Communications: radio wave antennas – Antennas – With means for moving directive antenna for scanning,...
Reexamination Certificate
2001-05-31
2004-02-03
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
With means for moving directive antenna for scanning,...
C343S894000, C342S359000
Reexamination Certificate
active
06686889
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an apparatus and a method for orienting an antenna to a signal transmitter using the shadow of the sun, and an antenna using the apparatus, more particularly, to an apparatus and a method for orienting an antenna to a signal transmitter with which the antenna is easily directed toward the transmitter by generating the shadow of the sun and adjusting the antenna so that the shadow coincides with a predetermined target point on a reflector.
BACKGROUND ART
Recently, as satellite broadcasting is popular, there are increased viewers who watch satellite broadcasting. As well known to those skilled in the art, a dipole antenna, a horn antenna, a reflector antenna and a phase-array antenna may be enumerated as examples of antennas for receiving broadcasting satellite signals.
Among them, a reflector antenna (so called, “a dish antenna”) which is generally used as a satellite antenna is simple in structure, is light and is easy to install. The reflector antenna comprises a base or bracket, a support post extended vertically upwards from the base or bracket, and an antenna assembly supported on the top of the support post. The antenna assembly comprises a dish-shaped reflector that reflects a signal, a reflected signal pickup unit including a feed horn positioned at a specific position relative to the reflector, and a Low Noise Block (LNB) to which the signal fed from the feed horn is inputted. In order to position the reflected signal pickup unit with regard to the reflector, a reflected signal pickup unit supporting arm is employed. On the end of the signal pickup unit supporting( arm, there is provided with a pickup unit holder for fixing the signal pickup unit. A signal from the LNB is inputted to a receiving unit of a television set through a cable.
Such a reflector has a flat or curved, preferably parabolic surface and various sizes in accordance with use. The feed horn and the LNB constituting the signal pickup unit may be located over a center of the reflector (a central feeding type), or may be located at an eccentric position so as to prevent the feed horn and the LNB from hindering a received signal (an offset feeding method). The feed horn and the LNB are preferably spaced apart from the reflector by the focal distance of the reflector. In addition, according to the method of collecting a signal and the shape of the reflector, the antennas may be classified into a parabolic antenna, a Cassegrain antenna, a Gregorian antenna and a horn reflector antenna.
These various antennas should have a high gain, a high efficiency and a high directivity to be employed as a satellite antenna. Furthermore, since a broadcast signal that is transmitted from a satellite rotating with the earth has a high, directivity, the satellite antenna should be precisely oriented toward the satellite. The allowable orientation angle tolerance is below 5°. Therefore, differing from an antenna for an aerial wave broadcasting, when the orientation angle of the satellite antenna is deviated from the allowance range, the antenna cannot receive the broadcast signal, and when the broadcast signal is digital, the directivity of the signal is more restricted.
Due to the high directivity of the satellite broadcast signal, the installation of the satellite antenna is difficult. That is, one person should adjust the direction of the satellite antenna while another person monitors a television set and confirms whether a good image is obtained or not.
Recently, there is proposed a method in which the direction of the satellite antenna is adjusted by means of a graduator and a compass on the basis of the position information (altitude and azimuth) of a satellite obtained through a computer program or a table. Additionally, there is proposed another method in which the direction of the satellite antenna may be precisely adjusted using a level meter, after the rough direction of the satellite antenna is first determined using the above-described method.
In U.S. Pat. No. 5,589,841, there is disclosed a technique in which a user may orient properly a satellite antenna by himself using an auxiliary device generating a human-perceptible guidance signals such as a sequence of beep tones, in proportion to the strength of the received broadcast signal without monitoring a television set. However, these auxiliary adjusting devices may not be attached to the satellite antenna permanently and the cost of the satellite antenna having these auxiliary adjusting devices is increased because the devices are very complex. Additionally, since such an adjusting device may be difficult to operate, an expert is required for installing and adjusting an antenna and, therefore, the cost of the installation and adjustment becomes increasing. Furthermore, when the direction of the satellite antenna is changed due to careless use or environmental causes after the satellite antenna is initially installed, an expert should be called to adjust the direction of the satellite antenna, which incurs an additional cost.
Of course, a non-directional satellite antenna or an satellite antenna having an electromotive orienting apparatus may be employed, but such an antenna may not be widely used because the structure of the antenna is complex and the cost of the antenna is too high.
In order to overcome this problem, there is suggested a method in which a relative position of a satellite with regard to the sun is determined and a satellite antenna is oriented toward the satellite using the shadow of the sun. One example of such methods is “The Sunshine-Shadow Method of Locating Satellite and Boresighting Dishes”, Satellite Retailer; Triple-D Publishing, Shelby, N.C., December, 1995. U.S. Pat. No. 5,760,739 invented by Richard A. Pauli disclosed a similar method in that an adjustable gnomon is mounted to a satellite antenna, setting information is calculated based on the relative position of a satellite with regard to the sun, the gnomon is two-dimensionally or three-dimensionally adjusted based on the setting information, and the direction of the satellite antenna is adjusted until the shadow of the gnomon becomes a point.
As an embodiment of the above invention of U.S. Pat. No. 5,760,739, a device for adjusting a gnomon along two axes or three axes is disclosed. However, according to the embodiment, a mechanical device, such as a warm gear, is employed so as to adjust the gnomon. However, such a mechanical device does not allow the directional precision, since a directional allowance angle for the satellite antenna falls within 1-2°. Additionally, since the size of the mechanical device should be large so as to adjust the gnomon along two-axes or three-axes, the device may be an obstacle in receiving the broadcast signal, thereby reducing the intensity of receiving the signal.
In another embodiment of the above invention of U.S. Pat. No. 5,760,739, a device in which two lines intersecting at specific points in a plane formed by the rim of the reflection dish are attached to the reflection dish and a satellite antenna are adjusted until the intersecting point of the shadow of the lines coincides with a predetermined target. Though such an adjusting device does not affect an intensity of receiving a broadcast signal, however, when the radius of curvature of the reflection dish is very large so that the surface of the reflection dish is close to a imaginary plane defined by the periphery of the dish, the distance between the lines and their shadow is too small. Therefore, although the directional angle is changed much, the movement of the shadow is not long, thereby causing difficulty in orienting the antenna toward the satellite precisely.
Furthermore, these two embodiments cause a problem in which a user should adjust the gnomon or the lines according to setting information that is calculated differently with dependence on the installation time and the installation position of the satellite antenna. These also cause a problem in which a user who has insufficient scientific knowledge may have difficulty in adj
Jeong Woong Seob
Kwon Tae In
Pak Soo Jung
Kwon Tae I.
Lee Hong Degerman Kang & Schmadeka
Wimer Michael C.
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