This application relates to the field of communication technologies, and in particular, to a phase shifter and a remote electrical tilt antenna.
A remote electrical tilt antenna of a base station implements down tilt adjustment of a beam of the base station antenna using a phase shifter, which makes the network coverage more flexible. The phase shifter is a core component of the base station antenna, and the performance of the phase shifter directly affects the overall performance of the antenna. Currently, a mainstream phase shifter in the industry changes a signal propagation rate by changing a dielectric constant around a feeder inside the phase shifter, to change a phase shift amount. Due to machining tolerances of various components in the phase shifter, there are differences in the coordination between the various components in the phase shifter, resulting in unstable performance of an antenna.
This application provides a phase shifter, to better ensure stability of an electrical performance of an antenna.
In an embodiment, a phase shifter includes a metal stripline, a first dielectric plate, and a second dielectric plate. The metal stripline includes a main body and a transmission section connected to the main body, and the metal stripline is clamped between the first dielectric plate and the second dielectric plate. The first dielectric plate and the second dielectric plate slide relative to the transmission section of the metal stripline along a length direction of the metal stripline. A limiting protrusion protrudes along the length direction on a surface of the first dielectric plate and/or the second dielectric plate facing the metal stripline. The limiting protrusion is located on a side portion of the metal stripline, and the limiting protrusion is configured to limit displacement of the first dielectric plate and the second dielectric plate relative to the metal stripline when the first dielectric plate and the second dielectric plate slide.
In an embodiment, a limiting protrusion is disposed on the first dielectric plate and/or the second dielectric plate, so as to limit displacement of the first dielectric plate and the second dielectric plate relative to the metal stripline when the first dielectric plate and the second dielectric plate slide. Therefore, the first dielectric plate and the second dielectric plate can slide along a width direction of the metal stripline without deviation, thereby realizing accurate control of phase change by the phase shifter.
In an embodiment of this application, when the first dielectric plate and the second dielectric plate slide relative to the metal stripline, the limiting protrusion moves along the side portion of the metal stripline, and an extension direction of the side portion is the same as the length direction.
In an embodiment, the limiting protrusion moves along the side portion of the metal stripline as the first dielectric plate and the second dielectric plate slide, and plays a guiding role for the movement of the first dielectric plate and the second dielectric plate, allowing the first dielectric plate and the second dielectric plate to slide along the side portion of the metal stripline, that is, the length direction of the metal stripline.
The limiting protrusion limits displacement of the first dielectric plate and the second dielectric plate relative to the metal stripline in the width direction, and the width direction is perpendicular to the length direction.
When the first dielectric plate and the second dielectric plate deviate relative to the metal stripline in the width direction, the limiting protrusion plays a blocking role, keeping the first dielectric plate always sliding along the length direction of the metal stripline, and avoiding deviating from the metal stripline in the width direction. In this way, the phase shifter can accurately implement phase change, and stability of electrical performance is not affected by differences in coordination of various components in the phase shifter.
In an embodiment, the limiting protrusion protrudes on the first dielectric plate, the limiting protrusion includes a body connected to the first dielectric plate and a limiting body located at an end portion of the body, the limiting body protrudes on one side of the body and extends towards the width direction, and the limiting body is located on a surface of the metal stripline facing away from the first dielectric plate. It may be understood that the metal stripline is stuck between the first dielectric plate and the limiting body in a height direction. The body defines a deviation of the first dielectric plate in the width direction, and the limiting body defines a deviation of the first dielectric plate in the height direction relative to the metal stripline.
In an implementation, a distance between the limiting protrusion and the side portion of the metal stripline is greater than 0 mm and less than or equal to 1 mm. In this way, there is a distance between the limiting protrusion and the side portion of the metal stripline, that is, the first dielectric plate is not in contact with the metal stripline, allowing the first dielectric plate and the second dielectric plate to slide smoothly along the metal stripline. In addition, the distance between the limiting protrusion and the side portion of the metal stripline is not too large, avoiding that the first dielectric plate and the second dielectric plate do not deviate relative to the metal stripline in the width direction when sliding.
