RELATED APPLICATION(S)

The present application claims priority from and the benefit of Chinese Patent Application No. 201910423143.6, filed May 21, 2019, the disclosure of which is hereby incorporated herein in its entirety.

FIELD

The present invention relates to communication systems and, in particular, to base station antennas having remote electronic tilt capabilities.

BACKGROUND

Cellular communications systems are used to provide wireless communications to fixed and mobile subscribers (herein “users”). A cellular communications system may include a plurality of base stations that each provides wireless cellular service for a specified coverage area that is typically referred to as a “cell.” Each base station may include one or more base station antennas that are used to transmit radio frequency (“RF”) signals to, and receive RF signals from, the users that are within the cell served by the base station. Base station antennas are directional devices that can concentrate the RF energy that is transmitted in certain directions (or received from those directions). The “gain” of a base station antenna in a given direction is a measure of the ability of the antenna to concentrate the RF energy in that particular direction. The “radiation pattern” of a base station antenna is compilation of the gain of the antenna across all different directions. The radiation pattern of a base station antenna is typically designed to service a pre-defined coverage area such as the cell or a portion thereof that is typically referred to as a “sector.” The base station antenna may be designed to have minimum gain levels throughout its pre-defined coverage area, and it is typically desirable that the base station antenna have much lower gain levels outside of the coverage area to reduce interference between sectors/cells. Early base station antennas typically had a fixed radiation pattern, meaning that once a base station antenna was installed, its radiation pattern could not be changed unless a technician physically reconfigured the antenna. Unfortunately, such manual reconfiguration of base station antennas after deployment, which could become necessary due to changed environmental conditions or the installation of additional base stations, was typically difficult, expensive and time-consuming.

More recently, base station antennas have been deployed that have radiation patterns that can be reconfigured from a remote location by transmitting control signals to the antenna. Base station antennas having such capabilities are typically referred to as remote electronic tilt (“RET”) antennas. The most common changes to the radiation pattern are changes in the down tilt angle (i.e., the elevation angle) and/or the azimuth angle. RET antennas allow wireless network operators to remotely adjust the radiation pattern of the antenna by transmitting control signals to the antenna that electronically alter the RF signals that are transmitted and received by the antenna.

Base station antennas typically comprise a linear array or a two-dimensional array of radiating elements such as patch, dipole or crossed dipole radiating elements. In order to electronically change the down tilt angle of these antennas, a phase taper may be applied across the radiating elements of the array, as is well understood by those of skill in the art. Such a phase taper may be applied by adjusting the settings on an adjustable phase shifter that is positioned along the RF transmission path between a radio and the individual radiating elements of the base station antenna. One widely-used type of phase shifter is an electromechanical “wiper” phase shifter that includes a main printed circuit board and a “wiper” printed circuit board that may be rotated above the main printed circuit board. Such wiper phase shifters typically divide an input RF signal that is received at the main printed circuit board into a plurality of sub-components, and then capacitively couple at least some of these sub-components to the wiper printed circuit board.

The sub-components of the RF signal may be capacitively coupled from the wiper printed circuit board back to the main printed circuit board along a plurality of arc-shaped traces, where each arc has a different diameter. Each end of each arc-shaped trace may be connected to a radiating element or to a sub-group of radiating elements. By physically (mechanically) rotating the wiper printed circuit board above the main printed circuit board, the locations where the sub-components of the RF signal capacitively couple back to the main printed circuit board may be changed, which thus changes the length of the respective transmission path from the phase shifter to an associated radiating element for each sub-component of the RF signal. The changes in these path lengths result in changes in the phases of the respective sub-components of the RF signal, and since the arcs have different radii, the phase changes along the different paths will be different. Thus, the above-described wiper phase shifters may be used to apply a phase taper to the sub-components of an RF signal that are applied to each radiating element (or sub-group of radiating elements). Exemplary phase shifters of this variety are discussed in U.S. Pat. No. 7,907,096 to Timofeev, the disclosure of which is hereby incorporated herein in its entirety. The wiper printed circuit board is typically moved using an electromechanical actuator such as a DC motor that is connected to the wiper printed circuit board via a mechanical linkage. These actuators are often referred to as RET actuators since they are used to apply the remote electronic down tilt.

Modern base station antennas often include two, three or more linear arrays of radiating elements. If the linear arrays include cross-polarized radiating elements, then a separate phase shifter is provided for each polarization (i.e., two phase shifters per linear array). Moreover, separate transmit and receive phase shifters are often provided for each linear array so that the transmit and receive radiation patterns may be independently adjusted, which may again double the number of phase shifters. Additionally, in some cases, some (or all) of the linear arrays may be formed using wideband radiating elements that support service in multiple frequency bands (e.g., the 700 MHz and 800 MHz frequency bands or two or more frequency bands within the 1.7-2.7 GHz frequency range). When such wideband linear arrays are used, separate phase shifters may be provided for each frequency band within the broader operating frequency range of the radiating elements. Since base station antennas with two to as many as eight linear arrays of cross-polarized radiating elements are being deployed, it is not uncommon for a base station antenna to have eight, twelve or even twenty-four adjustable phase shifters for applying remote electronic down tilts to the linear arrays.

