Sequential staggered waveform transmitting and processing method and millimeter wave MIMO (Multiple Input Multiple Output) radar system
By dividing the radar frequency band into staggered segments and using sequential transmission and splicing processing, the velocity-angle coupling problem of TDM/BPM-MIMO radar is solved, improving angle measurement accuracy and detection efficiency, and reducing computational complexity and circuit loss.
Patent Information
- Application Number
- CN202511257485.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-04
- Publication Date
- 2025-10-31
AI Technical Summary
Existing TDM/BPM-MIMO radars suffer from velocity-angle coupling problems when measuring the angle of high-speed moving targets. Traditional solutions have high computational complexity and large circuit initialization losses, making them difficult to apply effectively in consumer products.
The frequency band of the radar system is divided into N consecutive and non-overlapping interleaved segments. During transmission, the first segment of each interleaved segment and the last segment of the previous segment are transmitted sequentially by the same antenna. After reception, MIMO de-processing is performed and the echo signal is spliced to avoid frequent initialization.
It effectively reduces velocity-angle coupling error, improves angle measurement accuracy, reduces circuit initialization loss, reduces computational complexity, and improves detection efficiency.
Smart Images
Figure CN120871040A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of radar technology, specifically to a method for transmitting and processing sequentially interleaved waveforms and a millimeter-wave MIMO radar system. Background Technology
[0002] Millimeter-wave multiple-input multiple-output (MIMO) radar is widely used in automotive, consumer electronics, and other fields due to its high-resolution angle measurement capabilities. In MIMO radar systems, to achieve waveform separation and obtain an equivalent virtual aperture, different transmit antennas (Tx) need to transmit according to certain orthogonal rules. Time division multiplexing (TDM), frequency division multiplexing (FDM), code division multiplexing (CDM), and random phase modulation (BPM) are common waveform orthogonal schemes.
[0003] Among these, TDM and BPM schemes are particularly suitable for cost-sensitive consumer-grade millimeter-wave radar products due to their advantages such as simple implementation structure, low cost, and low inter-channel interference. However, TDM and BPM schemes have an inherent drawback: since the waveforms from multiple transmitting antennas are transmitted sequentially in different time slices, for a high-speed moving target, it has already undergone displacement during different transmission slices. This displacement leads to inconsistencies in the phase of the echoes received in different slices, thus introducing significant angle measurement errors in subsequent angle estimation, i.e., a velocity-angle coupling problem. The faster the target's radial velocity, the greater the resulting angle measurement error.
[0004] To address this issue, traditional techniques typically require collecting multiple chirp frames in a slower time dimension for joint processing, such as using algorithms like the Keystone transform for velocity-angle decoupling. However, these algorithms generally suffer from extremely high computational complexity, difficulty in controlling computational accuracy, and poor performance in handling high-speed target velocity blurring (aliasing) scenes, making them difficult to deploy in consumer-grade products that require real-time processing and have limited computing power.
[0005] In existing technologies, some solutions attempt to address this problem at the waveform design level. For example, the "Switching Scheme for a FMCW-MIMO Radar on a Moving Platform" (2012 European Radar Conference) proposed a segmented and interleaved chirp structure. This structure significantly shortens the time interval between different Tx transmitted waveforms, thereby reducing phase drift caused by target displacement and mitigating coupling effects at the source. However, this scheme requires dividing the chirp into dozens or even hundreds of interleaved segments, and the radar transceiver circuit needs to be reinitialized after each interleaved segment is transmitted. Frequent initialization processes result in significant time overhead and energy consumption, severely reducing the radar's detection efficiency and data rate. This makes the scheme unacceptable for mass-produced products that prioritize high performance and low power consumption. Summary of the Invention
[0006] The present invention aims to propose a method for transmitting and processing sequentially interleaved waveforms and a millimeter-wave MIMO radar system to solve the velocity-angle coupling problem of TDM / BPM-MIMO radar, while avoiding excessive computational complexity and huge losses during circuit initialization.
[0007] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:
[0008] In a first aspect, the present invention provides a method for transmitting and processing sequentially interleaved waveforms, the method comprising:
[0009] The available frequency band of the radar system is divided into N consecutive and non-overlapping staggered segments, where N is an integer greater than 1;
[0010] The N interleaved segments are transmitted one by one in sequence according to the segment number. The transmission process for the kth interleaved segment is as follows: a MIMO waveform composed of multiple segments is transmitted, and the frequency of the MIMO waveform is swept within the frequency band of the kth interleaved segment.
