CN112595898A - Method and device for measuring complex dielectric constant of liquid based on Wi-Fi signal - Google Patents

Method and device for measuring complex dielectric constant of liquid based on Wi-Fi signal Download PDF

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CN112595898A
CN112595898A CN202011421303.2A CN202011421303A CN112595898A CN 112595898 A CN112595898 A CN 112595898A CN 202011421303 A CN202011421303 A CN 202011421303A CN 112595898 A CN112595898 A CN 112595898A
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李超
李凡
方滨兴
殷丽华
孙哲
罗熙
李丹
王星
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Guangzhou University
Peng Cheng Laboratory
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Abstract

The invention discloses a method for measuring complex dielectric constant of liquid based on Wi-Fi signals, which comprises the following steps: acquiring a Wi-Fi signal transmitted by a Wi-Fi signal transmitter, and preprocessing the Wi-Fi signal to obtain channel state information of the Wi-Fi signal; the Wi-Fi signals comprise Wi-Fi signals passing through the liquid to be detected and Wi-Fi signals not passing through the liquid to be detected; carrying out noise reduction processing on the channel state information to obtain at least one group of stable amplitude ratio and phase difference values; and (3) passing the amplitude ratio and the phase difference value through a preset data processing module, and judging the processed result through a machine learning algorithm to obtain the complex dielectric constant of the liquid to be detected. By the method, the complex dielectric constant of the liquid can be obtained, and the complex dielectric constant can be further used for detecting the type and the content of the liquid, so that the liquid detection is met, and the cost of liquid identification is reduced.

Description

Method and device for measuring complex dielectric constant of liquid based on Wi-Fi signal
Technical Field
The invention relates to the technical field of intelligent equipment liquid identification, in particular to a method and a device for measuring a complex dielectric constant of liquid based on Wi-Fi signals.
Background
Currently, the existing liquid identification methods can be classified into the following two types:
the first is a method relying on expensive liquid identification equipment such as spectroscopic analysis, electrical analysis, and high-frequency electromagnetic wave (e.g., terahertz) measurement. Some of these methods can meet the above-mentioned requirements, allow identification of unknown liquids, and some can also measure the concentration of a component in a liquid. The method is the most common liquid identification method in a chemical laboratory, can detect trace substances, has high detection precision and mature technical development, and is mainly used for scientific research in the chemical laboratory at present; the electroanalysis method is characterized in that a special electrode is inserted into liquid, or liquid to be detected is dripped on the electrode, the conductivity and dielectric constant of the liquid or voltage or current change caused by response of certain special chemical sites on the electrode are detected, the liquid is identified, the detection precision can reach a trace level, and the electroanalysis method is currently applied to the fields of heavy metal ion detection, household blood glucose and blood lipid detection and the like; the high-frequency electromagnetic wave measurement method is a method for detecting by using a high-frequency electromagnetic wave transmitting antenna, a high-frequency electromagnetic wave receiving antenna and a signal processing circuit, performs liquid identification by detecting changes of electromagnetic wave signals, and is widely applied to the field of dangerous liquid detection at present.
The second is a method that relies on inexpensive existing equipment, such as optical recognition methods based on smart phones, RFID-based methods, etc. Most of the methods are based on constructing a liquid identification database to identify the liquid, and the essence of the methods is to compare known liquid with existing data information. The optical identification method based on the smart phone uses an optical depth camera of the smart phone and an optical sensor inside the smart phone to acquire data and calculate absorbance values of liquid in different directions so as to achieve the aim of identifying the liquid; the RFID-based method is characterized in that the type of liquid is identified after characteristics are extracted by detecting CSI information of a radio frequency signal emitted by an RFID chip attached to the liquid to be detected.
However, the prior art has the following defects:
the method relying on expensive liquid identification equipment is firstly limited by the price of the equipment and is difficult to popularize and use on a large scale. At the same time, these methods have their own disadvantages. The spectrum analysis method relies on expensive detection equipment, such as an infrared spectrometer, an ultraviolet-visible spectrophotometer and the like, and often needs to carry out detection in multiple ways to determine the type of liquid, the pretreatment process carried out before detection is very complex, the detection time is long, the detection cost is high, the equipment volume is large, and part of the detection equipment, such as a nuclear magnetic resonance spectrometer, even has certain damage to the bodies of detection personnel; the electroanalytical method depends on equipment such as an electrochemical workstation or a blood glucose detector, one special electrode only corresponds to a few ions or molecules to be detected, the detection range is very limited, many electrodes are disposable electrodes and cannot be reused, and in addition, the electrode is required to be contacted with liquid in the measurement process, the operation is complex, and the liquid to be detected can be polluted; the high-frequency electromagnetic wave measuring method relies on special equipment consisting of a high-frequency electromagnetic wave transmitting and receiving device and a signal processing circuit, such as a hazardous liquid detector and the like, is expensive, has single functions and low detection precision, can only carry out simple threshold value judgment, can distinguish aqueous solution and organic solution (hazardous liquid), preliminarily judges whether the liquid is flammable and explosive, but cannot identify the type of the liquid.
