A method and system for synchronization between millimeter wave fmcw radar devices

Abstract

This invention relates to the field of radar synchronization technology, specifically disclosing a synchronization method and system for millimeter-wave FMCW radar devices. The method includes: constructing a synchronization frame and a communication frame based on linear frequency modulated (LFM) signals. The synchronization frame contains multiple standard LFM signals with identical parameters, and the communication frame includes at least one standard LFM signal and multiple service LFM signals following the standard LFM signals. The master radar and slave radar complete initial synchronization, synchronization confirmation, and synchronization maintenance through the synchronization frame and communication frame. This invention designs the synchronization frame and communication frame structure, and designs strategies for initial synchronization, synchronization confirmation, and synchronization maintenance. It can achieve coarse synchronization between radar devices without relying on external hardware and communication links, and achieve precise time synchronization and long-term stable synchronization between radars without reducing the measurement refresh rate. Simultaneously, it can achieve integrated radar communication.

Description

Technical Field

[0001] This invention relates to the field of radar synchronization technology, and specifically to a synchronization method and system between millimeter-wave FMCW radar devices. Background Technology

[0002] Radar-communication integration is an inevitable trend in the development of electronic systems. By sharing hardware platforms such as antennas, RF front-ends, and signal processors, integrated radar-communication design can effectively reduce system size, weight, power consumption, and cost. Simultaneously, integration enables efficient sharing of spectrum resources, alleviating conflicts between radar and communication systems in frequency band usage. Furthermore, deep synergy can be achieved between radar detection and communication functions; detection information is used to optimize communication link scheduling, while communication data can assist radar in target identification and tracking, thereby significantly improving the system's response speed and overall performance in complex environments.

[0003] In integrated radar and communication systems, precise synchronization is the core foundation for ensuring the reliable implementation of radar functions (such as high-resolution ranging and velocity measurement) and communication functions (such as low bit error rate data transmission). Synchronization deviations directly lead to an increase in the communication bit error rate and significantly degrade the accuracy of radar target parameter estimation, affecting the performance of the entire system.

[0004] For FMCW communication and radar integrated systems, traditional synchronization techniques include: synchronization based on external references and synchronization based on signal design.

[0005] The core technology of synchronization schemes based on external references is to use a high-precision common clock source (such as GPS) or to synchronize via a dedicated communication link (such as 2.4GHz). Although this method has high synchronization accuracy, it requires additional hardware and links, resulting in higher system complexity and cost. Its performance fundamentally depends on the accessibility and stability of the external source.

[0006] The core technology of the synchronization scheme based on signal design is to optimize the structure of the integrated signal itself to achieve self-synchronization. The mainstream method is to embed a special synchronization header or training sequence in the integrated signal frame structure. This data-assisted synchronization header is used for the synchronization acquisition of the radar communication system. Since the synchronization header does not carry the actual communication data and radar detection information, its existence will directly occupy the system's time and frequency resources, resulting in a decrease in communication data rate and a decrease in radar measurement refresh rate, thereby impairing the core sensing and communication performance of the system.

[0007] Among signal-based synchronization schemes, one approach involves designing special chirp pattern pairs. This scheme utilizes the spectral response differential method to achieve precise time synchronization, which is then maintained by a PID closed-loop feedback control system. While offering high synchronization accuracy, in engineering implementation, these special chirp pattern pairs may introduce multiple feasible coarse synchronization lock points, posing a risk of lock ambiguity. Therefore, other mechanisms must be introduced for detection and correction. Furthermore, to maintain synchronization, the system needs to periodically send these special chirp pattern pairs to sustain closed-loop feedback control. These special chirp pattern pairs contain multiple invalid chirp cycles, which cannot be used for target detection, directly reducing the radar's effective detection probability and data update rate.

[0008] In summary, there is an urgent need for a synchronization method and system between millimeter-wave FMCW radar devices to solve the problems in the existing technology. Summary of the Invention

[0009] The purpose of this invention is to provide a synchronization method and system for millimeter-wave FMCW radar devices, and the specific technical solution is as follows: A synchronization frame and a communication frame based on linear frequency modulation (LFM) signals are constructed. The communication frame includes at least one standard LFM signal set at the frame header and multiple service LFM signals set after the standard LFM signal. The parameters of the standard LFM signals in different communication frames are completely identical, and the service LFM signals in the communication frames carry service information by changing their own starting frequency information. The main radar and the slave radar complete initial synchronization, synchronization confirmation, and synchronization maintenance through the communication frames and synchronization frames.

