RU2563581C1 - Remote determination of dielectric constant of dielectric object - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: claimed process comprises the steps that follow. Dielectric object is irradiated with microwave-radiation in N frequencies. Signal is registered that contains the data on dielectric constant of dielectric object with the help of registration channel incorporating registration means. Registered signal is subjected to coherent processing. Signal passed through dielectric signal is registered. Then, defined is the dependence of equation

where N is the quantity of microwave radiation frequencies, k is the microwave radiation frequency number (N frequencies), f_k is k^th frequency of said radiation, i is imaginary unit, c is light velocity in vacuum, Aobject_k is amplitude of signal registered in k^th radiation frequency in the presence of object in controlled area of space, Φobject_k is the phase of signal registered in k^th radiation frequency in the presence of object in controlled area of space in radians, Acn_k is amplitude of signal registered in k^th radiation frequency in the absence of object in controlled area of space, Φcn_k is the phase of signal registered in k^th radiation frequency in the absence of object in controlled area of space, on x - coordinate in axis X connecting the registration means and microwave radiation source. Magnitude x_max is defined whereat F has maximum magnitude. Dielectric constant is defined by the formula:

where L is physical dielectric object in axis X.

EFFECT: higher accuracy of dielectric constant determination for moving dielectric objects, process implementation irrespective of dielectric object illumination.

Description

The invention relates to the field of remote measurement of the physical characteristics of objects, in particular the dielectric constant of dielectrics.

There are practical problems when it is necessary to determine the dielectric constant of an object without direct contact with it of measuring equipment. In addition, the studied object in such cases can have a complex geometric shape, which makes it difficult to solve the problem.

A known method for determining the dielectric constant of a material, which consists in irradiating the test sample with an electromagnetic wave by a two-arm radiator, changing the phase difference of the signals in the arms of the radiator and measuring the amplitude of the transmitted wave at an angle and determining the dielectric constant; simultaneously with the change in the phase difference in the arms of the emitter, the dependence of the amplitude of the transmitted wave on the length of the arm is removed, and the dielectric constant is determined by the formula

,

,

where λ ₀ is the wavelength in free space; λ _b - wavelength in a two-arm emitter; Δ is the period of zeros of the amplitude of the transmitted wave, and the angle θ is selected from the relation

,

,

where d _k is the limiting size of the emitter arm (SU 1800333 A1, 03/07/1993).

The disadvantage of this method is the need for contact of the emitter with the object of determining the dielectric constant. In addition, this object must have a flat face to ensure contact with the emitter. These circumstances do not allow the use of this method for remote determination of the dielectric constant of objects.

A known method for determining the dielectric constant of a dielectric object by irradiating a dielectric object with a coherent microwave emitter at N frequencies; Irradiation is performed against the background of reflectors, which are the boundaries of the layers of the object, or the boundary of the dielectric object and air, or the physical body on which the studied dielectric object is placed. The signal reflected from the dielectric object and the reflector is recorded, the received signals are converted to the time domain, the peak time components in the time spectrum are extracted, the times of the selected peak time components are measured, and the dielectric constants and layer thicknesses are determined; sounding and reception are carried out in the sector of angles, and dielectric constant and layer thicknesses are determined by the formulas:

;

;

, $$\Delta l_i=\left(t_i-\frac{2}{c}{\displaystyle \sum _{p=\mathrm{one}}^{i-\mathrm{one}}\frac{\sqrt{{\epsilon }_{p_{\mathrm{one}}}\cdot \Delta l_p}}{\sqrt{\mathrm{one}-{\epsilon }_l/{\epsilon }_p\cdot Si{n}^2{\theta }_{P\mathrm{but}d\mathrm{one}}^{(i)}}}}\right)\cdot \frac{c\cdot \sqrt{\mathrm{one}-\frac{{\epsilon }_l}{{\epsilon }_i}Si{n}^2{\theta }_{P\mathrm{but}d\mathrm{one}}^{(i)}}}{2\sqrt{{\epsilon }_i}}$$

,

, где h₁ и h₂ - высоты от границы раздела первого и второго слоев до мест, откуда производится зондирование и места приема сигналов соответственно; $${\theta }_{пад1}^{\left(i\right)}$$

