CN113433555B - Laser heterodyne detection autonomous searching method for moving target in air - Google Patents
Laser heterodyne detection autonomous searching method for moving target in air Download PDFInfo
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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
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/04—Systems determining the presence of a target
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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
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/4802—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
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Abstract
The invention provides an autonomous searching method for laser heterodyne detection of an air moving target, which comprises the following steps: the laser heterodyne detection system firstly performs initial scanning detection on a space domain which may exist in a target to acquire echo information of a scanned area; extracting the amplitude and the speed extreme value of the echo of the initial scanning frame, and judging the type of the echo; continuing to scan along the original scanning direction, and extracting the amplitude and the speed extreme value of the echo of the frame; judging the type of the echo of the frame, comparing the size of the speed extreme value of the echo of the frame with that of the echo of the previous frame, controlling the scanning direction of the next frame according to the result, and extracting the amplitude value and the speed extreme value of the echo of the next frame; and repeating the steps until the amplitude value and the speed extreme value of the echo of a certain frame exceed the threshold. According to the invention, through laser fusion detection of the target body and the surrounding environment thereof, autonomous searching and tracking of the moving target are realized, and the pressure of an external searching and guiding means when the target is lost is reduced.
Description
Technical Field
The invention belongs to the technical field of laser radar detection, and particularly relates to an autonomous searching method for laser heterodyne detection of an air moving target.
Background
A low-detectability air target such as a stealth airplane and the like generates an atmospheric wind field disturbance which cannot be hidden due to high-speed movement, namely the wind field is in a state far higher than the conventional change characteristic of background atmosphere in a certain space-time range. Such perturbations have 3 significant features: (1) associated with a target type; (2) the dead time is long and can reach hundreds of seconds, the disturbance area is large, the disturbance area can reach hundreds of meters in the transverse direction and can last dozens of kilometers in the longitudinal direction; (3) the disturbance information can be measured by detecting aerosol scattering echoes through a laser radar. Therefore, counter-detection measures such as infrared radiation inhibition and stealth technology adopted by the target body are avoided. The target detection technology based on atmospheric disturbance opens up a new way for target detection.
When the laser radar is used for detecting atmospheric disturbance, laser echo generally originates from aerosol scattering, the echo is very weak, and a heterodyne detection system is often adopted for detecting wind field disturbance caused by a target in order to realize infinitesimal signal detection and multi-dimensional information acquisition. The detection system can obtain multi-dimensional information such as envelope, wind speed, wind direction and the like of echo signals. When the heterodyne laser radar system scans an airspace to be measured, the cross section of wind field disturbance distribution on an air target flight path is obtained by generally adopting a cross section scanning mode such as RHI (Range-Height Indicator) scanning or PPI (Plan-Position Indicator) scanning. The laser pulse beam is in the mrad magnitude, so that the laser pulse is generally difficult to irradiate a target body at a high probability, and the difficulty that the autonomous searching and tracking capacity of the traditional laser radar for the aerial target is weak is caused.
Chinese patent publication CN102721967A discloses a method for discovering an aerial target based on a wind field disturbance type, and chinese patent publication CN102902977A discloses a method for classifying an aerial target based on wind field disturbance characteristics. The existing research and literature mainly focuses on wake vortex detection and wake vortex characteristics of a single airplane, so that wake vortex warning is realized, flight safety is guaranteed, and airport capacity is improved. Actually, the time-frequency domain characteristics of the laser radar echo can be utilized to improve the target searching efficiency, when a laser beam irradiates a target body, the laser radar echo has obvious waveform information, when the laser beam is reflected on a heterodyne signal, the envelope of the laser radar echo is obviously different from distributed target echoes such as aerosol, and the interference of moving targets such as clouds, birds and unmanned planes can be eliminated by combining frequency shift information; when the laser beam does not irradiate the target body, judging the wind field disturbance characteristics from the laser echo, and searching the disturbance source by using the wind field disturbance rule until the target body is found.
