CN108072868A - A kind of precision distance measurement method based on the refinement of fmcw radar signal frequency - Google Patents
A kind of precision distance measurement method based on the refinement of fmcw radar signal frequency Download PDFInfo
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- CN108072868A CN108072868A CN201610992641.9A CN201610992641A CN108072868A CN 108072868 A CN108072868 A CN 108072868A CN 201610992641 A CN201610992641 A CN 201610992641A CN 108072868 A CN108072868 A CN 108072868A
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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
- G01S13/08—Systems for measuring distance only
Abstract
The present invention relates to a kind of precision distance measurement methods based on the refinement of fmcw radar signal frequency.Comprise the following steps：Docking, which is collected mail, first number carries out a Fourier transformation and draws V (f), and calculates its Amplitude maxima and the frequency corresponding to Second Largest ValueWithThen existWithIn the range of to V (f) carry out Lagrange's interpolation computing；Again by interpolation result and phase factorProduct calculating is carried out, draws Vc(f)；Then V is takenc(f) real part Re [Vc(Δ r)], utilize target elements J (k) and Re [Vc(Δ r)] correspondence, corresponding k when determining its minimum value using the method for curve matching*, calculate corresponding frequency f at this time*；It is final to utilizeObtain level meter accurately located position.The present invention can effectively solve the problem that the problem of can not meeting required precision using DFT Amplitude maximas estimated distance, while can have smoothing effect to signal noise, improve radar level gauge positioning accuracy.
Description
Technical field
The present invention relates to industrial level gauging fields, concretely relate to a kind of based on the refinement of fmcw radar signal frequency
Precision distance measurement method.
Background technology
High-precision liquid level measures the normal operation to various automatic Control Systems of Liquids Height, to ensureing the peace of various liquid goods
Full accumulating and to ensureing the fair and reasonable progress of various liquid goods trades, the loss of national wealth being avoided to have important meaning
Justice.
Radar surveying distance is contactless, thus is suitble to inflammable, explosive, high viscosity, severe corrosive, high temperature, height
Level gauging under the occasions such as pressure, conventional level measuring method is helpless at this time.CW with frequency modulation (FMCW) radar with
Pulse radar is compared to having many good qualities, particularly suitable for liquid level measuring system.
Liquid level distance can be calculated using the corresponding frequency of spectrum amplitude maximum of fmcw radar echo-signal, in reality
It is the discrete spectrum that signal is calculated using the discrete Fourier transform for receiving signal among border, but in the case where asking extremely high only
Required precision can not be met merely with DFT (discrete Fourier transform) Amplitude maxima estimated distances, it is necessary to take other methods
Improve precision.The present invention improves range measurement accuracy demand using Frequence zooming method.
The content of the invention
In view of the deficiencies of the prior art, present invention prize Frequence zooming method is fused in radar levelmeter location algorithm, is carried
A kind of precision distance measurement method based on the refinement of fmcw radar signal frequency is gone out.
Present invention technical solution used for the above purpose is：It is a kind of based on fmcw radar signal frequency refinement
Precision distance measurement method, comprises the following steps：
Step 1：Radar sends signal to liquid level, and receives the radar signal v (t) reflected from liquid level and carry out Fourier transformation
Obtain transformation results V (f)；
Step 2：Find out the frequency corresponding to radar signal V (f) Amplitude maximas after conversionWith amplitude Second Largest Value
Corresponding frequency
Step 3：WithIn the range of to V (f) carry out interpolation arithmetic obtain signal V'(f)；
Step 4：To V'(f) add in phase after obtain signalWherein
f0For signal carrier frequency, B is transmitting signal swept bandwidth, and T is frequency sweep cycle；
Step 5：Make Δ r=r*- T Δ Rf, take Vc(f) real part Re [Vc(Δr)]；Δ r represents estimated distance r*With
The deviation of actual range T Δs Rf,Represent distance resolution；
Step 6：Objective function
Wherein,M=round [2f0/ B], round represents rounding；Frequency sampling intervalN
ForWithIn the range of interpolation points；
Step 7：Find out abscissa positions k corresponding during J (k) amplitude minimums*, and calculate corresponding frequency f at this time*
=k*Δf；
Step 8：By frequency f*It substitutes intoDraw radar and the estimated distance r of liquid level to be measured*；C represents electromagnetic wave
Spread speed.