The method relying on the cheap existing equipment has low price, is easier to popularize compared with the prior method, but has some problems. The detection mode of the optical identification method based on the smart phone is complex, the identification can be completed only by collecting liquid information from multiple angles, and only transparent liquid in a transparent container can be detected, so that the optical identification method has certain requirements on the ambient light intensity, cannot detect liquid or colored liquid in an opaque container, and cannot be used under the condition of no light; some low-frequency electromagnetic wave detection methods represented by RFID tags have poor detection effect and very low precision, can only clearly distinguish whether liquid is flammable or explosive, can only distinguish a plurality of specific liquids, and have a plurality of misdetection phenomena on the liquid outside the range. Meanwhile, the methods can only identify the known liquid with collected data, are comparison type identification methods, have poor identification effect on the unknown liquid with data which is not collected, and even if the content of a certain component is changed, the unknown liquid is difficult to identify and cannot be identified. In addition, the methods almost all perform liquid identification based on the construction of a liquid identification database, only the existing liquid in the liquid identification database has identification capability, and the construction of the liquid identification database requires huge workload. At the same time, these methods are difficult to detect the content of a certain component in a liquid.
Disclosure of Invention
The purpose of the invention is: the method and the device for measuring the complex dielectric constant of the liquid based on the Wi-Fi signals can obtain the complex dielectric constant of the liquid, further can use the complex dielectric constant for detecting the type and the content of the liquid, and reduce the cost of liquid identification while meeting the requirement of liquid detection.
In order to achieve the above object, the present invention provides a method for measuring a complex permittivity of a liquid based on Wi-Fi signals, comprising:
acquiring a Wi-Fi signal transmitted by a Wi-Fi signal transmitter, and preprocessing the Wi-Fi signal to obtain channel state information of the Wi-Fi signal; the Wi-Fi signals comprise Wi-Fi signals passing through the liquid to be detected and Wi-Fi signals not passing through the liquid to be detected;
carrying out noise reduction processing on the channel state information to obtain at least one group of stable amplitude ratio and phase difference values; the amplitude ratio and the phase difference value are the amplitude ratio and the phase difference value of Wi-Fi signal data passing through the liquid to be detected and Wi-Fi signal data not passing through the liquid to be detected;
the amplitude ratio and the phase difference value pass through a preset data processing module, and the complex dielectric constant of the liquid to be measured is judged according to the processing result by a machine learning algorithm; wherein the machine learning algorithm comprises: linear regression algorithms, KNN algorithms, and RNN algorithms.
Further, the preset data processing module is specifically constructed by adopting the following formula:
the complex dielectric constant ∈ is expressed in the following form:
∈＝∈′+i∈″ (1)
the amplitude ratio and the phase difference satisfy the following relationship:
γ＝α+iβ (2)
Figure BDA0002821559980000041
Figure BDA0002821559980000042
Figure BDA0002821559980000043
Figure BDA0002821559980000044
the transmitting antenna is electrified with sine alternating current IT＝I0eiωtThen, the induced electromotive force generated by the electromagnetic wave at the receiving antenna is:
Figure BDA0002821559980000045
wherein:
Figure BDA0002821559980000046
S0＝πa2
wherein mu is dielectric permeability, I and omega are respectively the transmitting current and angular frequency of the transmitting coil, and NTAnd NRThe number of turns of the transmitting coil and the number of turns of the receiving coil are respectively, and a is the radius of the coil;
(3) the formula can be deformed into:
Figure BDA0002821559980000051
for the complex domain, any x satisfies the following equation:
xex＝z
then there are:
x＝W(z)
lnW+W＝lnz
where W (z) is referred to as a Lambert W function, then the propagation constant is:
Figure BDA0002821559980000052
recording:
Figure BDA0002821559980000053
then:
Figure BDA0002821559980000054
Figure BDA0002821559980000055
at this time, gamma2，L2It is known that W can be obtained from the formula (6)2
Figure BDA0002821559980000056
Therefore, the method comprises the following steps:
Figure BDA0002821559980000061
and (3) can be further described as:
Figure BDA0002821559980000062
the two are compared and taken from the natural logarithm to obtain:
Figure BDA0002821559980000063
wherein A is the amplitude ratio,
Figure BDA0002821559980000064
is the phase difference. At this time obtain
Figure BDA0002821559980000065
W is to be2And
Figure BDA0002821559980000066
substitution into formula (7) to obtain W1；
Gamma is obtained from the formula (5)1；
Let Q be gamma2And then:
Figure BDA0002821559980000067
in addition, the method comprises the following steps:
γ2＝ω2με-iωμσ
can obtain the product
Figure BDA0002821559980000068
Figure BDA0002821559980000069
Where ε is the dielectric constant and σ is the conductivity.
Further, the Wi-Fi signals transmitted by the Wi-Fi signal transmitter are obtained, and the Wi-Fi signals are preprocessed to obtain channel state information of the Wi-Fi signals; the Wi-Fi signals comprise Wi-Fi signals passing through the liquid to be detected and Wi-Fi signals not passing through the liquid to be detected; the method specifically comprises the following steps:
firstly, a Wi-Fi signal transmitter controls a transmitting terminal antenna group to transmit Wi-Fi signals according to a control instruction, secondly, a Wi-Fi signal receiver receives the Wi-Fi signals from the Wi-Fi signal transmitter and transmits the Wi-Fi signals to a signal processing unit, and the signal processing unit converts the Wi-Fi signals into channel state information of the Wi-Fi signals.
Further, the noise reduction processing method includes: gaussian filtering method, kalman filtering method, and wavelet denoising method.
The embodiment of the invention also provides a device for measuring the complex dielectric constant of liquid based on Wi-Fi signals, which comprises: the device comprises an acquisition module, a data processing module and a judgment module; wherein the content of the first and second substances,
the acquisition module is used for acquiring a Wi-Fi signal transmitted by a Wi-Fi signal transmitter and carrying out preprocessing operation on the Wi-Fi signal to obtain channel state information of the Wi-Fi signal; the Wi-Fi signals comprise Wi-Fi signals passing through the liquid to be detected and Wi-Fi signals not passing through the liquid to be detected;
the data processing module is used for carrying out noise reduction processing on the channel state information to obtain at least one group of stable amplitude ratio and phase difference value; the amplitude ratio and the phase difference value are the amplitude ratio and the phase difference value of Wi-Fi signal data passing through the liquid to be detected and Wi-Fi signal data not passing through the liquid to be detected;
the judging module is used for judging the complex dielectric constant of the liquid to be detected by passing the amplitude ratio and the phase difference value through a preset data processing module and passing the processed result through a machine learning model; wherein the machine learning algorithm comprises: linear regression algorithms, KNN algorithms, and RNN algorithms.
