Method and device for measuring target micro-motion information based on combination of single-frequency waveform and modulated waveform

Abstract

The present invention provides a method and device for measuring target micro-motion information based on a combination of a single-frequency waveform and a modulated waveform, which belongs to the field of long-distance space target perception, including designing parameters of laser modulation waveform and single-frequency waveform and pulse width ratio; using a signal generating device and a signal modulating device to modulate the laser signal; dividing the signal into two beams, one beam is used as signal light for target detection after being amplified by an amplifier, and the other beam is used as a local oscillator reference light and an echo signal for mixing; converting the mixed optical signal into an electrical signal and using a high-speed acquisition device for acquisition, and finally performing data processing to extract the distance and Doppler information of the target at the same time. The present invention can simultaneously obtain the extraction of the characteristics of the high-resolution distance and high-resolution Doppler information of the target that change with time, which is conducive to the acquisition of multi-dimensional characteristics of high-speed targets.

Description

Technical Field

[0001] The present invention belongs to the field of long-distance space target perception, and specifically relates to a target micro-motion information measurement method and device based on a combination of a single-frequency waveform and a modulated waveform, which can simultaneously realize coherent laser radar detection of high-resolution range change information and high-resolution Doppler information of long-distance targets. Background Art

[0002] As an important part of modern remote sensing technology, LiDAR technology plays a key role in many fields such as autonomous driving, aerospace, meteorological observation and military reconnaissance with its high precision, high resolution and non-contact measurement characteristics. Among them, coherent LiDAR has shown significant advantages in long-distance target detection because it can improve signal gain and suppress background noise through coherent detection technology.

[0003] Traditional coherent lidar devices mainly focus on measuring a single parameter, such as only focusing on the target distance or speed (Doppler shift). However, in complex and changing practical application scenarios, it is often necessary to simultaneously obtain high-resolution distance and Doppler information of the target for more comprehensive target recognition and tracking. This demand is particularly urgent in the fields of high-speed moving target detection and aerial target tracking.

[0004] In order to solve the above problems, the present invention proposes an innovative long-distance coherent laser radar detection device and method. The core of the device is to design a detection mechanism that can simultaneously obtain high-resolution target distance and Doppler sequence. By optimizing the laser emission signal waveform and combining an efficient signal processing algorithm, the device can simultaneously extract the information of the target's distance and speed changing over time in a single detection process, thereby achieving rapid and accurate detection of long-distance targets. Summary of the invention

[0005] The purpose of the present invention is to provide a laser radar device and method for measuring target micro-motion information based on a combination of a single-frequency waveform and a modulated waveform. By performing matched filtering and time-frequency analysis on the echo, the motion characteristics of the target's high-resolution distance information and high-resolution Doppler information that change over time can be acquired, thereby realizing multi-dimensional information detection of the target without increasing the complexity of the device.

[0006] The technical solution of the present invention is as follows: a method for measuring target micro-motion information based on a combination of a single-frequency waveform and a modulated waveform, the method comprising the following steps:

[0007] Step 1: According to the detection distance of the target and the required distance and resolution, alternate modulation is performed to generate a modulated waveform and a single-frequency waveform to obtain a modulated laser signal;

[0008] Step 2: A portion of the laser signal is emitted to the target as signal light, and the other portion is used as reference local oscillator light;

[0009] Step 3: Mix the target echo signal with the reference local oscillator light and convert it into an electrical signal, and process the electrical signal to extract the distance information and Doppler information contained therein.

[0010] Furthermore, in step 1, the bandwidth, pulse width and modulation slope of the required modulation signal, as well as the pulse width of the single-frequency signal are designed according to the detection distance of the target and the required distance and resolution, and the required modulation waveform is generated based on the set information.

[0011] Furthermore, the designed waveform ratio needs to meet the pre-set distance resolution and Doppler resolution requirements. The distance resolution needs to adjust the bandwidth and pulse width of the modulated waveform signal accordingly, and the Doppler resolution needs to adjust the pulse width of the single-frequency waveform signal accordingly.

[0012] Furthermore, based on the target speed and distance information obtained by the single-frequency waveform and the modulated waveform, the relevant parameters of the single-frequency waveform and the modulated waveform are modified by real-time feedback according to the preset distance resolution and Doppler resolution requirements.

