WO2023072111A1 - Autonomous-driving-oriented millimeter wave orthogonal waveform optimization method, and vehicle-borne radar system - Google Patents

Autonomous-driving-oriented millimeter wave orthogonal waveform optimization method, and vehicle-borne radar system Download PDF

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WO2023072111A1
WO2023072111A1 PCT/CN2022/127505 CN2022127505W WO2023072111A1 WO 2023072111 A1 WO2023072111 A1 WO 2023072111A1 CN 2022127505 W CN2022127505 W CN 2022127505W WO 2023072111 A1 WO2023072111 A1 WO 2023072111A1
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frequency modulation
signal
optimization method
radar system
millimeter
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French (fr)
Chinese (zh)
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施婷婷
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瞬联软件科技（北京）有限公司
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/93—Radar or analogous systems specially adapted for specific applications for anti-collision purposes
    • G01S13/931—Radar or analogous systems specially adapted for specific applications for anti-collision purposes of land vehicles
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/06—Systems determining position data of a target
    • G01S13/08—Systems for measuring distance only
    • G01S13/10—Systems for measuring distance only using transmission of interrupted, pulse modulated waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/28—Details of pulse systems
    • G01S7/282—Transmitters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/28—Details of pulse systems
    • G01S7/285—Receivers

Definitions

  • the present invention relates to a millimeter wave quadrature waveform optimization method, in particular to a millimeter wave quadrature waveform optimization method based on positive and negative frequency modulation and phase encoding for the needs of automatic driving, and to a vehicle-mounted radar system using the method, It belongs to the field of automatic driving technology.
  • the global auto industry has gradually formed a consensus that autonomous driving represents the future development direction of the auto industry.
  • the on-board sensing technology represented by the on-board radar system is the main means of data acquisition such as vehicle environment perception and traffic operation environment, and plays an irreplaceable and important role.
  • the automotive forward collision avoidance radar is a microwave radar sensor dedicated to the motor vehicle driver assistance system (ADAS), mainly used for active collision avoidance or pre-collision system (Precrash system), automatic emergency braking system (AEB) ), Adaptive Cruise Control (ACC), Blind Spot Detection (BSD), Front Collision Warning (FCW), Lane Change Assist (LCA), Departure Warning System (LDWS), Safe Distance Warning (TTC), Rear Cross Traffic Alarm (RCTA), assisting the motor vehicle to complete the obstacle avoidance function.
  • ADAS motor vehicle driver assistance system
  • Precrash system pre-collision system
  • AEB automatic emergency braking system
  • ACC Adaptive Cruise Control
  • BSD Blind Spot Detection
  • FCW Front Collision Warning
  • FCW Lane Change Assist
  • LWA Lane Change Assist
  • LDWS Departure Warning System
  • TTC Rear Cross Traffic Alarm
  • RCTA Rear Cross Traffic Alarm
  • automotive forward collision avoidance radar mostly adopts MIMO (Multi-Input Multi-Output) antenna design, that is, multiple transmission channels are used to transmit LFMCW (Linear Frequency Modulation Continuous Wave) signals in time division.
  • MIMO Multi-Input Multi-Output
  • LFMCW Linear Frequency Modulation Continuous Wave
  • the existing time-division MIMO technology is not specially developed for the requirements of automatic driving technology, and there are many shortcomings in specific performance.
  • technicians have carried out a lot of research work on reducing the detection cycle and optimizing the detection waveform.
  • a method for optimizing chirp continuous wave waveform under MIMO technology is disclosed.
  • the primary technical problem to be solved by the present invention is to provide a millimeter wave orthogonal waveform optimization method for automatic driving.
  • Another technical problem to be solved by the present invention is to provide a vehicle-mounted radar system using the method.
  • a millimeter-wave orthogonal waveform optimization method for automatic driving including the following steps:
  • the first transmission channel of the vehicle-mounted radar system transmits a positive frequency modulation signal
  • the second transmission channel transmits a negative frequency modulation signal
  • the positive frequency modulation signal and the negative frequency modulation signal are transmitted simultaneously and are orthogonal to each other;
  • the multi-channel receiving channel of the vehicle radar system simultaneously receives the positive frequency modulation signal and the negative frequency modulation signal, and after the power pre-amplification, the power is divided into two channels, and the two reference signals are respectively used for matching filtering;
  • the data of each receiving channel undergoes pulse Doppler accumulation, target detection, and target angle measurement in sequence.
  • the data in multiple frequency modulation cycles are subjected to Doppler-dimensional fast Fourier transform to form Range image data, based on which the azimuth angle of the target is estimated, and the angle measurement of the target by the vehicle radar system is realized.
  • the positive frequency modulation signal is divided into a plurality of sub-pulse signals, and a corresponding phase code is superimposed on the initial phase of each sub-pulse signal.
  • the expression of the positive frequency modulation signal is as follows:
  • A represents the signal modulation amplitude
  • i ⁇ 1 ⁇ 52 ⁇ represents the i-th sub-pulse
  • rect( ⁇ ) represents the rectangular function
  • T represents the time length of the FM cycle
  • B represents the bandwidth
  • Vc i represents the i-th sub-pulse of the Barker code sequence value
  • K represents the frequency modulation slope of the linear frequency modulation continuous wave signal
  • no phase encoding is performed on the negative FM signal.
  • the expression of the negative frequency modulation signal is as follows:
  • A represents the signal modulation amplitude
  • i ⁇ 1 ⁇ 52 ⁇ represents the i-th sub-pulse
  • rect( ⁇ ) represents the rectangular function
  • T represents the time length of the frequency modulation cycle
  • B represents the bandwidth
  • Bc i represents the i-th sub-pulse of the Barker code sequence value
  • K represents the frequency modulation slope of the linear frequency modulation continuous wave signal
  • the expressions of the two reference signals REF 0 and REF 1 are as follows:
  • the expression of the distance image data is as follows:
  • the reference signal is a power division coupled signal of the transmit signal.
  • a vehicle radar system which adopts the above-mentioned millimeter wave orthogonal waveform optimization method.
  • the millimeter-wave orthogonal waveform optimized by the method of the present invention can achieve higher waveform isolation, which is much higher than the dynamic measurement range of general radar, and can fully meet the needs of vehicle-mounted radar systems, especially Application requirements of forward collision avoidance radar for automobiles.
  • the present invention only needs less detection time to achieve the same angular resolution; compared with the common simultaneous MIMO technology, the present invention has a higher distance between channels and reduces the distance generated by the target cross-distance unit. Accumulate losses and have good commercial application value.
  • Fig. 1 is the schematic diagram of the vehicle-mounted radar system adopting the millimeter-wave orthogonal waveform optimization method provided by the present invention
  • Fig. 2 is a schematic diagram of phase encoding of positive frequency modulation signal S_0(t) and negative frequency modulation signal S_1(t);
  • Fig. 3 is the time-frequency diagram of positive frequency modulation signal S_0(t) and negative frequency modulation signal S_1(t);
  • Fig. 4 is the continuous wave signal schematic diagram of the zigzag band frequency modulation and phase coding that each transmission channel transmits;
  • Figure 5 is a schematic diagram of the impact of the number of waveform encoding cycles on the isolation index
  • Fig. 6 is a schematic diagram of the simulated results of range image signals of channels CH 0 and CH N-1 obtained by calculating the orthogonal waveform optimized according to the present invention.
  • the existing time-division MIMO technology is not specially developed for the requirements of automatic driving technology, and there are many shortcomings in specific performance.
  • the traditional automotive forward collision avoidance radar mostly adopts time-division MIMO technology, that is, M (M is a positive integer, the same below) transmission channels transmit signals sequentially, and the receiving channel receives target echoes generated by different transmission signals in time division.
