A method, system and device for measuring liquid electromagnetic parameters in the millimeter wave frequency band

Abstract

The present invention discloses a method, system and device for measuring electromagnetic parameters of liquid in the millimeter wave frequency band. The present invention adopts a time domain window method to suppress the interference caused by the reflected wave at the interface between liquid and air, and obtains the transmission coefficient S of millimeter waves when passing through liquids of different depths. 21 Time domain curve, convert the time domain curve into frequency domain curve, obtain the amplitude and phase of each frequency point, according to the liquid Dk value and S 21 Phase relationship and Df value and S 21 The electromagnetic parameters of the liquid are calculated by inverting the relationship between the amplitude and the amplitude. This measurement method does not require a complicated calibration process and is applicable to liquids with Dk values ​​less than 12. It can handle liquids with extremely low Df values ​​(less than one thousandth), and can achieve accurate measurement of the electromagnetic parameters of coolants and other related liquid materials in the millimeter wave frequency band.

Description

Technical Field

[0001] The present invention relates to a method, system and device for measuring electromagnetic parameters of liquid in the millimeter wave frequency band, and belongs to the field of microwave radio frequency technology. Background Art

[0002] Accurately determining the electromagnetic parameters of liquid materials within specific operating frequency bands is crucial in many applications. For example, in recent years, with the development of data centers, high-performance computing (HPC), edge computing, and artificial intelligence infrastructure, immersion cooling technology has become widely used. In these scenarios, all computing hardware systems are completely immersed in coolant to achieve efficient heat dissipation.

[0003] Commonly used coolants, such as fluorinated compounds and synthetic oils, exhibit different electromagnetic properties than air, which can significantly impact the electrical performance of high-speed interconnect components (such as slots and connectors). The coolant's higher dielectric constant can lead to decreased component impedance, increased insertion loss, and lower resonant frequency, adversely impacting high-speed link performance. Therefore, at microwave frequencies, coolants are expected to have a low dielectric constant (i.e., Dk value, approximately 2) and dielectric loss tangent (also known as dissipation factor, Df value, less than 0.02) to ensure optimal system operation.

[0004] Currently, methods for measuring the electromagnetic parameters of liquids in the millimeter-wave band primarily include the resonator method, the open-end coaxial probe method, and the free-space method. However, while the resonator method is suitable for electromagnetic parameter testing at some millimeter-wave frequencies, its structure limits the expansion of test frequencies to higher millimeter-wave frequencies. The open-end coaxial probe method covers frequencies up to 50 GHz but is less suitable for liquids with low dielectric constants and low dielectric loss tangents, such as coolants. Furthermore, the free-space technology solutions mentioned in existing literature have also failed to fully meet the demand for high-precision liquid electromagnetic parameter measurements in the millimeter-wave band. Summary of the Invention

[0005] The present invention provides a method, system and device for measuring liquid electromagnetic parameters in the millimeter wave frequency band, which solve the problems disclosed in the background technology.

[0006] According to one aspect of the present disclosure, a method for measuring liquid electromagnetic parameters in the millimeter wave frequency band is provided, comprising:

[0007] Get the first transmission coefficient S 21 The amplitude and phase of each frequency point in the frequency domain curve; among them, the first transmission coefficient S 21 The frequency domain curve is calculated based on the first transmission coefficient S in the time domain window. 21 The first transmission coefficient S is obtained by time domain curve conversion. 21 The time domain curve is the transmission coefficient S of the millimeter wave propagating through the first path21 Time domain curve; in the first path, the millimeter wave emitted by the transmitting unit penetrates the liquid to be measured at a preset depth h1 and is reflected at the reflecting unit, and the reflected millimeter wave penetrates the liquid to be measured and reaches the receiving unit;

[0008] Get the second transmission coefficient S 21 The amplitude and phase of each frequency point in the frequency domain curve; among them, the second transmission coefficient S 21 The frequency domain curve is based on the second transmission coefficient S in the time domain window 21 The second transmission coefficient S is obtained by converting the time domain curve. 21 The time domain curve is the transmission coefficient S of the millimeter wave propagating through the second path 21 Time domain curve; in the second path, the millimeter wave emitted by the transmitting unit penetrates the liquid to be measured at a preset depth h2 and is reflected at the reflecting unit, and the reflected millimeter wave penetrates the liquid to be measured and reaches the receiving unit;

[0009] According to the first transmission coefficient S 21 The phase and second transmission coefficient S of each frequency point in the frequency domain curve 21 The phase of each frequency point in the frequency domain curve is used to calculate the Dk value of the liquid to be tested at each frequency point at a preset depth;

[0010] According to the Dk value of the liquid to be tested at each frequency point at the preset depth, the first transmission coefficient S 21 The amplitude of each frequency point in the frequency domain curve and the second transmission coefficient S 21 The amplitude of each frequency point in the frequency domain curve is used to calculate the Df value of the liquid to be tested at each frequency point at a preset depth.