Further, the preset data processing module is specifically constructed by adopting the following formula:
the complex dielectric constant ∈ is expressed in the following form:
∈＝∈′+i∈″ (1)
the amplitude ratio and the phase difference satisfy the following relationship:
γ＝α+iβ (2)
Figure BDA0002821559980000081
Figure BDA0002821559980000082
Figure BDA0002821559980000083
Figure BDA0002821559980000084
the transmitting antenna is electrified with sine alternating current IT＝I0eiωtThen, the induced electromotive force generated by the electromagnetic wave at the receiving antenna is:
Figure BDA0002821559980000085
wherein:
Figure BDA0002821559980000086
S0＝πa2
wherein mu is dielectric permeability, I and omega are respectively the transmitting current and angular frequency of the transmitting coil, and NTAnd NRThe number of turns of the transmitting coil and the number of turns of the receiving coil are respectively, and a is the radius of the coil;
(3) the formula can be deformed into:
Figure BDA0002821559980000091
for the complex domain, any x satisfies the following equation:
xex＝z
then there are:
x＝W(z)
lnW+W＝lnz
where W (z) is referred to as a Lambert W function, then the propagation constant is:
Figure BDA0002821559980000092
recording:
Figure BDA0002821559980000093
then:
Figure BDA0002821559980000094
Figure BDA0002821559980000095
at this time, gamma2，L2It is known that W can be obtained from the formula (6)2
Figure BDA0002821559980000096
Therefore, the method comprises the following steps:
Figure BDA0002821559980000101
and (3) can be further described as:
Figure BDA0002821559980000102
the two are compared and taken from the natural logarithm to obtain:
Figure BDA0002821559980000103
wherein A is the amplitude ratio,
Figure BDA0002821559980000104
is the phase difference. At this time obtain
Figure BDA0002821559980000105
W is to be2And
Figure BDA0002821559980000106
substitution into formula (7) to obtain W1；
Gamma is obtained from the formula (5)1；
Let Q be gamma2And then:
Figure BDA0002821559980000107
in addition, the method comprises the following steps:
γ2＝ω2με-iωμσ
can obtain the product
Figure BDA0002821559980000108
Figure BDA0002821559980000109
Where ε is the dielectric constant and σ is the conductivity.
Further, the Wi-Fi signals transmitted by the Wi-Fi signal transmitter are obtained, and the Wi-Fi signals are preprocessed to obtain channel state information of the Wi-Fi signals; the Wi-Fi signals comprise Wi-Fi signals passing through the liquid to be detected and Wi-Fi signals not passing through the liquid to be detected; the method specifically comprises the following steps:
firstly, a Wi-Fi signal transmitter controls a transmitting terminal antenna group to transmit Wi-Fi signals according to a control instruction, secondly, a Wi-Fi signal receiver receives the Wi-Fi signals from the Wi-Fi signal transmitter and transmits the Wi-Fi signals to a signal processing unit, and the signal processing unit converts the Wi-Fi signals into channel state information of the Wi-Fi signals.
Further, the noise reduction processing method includes: gaussian filtering method, kalman filtering method, and wavelet denoising method.
An embodiment of the present invention further provides a computer terminal device, which is characterized by including:
one or more processors;
a memory coupled to the processor for storing one or more programs;
when executed by the one or more processors, cause the one or more processors to implement a method for measuring complex permittivity of a liquid based on Wi-Fi signals as in any one of the above.
An embodiment of the present invention further provides a computer-readable storage medium, on which a computer program is stored, where the computer program is executed by a processor to implement any one of the methods for measuring complex permittivity of a liquid based on Wi-Fi signals described above.
Compared with the prior art, the method and the device for measuring the complex dielectric constant of the liquid based on the Wi-Fi signal have the advantages that:
1. the liquid identification technology cost is reduced: by the invention, a user can realize unknown liquid identification and identification of certain component content in the liquid in a Wi-Fi environment without spending thousands of elements or even tens of thousands of elements in a liquid identification technology. The invention has low requirements on the performance and the computing power of the antenna and strong portability, and can be transplanted to any equipment with enough computing power and electromagnetic wave transceiving function;
2. the liquid identification library does not need to be established: at present, the liquid identification method relying on cheap equipment needs to spend huge time and energy to establish a liquid identification library. The method and the device enable various characteristic values without specific meanings in the past to correspond to the real physical quantity of the liquid by measuring the real complex dielectric constant of the liquid, so that a liquid identification library does not need to be established, and the identification of the type of unknown liquid and the identification of the content of a certain component in the liquid can be carried out only according to the existing real complex dielectric constant data of the liquid and a physical quantity-concentration curve fitted by a formula. .