As described above, RET actuators are provided in the antenna that are used to move elements on the phase shifters to adjust the down tilt angle of the antenna beams formed by the various linear arrays. While the same down tilt is typically applied to the phase shifters for the two different polarizations, allowing a single RET actuator and a single mechanical linkage to be used to adjust the phase shifters for both polarizations, modern base station antennas still often need four, six, twelve or even more RET actuators. Such large numbers of RET actuators and associated mechanical linkages can significantly increase the size, weight and cost of a base station antenna.

Conventionally, a separate RET actuator was provided for each phase shifter (or each pair of phase shifters if dual polarized radiating elements are used in a linear array). More recently, RET actuators have been proposed that may be used to move the wiper printed circuit board on as many as twelve phase shifters. For example, U.S. Patent Publication No. 2013/0307728 (“the '728 publication”) discloses a RET actuator that may be used to drive six different mechanical linkages for purposes of adjusting six (or twelve) different phase shifters using one so-called “multi-RET actuator.” U.S. Patent Publication No. 2017/0365923 (“the '923 publication”) discloses a number of additional multi-RET actuator designs.

As more complex base station antennas are introduced, requiring ever increasing numbers of independently controlled phase shifters, it can become difficult to design base station antennas that fit within customer-demanded limitations on the size of the antenna. While conventional multi-RET actuators occupy less volume within the antenna than the total volume occupied by the individual RET actuators that they replace, conventional multi-RET actuators tend to be large and cumbersome, and hence may be difficult to fit within some antenna designs. It can also be difficult to accommodate multiple multi-RET actuators within base station antenna designs, which is sometimes required.

SUMMARY

One of the objects of the present invention is to provide a multi-RET actuator that is capable of overcoming at least one of the defects in the prior art.

Embodiments of the present invention are directed to an actuator for multiple phase shifters. The actuator may include a motor, a linkage drive system including a plurality of drive mechanisms for driving mechanical linkages of multiple phase shifters, a linkage selection system that is configured to selectively connect the motor to a selected one of the drive mechanisms of the linkage drive system. The linkage selection system may include a support seat having a length direction that is transverse to a length direction of the mechanical linkage, a carrier disposed on the support seat and configured to carry the motor back and forth along a length direction of the support seat, and a movement transmission mechanism that is configured to switch between a movement state in which the movement transmission mechanism is configured to move the carrier and the motor to a position where an output of the motor can engage the selected one of the driving mechanisms, and a transmission state in which the movement transmission mechanism transfers a rotational movement of the output of the motor to the selected one of the drive mechanisms.

In some embodiments, the linkage selection system further includes a state changeover switch that is configured to switches the movement transmission mechanism between the movement state and the transmission state.

In some embodiments, the state changeover switch is a solenoid valve or a motor.

In some embodiments, the movement transmission mechanism includes a rack, a gear train that is configured to selectively mesh with the rack, and an output shaft of the movement transmission mechanism connected to the gear train.

In some embodiments, the rack is fixed to the support seat and extends along a length direction of the support seat.

In some embodiments, the gear train is mounted on one side of the carrier proximate the mechanical linkages, and the motor and the state changeover switch are mounted on another side of the carrier that is away from the mechanical linkages.

In some embodiments, the gear train includes a first gear that is directly connected to an output shaft of the motor and a second gear that is directly connected to an output shaft of the state changeover switch, wherein the first gear and the second gear are directly engaged or are engaged through one or more intermediate gears.

In some embodiments, the second gear remains engaged with both the first gear and the rack when the state changeover switch is in the movement state, and remains engaged with the first gear and disengaged from the rack when the state changeover switch is in the transmission state.

In some embodiments, the first gear and the second gear are both spur gears.

In some embodiments, the output shaft of the movement transmission mechanism is coaxially fixed to a center of the second gear.

In some embodiments, the support seat includes one or more guide rods and a base that supports the guide rods.

In some embodiments, the carrier spans the guide rod, and is configured for movement back and forth in a length direction of the support seat along the guide rod.

In some embodiments, the base includes a bottom plate fixed to a substrate of the actuator, and projecting arms projecting upwardly from both ends of the bottom plate and supporting the guide rod.

In some embodiments, the projecting arms support the guide rod above the substrate on both ends of the guide rod.

In some embodiments, the linkage drive system includes a support seat and a plurality of lead screws supported on the support seat.

In some embodiments, each lead screw is provided with a drive block for driving a reciprocal movement of the mechanical linkages, and each drive block is engaged with an external thread of a respective one of the lead screws by internal threads.

In some embodiments, each lead screw is provided with a connection portion on an end facing the linkage selection system that is configured to connect with an output shaft of the linkage selection system.

In some embodiments, the connection portion has a recess for receiving a top end of the output shaft of the linkage selection system, and the recess has a cross-sectional profile that matches a cross-sectional profile of the top end of the output shaft of the linkage selection system.

In some embodiments, the actuator includes a controller that is configured to control operation of the motor and operation of the state changeover switch.

