The present invention relates generally to an antenna in a mobile communication base station, and in particular, to a variable beam controlling antenna configured to control the horizontal beam width of the antenna and horizontal steering as well.

While a fixed antenna was used as a base station antenna in a mobile communication system in the early stage of development, in recent years, a vertical variable down-tilting antenna has been widely used due to its advantages. This vertical variable down-tilting antenna adjusts phase at a vertical array by use of a phase shifter, thereby controlling an antenna beam vertically in accordance with the overage of a cell site.

In recent years, even a technique for horizontally steering antenna beams in the directions of sectors according to the distribution of subscribers within a cell site has been developed. For the purpose of horizontal control of antenna beams, two ways are considered: electrical horizontal beam control through electrical phase control of a signal provided to each column and mechanical horizontal steering using a 1-column antenna.

Since the mechanical beam control scheme is favorable in antenna size and cost and has the electrical advantage of not causing horizontal side lobe, it is used widely. Needless to say, the vertical beam control scheme is done by a separate operation and thus it is applicable to both vertical tilting and horizontal steering.

Use of an antenna equipped with the two-dimensional control functions of vertical tilting and horizontal steering makes it possible dynamic network optimization according to subscriber distribution. However, problems may occur in an actual cell site with the use of the two-dimensional beam control only. In the most typical sector configuration, i.e., a three 120-degree sector configuration, when horizontal steering direction is adjusted according to subscriber distribution, shadowing can be produced or an overlapped zone increases between sectors. Accordingly, for adjustment of the horizontal steering direction, changing horizontal beam width is required to suppress the shadowing and minimize the overlap zone.

Easy and low-cost implementation of the horizontal beam width changing function has been very difficult so far. Conventionally, horizontal beam width is changed in three ways.

One of them is to adjust the angle and length of a reflector in a one-1column antenna. It is a classic method used for a vertical polarization antenna. Its example is disclosed in "Ref. Mobile Antenna System Handbook, K. Fujimoto and J. R. James pp. 133-134". However, distinctive drawbacks of the horizontal beam width changing method are that an antenna becomes very huge due to a valid reflector length and the isolation and cross polarization of a dual polarization antenna widely used at preset are degraded.

Another way to change horizontal beam width is a typical antenna technique in which a three or more-column antenna is horizontally implemented so that the antenna beam width is changed through control of the distribution ratio and phase of each column. An example of this technique is found in a Korean Patent Application No. 2003-7000418 entitled "Cellular Antenna" and filed by "Andrew Corporation". This method is not viable for commercialization in a mobile communication base station.

While a predetermined beam width is realized with use of a one-column or two-column antenna in a typical mobile communication base station, the above technique requires at least a three-column antenna. Therefore, antenna size and cost are increased. Moreover, to change the distribution ratio and phase, expensive and high-loss parts are used, thereby decreasing antenna gain. Therefore, an antenna employing this method is used for military purposes.

The other way is that a two- or more-column antenna is implemented horizontally and the horizontal steering directions of the reflectors in the columns are controlled to cross each other mechanically, to thereby control beam width. In practice, it is hard to form a typical antenna beam suitable for a sector with this kind of antenna. An example of this technique is found in a Korean Patent Application No. 2003-95761 entitled "Apparatus for Controlling Antenna Beam in a Mobile Communication Base Station" and filed by the present applicant. When a wide beam width is obtained by changing the antenna beam width, ripples are created in the forward direction of the antenna and a radiation pattern other than "Sharp Roll-off" increases an overlap zone between sectors. This method also requires at least a two-column antenna.

Accordingly, an object of the present invention is to provide a one-column antenna configured to control horizontal beam width.

Another object of the present invention is to provide a variable beam controlling antenna in a mobile communication base station, which is a one-column antenna configured to control horizontal beam width and thus to be suitable for high function, low cost and network optimization.

A further object of the present invention is to provide a variable beam controlling antenna in a mobile communication base station, which is a one-column antenna configured to control horizontal beam width and horizontal steering.

