CN115267347A - High-sensitivity dual-band microwave sensor for measuring low dielectric constant - Google Patents
High-sensitivity dual-band microwave sensor for measuring low dielectric constant Download PDFInfo
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- 229910052751 metal Inorganic materials 0.000 claims abstract description 31
- 239000000758 substrate Substances 0.000 claims abstract description 14
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- 238000005259 measurement Methods 0.000 claims abstract description 8
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 7
- 229910052802 copper Inorganic materials 0.000 claims abstract description 7
- 239000010949 copper Substances 0.000 claims abstract description 7
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
- G01R27/2688—Measuring quality factor or dielectric loss, e.g. loss angle, or power factor
- G01R27/2694—Measuring dielectric loss, e.g. loss angle, loss factor or power factor
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Abstract
The invention discloses a high-sensitivity dual-band microwave sensor for measuring a low dielectric constant, which consists of three layers, namely two layers of metal copper and one layer of dielectric substrate, wherein a metal patch layer, a dielectric layer and a ground layer are respectively arranged from top to bottom; the rectangular patch is added to the top of the resonance unit, so that the interaction between a field and a material is enhanced, the local field is obviously increased, and the measurement sensitivity is improved; the invention has two resonance points, can realize dual-band operation, has no-load frequency of 2GHz and 5.4GHz, and can simultaneously measure the dielectric constant of a sample to be Measured (MUT) in two working frequency bands. In addition, since both bands have high sensitivity, a small dielectric constant MUT can be measured.
Description
Technical Field
The invention belongs to the technical field of microwave sensors, and particularly relates to a high-sensitivity dual-band microwave sensor for measuring low dielectric constant.
Background
The dielectric constant is an important physical parameter for measuring the performance of the dielectric material, and is also a core basic parameter in the field of microwave electronics, and directly determines the propagation characteristic of electromagnetic waves in a substrate material. The dielectric properties of microwave substrate materials used in different circuits are different, so determining the dielectric constant of a material is a fundamental guarantee for designing microwave devices and circuits. At present, the measurement of dielectric constant of materials plays a very important role in various scientific fields. For example, in food testing, contaminants in food such as milk and oil can be detected by measuring the dielectric constant. In the medical industry, diabetic patients can be monitored for blood glucose levels, locating tumors that are hidden in healthy tissue and muscle. In the field of biology, the method can be used for thickness analysis of biological tissues and the like, and can also be used for label-free detection of biomolecules. In military, the dielectric constant measurement technology is also widely applied to the manufacture and detection of radar and various special materials. For the above cases, most of them require non-destructive and accurate measurement of the material. Various dielectric constant measurement methods have been developed, including a resonant cavity method, a microstrip line method, a free space method, a resonance method, and the like. The resonance-based microwave measurement method is unique among various methods due to the advantages of low cost, high sensitivity, nondestructive measurement, miniaturization and the like.
In recent years, scientists have developed a number of microwave sensors based on resonance. Most sensors are based on Split Ring Resonators (SRRs) or Complementary Split Ring Resonators (CSRRs). Such sensors have high accuracy and sensitivity, and they have high accuracy in measuring a MUT having a large dielectric constant (typically in the range of 1-10), but when the variation in the dielectric constant of the MUT is small (e.g., in the range of 1-2), the resulting shift in the resonant frequency is small, and thus the sensor cannot accurately detect the dielectric constant of the MUT. The main reason for this is that the sensitivity of the sensor is not high enough.
Disclosure of Invention
The invention aims to provide a high-sensitivity dual-band microwave sensor for measuring low dielectric constant, which has two working frequency bands of 2GHz and 5.4GHz respectively. Both bands have high sensitivity and can be used for measuring a small dielectric constant measured sample (MUT).
In order to solve the technical problems, the invention is realized by the following technical scheme:
a high-sensitivity dual-band microwave sensor for measuring a low dielectric constant is composed of two layers of metal copper and a layer of dielectric substrate, wherein a metal patch layer, a dielectric layer and a ground layer are respectively arranged from top to bottom; the metal patch layer comprises a microstrip transmission line and a square metal patch, a square spiral unit is etched on the grounding layer, the square spiral unit is used for generating resonance, and the square metal patch is used for being coupled with the square spiral unit.