[0011] The first segment of the MIMO waveform transmitted in the kth interleaved segment and the last segment of the MIMO waveform transmitted in the (k-1)th interleaved segment are transmitted sequentially from the same transmitting antenna, and the starting frequency of the frequency sweep of the first segment is equal to the ending frequency of the frequency sweep of the last segment.
[0012] The echo signal corresponding to each interleaving segment is received and processed. The echo signal of each interleaving segment is deMIMO processed to obtain the segmented waveform of M×Q channels in the segment, where M is the number of transmitting antennas and Q is the number of receiving antennas.
[0013] N segmented waveforms belonging to the same channel and originating from N different interleaved segments are spliced together in sequence according to segment number to form the complete echo waveform of that channel.
[0014] Furthermore, the MIMO waveform is a TDM-MIMO waveform or a BPM-MIMO waveform.
[0015] Furthermore, the available frequency band is a continuous frequency band without holes.
[0016] Furthermore, the modulation method used for the MIMO waveform is frequency-modulated continuous wave or step-frequency continuous wave.
[0017] In a second aspect, the present invention provides a millimeter-wave MIMO radar system comprising M transmitting antennas and Q receiving antennas, the system being configured to perform the sequential interleaved waveform transmission and processing method as described in the first aspect.
[0018] Thirdly, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the sequential interleaved waveform transmission and processing method as described in the first aspect.
[0019] The beneficial effects of this invention are as follows: The sequential interlaced waveform transmission and processing method and millimeter-wave MIMO radar system provided by this invention, by dividing the complete chirp into N interlaced segments and transmitting them sequentially, shortens the duration of each transmission segment to 1 / N of the original duration. The displacement of the target within a single segment and the resulting phase error are also reduced to 1 / N of the original duration, thereby effectively reducing velocity-angle coupling error and significantly improving the angle measurement accuracy in high-speed scenarios. Since the coupling error is significantly suppressed at the waveform level, the back-end signal processing can eliminate or greatly simplify complex velocity-angle decoupling operations (such as Keystone transform), thereby avoiding excessive computational complexity and significantly reducing the system's demand for digital signal processing computing power. Furthermore, the first segment of the next interlaced segment seamlessly connects to the last segment of the previous interlaced segment, utilizing the circuit state at the end of the previous segment, thereby eliminating most unnecessary circuit re-initialization processes, greatly reducing circuit initialization losses, and improving detection efficiency. Attached Figure Description
[0020] Figure 1 A waveform timing diagram of the transmit segments of a traditional TDM-MIMO radar system;
[0021] Figure 2 This is a schematic diagram illustrating the velocity-angle coupling caused by a traditional TDM-MIMO radar system.
[0022] Figure 3A waveform timing diagram illustrating the segmented and interleaved transmission of an existing MIMO radar system;
[0023] Figure 4 A flowchart illustrating the sequential interleaved waveform transmission and processing method provided in this embodiment;
[0024] Figure 5 This is a waveform timing diagram of the sequentially interleaved transmission segments of the MIMO radar system provided in the embodiment. Detailed Implementation
[0025] Figure 1 This diagram illustrates the waveform timing of a transmit slice in a conventional TDM-MIMO radar system. Please refer to [link / reference]. Figure 1 In a traditional TDM-MIMO radar system, each transmitting antenna has its own dedicated time slot for transmission. During the time slot corresponding to segment 0, only the first transmitting antenna operates, transmitting a complete chirp signal from fLow (low-frequency boundary) to fHigh (high-frequency boundary). After segment 0 ends, the second transmitting antenna starts operating, similarly transmitting a complete chirp signal from fLow to fHigh. This process continues, and if there are M transmitting antennas, M segments are needed to form a complete MIMO transmission cycle.
[0026] Please see Figure 2 In the radar coordinate system of the above scheme, when the target moves, due to the different transmission times of the different transmitting antenna segments, the target moves a distance within the time difference, which will generate an additional Doppler phase term. This additional phase is mixed into the original azimuth phase, resulting in inconsistent echo phases received by different segments, thus introducing significant angle measurement errors in subsequent angle estimation and generating velocity-angle coupling problems.
