Frequency synchronization method of multi-radar system and multi-radar system

Abstract

The invention provides a frequency synchronization method for a multi-radar system, and the method comprises the steps: a first radar control module controls a first radio frequency front-end module to transmit a radio frequency signal, and provides a frequency point of the radio frequency signal to a second radar control module; a second radar control module controls a second radio frequency front-end module to receive the radio frequency signal, and sets the actual set frequency of the local radio frequency signal according to the frequency point; the second radio frequency front-end module receives the radio frequency signal, calculates a frequency deviation according to a radio frequency point of the radio frequency signal and an actual set frequency, and notifies the second radar control module; the second radar control module generates a fine tuning control signal according to the frequency deviation to control the frequency calibration module, generates a frequency calibration signal and calibrates the actual set frequency of the local radio frequency signal; frequency fine tuning control signals corresponding to different frequency points at different moments are obtained and stored; the frequency calibration module generates a frequency calibration signal according to the frequency fine tuning control signal, and automatically corrects the actual set frequency of the local radio frequency signal.

Description

Technical Field

[0001] The present invention relates to the field of automotive radars, and in particular to a frequency synchronization method for a multi-radar system and a multi-radar system. Background Art

[0002] In existing imaging cascaded radar systems or coherent radars, multiple radar units are closely arranged, basically on the same PCB board. At the same time, all radar units need to use the same radio frequency / LO local oscillator signal, and this local oscillator signal attenuates rapidly with increasing distance, generally limited within 10 cm - 20 cm; this results in the close layout of radar units, making it impossible to adapt to the currently widely used distributed radar systems, and the equivalent aperture of the radar is small, the angle positioning accuracy is limited, and the system is complex.

[0003] Therefore, providing a new type of coherent radar system and frequency synchronization method to expand the freedom of the distance between radar units in the physical space, facilitate antenna layout, thereby increasing the equivalent aperture of the entire radar system and improving the angle positioning accuracy has become a technical problem that needs to be urgently solved by those skilled in the art. Summary of the Invention

[0004] In order to overcome the above technical defects, the purpose of the present invention is to provide a frequency synchronization method for a multi-radar system. By adding a frequency calibration module and adopting a new frequency calibration method, the frequency of the local radio frequency signal in the second radar is calibrated using the frequency of the radio frequency signal transmitted by the first radar, achieving precise frequency point calibration and automatic correction functions between multiple radars. It gets rid of the limitation of the physical space distance between different radars, facilitates the antenna layout of the distributed radar system, and at the same time improves the equivalent aperture and angle positioning accuracy of the entire radar system.

[0005] The present invention discloses a frequency synchronization method for a multi-radar system, a frequency synchronization method for a multi-radar system for performing frequency synchronization on a multi-radar system, the multi-radar system including: a first radar and a second radar; the first radar including a first radar control module and a first radio frequency front-end module; the second radar including a second radar control module and a second radio frequency front-end module; at least the second radar further including: a frequency calibration module; the method including:

[0006] The first radar control module controls the first radio frequency front-end module to send a radio frequency signal, and at the same time provides the frequency point of the radio frequency signal to the second radar control module;

[0007] The second radar control module controls the second radio frequency front-end module to receive the radio frequency signal, and at the same time sets the actual set frequency of the local radio frequency signal according to the frequency point;

[0008] The second RF front-end module receives the RF signal, calculates the frequency deviation based on the RF point and the actual set frequency of the RF signal, and notifies the second radar control module;

[0009] The second radar control module generates a frequency fine-tuning control signal indicating the frequency fine-tuning amplitude based on the frequency deviation to control the frequency calibration module, so as to generate a frequency calibration signal to calibrate the actual set frequency of the local RF signal;

[0010] Repeat the above steps to obtain frequency fine-tuning control signals indicating the corresponding frequency fine-tuning amplitudes corresponding to different frequency points at different times, and store them;

[0011] When the radar detection is officially carried out, the frequency calibration module generates a frequency calibration signal based on the frequency point and the corresponding frequency fine-tuning control signal to automatically correct the actual set frequency of the local RF signal.

[0012] Optionally, the step that the frequency calibration module generates a frequency calibration signal based on the frequency point and the corresponding frequency fine-tuning control signal to automatically correct the actual set frequency of the local RF signal specifically includes:

[0013] The frequency calibration module fits to form a frequency calibration curve in which the frequency calibration amplitude changes with time based on different frequency points at different times and the corresponding frequency fine-tuning control signals;

[0014] The frequency calibration module generates corresponding frequency calibration signals based on the frequency fine-tuning control signals corresponding to different frequency points at different times in the frequency calibration curve to sequentially and automatically correct the actual set frequencies of the corresponding local frequency signals.

[0015] Optionally, the step that the second radar control module generates a frequency fine-tuning control signal indicating the frequency fine-tuning amplitude based on the frequency deviation to control the frequency calibration module to generate a frequency calibration signal to calibrate the actual set frequency of the local RF signal further includes:

[0016] The second radar control module determines whether the frequency deviation exceeds the error threshold range;

[0017] If the judgment result is yes, then generate the frequency fine-tuning control signal based on the frequency deviation, control the frequency calibration module to generate the frequency calibration signal, and calibrate the actual set frequency of the local RF signal;

[0018] Until the judgment result is no, then this calibration is completed, and notify the first radar control module to start the calibration of the next frequency point.

[0019] Optionally, a radar communication line is connected between the first radar control module and the second radar control module, and they share a crystal oscillator;

[0020] Before transmitting the radio frequency signal, the first radar control module agrees on the same signal transmission and reception time with the second radar control module through the radar communication line;

[0021] The first radar control module provides the frequency point to the second radar control module through the radar communication line.

