A spherical conformal array antenna sensor for water quality detection based on passive RFID

Abstract

This invention proposes a passive RFID-based spherical conformal array antenna sensor for water quality monitoring. The sensor comprises a spherical conformal array antenna, a reconfigurable phase-delay transmission line based on a phase-shifting method, and a buoyancy regulator. The sensor is a hollow sphere with a cylindrical substrate embedded in its center. The spherical conformal array antenna is located on the outer surface of the upper half of the hollow sphere. The reconfigurable phase-delay transmission line based on a phase-shifting method comprises a delay line disposed on the upper surface of the cylindrical substrate and a slot provided within the cylindrical substrate, serving as a liquid channel. An outlet for the liquid channel is provided in the center of the cylindrical substrate, extending through the lower half of the sphere. The buoyancy regulator is located within the lower half of the hollow sphere. This invention transmits electromagnetic waves toward the spherical conformal array antenna sensor. The phase shift information in the backscattered signal can be used to detect changes in the dielectric constant of the liquid and monitor contaminants in the water, effectively achieving real-time, wireless, and low-cost water quality monitoring.

Description

Technical Field

[0001] The present invention relates to the field of antenna technology, and in particular to a water quality detection spherical conformal array antenna sensor based on passive RFID. Background Art

[0002] Reducing water pollution, a threat to life on Earth, remains a significant challenge. Furthermore, water pollution is often difficult to detect in real time, making it difficult to control once it spreads. Therefore, the importance of real-time water quality monitoring must be emphasized. In addition to water pollution in rivers, lakes, and oceans, reservoir pollution is also a concern, as there are over 80,000 reservoirs in the Yangtze and Yellow River basins. Floats are currently widely used in reservoirs, protecting water resources by covering the water surface and reducing evaporation.

[0003] Chipless RFID has been widely used in various fields, from the Internet of Things (IoT) to wireless communications, and is no exception in sensor design. By transmitting electromagnetic waves to RFID tags, the required information can be obtained by observing the phase characteristics of the backscattered electromagnetic waves at the receiving device.

[0004] Microstrip technology is used in microwave circuit elements such as transmission lines, resonators, filters, and antennas. Among these devices, microstrip antennas are the most widely used. Microstrip antennas have a well-defined structure and can be applied to various geometric shapes. Planar, cylindrical, and spherical antennas are the most common microstrip antennas.

[0005] Therefore, microstrip antennas can be used to form RFID-based spherical conformal array antennas to analyze the dielectric constant of the liquid and realize water pollution detection. Summary of the Invention

[0006] The purpose of the present invention is to address the problem of water quality detection and provide a spherical conformal array antenna sensor for water quality detection based on passive RFID. By emitting electromagnetic waves to the spherical conformal array antenna sensor and analyzing the phase characteristics of the backscattered electromagnetic waves, it can be used to detect changes in the dielectric constant of the liquid to monitor pollutants in the water, effectively realizing real-time, wireless and low-cost water quality monitoring.

[0007] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0008] A water quality detection spherical conformal array antenna sensor based on passive RFID, comprising a spherical conformal array antenna, a reconfigurable phase delay transmission line based on a phase shift method, and a buoyancy regulator;

[0009] The sensor is a hollow sphere as a whole, and a cylindrical substrate 3 is embedded in the center of the hollow sphere to divide the hollow sphere into an upper and a lower part. The main body of the upper part is the upper half hollow sphere substrate 1, and the upper half hollow sphere substrate 1 and the cylindrical substrate 3 enclose a closed upper hemisphere space; the spherical conformal array antenna is located on the outer surface of the upper half hollow sphere substrate 1, and the reconfigurable phase delay transmission line based on the phase shift method includes a delay line arranged on the upper surface of the cylindrical substrate 3 and an empty groove opened inside the cylindrical substrate 3 along the bottom of the delay line. The empty groove serves as a liquid channel, and an outlet of the liquid channel running through the lower hemisphere is provided in the center of the cylindrical substrate 3; the buoyancy regulator is arranged inside the lower half hollow sphere.