Further, a plurality of limiting protrusions are provided, and the plurality of limiting protrusions are located on one side of the first dielectric plate and/or the second dielectric plate and disposed at intervals along the length direction. Alternatively, a plurality of limiting protrusions are located on two opposite sides of the first dielectric plate and/or the second dielectric plate and disposed in pairs. Alternatively, the plurality of limiting protrusions are located on two opposite sides of the first dielectric plate and/or the second dielectric plate and disposed in a staggered manner. In an implementation, a plurality of limiting protrusions are provided, and the plurality of limiting protrusions are located on two opposite sides of the first dielectric plate and/or the second dielectric plate and are disposed at intervals along the length direction, and are located on two opposite sides of the metal stripline. In this embodiment, the first dielectric plate and/or the second dielectric plate are provided with a plurality of limiting protrusions on two opposite sides of the metal stripline, that is, the metal stripline is located between the limiting protrusions of the two sides, so that neither the first dielectric plate nor the second dielectric plate deviates in a direction toward the two opposite sides in a width direction, which further limits deviation in a width direction of the first dielectric plate and/or the second dielectric plate relative to the metal stripline.
In an embodiment, the limiting protrusion protrudes on the first dielectric plate, a groove is provided on a surface of the second dielectric plate opposite to the first dielectric plate, the first dielectric plate is connected to the second dielectric plate, and the limiting protrusion extends into the groove and is held and fastened in the groove, or the limiting protrusion is a hook, the limiting protrusion protrudes on the first dielectric plate, a slot is provided on a surface of the second dielectric plate opposite to the first dielectric plate, the first dielectric plate is connected to the second dielectric plate, and the hook is held in the slot.
In an embodiment, the metal stripline includes a signal input terminal and a signal output terminal, the metal stripline is fastened in the cavity, and the transmission section is suspended in the cavity. The signal input terminal and the signal output terminal are configured to electrically connect to a cable outside the cavity, and the first dielectric plate and the second dielectric plate are disposed in the cavity and are movable relative to the transmission section of the metal stripline.
In an embodiment, a signal that needs to be radiated out is transmitted to the cavity via the signal input terminal, and is transmitted to the signal output terminal along the direction of the metal stripline via a medium in the cavity. When the first dielectric plate and the second dielectric plate slide relative to the metal stripline, an equivalent dielectric constant of a medium in a transmission section between the signal input terminal and the signal output terminal changes, so that the signal changes in a phase of a signal transmitted from the signal output terminal. Therefore, the radiated signal can be made to have a required phase by moving the first dielectric plate and the second dielectric plate.
In an embodiment, the transmission section includes a first transmission section and a second transmission section, a gap extending along the length direction is formed between the first transmission section and the second transmission section, and the gap is provided with an opening in the length direction. A buckle is disposed on the first dielectric plate, a slot is provided at a position of the second dielectric plate relative to the buckle, the buckle passes through the gap and is held in the slot, and the buckle slides in the gap, so that the first dielectric plate and the second dielectric plate slide in a same direction relative to the metal stripline. The first dielectric plate and the second dielectric plate are relatively fastened by disposing a buckle structure, so as to limit displacement in a height direction of the first dielectric plate and the second dielectric plate. The structure is simple and can conveniently control changes of displacement in a height direction of the first dielectric plate and the second dielectric plate relative to the metal stripline. It is important that a gap generated by the metal stripline is directly used as a guide groove for sliding the first dielectric plate and the second dielectric plate. The buckle can slide in the gap and play a guiding role, the first dielectric plate and the second dielectric plate can be guided without changing any structure for the strip line of irregular structure. Compared to existing technologies, the machining precision is improved, the structural complexity is reduced, the consistency and stability of the electrical performance are ensured, the performance of the phase shifter is further ensured, and the gap includes an opening, which is also very convenient in assembly.
In an embodiment, the first dielectric plate includes a first side surface and a second side surface, the second dielectric plate includes a third side surface and a fourth side surface, an abutting protrusion protrudes on each of the first side surface and the third side surface, the cavity includes two opposite cavity walls, the first dielectric plate and the second dielectric plate slide in the cavity, and the abutting protrusions slide along the cavity walls. A sliding trajectory of the first dielectric plate and the second dielectric plate in the cavity can be limited through the abutting protrusions, and a structure is simple, which can better ensure the performance of the phase shifter.