[0010] Specifically, initial synchronization includes a search phase, a verification phase, and a frame start position positioning phase, wherein: Search phase: The main radar sends a synchronization frame, and the slave radar adjusts the start time of its own frame according to the first fixed step value, and searches in each synchronization frame period until it captures the synchronization frame sent by the main radar. Then it immediately ends the search state and enters the verification phase. Verification phase: After the radar completes the search, the start time of the frame is adjusted for three consecutive synchronization frame cycles. The second fixed step value is adjusted to be less than the first fixed step value. The signal measurement results of each synchronization frame cycle are recorded. If the acquisition is successful for three consecutive synchronization frame cycles and the acquisition frequency value conforms to the change pattern, the frame start position positioning phase is entered. If it is unsuccessful, the search phase is returned and the search continues. Frame start position positioning stage: Based on the linear frequency modulation signal pattern within the synchronization frame, the frame interval time, and the measurement status of each linear frequency modulation signal within the frame, determine the difference in the number of linear frequency modulation signals in the synchronization frames of the master radar and the slave radar, adjust the frame start time of the slave radar, and achieve initial synchronization of the frame start position between the two radar devices.

[0011] Specifically, during the search phase, a cross-search approach is adopted. The cross-search process includes: At time T0, the time deviation between the two radar devices is τ, and the adjustment step value is Δt1, where Δt1 is the first fixed step value, and τ represents the time synchronization error between the first linear frequency modulated signal in the radar synchronization frame and the kth linear frequency modulated signal in the main radar synchronization frame. At time T1, the time deviation between the two radar devices is τ-Δt1, and the adjustment step value is -2Δt1; At time T2, the time deviation between the two radar devices is τ+Δt1, and the adjustment step value is +3Δt1; At time T3, the time deviation between the two radar devices is τ-2Δt1, and the adjustment step value is -4Δt1; Repeat the above step value adjustment rule until the time deviation between the radar and the main radar is reduced to ξ, i.e., ξ=τ-NΔt1, when the radar acquires the synchronization frame sent by the main radar and the search ends; where N represents the parameter adjustment from the radar synchronization frame when acquisition is successful.

[0012] Specifically, in the frame start position positioning stage, a minimum interval time is set between frames, which is set to at least M linear frequency modulation signals, where M is an integer with a minimum value of 1; The initial synchronization of the frame start position between two radar devices includes the following process: The frame start positions of the radar and the main radar differ by k-1 linear frequency modulation (LFM) signals. During the time interval of the radar's (N-k+2) to (N-k+2+M-1)th LFM signal, the main radar does not transmit LFM signals. During the time intervals of other LFM signals, the main radar transmits LFM signals normally, and the measured values ​​are close. Based on the measurement results of each linear frequency modulated signal within the synchronization frame from the radar end, the number of linear frequency modulated signals differing between the start positions of the main radar and the slave radar frames is derived, thereby calculating the time adjustment amount (k-1). (T chirp +T idle And adjust the radar frame start time (k-1). (T chirp +T idle )+Δt3; Among them, T chirpT represents the duration of the linear frequency modulated signal; idle Δt3 represents the idle interval between adjacent linear frequency modulated signals; Δt3 is a control parameter used to ensure that, after time adjustment, bidirectional measurability is possible between the two radar devices, and a time margin is retained.

[0013] Specifically, the synchronous confirmation process includes: When switching from radar to radar synchronization confirmation state, the radar sends a communication frame carrying service information to the main radar. The main radar parses the communication frame to obtain the service information. The main radar returns a communication frame carrying service information in the same way. The radar parses the communication frame and switches to synchronization maintenance state to complete synchronization confirmation. The service information is radar synchronization information.

[0014] Specifically, the process of parsing the communication frame to obtain service information includes: The radar equipment receives communication frames carrying service information; The communication frame is mixed with the synchronization frame sent by itself to obtain the frequency difference between each linear frequency modulated signal in the communication frame and each linear frequency modulated signal in the local synchronization frame. The frequency difference corresponding to the standard linear frequency modulation (LFM) signal is Δf0, and the frequency difference corresponding to the service LFM signal is Δf. x The fixed frequency difference of the communication data is Δf u ; If the frequency difference Δf corresponds to the linear frequency modulation signal of the service x If the value is close to Δf0, it indicates that the communication data carried by the linear frequency modulation signal of this service is 0. If the value is close to the frequency difference Δf of the linear frequency modulation signal of this service, it indicates that the communication data carried by the linear frequency modulation signal of this service is 0. x Approaching Δf0+Δf u If , it means that the communication data carried by the linear frequency modulation signal of this service is 1; By analyzing all the service linear frequency modulation signals, the service information composed of communication data can be obtained.

