CN105466956B - Method and device for detecting moisture content in grain by using microwave signal - Google Patents
Method and device for detecting moisture content in grain by using microwave signal Download PDFInfo
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- CN105466956B CN105466956B CN201410466856.8A CN201410466856A CN105466956B CN 105466956 B CN105466956 B CN 105466956B CN 201410466856 A CN201410466856 A CN 201410466856A CN 105466956 B CN105466956 B CN 105466956B
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Abstract
The embodiment of the invention provides a method and a device for detecting the moisture content in grain by using microwave signals. The method mainly comprises the steps of generating two paths of microwave signals, wherein one path of microwave signal is transmitted through a coaxial line; the other path of microwave signal is transmitted out through a transmitting antenna and passes through grain to be measured for moisture; respectively carrying out down-conversion treatment on the two paths of microwave signals to obtain a comparison signal and a test signal, and measuring the amplitude attenuation A and the phase shift difference between the comparison signal and the test signal
Using said amplitude attenuation A, phase shift difference
The density-independent number ξ related to the grain is calculated through a density-independent algorithm, and the moisture content in the grain is calculated according to the density-independent number ξ and the temperature T of the grain.
Description
Technical Field
The invention relates to the technical field of grain moisture measurement, in particular to a method and a device for detecting moisture content in grains by using microwave signals.
Background
In the grain warehousing process, the moisture content detection has very important significance, and if grains with higher moisture content are not removed in time, the possibility of mildewing exists after warehousing. The existing grain moisture detection mode is manual sampling detection, and because the sampling detection method is low in efficiency, only reliable detection can be performed on samples, and universality is lacked, so that the possibility of mixing grains with high moisture content in grain piles is realized.
In the microwave frequency band, the dielectric constant of water is far greater than that of common materials, and the water in the materials becomes the main part determining the dielectric constant of the whole materials, particularly in the X wave band, the loss factor of water is high. Since the dielectric constant of water is much greater than that of general substances, the higher the moisture content in the object to be measured is, the larger the dielectric constant of the object to be measured is. On the other hand, the amplitude attenuation and phase shift of the microwave penetrating the object to be measured are related to the dielectric constant of the object to be measured. Therefore, the moisture content in the grain can be calculated by detecting the amplitude and phase difference of the microwave penetrating the grain and the microwave not penetrating the grain, detecting the amplitude and phase change of the microwave signal caused by the grain and combining other parameters of the grain, such as grain thickness, temperature and the like.
In the prior art, a method for measuring the moisture content in grains by using microwaves comprises the following steps: the microwave signal is transmitted to grain through a circuit, the penetrating microwave signal of the microwave signal after penetrating through the grain is received, the microwave signal is compared with the penetrating microwave signal, the energy loss and the phase shift of the microwave signal are detected, and the moisture content in the grain is calculated according to the energy loss and the phase shift.
The method for measuring the moisture content in the grain by using the microwave in the prior art has the following defects: the method can introduce the loss in the transmission path of the microwave signal into the measurement result except the loss generated by the grain, and secondly, because the frequency of the microwave signal used by the method is higher, the requirement on a circuit for carrying out energy loss and phase shift detection is higher, and the circuit is difficult to realize.
Disclosure of Invention
The embodiment of the invention provides a method and a device for detecting the moisture content in grain by using a microwave signal, so as to improve the detection precision of the moisture in the grain.
The invention provides the following scheme:
a method for detecting moisture content in grain by using microwave signals comprises the following steps:
generating two paths of microwave signals with the same frequency, the same phase and the same amplitude, wherein one path of microwave signal is transmitted through a coaxial line; the other path of microwave signal is transmitted out through a transmitting antenna, and the other path of microwave signal passes through grain to be measured for moisture;
obtaining a contrast signal after one path of microwave signal transmitted by the coaxial line is subjected to down-conversion treatment, obtaining a test signal after the other path of microwave signal passing through the grain is subjected to down-conversion treatment, and measuringDeriving amplitude attenuation A and phase shift difference between the contrast signal and the test signal
Using said amplitude attenuation A, phase shift difference
And calculating a density-independent number ξ related to the grain through a density-independent algorithm, and calculating the moisture content of the grain according to the density-independent number ξ and the temperature T of the grain.
The two paths of microwave signals with the same frequency, the same phase and the same amplitude are generated, and the method comprises the following steps:
the method comprises the steps of utilizing a quartz crystal oscillator to generate an original signal, transmitting the original signal to a frequency synthesizer, and carrying out frequency division processing on the original signal by the frequency synthesizer to obtain a phase discrimination frequency. The frequency synthesizer generates microwave signals according to the phase discrimination frequency;
and transmitting the microwave signals to a variable gain amplifier, amplifying the microwave signals by the variable gain amplifier, transmitting the amplified microwave signals to a power divider, and performing power division processing on the received microwave signals by the power divider to generate two paths of microwave signals with the same frequency, the same phase and the same amplitude.