Disclosure of Invention
In order to solve the technical problem, the invention provides an autonomous searching method for laser heterodyne detection of an air moving target, which comprises the following steps:
step 1, performing initial scanning detection on a predicted airspace of a target to acquire echo information of a scanned area;
step 2, extracting the amplitude and the speed extreme value of the echo of the initial scanning frame, and judging the type of the echo;
step 3, continuing to scan along the original scanning direction, and extracting the amplitude and the speed extreme value of the echo of the frame;
step 4, judging the type of the echo of the frame, comparing the size of the speed extreme value of the echo of the frame with that of the echo of the previous frame, controlling the scanning direction of the next frame according to the result, and extracting the amplitude value and the speed extreme value of the echo of the next frame;
and 5, repeating the steps until the amplitude and the speed extreme value of a certain frame of echo exceed the set amplitude threshold and the set speed extreme value threshold, and recording the azimuth of the frame of echo.
Further, the predicted airspace of the target is an area determined by infrared detectors, radar, or guidance information provided by an upper level.
Further, step 4 comprises the sub-steps of:
step 4.1, comparing the size of the speed extreme value of the echo of the current frame with that of the echo of the previous frame, and when the speed extreme value of the echo of the current frame is greater than that of the echo of the previous frame, continuing to scan the next frame according to the current scanning direction;
and 4.2, if the speed extreme value of the echo of the current frame is smaller than the speed extreme value of the echo of the previous frame, scanning the next frame towards the opposite direction of the current scanning direction.
Further, step 2 further comprises the substeps of:
step 2.1, preprocessing an echo signal of a scanned area, wherein the echo signal is an intermediate frequency echo signal;
step 2.2, Hilbert conversion is carried out on the preprocessed intermediate frequency echo signals to obtain a complex form of the intermediate frequency signals, a complex form signal modulus of the intermediate frequency signals is solved, and the maximum value of the modulus is an echo amplitude;
step 2.3, carrying out full-phase Fourier transform on the preprocessed intermediate frequency echo signal to obtain a signal frequency spectrum;
step 2.4, extracting a speed extreme value from the frequency spectrum by adopting a maximum discrete spectral peak estimation method;
step 2.5, the extracted echo amplitude is compared with a preset typical aerosol echo amplitude threshold, and if the echo amplitude is smaller than the preset typical aerosol echo amplitude threshold, the echo is judged to be from aerosol scattering in the atmosphere;
step 2.6, the extracted echo amplitude is compared with a preset typical aerosol echo amplitude threshold, and if the extracted echo amplitude is larger than the preset typical aerosol echo amplitude threshold, the step 2.7 is carried out;
step 2.7, comparing the speed extreme value extracted in the step 2.4 with a set speed threshold, and if the extracted speed extreme value is greater than the speed threshold, judging that the echo comes from the reflection of the target body; and if the speed extreme value is smaller than the speed threshold, judging that the echo comes from the atmospheric disturbance caused by the target motion.
Further, the preprocessing includes pulse accumulation and noise reduction processing.
Further, the target is a low detectability target.
Furthermore, the method uses a heterodyne laser radar system, the wavelength of the heterodyne laser radar system is 1.55 micrometers, the output energy is adjustable within the range of 0-400 muJ, the laser repetition frequency is 10kHz, the telescope receiving aperture is 0.2m, the sampling rate is 800MSPS, the field angle of the receiving and transmitting combined optical system is 0.1mrad, the scanning speed is 10 degrees/s, and the scanning has RHI and PPI scanning capabilities at the same time.
The method of the invention is adopted, and the heterodyne laser radar system is utilized to scan the airspace to be detected, aiming at improving the searching efficiency and reliability of low-detectability aerial moving targets such as stealth airplanes and the like. Discovering the existence of a stealth target body through envelope and amplitude isochronal domain characteristics of intermediate frequency signal echoes and combining frequency shift quantity; the method disclosed by the invention expands the search mode of the low-detectability moving target in the air, reduces the risk of losing the target and provides a feasible method for improving the target discovery probability of the traditional air detection laser radar.
