Patent Description:
A cellular communication system is used to provide wireless communication to fixed and mobile users. The cellular communication system may include a plurality of base stations, and each base station provides a wireless cellular service for a designated coverage area (generally referred to as a "cell"). Each base station may include one or more base station antennas, and the base station antenna is used to transmit radio frequency ("RF") signals to a user located in a cell served by the base station and receive RF signals from the user. The base station antenna is a directional device that can concentrate RF energy transmitted in certain directions or received from certain directions.

A modern base station antenna usually includes two, three or more linear (or planar) arrays of radiating elements, where each linear array has an electronically adjustable downtilt angle. The linear array usually includes a cross-polarized radiating element, and is provided with a separate phase shifter for electronically adjusting the downtilt angle of antenna beams for each polarization, so that the antenna can include twice the phase shifters of the linear array. In addition, in many antennas, a separate transmitting and receiving phase shifter is provided so that transmitting and receiving radiation patterns can be adjusted independently. This would again doubles the number of phase shifters. Therefore, it is not surprising that the base station antenna has eight, twelve, eighteen, thirty-two, or more phase shifters for applying remote electrical downtilt angles to linear arrays.

A remote electrical tilt ("RET") actuator and an associated transmission mechanism may be provided in the base station antenna to adjust the phase shifter. Conventionally, each phase shifter is equipped with a separate RET actuator, which results in the base station antenna including a large number of RET actuators, thereby significantly increasing the size, weight, and cost of the base station antenna. Therefore, in some cases, it is necessary to use a RET actuator including a single motor to simultaneously drive a plurality of phase shifters.

<FIG> shows a transmission mechanism <NUM> of the prior art, which attempts to use a single motor <NUM> to drive a plurality of shifters <NUM>. The transmission mechanism <NUM> includes a driving rod <NUM> driven by the motor <NUM> via a screw <NUM> and a plurality of connecting rods <NUM> parallel to the driving rod <NUM> and spaced apart from each other in a transverse direction perpendicular to an axial direction of the driving rod <NUM>. Each connecting rod <NUM> can drive one or more phase shifters to adjust downtilt angles thereof. A plurality of connecting rods <NUM> are fixed together via one or more connecting plates <NUM> to simultaneously move axially when driven by the driving rod <NUM>, thereby driving a plurality of phase shifters.

Limited by the output power of the motor <NUM>, the transmission mechanism <NUM> of the prior art can only drive a limited number of phase shifters. For example, currently a motor usually used in a base station antenna can generate a pulling force of about <NUM> lbf, while a pulling force of about <NUM> lbf is needed to drive a phase shifter. Therefore, a motor can only drive up to <NUM> phase shifters. However, in some cases, it is required that a single motor be used to drive at least <NUM> phase shifters, and the transmission mechanism <NUM> obviously cannot meet such requirement.

Moreover, since the plurality of connecting rods <NUM> are spaced apart from each other in the transverse direction, each connecting rod <NUM> has a moment arm as compared with the driving rod <NUM>, and has torque as a result. Since each connecting rod <NUM> has a different moment arm size compared with the driving rod <NUM>, the generated torque is also different, which will cause the plurality of connecting rods <NUM> to generate uneven driving forces and therefore affect the adjustment accuracy of the corresponding phase shifters.

Furthermore, as shown in <FIG>, in the prior art, each connecting rod <NUM> drives a movable element <NUM> of each phase shifter via a connecting element <NUM> fixed thereon to make the movable element <NUM> move in an arc-shaped groove <NUM>. When the movable element <NUM> deviates from the central position of the arc-shaped groove <NUM>, a pulling force <NUM> generated by the connecting rod <NUM> will generate a tangential component <NUM> and a radial component <NUM>, of which only the tangential component <NUM> can be used to drive the movable element <NUM>. This reduces the effective pulling force generated by the connecting rod <NUM>, thereby further reducing the number of phase shifters that can be driven by a single motor <NUM>. In addition, when the movable element <NUM> moves to both ends of the arc-shaped groove <NUM>, the movable element <NUM> may be stuck at the end portions of the arc-shaped groove <NUM> and be difficult to move out. Therefore, a larger force is required, which further reduces the number of phase shifters that can be driven by a single motor <NUM>.

Further prior art related to the preamble of claim <NUM> is seen in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

An object of the present invention is to provide a transmission mechanism for a base station antenna and a base station antenna including the transmission mechanism, which can overcome at least one defect in the prior art. The invention is described in independent claim <NUM>; preferred embodiments being seen in the dependent claims.