[0011] Furthermore, the Dk value of the liquid to be tested at each frequency point is calculated using the following formula:

[0012]

[0013] Where, is the Dk value of the liquid to be tested at the i-th frequency point, are the second transmission coefficient S 21 The phase and first transmission coefficient S of the i-th frequency point in the frequency domain curve 21 The phase of the i-th frequency point in the frequency domain curve, c is the speed of the millimeter wave in vacuum, f is the frequency of the transmitted millimeter wave, and Δh=h2-h1 is the depth difference of the liquid to be measured.

[0014] Furthermore, the Df value of the liquid to be tested at each frequency point is calculated using the following formula:

[0015]

[0016] Where, is the Dk value of the liquid to be tested at the i-th frequency point, Df iis the Df value of the liquid to be measured at the i-th frequency point, f is the frequency of the transmitted millimeter wave, μ0 and ε0 are the magnetic permeability and dielectric constant in vacuum respectively, α is the attenuation constant of the liquid to be measured, is the first transmission coefficient S 21 The amplitude of the i-th frequency point in the frequency domain curve, is the second transmission coefficient S 21 The amplitude of the i-th frequency point in the frequency domain curve, Δh = h2 - h1, is the depth difference of the liquid to be measured.

[0017] Furthermore, the first transmission coefficient S 21 Time domain curve and the second transmission coefficient S 21 The time domain peak of the frequency domain curve is the center time of the time domain window, and the width of the time domain window should be much smaller than 2Δt; where Δt is the time difference between the time domain peak and the millimeter wave reflected by the surface of the liquid to be measured.

[0018] Furthermore, the method also includes: adjusting the preset depths h1 and h2 multiple times to obtain Dk values ​​and Df values ​​corresponding to different depths, taking the average of all Dk values ​​as the final Dk value of the liquid to be tested at each frequency point, and taking the average of all Df values ​​as the final Df value of the liquid to be tested at each frequency point.

[0019] According to another aspect of the present disclosure, a system for measuring liquid electromagnetic parameters in the millimeter wave frequency band is provided, comprising:

[0020] The first acquisition module acquires the first transmission coefficient S 21 The amplitude and phase of each frequency point in the frequency domain curve; among them, the first transmission coefficient S 21 The frequency domain curve is calculated based on the first transmission coefficient S in the time domain window. 21 The first transmission coefficient S is obtained by time domain curve conversion. 21 The time domain curve is the transmission coefficient S of the millimeter wave propagating through the first path 21 Time domain curve; in the first path, the millimeter wave emitted by the transmitting unit penetrates the liquid to be measured at a preset depth h1 and is reflected at the reflecting unit, and the reflected millimeter wave penetrates the liquid to be measured and reaches the receiving unit;

[0021] The second acquisition module acquires the second transmission coefficient S 21 The amplitude and phase of each frequency point in the frequency domain curve; among them, the second transmission coefficient S 21 The frequency domain curve is based on the second transmission coefficient S in the time domain window 21 The second transmission coefficient S is obtained by converting the time domain curve. 21 The time domain curve is the transmission coefficient S of the millimeter wave propagating through the second path 21 Time domain curve; in the second path, the millimeter wave emitted by the transmitting unit penetrates the liquid to be measured at a preset depth h2 and is reflected at the reflecting unit, and the reflected millimeter wave penetrates the liquid to be measured and reaches the receiving unit;

[0022] The Dk value calculation module calculates the value of the first transmission coefficient S 21 The phase and second transmission coefficient S of each frequency point in the frequency domain curve 21 The phase of each frequency point in the frequency domain curve is used to calculate the Dk value of the liquid to be tested at each frequency point at a preset depth;

[0023] The Df value calculation module is based on the Dk value of the liquid to be tested at each frequency point, the first transmission coefficient S 21 The amplitude of each frequency point in the frequency domain curve and the second transmission coefficient S 21 The amplitude of each frequency point in the frequency domain curve is used to calculate the Df value of the liquid to be tested at each frequency point.

[0024] Furthermore, the system also includes an averaging module, which is configured to: adjust the preset depths h1 and h2 multiple times to obtain Dk values ​​and Df values ​​corresponding to different depths, and use the average of all Dk values ​​as the final Dk value of the liquid to be tested at each frequency point, and use the average of all Df values ​​as the final Df value of the liquid to be tested at each frequency point.