[0022] Optionally, the multi-radar system further includes a central control platform;

[0023] The central control platform controls the clock synchronization of the first radar and the second radar;

[0024] Before transmitting the radio frequency signal, the central control platform agrees that the first radar and the second radar transmit and receive signals at the same time;

[0025] The central control platform notifies the first radar control module to control the first RF front-end module to send a RF signal; at the same time, obtains the frequency point of the RF signal and notifies the second radar control module.

[0026] The present invention also discloses a multi-radar system, comprising: a first radar and a second radar; the first radar comprises a first radar control module and a first radio frequency front-end module; the second radar comprises a second radar control module and a second radio frequency front-end module;

[0027] At least the second radar further comprises: a frequency calibration module;

[0028] The first radar control module is used to control the first RF front-end module to transmit a radio frequency signal and provide a frequency point of the radio frequency signal to the second radar control module;

[0029] The second radar control module is used to control the second RF front-end module to receive the RF signal and set the actual set frequency of the local RF signal according to the frequency point;

[0030] The second RF front-end module is configured to receive the RF signal, calculate a frequency deviation based on the RF point of the RF signal and the actual set frequency, and notify the second radar control module;

[0031] The second radar control module is configured to generate a frequency fine-tuning control signal indicating a frequency fine-tuning amplitude according to the frequency deviation to control the frequency calibration module to generate a frequency calibration signal to calibrate the actual set frequency of the local radio frequency signal;

[0032] The frequency calibration module can also be used to obtain different frequency points and corresponding frequency fine-tuning control signals indicating the corresponding frequency fine-tuning amplitudes at different times after repeating the above steps, and store them;

[0033] When officially performing radar detection, the frequency calibration module is used to generate corresponding frequency calibration signals according to the stored different frequency points and corresponding frequency fine-tuning control signals at different times, so as to automatically correct the actual set frequency of the local radio frequency signal.

[0034] Optionally, the frequency calibration module is used to fit a frequency calibration curve in which the frequency calibration amplitude changes with time according to different frequency points and corresponding frequency fine-tuning control signals at different times;

[0035] And it is used to generate corresponding frequency calibration signals according to the frequency fine-tuning control signals corresponding to different frequency points at different times in the frequency calibration curve, so as to automatically correct the actual set frequency of the local frequency signal in turn.

[0036] Optionally, the second radar control module determines whether the frequency deviation exceeds the error threshold range;

[0037] If the judgment result is yes, the frequency fine-tuning control signal is generated according to the frequency deviation, and the frequency calibration module is controlled to generate the frequency calibration signal to calibrate the actual set frequency of the local radio frequency signal;

[0038] Until the judgment result is no, this calibration is completed, and the first radar control module is notified to start the next frequency point calibration.

[0039] Optionally, the frequency calibration module generates a frequency calibration signal indicating the electrical parameter deviation according to the frequency fine-tuning control signal indicating the frequency fine-tuning amplitude, and calibrates the frequency of the local frequency signal; the electrical parameter deviation includes a capacitance deviation or a voltage deviation generated according to the frequency fine-tuning amplitude.

[0040] Optionally, the second radio frequency front end includes a local radio frequency source for generating a local radio frequency signal.

[0041] After adopting the above technical solution, compared with the prior art, it has the following beneficial effects:

[0042] 1. A frequency calibration module is added inside the second radar to be calibrated, and a new frequency calibration method is adopted. The local radio frequency in the second radar is calibrated by the frequency of the radio frequency signal transmitted by the first radar, realizing accurate frequency point calibration and automatic correction functions between multiple radars.

[0043] 2. The frequency calibration module can fit a frequency calibration curve showing how the frequency calibration amplitude changes over time based on the frequency fine-tuning amplitudes corresponding to a finite number of frequency points, and perform automatic calibration based on the frequency calibration curve, thereby improving the calibration accuracy.

[0044] 3. It breaks away from the limitation on the physical space distance of different radars imposed by the configuration of the same radio frequency source / LO local oscillator signal. The spacing between radars can be freely increased, facilitating the antenna layout of the distributed radar system. At the same time, it also improves the equivalent aperture and angle positioning accuracy of the entire radar system.

[0045] 4. Even between different radars, unified control and time synchronization do not need to be achieved by clk and the control line (SPI) clk; the wiring harness connection between multiple radars is simplified, facilitating the expansion of the number of radars; it is more convenient for application in the distributed radar system. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is the structural block diagram of a multi-radar system according to an embodiment of the present invention Figure 1 ;

[0047] Figure 2 is the structural block diagram of a multi-radar system according to an embodiment of the present invention Figure 2 ;

[0048] Figure 3 is the internal structure and frequency calibration process block diagram of the second radio frequency front end according to an embodiment of the present invention;

[0049] Figure 4 is the flowchart of a frequency synchronization method for a multi-radar system according to an embodiment of the present invention;

[0050] Figure 5 is the schematic diagram of the time-frequency calibration amplitude fitting process by the frequency calibration module according to an embodiment of the present invention;

[0051] REFERENCE NUMERALS:

[0052] 1 - Central control platform;

[0053] 2 - First radar;

[0054] 21 - First transceiver antenna module;

[0055] 22 - First radio frequency front end module; [[ID=4…]]

[0056] 23 - First radar control module;

[0057] 231 - Crystal oscillator;

[0058] 24 - Frequency calibration module;

[0059] 3 - Second radar;

[0060] 31 - Second transceiver antenna module;

[0061] 32 - Second radio frequency front - end module;

[0062] 321 - Local radio frequency source;

[0063] 322 - Low - noise amplifier circuit;

[0064] 323 - Mixer;

[0065] 324 - Intermediate - frequency filter circuit;

[0066] 325 - ADC sampling unit;

[0067] 326 - Digital front - end unit;

[0068] 33 - Second radar control module;

[0069] 34 - Frequency calibration module;

[0070] 4 - Ethernet or serdes communication module. Detailed implementation mode

[0071] The advantages of the present invention will be further elaborated below in conjunction with the accompanying drawings and specific embodiments.