[0015] Specifically, the process of maintaining synchronization includes: The synchronization error between the main radar and the slave radar is calculated based on the frequency difference measured at both ends of the main radar and the slave radar, as well as the slope of the linear frequency modulated signal. The slave radar periodically adjusts the start time of its own communication frames based on the synchronization error value to achieve precise time synchronization between the slave radar and the master radar.

[0016] Specifically, the synchronization error value between the main radar and the slave radar The calculation expression is as follows: ; ; ; in, This indicates the time difference measured by the main radar. This indicates the time difference measured from the radar. This indicates the frequency difference measured at the main radar end. This represents the frequency difference measured by radar. The slope of the linear frequency modulated signal.

[0017] Specifically, the main radar and the slave radar also achieve radar communication integration through the aforementioned communication frames, the process of which includes: The master radar and slave radar complete initial synchronization through the communication frame. During the initial synchronization process, the master radar and slave radar achieve coarse time synchronization through the synchronization frame to ensure that the transmitted signals of the two radar devices enter the detection range of the other radar, thereby realizing basic two-way detection and radar communication. After the primary and secondary radars complete initial synchronization, the primary and secondary radars transmit service data through the standard linear frequency modulation (LFM) signal and the service LFM signal in the communication frame.

[0018] In addition, the present invention also includes a synchronization system between millimeter-wave FMCW radar devices for implementing the synchronization method between millimeter-wave FMCW radar devices as described above, the system comprising: At least one main radar; At least one from radar; Initial synchronization module: used to achieve initial synchronization between the slave radar and the master radar; Synchronization confirmation module: used to realize synchronization confirmation between the slave radar and the master radar; Synchronization Maintenance Module: Used to maintain synchronization between the slave radar and the master radar.

[0019] The application of the technical solution of the present invention has at least the following beneficial effects: The method of this invention designs a dedicated synchronization frame and communication frame structure, and designs an initial synchronization method and a coarse synchronization verification strategy, a fine synchronization method and a synchronization maintenance strategy. It can achieve unambiguous coarse synchronization between radar devices without the aid of external hardware and communication links, and achieve fine time synchronization between radars and long-term stable synchronization maintenance without reducing the measurement refresh rate. At the same time, it can realize radar communication integration.

[0020] The initial synchronization method of this invention accurately achieves unambiguous coarse-precision autonomous initial synchronization between devices, and the synchronization accuracy of this coarse synchronization can ensure that the transmitted signals of the two radar devices enter the detection range of the other radar, realizing basic two-way detection and radar communication.

[0021] The method of this invention is also based on the initial synchronization of two radar devices. Through the design of a dedicated communication frame structure, an integrated radar communication working mode is achieved, realizing the interaction mechanism between the two radar devices. This ensures that every linear frequency modulation signal used for communication can be used for measurement, realizing bidirectional data interaction without reducing the measurement refresh rate. At the same time, by utilizing bidirectional communication and bidirectional measurement functions, the time system interaction between the two radar devices is continuously realized, thereby completing the precise synchronization and synchronization maintenance between the radar devices and eliminating the time accumulation error introduced by the crystal oscillator deviation of the radar devices.

[0022] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a flowchart of the synchronization method between millimeter-wave FMCW radar devices in a preferred embodiment of the present invention; Figure 2 This is a detailed flowchart of the synchronization method between millimeter-wave FMCW radar devices in a preferred embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of the synchronous chirp frame in a preferred embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of a service chirp frame in a preferred embodiment of the present invention; Figure 5 This is a schematic diagram of the radar signal transmission method between master and slave radar devices in a preferred embodiment of the present invention; Figure 6 This is a schematic diagram of the cross-search during the initial synchronous search phase in a preferred embodiment of the present invention; Figure 7 This is a schematic diagram of the initial synchronization verification stage in a preferred embodiment of the present invention; Figure 8 This is a schematic diagram of the process of locating the start position of the initial synchronization frame in a preferred embodiment of the present invention; Figure 9 This is a schematic diagram of a service chirp frame under second-order modulation in a preferred embodiment of the present invention. Detailed Implementation

[0025] To enable those skilled in the art to better understand the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example: like Figure 1 and Figure 2 As shown, this embodiment provides a synchronization method between millimeter-wave FMCW radar devices, including: Construct a synchronization frame based on a linear frequency modulated (chirp) signal, wherein the synchronization frame comprises multiple standard linear frequency modulated signals with identical parameters.