[0025] According to another aspect of the present disclosure, there is provided a device for measuring electromagnetic parameters of liquid in the millimeter wave frequency band, comprising a computing terminal, a vector network analyzer, a transmitting antenna, a receiving antenna, and a liquid container;

[0026] The inner bottom surface of the liquid container is a reflective surface;

[0027] The transmitting antenna and the receiving antenna are located at a far-field position above the opening of the liquid container, and the transmitting end of the transmitting antenna and the receiving end of the receiving antenna are directed toward the opening of the liquid container;

[0028] The vector network analyzer controls the transmitting antenna to transmit millimeter waves and controls the receiving antenna to receive reflected millimeter waves, and obtains a first transmission coefficient S according to the transmitted millimeter waves and the reflected millimeter waves. 21 The amplitude and phase of each frequency point in the frequency domain curve, as well as the second transmission coefficient S 21 The amplitude and phase of each frequency point in the frequency domain curve;

[0029] The computing terminal adopts the liquid electromagnetic parameter measurement method in the millimeter wave frequency band to measure the liquid electromagnetic parameters in the millimeter wave frequency band.

[0030] The beneficial effects achieved by the present invention are as follows: the present invention uses a time domain window to suppress the interference caused by the reflected wave on the liquid surface, and obtains the transmission coefficient S of the millimeter wave when it passes through liquids of different depths. 21The time domain curve is converted into a frequency domain curve to obtain the amplitude and phase of each frequency point. The electromagnetic parameters of the liquid in the millimeter wave band are measured based on the amplitude and phase. This measurement method does not require a complex calibration process and is applicable to liquids with Dk values ​​less than 12. It can also handle liquids with extremely low Df values ​​(less than one thousandth). It can achieve accurate measurement of the electromagnetic parameters of coolants and other related liquid materials in the millimeter wave band. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A first flow chart of a method for measuring electromagnetic parameters of liquids in the millimeter wave frequency band;

[0032] Figure 2 A second flow chart of the method for measuring liquid electromagnetic parameters in the millimeter wave frequency band;

[0033] Figure 3 This is the first block diagram of the liquid electromagnetic parameter measurement system in the millimeter wave frequency band;

[0034] Figure 4 The second block diagram of the liquid electromagnetic parameter measurement system in the millimeter wave band

[0035] Figure 5 This is a schematic diagram of the structure of the liquid electromagnetic parameter measurement device in the millimeter wave frequency band. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. It is obvious that the embodiments described are only part of the embodiments of the present disclosure, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present disclosure and its application or use. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present disclosure.

[0037] Unless specifically stated otherwise, the relative arrangement of components and steps, the numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present disclosure.

[0038] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0039] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0040] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0041] It should be noted that like symbols and letters refer to like items in the following figures, so once an item is defined in one figure, it does not need to be further discussed in subsequent figures.

[0042] In order to solve the problem that existing methods cannot accurately measure the electromagnetic parameters of liquids, especially liquids with low dielectric constant and low dielectric loss tangent, in the millimeter wave frequency band, the present invention provides a method for measuring the electromagnetic parameters of liquids in the millimeter wave frequency band, aiming to obtain the millimeter wave transmission coefficient S through a first path and a second path. 21 , based on the millimeter wave transmission coefficient S 21 Electromagnetic parameter measurement is performed; wherein, in the first path, the millimeter wave emitted by the transmitting part penetrates the liquid to be measured at a preset depth h1 and is reflected by the reflecting part, and the reflected millimeter wave penetrates the liquid to be measured and reaches the receiving part; in the second path, the millimeter wave emitted by the transmitting part penetrates the liquid to be measured at a preset depth h2 and is reflected by the reflecting part, and the reflected millimeter wave penetrates the liquid to be measured and reaches the receiving part.

[0043] See Figure 1 , Figure 1 This is a first flow chart of a method for measuring electromagnetic parameters of liquids in a millimeter wave frequency band provided by the present invention. The method for measuring electromagnetic parameters of liquids in a millimeter wave frequency band can be performed by an electromagnetic parameter measuring device. The method for measuring electromagnetic parameters of liquids in a millimeter wave frequency band can at least include the following steps 1 to 4:

[0044] Step 1 of the embodiment is to obtain a first transmission coefficient S 21 The amplitude and phase of each frequency point in the frequency domain curve; among them, the first transmission coefficient S 21 The frequency domain curve is calculated based on the first transmission coefficient S in the time domain window. 21 The first transmission coefficient S is obtained by time domain curve conversion. 21 The time domain curve is the transmission coefficient S of the millimeter wave propagating through the first path 21 Time domain curve; in the first path, the millimeter wave emitted by the transmitting unit penetrates the liquid to be measured at a preset depth h1 and is reflected at the reflecting unit. The reflected millimeter wave penetrates the liquid to be measured and reaches the receiving unit.