[0072] Here, the exemplary embodiments will be described in detail, and the examples are shown in the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0073] The terms used in the present disclosure are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure. The singular forms "a", "the", and "said" used in the present disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0074] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "inside", "outside", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0075] In the description of the present invention, unless otherwise specified and defined, it should be noted that the terms "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the communication inside two components. It can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0076] In the following description, the use of suffixes such as "module", "component", or "unit" for representing components is only for the convenience of the description of the present invention, and it has no specific meaning by itself. Therefore, "module" and "component" can be used interchangeably.

[0077] Due to chip differences, there is a certain error between the frequencies of the RF signals emitted by different radars after each power-on (i.e., for example, from the actual set frequency of the radar and the frequency points of the main radar). Therefore, a multi-radar system capable of frequency calibration is set up as follows for subsequent signal fusion.

[0078] The present invention also provides a multi-radar system. Refer to Figure 1 or Figure 2 , which respectively show multi-radar systems in different embodiments in accordance with the present invention.

[0079] The multi-radar system shown includes: a first radar 2 and a second radar 3. The numbers of the first radar 2 and the second radar 3 are not limited and can be any number, one or more than two. The first radar 2 includes a first transceiver antenna module 21, a first radar control module 23, and a first RF front-end module 22. The second radar 3 includes a second transceiver antenna module 31, a second radar control module 33, and a second RF front-end module 32. At least the second radar 3 further includes: a frequency calibration module 34. Of course, frequency calibration modules 24, 34 can be provided in both the first radar 2 and the second radar 3. In a preferred example, the first radar 2 is the main radar and the second radar 3 is the slave radar. This multi-radar system is used to calibrate the frequency of the local frequency signal of the slave radar so that it is consistent with the frequency of the RF signal emitted by the main radar; at this time, the frequency calibration module 34 is at least provided in the slave radar. In other examples, it can also be that the first radar 2 is the slave radar and the second radar 3 is the main radar, and the system is used to calibrate the frequency of the main radar to be consistent with that of the slave radar; at this time, the frequency calibration module 24 is at least provided in the main radar, and the RF points in the slave radar are used to calibrate the frequency of the main radar. When frequency calibration modules 24, 34 are provided in both the first radar 2 and the second radar 3, that is: frequency calibration modules 34 are provided in both the main radar and the slave radar. At this time, the system can simultaneously achieve the mutual calibration function between the main radar and the slave radar.

[0080] The first radar control module 23 is configured to control the first RF front-end module 22 to transmit an RF signal, and at the same time provide the frequency point of the RF signal to the second radar control module 33. The first RF front-end module 22 transmits the RF signal through the first transceiver antenna module 21.

[0081] The second radar control module 33 is configured to control the second RF front-end module 32 to receive the RF signal, and set the actual set frequency of the local RF signal in the second RF front-end according to the frequency point.

[0082] The second RF front-end module 32 is configured to receive the RF signal, calculate the frequency deviation according to the RF point and the actual set frequency of the RF signal, and notify the second radar control module 33. The second RF front-end receives the RF signal through the second transceiver antenna module 31. Specifically, the second RF front-end module 32 includes a local RF source 321 for generating a local RF signal.

[0083] The second radar control module 33 is further configured to generate a frequency fine-tuning control signal indicating the frequency fine-tuning amplitude according to the frequency deviation to control the frequency calibration module 34 to generate a frequency calibration signal to calibrate the actual set frequency of the local RF signal, so that the transmission frequencies of the first radar 2 and the second radar 3 are kept consistent for subsequent radar signal fusion. In a specific example, the frequency calibration module 34 is configured to generate a frequency calibration signal indicating the electrical parameter deviation according to the frequency fine-tuning control signal indicating the frequency fine-tuning amplitude, and calibrate the frequency of the local frequency signal; the electrical parameter deviation includes a capacitance deviation or a voltage deviation generated according to the frequency fine-tuning amplitude.

[0084] The present invention realizes the frequency calibration process by setting a frequency calibration module 34 in the radar.

[0085] The frequency calibration module 34 is generally a high-precision voltage-controlled frequency module for adjusting the oscillation frequency. Common methods include, for example, the adjustable capacitance method and the adjustable voltage method. The principle of the adjustable capacitance method is: when the frequency calibration module 34 receives a positive frequency deviation or a negative frequency deviation, such as +0.000010 GHz, according to this frequency deviation, it can be equivalent to a capacitance deviation, and the adjustable capacitance is finely adjusted to correct the frequency; while the adjustable voltage method can be equivalent to a voltage change according to this frequency deviation, and the voltage is finely adjusted to correct the frequency.

[0086] The frequency calibration module 34 can also be configured to obtain different frequency points and corresponding frequency fine-tuning control signals indicating the corresponding frequency fine-tuning amplitudes at different times after repeating the above steps, and store them.