In an embodiment, the cavity includes a first sidewall and a second sidewall, opposite to each other and extending along the length direction of the metal stripline, two guide grooves are provided on each of the first sidewall and the second sidewall, and two opposite sides of the first dielectric plate are slidably mounted in one of the guide grooves on the first sidewall and the second sidewall, and two opposite sides of the second dielectric plate are slidably mounted in another guide groove on the first sidewall and the second sidewall. It may be understood that the guide groove is provided in the cavity, and the first dielectric plate and the second dielectric plate are mounted in the guide groove, so that the guide groove may play both a guiding role on the first dielectric plate and the second dielectric plate, and a limiting role on the first dielectric plate and the second dielectric plate.
The remote electrical tilt antenna includes a radiating element and the phase shifter, the radiating element is connected to the phase shifter, and an electromagnetic wave signal transmitted by the phase shifter is radiated out through the radiating element. Because the phase shifter provided in this application can perform phase shift control more accurately, the remote electrical tilt antenna has higher stability.
The phase shifter provided in this application is provided with a limiting protrusion on the first dielectric plate and/or the second dielectric plate of the phase shifter, which can limit displacement in a vertical sliding direction during the sliding process of the first dielectric plate and the second dielectric plate, and implement a guiding function of the sliding direction. Further, the consistency and stability of the electrical performance can be better ensured.
The following describes embodiments of this application with reference to the accompanying drawings in embodiments of this application.
This application provides a remote electrical tilt antenna. The remote electrical tilt antenna includes a phase shifter 100 shown in
Referring to
The signal is transmitted from one end of the metal stripline 20 to the other end of the metal stripline 20. The first dielectric plate 10 and the second dielectric plate 30 may slide relative to the transmission section of the metal stripline 20 along the length direction of the metal stripline 20, so as to change an area of the metal stripline 20 covered by the first dielectric plate 10 and the second dielectric plate 30. In this way, an equivalent dielectric constant of a medium in a transmission section through which the signal passes is changed, thereby changing power and a phase of a signal output from the metal stripline 20. The “transmission section through which the signal passes” refers to a signal transmission path of the signal on the metal stripline 20. The limiting protrusion 11 may limit positions of the first dielectric plate 10 and the second dielectric plate 30 relative to the metal stripline 20 in a direction perpendicular to a sliding direction, so that the dielectric plate can slide accurately in the length direction without width deviation. In addition, the first dielectric plate 10 and the second dielectric plate 30 can be guided, thereby realizing stability of the phase shifter 100 to a phase change.
Specifically, referring to
Continuing to refer to
In an embodiment, as shown in
Still referring to
The plurality of limiting protrusions 11 move with the movement of the first dielectric plate 10 and the second dielectric plate 30. Because the limiting protrusions 11 can limit the displacement of the first dielectric plate 10 relative to the metal stripline 20 in the width direction, the limiting protrusions 11 do not deviate from the side portion 201 of the metal stripline 20. In this way, the limiting protrusions 11 move along with the first dielectric plate 10 along the side portion 201 of the metal stripline 20, so as to guide the movement of the first dielectric plate 10, so that the first dielectric plate 10 can slide along the metal stripline 20 within a tolerance range. It should be noted that when the first dielectric plate 10 slides, the second dielectric plate 30 slides along with the first dielectric plate 10 in the same direction, and the limiting protrusion 11 also limits the second dielectric plate 30.
In an embodiment, the displacement of the first dielectric plate 10 relative to the metal stripline 20 during sliding is limited by disposing the limiting protrusion 11 on the first dielectric plate 10, so that the first dielectric plate 10 and the second dielectric plate 30 can accurately slide on the metal stripline 20 without deviation. In this way, relative positions of the metal stripline 20 and the two dielectric plates can be controlled and a phase shift function can be implemented while guiding of the dielectric plates and limiting of the dielectric plates in the width direction are implemented. An over-fit gap generated between the dielectric plates and an over-fit gap between the dielectric plate and the metal stripline 20 due to a tolerance are reduced, and consistency and stability of electrical performance of the phase shifter 100 can be ensured. A plurality of limiting protrusions 11 are provided, and the plurality of limiting protrusions 11 are disposed along a side of the first dielectric plate 10, so that when the first dielectric plate 10 slides along the length direction of the metal stripline 20, the limiting protrusions 11 can simultaneously limit the first dielectric plate 10 at a plurality of positions, which further strengthens the limit of the displacement of the first dielectric plate 10 relative to the metal stripline 20 by the limiting protrusion 11. Certainly, there may alternatively be one limiting protrusion 11, and the limiting protrusion protrudes at a middle position of the first dielectric plate 10.