[0010] Specifically, the spherical conformal array antenna includes four rectangular microstrip antennas 2, which are symmetrically arranged on the outer surface of the upper hemisphere and can divide the upper hemisphere into four identical quarter upper hemispheres; the rectangular microstrip antenna includes a rectangular microstrip patch 2-1 and a microstrip line 2-2, the rectangular microstrip patch is loaded with an embedded microstrip line, and conformal technology is used to make the patch surface fit the outer surface of the quarter upper hemisphere; one end of the microstrip line is embedded in the rectangular microstrip patch, and matching is achieved by digging grooves on both sides of the microstrip line to reduce the input impedance, and the other end of the microstrip line is located at the bottom of the quarter hemisphere for connecting to a reconfigurable phase delay transmission line.

[0011] Specifically, the reconfigurable phase delay transmission line includes four delay lines 4, which are respectively connected to the microstrip lines of four rectangular microstrip antennas; the cylindrical substrate 3 can be evenly divided into four identical quarter sectors, corresponding to four identical quarter upper hemispheres, and a delay line with a bend is set on the surface of each sector. One end of the delay line is tangent to the center of the arc edge of the quarter sector, and the other end of the delay line points to the right-angled vertex of the sector, and the right angle at the bend is chamfered; at the same time, an empty groove 5 is opened inside the substrate directly below the delay line along the delay line as a liquid channel for external liquid to flow in. The incision between the empty groove and the surface of the sphere is an inlet 11. The four empty grooves converge and connect at the center of the cylindrical substrate. An outlet 13 composed of a hollow cylinder and a cone is set at the bottom of the convergence point. The outlet 13 passes through the lower hemisphere for the liquid in the empty groove to flow out of the sphere.

[0012] Specifically, the buoyancy regulator 10 adjusts the overall weight of the sensor to suspend the sensor on the water surface, so that liquid can enter the sensor through the slot 5 of the cylindrical substrate without contacting the rectangular microstrip patch 2-1.

[0013] Furthermore, four support columns 12 are provided at the bottom of the cylindrical substrate 2 for supporting the cylindrical substrate so that it is located at the center of the hollow sphere.

[0014] Furthermore, the hollow sphere is made of Formlabs Clear SLA resin (relative dielectric constant εr =2.8, loss tangent tanδ=0.021, measurement frequency is 4.0 GHz), the thickness of the hollow sphere is 2 mm, and a cylindrical substrate is embedded in the center of the hollow sphere; the main material of the cylindrical substrate is Formlabs Clear SLA resin, and the height is 2 mm.

[0015] Furthermore, the rectangular microstrip antenna 2 is located on the outer surface of the upper half hollow sphere substrate 1, and includes: a metal rectangular microstrip patch, a metal microstrip line connected to the reconfigurable phase delay transmission line below; the metal microstrip line adopts an embedded feeding method; the upper side length of the rectangular microstrip patch is 10.03mm, the lower side length is 15.58mm, and the height is 13.51mm. The microstrip line is embedded in the rectangular patch by 2.85mm, and a groove with a width of 0.97mm is opened on the rectangular microstrip patches on both sides of the microstrip line.

[0016] Furthermore, the delay line is a rectangular delay line with eleven bends, and the right angles at the bends are chamfered. There are six fold lines in the parallel direction of the first rectangular delay line at the channel entrance 11, with lengths of 2.0mm, 2.2mm, 2.2mm, 2.2mm, 2.0mm from the inside to the outside respectively; there are five fold lines in the vertical direction, with lengths of 3.5mm, 9.8mm, 16.0mm, 18.8mm, and 9.8mm from the inside to the outside respectively; at the same time, a 1mm deep groove is opened inside the cylindrical substrate directly below the entire delay line as a liquid channel, that is, the cross-sectional area at the channel entrance 11 is 2mm×1mm, and the liquid channel is located 0.5mm below the delay line for liquid to flow in. Different liquids are injected into the liquid channel, and the dielectric constant of the liquid changes, which will cause corresponding changes in the delay phase of the delay line; the delay line corresponds to the rectangular microstrip antenna and is connected through a microstrip line.