The one way microwave signal through coaxial line transmission obtain contrast signal after down conversion processing, will another way microwave signal that passes grain obtains test signal after down conversion processing, include:
two circuits with completely consistent structures are arranged: the device comprises a test path and a comparison path, wherein the comparison path comprises a band-pass filter 1, a low-noise amplifier 1, a frequency mixer 1, a local oscillator 1 and a low-pass filter 1, and the test path comprises a band-pass filter 2, a low-noise amplifier 2, a frequency mixer 2, a local oscillator 2 and a low-pass filter 2;
the contrast path receives one path of microwave signal transmitted by the coaxial line, and the test path receives the other path of microwave signal passing through the grain; the local oscillator 1 generates a local oscillator signal and transmits the local oscillator signal to the frequency mixer 1, and the local oscillator 2 generates a local oscillator signal and transmits the local oscillator signal to the frequency mixer 2;
microwave signals in the comparison channel are processed by a band-pass filter 1 and a low-noise amplifier 1 respectively and then transmitted to a mixer 1, the mixer 1 performs frequency mixing processing on the received microwave signals and local oscillator signals to obtain a mixing signal 1, the mixing signal 1 is output to a low-pass filter 1, and the low-pass filter 1 performs low-pass filtering processing on the mixing signal 1 to generate a comparison signal;
the microwave signals in the test access are processed by a band-pass filter 2 and a low-noise amplifier 2 respectively and then transmitted to a mixer 2, the mixer 2 performs frequency mixing processing on the received microwave signals and local oscillation signals to obtain a mixing signal 2, the mixing signal 2 is output to a low-pass filter 2, and the low-pass filter 2 performs low-pass filtering processing on the received mixing signal 2 to generate test signals.
The difference of phase shift and attenuation A by the amplitude
Calculating a density-independent number ξ related to the grain by a density-independent algorithm, and calculating the moisture content of the grain according to the density-independent number ξ and the temperature T of the grain, wherein the method comprises the following steps:
sampling a plurality of grain samples with different temperatures and different water contents, obtaining a comparison signal and a test signal corresponding to each grain sample by using the test access and the comparison access, and obtaining the amplitude attenuation A and the phase shift difference of each grain sample by measuring the comparison signal and the test signal through the energy loss and phase shift detection circuit
Using the difference between amplitude attenuation A and phase shift of each grain sampleCalculating the parameters k, af、a、b、c；
According to the determined parameters k, afA, b and c, and the thickness d, the energy attenuation A and the phase shift phi of the grain, and calculating a density independent number ξ related to the grain according to the following formula 5 and formula 6;
equation 5
The moisture content M of the grain is calculated from the following equation 8
The grain sample under different temperatures and different moisture contents is sampled, the test access and the comparison access are utilized to obtain a comparison signal and a test signal corresponding to each grain sample, and the amplitude attenuation A and the phase shift difference of each grain sample are obtained by measuring the comparison signal and the test signal through the energy loss and phase shift detection circuit
Using the difference between amplitude attenuation A and phase shift of each grain sample
Calculating the parameters k, afA, b, c, comprising:
1. sampling N grain samples off line;
2. taking N from N1Dividing the grain sample into N1The grain samples are configured into grain samples with different temperatures and different moisture contents, and the corresponding grain samples are obtained by utilizing the testing passage and the comparison passageComparing the signals with the test signal, and measuring the amplitude attenuation A of each grain sample by using the comparison signal and the test signal through the energy loss and phase shift detection circuitjDifference phi from phase shiftjAnd density of each grain sample ρj，j＝1,2,…,N1；
3. Calculating epsilonj＝ε′j-iε″j。
D in the above equations 1 and 2 is the density of the grain, λ0Is the wavelength of the microwave signal and,
calculating epsilon according to the formula 1 and the formula 2, and combining the formulas
Calculating the intercept k and the slope a by using a least square methodf；
4. Taking N from N2Sample to be tested is divided into N2Preparing grain samples into grain samples with different temperatures and different moisture contents, and respectively measuring the parameters of each grain sample: temperature TpAttenuation ApWith a phase shift phip，p＝1,2,…,N2。
Calculating epsilonp＝ε′p-iε″p。
Computing
Equation 3
Combined typeEquation 4
And solving the parameters a, b and c by using a least square method according to the formula 3 and the formula 4.
An apparatus for detecting moisture content in grain using microwave signals, comprising:
the microwave signal generating circuit is used for generating two paths of microwave signals with the same frequency, the same phase and the same amplitude;
the microwave signal transmission module is used for transmitting one path of microwave signal through a coaxial line and transmitting the other path of microwave signal through a transmitting antenna, and the other path of microwave signal penetrates through grain to be measured for moisture;
the receiving signal processing circuit is used for carrying out down-conversion processing on one path of microwave signal transmitted by the coaxial line to obtain a comparison signal, and carrying out down-conversion processing on the other path of microwave signal passing through the grain to obtain a test signal;
an energy loss and phase shift detection circuit for measuring amplitude attenuation A and phase shift difference between the comparison signal and the test signal
A data processing and man-machine interface circuit for utilizing the amplitude attenuation A and the phase shift difference
And calculating a density-independent number ξ related to the grain through a density-independent algorithm, and calculating the moisture content of the grain according to the density-independent number ξ and the temperature T of the grain.
The microwave signal generating circuit is specifically configured to generate an original signal by using a quartz crystal oscillator, transmit the original signal to a frequency synthesizer, and perform frequency division processing on the original signal by the frequency synthesizer to obtain a phase discrimination frequency. The frequency synthesizer generates microwave signals according to the phase discrimination frequency;
and transmitting the microwave signals to a variable gain amplifier, amplifying the microwave signals by the variable gain amplifier, transmitting the amplified microwave signals to a power divider, and performing power division processing on the received microwave signals by the power divider to generate two paths of microwave signals with the same frequency, the same phase and the same amplitude.