[0013] Furthermore, the modulation waveform is loaded into the waveform generator and input into the signal modulator to realize the modulation of the laser signal.

[0014] Furthermore, the laser signal is divided into two beams by a beam splitter, one beam is used as signal light, which is power-amplified by a signal amplifier and then transmitted to the target through a transmitting device; the other beam is used as a reference local oscillator light to participate in mixing.

[0015] Furthermore, the electrical signal processing includes extracting the distance information contained in the modulated echo signal by using a one-dimensional Fourier transform, and extracting the time-varying Doppler information contained in the single-frequency waveform by using a time-frequency analysis method such as a short-time Fourier transform.

[0016] On the other hand, the present invention also provides a target micro-motion information measurement device based on a combination of a single-frequency waveform and a modulated waveform, the device comprising:

[0017] A laser generating device, used for generating a laser signal;

[0018] A waveform generating device, used for generating the waveform of the required modulation signal and single frequency signal according to the detection distance of the target and the required distance and resolution;

[0019] A signal modulation device, used for alternately modulating the laser signal according to the waveform generated by the waveform generation device to generate a modulated waveform and a single-frequency waveform;

[0020] A light splitting device, used to split the modulated laser signal into two beams, one of which is used as signal light and the other is used as reference local oscillator light;

[0021] A signal amplifying device, used for amplifying the power of the signal light;

[0022] The transmitting and receiving device is used to transmit the amplified signal light to the target and obtain the target echo signal;

[0023] A frequency mixing device, used for mixing the target echo signal with the reference local oscillator light;

[0024] A photoelectric conversion device, used for converting the mixed signal into an electrical signal;

[0025] A high-speed acquisition device, used to collect electrical signals and send them to a data processing device;

[0026] The data processing device is used to extract the distance information contained in the modulated echo signal and the time-varying Doppler information contained in the single-frequency waveform.

[0027] The beneficial effects of the present invention are:

[0028] The core of the invention is to design a detection mechanism that can simultaneously obtain high-resolution target distance and Doppler sequence. By optimizing the laser emission signal waveform and combining it with an efficient signal processing algorithm, the device can simultaneously extract information about the distance and speed of the target over time during a single detection process, thus achieving rapid and accurate detection of long-distance targets. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a flow chart of a method for measuring target micro-motion information based on a combination of a single-frequency waveform and a modulated waveform in a specific implementation manner of the present invention.

[0030] Figure 2 It is a structural diagram of a coherent laser radar device in a specific implementation manner of the present invention. DETAILED DESCRIPTION

[0031] The present invention is described in detail below in conjunction with the accompanying drawings, but it should be understood that the embodiments and the accompanying drawings are only used to exemplify the present invention and cannot constitute any limitation on the protection scope of the present invention. All reasonable changes and combinations within the scope of the inventive concept of the present invention fall within the protection scope of the present invention.

[0032] like Figure 1 As shown, the present invention provides a method for measuring target micro-motion information based on a combination of a single-frequency waveform and a modulated waveform to achieve detection of the target, including the following steps.

[0033] Step 1: Design the required signal waveform according to the application scenario. The main influencing factors are the detection distance and the required detection accuracy, including distance resolution and Doppler resolution. The distance resolution that can be achieved by the modulated signal is inversely proportional to the bandwidth of the signal, that is, the wider the signal bandwidth, the higher the distance resolution. This is because a wider bandwidth means that more subtle frequency differences can be distinguished in the frequency domain, thereby being able to measure the target distance more accurately. The formula is expressed as:

[0034]

[0035] in, is the distance resolution, is the speed of light, is the signal bandwidth. In addition, in signal processing, the coherent integration time (CIT) is one of the key factors that determine the Doppler resolution. The longer the CIT, the more signal energy the radar device can accumulate, which helps to improve the Doppler resolution. This is because a longer accumulation time can make it easier for the radar device to distinguish targets with slight speed differences. Therefore, the present invention needs to consider the proportion of the modulated signal and the single-frequency signal in the initial setting, as well as the bandwidth setting of the modulated waveform.