[0087] When the radar detection is officially carried out, the frequency calibration module 34 is used to generate corresponding frequency calibration signals according to different frequency points and corresponding frequency fine-tuning control signals at different times stored, so as to automatically correct the actual set frequency of the local radio frequency signal. Since the frequency calibration module 34 can generate frequency calibration signals automatically according to the frequency fine-tuning control signals corresponding to the frequency points at different times stored, that is, according to the frequency fine-tuning amplitude that should be corrected at the frequency points at different times, and automatically correct the actual set frequency of the local radio frequency signal. The present invention precisely utilizes the frequency calibration module 34 and the limited number of frequency point calibrations in the early stage to obtain the frequency deviation between the master and slave radars, so as to achieve automatic calibration in the subsequent calibration process and make up for the problem of asynchronous frequencies of different radars caused by chip differences.

[0088] The multi-radar system provided by the present invention adopts a non-coupled multi-radar system architecture and system. Between multiple radar units, it is not necessary to use the same radio frequency source / LO local oscillator signal. Instead, a frequency calibration module 34 is added inside the second radar 3 to be calibrated, and a new frequency calibration method is adopted. By calibrating the local radio frequency in the second radar 3 through the frequency of the radio frequency signal transmitted by the first radar 2, precise frequency synchronization and automatic calibration functions can be achieved between multiple radars; thus, the performance effect of the multi-radar system can be achieved; at the same time, since it is not necessary to use the same radar local oscillator / LO signal, the configuration of the same radio frequency source / LO local oscillator signal is freed from the limitation on the physical space distance of different radars. The distance between radars can be freely increased, which is convenient for the antenna layout of the distributed radar system, and at the same time, the equivalent aperture and angle positioning accuracy of the entire radar system are also improved.

[0089] In a further solution of the present invention, during the process that the second radar control module 33 generates a frequency fine-tuning control signal indicating the frequency fine-tuning amplitude according to the frequency deviation to control the frequency calibration module 34 to generate a frequency calibration signal to calibrate the actual set frequency of the local radio frequency signal, the second radar control module 33 is further used to judge whether the frequency deviation exceeds the error threshold range; if the judgment result is yes, then generate the frequency fine-tuning control signal according to the frequency deviation, control the frequency calibration module 34 to generate the frequency calibration signal, and calibrate the actual set frequency of the local radio frequency signal; repeat the above steps until the judgment result is no, then this calibration is completed (that is, the calibration of this frequency point is completed), and notify the first radar control module 23 to start the calibration of the next frequency point. Otherwise, if it does not exceed the error threshold range, no calibration is required.

[0090] In a preferred embodiment of the present invention, the frequency calibration module 34 can also be used to fit a frequency calibration curve showing the variation of the frequency calibration amplitude over time based on the plurality of frequency fine-tuning control signals for different frequency points at different times; and before the radar performs actual detection, at different times, it is used to generate corresponding frequency calibration signals based on the frequency calibration curve to automatically correct the actual set frequencies of the local frequency signals in sequence, thereby improving the calibration accuracy.

[0091] Figure 3 Fig. shows the internal structure of the second RF front-end and the block diagram of the frequency calibration process according to an embodiment of the present invention.

[0092] Refer to Figure 3 , the second RF front-end module 32 specifically includes a low-noise amplifier circuit 322, a mixer 323, an intermediate-frequency filter circuit 324, an ADC sampling unit 325, a digital front-end unit 326, and the local RF source 321.

[0093] After the second transceiver antenna module 31 receives the RF signal transmitted by the first radar 2, it inputs the signal to the low-noise amplifier circuit 322 for low-noise amplification processing to amplify the signal. At the same time, the local RF signal of the local RF source 321 of the second radar 3 itself is also set to the same frequency as the RF signal transmitted by the first radar 2 (i.e., the same frequency as the RF point), but the frequency point is slightly different from the frequency of the set local RF signal. These two signals with different frequencies enter the mixer 323 for mixing, generating an intermediate-frequency frequency deviation. This frequency deviation is filtered by the intermediate-frequency filter circuit 324 and then subjected to ADC sampling (for example, using a 12-bit ADC with a resolution of 2 to the power of 12). Finally, after passing through the digital front-end unit 326, a digital signal indicating the frequency deviation is output. This frequency deviation is notified to the second radar control module 33. The second radar control module 33 also determines whether the frequency deviation exceeds the error threshold range; if the determination result is yes, it generates the frequency fine-tuning control signal based on the frequency deviation, controls the frequency calibration module 34 to generate the frequency calibration signal, and calibrates the actual set frequency of the local RF signal; (otherwise, no calibration is required) Repeat the above steps until the determination result is no, then this calibration is completed (i.e., the calibration of this frequency point is completed), and the first radar control module 23 is notified to start the calibration of the next frequency point. After repeating the above steps, the frequency calibration module 34 fits a frequency calibration curve showing the variation of the frequency calibration amplitude over time based on the frequency fine-tuning control signals corresponding to different frequency points at different times; and before the radar performs actual detection, it is used to generate corresponding frequency calibration signals based on the frequency fine-tuning control signals corresponding to the frequency points at different times in the frequency calibration curve to automatically correct the actual set frequencies of the corresponding local frequency signals in sequence.

[0094] Continue to refer to Figure 1 or Figure 2 Optionally, the multi-radar system further includes a central control platform 1, which communicates with the first radar control module 23 and the second radar control module 33 through Ethernet or a Serdes communication module.