The received signal processing circuit is specifically used for setting two circuits with completely consistent structures: the device comprises a test path and a comparison path, wherein the comparison path comprises a band-pass filter 1, a low-noise amplifier 1, a frequency mixer 1, a local oscillator 1 and a low-pass filter 1, and the test path comprises a band-pass filter 2, a low-noise amplifier 2, a frequency mixer 2, a local oscillator 2 and a low-pass filter 2;
the contrast path receives one path of microwave signal transmitted by the coaxial line, and the test path receives the other path of microwave signal passing through the grain; the local oscillator 1 generates a local oscillator signal and transmits the local oscillator signal to the frequency mixer 1, and the local oscillator 2 generates a local oscillator signal and transmits the local oscillator signal to the frequency mixer 2;
microwave signals in the comparison channel are processed by a band-pass filter 1 and a low-noise amplifier 1 respectively and then transmitted to a mixer 1, the mixer 1 performs frequency mixing processing on the received microwave signals and local oscillator signals to obtain a mixing signal 1, the mixing signal 1 is output to a low-pass filter 1, and the low-pass filter 1 performs low-pass filtering processing on the mixing signal 1 to generate a comparison signal;
the microwave signals in the test access are processed by a band-pass filter 2 and a low-noise amplifier 2 respectively and then transmitted to a mixer 2, the mixer 2 performs frequency mixing processing on the received microwave signals and local oscillation signals to obtain a mixing signal 2, the mixing signal 2 is output to a low-pass filter 2, and the low-pass filter 2 performs low-pass filtering processing on the received mixing signal 2 to generate test signals.
The data processing and man-machine interface circuit is specifically used for sampling a plurality of grain samples with different temperatures and different moisture contents, obtaining a comparison signal and a test signal corresponding to each grain sample by using the test access and the comparison access, and obtaining the amplitude attenuation A and the phase shift difference of each grain sample by measuring the comparison signal and the test signal through the energy loss and phase shift detection circuit
Using the difference between amplitude attenuation A and phase shift of each grain sample
Calculating the parameters k, af、a、b、c；
According to the determined parameters k, afA, b and c, and the thickness d, the energy attenuation A and the phase shift phi of the grain, and calculating a density independent number ξ related to the grain according to the following formula 5 and formula 6;
The moisture content M of the grain is calculated from the following equation 8
Equation 8.
The data processing and man-machine interface circuit is specifically used for executing the following processing procedures:
1. sampling N grain samples off line;
2. taking N from N1Dividing the grain sample into N1The grain samples are configured into grain samples with different temperatures and different moisture contents, the test access and the comparison access are utilized to obtain a comparison signal and a test signal corresponding to each grain sample, and the amplitude attenuation A of each grain sample is obtained by measuring the comparison signal and the test signal through the energy loss and phase shift detection circuitjDifference phi from phase shiftjAnd density of each grain sample ρj，j＝1,2,…,N1；
3. Calculating epsilonj＝ε′j-iε″j。
D in the above equations 1 and 2 is the density of the grain, λ0Is the wavelength of the microwave signal and,
calculating epsilon according to the formula 1 and the formula 2, and combining the formulas
Calculating the intercept k and the slope a by using a least square methodf；
4. Taking N from N2Sample to be tested is divided into N2Preparing grain samples into grain samples with different temperatures and different moisture contents, and respectively measuring the parameters of each grain sample: temperature TpAttenuation ApWith a phase shift phip，p＝1,2,…,N2。
Calculating epsilonp＝ε′p-iε″p。
Computing
Equation 3
Combined type
Equation 4
And solving the parameters a, b and c by using a least square method according to the formula 3 and the formula 4.
According to the technical scheme provided by the embodiment of the invention, the comparison channel which is completely consistent with the test channel is arranged, and the two paths of microwave signals in the comparison channel and the test channel are subjected to down-conversion treatment simultaneously, so that the frequency of the microwave signals during the detection of energy loss and phase shift can be reduced, the detection circuit of the energy loss and the phase shift is easy to realize, and the detection precision of the moisture in the grain is improved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive labor.
Fig. 1 is a process flow of a method for detecting moisture content in grain by using microwave signals according to an embodiment of the present invention;
fig. 2 is a schematic circuit diagram of a microwave signal generating circuit according to an embodiment of the present invention;
fig. 3 is a schematic circuit diagram of a received signal processing circuit according to an embodiment of the present invention;
fig. 4 is a structural diagram of an implementation of an apparatus for detecting moisture content in grain by using microwave signals according to an embodiment of the present invention, in which a microwave signal generating circuit 41, a microwave signal transmitting module 42, a received signal processing circuit 43, an energy loss and phase shift detecting circuit 44, and a data processing and man-machine interface circuit 45 are shown.
Detailed Description
For the convenience of understanding the embodiments of the present invention, the following description will be further explained by taking several specific embodiments as examples in conjunction with the drawings, and the embodiments are not to be construed as limiting the embodiments of the present invention.
Example one
After the embodiment of the invention generates the required microwave signal, the microwave signal is divided into two paths, one path is transmitted through an antenna, is received by the antenna after transmitting grains, and the other path is connected by a coaxial line. After the two paths of signals are subjected to down-conversion and filtering, the amplitude and phase shift difference of the two paths of signals after down-conversion is detected through energy loss and phase shift detection, the amplitude and phase shift difference before down-conversion is obtained through analysis of the difference, and the grain moisture content is calculated through a density-independent algorithm by an upper computer.
The embodiment provides a processing flow of a method for detecting moisture content in grain by using microwave signals, which is shown in fig. 1 and comprises the following processing steps:
step S110, generating a microwave signal by a microwave signal generating circuit.
Fig. 2 shows a schematic circuit diagram of a microwave signal generating circuit according to this embodiment, which includes a quartz crystal oscillator with a temperature compensation, a frequency synthesizer with a VCO (voltage-controlled oscillator), and a variable gain amplifier. And transmitting an original signal generated by the quartz crystal oscillator to a frequency synthesizer, and carrying out frequency division processing on the signal by the frequency synthesizer to obtain a phase discrimination frequency. The frequency synthesizer generates a microwave signal according to the phase discrimination frequency, transmits the microwave signal to the variable gain amplifier, amplifies the microwave signal by the variable gain amplifier, and transmits the amplified microwave signal to the power divider.