[0027] A communication frame based on a chirp signal is constructed. The communication frame includes at least one standard chirp signal set at the frame header and multiple service chirp signals set after the standard chirp signal. The parameters of the standard chirp signal in different communication frames are completely identical, and the service chirp signals in the communication frames carry service information by changing their own starting frequency information.

[0028] The constructed synchronization frame and the communication frame have the same frame structure, but the multiple linear frequency modulation signals within the frame are different.

[0029] It should be noted that the synchronization frame constructed in this embodiment can also be called a synchronization chirp frame, and the corresponding frame structure is defined as the synchronization chirp frame structure; the communication frame constructed can also be called a service chirp frame (radar-communication integrated chirp frame), and the corresponding frame structure is defined as the radar-communication integrated chirp frame structure.

[0030] Among them, such as Figure 3 As shown, a synchronous chirp frame contains N chirps. The parameters of these N chirps (including the starting frequency f) are... start Bandwidth B, frequency modulation slope S, duration T chirp End frequency f end The chirp is completely identical to the chirp in this embodiment, which defines it as a standard chirp. Figure 3 (Middle yellow section). The duration of a single chirp is T. chirp The idle interval between chirps is T. idle The time interval between chirp frames is T. inter chirp frame period T frame =(T chirp +T idle ) N+T inter This synchronization chirp frame does not distinguish between radar devices and is used to complete the initial synchronization between two radar devices.

[0031] Furthermore, such as Figure 4 As shown, the service chirp frame contains two types of chirps, namely two standard chirps ( Figure 4 (The yellow part in the middle) and N-2 business chirps ( Figure 4 (The green portion in the middle) In this embodiment, two standard chirs are preferred, but one or more standard chirs can be used in other business scenarios. The chirp frequency modulation slope S and the duration T of a single chirp are also considered. chirp The bandwidth occupied (B) is exactly the same; the difference lies in the starting frequency (f) of the service chirp. start Variable, used to carry service data. The frame period T of the service chirp frame. frame Number of chirps within a frame N, and inter-chirp interval T idle Frame interval time T inter These parameters are all consistent with the synchronized chirp frames.

[0032] In this embodiment, the number of chirps N, the frequency modulation slope S, and the duration T of a single chirp in the communication frame are... chirp Bandwidth occupied (B), idle interval between chirps (T) idle Frame interval time T inter Frame period T frame The starting frequency f of the standard chirp start The starting frequency of the service chirp can be selected according to the application requirements.

[0033] Furthermore, in this embodiment, the radar devices achieve integrated radar communication through time-division multiplexing and simultaneous detection. By transmitting time information via bidirectional radar communication and calculating synchronization time errors, precise time synchronization and synchronization maintenance are achieved between the radar devices, overcoming the drift of their individual local clocks and maintaining a long-term synchronized state. Specific radar signal transmission methods are as follows: Figure 5 As shown, in this embodiment, two communication frame periods are defined as one communication period. In the first communication frame period, the radar sends service data (sends service chirp frames), and the main radar receives service data (sends synchronization chirp frames). In the second chirp frame period, the main radar sends service data (sends service chirp frames), and the radar receives service data (sends synchronization chirp frames). In this way, one bidirectional data interaction and real-time bidirectional measurement can be completed within one communication period.

[0034] The master radar and slave radar synchronize through the synchronization frame and communication frame. The synchronization process includes initial synchronization, synchronization confirmation, and synchronization maintenance (steps S100-S300). S100: Initial synchronization, which includes a search phase, a verification phase, and a frame start position positioning phase, wherein: S101: Search Phase: The main radar sends a synchronization frame, and the slave radar adjusts the start time of its own synchronization frame according to the first fixed step value. It searches in each synchronization frame period until it captures the synchronization frame sent by the main radar. Then it immediately ends the search state and enters the verification phase. S102: Verification Phase: After the radar completes the search, the start time of the frame is adjusted for three consecutive synchronization frame cycles. The second fixed step value is adjusted to be less than the first fixed step value. The signal measurement results of each synchronization frame cycle are recorded. If the radar successfully acquires the signal for three consecutive synchronization frame cycles and the acquisition frequency value conforms to the change pattern, the radar enters the frame start position positioning phase. If the acquisition fails, the radar returns to the search phase and continues searching. This verification process can effectively suppress the interference of signals from other radar equipment and the radar's own reflected signals on synchronization.