Drawings
FIG. 1 is a schematic flow chart of a method for measuring complex dielectric constant of a liquid based on Wi-Fi signals according to a first embodiment of the present invention;
FIG. 2 is a schematic diagram illustrating an overall structure of a method for measuring complex dielectric constant of a liquid based on Wi-Fi signals according to a first embodiment of the present invention;
FIG. 3 is a schematic diagram illustrating a method for measuring complex dielectric constant of a liquid based on Wi-Fi signals according to a first embodiment of the present invention;
FIG. 4 is a schematic deployment diagram of a Wi-Fi signal transmitting and receiving device based on a method for measuring a complex dielectric constant of a liquid according to an embodiment of the present invention;
fig. 5 is a schematic overall deployment diagram of a measurement apparatus for measuring a complex dielectric constant of a liquid based on a Wi-Fi signal according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of a device for measuring a complex dielectric constant of a liquid based on Wi-Fi signals according to a second embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be understood that the step numbers used herein are for convenience of description only and are not intended as limitations on the order in which the steps are performed.
It is to be understood that the terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
The terms "comprises" and "comprising" indicate the presence of the described features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
The term "and/or" refers to and includes any and all possible combinations of one or more of the associated listed items.
The first embodiment of the present invention:
referring to fig. 1-5, a method for measuring complex dielectric constant of a liquid based on Wi-Fi signals according to an embodiment of the present invention at least includes the following steps:
s101, acquiring a Wi-Fi signal transmitted by a Wi-Fi signal transmitter, and preprocessing the Wi-Fi signal to obtain channel state information of the Wi-Fi signal; the Wi-Fi signals comprise Wi-Fi signals passing through the liquid to be detected and Wi-Fi signals not passing through the liquid to be detected;
it should be noted that, for step S101, the Wi-Fi signal transmitter and receiver structure and function are as follows:
1.1) transmitting end antenna group: is responsible for the emission of Wi-Fi signals. The antenna group at the transmitting end needs at least two antennas, the more the number of the antennas used in the antenna group is, the better the identification effect is, and each time one antenna is added or reduced, or other antennas at different positions are used, the new antenna array is adopted;
1.2) a signal transmitting module: and the system is responsible for receiving the instruction of the user terminal and generating a specified format of directional data packet to be transmitted. This module is completed by an on-chip Wi-Fi signal transmitter, which is a device that transmits Wi-Fi signals, including but not limited to Wi-Fi routers;
1.3) receiving end antenna group: is responsible for the reception of Wi-Fi signals. The receiving end antenna group needs at least one antenna, the more the number of the antennas used in the antenna group is, the better the identification effect is, and each time one antenna is increased or decreased, or other antennas in different positions are used, the new antenna array is adopted;
1.4) a signal receiving module: and the device is responsible for receiving the directional data packet with the specified format sent by the Wi-Fi signal transmitter. This module is completed by a chip in the Wi-Fi signal receiver, which is a device that receives Wi-Fi signals, including but not limited to a Wi-Fi router.
It should be noted that, for the liquid to be measured, the following conditions need to be satisfied:
2.1) position of liquid to be detected: the position of the liquid to be measured needs to be fixed, as shown in fig. 4, in this example, the position of the liquid to be measured should be as close to the receiving antenna 1 in the receiving end antenna group as possible, be away from the receiving antenna 2, and be located on the straight line connecting the receiving antenna 1 and the transmitting antenna, so as to ensure that the path from the receiving antenna 1 to the transmitting antenna passes through the liquid to be measured, and the path from the receiving antenna 2 to the transmitting antenna only passes through the air;
2.2) a liquid container to be tested: the liquid container to be detected is required to be a non-metal container, whether the liquid container is transparent or not can be determined, and the diameter of the liquid container is required to be determined;
2.3) liquid level to be detected: the liquid level cannot be too low and needs to exceed a specified liquid level according to different used equipment.
It should be noted that, for the preprocessing operation, the method includes:
3.1) data packet analysis: the data packet with the specified format obtained by the signal receiving module is analyzed into a channel state information packet;
3.2) extracting amplitude and phase: and processing the channel state information matrix in the channel state information packet into amplitude and phase information of electromagnetic waves, and sending the amplitude and phase information to the noise reduction module.
S102, carrying out noise reduction processing on the channel state information to obtain at least one group of stable amplitude ratio and phase difference values; the amplitude ratio and the phase difference value are the amplitude ratio and the phase difference value of Wi-Fi signal data passing through the liquid to be detected and Wi-Fi signal data not passing through the liquid to be detected;
it should be noted that, for the denoising process, methods such as gaussian filtering, kalman filtering, wavelet denoising, and the like are used to remove noise contained in the amplitude ratio and the phase difference, so as to obtain a stable amplitude ratio and a stable phase difference value, and send the values to the data processing module. The amplitude ratio and the phase difference are the amplitude ratio and the phase difference between electromagnetic wave signals passing through two paths of the transmitting antenna to the receiving antenna 1 and the receiving antenna 2, and because one path passes through the liquid to be detected and the other path only passes through the air between the two paths, the purpose of liquid identification is achieved by measuring the difference. In a similar way, by increasing the number of transmitting antennas and the number of receiving antennas, more sets of amplitude ratios and phase differences can be obtained, more sets of data for liquid identification can be obtained, and the identification accuracy can be improved.
S103, the amplitude ratio and the phase difference value pass through a preset data processing module, and the complex dielectric constant of the liquid to be detected is judged according to the processing result through a machine learning algorithm; wherein the machine learning algorithm comprises: linear regression algorithms, KNN algorithms, and RNN algorithms.