Further, the thickness of the metal patch layer and the ground layer is 0.017mm, and the metal material is copper.
Further, the dimensions of the dielectric layer are 30mm × 25mm × 1.6mm, and an FR4 material with a dielectric constant of 4.4 and a loss tangent of 0.02 is used.
Furthermore, the size of the square spiral structure etched in the ground layer is 6mm multiplied by 6mm, the square spiral structure is composed of 8 grooved rectangles, the width of each grooved rectangle is 0.5mm, and the distance between adjacent grooved rectangles is 0.5mm.
Furthermore, the size of the microstrip transmission line in the metal patch layer is 3mm × 30mm × 0.017mm, and the size of the square metal patch is 6mm × 6mm × 0.017mm.
Furthermore, the square metal patch and the grooved square spiral structure are both square, and the central points of the square metal patch and the grooved square spiral structure are symmetrical about the dielectric substrate.
Further, during measurement, the MUT is placed right above the grooved square spiral structure, and the air gap between the grooved square spiral structure and the grooved square spiral structure is reduced as much as possible.
The invention has the following beneficial effects:
1. according to the invention, two working frequency bands are generated through a single square spiral unit, wherein the working frequency bands are respectively 2GHz and 5.4GHz, the dielectric constants of the MUT can be measured through the two frequency bands, the S21 of the two frequency bands is effectively increased by adding one square patch corresponding to CSSR at one side of the microstrip line, the S21 of the first frequency band is increased by 11.7%, great help is provided for determining the loss tangent of the MUT, and when the thickness of the MUT is more than 2mm, the response of the sensor under each thickness is almost unchanged.
2. The advantage of the present invention over existing microwave sensors is that by finding that both bands of the present invention have high sensitivity, and the second band has a sensitivity of up to 8.8%, the real part of the dielectric constant of the MUT can be determined more accurately. Therefore, the structure can measure MUT with the dielectric constant within the range of 1-10, and can also measure MUT with smaller discrimination between the dielectric constants of 1-2, thereby improving the precision of dielectric constant measurement.
Of course, it is not necessary for any product in which the invention is practiced to achieve all of the above-described advantages at the same time.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings 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 that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic diagram of a front structure of a substrate of a high-sensitivity dual-band microwave sensor for measuring a low dielectric constant according to the present invention;
FIG. 2 is a schematic diagram of a reverse structure of a substrate of a high-sensitivity dual-band microwave sensor for measuring a low dielectric constant according to the present invention;
FIG. 3 is a comparison diagram of S21 before and after adding a square metal patch of the high-sensitivity dual-band microwave sensor for measuring low dielectric constant of the present invention;
FIG. 4 is a S21 diagram (at 2 GHz) of a high-sensitivity dual-band microwave sensor for measuring different dielectric constants according to the present invention;
FIG. 5 is a S21 diagram (at 5.4 GHz) of a high-sensitivity dual-band microwave sensor for measuring different dielectric constants with low dielectric constant according to the present invention;
FIG. 6 shows ε 'of a high-sensitivity dual-band microwave sensor for measuring low dielectric constant according to the present invention'r'3 and ε'rLoss tangent at time =8 and S21 amplitude dependence plot (at 2 GHz);
FIG. 7 shows ε 'of a high-sensitivity dual-band microwave sensor for measuring low dielectric constant according to the present invention'r'3 and ε'rGraph of loss tangent value at 8 times versus S21 amplitude (at 5.4 GHz);
FIG. 8 is a graph showing the relationship between the dielectric constant and the resonant frequency of a high-sensitivity dual-band microwave sensor for measuring a low dielectric constant according to the present invention (at 2 GHz);
FIG. 9 is a graph showing the relationship between the dielectric constant and the resonant frequency of a high-sensitivity dual-band microwave sensor for measuring a low dielectric constant according to the present invention (at 5.4 GHz);
FIG. 10 is a graph showing the relationship between the loss tangent and the Q value at 2GHz for different MUT thicknesses of a high-sensitivity dual-band microwave sensor with low dielectric constant according to the present invention;
FIG. 11 is a graph showing the relationship between loss tangent and Q value (at 2 GHz) for different dielectric constants of a high-sensitivity dual-band microwave sensor for measuring a low dielectric constant according to the present invention;
FIG. 12 is a fitting model diagram (at 2 GHz) of a high-sensitivity dual-band microwave sensor for measuring low dielectric constant according to the present invention.
