CN106840310A - A kind of CW/FM continuous wave/frequency modulated modulated indicator water gage measuring method - Google Patents
A kind of CW/FM continuous wave/frequency modulated modulated indicator water gage measuring method Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
- G01F23/28—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
- G01F23/284—Electromagnetic waves
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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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Abstract
The present invention discloses a kind of CW/FM continuous wave/frequency modulated modulated indicator water gage measuring method, the method wide range, big variability are realized using Chirp Z+FFT method combination auto gain control methods in the case of water level measurement, the features such as with high precision, stability high, low in energy consumption, strong anti-interference ability and repeatability strong.The present invention can be used independently as high accuracy level measuring, and sensor is used, and also can realize water level early warning and unattended automation water level monitoring with acquisition terminal composition intelligent integral monitoring device.
Description
Technical field：
The invention belongs to liquid level observation technology field, it is related to a kind of CW/FM continuous wave/frequency modulated modulated indicator water gage measuring method.
Background technology：
The indicator water gage of the country's big variability level measuring of wide range relies primarily on import at present, based on German brand,
And it is expensive.Domestic indicator water gage is more from the repacking of industrial level meter, and its main method for using is pulse radar body
System, level measuring is realized using time difference method.Theoretical according to modern radar, the resolution ratio of radar range finding is proportional to the band of sending signal
Wide or time width.Due to transmission power limitation, it is impossible to while obtain larger time width and bandwidth, wide range and water level variability compared with
During big level measuring, because reflected signal becomes very weak, phase information can be submerged in noise, have impact on wide range water level
Certainty of measurement and stability, its certainty of measurement are mostly 1.0cm or 2.0cm, can not meet the big luffing level measuring of wide range
The degree of accuracy and stability requirement.
To overcome above mentioned problem, it is necessary to carry out technological improvement, reach the certainty of measurement and stability of domestic indicator water gage
To or more than import indicator water gage level.
The content of the invention：
The present invention is directed to prior art situation, designs a kind of CW/FM continuous wave/frequency modulated modulated indicator water gage measuring method, the method
Based on continuous frequency modulation radar modulation system, using Chirp-Z+FFT algorithm combination auto gain control methods realize wide range,
The measurement of water level in the case of big variability, with high precision, stability it is high, it is low in energy consumption the characteristics of.
To achieve these goals, the present invention is as follows using concrete technical scheme：
A kind of CW/FM continuous wave/frequency modulated modulated indicator water gage measuring method, the water-level gauge mainly includes that main control module, radar are modulated
Ripple transmitter module, two-way radar signal receiver module, automatic growth control module and plane microstrip antenna, two-way radar signal connect
Receive module to set to form two receiving channels, the key step of the method is as follows：
(1) before system carries out level measuring, the setting two the one of receiving channel of automatic growth control module is set first
The gain scale factor of level and two-stage amplifier；
(2) radar modulating wave transmitter module continuously sends one section of radar modulation wave signal A1, is produced by plane microstrip antenna
The CW/FM continuous wave/frequency modulated modulated swept-frequency signal S1 of raw sensed water level, the CW/FM continuous wave/frequency modulated modulated swept-frequency signal S1 form micro- after water-reflected to be measured
Ripple echo-signal R1, echo-signal R1 are separately input to two-way radar signal receiver module after being received；
(3) two groups (amplitude is identical, frequency is equal, phase differs 90 °) are exported after receiving single treatment through radar signal orthogonal
Discrete digital signal x1(nTs) and x2(nTs) give main control module；
(4) above-mentioned two groups of discrete digital signals are changed the x (nT that pluralize by main control module as the following formulas) form, then to x
(nTs) FFT Fast Fourier Transform (FFT)s are carried out, each corresponding frequency values of signal considerable spectral point is obtained, then through modulus, reject nothing
Frequency spectrum point, obtains corresponding water level apart from frequency spectrum data, and obtains maximum spectrum point；
x(nTs)=x1(nTs)+j x2(nTs)
Wherein TsThe sampling period is represented, n represents sampling number, and j represents the imaginary part of plural number；
(5) above-mentioned water level obtains the very big frequency of each signal apart from frequency spectrum data through the multiple accumulated process of coherent accumulation algorithm
The water level of point is composed apart from frequency spectrum data average value；And compare with thresholding, the bad value less than thresholding is rejected, further try to achieve maximum
The frequency values of frequency spectrum point；
(6) Chirp-Z changes are carried out around the maximum spectrum point that coherent accumulation algorithm is tried to achieve by Chirp-Z fitting algorithms again
Change and process of fitting treatment obtains the frequency values for corresponding to real water level；
(7) spectrum value of the real water level value of above-mentioned correspondence is converted into water level value through frequency spectrum conversion formula, the value can be made
For measured value is exported.
