CN104964991B - Microwave radar main frame for radar type microwave water measurer device - Google Patents

Abstract

The invention discloses the microwave radar main frame for radar type microwave water measurer device, include the orthogonal mixing unit of the power detecting unit of the transmitter unit of the continuous single-frequency microwave signal of transmitting, continuous single-frequency microwave signal, continuous single-frequency microwave signal and the orthogonal mixing of beacon signal progress.

Description

Microwave radar host for radar type microwave water measuring instrument

technical field

The invention relates to a water measuring device, which is a radar-type microwave water measuring instrument widely used in industries such as industry, agriculture, and medical treatment, and is used to measure the moisture content of materials (the percentage of water weight in materials and the total weight of materials) Fast, non-contact, accurate online measurement.

Background technique

In industries such as industry, agriculture, and medical care, the moisture content of materials such as building materials, crops, grains, textiles, and medical raw materials needs to be accurately measured and controlled in order to better control product quality. At present, the commonly used methods for measuring the moisture content of materials include heating and drying weighing method, infrared reflectance water measurement method, microwave resonant cavity method, microwave transmission method and so on. The heating and drying weighing method is a national standard measurement method with high precision, but the measurement speed is slow. It can only test the moisture content of a small amount of samples. It cannot be used for online rapid testing, and it only reflects the moisture content of the sample. Uniformity, the moisture content of the sample may deviate from the average moisture content of the real material, so to reflect the average moisture content of the real material requires multiple sampling measurements for statistical analysis, the test cycle is long and the efficiency is low. Infrared reflectivity water measurement method is to use the difference in the reflectivity of infrared rays of specific wavelengths for samples with different water contents, and to invert the water content of samples by measuring infrared reflectivity, which can be used for online testing, but because infrared rays are mainly reflected on the surface of materials, they are harmful to materials. The penetration depth is small, so it is mainly used to measure the water content of the surface layer of the material, and it is difficult to accurately measure the water content of the material body. The microwave resonant cavity method is to place the microwave resonant cavity near the water-containing material, and the water-containing material will perturb the resonant cavity to shift the resonance frequency. Since the dielectric constant of the material with different water content is quite different, the material with different water content , the frequency offset of the microwave resonator is different. The microwave resonant cavity is connected to the microwave oscillator circuit, and the moisture content of the material is obtained by inversion according to the deviation between the frequency of the microwave oscillation signal and the nominal value. The microwave resonator method usually only reflects the moisture content of the material near the resonator, and cannot reflect the average moisture content of the material as a whole. In addition, it is necessary to ensure that the material and the resonator have a specific relative positional relationship to ensure the accuracy of the test. For example, during the test process, the material surface and The test surface of the resonant cavity needs to be in close contact at all times, which has high requirements on the shape of the material, the size of the sample, the state of motion and the installation position of the equipment, and is subject to many restrictions in practical applications.

Contents of the invention

The purpose of the present invention is to provide a microwave radar host for radar-type microwave water measuring instruments, which has good test accuracy and strong versatility, non-contact, rapid material average moisture content test technology.

The purpose of the present invention is mainly achieved through the following technical solutions:

The microwave radar host for radar-type microwave water measuring instruments, including a transmitting unit for transmitting continuous single-frequency microwave signals, a power detection unit for continuous single-frequency microwave signals, and a quadrature mixing unit for quadrature mixing of continuous single-frequency microwave signals and beacon signals mixing unit.

The transmitting unit includes a sequentially linked switch driver A, a single-pole double-throw switch, a directional coupler A, and a transmitting antenna; the switch driver A is controlled by a frequency selection signal, the single-pole double-throw switch is controlled by the switch driver A, and the directional coupler A receives the output signal of the single-pole double-throw switch to generate a continuous single-frequency microwave signal to the transmitting antenna. The single-pole double-throw switch is also controlled by the phase-locked frequency source A and the phase-locked frequency source B. The phase-locked frequency source A and the phase-locked frequency source B Both receive the vibration signal of the crystal oscillator, and the crystal oscillator sends a reference clock signal to the data processing terminal at the same time.