  • M M is a positive integer, the same below
  • the present invention firstly provides a millimeter wave orthogonal waveform optimization method for automatic driving requirements.
  • N is a positive integer
  • the reason for designing only 2 transmission signals here is that when the number of transmission channels is greater than 2, the signal isolation advantage brought by the positive and negative frequency modulation signals will not be able to be used, and the isolation of the generated orthogonal signals will be reduced.
  • the angular resolution of the radar using MIMO technology is determined by M*N, it is a more economical choice to expand the number of receiving channels with lower cost and lower heat consumption.
  • the voltage ratio of the mismatch signal and the matching signal is defined as the waveform isolation, which evaluates the isolation level of the vehicle radar system.
  • the invention improves the waveform isolation between the two transmission signals by optimizing the orthogonal characteristic of the transmission signal, thereby improving the angle resolution capability of the vehicle radar system on the premise of maintaining the target detection period.
  • the specific implementation process of the optimization method is described in detail below:
  • FIG. 1 is a schematic diagram of a vehicle-mounted radar system adopting the millimeter wave orthogonal waveform optimization method provided by the present invention.
  • the vehicle radar system used includes 2 transmission channels (including transmission antennas TX 0 , TX 1 ) and N reception channels (abbreviated as 2 transmissions and N receptions). Simultaneous MIMO radar.
  • the two transmitting channels have frequency modulation and phase modulation capabilities respectively;
  • the distance between the transmitting antenna and the receiving antenna is 2N times the wavelength ⁇ of the transmitting signal.
  • the two transmission channels start to work at the same time, and waveform modulation is performed on the positive frequency modulation signal and the negative frequency modulation signal respectively transmitted by the two transmission channels.
  • the positive frequency modulation signal and the negative frequency modulation signal are orthogonal to each other.
  • the two transmission signals need to be modulated by phase encoding.
  • the specific waveform modulation method can be as follows: the first transmission channel TX 0 is designed as a positive frequency modulation signal S_0(t), the frequency modulation slope K is the ratio of the bandwidth B to the frequency modulation period (referred to as Prt), and the signal within one Prt period Divided into several sub-pulse signals.
  • the number of sub-pulses needs to be an integer multiple of 13, and every 13 sub-pulses is 1 encoding period.
  • the encoding method of several cycles depends on the specific radar waveform design.
  • the isolation metrics have less impact.
  • the isolation achieved by the 4-cycle encoding method is the best.
  • A represents the signal modulation amplitude
  • i ⁇ 1 ⁇ 52 ⁇ represents the i-th sub-pulse
  • rect( ⁇ ) represents the rectangular function
  • T represents the time length of the FM cycle (Prt)
  • B represents the bandwidth
  • Bc i is The i-th value of the Barker code sequence
  • K represents the frequency modulation slope of the LFMCW (Linear Frequency Modulation Continuous Wave) signal
  • the schematic diagram of the phase encoding of the positive FM signal S_0(t) is shown in the upper part of the figure, and the schematic diagram of the phase encoding of the negative FM signal S_1(t) is shown in the lower part of the figure.
  • One encoding cycle is the time length of a Prt, the minimum encoding time unit is ⁇ t, and ⁇ t is the time length T of Prt
  • the time-frequency schematic diagram of the positive frequency modulation S_0(t) signal is shown in the left half of Fig. 3.
  • the positions of f 1 and f 2 only indicate which is the start frequency and which is the stop frequency, and the actual values are the same.
  • the second transmit channel TX 1 is designed as a negative frequency modulation signal S_1(t), and the frequency modulation slope is the ratio of the bandwidth B to the cycle time Prt.
  • the negative FM signal S_1(t) is not phase-encoded, and the expression is shown in formula (2):
  • the negative frequency modulation signal S_1(t) is also an LFMCW signal, and its time-frequency schematic diagram is shown in the right half of Fig. 3 .
  • the FM frequency is FM from f 2 to f 1
  • the bandwidth B
  • the time is 1 FM cycle, that is, the time length T of 1 Prt.
  • each transmit channel transmits a zigzag LFMCW signal with frequency modulation and phase encoding, and performs binary phase encoding on the LFMCW signal within a single Prt period.
  • the Barker code with a length of 13 is (1, 1, 1, 1, 1, -1, -1, 1, 1, -1, 1, -1, 1), which is expanded to 4 times the length to generate a 52-bit Barker code, which can be expressed as:
  • the phase is - ⁇ or ⁇ according to the Barker code, and the sub-pulse with the phase of ⁇ is recorded as "1", and the sub-pulse with the phase of - ⁇ is recorded as "-1".
  • the number of equal parts to divide the frequency modulation period (Prt) can be determined by simulation in combination with the specific radar waveform design, and it only needs to be guaranteed to be an integer multiple of 13.
  • the 2 transmission channels TX 0 and TX 1 transmit signals at the same time, and the 2 transmission signals reach the N receiving channels after being reflected by the target, and the N receiving channels RX 0 ⁇ RX N receive signals at the same time.
  • the 2 channels are copied (power divided) and then the 2 channels of reference signals TEF 0 and REF 1 are used for matched filtering.
  • the engineering implementation is to use a mixer to mix the frequency, and the source of the reference signal can be the power division coupling signal of the transmitted signal as the local oscillator signal. Utilizing the orthogonal characteristics of the 2 transmission signals, 8 reception signals with spatial resolution can be obtained, so as to realize the radar signal detection of the vehicle radar system.
  • the echo delay time of the two transmitted signals after being reflected by the target at a distance R is c is the speed of light
  • the echo signal R 0 (t) received by the receiving channel 0 contains both TX 0 and TX 1 transmission signals, which can be specifically expressed as:
  • N channels receive signals at the same time.
  • the received signal phase of the RX 0 ⁇ RX N channel differs by a fixed value, and the fixed deviation phase is used to estimate The deviation angle of the target compared to the normal direction of the radar antenna, the more channels, the higher the angular resolution.
  • the N receiving channels receive signals at the same time, similar to the signal processing method of the RX 0 channel, the distance image signals CH 0 (f) ⁇ CH 2N-1 (f) can be obtained in sequence.
  • the specific calculation method is:
  • the data of each channel undergoes PD (Pulse Doppler) accumulation, target detection, and target angle measurement in sequence.
  • PD Pulse Doppler
  • the data of multiple Prts are subjected to FFT (Fast Fourier Transform) in the Doppler dimension, which can be
  • FFT Fast Fourier Transform
  • the moving target is separated from the stationary target to form range image data.
  • the signals at the same positions of CH 1 (f) to CH 2N-1 (f) are taken out to obtain complex signals of 2N channels of targets.
  • the complex signal contains a fixed phase difference formed by the direction angle of the target deviating from the normal line of the antenna.
  • the deflection angle of the target deviating from the normal line of the radar antenna can be calculated, and the target’s angle can be estimated accordingly.
  • Azimuth angle to realize the angle measurement of the vehicle radar system to the target.
  • the target detection method can use the traditional Ca-Cfar moving target detection algorithm to extract the local peak point on the range Doppler plane, and the distance and Doppler position corresponding to the local peak point can be calculated Detect the distance and speed of the target. Finally, FFT is performed according to the peak point data of 2N channels, and the deviation angle of the target relative to the normal line of the radar antenna can be calculated.
  • the above method is a commonly used MIMO radar signal processing method, which will not be described in detail here.
  • the time-domain signals of CH 0 and CH N can be obtained, and the one-dimensional range image can be obtained by performing FFT conversion to the frequency domain. information, the calculation method is expressed as:
  • the waveform isolation is defined as the ratio of the correct matching signal to the waveform leakage power of the adjacent transmission channel, specifically:
  • the meaning of the waveform isolation index is the logarithm of the ratio of the power of the matched signal to the power of the adapted signal for a target signal at an echo point. This index can be used to evaluate the quality of the orthogonal waveform design, that is, the higher the waveform isolation index, the smaller the interference between MIMO radar channels.