It is of the invention it is further design be：
In step (5), in the hope of the water level of each signal considerable spectral point make apart from 4 times of frequency spectrum data average value values
It is threshold value.
In step (5), coherent accumulation algorithm cumulative frequency is set to 100 times.
The spectrum value of correspondence real water level determines in the following manner in step (6)：Calculated with coherent accumulation algorithm
Maximum spectrum point takes M point and carries out Chirp-Z conversion as main lobe position, around main lobe close position, obtains each extreme value of correspondence
Point ZrFrequency spectrum X (the z of (r=0,1 ..., M-1)r)；|X(zr) | the corresponding frequency values of maximum be the real water level value of correspondence.
Above-mentioned M takes 9, and the absolute error of the measurement of water level is less than 0.1%.
In step (7), measured value output sets accumulation n times, averages as real water level value.Above-mentioned N takes 100, consumption
Shi great Yue 20s.
The present invention has the following advantages that compared to existing technology：
1st, method of the present invention continuous frequency modulation radar modulation system, using Chirp-Z+FFT method combination automatic gains
Control method realizes the measurement of water level in the case of wide range, big variability, with high precision, stability is high, low in energy consumption, strong anti-interference
The features such as ability and strong repeatability.
2nd, the present invention can be used independently as high accuracy level measuring, and sensor is used, and also can constitute intelligence with acquisition terminal
The integrated monitoring device of energy realizes water level early warning and unattended automation water level monitoring.
Brief description of the drawings:
Fig. 1 is circuit theory diagrams of the invention.
Fig. 2 is water-level gauge measuring principle figure.
Fig. 3 is main control process flow figure of the invention.
Fig. 4 is coherent accumulation algorithm flow chart in the present invention.
Fig. 5 is water level conversion calculation flow chart in the present invention.
Fig. 6 automatic growth control block flow diagrams.
Specific embodiment：
Control process of the invention and hardware configuration schematic diagram are described in detail below in conjunction with the accompanying drawings.
Embodiment one：
As shown in figure 1, the hardware design of CW/FM continuous wave/frequency modulated modulated indicator water gage measurement of the present invention is as follows：
Mainly include main control module, radar modulating wave transmitter module, two-way radar signal receiver module and its automatic gain
Control module, plane microstrip antenna.
Radar modulating wave transmitter module includes (DDS) triangular-wave generator, (MOD) modulator, (VCO) pressure for being sequentially connected
Control oscillator and (DISP) circulator；Radar signal receiver module includes (MIX) high-frequency mixer, (AMP) that are sequentially connected
Level amplifier, (LPF) low pass filter, (AMP) two-stage amplifier and A/D converter；Main control module uses TMS320F28M35
Dual core processor, including dsp processor, CPU processor, FPU floating point calculators, program storage FLASH and RAM memory.
Main control module is connected with radar modulating wave transmitter module and radar signal receiver module respectively；Plane microstrip antenna
Transmitting terminal is connected with the circulator of radar modulating wave transmitter module, the high-frequency mixer phase of receiving terminal and radar signal receiver module
Even, input of the output end of the circulator also respectively with the high-frequency mixer of two-way radar signal receiver module is connected, often
Individual radar signal receiver module is furnished with automatic growth control module, and automatic growth control module difference one-level, two-stage amplifier connect
Connect.
