Multi-wave-reflector antenna dish

Details Multi-wave-reflector antenna dish Multi-wave-reflector antenna dish

2001-03-05

2002-12-10

Ho, Tan (Department: 2821)

Communications: radio wave antennas

Antennas

Wave guide type

C343S840000, C343S779000

Reexamination Certificate

active

06492954

ABSTRACT:

REFERENCE TO RELATED APPLICATIONS
The present application claims priority to Taiwan application No. 089109978 entitled “Multi-wave-reflector antenna dish” filed on May 24, 2000.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the structure of an antenna dish and more particularly to a multi-wave-reflector antenna dish, which has a minimal dish surface and simultaneously receives signals from a plurality of satellites, at fixed angles from each other; and related manufacturing techniques.
2. Description of the Related Art
In general, based on the fact that a direct broadcast satellite (DBS) is a point-to-multipoint, a ground receiver is capable of receiving signals directly from synchronized satellites by means of a small receiving antenna, a tuner device and household equipment. The process of transmission via satellite is as shown in
FIG. 1
, wherein program signals, digital audio as well as video, are transmitted with precision to an orbiting synchronized satellite
15
by manipulating an up-link antenna dish (transmitting antenna)
10
. After individual users receive downlink signals transmitted by the satellite
15
through the antenna dish
20
and select desired satellite programs using a panel control on the satellite TV receiver
25
, video and stereo audio signals are separated and played on the TV set
30
.
FIG. 2
shows each component of the antenna dish
40
for receiving satellite signals with precision. The receiving antenna dish
40
comprises a parabolic reflector
42
for receiving and having satellite signals concentrated on the focal point. In addition, a LNBF (low noise block with integrated feed) module is installed on the parabolic reflector
42
to convert incoming radio frequency signals into intermediate frequency signals and send said signals to the tuner. Waves parallel to the axis of the parabolic reflector
42
are reflected by the reflector and concentrated on the focal point where the LNBF module
44
is positioned. Note that LNBF module
44
comprises a waveguide antenna
46
to receive microwave signals on the front end thereof and a circuit system
48
to process the signals on the rear end thereof. Furthermore, in addition to noise filtering, the LNBF module
44
also amplifies received signals from the parabolic reflector
42
to an acceptable scale for processing.
It should be noted that the conventional antenna dish
40
as shown in
FIG. 2
is a circular parabolic antenna. Accordingly the equation of the aperture thereof can be expressed as X{circumflex over ( )}2+Y{circumflex over ( )}2=4fz, wherein f refers to the focal length of the circular dish.
Provided that the LNBF module is positioned at the only focal point of the circular dish and the reflector is orientated to the desired satellite, the said antenna is ready for reception and demodulation of the signals. As a result of the strong concentrating character of the focal point on the circular dish, the LNBF module
44
on the focal point receives signals with extremely high S/N (signal to noise) ratio. This significantly enhances reception. In other words, in conventional antenna designs, the strong concentrating character of the focal point on the circular dish contributes to gain raise, lower spillover loss and a better quality of received signal.
On the other hand, it is also the same strong concentrating character at the focal point on the circular dish that suppresses gain from unfocused waves and generates a considerably lower gain than it does from the axis of the circular dish. Therefore, when LNBF module
44
positioned at a non-focal point on the focal plane, the received S/N ratio is noticeably lower than that when LNBF module
44
is positioned at the focal point. In other words, a circular antenna dish can only receive signals from a targeted satellite and is not capable of receiving signals from other satellites. If one wants to receive signals from any other satellites using the same antenna dish, the orientation and the angle of elevation have to be readjusted in order to bring the axis of the paraboloid reflector
42
parallel to signal waves from other satellites, to concentrate the signal waves on LNBF module
44
. There are alternatives to receive signals from a plurality of satellites such as installing several antenna dishes, but these alternatives are costly and require a large area.
It is noted that the quantity of communication satellites for transmitting various programs has continued to grow with the rapid development of communication satellite systems. From a user's perspective, the capability to simultaneously receive programs broadcast from several satellites on a single antenna dish saves both cost and space. It is also more convenient and practical for users.
SUMMARY OF THE INVENTION
The objective of the present invention is to provide a multi-wave-reflector antenna dish that simultaneously receives signals from a plurality of satellites, at fixed angles from each other.
Another objective of the present invention is to provide an antenna dish that simultaneously receives signals from a plurality of satellites by integrating a reflector and a plurality of LNBF modules.
One other objective of the present invention is to provide an antenna dish having a reflector with a super ellipse projected aperture. This enables the reflector to raise gain and cut spillover loss at a non-focal point by minimizing the cross area of the antenna.
The present invention provides a multi-wave-reflector antenna dish that simultaneously receives signals from a plurality of satellites at fixed angles from each other and relevant design techniques. The antenna dish comprises a reflector with a superquadric projected aperture and a plurality of LNBF modules. The reflector is formed by projecting a superquadric on the paraboloid, projected aperture cutting and surface distortion of the aperture based on the generalized diffraction synthesis technique. Surface distortion involves required condition values such as radiation pattern, gain, and sidelobe level. Repeat computations are then conducted based on these variables, accordingly, to form a reflector that simultaneously focuses signals from different satellites on the LNBF module with the same radiation pattern and gain.


REFERENCES:
patent: 3680143 (1972-07-01), Ajioka et al.
patent: 4757323 (1988-07-01), Duret et al.
patent: 6219003 (2001-04-01), Chandler
patent: 6243048 (2001-06-01), Luh

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