The above objects are achieved by providing a variable beam controlling antenna for a mobile communication base station. In the antenna, at least two radiator portions are arranged in sequence vertically to have the same rotational center, each having a reflector with at least one radiator installed therein. At least one force generator provides rotational force, controlled by an external control signal, and a force transfer portion transfers the rotational force generated from the force generator to at least one reflector and thus rotates the at least one reflector.

The antenna is adapted to control the horizontal width of a bean of said antenna by said external control signal.

It is preferred that the antenna further includes a second force generator for providing rotational force to rotate the entire radiator portions, and a second force transfer portion for transferring the rotational force generated from the second force generator to the radiators and thus rotating the entire radiators.

• FIG. 1 is a schematic view of a variable beam controlling antenna installed in a mobile communication base station according to an embodiment of the present invention;
• FIG. 2 schematically illustrates an example of the rotational positions of reflectors in the antenna illustrated in FIG. 1;
• FIG. 3 is a schematic view of a variable beam controlling antenna installed in a mobile communication base station according to another embodiment of the present invention;
• FIG. 4 is an exemplary view of the results of a beam width control simulation of the antenna illustrated in FIG. 1;
• FIG. 5 is an exemplary view of the results of a beam width control simulation of the antenna illustrated in FIG. 3;
• FIGs. 6A, 6B and 6C are perspective views illustrating an important portion of a variable beam controlling antenna in a mobile communication base station according to a third embodiment of the present invention;
• FIG. 7 is a partially enlarged perspective view of the bottom of a second radiator in the important portion of the antenna illustrated in FIGs. 6A, 6B and 6C; and
• FIGs. 8A and 8B are exemplary views of an antenna modified from the antenna illustrated in FIGs. 6A and 6B.

Preferred embodiments of the present invention will be described below in detail with the attached drawings. Details such as specific components are described in the following description, and it is obvious to those skilled in the art that the details are provided for comprehensive understanding of the present invention and thus variations or modifications can be made to them within the scope of the present invention as defined by the claims.

FIG. 1 is a schematic view of a variable beam controlling antenna installed in a mobile communication base station according to an embodiment of the present invention and FIG. 2 schematically illustrates an example of the rotational positions of reflectors in the antenna illustrated in FIG. 1.

Referring to FIGs. 1 and 2, an antenna for changing horizontal beam width according to an embodiment of the present invention is of a one-column antenna structure. It has three separate radiator portions in a vertical direction. That is, a first radiator portion 10, a second radiator portion 20, and a third radiator portion 20 are separately configured.

Each radiator portion is configured to have a reflector with antenna devices including at least one radiator appropriately arranged therein in order to receive and transmit radio signals for mobile communications.

In the example illustrated in FIG. 1, the first radiator portion 10 is provided with a first reflector 11 including first, second and third radiators 111, 112 and 113. The second radiator portion 20 is provided with a second reflector 21 including fourth, fifth and sixth radiators 211, 212 and 213. The third radiator portion 30 is provided with a third reflector 31 including seventh, eighth and ninth radiators 311, 312 and 313.

In accordance with the embodiment of the present invention, the first, second and third reflectors 11, 21 and 31 are configured to rotate upon the same rotational center in the first, second and third radiator portions 10, 20 and 30. Or they can be configured to rotate upon different rotational centers, more or less out, of the common rotational center.

First, second and third force generators 13, 23 and 33 are provided to generate rotational force to the first, second and third reflectors 11, 21, and 31 in response to an external control signal. They can be motors.

First, second and third force transfer portions 12, 22 and 32 are provided to transfer rotational force generated from the first, second and third force generators 13, 23 and 33 to the first, second and third reflectors 11, 21 and 31 and thus rotate them. The first, second and third force transfer portions 12, 22 and 32 are configured to include a plurality of gears, a shaft and a bearing.

The external control signal that controls the operation of the first, second and third force generators 13, 23 and 33 can be provided by cable or wirelessly from a source, that is, from near to the antenna, a base station body (not shown), or a base station controller.