The power detection unit includes a directional coupler B, a detector, and an amplifier connected in sequence, and the directional coupler B receives the continuous single-frequency microwave signal of the transmitting unit.

The quadrature mixing unit includes a sequentially linked receiving antenna, a low-noise amplifier, and a quadrature mixer. The quadrature mixer receives the continuous single-frequency microwave signal of the transmitting unit or the continuous single-frequency microwave signal of the receiving power detection unit, and receives The antenna receives the beacon signal sent by the beacon device. After the beacon signal is amplified by the low noise amplifier, it is quadrature mixed with the continuous single-frequency microwave signal through the quadrature mixer. The quadrature mixer outputs 2 quadrature mixers. One channel of quadrature mixing signal is output to intermediate frequency filter A, and then the intermediate frequency in-phase component signal is output to the data processing terminal through intermediate frequency amplifier A, and the other channel of quadrature mixing signal is output to intermediate frequency filter B, and then through intermediate frequency amplifier B Output the intermediate frequency quadrature component signal to the data processing terminal.

Radar type microwave water measuring instrument, including the following components:

Rack base: used to place samples of materials to be tested;

Microwave radar host: used to transmit continuous single-frequency microwave signals to transmit the material samples to be tested, receive the beacon signals emitted by the beacon device, and send the output data to the data processing terminal;

Beacon device: used to receive the microwave signal transmitted through the material sample to be tested, and modulate the received microwave signal to form a beacon signal, and transmit the beacon signal to the microwave radar host;

Data processing terminal: the data processing terminal outputs the frequency selection signal to the microwave radar host, and the microwave radar host outputs a continuous single-frequency microwave signal of the corresponding frequency according to the frequency selection signal, and the data processing terminal is also used to receive the output data of the microwave radar host and calculate the Measure the moisture content of the material sample.

According to the above-mentioned various devices, the working principle of the present invention is: the material sample to be tested is placed between the microwave radar host and the beacon device. During the test, under the control of the data processing terminal, the radar emits two continuous single-frequency microwave signals in sequence. After the continuous single-frequency microwave signal is transmitted through the material sample to be tested, the continuous single-frequency microwave signal is received by the beacon device and modulated to form a beacon signal, and the beacon device forwards the beacon signal. Microwave radar host receives, each time the microwave radar host receives the beacon signal, it respectively tests the amplitude of the in-phase component (I) and quadrature component (Q) of the beacon signal relative to the continuous single-frequency microwave signal, and compares the I, Q The amplitude information is transmitted to the data processing terminal for processing.

In the data processing terminal, based on the complex permittivity model and the dielectric relaxation model of water including material medium, water and air, the I and Q amplitude information and The pre-stored system calibration parameters are processed to obtain the weight ratio of the material medium and water in the mixed medium, so as to obtain the water content of the material body, that is, the weight of water accounts for the weight percentage of the water-containing material, and the test accuracy can reach 0.1%.

The output data includes the reference clock signal, the power detection signal of the continuous single-frequency microwave signal, the intermediate frequency in-phase component output after the continuous single-frequency microwave signal and the beacon signal are subjected to quadrature mixing, and the continuous single-frequency microwave signal and the beacon signal. The intermediate frequency quadrature component output after the signal is quadrature mixed.

In terms of structure: the microwave radar host is located directly above the base of the rack, the beacon is located directly below the microwave radar host, the beacon is set on the rack base, the microwave radar antenna of the microwave radar host faces the rack base, and the beacon The beacon antenna of the device faces the microwave radar host, the frequency selection signal output end of the data processing terminal is connected to the frequency selection signal end of the microwave radar host, and the output data end of the microwave radar host is connected to the data input end of the data processing terminal.

The above structure also includes an integrated frame arranged on the frame base, the microwave radar host is installed on the integrated frame, and the data processing terminal is also installed on the integrated frame.

