Communications: radio wave antennas – Antennas – Wave guide type
Reexamination Certificate
2000-05-18
2001-11-06
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
Wave guide type
Reexamination Certificate
active
06313808
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a feedhorn for a parabolic antenna used in a receiving unit of an antenna for receiving a satellite broadcast signal. More particularly, the invention relates to a feedhorn suitable to receive radio waves from a plurality of neighboring satellites.
2. Description of the Related Art
An example of a conventional feedhorn for receiving radio waves from a plurality of neighboring satellites will be described. Japanese Unexamined Patent Publication No. Hei 10-163737 discloses a feedhorn in which two waveguides are integrally formed and which can receive radio waves from neighboring two satellites.
In such a conventional feedhorn
23
, as shown in
FIGS. 12 and 13
, first and second circular waveguides
21
a
and
21
b
each having a predetermined length and a diameter are formed. Around the first and second circular waveguides
21
a
and
21
b
, first and second grooves
22
a
and
22
b
each having a predetermined depth are formed by partition walls
22
c
,
22
d
, and
22
e.
As shown in
FIG. 13
, the partition walls
22
c
,
22
d
, and
22
e
are formed so that their aperture end faces at the front end are flush with the same plane and their heights are the same.
A substrate
24
is disposed at the bottom of the first and second circular waveguides
21
a
and
21
b
. A feeding point
25
is provided so as to be positioned in the center of the bottom face of each of the circular waveguides
21
a
and
21
b
by printed wiring formed on the substrate
24
. Further, a terminating unit
26
is attached to the bottom face of the feedhorn
23
.
The conventional feedhorn
23
is attached to a receiving antenna and can receive radio waves transmitted from neighboring two broadcasting satellites by the first and second waveguides
21
a
and
21
b.
A predetermined angle is, however, formed between the two neighboring broadcasting satellites to the feedhorn on the ground. Consequently, although either one of the aperture end faces formed on the same plane of the first and second circular waveguides
21
a
and
21
b
of the feedhorn can be adjusted at the predetermined angle formed by the neighboring two broadcasting satellites to the feedhorn, the other one cannot be adjusted. There is consequently a problem that radio waves from either one of the neighboring two broadcasting satellites cannot be properly received.
In order to solve the problem, it is possible to prepare two feedhorns (not shown) each having a single waveguide and attach the feedhorns to a receiving antenna so as to position each of the waveguides of the feedhorns at the angle formed by the neighboring two broadcasting satellites to feedhorn. There is, however, a problem such that assembly of the receiving antenna to which the feedhorns each having a single waveguide are separately attached is complicated and the cost is high.
The number of satellites recently launched is very large. A feedhorn provided with two waveguides can receive radio waves from only two satellites and has a problem that the feedhorn cannot receive radio waves from three or more satellites.
SUMMARY OF THE INVENTION
The present invention has been achieved to solve the problems and its object is to provide an easy-to-manufacture low-cost feedhorn capable of properly receiving radio waves transmitted from a plurality of neighboring satellites.
As a first solving means for solving the problems, there is provided a feedhorn comprising: first and second waveguides at least in positions so as to face each other over a center line, each having an axis parallel to the center line; and first and second horns linked to the first and second waveguides, respectively, on extension lines of the axes of the first and second waveguides, wherein the first waveguide and the first horn have an aperture formed in the axial direction, the second waveguide and the second horn have an aperture formed in the axial direction, the former aperture is provided with an aperture end face at an outer end of the first horn, the latter aperture is provided with an aperture end face at an outer end of the second horn, the diameter of the aperture on the aperture end face side is larger than that on the side of each of the first and second waveguides, the aperture on the side of each of the first and second horns conically tapers inward, and each of the aperture end faces of the first and second horns of the first and second waveguides is tilted toward the center line by a predetermined angle so that the first and second horns are perpendicular to the travel directions of radio waves transmitted from at least two broadcasting satellites orbiting around the earth and reflected by an antenna on the ground.
As a second solving means for solving the problems, on the internal conical face, a plurality of concentrical grooves having different distances from the axis are formed at a predetermined depth by being partitioned with partition walls, an end face of each of the partition walls is formed flatly, the partition walls are arranged so that their heights are different from each other like stairs, and the end face of each of the partition walls is formed in parallel with the aperture end face of the horn.
As a third solving means for solving the problems, the depth direction of each of the grooves is in parallel with the center line.
As a fourth solving means for solving the problems, an inclination angle of each of the aperture end faces of the first and second waveguides and the end faces of the partition walls lies within the range from 2 to 10 degrees with respect to a plane which perpendicularly crosses the center line.
As a fifth solving means for solving the problems, an inclination angle of each of the aperture end faces of the first and second waveguides and the end faces of the partition walls is set to the half of an angle formed between a plurality of neighboring broadcasting satellites and a receiving antenna on the ground for receiving radio waves transmitted from the broadcasting satellites.
As a sixth solving means for solving the problems, a third waveguide having an axis parallel to the center line is disposed between the first and second waveguides in positions off from the center line, the third waveguide has a third horn which is on an extension line of the axis and is linked to the third waveguide, an aperture is formed in the axial direction in the third waveguide and the third horn, the aperture is provided with an aperture end face at the outer end of the third horn, the diameter of the aperture on the aperture end face side is larger than that on the third waveguide side, the aperture on the third horn side conically tapers inward, and the aperture end face of each of the first, second, and third horns is inclined toward the center line at a predetermined angle so that the first, second, and third horns are perpendicular to the travel directions of radio waves which are transmitted from neighboring three broadcasting satellites orbiting around the earth and reflected by an antenna on the ground.
As a seventh solving means for solving the problems, the first, second, and third waveguides are arranged in a state where a line connecting the axes of the first and second waveguides is deviated from the axis of the third waveguide by a predetermined distance.
REFERENCES:
patent: 5635944 (1997-06-01), Weinstein et al.
patent: 5812096 (1998-09-01), Tilford
patent: 10-163737 (1998-06-01), None
patent: 11-274847 (1999-10-01), None
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Wimer Michael C.
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