In a first aspect of the present invention, a transmission mechanism for a base station antenna is provided. The transmission mechanism includes: a worm gear unit, which includes a worm driven by a motor and a worm gear meshed and connected with the worm; at plurality of gear pairs, each gear pair including a small gear and a large gear that mesh with each other, the small gear and the worm gear being mounted on a common first drive shaft so that the small gear and the worm gear rotate synchronously, the small gears being spaced apart from each other, each of the large gears being mounted spaced apart from each other on a second drive shaft; a plurality of connecting rods, each connecting rod including a first rack element fixedly mounted thereon, wherein the large gear of each gear pair is meshed and connected with the first rack element on a corresponding connecting rod so as to axially move the connecting rod via the first rack element when the large gear of each gear pair rotates.

According to an embodiment of the present invention, the transmission mechanism may further include an arc-shaped connecting member adapted to be fixedly connected to a movable element of a phase shifter, and the arc-shaped connecting member is configured to be rotationally driven to cause the movable element of the phase shifter to move along an arc.

According to an embodiment of the present invention, the arc-shaped connecting member may be configured as an arc-shaped rack, a plurality of teeth are provided on a front end surface of the arc-shaped rack, each connecting rod may include at least one second rack element mounted thereon, and the second rack element is meshed and connected with the plurality of teeth of the arc-shaped rack so as to rotate the arc-shaped rack when the connecting rod moves axially.

According to an embodiment of the present invention, the worm may extend in a direction of the connecting rods, and the first drive shaft may extend in a direction perpendicular to the connecting rods.

According to an embodiment of the present invention, the gear ratio of the worm gear and the worm may be from <NUM> to <NUM>.

According to an embodiment of the present invention, the first drive shaft may have a non-circular cross section, and the small gear may have a non-circular hole used for the first drive shaft.

According to an embodiment of the present invention, the first drive shaft may be integrally formed with the worm gear and/or the small gear.

According to an embodiment of the present invention, each gear pair may include a supporting member used for the small gear.

According to an embodiment of the present invention, the small gear may include a body including a tooth portion provided with teeth and a shaft portion adapted to be mounted in the supporting member to enable the small gear to rotate. The supporting member may include an annular sleeve, and the shaft portion of the small gear may be rotatably mounted in the annular sleeve.

According to an embodiment of the present invention, the first rack element may include a bottom plate, a vertical plate extending vertically upward from one side of the bottom plate, and a rack located at a top end of the vertical plate, and the vertical plate is provided with a connecting element for connecting with the connecting rods.

According to an embodiment of the present invention, the connecting element may include one or more selected from the group consisting of a post, a snap clip, a bolt, a hook and a connecting fastener, and a groove.

According to an embodiment of the present invention, the transmission mechanism may be configured to simultaneously drive at least <NUM> phase shifters by a single motor.

In a second aspect of the present invention, a base station antenna is provided. The base station antenna may include the transmission mechanism for a base station antenna according to any one embodiment of the present invention.

It should be noted that various aspects of the present invention described for one embodiment may be included in other different embodiments, although specific description is not made for the other different embodiments. In other words, all the embodiments and/or features of any embodiment may be combined in any manner and/or combination, as long as they are not contradictory to each other.

Multiple aspects of the present invention will be better understood after the following specific embodiments are read with reference to the attached drawings. In the attached drawings:.

It should be understood that in all the attached drawings, the same reference numerals and signs denote the same elements. In the attached drawings, the size of certain features may be changed and are not drawn to scale for clarity.

The present invention will be described below with reference to the attached drawings, and the attached drawings illustrate several embodiments of the present invention. However, it should be understood that the present invention may be presented in many different ways and is not limited to the embodiments described below; in fact, the embodiments described below are intended to make the disclosure of the present invention more complete and to fully explain the protection scope of the present invention to those skilled in the art. It should also be understood that the embodiments disclosed in the present invention may be combined in various ways so as to provide more additional embodiments.

It should be understood that the terms in the specification are only used to describe specific embodiments and are not intended to limit the present invention. Unless otherwise defined, all terms (including technical terms and scientific terms) used in the specification have the meanings commonly understood by those skilled in the art. For brevity and/or clarity, well-known functions or structures may not be described in detail.

The singular forms "a", "an", "the" and "this" used in the specification all include plural forms unless clearly indicated. The words "include", "contain" and "have" used in the specification indicate the presence of the claimed features, but do not exclude the presence of one or more other features. The word "and/or" used in the specification includes any or all combinations of one or more of the related listed items.

