RU2234688C1 - Method for measuring electrophysical parameters of probed material and distance to it (variants), device for realization of said method and method for calibrating said device - Google Patents

Abstract

FIELD: measuring equipment engineering.

SUBSTANCE: method variants include singling out low frequency components of resulting signal and singling out from these of informational component, matching distance to probed material and component provided by reflections from irregularities of antenna-feeder line. On basis of singled out components distance and reflection coefficient of probed material are calculated for the case when spectrum of singled out "null" component matches spectrum which was recorded during calibration. If differences of spectrums are substantial, then in first variant of method measurement errors values are calculated, which are result of changing of parameters of antenna-feeder line, and said values are taken into consideration during calculation. Errors values are calculated on basis of graduating dependencies from coefficient of spectrum asymmetry. In second variant correction of distance and of reflection coefficient is performed by comparing spectrum of informational component to spectrum of formed standard signal. By changing delay and phase best match of spectrums is reached, and resulting frequency and phase of formed signal are taken as ones sought for. In both variants of method additional delay of electromagnetic waves in antenna, which is result of sticking of precipitations, is determined and taken into consideration during correction of results of distance measurement and reflection coefficient of probed material. Said method is realized by a device having an antenna, controlled probing signal source connected to processor output, power divisor, directed transceiver, mixer, inputs of which are connected to outputs of directed transceiver and power divisor, connected in series and controlled differentiating filter, low frequency filter, circuit of preliminary analog handling and analog-digital converter, output of which is connected to input of processor, controlling circuit, input of which is connected to output of processor, and outputs are connected to respective controlled filters. Method for calibrating device includes calculation on basis of singled out zero and information components of respective standard spectrums, values of their distortions and of correcting coefficient.

EFFECT: lower measurements error during change of parameters of antenna-feeder line and wider functional capabilities due to measurement of electrodynamic parameters of probed material.

4 cl, 6 dwg

Description

The invention relates to a control and measuring technique and can be used to determine the level and electrophysical parameters of liquid and bulk materials in storages and closed tanks.

A number of known methods [1, 2, 3, 4, 5] and devices [3, 4, 5, 6, 7] measure the distance to the probed material, which are based on measuring the propagation time of waves from the emitter to the surface of the probed material and vice versa.

The closest set of essential features to the claimed one (prototype) is a radar meter and a method of measuring the level in tanks [8], which includes the formation of a probing radio frequency signal with periodic frequency modulation, radiation of the generated signal in the direction of the probed material, reception after the propagation time of the reflected signal, mixing it with part of the emitted signal, the allocation of low-frequency components of the resulting signal and the selection of components from them, respectively vuyuschih range to the sensed material, determining the radio propagation time and calculation of the distance from the known velocity of propagation and frequency tuning range.

The specified range measurement method is carried out by a radar level gauge containing a series-connected control voltage generation circuit, a controlled probe signal generator, a frequency multiplier, a bandpass filter, an amplifier, two directional couplers, an antenna, a mixer connected by its inputs to the outputs of two directional couplers, and the output in series connected by an amplifier, differentiating filter, low-pass filter, amplifier, analog-to-digital converter, the output of which о is connected to the first input of the signal processor, the second and third inputs of which are connected respectively to a crystal oscillator and a frequency divider, and one of the outputs is connected to a control voltage generating circuit that contains a digital-to-analog converter, an amplifier, and a low-pass filter, while the input of the frequency divider is connected with the output of a controlled probe signal generator. The inputs and outputs of the signal processor are connected to level indicators.

Known methods for measuring ranges and level gauges that implement the known methods have at least two disadvantages. The accuracy of range measurement, low for a number of cases, and the inability to determine the electrophysical parameters of the probed material, by which it could be judged on its composition.

These shortcomings are largely due to signal reflections in the antenna-feeder path, their inconstancy and a change in the electrical length of the antenna-feeder path. The inconstancy of the reflection coefficients from the antenna and the change in the electric length of the antenna-feeder path, in turn, are due to the buildup of various precipitation on the antenna design elements, a change in the temperature of the medium, and other external factors.

The purpose of the invention is to reduce the error of level measurement and expand the functionality by measuring the electrophysical parameters of the probed material, which can be used to judge its composition.

This goal is achieved by the fact that in the method of measuring the distance from the emitter to the surface of the probed material and its electrophysical parameters, including generating a probing radio frequency signal with periodic frequency modulation, emitting a generated signal in the direction of the probed material, receiving after the propagation time of the reflected signal, mixing it with part radiated signal, the allocation of low-frequency components of the resulting signal and the allocation of information content from them which complies with the range of the probed material, calculating the spectrum of the information component and its center frequency, calculating the propagation time of the radio frequency signal to the surface of the probed material and vice versa, and calculating the distance from the known velocity and propagation time of the radio waves, additionally zero components are determined from the low-frequency components of the resulting signal parasitic passage of the probe signal into the receiving path, reflection from inhomogeneities th antenna feedlines and precipitation layer on the antenna, calculating a range of zero components and calculating the measure of its difference from the reference. If the measure of difference in the spectra exceeds the control level, the additional delay of radio waves caused by precipitation on the antenna during propagation in the antenna and the measurement error of the distance caused by the additional distortion of the spectrum of the information component are determined and these values are taken into account when correcting the distance calculation results. The additional delay of radio waves during propagation in the antenna caused by precipitation on the antenna is calculated from the extracted zero components using additional measurements of the module and the phase of the zero component at the center frequencies of at least two frequency tuning subbands. The boundaries of the frequency tuning subbands are predetermined.