When a tall building is constructed or a new base station is built in a near area, or when radiation environment changes due to a temporary increase of calls in number, for optimum cell planning, an appropriate control signal is applied to the first, second and third force generators 13, 23 and 33, to thereby rotate the first, second and third reflectors 11, 21 and 31 to an appropriate degree.

In the antenna having the above-described configuration, the first, second and third radiator portions 10, 20 and 30 are contained in one radome 50 serving as a housing, which is sealed with upper and lower caps (not shown). Thus, the radome 50 makes the first, second and third radiator portions 10, 20 and 30 collectively look a single antenna.

FIG. 3 is a schematic view of a variable beam controlling antenna installed in a mobile communication base station according to another embodiment of the present invention. The antenna is identical to the antenna illustrated in FIG. 1 in configuration and principle. While the radiators in the first, second and third reflectors 11, 21 and 31 are of a one-column array structure in the antenna of FIG. 1, radiators are arranged in two columns in reflectors in the second embodiment of the present invention illustrated in FIG. 3.

FIG. 4 is an exemplary view of the results of a beam width control simulation of the antenna illustrated in FIG. 1 and FIG. 5 is an exemplary view of the results of a beam width control simulation of the antenna illustrated in FIG. 3. Referring to FIGs. 4 and 5, the variations of a horizontal beam width according to the rotational angles (directions) of the first and third reflectors 11 and 31 with respect to the second reflector 21 in the middle are shown and it is noted that good beamforming is achieved. The simulation results shown in FIGs. 4 and 5 are summarized in Table 1 and Table 2 below. Beam width 65 90 120 Radiator direction 0 ±41 ±54 Beam width 33 45 65 90 Radiator direction 0 ±24 ±30 ±36

The variable beam controlling antenna for a mobile communication base station according to the first and second embodiments of the present invention can variably control the horizontal beam width by appropriate control of the mutual rotational directions of the first, second and third radiator portions 10, 20 and 30 arranged vertically in one column, and can form a beam with less ripples in the forward direction of the antenna.

While it has been described that the first, second and third radiator portions 10, 20 and 30 are provided with their respective first, second and third force generators 13, 23 and 33 to rotate the first, second and third reflectors 11, 21 and 31, it can be further contemplated that the first, second and third reflectors 11, 21 and 31 are partially or wholly rotated by use of a single force generator and a force transfer portion with a plurality of gears and a gear shaft for transferring force generated from the force generator to the first, second and third radiator portions 10, 20 and 30 partially or wholly.

FIGs. 6A, 6B and 6C are perspective views illustrating an important portion of a variable beam controlling antenna in a mobile communication base station according to a third embodiment of the present invention. Specifically, FIG. 6A illustrates the rear of the important portion of the antenna viewed from the upper left, FIG. 6B illustrates the rear of the important portion of the antenna viewed from the lower right, and FIG. 6C illustrates the rear of the important portion of the antenna viewed from a lower height than from the upper left. In FIG. 6C, a force generator is not shown. FIG. 7 is a partially enlarged perspective view of the bottom of a second radiator in the important portion of the antenna illustrated in FIGs. 6A, 6B and 6C, equivalent to a view of the front of the important portion of the antenna from the upper left.

Referring to FIG. 6A to FIG. 7, like the antennas illustrated in FIGs. 1 and 3, this antenna has three vertical separate radiator portions and first, second and third reflectors 11', 21' and 31' vertically arranged so as to the same rotational center. As in the first embodiment, the first, second and third reflectors 11', 21' and 31' may not have the same rotational center.

The second reflector 21' is fixed to a radome (not shown) by fixing guides 440a and 440b of FIG. 7 and the first and third reflectors 11' and 31' are rotatably installed.

A force generator 33' including a motor is installed under the third reflector 31' and the rotational shaft of the motor is connected to the third reflector 31' by a gear so that the third reflector 31' is rotated along with the rotation of the motor.

In this structure, the first reflector 11' is configured to rotate in the opposite direction with conjunction of the rotation of the third reflector 31' through a force transfer portion with a plurality of gears and a gear shaft. First to fifth gears 411 to 415 and a gear shaft 416 collectively form the force transfer portion.