In the specification, when it is described that an element is "on" another element, "attached" to another element, "connected" to another element, "coupled" to another element, or "in contact with" another element, etc., the element may be directly on another element, attached to another element, connected to another element, coupled to another element, or in contact with another element, or an intermediate element may be present.

In the specification, the terms "first", "second", "third", etc. are only used for convenience of description and are not intended to be limiting. Any technical features represented by "first", "second", "third", etc. are interchangeable.

In the specification, terms expressing spatial relations such as "upper", "lower", "front", "rear", "top", and "bottom" may describe the relation between one feature and another feature in the attached drawings. It should be understood that, in addition to the orientations shown in the attached drawings, the terms expressing spatial relations further include different orientations of a device in use or operation. For example, when a device in the attached drawings is turned upside down, the features originally described as being "below" other features now can be described as being "above" the other features. The device may also be oriented in other directions (rotated by <NUM> degrees or in other orientations), and in this case, a relative spatial relation will be explained accordingly.

Referring to <FIG> and <FIG>, a transmission mechanism <NUM> for a base station antenna according to an embodiment of the present invention is shown. The transmission mechanism <NUM> includes a plurality of connecting rods <NUM> arranged in parallel. The plurality of connecting rods <NUM> may be driven by a single motor <NUM> simultaneously to move axially, and each connecting rod <NUM> may drive a movable element (for example, a brush piece of a rotating brush-type phase shifter) of one or more phase shifters <NUM> when moving axially to adjust a directional angle (for example, an elevation angle or a downtilt angle) of antenna beams generated by the base station antenna. In the embodiments shown in <FIG> and <FIG>, the transmission mechanism <NUM> includes eight connecting rods <NUM> arranged in parallel, and each connecting rod <NUM> can simultaneously drive two pairs of shifters <NUM> spaced apart in the axial direction of the connecting rod <NUM>. Therefore, the transmission mechanism <NUM> can simultaneously drive <NUM> phase shifters. However, the present invention is not limited thereto, and the transmission mechanism <NUM> of the present invention may be used to drive any other number of phase shifters. In an embodiment of the present invention, the connecting rod <NUM> may be made of glass fiber, other plastics, or metal.

The transmission mechanism <NUM> includes a worm gear unit. As shown more clearly in <FIG>, the worm gear unit includes a worm <NUM> extending in the direction of the connecting rod <NUM> and a worm gear <NUM> meshed and connected with the worm <NUM>. The worm <NUM> is configured to be driven by the motor <NUM> to rotate about its longitudinal axis. To this end, one end of the worm <NUM> may be directly or indirectly connected with an output shaft of the motor <NUM>, and the other end of the worm <NUM> may be supported by a supporting element <NUM>. The worm gear <NUM> may be arranged above the worm <NUM> and rotate driven by the worm <NUM>. The central axis of the worm gear <NUM> may be arranged to be perpendicular to the worm <NUM>.

In an embodiment according to the present invention, the output torque of the motor <NUM> may be amplified to varying degrees by selecting the gear ratio of the worm gear <NUM> and the worm <NUM> of the worm gear unit, so that a single motor <NUM> can drive a larger number of phase shifters. Generally speaking, the number of heads of the worm <NUM> may be <NUM> to <NUM>, and the number of teeth of the worm gear <NUM> may be several times the number of the heads of the worm <NUM>. In an embodiment according to the present invention, the number of heads of the worm <NUM> may be <NUM>, and the number of teeth of the worm gear <NUM> may be <NUM> to <NUM>. Therefore, the gear ratio of the worm gear <NUM> and the worm <NUM> is from <NUM> to <NUM>. In this way, the worm gear unit can amplify the output torque of the motor <NUM> by <NUM> to <NUM> times, so that when the same motor is used for driving, the pulling force generated by the transmission mechanism <NUM> is <NUM> to <NUM> times the pulling force generated by the transmission mechanism <NUM> in the prior art. The gear ratio of the worm gear <NUM> and the worm <NUM> may also be in other appropriate ranges, such as <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, and so on.

The worm gear unit can reduce the output rotation speed of the motor <NUM> while amplifying the output torque of the motor <NUM>, and a lower rotation speed makes it possible to adjust the phase shifter more accurately. In addition, comparing with the screw <NUM> used in the prior art, the worm <NUM> of the worm gear unit can have a smaller length, which can reduce the space occupied by the transmission mechanism <NUM> in the base station antenna.