Further, a distance between the limiting protrusion 11 and the side portion 201 of the metal stripline 20 is greater than 0 mm and less than or equal to 1 mm. In this embodiment, the distance between the limiting protrusion 11 and the side portion 201 of the metal stripline 20 is 0.5 mm. In another embodiment, the distance between the limiting protrusion 11 and the side portion 201 of the metal stripline 20 may alternatively be greater than 0 mm and less than 0.5 mm, or greater than 0.5 mm and less than 1 mm. In this way, there is a distance between the limiting protrusion 11 and the side portion 201 of the metal stripline 20, that is, the first dielectric plate 10 is not in contact with the metal stripline 20, allowing the first dielectric plate 10 to slide smoothly along the metal stripline 20. In addition, the distance between the limiting protrusion 11 and the side portion 201 of the metal stripline 20 is not too large, avoiding that a deviation distance between the first dielectric plate 10 and the metal stripline 20 in the width direction is too large when the first dielectric plate slides.
Referring to
Referring to
Further, when the transmission section of the metal stripline 20 is of a wavy structure (not shown), the wavy transmission section includes a plurality of convex portions and a plurality of concave portions, and the convex portions and the concave portion are disposed at intervals. The concave portion includes an opening, located between two convex portions adjacent to the concave portion. A size of the limiting protrusion 11 along the length direction is greater than a size of the opening along the length direction, so that the limiting protrusion 11 does not fall into it) the concave portion when the first dielectric plate 10 slides relative to the metal stripline 20, avoiding affecting sliding of the first dielectric plate in the length direction.
In an embodiment, the limiting protrusion 11 may alternatively be of a continuous strip-shaped structure (not shown), and the strip-shaped limiting protrusion 11 is disposed on the first dielectric plate 10 along the length direction. When the first dielectric plate 10 deviates from the metal stripline 20 in the width direction at any sliding position, the limiting protrusion 11 can limit a further deviation of the first dielectric plate 10 in time, and correct the first dielectric plate 10 to an original sliding track. In this way, the first dielectric plate 10 can slide along the length direction of the metal stripline 20 without deviation in the width direction. The limiting protrusion 11 is not limited to the shape described in this embodiment. The shape of the limiting protrusion can be changed, for example, a trapezoidal block or a ball, provided that performance and sliding of the dielectric plate are not affected.
Referring to
A second embodiment of this application is not shown in the figure. A difference from the foregoing embodiment lies in that the plurality of limiting protrusions 11 protrudes on the third surface 301 of the second dielectric plate 30 along the length direction, and the plurality of limiting protrusions 11 are located on the side portion 201 of the metal stripline 20. The limiting protrusion 11 is configured to limit displacement of the second dielectric plate 30 relative to the metal stripline 20 when the second dielectric plate 30 slides. The second dielectric plate 30 slides relative to the metal stripline 20 along the length direction. When the second dielectric plate 30 deviates relative to the metal stripline 20 in the width direction, the limiting protrusion 11 plays a blocking role, so that the second dielectric plate 30 always slides along the length direction of the metal stripline 20 without deviation in width. When no limiting protrusion 11 is disposed on the first dielectric plate 10, the second dielectric plate 30 drives the first dielectric plate 10 to slide, which can also ensure a sliding trajectory of the first dielectric plate 10.
In an embodiment, the plurality of limiting protrusions 11 are disposed on a side of the second dielectric plate 30 at intervals along the length direction. That is, the plurality of limiting protrusions 11 may be located on a side of the second dielectric plate 30 close to a first side portion 201, or may be located on a side of the first dielectric plate 10 close to a second side portion 201. In some embodiments, the plurality of limiting protrusions 11 may alternatively be located on two opposite sides of the second dielectric plate 30 and disposed at intervals along the length direction, and are located on two opposite sides of the metal stripline 20. The metal stripline 20 is located between the limiting protrusions 11 on two sides, and the limiting protrusions can limit the second dielectric plate 30, so that the second dielectric plate 30 can accurately slide along the length direction of the metal stripline 20, to further avoid a deviation of the second dielectric plate 30 in the width direction relative to the metal stripline 20.
