CN108508413A - Target detection method based on probability statistics under low signal-to-noise ratio condition - Google Patents
Target detection method based on probability statistics under low signal-to-noise ratio condition Download PDFInfo
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- CN108508413A CN108508413A CN201710875752.6A CN201710875752A CN108508413A CN 108508413 A CN108508413 A CN 108508413A CN 201710875752 A CN201710875752 A CN 201710875752A CN 108508413 A CN108508413 A CN 108508413A
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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
- G01S7/02—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
- G01S7/292—Extracting wanted echo-signals
- G01S7/2923—Extracting wanted echo-signals based on data belonging to a number of consecutive radar periods
- G01S7/2927—Extracting wanted echo-signals based on data belonging to a number of consecutive radar periods by deriving and controlling a threshold value
-
- 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
- G01S13/42—Simultaneous measurement of distance and other co-ordinates
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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
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/06—Systems determining position data of a target
- G01S13/42—Simultaneous measurement of distance and other co-ordinates
- G01S13/44—Monopulse radar, i.e. simultaneous lobing
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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
- G01S7/02—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
- G01S7/292—Extracting wanted echo-signals
- G01S7/2923—Extracting wanted echo-signals based on data belonging to a number of consecutive radar periods
- G01S7/2926—Extracting wanted echo-signals based on data belonging to a number of consecutive radar periods by integration
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- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Computer Networks & Wireless Communication (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Radar Systems Or Details Thereof (AREA)
Abstract
The invention belongs to the technical field of radar signal processing, and particularly relates to a target detection method based on probability statistics under a low signal-to-noise ratio condition. The method comprises the steps of taking a single pulse in observation time as a processing object, covering an interested observation area by adopting a simultaneous multi-beam method, obtaining a target echo envelope after pulse compression of all pulse echoes in the observation area, carrying out constant false alarm detection on the echo envelope, carrying out statistics and recording on echo envelope detection frequencies of different azimuth units and distance units, and finally drawing a probability histogram to carry out detection judgment according to threshold crossing frequency distribution of the different azimuth units and distance units so as to finish a target detection process. The method provided by the invention is not only suitable for single-pulse target detection under low signal-to-noise ratio, but also can be used as an auxiliary detection means for target detection which is not ideal after multi-pulse long-time accumulation. The method provided by the invention has small data processing amount, meets the real-time processing requirement of a hardware platform, and is suitable for engineering realization.
Description
Technical field
The invention belongs to Radar Signal Processing Technology field more particularly to a kind of Low SNRs based on probability statistics
Under object detection method.
Background technology
Low signal-to-noise ratio target detection is the hot issue of modern radar research.Radar is believed as primary electron in modern war
Breath equipment is responsible for always battle field information acquisition, processing and circuit and realizes task, only determines whether interested target deposits
, and the relevant informations such as target velocity, angle are obtained, locating and tracking, imaging identification could be carried out to target.With in battlefield
Electromagnetic environment becomes increasingly complex, and clutter and noise jamming are serious, stealth technology with the detectable feature for reducing target, it is low
Can acquisition techniques with pole Wideband FM Technique, noise like modulation and or directional diagram pseudo random scanning, these factors will cause
The echo signal signal-to-noise ratio received is very low so that the detection of radar becomes extremely difficult.It is received in echo signal same
When, some unwanted interference signals are inevitably received, and the ambient noise interference in electromagnetic environment is radar letter
It is intrinsic when number processing, therefore in order to determine that echo signal whether there is in radar return, radar signal processor must have
The link that the presence or absence of target is judged.The Radar Targets'Detection system of early stage is to the judgement of target all dependent on operation
The experience of personnel, modern radar system use automatic checkout system, overcome target detection performance and are limited by staff's ability
Make this disadvantage.Statistical decision theory is applied in target detection by automatic checkout system, a detection threshold is previously set, so
Afterwards target is detected according to decision rule.However, if detection threshold is set as constant, then under non-stationary clutter, work as background
When the mean power of clutter increases several decibels, false-alarm probability can rapidly rise, so that computer process ability is saturated, influence
Radar system works normally.So constant false alarm rate detection method is used during Radar Targets'Detection, according to the change of noise intensity
Change adaptively changes detection threshold, to obtain maximized detection probability and constant false-alarm probability, but constant false alarm rate mesh
Mark detection technique requires signal-to-noise ratio, and testing result is bad under Low SNR.Many scholars are directed to Low SNR
Under target detection problems propose long time integration method, but with the development of new system radar and increasingly sophisticated electromagnetic interference
The object detection method of environment, long time integration also not necessarily effectively improves signal-to-noise ratio sometimes, therefore target detection effect is paid no attention to
Think.