[0035] S103: Frame start position positioning stage: Based on the linear frequency modulation signal pattern within the synchronization frame, the frame interval time, and the measurement status of each linear frequency modulation signal within the frame, determine the difference in the number of linear frequency modulation signals in the synchronization frame between the master radar and the slave radar, adjust the frame start time of the slave radar, and achieve initial synchronization of the frame start position between the two radar devices.

[0036] Specifically, in S101, a cross-search method is adopted, such as... Figure 6 As shown, the cross-search process includes: At time T0, the time deviation between the two radar devices is τ, and the adjustment step value is Δt1, where Δt1 is the first fixed step value, and τ represents the time synchronization error between the first linear frequency modulated signal in the radar synchronization frame and the kth linear frequency modulated signal in the main radar synchronization frame. At time T1, the time deviation between the two radar devices is τ-Δt1, and the adjustment step value is -2Δt1; At time T2, the time deviation between the two radar devices is τ+Δt1, and the adjustment step value is +3Δt1; At time T3, the time deviation between the two radar devices is τ-2Δt1, and the adjustment step value is -4Δt1; Repeat the above step value adjustment rule until the time deviation between the radar and the main radar is reduced to ξ, i.e., ξ=τ-NΔt1, when the radar acquires the synchronization frame sent by the main radar and the search ends; where N represents the parameter adjustment from the radar synchronization frame when acquisition is successful.

[0037] The initial synchronization process in this embodiment does not rely on external hardware and communication links to achieve coarse synchronization between radar devices, and the synchronization accuracy of this coarse synchronization can ensure that the transmitted signals of the radar devices all enter the detection range of the other radar, thus enabling bidirectional detection and radar communication.

[0038] Specifically, in S102, for the FMCW signal, the slope of the linear frequency modulated signal is S = Δf / Δt, where Δf represents the frequency change within the range of Δt. After entering the measurement interval, with the distance between the master and slave radars remaining constant, the frequency difference measured by the slave radar changes linearly with the synchronization error between the master and slave radars. Setting a second fixed step value Δt2, the frequency difference measured by the slave radar should change in a regular pattern: i.e., f -> fS Δt2->f-2 S Δt2->f-3 S Δt2. The process of the master-slave radar verification stage in this embodiment is as follows: Figure 7 As shown.

[0039] Specifically, in S103, a minimum interval time is set between frames, which is set to at least M linear frequency modulation signals, where M is an integer with a minimum value of 1; like Figure 8 As shown, the initial synchronization of the frame start position between two radar devices includes the following process: The frame start positions of the radar and the main radar differ by k-1 linear frequency modulation (LFM) signals. During the time interval of the radar's (N-k+2) to (N-k+2+M-1)th LFM signal, the main radar does not transmit LFM signals. During the time intervals of other LFM signals, the main radar transmits LFM signals normally, and the measured values ​​are close. Based on the measurement results of each linear frequency modulated signal within the synchronization frame from the radar end, the number of linear frequency modulated signals differing between the start positions of the main radar and the slave radar frames is derived, thereby calculating the time adjustment amount (k-1). (T chirp +T idle And adjust the radar frame start time (k-1). (T chirp +T idle )+Δt3; Among them, T chirp T represents the duration of the linear frequency modulated signal; idle Δt3 represents the idle interval between adjacent linear frequency modulated signals; Δt3 is a control parameter used to ensure that, after time adjustment, bidirectional measurability is possible between the two radar devices, and a time margin is retained.

[0040] S200: Synchronization confirmation. The synchronization confirmation process includes: When switching from radar to radar synchronization confirmation state, the radar sends a communication frame carrying service information to the main radar. The main radar parses the communication frame to obtain the service information. The main radar returns a communication frame carrying service information in the same way. The radar parses the communication frame and switches to synchronization maintenance state to complete synchronization confirmation. The service information is radar synchronization information.