  • the present invention takes the following radar waveform parameter design as an example to simulate the waveform isolation index that can be achieved by using the positive and negative frequency modulation plus 52-bit intrapulse phase encoding method proposed in the embodiment of the present invention.
  • serial number parameter name parameter value Parameter interpretation 1 m 2 Number of transmit channel hardware 2 N 4 Number of receiving channel hardware 3 Prt 520us FM cycle 4 R 300m target distance 5 A 1V signal amplitude
  • the isolation result simulation is performed, and the simulation result is shown in FIG. 6 .
  • the waveform isolation index can be obtained as 60dB, which is much higher than the dynamic measurement range of general radars, and can fully meet the needs of vehicle radars. systems, especially automotive forward collision avoidance radar. It can be seen from this that the frequency quadrature combined with phase quadrature waveform optimization method provided by the present invention can significantly improve the waveform isolation of millimeter wave signals.
  • the high-isolation transmit waveform optimized by the method of the present invention can replace the commonly used time-division MIMO technology.
  • the commonly used time-division MIMO technology uses a time-sharing method to sequentially open the signals of the transmission channels to avoid signal crosstalk between two transmission channels.
  • the two transmission signals can be opened simultaneously, while the angular resolution of the forward collision avoidance radar of the automobile is kept constant, the detection period is significantly shortened (for example, time-division MIMO technology One-half of the required time), and reduce the cumulative loss produced by the target cross-distance unit, which has good commercial application value.

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Abstract

An autonomous-driving-oriented millimeter wave orthogonal waveform optimization method, and a corresponding vehicle-borne radar system. The optimization method comprises the following steps: a first transmitting channel of a vehicle-borne radar system transmitting a positive frequency modulation signal, and a second transmitting channel thereof transmitting a negative frequency modulation signal, wherein the positive frequency modulation signal and the negative frequency modulation signal are simultaneously transmitted and are orthogonal to each other; a plurality of receiving channels simultaneously receiving the signals, which are transmitted by the first transmitting channel and the second transmitting channel, performing power pre-amplification on the signals and then performing power division on the signals to form two paths of signals, and respectively using two reference signals to perform matched filtering; sequentially performing PD accumulation, target detection and target angle measurement on data of each receiving channel, wherein during the PD accumulation, FFT in the Doppler dimension is performed on the data within a plurality of frequency modulation periods, so as to form range profile data, and according to the distance image data, and estimating an azimuth angle of a target, so as to realize angle measurement performed by a vehicle-borne radar system on the target. By means of the method, the waveform isolation between transmitted signals is improved, thereby improving the angular resolution of a vehicle-borne radar system.

Description

面向自动驾驶的毫米波正交波形优化方法及车载雷达***Optimization method of millimeter wave orthogonal waveform and vehicle radar system for autonomous driving 技术领域technical field
本发明涉及一种毫米波正交波形优化方法，尤其涉及一种面向自动驾驶的需要，基于正、负调频和相位编码的毫米波正交波形优化方法，同时涉及采用该方法的车载雷达***，属于自动驾驶技术领域。The present invention relates to a millimeter wave quadrature waveform optimization method, in particular to a millimeter wave quadrature waveform optimization method based on positive and negative frequency modulation and phase encoding for the needs of automatic driving, and to a vehicle-mounted radar system using the method, It belongs to the field of automatic driving technology.
背景技术Background technique
当前，全球汽车行业逐渐形成共识，认为自动驾驶代表了未来汽车行业的发展方向。在自动驾驶技术中，以车载雷达***为代表的车载传感技术是车辆环境感知和交通运行环境等数据采集的主要手段，发挥着不可替代的重要作用。At present, the global auto industry has gradually formed a consensus that autonomous driving represents the future development direction of the auto industry. In the autonomous driving technology, the on-board sensing technology represented by the on-board radar system is the main means of data acquisition such as vehicle environment perception and traffic operation environment, and plays an irreplaceable and important role.
在车载雷达***中，汽车前向防撞雷达是专用于机动车驾驶辅助***(ADAS)的微波雷达传感器，主要用于主动碰撞避免或预碰撞***(Precrash system)、自动紧急制动***(AEB)、自适应巡航***(ACC)、盲点检测(BSD)、前防追尾预警(FCW)、车道改变辅助(LCA)、偏移报警***(LDWS)、安全车距预警(TTC)、后方横向交通告警(RCTA)，辅助机动车完成障碍物规避功能。由于汽车实际行驶的路况错综复杂，需要汽车前向防撞雷达具备高分辨率、高刷新率(低检测周期)，这样才能对汽车行驶环境进行更精确、更快速的环境感知。In the automotive radar system, the automotive forward collision avoidance radar is a microwave radar sensor dedicated to the motor vehicle driver assistance system (ADAS), mainly used for active collision avoidance or pre-collision system (Precrash system), automatic emergency braking system (AEB) ), Adaptive Cruise Control (ACC), Blind Spot Detection (BSD), Front Collision Warning (FCW), Lane Change Assist (LCA), Departure Warning System (LDWS), Safe Distance Warning (TTC), Rear Cross Traffic Alarm (RCTA), assisting the motor vehicle to complete the obstacle avoidance function. Due to the intricate road conditions on which the car actually drives, it is necessary for the car's forward collision avoidance radar to have high resolution and high refresh rate (low detection cycle), so as to have a more accurate and faster environmental perception of the car's driving environment.
现有技术中，汽车前向防撞雷达多采用MIMO(Multi-Input Multi-Output)天线设计，即利用多个发射通道分时发送LFMCW(线性调频连续波)信号。但是，现有的时分MIMO技术并不是专门针对自动驾驶技术的需求开发的，在具体性能上存在很多不足。为此，技术人员在降低检测周期、优化检测波形等方面开展了很多研究工作。例如，在申请号为201910711214.2的中国发明申请中，公开了一种MIMO技术下的线性调频连续波波形优化方法。它首先在发射线性调频连续波的基础上，给每一个发射端发出波形的每一个脉冲添加一个随机相位，使发射波形在多普勒维得以分离，其次以波形的主瓣增益、主副瓣比、主瓣宽度等作为评价指标对波形进行优化，通过模式搜索方法计算出使评价指标达到最优的相位序列，代入到发射波形中实现优化。但是，当目标速度足够大时，导致 不同的发射波形到达目标之间产生相位差，最终导致在测角度过程中目标出现***，波形优化效果受到影响。In the prior art, automotive forward collision avoidance radar mostly adopts MIMO (Multi-Input Multi-Output) antenna design, that is, multiple transmission channels are used to transmit LFMCW (Linear Frequency Modulation Continuous Wave) signals in time division. However, the existing time-division MIMO technology is not specially developed for the requirements of automatic driving technology, and there are many shortcomings in specific performance. To this end, technicians have carried out a lot of research work on reducing the detection cycle and optimizing the detection waveform. For example, in the Chinese invention application with application number 201910711214.2, a method for optimizing chirp continuous wave waveform under MIMO technology is disclosed. It first adds a random phase to each pulse of the waveform sent by each transmitter on the basis of transmitting linear frequency modulation continuous wave, so that the transmitted waveform can be separated in the Doppler dimension, and then the main lobe gain of the waveform, the main and side lobes Ratio, main lobe width, etc. are used as evaluation indicators to optimize the waveform, and the phase sequence that makes the evaluation index optimal is calculated by the mode search method, and then substituted into the transmitted waveform to achieve optimization. However, when the speed of the target is large enough, there will be a phase difference between different transmitted waveforms arriving at the target, which will eventually cause the target to split during the angle measurement process, and the waveform optimization effect will be affected.