Reference spectra are calculated and recorded during the calibration of the distance meter according to the selected zero and information components. Recording of these spectra is performed in the absence of interfering reflections at a distance from the antenna to the surface of the material, ensuring the absence of interaction of the spectra of the selected information and zero components.

In the first version of the method for measuring the distance and the electrophysical parameters of the material, the error in measuring the distance due to the distortion of the spectrum of the information component is taken into account by calculating the asymmetry of the spectrum of the information component and comparing the calculated value of the asymmetry with the calculated for different reflection coefficients from the antenna-feeder path and various reflection coefficients from the probed material. These calculations are performed in the full frequency tuning range and in the tuning range, which is part of the full. The result of the calculation of the distance is adjusted taking into account the additional delay of the radio waves caused by precipitation on the antenna.

In the second variant of the method for measuring the distance and the electrophysical parameters of the material, the error in measuring the distance due to the distortion of the spectrum of the information component is taken into account by forming an undistorted low-frequency component with a delay corresponding to the center frequency of the spectrum of the extracted information component. Using this component, the sum of the spectra is calculated, the first term of which is formed by the spectrum of the undistorted component, and the second term is formed by the spectrum of the signal with an amplitude equal to the product of the correction coefficient and the amplitude of the measured zero component and the amplitude of the formed undistorted component, phase equal to zero, and the delay corresponding to the delay difference of the specified undistorted low-frequency component and the zero component. Next, the resulting amount is compared with the spectrum of the extracted information component and the amplitude, delay and phase of the generated undistorted component are changed to best match the spectrum of the extracted information component. The center frequency and phase of the generated undistorted low-frequency component of the signal are taken as the frequency of the signal spectrum corresponding to the range to the probed material and its phase with the best coincidence of the spectra of the information component and the generated sum. In this case, the distance and phase of the reflection coefficient from the probed material calculated by the found center frequency and the phase of the undistorted low-frequency component are adjusted for the amount of additional delay in the precipitation layer on the antenna.

This goal is also achieved by the fact that in a device containing: an antenna; a controlled sounding signal source (UISS), the control input of which is connected to the first output of the processor, and the output is connected to a series-connected power divider (DM) and a directional coupler (BUT); a mixer (Cm), the inputs of which are connected respectively to the second output of the DM and to the second output of the BUT, and are connected in series to the preliminary analog processing circuit (SAA) and the analog-to-digital converter (ADC), the output of which is connected to the input of the processor, two additional controlled filters are introduced (UV), each of which has two inputs and one output, and a control circuit with one input and two outputs. The first input of the first UV is connected to the output of the mixer. The output of the first UV is connected to the first input of the second UV, the output of which is connected to the input of the SPAO. The second inputs of the first and second UV are connected to the corresponding outputs of the control circuit, the input of which is connected to the second output of the processor. In this case, the first UV is made in the form of a differentiating UV, the second UV is made in the form of a controlled low-pass filter (LPF), and the control circuit is made in the form of a controlled switch. The third processor output is the information output of the device.

The inventive method of measuring the distance and electrophysical parameters of the sensed material and the device for its implementation have a combination of features not known from the prior art for methods and devices for this purpose, which allows us to conclude that the criterion of "novelty".

To analyze the inventive step, the following should be considered.

A known method of measuring the electrophysical parameters of the medium by means of radar, based on the measurement and analysis of the frequency dependence of the reflection coefficient of radio waves [9]. In this method, the phase of the reflection coefficient from the material is measured at each emitted frequency from a discrete series of frequencies, and taking into account the dependence of the phase on the distance to the surface of the material and eliminating the ambiguity of reference is solved by using an additional radar channel, the carrier frequency of which exceeds the frequency of the measuring channel by several orders of magnitude. An additional channel provides the formation of a reference signal, the phase of which is determined only by the distance to the material boundary. The signal of the reference channel is modulated by harmonic oscillation, the initial phase and frequency of which coincide with the initial phase and frequency of the signal of the measuring channel. The demodulated signal of the reference radar channel acts as a reference signal, relative to the phase of which the phase change of the signal of the measuring channel is estimated. This does not take into account changes in the phase of the received signal when changing the parameters of the antenna. Therefore, in the known method, it is necessary to ensure the stability of the parameters of the antenna-feeder path.

In the claimed method, the measurement of range and reflection coefficient is carried out at the same frequencies. The connection between the phase of the frequency-modulated probe signal, the phase of the reflection coefficient and the phase of the signal of the differential frequency is used, and the influence of the antenna parameters and their changes on measuring the distance to the probed material and the phase of the reflection coefficient are taken into account. The necessary parameters are measured in one variant of the method by measuring the central frequency of the information component of the spectrum of the differential frequency signal, measuring the distortion of the spectrum of the information component and comparing it with the amount of spectrum distortion, for which calibration dependences of the values of the center frequency and phase corrections are known. In another embodiment of the measurement method, the spectrum of the information component is compared with the spectrum of the reference signal, for which the center frequency and phase are known.

Thus, in contrast to the known method, an additional reference radar channel is excluded and a comparison with reference values is introduced.

To eliminate the ambiguity of measurements, which can be a multiple of half the wavelength, a measurement has been introduced on at least two partial sub-bands of the frequency tuning and on the full tuning range.

There is also a known method and device for measuring liquid level [4]. The method includes generating a probe signal with a periodically changing frequency and mixing the probe signal with an echo signal, receiving a difference frequency signal at the output of the mixer, filtering the difference frequency signal with a band-pass filter to suppress frequencies below the lower cut-off frequency and above the upper frequency, microprocessor control of the lower cut-off frequency so that the signal suppression is minimized, the frequency of which corresponds to the range to the probed material (information component), and the suppression Signals are generated whose frequencies are lower than the frequency of the information component.