Preferably, the base of the rack is provided with a groove, and the beacon and the beacon antenna of the beacon are both arranged in the groove.

The beacon device should receive the microwave signal transmitted through the sample of the material to be tested, and modulate the received microwave signal to form a beacon signal, and transmit the beacon signal to the microwave radar host. Therefore, the preferred beacon device includes Battery, switch driver B, square wave oscillator, reflective microwave single-pole single-throw switch, matching load, the battery is connected to the switch driver B and the square wave oscillator for power supply, and the switch driver B is connected to the reflective microwave single-pole single-throw switch for driving , the square wave oscillator is matched with the switch driver B, the reflective microwave single-pole single-throw switch is matched with the matching load, and the reflective microwave single-pole single-throw switch is also connected with the beacon antenna of the beacon.

Preferably, the microwave radar host includes a transmitting unit for transmitting continuous single-frequency microwave signals, a power detection unit for continuous single-frequency microwave signals, and a quadrature mixing unit for performing quadrature mixing on continuous single-frequency microwave signals and beacon signals.

Preferably, the transmitting unit includes a sequentially linked switch driver A, a single-pole double-throw switch, a directional coupler A, and a transmitting antenna; the switch driver A is controlled by a frequency selection signal, and the single-pole double-throw switch is controlled by the switch driver A, The directional coupler A receives the output signal of the single-pole double-throw switch to generate a continuous single-frequency microwave signal to the transmitting antenna. The single-pole double-throw switch is also controlled by the phase-locked frequency source A and the phase-locked frequency source B. The phase-locked frequency source A and the phase-locked The frequency source B both receives the vibration signal of the crystal oscillator, and the crystal oscillator sends a reference clock signal to the data processing terminal at the same time.

Preferably, the power detection unit includes a directional coupler B, a detector, and an amplifier connected in sequence, and the directional coupler B receives the continuous single-frequency microwave signal of the transmitting unit.

Preferably, the quadrature mixing unit includes sequentially linked receiving antennas, low-noise amplifiers, and quadrature mixers, and the quadrature mixer receives continuous single-frequency microwave signals from the transmitting unit or receives continuous single-frequency microwave signals from the power detection unit. signal, the receiving antenna receives the beacon signal sent by the beacon device, the beacon signal is amplified by the low-noise amplifier and then quadrature-mixed with the continuous single-frequency microwave signal through the quadrature mixer, and the quadrature mixer outputs 2 channels Quadrature mixing signal, one channel of quadrature mixing signal is output to intermediate frequency filter A, and then the intermediate frequency in-phase component signal is output to the data processing terminal through intermediate frequency amplifier A, and the other channel of quadrature mixing signal is output to intermediate frequency filter B, and then passed through The intermediate frequency amplifier B outputs the intermediate frequency quadrature component signal to the data processing terminal.

The advantages of the present invention are as follows: The microwave radar transmission type water measurement scheme adopted in the present invention is a non-contact water measurement scheme. During the test, the material to be tested only needs to be within the irradiation space of the radar beam, without contact with the test instrument , there is no special requirement for the precise shape, size and motion state of the material, and it can be used as a general method for testing the moisture content of various materials in various industrial applications. The data processing method of the present invention is based on the complex permittivity model and the dielectric relaxation model of water including material medium, water and air 3 kinds of component mixed media, adopts dual-frequency test and fully utilizes the amplitude and phase information of radar signals, The test error can reach less than 0.1%, and the test accuracy is not affected by the air content in the material. It has good test accuracy and consistency for loose materials such as fibers, grains, and medicinal materials. The system calibration of the microwave radar transmission type water measurement scheme of the present invention is very simple, and only one calibration test is required for a class of material samples, and there is no special requirement for the shape, size, and density of the samples for calibration testing. The microwave radar transmission type water measurement scheme of the present invention, the test result is the average body water content (weight ratio) of the material to be tested, which can more accurately reflect the water content of the material being tested compared with the traditional microwave resonator and other test methods that only test the water content of the surface layer of the material. It can be used to measure the water content of materials, which can adapt to a wider range of test application requirements. The test speed of the present invention is very fast, and the time for one test is less than 1 ms, which can meet the fast, real-time and online test requirements for the moisture content of materials in the conveying state.

