A water resonant antenna with adjustable operating frequency

Abstract

This invention discloses a water resonant antenna with tunable operating frequency. The invention includes a metal ground plane, a feeding structure, a container, and a water radiator. The container is fixedly mounted on the metal ground plane, and a radiation chamber is formed inside the container. The water radiator is placed inside the radiation chamber. The lower part of the feeding structure is positioned below the metal ground plane, and the upper part of the feeding structure extends upwards through the metal ground plane and the bottom of the container, then is installed on the inner wall of the radiation chamber. The water radiator is in contact with the feeding structure. After the feeding structure feeds power to the water radiator, the water radiator resonates and generates electromagnetic radiation. Adjusting the height of the water radiator changes the antenna's operating frequency, thus achieving frequency tuning. This invention uses water as the resonator and, through a novel container and feeding structure, achieves frequency adjustment of the antenna by regulating the water level. The structure is simple and flexible, and can be used in IoT applications such as water level monitoring.

Description

Technical Field

[0001] This invention belongs to the field of electronic technology and relates to a reconfigurable antenna, specifically a water resonant antenna with tunable operating frequency. Background Technology

[0002] With the rapid development of wireless communication systems, in order to realize complex functions such as communication and navigation, the number of antennas required by the equipment is increasing. People have begun to hope that one antenna can realize the functions of multiple antennas. Such antennas are called reconfigurable antennas. Reconfigurable antennas are divided into frequency reconfigurable antennas and beam reconfigurable antennas.

[0003] In recent years, various materials have been used in antenna design, among which water has attracted widespread attention due to its high transparency, non-toxicity, and ease of access. Furthermore, its fluidity provides a natural advantage in the field of reconfigurable antennas. Water antennas can be divided into pure water and saltwater antennas. Pure water is often used as a dielectric resonant antenna or in the design of dielectric-loaded antennas, while saltwater antennas are typically designed based on their metal-like conductivity. Some scholars have studied the frequency reconfigurability of pure water antennas, demonstrating that for a pure water columnar antenna using a traditional feed structure, its resonant frequency depends on its cross-sectional area and is minimally affected by the water level. Therefore, in publicly available designs, frequency tuning is achieved by creating multi-layered containers and changing the cross-sectional area of ​​the water column. Summary of the Invention

[0004] To address the problems and needs existing in the background technology, this invention provides a water resonant antenna with tunable operating frequency. This invention employs a bent-type feed structure and a cross-stacked periodic resonator structure. This feed structure can form a periodic equivalent resonant circuit with the water resonator, and its resonant frequency changes with the water level, thus achieving adjustment of the antenna's operating frequency by changing the water level. This resonator structure, while ensuring sufficient contact with the feed structure, enhances the coupling effect within the resonator, improving the antenna's radiation efficiency. The overall structure is simple and flexible, making it suitable for applications such as water level monitoring, and has excellent application prospects.

[0005] The technical solution of the present invention is as follows:

[0006] This invention includes a metal ground plane, a feeding structure, a container, and a water radiator. The container is fixedly installed on the metal ground plane, and a radiation chamber is formed inside the container. The water radiator is placed inside the radiation chamber. The lower part of the feeding structure is located below the metal ground plane, and the upper part of the feeding structure extends upwards through the metal ground plane and the bottom of the container, and is installed on the inner wall of the radiation chamber. The water radiator is in contact with the feeding structure. After the feeding structure feeds power to the water radiator, the water radiator resonates and generates electromagnetic radiation. Adjusting the height of the water radiator changes the operating frequency of the antenna, thereby achieving frequency tuning.

[0007] The metal ground plane is a metal plate, and the side length of the metal plate is more than 5 times the length of the container.

[0008] The power supply structure includes a coaxial line and a microstrip line. The lower end of the coaxial line is located below the metal ground plane, and the microstrip line is located inside the radiation cavity of the container and is close to the inner wall of the radiation cavity. The upper end of the coaxial line extends upward from the metal ground plane and the bottom of the container and is electrically connected to the lower end of the microstrip line.

[0009] The coaxial cable includes an inner conductor, a dielectric layer, and a shielding layer. The dielectric layer and the shielding layer are sequentially fitted outside the inner conductor. The lower ends of the inner conductor, dielectric layer, and shielding layer are located below the metal ground plane. The upper ends of the dielectric layer and shielding layer extend through the metal ground plane and are located on the lower surface of the container. The upper end of the inner conductor extends through the metal ground plane and the bottom of the container and is electrically connected to the lower end of the microstrip line in the radiation cavity.