In the present invention, radar signal receiver module arranges two groups parallel, forms two passages.Two groups of radar signals receive mould
The input of block is connected with the receiving terminal of plane microstrip antenna respectively, and output end is connected with main control module respectively, circulator it is defeated
Go out end to be connected with two groups of high-frequency mixers respectively.Two-way output amplitude is identical, frequency is equal, the orthogonal signalling of 90 ° of phase difference.
Control flow of the invention is substantially as follows：
As shown in figure 3, main control module calls control linear delta modulation ripple to produce, start A/D collections and complete difference frequency signal
Collection, the cycle of collection and programmable frequency；Main control module CPU call FFT module to gather orthogonal binary channels difference frequency
Signal makees conversion process, obtains each corresponding frequency values of considerable spectral point, calls and seeks spectrum block, rejects the frequency of useless target
Spectrum point, tries to achieve corresponding water level distance spectrum；FFT intrinsic spectrum leakage effect and spectral overlay effect are considered in practice
White noise influence in influence and signals transmission, the distance spectrum of correspondence maximum spectrum may deviate actual distance value；For
Reduce measurement error, improve accuracy of detection, the present invention designs and employ water level detecting coherent accumulation algorithm and Chirp-Z fittings
Algorithm；Coherent accumulation algorithm is accumulated by n times, improves signal to noise ratio, essentially eliminates the influence of white noise；Chirp-Z is fitted
Algorithm carries out Chirp-Z conversion around the maximum spectrum point that coherent accumulation algorithm is tried to achieve and process of fitting treatment obtains correspondence real water level
Frequency values；This is converted into water level value through frequency spectrum conversion formula, can be exported as measured value.
Embodiment two：
As shown in Fig. 2 F coordinate dark lines represent triangular wave transmission signal, light line represents receiver to radar locating principle
Received IF signal after detection；FbCoordinate representation is transmitting-receiving difference frequency signal, it is seen that due to the presence that radio-frequency propagation postpones, caused
Transmitting-receiving frequency has a difference on the frequency Fb, this frequency values and target range direct ratio change；
If using fbupRepresent the frequency-splitting of ascent stage transmitting-receiving radar signal of triangular wave swept frequency in fig. 2 (on abbreviation
Frequency sweep frequency difference), fbdownRepresent the frequency-splitting (referred to as lower frequency sweep frequency difference) of the descending branch transceiving radio frequency of Fig. 2 intermediate cam ripple frequency sweeps；
Upper frequency sweep frequency difference f may certify that according to modern radar theorybupWith lower frequency sweep frequency difference fbdownThere is following relation:
Fb=fbup-fbdown=(4 μ R)/C+ (2v μ T)/C (1)
In formula：T is that frequency modulation cycle, μ are that chirp rate is constant, C for the light velocity factor is also that constant, R are targets to radar
The distance of antenna plane；Section 1 (4 μ R)/C represents the frequency that range delay is produced in formula, and Section 2 (2v μ T)/C is represented under
Frequency sweep section moves the spacing of vT with the target radial that v speed is moved, and SEA LEVEL VARIATION (being less than 6m/s) is very little compared with the light velocity
, Section 2 can be ignored, then obtain target range:
R=(C/4 μ) Fb=(CT/4B) Fb (2)
Wherein B identifies the frequency bandwidth of frequency sweep.
The present invention uses Optimization Algorithm, and obtains accurate water level measurements by accurately detection Fb.
Embodiment three：
As shown in figure 3, CW/FM continuous wave/frequency modulated modulated indicator water gage measuring method of the present invention, the water-level gauge is mainly including master control mould
Block, radar modulating wave transmitter module, radar signal receiver module, automatic growth control module and plane microstrip antenna, the method
Key step it is as follows：
Step 1), before the measurement of main control module actual water level, automatic growth control module is called first, and (module can use soft
Part is realized), by the stride of the number of times (time) and tracking of principle of optimality and requirement of real-time setting tracking, export digitized increasing
Beneficial scale factor；Two gains of the firsts and seconds amplifier of receiving channel of control so that echo-signal hour, increase increases
Benefit；Reduce gain when signal is big；Signal is maintained to be operated in amplifier linear zone and response speed in a wide range, it is ensured that to be
The precision and stability of system level measuring.After the gain of amplifier sets, actual water level monitoring is proceeded by.