In a third embodiment of this application (not shown), a difference from the foregoing embodiment lies in that the limiting protrusions 11 are disposed on both the first dielectric plate 10 and the second dielectric plate 30. That is, the limiting protrusions 11 protrude on both the first surface 101 of the first dielectric plate 10 and the third surface 301 of the second dielectric plate 30 along the length direction, and the limiting protrusion 11 is located on the side portion 201 of the metal stripline 20. The limiting protrusion 11 is configured to limit displacement of the first dielectric plate 10 and the second dielectric plate 30 relative to the metal stripline 20 when the first dielectric plate 10 and the second dielectric plate 30 slide. In an embodiment, the limiting protrusion 11 limits the displacement of the first dielectric plate 10 and the second dielectric plate 30 relative to the metal stripline 20 in the width direction. The first dielectric plate 10 and the second dielectric plate 30 slide relative to the metal stripline 20 in the length direction. When the first dielectric plate 10 and the second dielectric plate 30 deviate relative to the metal stripline 20 in the width direction, the limiting protrusion 11 plays a blocking role, so that the metal stripline 20 is always located between the limiting protrusions 11 on two sides, and the first dielectric plate 10 and the second dielectric plate 30 do not deviate from the metal stripline 20 in width.
In an embodiment, when the first dielectric plate 10 and the second dielectric plate 30 slide relative to the metal stripline 20, the limiting protrusion 11 moves along the side portion 201 of the metal stripline 20. As the first dielectric plate 10 and the second dielectric plate 30 move along the side portion 201 of the metal stripline 20, the limiting protrusion 11 can guide the movement of both the first dielectric plate 10 and the second dielectric plate 30, so that the first dielectric plate 10 and the second dielectric plate 30 can smoothly slide along the length direction of the metal stripline 20.
In an embodiment, the plurality of limiting protrusions 11 may protrude on one side or two sides of the first surface 101 of the first dielectric plate 10, or may protrude on one side or two sides of the third surface 301 of the second dielectric plate 30. Alternatively, the limiting protrusions 11 on the first dielectric plate 10 and the second dielectric plate 30 may be located on two sides of the metal stripline 20. In some embodiments, the plurality of limiting protrusions 11 are located on two opposite sides of the first dielectric plate 10 and the second dielectric plate 30 and are disposed at intervals along the length direction, and are located on two opposite sides of the metal stripline 20. That is, the plurality of limiting protrusions 11 are disposed on the first dielectric plate 10 and the second dielectric plate 30 near the two side portions 201, and the metal stripline 20 is located between the limiting protrusions 11 on two sides. When both the first dielectric plate 10 and the second dielectric plate 30 are provided with the plurality of limiting protrusions 11 on the two sides of the metal stripline 20, the limiting protrusions 11 can limit both the first dielectric plate 10 and the second dielectric plate 30 in an X-axis positive direction and an X-axis negative direction, so that both the first dielectric plate 10 and the second dielectric plate 30 can accurately slide along the length direction of the metal stripline 20. This further limits deviations of the first dielectric plate 10 and the second dielectric plate 30 relative to the metal stripline 20 in the width direction.
In an embodiment of this application, the limiting protrusion 11 includes a body and a limiting body (not shown) located at an end portion of the body. The limiting body protrudes on one side of the body and extends towards the width direction. The limiting body is located on a surface of the metal stripline 20 facing away from the first dielectric plate 10.
Specifically, the first embodiment in which the limiting protrusion 11 is disposed on the first dielectric plate 10 is used as an example. The limiting protrusion 11 protrudes on the second surface 102 of the first dielectric plate 10, the body protrudes on the second surface 102, and the other end is connected to the limiting body. The limiting body is away from one side of the body and located on the lower surface 204 of the metal stripline 20. That is, the metal stripline 20 is stuck between the first dielectric plate 10 and the limiting body in a height direction. When the first dielectric plate 10 slides along the length direction of the metal stripline 20, the limiting body prevents the first dielectric plate 10 from deviating in the height direction and displacing in the width direction relative to the metal stripline 20. This further enables the first dielectric plate 10 to slide along the length direction of the metal stripline 20 more accurately. The “height direction” herein refers to a direction perpendicular to the surface of the metal stripline 20.