It should be noted that, in step S103, the data processing module calculates according to a formula, calculates a plurality of groups of α + i β, and integrates information required for identification, such as the device model, the router channel used, the pseudo permittivity value and the pseudo conductivity value corresponding to the antenna array, and the like, and information input by the user, such as the measurement requirement, the type of the selected antenna array, the diameter of the cylindrical non-metallic container, the inter-device distance, and the like, into an identification data packet, and sends the identification data packet to the complex permittivity prediction module;
the complex dielectric constant prediction module predicts real parameter values according to alpha + i beta to obtain predicted epsilon '+ i epsilon' for identification, replaces alpha + i beta in an identification data packet and sends the identification data packet to the physical quantity comparison module;
the physical quantity comparison module receives the type of the liquid to be detected sent by the user terminal and identifies all information in the data packet, calls out a corresponding liquid physical quantity curve, compares the curve with epsilon '+ i epsilon' obtained by the complex dielectric constant prediction module to obtain the type or the content of a certain component of the liquid to be detected, and sends the detection result to the user terminal; and the user terminal receives the final identification result sent by the physical quantity comparison module and displays the final identification result to the user.
In an embodiment of the present invention, the preset data processing module is specifically constructed by using the following formula:
the complex dielectric constant ∈ is expressed in the following form:
∈＝∈′+i∈″ (1)
the amplitude ratio and the phase difference satisfy the following relationship:
γ＝α+iβ (2)
Figure BDA0002821559980000161
Figure BDA0002821559980000162
Figure BDA0002821559980000163
Figure BDA0002821559980000164
the transmitting antenna is electrified with sine alternating current IT＝I0eiωtThen, the induced electromotive force generated by the electromagnetic wave at the receiving antenna is:
Figure BDA0002821559980000165
wherein:
Figure BDA0002821559980000166
S0＝πa2
wherein mu is dielectric permeability, I and omega are respectively the transmitting current and angular frequency of the transmitting coil, and NTAnd NRThe number of turns of the transmitting coil and the number of turns of the receiving coil are respectively, and a is the radius of the coil;
(3) the formula can be deformed into:
Figure BDA0002821559980000167
for the complex domain, any x satisfies the following equation:
xex＝z
then there are:
x＝W(z)
lnW+W＝lnz
where W (z) is referred to as a Lambert W function, then the propagation constant is:
Figure BDA0002821559980000171
recording:
Figure BDA0002821559980000172
then:
Figure BDA0002821559980000173
Figure BDA0002821559980000174
at this time, gamma2，L2It is known that W can be obtained from the formula (6)2
Figure BDA0002821559980000175
Therefore, the method comprises the following steps:
Figure BDA0002821559980000181
and (3) can be further described as:
Figure BDA0002821559980000182
the two are compared and taken from the natural logarithm to obtain:
Figure BDA0002821559980000183
wherein A is the amplitude ratio,
Figure BDA0002821559980000184
is the phase difference. At this time obtain
Figure BDA0002821559980000185
W is to be2And
Figure BDA0002821559980000186
substitution into formula (7) to obtain W1；
Gamma is obtained from the formula (5)1；
Let Q be gamma2And then:
Figure BDA0002821559980000187
in addition, the method comprises the following steps:
γ2＝ω2με-iωμσ
can obtain the product
Figure BDA0002821559980000188
Figure BDA0002821559980000189
Where ε is the dielectric constant and σ is the conductivity.
In one implementation of the present invention, the obtaining unit obtains a Wi-Fi signal transmitted by a Wi-Fi signal transmitter, and pre-processes the Wi-Fi signal to obtain channel state information of the Wi-Fi signal; the Wi-Fi signals comprise Wi-Fi signals passing through the liquid to be detected and Wi-Fi signals not passing through the liquid to be detected; the method specifically comprises the following steps:
firstly, a Wi-Fi signal transmitter controls a transmitting terminal antenna group to transmit Wi-Fi signals according to a control instruction, secondly, a Wi-Fi signal receiver receives the Wi-Fi signals from the Wi-Fi signal transmitter and transmits the Wi-Fi signals to a signal processing unit, and the signal processing unit converts the Wi-Fi signals into channel state information of the Wi-Fi signals.
In an embodiment of the present invention, the noise reduction processing method includes: gaussian filtering method, kalman filtering method, and wavelet denoising method.
For the present embodiment, it can be specifically understood by the following examples:
as shown in fig. 5, the specific implementation example of the complex dielectric constant measuring method based on Wi-Fi signals and applicable to liquid identification is shown, a Wi-Fi signal transmitter and a Wi-Fi signal receiver are two Wi-Fi routers, signal processing, noise reduction, data processing, complex dielectric constant prediction and physical quantity comparison are completed by one computer, a user controls a smartphone terminal to start identifying liquid after putting the liquid to be detected as required through operation prompt of the smartphone, and finally obtains an identification result on a smartphone screen. At this point the user wants to identify the type of unknown liquid in a bottle. The specific process of application is as follows:
1. a user accesses the system by using the smart phone and places the container filled with the liquid to be detected at a designated position according to requirements;
2. the user inputs information such as the selected antenna array type of type three, the container diameter of 10cm, the router spacing of 1m and the like in the smart phone, the information is sent to the data processing module for next processing, the user inputs a measurement requirement of testing unknown liquid type, the information is sent to the physical quantity comparison module, and the user sends a testing starting instruction to the router at the sending end;
3. the receiving end router receives a data packet containing information and sends the data packet to a signal processing module on a computer;
4. after receiving the data packet, the computer converts the data packet into channel state information of an electromagnetic wave signal, performs noise reduction processing on the channel state information to obtain a stable amplitude ratio and a stable phase difference, inputs the channel state information into a data processing module of the computer, calculates a required pseudo-dielectric constant value and a pseudo-conductivity value, integrates a router model number TP-LINK WDR4900, a used router channel 36, alpha + i beta 10+0.5i corresponding to an antenna array and the like into an identification data packet, and sends the identification data packet to a complex dielectric constant prediction module;
5. after receiving the identification data packet, the complex dielectric constant prediction module predicts the real parameter value according to alpha + i beta to obtain the predicted epsilon '+ i epsilon' for identification, which is 2+6i, replaces the alpha + i beta in the identification data packet, and sends the identification data packet to the physical quantity comparison module;
6. the physical quantity comparison module receives a final identification data packet and a requirement for identifying a bottle of unknown liquid sent by a user terminal, extracts a real complex dielectric constant of the liquid, namely 2+6i, searches a liquid physical parameter table, finds that the real complex dielectric constant of the ice black tea is 1.99+5.9i, the predicted complex dielectric constant of the liquid is closest to the complex dielectric constant of the ice black tea, generates an identification result that the liquid is the ice black tea, and sends the identification result to a smart phone of a user;
7. and the smart phone of the user receives the identification result finally fed back by the physical quantity comparison module, and displays the result to the user on a smart phone screen to inform the user that the unknown liquid is the ice black tea.
