CN106443613A - Method for improving vibration-measuring signal to noise ratio of radar - Google Patents
Method for improving vibration-measuring signal to noise ratio of radar Download PDFInfo
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- CN106443613A CN106443613A CN201610402974.1A CN201610402974A CN106443613A CN 106443613 A CN106443613 A CN 106443613A CN 201610402974 A CN201610402974 A CN 201610402974A CN 106443613 A CN106443613 A CN 106443613A
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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
- G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
- G01S7/415—Identification of targets based on measurements of movement associated with the target
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
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- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- General Physics & Mathematics (AREA)
- Computer Networks & Wireless Communication (AREA)
- Electromagnetism (AREA)
- Radar Systems Or Details Thereof (AREA)
Abstract
The invention discloses a method for improving the vibration-measuring signal to noise ratio of radar. The method includes: assuming that the absolute value of E'-bar is equal to (the absolute value of E-bar)/2, based on this, according to E'-bar=E-bar-D, obtaining D shown in the description, and when a target does not vibrate, according to E'=E-D and D shown in the description, obtaining E' shown in the description, and extracting the phase phi'<M> of E'/E'-bar; obtaining the noise average power of each theta value based on the variance E shown in the description of the phase phi'<M>; when the target vibrates, extracting the phase phi'<M> of E'/E'-bar by theta according to E'=E-D and D shown in the description; based on peak points in a phi'<M> frequency spectrum, obtaining the signal average power of each theta value; and extracting the phase phi'<M> of E'/E'-bar as an output result of final vibration measurement by taking D (shown in the description) corresponding to theta<max> as a constant vector subtracted from E based on the signal average power of each theta value and the noise average power of each theta value. According to the method, the problem of the influence of vibration-measuring clutter of the radar on the signal to noise ratio can be solved.
Description
Technical field
The invention belongs to radar vibration measuring technical field, and in particular to a kind of method for improving for radar vibration measuring signal to noise ratio.
Background technology
Vibration is the common phenomenon of nature and engineering circles, conventional vibration measurement method be divided into contact vibration measurement and
Contactless vibration measurement.Contact vibration measurement needs, by measuring instrument on Vibration Targets, therefore to influence whether target
The vibration of itself.Vibration measurement with laser in contactless vibration measurement has very high vibration measuring precision, but target surface can be subject to thick
Rough degree and the impact of weather, and do not possess penetration capacity.Radar can be worked all-time anf all-weather, and can be worn
Barrier is measured to target thoroughly, is carried out contactless vibration measurement hence with radar and has been obtained extensive research.According to
Doppler's theorem, when electromagnetic wave irradiation is to Vibration Targets, target can produce modulation to radar return Doppler, as long as demodulating
Echo-signal can just obtain the vibration information of target, so as to reach the function of vibration measurement.
When being measured to Vibration Targets using radar, in echo will comprising Vibration Targets echo, clutter, thermal noise and
Phase noise, their joint effects the signal to noise ratio of vibration measurement.When the clutter in the range cell of target place be can not ignore,
It plays certain linear modulation effect to intended vibratory.Under conditions of oscillation intensity and noise level are certain, target is located
The echo-signal of range cell is played a decisive role to modulation degree with the phase contrast of total echo-signal of target place range cell, no
Same phase contrast can cause the relatively macrorelief of phase measurement signal to noise ratio.Only when phase contrast is 0, system can reach the letter of optimum
Make an uproar ratio；In the case of other, signal to noise ratio all occurs certain loss；Particularly when phase contrast, there is signal to noise ratio for 0, substantially no mesh
Mark Vibration ability.In order that system reaches the phase measurement signal to noise ratio of optimum, the present invention proposes a kind of for radar survey
The method that signal to noise ratio of shaking improves.
Content of the invention
In view of this, the present invention proposes a kind of method for improving for radar vibration measuring signal to noise ratio, can solve the problem that radar vibration measuring
Impact problem of the clutter to signal to noise ratio.