Description of drawings

Figure 1 is a schematic diagram of the present invention.

Figure 2 is a block diagram of the microwave radar host circuit.

Fig. 3 is a circuit block diagram of a beacon device.

The reference signs in the figure are respectively represented as: 1. microwave radar host, 2. microwave radar antenna, 3. beacon device, 4. beacon device antenna, 5. data processing terminal, 6. integrated rack, 7. Frame base, 8. Material samples to be tested.

detailed description

The present invention will be further described in detail below in conjunction with the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

Example 1:

As shown in Figure 1, the microwave radar host used for radar-type microwave water measuring instruments includes a frame base 7, a microwave radar host 1, a beacon 3, and a data processing terminal 5,

Rack base 7: used to place the material sample 8 to be tested;

Microwave radar host 1: used to emit continuous single-frequency microwave signals to transmit the material sample 8 to be tested, receive the beacon signal emitted by the beacon device 3, and send the output data to the data processing terminal 5;

Beacon device 3: used to receive the microwave signal transmitted through the sample 8 of the material to be tested, and modulate the received microwave signal to form a beacon signal, and transmit the beacon signal to the microwave radar host 1;

Data processing terminal: the data processing terminal outputs a frequency selection signal to the microwave radar host 1, and the microwave radar host 1 outputs a continuous single-frequency microwave signal of a corresponding frequency according to the frequency selection signal, and the data processing terminal is also used to receive the output data of the microwave radar host 1 and Calculate the water content of the material sample to be tested.

The output data includes the reference clock signal, the power detection signal of the continuous single-frequency microwave signal, the intermediate frequency in-phase component output after the continuous single-frequency microwave signal and the beacon signal are subjected to quadrature mixing, and the continuous single-frequency microwave signal and the beacon signal. The intermediate frequency quadrature component output after the signal is quadrature mixed.

According to the above-mentioned various devices, the working principle of the present invention is: the material sample to be tested is placed between the microwave radar host and the beacon device. During the test, under the control of the data processing terminal, the radar emits two continuous single-frequency microwave signals in sequence. After the continuous single-frequency microwave signal is transmitted through the material sample to be tested, the continuous single-frequency microwave signal is received by the beacon device 3 and modulated to form a beacon signal, and the beacon device 3 forwards the beacon signal, and the beacon signal is transmitted through the material sample to be tested After being received by the microwave radar host, after the microwave radar host receives the beacon signal each time, it tests the amplitude of the in-phase component (I) and the quadrature component (Q) of the beacon signal relative to the continuous single-frequency microwave signal, and compares the I , Q amplitude information is transmitted to the data processing terminal 5 for processing. In the data processing terminal 5, based on the complex permittivity model and the dielectric relaxation model of water including the material medium, water and air, the three-component mixed medium, the I and Q amplitude information on the frequency of two continuous single-frequency microwave signals are used And the pre-stored system calibration parameters are processed to obtain the weight ratio of the material medium and water in the mixed medium, so as to obtain the water content of the material body, that is, the weight of water accounts for the weight percentage of the water-containing material, and the test accuracy can reach 0.1%.

As shown in Figure 1, structurally speaking: the microwave radar host is located directly above the frame base 7, the beacon device 3 is located directly below the microwave radar host, the beacon device 3 is arranged on the frame base 7, and the microwave radar host 1 The microwave radar antenna 2 faces the frame base, the beacon antenna 4 of the beacon 3 faces the microwave radar host, the frequency selection signal output end of the data processing terminal 5 is connected with the frequency selection signal end of the microwave radar host 1, and the microwave radar host The output data end of 1 is connected with the data input end of data processing terminal 5. The above structure also includes an integrated frame 6 arranged on the frame base 7 , the microwave radar host is installed on the integrated frame 6 , and the data processing terminal 5 is also installed on the integrated frame 6 . Preferably, the frame base 7 is provided with a groove, and the beacon 3 and the beacon antenna 4 of the beacon 3 are both arranged in the groove.