[0041] Furthermore, the process of parsing the communication frame to obtain service information includes: The radar equipment receives a communication frame carrying service information; it mixes the communication frame with its own transmitted synchronization frame to obtain the frequency difference between each linear frequency modulated signal in the communication frame and each linear frequency modulated signal in the local synchronization frame. The frequency difference corresponding to the standard linear frequency modulation (LFM) signal is Δf0, and the frequency difference corresponding to the service LFM signal is Δf. x The fixed frequency difference of the communication data is Δf u ; If the frequency difference Δf corresponds to the linear frequency modulation signal of the service x If the value is close to Δf0, it indicates that the communication data carried by the linear frequency modulation signal of this service is 0. If the value is close to the frequency difference Δf of the linear frequency modulation signal of this service, it indicates that the communication data carried by the linear frequency modulation signal of this service is 0. x Approaching Δf0+Δf u If , it means that the communication data carried by the linear frequency modulation signal of this service is 1; By analyzing all the service linear frequency modulation signals, the service information composed of communication data can be obtained.

[0042] It should be noted that in the integrated radar-communication chirp frame (service chirp frame), the first two chirs are standard chirs, and the following N-2 chirs are service chirs. In this embodiment, the slope of the standard chirp is set to S, and the starting frequency is f0. The service chirp modulates the communication information onto the initial frequency parameters of the chirp, and the starting frequency of the service chirp is f0. x =f0+X Δf u X represents the symbol information to be transmitted, which is related to the modulation order, and Δf u This is a pre-agreed fixed frequency difference.

[0043] like Figure 9 As shown, this is a service chirp frame under second-order modulation. Green represents standard chirp, and red represents service chirp. The symbol information X to be transmitted can be set to 0 or 1. Assume f0 + Δf u=f1, the starting frequencies of each chirp in the service chirp frame are f0, f0, f1, f0, f0, f0, ..., f1, f0, f1, f1, f0, then the communication data / symbol information carried by the service chirp frame are 0 (standard chirp), 0 (standard chirp), 1, 0, 0, 0, ..., 1, 0, 1, 1, 0, where the first two f0 are communication reference chirs and do not require data recovery.

[0044] S300: Synchronization maintenance, the synchronization maintenance process includes: Based on the periodic exchange of time information (frequency difference information) between the master and slave radars, the synchronization error between the master and slave radars is calculated according to the frequency difference measured at both ends of the master and slave radars and the slope of the linear frequency modulation signal. The slave radar periodically adjusts the start time of its own communication frames based on the synchronization error value to achieve precise time synchronization between the slave radar and the master radar.

[0045] Specifically, the synchronization error value between the master radar and the slave radar The calculation expression is as follows: ; ; ; in, This indicates the time difference measured by the main radar. This indicates the time difference measured from the radar. This indicates the frequency difference measured at the main radar end. This represents the frequency difference measured by radar. The slope of the linear frequency modulated signal.

[0046] In this embodiment, a precise time synchronization adjustment (synchronization maintenance) is continuously performed every P communication cycles to eliminate the cumulative time error introduced by the master-slave radar crystal oscillator deviation and maintain a long-term synchronized state. The selection of the adjustment period P depends on the crystal oscillator specifications.

[0047] Furthermore, the main radar and the slave radar also achieve radar communication integration through the aforementioned communication frames, the process of which includes: After the primary and secondary radars complete initial synchronization, the primary and secondary radars transmit service data through the standard linear frequency modulation (LFM) signal and the service LFM signal in the communication frame.

[0048] Specifically, in the integrated radar-communication operation mode, for the first chirp frame period, the measurement frequency difference Δf of two standard chirps can be calculated from the radar end. s0And using known business data X and frequency information Δf measured by each chirp. sx Recover the measurement data Δf of each service chirp. sy =Δf sx -X Δf u At the main radar end, the measurement results Δf of two standard chirps can be calculated. m0 And using the recovered business data X, and the frequency information Δf measured by each chirp, mx Recover the measurement data Δf of each service chirp. my =Δf mx -X Δf u Similarly, during the second chirp frame cycle, both the master and slave radars can simultaneously complete measurements of each chirp and transmit / receive one set of service data. Since coarse time synchronization between the master and slave radars has been completed during the initial synchronization period, all chirs in the service chirp frame can be used for measurement, including the standard chirp used for communication reference and the service chirp used for transmitting service data. This ensures that the addition of communication functionality does not affect the core data refresh rate of radar measurements.