Realize specific embodiments of the present invention as follows：
A kind of method for improving for radar vibration measuring signal to noise ratio, comprises the following steps that：
Step one, orderWhereinFor target under noise free conditions static when target place range cell peak value
Point signal, E' deducts, for slow time signal E of target place range cell peak point, the remaining letter that a constant vector D is obtained
Number,Average for E'；It is based onObtainAccording toObtain
θ isWithVector angle；
Step 2：When target is not vibrated, θ is incremented by with fixed step size in 0～360 ° of span, according to E '=E-D
WithObtainFoundationWithExtractPhase place Φ 'M；Based on phase place Φ 'MVariance E (| Φ 'M|2), obtain the noise average power of each θ value；
Step 3：In intended vibratory, θ is incremented by with fixed step size in 0～360 ° of span, according to E '=E-D andObtainFoundationWithExtract
Phase place Φ 'M；To Φ 'MMake fast Fourier transform and obtain Φ 'MFrequency spectrum, and extract Φ 'MPeak point in frequency spectrum, based on Φ 'M
Peak point in frequency spectrum, obtains the average power signal of each θ value；
Step 4：The making an uproar of each θ value for obtaining with step 2 of average power signal of each the θ value for being obtained based on step 3
Sound mean power, obtains the phase measurement average signal-to-noise ratio of each θ value, selects according to the phase measurement average signal-to-noise ratio of each θ value
Corresponding θ when selecting signal to noise ratio maximum, is denoted as θmax；
Step 5：θ by step 4maxCorrespondingAs the constant arrow for deducting from E in step one
Amount, is based onWithExtractPhase place Φ 'MAs resulting vibration
The output result of measurement.
Beneficial effect：
(1) present invention contains the situation of clutter for micro-vibration target place range cell, and establishing phase place derives vibration measuring
Model, calculates simply, and easily realizes, and is capable of quantitative description impact of the clutter to radar vibration measuring signal to noise ratio.
(2) a kind of method for improving for radar vibration measuring signal to noise ratio proposed by the present invention, can not only improve radar vibration measuring
Signal to noise ratio, also has the effect that suppression phase noise affects on vibration measuring, so as to improve the observing capacity to micro-vibration target.
Description of the drawings
Fig. 1 is that one vertical frame dimension of target scene differentiates one-dimensional picture figure；
Fig. 2 is the variation diagram of intended vibratory scene signals mean power and noise average power with θ；
Fig. 3 be before processing after phase measurement signal to noise ratio with θ variation diagram；
Fig. 4 is optimum signal to noise ratio output phase power spectrogram；
Fig. 5 is the method flow diagram of radar vibration measuring signal to noise ratio improvement.
Specific embodiment
Develop simultaneously embodiment below in conjunction with the accompanying drawings, describes the present invention.
The mentality of designing of the present invention is as follows：Based on the slow time signal of target place range cell peak point, high score is set up
Distinguish that phase place derives vibration measuring model, derive, according to high-resolution phase place, the signal to noise ratio that vibration measuring model obtains phase measurement；
Radar enters row distance pulse pressure and forms the high-resolution containing Vibration Targets to Vibration Targets Emission High Resolution waveform to echo
One-dimensional picture, it is assumed that target does not occur walking about for more range cell in vibration processes, target place range cell peak point slow
Time signal E can be write as the form of (1)：
Wherein, S, C and N are respectively the signal in the slow time echo that micro-vibration target place range cell peak point is constituted
Component, clutter component and component of thermal noise, S0Represent the echo strength of micro-vibration target, Φs0It is target backscattering coefficient institute
The phase place of carrying, R0It is the distance of target, λ is that transmission signal wavelength, M (t) is the vibration signal of target, ΦsnT () is that target is returned
The phase noise that ripple is carried, C0Represent the echo strength of clutter, Φc0It is the stationary phase of clutter, ΦcnT () is that clutter echo is taken
The phase noise of band.
Order With
Under target place range cell peak point signal when representing that under noise free conditions, target is static respectively, noise free conditions, target is static
When the target component of target place range cell peak point signal and noise free conditions under target static when distance that target is located single
First peak point signal noise component.
Assume
That is the phase noise in intended vibratory phase place | 4 π M (t)/λ |, target | Φsn(t) |, the phase noise on clutter |
Φcn(t) |, the ratio of thermal noise and object element static reflected wave amplitudeFar smaller than 1.Under this condition, to formula
(1) do Taylor series expansion and following expression obtained,
Wherein, o () represents higher order indefinite small.
Using target phase place under static state as stationary phase, from the phase measurement of E, stationary phase is deducted,
Only related to intended vibratory and noise phase term can be obtained, i.e.,
Wherein, Re () and Im () represent real and imaginary part respectively, and o is the unified representation of every high-order a small amount of,Due to the slow time echo that micro-vibration target place range cell peak point is constituted
In the slow time echo that constitutes with micro-vibration target place range cell peak point of clutter component C in component of signal S source
In same Range resolution unit, Φsn(t) and ΦcnStatistic correlation between (t) with height, therefore Φn(t)≈Φsn
(t)≈Φcn(t).