Compared with the prior art, the method for measuring the complex dielectric constant of the liquid based on the Wi-Fi signal has the following beneficial effects:
1. the liquid identification technology cost is reduced: by the invention, a user can realize unknown liquid identification and identification of certain component content in the liquid in a Wi-Fi environment without spending thousands of elements or even tens of thousands of elements in a liquid identification technology. The invention has low requirements on the performance and the computing power of the antenna and strong portability, and can be transplanted to any equipment with enough computing power and electromagnetic wave transceiving function;
2. the liquid identification library does not need to be established: at present, the liquid identification method relying on cheap equipment needs to spend huge time and energy to establish a liquid identification library. The method and the device enable various characteristic values without specific meanings in the past to correspond to the real physical quantity of the liquid by measuring the real complex dielectric constant of the liquid, so that a liquid identification library does not need to be established, and the identification of the type of unknown liquid and the identification of the content of a certain component in the liquid can be carried out only according to the existing real complex dielectric constant data of the liquid and a physical quantity-concentration curve fitted by a formula.
Second embodiment of the invention:
referring to fig. 6, an apparatus 200 for measuring complex dielectric constant of a liquid based on Wi-Fi signals according to an embodiment of the present invention includes: an acquisition module 201, a data processing module 202 and a judgment module 203; wherein the content of the first and second substances,
the acquisition module 201 is configured to acquire a Wi-Fi signal transmitted by a Wi-Fi signal transmitter, and perform a preprocessing operation on the Wi-Fi signal to obtain channel state information of the Wi-Fi signal; the Wi-Fi signals comprise Wi-Fi signals passing through the liquid to be detected and Wi-Fi signals not passing through the liquid to be detected;
the data processing module 202 is configured to perform noise reduction processing on the channel state information to obtain at least one group of stable amplitude ratio and phase difference; the amplitude ratio and the phase difference value are the amplitude ratio and the phase difference value of Wi-Fi signal data passing through the liquid to be detected and Wi-Fi signal data not passing through the liquid to be detected;
the judging module 203 is configured to pass the amplitude ratio and the phase difference value through a preset data processing module, and pass the processed result through a machine learning model to judge a complex dielectric constant of the liquid to be measured; wherein the machine learning algorithm comprises: linear regression algorithms, KNN algorithms, and RNN algorithms.
In an embodiment of the present invention, the preset data processing module is specifically constructed by using the following formula:
the complex dielectric constant ∈ is expressed in the following form:
∈＝∈′+i∈″ (1)
the amplitude ratio and the phase difference satisfy the following relationship:
γ＝α+iβ (2)
Figure BDA0002821559980000221
Figure BDA0002821559980000222
Figure BDA0002821559980000223
Figure BDA0002821559980000224
the transmitting antenna is electrified with sine alternating current IT＝I0eiωtThen, the induced electromotive force generated by the electromagnetic wave at the receiving antenna is:
Figure BDA0002821559980000225
wherein:
Figure BDA0002821559980000226
S0＝πa2
wherein mu is dielectric permeability, I and omega are respectively the transmitting current and angular frequency of the transmitting coil, and NTAnd NRThe number of turns of the transmitting coil and the number of turns of the receiving coil are respectively, and a is the radius of the coil;
(3) the formula can be deformed into:
Figure BDA0002821559980000231
for the complex domain, any x satisfies the following equation:
xex＝z
then there are:
x＝W(z)
lnW+W＝lnz
where W (z) is referred to as a Lambert W function, then the propagation constant is:
Figure BDA0002821559980000232
recording:
Figure BDA0002821559980000233
then:
Figure BDA0002821559980000234
Figure BDA0002821559980000235
at this time, gamma2，L2It is known that W can be obtained from the formula (6)2
Figure BDA0002821559980000241
Therefore, the method comprises the following steps:
Figure BDA0002821559980000242
and (3) can be further described as:
Figure BDA0002821559980000243
the two are compared and taken from the natural logarithm to obtain:
Figure BDA0002821559980000244
wherein A is the amplitude ratio,
Figure BDA0002821559980000245
is the phase difference. At this time obtain
Figure BDA0002821559980000246
W is to be2And
Figure BDA0002821559980000247
substitution into formula (7) to obtain W1；
Gamma is obtained from the formula (5)1；
Let Q be gamma2And then:
Figure BDA0002821559980000248
in addition, the method comprises the following steps:
γ2＝ω2με-iωμσ
can obtain the product
Figure BDA0002821559980000249
Figure BDA0002821559980000251
Where ε is the dielectric constant and σ is the conductivity.