[0027] Figure 3 This diagram illustrates the waveform timing of segmented and interleaved transmission in an existing MIMO radar system. Please refer to [link / reference]. Figure 3Existing technologies employ a segmented and interleaved chirp structure, dividing a complete chirp (from fLow to fHigh) into N segments, each with an extremely short duration. While this approach reduces target displacement and phase error within a single segment, the phase-locked loop (PLL) circuit of the millimeter-wave radar transmitter requires a frequency sweep and setup time. This process involves reconfiguring parameters such as the new starting frequency and slope, and adjusting the internal voltage-controlled oscillator to lock and stabilize the output frequency at the specified new starting frequency. This process generates frequency overshoot and jitter, requiring a period of stabilization before effective linear frequency modulation (LFM) signals can be transmitted. Furthermore, when the receiver channel restarts or significantly adjusts its gain for a new interleaving segment, its internal high-pass filter (HPF) and low-pass filter (LPF) undergo a transient response. The filters cannot instantly establish a stable operating state and require a certain stabilization time to eliminate ringing and bring the output to a certain tolerance range of the final steady-state value. During this period, the output signal is invalid. Therefore, after each interleaved transmission, the radar transceiver circuit needs to be reinitialized, and additional time needs to be allowed for the transmit PLL to lock and for the receiver filter to stabilize. Frequent initialization processes result in significant time overhead and energy loss, severely reducing the radar's detection efficiency and data rate. Furthermore, the filter stabilization time also wastes effective detection time and energy.
[0028] To address the velocity-angle coupling problem in TDM / BPM-MIMO radar systems while avoiding excessive computational complexity and significant losses during circuit initialization, this invention proposes a technical solution.
[0029] In this invention, firstly, the complete, long chirp (from fLow to fHigh) is divided into N consecutive and non-overlapping interleaved segments. Each interleaved segment scans only 1 / N of the total bandwidth, directly shortening the duration of each transmission segment. The displacement of the target within a single segment and the resulting phase error are also reduced to 1 / N of the original value, effectively reducing velocity-angle coupling error and significantly improving angle measurement accuracy in high-speed scenarios. Secondly, the starting frequency of the k-th interleaved segment is the ending frequency of the (k-1)-th interleaved segment. The entire transmission waveform is continuously scanned in frequency without any jumps or backsliding. The antenna responsible for activating the first segment of the k-th interleaved segment transmission and the antenna responsible for activating the last segment of the (k-1)-th interleaved segment transmission... The antenna is the same, which ensures that the antenna switching point also occurs at a time of frequency continuity. Since the frequency and antenna state are sequential, the radar's RF front-end (especially the PLL) can work continuously like a complete chirp, naturally scanning from the end frequency of the previous interleaving segment to the end frequency of the next interleaving segment without the need for a time-consuming initialization process, completely eliminating the huge time and energy loss caused by frequent initialization. Finally, the echo of each interleaving segment is subjected to independent deMIMO processing to obtain M×Q virtual channel data in each segment. Data from N different interleaving segments belonging to the same virtual channel are spliced together in order of frequency from low to high, thereby reconstructing a complete, high-bandwidth chirp signal in the digital domain.
[0030] The technical solutions in this embodiment will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.
[0031] Figure 4 A flowchart illustrating a method for transmitting and processing sequentially interleaved waveforms is shown below. Please refer to [link / reference]. Figure 1 The method includes the following steps:
[0032] Step 1: Divide the available frequency bands of the radar system into N consecutive and non-overlapping staggered segments, where N is an integer greater than 1.
[0033] The available frequency band is a continuous frequency band without holes, ranging from fLow (low-frequency boundary) to fHigh (high-frequency boundary).
[0034] Please see Figure 5 In this embodiment, three equal segmentation points are set between fLow and fHigh, namely fLow×0.75+fHigh×0.25, fLow×0.5+fHigh×0.5, and fLow×0.25+fHigh×0.75. Based on these segmentation points, the available frequency band is divided into four continuous and non-overlapping interleaved segments, wherein:
[0035] The first interlacing segment is: fLow ~ (fLow × 0.75 + fHigh × 0.25);
[0036] The second alternation segment is: (fLow×0.75+fHigh×0.25)~(fLow×0.5+fHigh×0.5);
[0037] The third alternation segment is: (fLow×0.5+fHigh×0.5)~(fLow×0.25+fHigh×0.75);
[0038] The fourth interleaved segment is: (fLow×0.25+fHigh×0.75)~fHigh.