Drawings
FIG. 1 is a schematic diagram of scanning of an airspace to be measured by a heterodyne laser radar;
FIG. 2 is a flow chart of an aerial target searching method based on laser echo time-frequency domain characteristics according to the present invention;
fig. 3 is a schematic diagram of pulse accumulation and full-phase FFT processing.
Fig. 4 is a flowchart for determining the type of echo.
Detailed Description
The invention aims to provide an air moving target small-area autonomous searching and tracking method based on laser echo time-frequency domain characteristics, which improves the searching and tracking capacity of a laser radar on targets, particularly low-detectability targets, can reduce the pressure of an external searching and guiding means when the targets are lost, and realizes the small-area autonomous searching and tracking on the air moving targets.
In order to achieve the purpose, the invention adopts the following technical scheme:
firstly, a laser heterodyne detection system performs initial scanning detection on a target possibly existing in an airspace to acquire echo information of a scanned area;
extracting the amplitude value and the speed extreme value of the echo of the initial scanning frame, and judging the type of the echo;
step three, continuing to scan along the original scanning direction, and extracting the amplitude and the speed extreme value of the echo of the frame;
judging the type of the echo of the frame, comparing the size of the speed extreme value of the echo of the frame with that of the echo of the previous frame, controlling the scanning direction of the next frame according to the result, and extracting the amplitude value and the speed extreme value of the echo of the next frame;
and step five, repeating the step four until the amplitude and the speed extreme value of the echo of a certain frame exceed the set amplitude threshold and the set speed extreme value threshold.
Further, the specific implementation process of extracting the amplitude and the velocity extreme value of the echo of the initial scanning frame in the step two is as follows:
step 21, preprocessing such as pulse accumulation and noise reduction is carried out on the intermediate frequency echo signals acquired by the laser heterodyne detection system;
step 22, performing Hilbert change on the preprocessed intermediate frequency signal to obtain a complex form of the intermediate frequency signal, solving a complex form signal module value, namely a signal envelope, and taking a maximum value of the envelope from the signal envelope, namely an echo amplitude value;
step 23, performing full-phase Fourier transform on the preprocessed intermediate-frequency echo signal to obtain a signal frequency spectrum;
and 24, extracting a speed extreme value from the frequency spectrum by adopting a maximum discrete spectrum peak estimation method.
Further, the specific implementation process of judging the echo type in the step two is as follows:
step 25, comparing the extracted amplitude value with a set typical aerosol echo amplitude threshold value, and if the extracted amplitude value is smaller than the echo amplitude threshold value, judging that the echo comes from aerosol scattering in the atmosphere;
step 26, when the amplitude is larger than the threshold of the echo amplitude, comparing the extracted speed extreme value with a set speed threshold, and if the speed extreme value is larger than the speed threshold, judging that the echo is reflected from the target body; if the speed extreme value is smaller than the speed threshold, the echo is judged to come from the atmospheric disturbance caused by the target, in particular the low detectability target.
Further, the specific implementation process of controlling the scanning direction of the next frame according to the result in the fourth step is as follows: after judging the echo type, when the laser echo is atmospheric aerosol scattering or atmospheric disturbance caused by the movement of a target, particularly a low-detectability target, comparing the size of the speed extreme value of the echo of the current frame with that of the echo of the previous frame, and when the speed extreme value of the echo of the current frame is greater than that of the echo of the previous frame, continuing to scan the next frame according to the current scanning direction; if the speed extreme value of the echo of the current frame is smaller than the speed extreme value of the echo of the previous frame, the next frame is scanned towards the opposite direction of the current scanning direction.
The following detailed description of embodiments of the invention refers to the accompanying drawings.