[0010] The microstrip line includes a first microstrip line and a second microstrip line. The first microstrip line is disposed on the bottom surface of the radiation chamber, and the second microstrip line is disposed on the side wall of the radiation chamber. One end of the first microstrip line is electrically connected to a coaxial line, and the other end of the first microstrip line is electrically connected to the lower end of the second microstrip line. The upper end of the second microstrip line extends upward along the side wall of the radiation chamber.

[0011] The radiating chamber within the container is composed of multiple alternating, interconnected transverse and longitudinal sub-chambers. Water radiators are filled within the transverse and longitudinal sub-chambers, each consisting of multiple water radiators. The transverse and longitudinal sub-chambers are identical in size. The sidewalls containing the short sides of all transverse sub-chambers and the sidewalls containing the long sides of all longitudinal sub-chambers are on the same vertical plane, forming a periodic I-shaped cavity wall. The upper part of the power supply structure is mounted on this periodic I-shaped cavity wall. The upper and lower end faces of each longitudinal sub-chamber are connected to the end faces of the corresponding transverse sub-chambers, and the upper and lower end faces of each transverse sub-chamber are connected to the end faces of the corresponding longitudinal sub-chambers.

[0012] The water radiator is pure water.

[0013] The resonant frequency of the water radiation unit is calculated using the following formula:

[0014]

[0015]

[0016]

[0017] a2 = 0.16

[0018] Where f is the resonant frequency of the water radiating element, in GHz; w is the width of the water radiating element; d is the length of the water radiating element; b is twice the water level height of the water radiating element in the corresponding transverse or longitudinal sub-chamber, in cm; ε r denoted as the relative permittivity of pure water; a0 is the first geometric constant of the water radiating element; a1 is the second geometric constant of the water radiating element; and a2 is the third geometric constant of the water radiating element.

[0019] The equivalent circuit model of the water resonant antenna is composed of multiple series and parallel units connected in series. Each series and parallel unit has the same structure, including equivalent impedance, equivalent capacitance and equivalent inductance. The equivalent capacitance and equivalent inductance are connected in parallel and then connected in series with the equivalent impedance. The operating frequency of the water resonant antenna is the resonant frequency of the equivalent circuit model.

[0020] The formula for calculating the equivalent impedance is as follows:

[0021]

[0022] Where Z is the equivalent impedance value, ε r Where is the relative permittivity of the container material, W is the width of the microstrip line, H is the wall thickness of the container, and T is the thickness of the microstrip line.

[0023] The equivalent capacitance and equivalent inductance are calculated using the following formulas:

[0024]

[0025] Where L is the inductance of the equivalent inductance, C is the capacitance of the equivalent capacitance, and f is the resonant frequency of the water radiation unit.

[0026] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0027] This invention designs a feeding structure that allows the operating frequency of a cylindrical pure water antenna to change with varying water levels. It fully utilizes the advantages of water as an antenna material, leveraging its fluidity to design a tunable antenna. Addressing the real-world need for water level monitoring, the feeding structure reflects changes in water level in the antenna's operating frequency, making it suitable for IoT scenarios such as water level monitoring. The antenna structure is simple and highly flexible, thus possessing potential applications in antenna design for improving wireless communication cellular coverage or in aerospace applications. Attached Figure Description

[0028] Figure 1 This is a top view of the overall structure of the present invention;

[0029] Figure 2 This is a bottom view of the overall structure of the present invention;

[0030] Figure 3 This is a schematic diagram of the power supply structure of the present invention;

[0031] Figure 4 This is a schematic diagram of the container structure of the present invention;

[0032] Figure 5 This is a schematic diagram of the water radiator structure of the present invention;

[0033] Figure 6 This is a schematic diagram illustrating the calculation of the resonant frequency of the water radiation unit in this invention;

[0034] Figure 7 This is a schematic diagram of the equivalent circuit model in this invention;

[0035] Figure 8 The working frequency scanning results of the tunable water resonant antenna of the present invention at different water levels;

[0036] Figure 9 The image shows the far-field radiation pattern of the tunable water resonant antenna of this invention at 1.06 GHz.