The transmission mechanism <NUM> further includes a plurality of gear pairs, and each gear pair is used to drive a corresponding connecting rod <NUM>. In the embodiments shown in <FIG> and <FIG>, since the transmission mechanism <NUM> includes eight connecting rods <NUM>, it correspondingly includes eight gear pairs. The gear pair is used to further amplify the output torque of the motor <NUM>. As shown more clearly in <FIG> and <FIG>, each gear pair includes a small gear <NUM> and a large gear <NUM> meshed with the small gear <NUM>. All the small gears <NUM> of the plurality of gear pairs and the worm gear <NUM> are mounted on a common drive shaft <NUM> so that the small gears <NUM> rotate synchronously with the worm gear <NUM>. The drive shaft <NUM> extends in a direction perpendicular to the connecting rod <NUM>, and the small gears <NUM> of the plurality of gear pairs are spaced apart from each other on the drive shaft <NUM>. The drive shaft <NUM> can ensure that the small gears <NUM> of the plurality of gear pairs have the same rotation speed, and can evenly transmit the output torque of the worm gear <NUM> to each small gear <NUM> via the drive shaft <NUM>. This can solve the problem that the driving forces of the plurality of connecting rods <NUM> are uneven in the transmission mechanism <NUM> in the prior art, and thus can more accurately adjust a plurality of phase shifters in the base station antenna synchronously.

Similarly, all the large gears <NUM> of the plurality of gear pairs are also mounted on a common drive shaft <NUM> and are spaced apart from each other. The drive shaft <NUM> makes all the large gears <NUM> of the plurality of gear pairs have the same rotation speed and therefore have a uniform output torque.

According to needs, the output torque of the motor <NUM> may be further amplified to varying degrees and the output rotation speed of the motor <NUM> may be reduced at the same by selecting the gear ratio of the large gear <NUM> and the small gear <NUM>. This makes it possible not only to use a single motor <NUM> to drive a larger number of phase shifters at the same time, but also to adjust the phase shifters more accurately at a lower speed.

In an embodiment according to the present invention, the drive shaft <NUM> may have a non-circular (for example, rectangular) cross-section, which extends through a non-circular hole provided in the center of the small gear <NUM> for matching with the non-circular cross section of the drive shaft <NUM>, so that the small gear <NUM> is not rotatable relative to the drive shaft <NUM>. Similarly, the drive shaft <NUM> may have a non-circular (for example, rectangular) cross section, which extends through a non-circular hole provided in the center of the large gear <NUM> for matching with the non-circular cross section of the drive shaft <NUM>, so that the large gear <NUM> is not rotatable relative to the drive shaft <NUM>. In another embodiment of the present invention, the drive shaft <NUM> may be integrally formed with the small gear <NUM> and the worm gear <NUM>, and the drive shaft <NUM> may be integrally formed with the large gear <NUM>.

In order to enhance the support for the small gear <NUM>, a supporting member <NUM> may be further provided for each small gear of the plurality of gear pairs. <FIG> respectively show the specific structures of the small gear <NUM> and the supporting member <NUM> according to an embodiment of the present invention. The small gear <NUM> may include a body having a non-circular hole <NUM>. The body includes a tooth portion <NUM> provided with teeth and a shaft portion <NUM> adapted to be mounted in the supporting member <NUM> to enable the small gear to rotate. Both ends of the shaft portion <NUM> are provided with flanges <NUM> and <NUM>, and the flanges <NUM> and <NUM> restrict the translation of the small gear <NUM> relative to the supporting member <NUM>. The supporting member <NUM> may include a base <NUM>, a body <NUM> extending upright from the base <NUM>, and an annular sleeve <NUM> at the top end of the body <NUM>. The base <NUM> may be fixed in the base station antenna. The shaft portion <NUM> of the small gear <NUM> may be rotatably mounted in the annular sleeve <NUM>, wherein the flanges <NUM> and <NUM> are respectively located on two sides of the annular sleeve <NUM> to restrict the translation of the small gear <NUM> relative to the supporting member <NUM>. The supporting member <NUM> may be configured as a separate structure for ease of the installation of the small gear <NUM>.

Returning to <FIG>, each gear pair of the transmission mechanism <NUM> drives a corresponding connecting rod <NUM> through a rack element <NUM> meshed and connected with the large gear <NUM>. The rack element <NUM> may be fixedly mounted on the connecting rod <NUM>. As a result, when the large gear <NUM> rotates, the large gear <NUM> can axially move the connecting rod <NUM> via the rack element <NUM>, thereby moving the movable element of one or more phase shifters <NUM>. Each large gear <NUM> can drive the corresponding connecting rod <NUM> more stably and efficiently through the rack element <NUM>.