The microwave signal is X-band microwave with high frequency.
And step S120, the power divider performs power division processing on the received microwave signals to generate two paths of microwave signals with the same frequency, phase and amplitude, one path of microwave signals is output through a coaxial line, the other path of microwave signals is emitted through an emitting antenna, and the microwave signals need to penetrate through grains to be measured for moisture to interact with the grains.
Step S130, the one path of microwave signal output by the coaxial line and the other path of microwave signal transmitted by the transmitting antenna are all transmitted to the received signal processing circuit.
A schematic circuit structure diagram of a received signal processing circuit provided in this embodiment is shown in fig. 3, where the received signal processing circuit includes two completely identical circuits: the test path receives the microwave signal transmitted by the transmitting antenna, and the comparison path receives the microwave signal output by the coaxial line.
The test path and the comparison path comprise a band-pass filter, a low-noise amplifier, a frequency mixer, a local oscillator and a low-pass filter. The local oscillators include a quartz crystal oscillator with temperature compensation and a frequency synthesizer with VCO. The original signal generated by the quartz crystal oscillator is transmitted to the frequency synthesizer, the frequency synthesizer performs frequency division processing on the signal to obtain phase discrimination frequency, the frequency synthesizer generates a local oscillator signal according to the phase discrimination frequency, and the local oscillator signal is transmitted to the frequency mixer. The two local oscillators use the same crystal oscillator to ensure that the phases of output signals are consistent. The frequency of the local oscillation signal generated by the local oscillation is lower than the frequency of the microwave signal generated by the microwave signal generating circuit.
The microwave signal in the above-mentioned comparison path is processed by the band-pass filter 1 and the low-noise amplifier 1, respectively, and then transmitted to the mixer 1. The mixer 1 performs mixing processing on the received microwave signal and local oscillator signal to obtain a mixed signal 1, and outputs the mixed signal to the low-pass filter 1. The low-pass filter 1 performs low-pass filtering processing on the received mixing signal to generate a contrast signal with a lower frequency, and transmits the contrast signal to the energy loss and phase shift detection circuit.
The microwave signal in the test path is processed by the band-pass filter 2 and the low-noise amplifier 2, and then transmitted to the mixer 2. The mixer 2 performs mixing processing on the received microwave signal and local oscillation signal to obtain a mixed signal, and outputs the mixed signal to the low-pass filter 2. The low pass filter 2 performs low pass filtering processing on the received mixing signal to generate a test signal with a lower frequency, and transmits the test signal to the energy loss and phase shift detection circuit.
Step S140, the amplitude attenuation A and the phase shift difference between the comparison signal and the test signal are measured by the energy loss and phase shift detection circuit
Using the above amplitude attenuation A and phase shift difference
Analyzing to obtain amplitude attenuation A' and phase shift difference between two paths of microwave signals corresponding to the comparison signal and the test signal before mixingThe above amplitude attenuation A' and phase shift difference
Amplitude attenuation A' and phase shift difference corresponding to grain with water content to be measured passing through the microwave signal
The microwave signal in the test channel before mixing is:the microwave signal in the contrast channel is:
the frequency mixer in the test channel willSignal generated by integrating with frequencyPerforming mixing processing to obtain
The mixers in the contrast channels will
Signal generated by integrating with frequency
Performing mixing processing to obtain
the mixing and low pass filtering processes described above constitute the down conversion process.
The amplitude attenuation between the contrast signal and the test signal measured by the energy loss and phase shift detection circuit is
The phase difference is
From the two formulas, the amplitude attenuation (U) of the two microwave signals before mixing can be analyzed from the amplitude attenuation and the phase difference between the contrast signal and the test signal after down-conversion filtering2-U1) The phase difference is
The energy loss and phase shift detection circuit is used for measuring the amplitude attenuation A and the phase shift difference corresponding to the grain of the moisture to be measured
And transmitting the data to a data processing and man-machine interface circuit.
Step S150, the data processing and man-machine interface circuit includes an a/D conversion circuit, an MCU (Micro control unit), an interface circuit, and an upper computer. The energy attenuation A and the phase shift phi information output by the energy loss and phase shift detection circuit are sent to the MCU after A/D conversion, the MCU sends the energy attenuation A and the phase shift phi information to the upper computer through the interface circuit, and the upper computer calculates and displays the current grain moisture content by combining parameters such as grain thickness and temperature through the density-independent compensation algorithm.
The upper computer utilizes the amplitude attenuation A and the phase shift difference
And the density-independent number ξ related to the grain to be measured is calculated by a density-independent algorithm according to the existing parameters, and the grain moisture content is obtained according to the density-independent number ξ and the temperature T of the grain to be measured.
The density independent compensation algorithm flow is as follows, firstly, parameters k and a need to be calculatedfA, b, c, where k is the intercept, afIs a slope of the light beam in the direction of the light beam,
through the analysis of experimental data, it can be found that:
approximately linear relationship with moisture content M, temperature T:
and a, b and c are linear coefficients of the two.
1. Sampling N grain samples off line;
2. taking N from N1Dividing the grain sample into N1The grain samples are prepared into grain samples under different temperatures and different moisture contents. Due to the dielectric loss epsilon' of water in the microwave frequency rangerAbout 40, and epsilon of general media "r<1; therefore, the epsilon of the grain sample can be considered after the grain sample is dried "r0 is added, and k is equal to epsilon'rAnd rho, wherein k is intercept, and rho is density of the grain sample.