In the present invention, we are designed using digital negative anti-by way of hardware and software is combined in receiver module
Feedback formula automatic growth control module, the gain that can receive amplifier according to the size adjust automatically of input signal is preferably solved
The big luffing high accuracy water level test problems of wide range, method is as follows：
Before actual water level measurement, automatic growth control module is called, tracked by principle of optimality and requirement of real-time setting
Maximum times Nmax (time) and amplifier allow the maximum amplitude Vomax of output, the maximum number that automatic growth control module is allowed
Word yield value Kmax, the stride Step=Kmax/Nmax of tracking, export digitized gain scale factor K；
As shown in fig. 6, initialization, the first echo-signal of receiving channel are sampled through ADC, fft algorithm is then called to estimate
Go out preliminary water level value, and convert thereof into the output valve Vo of amplifier, its amplitude reflects the size of water level.When signal hour,
I.e. amplifier output Vo be less than maximum amplitude Vomax when, according to maximum number yield value and tracking stride, increase one-level and/or
The gain of two-stage amplifier；When signal is too big, i.e., when amplifier output is more than maximum amplitude Vomax, according to maximum number gain
Value and the stride of tracking, reduce the gain of one-level and/or two-stage amplifier；So determine appropriate gain scale factor.Very wide
In the range of maintain signal be operated in amplifier linear zone and response speed, it is ensured that systematic water level measurement precision and stability.
This method can realize the water level monitoring of 0-35m luffings, and error is less than 2mm；Water level variability is small more than 40cm/min
The measurement of stable level can be realized when 100cm/min.
Step 2), radar modulating wave transmitter module continuously sends one section of (cycle and amplitude are adjustable) radar modulation wave signal
A1, the CW/FM continuous wave/frequency modulated modulated swept-frequency signal S1, CW/FM continuous wave/frequency modulated modulated swept-frequency signal S1 of sensed water level are produced by plane microstrip antenna
Microwave echoes signal R1, microwave echoes signal R1 are formed after water-reflected to be measured radar signal reception mould is input to after being received
Block；
Step 3), processed through two-way radar signal receiver module, processing procedure is eliminated after including mixing detection, phase shift treatment
High frequency carrier, sends out orthogonal two-way difference frequency analog signal IQ and IF, difference frequency signal IQ and IF be that amplitude is identical, frequency is equal,
Phase differs 90 ° of orthogonal signalling, complex signal needed for follow-up DFT transform is naturally constituted, to realize the quick fortune of frequency spectrum
Calculate.IQ and IF is sent to the converter of rear class after one-level operational amplifier, low pass filter, two-level operating amplifier treatment,
Two-way difference frequency analog signal exports discrete digital signal x respectively after being changed through A/D1(nTs) and x2(nTs) give main control module；
Wherein, n represents sample sequence number (0,1 ... N-1), TsRepresent the sampling period；N represents maximum sampling number, this
Take at 2048 points in example.
Step 4), main control module is by above-mentioned two groups of discrete digital signal x1(nTs) and x2(nTs) be converted to plural form x
(nTs), then to x (nTs) FFT Fast Fourier Transform (FFT)s are carried out, each corresponding frequency values of signal considerable spectral point is obtained, then
Through spectrum block, the frequency spectrum point of useless target is rejected, obtain correspondence frequency spectrum data, and obtain maximum spectrum point；
Main control module is converted into plural number i.e.：x(nTs)=x1(nTs)+j x2(nTs)。
Wherein, TsThe sampling period is represented, n represents sample sequence number (0,1 ... N-1), and j represents the imaginary part of plural number；
Discrete digital signal x (nTs), to Ts1 is set to after making normalized, discrete sequence theoretical from Fourier transformation
Fourier (DFT) conversion of row x (n) is represented by：
X (k) represents the frequency spectrum of difference frequency signal, W in formulaN=e-j2π/NRepresent the dish-shaped factor；K represents sampled point, k=0,
1,…,N/2；Frequency spectrum is tried to achieve using quick FFT to (3) formula；
Frequency spectrum A (k) is tried to achieve according to following formula：
A (k)=1/N(ReX(k)2+ImX(k)2) (4)
In formula (4), A (k) is the frequency spectrum function of sampled point k；N represents maximum sampling number；
According to fk=kfs/ N, tries to achieve the frequency of correspondence sampled point k=0,1 ..., N/2 each point；
Wherein fsIt is sample frequency, with TsIt it is the corresponding sampling period, N is maximum sampling number；
It is theoretical from modern radar, it is f at the maximum of frequency spectrumk=FbThe range points of point correspondence target, according to (2) formula
The corresponding water level value R of maximum spectrum can directly be calculated.
