Wave transmission lines and networks – Wave mode converters
Reexamination Certificate
2001-01-04
2003-02-18
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Wave mode converters
C333S137000, C333S135000, C343S756000
Reexamination Certificate
active
06522215
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a converter for receiving a satellite signal with a dual frequency band. More specifically, the present invention relates to a converter of an antenna for satellite broadcasting or communication and to an input waveguide portion of a converter receiving two circularly polarized waves (right-hand and left-hand circularly polarized waves) with two separate frequency bands such as Ku and Ka bands.
2. Description of the Background Art
Parabolic antennas are mostly used as antennas for satellite broadcasting or communication. A parabolic antenna includes a reflecting mirror facing a satellite, a primary radiator receiving radiowaves collected by the reflecting mirror, and a converter for performing amplification and frequency conversion on the radiowaves received by the primary radiator. Many of the recent small-sized parabolic antennas have a primary radiator and a converter which are integrated together.
In these days, Ku band (frequencies extending from about 10.7 to 14.5 GHz) is mainly used for satellite broadcasting or communication. However, especially in these countries such as United States, frequency bands of Ku band are becoming densely allocated. In addition, for high-definition television broadcast requiring a wide frequency band or for data communication required to operate at high speed with large capacity, use of Ka band (at a higher frequency of about 20 GHz) is planned.
The Ku and Ka bands coexist, so that the demand of receiving radiowaves with two frequency bands by one antenna and converter naturally arises. Conventional techniques related to a primary radiator for a dual frequency band include use of a primary radiator which handles both C band (at a frequency of about 4 GHz) and Ku band.
FIG. 20
is a diagram showing an interior of a waveguide of a conventional primary radiator for a dual frequency band, and
FIG. 21
is a cross sectional view thereof. The primary radiator for dual frequency band shown in
FIGS. 20 and 21
is disclosed in Japanese Utility Model Laying-Open No. 63-33206.
Referring to
FIGS. 20 and 21
, the primary radiator for dual frequency band is a circular waveguide (a coaxial waveguide) of a dual structure where a signal with a low frequency band f
1
(hereinafter referred to as f
1
) is transmitted through an outer waveguide
201
and a signal with a high frequency band f
2
(hereinafter referred to as f
2
) is transmitted through an inner waveguide
211
. The primary radiator for dual frequency band receives circularly polarized waves. 90° phasers
202
and
212
, respectively for f
1
and f
2
signals, are provided inside outer waveguide
201
and inner waveguide
211
.
Referring to
FIG. 20
, circularly polarized wave signal f
1
from the right side is transmitted through outer waveguide
201
, converted to a linearly polarized wave signal by 90° phaser
202
, and further transmitted to a rectangular branching waveguide
204
through a step converter
203
from outer waveguide
201
.
Circularly polarized wave signal f
2
is transmitted through inner waveguide
211
and converted by a linearly polarized wave signal by 90° phaser
212
. Linearly polarized wave signal f
2
is received by a probe
213
in the waveguide and transmitted to a converter circuit for f
2
(not shown) through a coaxial line
214
.
As shown in
FIG. 21
, coaxial line
214
includes a middle conductor
215
, outer conductors
217
outside thereof, and electrical inductors
216
between middle conductor
215
and outer conductors
217
. Middle conductor
215
is electrically connected to probe
213
. Outer conductors
217
are electrically connected to inner waveguide
211
and outer waveguide
201
, respectively.
It is noted that signal f
1
which has been converted to the linearly polarized wave is also transmitted to a converter circuit for f
1
through a probe (not shown) from branching waveguide
204
.
As shown in
FIG. 20
, the conventional primary radiator for dual frequency band is of course applicable to Ku and Ka bands, but can receive only one polarized wave (right-hand or left-hand circularly polarized wave) with one frequency band. This is because only one coaxial line for f
2
can be arranged. If two polarized waves (right-hand and left-hand circularly polarized waves) are to be received with frequency band f
2
, in addition to a horizontally arranged probe
213
and coaxial line
214
, one more probe and coaxial line must be arranged in an orthogonal direction (a perpendicular direction in FIG.
20
). However, with such a structure, two orthogonal coaxial lines for f
2
pass through outer waveguide
201
and short-circuiting is caused by two orthogonal outer conductors. As a result, any polarized wave cannot pass through outer waveguide
201
.
The only polarized wave that allows signal f
1
to pass through outer waveguide
201
is that which is orthogonal to the coaxial line for f
2
. Thus, only one polarized wave can be received with each of frequency bands of f
1
and f
2
. As frequency bands for satellite broadcasting or communication become more densely allocated as in recent years, a communication means which utilizes two polarized waves within the same frequency band becomes popular for the purpose of effectively utilizing radial waves. Therefore, a primary radiator or converter which can receive only one polarized wave with one frequency band would not be sufficient.
SUMMARY OF THE INVENTION
Therefore, a main object of the present invention is to provide a converter for receiving a satellite signal with a dual frequency band capable of implementing a primary radiator receiving two different circularly polarized waves with respective frequency bands in a converter receiving two frequency bands.
The present invention is a converter for receiving a satellite signal with a dual frequency band having a waveguide of a dual structure with a first waveguide and a second waveguide coaxially arranged therein. A plurality of sections are arranged between the first and second waveguides and one section is arranged inside the second waveguide.
Another aspect of the present invention is a converter for receiving a satellite signal with a dual frequency band having a waveguide of a dual structure with a first waveguide and a second waveguide coaxially arranged therein. First and second sections are arranged between the first and second waveguides, and a third section is arranged inside the second waveguide.
According to the present invention, a primary radiator of receiving two different circularly polarized waves (right-hand and left-hand circularly polarized waves) of respective frequency bands can be implemented.
Preferably, the first and second waveguides have a square or circular shape.
Preferably, the first, second and third sections are arranged in parallel with the axial direction.
Preferably, the first and second sections are arranged in parallel with the axial direction, and the first and second sections are arranged orthogonally to the third section.
Preferably, the first, second and third sections are stepped in a width direction.
More preferably, the first, second and third sections are tapered from the output side to the input side.
More preferably, the first, second and third sections are stepped in the axial direction both in thickness and width directions.
More preferably, the first, second and third sections are tapered in the axial direction both in the thickness and width directions from the output side to the input side.
Still another aspect of the present invention is a converter for receiving a satellite signal with a dual frequency band having a waveguide of a dual structure with a-first waveguide and a second waveguide coaxially arranged therein. The first and second sections as well first and second probes are arranged between the first and second waveguides, and a third section as well as the third and fourth probes are arranged in the second wave guide.
Preferably, the first and second waveguides have a square or circular cross section in a dire
Glenn Kimberly E
Nixon & Vanderhye P.C.
Pascal Robert
Sharp Kabushiki Kaisha
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