The dried and dried sample needs to be collected, the sample collection range is expanded, and the intercept k and the slope a are improvedfTo the accuracy of (2). Therefore, the sample collection should include grain samples from dry to high moisture content. Fixing the testing frequency, and respectively detecting the grain sample pairs according to the processing flow from the step S110 to the step S140The parameters are as follows: density pjAttenuation AjWith a phase shift phij，j＝1,2,…,N1。
3. Calculating epsilonj＝ε′j-iε″j。
According to the following steps:
equation 1
D in the above equations 1 and 2 is the thickness of the grain, λ0For the wavelength of the microwave signal generated by the microwave signal generating circuit,
calculating epsilon according to the formula 1 and the formula 2, and combining the formulas
Calculating the intercept k and the slope a by using a least square methodf。
Taking N from N2And (4) preparing samples to be detected, and preparing samples at different temperatures and different water contents. The testing frequency is the same as the testing frequency, and the parameters of the grains are respectively detected: temperature TpAttenuation ApWith a phase shift phip，p＝1,2,…,N2。
Calculating epsilonp＝ε′p-iε″p。
Computing
Equation 3
Combined type
Equation 4
And solving a, b and c by using a least square method.
The above process is not only applicable to the process of collecting and calculating parameters of the sample, but also applicable to the process of off-line measurement or on-line measurement.
According to the determined parameters k, afA, b and c, the thickness d of the grain to be measured, the energy attenuation A and the phase shift phi of the grain to be measured, which are measured by the energy loss and phase shift detection circuit, and the density independent number ξ related to the grain are calculated by the following formula 5 and formula 6;
The moisture content M of the grain is calculated from the following equation 8
Equation 8.
The power divider, the low-pass filter and the band-pass filter in the circuit are all made of microstrip lines, and input and output impedances are all 50 omega.
The transmitting antenna and the receiving antenna both adopt horn antennas with 50-ohm impedance. The receiving antenna is installed opposite to the transmitting antenna.
Example two
The embodiment provides a device for detecting moisture content in grain by using microwave signals, and a specific implementation structure of the device is shown in fig. 4, and the device specifically comprises the following modules:
a microwave signal generating circuit 41 for generating two paths of microwave signals with the same frequency, the same phase and the same amplitude;
the microwave signal transmission module 42 is configured to transmit one path of microwave signal through a coaxial line, and transmit the other path of microwave signal through a transmitting antenna, where the other path of microwave signal passes through grain to be measured for moisture;
the received signal processing circuit 43 is configured to perform down-conversion processing on the one path of microwave signal transmitted through the coaxial line to obtain a comparison signal, and perform down-conversion processing on the other path of microwave signal passing through the grain to obtain a test signal;
an energy loss and phase shift detection circuit 44 for measuring the amplitude attenuation A and phase shift difference between the contrast signal and the test signal；
A data processing and man-machine interface circuit 45 for utilizing said amplitude attenuation A, phase shift difference
And calculating a density-independent number ξ related to the grain through a density-independent algorithm, and calculating the moisture content of the grain according to the density-independent number ξ and the temperature T of the grain.
Further, the microwave signal generating circuit 41 is specifically configured to generate an original signal by using a quartz crystal oscillator, transmit the original signal to a frequency synthesizer, and perform frequency division processing on the original signal by the frequency synthesizer to obtain a phase discrimination frequency. The frequency synthesizer generates microwave signals according to the phase discrimination frequency;
and transmitting the microwave signals to a variable gain amplifier, amplifying the microwave signals by the variable gain amplifier, transmitting the amplified microwave signals to a power divider, and performing power division processing on the received microwave signals by the power divider to generate two paths of microwave signals with the same frequency, the same phase and the same amplitude.
Further, the received signal processing circuit 43 is specifically configured to set two circuits with completely identical structures: the device comprises a test path and a comparison path, wherein the comparison path comprises a band-pass filter 1, a low-noise amplifier 1, a frequency mixer 1, a local oscillator 1 and a low-pass filter 1, and the test path comprises a band-pass filter 2, a low-noise amplifier 2, a frequency mixer 2, a local oscillator 2 and a low-pass filter 2;
the contrast path receives one path of microwave signal transmitted by the coaxial line, and the test path receives the other path of microwave signal passing through the grain; the local oscillator 1 generates a local oscillator signal and transmits the local oscillator signal to the frequency mixer 1, and the local oscillator 2 generates a local oscillator signal and transmits the local oscillator signal to the frequency mixer 2;
microwave signals in the comparison channel are processed by a band-pass filter 1 and a low-noise amplifier 1 respectively and then transmitted to a mixer 1, the mixer 1 performs frequency mixing processing on the received microwave signals and local oscillator signals to obtain a mixing signal 1, the mixing signal 1 is output to a low-pass filter 1, and the low-pass filter 1 performs low-pass filtering processing on the mixing signal 1 to generate a comparison signal;
the microwave signals in the test access are processed by a band-pass filter 2 and a low-noise amplifier 2 respectively and then transmitted to a mixer 2, the mixer 2 performs frequency mixing processing on the received microwave signals and local oscillation signals to obtain a mixing signal 2, the mixing signal 2 is output to a low-pass filter 2, and the low-pass filter 2 performs low-pass filtering processing on the received mixing signal 2 to generate test signals.