Invention content
The present invention proposes a kind of low letter based on probability statistics for the target detection problems in the research of above-mentioned modern radar
It makes an uproar the object detection method than under the conditions of.Present invention is generally not limited to the working systems of radar, are applicable not only to the low letter of pulse
It makes an uproar than target detection, and suitable for the low signal-to-noise ratio target detection after multiple-pulse long time integration.The present invention can effectively improve
Target detection accuracy rate under Low SNR, and the data volume of algorithm process is small, is easy to engineering and realizes.
Technical scheme of the present invention comprises the steps of：
S1. the azimuth-range range that power covers in being worked according to radar carries out orientation to interested observation area
Unit and range cell divide, wherein localizer unit θ ∈ { θi| i=1,2 ..., M } and range cell r ∈ { rj| j=1,2 ...,
N }, M and N indicate the zone aspect number of unit and range cell number respectively；
S2. according to the dividing elements of the observation area interested of radar antenna direction in step S1, receiver antenna is each
Unit channel acquires the echo-signal of different direction unit and range cell using band logical quadrature sampling；
S3. the echo-signal received to step S2 acquisitions carries out data prediction, then obtains base band through Digital Down Convert
Echo-signal carries out low-pass filtering to base band echo-signal, eliminates the interference other than bandwidth and noise；
S4. according to the localizer unit { θ that interested observation area divides in step S1i| i=1,2 ..., M }, to be formed
The corresponding wave beam of i-th of localizer unit, the method for taking simultaneous multiple beams carry out the localizer unit divided in covering observation area
{θi| i=1,2 ..., M } obtain the corresponding wave beam weight vector W of i-th of localizer uniti=[w0i,w1i,…,w1i,…,wLi], wli
For l (l ∈ (0,1 ... L-1)) a unit channel weighting coefficient, L is the unit number for the array antenna that receiver uses；
S5. the obtained base band echo-signals of the beam weight vector sum step S3 that step S4 is obtained are multiplied to obtain containing orientation
The base band echo-signal of information；
S6. process of pulse-compression is carried out to the base band echo-signal containing azimuth information in step S5, pulse compression utilizes
Matched filtering method is realized, the compressed base band echo-signal of the pulse containing azimuth information is finally obtained；
S7. according to the compressed base band echo-signal of the pulse containing azimuth information obtained in step S6, when to observation
The envelope of interior all echo-signals carries out Threshold detection, and statistic record each echo envelope crosses range cell and the side of thresholding
Bit location；
S8. the range cell and localizer unit statistical result that thresholding is crossed according to echo envelope in step S7, respectively to difference
Localizer unit and the corresponding detection frequency of different distance unit do probability histogram；
S9. it is detected and sentences according to the different direction unit and different distance orthant probabilities histogram that are obtained in step S8
Certainly, it compares in different direction unit and the corresponding probability histogram of range cell and detects channel zapping, move into one's husband's household upon marriage in probability histogram
Limit inspection frequency is apparently higher than existing for other judgement targets, corresponding localizer unit and range cell be target orientation and
Range information；
S10. it if the detection judgement of probability histogram can not provide accurate object detection results in step S9, uses
Improved probability histogram as described below detects decision method：It is general according to azimuth-range cell size adjustment in step S1
The window width of rate histogram repeats the probability histogram detection judgement for carrying out step S9, until the channel zapping of probability histogram
Object detection results can be obviously provided, finally export object detection results；
The target detection under Low SNR for using long time integration, after pulse compression will be obtained in step S6
Echo-signal carry out long time integration, after obtaining the echo-signal after long time integration, repeat step S7-S10.
The present invention has the following advantages：
(1) method proposed by the invention can improve radar to seeing in the case where signal-to-noise ratio is low and false-alarm probability height
Survey the target detection performance in region.
(2) method proposed by the invention is suitable for pulse target detection.
(3) method proposed by the invention is suitable for the low signal-to-noise ratio target detection after long time integration.