It is described to V'(f) add in phase after obtain signalComprise the following steps：
The phase changed with frequency is added in the basic function of V (f), i.e.,
Phasef0For the centre frequency of radar emission signal, B is the bandwidth of transmitting signal, and T is
Emit the signal period,T is the time.
Real part Re [the Vc(Δ r)] it is as follows：
The invention has the advantages that and advantage：
1. the present invention, using Frequence zooming method, the shorter FFT of utilization (Fast Fourier Transform (FFT)) is obtained and longer FFT
Same frequency resolution reduces operand；
2. the noise received in signal smoothly, improve the signal-to-noise ratio of operation result by the present invention using object function；
3. the present invention is improved liquid level distance and is surveyed using the precision distance measurement method based on the refinement of fmcw radar signal frequency
Accuracy of measurement.
Description of the drawings
Fig. 1 is flow diagram of the present invention；
Fig. 2 is two sampled points in the present invention in main lobe with distance change situation schematic diagram；
Fig. 3 is Re [V in the range of a Range resolution unit Δ R in the present inventionc(Δ r)] with Δ r change curves.
Fig. 4 (a) is V in the present inventionc(k) envelope of curves curve.
Fig. 4 (b) is J (k) curves in the present invention.
Specific embodiment
The present invention is described in further detail with reference to the accompanying drawings and embodiments.
The present invention carries out ranging using radar.By radar be placed in at a certain distance from oil level, radar and oil level it
Between clear, emit radar signal；Then the radar signal reflected from liquid level is received by radar and is handled：It is first
First docking, which is collected mail, number to be carried out a Fourier transformation and draws V (f), and calculates its Amplitude maxima and the frequency corresponding to Second Largest Value
WithThen existWithIn the range of to V (f) carry out interpolation arithmetic；Again by interpolation result and phase factorInto
Row product calculates, and draws Vc(f)；Then V is takenc(f) real part Re [Vc(Δ r)], utilize target elements J (k) and Re [Vc(Δ
R) correspondence], corresponding k when determining its minimum value using the method for curve matching*, calculate corresponding frequency f at this time*；
It is final to utilizeObtain level meter accurately located position.
As shown in Figure 1, it is flow diagram of the present invention.
Step 1：It docks collection of letters v (t) and carries out Fourier transformation, set its transformation results as V (f)；
Step 2：Find out the frequency corresponding to V (f) Amplitude maximasWith the frequency corresponding to amplitude Second Largest Value
Step 3：WithIn the range of carry out curve fitting to V (f) interpolation arithmetic, obtain V'(f)；
Step 4：OrderWhereinf0For signal carrier frequency, B believes for transmitting
Number swept bandwidth, T is frequency sweep cycle；
Step 5：Due to Vc(f) real part peak position and Vc(f) amplitude peak position is identical, while the former is at peak value
Variation faster, to increase contrast, takes Vc(f) real part, with season Δ r=r*- T Δ Rf, (Δ r represent estimated distance with
The deviation of actual range), obtain Re [Vc(Δr)]；
Step 6：Make M=round [2f0/ B], frequency sampling intervalWherein：N isWithModel
Interpolation points in enclosing, objective function
Wherein
Step 7：Find out the corresponding k of minimum of J (k)*, and calculate corresponding frequency f at this time*=k*Δf；
Step 8：Result of calculation is substituted intoDraw liquid level to be measured distance.
The frequency corresponding to V (f) Amplitude maximas is found out in step 2With the discrete frequency corresponding to amplitude Second Largest Value
In step 3WithBetween refine frequency,WithIn the range of be inserted into interval smaller discrete frequency into
Point, V (f) corresponding amplitude and phase in these frequency contents is calculated by lagrange-interpolation, obtains interpolation arithmetic
Frequency-region signal V'(f afterwards).
The phase concrete form for the reflected signal that radar receives is in step 4,
Wherein, f0To emit signal center frequency, B is the bandwidth of transmitting signal, and T is the transmitting signal period,
For the frequency shift (FS) for the transmitting signal that radar receives.
The phase changed with frequency is added in the basic function of V (f), V (f) is revised as
In V in step 5c(f) substitute into Δ r (deviation for representing estimated distance and actual range) in, real part it is writeable into
Wherein, Δ r=r*- T Δ Rf,For system distance resolution.
