A microstrip antenna sensor

Abstract

The present invention discloses a microstrip antenna sensor. In the present invention, a coating with raised edges is covered on a measuring patch. When foreign matter causes a change in the environmental dielectric constant, electric field lines under the edge effect pass through the coating above the measuring patch and then enter into a dielectric base layer, thereby greatly reducing the fluctuation level of the sensor's resonant frequency as the environment changes, and improving the sensor's environmental foreign matter anti-interference capability and monitoring reliability.

Description

Technical Field

[0001] The invention relates to a microstrip antenna sensor and belongs to the field of metal structure safety monitoring based on the microstrip antenna sensor. Background Art

[0002] Metal structures are widely used in engineering fields such as machinery, metallurgy, roads and bridges, ocean and aerospace. The working environment is harsh, and crack initiation and expansion, deformation and stress concentration often occur in weak areas and complex stress areas. In order to ensure the healthy state of mechanical equipment during service, it is necessary to focus on parameters such as metal structure strain and cracks.

[0003] Microstrip antenna sensor is a new type of metal structure health monitoring sensor. It has the advantages of small size, light weight, simple manufacturing, low cost, easy filmization and passive wireless. In recent years, it has been widely used in the field of metal structure safety monitoring. However, in engineering, the metal structure parameter monitoring of microstrip antenna sensors is often affected by environmental foreign matter such as water, dust and ice, resulting in misjudgment, which greatly reduces the reliability of parameter monitoring of microstrip antenna sensors. Summary of the invention

[0004] The present invention provides a microstrip antenna sensor, which solves the problem disclosed in the background technology.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A microstrip antenna sensor comprises a dielectric substrate, a measuring patch, a covering layer and a feeder arranged on the dielectric substrate, wherein the feeder is connected to the measuring patch, the covering layer covers the measuring patch, and the edge of the covering layer is raised.

[0007] The feeder line is composed of multiple feeder line segments connected in series. The innermost feeder line segment is connected to the measurement patch, and the outermost feeder line segment is externally connected to the excitation port. The width of the same feeder line segment is consistent, and the width of the feeder line segment gradually decreases from the outside to the inside.

[0008] The width of the innermost feeder segment and the characteristic impedance satisfy the following relationship:

[0009]

[0010] Among them, Z c is the characteristic impedance of the innermost feeder segment, Z0 is the characteristic impedance of the excitation port, Z1 is the input impedance of the measurement patch, ε r is the relative dielectric constant, h is the thickness of the dielectric base, W l is the width of the innermost feeder segment.

[0011] The measurement patch size is designed according to different resonant frequencies.

[0012] A ground plate is also arranged at the bottom of the dielectric substrate.

[0013] The materials of the dielectric base layer and the cladding layer are both FR4.

[0014] The beneficial effects achieved by the present invention are as follows: the present invention covers the measuring patch with a coating having raised edges. When foreign matter causes a change in the environmental dielectric constant, the electric field lines under the edge effect pass through the coating above the measuring patch and then enter the dielectric base layer, thereby greatly reducing the fluctuation level of the sensor's resonant frequency with environmental changes, and improving the sensor's ability to resist interference from environmental foreign matter and monitoring reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of the present invention;

[0016] Figure 2(a) shows the effect of ice temperature on the resonant frequency of the uncoated microstrip antenna sensor;

[0017] FIG2( b ) shows the effect of ice temperature on the resonant frequency of the present invention;

[0018] Figure 3(a) shows the effect of dust on the resonant frequency of the uncoated microstrip antenna sensor;

[0019] FIG3( b ) shows the effect of dust on the resonant frequency of the present invention;

[0020] Figure 4(a) shows the effect of water temperature on the resonant frequency of the uncoated microstrip antenna sensor;

[0021] FIG. 4( b ) shows the effect of water temperature on the resonant frequency of the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0023] like Figure 1 As shown, a microstrip antenna sensor includes a ground plate 5, a dielectric base layer 1 fixed on the ground plate 5, a measuring patch 2 glued to the dielectric base layer 1 with glue, a covering layer 3 and a feed line 4, one end of the feed line 4 is connected to the measuring patch 2, and the other end is externally connected to the excitation port, the covering layer 3 covers the measuring patch 2, and the edge of the covering layer 3 is raised.

