Communications: radio wave antennas – Antennas – With means for moving directive antenna for scanning,...
Reexamination Certificate
2000-07-11
2002-06-11
Le, Hoanganh (Department: 2821)
Communications: radio wave antennas
Antennas
With means for moving directive antenna for scanning,...
C343S757000
Reexamination Certificate
active
06404399
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radar antenna having a parabolic reflector and a plane reflector.
2. Description of the Related Art
FIG. 9
is a structural view showing an example of a conventional radar antenna. In the figure, a parabolic reflector
2
for reflecting a radio wave is disposed in a case
1
. The parabolic reflector
2
is driven by an actuator
3
to change the direction of the radio wave. A primary radiator
4
for radiating the radio wave toward the parabolic reflector
2
is supported by the parabolic reflector
2
. The primary radiator
4
is disposed at a distance that equals to the distance from the parabolic reflector
2
to the focal point of the parabolic reflector
2
.
FIG. 10
is a structural view showing another conventional radar antenna disclosed, for example, on page
243
of “INTRODUCTION TO RADAR SYSTEMS, second edition” by Merril I. Skolnik. In the figure, a parabolic reflector
6
is integrally formed as a part of a case
5
. A plane reflector
7
is disposed in the case
5
so as to face the parabolic reflector
6
. The plane reflector
7
is driven by an actuator
8
to change the direction of the radio wave. A primary radiator
9
for radiating the radio wave toward the parabolic reflector
6
is provided in the middle of the plane reflector
7
.
In the radar antenna illustrated in
FIG. 9
, however, in order to change the direction of the radio wave, it is necessary to drive the whole assembly of the parabolic reflector
2
and the primary radiator
4
, and thus, the mechanism has to be large.
On the other hand, since the radar antenna illustrated in
FIG. 10
employs a structure in which only the plane reflector having a polarization twist reflecting unit is driven, the mechanism is simplified. However, since it is necessary to secure the focal distance of the parabolic reflector
6
between the parabolic reflector
6
and the plane reflector
7
, the thickness of the antenna has to be large. Further, since the front face of the antenna is parabolized, when the antenna is actually mounted, it is necessary to additionally provide a radome (not shown) taking the design into consideration. Further, in such a case, since it is necessary to keep certain distance between the parabolic reflector
6
and the radome in order to maintain the performance, the thickness of the antenna becomes still larger, and loss due to the radome is caused.
Japanese Patent Application Laid-open No. Hei 3-277002 discloses a radar antenna having a combination of two parabolic reflectors. However, in such a case, it also requires a radome when it is mounted, and a loss due to the radome is caused.
SUMMARY OF THE INVENTION
The present invention has been made to solve the problems described in the above, and therefore has an object to provide a radar antenna that is thin and capable of preventing a large loss and simplifying the structure of a mechanism thereof.
To this end, according to one aspect of the present invention, there is provided a radar antenna comprising: a parabolic reflector including a first dielectric, a plurality of first linear conductors and a back conductor, the first dielectric having first and second paraboloids, the first linear conductors being provided in parallel with one another at intervals on the first paraboloid for reflecting a radio wave, the back conductor being provided on the second paraboloid for reflecting the radio wave which has passed between the first linear conductors and through the first dielectric; a plane reflector for passing through the radio wave reflected by the parabolic reflector, including a plate-like second dielectric and a plurality of second linear conductors for reflecting the radio wave toward the parabolic reflector, the second dielectric having an opposing surface which opposes the first paraboloid, the second linear conductors being provided in parallel with one another at intervals on the opposing surface; a primary radiator for radiating the radio wave toward the plane reflector; and a driving unit for moving the parabolic reflector to change the reflection angle of the radio wave.
According to another aspect of the present invention, there is provided a radar antenna comprising: a parabolic reflector including a first dielectric, a plurality of first linear conductors and a back conductor, the first dielectric having first and second paraboloids, the first linear conductors being provided in parallel with one another at intervals on the first paraboloid for reflecting a radio wave, the back conductor being provided on the second paraboloid for reflecting the radio wave which has passed between the first linear conductors and through the first dielectric; a plane reflector for passing through the radio wave reflected by the parabolic reflector, including a plate-like second dielectric and a plurality of second linear conductors for reflecting the radio wave toward the parabolic reflector, the second dielectric having an opposing surface which opposes the first paraboloid, the second linear conductors being provided in parallel with one another at intervals on the opposing surface; a primary radiator for radiating the radio wave toward the plane reflector; and a driving unit for moving the plane reflector to change the reflection angle of the radio wave.
REFERENCES:
patent: 3708795 (1973-01-01), Lyons
patent: 3793637 (1974-02-01), Meek
patent: 4253190 (1981-02-01), Csonka
patent: 4563064 (1986-01-01), Garas
patent: 4740791 (1988-04-01), Darbowitch et al.
patent: 5844527 (1998-12-01), Takashima et al.
patent: 6150991 (2000-11-01), Hulderman
patent: 3-277002 (1991-12-01), None
Introduction To Radar Systems, Second Edition, by M. Skolnik pp. 242-243.
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