[0017] Furthermore, liquid is injected into the inlet of the liquid channel to control the relative dielectric constant of the water medium in the channel. One horn antenna is used as a transmitting antenna and the other horn antenna is used as a receiving antenna, which are respectively connected to the ports of a vector network analyzer (VNA). The VNA is used to measure the phase shift of the reflected signal from the receiving horn antenna to determine the water quality.

[0018] The present invention proposes a water quality monitoring float sensor based on passive RFID in a 5.8GHz RFID system, which satisfies the omnidirectional radiation pattern. As the relative dielectric constant of the liquid decreases, a significant phase shift can be observed. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a three-dimensional stereoscopic view of a spherical conformal array antenna sensor for water quality detection according to an embodiment of the present invention.

[0020] Figure 2 This is a front view of the rectangular microstrip antenna according to an embodiment of the present invention.

[0021] Figure 3 This is a three-dimensional stereoscopic image of a reconfigurable phase delay transmission line based on a phase shift method according to an embodiment of the present invention.

[0022] Figure 4 This is a measurement scene diagram of the spherical conformal array antenna sensor for water quality detection according to an embodiment of the present invention.

[0023] Figure 5 This is a simulation diagram of the phase shift under different dielectric constants of the liquid channel according to an embodiment of the present invention.

[0024] in,

[0025] Upper half hollow sphere substrate 1,

[0026] Rectangular microstrip antenna 2, rectangular microstrip patch 2-1, microstrip line 2-2,

[0027] Cylindrical substrate 3, delay line 4, empty slot 5,

[0028] Buoyancy regulator 10 , support column 12 , inlet 11 , outlet 13 . DETAILED DESCRIPTION

[0029] The technical solution provided by this application will be further described below in conjunction with specific embodiments and accompanying drawings. The advantages and features of this application will become more apparent with reference to the following description.

[0030] A water quality detection spherical conformal array antenna sensor based on passive RFID comprises a spherical conformal array antenna, a reconfigurable phase delay transmission line based on a phase shift method, and a buoyancy regulator.

[0031] like Figure 1 As shown, the sensor is a hollow sphere as a whole, and a cylindrical substrate 3 is embedded in the center of the hollow sphere to divide the hollow sphere into an upper and a lower part. The main body of the upper part is the upper half hollow sphere substrate 1, and the upper half hollow sphere substrate 1 and the cylindrical substrate 3 enclose a closed upper hemisphere space; the spherical conformal array antenna is located on the outer surface of the upper half hollow sphere substrate 1, and the reconfigurable phase delay transmission line based on the phase shift method includes a delay line arranged on the upper surface of the cylindrical substrate 3 and an empty groove opened inside the cylindrical substrate 3 along the bottom of the delay line. The empty groove serves as a liquid channel, and an outlet of the liquid channel running through the lower hemisphere is provided in the center of the cylindrical substrate 3; the buoyancy regulator is arranged inside the lower half hollow sphere.

[0032] Furthermore, four support columns 12 are provided at the bottom of the cylindrical substrate 3 for supporting the cylindrical substrate so that it is located at the center of the hollow sphere.

[0033] Specifically, the spherical conformal array antenna includes four rectangular microstrip antennas 2, which are symmetrically arranged on the outer surface of the upper hemisphere, and can divide the upper hemisphere into four equal quarter upper hemispheres; Figure 2 The rectangular microstrip antenna 2 includes a rectangular microstrip patch 2-1 and a microstrip line 2-2. The rectangular microstrip patch is loaded with an embedded microstrip line, and conformal technology is used to make the patch surface conform to the outer surface of a quarter upper hemisphere. One end of the microstrip line is embedded in the rectangular microstrip patch, and matching is achieved by digging grooves on both sides of the microstrip line to reduce the input impedance. The other end of the microstrip line is located at the bottom of the quarter hemisphere for connecting to a reconfigurable phase delay transmission line. Figure 2 shown.

