Wave transmission lines and networks – Wave mode converters
Reexamination Certificate
2001-08-06
2003-12-16
Cho, James (Department: 2819)
Wave transmission lines and networks
Wave mode converters
C333S157000
Reexamination Certificate
active
06664866
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a circular waveguide polarizer to be used mainly in VHF band, UHF band, microwave band, and millimeter wave band.
BACKGROUND ART
FIG. 1
is a schematic configuration diagram of a conventional circular waveguide polarizer described, for example, in Proc. of The Institute of Electronics and Communication Engineers (published in September 1980, Vol. 63-B, No. 9, pp. 908-915). In the figure, reference numeral
1
denotes a circular waveguide, reference numeral
2
denotes a plurality of metallic posts inserted into the circular waveguide
1
through a side wall of the waveguide in pairs with respect to an axis C
1
of the waveguide and arranged at predetermined certain intervals along the direction of the pipe axis C
1
of the waveguide
1
, and reference numeral P
1
and P
2
denote an input end and an output end, respectively.
FIG. 2
is an explanatory diagram showing a conventional electromagnetic field distribution of a horizontally polarized wave and a vertically polarized wave.
The operation of the conventional circular waveguide polarizer will now be described.
It is here assumed that a linearly polarized wave in a frequency band f capable of being propagated through the circular waveguide
1
is propagated in a fundamental transmission mode (TE
11
mode) through the circular waveguide
1
and is incident from the input end P
1
in a 45° inclined state of its polarization plane from an insertion plane of the metallic posts
2
as shown in FIG.
1
. At this time, the incident linearly polarized wave can be regarded as being a combined wave of a linearly polarized wave perpendicular to the insertion surfaces of the metallic posts
2
and a linearly polarized wave horizontal to the insertion plane of the metallic posts
2
, both having been incident in phase. Polarization components perpendicular to the insertion plane of the metallic posts
2
, as shown on the right-hand side in
FIG. 2
, pass through the circular waveguide
1
with little influence from the metallic posts
2
and are outputted from the output end P
2
due to the fact that an electric field intersects the metallic posts perpendicularly. On the other hand, the passing phase of polarization components horizontal to the insertion plane of the metallic posts
2
, as shown on the left-hand side in
FIG. 2
, is delayed due to the fact that the metallic posts
2
serve as a capacitive susceptance since a magnetic field intersects the metallic posts
2
perpendicularly.
Thus, in the circular waveguide polarizer shown in
FIG. 1
, the metallic posts
2
act as a capacitive susceptance for the polarization component which is horizontal to the insertion plane. Therefore, the number, spacing and insertion length of the metallic posts
2
are appropriately designed so that a passing phase difference between the polarization component outputted from the output end P
2
and perpendicular to the insertion plane of the metallic posts
2
on the one hand and the polarization component outputted from the output end P
2
and horizontal to the insertion plane of the metallic posts
2
on the other hand is 90°. Thus, there is obtained a circularly polarized wave as a combined wave of both polarization components outputted from the output end P
2
. Namely, the linearly polarized wave incident from the input end P
1
is outputted as a circularly polarized wave from the output end P
2
.
In the conventional circular waveguide polarizer constructed as above, since the metallic posts
2
are projected into the circular waveguide
1
, disturbance is imparted to a section with a dense electric field distribution within the circular waveguide
1
, allowing a phase delay to occur. Thus, the phase delay quantity or the reflection quantity vary greatly with a delicate change in insertion quantity of the metallic posts
2
into the circular waveguide
1
. Therefore, the adjustment to obtain a desired passing phase characteristic or a reflection amplitude characteristic requires much time and there has been the problem that mass production and cost reductions are difficult.
Moreover, since the metallic posts
2
are projected to a section with a dense electric field distribution within the circular waveguide
1
, there has been the problem that electric power resistance and low loss characteristic required of the circular waveguide polarizer are impaired.
The present invention has been accomplished for solving the above-mentioned problems and it is an object of the present invention to provide a high-performance low-cost circular waveguide polarizer.
DISCLOSURE OF THE INVENTION
According to the present invention, a circular waveguide polarizer is provided with side grooves arranged in a side wall of a circular waveguide.
Therefore, by appropriately designing the number, spacing, radial depth, circumferential width, length in a pipe axis direction, and the like of such side grooves, it is possible to delay a passing phase of a polarization component perpendicular to the installation plane of the side grooves by 90° relative to a passing phase of a polarization component horizontal to the side groove installation plane. Thus, there is obtained an advantageous effect such that there can be realized a circular waveguide polarizer in which a linearly polarized wave incident from an input end is outputted as a circularly polarized wave from an output end.
Moreover, the side grooves are formed in the side wall of the circular waveguide and disturbance is imparted to a section with a coarse electromagnetic field distribution in a transmission mode (e.g., circular waveguide TE
11
mode) to give a phase delay. Therefore, the amount of phase delay does not vary largely even with a delicate change in the width, depth and length of each side groove. That is, the deterioration in characteristics caused by a machining error for example is small and it becomes possible to effect mass production and the reduction of cost.
Further, since metallic projections such as metallic posts are not arranged in the circular waveguide, the circular waveguide polarizer has superior characteristics with respect to electric power resistance and loss.
In the circular waveguide polarizer according to the present invention, first to n
th
side grooves may be formed in a side wall of a circular waveguide, the side grooves are arranged along the pipe axis direction so as to be symmetrical with respect to a plane which divides the circular waveguide right and left into two.
With this arrangement, the circular waveguide polarizer displays improved reflection matching.
In the circular wave polarizer according to the present invention, first to n
th
side grooves may be formed in the side wall of the circular waveguide along the pipe axis direction so as to be symmetric with respect to a plane which divides the circular waveguide right and left into two, and further, n+1
th
to 2n
th
side grooves may be formed in positions opposed to the first to n
th
side grooves with respect to the axis of the circular waveguide.
With this arrangement, it is possible to suppress the generation of higher-order modes, and the circular waveguide polarizer can operate with improved characteristics over a wide band.
In the circular waveguide polarizer according to the present invention, a first side groove may be formed in the side wall of the circular waveguide and a second side groove may be formed in a position opposed to the first side groove with respect to the axis of the circular waveguide.
With this arrangement, it is possible to suppress the generation of higher-order modes and there is obtained a large phase delay at a short pipe axis length, so that the circular waveguide polarizer can be downsized and can operate with improved characteristics over a wide band.
In the circular waveguide polarizer according to the present invention, a radial depth of each of the first and second side grooves may be gently varied in the pipe axis direction.
With this arrangement, it is possible to suppress the generation of higher-order modes and there is
Miyazaki Moriyasu
Yoneda Naofumi
Cho James
Mitsubishi Denki & Kabushiki Kaisha
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