[0024] The ground plate 5 is a metal structure, and the material of the dielectric base layer 1 is an insulating material, which can be FR4. The size of the dielectric base layer 1 is designed based on the size of the ground plate 5, the measuring patch 2 and the feed line 4. Its length must be greater than the sum of the length of the feed line 4 and the width of the measuring patch 2, and its width must be greater than the length of the measuring patch 2. Generally, the length can be 130mm, the width can be 40mm, and the thickness can be 0.5~2mm, which can be 1mm.

[0025] The measuring patch 2 is made of good conductor copper material, that is, copper sheet. In theory, the thinner the copper sheet, the better, but the thinner it is, the higher the cost, so the thickness can be determined according to the actual situation. The coating 3 is made of FR4. The measuring patch 2 and the coating 3 are different in size. The former is small in size, and the latter is obtained by simulating the size of the measuring patch 2. The length of the coating 3 is ≥L+8mm, the width is ≥W+8mm, the thickness is ≥5.5mm, and the height of the protrusion is ≥0.2mm. It is ensured that the effective dielectric constant has a strong anti-interference ability after adding the edge protrusion of the coating 3 to improve the measurement accuracy; where L and W are the length and width of the measuring patch 2, respectively.

[0026] The size of the measuring patch 2 is generally designed according to different resonant frequencies. For example, if the resonant frequencies are 2.05 GHz and 2.54 GHz, the size of the measuring patch 2 can be designed as: length 35 mm, width 28 mm, thickness 0.035 mm. Based on the simulation software design optimization, the size of the coating 3 can be designed as: length 71 mm, width 42 mm, thickness 5.5 mm, and protrusion height 0.2 mm.

[0027] The above two sizes are only two representative sizes. In practice, the sizes of the dielectric substrate 1, the measuring patch 2 and the covering layer 3 are not unique and can be independently designed according to the design standards based on the actual measurement requirements.

[0028] The feeder line 4 is generally composed of multiple feeder line segments connected in series, the innermost feeder line segment is connected to the measurement patch 2, and the outermost feeder line segment is externally connected to the excitation port. The width of the same feeder line segment is consistent, and the width of the feeder line segment gradually decreases from the outside to the inside.

[0029] The structure of feeder 4 is designed based on the principle of 1 / 4 wavelength impedance converter under the premise of considering reasonable power distribution. The length of the innermost feeder segment is 1 / 4 of the wavelength of measurement patch 2. The input impedance Z1 of measurement patch 2 and the characteristic impedance Z1 of the innermost feeder segment are measured. c The characteristic impedance Z0 of the excitation port satisfies:

[0030]

[0031] The width of the innermost feeder segment and the characteristic impedance satisfy the following relationship:

[0032]

[0033] Among them, ε r is the relative dielectric constant, h is the thickness of the dielectric base, W l is the width of the innermost feeder segment.

[0034] Based on the above principle, a structure as shown in the figure can be designed, where the feed line 4 between the measurement patch 2 and the excitation port is composed of two connected sections, the lengths of the two sections can be 12.5 mm and 58.5 mm respectively, and the widths can be 1 mm and 1.5 mm respectively.

[0035] In order to verify the effect of the above-mentioned microstrip antenna sensor, the microstrip antenna sensors with and without coating 3 are placed in a constant temperature test machine, and a coaxial connector interface is welded on the feed line 4 of the microstrip antenna sensor, which is connected to a vector network analyzer through a radio frequency jumper.

[0036] Ice layers of the same temperature, dust of the same thickness, and water layers of the same temperature were added to the two microstrip antenna sensors with and without coating 3. To ensure quantitative analysis of foreign matter, a PMMA container was used to test the microstrip antenna sensor under different environmental foreign matter conditions. The PMMA container was fixed on the measuring patch 2 of the microstrip antenna sensor with plastic glue, and a watertightness test was performed to ensure that the container was tightly connected to the sensor.