This method is implemented by a device comprising: a voltage controlled oscillator (VCO) with a control input and signal output; power divider (DM) with one input and two outputs; mixer; controlled high-pass filter (HPF) with one output and two inputs; low pass filter (low-pass filter); adjustable amplifier with one output and two inputs; analog-to-digital converter (ADC); microprocessor with three outputs and one input; sawtooth voltage generator. The signal output of the VCO is connected to the input of the DM, the two outputs of which are connected respectively to the inputs of the antenna and the mixer, and the output of the mixer is connected to the first input of the HPF, the second input of which is connected to the first output of the microprocessor, and the output is connected to the input of the LPF. The output of the low-pass filter is connected to the first input of the adjustable amplifier, the second input of which is connected to the second output of the microprocessor, and the output is connected to the input of the ADC. The ADC output is connected to the microprocessor input. The third output of the microprocessor is connected to the input of a sawtooth generator, the output of which is connected to the control input of the VCO.

Thus, in the known method, after receiving the difference frequency signal, i.e. at a low frequency, zero components are filtered out (suppressed), due to the parasitic passage of the probe signal into the receiving path, reflection from the inhomogeneities of the antenna-feeder path and the precipitation layer on the antenna. At the same time, it does not take into account that due to the interaction in the mixer of high-frequency signals reflected from the antenna and from the probed material, additional low-frequency spectral components appear in the difference-frequency signal, which correspond to the distances between the inhomogeneities in the antenna-feeder path and the probed material. These components appear in the form of "virtual" reflectors located next to the probed material and cannot be suppressed by filtering (suppressing) the zero components of the difference frequency signal (as proposed in the said patent). The indicated spectral components ("virtual" reflectors) lead to the appearance of an error in the measurement of distance. In accordance with the known method, a controlled high-pass filter is included in the level measuring device after the mixer, which constantly suppresses zero components and is adjusted so that when the measured level changes, the filter suppresses spectral components from reflectors, the distance to which is less than the distance to the probed material . However, as already indicated, any filter cannot suppress the spectral components of "virtual" reflectors.

In the inventive method, zero components are additionally extracted and used to correct the results of distance measurement and analysis of the electrodynamic parameters of the probed material. In accordance with this, controlled filters are included at the output of the device mixer, which do not suppress the zero components, as in the known device, but periodically select zero components or a mixture of the information component with the “virtual” component. Thus, the device is characterized by the presence of additional elements (controlled filter and control device) and the parameters of the element (filter) connected to the output of the mixer, which is also a sign of the device.

These differences lead to the appearance of qualitatively new properties of the claimed method and device - the ability to measure the magnitude of the errors that arise due to "virtual" reflectors in front of the probed material, and to correct the measurement results by the value of the measurement error. These new properties thereby increase the accuracy of measurements and, in addition, allow the measurement of the electrodynamic parameters of the probed material.

These differences do not follow explicitly from available scientific and technical sources, which allows us to conclude that the claimed technical solution meets the criteria of the invention "Inventive step".

The invention is illustrated using the drawings shown in figures 1-6.

1 shows an antenna with a dielectric cap and adhering deposits.

Figure 2 shows the calibration curves for determining the phase of the coefficient of reflection from the material.

Figure 3 shows the calibration curves for determining the correction value of the center frequency of the spectrum of the information component.

Figure 4 shows a structural diagram of a device for measuring the distance and electrophysical parameters of the probed material.

Figure 5 shows the first variant of a controlled source of the probing signal.

Figure 6 shows a second variant of the controlled source of the probing signal.

The method of measuring the distance and electrophysical parameters of the probed material is as follows.

u_г на смесительном элементе, вольт-амперная характеристика которого содержит множество составляющих, в том числе квадратичную составляющую i_см=Au $\genfrac{}{}{0ex}{}{\text{2}}{\text{см}}$ (здесь А - постоянный коэффициент). При правильном выборе режима работы смесителя квадратичная составляющая во много раз превышает составляющие более высоких степеней, поэтому можно считать, что сигнал u содержит только сумму постоянных и низкочастотных составляющих:After the radiation of the generated probing RF signal with periodic linear frequency modulation (or with discrete frequency tuning according to a linear law) is emitted, the propagation time is received after the propagation time of the signal u _m reflected by the probed material and the signal u _a reflected by inhomogeneities in the antenna-feeder path. Then mix them with part of the emitted signal

u _g on the mixing element, the current-voltage characteristic of which contains many components, including the quadratic component i _{cm =} Au $\genfrac{}{}{0ex}{}{\text{2}}{\text{cm}}$ (here A is a constant coefficient). With the correct choice of the mixer operating mode, the quadratic component is many times higher than the components of higher degrees, so we can assume that the signal u contains only the sum of the constant and low-frequency components:

For frequency modulation, ω (t) = ω ₀ + ω _modes (t) with a carrier frequency ω ₀ and a variable part ω _modes (t), the low-frequency components of expression (1) provided that the propagation time of the probe signal to the material and vice versa is τ _m less than the modulation period T _mod , have the form:

where U _g is the amplitude of the local oscillator voltage;

U _m is the voltage amplitude of the signal reflected by the probed material;

φ _m is the phase of the wave reflected from the material;

U _a is the voltage amplitude of the signal reflected from the antenna;

τ _a is the propagation time of the probe signal to the inhomogeneity in the antenna and back (to the dielectric cover and back)

φ _a is the phase of the wave reflected from the inhomogeneity in the antenna.