[0039] All interleaved segments cover frequency bands that do not overlap and, when combined, precisely cover fLow to fHigh. That is, the starting frequency of each interleaved segment is immediately followed by the ending frequency of the previous interleaved segment, making the entire transmission process continuous, seamless, and without any jumps in frequency, thus achieving frequency extension.
[0040] The radar system in this embodiment includes multiple transmitting antennas. Figure 5 Each segment corresponds to a different transmitting antenna. For example, segment 0 represents the transmission period of the first transmitting antenna, and segment 1 represents the transmission period of the second transmitting antenna.
[0041] Step 2: Transmit the N interleaved segments one by one in sequence according to the segment number. The transmission process for the kth interleaved segment is as follows: transmit a MIMO waveform composed of multiple segments, and sweep the frequency of the MIMO waveform within the frequency band of the kth interleaved segment.
[0042] The first segment of the MIMO waveform transmitted in the k-th interleaved segment and the last segment of the MIMO waveform transmitted in the (k-1)-th interleaved segment are transmitted sequentially from the same transmitting antenna, and the starting frequency of the sweep of the first segment is equal to the ending frequency of the sweep of the last segment.
[0043] Please see Figure 5 When transmitting MIMO waveforms in multiple interleaved segments, the last segment (segment 1) of the first interleaved segment is transmitted by the second transmitting antenna, and the first segment (segment 1) of the second interleaved segment is also transmitted by the second transmitting antenna. That is, the antenna is continuously transmitted from the end of one interleaved segment to the beginning of the next interleaved segment, thus achieving antenna continuity.
[0044] The MIMO waveform can be a TDM-MIMO waveform or a BPM-MIMO waveform, and the modulation method used for the MIMO waveform can be a frequency modulated continuous wave (FMCW) or a stepped frequency continuous wave (SFCW).
[0045] Since the frequency and antenna are sequential, the radar's PLL circuit works continuously and stably, naturally scanning from one frequency band to the next without needing to stop, reset, or relock to fLow, thus completely eliminating the huge time and energy losses caused by frequent initialization.
[0046] Step 3: Receive and process the echo signal corresponding to each interleaved segment, and perform MIMO deprocessing on the echo signal of each interleaved segment to obtain the segmented waveform of M×Q channels in that segment, where M is the number of transmitting antennas and Q is the number of receiving antennas.
[0047] It can be understood that the receiver performs independent deMIMO processing on the echo of each interleaved segment, obtaining M×Q virtual channel data within each segment. That is, the mixed signal received in each interleaved segment is separated and the virtual channel signal corresponding to each transmitting antenna is reconstructed.
[0048] Specifically, at each receiving antenna of the radar, the received signal is the superposition of the echoes reflected from all transmitting antennas. For a system with Q receiving antennas, Q mixed echo signals will be obtained during the reception time of any interleaving segment. The essence of MIMO de-processing is waveform separation. Since the transmitted waveforms are orthogonal (whether TDM or BPM), the receiver can utilize this orthogonality to separate the components belonging to different transmitting antennas in the mixed signal. After completing MIMO de-processing, for the current interleaving segment, we obtain data from M×Q virtual channels. For example, a 3Tx4Rx radar system, after MIMO de-processing, will obtain signals from 3x4=12 virtual channels.
[0049] Step 4: Combine the N segmented waveforms belonging to the same channel and from N different interleaved segments in order of segment number to form the complete echo waveform of the channel.
[0050] Understandably, this step is used to stitch together all the scattered segmented waveforms transmitted by the same antenna in frequency order, ultimately forming a complete high-bandwidth signal for each virtual channel, thereby reconstructing a complete, high-bandwidth Chirp signal in the digital domain.
[0051] Specifically, after N interleaved transmission and reception segments, a total of N × M × Q segmented waveforms are obtained. For a given virtual channel, a small segment of its signal is found from the first segment, the next small segment from the second segment, and so on, until the last segment is found from the Nth segment. Then, in the digital domain, the N segmented waveforms belonging to the same virtual channel are concatenated end-to-end according to the segment number order (k=1, 2, 3, ..., N). Because this embodiment uses a frequency-delayed design during transmission, these segmented waveforms are completely continuous and seamless in frequency. After splicing, a completely new chirp signal is obtained. This chirp has a bandwidth from fLow to fHigh, thus possessing complete distance resolution and can be used for final high-resolution processing.