[0045] Step 2 of the embodiment, obtaining the second transmission coefficient S 21 The amplitude and phase of each frequency point in the frequency domain curve; among them, the second transmission coefficient S 21 The frequency domain curve is based on the second transmission coefficient S in the time domain window 21 The second transmission coefficient S is obtained by converting the time domain curve. 21The time domain curve is the transmission coefficient S of the millimeter wave propagating through the second path 21 Time domain curve; in the second path, the millimeter wave emitted by the transmitting unit penetrates the liquid to be measured at a preset depth h2 and is reflected at the reflecting unit, and the reflected millimeter wave penetrates the liquid to be measured and reaches the receiving unit.

[0046] It should be noted that in the above steps 1 and 2, the first path and the second path are almost the same, that is, the position of the transmitting part, the position of the receiving part, and the position of the reflecting part are completely consistent, and the transmitting direction and the receiving direction of the millimeter wave are also completely consistent. The only difference is that the liquid depth h1 in the first path is increased to h2. This can prevent inaccurate parameter measurement due to different conditions and ensure the accuracy of parameter measurement.

[0047] The time domain windows in steps 1 and 2 above use time domain windows of the same time width. In some embodiments, the time domain window width can be set according to the depth of the liquid. Assuming that the preset depth of the liquid is h, the time domain window width should be much smaller than twice the time Δt required for the electromagnetic wave to pass through the 2h path. It can be taken as one tenth of 2Δt, where Δt is the time difference between the time domain peak and the millimeter wave reflected from the surface of the liquid to be measured, that is, S 21 The time difference between the first reflected signal in front of the time domain peak on the curve and the time domain peak. This setting can ensure that the time domain window can filter out the reflected wave on the liquid surface from the received millimeter wave, thereby ensuring the purity of the received wave and improving the accuracy of the measurement result; and in the above steps, when obtaining the first and second transmission coefficients S in the time domain window 21 When observing the time domain curve, you can first observe the time domain peak of the curve and use the time of the time domain peak as the center time of the time domain window. The time corresponding to the time domain peak is exactly the transmission time of the required signal, so you can accurately obtain the required signal.

[0048] In step 3 of the embodiment, according to the first transmission coefficient S 21 The phase and second transmission coefficient S of each frequency point in the frequency domain curve 21 The phase of each frequency point in the frequency domain curve is used to calculate the Dk value of the liquid to be tested at each frequency point at a preset depth.

[0049] At a given frequency and propagation distance, the phase change is directly related to the Dk value of the propagation medium. Therefore, the above calculation of the Dk value of the liquid to be tested at each frequency point can be expressed as:

[0050]

[0051] Where, is the Dk value of the liquid to be tested at the i-th frequency point, are the second transmission coefficient S 21 The phase and first transmission coefficient S of the i-th frequency point in the frequency domain curve 21The phase of the i-th frequency point in the frequency domain curve, c is the speed of the millimeter wave in vacuum, f is the frequency of the transmitted millimeter wave, and Δh=h2-h1 is the depth difference of the liquid to be measured.

[0052] A time domain window is used to filter out the first reflected wave incident from the air to the liquid surface and the second and subsequent transmitted waves from the liquid to the air. Regardless of whether it is a low dielectric constant liquid or a high dielectric constant liquid, the transmission coefficient S of the millimeter wave passing through the liquid is 21 The phase is not affected by interference signals, so the Dk value of the liquid can be calculated with high accuracy.

[0053] In step 4 of the embodiment, according to the Dk value of the liquid to be tested at each frequency point, the first transmission coefficient S 21 The amplitude of each frequency point in the frequency domain curve and the second transmission coefficient S 21 The amplitude of each frequency point in the frequency domain curve is used to calculate the Df value of the liquid to be tested at each frequency point.

[0054] The second transmission coefficient S 21 With the first transmission coefficient S 21 The amplitude ratio reflects the attenuation of the millimeter wave propagating in the liquid for a distance of 2h, which is given by the following formula for the attenuation constant α. At the same time, the relationship between the attenuation constant and the Df value can be expressed by the following formula:

[0055] When testing the liquid at the preset depths h1 and h2, the attenuation constant α and the first and second transmission coefficients S 21 The magnitude of has the following relationship:

[0056]

[0057] The Df value of the liquid to be tested at different frequency points can be further calculated, which is given by the following formula:

[0058]

[0059] Where Df i is the Df value of the liquid to be measured at the i-th frequency point, μ0 and ε0 are the magnetic permeability and dielectric constant in vacuum respectively, α is the attenuation constant of the liquid to be measured, is the first transmission coefficient S 21 The amplitude of the i-th frequency point in the frequency domain curve, is the second transmission coefficient S 21 The amplitude of the i-th frequency point in the frequency domain curve.