As shown in Figure 3: the beacon device 3 should receive the microwave signal transmitted through the material sample 8 to be tested, modulate the received microwave signal to form a beacon signal, and transmit the beacon signal to the microwave radar host 1, Therefore preferred described beacon device 3 comprises battery, switch driver B, square wave oscillator, reflective microwave SPST switch, matching load, battery is all connected with switch driver B, square wave oscillator power supply, switch driver B and The reflective microwave SPST switch is connected for driving, the square wave oscillator is matched with the switch driver B, the reflective microwave SPST switch is connected with the matching load, and the reflective microwave SPST switch is also connected with the beacon of the beacon device 3 Connector antenna 4.

As shown in Figure 2, preferably, the microwave radar host includes a transmitting unit for transmitting continuous single-frequency microwave signals, a power detection unit for continuous single-frequency microwave signals, and a quadrature mixing unit for performing quadrature mixing between continuous single-frequency microwave signals and beacon signals cross-mixing unit. Preferably, the transmitting unit includes a sequentially linked switch driver A, a single-pole double-throw switch, a directional coupler A, and a transmitting antenna; the switch driver A is controlled by a frequency selection signal, and the single-pole double-throw switch is controlled by the switch driver A, The directional coupler A receives the output signal of the single-pole double-throw switch to generate a continuous single-frequency microwave signal to the transmitting antenna. The single-pole double-throw switch is also controlled by the phase-locked frequency source A and the phase-locked frequency source B. The phase-locked frequency source A and the phase-locked The frequency source B both receives the vibration signal of the crystal oscillator, and the crystal oscillator sends a reference clock signal to the data processing terminal at the same time. Preferably, the power detection unit includes a directional coupler B, a detector, and an amplifier connected in sequence, and the directional coupler B receives the continuous single-frequency microwave signal of the transmitting unit. Preferably, the quadrature mixing unit includes sequentially linked receiving antennas, low-noise amplifiers, and quadrature mixers, and the quadrature mixer receives continuous single-frequency microwave signals from the transmitting unit or receives continuous single-frequency microwave signals from the power detection unit. signal, the receiving antenna receives the beacon signal sent by the beacon device 3, the beacon signal is amplified by the low-noise amplifier and then quadrature-mixed with the continuous single-frequency microwave signal through the quadrature mixer, and the quadrature mixer outputs 2 One channel of quadrature mixing signal, one channel of quadrature mixing signal is output to intermediate frequency filter A, and then the intermediate frequency in-phase component signal is output to the data processing terminal through intermediate frequency amplifier A, and the other channel of quadrature mixing signal is output to intermediate frequency filter B, and then The intermediate frequency quadrature component signal is output to the data processing terminal through the intermediate frequency amplifier B. The microwave radar antenna 2 includes the above-mentioned receiving antenna and transmitting antenna.

The water content measurement method of the microwave radar main engine used for radar-type microwave water measuring instruments is as follows:

Step 1: Calculate the distance R between the exit surface of the microwave radar antenna 2 and the beacon antenna 4, and R can be accurately measured.

Step 2: Calibration test to obtain dimensionless system constants.