发明内容Contents of the invention
本发明所要解决的首要技术问题在于提供一种面向自动驾驶的毫米波正交波形优化方法。The primary technical problem to be solved by the present invention is to provide a millimeter wave orthogonal waveform optimization method for automatic driving.
本发明所要解决的另一技术问题在于提供一种采用该方法的车载雷达***。Another technical problem to be solved by the present invention is to provide a vehicle-mounted radar system using the method.
为了实现上述目的，本发明采用下述的技术方案：In order to achieve the above object, the present invention adopts following technical scheme:
根据本发明实施例的第一方面，提供一种面向自动驾驶的毫米波正交波形优化方法，包括如下步骤：According to the first aspect of the embodiments of the present invention, there is provided a millimeter-wave orthogonal waveform optimization method for automatic driving, including the following steps:
车载雷达***的第一发射通道发射正调频信号，第二发射通道发射负调频信号，所述正调频信号和所述负调频信号同时发射并相互正交；The first transmission channel of the vehicle-mounted radar system transmits a positive frequency modulation signal, and the second transmission channel transmits a negative frequency modulation signal, and the positive frequency modulation signal and the negative frequency modulation signal are transmitted simultaneously and are orthogonal to each other;
车载雷达***的多路接收通道同时接收所述正调频信号和所述负调频信号，经过功率前级放大后功分为2路并分别采用2路参考信号进行匹配滤波；The multi-channel receiving channel of the vehicle radar system simultaneously receives the positive frequency modulation signal and the negative frequency modulation signal, and after the power pre-amplification, the power is divided into two channels, and the two reference signals are respectively used for matching filtering;
每路接收通道的数据依次进行脉冲多普勒积累、目标检测、目标测角，其中在脉冲多普勒积累时将多个调频周期内的数据进行多谱勒维度的快速傅里叶变换，形成距离像数据，据此估计目标的方位角度，实现车载雷达***对目标的角度测量。The data of each receiving channel undergoes pulse Doppler accumulation, target detection, and target angle measurement in sequence. During the pulse Doppler accumulation, the data in multiple frequency modulation cycles are subjected to Doppler-dimensional fast Fourier transform to form Range image data, based on which the azimuth angle of the target is estimated, and the angle measurement of the target by the vehicle radar system is realized.
其中较优地，所述正调频信号分为多个子脉冲信号，在每个子脉冲信号的初始相位叠加对应的相位编码。Wherein preferably, the positive frequency modulation signal is divided into a plurality of sub-pulse signals, and a corresponding phase code is superimposed on the initial phase of each sub-pulse signal.
其中较优地，所述正调频信号的表达式如下所示：Wherein preferably, the expression of the positive frequency modulation signal is as follows:
Figure PCTCN2022127505-appb-000001
Figure PCTCN2022127505-appb-000001
其中，A代表信号调制幅度，i∈{1～52}代表第i个子脉冲，rect(·)代表矩形函数，T表示调频周期的时间长度，B表示带宽，Vc i为巴克码序列的第i个值，K代表线性调频连续波信号的调频斜率，计算方法为
Figure PCTCN2022127505-appb-000002
Among them, A represents the signal modulation amplitude, i∈{1～52} represents the i-th sub-pulse, rect(·) represents the rectangular function, T represents the time length of the FM cycle, B represents the bandwidth, and Vc i represents the i-th sub-pulse of the Barker code sequence value, K represents the frequency modulation slope of the linear frequency modulation continuous wave signal, and the calculation method is
Figure PCTCN2022127505-appb-000002
其中较优地，所述负调频信号不进行相位编码。Wherein preferably, no phase encoding is performed on the negative FM signal.
其中较优地，所述负调频信号的表达式如下所示：Wherein preferably, the expression of the negative frequency modulation signal is as follows:
Figure PCTCN2022127505-appb-000003
Figure PCTCN2022127505-appb-000003
其中，A代表信号调制幅度，i∈{1～52}代表第i个子脉冲，rect(·)代表矩形函数，T表示调频周期的时间长度，B表示带宽，Bc i为巴克码序列的第i个值，K代表线性调频连续波信号的调频斜率，计算方法为
Figure PCTCN2022127505-appb-000004
Among them, A represents the signal modulation amplitude, i∈{1～52} represents the i-th sub-pulse, rect(·) represents the rectangular function, T represents the time length of the frequency modulation cycle, B represents the bandwidth, and Bc i represents the i-th sub-pulse of the Barker code sequence value, K represents the frequency modulation slope of the linear frequency modulation continuous wave signal, and the calculation method is
Figure PCTCN2022127505-appb-000004
其中较优地，2路参考信号REF 0和REF 1的表达式如下所示： Preferably, the expressions of the two reference signals REF 0 and REF 1 are as follows:
Figure PCTCN2022127505-appb-000005
Figure PCTCN2022127505-appb-000005
其中较优地，所述距离像数据的表达式如下所示：Wherein preferably, the expression of the distance image data is as follows:
Figure PCTCN2022127505-appb-000006
Figure PCTCN2022127505-appb-000006
其中较优地，所述参考信号是发射信号的功分耦合信号。Preferably, the reference signal is a power division coupled signal of the transmit signal.
其中较优地，所述多路接收通道分别具有相应的接收天线，各接收天线之间的间距长度d＝0.5λ，发射天线之间以及发射天线与接收天线的间距为发射信号波长λ的2N倍，其中N为正整数。Preferably, the multi-channel receiving channels have corresponding receiving antennas, the distance between the receiving antennas is d=0.5λ, and the distance between the transmitting antennas and between the transmitting antennas and the receiving antennas is 2N of the wavelength λ of the transmitting signal. times, where N is a positive integer.
根据本发明实施例的第二方面，提供一种车载雷达***，采用上述的毫米波正交波形优化方法。According to the second aspect of the embodiments of the present invention, a vehicle radar system is provided, which adopts the above-mentioned millimeter wave orthogonal waveform optimization method.
与现有技术相比较，经过本发明所述方法优化后的毫米波正交波形，可以实现较高的波形隔离度，远高于一般雷达的动态测量范围，可以充分满足车载雷达***，尤其是汽车前向防撞雷达的使用需求。相对于时分MIMO技术，本发明只需要较少的检测时间达到相同的角度分辨率；相对于普通的同时MIMO技术，本发明具有更高的通道间距离度，并降低目标跨距离单元所产生的积累损失，具有很好的商业应用价值。Compared with the prior art, the millimeter-wave orthogonal waveform optimized by the method of the present invention can achieve higher waveform isolation, which is much higher than the dynamic measurement range of general radar, and can fully meet the needs of vehicle-mounted radar systems, especially Application requirements of forward collision avoidance radar for automobiles. Compared with the time-division MIMO technology, the present invention only needs less detection time to achieve the same angular resolution; compared with the common simultaneous MIMO technology, the present invention has a higher distance between channels and reduces the distance generated by the target cross-distance unit. Accumulate losses and have good commercial application value.
附图说明Description of drawings
图1为采用本发明提供的毫米波正交波形优化方法的车载雷达***示意图；Fig. 1 is the schematic diagram of the vehicle-mounted radar system adopting the millimeter-wave orthogonal waveform optimization method provided by the present invention;
图2为正调频信号S_0(t)和负调频信号S_1(t)的相位编码示意图；Fig. 2 is a schematic diagram of phase encoding of positive frequency modulation signal S_0(t) and negative frequency modulation signal S_1(t);
图3为正调频信号S_0(t)和负调频信号S_1(t)的时间频率示意图；Fig. 3 is the time-frequency diagram of positive frequency modulation signal S_0(t) and negative frequency modulation signal S_1(t);
图4为每个发射通道发射的锯齿形带频率调制和相位编码的连续波信号示意图；Fig. 4 is the continuous wave signal schematic diagram of the zigzag band frequency modulation and phase coding that each transmission channel transmits;
图5为波形编码周期数对隔离度指标的影响示意图；Figure 5 is a schematic diagram of the impact of the number of waveform encoding cycles on the isolation index;
图6为根据本发明优化设计的正交波形，计算得到CH 0和CH N-1通道的距离像信号仿真结果示意图。 Fig. 6 is a schematic diagram of the simulated results of range image signals of channels CH 0 and CH N-1 obtained by calculating the orthogonal waveform optimized according to the present invention.