[0060] It should be noted that the temperature drift of the instrument will have a certain impact on the measurement results of the liquid electromagnetic parameters. Therefore, in some embodiments, see Figure 2, the same liquid will be measured at different depths, that is, the preset depths h1 and h2 will be adjusted multiple times to obtain the Dk and Df values ​​corresponding to different depths. The average value of all Dk values ​​will be used as the final Dk value of the liquid to be tested at each frequency point, and the average value of all Df values ​​will be used as the final Df value of the liquid to be tested at each frequency point.

[0061] It should be noted that, for the convenience of measurement, it is assumed that the initial depth of the liquid to be measured is H. Each adjustment can increase the liquid to be measured on H. Assuming that it is increased N-1 times, N transmission coefficients S can be obtained. 21 Frequency domain curve, two different depth combinations are grouped together, such as the last depth combined with the first positive depth, the last depth combined with the second positive depth, etc., according to the transmission coefficient S corresponding to a group of depths 21 Frequency domain curves can be used to calculate a single Dk and Df value. Multiple Dk and Df values ​​can be calculated for multiple groups, and the final accurate Dk and Df values ​​are obtained by averaging. This averaging eliminates the effects of instrument temperature drift on liquid electromagnetic parameter measurements.

[0062] The method disclosed in the embodiment uses a time domain window to suppress the interference caused by the reflected wave on the liquid surface, and obtains the transmission coefficient S of the millimeter wave when it passes through liquids of different depths. 21 The time domain curve is converted into a frequency domain curve to obtain the amplitude and phase of each frequency point. The electromagnetic parameters of the liquid in the millimeter wave band are measured based on the amplitude and phase. This measurement method does not require a complex calibration process and is applicable to liquids with Dk values ​​less than 12. It can also handle liquids with extremely low Df values ​​(less than one thousandth). It can achieve accurate measurement of the electromagnetic parameters of coolants and other related liquid materials in the millimeter wave band.

[0063] See also Figure 3 , Figure 3 This is a first block diagram of a liquid electromagnetic parameter measurement system in the millimeter wave frequency band provided by the present invention. Figure 3 The system is a virtual system that can be loaded and executed by a computer device, which includes an electromagnetic parameter measurement device, Figure 3 The system may include a first acquisition module, a second acquisition module, a Dk value calculation module, and a Df value calculation module, which, when used to perform the above-mentioned liquid electromagnetic parameter measurement method in the millimeter wave frequency band, can:

[0064] A first acquisition module is used to obtain a first transmission coefficient S 21 The amplitude and phase of each frequency point in the frequency domain curve; among them, the first transmission coefficient S 21 The frequency domain curve is calculated based on the first transmission coefficient S in the time domain window. 21 The first transmission coefficient S is obtained by time domain curve conversion. 21The time domain curve is the transmission coefficient S of the millimeter wave propagating through the first path 21 Time domain curve; in the first path, the millimeter wave emitted by the transmitting unit penetrates the liquid to be measured at a preset depth h1 and is reflected at the reflecting unit. The reflected millimeter wave penetrates the liquid to be measured and reaches the receiving unit.

[0065] The second acquisition module is used to obtain the second transmission coefficient S 21 The amplitude and phase of each frequency point in the frequency domain curve; among them, the second transmission coefficient S 21 The frequency domain curve is based on the second transmission coefficient S in the time domain window 21 The second transmission coefficient S is obtained by converting the time domain curve. 21 The time domain curve is the transmission coefficient S of the millimeter wave propagating through the second path 21 Time domain curve; in the second path, the millimeter wave emitted by the transmitting unit penetrates the liquid to be measured at a preset depth h2 and is reflected at the reflecting unit, and the reflected millimeter wave penetrates the liquid to be measured and reaches the receiving unit.

[0066] The Dk value calculation module is used to calculate the Dk value according to the first transmission coefficient S 21 The phase and second transmission coefficient S of each frequency point in the frequency domain curve 21 The phase of each frequency point in the frequency domain curve is used to calculate the Dk value of the liquid to be tested at each frequency point.