In one embodiment of the present invention, the obtaining unit obtains a Wi-Fi signal transmitted by a Wi-Fi signal transmitter, and preprocesses the Wi-Fi signal to obtain channel state information of the Wi-Fi signal; the Wi-Fi signals comprise Wi-Fi signals passing through the liquid to be detected and Wi-Fi signals not passing through the liquid to be detected; the method specifically comprises the following steps:
firstly, a Wi-Fi signal transmitter controls a transmitting terminal antenna group to transmit Wi-Fi signals according to a control instruction, secondly, a Wi-Fi signal receiver receives the Wi-Fi signals from the Wi-Fi signal transmitter and transmits the Wi-Fi signals to a signal processing unit, and the signal processing unit converts the Wi-Fi signals into channel state information of the Wi-Fi signals.
In an embodiment of the present invention, the noise reduction processing method includes: gaussian filtering method, kalman filtering method, and wavelet denoising method.
Third embodiment of the invention:
the embodiment of the invention provides computer terminal equipment, which comprises one or more processors; a memory coupled to the processor for storing one or more programs; when executed by the one or more processors, cause the one or more processors to implement a method for measuring complex permittivity of a liquid based on Wi-Fi signals as in any one of the above.
The fourth embodiment of the present invention:
an embodiment of the present invention provides a computer-readable storage medium, on which a computer program is stored, where the computer program, when executed by a processor, implements any one of the methods for measuring a complex permittivity of a liquid based on Wi-Fi signals as described above.
In conclusion, the complex dielectric constant of the liquid can be obtained through the method, and the complex dielectric constant can be further used for detecting the type and the content of the liquid, so that the liquid detection is met, and meanwhile, the liquid identification cost is reduced. The invention has low requirements on the performance and the computing power of the antenna and strong portability, and can be transplanted to any equipment with enough computing power and electromagnetic wave transceiving function.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and substitutions can be made without departing from the technical principle of the present invention, and these modifications and substitutions should also be regarded as the protection scope of the present invention.

Claims (10)

1. A method for measuring the complex dielectric constant of a liquid based on Wi-Fi signals is characterized by comprising the following steps:
acquiring a Wi-Fi signal transmitted by a Wi-Fi signal transmitter, and preprocessing the Wi-Fi signal to obtain channel state information of the Wi-Fi signal; the Wi-Fi signals comprise Wi-Fi signals passing through the liquid to be detected and Wi-Fi signals not passing through the liquid to be detected;
carrying out noise reduction processing on the channel state information to obtain at least one group of stable amplitude ratio and phase difference values; the amplitude ratio and the phase difference value are the amplitude ratio and the phase difference value of Wi-Fi signal data passing through the liquid to be detected and Wi-Fi signal data not passing through the liquid to be detected;
the amplitude ratio and the phase difference value pass through a preset data processing module, and the complex dielectric constant of the liquid to be measured is judged according to the processing result by a machine learning algorithm; wherein the machine learning algorithm comprises: linear regression algorithms, KNN algorithms, and RNN algorithms.
2. The method for measuring the complex dielectric constant of the liquid based on the Wi-Fi signal according to claim 1, wherein the preset data processing module is specifically constructed by using the following formula:
the complex dielectric constant ∈ is expressed in the following form:
∈＝∈′+i∈″ (1)
the amplitude ratio and the phase difference satisfy the following relationship:
γ＝α+iβ (2)
Figure FDA0002821559970000011
Figure FDA0002821559970000021
Figure FDA0002821559970000022
Figure FDA0002821559970000023
the transmitting antenna is electrified with sine alternating current IT＝I0eiωtThen, the induced electromotive force generated by the electromagnetic wave at the receiving antenna is:
Figure FDA0002821559970000024
wherein:
Figure FDA0002821559970000025
S0＝πa2
wherein mu is dielectric permeability, I and omega are respectively the transmitting current and angular frequency of the transmitting coil, and NTAnd NRThe number of turns of the transmitting coil and the number of turns of the receiving coil are respectively, and a is the radius of the coil;
(3) the formula can be deformed into:
Figure FDA0002821559970000026
for the complex domain, any x satisfies the following equation:
xex＝z
then there are:
x＝W(z)
lnW+W＝lnz
where W (z) is referred to as a Lambert W function, then the propagation constant is:
Figure FDA0002821559970000031
recording:
Figure FDA0002821559970000032
then:
Figure FDA0002821559970000033
Figure FDA0002821559970000034
at this time, gamma2，L2It is known that W can be obtained from the formula (6)2
Figure FDA0002821559970000035
Therefore, the method comprises the following steps:
Figure FDA0002821559970000036
and (3) can be further described as:
Figure FDA0002821559970000041
the two are compared and taken from the natural logarithm to obtain:
Figure FDA0002821559970000042
wherein A is the amplitude ratio,
Figure FDA0002821559970000048
is the phase difference. At this time obtain
Figure FDA0002821559970000043
W is to be2And
Figure FDA0002821559970000044
substitution into formula (7) to obtain W1；
Gamma is obtained from the formula (5)1；
Let Q be gamma2And then:
Figure FDA0002821559970000045
in addition, the method comprises the following steps:
γ2＝ω2με-iωμσ
can obtain the product
Figure FDA0002821559970000046
Figure FDA0002821559970000047
Where ε is the dielectric constant and σ is the conductivity.
3. The method for measuring the complex dielectric constant of the liquid based on the Wi-Fi signals as claimed in claim 1, wherein the Wi-Fi signals transmitted by the Wi-Fi signal transmitter are obtained and preprocessed to obtain the channel state information of the Wi-Fi signals; the Wi-Fi signals comprise Wi-Fi signals passing through the liquid to be detected and Wi-Fi signals not passing through the liquid to be detected; the method specifically comprises the following steps:
firstly, a Wi-Fi signal transmitter controls a transmitting terminal antenna group to transmit Wi-Fi signals according to a control instruction, secondly, a Wi-Fi signal receiver receives the Wi-Fi signals from the Wi-Fi signal transmitter and transmits the Wi-Fi signals to a signal processing unit, and the signal processing unit converts the Wi-Fi signals into channel state information of the Wi-Fi signals.