[0095] The multi-radar system of the present invention can be designed in two different architectures. In one embodiment shown in the present invention Figure 1 A radar communication line is connected between the first radar control module 23 and the second radar control module 33, and a crystal oscillator 231 (clock source) is shared. Before transmitting the RF signal, the first radar control module 23 agrees on the same signal transceiver time with the second radar control module 33 through the radar communication line. The first radar control module 23 provides the frequency point to the second radar control module 33 through the radar communication line. The second radar control module 33 notifies the first radar control module 23 to perform the next frequency point calibration through the radar communication line. In a specific example, the clock source is generally a 40MHz or 50MHz crystal oscillator 231, and the crystal oscillator 231 is arranged in the first radar control module 23; the radar communication line can specifically be SPI or other similar digital interfaces (such as GPIO or UART interfaces).

[0096] In the present invention Figure 2 In another more preferred embodiment shown in the present invention, the multi-radar system further includes a central control platform; the central control platform 1 controls the clock synchronization of the first radar 2 and the second radar 3. Before transmitting the RF signal, the central control platform 1 agrees that the first radar 2 and the second radar 3 perform signal transceiver at the same time. The central control platform 1 notifies the first radar control module 23 to control the first RF front-end module 22 to transmit the RF signal; at the same time, it obtains the frequency point of the RF signal and notifies the second radar control module 33. In this embodiment, there is no need to transmit and control clk between the first radar 2 and the second radar 3 through clk and a control line (SPI). Instead, the central control platform 1 directly communicates with the intermediate control unit using Ethernet or a serdes communication module 4 to achieve unified control; there is no need to set a CLK and a control line harness SPI between the main radar control module and the slave radar control module, which simplifies the harness connection between multiple radars, is applicable to multiple slave radar systems, and is convenient for expanding the number of radars; it is convenient for application in a distributed radar system.

[0097] Figure 4 Shows a schematic flow diagram of a frequency synchronization method for a multi-radar system according to the present invention. Refer to Figure 4, the present invention provides a frequency synchronization method for a multi-radar system, which is used to synchronize the radio frequency signals transmitted by different radars in the multi-radar system. The method includes steps S1 - S6:

[0098] S1: The first radar control module controls the first radio frequency front-end module to send a radio frequency signal, and at the same time provides the frequency point of the radio frequency signal to the second radar control module.

[0099] S2: The second radar control module controls the second radio frequency front-end module to receive the radio frequency signal, and at the same time sets the actual set frequency of the local radio frequency signal according to the frequency point.

[0100] S3: The second radio frequency front-end module receives the radio frequency signal, calculates the frequency deviation according to the radio frequency point and the actual set frequency of the radio frequency signal, and notifies the second radar control module.

[0101] S4: The second radar control module generates a frequency fine-tuning control signal indicating the frequency fine-tuning amplitude according to the frequency deviation to control the frequency calibration module, so as to generate a frequency calibration signal to calibrate the actual set frequency of the local radio frequency signal.

[0102] S5: Repeat the above steps. The frequency calibration module obtains different frequency points at different times and the corresponding frequency fine-tuning control signals indicating the corresponding frequency fine-tuning amplitudes, and stores them.

[0103] S6: When officially performing radar detection, the frequency calibration module generates corresponding frequency calibration signals according to the different frequency points and the corresponding frequency fine-tuning control signals stored at different times, so as to automatically correct the actual set frequency of the local radio frequency signal.

[0104] In order to avoid the frequency error of the radio frequency signals between different radars when the radars are restarted due to differences in the chips in different radars, the present invention provides a frequency synchronization method for a non-coupled coherent distributed radar. A frequency calibration module is added to the first radar and the second radar, and a frequency calibration method based on the frequency calibration module is proposed. After each restart of the vehicle or after a certain period of time, the frequencies of the first radar unit and the second radar unit are calibrated. On the one hand, multiple radars do not need to use the same radio frequency source / LO local oscillator signal, and accurate frequency synchronization can be achieved, thus achieving the performance effect of the multi-radar system. On the other hand, since the same radar local oscillator / LO signal does not need to be used, the distance between the radars can be increased in the physical space, which is convenient for antenna layout, more suitable for distributed radar systems, and further improves the equivalent aperture of the entire radar system and enhances the angle positioning accuracy.

[0105] In a further preferred embodiment of the present invention, step S6 specifically includes steps S61 - S62:

[0106] S61: The frequency calibration module fits a frequency calibration curve of the frequency calibration amplitude varying with time based on different frequency points and corresponding frequency fine-tuning control signals at different times.

[0107] S62: The frequency calibration module generates corresponding frequency calibration signals based on the frequency fine-tuning control signals corresponding to different frequency points at different times in the frequency calibration curve, so as to automatically correct the actual set frequency of the local frequency signal in sequence.

[0108] In the technical solution provided by the present invention, the frequency calibration module can fit a frequency calibration curve of the frequency calibration amplitude varying with time based on the several frequency fine-tuning control signals at different times; and before the radar actually conducts detection, corresponding frequency calibration signals are generated based on the frequency calibration curve, and the frequency calibration amplitude between the frequency fine-tuning amplitudes corresponding to a finite number of frequency test points (calibrating dozens of frequency points) of the frequency calibration module is accurately fitted, so as to realize the automatic correction of the actual set frequency of the local frequency signal set at different times.

[0109] Taking the first radar as the master radar and the second radar as the slave radar (meanwhile, the master and slave radars are connected by an SPI communication line, as Figure 1 shown) as an example, a frequency synchronization method for a multi-radar system of the present invention will be described in detail:

[0110] Logically, it is necessary to perform calibration every once in a while or every time the vehicle starts or the radar is powered on. Since the startup of the radar device is unstable, calibration is required every time it starts to ensure accuracy.