[0037] Before the test, the constant temperature test machine and the refrigeration compressor were pre-operated for thirty minutes to ensure the stability of the equipment parameters during the subsequent test. Two types of microstrip antenna sensors, one with coating 3 and one without coating 3, were placed in the equipment and connected to the vector network analyzer through a coaxial connector. The frequency domain signals of the two microstrip antennas were collected simultaneously through the multi-port function of the vector network analyzer to ensure that the test conditions of the two microstrip antenna sensors were consistent.

[0038] The temperature of the refrigeration compressor was controlled at -10℃, and an industrial thermometer was used to monitor the ambient temperature at the sensor to ensure that the sensor surface was not frozen. The ambient temperature was kept the same and constant for 5 minutes before the test. The resonant frequency images of the microstrip antenna sensor with and without coating 3 were observed using vector network analysis, as shown in Figure 2 (a) and (b). The test shows that compared with the microstrip antenna sensor without coating 3, the resonant frequency fluctuation of the microstrip antenna sensor with coating 3 decreased by more than 95%, and the coating 3 has a strong anti-icing performance.

[0039] Dust is evenly spread on the surface of the sensor with or without coating 3, and the dust accumulation thickness is controlled to be 1mm. The resonant frequency images of the microstrip antenna sensor with and without coating 3 are observed by vector network analysis, as shown in Figure 3 (a) and (b). The experiment shows that compared with the microstrip antenna sensor without coating 3, the resonant frequency fluctuation of the microstrip antenna sensor with coating 3 decreases by more than 90%, and the coating 3 has a strong dust resistance performance.

[0040] The temperature of the constant temperature test machine was controlled at 40°C, and an industrial thermometer was used to monitor the temperature in the test machine in real time. The ambient temperature in the test machine was kept constant for 5 minutes before the test. After the same volume of 20°C water was spread on the coating 3 for 5 minutes, the resonant frequency images of the microstrip antenna sensor with and without coating 3 were observed using vector network analysis, as shown in Figures 4(a) and (b). The test shows that compared with the microstrip antenna sensor without coating 3, the resonant frequency fluctuation of the microstrip antenna sensor with coating 3 is reduced by more than 95%, and the coating 3 has a strong water and temperature resistance.

[0041] The above-mentioned microstrip antenna sensor covers a coating 3 with raised edges on the measuring patch 2. When foreign matter causes the environmental dielectric constant to change, the electric field lines under the edge effect pass through the coating 3 above the measuring patch 2 and enter the dielectric base layer 1, which greatly reduces the fluctuation level of the sensor's resonant frequency with environmental changes, and improves the sensor's environmental foreign matter anti-interference ability and monitoring reliability.

[0042] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, without departing from the technical principles of the present invention, several improvements and deformations can be made, such as the size design of the dielectric base layer 1, the measurement patch 2 and the covering layer 3, etc. These improvements and deformations should also be regarded as the protection scope of the present invention.

Claims

1. A microstrip antenna sensor, characterized in that: It includes a dielectric base layer, a measuring patch and a feeder arranged on the dielectric base layer. The feeder is connected to the measuring patch. The measuring patch is covered with a coating with a raised edge. The size of the measuring patch is designed according to different resonant frequencies. The coating material is FR4, and the size of the measuring patch is smaller than the coating size.

2. A microstrip antenna sensor according to claim 1, characterized in that: The feeder line is composed of multiple feeder line segments connected in series. The innermost feeder line segment is connected to the measurement patch, and the outermost feeder line segment is externally connected to the excitation port. The width of the same feeder line segment is consistent, and the width of the feeder line segment gradually decreases from the outside to the inside.

3. A microstrip antenna sensor according to claim 2, characterized in that: The width of the innermost feeder segment and the characteristic impedance satisfy the following relationship: Among them, Z c is the characteristic impedance of the innermost feeder segment, Z0 is the characteristic impedance of the excitation port, Z1 is the input impedance of the measurement patch, ε r is the relative dielectric constant, h is the thickness of the dielectric base, W l is the width of the innermost feeder segment.

4. The microstrip antenna sensor according to claim 1, characterized in that: A ground plate is also arranged at the bottom of the dielectric substrate.

5. A microstrip antenna sensor according to any one of claims 1 to 4, characterized in that: The dielectric base material is FR4.

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