Formula (4) can be write as under conditions of first approximation：
Formula (5) i.e. micro-vibration high-resolution phase place derive vibration measuring model, it disclose intended vibratory signal, target echo,
With target range unit clutter, the contribution of phase noise, thermal noise to object element phase measurement.
Derive, according to high-resolution phase place, signal to noise ratio, the i.e. Section 1 of defined formula (5) that vibration measuring model obtains phase measurement
Mean power is phase measurement signal to noise ratio with the ratio of second and third mean power, is designated as SNRM, then
Wherein, PΦ=E (| Φn(t)|2) it is phase noise mean power, PN=E (| Im (N (t)) |2) average for thermal noise
Power, It is target mean amplitude of tide, T is that vibration duration, α isBetween angle.
As can be seen that phase measurement signal to noise ratio is the function of α from formula (6).Certain in oscillation intensity and noise level
Under conditions of, different α values can cause the relatively macrorelief of phase measurement signal to noise ratio.Obviously, only when α is 0, system can reach
To optimum signal to noise ratio；In the case of other, signal to noise ratio all occurs certain loss；Particularly when α=90 °, there is SNRM=0,
Substantially no intended vibratory observing capacity.In order that system reaches the phase measurement signal to noise ratio of optimum, intend below deducting using from E
The mode of one constant vector D is improving observing capacity of the phase measurement to intended vibratory.
Based on the signal to noise ratio of phase measurement, one will be deducted in slow time signal E of target place range cell peak point
Constant vector D, obtaining the phase place after improving derives vibration measuring model and phase measurement signal to noise ratio；
Note D is a time-independent constant vector, and E' deducts a constant vector D for E and obtains remaining signal,
For the average of E', then E '=E-D,MeetThen still by the phase place that step one is provided, vibration measuring mould is derived
Type, has
Wherein, θ isWithVector angle
Signal to noise ratio after the digital processing can be derived according to formula (7), remember that new signal to noise ratio is SNR 'M, then
From formula (8), under conditions of oscillation intensity and noise level are certain, θ is to adjust SNR 'MUnique because
Element, adjusts θ and can adjust the size that intended vibratory average power signal and phase noise mean power are contributed to signal to noise ratio, and D
The size of vector has no effect on SNR 'M.SNR′MBe the periodic function of θ, maximum and most can be obtained within θ ∈ [0, the 360 °] cycle
Little value.
Obtaining the phase place after improving derives vibration measuring model and phase measurement signal to noise ratio, and the size of D vector has no effect on SNR
′M；
Based on above-mentioned mentality of designing, a kind of method for improving for radar vibration measuring signal to noise ratio, its concrete steps includes：
Step one：OrderWhereinFor target under noise free conditions static when target place range cell peak point signal, E'
Deduct, for slow time signal E of target place range cell peak point, the residual signal that a constant vector D is obtained,For the equal of E'
Value；BecauseWithIt is all complex vector, can be write as exponential form,θ1And θ2RespectivelyWith's
Argument, makes θ=θ1-θ2, i.e. θ isWithVector angle, be based on
Can then obtainAccording toObtainθ span is 0～360 °；
Step 2：When target is not vibrated, θ is incremented by with fixed step size in 0～360 °, to each θ, according to E '=
E-D, tries to achieve corresponding residual signalExtractPhase place Φ 'M, i.e.,
As now target is non-vibrating, so Φ 'MIn only include noise (thermal noise and phase noise).Ask phase place Φ 'MVariance
E(|Φ'M|2), as the noise average power of each θ value；
Step 3：In intended vibratory, θ is incremented by with fixed step size in 0～360 °, to each θ, according to E '=
E-D, tries to achieve corresponding residual signalExtractPhase place Φ 'M, i.e.,
To Φ 'MΦ ' is obtained as fast Fourier transformMFrequency spectrum, and extract Φ 'MPeak point in frequency spectrum, based on Φ 'MPeak in frequency spectrum
Value point, obtains the relational expression of average power signal and θ；That is Φ 'MPeak point modulus value in frequency spectrum square divided by fast Fourier
The points of conversion are the average power signal of each θ value；
Step 4：Average power signal and the relational expression of θ for being obtained based on step 3 is average with the noise that step 2 is obtained
Power and the ratio of the relational expression of θ, obtain the phase measurement average signal-to-noise ratio of each θ value, average according to the phase measurement of each θ value
Corresponding θ when signal to noise ratio selects signal to noise ratio maximum, is denoted as θmax.