具体实施方式Detailed ways
下面结合附图和具体实施例对本发明的技术内容做进一步的详细说明。The technical content of the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.
前已述及，现有的时分MIMO技术并不是专门针对自动驾驶技术的需求开发的，在具体性能上存在很多不足。例如，传统的汽车前向防撞雷达多采用时分MIMO技术，即M(M为正整数，下同)个发射通道依次发射信号，接收通道分时接收不同发射信号产生的目标回波，其缺点是检测周期较长，需要M个发射周期才能输出一次完整的检测结果。As mentioned above, the existing time-division MIMO technology is not specially developed for the requirements of automatic driving technology, and there are many shortcomings in specific performance. For example, the traditional automotive forward collision avoidance radar mostly adopts time-division MIMO technology, that is, M (M is a positive integer, the same below) transmission channels transmit signals sequentially, and the receiving channel receives target echoes generated by different transmission signals in time division. The reason is that the detection cycle is relatively long, and it takes M transmission cycles to output a complete detection result.
为此，本发明首先提供一种面向自动驾驶需求的毫米波正交波形优化方法。该优化方法通过设计2路正交的波形(分别是正调频信号和负调频信号，统称为发射信号)，用于实现2发N(即M＝2，N为正整数)收的车载雷达***。这里只设计2路发射信号的考虑是当发射 通道数量大于2时，将无法利用正、负调频信号所带来的信号隔离优势，所产生的正交信号的隔离度有所下降。并且，由于采用MIMO技术的雷达的角度分辨率由M*N决定，扩展成本更低、热耗更低的接收通道数量是更加经济的选择。To this end, the present invention firstly provides a millimeter wave orthogonal waveform optimization method for automatic driving requirements. The optimization method designs two orthogonal waveforms (respectively positive and negative frequency modulation signals, collectively referred to as transmission signals) to realize a 2 transmission N (ie M=2, N is a positive integer) receiving vehicle radar system. The reason for designing only 2 transmission signals here is that when the number of transmission channels is greater than 2, the signal isolation advantage brought by the positive and negative frequency modulation signals will not be able to be used, and the isolation of the generated orthogonal signals will be reduced. Moreover, since the angular resolution of the radar using MIMO technology is determined by M*N, it is a more economical choice to expand the number of receiving channels with lower cost and lower heat consumption.
在车载雷达***中，定义失配信号与匹配信号的电压比值为波形隔离度，该指标评价了车载雷达***的隔离水平。本发明通过优化发射信号的正交特性，改善了2路发射信号之间的波形隔离度，从而在保持目标检测周期的前提下，提高了车载雷达***的角度分辨能力。下面，对该优化方法的具体实现过程进行详细说明：In the vehicle radar system, the voltage ratio of the mismatch signal and the matching signal is defined as the waveform isolation, which evaluates the isolation level of the vehicle radar system. The invention improves the waveform isolation between the two transmission signals by optimizing the orthogonal characteristic of the transmission signal, thereby improving the angle resolution capability of the vehicle radar system on the premise of maintaining the target detection period. The specific implementation process of the optimization method is described in detail below:
图1为采用本发明所提供的毫米波正交波形优化方法的车载雷达***示意图。在该毫米波正交波形优化方法的一个实施例中，所采用的车载雷达***为包括2路发射通道(包含发射天线TX 0、TX 1)和N路接收通道(简称为2发N收)的同时MIMO雷达。其中，2路发射通道分别具备频率调制和相位调制能力；N路接收通道分别具有接收天线RX 0～RX N，这些接收天线RX 0～RX N之间的间距长度d＝0.5λ，发射天线之间以及发射天线与接收天线的间距为发射信号波长λ的2N倍。 FIG. 1 is a schematic diagram of a vehicle-mounted radar system adopting the millimeter wave orthogonal waveform optimization method provided by the present invention. In one embodiment of the millimeter wave orthogonal waveform optimization method, the vehicle radar system used includes 2 transmission channels (including transmission antennas TX 0 , TX 1 ) and N reception channels (abbreviated as 2 transmissions and N receptions). Simultaneous MIMO radar. Among them, the two transmitting channels have frequency modulation and phase modulation capabilities respectively; the N receiving channels respectively have receiving antennas RX 0 ~ RX N , the distance between these receiving antennas RX 0 ~ RX N is d=0.5λ, and the distance between the transmitting antennas The distance between the transmitting antenna and the receiving antenna is 2N times the wavelength λ of the transmitting signal.
在图1所示的车载雷达***的实施例中，2路发射通道同时开始工作，对2路发射通道分别发射的正调频信号和负调频信号进行波形调制。其中，正调频信号和负调频信号相互正交。此时，这2路发射信号需要通过相位编码的方法进行波形调制。具体的波形调制方法可以为：第一个发射通道TX 0设计为正调频信号S_0(t)，调频斜率K为带宽B与调频周期(简称为Prt)的比值，并且将一个Prt周期内的信号分为若干个子脉冲信号。为了保证巴克码编码的完整性，子脉冲个数需要是13的整数倍，每13个子脉冲为1个编码周期，具体选用几个周期的编码方式取决于具体的雷达波形设计，但编码方式对隔离度指标的影响较小。在本发明实施例中，在经过波形设计并进行隔离度仿真后，得出4个周期的编码方式所实现的隔离度最优。相应的比较结果如图5所示，因此本发明实施例以4×13＝52个子脉冲来举例说明，即在每个子脉冲信号的初始相位叠加上对应的52位巴克码(即相位编码，下同)。 In the embodiment of the vehicle-mounted radar system shown in FIG. 1 , two transmission channels start to work at the same time, and waveform modulation is performed on the positive frequency modulation signal and the negative frequency modulation signal respectively transmitted by the two transmission channels. Wherein, the positive frequency modulation signal and the negative frequency modulation signal are orthogonal to each other. At this time, the two transmission signals need to be modulated by phase encoding. The specific waveform modulation method can be as follows: the first transmission channel TX 0 is designed as a positive frequency modulation signal S_0(t), the frequency modulation slope K is the ratio of the bandwidth B to the frequency modulation period (referred to as Prt), and the signal within one Prt period Divided into several sub-pulse signals. In order to ensure the integrity of Barker code encoding, the number of sub-pulses needs to be an integer multiple of 13, and every 13 sub-pulses is 1 encoding period. The encoding method of several cycles depends on the specific radar waveform design. The isolation metrics have less impact. In the embodiment of the present invention, after waveform design and isolation simulation, it is obtained that the isolation achieved by the 4-cycle encoding method is the best. The corresponding comparison results are shown in Figure 5, so the embodiment of the present invention is illustrated with 4*13=52 sub-pulses, that is, the initial phase superposition of each sub-pulse signal corresponds to a 52-bit Barker code (i.e. phase encoding, below same).
