Information
-
Patent Grant
-
6778146
-
Patent Number
6,778,146
-
Date Filed
Friday, September 20, 200222 years ago
-
Date Issued
Tuesday, August 17, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Brinks Hofer Gilson & Lione
-
CPC
-
US Classifications
Field of Search
US
- 343 786
- 343 772
- 343 775
- 343 779
- 343 783
- 343 784
- 343 785
- 333 21 A
- 333 26
-
International Classifications
-
Abstract
In a satellite broadcast reception converter, probes are equipped in a circular hole formed in a first circuit board, and plural fixing holes are formed around the circular hole. Snap pawls are formed at open ends of the waveguides formed of sheet metal. The respective snap pawls are inserted in the fixing holes of the first circuit board so as to project to the back surface side of the first circuit board, and the fixing holes of the short caps are snapped into the snap pawls. A dielectric feeder of synthetic resin supported on each waveguide has a first split body with radiation portion projected from the open end of each waveguide and a second split body having a phase converter fixed in the waveguide. The first and second split bodies are unified by inserting a projection equipped to the second split body into a through hole formed at the center of the first split body.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a satellite broadcast reception converter for receiving electric waves transmitted from a satellite, and particularly to a satellite broadcast reception converter suitable for receiving circularly polarized electric waves transmitted from a satellite.
2. Description of the Related Art
A satellite broadcast reception converter mounted in an outdoor antenna device is equipped with a waveguide having a hollow structure to which electric waves transmitted from a satellite are incident, a probe disposed at a predetermined position in the waveguide, a short cap for reflecting electric waves propagating in the waveguide to make the probe detect the electric waves, a circuit board having a processing circuit for performing appropriate processing (amplification, frequency conversion, etc.) on signals detected by the probe, etc. and the circuit board is usually covered by a shield case.
There has been hitherto known one of such satellite broadcast reception converters in which a waveguide and a shield case are integrally formed by aluminum die casting and a circuit board and a short cap are fixed in the shield case. In this case, a probe is formed on the circuit board by pattern formation, and if the short cap is fixed to the shield case by plural screws after the circuit board and the short cap are successively installed in the shield case, the circuit board could be pinched and fixed between the shield case and the short cap.
Further, in a satellite broadcast reception converter mounted on an outside antenna device for example when a right-handed circularly polarized or left-handed circularly polarized electric wave transmitted from a satellite is received, it is necessary to convert the circularly polarized wave incident into the waveguide to a linearly polarized wave in the phase converter and couple the linearly polarized wave to the probe for reception.
Still further, there has been also known a satellite broadcast reception converter in which a waveguide having a horn portion is formed of alloy of aluminum, zinc, etc. by die casting and then a phase converter called as a ridge is integrally formed on the inner wall surface of the waveguide and a circularly polarized wave incident from the horn portion into the waveguide is converted to a linearly polarized wave by the ridge. That is, the circularly polarized wave corresponds to a polarized wave having the rotating composite vector between two linearly-polarized waves that are equal in amplitude and have a phase difference of 90 degrees therebetween. Therefore, when the circularly-polarized wave passes through the ridge, the phase difference of 90 degrees is set to zero, and thus it is converted to the linearly polarized wave.
However, in the conventional satellite broadcast reception converter described above, the horn portion having desired aperture diameter and length is integrally formed at the tip of the waveguide, and the ridge having desired length and extending in the axial line direction is integrally formed on the inner wall surface of the waveguide. Therefore, not only the waveguide must be designed to be long in the axial line direction and thus miniaturization thereof is disturbed, but also the ridge serving as the phase converter is designed in an under-cut shape to make and thus a metal mold for die casting is complicated. As a result, the manufacturing cost is increased.
Therefore, there has been recently proposed a satellite broadcast reception converter in which a dielectric feeder achieved by integrally forming a radiation portion and a phase converter is used, the radiation portion is projected forwardly from the open end of a waveguide and the phase converter inserted and fixed in the waveguide is intersected to a probe at an angle of about 45 degrees. In this satellite broadcast reception converter, when a circularly polarized wave transmitted from a satellite is incident from the radiation portion of the dielectric feeder, the circularly polarized wave is converted to a linearly polarized wave in the phase converter while propagating in the dielectric feeder, and the linearly polarized wave goes into the deep portion of the waveguide and coupled to the probe.