The specific steps of the calibration test are as follows:

When there is no material sample, the microwave radar host 1 sequentially transmits microwave signals of frequencies f ₁ and f ₂ (f ₁ <f ₂ ) for calibration testing. When the frequency is f _i (i=1,2), the microwave radar transmission power is P _ti , the antenna gain G _i of the microwave radar antenna 2, the antenna gain of the beacon antenna (4) is G _ai , and the microwave radar receives The magnitudes of the in-phase component and the quadrature component of the beacon signal are I _i and Q _i respectively, then:

I _i =A _i cosΦ _i (Formula 1);

Q _i ＝A _i sinΦ _i (Formula 2);

where A _i is the absolute value of the amplitude of the received beacon signal, Φ _i is the phase of the beacon signal relative to the transmitted signal, and have:

(Formula 3);

(Formula 4);

In the formula, λ _0i is the vacuum wavelength of the electromagnetic wave with frequency f _i , L _0i and Φ _0i are the system intrinsic loss factor and transmission phase at frequency f _i respectively, and Z ₀ =50Ω is the characteristic impedance of the transmission line.

The transmitted signal couples part of the power through the coupler, and the detection generates the monitoring voltage V _i as:

(Formula 5);

_ki is a proportionality factor.

So you can get:

(Formula 6);

(Formula 7);

When the system is designed for broadband, and f ₁ and f ₂ satisfy:

(Formula 8);

Then approximately k ₁ =k ₂ =k, L ₀₁ =L ₀₂ =L ₀ , Φ ₀₁ =Φ ₀₂ =Φ ₀ ,

For general antennas there are:

(Formula 9);

(Formula 10);

Among them, A and A _a are the effective areas of the radar antenna and the beacon antenna respectively, which are approximately constant in the system operating frequency band.

So approximately:

(Formula 11);

(Formula 12);

in is a dimensionless system constant.

The third step: measure the sample of the material to be tested, and find out.

The specific steps of measuring the sample of the material to be tested are as follows: when the sample of the material to be tested is placed, _two tests are also carried out at frequencies f1 and _f2 , and the in _- phase component and quadrature The amplitudes of the components are I _i ' and Q _i ' respectively, similarly:

(Formula 13);

(Formula 14);

In the formula, β _i and α _i are the real part and imaginary part of the complex propagation constant γ _i of the electromagnetic wave with frequency f _i in space when there are material samples, and have:

(Formula 15);

where ε _ci ', ε _ci ” and ε ci ” are respectively the real part and imaginary part of the complex dielectric constant of the medium on the electromagnetic wave propagation path when the frequency is f _i in the case of material samples.

According to the known quantities x _i , y _i , Xi and Y _{i , α i can} be solved:

(Formula 16);

and obtain:

(Formula 17);

(Formula 18);

Suppose the angle φ _i (0≤φ _i <2π) satisfies with Then there are:

(Formula 19);

n _i is a certain positive integer.

Therefore:

(Formula 20);

Under the conditions of (Equation 8), it can be approximately considered that the group velocity of electromagnetic waves at frequencies f ₁ and f ₂ is equal, and the transmission time of electromagnetic waves is also equal. Suppose the two are respectively v _g and τ _d :

(Formula 21);

(Equation 21) where C is the speed of light in air.

When the conditions are met:

(Formula 22);

When , the value of m in (Formula 21) satisfies:

(Formula 23);

(Equation 22)| _εc | _max is the maximum value of the complex dielectric constant modulus of the water-containing material at the frequency f ₁ or f ₂ . After substituting m obtained from (Formula 23) into (Formula 21) to obtain _τd , the value of _ni can be obtained as:

n ₁ =fix(f ₁ τ _d ), n ₂ =n ₁ +m (Formula 24);

(Formula 24) is substituted into (Formula 20) to obtain β _i . According to (Formula 15), calculate ε _ci ', ε _ci ”:

(Formula 25);

(Formula 26);

Assuming that the volume ratios of air, dry materials and water in the electromagnetic wave propagation space are p:q:r, p+q+r=1, then:

ε′ _ci -jε″ _ci = pε _a + qε _d + rε _wi (Formula 27);

Where ε _a , ε _d , ε _wi are the dielectric constants of air, dry material and water respectively, ε _a ≈1, p+q+r=1. Usually dry materials have no dielectric loss, so ε _d is a positive real number.

then:

ε' _ci -1-jε″ _ci = q(ε _d -1)+r(ε _wi -1) (Formula 28);