(4) method proposed by the invention can be used for multi-target detection.
(5) method data processing amount proposed by the invention is small, is suitble to processing in real time, is easy to engineering and realizes.
Description of the drawings
Fig. 1 is method implementing procedure figure proposed by the present invention；
Fig. 2 is the observation area localizer unit and range cell division schematic diagram involved by method proposed by the present invention；
Fig. 3 be the present invention a specific embodiment in receive signal while multi-beam method schematic diagram；
Fig. 4 be the present invention a specific embodiment in constant false alarm target detection schematic diagram；
Fig. 5 be the present invention a specific embodiment in measured data 1 probability histogram of localizer unit；
Fig. 6 be the present invention a specific embodiment in measured data 2 probability histogram of localizer unit；
Fig. 7 be the present invention a specific embodiment in probability histogram after unit variation；
Fig. 8 is the relational graph that the present invention emulates detection probability and signal-to-noise ratio under different false-alarm probabilities；
Fig. 9 is the relational graph that the present invention emulates detection probability and false-alarm probability under different signal-to-noise ratio；
Specific implementation mode
Below in conjunction with the accompanying drawings and specific embodiment is further elaborated the present invention.
For this example by taking pulse radar as an example, signal modulation form is linear frequency modulation, carrier frequency 300MHz, bandwidth
5MHz, it is 0.5m that receiver, which uses the linear array antenna that the equidistant level of Unit 10 is structured the formation, wavelength X 1m, cell spacing d,
Antenna installs servo-control system, can control antenna towards interested observation area, and the bearing range of observation area is-
45 ° to 45 °, distance range is 130Km to 200Km, and localizer unit size is 10 °, range cell 30m.
Method implementing procedure figure of the present invention in referring to Fig.1, target under the Low SNR based on probability statistics
Detection method mainly comprises the steps of：
S1. the azimuth-range range that the covering of radar power is determined according to the systematic parameter of radar, utilizes antenna servo system
Control radar antenna unite towards interested observation area in radar power coverage area, dividing elements are carried out to the region,
Middle localizer unit θ ∈ { θi| i=1,2 ..., M } and range cell r ∈ { rj| j=1,2 ..., N }, M and N indicate the region side respectively
Bit location number and range cell number, Fig. 2 be in observation area involved by method proposed by the present invention localizer unit and away from
From dividing elements schematic diagram；
S2. according to the dividing elements of the observation area interested of radar antenna direction in step S1, receiver antenna is each
Unit channel acquires the echo-signal of different direction unit and range cell using band logical quadrature sampling；
S3. the data predictions such as it is amplified and filters to collected echo-signal in step S2, then through becoming under number
Base band echo-signal is obtained after frequency, and low-pass filtering is carried out to base band echo-signal, eliminates the interference other than bandwidth and noise：Base band
Echo-signal is transferred to signal-processing board by optical fiber and is handled in real time, while can be transferred to large capacity disc by optical fiber
Later stage signal processing is used in array；
S4. the method for taking simultaneous multiple beams carries out the orientation list in the observation area interested divided in covering step S1
Member obtains the corresponding wave beam weight vector of all localizer units：Because the signal-to-noise ratio of target echo is very low, in order to more completely connect
Receive the target echo signal in area-of-interest, it is necessary to which the method by using simultaneous multiple beams in digital beam forming technology is same
When form multiple wave beams to cover interested observation area, this step the specific implementation process is as follows：
Reception antenna is the linear array antenna that the equidistant level of L units is structured the formation, according to the area of observation coverage interested in step S1
Domain localizer unit divides { θi| i=1,2 ..., M }, to form corresponding wave beam pair l (the l ∈ (0,1 ... of i-th of localizer unit
L-1)) a unit channel weighting coefficient wli：
Wherein alFor the amplitude weighting coefficient of first of unit of array antenna, then the corresponding beam weight arrow of i-th of localizer unit
Measure WiFor：
S5. by the wave beam weight vector W of different direction unit in step S4iWith the base in antenna different units channel in step S3
The base band echo-signal containing azimuth information is obtained with echo signal multiplication：The wave beam weight vector of different direction unit is multiplied by day
The base band echo-signal in line different units channel obtains the corresponding base band echo-signal of different direction unit, and antenna element is logical at this time
The base band echo-signal in road is converted to the base band echo-signal of localizer unit, i.e. the base band echo-signal containing azimuth information；
S6. pulse compression is carried out to the base band echo-signal containing azimuth information obtained in step S5, pulse compression is logical
Overmatching filtering technique is realized, convolution is carried out with the echo-signal containing azimuth information by constructing filter receptance function h (t)
It is multiplied, finally obtains the compressed base band echo-signal of the pulse containing azimuth information；