Step 5：The θ that step 4 is obtainedmaxCorrespondingAs finally will from E deduct constant
Vector,ExtractPhase place Φ 'MSurvey as resulting vibration
The output result of amount.
Embodiment
The present invention gives one embodiment using frequency modulated continuous wave radar, and experimental condition is as shown in table 1 below.
1 experimental condition of table
| Service band | W-waveband |
| Signal bandwidth | 1.2GHz |
| Pulse recurrence frequency | 2kHz |
| Measurement distance | About 7m |
| Podium level | About 60cm |
| Experimental situation | Corridor |
| Vibration Targets | Post the sound equipment of tinfoil paper material |
| Frequency of vibration | 700Hz |
The one-dimensional picture of target scene is as shown in figure 1, Vibration Targets are located in front of radar at about 6.875 meters of positions.Intended vibratory
Scene signals mean power and noise average power are as shown in Figure 2 with the change of θ.After before processing, phase measurement signal to noise ratio is with θ's
Change is as shown in Figure 3.It can be seen that by processing, the optimum signal to noise ratio of actual measurement can improve 13dB, worst decline 3dB.Selection makes defeated
Go out the θ process of signal to noise ratio optimum, obtain optimum signal to noise ratio output power spectrum as shown in Figure 4, it can be seen that compare before processing
Noise is significantly suppressed.The method flow diagram that radar vibration measuring signal to noise ratio improves is as shown in Figure 5.
In sum, presently preferred embodiments of the present invention is these are only, is not intended to limit protection scope of the present invention.
All any modification, equivalent substitution and improvement that within the spirit and principles in the present invention, is made etc., should be included in the present invention's
Within protection domain.
Claims (1)
1. a kind of for radar vibration measuring signal to noise ratio improve method, it is characterised in that comprise the following steps that：
Step one, orderWhereinFor target under noise free conditions static when target place range cell peak point letter
Number, E' deducts, for slow time signal E of target place range cell peak point, the residual signal that a constant vector D is obtained,
Average for E'；It is based onObtainAccording toObtainθ is
WithVector angle；
Step 2：When target is not vibrated, θ is incremented by with fixed step size in 0～360 ° of span, according to E '=E-D andObtainFoundationWithExtract
Phase place Φ 'M；Based on phase place Φ 'MVariance E (| Φ 'M|2), obtain the noise average power of each θ value；
Step 3：In intended vibratory, θ is incremented by with fixed step size in 0～360 ° of span, according to E '=E-D andObtainFoundationWithExtract
Phase place Φ 'M；To Φ 'MMake fast Fourier transform and obtain Φ 'MFrequency spectrum, and extract Φ 'MPeak point in frequency spectrum, based on Φ 'M
Peak point in frequency spectrum, obtains the average power signal of each θ value；
Step 4：The noise of each θ value that the average power signal of each the θ value for being obtained based on step 3 is obtained with step 2 is put down
All power, obtains the phase measurement average signal-to-noise ratio of each θ value, selects letter according to the phase measurement average signal-to-noise ratio of each θ value
Make an uproar than corresponding θ during maximum, be denoted as θmax；
Step 5：θ by step 4maxCorrespondingAs the constant vector for deducting from E in step one, base
InWithExtractPhase place Φ 'MMeasure as resulting vibration
Output result.
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| WO2021109473A1 (en) * | 2020-01-13 | 2021-06-10 | 上海交通大学 | Microwave sensing-based full-field vibration measurement method and system |
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| US20140128748A1 (en) * | 2010-05-17 | 2014-05-08 | National Sun Yat-Sen University | Motion/vibration sensor |
| CN105277938A (en) * | 2015-10-22 | 2016-01-27 | 北京理工大学 | Vibration amplitude high-precision microwave measurement method based on least squares estimation |
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Patent Citations (5)
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| US20140128748A1 (en) * | 2010-05-17 | 2014-05-08 | National Sun Yat-Sen University | Motion/vibration sensor |
| KR20130047979A (en) * | 2011-11-01 | 2013-05-09 | 현대모비스 주식회사 | Radar system and radar signal processing method capable of adjusting amplitude gain |
| KR20140031028A (en) * | 2012-09-04 | 2014-03-12 | 현대모비스 주식회사 | Method for processing radar signal auto adjustable of voltage offset |
| CN103197301A (en) * | 2013-03-19 | 2013-07-10 | 中国人民解放军海军航空工程学院 | Sea surface micro-motion target Radon-linear contact transformation long-time phase-coherent accumulation detecting method |
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