Further, the data processing and human-computer interface circuit 45 is specifically configured to sample a plurality of grain samples at different temperatures and with different moisture contents, obtain a comparison signal and a test signal corresponding to each grain sample by using the test path and the comparison path, and obtain the amplitude attenuation a and the phase shift difference of each grain sample by measuring the comparison signal and the test signal through the energy loss and phase shift detection circuit
Using the difference between amplitude attenuation A and phase shift of each grain sample
Calculating the parameters k, af、a、b、c；
According to the determined parameters k, afA, b, c, and thickness d, energy of said grainThe quantity attenuation A and the phase shift phi are measured, and the density independent number ξ related to the grain is calculated by the following formula 5 and formula 6;
Equation 7
The moisture content M of the grain is calculated from the following equation 8
Equation 8.
Further, the data processing and human-computer interface circuit 45 is specifically configured to perform the following processing procedures:
1. sampling N grain samples off line;
2. taking N from N1Dividing the grain sample into N1The grain samples are configured into grain samples with different temperatures and different moisture contents, the test access and the comparison access are utilized to obtain a comparison signal and a test signal corresponding to each grain sample, and the amplitude attenuation A of each grain sample is obtained by measuring the comparison signal and the test signal through the energy loss and phase shift detection circuitjDifference phi from phase shiftjAnd density of each grain sample ρj，j＝1,2,…,N1；
3. Calculating epsilonj＝ε′j-iε″j。
D in the above equations 1 and 2 is the density of the grain, λ0Is the wavelength of the microwave signal and,
calculating epsilon according to the formula 1 and the formula 2, and combining the formulas
Calculating the intercept k and the slope a by using a least square methodf；
4. Taking N from N2Sample to be tested is divided into N2Preparing grain samples into grain samples with different temperatures and different moisture contents, and respectively measuring the parameters of each grain sample: temperature TpAttenuation ApWith a phase shift phip，p＝1,2,…,N2。
Calculating epsilonp＝ε′p-iε″p。
Computing
Equation 3
Combined type
Equation 4
And solving the parameters a, b and c by using a least square method according to the formula 3 and the formula 4.
The specific process of using the device of the embodiment of the invention to detect the moisture content in the grain by using the microwave signal is similar to the method embodiment, and the detailed description is omitted here.
In summary, in the embodiment of the present invention, the comparison channel completely consistent with the test channel is provided, and the two paths of microwave signals in the comparison channel and the test channel are processed by down-conversion at the same time, so that the frequency of the microwave signal when detecting the energy loss and the phase shift can be reduced, the detection circuit for detecting the energy loss and the phase shift is easy to implement, and the detection accuracy of the moisture in the grain is improved.
And signal paths between the power divider and the band-pass filter of the two signal channels are different. The other parts of the circuits are the same, the loss except the loss generated by the grain is the same, the loss except the loss generated by the grain can be counteracted at the energy loss and phase shift detection part, and the compared result is the loss generated by the grain, so that the defect that the loss except the loss generated by the grain in the transmission path of the microwave signal is introduced into the measurement result in the background technology is overcome.
Those of ordinary skill in the art will understand that: the figures are merely schematic representations of one embodiment, and the blocks or flow diagrams in the figures are not necessarily required to practice the present invention.
From the above description of the embodiments, it is clear to those skilled in the art that the present invention can be implemented by software plus necessary general hardware platform. Based on such understanding, the technical solutions of the present invention may be embodied in the form of a software product, which may be stored in a storage medium, such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the method according to the embodiments or some parts of the embodiments.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for apparatus or system embodiments, since they are substantially similar to method embodiments, they are described in relative terms, as long as they are described in partial descriptions of method embodiments. The above-described embodiments of the apparatus and system are merely illustrative, and the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. A method for detecting moisture content in grain by using microwave signals is characterized by comprising the following steps: generating two paths of microwave signals with the same frequency, the same phase and the same amplitude, wherein one path of microwave signal is transmitted through a coaxial line; the other path of microwave signal is transmitted out through a transmitting antenna, and the other path of microwave signal passes through grain to be measured for moisture;
obtaining a contrast signal after one path of microwave signal transmitted by the coaxial line is subjected to down-conversion treatment, obtaining a test signal after the other path of microwave signal passing through the grain is subjected to down-conversion treatment, and measuring the amplitude attenuation A and the phase shift difference between the contrast signal and the test signal
Using said amplitude attenuation A, phase shift difference
And calculating a density-independent number ξ related to the grain through a density-independent algorithm, and calculating the moisture content of the grain according to the density-independent number ξ and the temperature T of the grain.
2. The method for detecting moisture content in grain according to claim 1, wherein said generating two microwave signals with same frequency, phase and amplitude comprises:
generating an original signal by using a quartz crystal oscillator, transmitting the original signal to a frequency synthesizer, and performing frequency division processing on the original signal by the frequency synthesizer to obtain a phase discrimination frequency; the frequency synthesizer generates microwave signals according to the phase discrimination frequency;
and transmitting the microwave signals to a variable gain amplifier, amplifying the microwave signals by the variable gain amplifier, transmitting the amplified microwave signals to a power divider, and performing power division processing on the received microwave signals by the power divider to generate two paths of microwave signals with the same frequency, the same phase and the same amplitude.