This step the specific implementation process is as follows：
The signal modulation form of pulse radar is linear frequency modulation, then radar emission signal baseband signal s (t) expression formulas
For：
Wherein TpTo emit the pulse width of signal, B is the bandwidth of echo-signal, K=B/TpBe echo-signal frequency modulation it is oblique
Rate.If the pulse carrier frequency of radar system is not constant constant, by the waveform of nth bar transmitting signal after Carrier ModulationFor：
WhereinAnd tnThe respectively fast time (sampling interval in pulse) of transmitting signal and (adopting between pulse of slow time
Sample interval),tn=nTr, wherein TrFor radar transmitted pulse repetition period, fnFor the carrier frequency of nth bar pulse.It is false
It is r in the initial distance at t=0 moment if moving target moves with uniform velocity away from radar direction0, speed v0, then target range r
(t) relational expression changed over time：
R (t)=r (tn)=r0+v0tn
The echo time delay τ of targetnFor：
The nth bar target echo so received whithin a period of timeIt can be expressed as：
Wherein ArIt is the complex magnitude of echo-signal, the base band echo containing azimuth information after coherent demodulationFor：
Pulse compression is completed by matched filtering, and filter response h (t) is that the reversion of transmitting signal baseband signal is total
Yoke.
By filter receptance function h (t) and the base band echo-signal containing azimuth informationConvolution multiplication is carried out, most
The compressed base band echo-signal of the pulse containing azimuth information is obtained afterwards
" * " indicates that convolution is multiplied.
S7. according to the compressed echo-signal of the pulse containing azimuth information obtained in step S6, in observation time
The envelope of all echo-signals carries out Threshold detection, and statistic record each echo envelope crosses the range cell and orientation list of thresholding
Member：Threshold detection in this step uses unit average constant false alarm rate detection method, and statistic record is each in threshold detection process
Pulse echo envelope crosses the localizer unit and range cell of thresholding, and Fig. 4 simulation units of the present invention are averaged the inspection of constant false alarm rate target
Survey process example figure；
S8. the localizer unit and range cell statistical result that thresholding is crossed according to echo envelope in step S7, respectively to difference
Localizer unit and the corresponding detection frequency of different distance unit do probability histogram：Probability histogram is provided to target detection knot
The global description of fruit, the frequency that the same unit occurs can regard the detection probability of its target as, therefore will be put down in the present embodiment
For horizontal axis as range cell, it is corresponding that the longitudinal axis was used as the frequency of thresholding to draw different direction unit respectively in the rectangular coordinate system of face
Probability histogram, Fig. 5 and Fig. 6 provide the probability histogram of localizer unit 1 and localizer unit 2 in measured data；
S9. it is detected and sentences according to the different direction unit and different distance orthant probabilities histogram that are obtained in step S8
Certainly, in probability histogram over-threshold detection frequency be apparently higher than other judgement targets existing for, corresponding localizer unit and away from
From the azimuth-range information that unit is target：For radar in order to improve target detection probability, false-alarm probability usually setting is very high,
Detection threshold can be caused low in this way, target may be caused detection inaccurate by clutter and noise jamming when single detects, and be counted at this time
All echo envelopes cross the localizer unit and range cell of thresholding in observation time, are detected to the same azimuth-range unit
Frequency to be apparently higher than other judgements be that target exists, therefore can be carried out to target using the channel zapping of probability histogram
Detection judgement；
S10. it if the detection judgement of probability histogram can not provide accurate object detection results in step S9, uses
Improved probability histogram as described below detects decision method：It is general according to azimuth-range cell size adjustment in step S1
The window width of rate histogram repeats the probability histogram detection judgement for carrying out step S9, until the channel zapping of probability histogram
Object detection results can be obviously provided, finally export object detection results：
Compressed echo, echo envelope center τ are rushed according to step S6 middle arteriesnDetermine the distance list residing for target
Member, but echo envelope center τnIt is a variable, as target movement may cause the same distance of echo single across range cell
First energy dissipation, causes signal-to-noise ratio to decline.When covering observation area using the method for simultaneous multiple beams, divided when localizer unit
When closely spaced, target movement is easy to lead to the energy dissipation of the same localizer unit of echo across localizer unit, causes noise
Than declining.Therefore, target movement may make the energy of target echo be diffused into other range cells and localizer unit, lead to mesh
Marking echo signal-to-noise ratio reduces.The present invention takes a kind of probability histogram to improve detection decision method, can be according to orientation in step S1
The window width of probability histogram is adjusted with range cell size, improves target detection performance.Fig. 7 provides a comparison diagram 6 apart from list
Probability histogram after member increase.