R=(C/4 μ) Fb=(CT/4B) Fb (2)
Step 5), frequency spectrum data substantially eliminates the intrinsic frequency spectrum of FFT and lets out through the multiple accumulated process of coherent accumulation algorithm
White noise influence in leakage effect and signals transmission.
Shown in Fig. 4, the present invention devises water level detecting coherent accumulation algorithm, to reduce shadow of the noise to water level detecting precision
Ring, coherent accumulation algorithm is substantially to make sample value A (k) (k=0,1 ... N/2-1) that N/2 point samplings obtain frequency spectrum to formula (4), right
Answer each k point value cumulative M times, average value is obtained after adding up, its result improves the signal to noise ratio of signal.It is implemented as follows：
Module first initializes cumulative number N=0, and frequency spectrum cumulant L (k)=0, module is cumulative M times to each frequency spectrum sampling point,
The value of M can be according to setting be actually needed, and this project takes M=100, and module judges whether accumulation completes, and module is to having added up
Into each point spectrum value calculate mean power, and set 4 times of mean power as judging threshold, whether judgement distance objective is deposited
Or whether beyond detection range.Bad value less than thresholding is rejected according to judging threshold, the frequency spectrum to accumulating is tried to achieve most
The frequency values of big frequency spectrum point, the frequency values its signal to noise ratio improves M times, and the measurement error of noise introducing reduces M times.
Step 6), then M points Chirp-Z is made around above-mentioned maximum spectrum point by Chirp-Z fitting algorithms convert and be fitted
The frequency values of correspondence more accurate water level are obtained in treatment；
The present invention is missed for the frequency measurement that the intrinsic spectrum leakage effect of FFT and spectral overlay effects are caused
Difference is designed and converts software algorithm using Chirp-Z, and implementation process is as follows：
The frequency spectrum (i.e. distance spectrum) obtained with FFT modes is digital spectral, shows as having fixed distance to adopt in distance axis
Sample is spaced.By increasing sampling number N, can reduce distance interval, improve water level measurement accuracy；At actual digital signal
The limitation of reason level and arithmetic speed, the value of N can not possibly be too big, therefore always has certain sampling in the distance by radar spectrum of reality
Interval.Due to " fence effect " and spectral overlay effect of FFT so that the frequency spectrum for directly being obtained using FFT has fixed adopting
Sample is spaced △ f, and correspondence has fixed sampling interval Δ R in distance domain, consequently, it is possible to producing the range error of maximum Δ R/2.
To improve frequency estimation accuracy and then improving water level detecting precision, present invention design becomes conversion using Chirp--Z
Method.The method can FFT points need not increase it is very big in the case of, the accuracy of detection for significantly improving water level is detected without influence
System operations speed.
Its step is：According to the maximum spectrum point i.e. main lobe position that coherent accumulation algorithm is calculated, around main lobe juxtaposition
Put and take M point and carry out Chirp-Z conversion, its algorithm such as following formula：
Wherein n=0,1 ..., N-1 (6)
A, W are dependent complex parameter in formula,CZT is represented
Chirp-Z is converted, θ0It is initial argument phi0=2 π/N is argument increment.
A is taken in this example0=W0When=1, the X (z of the Chirp-Z conversion of above formular) it is corresponding pole on Z plane unit circle
Value point ZrThe frequency spectrum of (r=0,1 ..., M-1)；|X(zr) | the corresponding more precise frequency value of maximum, that is, correspond to real water level
Value.L-G simulation test shows to take appropriate M values, takes into account real-time and accuracy of detection requirement, takes appropriate M values, can make accuracy of detection
Improve the 1-2 order of magnitude.The present invention takes M=9 so that the absolute error of water level detecting is less than 0.1%.
