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.
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, xe2x80x9ca dish antennaxe2x80x9d) 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 5xc2x0. 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 xe2x80x9cThe Sunshine-Shadow Method of Locating Satellite and Boresighting Dishesxe2x80x9d, 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 1-2xc2x0. 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 adjusting the gnomon or lines according to the pre-calculated altitude and azimuth.
In a further embodiment of U.S. Pat. No. 5,760,739, a gnomon is fixed, a track line that the shadow of the gnomon makes over time and a straight time line that corresponds to a particular time of the antenna installation are provided on a surface of the reflector, and a reflection dish is adjusted so that the shadow of the gnomon coincides with the intersecting point of the selected two lines. However, according to the latitude and longitude of a location at which the satellite antenna is installed, the shadow track line may vary differently and time line is given differently. That is, since the lines are formed differently depending on season, date and the location of the installation of the antenna, this embodiment may not used for all the installation and time. Consequently, this embodiment can be used only when the satellite antenna is installed at a limited location and time. Therefore, when the antenna is installed beyond the above-defined limitation, this embodiment may not be available at all. In addition, since the gnomon is located over the center of the reflection dish, the gnomon hinders the reception of a broadcast signal. Further, when the gnomon is close to the reflection dish, the distance between the gnomon and its shadow is short, thereby deteriorating the directional precision.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a method of orienting a satellite antenna toward a transmitter using the shadow of the sun, allowing a non-skilled user to easily adjust the direction of the satellite antenna toward the satellite without reducing the performance of the reception of a broadcast signal.
Another object of the present invention is to provide an apparatus for orienting a satellite antenna toward a transmitter, capable of easily orienting the satellite antenna to the transmitter without using a complex antenna orienting apparatus, which may be achieved by means of a shadow generating means and a target indicating means because the shadow of the sun is easily generated and the antenna is easily adjusted so that the shadow coincides with a target point on a reflector.
A further object of the present invention is to provide a reflector satellite antenna equipped with such an antenna orienting apparatus, capable of easily orienting an antenna toward a transmitter and easily installing an antenna.
In order to accomplish the above object, the present invention provides an apparatus for orienting an antenna toward a transmitter, which is used with an antenna, comprising shadow generating means fixedly mounted to the antenna so as to generate a shadow of the sun, and target indicating means for specifying a target point on a reflector, at which a predetermined portion of the shadow generated by the shadow generating means should be positioned when the antenna is correctly oriented toward the transmitter.
In addition, the present invention provides a method for orienting an antenna toward a transmitter, which is used with an antenna, comprising the steps of mounting a shadow generating means to the antenna, determining a target point on the reflector, at which a predetermined part of the shadow generated by the shadow generating means should be positioned when the antenna is correctly directed toward the transmitter, on the basis of the type of a satellite (including the position thereof), location information of the antenna and time information of an antenna orienting operation, and adjusting a direction of the antenna so that the predetermined part of a shadow generated by the shadow generating means coincides with the target point.
Furthermore, the present invention provides an antenna comprising an antenna assembly having a reflector that reflects a signal, a reflected signal pickup unit which consists of a feed horn and a low noise block (LNB) and feeds a reflected signal, a signal pickup unit supporting arm that supports and positions the reflected signal pickup with regard to the reflector, and a pickup unit holder that is mounted to an end of the signal pickup unit supporting arm and supports the reflected signal pickup unit, means for supporting the antenna assembly, and an adjustable mounting mechanism for adjusting the antenna assembly in two directions, wherein the antenna further includes a shadow generating means fixedly mounted to the antenna so as to generate a shadow of the sun, and target indicating means provided on the reflector for indicating a target point at which a predetermined part of the shadow generated by the shadow generating means should be positioned when the antenna is correctly oriented toward the transmitter.
The shadow generating means may consist of a bar that is fixed at its first end to a reflected signal pickup unit or pickup unit holder of the antenna and is fixed at its second end to a periphery of the reflector, and one or more projecting marks formed on predetermined parts of the bar. And, the target indicating means may consist of a set of a plurality of intersectional lines that are provided on a surface of the reflector. The target point may be specified by coordinate values defined by the intersectional lines and/or one of blocks that are formed by the intersectional lines.
According to another embodiment, the shadow generating means may consist of a bar that is fixed at its first end to a reflected signal pickup or pickup holder of the antenna and is fixed at its second end to a periphery of the reflector, and a plurality of projecting figure-shaped graduations formed on the bar. And, the target indicating means may consist of one or more lines provided on the surface of the reflector with forming an angle with shadow generating means and marked with graduations. In this embodiment, the target point on the target indicating means may be specified by two coordinate values that are determined by an intersection point at which a shadow of the bar of the shadow generating means intersects the line(s) of the target indicating means.
The apparatus and the antenna may comprise a level that is mounted to the antenna and serves to confirm whether the support post for supporting the antenna assembly is perpendicularly positioned relative to an antenna installation site when viewed from the front. In addition, the apparatus and the antenna may include an obstacle observing means consisting of a rod that is extended from a portion of the reflector along an antenna orienting direction, and a foresight and a backsight that are spaced apart from each other and are formed on the rod.
In the method of the present invention, determining the target point on the target indicating means, at which a predetermined portion of a shadow should be positioned, may be performed by a computer program, which determines the target point on the basis of the type of a satellite, location information of the antenna and/or time information of an antenna orienting operation.
The method may further comprise the steps of confirming whether the antenna is positioned in an initial reference state in which a support post of the antenna is perpendicularly positioned, and adjusting the antenna to be in the initial reference state when the antenna is not in the initial reference state.
The method may further comprise the step of confirming whether there is an obstacle hindering the reception of the signal in an antenna orienting direction after the direction of the antenna is adjusted toward the transmitter.