The low-frequency component u _gm carries information about the distance to the probed material and about the phase of the reflection coefficient from the probed material. The low-frequency components u _um and u _am are usually impossible to separate, because τ _and usually less than the resolution of the range finder. These components are allocated in the form of an indivisible sum (u _gm + u _am ). In this case, the low-frequency component u _am is “spurious,” corresponding to the appearance of “virtual” reflectors located next to the probed material, and distorting information about the distance to the probed material and about the phase of the reflection coefficient. These distortions are manifested, for example, in the spectral processing of a signal in the distortion of the spectrum shape of the resulting component (u _gm + u _am ). In this case, the spectrum of the resulting component becomes asymmetric. The asymmetry of the spectrum leads to a shift in the center frequency by Δω and the corresponding error in calculating the distance by Δ R.

With constant reflection from the antenna, U _a = const and φ _a = const, the error Δ R is independent of the distance and its influence can be excluded when calibrating the distance meter. However, when the temperature changes, precipitation sticks to the antenna and other external factors, U _a and φ _a change, which leads to the appearance of an error in determining the distance and the inability to determine the phase of the reflection coefficient from the material.

The error in determining the distance consists of two terms. The first term appears due to the indicated asymmetry of the spectrum and the variability of this asymmetry. The second term appears due to a change in the electric length of the antenna-feeder path due to the buildup of precipitation 1 on the antenna 2, for example on the dielectric cover 3, as shown in FIG.

составляющую u_а, обусловленную отражением от антенны, измеряют ее амплитуду U_а и вычисляют отношение

учитывая, что

при U_м и U_а много меньше U_г. Затем вычисляют спектр нулевых составляющих S_a(ω _j) на дискретных частотах ω _j, применяя прямое дискретное преобразование Фурье к составляющей u_a, находят его центральную частоту или эквивалентное ей τ _a, фазу φ _a и меру отличия спектра от эталонного S_эт(ω _j). В качестве меры отличия спектров может использоваться любая математическая метрика, используемая для оценки различия двух функций. Например, Эвклидова метрика [12] ρ :In both cases, to compensate for the influence of spectrum asymmetry due to the parasitic component u _am , a constant component is isolated from the sum of the constant and low-frequency components of the resulting signal u

component u _a , due to reflection from the antenna, measure its amplitude U _a and calculate the ratio

considering that

when U _m and U _{a are} much less than U _g . Then, the spectrum of zero components S _a (ω _j ) is calculated at discrete frequencies ω _j , applying the direct discrete Fourier transform to the component u _a , its center frequency or its equivalent τ _a , phase φ _a and the difference between the spectrum and the reference S _et (ω _j ). As a measure of the difference in spectra, any mathematical metric used to assess the difference between the two functions can be used. For example, the Euclidean metric [12] ρ:

where m is the total number of discrete frequencies in the spectrum.

If the measure exceeds the differences in the spectra of the control level, the values of the errors that occur are calculated.

его центральную частоту ω Σ и коэффициент асимметрии спектра β [10]:In the first variant of the method, from the sum of the constant and low-frequency components of the resulting signal, the sum of the components (u _gm + u _am ) is also extracted, its discrete spectrum is calculated

its central frequency ω Σ and the spectrum asymmetry coefficient β [10]:

- k-е центральные моменты спектра S(ω _j).Where

are the kth central moments of the spectrum S (ω _j ).

в к оторых в функциональной зависимости

отношение

является параметром (фиг.2, кривые 4 и 5), а величину поправки Δ ω определяют, используя набор градуировочных кривых

которые вычисляют для различных соотношений

(фиг.3, кривые 6 и 7) и для различных значений разности фаз (φ _м-φ _a). Градуировочные кривые на фиг.3 приведены только для одного значения (φ _м-φ _a). Для исключения неоднозначности определения Δ ω _изм вычисления величины асимметрии спектра выполняют в полном диапазоне перестройки частоты и в диапазоне перестройки, составляющем часть полного. В последнем случае (кривая 8 на фиг.3) одинаковым значениям Δ ω _изм должны соответствовать меньшие значения коэффициента асимметрии: β _{изм,част}<β _{изм,полн}.The magnitude of the asymmetry coefficient β calculates the phase difference (φ _m -φ _a ) = (φ _m -φ _a ) _ISM - (φ _m -φ _a ) _et and the correction value Δ ω = Δ ω _ism -Δ ω _et , for which the central frequency of the spectrum of the information component u _um differs. Here (φ _m -φ _a ) _ISM and Δ ω _ISM are the values of the phase difference and frequency displacement, calculated from the calculated asymmetry coefficient; (φ _m -φ _a ) _et and Δ ω _et are the phase difference and frequency offsets calculated from the reference spectrum during calibration. The magnitude of the phase difference (φ _m -φ _a ) is determined using a set of calibration curves

in to in functional dependence

the attitude

is a parameter (figure 2, curves 4 and 5), and the correction value Δ ω is determined using a set of calibration curves

which are calculated for various ratios

(figure 3, curves 6 and 7) and for different values of the phase difference (φ _m -φ _a ). The calibration curves in figure 3 are shown for only one value (φ _m -φ _a ). To eliminate the ambiguity of determining _{Δω from the} calculation of the asymmetry of the spectrum, they are performed in the full range of frequency tuning and in the tuning range, which is part of the full. In the latter case (curve 8 in FIG. 3), the smaller values of the asymmetry coefficient should correspond to the same values of Δ ω _ISM : β _{ISM, part} <β _{ISM, full} .