[0036] Step 2: Generate the required modulation waveform according to the information set in step 1. The modulation form is the alternating modulation of the modulation waveform and the single-frequency waveform. For a linear modulation signal, the frequency changes with time. A basic modulation signal form can be expressed as:

[0037]

[0038] in, is the initial frequency, is the modulation slope, which represents the rate at which the frequency changes over time, and Represent the amplitude and phase of the signal respectively. The frequency of the single-frequency signal remains unchanged, and its expression is:

[0039]

[0040] in Indicates the carrier frequency of the signal.

[0041] Step 3: Load the modulation waveform generated in step 2 into the waveform generator and input it into the signal modulator to realize the modulation of the laser signal.

[0042] Step 4: Use a beam splitter to split the laser signal in step 3 into two beams, one as reference local oscillator light and the other as signal light.

[0043] Step 5: Amplify the power of the signal light using a signal amplifier, and then transmit it to the target through a transmitting device.

[0044] Step 6: Use a receiving device to receive the echo signal, mix the echo signal with the reference local oscillator signal, and then input it into the photoelectric conversion device to convert it into an electrical signal. The received echo signal is attenuated in the path and there is a time delay after being reflected by the target. The received modulated signal waveform can be expressed as:

[0045]

[0046] in is the amplitude of the received signal (which may be reduced due to path losses), is the signal round trip time (distance to target is proportional to ,in is the speed of light), It is the additional phase introduced by reflections and other factors.

[0047] The modulated signal is beat (multiplied) with the generated signal, and then a low-pass filter can be used to extract the required low-frequency component (difference frequency signal). The original signal and the signal after the beat can be expressed as:

[0048]

[0049]

[0050] The present invention can finally obtain a frequency difference signal. The difference frequency is related to the distance and speed of the target:

[0051]

[0052] Where B is the received signal amplitude, To measure the phase difference introduced by the optical path, The difference frequency of the beat frequency signal can be expressed as the frequency difference caused by the signal delay and the target motion Doppler

[0053] .

[0054] Where c is the speed of light, and v is the radial motion speed of the target toward the LiDAR observation direction.

[0055] The principle of coherent detection using a single-frequency signal is similar to this. The form of the transmitted signal and the received signal can be expressed as:

[0056]

[0057]

[0058] in and represent the amplitudes of the transmitted and received signals, respectively. represents the frequency of the transmitted signal, is the initial phase, is the frequency offset, is the additional phase shift introduced, It is the phase change introduced by time delay or other dynamic factors. The signal after beat frequency processing can be expressed as:

[0059]

[0060] By measuring the frequency deviation of the beat signal , the present invention can extract information about the radial velocity of the target.

[0061] Step 7, use a high-speed acquisition device to collect the electrical signal generated in step 6, and use a data processing device to extract the information contained therein. First, the echo signal needs to be processed in segments, and the signal is distinguished according to the modulation signal area and the single-frequency signal area according to the waveform characteristics of the signal; the signal in the modulation signal area and the signal in the single-frequency area are respectively combined into a two-dimensional signal matrix according to different pulse segments; the two groups of signals are processed separately, and the proposed data processing method includes but is not limited to time-frequency analysis methods such as one-dimensional Fourier transform and short-time Fourier transform, so as to obtain the high-resolution distance sequence and high-resolution Doppler sequence of the target. The signal after mixing already contains the distance and Doppler information of the target. The present invention can perform Fourier transform on the time series of each pulse segment respectively, extract the frequency information therein, and realize the inversion of the target distance and Doppler information.

[0062] On the other hand, Figure 2 As shown, the present invention also provides a target micro-motion information measuring device based on a combination of a single-frequency waveform and a modulated waveform, the device comprising: a laser generating device, a waveform generating device, a signal modulating device, a spectroscopic device, a signal amplifying device, a transmitting and receiving device, a frequency mixing device, a photoelectric conversion device, a high-speed acquisition device and a data processing device.