3. The method for detecting the moisture content in the grain by using the microwave signal according to claim 1, wherein the step of performing down-conversion processing on the one path of microwave signal transmitted through the coaxial line to obtain a contrast signal and the step of performing down-conversion processing on the other path of microwave signal passing through the grain to obtain a test signal comprises the steps of:
two circuits with completely consistent structures are arranged: the device comprises a test path and a comparison path, wherein the comparison path comprises a band-pass filter 1, a low-noise amplifier 1, a frequency mixer 1, a local oscillator 1 and a low-pass filter 1, and the test path comprises a band-pass filter 2, a low-noise amplifier 2, a frequency mixer 2, a local oscillator 2 and a low-pass filter 2;
the contrast path receives one path of microwave signal transmitted by the coaxial line, and the test path receives the other path of microwave signal passing through the grain; the local oscillator 1 generates a local oscillator signal and transmits the local oscillator signal to the frequency mixer 1, and the local oscillator 2 generates a local oscillator signal and transmits the local oscillator signal to the frequency mixer 2;
microwave signals in the comparison channel are processed by a band-pass filter 1 and a low-noise amplifier 1 respectively and then transmitted to a mixer 1, the mixer 1 performs frequency mixing processing on the received microwave signals and local oscillator signals to obtain a mixing signal 1, the mixing signal 1 is output to a low-pass filter 1, and the low-pass filter 1 performs low-pass filtering processing on the mixing signal 1 to generate a comparison signal;
the microwave signals in the test access are processed by a band-pass filter 2 and a low-noise amplifier 2 respectively and then transmitted to a mixer 2, the mixer 2 performs frequency mixing processing on the received microwave signals and local oscillation signals to obtain a mixing signal 2, the mixing signal 2 is output to a low-pass filter 2, and the low-pass filter 2 performs low-pass filtering processing on the received mixing signal 2 to generate test signals.
4. The method as claimed in claim 1, wherein the amplitude attenuation A and the phase shift difference are used to detect the moisture content in the grain
Calculating a density-independent number ξ related to the grain by a density-independent algorithm, and calculating the moisture content of the grain according to the density-independent number ξ and the temperature T of the grain, wherein the method comprises the following steps:
sampling a plurality of grain samples with different temperatures and different water contents, obtaining a comparison signal and a test signal corresponding to each grain sample by using the test access and the comparison access, and obtaining the amplitude attenuation A and the phase shift difference of each grain sample by measuring the comparison signal and the test signal through the energy loss and phase shift detection circuitUsing the difference between amplitude attenuation A and phase shift of each grain sample
Calculating parameters k and slope afA, b, c; a. b and c are linear coefficients respectively;
according to the determined parameters k, afA, b, c, and the thickness d, energy attenuation a and phase shift phi of the grain, calculating a density independent number ξ related to the grain from the following formula 5, formula 6 and formula 7;
wherein epsilonrA relative dielectric constant; lambda [ alpha ]0A microwave signal wavelength; tan (r) is2δ is the square of the energy loss tangent or the square of the dielectric loss tangent; epsilon' is the energy storage property of the medium; ε' is the energy-consuming property of the medium; the moisture content M of the grain is calculated from the following equation 8
5. The method according to claim 4, wherein the method comprises sampling a plurality of grain samples with different temperatures and different moisture contents, obtaining a test signal and a comparison signal corresponding to each grain sample by using the test path and the comparison path, and obtaining the amplitude attenuation Aj and the phase shift difference φ of each grain sample by using the test signal and the comparison signal through the energy loss and phase shift detection circuit to measurejUsing the difference between the amplitude attenuation A and the phase shift of each grain sample
Calculating parameters k and slope afA, b, c, a, b, c are linear coefficients respectively, including:
1. sampling N grain samples off line;
2. taking N from N1Dividing the grain sample into N1The grain samples are configured into grain samples with different temperatures and different moisture contents, and each grain sample is obtained by utilizing the testing passage and the comparison passage to correspond toThe comparison signal and the test signal are used for measuring the amplitude attenuation A of each grain sample by the energy loss and phase shift detection circuit through the comparison signal and the test signaljDifference phi from phase shiftjAnd density of each grain sample ρj，j＝1,2,…,N1；
3. Calculating epsilonj＝ε′j-iε″j
D in the above equations 1 and 2 is the density of the grain, λ0Is the wavelength of the microwave signal and,
calculating epsilon according to the formula 1 and the formula 2, and combining the formulas
Calculating the intercept k and the slope a by using a least square methodf；
4. Taking N from N2Sample to be tested is divided into N2Preparing grain samples into grain samples with different temperatures and different moisture contents, and respectively measuring the parameters of each grain sample: temperature TpAttenuation ApWith a phase shift phip，p＝1,2,…,N2；
Calculating epsilonp＝ε′p-iε″p
Computing
Combined type
And solving the parameters a, b and c by using a least square method according to the formula 3 and the formula 4.
6. An apparatus for detecting moisture content in grain using microwave signals, comprising: the microwave signal generating circuit is used for generating two paths of microwave signals with the same frequency, the same phase and the same amplitude;
the microwave signal transmission module is used for transmitting one path of microwave signal through a coaxial line and transmitting the other path of microwave signal through a transmitting antenna, and the other path of microwave signal penetrates through grain to be measured for moisture;
the receiving signal processing circuit is used for carrying out down-conversion processing on one path of microwave signal transmitted by the coaxial line to obtain a comparison signal, and carrying out down-conversion processing on the other path of microwave signal passing through the grain to obtain a test signal;
an energy loss and phase shift detection circuit for measuring amplitude attenuation A and phase shift difference between the comparison signal and the test signal
A data processing and man-machine interface circuit for utilizing the amplitude attenuation A and the phase shift difference
And calculating a density-independent number ξ related to the grain through a density-independent algorithm, and calculating the moisture content of the grain according to the density-independent number ξ and the temperature T of the grain.