Accordingly, according to the satellite broadcast reception converter using such a dielectric feeder, it is unnecessary to form a horn portion and a ridge (phase converter) integrally with a waveguide, so that the shape of the waveguide is simplified and the manufacturing cost can be reduced. In addition, the phase difference to the linearly polarized wave is large even when the overall length of the dielectric feeder is set to a relatively short value, the overall length of the waveguide itself can be shortened.
According to the conventional satellite broadcast reception converters thus constructed, the waveguide and the shield case are integrally formed by using aluminum die casting, and the circuit board and short cap are fixed in the shield case by using the plural screws. Therefore, the angularity between the probe pattern-formed on the circuit board and the axial line of the waveguide can be kept, and electric waves propagating in the waveguide can be surely detected. However, plural screws are required to fix the circuit board and the short cap, and also a subsequent step of coating adhesive agent to prevent loosening of the screws is needed. Therefore, the number of parts and the number of working steps are increased, which greatly causes rise-up of the manufacturing cost of the satellite broadcast reception converter.
In the satellite broadcast reception converter using the dielectric feeder, there is a merit that the manufacturing cost can be reduced and it can be miniaturized because a waveguide having a simple shape and a short length is available, however, it has some problem. That is, although the dielectric feeder is formed by injection-molding synthetic resin material, occurrence of surface sink and bubbles in synthetic resin is generally intensified when it is contracted as the volume (volumetric capacity) thereof increases. Therefore, high dimensional precision is not achievable with the dielectric feeder which is achieved by integrally forming a radiation portion and a phase converter like the prior art described above. Particularly when polyethylene (PE) which is low in price and has a low dielectric dissipation factor is used as the material of the dielectric feeder, there is a problem that the contraction after the injection molding is large and occurrence of bubbles is remarkable, so that the dimensional precision of each part of the dielectric feeder is extremely lowered, and the reception efficiency of electric waves transmitted from a satellite is lowered.
SUMMARY OF THE INVENTION
The present invention has been implemented in view of the foregoing situation of the prior arts, and has an object to provide a satellite broadcast reception converter in which a waveguide and a short cap can be simply fixed to a circuit board having a probe, and also which is suitable for reduction of the manufacturing cost and miniaturization and can enhance the dimensional precision of a dielectric feeder.
In order to attain the above object, according to a first aspect of the present invention, there is provided a satellite broadcast reception converter characterized by comprising a circuit board having a probe, at least one waveguide formed of sheet metal disposed vertically to the circuit board and at least one short cap designed to have a bottom through which the open end of the waveguide is closed, wherein snap pawls formed at the open end of the waveguide are inserted into fit holes formed in the circuit board and the short cap is fixedly fitted to the snap pawls to pinch the circuit board between the waveguide and the short cap.
According to the satellite broadcast reception converter thus constructed, the circuit board can be pinched and fixed by the waveguide and the short cap through a simple work of fixedly fitting the short cap to the snap pawls by utilizing the characteristic of springs (spring elasticity) of the waveguide formed of sheet metal. Therefore, the number of parts and the number of working steps can be greatly reduced, so that the manufacturing cost of the satellite broadcast reception converter can be reduced.
In the above construction, it is preferable that the short cap is soldered to an earth pattern formed on the circuit board. In this case, if the short cap is fixedly fitted to the snap pawls under the state that cream solder is coated on the earth pattern in advance, then the short cap could be easily soldered to the earth pattern by melting the cream solder in a reflow furnace.
Further, in the above construction, parallel portions extending in the axial line direction of the waveguide are formed at four confronting positions on the peripheral surface of the waveguide, and a snap pawl is extensively equipped to the top of each parallel portion, whereby each snap pawl of the waveguide can be inserted into the corresponding fitting hole of the circuit board with no rattle, and the relative positioning between the waveguide and the probe can be surely performed.
Still further, in the above construction, it is preferable that the circuit board and the short cap are covered by the shield case, the waveguide is inserted through a through hole formed in the shield case and projected to the outside and also the circuit board is fixed in the shield case. When the waveguide to which high dimensional precision is required is separated from the shield case as described above, the management of the dimensional precision of the waveguide can be enhanced.
Still further, in the above construction, it is preferable that the shield case is formed of sheet metal, and support portions are formed at the peripheral edge of the through hole formed in the shield case by bending the shield case. This construction enables the peripheral surface of the waveguide inserted in the through hole to be surely supported by the support portions.