[0063] A laser generating device, used for generating a laser signal;

[0064] A waveform generating device, used for generating the waveform of the required modulation signal and single frequency signal according to the detection distance of the target and the required distance and resolution;

[0065] A signal modulation device, used for alternately modulating the laser signal according to the waveform generated by the waveform generation device to generate a modulated waveform and a single-frequency waveform;

[0066] A light splitting device, used to split the modulated laser signal into two beams, one of which is used as signal light and the other is used as reference local oscillator light;

[0067] A signal amplifying device, used for amplifying the power of the signal light;

[0068] The transmitting and receiving device is used to transmit the amplified signal light to the target and obtain the target echo signal;

[0069] A frequency mixing device, used for mixing the target echo signal with the reference local oscillator light;

[0070] A photoelectric conversion device, used for converting the mixed signal into an electrical signal;

[0071] A high-speed acquisition device, used to collect electrical signals and send them to a data processing device;

[0072] The data processing device is used to extract the distance information contained in the modulated echo signal and the time-varying Doppler information contained in the single-frequency waveform.

[0073] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for measuring target micro-motion information based on a combination of a single-frequency waveform and a modulated waveform, characterized in that: The method comprises the following steps: Step 1: According to the target detection distance and the required distance and resolution, consider the proportion of the modulation signal and the single-frequency signal, design the bandwidth, pulse width and modulation slope of the required modulation signal, and the pulse width of the single-frequency signal, and alternately modulate the modulation waveform and the single-frequency waveform based on the set information. For the linear modulation signal, its frequency changes with time, while the frequency of the single-frequency signal remains unchanged, and the modulated laser signal is obtained; Step 2: A portion of the laser signal is emitted to the target as signal light, and the other portion is used as reference local oscillator light; Step 3: Mix the target echo signal with the reference local oscillator light and convert it into an electrical signal, process the electrical signal, and distinguish the signal according to the modulation signal area and the single-frequency signal area according to the waveform characteristics of the signal; combine the signal in the modulation signal area and the signal in the single-frequency area into a two-dimensional signal matrix according to different pulse segments; perform data processing on the two groups of signals respectively, extract the distance information contained in the modulated echo signal by using a one-dimensional Fourier transform, and extract the time-varying Doppler information contained in the single-frequency waveform by using a time-frequency analysis method; The designed waveform ratio must meet the pre-set range resolution and Doppler resolution requirements. The range resolution corresponds to adjusting the bandwidth and pulse width of the modulated waveform signal, and the Doppler resolution corresponds to adjusting the pulse width of the single-frequency waveform signal. Based on the target speed and distance information obtained by the single-frequency waveform and the modulated waveform, the relevant parameters of the single-frequency waveform and the modulated waveform are modified in real time according to the preset distance resolution and Doppler resolution requirements.

2. The method for measuring target micro-motion information based on a combination of a single-frequency waveform and a modulated waveform according to claim 1, characterized in that: The modulation waveform is loaded into the waveform generator and input into the signal modulator to realize the modulation of the laser signal.

3. The method for measuring target micro-motion information based on a combination of a single-frequency waveform and a modulated waveform according to claim 1, characterized in that: The laser signal is divided into two beams by a beam splitter. One beam is used as signal light, which is amplified by a signal amplifier and then emitted to the target through a transmitting device. The other beam is used as a reference local oscillator light to participate in mixing.

4. A target micro-motion information measuring device based on the target micro-motion information measuring method of claim 1, which is characterized by: The device includes: A laser generating device, used for generating a laser signal; A waveform generating device, used for generating the waveform of the required modulation signal and single frequency signal according to the detection distance of the target and the required distance and resolution; A signal modulation device, used for alternately modulating the laser signal according to the waveform generated by the waveform generation device to generate a modulated waveform and a single-frequency waveform; A light splitting device, used to split the modulated laser signal into two beams, one of which is used as signal light and the other is used as reference local oscillator light; A signal amplifying device, used for amplifying the power of the signal light; The transmitting and receiving device is used to transmit the amplified signal light to the target and obtain the target echo signal; A frequency mixing device, used for mixing the target echo signal with the reference local oscillator light; A photoelectric conversion device, used for converting the mixed signal into an electrical signal; A high-speed acquisition device, used to collect electrical signals and send them to a data processing device; The data processing device is used to extract the distance information contained in the modulated echo signal and the time-varying Doppler information contained in the single-frequency waveform.

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