[0034] Specifically, the reconfigurable phase delay transmission line includes four delay lines 4, which are respectively connected to the microstrip lines of four rectangular microstrip antennas. Figure 1 、 3 As shown, the cylindrical substrate 3 can be evenly divided into four identical quarter sectors, corresponding to four identical quarter upper hemispheres. A delay line with a bend is set on the surface of each sector. One end of the delay line is tangent to the center of the arc edge of the quarter sector, and the other end of the delay line points to the right-angled vertex of the sector, and the right angle at the bend is chamfered; at the same time, a slot 5 is opened inside the substrate directly below the delay line along the delay line as a liquid channel for external liquid to flow in, and the cutout between the slot and the surface of the sphere is an inlet 11. The four slots converge and connect at the center of the cylindrical substrate, and an outlet 13 composed of a hollow cylinder and a frustum is set at the bottom of the convergence point. The outlet 13 passes through the lower hemisphere to allow the liquid in the slot to flow out of the sphere.

[0035] Specifically, the buoyancy regulator 10 adjusts the overall weight of the sensor to suspend the sensor on the water surface, so that liquid can enter the sensor through the slot 5 of the cylindrical substrate without contacting the rectangular microstrip patch 2-1.

[0036] In the embodiment, the hollow sphere is made of Formlabs Clear SLA resin (relative dielectric constant ε r =2.8, loss tangent tanδ=0.021, measurement frequency is 4.0 GHz), the thickness of the hollow sphere is 2 mm, and a cylindrical substrate is embedded in the center of the hollow sphere; the main body of the cylindrical substrate 2 is made of Formlabs Clear SLA resin and has a height of 2 mm.

[0037] like Figure 1 、 Figure 2As shown, the rectangular microstrip antenna 2 is located on the outer surface of the upper half-hollow spherical substrate 1 and comprises a metal rectangular microstrip patch and a metal microstrip line connected to the reconfigurable phase delay transmission line below. The metal microstrip line uses an embedded feed method. The rectangular microstrip patch has an upper side length of 10.03mm, a lower side length of 15.58mm, and a height of 13.51mm. The microstrip line is embedded 2.85mm into the rectangular patch. A 0.97mm-wide slot is provided in each of the rectangular microstrip patches on either side of the microstrip line.

[0038] like Figure 3 As shown, the delay line is a rectangular delay line with eleven bends, and the right angles at the bends are chamfered. There are six broken lines in the parallel direction of the first rectangular delay line at the channel entrance 11, with lengths of 2.0mm, 2.2mm, 2.2mm, 2.2mm, and 2.0mm from the inside to the outside; there are five broken lines in the vertical direction, with lengths of 3.5mm, 9.8mm, 16.0mm, 18.8mm, and 9.8mm from the inside to the outside.

[0039] like Figure 3 As shown, a 1mm deep slot is provided inside the cylindrical substrate directly below the delay line, serving as a liquid channel. Specifically, the cross-sectional area at the channel entrance 11 is 2mm x 1mm. The liquid channel is located 0.5mm below the delay line, allowing liquid to flow in. Injecting different liquids into the liquid channel changes the dielectric constant of the liquid, which in turn changes the delay phase of the delay line. The delay line corresponds to the rectangular microstrip antenna and is connected via a microstrip line.

[0040] like Figure 1 As shown, in order to ensure that the liquid channel inlet 11 can be immersed in water, the buoyancy regulator 10 is configured in the volume of the lower half of the entire ball to increase the mass of the entire ball, so that the sensor can float on the liquid surface and the liquid can enter the liquid channel under the reconfigurable phase delay transmission line based on the phase shift method.

[0041] like Figure 4 As shown, liquid is injected into the inlet 11 of the liquid channel to control the relative dielectric constant of the water medium in the channel. One horn antenna serves as a transmitting antenna, and the other horn antenna serves as a receiving antenna, connected to the ports of a vector network analyzer (VNA). The VNA measures the phase shift of the reflected signal from the receiving horn antenna to determine the water quality. When the water quality detection spherical conformal array antenna sensor is stably floating on the water surface, the liquid channel in the reconfigurable phase delay transmission line based on the phase shift method is ensured to be filled with liquid, and the rectangular microstrip antenna is maintained at a certain distance from the water surface to minimize water damage to the antenna array.