FIG. 13 is a diagram of a high sensitivity dual-band microwave sensor for measuring low dielectric constant according to the present invention.
Fig. 14 is a diagram of a measuring apparatus of a high-sensitivity dual-band microwave sensor for measuring a low dielectric constant according to the present invention.
In the drawings, the reference numbers indicate the following list of parts:
1. a metal patch layer; 2. a dielectric layer; 3. and a ground layer.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it is to be understood that the terms "upper", "middle", "outer", "inner", "lower", "around", and the like, indicate an orientation or positional relationship for the convenience of description and simplicity of description, but do not indicate or imply that the referenced components or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus are not to be construed as limiting the present invention.
As shown in fig. 1, which is a schematic structural diagram of the front side of a substrate of a high-sensitivity dual-band microwave sensor for measuring a low dielectric constant of the present invention, the substrate is composed of two layers of metal copper and a layer of dielectric substrate, and the metal patch layer 1, the dielectric layer 2 and the ground layer 3 are respectively arranged from top to bottom; the thickness of the metal patch layer 1 and the ground layer 3 is 0.017mm, and the metal material is copper; the size of the dielectric layer 2 is 30mm multiplied by 25mm multiplied by 1.6mm, and an FR4 material with the dielectric constant of 4.4 and the loss tangent value of 0.02 is adopted; the size of the microstrip transmission line in the metal patch layer 1 is 3mm multiplied by 30mm multiplied by 0.017mm, and the size of the square metal patch is 6mm multiplied by 0.017mm; the square metal patch and the grooved square spiral structure are both square, and the central points of the square metal patch and the grooved square spiral structure are symmetrical about the dielectric substrate.
As shown in fig. 2, which is a schematic view of the reverse structure of the substrate of the high-sensitivity dual-band microwave sensor for measuring low dielectric constant of the present invention, as shown in the figure, the size of the square spiral structure etched in the ground layer 3 is 6mm × 6mm, and the square spiral structure is composed of 8 grooved rectangles, the width of each grooved rectangle is 0.5mm, and the distance between adjacent grooved rectangles is 0.5mm;
as shown in fig. 3, the improved structure has increased S21 amplitude for both bands, where S21 is increased by 2.8dB at 2GHz, by 11.7%, and the quality factor reaches 207.
As shown in fig. 4, in the first frequency band, as the dielectric constant of the MUT gradually increases, the resonance frequency gradually shifts to a low frequency.
As shown in fig. 5, in the second frequency band, as the dielectric constant of the MUT gradually increases, the resonant frequency gradually shifts to a low frequency, which is consistent with the change in fig. 4.
As shown in fig. 6, in the first frequency band, for the MUT with a fixed dielectric constant, when the loss tangent is gradually increased, the resonant frequency is not substantially shifted, but is merely changed with the S21 amplitude being decreased.
As shown in fig. 7, in the second frequency band, it is also illustrated that the loss tangent has substantially no influence on the frequency offset.
As shown in FIG. 8, in the first frequency band, when the thickness of the MUT is greater than 3mm, the relationship between the resonant frequency and the dielectric constant is substantially consistent, the dielectric constant of the MUT can be calculated from the first resonant frequency by fitting the equation, and the degree of fitting R is obtained2＞0.99。
As shown in FIG. 9, in the second frequency band, the relationship between the resonant frequency and the dielectric constant is more consistent, which means that the influence of MUY on the fitting relationship at the second frequency band is less, the dielectric constant of MUT can be calculated from the second resonant frequency by fitting equation, and the fitting degree R is higher2＞0.99。
As shown in FIG. 10, the relationship between the loss tangent and the Q value is shown for different thicknesses.