The adjusted value of the frequency ω _{p of} the difference frequency signal for the component corresponding to the range R to the probed material is determined as the sum - ω _p = ω ∑ + Δ ω, and from the calculated frequency of the difference frequency signal, known to the frequency tuning range, the modulation period and the propagation speed of radio waves calculate the specified distance.

The phase of the reflection coefficient from the probed material is determined by summing the measured phase value φ _{a of the} component u _a and the phase difference determined by the calibration curves (φ _m -φ _a ):

φ _m = φ _a + (φ _m -φ _a ).

и его центральную частоту ω Σ .In the second embodiment of the method, the sum of the components (u _gm + u _am ), which is informational but distorted by the term u _am , is also extracted from the low-frequency components of the resulting signal, and the spectrum of the indicated sum is calculated

and its center frequency ω Σ.

и задавая амплитуду неискаженной составляющей результирующего сигнала U_м, с помощью прямого преобразования Фурье вычисляют сумму спектров

первое слагаемое которой

образовано сформированной неискаженной низкочастотной составляющейGiven the obtained amplitude value U _g , the ratio of amplitudes

and setting the amplitude of the undistorted component of the resulting signal U _m , using the direct Fourier transform calculate the sum of the spectra

whose first term

formed by the formed undistorted low-frequency component

определяемой через центральную частоту ω ∑ спектра выделенной информационной составляющей (u_гм+u_ам), период модуляции Т_мод и диапазон перестройки частоты Δ ω _мод, а второе слагаемое образовано спектром

составляющей u_амф, вычисленной по измеренным значениям τ _а, φ _а, U_а и заданным τ _мф, φ _мф и U_мф:with an amplitude equal to AU _g U _mf , phase φ _mf = 0 and delay

defined through the center frequency ω ∑ of the spectrum of the extracted information component (u _gm + u _am ), the modulation period T _modes and the frequency tuning range Δ ω _modes , and the second term is formed by the spectrum

component u _amph calculated from the measured values of τ _a , φ _a , U _a and given τ _mf , φ _mf and U _mf :

сравнивают с амплитудным спектром выделенной искаженной информационной составляющей

изменяют величину τ _мф, фазу φ _мф и амплитуду U_мф до наилучшего совпадения этих спектров, т.е. до достижения минимума указанной ранее меры отличия ρ между ними. За центральную частоту спектра сигнала, соответствующую дальности до зондируемого материала, фазу этого сигнала φ _м и амплитуду U_м принимают частоту, фазу и амплитуду слагаемого и u_гмф при наилучшем совпадении спектра информационной составляющей

и спектра сформированной суммы

по которым определяют искомое расстояние, модуль и фазу коэффициента отражения.Amplitude spectrum of the generated sum

compared with the amplitude spectrum of the selected distorted information component

change the value of τ _MF , phase φ _MF and amplitude U _mF to the best match of these spectra, i.e. until the minimum of the measure of ρ difference between them is reached. For the central frequency of the signal spectrum corresponding to the range to the probed material, the phase of this signal φ _m and the amplitude U _m take the frequency, phase and amplitude of the term and u _GMP with the best coincidence of the spectrum of the information component

and the spectrum of the generated amount

which determine the desired distance, modulus and phase of the reflection coefficient.

If the length of the antenna-feeder path is such that the zero component has more than one and a half beat periods and the amplitude of the wave reflected from the antenna is more than ten times the amplitude of the waves reflected by other elements of the feeder path, then without changing the essence of the claimed method, it is possible to determine the amplitude values of voltages u _um and u _am as follows. Using the extracted information component, its maximum (u _gm + u _am ) _max and minimum (u _gm + u _am ) _min values are measured, which are respectively equal to the sum of U _gm + U _am and the difference U _gm- U _{am of the} amplitude values of these voltages. The half-sum of these values will give the amplitude of the term u _um , and the half-difference will give the amplitude of the term u _am .

In both variants of the method for measuring the distance to the surface of the probed material and its electrophysical parameters, the error term Δ l _el due to a change in the electric length of the antenna-feeder path due to the adherence of the precipitation layer d _os with relative dielectric constant ε ₀ is determined identically.

In the case of placing a dielectric protective cover in the aperture of the antenna (figure 1), this term will be:

In this expression, d _oc and ε ₀ are generally unknown.

The reflection coefficient V from the cover with a layer of precipitation can be written in the form [11, p. 57]:

Where

- импеданс свободного пространства (воздуха);

- impedance of free space (air);

- импеданс крышки;

- impedance of the cap;

- импеданс газовой среды над зондируемым материалом;

- impedance of the gaseous medium above the sensed material;

- импеданс осадков на крышке;

- impedance of precipitation on the cover;

i is the imaginary unit;

μ _air , ε _air - respectively, the magnetic and dielectric constant of air;

μ _cr , ε _cr - respectively, the magnetic and dielectric constant of the cover material;

μ _gas , ε _gas , respectively, the magnetic and dielectric permittivities of the gaseous medium above the probed material;

μ _OS , ε _OS - respectively, the magnetic and dielectric constant of the sediment layer.