[0049] The synchronization method between millimeter-wave FMCW radar devices provided in this embodiment can accurately achieve unambiguous, coarse-precision autonomous initial synchronization between devices without the aid of external hardware and communication links. This coarse synchronization ensures that the transmitted signals from both the master and slave radars enter the detection range of the other radar, enabling basic bidirectional detection and radar communication. Furthermore, based on the initial synchronization of the master and slave radar devices, this embodiment's method, through the design of an integrated radar communication chirp frame structure and an interaction mechanism between the master and slave radar devices, ensures that every chirp used for communication can be used for measurement. This achieves bidirectional data interaction without reducing the measurement refresh rate. Simultaneously, by utilizing bidirectional communication and bidirectional measurement functions, continuous time system interaction between the master and slave devices is achieved, enabling fine synchronization and synchronization maintenance between devices, eliminating the time accumulation error introduced by the master and slave radar crystal oscillator deviation.

[0050] This embodiment also includes a synchronization system between millimeter-wave FMCW radar devices, used to implement the synchronization method between millimeter-wave FMCW radar devices as described above, the system comprising: At least one main radar; At least one from radar; Initial synchronization module: used to achieve initial synchronization between the slave radar and the master radar; Synchronization confirmation module: used to realize synchronization confirmation between the slave radar and the master radar; Synchronization Maintenance Module: Used to maintain synchronization between the slave radar and the master radar.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A synchronization method between millimeter-wave FMCW radar devices, characterized in that, include: A synchronization frame and a communication frame based on linear frequency modulation (LFM) signals are constructed. The synchronization frame contains multiple standard LFM signals with identical parameters, and the communication frame includes at least one standard LFM signal and multiple service LFM signals set after the standard LFM signal. The parameters of the standard LFM signals in different communication frames are completely identical, and the service LFM signals in the communication frames carry service information by changing their own starting frequency information. The frame structure of the communication frame is the same as that of the synchronization frame, but the LFM signals contained in the frame are different. The master radar and the slave radar complete initial synchronization, synchronization confirmation, and synchronization maintenance through the synchronization frame and communication frame; Initial synchronization includes a search phase, a verification phase, and a frame start position positioning phase, wherein: Search phase: The main radar sends a synchronization frame, and the slave radar adjusts the start time of its own synchronization frame according to the first fixed step value, and searches in each synchronization frame period until it captures the synchronization frame sent by the main radar. Then, the search state ends immediately and the verification phase begins. Verification phase: After the radar completes the search, the start time of the frame is adjusted for three consecutive synchronization frame cycles. The second fixed step value is adjusted to be less than the first fixed step value. The signal measurement results of each synchronization frame cycle are recorded. If the acquisition is successful for three consecutive synchronization frame cycles and the acquisition frequency value conforms to the change pattern, the frame start position positioning phase is entered. If it is unsuccessful, the search phase is returned and the search continues. Frame start position positioning stage: Based on the intra-frame linear frequency modulation signal pattern, frame interval time, and intra-frame linear frequency modulation signal measurement status, determine the difference in the number of linear frequency modulation signals in the synchronization frames of the master radar and slave radar, adjust the frame start time of the slave radar, and achieve initial synchronization of the frame start position between the two radar devices. The process of maintaining synchronization includes: The synchronization error between the main radar and the slave radar is calculated based on the frequency difference measured at both ends of the main radar and the slave radar, as well as the slope of the linear frequency modulated signal. The slave radar periodically adjusts the start time of its own communication frames based on the synchronization error value to achieve precise time synchronization between the slave radar and the master radar.

2. The synchronization method between millimeter-wave FMCW radar devices according to claim 1, characterized in that, During the search phase, a cross-search approach is adopted. The cross-search process includes: At time T0, the time deviation between the two radar devices is τ, and the adjustment step value is Δt1, where Δt1 is the first fixed step value, and τ represents the time synchronization error between the first linear frequency modulated signal in the radar synchronization frame and the kth linear frequency modulated signal in the main radar synchronization frame. At time T1, the time deviation between the two radar devices is τ-Δt1, and the adjustment step value is -2Δt1; At time T2, the time deviation between the two radar devices is τ+Δt1, and the adjustment step value is +3Δt1; At time T3, the time deviation between the two radar devices is τ-2Δt1, and the adjustment step value is -4Δt1; Repeat the above step value adjustment rule until the time deviation between the radar and the main radar is reduced to ξ, i.e., ξ=τ-NΔt1, when the radar acquires the synchronization frame sent by the main radar and the search ends; where N represents the parameter adjustment from the radar synchronization frame when acquisition is successful.