As shown in FIG. 11, the loss tangent and the Q value are shown in the graph for different dielectric constants.
As shown in fig. 12, a three-dimensional coordinate model was created using the dielectric constant, the loss tangent, and the Q value as variables in common.
Fig. 13 is a schematic diagram of the microwave sensor.
Fig. 14 shows a measuring apparatus of the present microwave sensor.
In the description herein, references to the description of "one embodiment," "an example," "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The preferred embodiments of the invention disclosed above are intended to be illustrative only. The preferred embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention. The invention is limited only by the claims and their full scope and equivalents.
Claims (7)
1. A high-sensitivity dual-band microwave sensor for measuring low dielectric constant is characterized in that: the microwave sensor consists of two layers of metal copper and a layer of dielectric substrate, and comprises a metal patch layer (1), a dielectric layer (2) and a ground layer (3) from top to bottom; the metal patch layer (1) comprises a microstrip transmission line and a square metal patch, a square spiral unit is etched on the ground layer (3) and used for generating resonance, and the square metal patch is used for being coupled with the square spiral unit.
2. The high-sensitivity dual-band microwave sensor for measuring a low dielectric constant of claim 1, wherein: the thickness of the metal patch layer (1) and the ground layer (3) is 0.017mm, and the metal material is copper.
3. The high-sensitivity dual-band microwave sensor for measuring a low dielectric constant of claim 1, wherein: the size of the dielectric layer (2) is 30mm multiplied by 25mm multiplied by 1.6mm, and an FR4 material with the dielectric constant of 4.4 and the loss tangent value of 0.02 is adopted.
4. The high-sensitivity dual-band microwave sensor for measuring a low dielectric constant of claim 1, wherein: the size of a square spiral structure etched in the grounding layer (3) is 6mm multiplied by 6mm, the square spiral structure is composed of 8 sections of grooved rectangles, the width of each section of grooved rectangle is 0.5mm, and the distance between adjacent grooved rectangles is 0.5mm.
5. The high-sensitivity dual-band microwave sensor for measuring a low dielectric constant of claim 1, wherein: the size of the microstrip transmission line in the metal patch layer (1) is 3mm multiplied by 30mm multiplied by 0.017mm, and the size of the square metal patch is 6mm multiplied by 0.017mm.
6. The high-sensitivity dual-band microwave sensor for measuring a low dielectric constant of claim 1, wherein: the square metal patch and the grooved square spiral structure are both square, and the central points of the square metal patch and the grooved square spiral structure are symmetrical relative to the dielectric substrate.
7. The high-sensitivity dual-band microwave sensor for measuring a low dielectric constant of claim 1, wherein: during measurement, the MUT is placed right above the grooved square spiral structure, and the air gap between the grooved square spiral structure and the grooved square spiral structure is reduced as much as possible.
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| CN112782486A (en) * | 2021-01-26 | 2021-05-11 | 南京邮电大学 | Multi-frequency-point dielectric constant measuring device based on stepped impedance resonance structure |
| CN113640587A (en) * | 2021-08-26 | 2021-11-12 | 安徽师范大学 | Dual-band lossless dielectric constant measuring sensor based on spiral resonator |
| CN114545094A (en) * | 2022-04-08 | 2022-05-27 | 河南师范大学 | High-sensitivity microwave sensor for measuring dielectric constant of material |
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2022
- 2022-06-08 CN CN202210642902.XA patent/CN115267347A/en active Pending
Patent Citations (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20020053959A1 (en) * | 2000-02-24 | 2002-05-09 | Murata Manufacturing Co., Ltd. | Dual mode band-pass filter |
| US20090058731A1 (en) * | 2007-08-30 | 2009-03-05 | Gm Global Technology Operations, Inc. | Dual Band Stacked Patch Antenna |
| CN203351744U (en) * | 2013-06-28 | 2013-12-18 | 中国计量学院 | Square spiral double-frequency microstrip antenna |
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