[0111] (1). Before the formal calibration starts, the frequency points of the master radar during the waveform formation period are notified to the slave radar, and the slave radar uses the same waveform formation function to form its own eigen for demodulation, so that the slave radar knows in advance the frequency points of the RF signals that will be jointly transmitted subsequently, but does not affect the subsequent sequential reception of the known frequency points that need to be calibrated transmitted by the master radar.

[0112] (2) Before the main radar transmits the RF signal, the main radar control module and the slave radar control module agree on the same signal transmission and reception time. Specifically, the main radar control module in the main radar and the slave radar control module in the slave radar share a CLK clock control unit (crystal oscillator), so the time scales of the main radar control module and the slave radar control module are the same. Before calibration, the main radar control module notifies the slave radar control module through the SPI line to turn on RF reception at the same time interval or moment, and the main radar control module will also turn on RF transmission at the same time interval or moment, so as to ensure that the main radar control module and the slave radar control module perform signal transmission and reception simultaneously at the agreed same signal transmission and reception time.

[0113] (3) Formally start frequency calibration.

[0114] Execute step S1: The main radar control module controls the main RF front-end module to transmit an RF signal, and at the same time provides the frequency point of the RF signal to the slave radar control module.

[0115] Execute step S2: The slave radar control module controls the slave RF front-end module to receive the RF signal, and at the same time sets the actual set frequency of the local RF signal emitted by the local RF source according to the frequency point.

[0116] Execute step S3: The slave RF front-end module receives the RF signal, calculates the frequency deviation according to the RF point and the actual set frequency of the RF signal, and notifies the slave radar control module.

[0117] On Figure 1 the basis of combining with Figure 3, the specific processes of steps S1 - S3 are illustrated by way of example, that is: the master radar transmits a radio frequency signal with a fixed frequency, such as an electromagnetic wave with a frequency of 77.2456 GHz, and at the same time notifies the slave radar control module of this frequency point through SPI. After receiving the frequency point, the slave radar control module controls the receiving function of the slave radar RF front - end module to be turned on and sets the receiving frequency to the same frequency, such as 77.2456 GHz. After the transceiver antenna module receives the radio frequency signal transmitted by the master radar, the frequency will be slightly different. The actual frequency is 77.245605 GHz, and it is input to the low - noise amplifier circuit for low - noise amplification processing to amplify the signal. The local radio frequency signal of the local radio frequency source of the slave radar itself is also set to the same frequency as the radio frequency signal transmitted by the master radar, that is, the same frequency as the said radio frequency point, that is, also set to 77.2456 GHz, but the frequency will be slightly different, actually 77.245615 GHz. The signals with these two different frequencies (77.2456 GHz and 77.245615 GHz) enter the mixer for mixing, and an intermediate - frequency frequency deviation will be generated, such as 0.000010 GHz. This frequency deviation is filtered through the intermediate - frequency filter circuit and then subjected to ADC sampling (for example, using a 12 - bit ADC with a resolution of 2 to the 12th power). Finally, after passing through the digital front - end, it will become a digital signal indicating the frequency deviation and be output. This frequency deviation (0.000010 GHz) is notified to the slave radar processing control module.

[0118] Execute step S4: The slave radar control module generates a frequency fine - tuning control signal indicating the frequency fine - tuning amplitude based on the frequency deviation to control the frequency calibration module to generate a frequency calibration signal to calibrate the actual set frequency of the local radio frequency signal.

[0119] Step S4 further includes: determining whether the frequency deviation exceeds the error threshold range; if the determination result is yes, generating the frequency fine - tuning control signal based on the frequency deviation, controlling the frequency calibration module to generate the frequency calibration signal, and calibrating the actual set frequency of the local radio frequency signal; (otherwise, no calibration is required) repeating the above steps until the determination result is no, then this calibration is completed (that is, the calibration of this frequency point is completed), and the master radar control module is notified to start the calibration of the next frequency point.

[0120] In a specific example, the calibration process of the frequency of a local radio frequency source is as follows: Assume that during the primary and secondary frequency calibration processes, the intermediate frequency deviation feedback by the radio frequency front end is 0.000010 GHz. A frequency fine-tuning control signal is output from the radar control module to control the frequency calibration module to adjust the actual set frequency of the local radio frequency source. For example, the frequency fine-tuning control signal indicates that the frequency fine-tuning amplitude of the local radio frequency signal of the radar is: minus 0.000005 GHz. After fine-tuning, the actual set frequency of the local radio frequency source of the radar is adjusted to 77.245610 GHz and continues to be output to the mixer. After the radio frequency front end compares the adjusted actual set frequency with the radio frequency point, the primary and secondary fine-tuned frequency deviation is 0.000005 GHz. After the radar control module receives the primary and secondary fine-tuned frequency deviation, it determines whether the frequency deviation exceeds the error threshold range (0 or close to 0); if the judgment result is yes, the above calibration process is continued, and through repeated adjustment, until the intermediate frequency deviation is controlled within the error threshold range, the frequency calibration of this frequency point is completed; until the frequency deviation is controlled within the error threshold range, the calibration of this frequency point is completed.

[0121] Execute step S5: Repeat the above steps S1 to S4. The frequency calibration module obtains different frequency points at different times and the corresponding frequency fine-tuning control signals indicating the corresponding frequency fine-tuning amplitudes, and stores them.