[0037] In the figure: 1. Metal ground plane; 2. Feed structure; 21. Coaxial line; 211. Inner conductor; 212. Dielectric layer; 213. Shielding layer; 22. Microstrip line; 221. First microstrip line; 222. Second microstrip line; 3. Container; 31. Space unit; 311. Lateral sub-cavity; 312. Longitudinal sub-cavity; 4. Water radiator; 41. Water radiating unit; 5. Equivalent circuit model; 5. Series and parallel unit; 51. Equivalent impedance; 512. Equivalent capacitance; 513. Equivalent inductance; 514. Detailed Implementation

[0038] To make the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0039] like Figure 1 and Figure 2 As shown, it includes a metal ground plane 1, a power supply structure 2, a container 3, and a water radiator 4;

[0040] Container 3 is fixedly installed on the metal ground plane 1. A radiation chamber is formed inside container 3, with an opening at the top, which is also the top opening of the radiation chamber. Water can flow into the radiation chamber from the top. A water radiator 4, composed of pure water, is placed (filled) inside the radiation chamber. The lower part of the feed structure 2 is positioned below the metal ground plane 1, and the upper part of the feed structure 2 extends upwards through the metal ground plane 1 and the bottom of container 3 before being installed on the inner wall of the radiation chamber. The water radiator 4 surrounds the feed structure 2, making contact between them. After the feed structure 2 feeds power to the water radiator 4, the water radiator 4 resonates and generates electromagnetic radiation. The height of the water radiator 4 is adjustable; adjusting the height changes the antenna's operating frequency, thus achieving frequency tuning.

[0041] The metal ground plane 1 is a metal plate with a side length greater than 5 times the length of the longer side of the container 3. Its typical shape is rectangular. When the metal plate is rectangular, the width of the rectangle is greater than 5 times the length of the container 3 (the length of the longer side compared to the width of the container 3). In this embodiment, the metal ground plane 1 is a square with a side length of 100 mm and a thickness of 0.1 mm.

[0042] like Figure 3 As shown, the power supply structure 2 includes a coaxial line 21 and a microstrip line 22. The lower end of the coaxial line 21 is located below the metal ground plane 1. The microstrip line 22 is located inside the radiation chamber of the container 3 and is closely attached to the inner wall of the radiation chamber (including the bottom and side walls). The upper end of the coaxial line 21 extends upward from the metal ground plane 1 and the bottom of the container 3 and is electrically connected to the lower end of the microstrip line 22. The upper end of the microstrip line 22 extends upward along the inner wall of the radiation chamber.

[0043] The coaxial cable 21 includes an inner conductor 211, a dielectric layer 212, and a shielding layer 213. The dielectric layer 212 and the shielding layer 213 are sequentially fitted around the inner conductor 211. The inner conductor 211 is a metal pillar, and the shielding layer 213 is the outermost cylindrical structure made of metal. The dielectric layer 212 is a cylindrical structure located between the inner conductor 211 and the shielding layer 213, and has the same height as the shielding layer 213. In this implementation, the lower ends of the inner conductor 211, dielectric layer 212, and shielding layer 213 are flush. The lower ends of the inner conductor 211, dielectric layer 212, and shielding layer 213 are positioned below the metal ground plane 1. The upper ends of the dielectric layer 212 and shielding layer 213 extend through the metal ground plane 1 and are positioned on the lower surface of the container 3 (i.e., do not extend into the container 3). In this implementation, a hole is opened at the center of the metal ground plane 1, with a diameter equal to the outer diameter of the dielectric layer 212 (3.16 mm in this embodiment). This hole allows the inner conductor 211 to pass through the center for power feeding without short-circuiting the inner conductor 211 with the shielding layer 213. The upper end of the inner conductor 211 extends through the metal ground plane 1 and the bottom of the container 3 and is electrically connected to the lower end of the microstrip line 22 (i.e., one end of the first microstrip line 221) within the radiation cavity. In this embodiment, the diameter of the inner conductor 211 is 0.746 mm. The shielding layer has an inner diameter of 3.16 mm and an outer diameter of 3.2 mm. The dielectric layer has an inner diameter of 0.746 mm and an outer diameter of 3.16 mm. The dielectric layer is made of nylon and has a relative permittivity of 3.

