Communications: radio wave antennas – Antennas – Wave guide type
Reexamination Certificate
2000-02-07
2002-05-14
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
Wave guide type
C343S786000, C343S783000, C343S895000
Reexamination Certificate
active
06388633
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a multibeam antenna which is used for receiving micro waves from plural geostationary satellites.
Recently, many geostationary broadcasting satellites and geostationary communication satellites have been launched. The need for receiving micro waves from, for example, two adjacent satellites by using a single antenna and selectively using one of the received micro waves is increasing.
Conventionally, a multibeam antenna which receives micro waves from plural satellites is configured so that micro waves from plural satellites are reflected and focused by a single parabola reflector and the focused satellite signals respectively enter different primary radiators.
Horn type primary radiators (or feedhorns) are used as the primary radiators. When two satellite micro waves are to be received, for example, two horn type primary radiators are supported by an arm so as to be placed at the reflection and focusnce position of the parabola reflector. The elevation angles for the satellites with respect to the ground are different from each other. Furthermore, the degree of the difference in elevation angle is varied depending on the receiving areas. For each receiving area, therefore, the inclination of the horn arrangement of the primary radiators with respect to an axis which is in parallel with the ground must be adjusted.
Hereinafter, the inclination of the horn arrangement of primary radiators with respect to an axis which is in parallel with the ground is referred to as the inclination angle.
In the case where satellite signals to be received are linearly polarized, the inclination of each incident micro wave with respect to the ground is changed depending on the satellites and receiving areas. For each receiving area, therefore, the reception polarization angle of each primary radiator must be adjusted.
When the direction of the conventional multibeam antenna for linearly polarized waves is to be adjusted, therefore, the arrangement inclination angles of primary-radiator horns with respect to each satellite, and the reception polarization angles of primary radiators must be adjusted in accordance with the receiving area. This produces problems in that a mechanism for adjusting the angles is complicated in structure, and that the adjusting work is cumbersome.
Conventionally, a flaring horn type primary radiator is usually used as a primary radiator of an antenna for satellite broadcasting. Even when a parabola reflector has a small diameter of, for example, 45 cm &phgr;, the arrangement distance among the primary radiators can be sufficiently made large as far as adjacent satellites from which micro waves are to be received are separated from each other by an elongation of about 8 deg. Consequently, flaring horns of primary radiators can be adjacently arranged without interfering with each other. By contrast, in the case where adjacent satellites from which micro waves are to be received are separated from each other by a small elongation of 4 deg., the arrangement distance among the primary radiators is as small as about 25 mm. As a result, when such flaring horn type primary radiators are used, the radiator horns interfere or contact with each other and hence it is impossible to constitute a multibeam antenna, thereby producing a problem in that plural antennas respectively for satellites from which micro waves are to be received must be installed.
As discussed above, in a primary radiator of a 45-cm &phgr; dual-beam antenna system which receives micro waves of the 12 GHz band from two satellites of an elongation of 4 deg., for example, the horn interval is about 25 mm. When a primary radiator of such an antenna is configured by a usual flare horn as shown in FIGS.
22
(A) and
22
(B), the aperture diameter is about 30 mm. Therefore, the antenna cannot be structurally configured. In order to realize such an antenna system, it is required to set the aperture diameter of a primary radiator to be 25 mm or less. In a circular waveguide designated as WCI-120 in EIAJ (Standard of Electronic Industries Association of Japan), the inner diameter of the waveguide is 17.475 mm. When such a waveguide is used, therefore, the horn has substantially a flare angle of about 0 deg. in consideration of the production process of an actual product. In other words, the horn has a circular waveguide section aperture as shown in FIGS.
23
(A) and
23
(B).
FIG.
22
(A) is a front view of the conventional flare horn type primary radiator, and FIG.
22
(B) is a section view taken along the line A-A′ of FIG.
22
(A). FIG.
23
(A) is a front view of a conventional circular waveguide type primary radiator, and FIG.
23
(B) is a section view taken along the line A-A′ of FIG.
23
(A).
In FIG.
22
(A) and
22
(B),
131
designates a flared waveguide which is disposed on a substrate
132
. A feeding point
133
is configured by a printed circuit formed on the substrate
132
, so as to be positioned at the center of the bottom face of the flared waveguide
131
.
The circular waveguide type primary radiator shown in FIGS.
23
(A) and
23
(B) is a circular waveguide
135
in place of the flared waveguide
131
. The other components are configured in the same manner as those of the flare horn type primary radiator of FIG.
22
(A).
FIG. 24
shows the radiational pattern of the circular waveguide type primary radiator. In the case where the reflector is offset, the radiation angle of the primary radiator is about 40 deg. In the directional pattern of
FIG. 24
, the leakage power is large in the reflector irradiation, and the unevenness of the electric field in the reflector irradiation range is large. Therefore, the antenna gain is lowered.
Methods such as that in which the horn aperture diameter is reduced, that in which a helical antenna is used with supplying a power through a coaxial system, and that in which a traveling-wave type antenna such as a circular waveguide feed poly-rod antenna is used as a primary radiator may be used as means for solving the problems discussed above, In the conventional multibeam antenna, moreover, received-signal cables extending from converters for primary radiators are connected to an external switching device, and one satellite broadcasting program which is to be received is selected by controlling the switching operation of the switching device. This configuration involves problems in that the user must purchase such an external switching device, and that a wiring work and the like are required.
When an integral converter is configured by using plural primary radiators, substrate-printed probes
202
are formed on a single substrate
201
as shown in
FIG. 29
, and all other circuits also are disposed on the substrate
201
. Each of the substrate-printed probes
202
comprises a horizontally-polarized-wave probe
202
a
and a vertically-polarized-wave probe
202
b
. The substrate-printed probes
202
are disposed in power feeding portions of plural (for example, two) primary radiator apertures
203
, respectively. Signals output from the horizontally-polarized-wave probe
202
a
and the vertically-polarized-wave probe
202
b
are amplified by high-frequency amplifiers
203
a
and
203
b
, and then subjected to selection by horizontal/vertical changeover switches
204
a
and
204
b
. Signals which are selected by the horizontal/vertical changeover switches
204
a
and
204
b
are then subjected to further selection by a satellite changeover switch
205
. The selected signal is amplified by a high-frequency amplifier
206
, and then supplied to a frequency converter
207
. The oscillation output of a local oscillator
208
is supplied to the frequency converter
207
. The frequency converter
207
outputs, as an intermediate-frequency signal, a signal of a frequency which is equal to the difference in frequency between the signal from the high-frequency amplifier
206
and that from the local oscillator
208
. The signal output from the frequency converter
207
is amplified by an intermediate-frequency amplifier
209
Hagiwara Shuji
Higuchi Hirofumi
Imaizumi Hiroaki
Manabe Ryotaro
Sakauchi Koji
Wimer Michael C.
Yagi Antenna Co., Ltd.
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