For the low signal-to-noise ratio target detection using long time integration, the compressed echo letter of pulse will be obtained in step S6
Number carrying out long time integration obtains the echo-signal after long time integration, repeats step S7-S10；
This step the specific implementation process is as follows：
Long time integration method to the compressed echo of n pulse obtained in step S6 by carrying out cumulative realization.Root
According to whether the phase information of echo is utilized, long time integration method is divided into correlative accumulation and non-inherent accumulation.For correlative accumulation,
Echo envelope after long time integrationFor：
Therefore for echo-signal with being added, echo amplitude increases to original N times, signal energy product during correlative accumulation
Tired increase is original N2Times, and noise phase changes at random within integration time, it is original N times that noise power, which increases, institute
Original N times is risen to signal-to-noise ratio after correlative accumulation.
For non-inherent accumulation, the echo envelope after long time integrationFor：
Due to having abandoned the phase information of echo, non-inherent accumulation wants much lower relative to the accumulation efficiency of correlative accumulation,
It is worth noting that as the carrier frequency f of echo-signalnWhen variation, phase relation is destroyed between pulse, usually uses non-inherent accumulation at this time
Method completes the long time integration of target echo, may result in target when long time integration in addition across Range cell migration, shadow
Ring target detection performance.
The relational graph (Fig. 8, Fig. 9) of the target detection probability and signal-to-noise ratio and false-alarm probability that are emulated from the present invention can be seen
Go out, in the target detection under Low SNR, detection probability increases with the increase of false-alarm probability, but when false-alarm is general
Detection threshold is lower when rate increases, and the testing result of target causes the Detection accuracy of target to decline it is easy to appear erroneous judgement.
The signal-to-noise ratio accumulated in application scenes using long time integration method may still reach to the requirement of fall short detection, especially
It is receive pulse echo between phase relation be difficult to determine, after long time integration signal-to-noise ratio improve is not obvious.Therefore
Low signal-to-noise ratio object detection method proposed by the present invention based on probability statistics is processing pair with the single pulse in observation time
As, observation area interested is covered using simultaneous multiple beams method, by all pulse echos in observation area through pulse
Target echo envelope is obtained after compression, then to echo envelope do after CFAR detection statistic record different direction unit and away from
Echo envelope from unit detects frequency, finally draws excessively thresholding of the probability histogram according to different direction unit and range cell
Channel zapping be detected judgement to complete target detection process.Method proposed by the present invention is not only adapted to low signal-to-noise ratio
Under pulse target detection, be also used as the undesirable auxiliary detection means of target detection after multiple-pulse long time integration.
Method data processing amount proposed by the present invention is small, meets the real time handling requirement of hardware platform, is suitable for engineering and realizes.