According to the dielectric relaxation model of water, the dielectric constant of water is:

(Formula 29);

where ε _s ≈80 and ε _∞ ≈4.9 are the direct current and infinitely high frequency dielectric constants of water, respectively. τ is the dielectric relaxation time of water, τ≈2×10 ^-11 s for pure water, and has different values for water contained in different materials. The real and imaginary parts of ε _wi are:

(Formula 30);

(Formula 31);

Assume

(Formula 32);

According to (Formula 28) the real and imaginary parts are equal respectively, and substituting (Formula 29) and (Formula 32), we can get:

(Formula 33);

(Formula 34);

From (Formula 33), (Formula 34):

(Formula 35);

According to (Equation 35), the parameter τ can be eliminated to get:

(Formula 36);

(Equation 36) in

Substitute into (Formula 35) to obtain 2πf _i τ, and substitute into (Formula 33) to obtain r; substitute r into (Formula 32) to obtain q(ε _d -1):

(Formula 37);

(Formula 38);

According to the volume ratio q:r of dry material and water, the water content w (weight ratio) of the available material is:

(Formula 39);

(Equation 39) in It is a dimensionless constant for a specific material, and its value can be obtained through system calibration.

Step 4: Carry out system calibration,

The specific method of system calibration is as follows: adopt a piece of water-containing material sample (moisture content is not zero, can be humidified in advance), first use the microwave radar water measuring instrument of the present invention to carry out a test, by (formula 37), (formula 38) Get r ₀ and q ₀ (ε _d -1). Then use the standard test method for water content of the sample (according to GB/T462-2003 "Determination of Moisture in Paper and Cardboard" or GB/T12087-2008 "Oven Method for Determination of Starch Moisture" and other national standard test methods) to measure its accurate water content. Rate W ₀ . According to (Formula 39), it can be solved:

(Formula 40);

After calibration, the microwave radar water meter can be used for online testing of the moisture content of such materials. The calculation process is to calculate α _i and β _i from (Formula 16) and (Formula 20), then calculate ε _ci ', ε _ci " from (Formula 25) (Formula 26), and then use (Formula 36), (Formula 37 )calculate and r, and finally get the water content of the material according to (Formula 39).

The microwave radar water measurement data processing method proposed by the present invention is based on an accurate complex permittivity model and a dielectric relaxation theoretical model of water including material medium, water and air, and has theoretical accuracy. _The only approximate assumptions that may introduce errors in data processing are the assumption that the system has equal intrinsic _loss factors and transmission phases at the calibration test frequencies f1 and f2. During system design, the difference between f ₁ and f ₂ is usually less than 100MHz, and (f ₁ +f ₂ )/2 generally uses a frequency band above 20GHz, and the relative operating bandwidth is less than 0.5%, so the error introduced by this assumption can be ignored.

In order to achieve a test accuracy of more than 0.1%, each signal component measured by the radar should have an amplitude accuracy of more than 1%. For this reason, according to the actual test distance R, it is necessary to ensure that the beacon signal received by the radar has a signal-to-noise ratio above 40dB, which can be achieved by designing an appropriate radar transmit power. Generally, for a working frequency of 20GHz, the test distance R=1m, the receiving noise figure is 3dB, and the receiver noise bandwidth is 50kHz. To ensure the signal-to-noise ratio, the required transmitting power is less than 1mW. At the same time, the frequency of the radar transmitting signal should have an accuracy and stability of more than 10 ^-5 .