[0067] The Df value calculation module is used to calculate the Dk value of the liquid to be tested at each frequency point, the first transmission coefficient S 21 The amplitude of each frequency point in the frequency domain curve and the second transmission coefficient S 21 The amplitude of each frequency point in the frequency domain curve is used to calculate the Df value of the liquid to be tested at each frequency point.

[0068] It should be noted that the temperature drift of the instrument will have a certain impact on the measurement results of the liquid electromagnetic parameters. Therefore, in some embodiments, see Figure 4 The system also includes an averaging module, configured to repeatedly adjust the preset depths h1 and h2 to obtain Dk and Df values ​​corresponding to different depths. The average of all Dk values ​​is used as the final Dk value of the measured liquid at each frequency point, and the average of all Df values ​​is used as the final Df value of the measured liquid at each frequency point. The averaging module eliminates the impact of instrument temperature drift on the liquid electromagnetic parameter measurement results.

[0069] The system disclosed in the embodiment uses a time domain window to suppress the interference caused by the reflected wave on the liquid surface (i.e., the interface with the air) and obtains the transmission coefficient S of the millimeter wave when it passes through liquids of different depths. 21The time domain curve is converted into a frequency domain curve to obtain the amplitude and phase of each frequency point. The electromagnetic parameters of the liquid in the millimeter wave band are measured based on the amplitude and phase. This measurement method does not require a complex calibration process and is applicable to liquids with a wide range of Dk values. It can also handle liquids with extremely low Df values ​​(less than one thousandth). It can achieve accurate measurement of the electromagnetic parameters of coolants and other related liquid materials in the millimeter wave band.

[0070] See also Figure 5 , Figure 5 This is a schematic diagram of a device for measuring liquid electromagnetic parameters in the millimeter wave frequency band provided by the present invention. Figure 5 The device can realize the above-mentioned method for measuring liquid electromagnetic parameters in the millimeter wave frequency band. In order to improve the measurement accuracy and reduce the interference of reflection and multipath to the test, the device can be installed in a semi-open darkroom. The device includes at least a computing terminal, a vector network analyzer, a transmitting antenna, a receiving antenna and a liquid container.

[0071] The liquid container is an open top container, and the bottom of the container is a reflective surface. In order to reduce the interference of reflection and multipath on the test, the rest of the container needs to be covered with absorbing materials except the reflective surface. 21 When the frequency domain curve is obtained, the liquid to be tested is injected into the container at different depths, and then millimeter waves are emitted toward the reflecting surface.

[0072] Figure 5 In the embodiment, the liquid container is a rectangular water tank placed on the base. The bottom of the water tank is a stainless steel plate, and the surrounding area is an acrylic plate covered with absorbing material. The length and width of the water tank can be 380mm and 280mm respectively. In order to facilitate the discharge of liquid, a drain valve can be installed at the bottom of one corner of the water tank.

[0073] The transmitting antenna and the receiving antenna are located in the far field position above the opening of the liquid container, that is, the transmitting antenna and the receiving antenna are at a distance from the reflecting surface that meets the far field condition, so that the millimeter waves reaching the liquid surface are incident in a plane wave state, and the transmitting end of the transmitting antenna and the receiving end of the receiving antenna are facing the opening of the liquid container.

[0074] Figure 5 In the example, the transmitting antenna and the receiving antenna are horn antennas. The far-field position is related to the parameters of the horn antenna. For example, if the wavelength corresponding to the highest test frequency supported by the horn antenna is λ and the maximum size of the antenna aperture is D, then the height H of the horn antenna from the water tank should satisfy H greater than or equal to 2D. 2 / λ; therefore, if the diameter of the horn antenna used in the device is 77mm and the maximum operating frequency is 40GHz, the distance that meets the far-field condition is 1581mm.

[0075] In order to facilitate the installation of transmitting antenna and receiving antenna, Figure 5An additional bracket is provided, through which the transmitting antenna and the receiving antenna are mounted above the opening of the liquid container.

[0076] The vector network analyzer is connected to the transmitting antenna and the receiving antenna to control the transmitting antenna to transmit millimeter waves and the receiving antenna to receive reflected millimeter waves, and obtains a first transmission coefficient S according to the transmitted millimeter waves and the reflected millimeter waves. 21 The amplitude and phase of each frequency point in the frequency domain curve, as well as the second transmission coefficient S 21 The amplitude and phase of each frequency point in the frequency domain curve.

[0077] The frequency, bandwidth, and number of measurement points can be set through the vector network analyzer, such as setting a 12GHz bandwidth and 60001 sweep points.

[0078] It should be noted that the actual phase value of the vector network analyzer needs to be 360n (n = 0, -1, -2, ...) is added to give the phase change relationship corresponding to the actual delay.