Step 7), water level modular converter is utilized using the frequency values tried to achieve, accurate water level value is converted into, as shown in Figure 5.
Water level value is exported by RS485 in digital form, while exporting the water level signal of 4-20mA in analog quantity form.
Fig. 5 is water level modular converter algorithm flow, and this module is using above-mentioned | X (zr) | the corresponding frequency values of maximum are made
It is precise frequency value, using formula (2) by frequency conversion into water level value, the value can be used as measured value.
In practical application, to consider the influence of wave or floater to measuring, also can be by the mean algorithm of distance
Eliminate these influences.Module completes certain hour distance measurement value and adds up, and can be arranged as required to cumulative frequency N values.Water level is changed
Module is calculated apart from N point averages as the real water level value that need to be surveyed, and the water level value of actual measurement is exported by RS485 communication interfaces and is arrived
User terminal.R=(C/4 μ) Fb=(CT/4B) Fb (2)
The present invention is taken N=100 times, about takes 20 seconds, and wave and floater pair are essentially eliminated through simulating, verifying
The influence of water level detecting.
Test case one:
The method of testing of engineering prototype in the present invention, and test waveform and detection data table it is as follows：Using installed in removable
Area Objects mimic water-depth on dynamic scale, using laser range finder measurement data as true value.Test, resolving power inspection is repeated several times
During survey, 5m, 10m, 20m, 30m difference water level+0.4m scopes respectively by step pitch 50mm move Area Objects, here choosing list 10m,
The measurement data that 20m is repeated 5 times, tries to achieve maximum absolute error and mean error.0~20m of range excursion, water level variability
Degree of accuracy detection is carried out under the conditions of 1m/min.
Top is modulated triangular wave in Fig. 2, and the rising edge of triangular wave is upper frequency sweep ripple, and trailing edge is lower frequency sweep ripple；Under Fig. 2
Side is that upper frequency sweep and lower frequency sweep receive difference frequency ripple.
Five detection tables of the water level 10m step pitches 50mm of table 1
Five detection tables of the water level 20m step pitches 50mm of table 2
Repeated detection result shows that maximum absolute error is 2mm during 0~20m scopes, and mean error is not more than 1mm, differentiates
Power is better than 1mm.
Main performance of the present invention and technical indicator：
(1) signal output：RS485+4-20mA is exported.
(2) range ability：0.8~35m.
(3) stability：<0.2%FS/.
(4) composition error (including：Linearly, sluggish, repeatability)：0.2%FS.
(5) certainty of measurement：±3mm(0.8—35m)
(6) time of measuring：20s
(7) field angle≤10 °
(8) power supply：9-16VDC
(9) power consumption：5mA
(10) environment temperature：-25°--+60°
(11) ambient humidity：0-90H
(12) dielectric strength：UDC 500V≥200MΩ
(13) degree of protection：IP55.
Claims (7)
1. a kind of CW/FM continuous wave/frequency modulated modulated indicator water gage measuring method, the water-level gauge mainly includes main control module, radar modulating wave
Transmitter module, two-way radar signal receiver module, automatic growth control module and plane microstrip antenna, two-way radar signal are received
Module sets to form two receiving channels, and the key step of the method is as follows：
（1）Before system carries out level measuring, first set automatic growth control module two one-levels of receiving channel of setting and
The gain scale factor of two-stage amplifier；
（2）Radar modulating wave transmitter module continuously sends one section of radar modulation wave signal A1, and inspection is produced by plane microstrip antenna
The CW/FM continuous wave/frequency modulated modulated swept-frequency signal S1 of water level is surveyed, the CW/FM continuous wave/frequency modulated modulated swept-frequency signal S1 forms microwave after water-reflected to be measured and returns
Ripple signal R1, echo-signal R1 are separately input to two-way radar signal receiver module after being received；
Cheng Hao（3）Two groups of quadrature discrete data signal x are exported after receiving single treatment through radar signal1(nTs) and x2(nTs) to master
Control module；
（4）Above-mentioned two groups of discrete digital signals are changed the x (nT that pluralize by main control module as the following formulas) form, then to x (nTs) enter
Row FFT Fast Fourier Transform (FFT)s, obtain each corresponding frequency values of signal considerable spectral point, then through modulus, reject useless frequency
Spectrum point, obtains corresponding water level apart from frequency spectrum data, and obtain maximum spectrum point；
x（nTs） = x1(nTs) +j x2(nTs)
Wherein TsThe sampling period is represented, n represents sampling number, and j represents the imaginary part of plural number；
（5）Above-mentioned water level, through the multiple accumulated process of coherent accumulation algorithm, obtains each signal considerable spectral point apart from frequency spectrum data
Water level apart from frequency spectrum data average value；And compare with thresholding, the bad value less than thresholding is rejected, further try to achieve maximum spectrum
The frequency values of point；
（6）Chirp-Z is carried out around the maximum spectrum point that coherent accumulation algorithm is tried to achieve by Chirp-Z fitting algorithms again to convert simultaneously
Process of fitting treatment obtains the frequency values of correspondence real water level；
（7）The spectrum value of the real water level value of above-mentioned correspondence is converted into water level value through frequency spectrum conversion formula, the value can be used as reality
Measured value is exported.