It may be understood that the limiting protrusion 11 in this embodiment may be further disposed on the second dielectric plate 30, or may be disposed on both the first dielectric plate 10 and the second dielectric plate 30. When the limiting protrusion 11 is disposed on the second dielectric plate 30, the body is connected to the second dielectric plate 30, and the limiting body is located on a surface of the metal stripline 20 facing away from the second dielectric plate 30. That is, the limiting body is away from one side of the body and located on the upper surface 203 of the metal stripline 20, and the metal stripline 20 is stuck between the second dielectric plate 30 and the limiting body in the height direction. The body of the limiting protrusion 11 limits a deviation of the second dielectric plate 30 in the width direction, and the limiting body limits a deviation of the second dielectric plate 30 relative to the metal stripline 20 in the height direction. When the limiting protrusions 11 are disposed on both the first dielectric plate 10 and the second dielectric plate 30, the limiting protrusion 11 on the first dielectric plate 10 simultaneously limits deviations of the first dielectric plate 10 relative to the metal stripline 20 in the width direction and the height direction. The limiting protrusion 11 on the second dielectric plate 30 simultaneously limits deviations of the second dielectric plate 30 relative to the metal stripline 20 in the width direction and the height direction.
Referring to
Further, a single buckle body also protrudes on one side of the first dielectric plate 10, and a side edge of the second dielectric plate 30 corresponding to the buckle body forms an opening groove toward the inside of the dielectric plate. The buckle body is buckled on the opening groove and does not interfere with the metal stripline 20. Disposition of the buckle 15 and the buckle body can fasten the first dielectric plate 10 and the second dielectric plate 30, and in particular, can define a consistency between a length direction and a height direction.
Referring to
In an embodiment, a signal that needs to be radiated out is transmitted to the cavity 50 via the signal input terminal, and is transmitted to the signal output terminal along the direction of the metal stripline 20 via a medium in the cavity 50. The medium in the cavity 50 includes the first dielectric plate 10 and the second dielectric plate 30 that are laminated on a surface of the metal stripline 20, and air around the metal stripline 20. When the first dielectric plate 10 and the second dielectric plate 30 move along the metal stripline 20, an equivalent dielectric constant of a medium in a transmission section between the signal input terminal and the signal output terminal changes, so that a phase of a signal transmitted from the signal output terminal changes. For example, before the first dielectric plate 10 and the second dielectric plate 30 move, the medium in the transmission section includes only air between the metal stripline 20 and the cavity 50. After the first dielectric plate 10 and the second dielectric plate 30 move by a distance, the first dielectric plate 10 and the second dielectric plate 30 move to the transmission section. Therefore, the medium in the transmission section includes the first dielectric plate 10, the second dielectric plate 30, and air between the metal stripline 20 and the cavity 50 in the transmission section, so that the equivalent dielectric constant of the medium in the transmission section changes, and the phase of the signal output by the signal output terminal changes. In addition, when the first dielectric plate 10 and the second dielectric plate 30 are continuously moved, areas of the first dielectric plate 10 and the second dielectric plate 30 in the transmission section change continuously, even if the equivalent dielectric constant of the medium in the transmission section changes, and finally the phase of the signal output by the signal output terminal can be continuously changed. Therefore, in this application, the first dielectric plate 10 and the second dielectric plate 30 can be moved by a distance based on an actual requirement, so that a radiated signal has a required phase.
Further, in an embodiment, the transmission section of the metal stripline 20 is suspended in the cavity 50, and the metal stripline 20 does not need to be disposed on a substrate, thereby reducing signal energy loss caused by the substrate and increasing a gain of the remote electrical tilt antenna. In addition, heat generated due to the signal energy loss can be reduced, thereby lowering a requirement of the phase shifter 100 for heat dissipation and heat resistance performance of an internal structural part, and enhancing temperature resistance reliability of each structure in the remote electrical tilt antenna.
As shown in
In an embodiment, as shown in
The above are merely some embodiments and implementations of this application, and are not intended to limit the protection scope of this application. Any variations or replacements readily figured out by a person skilled in the art within the technical scope disclosed in this application. The variations or replacements shall fall within the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.
This application is a continuation of International Application No. PCT/CN2020/142314, filed on Dec. 31, 2020, the disclosure of which is hereby incorporated by reference in its entirety.
Number | Date | Country | |
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Parent | PCT/CN2020/142314 | Dec 2020 | US |
Child | 18215330 | US |