и его фазы φ _V в этом выражении получают систему двух уравнений с двумя неизвестными, в которых должны быть известны измеренные значения модуля и фазы коэффициента отражения от крышки антенны, а также параметры крышки. В общем случае система двух уравнений решается графически или численно. Однако в частном случае, который обычно и используют на практике, решение записывается в явном виде.Equation (2) contains two unknown quantities ε _OS and d _OS . Isolation of the reflection coefficient module

and its phases φ _V in this expression, a system of two equations with two unknowns is obtained, in which the measured values of the modulus and phase of the reflection coefficient from the antenna cover, as well as the parameters of the cover, should be known. In the general case, the system of two equations is solved graphically or numerically. However, in the particular case, which is usually used in practice, the decision is written in explicit form.

The antenna is usually designed so that, under normal conditions, it is best aligned. Such results can be obtained if the cap thickness is equal to half the wavelength of the signal in the cap material. In this case, the lid has no effect on the incident wave [11, p. 48].

It is obvious that the sealing insert located in the mouth of the horn and coordinated in the best way also does not have any effect on the incident wave.

Thus, the reflection coefficient from the cover with the precipitation layer will be equal to the reflection coefficient from the precipitation layer. In addition, usually Z _gas ≈ Z _air . In this case, expression (2) is reduced to

The solution of this equation gives the values of ε _OS and d _OS :

и

:The values of φ _V and V are calculated from the selected and measured values

and

:

используя соотношение

, известное из конструктивных особенностей. Здесь

using the ratio

known for design features. Here

The constant phase difference φ _K between the signals in the local oscillator channel and in the channel of the probing signal is taken into account when calibrating the range meter; therefore, it does not affect the measurement error.

From here:

Given the measurement error due to changes in the electrical length of the antenna-feeder path, the distance to the probed material:

The calculation of the additional delay of radio waves during propagation in the antenna caused by precipitation on the antenna from measurements of the module and phase of the low-frequency component of the difference signal at at least two frequencies of the frequency tuning range allows eliminating the ambiguity in determining d _oc multiple of half the wavelength in the precipitation material.

и отраженных

волн циркуляторами или направленными ответвителями.Without changing the essence of the method, it is possible to widely measure the modulus and phase of the reflection coefficient from the antenna widely used in measurement technology with highlighting incident

and reflected

waves circulators or directional couplers.

Also, without changing the essence of the method, it is possible to calculate the additional delay of radio waves propagating in the antenna using the experimentally measured dependences on the thickness and dielectric constant of the sediment layer of the module and the phase of the reflection coefficient from the sealing cover or insert.

An additional decrease in the measurement error, which is caused by a change in the parameters of the antenna-feeder path, is achieved by performing additional measurements, for example, in bench conditions during calibration of the range meter. The essence of additional measurements is to simulate changes in the parameters of the antenna-feeder path and eliminate the influence on the measurement error of these changes. Calibration of the distance meter consists in selecting and storing the specified values of τ _a and φ _a when the signal is reflected from the antenna with a reference reflector.

A device for measuring distance and analysis of the electrophysical parameters of the sensed material (Fig. 4) contains an antenna 9, a controlled source of a sounding signal (UISS) 10, the input of which is connected to the first output of the processor 11, and the output is connected to a series-connected power divider (DM) 12 and a directional coupler (HO) 13, the first output of which is connected to the antenna 9, a mixer (Cm) 14, the inputs of which are connected respectively to the second output of the DM 12 and the second output of the HO 13, and the output of the mixer is connected to two in series remote controlled filters (UV1) 15 and (UV2) 16, each of which has two inputs and one output, and the output of UV2 16 is connected to the input of the preliminary analog processing circuit (SPAO) 17, the output of which is through an analog-to-digital converter (ADC) 18 connected to the input of the processor 11, the second output of the processor 11 is connected to the input of the control circuit 19, the first and second outputs of which are connected to the control inputs of the respective controlled filters UV1 15 and UV2 16, the first UV1 15 made in the form of a differentiating filter, the second UV2 16 made in the form of a low-pass filter (LPF), and the control circuit 19 is made in the form of a switch that controls the filters UV1 15 and UV2 16, the third output of the processor 11 is the information output of the device.

A controlled source of the probing signal can be performed, for example, in accordance with the schemes presented in figure 5 and 6.

The UIZS shown in Fig.6 contains: a processor 20, the first input of which is the UISS input, the first output is connected to a digital-to-analog converter (DAC) 21 connected in series, an amplifier 22, a voltage controlled oscillator (VCO) 23, HO 24, the first output which is the UIZS output, the second output of which is connected to the first input of the mixer 25, the second input of which is connected to the reference generator 26, a filter amplifier 27, the input of which is connected to the output of the mixer 25, a controlled frequency divider 28, the first input of which is connected to the output of the filter amplifier 27, the second input is connected to the second output of the processor 20, and the output is connected to the first input of the frequency detector 29, the second input of which is connected to the output of the crystal oscillator 30, and the output is connected to the second input of the processor 20.

This circuit operates in two modes. In the first mode, the UISS is calibrated when the shape of the modulating voltage is selected so that the frequency of the generated signal changes according to a stepwise linear law. To do this, the processor 20, during calibration, sequentially provides the generated frequency codes to the controlled divider 28 and the modulation voltage codes to the DAC 21. For each code of the generated frequency, in accordance with the code of the modulation voltage, the DAC 21 generates a modulating voltage, which through the amplifier 22 acts on the VCO 23. A part of the output signal from the VCO 23 through the NO 24 is supplied to the mixer 25, where it is converted to an intermediate frequency using the signal of the reference generator 26. The intermediate frequency signal through a filter amplifier 27 and a controlled frequency divider 28 is fed to a frequency detector 29, the second input of which receives a signal from a crystal oscillator 30. If these frequencies ignalov do not match, the processor 20 changes the voltage modulation code until such time until there is a coincidence of frequencies. A sign of this event will be the appearance of a signal of a logical unit at the output of the frequency detector 29 and, therefore, at the second input of the processor 20. In this case, the processor remembers the received modulation voltage code and repeats the whole procedure for the new frequency value of the generated signal. Calibration ends when this procedure is performed for all frequencies of a given frequency tuning range. In the second mode of operation of the UIZS, the modulating voltage code is periodically generated at the first output of the processor 20 in accordance with the frequency code supplied to its first input.