Due to the fact that a certain anti-detection measure is adopted for the low-detectability target, the capability of accurately acquiring target information is weakened, more false alarms exist, the guiding information can be provided for the heterodyne laser radar, and therefore the target searching efficiency and reliability are improved by means of the video domain characteristics of the echo. Referring to fig. 1, the method for searching an aerial target includes the following steps:
firstly, a laser heterodyne detection system performs initial scanning detection on a target possibly existing in an airspace to acquire echo information of a scanned area;
in this embodiment, the possible airspace of the target is an airspace in which low-detectability airborne targets such as stealth aircraft may appear, and the basic principle is as follows:
under the support of guiding information of other detection systems such as infrared and radar, a laser heterodyne detection system detects a small area where a target may exist, and a transmitting optical system is used for transmitting a laser pulse train to an airspace to be detected, as shown in fig. 2.
Separating partial energy from seed light for emitting laser pulse as local oscillator light with frequency off 0After passing through the acousto-optic frequency shifter, the frequency becomesf 0+∆f shift Thereby having heterodyne detection capability. The receiving optical system collects the backward scattering laser echo of the low detectivity target body or aerosol particle, and the frequency isf s Here, the heterodyne detection intermediate frequency signal may be expressed as:
in the formula (I), the compound is shown in the specification,ρin order to achieve the responsivity of the photodetector,η h in order for the laser heterodyne detection system to be efficient,Gis the gain of the detection circuit or circuits,P s (t) is the power of the echo,P l is the local oscillator optical power, phi s And phi l Respectively a signal light and a local oscillator light phase,n(t) is the noise, and (t) is the noise,ω IF =2π(f 0+∆f shift - f s ) When is coming into contact withω IF <2π∆f shift When the wind direction deviates from the detection system, whenω IF >2π∆f shift When the wind direction is detected, the wind direction is explained,
the envelope of the intermediate frequency signal is reflected, and when echo comes from aerosol echo, the echo envelope of each range gate is relatively flat; when coming from the target body, the echo envelope presents significant waveform information.
Extracting the amplitude value and the speed extreme value of the echo of the initial scanning frame, and judging the type of the echo;
1) intermediate frequency echo signal preprocessing
The echo of a single laser pulse is weak, the requirement of a subsequent data processing algorithm on the signal to noise ratio is difficult to meet, and the envelope amplitude and the speed extreme value of the intermediate frequency signal can be effectively extracted through the preprocessing processes of pulse accumulation, noise reduction and the like.
Pulse accumulation
Due to the existence of factors such as spontaneous radiation, certain wave bands exist in energy and phase of light pulses emitted by the laser and the amplifier, and the pulse accumulation effect is reduced. Obtaining the initial phase of the emitted laser light helps to improve the pulse accumulation effect. In pulse accumulation, the respective pulse data are first phase-aligned, and the accumulation process is as shown in fig. 3. In the range-resolved lidar, the intermediate frequency signal echo sequence can be expressed as,
in the formula (I), the compound is shown in the specification,i=(1,2,…,N) Is the serial number of the pulse,m=(1,2,…,M) Is the range gate label of the echo in each cycle,n(t) Is a white noise, and is,φ(i) Is the firstiRandom initial phase of each pulse, the value being 0 and 2πAre uniformly distributed. Phi ( m (t) Comprises the firstmFrequency shift information of wind speed in the individual range gates. Since the repetition frequency of the laser pulse is high, phi can be considered m (t) In thatNThe pulse time is kept constant.
In the context of figure 3 of the drawings,G i,m the mth range gate representing the ith pulse. By accumulating signals of different pulse periods at the same detection distance, the total accumulated signal after phase alignment can be expressed as,
in the formula (I), the compound is shown in the specification,H i,m (t) Is thatV i,m (t) The Hilbert transform of (a) is,jis an imaginary unit.
