CN203177928U - Echo sampling unit and pulse type radar material level meter with the same - Google Patents
Echo sampling unit and pulse type radar material level meter with the same Download PDFInfo
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- CN203177928U CN203177928U CN 201220488569 CN201220488569U CN203177928U CN 203177928 U CN203177928 U CN 203177928U CN 201220488569 CN201220488569 CN 201220488569 CN 201220488569 U CN201220488569 U CN 201220488569U CN 203177928 U CN203177928 U CN 203177928U
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Abstract
The utility model relates to an echo sampling unit and a pulse type radar material level meter with the same. The echo sampling unit comprises a pulse excitation module which respectively supplies a pulse signal to a transmission pulse generator and a reference pulse generator. The output of the transmission pulse generator is connected with a transmission antenna. The output end of the reference pulse generator is connected with a frequency mixer. The frequency mixer is simultaneously connected with a receiving antenna. The output end of the frequency mixer is connected with an A/D converter through a signal amplifier and a low-pass filter. The output end of the A/D converter is connected with a material surface echo identification module in a data processing and time sequence control unit. The output of the material surface echo identification module is connected with a material level calculation module through a propagation time-delay accurate measuring module. The data processing and time sequence control unit further comprises a time sequence control module which supplies a time sequence signal to the pulse excitation module. The echo sampling unit can automatically identify the real echo for adapting for various kinds of operation environments and reducing mounting requirement. Furthermore the echo sampling unit can obtain time measurement resolution with sub-sampling interval and improves material level measurement accuracy.
Description
Technical field
The utility model relates to and utilizes radar that tank body thing position is measured, and is specifically related to a kind of echo samples unit and uses the pulse radar level meter of this unit.
Background technology
The pulse radar level meter is that microwave is measured through the propagation delay of object plane reflected back receiver from transmitter with the high-degree of conversion of object plane to be measured.It has noncontact, to the gas phase condition of object plane upper space change insensitive, work range greatly, measuring accuracy advantage high, easy for installation, can be widely used in hydraulic engineering, field of petrochemical industry.Because microwave is propagated with the light velocity in air, for reaching millimetre-sized level gauging precision, must realize the accurate mensuration of picosecond to round trip delay time.
The round trip delay time of microwave propagation is extremely short, and it is directly measured, and realizes that cost height, difficulty are big, is unsuitable for being applied to the radar levelmeter of technical grade.In view of the pulse repetition rate of the radar pace of change far above the thing position, reflection echo can be thought the high-frequency signal that a kind of periodicity repeats.Utilization is slightly less than the equivalent time sampling method that the sample frequency of pulse repetition rate removes to gather reflection echo, can realize measuring indirectly with lower sample frequency the echo of ghz band, reduction is to the requirement of device, as document S Schuster, S Scheiblhofer, R Feger, A Stelzer.Signal Model and Statistical Analysis for the Sequential Sampling Pulse Radar Technique.Radar Conference, 2008:1-6. with Wolfgang Weidmann, Dirk Steinbuch.A High Resolution Radar for Short Range Automotive Applications.28th European Microwave Conference Amsterdam1998:590-594.
Echo is carried out after the equivalent time sampling, need further to judge the moment that echo reaches.Threshold method is a kind of simple directly method, and processing speed is fast, but the selection of threshold value is subjected to signal amplitude and The noise.Centroid method with the barycenter of signal as the position feature point, it has higher stability with respect to threshold method, but measuring accuracy depends on signal shape and window size, see document " Song Jianhui. survey long some gordian technique researchs based on the cable of Time Domain Reflectometry principle. Harbin Institute of Technology, 2010. ".The absolute value of Jacovitti and the Scarano difference by asking for echoed signal and reference signal and the position of quadratic sum minimum, judge the moment that echo arrives, under high s/n ratio, can obtain precision preferably, see document " Giovanni Jacovitti; Gaetano Scarano.Discrete Time Techniques for Time Delay Estimation.IEEE TRANSACTIONS ON SIGNAL PROCESSING; 1993,41 (2): 525-533. ".Correlation method is by asking for echoed signal and the peaked position of reference signal related function also can obtain propagation delay, and can limit the error that white noise is introduced preferably.Utilize the para-curve match that peak point is carried out fine search and can obtain the sub-sampling time measurement accuracy.But this method belongs to inclined to one side estimation is arranged, and be positioned at the middle time error maximum of two sampled points at peak value.