2. CW/FM continuous wave/frequency modulated modulated indicator water gage measuring method, step according to claim 1（5）In, in the hope of each
The water level of signal considerable spectral point is apart from 4 times of frequency spectrum data average value values as threshold value.
3. CW/FM continuous wave/frequency modulated modulated indicator water gage measuring method, step according to claim 2（5）In, coherent accumulation algorithm
Cumulative frequency is set to 100 times.
4. CW/FM continuous wave/frequency modulated modulated indicator water gage measuring method, step according to claim 1,2 or 3（6）Middle correspondence is true
The spectrum value of water level determines in the following manner：The maximum spectrum point calculated using coherent accumulation algorithm encloses as main lobe position
Taking M point around main lobe close position carries out Chirp-Z conversion, obtains each extreme point Z of correspondencer（R=0,1 ..., M-1）Frequency spectrum
X（zr）；|X（zr）| the corresponding frequency values of maximum be the real water level value of correspondence.
5. CW/FM continuous wave/frequency modulated modulated indicator water gage measuring method according to claim 4, above-mentioned M takes 9, the measurement of water level
Absolute error is less than 0.1%.
6. CW/FM continuous wave/frequency modulated modulated indicator water gage measuring method, step according to claim 4（7）In, measured value output sets
Accumulation n times are put, is averaged as real water level value.
7. CW/FM continuous wave/frequency modulated modulated indicator water gage measuring method according to claim 6, above-mentioned N takes 100.
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| CN109298423A (en) * | 2018-10-22 | 2019-02-01 | 南京信大气象科学技术研究院有限公司 | A kind of survey wave radar based on continuous wave |
| CN109724672A (en) * | 2019-03-01 | 2019-05-07 | 北京锐达仪表有限公司 | The transmitter and electromagnetic wave level switch of electromagnetic wave level switch |
| CN110763302A (en) * | 2019-11-20 | 2020-02-07 | 北京航空航天大学 | FMCW high-precision liquid level measurement method based on iterative frequency estimation |
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| CN114942053A (en) * | 2022-04-28 | 2022-08-26 | 国家石油天然气管网集团有限公司华南分公司 | High-precision radar level gauge distance measuring method based on phase estimation |
| CN114942053B (en) * | 2022-04-28 | 2024-05-31 | 国家石油天然气管网集团有限公司华南分公司 | High-precision radar level meter ranging method based on phase estimation |
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| CN110763302A (en) * | 2019-11-20 | 2020-02-07 | 北京航空航天大学 | FMCW high-precision liquid level measurement method based on iterative frequency estimation |
| CN113534145A (en) * | 2021-09-16 | 2021-10-22 | 北京安达维尔航空设备有限公司 | Altimeter height measurement method and system based on linear frequency modulation continuous wave system |
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| CN114942053B (en) * | 2022-04-28 | 2024-05-31 | 国家石油天然气管网集团有限公司华南分公司 | High-precision radar level meter ranging method based on phase estimation |
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