[0122] Execute step S6: When the radar detection is officially carried out, the frequency calibration module generates corresponding frequency calibration signals according to the stored frequency points and frequency fine-tuning control signals corresponding to different times to automatically correct the actual set frequency of the local radio frequency signal. Step S6 specifically includes the following steps S61 and S62:

[0123] Execute step S61: The frequency calibration module fits to form a frequency calibration curve in which the frequency calibration amplitude changes with time according to the stored different frequency points and corresponding frequency fine-tuning control signals at different times.

[0124] Figure 5 Shows the schematic diagram of the fitting process of the frequency calibration module for time-frequency calibration amplitude. Refer to Figure 5, the process of obtaining and fitting the frequency calibration amplitude (i.e., the frequency calibration slope) is as follows: The main radar control module designs the frequency points to be calibrated, such as F1, F2, F3... and the corresponding calibration times t1, t2, t3...; The slave radar receives these frequency points corresponding to the RF signals at the corresponding times and compares them with the actual set RF frequencies f1, f2, f3... of the local RF signals to obtain the frequency differences Δf1, Δf2, Δf3,... and performs frequency calibration through the frequency calibration module of the slave radar to reduce Δf1, Δf2, Δf3 to approach 0. For the frequency deviations between F1 / F2 and F2 / F3, the frequency calibration module can use Δf1, Δf2, Δf3... to obtain a fitting curve, so as to obtain the frequency differences between F1 and F2, and between F2 and F3 from the fitting curve, that is, the frequency fine-tuning amplitudes at different times when the error threshold approaches 0 are obtained.

[0125] S62: The frequency calibration module generates corresponding frequency calibration signals according to different frequency points and corresponding frequency fine-tuning control signals at different times in the frequency calibration curve to automatically correct the actual set frequency of the local RF signal.

[0126] Through step S61 and step S62, the fitting curve is obtained by calibrating a limited number of frequency points, filling the gap of the frequency deviation between frequency points, and improving the accuracy of subsequent automatic calibration; the strict frequency synchronization between the main radar and the slave radar is achieved; after the slave radar unit completes the frequency calibration, the frequency configuration method (the relationship between the frequency deviation shown by the fitting curve and time) can be notified to the main radar control module through SPI, which is convenient for the main radar control module to comprehensively evaluate the frequency deviation of the radar system.

[0127] After the main radar and the slave radar achieve frequency synchronization, the main radar and the slave radar send the designed frequency-modulated continuous wave at the same time. The main radar itself can receive the frequency-modulated continuous wave it sends and the frequency-modulated continuous wave sent by the slave radar, perform mixing and sampling, and transmit the data to the HPC or the central processor through protocols such as Ethernet or serdes; perform merging processing to achieve the effect of multi-radar system processing.

[0128] In an optional solution, a radar communication line is connected between the first radar control module and the second radar control module, and they share a crystal oscillator; before transmitting the RF signal, the first radar control module agrees on the same signal transceiver time with the second radar control module through the radar communication line; the first radar control module provides the frequency points to the second radar control module through the radar communication line.

[0129] In another alternative solution, the multi-radar system further includes a central control platform; the central control platform controls the clock synchronization of the first radar and the second radar; before transmitting the radio frequency signal, the central control platform agrees that the first radar and the second radar perform signal transceiver at the same moment; the central control platform notifies the first radar control module to control the first radio frequency front-end module to transmit the radio frequency signal; meanwhile, it acquires the frequency point of the radio frequency signal and notifies the second radar control module.

[0130] In summary, the present invention provides a multi-radar system and a frequency synchronization method for a multi-radar system, realizing accurate frequency point calibration and automatic correction functions among multiple radars. It gets rid of the limitation of the configuration of the same radio frequency source / LO local oscillator signal on the physical space distance of different radars. The distance between radars can be freely increased, facilitating the antenna layout of the distributed radar system. At the same time, it also improves the equivalent aperture and angle positioning accuracy of the entire radar system.

[0131] The present invention also realizes, through the frequency calibration module, fitting the frequency fine-tuning amplitudes corresponding to a limited number of frequency points to form a frequency calibration curve in which the frequency calibration amplitude changes with time, and performing automatic correction according to the frequency calibration curve, improving the correction accuracy.

[0132] In a further preferably multi-radar system architecture, even between different radars, there is no need to achieve unified control and time synchronization by clk and the control line (SPI) clk; it simplifies the wiring harness connection between multiple radars and facilitates the expansion of the number of radars; the multi-radar system referred to in the present invention can, for example, include but is not limited to a coherent radar system or a distributed radar system, and the architecture of the multi-radar system in this embodiment is more convenient for application in a distributed radar system.

[0133] It should be noted that the embodiments of the present invention have good implementability and are not any form of limitation to the present invention. Any person skilled in the art may use the disclosed technical content to modify or transform it into an equivalent effective embodiment. However, as long as it does not depart from the technical solution of the present invention, any modification, equivalent change or modification made to the above embodiments based on the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A frequency synchronization method for a multi-radar system, used to synchronize the frequencies of a multi-radar system, the system comprising: A first radar and a second radar; the first radar includes a first radar control module and a first radio frequency front-end module; The second radar includes a second radar control module and a second radio frequency front-end module; At least the second radar further includes: a frequency calibration module; characterized in that the method includes: The first radar control module controls the first radio frequency front-end module to send a radio frequency signal, and at the same time provides the frequency point of the radio frequency signal to the second radar control module; The second radar control module controls the second radio frequency front-end module to receive the radio frequency signal, and sets the actual set frequency of the local radio frequency signal according to the frequency point; The second radio frequency front-end module receives the radio frequency signal, calculates the frequency deviation according to the frequency point of the radio frequency signal and the actual set frequency, and notifies the second radar control module; The second radar control module generates a frequency fine-tuning control signal indicating the frequency fine-tuning amplitude according to the frequency deviation to control the frequency calibration module to generate a frequency calibration signal to calibrate the actual set frequency of the local radio frequency signal; Repeat the above steps to obtain frequency fine-tuning control signals indicating corresponding frequency fine-tuning amplitudes corresponding to different frequency points at different times, and store them; When officially performing radar detection, the frequency calibration module generates a frequency calibration signal according to the frequency point and the corresponding frequency fine-tuning control signal to automatically correct the actual set frequency of the corresponding local radio frequency signal.