② noise reduction treatment
Because the atmospheric environment is complicated and changeable, especially when detecting wind field disturbance, the laser echo has obvious non-stationarity, so when filtering, need compromise high frequency and low frequency characteristic. After the wavelet basis function is selected, multi-scale wavelet transformation is carried out on the echo signal to obtain low-frequency and high-frequency coefficients of the echo signal in a wavelet domain; performing corresponding processing on the wavelet high-frequency coefficient obtained by transformation, and performing operations of zeroing, shrinking and reserving the high-frequency coefficient representing noise in the wavelet domain through a certain threshold selection rule to achieve signal denoising; and finally, performing data reconstruction processing by utilizing inverse wavelet transform, thereby achieving the purpose of denoising the echo signal by a certain noise.
Make the wavelet baseψ 0(η) Can be used for practical application, the wavelet basis must have an integral mean value of zero, is localized in both time and frequency space, and can use typical Morlet, Paul, DOG and other wavelet basis functionsAnd performing signal noise reduction processing. Taking the Morlet wavelet basis as an example:
in the formula (I), the compound is shown in the specification,γis a dimensionless frequency, to satisfy the above conditions,γ=6。
2) extracting amplitude of echo
During heterodyne detection, the amplitude of an echo can be obtained only by extracting the envelope of an intermediate frequency signal. A real signals(t) The Hilbert transform of (a):
in the formula, is convolution. The signal is corresponding to the complex form signalz(t) Can be expressed as:
s(t) Is noted asS(ω) Then, thenz(t) Corresponding frequency spectrumZ(ω) Comprises the following steps:
envelope function of signale(t) Is thatz(t) The value of (a) is, that is,e(t)=|z(t)|。
in the present embodiment, forV m (t) Processing according to the above process to obtain envelope of signalP h (t) The pulse envelope is the waveform of the transmitted pulse modulated by the atmospheric environment and the characteristics of the target. Further, according to the envelopeP h (t) Extracting the amplitudeP m ，
3) Extraction speed limit
The full-phase FFT (apFFT) has excellent capacity of suppressing spectrum leakage, so that the interference among spectrums of each frequency component is reduced, the intermediate frequency signal is more prominent, the frequency and the amplitude of the signal are favorably extracted, and no additional correction measure is needed. In this embodiment, apFFT is used instead of conventional FFT. After using the apFFT, a sequence of data length 2N-1 becomes a sequence of length N for the following data vector:
the processing flow for performing the apFFT mainly comprises 2 steps:
(1) carrying out period extension on each data vector with the length of N;
(2) summing the data sequences in a vertical direction, so as to obtain a data vector with full phase,
as can be seen from the above equation, apFFT is equivalent to a pairx(0) And the data of 2N-1 as the center is obtained by weighting the data by a convolution window, then carrying out N bit shift and summing.x ap Is the result of the apFFT with a rectangular window (no windowing). When the sampling data is subjected to windowing processing, the frequency spectrum leakage can be better inhibited. The conventional FFT and apFFT spectra are
It can be seen that the amplitude of apFFT is the square of the amplitude of the conventional FFT, and other spectral lines except the main spectral line are attenuated quickly, so that the main spectral line can be more prominent. The phase of each spectral line of the apFFT is the phase corresponding to the data center point, is irrelevant to frequency deviation and has phase invariance. The data windowing can further reduce the spectral leakage. The generalized cosine window function is most widely applied in FFT spectrum detection, and the basic expression is as follows,
in the formula (I), the compound is shown in the specification,Kanda i are characterized by different window functions whenK=1，a 0=a 1When =0.5, the equation is Hanning window, and the window function isKOptimal interpolation window in case of = 1.
Further on, from the spectrumX ap (k) The extraction adopts maximum discrete spectrum peak estimation and corresponds to the second in the frequency spectrumk m Point when echo sampling rate isf s The velocity corresponding to the frequency shift of the echo can be expressed as:
compared with the supersonic cruising speed of a stealth aircraft, the target speed of cloud layers, flying birds and the like is low, and a wind speed threshold value can be setv th =0.1MachWhen is coming into contact withv>v th The pulse envelope is considered to be an echo of a low detectability target body.