Claims (6)
1. object detection method under a kind of Low SNR based on probability statistics, which is characterized in that this method includes following
Step：
S1. the azimuth-range range that power covers in being worked according to radar carries out localizer unit to interested observation area
It is divided with range cell, wherein localizer unit θ ∈ { θi| i=1,2 ..., M } and range cell r ∈ { rj| j=1,2 ..., N }, M
Indicate the zone aspect number of unit and range cell number respectively with N；
S2. according to the dividing elements in step S1 in observation area, receiver antenna acquisition receives the echo letter in different units
Number；
S3. the echo-signal received to step S2 acquisitions carries out data prediction, then obtains base band echo through Digital Down Convert
Signal carries out low-pass filtering to base band echo-signal, eliminates the interference other than bandwidth and noise；
S4. according to the localizer unit { θ that interested observation area divides in step S1i| i=1,2 ..., M }, to be formed i-th
The corresponding wave beam of localizer unit, the method for taking simultaneous multiple beams cover the localizer unit { θ divided in observation areai| i=1,
2 ..., M }, obtain the corresponding wave beam weight vector W of i-th of localizer uniti=[w0i,w1i,…,w1i,…,wLi], wliFor l (l ∈
(0,1 ... L-1)) a unit channel weighting coefficient, L is the unit number for the array antenna that receiver uses；
S5. the obtained base band echo-signals of the beam weight vector sum step S3 that step S4 is obtained are multiplied to obtain containing azimuth information
Echo-signal；
S6. process of pulse-compression is carried out to the echo-signal containing azimuth information in step S5, pulse compression utilizes matched filtering
Method is realized, the compressed echo-signal of the pulse containing azimuth information is finally obtained；
S7. according to the compressed echo-signal of the pulse containing azimuth information obtained in step S6, to owning in observation time
The envelope of echo-signal carries out Threshold detection, and statistic record each echo envelope crosses the range cell and localizer unit of thresholding；
S8. the range cell and localizer unit statistical result that thresholding is crossed according to echo envelope in step S7, respectively to different direction
Unit and the corresponding detection frequency of different distance unit do probability histogram；
S9. judgement is detected according to the different direction unit and different distance orthant probabilities histogram that are obtained in step S8, it is right
Channel zapping is detected in probability histogram more corresponding with range cell than different direction unit, and thresholding inspection frequency is crossed in probability histogram
Degree is apparently higher than existing for other judgement targets, and corresponding localizer unit and range cell are the azimuth-range letter of target
Breath；
S10. if the detection judgement of probability histogram can not provide accurate object detection results in step S9, using as follows
The improved probability histogram detects decision method：It is straight according to azimuth-range cell size adjustment probability in step S1
The window width of square figure repeats the probability histogram detection judgement for carrying out step S9, until the channel zapping of probability histogram can be bright
It is aobvious to provide object detection results, finally object detection results are exported.
2. object detection method under the Low SNR based on probability statistics according to claim 1, it is characterised in that：Step
The process of process of pulse-compression in rapid S6 is as follows：
The signal modulation form of pulse radar is linear frequency modulation, then radar emission signal baseband signal s (t) expression formulas are：
Wherein TpTo emit the pulse width of signal, B is the bandwidth of echo-signal, K=B/TpIt is the chirp rate of echo-signal；
If the pulse carrier frequency of radar system is not constant constant, by the waveform of nth bar transmitting signal after Carrier Modulation
For：
WhereinAnd tnThe respectively fast time and slow time of transmitting signal,tn=nTr, wherein TrFor radar emission
Pulse repetition period, fnFor the carrier frequency of nth bar pulse；Assuming that moving target moves with uniform velocity away from radar direction, in t=0
The initial distance at quarter is r0, speed v0, then target range r (t) is changed over time relational expression：
R (t)=r (tn)=r0+v0tn
The echo time delay τ of targetnFor：
The nth bar target echo so received whithin a period of timeIt can be expressed as：
Wherein ArIt is the complex magnitude of echo-signal, the base band echo containing azimuth information after coherent demodulationFor：
Pulse compression is completed by matched filtering, and filter responds the reversion that h (t) is baseband signal and is conjugated：
By filter receptance function h (t) and contain the echo-signal of azimuth informationCarry out convolution multiplication, finally obtain containing
The compressed base band echo-signal of pulse of azimuth information
" * " indicates that convolution is multiplied.
3. object detection method under the Low SNR based on probability statistics according to claim 1, it is characterised in that：Step
Threshold detection in rapid S7 uses unit average constant false alarm rate detection method.
4. special according to object detection method under the Low SNR based on probability statistics described in claims 1 to 3 any bar
Sign is：The target detection under Low SNR for using long time integration, after pulse compression will be obtained in step S6
Echo-signal carry out long time integration, after obtaining the echo-signal after long time integration, repeat step S7-S10.
5. object detection method under the Low SNR based on probability statistics according to claim 4, it is characterised in that：Institute
Long time integration method is stated by carrying out cumulative realization to the compressed echo of n pulse obtained in step S6.
6. object detection method under the Low SNR based on probability statistics according to claim 4, it is characterised in that：Institute
It states long time integration method and is divided into correlative accumulation and non-inherent accumulation.
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