The working method of the microwave radar host for the radar type microwave water measuring instrument can adopt the following steps:

1. Determine the required test distance according to the application requirements (material size, water meter installation space, etc.);

2. Refer to (Formula 8) and (Formula 22) to select radar operating frequencies f ₁ and f ₂ . Considering the system operating bandwidth, f ₁ and f ₂ are generally above the Ku frequency band; select the beacon switch modulation frequency, and its value should be Much higher than the Doppler frequency generated by the sample movement in the test environment, generally 10 ~ 100kHz;

3. According to the installation and use requirements, design the radar antenna and beacon antenna form, usually choose the horn antenna, the antenna gain is 10 ~ 15dB;

4. According to the test distance determined in step 2 and the antenna gain determined in step 3, design the radar transmit power, receive noise figure and receiver noise bandwidth to ensure that the signal-to-noise ratio of the beacon signal received by the radar is greater than 40dB. The specific design can refer to the radar system equation;

5. According to the radar design parameters determined in step 4, build the radar host according to the block diagram shown in attached drawing 2; build the beacon device and other components according to attached drawing 3;

6. According to the test distance determined in step 2, the test sample placement method and the operation display requirements, design an integrated rack;

7. According to the working principle of the radar-type microwave water measuring instrument and the radar test data processing principle and system calibration principle of (formula 1) to (formula 40), design data processing software;

8. According to the operation display or test application automatic control requirements of the radar microwave water meter, design a reasonable man-machine interface and interface with the upper computer and lower computer;

9. Carry out software and hardware system integration, and complete the construction of the radar microwave water measuring instrument system.

As described above, the present invention can be well realized.

Claims (4)

1. The microwave radar host for radar-type microwave water measuring instruments is characterized in that: it includes a transmitting unit for transmitting continuous single-frequency microwave signals, a power detection unit for continuous single-frequency microwave signals, and a continuous single-frequency microwave signal for normalization with beacon signals. Quadrature mixing unit for cross mixing; the quadrature mixing unit outputs the intermediate frequency in-phase component signal and the intermediate frequency quadrature component signal to the data processing terminal; in the data processing terminal, based on the mixed medium containing material medium, water and air The complex permittivity model and the dielectric relaxation model of water use the amplitude information of the in-phase component signal and the quadrature component signal on the frequency of two continuous single-frequency microwave signals and the pre-stored system calibration parameters to process and obtain the material medium in the mixed medium And water weight ratio, so as to obtain the water content of the material body, that is, the weight of water accounts for the weight percentage of the water-containing material. 2. The microwave radar host for radar type microwave water measuring instrument according to claim 1, characterized in that: the transmitting unit comprises a sequentially linked switch driver A, a single-pole double-throw switch, a directional coupler A, a transmitting Antenna; the switch driver A is controlled by the frequency selection signal, the SPDT switch is controlled by the switch driver A, and the directional coupler A receives the output signal of the SPDT switch to generate a continuous single-frequency microwave signal to the transmitting antenna, and the SPDT switch returns Controlled by the phase-locked frequency source A and the phase-locked frequency source B, both the phase-locked frequency source A and the phase-locked frequency source B receive the vibration signal of the crystal oscillator, and the crystal oscillator sends a reference clock signal at the same time. 3. The microwave radar host for radar type microwave water measuring instrument according to claim 1, characterized in that: the power detection unit comprises a directional coupler B, a wave detector, and an amplifier connected in sequence, and the directional coupler B receives and transmits The unit's continuous single-frequency microwave signal. 4. the microwave radar host computer that is used for radar type microwave water measuring instrument according to claim 1, is characterized in that: quadrature frequency mixing unit comprises receiving antenna, low-noise amplifier, quadrature mixer of sequential link, and quadrature The cross-mixer receives the continuous single-frequency microwave signal of the transmitting unit or the continuous single-frequency microwave signal of the receiving power detection unit, and the receiving antenna receives the beacon signal, and the beacon signal is amplified by the low-noise amplifier and passed through the quadrature The single-frequency microwave signal is subjected to quadrature mixing, and the quadrature mixer outputs 2 quadrature mixing signals, one quadrature mixing signal is output to the intermediate frequency filter A, and then the intermediate frequency in-phase component signal is output through the intermediate frequency amplifier A, and the other The quadrature mixing signal is output to the intermediate frequency filter B, and then the intermediate frequency quadrature component signal is output through the intermediate frequency amplifier B.