When having plano-convex portion in the close storage tank sidewall in the installation site of radar levelmeter or the tank body, sidewall peace protuberance can produce spurious echo.Tank interior also often contains barriers such as pipeline, ladder, mixing agitator, also can reflection echo.When the thing position was higher in the jar, microwave can repeatedly reflect between tank deck and object plane simultaneously.These all can form false thing position signal, as it not being handled or distinguish the measurement result that will lead to errors.Solve at the many mounting meanss from radar levelmeter of this problem at present, avoid the generation of spurious signal as far as possible.Yet owing to the actual installation environmental limit, spurious signal can not be eliminated fully by adjusting to install under some situation, and this just need identify true echoed signal in the signal processing of radar levelmeter.
Summary of the invention
In order to overcome the shortcoming of above-mentioned prior art, the purpose of this utility model is the pulse radar level meter that the echo samples unit is provided and uses this unit, can distinguish the various spurious echos in the measuring process, and the due in of true echo accurately judged, thereby obtain high-precision level gauging result.
In order to achieve the above object, the technical solution adopted in the utility model is:
A kind of echo samples unit, comprise the pulse excitation module, the pulse excitation module provides pulse signal to firing pulse generator and reference pulse generator respectively, antenna is penetrated in the output pulse sending and receiving of firing pulse generator, the output pulse of reference pulse generator connects frequency mixer, frequency mixer connects receiving antenna simultaneously, the output of frequency mixer connects signal amplifier, the output of signal amplifier connects low-pass filter, the output of low-pass filter connects the A/D transducer, and described pulse excitation module connects a time-sequence control module and provides clock signal by it.
The output of described A/D transducer connects the object plane echo identification module in data processing and the sequential control module, the output of described object plane echo identification module connects the accurate measurement module of propagation delay, the output of the accurate measurement module of propagation delay connects level meter and calculates module, and described data are handled and the sequential control module is an independent processor.The arm processor of STM32F103 series for example.
Described object plane echo identification module be data handle and the sequential control module in a functional module, it utilizes features such as the intensity of echo and round trip delay time that echo is carried out true echo similarity assessment, identifies the liquid level echo from spurious echo.
The accurate measurement module of described propagation delay is a functional module in data processing and the sequential control module, it carries out relevant with reference signal the actual ghosts signal, and the Hilbert conversion of calculating related function, utilize interpolating method to obtain zero crossing between maximal value and the minimum value, obtain the accurate echo travel-time.
Compared with prior art, the utility model has the advantages that:
Can identify automatically true echo, can adapt to various working environments, reduce the requirement to mounting condition.And can obtain sub-sampling interlude Measurement Resolution, the level gauging precision is improved.
Description of drawings
Fig. 1 is the utility model pulse radar level meter system architecture synoptic diagram.
Fig. 2 is the workflow diagram of the utility model object plane echo identification module.
Fig. 3 accurately asks for the principle of echo propagation delay for related function Hilbert conversion zero-crossing method.
Embodiment
Below in conjunction with accompanying drawing the utility model is described in further details.
As shown in Figure 1, the utility model is handled and the sequential control module for the pulse radar level meter comprises equivalent time sampling unit and data, and can be by data bus and external communication.Described equivalent time sampling unit comprises the pulse excitation module, the pulse excitation module provides pulse signal to firing pulse generator and reference pulse generator respectively, antenna is penetrated in the output pulse sending and receiving of firing pulse generator, the output pulse of reference pulse generator connects frequency mixer, frequency mixer connects receiving antenna simultaneously, the output of frequency mixer connects signal amplifier, the output of signal amplifier connects low-pass filter, the output of low-pass filter connects the A/D transducer, described data are handled and the sequential control module comprises object plane echo identification module, object plane echo identification module connects the output of described A/D transducer, the output of object plane echo identification module connects the accurate measurement module of propagation delay, the output of the accurate measurement module of propagation delay connects level meter and calculates module, and data are handled and the sequential control module also comprises the time-sequence control module that clock signal is provided to described pulse excitation module.The work schedule of data processing and each module of sequential control module control level meter accurately measures level meter through the identification of object plane echo, propagation delay simultaneously and calculates the result.
Principle of the present utility model is:
It is the basis that guarantees the level gauging precision that echoed signal is gathered accurately.Because the microwave that radar levelmeter is launched is in ghz band, existing A/D transducer also is difficult to directly it be realized undistorted collection.So adopting the method for equivalent time sampling measures indirectly to it.If the repetition period of echoed signal is T, its time interval with T+ Δ T is sampled, then pass through the T/ Δ after T cycle, just can obtain broadened complete waveform.