2. The frequency synchronization method for a multi-radar system according to claim 1, characterized in that The step of the frequency calibration module generating a frequency calibration signal according to the frequency point and the corresponding frequency fine-tuning control signal to automatically correct the actual set frequency of the corresponding local radio frequency signal specifically includes: The frequency calibration module fits to form a frequency calibration curve in which the frequency calibration amplitude changes with time according to different frequency points at different times and the corresponding frequency fine-tuning control signals; The frequency calibration module generates corresponding frequency calibration signals according to the frequency fine-tuning control signals corresponding to different frequency points at different times in the frequency calibration curve to automatically correct the actual set frequency of the corresponding local frequency signal in sequence.

3. The frequency synchronization method for a multi-radar system according to claim 1, characterized in that The step of the second radar control module generating a frequency fine-tuning control signal indicating the frequency fine-tuning amplitude according to the frequency deviation to control the frequency calibration module to generate a frequency calibration signal to calibrate the actual set frequency of the local radio frequency signal further includes: The second radar control module judges whether the frequency deviation exceeds the error threshold range; If the judgment result is yes, generate the frequency fine-tuning control signal according to the frequency deviation, control the frequency calibration module to generate the frequency calibration signal, and calibrate the actual set frequency of the local radio frequency signal; When the judgment result is negative, this calibration is completed, and the first radar control module is notified to start calibrating the next frequency point.

4. The frequency synchronization method of the multi-radar system according to claim 1, wherein A radar communication line is connected between the first radar control module and the second radar control module, and they share a crystal oscillator; Before transmitting the radio frequency signal, the first radar control module agrees on the same signal transmission and reception time with the second radar control module through the radar communication line; The first radar control module provides the frequency point to the second radar control module through the radar communication line.

5. The frequency synchronization method of the multi-radar system according to any one of claims 1-3, characterized in that, The multi-radar system further includes a central control platform; The central control platform controls the clock synchronization of the first radar and the second radar; Before transmitting radio frequency, the central control platform agrees that the first radar and the second radar perform signal transmission and reception at the same time; The central control platform notifies the first radar control module to control the first radio frequency front-end module to transmit a radio frequency signal; at the same time, obtain the frequency point of the radio frequency signal and notify the second radar control module.

6. A multi-radar system, comprising: The first radar and the second radar; the first radar includes a first radar control module and a first radio frequency front-end module; The second radar includes a second radar control module and a second radio frequency front-end module; It is characterized in that at least the second radar further includes: a frequency calibration module; The first radar control module is used to control the first radio frequency front-end module to transmit a radio frequency signal, and at the same time provide the frequency point of the radio frequency signal to the second radar control module; The second radar control module is used to control the second radio frequency front-end module to receive the radio frequency signal, and set the actual set frequency of the local radio frequency signal according to the frequency point; The second radio frequency front-end module is used to receive the radio frequency signal, calculate the frequency deviation according to the radio frequency point and the actual set frequency of the radio frequency signal, and notify the second radar control module; The second radar control module is used to generate a frequency fine-tuning control signal indicating the frequency fine-tuning amplitude according to the frequency deviation to control the frequency calibration module to generate a frequency calibration signal to calibrate the actual set frequency of the local radio frequency signal; The frequency calibration module can also be used to obtain different frequency points and corresponding frequency fine-tuning control signals indicating the corresponding frequency fine-tuning amplitudes at different times after repeating the above steps, and store them; When officially performing radar detection, the frequency calibration module is used to generate corresponding frequency calibration signals according to the stored different frequency points and corresponding frequency fine-tuning control signals at different times to automatically correct the actual set frequency of the corresponding local radio frequency signal.

7. The multi-radar system according to claim 6, wherein The frequency calibration module is used to fit a frequency calibration curve in which the frequency calibration amplitude changes with time according to different frequency points and corresponding frequency fine-tuning control signals at different times; and a frequency fine-tuning control signal corresponding to different frequency points at different times in the frequency calibration curve is used to generate a corresponding frequency calibration signal to automatically correct the actual set frequency of the corresponding local frequency signal in sequence.

8. The multi-radar system according to claim 7, wherein the second radar control module determines whether the frequency deviation exceeds an error threshold range; if the determination result is yes, a frequency fine-tuning control signal is generated according to the frequency deviation, and the frequency calibration module is controlled to generate the frequency calibration signal to calibrate the actual set frequency of the local radio frequency signal; until the determination result is no, this calibration is completed, and the first radar control module is notified to start calibrating the next frequency point.

9. The multi-radar system according to claim 7, wherein the frequency calibration module generates a frequency calibration signal indicating an electrical parameter deviation according to a frequency fine-tuning control signal indicating the frequency fine-tuning amplitude to calibrate the frequency of the local frequency signal; the electrical parameter deviation includes a capacitance deviation or a voltage deviation generated according to the frequency fine-tuning amplitude.

10. The multi-radar system according to claim 6, wherein the second radio frequency front end includes a local radio frequency source for generating the local radio frequency signal.

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