4) Determining echo type
Based on the principle, the specific process of judging whether the echo comes from the target body or the atmospheric aerosol or the target atmospheric disturbance according to the time domain and frequency shift characteristics of the amplitude, the speed extreme value and the like of the echo is as follows:
step 41, judgmentP h (t) Amplitude ofP m Whether a typical aerosol echo amplitude threshold is exceededP am ；
Step 42, whenP m <P am Then, the laser echo is judged to be from aerosol scattering;
step 43, whenP m >P am Then, extracting the Doppler frequency shift of the intermediate frequency signal corresponding to the signal envelope area to further obtain a speed extreme value, and if the speed extreme value exceeds a speed threshold value, judging that the laser echo comes from a target body, but not from a cloud layer, a flying bird and other targets, namely searching the target body;
step 44, whenP m >P am When the speed is at the extreme valuev max Less than a speed thresholdv th And judging that the laser echo comes from the target atmospheric disturbance.
Step three, continuing to scan along the original scanning direction, and extracting the amplitude and the speed extreme value of the echo of the frame;
if the laser echo meets the judgment condition that the echo comes from the target body in the step two, the laser beam is indicated to be accurately irradiated to the target body, the laser heterodyne detection system is indicated to search the target, at the moment, the scanning direction of the current scanning frame can be kept, the next frame scanning is carried out, and the searching is continued to find whether other targets exist.
If the laser echo does not come from the target body, it indicates that the laser heterodyne detection system does not search the target, at this time, the next frame of scanning is required to be performed according to the original scanning, the amplitude value and the speed extreme value of the echo of the frame are extracted by the same method as the second step, and whether the target is searched or not is determined by judging the type of the echo.
Judging the type of the echo of the frame, comparing the size of the speed extreme value of the echo of the frame with that of the echo of the previous frame, controlling the scanning direction of the next frame according to the result, and extracting the amplitude value and the speed extreme value of the echo of the next frame;
the step of judging the echo type of the current frame is the same as the step of judging the echo type in the step two. If the echo is judged to be from the target body, a new target body is searched, and if the echo is not from the target body, the motion direction of the target, particularly the low-detectability target, can be judged by comparing the magnitude of the speed extreme value of the echo. This is because the wind field disturbance generated by the low detectability air moving object will last for a long time and gradually decay in intensity with time, and then the intensity of the wind field disturbance generated by the moving object just flying through the air moving object will be greater than that of the wind field disturbance generated by the previous flying through, which shows that the speed extreme value will be greater, so by comparing the magnitudes of the speed extreme values, the laser scanning direction is scanned towards the flying direction of the moving object, and finally the object will be searched.
And step five, repeating the step four until the amplitude and the speed extreme value of the echo of a certain frame exceed the set amplitude threshold and the set speed extreme value threshold.
When the amplitude and the speed extreme value of a frame of echo both exceed the set amplitude threshold and speed extreme value threshold, the target is considered to be searched, and the laser echo is of the target body at the moment, namely the laser detection system searches the target body.
The atmospheric background database in the embodiment is obtained by observing the region to be measured for a long time, and comprises an atmospheric background wind field extreme value, clear air turbulence structure information, corresponding meteorological conditions such as temperature and humidity. Determining the wind speed threshold of each range gate signal during heterodyne laser radar scanning according to the atmospheric background databasev th (i,j) Whereini,jIs a positive integer and represents the number of each scanning point in space.
In the scanning frame, if the wind speed corresponding to any point P in spacev(i,j) Higher thanv th (i,j) Judging that the moving target disturbs the wind field; if notv(i,j)|≤v th And if so, determining that the scanning direction of the laser radar is unchanged.