相应地，正调频信号S_0(t)的表达式如式(1)所示：Correspondingly, the expression of the positive frequency modulation signal S_0(t) is shown in formula (1):
Figure PCTCN2022127505-appb-000007
Figure PCTCN2022127505-appb-000007
在上述公式中，A代表信号调制幅度，i∈{1～52}代表第i个子脉冲，rect(·)代表矩形函数，T表示调频周期(Prt)的时间长度，B表示带宽，Bc i为巴克码序列的第i个值，K代表LFMCW(线性调频连续波)信号的调频斜率，计算方法为
Figure PCTCN2022127505-appb-000008
In the above formula, A represents the signal modulation amplitude, i∈{1～52} represents the i-th sub-pulse, rect(·) represents the rectangular function, T represents the time length of the FM cycle (Prt), B represents the bandwidth, and Bc i is The i-th value of the Barker code sequence, K represents the frequency modulation slope of the LFMCW (Linear Frequency Modulation Continuous Wave) signal, and the calculation method is
Figure PCTCN2022127505-appb-000008
正调频信号S_0(t)的相位编码示意图如图上半部分所示，负调频信号S_1(t)的相位编码示意图如图下半部分所示。其中一个编码周期为一个Prt的时间长度，最小编码时间单元为Δt，Δt为Prt的时间长度T的
Figure PCTCN2022127505-appb-000009
正调频S_0(t)信号的时间频率示意图如图3左半部分所示，该信号为LFMCW信号，调频频率从f 1调频到f 2，带宽B＝|f 2-f 1|，时间为1个调频周期，即1个Prt的时间长度T。这里，f 1和f 2的位置只示意了哪个是起始频率，哪个是终止频率，实际值是一样的。 The schematic diagram of the phase encoding of the positive FM signal S_0(t) is shown in the upper part of the figure, and the schematic diagram of the phase encoding of the negative FM signal S_1(t) is shown in the lower part of the figure. One encoding cycle is the time length of a Prt, the minimum encoding time unit is Δt, and Δt is the time length T of Prt
Figure PCTCN2022127505-appb-000009
The time-frequency schematic diagram of the positive frequency modulation S_0(t) signal is shown in the left half of Fig. 3. The signal is an LFMCW signal, and the frequency modulation frequency is from f 1 to f 2 , the bandwidth B=|f 2 -f 1 |, and the time is 1 FM cycle, that is, the time length T of 1 Prt. Here, the positions of f 1 and f 2 only indicate which is the start frequency and which is the stop frequency, and the actual values are the same.
第二个发射通道TX 1设计为负调频信号S_1(t)，调频斜率为带宽B与周期时间Prt的比值。负调频信号S_1(t)不进行相位编码，表达式如式(2)所示： The second transmit channel TX 1 is designed as a negative frequency modulation signal S_1(t), and the frequency modulation slope is the ratio of the bandwidth B to the cycle time Prt. The negative FM signal S_1(t) is not phase-encoded, and the expression is shown in formula (2):
Figure PCTCN2022127505-appb-000010
Figure PCTCN2022127505-appb-000010
负调频信号S_1(t)也为LFMCW信号，其时间频率示意图如图3右半部分所示。其中，调频频率从f 2调频到f 1，带宽B＝|f 1-f 2|，时间为1个调频周期，即1个Prt的时间长度T。 The negative frequency modulation signal S_1(t) is also an LFMCW signal, and its time-frequency schematic diagram is shown in the right half of Fig. 3 . Wherein, the FM frequency is FM from f 2 to f 1 , the bandwidth B=|f 1 −f 2 |, and the time is 1 FM cycle, that is, the time length T of 1 Prt.
在本发明的一个实施例中，如图4所示，每个发射通道发射锯齿形带频率调制和相位编码的LFMCW信号，将LFMCW信号在单个Prt周期内 进行二进制的相位编码。在一个Prt周期内，将其按时间分为4×13＝52等份，设计二进制的相位编码，长度为τ。长度为13的巴克码为(1，1，1，1，1，-1，-1，1，1，-1，1，-1，1)，扩展为4倍长度，生成52位的巴克码，可以表示为：In one embodiment of the present invention, as shown in FIG. 4 , each transmit channel transmits a zigzag LFMCW signal with frequency modulation and phase encoding, and performs binary phase encoding on the LFMCW signal within a single Prt period. In a Prt period, it is divided into 4*13=52 equal parts according to time, and a binary phase code is designed with a length of τ. The Barker code with a length of 13 is (1, 1, 1, 1, 1, -1, -1, 1, 1, -1, 1, -1, 1), which is expanded to 4 times the length to generate a 52-bit Barker code, which can be expressed as:
Figure PCTCN2022127505-appb-000011
Figure PCTCN2022127505-appb-000011
在上述实施例中，时间长度为Prt的LFMCW信号被分为52个较短的、连续的子脉冲，每个子脉冲的时间宽度是Δτ＝T/(13×4)，相对于某个子脉冲的相位根据巴克码选择-π或π，把相位为π的子脉冲记为“1”，把相位为-π的子脉冲记为“-1”。需要说明的是，将调频周期(Prt)切分为多少等份，可以结合具体的雷达波形设计来仿真确定，只需要保证是13的整数倍即可。In the above embodiment, the LFMCW signal with a time length of Prt is divided into 52 shorter, continuous sub-pulses, and the time width of each sub-pulse is Δτ=T/(13×4), relative to a certain sub-pulse The phase is -π or π according to the Barker code, and the sub-pulse with the phase of π is recorded as "1", and the sub-pulse with the phase of -π is recorded as "-1". It should be noted that the number of equal parts to divide the frequency modulation period (Prt) can be determined by simulation in combination with the specific radar waveform design, and it only needs to be guaranteed to be an integer multiple of 13.
车载雷达***在工作时，2路发射通道TX 0和TX 1同时发射信号，2路发射信号经过目标的反射后达到N路接收通道，N路接收通道RX 0～RX N同时接收信号。 When the vehicle radar system is working, the 2 transmission channels TX 0 and TX 1 transmit signals at the same time, and the 2 transmission signals reach the N receiving channels after being reflected by the target, and the N receiving channels RX 0 ~ RX N receive signals at the same time.
对于N路接收通道RX 0～RX N接收的信号，在信号经过功率前级放大后，复制(功分)2路后分别采用2路参考信号TEF 0和REF 1进行匹配滤波。工程实现为利用混频器混频，其中参考信号的来源可以是发射信号的功分耦合信号，作为本振信号。利用2路发射信号的正交特性，可以得到8路具有空间分辨能力的接收信号，从而实现车载雷达***的雷达信号检测。 For the signals received by the N receiving channels RX 0 ~ RX N , after the signal is amplified by the power stage, the 2 channels are copied (power divided) and then the 2 channels of reference signals TEF 0 and REF 1 are used for matched filtering. The engineering implementation is to use a mixer to mix the frequency, and the source of the reference signal can be the power division coupling signal of the transmitted signal as the local oscillator signal. Utilizing the orthogonal characteristics of the 2 transmission signals, 8 reception signals with spatial resolution can be obtained, so as to realize the radar signal detection of the vehicle radar system.