[0042] Based on the above structural scheme, the spherical conformal array antenna sensor for water quality detection based on passive RFID of the present invention is composed of a spherical conformal reflective antenna array and a water quality detection delay line structure based on the phase shift method. The four-unit antenna array satisfies the omnidirectional radiation of the directional pattern, and the phase transmission line at 0.5mm on the liquid channel adopts a bent microstrip delay line structure to achieve a larger phase shift.

[0043] In the embodiment, the relative dielectric constant of the liquid is changed by changing the ratio of oil to water. Simulation verifies that as the relative dielectric constant of the liquid decreases, the phase shift of the backscattered wave increases sharply, and the phase shift caused by oil and water is obvious, thereby facilitating real-time monitoring of pollutants such as oil in water quality.

[0044] Figure 5 The figure shows the phase shift simulation diagram of the liquid channel under different dielectric constants according to the embodiment of the present invention. r =81.0) is used as the reference standard, and the horizontal axis is the relative dielectric constant from ε r = 1.0 to ε r =81.0 to simulate the change of water quality, and the vertical axis is the phase shift. When the channel is empty (the liquid channel is filled with air and no liquid is injected), the relative dielectric constant ε r =1.0, the phase shift caused is 358.11°; when the channel is filled with oil, the relative dielectric constant ε r = 2.4, resulting in a phase shift of 248.41°. Due to the significant difference in the relative dielectric constants of oil and water, the phase shift can be clearly distinguished by observing the phase shift of the reflected signal from the receiving horn antenna. The designed spherical conformal reflector antenna array sensor for water quality testing can be used to monitor oil contamination in water, which is of certain significance for achieving compliance with total pollutant emission standards and measuring oil content in water.

[0045] The above description is only a description of the preferred embodiments of the present application and does not limit the scope of the present application. Any changes or modifications made by any person skilled in the art based on the above disclosed technical content should be regarded as equivalent valid embodiments and fall within the scope of protection of the technical solution of the present application.

Claims

1. A water quality detection spherical conformal array antenna sensor based on passive RFID, characterized in that: Including spherical conformal array antenna, reconfigurable phase delay transmission line based on phase shift method and buoyancy regulator; The sensor is a hollow sphere as a whole. A cylindrical substrate (3) is embedded in the center of the hollow sphere to divide the hollow sphere into an upper part and a lower part. The main body of the upper part is the upper half hollow sphere substrate (1). The upper half hollow sphere substrate (1) and the cylindrical substrate (3) enclose a closed upper hemisphere space. The spherical conformal array antenna is located on the outer surface of the upper half hollow sphere substrate (1). The reconfigurable phase delay transmission line based on the phase shift method includes a delay line arranged on the upper surface of the cylindrical substrate (3) and an empty groove opened inside the cylindrical substrate (3) along the bottom of the delay line. The empty groove serves as a liquid channel, and an outlet of the liquid channel penetrating the lower hemisphere is provided in the center of the cylindrical substrate (3). The buoyancy regulator is arranged inside the lower half hollow sphere. Four support columns (12) are provided at the bottom of the cylindrical substrate (3) for supporting the cylindrical substrate so that it is located at the center of the hollow sphere; The spherical conformal array antenna comprises four rectangular microstrip antennas (2), which are symmetrically arranged on the outer surface of the upper hemisphere and can evenly divide the upper hemisphere into four identical quarter upper hemispheres; the rectangular microstrip antenna (2) comprises a rectangular microstrip patch (2-1) and a microstrip line (2-2), the rectangular microstrip patch is loaded with an embedded microstrip line, and conformal technology is used to make the patch surface conform to the outer surface of the quarter upper hemisphere; One end of the microstrip line is embedded in the rectangular microstrip patch, and matching is achieved by digging grooves on both sides of the microstrip line to reduce the input impedance. The other end of the microstrip line is located at the bottom of the quarter hemisphere and is used to connect to the reconfigurable phase delay transmission line. The reconfigurable phase delay transmission line includes four delay lines (4), which are respectively connected to the microstrip lines of four rectangular microstrip antennas. The cylindrical substrate (3) can be evenly divided into four identical quarter sectors, corresponding to four identical quarter upper hemispheres. A delay line with a bend is set on the surface of each sector. One end of the delay line is tangent to the center of the quarter sector arc edge, and the other end of the delay line points to the right-angle vertex of the sector, and the right angle at the bend is cut. At the same time, an empty groove (5) is opened inside the substrate directly below the delay line along the delay line as a liquid channel for external liquid to flow in. The incision of the empty groove and the surface of the sphere is an inlet (11). The four empty grooves converge and connect at the center of the cylindrical substrate. An outlet (13) composed of a hollow cylinder and a frustum is set at the bottom of the convergence point. The outlet (13) passes through the lower hemisphere for the liquid in the empty groove to flow out of the sphere.