In this embodiment, whenv(i,j)>v th When, assume the current frame is the firstkFrame in whichkIs a positive integer. Extracting the speed extreme value of the current framev max,k Andv min,k (ii) a Scanning the next frame according to the initial scanning direction and the first step and the second step, wherein the direction is recorded asD(k,k+1)；
If it is firstkThe wind field disturbance of the moving target exists in the +1 frame scanning result, and the extreme value is extractedv max,k+1Andv max,k+2. If it is not
If so, keeping the scanning direction of each current frame, and showing that the wind field disturbance of the moving target is gradually enhanced, wherein the scanning direction of each frame is gradually close to the target body; if it is not
Then will bekDirection of +2 frame scanningD(k,k+1) is the opposite.
And repeating the process until the target ontology is searched.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the embodiments of the present invention and not for limiting, and although the embodiments of the present invention are described in detail with reference to the above preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the embodiments of the present invention without departing from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (6)
1. A laser heterodyne detection autonomous searching method for an air moving target is characterized by comprising the following steps:
step 1, performing initial scanning detection on a predicted airspace of a target to acquire echo information of a scanned area;
step 2, extracting the amplitude and the speed extreme value of the echo of the initial scanning frame, and judging the type of the echo;
step 3, continuing to scan along the original scanning direction, and extracting the amplitude and the speed extreme value of the echo of the frame;
step 4, judging the type of the echo of the frame, comparing the size of the speed extreme value of the echo of the frame with that of the echo of the previous frame, controlling the scanning direction of the next frame according to the result, and extracting the amplitude value and the speed extreme value of the echo of the next frame; step 4 comprises the substeps of:
step 4.1, comparing the size of the speed extreme value of the echo of the current frame with that of the echo of the previous frame, and when the speed extreme value of the echo of the current frame is greater than that of the echo of the previous frame, continuing to scan the next frame according to the current scanning direction;
step 4.2, if the speed extreme value of the echo of the current frame is smaller than the speed extreme value of the echo of the previous frame, the next frame is scanned towards the opposite direction of the current scanning direction;
and 5, repeating the step 4 until the amplitude and the speed extreme value of a certain frame of echo exceed the set amplitude threshold and the set speed extreme value threshold, and recording the azimuth of the frame of echo.
2. The method of claim 1, wherein the predicted airspace of presence of the target is an area determined by infrared detectors, radar, or guidance information provided by an upper level.
3. The method of claim 1, wherein step 2 further comprises the sub-steps of:
step 2.1, preprocessing an echo signal of a scanned area, wherein the echo signal is an intermediate frequency echo signal;
step 2.2, Hilbert conversion is carried out on the preprocessed intermediate frequency echo signals to obtain a complex form of the intermediate frequency signals, a complex form signal modulus of the intermediate frequency signals is solved, and the maximum value of the modulus is an echo amplitude;
step 2.3, carrying out full-phase Fourier transform on the preprocessed intermediate frequency echo signal to obtain a signal frequency spectrum;
step 2.4, extracting a speed extreme value from the frequency spectrum by adopting a maximum discrete spectral peak estimation method;
step 2.5, the extracted echo amplitude is compared with a preset typical aerosol echo amplitude threshold, and if the echo amplitude is smaller than the preset typical aerosol echo amplitude threshold, the echo is judged to be from aerosol scattering in the atmosphere;
step 2.6, the extracted echo amplitude is compared with a preset typical aerosol echo amplitude threshold, and if the extracted echo amplitude is larger than the preset typical aerosol echo amplitude threshold, the step 2.7 is carried out;
step 2.7, comparing the speed extreme value extracted in the step 2.4 with a set speed threshold, and if the extracted speed extreme value is greater than the speed threshold, judging that the echo comes from the reflection of the target body; and if the speed extreme value is smaller than the speed threshold, judging that the echo comes from the atmospheric disturbance caused by the target motion.
