Antenna assembly
An antenna assembly including an antenna reflector steering mechanism is disclosed. A reflector steering structure for adjusting the horizontal azimuth of a reflector includes a drive motor disposed on the rear surface of the reflector, a planet gear rotated by the drive motor, and a sectorial rack gear engaged with the planet gear and fixed to a support shaft, thereby achieving a compact design of an entire antenna structure. Further, by applying a structure with enhanced electrical insulation to rolling and slide contact portions of the drive unit and a portion undergoing change in contact pressure, radio performance of the antenna system may be prevented from changing according to steering of the reflector.
1. An antenna assembly comprising:
a reflector having an antenna element disposed on a front surface thereof;
a support shaft spaced apart from the reflector; and
an antenna reflector steering mechanism configured to pivot the reflector about the support shaft,
wherein the antenna reflector steering mechanism comprises:
a sectorial rack gear coupled to the support shaft and provided with a sectorial gear portion on an outer circumferential surface thereof;
a planetary gear engaging with the sectorial rack gear;
a gear housing provided with at least one boss arranged on one side thereof and rotatably connected to the support shaft and a fixing portion arranged on an opposite side thereof and coupled with a rear surface of the reflector; and
a drive motor fixed to the gear housing and connected to the planetary gear to revolve the planetary gear around the support shaft along the sectorial rack gear,
wherein the antenna reflector steering mechanism comprises:
a steering mechanism unit arranged on an upper portion of the reflector with respect to a height of the reflector; and
a steering mechanism unit arranged on a lower portion of the reflector.
2. The antenna assembly of claim 1 , wherein the sectorial rack gear comprises a protrusion at both ends of the sectorial gear portion,
wherein the protrusion is configured to prevent the planetary gear from being separated.
3. The antenna assembly of claim 1 , wherein the planetary gear comprises an insulation band surrounding a circumferential surface thereof,
wherein the insulation band is flexible so as to be deformed along a curved profile of engaged portions of the planetary gear and the sectorial rack gear.
4. The antenna assembly of claim 3 , wherein the insulation band is formed of a material selected from the group consisting of fluorine resin and ultra-high molecular weight polyethylene.
5. The antenna assembly of claim 1 , wherein the sectorial gear and the planetary gear are formed of aluminum, and a surface thereof is anodized.
6. The antenna assembly of claim 1 , wherein the gear housing is formed in a clevis shape such that two bosses disposed on one side are rotatably connected to the support shaft and the sectorial rack gear is accommodated between the two bosses.
7. The antenna assembly of claim 1 , wherein the gear housing further comprises:
an insulation insert and an insulation tape for electrically insulating the fixing portion when the fixing portion is fixed to the rear surface of the reflector.
8. The antenna assembly of claim 1 , wherein the boss of the gear housing comprises:
three or more columns of grooves formed on an inner circumferential surface of the boss and arranged in an axial direction of the boss; and
a plurality of ball bearings of a nonconductive material accommodated in the grooves.
9. The antenna assembly of claim 8 , wherein the ball bearings are formed of a material selected from the group consisting of a polymer material and a ceramic material.
10. The antenna assembly of claim 8 , wherein a size and number of the ball bearings are determined so as to serve as axial and radial bearings to reduce rotational resistance of the gear housing when the gear housing is pivoted about the support shaft.
11. The antenna assembly of claim 1 , wherein the support shaft comprises:
an upper shaft;
a lower shaft; and
an intermediate shaft disposed between the upper shaft and the lower shaft and coupled to the upper shaft and the lower shaft by a coupling.
12. The antenna assembly of claim 11 , wherein the coupling electrically insulates the shafts connected to both sides thereof.
13. The antenna assembly of claim 1 , wherein the drive motor is a direct current (DC) motor.
14. The antenna assembly of claim 1 , wherein the drive motor comprises at least one rotary encoder,
wherein the drive motor is controlled by a remote electric tilt (RET) controller.
15. The antenna assembly of claim 1 , further comprising:
an auxiliary bracket comprising a body allowing the support shaft to pass therethrough and an arm extending from both sides of the body to lateral sides of the reflector such that ends thereof are fixed to the reflector.
16. A mobile communication base station antenna comprising three antenna assemblies of claim 1 , wherein each of the three antenna assemblies is disposed in each sector of a circumference divided into three sectors.