison frequency signal with a reference frequency signal generated with reference to the global reference signal.

9. The radar system according to any one of the prior claims (1a to 1d), wherein the local reference oscillator (4) is an oscillator that operates at least locally at a constant frequency.

10. A method for operating a radar system (1a to 1d) having a number of radar devices (3a-1 to 3a-n; 3b-1 to 3b-n; 3c-1 to 3c-n; 3d-1 to 3d-n), wherein at least one of the radar devices (3a-1 to 3a-n; 3b-1 to 3b-n; 3c-1 to 3c-n; 3d-1 to 3d-n) has a local reference oscillator (4) configured to generate a local reference signal, and in each of the following steps, A global reference signal is generated (S1) by a global reference oscillator (2), and, Using the global reference signal, synchronize (S2) the local reference oscillator (4) of at least one of the radar devices (3a-1 to 3a-n; 3b-1 to 3b-n; 3c-1 to 3c-n; 3d-1 to 3d-n) with the global reference oscillator (2). Methods that include...

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