具体地说，根据上述公式(1)和(2)，2路发射信号在经过距离为R的目标反射后，回波延迟时间
Figure PCTCN2022127505-appb-000012
c为光速，则接收通道0所接收的回波信号R 0(t)同时包含TX 0和TX 1两种发射信号，具体可以表示为： Specifically, according to the above formulas (1) and (2), the echo delay time of the two transmitted signals after being reflected by the target at a distance R is
Figure PCTCN2022127505-appb-000012
c is the speed of light, then the echo signal R 0 (t) received by the receiving channel 0 contains both TX 0 and TX 1 transmission signals, which can be specifically expressed as:
Figure PCTCN2022127505-appb-000013
Figure PCTCN2022127505-appb-000013
为了从R 0(t)中区分出TX 0和TX 1接收信号，需要分别采用不同的参考信号与回波信号进行匹配滤波，在硬件实现上为混频处理。其中，2路参考信号REF 0和REF 1的表达式见公式(5)： In order to distinguish the received signals of TX 0 and TX 1 from R 0 (t), it is necessary to use different reference signals and echo signals for matching filtering, which is frequency mixing processing in hardware implementation. Among them, the expressions of the two reference signals REF 0 and REF 1 are shown in formula (5):
Figure PCTCN2022127505-appb-000014
Figure PCTCN2022127505-appb-000014
在车载雷达***正常工作时，N路通道同时接收信号。由MIMO雷达的基本知识可知，由于多个通道间距为固定长度d，对于雷达视角内的任一目标，RX 0～RX N通道接收信号相位以此相差一个固定值，通过该固定偏差相位来估计目标相比于雷达天线法线方向的偏差角，通道数越多，角度分辨率越高。当N路接收通道同时接收信号时，类似RX 0通道的信号处理方法，可以依次求得距离像信号CH 0(f)～CH 2N-1(f)，具体计算方法为： When the vehicle radar system is working normally, N channels receive signals at the same time. According to the basic knowledge of MIMO radar, since the distance between multiple channels is a fixed length d, for any target within the radar viewing angle, the received signal phase of the RX 0 ~ RX N channel differs by a fixed value, and the fixed deviation phase is used to estimate The deviation angle of the target compared to the normal direction of the radar antenna, the more channels, the higher the angular resolution. When the N receiving channels receive signals at the same time, similar to the signal processing method of the RX 0 channel, the distance image signals CH 0 (f) ~ CH 2N-1 (f) can be obtained in sequence. The specific calculation method is:
Figure PCTCN2022127505-appb-000015
Figure PCTCN2022127505-appb-000015
每个通道的数据依次进行PD(脉冲多普勒)积累、目标检测、目标测角，其中在PD积累时将多个Prt的数据进行多谱勒维度的FFT(快速傅里叶变换)，可以对具有运动特性的目标与静止目标分离，形成距离像数据。将CH 1(f)～CH 2N-1(f)的相同位置的信号取出，获得2N路目标的复数信号。该复数信号中包含由目标偏离天线法线方向角度所形成的固定相 位差，通过对2N路目标的复数信号进行FFT，即可以计算出目标偏离雷达天线法线的偏角，据此估计目标的方位角度，实现车载雷达***对目标的角度测量。 The data of each channel undergoes PD (Pulse Doppler) accumulation, target detection, and target angle measurement in sequence. During PD accumulation, the data of multiple Prts are subjected to FFT (Fast Fourier Transform) in the Doppler dimension, which can be The moving target is separated from the stationary target to form range image data. The signals at the same positions of CH 1 (f) to CH 2N-1 (f) are taken out to obtain complex signals of 2N channels of targets. The complex signal contains a fixed phase difference formed by the direction angle of the target deviating from the normal line of the antenna. By performing FFT on the complex signal of the 2N-way target, the deflection angle of the target deviating from the normal line of the radar antenna can be calculated, and the target’s angle can be estimated accordingly. Azimuth angle, to realize the angle measurement of the vehicle radar system to the target.
下面，对此展开具体说明：目标检测的方法可采用传统的Ca-Cfar动目标检测算法，在距离多谱勒平面上提取局部峰值点，局部峰值点对应的距离和多谱勒位置可推算出检测目标的距离和速度。最后根据2N个通道的峰值点数据做FFT，可以计算出目标相对于雷达天线法线偏差角。上述方法为常用的MIMO雷达信号处理方法，这里不再详细说明了。Below, this will be explained in detail: the target detection method can use the traditional Ca-Cfar moving target detection algorithm to extract the local peak point on the range Doppler plane, and the distance and Doppler position corresponding to the local peak point can be calculated Detect the distance and speed of the target. Finally, FFT is performed according to the peak point data of 2N channels, and the deviation angle of the target relative to the normal line of the radar antenna can be calculated. The above method is a commonly used MIMO radar signal processing method, which will not be described in detail here.
在本发明的一个实施例中，2路接收信号分别进行混频处理后，可以得CH 0和CH N两个通道的时域信号，对其做FFT转换到频域即可得到一维距离像信息，计算方法表示为： In one embodiment of the present invention, after the two received signals are mixed separately, the time-domain signals of CH 0 and CH N can be obtained, and the one-dimensional range image can be obtained by performing FFT conversion to the frequency domain. information, the calculation method is expressed as:
Figure PCTCN2022127505-appb-000016
Figure PCTCN2022127505-appb-000016
式中“*”为点乘处理，在硬件实现上代表混频，得到CH 0(t)和CH N(t)通道的距离像表达式为： In the formula, "*" is dot product processing, which represents frequency mixing in hardware implementation, and the expression of the distance image of CH 0 (t) and CH N (t) channels is:
Figure PCTCN2022127505-appb-000017
Figure PCTCN2022127505-appb-000017
在本发明中，定义波形隔离度为正确匹配信号与相邻发射通道波形泄漏功率的比值，具体为：In the present invention, the waveform isolation is defined as the ratio of the correct matching signal to the waveform leakage power of the adjacent transmission channel, specifically:
Figure PCTCN2022127505-appb-000018
Figure PCTCN2022127505-appb-000018
波形隔离度指标的含义为针对某个回波点目标信号，匹配信号的功率与适配信号功率比值的对数。该指标可以用来评估正交波形设计的好坏，即波形隔离度指标越高，代表MIMO雷达通道之间的干扰越小。The meaning of the waveform isolation index is the logarithm of the ratio of the power of the matched signal to the power of the adapted signal for a target signal at an echo point. This index can be used to evaluate the quality of the orthogonal waveform design, that is, the higher the waveform isolation index, the smaller the interference between MIMO radar channels.
本发明以如下雷达波形参数设计为例，仿真本发明实施例提出的采用正负调频加52位脉内相位编码的方法，所能达到的波形隔离度指标。The present invention takes the following radar waveform parameter design as an example to simulate the waveform isolation index that can be achieved by using the positive and negative frequency modulation plus 52-bit intrapulse phase encoding method proposed in the embodiment of the present invention.
在本发明的实施例中，经过优化的毫米波正交波形的参数实例如表1所示：In an embodiment of the present invention, an example of parameters of the optimized millimeter wave orthogonal waveform is shown in Table 1:
表1Table 1
编号serial number 参数名称parameter name 参数值parameter value 参数释义Parameter interpretation
11 M m 22 发射通道硬件路数Number of transmit channel hardware
22 N N 44 接收通道硬件路数Number of receiving channel hardware
33 PrtPrt 520us520us 调频周期FM cycle
44 RR 300m300m 目标距离target distance
55 AA 1V1V 信号幅度signal amplitude
利用本发明所提供的毫米波正交波形优化方法，进行隔离度结果仿真，仿真结果如图6所示。由该仿真结果可知，本发明实施例中设计了基于2发N收的毫米波正交波形，可以获得波形隔离度的指标为60dB，远高于一般雷达的动态测量范围，可以充分满足车载雷达***，尤其是汽车前向防撞雷达的使用需求。由此可以看出，本发明所提供的频率正交结合相位正交的波形优化方法，可以明显改善毫米波信号的波形隔离度。Using the millimeter-wave orthogonal waveform optimization method provided by the present invention, the isolation result simulation is performed, and the simulation result is shown in FIG. 6 . From the simulation results, it can be seen that in the embodiment of the present invention, a millimeter-wave orthogonal waveform based on 2 transmissions and N receptions is designed, and the waveform isolation index can be obtained as 60dB, which is much higher than the dynamic measurement range of general radars, and can fully meet the needs of vehicle radars. systems, especially automotive forward collision avoidance radar. It can be seen from this that the frequency quadrature combined with phase quadrature waveform optimization method provided by the present invention can significantly improve the waveform isolation of millimeter wave signals.
