Communications: radio wave antennas – Antennas – Wave guide type
Reexamination Certificate
2000-03-01
2001-02-06
Le, Hoanganh (Department: 2821)
Communications: radio wave antennas
Antennas
Wave guide type
C343S7810CA, C343S7810CA
Reexamination Certificate
active
06184840
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a parabolic reflector antenna and, more particularly, to a parabolic reflector antenna for signal transmission between the radio communication base station (BS) and the mobile terminals.
2. Related Art
The parabolic reflector antenna is a high gain antenna with orientation that is mostly used in radar systems, microwave systems and satellite systems. Its reflector is shaped into one that can readily collect radio signals. It is also termed open antenna. Since the dimension of the reflector is much larger than the signal wavelength, so it can be applied to electromagnetic radiation. The parabolic reflector antenna comprises two main components: one is a parabolic reflector and the other is a feedback active unit. Basically, the active unit is the original antenna for signal feedback. Usually, the electromagnetic energy is directed toward the reflector using dipoles, dipole arrays, and waveguides. The reflector is a passive device with no power. It is solely used to focus and direct the electromagnetic energy supplied from the original antenna by reflecting and to spread the energy into space.
The parabolic reflector is a dish disk, so it is also called the dish antenna. The function principle of the parabolic reflector can be elucidated in terms of the geometric properties of parabolas. Please refer to FIG.
1
. In the x-y coordinate system, a parabolic curve can be expressed by
y
2
=4
fx,
(1)
where f is the distance from the parabolic vertex to the focus F of the parabola. According to the geometric characters of parabolas, the sum of the distances from any point (such as A, B and C) on the parabola to the focus F and to points on the line y
1
-y
2
parallel to the directrix is a constant. That is,
FA+AA′=FB+BB′=FC+CC′=K, (2)
where K is a constant. The parabolic reflector is a disk-like curved surface formed by rotating a parabola about the x-axis, which is called the paraboloid. The paraboloid is often used in car headlights for focusing light. If the electromagnetic energy is radiated from the focus F and reflected by the parabolic reflector, all simultaneously emitted radiation wave fronts reach the line Y
1
-Y
2
at the same time. The distances traveled by all waves are equal, and the wave shapes and phases on this line are the same. Therefore, this reflector can focus the electromagnetic energy into a beam along the x-axis and form a high gain directional radiation.
In particular, the feedback device of the parabolic reflector antenna is the actual supplier of electromagnetic energy radiation, and is thus called the primary antenna. The primary antenna is positioned on the focus of the parabolic reflector for obtaining the best emission or reception effects. Aside from dipole antenna, the primary antenna often uses waveguides to form a horn feed in the microwave frequencies.
SUMMARY OF THE INVENTION
It is a major object of the present invention to provide a parabolic reflector antenna that functions as a good signal transmission terminal between the radio communication base station and mobile terminal devices.
The parabolic reflector antenna includes a first cover and a second cover, a main-dish with a main reflecting surface, a sub-dish with a sub-reflecting surface, and a feedback device. By determining the preferred curvatures and relative positions of the main-dish and the sub-dish, means for determining the size of the feedback device and relevant distances in between, and defining all the parameters of both the parabola in the main reflecting surface and the hyperbola in the sub-reflecting surface, the present invention determines preferred shapes for the main-dish and sub-dish so as to provide a parabolic reflector antenna with better signal reception and emission effects.
Furthermore, the parabolic reflector antenna disclosed in this invention provides a feedback device with a square horn waveguide and a circular horn waveguide connecting together for converting the signals from the signal source in electrical communication with the square horn waveguide to electromagnetic radiation in the circular horn waveguide.
The present invention fixes the sub-dish with the sub-reflecting surface onto the first cover using a screw, which can conveniently adjust the position of the whole sub-dish.
The first cover and the second cover include a convex rim portion and a concave rim portion, respectively. They are combined by ultrasonic wave welding and are thus beautiful and waterproof.
Moreover, the feedback device is fabricated by covered injection molding and combined with the second cover using ultrasonic wave welding. Therefore, it is easy to manufacture and is waterproof.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: 4581615 (1986-04-01), Levy
patent: 6107973 (2000-08-01), Knop et al.
Hsin-Loug Lin
Ta-Lun Lee
Birch & Stewart Kolasch & Birch, LLP
Le Hoang-anh
SmartAnt Telecomm Co., Ltd.
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