3. The synchronization method between millimeter-wave FMCW radar devices according to claim 1, characterized in that, During the frame start position positioning stage, a minimum interval time is set between frames. The minimum interval time is set to at least M linear frequency modulation signals, where M is an integer with a minimum value of 1. The initial synchronization of the frame start position between two radar devices includes the following process: The frame start positions of the radar and the main radar differ by k-1 linear frequency modulation (LFM) signals. During the time interval of the radar's (N-k+2) to (N-k+2+M-1)th LFM signal, the main radar does not transmit LFM signals. During the time intervals of other LFM signals, the main radar transmits LFM signals normally, and the measured values ​​are close. Based on the measurement results of each linear frequency modulated (LFM) signal within the synchronization frame from the radar end, the number of LFM signals differing between the start positions of the main radar and the slave radar frames is derived, thereby calculating the time adjustment amount (k-1)*(T). chirp +T idle ), and adjust the radar frame start time (k-1)*(T) chirp +T idle )+Δt3; Among them, T chirp T represents the duration of the linear frequency modulated signal; idle Δt3 represents the idle interval between adjacent linear frequency modulated (LFM) signals; Δt3 is a control parameter used to ensure that bidirectional measurability is possible between the two radar devices after time adjustment, and that a time margin is retained; N represents the total number of LFM signals in the synchronization frame.

4. The synchronization method between millimeter-wave FMCW radar devices according to claim 1, characterized in that, The process of synchronous confirmation includes: When switching from radar to radar synchronization confirmation state, the radar sends a communication frame carrying service information to the main radar. The main radar parses the communication frame to obtain the service information. The main radar returns a communication frame carrying service information in the same way. The radar parses the communication frame and switches to synchronization maintenance state to complete synchronization confirmation. The service information is radar synchronization information.

5. The synchronization method between millimeter-wave FMCW radar devices according to claim 4, characterized in that, The process of parsing the communication frame to obtain service information includes: The radar equipment receives communication frames carrying service information; The communication frame is mixed with the synchronization frame sent by itself to obtain the frequency difference between each linear frequency modulated signal in the communication frame and each linear frequency modulated signal in the local synchronization frame. The frequency difference corresponding to the standard linear frequency modulation (LFM) signal is Δf0, and the frequency difference corresponding to the service LFM signal is Δf. x The fixed frequency difference of the communication data is Δf u ; If the frequency difference Δf corresponds to the linear frequency modulation signal of the service x If the value is close to Δf0, it indicates that the communication data carried by the linear frequency modulation signal of this service is 0. If the value is close to the frequency difference Δf of the linear frequency modulation signal of this service, it indicates that the communication data carried by the linear frequency modulation signal of this service is 0. x Approaching Δf0+Δf u If , it means that the communication data carried by the linear frequency modulation signal of this service is 1; By analyzing all the service linear frequency modulation signals, the service information composed of communication data can be obtained.

6. The synchronization method between millimeter-wave FMCW radar devices according to claim 1, characterized in that, Synchronization error value between master radar and slave radar The calculation expression is as follows: ； ； ； in, This indicates the time difference measured by the main radar. Indicates the time difference measured from the radar end. This indicates the frequency difference measured at the main radar end. This represents the frequency difference measured by radar. The slope of the linear frequency modulated signal.

7. The synchronization method between millimeter-wave FMCW radar devices according to claim 1, characterized in that, The main radar and the slave radar also achieve integrated radar communication through the aforementioned communication frames, the process of which includes: The master radar and the slave radar complete initial synchronization through the synchronization frame. During the initial synchronization process, the master radar and the slave radar achieve coarse time synchronization between the radar devices through the synchronization frame, ensuring that the transmitted signals of the two radar devices enter the detection range of the other radar, and realizing basic two-way detection and radar communication. After the primary and secondary radars complete initial synchronization, the primary and secondary radars transmit service data through the standard linear frequency modulation (LFM) signal and the service LFM signal in the communication frame.

8. A synchronization system between millimeter-wave FMCW radar devices, characterized in that, For implementing the synchronization method between millimeter-wave FMCW radar devices as described in any one of claims 1-7, the system comprises: At least one main radar; At least one from radar; Initial synchronization module: used to achieve initial synchronization between the slave radar and the master radar; Synchronization confirmation module: used to realize synchronization confirmation between the slave radar and the master radar; Synchronization Maintenance Module: Used to maintain synchronization between the slave radar and the master radar.

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