[0079] The computing terminal uses the above-mentioned method for measuring electromagnetic parameters of liquid in the millimeter wave frequency band to measure the electromagnetic parameters of liquid in the millimeter wave frequency band. The computing terminal here is a computer device.

[0080] The measurement process of the above device can be as follows:

[0081] S1) Calculate the far-field conditions based on the frequency and horn antenna aperture, and set up the horn antenna at the far-field position, at the same height and pointing vertically downward;

[0082] S2) Leveling the sink;

[0083] S3) Laying absorbing materials around the water tank and on the bracket;

[0084] S4) Set the test frequency, bandwidth, and measurement points. It is recommended to use a bandwidth of more than 12 GHz and a sweep point number of more than 30,000.

[0085] S5) Transmission coefficient S between two horn antennas 21 The curve is averaged;

[0086] S6) Determine the liquid volume so that the liquid depth after pouring into the water tank reaches a certain value, which is recommended to be no less than 10 mm, and set the time domain gate width, which is recommended to be no more than 10 ps;

[0087] S7) Add a volume of liquid V1 to the water tank, wait until the liquid surface spreads to the entire bottom of the water tank and calms down, set the time domain window center time and time width in the time domain measurement mode, open the time domain window, switch to the frequency domain, and save the transmission coefficient S 21 amplitude and phase.

[0088] S9) Increase the liquid volume to Vi (i = 2, 3, ..., N), wait until the liquid surface spreads to the entire bottom of the tank and calms down, reset the time domain window center time and time width in the time domain measurement mode, open the time domain window, switch to the frequency domain, and save the transmission coefficient S 21 The amplitude and phase of the signal are measured multiple times and the data is saved. The total number of measurements should be at least 6.

[0089] S10) The Nth measurement is paired with the previous 1 to N-1 measurements respectively to obtain measurement data at N-1 liquid depth differences. The calculation terminal uses the above-mentioned liquid electromagnetic parameter calculation formula in the millimeter wave frequency band to calculate the liquid electromagnetic parameters in the millimeter wave frequency band for each liquid volume, and calculates the average value of Dk and Df as the liquid electromagnetic parameter measurement value.

[0090] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for measuring liquid electromagnetic parameters in the millimeter wave frequency band, characterized in that: include: Get the first transmission coefficient S 21 The amplitude and phase of each frequency point in the frequency domain curve; among them, the first transmission coefficient S 21 The frequency domain curve is calculated based on the first transmission coefficient S in the time domain window. 21 The first transmission coefficient S is obtained by time domain curve conversion. 21 The time domain curve is the transmission coefficient S of the millimeter wave propagating through the first path 21 Time domain curve; in the first path, the millimeter wave emitted by the transmitting unit penetrates the liquid to be measured at a preset depth h1 and is reflected at the reflecting unit, and the reflected millimeter wave penetrates the liquid to be measured and reaches the receiving unit; Get the second transmission coefficient S 21 The amplitude and phase of each frequency point in the frequency domain curve; among them, the second transmission coefficient S 21 The frequency domain curve is based on the second transmission coefficient S in the time domain window 21 The second transmission coefficient S is obtained by converting the time domain curve. 21 The time domain curve is the transmission coefficient S of the millimeter wave propagating through the second path 21 Time domain curve; in the second path, the millimeter wave emitted by the transmitting unit penetrates the liquid to be measured at a preset depth h2 and is reflected at the reflecting unit, and the reflected millimeter wave penetrates the liquid to be measured and reaches the receiving unit; According to the first transmission coefficient S 21 The phase and second transmission coefficient S of each frequency point in the frequency domain curve 21 The phase of each frequency point in the frequency domain curve is used to calculate the Dk value of the liquid to be tested at each frequency point; According to the Dk value of the liquid to be tested at each frequency point, the first transmission coefficient S 21 The amplitude of each frequency point in the frequency domain curve and the second transmission coefficient S 21 The amplitude of each frequency point in the frequency domain curve is used to calculate the Df value of the liquid to be tested at each frequency point.

2. The method according to claim 1, characterized in that Calculate the Dk value of the liquid to be tested at each frequency point using the following formula: Where, is the Dk value of the liquid to be tested at the i-th frequency point, are the second transmission coefficient S 21 The phase and first transmission coefficient S of the i-th frequency point in the frequency domain curve 21 The phase of the i-th frequency point in the frequency domain curve, c is the speed of the millimeter wave in vacuum, f is the frequency of the transmitted millimeter wave, and Δh=h2-h1 is the depth difference of the liquid to be measured.