Both comprised real object plane echo in the echoed signal that equivalent time sampling obtains, also may contain by tank base, sidewall, the spurious echo of barriers such as jar inner catheter, ladder, stirrer reflection and the multiple echo between object plane and the tank body top.In order to obtain correct measurement result, must from the signal that contains various spurious echos, identify real object plane echo.At this, mainly distinguish according to echo round trip delay time (RTDT, Round-trip Delay Time) and backward energy.By analyzing the communication process of pulse in tank body, can obtain following deduction: (1) if the RTDT of certain echo can not be represented by the integral multiple of echo RTDT before, then this echo may be for the spurious echo (2) of object plane echo or tank body, barrier if the RTDT that echo arranged for before the integral multiple of certain echo RTDT, then Zhi Qian echo may for the RTDT of object plane echo or multiple echo (3) barrier spurious echo less than object plane echo RTDT.If certain echo satisfies simultaneously and infers (1) and (2), just can determine that it is the object plane echo.Considering that the reflected back wave intensity can increase with order of reflection reduce, and is proportional to material reflectance and reflective surface area simultaneously again, and true object plane echo strength must be greater than multiple echo as can be known, and can obviously not be weaker than the echo strength of tank body, barrier.If a certain echo strength is significantly higher than other in all echoes, then it is that the probability of object plane echo is very big.Can obtain the probability that each echo is the object plane echo by analysis-by-synthesis round trip delay time and backward energy, get probability the maximum as true echo, be used for level meter and calculate.
As shown in Figure 2, the workflow of object plane echo identification module is: at first the acquired original data are carried out threshold ratio, detect the echoed signal that collects, and its RTDT of rough calculation.If comprise a plurality of echoed signals in the data, then further calculate energy similarity and the RTDT similarity of each echo and object plane echo, comprehensively the two judges the object plane echo.Three deduction conditions that adopt in determining the process of RTDT similarity are: the RTDT of (1) object plane echo can not by the integral multiple of echo RTDT before represent (2) when the RTDT that has echo for before during the integral multiple of certain echo RTDT, then Zhi Qian echo may for the RTDT of object plane echo or multiple echo (3) barrier spurious echo less than object plane echo RTDT.
Finish after the identification to true echo, need accurately measure its propagation delay.The related function of getting true echoed signal r (n) and desirable echoed signal f (n) is
Related function C then
Rf(k) peak point can be used as the reference point of accurate judgement echo due in.Directly adopt the method for parabolic interpolation to ask for related function C
Rf(k) the peak point position is a kind of inclined to one side estimation that has, and has system deviation.Because the zero crossing between the related function Hilbert conversion maximin is corresponding with its peak point just.Therefore, can be with pair correlation function C
Rf(k) search of peak point is converted into its Hilbert conversion H[C
Rf(k)] search of zero crossing, as shown in Figure 3.Utilize Fourier transform can obtain the fast algorithm of related function Hilbert conversion:
H[C
rf(k)]=FFT
-1[jsign(f)FFT[r(k)]FFT[f(k)]
*]
Obtain the Hilbert conversion H[C of related function
Rf(k)] after, at first seek its maximal value and minimum point, utilize fitting method then, obtain the exact position of zero crossing, thereby determine the propagation delay of echo.So just, can realize the propagation delay measuring accuracy in sub-sampling cycle, and time difference method can promote along with the improvement of echoed signal signal to noise ratio (S/N ratio).
The course of work of the present utility model is:
When utilizing the utility model pulsed level meter to carry out equivalent time sampling, be the two-way clock signal of T and T+ Δ T by the pulse excitation module generation cycle at first, be respectively applied to stimulated emission pulse and reference pulse.The crystal oscillator that the two-way Generation of Clock Signal can be formed by the crystal oscillator that two frequencies approach to or in one tunnel clock signal, add delay unit and realize.Send pulse and sent by emitting antenna, receive through being received antenna after the reflection, multiply each other in frequency mixer with reference pulse, just can obtain broadened echoed signal by signal amplification and low-pass filtering again, can use A/D transducer commonly used to gather this.