[0044] The microstrip line 22 includes a first microstrip line 221 and a second microstrip line 222. The first microstrip line 221 is disposed close to the bottom surface of the radiation chamber, and the second microstrip line 222 is disposed close to the side wall of the radiation chamber. One end of the first microstrip line 221 is electrically connected to the upper end of the coaxial line 21, and the other end of the first microstrip line 221 is electrically connected to the lower end of the second microstrip line 222. The upper end of the second microstrip line 222 extends upward along the side wall of the radiation chamber. The first microstrip line 221 and the second microstrip line 222 have the same width, which is 1 mm in this embodiment. The first microstrip line 221 has a length of 2.5 mm and a thickness of 0.1 mm; the height of the second microstrip line 22 is the same as the height of the container 3, which is 150 mm.

[0045] The container 3 is made of a dielectric material; in this embodiment, the dielectric material is polytetrafluoroethylene (PTFE) with a relative permittivity of 2.1. The container 3 has a rectangular columnar structure with a certain thickness at the bottom, and is fixed to the metal ground plane 1. The bottom of the container 3 has an opening with a diameter identical to that of the inner conductor 211, allowing the inner conductor 211 to pass through the bottom and connect to the first microstrip line 221 for power feeding. The radiation chamber inside the container 3 is composed of multiple horizontal sub-chambers 311 and vertical sub-chambers 312, stacked and connected alternately in both directions, as shown in the figure. Figure 4 and 5As shown, the long side of the transverse sub-chamber 311 and the long side of the longitudinal sub-chamber 312 are arranged perpendicularly. Water radiators 4 are filled with water radiating units 41 in both the transverse and longitudinal sub-chambers 311 and 312, as shown. Figure 6 As shown, the water radiator 4 is composed of multiple water radiating units 41. Except for the transverse / longitudinal sub-cavities at the top and bottom of the radiating chamber, the transverse sub-cavities 311 and the longitudinal sub-cavities 312 have the same dimensions (i.e., the same length, width, and height). The sidewalls of all transverse sub-cavities 311 with their short sides and the sidewalls of all longitudinal sub-cavities 312 with their long sides are on the same vertical plane and form a periodic I-shaped cavity wall. That is, each longitudinal sub-cavity 312 is located on the side closest to the transverse sub-cavities 311, and the sidewalls of the longitudinal sub-cavities 312 with their long sides are on the same vertical plane. The short side walls of the transverse sub-chambers 311 are flush with each other. Each transverse sub-chamber 311 is located in the middle of the corresponding longitudinal sub-chamber 312. In the side sectional view of the radiating chamber, the chamber is a second microstrip line 222 on the upper part of multiple T-shaped feed structures 2, which is tightly mounted on the periodic I-shaped cavity wall. The upper and lower end faces of each longitudinal sub-chamber 312 are connected to the end faces of the corresponding transverse sub-chambers 311, and the upper and lower end faces of each transverse sub-chamber 311 are connected to the end faces of the corresponding longitudinal sub-chambers 312. In this embodiment, the length, width, and height of the container 3 are 12mm, 12mm, and 151mm, respectively, and the bottom thickness is 1mm. In this embodiment, there are 25 transverse sub-chambers 311 and 25 longitudinal sub-chambers 312. The long side of the transverse sub-chamber 311 and the length of the longitudinal sub-chamber 312 are 10mm, the width is 5mm, and the height is 3mm.

[0046] Water radiating units 41 are contained in transverse sub-chambers 311 and longitudinal sub-chambers 312. Therefore, the shape of the water radiator 4 depends on the geometry of the transverse sub-chambers 311 and longitudinal sub-chambers 312 and the water level in the corresponding sub-chambers. Each water radiating unit 41 is a cuboid with the same geometry as the transverse sub-chambers 311 and longitudinal sub-chambers 312.

[0047] The resonant frequency of the water radiation unit 41 is calculated using the following formula:

[0048]

[0049]

[0050]

[0051] a2 = 0.16

[0052] Where f is the resonant frequency of the water radiation unit 41, in GHz; w is the width of the water radiation unit 41; d is the length of the water radiation unit 41; b is twice the water level height of the water radiation unit 41 in the corresponding transverse sub-chamber 311 or longitudinal sub-chamber 312, in cm; εr denoted as the relative permittivity of pure water; a0 is the first geometric constant of the water radiation unit 41, a1 is the second geometric constant of the water radiation unit 41, and a2 is the third geometric constant of the water radiation unit 41.