Re[Vc(Δ r)] the amplitude deviation delta r that adjusts the distance it is more sensitive, utilize its amplitude peak estimated distance than directly profit
It is more accurate with the amplitude peak estimated distance of V (f).
It is present with multiple peak values in step 6 in V (f) main lobes, while in view of influence of noise, utilizes Re [Vc(Δr)]
The symmetry of function determines its maximum of points using curve matching method.Objective function：
When k points correspond to Vc(k) during the maximum of points of curve, J (k) values reach minimum, find Vc(maximum of Δ r) becomes
Find the minimum value of J (k).J (k) compares V near minimum pointc(k) it is steep many in vicinity variation, find actual range
Corresponding k*Easily.
Step 8 calculates the actual range r of liquid level*, according to the following formula：
As shown in Fig. 2, for received in the present invention two sampled points of the discrete Fourier transform in main lobe of signal with away from
From situation of change.Abscissa is the discretization sequence of frequency, and ordinate is the normalization amplitude of frequency-region signal V (f).
The N points Fourier variation of radar sampling sequence x (n) is actually that x (n) is decomposed into N number of frequency content, corresponding
Frequency be fk=k Δ f, frequency interval are Δ f=1/T.When the frequency of echo-signal is just the integral multiple of Δ f, V
(k) only there are one sampled points in the main lobe of V (f) (just in its maximum position)；And in other cases, due to direct computation of DFT
The fence effect that leaf changes, there are two sampled point, k in the main lobe of V (f) by V (k)1And k2, corresponding sample frequency isWithTherefore need to pass throughWithFrequence zooming is to determine the position of the corresponding amplitude peak of actual liquid level in frequency range.
It is illustrated in figure 3 Re [V in the range of a Range resolution unit Δ Rc(Δ r)] with Δ r change curves, it emulates herein
Parameter setting in curve is as follows：f0=10GHz, B=1.5GHz, Δ R=100mm.From curve as can be seen that as Δ r=0
When, Vc(Δ r) reaches maximum；Near peak value, even if r variations are smaller, but Re [V can be causedc(Δ r)] more significantly become
Change.
As Fig. 4 (a) and Fig. 4 (b) show Vc(k) envelope of curves and J (k) curves.Transverse axis represents k, and the longitudinal axis represents mesh
Scalar functions.Although near peak value, Re [Vc(Δ r)] peak change it is more apparent, but in the main lobe of V (f), Re [Vc(Δ
R)] it is present with multiple peak values, objective function J (k) finds Vc(maximum of Δ r) becomes obtaining the minimum value of J (k).Figure
Shown in J (k) curves such as Fig. 4 (b) of 4 (a) corresponding identical parameters.Compare two figures, the latter is near minimum point than the former in pole
Variation is more precipitous at big value, therefore it is more easy to find the corresponding difference frequencies of J (k).
Claims (3)
- A kind of 1. precision distance measurement method based on the refinement of fmcw radar signal frequency, it is characterised in that：Comprise the following steps：Step 1：Radar sends signal to liquid level, and receives radar signal v (t) the progress Fourier transformation reflected from liquid level and obtain Transformation results V (f)；Step 2：Find out the frequency corresponding to radar signal V (f) Amplitude maximas after conversionCorresponding to amplitude Second Largest Value FrequencyStep 3：WithIn the range of to V (f) carry out interpolation arithmetic obtain signal V'(f)；Step 4：To V'(f) add in phase after obtain signalWhereinf0For Signal carrier frequency, B are transmitting signal swept bandwidth, and T is frequency sweep cycle；Step 5：Make Δ r=r*- T Δ Rf, take Vc(f) real part Re [Vc(Δr)]；Δ r represents estimated distance r*With reality The deviation of distance T Δs Rf,Represent distance resolution；Step 6：Objective functionWherein,M=round [2f0/ B], round represents rounding；Frequency sampling intervalN is WithIn the range of interpolation points；Step 7：Find out abscissa positions k corresponding during J (k) amplitude minimums*, and calculate corresponding frequency f at this time*=k* Δf；Step 8：By frequency f*It substitutes intoDraw radar and the estimated distance r of liquid level to be measured*；C represents Electromagnetic Wave Propagation Speed.