另一方面，经过本发明所述方法优化后的高隔离度发射波形，可以替代常用的时分MIMO技术。常用的时分MIMO技术采用分时方式依次打开发射通道的信号，用来避免两个发射通道间的信号串扰。在采用本发明实施例提供的波形优化方法后，可以将2路发射信号同时打开，在将汽车前向防撞雷达的角度分辨率不变的同时，将检测周期显著缩短(例如为时分MIMO技术所需时间的二分之一)，并降低目标跨距离单元所产生的积累损失，具有很好的商业应用价值。On the other hand, the high-isolation transmit waveform optimized by the method of the present invention can replace the commonly used time-division MIMO technology. The commonly used time-division MIMO technology uses a time-sharing method to sequentially open the signals of the transmission channels to avoid signal crosstalk between two transmission channels. After adopting the waveform optimization method provided by the embodiment of the present invention, the two transmission signals can be opened simultaneously, while the angular resolution of the forward collision avoidance radar of the automobile is kept constant, the detection period is significantly shortened (for example, time-division MIMO technology One-half of the required time), and reduce the cumulative loss produced by the target cross-distance unit, which has good commercial application value.
以上对本发明所提供的面向自动驾驶的毫米波正交波形优化方法及车载雷达***进行了详细的说明。对本领域的一般技术人员而言，在不背离本发明实质内容的前提下对它所做的任何显而易见的改动，都将属于本发明专利权的保护范围。The method for optimizing the millimeter-wave orthogonal waveform for automatic driving and the vehicle-mounted radar system provided by the present invention have been described in detail above. For those skilled in the art, any obvious changes made to it without departing from the essence of the present invention will fall within the protection scope of the patent right of the present invention.

Claims (10)

  1. 一种面向自动驾驶的毫米波正交波形优化方法，其特征在于包括如下步骤：A method for optimizing millimeter-wave orthogonal waveforms for automatic driving, characterized in that it comprises the following steps:
    车载雷达***的第一发射通道发射正调频信号，第二发射通道发射负调频信号，所述正调频信号和所述负调频信号同时发射并相互正交；The first transmission channel of the vehicle-mounted radar system transmits a positive frequency modulation signal, and the second transmission channel transmits a negative frequency modulation signal, and the positive frequency modulation signal and the negative frequency modulation signal are transmitted simultaneously and are orthogonal to each other;
    车载雷达***的多路接收通道同时接收所述正调频信号和所述负调频信号，经过功率前级放大后功分为2路并分别采用2路参考信号进行匹配滤波；The multi-channel receiving channel of the vehicle radar system simultaneously receives the positive frequency modulation signal and the negative frequency modulation signal, and after the power pre-amplification, the power is divided into two channels, and the two reference signals are respectively used for matching filtering;
    每路接收通道的数据依次进行脉冲多普勒积累、目标检测、目标测角，其中在脉冲多普勒积累时将多个调频周期内的数据进行多谱勒维度的快速傅里叶变换，形成距离像数据，据此估计目标的方位角度，实现车载雷达***对目标的角度测量。The data of each receiving channel undergoes pulse Doppler accumulation, target detection, and target angle measurement in sequence. During the pulse Doppler accumulation, the data in multiple frequency modulation cycles are subjected to Doppler-dimensional fast Fourier transform to form Range image data, based on which the azimuth angle of the target is estimated, and the angle measurement of the target by the vehicle radar system is realized.
  2. 如权利要求1所述的毫米波正交波形优化方法，其特征在于：The millimeter-wave orthogonal waveform optimization method according to claim 1, characterized in that:
    所述正调频信号分为多个子脉冲信号，在每个子脉冲信号的初始相位叠加对应的相位编码。The positive FM signal is divided into multiple sub-pulse signals, and a corresponding phase code is superimposed on the initial phase of each sub-pulse signal.
  3. 如权利要求2所述的毫米波正交波形优化方法，其特征在于所述正调频信号的表达式如下所示：The millimeter-wave quadrature waveform optimization method according to claim 2, wherein the expression of the positive frequency modulation signal is as follows:
    Figure PCTCN2022127505-appb-100001
    Figure PCTCN2022127505-appb-100001
    其中，A代表信号调制幅度，i∈{1～52}代表第i个子脉冲，rect(·)代表矩形函数，T表示调频周期的时间长度，B表示带宽，Bc i为巴克码序列的第i个值，K代表线性调频连续波信号的调频斜率，计算方法为
    Figure PCTCN2022127505-appb-100002
    Among them, A represents the signal modulation amplitude, i∈{1～52} represents the i-th sub-pulse, rect(·) represents the rectangular function, T represents the time length of the frequency modulation cycle, B represents the bandwidth, and Bc i represents the i-th sub-pulse of the Barker code sequence value, K represents the frequency modulation slope of the linear frequency modulation continuous wave signal, and the calculation method is
    Figure PCTCN2022127505-appb-100002
  4. 如权利要求1所述的毫米波正交波形优化方法，其特征在于：The millimeter-wave orthogonal waveform optimization method according to claim 1, characterized in that:
    所述负调频信号不进行相位编码。The negative FM signal is not phase-encoded.
  5. 如权利要求4所述的毫米波正交波形优化方法，其特征在于所述负调频信号的表达式如下所示：The millimeter-wave quadrature waveform optimization method according to claim 4, wherein the expression of the negative frequency modulation signal is as follows:
    Figure PCTCN2022127505-appb-100003
    Figure PCTCN2022127505-appb-100003
    其中，A代表信号调制幅度，i∈{1～52}代表第i个子脉冲，rect(·)代表矩形函数，T表示调频周期的时间长度，B表示带宽，Bc i为巴克码序列的第i个值，K代表线性调频连续波信号的调频斜率，计算方法为
    Figure PCTCN2022127505-appb-100004
    Among them, A represents the signal modulation amplitude, i∈{1～52} represents the i-th sub-pulse, rect(·) represents the rectangular function, T represents the time length of the frequency modulation cycle, B represents the bandwidth, and Bc i represents the i-th sub-pulse of the Barker code sequence value, K represents the frequency modulation slope of the linear frequency modulation continuous wave signal, and the calculation method is
    Figure PCTCN2022127505-appb-100004
  6. 如权利要求3或5所述的毫米波正交波形优化方法，其特征在于2路参考信号REF 0和REF 1的表达式如下所示： The millimeter-wave orthogonal waveform optimization method according to claim 3 or 5, wherein the expressions of the two reference signals REF 0 and REF 1 are as follows:
    Figure PCTCN2022127505-appb-100005
    Figure PCTCN2022127505-appb-100005
  7. 如权利要求6所述的毫米波正交波形优化方法，其特征在于所述距离像数据的表达式如下所示：The millimeter-wave orthogonal waveform optimization method according to claim 6, wherein the expression of the range image data is as follows:
    Figure PCTCN2022127505-appb-100006
    Figure PCTCN2022127505-appb-100006
  8. 如权利要求1所述的毫米波正交波形优化方法，其特征在于：The millimeter-wave orthogonal waveform optimization method according to claim 1, characterized in that:
    所述参考信号是发射信号的功分耦合信号。The reference signal is a power division coupled signal of the transmitted signal.
  9. 如权利要求1所述的毫米波正交波形优化方法，其特征在于：The millimeter-wave orthogonal waveform optimization method according to claim 1, characterized in that:
    所述多路接收通道分别具有相应的接收天线，各接收天线之间的间距长度d＝0.5λ，发射天线之间以及发射天线与接收天线的间距为发 射信号波长λ的2N倍，其中N为正整数。The multi-channel receiving channels have corresponding receiving antennas respectively, the spacing length d=0.5λ between the receiving antennas, and the spacing between the transmitting antennas and the transmitting antennas and the receiving antennas are 2N times of the transmitting signal wavelength λ, where N is positive integer.
  10. 一种车载雷达***，其特征在于采用权利要求1～9中任意一项所述的毫米波正交波形优化方法。A vehicle-mounted radar system, characterized in that the millimeter-wave orthogonal waveform optimization method described in any one of claims 1-9 is adopted.
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