2. The passive RFID-based spherical conformal array antenna sensor for water quality detection according to claim 1, characterized in that: The buoyancy regulator (10) adjusts the overall weight of the sensor so that the sensor is suspended on the water surface, allowing liquid to enter the sensor through the empty groove (5) of the cylindrical substrate without contacting the rectangular microstrip patch (2-1).

3. The passive RFID-based spherical conformal array antenna sensor for water quality detection according to claim 1, characterized in that: Four support columns (12) are provided at the bottom of the cylindrical substrate (2) for supporting the cylindrical substrate so that it is located at the center of the hollow sphere.

4. The passive RFID-based spherical conformal array antenna sensor for water quality detection according to claim 1, characterized in that: The hollow sphere is made of Formlabs Clear SLA resin with a relative dielectric constant of =2.8, loss tangent = 0.021, the measurement frequency is 4.0 GHz, the thickness of the hollow sphere is 2 mm, and a cylindrical substrate is embedded in the center of the hollow sphere; the main material of the cylindrical substrate is Formlabs Clear SLA resin, and the height is 2 mm; The rectangular microstrip antenna (2) is located on the outer surface of the upper hollow sphere substrate (1), and comprises: a metal rectangular microstrip patch, a metal microstrip line connected to a reconfigurable phase delay transmission line below; the metal microstrip line adopts an embedded feeding method; the upper side length of the rectangular microstrip patch is 10.03 mm, the lower side length is 15.58 mm, and the height is 13.51 mm; the microstrip line is embedded in the rectangular patch by 2.85 mm, and a groove with a width of 0.97 mm is provided on the rectangular microstrip patches on both sides of the microstrip line; The delay line is a rectangular delay line with eleven bends, and the right angles at the bends are cut. There are six fold lines in the parallel direction of the first rectangular delay line at the channel entrance (11), and the lengths from the inside to the outside are 2.0mm, 2.2mm, 2.2mm, 2.2mm, 2.0mm respectively; there are five fold lines in the vertical direction, and the lengths from the inside to the outside are 3.5mm, 9.8mm, 16.0mm, 18.8mm, and 9.8mm respectively; at the same time, a 1mm deep slot is opened inside the cylindrical substrate directly below the entire delay line as a liquid channel, that is, the cross-sectional area at the channel entrance is 2mm×1mm, and the liquid channel is located 0.5mm below the delay line for liquid to flow in. Different liquids are injected into the liquid channel, and the dielectric constant of the liquid changes the delay phase of the delay line, which will produce corresponding changes; the delay line corresponds to the rectangular microstrip antenna and is connected by a microstrip line.

5. The passive RFID-based spherical conformal array antenna sensor for water quality detection according to claim 1, characterized in that: Liquid is injected into the inlet of the liquid channel to control the relative dielectric constant of the water medium in the channel. One horn antenna is used as a transmitting antenna and the other horn antenna is used as a receiving antenna. They are respectively connected to the ports of the vector network analyzer (VNA). The VNA is used to measure the phase shift of the reflected signal from the receiving horn antenna to determine the water quality.

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