7. The apparatus for detecting moisture content in grain using microwave signal as claimed in claim 6, wherein:
the microwave signal generating circuit is specifically used for generating an original signal by using a quartz crystal oscillator, transmitting the original signal to a frequency synthesizer, and performing frequency division processing on the original signal by the frequency synthesizer to obtain a phase discrimination frequency; the frequency synthesizer generates microwave signals according to the phase discrimination frequency;
and transmitting the microwave signals to a variable gain amplifier, amplifying the microwave signals by the variable gain amplifier, transmitting the amplified microwave signals to a power divider, and performing power division processing on the received microwave signals by the power divider to generate two paths of microwave signals with the same frequency, the same phase and the same amplitude.
8. The apparatus for detecting moisture content in grain using microwave signal as claimed in claim 6, wherein:
the received signal processing circuit is specifically used for setting two circuits with completely consistent structures: the device comprises a test path and a comparison path, wherein the comparison path comprises a band-pass filter 1, a low-noise amplifier 1, a frequency mixer 1, a local oscillator 1 and a low-pass filter 1, and the test path comprises a band-pass filter 2, a low-noise amplifier 2, a frequency mixer 2, a local oscillator 2 and a low-pass filter 2;
the contrast path receives one path of microwave signal transmitted by the coaxial line, and the test path receives the other path of microwave signal passing through the grain; the local oscillator 1 generates a local oscillator signal and transmits the local oscillator signal to the frequency mixer 1, and the local oscillator 2 generates a local oscillator signal and transmits the local oscillator signal to the frequency mixer 2; microwave signals in the comparison channel are processed by a band-pass filter 1 and a low-noise amplifier 1 respectively and then transmitted to a mixer 1, the mixer 1 performs frequency mixing processing on the received microwave signals and local oscillator signals to obtain a mixing signal 1, the mixing signal 1 is output to a low-pass filter 1, and the low-pass filter 1 performs low-pass filtering processing on the mixing signal 1 to generate a comparison signal;
the microwave signals in the test access are processed by a band-pass filter 2 and a low-noise amplifier 2 respectively and then transmitted to a mixer 2, the mixer 2 performs frequency mixing processing on the received microwave signals and local oscillation signals to obtain a mixing signal 2, the mixing signal 2 is output to a low-pass filter 2, and the low-pass filter 2 performs low-pass filtering processing on the received mixing signal 2 to generate test signals.
9. The apparatus for detecting moisture content in grain using microwave signal as claimed in claim 6, wherein:
the data processing and man-machine interface circuit is specifically used for sampling a plurality of grain samples with different temperatures and different moisture contents, obtaining a comparison signal and a test signal corresponding to each grain sample by using the test access and the comparison access, and obtaining the amplitude attenuation A and the phase shift difference of each grain sample by measuring the comparison signal and the test signal through the energy loss and phase shift detection circuit
Using the difference between amplitude attenuation A and phase shift of each grain sample
Calculating parameters k and slope afA, b, c; a. b and c are linear coefficients respectively;
according to the determined parameters k, afA, b, c, and the thickness d, energy attenuation a and phase shift phi of the grain, calculating a density independent number ξ related to the grain from the following formula 5, formula 6 and formula 7;
wherein epsilonrA relative dielectric constant; lambda [ alpha ]0A microwave signal wavelength; tan (r) is2δ is the square of the energy loss tangent or the square of the dielectric loss tangent; epsilon' is the energy storage property of the medium; εIs the energy consumption characteristic of the medium;
the moisture content M of the grain is calculated from the following equation 8
10. The apparatus for detecting moisture content in grain using microwave signal according to claim 9, wherein:
the data processing and man-machine interface circuit is specifically used for executing the following processing procedures:
1. sampling N grain samples off line;
2. taking N from N1Dividing the grain sample into N1The grain samples are configured into grain samples with different temperatures and different moisture contents, the testing channel and the comparison channel are utilized to obtain testing signals and comparison signals corresponding to each grain sample, and the amplitude attenuation A of each grain sample is obtained by measuring the testing signals and the comparison signals through the energy loss and phase shift detection circuitjDifference phi from phase shiftjAnd density of each grain sample ρj，j＝1,2,...,N1；
3. Calculating epsilonj＝ε′j-iε″j
D in the above equations 1 and 2 is the density of the grain, λ0Is the wavelength of the microwave signal and,
calculating epsilon according to the formula 1 and the formula 2, and combining the formulas
Calculating the intercept k and the slope a by using a least square methodf；
4. Taking N from N2Sample to be tested is divided into N2Preparing grain samples into grain samples with different temperatures and different moisture contents, and respectively measuring the parameters of each grain sample: temperature TpAttenuation ApWith a phase shift phip，p＝1,2,…,N2
Calculating epsilonp＝ε′p-iε″p
Computing
Combined type
And solving the parameters a, b and c by using a least square method according to the formula 3 and the formula 4.
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| CN107192635B (en) * | 2017-06-14 | 2019-06-07 | 中国科学院遥感与数字地球研究所 | The method and system of nondestructive measurement density of wood |
| CN108398441A (en) * | 2018-02-11 | 2018-08-14 | 杨厚荣 | Online non-contact microwave radar Moisture Meter and its measurement method are realized |
| CN109709112A (en) * | 2018-12-06 | 2019-05-03 | 珠海格力电器股份有限公司 | A kind of method, storage medium and the terminal of grain storage device and grain monitoring |
| CN110596152B (en) * | 2019-09-16 | 2024-02-20 | 安徽大洋自动化科技有限公司 | Intelligent detection device for grain moisture volume weight |
| CN110793979B (en) * | 2019-10-16 | 2021-04-06 | 中国科学院遥感与数字地球研究所 | Method and device for measuring wood density of standing tree |
| CN110954579B (en) * | 2019-11-21 | 2021-10-15 | 北京京邦达贸易有限公司 | Fruit and vegetable component content measuring method and system |
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