- угол приема сигнала, отраженного от границы раздела i- и i+1-го слоев со скоростью света; t_i - частота i-й пиковой составляющей временного спектра, соответствующей отражению сигнала от границы раздела i- и i+1-го слоев; d - проекция на зондируемую поверхность расстояния между местом, откуда производится зондирование, и местом приема сигналов (RU 2039352 С1, 09.07.1995).where i is the number of layers; ε _i , ε _p is the dielectric constant of the i and p layers; ε _l is the dielectric constant of the medium from which sounding and reception of signals are carried out; Δl _i is the thickness of the i-th layer; $$\Delta =\frac{h_{\mathrm{one}}-h_2}{2}$$

where h ₁ and h ₂ are the heights from the interface of the first and second layers to the places from which sounding is made and the places of signal reception, respectively; $${\theta }_{P\mathrm{but}d\mathrm{one}}^{\left(i\right)}$$

- the angle of reception of the signal reflected from the interface of the i- and i + 1-st layers with the speed of light; t _i is the frequency of the i-th peak component of the time spectrum corresponding to the reflection of the signal from the interface of the i- and i + 1-st layers; d is the projection on the probed surface of the distance between the place from which the sounding is made and the place of reception of signals (RU 2039352 C1, 07/09/1995).

The disadvantage of this method is the need for parallelism of the layers of the dielectric object, and if it consists of a monolayer, then parallelism of its faces is necessary. In this regard, the method can be implemented in relation to specially manufactured objects. In addition, to implement the method, it is necessary to comply with certain angles of incidence and reflection of microwave radiation relative to a dielectric object.

The above does not allow the practical use of the method for determining the dielectric constant of a moving and hidden object with non-parallel layers or faces, in particular, for covertly determining the presence of dielectric explosives hidden on the human body. As you know, the dielectric constant of the vast majority of these substances is in the range of 2.9-3.1.

A known method for determining the dielectric constant of a dielectric object against the background of the reflector by irradiating the dielectric object with coherent microwave radiation at N frequencies, registering the signal reflected from the dielectric object and the reflector, carry out coherent processing of the registered signal to obtain a three-dimensional microwave image of the dielectric object and reflector, additionally receive video image of the area in which the dielectric object and the reflector are located using two or more cameras that are synchronized with the source of microwave radiation, the received video is converted to digital form and build a three-dimensional video image of said region, converted three-dimensional video image and microwave image in a common coordinate system, is determined by the microwave image in the global coordinate system Z ₁ the distance between the source of microwave radiation and the reflector portion of the microwave image, free of the dielectric object, and distance Z ₂ between the microwave source and the microwave portion of the image in the dielectric reflector zone one object, the video image determined in the overall system length Z ₃ coordinates between microwave radiation source and the moving image of the dielectric object, the determined dielectric constant ε of the dielectric object from the relationship:

(RU 2408005 C1, 12/27/2010).

The disadvantage of the prototype method is the low accuracy of determining the dielectric constant ε during the movement of the investigated dielectric object, which requires compensation for very accurate synchronization of a moving object and a reflector, as well as synchronization of the video camera and means for recording the reflected signal; such synchronization is difficult to achieve and in any case does not provide the required accuracy in determining ε. In addition, the prototype method requires lighting sufficient for the operation of cameras.

The objective of the present invention is to improve the accuracy of determining the dielectric constant of moving dielectric objects, as well as providing the possibility of implementing the method regardless of the illumination of the dielectric object.

According to the invention, in a method for remotely determining the dielectric constant of a dielectric object, including irradiating a dielectric object with coherent microwave radiation at N frequencies, registering a signal carrying dielectric permittivity information of a dielectric object using a recording channel containing recording means, and coherent processing of the registered signal, a signal is recorded passing through a dielectric object, then determine the dependence of the expression:

where N is the number of frequencies of microwave radiation,

k is the frequency number of microwave radiation from N frequencies,

f _k - k-th frequency of microwave radiation from N frequencies,

i is the imaginary unit

C is the speed of light in vacuum,

Aobject _k is the amplitude of the recorded signal at the kth radiation frequency in the presence of an object in a controlled region of space,

Fobject _k is the phase of the recorded signal at the kth radiation frequency in the presence of an object in a controlled region of space, expressed in radians,

Acn _k is the amplitude of the recorded signal at the k-th radiation frequency in the absence of an object in a controlled region of space,

Фcn _k - phase of the recorded signal at the k-th frequency of radiation in the absence of an object in a controlled region of space,

from x - coordinates along the X axis connecting the recording means and the microwave radiation source, determine the value of x _max at which F has a maximum value, and the dielectric constant is determined by the formula:

where L is the physical size of the dielectric object along the X axis.

The applicant has not identified any technical solutions identical to the claimed one, which allows us to conclude that the invention meets the condition of patentability “Novelty”.