<FIG> shows the specific structure of the rack element <NUM> according to an embodiment of the present invention. The rack element <NUM> may include a bottom plate <NUM>, a vertical plate <NUM> extending vertically upward from one side of the bottom plate <NUM>, and a rack <NUM> located at the top end of the vertical plate <NUM>. The rack <NUM> includes a plurality of teeth to be meshed with the large gear <NUM>. The vertical plate <NUM> is provided with a connecting element for connecting with the connecting rod <NUM>. The connecting element may include a series of posts <NUM> and a pair of snap clips <NUM>. The post <NUM> is accommodated in a corresponding cylindrical hole in the corresponding connecting rod <NUM>, and the snap clip <NUM> holds the connecting rod <NUM> in place when the post is inserted into the cylindrical hole of the connecting rod <NUM>, thereby causing the rack element <NUM> to be fixed to the connecting rod <NUM>. However, it should be understood that any one of a variety of connecting elements may be used, for example, a post, a bolt, a hook and a connecting fastener, a groove, etc..

In order to solve the problem that the pulling force <NUM> generated by the connecting rod <NUM> of the transmission mechanism <NUM> in the prior art will generate the tangential component <NUM> and the radial component <NUM> when the movable element <NUM> deviates from the central position of the arc-shaped groove <NUM>, the transmission mechanism <NUM> of the present invention further includes an arc-shaped connecting member <NUM> adapted to drive the movable element of the phase shifter to move together along an arc. As shown in <FIG> and <FIG>, the arc-shaped connecting member <NUM> is configured in the form of an arc-shaped rack, and teeth <NUM> are provided on the front end surface of the arc-shaped connecting member <NUM>. The movable element (for example, a brush piece of a rotating brush type phase shifter) of the phase shifter may be fixedly connected with the arc-shaped connecting member <NUM> at the central position of the arc-shaped connecting member <NUM> so as to move driven by the arc-shaped connecting member <NUM>. The teeth of the arc-shaped connecting member <NUM> are meshed with teeth <NUM> of a rack element <NUM> fixed on the connecting rod <NUM>, so that the arc-shaped connecting member <NUM> rotates when the rack element <NUM> moves axially, thereby driving the movable element of the phase shifter to rotate.

Unlike the rack element <NUM>, the rack element <NUM> includes a bottom plate <NUM>. One surface of the bottom plate <NUM> is provided with a rack <NUM> including a plurality of teeth <NUM>, and the opposite surface of the bottom plate <NUM> is provided with a connecting element such as a post and a snap clip to fix the rack element <NUM> on the connecting rod <NUM>. In the embodiments shown in <FIG> and <FIG>, each rack element <NUM> fixed on the connecting rod <NUM> can drive the movable elements of a pair of phase shifters. Therefore, the rack element <NUM> may include two sets of teeth <NUM> arranged in a mirror image, and each set of teeth <NUM> is meshed with the teeth <NUM> of an arc-shaped connecting member <NUM>. Accordingly, the two movable elements in each pair of phase shifters are arranged so that their end portions with which the arc-shaped connecting members <NUM> are connected face each other.

With the help of the arc-shaped connecting member <NUM>, the pulling force of the connecting rod <NUM> is always maintained in the axial direction of the connecting rod <NUM> without component in any other directions. As a result, the pulling force of the connecting rod <NUM> can all be used to move the movable element of the phase shifter without any efficiency loss. In addition, when the arc-shaped connecting member <NUM> is used, the arc-shaped groove <NUM> in the prior art is no longer needed. Therefore, there will not be the problem that the removable element of the phase shifter get stuck in the arc-shaped groove <NUM> and is difficult to move out.

Claim 1:
A transmission mechanism for a base station antenna, including:
a worm gear unit, which includes a worm (<NUM>) driven by a motor (<NUM>) and a worm gear (<NUM>) meshed and connected with the worm;
the transmission mechanism characterised by comprising:
a plurality of gear pairs, each gear pair including a small gear (<NUM>) and a large gear (<NUM>) that mesh with each other, the small gear and the worm gear being mounted on a common first drive shaft (<NUM>) so that the small gear and the worm gear rotate synchronously, the small gears being spaced apart from each other, each of the large gears being mounted spaced apart from each other on a second drive shaft (<NUM>); and
a plurality of connecting rods (<NUM>) arranged in parallel, each connecting rod including a first rack element (<NUM>) fixedly mounted thereon, wherein the large gear (<NUM>) of each gear pair is meshed and connected with the first rack element (<NUM>) on a corresponding connecting rod (<NUM>) so as to axially move the connecting rod (<NUM>) via the first rack element (<NUM>) when the large gear (<NUM>) of each gear pair rotates.