Both comprise the object plane echo in the acquired original data that equivalent time sampling obtains, also may contain various spurious echos, and needed to adopt method shown in Figure 2 that the object plane echo is identified.At first image data is carried out threshold ratio, detect echoed signal wherein, and with the corresponding RTDT of threshold method rough calculation.If only collect single echo, then can determine that it is the object plane echo at once.Otherwise need further to judge from energy point of view.After calculating each backward energy, it is sorted.If backward energy presents unimodal phenomenon, namely the energy of strong echo can determine then that apparently higher than other echoes the strongest echo is the object plane echo.Otherwise need obtain the similarity P of each backward energy according to energy ordering i
E(i).Because the energy of object plane echo should should make P greater than spurious echo generally speaking
E(i) reduce with the i increase.Then further judge according to RTDT.At first investigate deduction condition (1), if do not satisfy, namely echo RTDT be the integral multiple of certain echo RTDT before, and then this echo should be multiple echo, is set at the RTDT similarity of itself and object plane echo low.If satisfy, then echo may be object plane echo or the spurious echo that is reflected by tank body, barrier, need to utilize deduction (2) to judge that further namely when the RTDT that has echo was the integral multiple of certain echo RTDT before, then Zhi Qian echo may be object plane echo or multiple echo.If echo satisfies the condition of inferring (1) and (2) simultaneously, can affirm that then it is the object plane echo, is made as height with its RTDT similarity.As if not satisfying the condition of inferring (2), can not determine that then echo is the object plane echo, still by the spurious echo of tank body, barrier reflection, need adjust the RTDT similarity of echo according to the RTDT that infers (3) barrier spurious echo less than object plane echo RTDT.Energy and the RTDT similarity of last comprehensive echo are judged most probable object plane echo.
Determine after the object plane echo, need its round trip delay time of further accurate Calculation RTDT.At first, calculate the Hilbert conversion of echoed signal r (n) and desirable echoed signal f (n) related function:
H[C
rf(k)]=FFT
-1[jsign(f)FFT[r(k)]FFT[f(k)]
*]
The position of maximizing point and minimum point then, the target zero crossing is between the two.Utilize the data of near zero-crossing point by the method for fitting of a polynomial, obtain its exact position k
tAccording to the magnification T/ Δ T of equivalent time sampling and the period T of A/D sampling
sThe round trip delay time of determining echo is: T
RD=k
t* Δ T/T * T
sAt last, calculate thing position height thus, and export by data bus.
Claims (2)
1. echo samples unit, it is characterized in that, comprise the pulse excitation module, the pulse excitation module provides pulse signal to firing pulse generator and reference pulse generator respectively, antenna is penetrated in the output pulse sending and receiving of firing pulse generator, the output pulse of reference pulse generator connects frequency mixer, frequency mixer connects receiving antenna simultaneously, the output of frequency mixer connects signal amplifier, the output of signal amplifier connects low-pass filter, the output of low-pass filter connects the A/D transducer, and described pulse excitation module connects a time-sequence control module and provides clock signal by it.
2. a right to use requires the pulse radar level meter of 1 described echo samples unit, it is characterized in that, the output of described A/D transducer connects the object plane echo identification module in data processing and the sequential control module, the output of described object plane echo identification module connects the accurate measurement module of propagation delay, the output of the accurate measurement module of propagation delay connects level meter and calculates module, and described data are handled and the sequential control module is an independent processor.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103674177A (en) * | 2013-12-19 | 2014-03-26 | 重庆川仪自动化股份有限公司 | Signal processing method and device |
| CN104913830A (en) * | 2015-05-15 | 2015-09-16 | 中国科学院沈阳自动化研究所 | Radar level instrument signal processing method based on curve fitting |
| CN105526990A (en) * | 2015-12-18 | 2016-04-27 | 合肥市恒昌自动化控制有限责任公司 | Dynamic algorithm of guided wave radar material level gauge |
| DE102015100555A1 (en) * | 2015-01-15 | 2016-07-21 | Endress + Hauser Gmbh + Co. Kg | level meter |
-
2012
- 2012-09-21 CN CN 201220488569 patent/CN203177928U/en not_active Expired - Fee Related
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103674177A (en) * | 2013-12-19 | 2014-03-26 | 重庆川仪自动化股份有限公司 | Signal processing method and device |
| CN103674177B (en) * | 2013-12-19 | 2016-08-17 | 重庆川仪自动化股份有限公司 | A kind of signal processing method and device |
| DE102015100555A1 (en) * | 2015-01-15 | 2016-07-21 | Endress + Hauser Gmbh + Co. Kg | level meter |
| US10267666B2 (en) | 2015-01-15 | 2019-04-23 | Endress+Hauser SE+Co. KG | Fill level measurement device |
| CN104913830A (en) * | 2015-05-15 | 2015-09-16 | 中国科学院沈阳自动化研究所 | Radar level instrument signal processing method based on curve fitting |
| CN105526990A (en) * | 2015-12-18 | 2016-04-27 | 合肥市恒昌自动化控制有限责任公司 | Dynamic algorithm of guided wave radar material level gauge |
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