Communications: radio wave antennas – Antennas – With means for moving directive antenna for scanning,...
Reexamination Certificate
1999-03-09
2001-03-20
Phan, Tho (Department: 2821)
Communications: radio wave antennas
Antennas
With means for moving directive antenna for scanning,...
C343S705000, C343S853000, C343S882000
Reexamination Certificate
active
06204823
ABSTRACT:
FIELD OF THE INVENTION
This invention is related to an antenna positioner that mounts an antenna and adjusts elevation and azimuth. More particularly, this invention is related to a low profile antenna positioner that can receive direct broadcast satellite signals while mounted on an aircraft and the like.
BACKGROUND OF THE INVENTION
Direct broadcast satellite (DBS) signals are often transmitted to aircraft and other moving vehicles. These transmitted signals are often KU-band television signals that are transmitted to commercial aircraft, trains and other moving vehicles, and are typically UHF and VHF band signals, which can be received on small antennas, such as the common 18″ disks placed on the sides of houses. The antenna can also be formed as a phased array antenna, and designed as a flat plate, as is known to those skilled in the art. Many different types of housings and positioners have been designed to point the antenna's main beam at the desired direct broadcast satellite while an aircraft maintains various commercial cruise flight dynamics. These dynamics include a role of 5°/second and 5°/second
2
; a pitch of 5°/second and 3°/second
2
; and a yaw of 5°/second and 5°/second
2
.
One current method has been to use a mechanical device with an in-line jack screw actuator for elevation and a direct drive azimuth. In most types of controls, an antenna controller receives position commands and directs movement of various motors. However, these type of requirements are not adequate because with a mechanical system, the slew rate is slow and motors often overheat in maintaining positions. Also, the controller does not include a rate feed forward, which is desirable. Also, many prior art antenna positioners have mechanical designs that allow control over azimuth and elevation, but the motors and drive mechanics have excessive backlash. Also, many prior art designs do not fit into low profile housings that are adapted for mobile applications, such as mounting on the fuselage of an aircraft.
U.S. Pat. No. 5,025,262 to Abdelrazik et al. discloses a pedestal with a helical element antenna that is mechanically steered with reference to an azimuth axis and elevation axis. A mechanical steering system includes a supporting frame having an azimuth member and an elevation member that is integral with the azimuth member. It includes a longitudinal axis displaced from the azimuth axis.
U.S. Pat. Nos. 5,689,276 and 5,420,598 to Uematsu et al. disclose an antenna housing for a satellite antenna device, which mounts on a moving body and includes an automatic tracking mechanism. An elevation motor is fixed to a rotary base. A series of pulleys and shafts act as a driving mechanism. A rack has teeth formed along a circle about the rotating axis in elevation direction of the antenna unit A. The teeth of the rack mesh with the pinion gear to be driven circumferentially by the driving torque transmitted to a pinion gear. Thus, the antenna unit is driven for rotation in the elevation direction. An azimuth motor is fixed on the rotary base. Through a sufficient pulley mechanism, the driving torque of the azimuth motor is transmitted to the pinion, which meshes with teeth of a belt such that the driving torque of the azimuth motor is transmitted through the pulleys.
U.S. Pat. No. 5,153,485 to Yamada et al. discloses a high gain antenna that is mounted on board an automobile for reception of satellite broadcasting. The system uses a beam antenna in the form of a flat plate that is secured to an antenna bracket. A turntable has a disk-shaped spur gear that includes a gear around its lateral side. Turntables are rotatably mounted on a stationary base by a bearing. Reduction gearing in a motor is mounted on the support plate and secured to a stationary plate base. The beam antenna can be moved in both azimuth and elevation.
Many of these systems suffer some of the drawbacks noted above.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an antenna positioner that is mechanically efficient and allows control over a substantially elongate antenna, such as a phased array antenna.
It is still another object of the present invention to provide a low profile antenna positioner that can be packaged in a mobile platform and used with a flat, substantially elongate antenna.
It is still another object of the present invention to provide a low profile antenna positioner where the elevation and azimuth can be controlled with minimum backlash.
In accordance with the present invention, an antenna positioner now allows adequate control over azimuth and elevation with minimum backlash. The antenna of the present invention can also be placed in a low profile configuration for a mobile platform, which not only includes an aircraft, but also includes other mobile applications, such as an automobile. The antenna positioner includes a housing, which in one preferred aspect of the present invention is an annular configured housing having a diameter at least twice the height of the housing. A central hub is mounted within the housing. A substantially planar configured support plate is rotatably mounted on the central hub within the housing and an antenna is pivotally mounted on the support plate.
An elevation drive mechanism is mounted on the support plate and interconnects the antenna for pivoting the antenna a predetermined angle and adjusting elevation of the antenna. An azimuth drive mechanism is also mounted on the support plate and interconnects the central hub and rotates the support plate relative to the central hub a predetermined arcuate distance relative to the central hub for adjusting azimuth of the antenna. A controller is operatively connected to the elevation drive mechanism and the azimuth drive mechanism and controls the azimuth and elevation drive mechanisms and adjusts elevation and azimuth. The antenna also extends across a substantial portion of the housing defined by a chord having a length about the diameter of the housing.
In one preferred aspect of the present invention, the azimuth drive mechanism includes a servomotor having an output shaft and a gear mounted on the output shaft that engages the central hub. An antenna support shaft is mounted on the antenna such that rotation of the support shaft pivots the antenna and adjusts elevation. The elevation drive mechanism is operatively connected to the support shaft. The elevation drive mechanism can be formed as a servomotor having an output shaft and a drive mechanism that engages the output shaft of the servomotor and the support shaft, forming a pull/pull drive.
Hinges can mount the antenna to the support plate. The support shaft includes an end connected to one of the hinges such that upon rotation of the support shaft, the hinge moves for pivoting the antenna. The antenna can be a phased array antenna that is configured as a flat plate.
A controller is also preferably mounted on the support plate. The central hub is substantially annular configured and can include an inner bearing race. The support plate further comprises an annular configured support mount having an outer bearing race that cooperates with the inner bearing race. The annular configured support mount can include a ring gear mounted on the support mount. The azimuth drive mechanism engages the ring gear for rotating the support plate relative to the fixed central hub. The azimuth drive mechanism can further comprise a servomotor having an output shaft and a pinion gear mounted on the output shaft for engaging and driving the ring gear and rotating the support plate.
In one preferred aspect of the present invention, the azimuth drive mechanism includes two servomotors, each having an output shaft. Each output shaft has a pinion gear that engages the ring gear. In one aspect of the present invention, the ring gear and pinion gear establish about a 16:1 gear reduction ratio. The support plate can be preferably formed from material having a honeycomb structure, such as an expanded plastic that is lightweight but strong.
REFERENCES:
Green Dennis A.
Ostby Amy J.
Spano Dawson P.
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Harris Corporation
Phan Tho
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