- 2. a kind of precision distance measurement method based on the refinement of fmcw radar signal frequency according to claim 1, feature Be described to V'(f) add in phase after obtain signalComprise the following steps：The phase changed with frequency is added in the basic function of V (f), i.e.,<mrow> <msub> <mi>V</mi> <mi>c</mi> </msub> <mrow> <mo>(</mo> <mi>f</mi> <mo>)</mo> </mrow> <mo>=</mo> <munderover> <mo>&Integral;</mo> <mn>0</mn> <mi>&infin;</mi> </munderover> <mi>v</mi> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mrow> <mo>&lsqb;</mo> <mrow> <mi>f</mi> <mi>t</mi> <mo>+</mo> <mi>f</mi> <mrow> <mo>(</mo> <mrow> <mfrac> <msub> <mi>f</mi> <mn>0</mn> </msub> <mi>B</mi> </mfrac> <mo>-</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> </mrow> <mo>)</mo> </mrow> <mi>T</mi> </mrow> <mo>&rsqb;</mo> </mrow> </mrow> </msup> <mi>d</mi> <mi>t</mi> <mo>=</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mi>f</mi> <mrow> <mo>(</mo> <mrow> <mfrac> <msub> <mi>f</mi> <mn>0</mn> </msub> <mi>B</mi> </mfrac> <mo>-</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> </mrow> <mo>)</mo> </mrow> <mi>T</mi> </mrow> </msup> <mi>V</mi> <mrow> <mo>(</mo> <mi>f</mi> <mo>)</mo> </mrow> </mrow>Phasef0For the centre frequency of radar emission signal, B is the bandwidth of transmitting signal, and T is transmitting Signal period,T is the time.
- 3. a kind of precision distance measurement method based on the refinement of fmcw radar signal frequency according to claim 1, feature It is the real part Re [Vc(Δ r)] it is as follows：<mrow> <mi>Re</mi> <mo>&lsqb;</mo> <msub> <mi>V</mi> <mi>c</mi> </msub> <mrow> <mo>(</mo> <mi>&Delta;</mi> <mi>r</mi> <mo>)</mo> </mrow> <mo>&rsqb;</mo> <mo>=</mo> <mfrac> <mi>T</mi> <mn>2</mn> </mfrac> <mi>sin</mi> <mi> </mi> <mi>c</mi> <mrow> <mo>(</mo> <mfrac> <mrow> <mi>&Delta;</mi> <mi>r</mi> </mrow> <mrow> <mi>&Delta;</mi> <mi>R</mi> </mrow> </mfrac> <mo>)</mo> </mrow> <mi>c</mi> <mi>o</mi> <mi>s</mi> <mrow> <mo>(</mo> <mi>&pi;</mi> <mfrac> <mrow> <mi>&Delta;</mi> <mi>r</mi> </mrow> <mrow> <mi>&Delta;</mi> <mi>R</mi> </mrow> </mfrac> <mfrac> <mrow> <mn>2</mn> <msub> <mi>f</mi> <mn>0</mn> </msub> </mrow> <mi>B</mi> </mfrac> <mo>)</mo> </mrow> </mrow>
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Cited By (3)
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| CN110770598A (en) * | 2018-11-20 | 2020-02-07 | 深圳市大疆创新科技有限公司 | Microwave radar, data processing method thereof and unmanned aerial vehicle |
| CN112881997A (en) * | 2020-12-29 | 2021-06-01 | 中国航空工业集团公司西安飞机设计研究所 | High-precision combined leveling method based on radar laser target |
| CN113466552A (en) * | 2021-07-14 | 2021-10-01 | 南京海兴电网技术有限公司 | Frequency tracking method under constant-interval sampling |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110770598A (en) * | 2018-11-20 | 2020-02-07 | 深圳市大疆创新科技有限公司 | Microwave radar, data processing method thereof and unmanned aerial vehicle |
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| CN113466552A (en) * | 2021-07-14 | 2021-10-01 | 南京海兴电网技术有限公司 | Frequency tracking method under constant-interval sampling |
| CN113466552B (en) * | 2021-07-14 | 2024-02-02 | 南京海兴电网技术有限公司 | Frequency tracking method under fixed-interval sampling |
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