4. The method for measuring the complex dielectric constant of the liquid based on the Wi-Fi signal as claimed in claim 1, wherein the noise reduction processing method comprises: gaussian filtering method, kalman filtering method, and wavelet denoising method.
5. An apparatus for measuring complex dielectric constant of a liquid based on Wi-Fi signals, comprising: the device comprises an acquisition module, a data processing module and a judgment module; wherein the content of the first and second substances,
the acquisition module is used for acquiring a Wi-Fi signal transmitted by a Wi-Fi signal transmitter and carrying out preprocessing operation on the Wi-Fi signal to obtain channel state information of the Wi-Fi signal; the Wi-Fi signals comprise Wi-Fi signals passing through the liquid to be detected and Wi-Fi signals not passing through the liquid to be detected;
the data processing module is used for carrying out noise reduction processing on the channel state information to obtain at least one group of stable amplitude ratio and phase difference value; the amplitude ratio and the phase difference value are the amplitude ratio and the phase difference value of Wi-Fi signal data passing through the liquid to be detected and Wi-Fi signal data not passing through the liquid to be detected;
the judging module is used for judging the complex dielectric constant of the liquid to be detected by passing the amplitude ratio and the phase difference value through a preset data processing module and passing the processed result through a machine learning model; wherein the machine learning algorithm comprises: linear regression algorithms, KNN algorithms, and RNN algorithms.
6. The device for measuring the complex dielectric constant of the liquid based on the Wi-Fi signal according to claim 5, wherein the preset data processing module is specifically constructed by adopting the following formula:
the complex dielectric constant ∈ is expressed in the following form:
∈＝∈′+i∈″ (1)
the amplitude ratio and the phase difference satisfy the following relationship:
γ＝α+iβ (2)
Figure FDA0002821559970000061
Figure FDA0002821559970000062
Figure FDA0002821559970000063
Figure FDA0002821559970000064
the transmitting antenna is electrified with sine alternating current IT＝I0eiωtThen, the induced electromotive force generated by the electromagnetic wave at the receiving antenna is:
Figure FDA0002821559970000065
wherein:
Figure FDA0002821559970000066
S0＝πa2
wherein mu is dielectric permeability, I and omega are respectively the transmitting current and angular frequency of the transmitting coil, and NTAnd NRThe number of turns of the transmitting coil and the number of turns of the receiving coil are respectively, and a is the radius of the coil;
(3) the formula can be deformed into:
Figure FDA0002821559970000071
for the complex domain, any x satisfies the following equation:
xex＝z
then there are:
x＝W(z)
lnW+W＝lnz
where W (z) is referred to as a Lambert W function, then the propagation constant is:
Figure FDA0002821559970000072
recording:
Figure FDA0002821559970000073
then:
Figure FDA0002821559970000074
Figure FDA0002821559970000081
at this time, gamma2，L2It is known that W can be obtained from the formula (6)2
Figure FDA0002821559970000082
Therefore, the method comprises the following steps:
Figure FDA0002821559970000083
and (3) can be further described as:
Figure FDA0002821559970000084
the two are compared and taken from the natural logarithm to obtain:
Figure FDA0002821559970000085
wherein A is the amplitude ratio,
Figure FDA0002821559970000089
is the phase difference. At this time obtain
Figure FDA0002821559970000086
W is to be2And
Figure FDA0002821559970000087
substitution into formula (7) to obtain W1；
Gamma is obtained from the formula (5)1；
Let Q be gamma2And then:
Figure FDA0002821559970000088
in addition, the method comprises the following steps:
γ2＝ω2με-iωμσ
can obtain the product
Figure FDA0002821559970000091
Figure FDA0002821559970000092
Where ε is the dielectric constant and σ is the conductivity.
7. The device for measuring the complex dielectric constant of the liquid based on the Wi-Fi signal as claimed in claim 5, wherein the device is used for acquiring the Wi-Fi signal transmitted by the Wi-Fi signal transmitter and preprocessing the Wi-Fi signal to obtain the channel state information of the Wi-Fi signal; the Wi-Fi signals comprise Wi-Fi signals passing through the liquid to be detected and Wi-Fi signals not passing through the liquid to be detected; the method specifically comprises the following steps:
firstly, a Wi-Fi signal transmitter controls a transmitting terminal antenna group to transmit Wi-Fi signals according to a control instruction, secondly, a Wi-Fi signal receiver receives the Wi-Fi signals from the Wi-Fi signal transmitter and transmits the Wi-Fi signals to a signal processing unit, and the signal processing unit converts the Wi-Fi signals into channel state information of the Wi-Fi signals.
8. The device for measuring the complex dielectric constant of the liquid based on the Wi-Fi signal as claimed in claim 5, wherein the noise reduction processing method comprises: gaussian filtering method, kalman filtering method, and wavelet denoising method.
9. A computer terminal device, comprising:
one or more processors;
a memory coupled to the processor for storing one or more programs;
the one or more programs, when executed by the one or more processors, cause the one or more processors to implement the method for measuring complex permittivity of a liquid based on Wi-Fi signals of any one of claims 1-4.
10. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the method for measuring a complex permittivity of a liquid based on Wi-Fi signals of any one of claims 1 to 4.
CN202011421303.2A 2020-12-07 2020-12-07 Method and device for measuring complex dielectric constant of liquid based on Wi-Fi signal Pending CN112595898A (en)

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