UIZS, performed according to the scheme of Fig.6, contains: a digital signal sample synthesizer (DDS synthesizer) 31 (for example, commercially available from Peregrine), the first input of which is the UISS input, and the second input of which is connected to the output of the reference crystal oscillator 32, a frequency divider 33, the input of which is connected to the DDS output of the synthesizer 31, a phase detector 34 with two inputs, the first of which is connected to the output of the frequency divider 33, and the second is connected to the frequency divider 35, the integrator 36, connected by its input to the output of the phase detector 34, and the output - input of VCO 37, DK 38, connected to its input to an output of the VCO 37, the first output - to an input of frequency multiplier 39, whose output is the output UIZS and second output - to the input of the frequency divider 35.

This circuit is based on a standard frequency synthesizer based on a PLL loop, which includes a phase detector 34, an integrator 36, a VCO 37, HO 38 and a frequency divider 35. The frequency is controlled by changing the frequency of the reference signal, which is input to the phase detector 34 from the DDS synthesizer 31 through a frequency divider 33. The code that controls the synthesized frequency is fed to the DDS input of the synthesizer 31, which generates a stable-frequency sinusoidal signal based on the signal of the reference crystal oscillator 32. The output signal of the phase vector 34, proportional to the phase difference of the reference signal and the signal received from the VCO 37 through the HO 38 and the frequency divider 35, controls through the integrator 36 the frequency of the VCO 37 until the phase balance occurs. The signal from the VCO 37 through the directional coupler 38 and the frequency multiplier 39 is fed to the output of the UISS.

UIZS made using standard elements according to standard schemes. However, in the first scheme shown in Fig. 5, the frequency tuning speed in the operating mode is determined only by the dynamics of tuning of the VCO 23. Therefore, it can be as high as possible in this scheme, which is beneficial from the point of view of reducing the influence of phase noise of the VCO 23. However, this scheme requires periodic calibrations with interruption of the measurement process. In UIZS, made according to the scheme of Fig.6, the speed of the frequency tuning is determined by the dynamics of the tuning of the PLL, therefore it is lower, but it is not necessary to interrupt the measurement process.

A device for measuring the distance and electrophysical parameters of the sensed material works as follows. The control input UIZS 10 receives control codes for the frequency of the probing signal. From the output of the UIZS 10, the main part of the power of the generated probing frequency-modulated signal through a series-connected DM 12, HO 13 and antenna 9 is emitted in the direction of the probed material. Accepted by antenna 9, the echo signal through the second output of HO 13 is fed to the first input of mixer 14, the second input of which receives part of the power of the probing frequency-modulated signal from the second output of DM 12. The difference frequency signal through series-connected UV 15, SPAO 16, ADC 17 arrives at the input of the processor 11. UV 15 with the appropriate command from the processor 11 periodically selects either the information component of the resulting signal corresponding to the range to the probed material, or zero components, due to the “parasitic” passage of the probe signal into the receiving path, reflection from the inhomogeneities of the antenna-feeder path and the sediment layer on the antenna. For the zero component, the processor 11 using the discrete Fourier transform calculates the spectrum, compares it with the reference spectrum recorded during the calibration of the device, and calculates the measure of difference between these spectra. If the measure of difference is below the control level, the processor calculates the distance and reflection coefficient from the measured spectra of information and zero components. If the measure exceeds the control level difference, the processor performs calculations in accordance with the described measurement method. In this case, the processor generates control commands on the UIZS 10 and UV1 15 and UV2 16.

UIZS can be made in the form of an amplifier with a calibrated gain.

The simulation and testing of the prototype distance meter showed that the proposed method (options) and device for its implementation provide a reduction in measurement error due to a change in the parameters of the antenna-feeder path more than 4 times and provide enhanced functionality by measuring the reflection coefficient from probed material.

Sources of information

1. A.S. USSR No. 1642250, MKI G 01 F 23/28, publ. 04/15/91, B.I. Number 14.

2. US patent No. 4665403 from 05/12/87.

3. A.S. USSR No. 1700379, MKI G 01 F 23/28, publ. 12/23/91, B.I. No. 47.

4. US Patent No. 5365178 of 11/15/94.

5. US patent No. 5387918 from 02/07/95

6. US patent No. 5504490 dated 04/04/96.

7. US patent No. 5546088 from 08.13.96.

8. US patent No. 6107957 from 08/22/2000

9. Lobach V.G. Radar measurements of layered medium parameters. Izv. Universities. Radio Electronics, 2002, No. 3.

10. Atayants B. A., Parshin V. S. Recognition of random signals from spectral moments. Izv. Universities. Radio Electronics, 1983, No. 12.