The first gear is attached to an upper end portion of the third reflector 31' so that it can rotate along with the rotation of the third reflector 31'. The second gear 412 is installed to rotate in engagement with the first gear 411 and the third gear 413 is installed to rotate in engagement with the second gear 412. The fifth gear 415 is attached to a lower end portion of the first reflector 11' so that the first reflector 11' can rotate along with the rotation of the fifth gear 415. The second gear 414 is installed to rotate in engagement with the fifth gear 415.

The third gear 413 is connected to the fourth gear 414 by the gear shaft 416. When the third gear 413 rotates, this gear shaft 416 rotates, thereby in turn rotating the fourth gear 414.

When the third reflector 33' rotates by driving the force generator 33', the first to fifth gears 411 to 415 rotate in sequence. Consequently, the first reflector 11' rotates in the opposite direction to the rotation of the third reflector 33'.

In this variable beam controlling antenna according to the third embodiment of the present invention, the first and third reflectors 11' and 31' interwork with each other with respect to the second reflector 21' and thus rotate in the opposite directions. Hence, the horizontal beam width can be variably controlled. Meanwhile, in FIG 6A to FIG 7, support rods 430 are provided at appropriate positions to firmly support the second reflector 21'.

FIGs. 8A and 8B are exemplary views of an antenna modified from the antenna illustrated in FIGs. 6A and 6B. FIG 8A illustrates the rear of an important portion of the antenna viewed from the upper left and FIG. 8B illustrates the rear of the important portion of the antenna viewed from the lower right. Referring to FIGs. 8a and 8B, this antenna is almost the same in configuration as the antenna of the third embodiment. It has a second force generator 53 with a motor (not shown) for rotating the entire first, second and third reflectors 11', 21' and 31' to control horizontal steering as well as a horizontal beam width, and a second force transfer portion 52.

The second force generator 53 operates in response to an external control signal. It is provided with a motor for rotating the entire first, second and third reflectors 11', 21' and 31'. The second force transfer portion 52 is provided to a lower portion of a fixed frame of the force generator 33'. Thus, the rotational shaft of the motor in the second force generator 53 is connected to the fixed frame of the force generator 33' by a gear, so that the fixed frame is rotated along with the rotation of the motor. Hence, the rotation of the fixed frame in the force generator 33' leads to the rotation of the entire first, second and third reflectors 11', 21' and 31'.

While it has been described that the second reflector 21' is fixed to the radome (not shown) by the fixing guides 440a and 440b of FIG 7 in FIGs. 6A, 6B and 6C, the second reflector 21' is installed rotatably and thus not fixed to a radome in the antenna configuration shown in FIGs. 8A and 8B.

In the modified antenna, the first, second and third reflectors 11', 21' and 31' are wholly rotated so that the horizontal steering of the antenna can be controlled variably.

While it has been described that the antenna according to the embodiments of the present invention has three separate radiator portions, it can be further contemplated as other embodiments that it has two or four or more radiator portions. This radiator configuration can be designed appropriately taking into account vertical side lobe characteristics, implementation complexity, and cost.

In addition, while the radiator portions are configured to rotate by use of a force generator and a force transfer portion, that is, by a mechanical horizontal beam width changing scheme, an electrical horizontal beam width changing scheme can be adopted instead, in which the horizontal beam with of the antenna is controlled by controlling the phases of signals transmitted from the radiators of the radiator portions, like an electrical horizontal steering scheme that controls horizontal steering.

As described above, the variable beam controlling antenna for a mobile communication base station according to the present invention can be fabricated with low cost and allows for easy automatic optimization required for a recent mobile communication wireless network because it is configured to be a one-column antenna capable of controlling a horizontal beam width. Although conventionally, many kinds of antennas with different beam widths are needed for base station sectors, the single antenna easily changes its beam width in the present invention.

Furthermore, this one-column antenna can control horizontal steering as well as the horizontal beam width.