[0053] In this embodiment, the width w of the water radiating unit 41 is 0.5cm, the length d is 1cm, and the height is 0.3cm, therefore b is 0.6cm, and the relative permittivity ε of water is... r The value is 78. After calculation, the first geometric constant a0 of the water resonant unit 41 is 2.17, the second geometric constant a1 is 2.35, the third geometric constant a2 is 0.16, and the resonant frequency f of the water radiation unit 41 is 4.5GHz.

[0054] like Figure 7 As shown, the equivalent circuit model 5 of the water resonant antenna is composed of multiple series-parallel units 51 connected in series. Each series-parallel unit 51 has the same structure, including an equivalent impedance 512, an equivalent capacitance 513, and an equivalent inductance 514. The equivalent capacitance 513 and the equivalent inductance 514 are connected in parallel and then connected in series with the equivalent impedance 512. The end of each series-parallel unit 51 closest to the equivalent impedance 512 is connected to the end of another series-parallel unit 51 closest to the equivalent capacitance 513 and the equivalent inductance 514. The operating frequency of the water resonant antenna is the resonant frequency of the equivalent circuit model 5.

[0055] The equivalent impedance 512 is used for the resonance of the equivalent microstrip line 22. The formula for calculating the equivalent impedance 512 is as follows:

[0056]

[0057] Where Z is the equivalent impedance of 512, and ε r Where is the relative permittivity of the material of container 3, W is the width of microstrip line 22, H is the wall thickness of container 3, and T is the thickness of microstrip line 22.

[0058] In this embodiment, ε r Given that the width W of microstrip line 22 is 1 mm, the wall thickness H of container 3 is 1 mm, and the thickness T of microstrip line 22 is 0.1 mm, the calculated equivalent impedance is 22.9 ohms.

[0059] The equivalent capacitance 513 and equivalent inductance 514 are used for the resonance of the equivalent water radiation unit 41, and their values ​​can be calculated using the following formula:

[0060]

[0061] Where L is the inductance of the equivalent inductance 514, C is the capacitance of the equivalent capacitance 513, and f is the resonant frequency of the water radiation unit 41.

[0062] When the water level changes, the number of series and parallel units 51 in the equivalent circuit model 5 will change, and the values ​​of the equivalent impedance 512, equivalent capacitance 513 and equivalent inductance 514 of the last series and parallel unit 51 will also change with the change of the water level in the corresponding water radiation unit 41, thereby affecting the resonant frequency of the antenna.

[0063] like Figure 8 As shown, when the water level changes, the number of series and parallel units (51) in the equivalent circuit model (5) will change, and the values ​​of the equivalent impedance (512), equivalent capacitance (513), and equivalent inductance (514) of the last series and parallel unit (51) will also change, thus affecting the antenna's operating frequency. When the water level increases from 10mm to 150mm, the antenna's operating frequency decreases from 1.372GHz to 0.89GHz. When the water level is 70mm, the antenna operates at 1.06GHz, and the far-field radiation pattern of the antenna at this time is shown in the figure. Figure 9 As shown, it exhibits good omnidirectional radiation characteristics.

[0064] In summary, this invention provides a water resonant antenna with a tunable operating frequency. The antenna's operating frequency can be tuned by adjusting the water level of the radiator; a 5mm change in water level results in approximately a 17MHz change in the antenna's operating frequency.

[0065] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above examples based on the technical essence of the present invention without departing from the technical solution of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A water resonant antenna with tunable operating frequency, characterized in that, It includes a metal ground plane (1), a power supply structure (2), a container (3), and a water radiator (4); The container (3) is fixedly installed on the metal ground plane (1). A radiation chamber is opened inside the container (3). A water radiator (4) is placed inside the radiation chamber. The lower part of the feeding structure (2) is set below the metal ground plane (1). The upper part of the feeding structure (2) goes up and passes through the metal ground plane (1) and the bottom of the container (3) and is installed on the inner wall of the radiation chamber. The water radiator (4) is in contact with the feeding structure (2). After the feeding structure (2) feeds the water radiator (4), the water radiator (4) resonates and generates electromagnetic radiation. The height of the water radiator (4) is adjusted to change the working frequency of the antenna and achieve the tuning of the working frequency. The water radiator (4) is filled with water radiating units (41), and the resonant frequency of the water radiating units (41) is calculated using the following formula: Where f is the resonant frequency of the water radiation unit (41) in GHz; w is the width of the water radiation unit (41); d is the length of the water radiation unit (41); and b is twice the water level height of the water radiation unit (41) in the corresponding transverse sub-chamber (311) or longitudinal sub-chamber (312) in cm. is the relative permittivity of the water radiator (4); The first geometric constant of the water radiation unit (41) is... The second geometric constant of the water radiation unit (41) is... is the third geometric constant of the water radiation unit (41).