[0052] In summary, the sequential interleaved waveform transmission and processing method provided in this embodiment, by dividing the complete chirp into N interleaved segments and transmitting them sequentially, shortens the duration of each transmission segment to 1 / N of the original duration. The displacement of the target within a single segment and the resulting phase error are also reduced to 1 / N of the original duration, thereby effectively reducing velocity-angle coupling errors and significantly improving angle measurement accuracy in high-speed scenarios. Since the coupling error is significantly suppressed at the waveform level, the back-end signal processing can eliminate or greatly simplify complex velocity-angle decoupling operations (such as Keystone transform), thus avoiding excessive computational complexity and significantly reducing the system's demand for digital signal processing computing power. Furthermore, the first segment of the next interleaved segment seamlessly connects to the last segment of the previous interleaved segment, utilizing the circuit state at the end of the previous segment, thereby eliminating most unnecessary circuit re-initialization processes, greatly reducing circuit initialization losses, and improving detection efficiency. This embodiment is compatible with existing TDM-MIMO and BPM-MIMO waveform structures. Without changing the antenna hardware design, it can improve system performance without significantly increasing system complexity and cost. It is easy to upgrade and apply on existing product platforms. It is also applicable to various modulation methods such as FMCW and SFCW, and requires continuous frequency bands, which meets the application scenarios of most millimeter-wave radars. It has good versatility and scalability.
[0053] Based on the above technical solution, this embodiment also proposes a millimeter-wave MIMO radar system, including M transmitting antennas and Q receiving antennas. The system is configured to perform the sequential interleaved waveform transmission and processing method described in the embodiment.
[0054] It is understood that since the millimeter-wave MIMO radar system described in this embodiment is a system for implementing the sequential interleaved waveform transmission and processing method described in the embodiment, the system disclosed in the embodiment is relatively simple to describe because it corresponds to the method disclosed in the embodiment. For relevant parts, please refer to the description of the method, and it will not be repeated here.
[0055] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.
Claims
1. A method for transmitting and processing sequentially interleaved waveforms, characterized in that, The method includes: The available frequency band of the radar system is divided into N consecutive and non-overlapping staggered segments, where N is an integer greater than 1; The N interleaved segments are transmitted one by one in sequence according to the segment number. The transmission process for the kth interleaved segment is as follows: a MIMO waveform composed of multiple segments is transmitted, and the frequency of the MIMO waveform is swept within the frequency band of the kth interleaved segment. The first segment of the MIMO waveform transmitted in the kth interleaved segment and the last segment of the MIMO waveform transmitted in the (k-1)th interleaved segment are transmitted sequentially from the same transmitting antenna, and the starting frequency of the frequency sweep of the first segment is equal to the ending frequency of the frequency sweep of the last segment. The echo signal corresponding to each interleaving segment is received and processed. The echo signal of each interleaving segment is deMIMO processed to obtain the segmented waveform of M×Q channels in the segment, where M is the number of transmitting antennas and Q is the number of receiving antennas. N segmented waveforms belonging to the same channel and originating from N different interleaved segments are spliced together in sequence according to segment number to form the complete echo waveform of that channel.
2. The method for transmitting and processing sequentially interleaved waveforms according to claim 1, characterized in that, The MIMO waveform is either a TDM-MIMO waveform or a BPM-MIMO waveform.
3. The method for transmitting and processing sequentially interleaved waveforms according to claim 1, characterized in that, The available frequency band is a continuous frequency band without holes.
4. The method for transmitting and processing sequentially interleaved waveforms according to claim 1, characterized in that, The MIMO waveform uses either frequency-modulated continuous wave or stepped-frequency continuous wave modulation.
5. A millimeter-wave MIMO radar system, comprising M transmitting antennas and Q receiving antennas, characterized in that, The system is configured to perform the sequential interleaved waveform transmission and processing method as described in any one of claims 1 to 4.
6. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the sequential interleaved waveform transmission and processing method as described in any one of claims 1 to 4.