The implementation of the features of the claimed method leads to the achievement of a technical result, which consists in increasing the accuracy of determining the dielectric constant of a moving object, since it eliminates the need to synchronize this object with any means used in the implementation of the method; in addition, the method can be implemented in any lighting, since it does not contain operations related to the receipt and processing of video images.

The applicant has not identified sources of information that would contain information about the influence of the distinguishing features of the invention on the achieved technical result.

These new properties of the object determine, according to the applicant, the compliance of the invention with the condition of patentability "Inventive step".

The implementation of the method is illustrated by a specific example. To implement the method, a dielectric object was taken - beeswax. The test sample was irradiated with coherent microwave radiation sequentially at 16 fixed frequencies within the range of 8-18 GHz. Irradiation was carried out using an emitter, which in a specific example is a switched antenna array consisting of 256 elementary spatially separated transmitting antennas. The signal that passed through the dielectric under study in the form of two quadrature components is recorded in this example using a Vivaldi broadband antenna connected to a 12-bit analog-to-digital converter. From the ADC output through the switching circuit, the data corresponding to the electric component of the registered electromagnetic field that passed through the dielectric object entered the computer, where after coherent processing an array of values (256 values) of the optical signal elongation from each transmitting element of the antenna array to the recorder was formed, in which F for each pair of transceiver elements takes a maximum value.

where N is the number of frequencies of microwave radiation,

k is the frequency number of microwave radiation from N frequencies,

f _k - k-th frequency of microwave radiation from N frequencies,

i is the imaginary unit

C is the speed of light in vacuum,

Aobject _k is the amplitude of the recorded signal at the kth radiation frequency in the presence of an object in a controlled region of space,

Fobject _k is the phase of the recorded signal at the kth radiation frequency in the presence of an object in a controlled region of space, expressed in radians,

Acn _k is the amplitude of the recorded signal at the k-th radiation frequency in the absence of an object in a controlled region of space,

Фcn _k is the phase of the recorded signal at the kth radiation frequency in the absence of an object in a controlled region of space.

For each direction connecting the emitter of the antenna array and the registrar, the physical size L of the investigated dielectric object was determined by direct measurement. In this case, the dielectric constant of the dielectric object was determined for each elementary transmitting antenna with one recording means from the relation:

256 dielectric constant values are formed for various spatially separated directions, which allows one to construct the spatial distribution of the dielectric constant of a dielectric object. The determination of the average value of the dielectric constant of an object is achieved by averaging the values of the array of dielectric permittivities of each of the directions.

In a specific example of a dielectric object - beeswax at L = 10 cm x _max was 6.12 cm and the dielectric constant ε was 2.6.

The claimed method provides an increase in the accuracy of determining the dielectric constant of a moving object in comparison with the prototype by 25-40% at a speed of 0.5-1.5 m / s.

Taking into account a significant increase in the accuracy of determining the ε value of a moving object under study, it is possible to significantly reduce the number of errors in identifying an object as an explosive, such as TNT, nitroglycerin, hexagen, and other dielectric objects.

The claimed method can also be used to determine ε dielectrics used in industry.

To implement the method, well-known equipment and tools are used, which allows us to conclude that this invention meets the patentability condition "Industrial Applicability".

Claims (1)

A method for remotely determining the dielectric constant of a dielectric object, including irradiating the dielectric object with coherent microwave radiation at N frequencies, registering a signal carrying information about the dielectric constant of the dielectric object using a recording channel containing recording means, and coherent processing of the registered signal, characterized in that the signal passing through the dielectric object, then determine the dependence of the expression:

where N is the number of frequencies of microwave radiation,
k is the frequency number of microwave radiation from N frequencies,
f _k - k-th frequency of microwave radiation from N frequencies,
i is the imaginary unit
C is the speed of light in vacuum,
Aobject _k is the amplitude of the recorded signal at the kth radiation frequency in the presence of an object in a controlled region of space,
Fobject _k is the phase of the recorded signal at the kth radiation frequency in the presence of an object in a controlled region of space, expressed in radians,
Acn _k is the amplitude of the recorded signal at the k-th radiation frequency in the absence of an object in a controlled region of space,
Фcn _k - phase of the recorded signal at the k-th frequency of radiation in the absence of an object in a controlled region of space,
from x - coordinates along the X axis connecting the recording means and the microwave radiation source, determine the value of x _max at which F has a maximum value, and the dielectric constant is determined by the formula:

where L is the physical size of the dielectric object along the X axis.