2. The water resonant antenna with tunable operating frequency according to claim 1, characterized in that, The metal ground plane (1) is a metal plate with a side length greater than 5 times the length of the container (3).

3. The water resonant antenna with tunable operating frequency according to claim 1, characterized in that, The power supply structure (2) includes a coaxial line (21) and a microstrip line (22). The lower end of the coaxial line (21) is located below the metal ground plane (1). The microstrip line (22) is located in the radiation chamber of the container (3) and is close to the inner wall of the radiation chamber. The upper end of the coaxial line (21) passes through the metal ground plane (1) and the bottom of the container (3) and is electrically connected to the lower end of the microstrip line (22).

4. A water resonant antenna with tunable operating frequency according to claim 3, characterized in that, The coaxial line (21) includes an inner conductor (211), a dielectric layer (212), and a shielding layer (213). The dielectric layer (212) and the shielding layer (213) are sequentially fitted outside the inner conductor (211). The lower ends of the inner conductor (211), the dielectric layer (212), and the shielding layer (213) are set below the metal ground plane (1). The upper ends of the dielectric layer (212) and the shielding layer (213) pass through the metal ground plane (1) and are set on the lower surface of the container (3). The upper end of the inner conductor (211) passes through the metal ground plane (1) and the bottom of the container (3) and is electrically connected to the lower end of the microstrip line (22) in the radiation cavity.

5. A water resonant antenna with tunable operating frequency according to claim 3, characterized in that, The microstrip line (22) includes a first microstrip line (221) and a second microstrip line (222). The first microstrip line (221) is disposed on the bottom surface of the radiation chamber, and the second microstrip line (222) is disposed on the side wall of the radiation chamber. One end of the first microstrip line (221) is electrically connected to the coaxial line (21), and the other end of the first microstrip line (221) is electrically connected to the lower end of the second microstrip line (222). The upper end of the second microstrip line (222) extends upward along the side wall of the radiation chamber.

6. A water resonant antenna with tunable operating frequency according to claim 1, characterized in that, The radiation chamber inside the container (3) is composed of multiple horizontal sub-chambers (311) and vertical sub-chambers (312) stacked and connected alternately. The horizontal sub-chambers (311) and vertical sub-chambers (312) have the same size. The side walls of the short sides of all horizontal sub-chambers (311) and the side walls of the long sides of all vertical sub-chambers (312) are on the same vertical plane and form a periodic I-shaped cavity wall. The upper part of the power supply structure (2) is installed on the periodic I-shaped cavity wall. The upper and lower end faces of each vertical sub-chamber (312) are connected to the end faces of the corresponding horizontal sub-chambers (311), and the upper and lower end faces of each horizontal sub-chamber (311) are connected to the end faces of the corresponding vertical sub-chambers (312).

7. A water resonant antenna with tunable operating frequency according to claim 1, characterized in that, The water radiator (4) is pure water.

8. A water resonant antenna with tunable operating frequency according to claim 1, characterized in that, The equivalent circuit model (5) of the water resonant antenna is composed of multiple series-parallel units (51) connected in series. Each series-parallel unit (51) has the same structure, including equivalent impedance (512), equivalent capacitance (513) and equivalent inductance (514). The equivalent capacitance (513) and equivalent inductance (514) are connected in parallel and then connected in series with the equivalent impedance (512). The operating frequency of the water resonant antenna is the resonant frequency of the equivalent circuit model (5).

9. A water resonant antenna with tunable operating frequency according to claim 8, characterized in that, The formula for calculating the equivalent impedance (512) is as follows: Where Z is the impedance value of the equivalent impedance (512), W is the width of the microstrip line (22), H is the wall thickness of the container (3), and T is the thickness of the microstrip line (22). The equivalent capacitance (513) and equivalent inductance (514) are calculated using the following formulas: Where L is the inductance value of the equivalent inductance (514) and C is the capacitance value of the equivalent capacitance (513).

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