3. The method according to claim 1, characterized in that Calculate the Df value of the liquid to be tested at each frequency point using the following formula: Where, is the Dk value of the liquid to be tested at the i-th frequency point, Df i is the Df value of the liquid to be measured at the i-th frequency point, f is the frequency of the transmitted millimeter wave, μ0 and ε0 are the magnetic permeability and dielectric constant in vacuum respectively, α is the attenuation constant of the liquid to be measured, is the first transmission coefficient S 21 The amplitude of the i-th frequency point in the frequency domain curve, is the second transmission coefficient S 21 The amplitude of the i-th frequency point in the frequency domain curve, Δh = h2 - h1, is the depth difference of the liquid to be measured.

4. The method according to claim 1, wherein The first transmission coefficient S 21 Time domain curve and the second transmission coefficient S 21 The time domain peak of the frequency domain curve is the center time of the time domain window, and the width of the time domain window is much smaller than 2Δt; where Δt is the time difference between the time domain peak and the reflected wave of the liquid surface to be measured.

5. The method according to claim 1, wherein The method further comprises: Adjust the preset depths h1 and h2 multiple times to obtain the Dk and Df values ​​corresponding to different depths. The average of all Dk values ​​is used as the final Dk value of the liquid to be tested at each frequency point, and the average of all Df values ​​is used as the final Df value of the liquid to be tested at each frequency point.

6. A system for measuring liquid electromagnetic parameters in the millimeter wave frequency band, characterized in that: include: The first acquisition module acquires the first transmission coefficient S 21 The amplitude and phase of each frequency point in the frequency domain curve; among them, the first transmission coefficient S 21 The frequency domain curve is calculated based on the first transmission coefficient S in the time domain window. 21 The first transmission coefficient S is obtained by time domain curve conversion. 21 The time domain curve is the transmission coefficient S of the millimeter wave propagating through the first path 21 Time domain curve; in the first path, the millimeter wave emitted by the transmitting unit penetrates the liquid to be measured at a preset depth h1 and is reflected at the reflecting unit, and the reflected millimeter wave penetrates the liquid to be measured and reaches the receiving unit; The second acquisition module acquires the second transmission coefficient S 21 The amplitude and phase of each frequency point in the frequency domain curve; among them, the second transmission coefficient S 21 The frequency domain curve is based on the second transmission coefficient S in the time domain window 21 The second transmission coefficient S is obtained by converting the time domain curve. 21 The time domain curve is the transmission coefficient S of the millimeter wave propagating through the second path 21 Time domain curve; in the second path, the millimeter wave emitted by the transmitting unit penetrates the liquid to be measured at a preset depth h2 and is reflected at the reflecting unit, and the reflected millimeter wave penetrates the liquid to be measured and reaches the receiving unit; The Dk value calculation module calculates the value of the first transmission coefficient S 21 The phase and second transmission coefficient S of each frequency point in the frequency domain curve 21 The phase of each frequency point in the frequency domain curve is used to calculate the Dk value of the liquid to be tested at each frequency point at a preset depth; The Df value calculation module is based on the Dk value of the liquid to be tested at each frequency point, the first transmission coefficient S 21 The amplitude of each frequency point in the frequency domain curve and the second transmission coefficient S 21 The amplitude of each frequency point in the frequency domain curve is used to calculate the Df value of the liquid to be tested at each frequency point at a preset depth.

7. The system according to claim 6, characterized in that The system further includes an averaging module configured to: Adjust the preset depths h1 and h2 multiple times to obtain the Dk and Df values ​​corresponding to different depths. The average of all Dk values ​​is used as the final Dk value of the liquid to be tested at each frequency point, and the average of all Df values ​​is used as the final Df value of the liquid to be tested at each frequency point.

8. A device for measuring liquid electromagnetic parameters in the millimeter wave frequency band, characterized in that: It includes a computing terminal, a vector network analyzer, a transmitting antenna, a receiving antenna and a liquid container; The inner bottom surface of the liquid container is a reflective surface; The transmitting antenna and the receiving antenna are located at a far-field position above the opening of the liquid container, and the transmitting end of the transmitting antenna and the receiving end of the receiving antenna are directed toward the opening of the liquid container; The vector network analyzer controls the transmitting antenna to transmit millimeter waves and controls the receiving antenna to receive reflected millimeter waves, and obtains a first transmission coefficient S according to the transmitted millimeter waves and the reflected millimeter waves. 21 The amplitude and phase of each frequency point in the frequency domain curve, as well as the second transmission coefficient S 21 The amplitude and phase of each frequency point in the frequency domain curve; The computing terminal adopts the method described in any one of claims 1 to 5 to measure the electromagnetic parameters of the liquid in the millimeter wave frequency band.

Images