11. Brekhovskikh L.M. Waves in layered media. Publishing House of the USSR Academy of Sciences, Moscow. 1957

12. Gorelik A.L., Skripkin V.A. Recognition methods. Uch. manual for universities: M. Higher. School., 1977, 208 p.

Claims (10)

1. A method of measuring the electrophysical parameters of the sensed material and the distance to it, including the formation of a probing radio frequency signal with periodic frequency modulation, radiation of the generated signal in the direction of the probed material, receiving, after the propagation time, the reflected signal, mixing it with part of the emitted signal, highlighting low-frequency components the resulting signal and extracting from them information components corresponding to the range to the probed material, you calculating the spectrum of the information component and determining its center frequency, calculating the propagation time of the radio frequency signal to the surface of the probed material and vice versa, and calculating the distance from the known velocity and propagation time of the radio waves, characterized in that zero components are additionally distinguished from the low-frequency components of the resulting signal due to the parasitic passage of the probing signal to the receiving path, reflection from heterogeneities of the antenna-feeder path and with After the precipitation on the antenna, the spectrum of the zero components is calculated and a measure of its difference from the reference is calculated, if the difference in the spectra of the control level is exceeded, the additional delay of radio waves during propagation in the antenna caused by precipitation on the antenna is determined, the amount of additional distortion of the spectrum of the information component is calculated and the specified additional delay is taken into account radio waves and spectrum distortion of the information component when correcting the results of calculating the distance to the probed material, and p about the calculated distance and the module and phase of the information component corresponding to the range to the probed material, calculate the reflection coefficient from the probed material, which is used to judge its electrophysical parameters. 2. The method according to claim 1, characterized in that if the difference in the spectra of the control level is exceeded, the additional delay of radio waves during propagation in the antenna caused by precipitation on the antenna is calculated from the extracted zero components and additional measurements of the module and phase of the zero component, at least at two frequencies of the deviation range. 3. The method according to claim 1, characterized in that when the difference in the spectra of the control level is exceeded, the correction of the results of calculating the distance to the probed material is performed by calculating the asymmetry of the spectrum of the information component and comparing the calculated asymmetry value with the calculated value for various reflections from the antenna-feeder path and different reflection coefficients from the probed material. 4. The method according to claim 5, characterized in that the magnitude of the asymmetry of the spectrum is calculated by the information component in the full range of deviation and in the range of deviation, which is part of the full. 5. A method for measuring the electrophysical parameters of the sensed material and the distance to it, including generating a probing RF signal with periodic frequency modulation, emitting the generated signal in the direction of the probed material, receiving, after the propagation time, the reflected signal, mixing it with part of the emitted signal, highlighting low-frequency components the resulting signal and extracting from them information components corresponding to the range to the probed material, you calculating the spectrum and its center frequency, calculating the propagation time of the radio frequency signal to the surface of the probed material and vice versa, and calculating the distance from the known velocity and propagation time of the radio waves, characterized in that zero components are additionally isolated from the low-frequency components of the resulting signal due to the parasitic passage of the probing signal to the receiving the path, by reflection from inhomogeneities of the antenna-feeder path and the sediment layer on the antenna, the spectrum of n of the hive components and compare it with the reference one, if the difference in the spectra of the control level is exceeded, the additional delay of the radio waves during propagation in the antenna caused by precipitation on the antenna is calculated, an undistorted low-frequency component is formed with a delay corresponding to the center frequency of the spectrum of the extracted information component, and the sum of the spectra is calculated, the first term which is formed by the spectrum of the undistorted component, and the second term is formed by the spectrum of the signal with an amplitude equal to the construction of the correction coefficient on the amplitude of the measured zero components and on the amplitude of the generated undistorted component, a phase equal to zero, and a delay corresponding to the delay difference of the specified undistorted low-frequency component and the zero component, compare the resulting amount with the spectrum of the extracted information component, change the delay and phase of the formed undistorted component until the best match of the formed sum of spectra with the spectrum of the selected information component is taken as the signal frequency corresponding to the distance to the probed material and its phase, the center frequency and the phase of the undistorted formed component with the best match between the spectra of the information component and the generated sum, while the distance and phase of the reflection coefficient are adjusted for the additional delay in the precipitation layer on the antenna from the probed material, calculated by the found center frequency and phase of the formed undistorted component. 6. The method according to claim 5, characterized in that if the difference in the spectra of the control level is exceeded, the additional delay of radio waves during propagation in the antenna caused by precipitation on the antenna is calculated from the extracted zero components and additional measurements of the module and phase of the zero component, at least at two frequencies of the deviation range. 7. A device for measuring the electrophysical parameters of the sensed material and the distance to it, containing a controlled source of the probing signal, the input of which is connected to the first output of the processor, and the output is connected to a series-connected power divider and directional coupler, the first output of which is connected to the antenna, mixer, inputs which are connected respectively to the output of the signal power divider and to the second output of the directional coupler, and the preliminary connected circuit logic processing and an analog-to-digital converter, the output of which is connected to the processor input, characterized in that two controlled filters are introduced into it, each with two inputs and one output, and a control circuit with one input and two outputs, the first input of the first controlled filter connected to the output of the mixer, the output of the first controllable filter is connected to the first input of the second controllable filter, the output of which is connected to the input of the preliminary analog processing circuit, the input of the control circuit is connected to the second Exit processor and two output control circuits are connected to second inputs of respective controllable filters. 8. The device according to claim 7, characterized in that the first controllable filter is made in the form of a differentiating filter, and the second is a low-pass filter. 9. A method of calibrating a device for measuring the electrophysical parameters of the probed material and the distance to it, including the calculation and recording of reference parameters, characterized in that the corresponding reference spectra, their distortion value and the correction factor are calculated and recorded by the extracted zero component and the extracted information component. 10. The method according to claim 9, characterized in that the recording of the reference spectra is performed in the absence of interfering reflections and at a distance from the antenna to the surface of the material, ensuring the absence of interaction of the spectra of the selected information and the selected zero components.

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