4. The method of claim 3, wherein the pre-processing comprises pulse accumulation and noise reduction processing.
5. The method of claim 3, wherein the target is a low detectability target.
6. The method of claim 1, wherein the method uses a heterodyne lidar system with a wavelength of 1.55 μm, an adjustable output power in the range of 0-400 μ J, a laser repetition frequency of 10kHz, a telescope receiving aperture of 0.2m, a sampling rate of 800MSPS, a combined optics field of view of 0.1mrad, a scanning speed of 10 °/s, and scanning with both RHI and PPI scanning capabilities.
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Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5539408A (en) * | 1994-07-08 | 1996-07-23 | Deutsche Forschungsanstalt Fur Luft- Und Raumfahrt E.V. | Method for the detection, localization and velocity determination of moving targets from raw radar data from a coherent, single- or multi-channel image system carried along in a vehicle |
| CN102721967A (en) * | 2012-06-21 | 2012-10-10 | 中国人民解放军电子工程学院 | Method for discovering target in air based on disturbance type of wind field |
| RU2012157521A (en) * | 2012-12-27 | 2014-07-10 | Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Московский авиационный институт (национальный исследовательский университет)" (МАИ) | METHOD FOR MEASURING RADIAL SPEED OF AIRCRAFT AIRCRAFT WITH ONE-PULSE ANTENNA SYSTEM |
| CN104597455A (en) * | 2015-02-12 | 2015-05-06 | 中国科学技术大学 | Medium-frequency-agile all-fiber coherent wind lidar system |
| CN109765526A (en) * | 2018-12-29 | 2019-05-17 | 北京邮电大学 | A kind of Target Searching Method and device based on spatial spectrum |
| CN111929702A (en) * | 2020-09-23 | 2020-11-13 | 中国人民解放军国防科技大学 | Aerial target atmospheric disturbance variable-resolution detection method, storage medium and system |
| CN112526474A (en) * | 2020-11-23 | 2021-03-19 | 哈尔滨工程大学 | FMCW radar range-velocity joint estimation method based on full-phase Fourier transform |
-
2021
- 2021-08-27 CN CN202110991568.4A patent/CN113433555B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5539408A (en) * | 1994-07-08 | 1996-07-23 | Deutsche Forschungsanstalt Fur Luft- Und Raumfahrt E.V. | Method for the detection, localization and velocity determination of moving targets from raw radar data from a coherent, single- or multi-channel image system carried along in a vehicle |
| CN102721967A (en) * | 2012-06-21 | 2012-10-10 | 中国人民解放军电子工程学院 | Method for discovering target in air based on disturbance type of wind field |
| RU2012157521A (en) * | 2012-12-27 | 2014-07-10 | Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Московский авиационный институт (национальный исследовательский университет)" (МАИ) | METHOD FOR MEASURING RADIAL SPEED OF AIRCRAFT AIRCRAFT WITH ONE-PULSE ANTENNA SYSTEM |
| CN104597455A (en) * | 2015-02-12 | 2015-05-06 | 中国科学技术大学 | Medium-frequency-agile all-fiber coherent wind lidar system |
| CN109765526A (en) * | 2018-12-29 | 2019-05-17 | 北京邮电大学 | A kind of Target Searching Method and device based on spatial spectrum |
| CN111929702A (en) * | 2020-09-23 | 2020-11-13 | 中国人民解放军国防科技大学 | Aerial target atmospheric disturbance variable-resolution detection method, storage medium and system |
| CN112526474A (en) * | 2020-11-23 | 2021-03-19 | 哈尔滨工程大学 | FMCW radar range-velocity joint estimation method based on full-phase Fourier transform |
Non-Patent Citations (1)
| Title |
|---|
| Echo characteristics of polarized heterodyne lidar in nonspherical aerosol environments;Xiao Dong 等;《International Journal for Light and Electron Optics》;20191231;第302-312页 * |
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