Communications: radio wave antennas – Antennas – With spaced or external radio wave refractor
Reexamination Certificate
2000-03-22
2001-05-01
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
With spaced or external radio wave refractor
C343S7810CA
Reexamination Certificate
active
06225957
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an antenna apparatus, and especially to an antenna apparatus provided with a primary horn, a sub-reflector, and a main refractor.
BACKGROUND OF THE INVENTION
FIG. 1
shows a conventional antenna apparatus. As shown in
FIG. 1
, the sub-reflector
2
is situated on a principal axis of the main reflector
1
opposite to the same, and the primary horn
3
is situated between the sub-reflector
2
and the main reflector
1
.
In case that an electric wave is transmitted by the antenna apparatus shown in
FIG. 1
, a transmitting power is supplied to the primary horn
3
from a transmitter (not shown). The electric wave radiated from the primary horn
3
illuminates the sub-reflector
2
, and is reflected thereby to the main reflector
1
. The electric wave reflected by the sub-reflector
2
is again reflected by the main reflector
1
, converted into a parallel beam, and transmitted to a receiving antenna apparatus passing along a path
13
A to
13
B for the transmitting wave.
However, according to the aforementioned conventional antenna apparatus, both the desired and undesired waves are reflected by the sub-reflector
2
and the main reflector
1
, and radiated to the outside passing along the path
13
A to
13
B for the transmitting wave. Accordingly, the undesired wave is radiated to the outside of the antenna apparatus also.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide a transmitting antenna apparatus in which an undesired transmitting wave involved in an electric wave radiated from a primary horn is suppressed.
It is a further object of the invention to provide a receiving antenna apparatus in which an interference wave involved in an electric wave received via a main reflector and a sub-reflector is suppressed.
According to the first feature of the invention, an antenna apparatus having a primary horn serving as an output source of an electric wave, a main reflector formed of a parabolic mirror for radiating the electric wave as a parallel beam in a predetermined direction, and a sub-reflector for reflecting the electric wave radiated from the primary horn to the main reflector, comprises:
a dielectric refractor which refracts the electric waves radiated from the primary horn so that an desired wave in a desired frequency band illuminates the sub-reflector, and an undesired wave outside the desired frequency band does not illuminate the sub-reflector, and
electric wave-absorbers which are situated near an outer periphery of the sub-reflector, and absorb the undesired refracted wave outside the desired frequency band.
According to the aforementioned structure, although the electric waves radiated from the primary horn involve an undesired transmitting wave outside the desired frequency band as well as a desired transmitting wave, the dielectric refractor refracts the electric waves incident thereon so that the electric waves outside the desired frequency band reaches the electric wave absorbers situated near the outer periphery of the sub-reflector
2
, and only the electric wave in the desired frequently band reaches the sub-reflector
2
. The sub-reflector
2
reflects only the electric wave in the desired frequency band to the main reflector, and the undesired transmitting wave is not reflected thereto. Accordingly, the undesired transmitting wave involved in the electric waves radiated from the primary horn can be suppressed.
According to the second feature of the invention, an antenna apparatus having a main reflector formed of a parabolic mirror for receiving an electric wave propagated from a transmitting source, a sub-reflector for reflecting the electric wave reflected by the main reflector in a predetermined direction and a primary horn for receiving the electric wave reflected by the sub-reflector, comprises:
a dielectric refractor which refracts the electric waves reflected by the sub-reflector so that an desired wave in a desired frequency band illuminates an aperture of the primary horn, and an interference wave outside the desired frequency band does not illuminate the aperture of the primary horn, and
electric wave-absorbers which are situated near an outer periphery of the primary horn and absorb the interference wave outside the desired frequency band refracted by the refractor.
According to the aforementioned structure, although an interference wave is involved in the electric waves received via the main reflector and the sub-reflector, since the refractive index of the dielectric refractor varies in accordance with a frequency, only the desired receiving wave in the desired frequency band reaches the primary horn, and the interference wave outside the desired receiving frequency band reaches the electric wave-absorbers to be absorbed thereby. Accordingly, even in case that the interference wave is involved in the electric waves received via the main reflector and the sub-reflector, the interference wave can be suppressed and an undesirable influence on the desired receiving wave can be reduced.
REFERENCES:
patent: 2939142 (1960-05-01), Fernsler
patent: 3763493 (1973-10-01), Shimada et al.
patent: 4218683 (1980-08-01), Hemming
patent: 5929819 (1999-07-01), Grinberg
patent: 0 510 588 A1 (1992-10-01), None
English Abstract of JP 11-340730, published Dec. 10, 1999.
English Abstract of JP 60-85773, published Mar. 25, 1994.
English Abstrac of JP 3-199990, published Aug. 30, 1991.
NEC Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
Wimer Michael C.
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