In order to attain the above object, according to a second aspect of the present invention, there is provided a satellite broadcast reception converter characterized by comprising at least one waveguide that is closed at one end thereof and opened at the other end thereof, at least one probe projecting in the center axis direction of the waveguide and at least one dielectric feeder that is supported by the waveguide and formed of synthetic resin, wherein the dielectric feeder comprises a first split body having a radiation portion projecting from the open end of the waveguide and a second split body having a phase conversion portion fixed in the waveguide, and a projection equipped to the second split body is inserted in a through hole formed at the center portion of the first split body to unify the first split body and said second body into one body.
According to the satellite broadcast reception converter thus constructed, the dielectric feeder is constructed by the unified first and second split bodies which are separated from each other. Therefore, the volume (volumetric capacity) of each of the first and second split bodies as a single body is reduced, so that occurrence of surface sink and bubbles can be suppressed. In addition, the dielectric feeder is divided at the portion at which the through hole and the projection are jointed to each other, and the dividing face is located at a position far away from the center of the first split body at which the electric field intensity is largest, so that an electrical adverse effect caused by the division can be suppressed.
In the above construction, it is preferable that the second split body is equipped with an impedance converter which is narrowed in an arcuate shape from the open end of the waveguide to the phase converter, the projection is equipped to an end face of the impedance converter and the first and second split bodies are jointed to each other at the end face of the impedance converter. By providing the impedance converter as described above, the reflection components of electric waves propagating from the radiation portion through the impedance converter to the phase converter can be greatly reduced. In addition, the phase difference to the linearly polarized wave is large even when the length of the portion extending from the impedance converter to the phase converter is reduced, so that the overall length of the waveguide can be greatly reduced.
In this case, the projection may be strongly engaged with the through hole, however, it is preferable that an engaging projection is formed on the inner wall surface of the through hole, and an engaging recess portion is formed on the outer wall surface of the projection, the engaging projection and the engaging recess portion being snap-jointed to each other. By using such snap-joint, even when there is some dimensional dispersion between the projection and the through hole, the projection and the through hole can be simply and surely jointed to each other. At this time, it is preferable that representing the length from the rear end face of said radiation portion to said engaging projection by A and representing the length from the end face of the impedance converter to the engaging recess portion by B, A and B are set to satisfy the relation of A>B because the engaging projection and the engaging recess portion can be surely snap-jointed to each other with no rattle.
In the above construction, it is preferable that the radiation portion is designed in a conical shape which forwardly expands from the open end of the waveguide like a horn, and the end face of the impedance converter is jointed to the rear end face of the radiation portion. With this construction, the dividing face vertical to the travel direction of the electric waves propagating in the dielectric feeder is reduced, so that the reflection of the electric waves at the dividing face can be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a cross-sectional view showing a satellite broadcast reception converter according to an embodiment;
FIG. 2
is a cross-sectional view showing the satellite broadcast reception converter which is taken from another side;
FIG. 3
is a perspective view showing a waveguide;
FIG. 4
is a front view of the waveguide;
FIG. 5
is a perspective view showing a dielectric feeder;
FIG. 6
is a front view showing the dielectric feeder;
FIG. 7
is an exploded view showing the dielectric feeder;
FIG. 8
is a diagram showing a state that the dielectric feeder is fixed to the waveguide;
FIG. 9
is a diagram showing the difference between two dielectric feeders;
FIG. 10
is an exploded perspective view showing a shield case, a circuit board and a short cap;
FIG. 11
is a back side view of the shield case;
FIG. 12
is a diagram showing a state that the circuit board is fixed to the shield case;
FIG. 13
is a cross-sectional view taken along B—B line of
FIG. 12
;
FIG. 14
is a diagram showing a part mounting face of a first circuit board;
FIG. 15
is a diagram showing the positional relationship between a phase converter of the dielectric feeder and a minute radiation pattern;
FIG. 16
is a cross-sectional view showing the fixing state of the waveguide, the circuit board and the short cap;
FIG. 17
is a diagram showing the relationship between the correcting portion of a waterproof cover and a radiation pattern;
FIG. 18
is a diagram showing a modification of the correcting portion;
FIG. 19
is a block diagram showing a converter circuit;
FIG. 20
is a diagram showing a layout state of circuit parts; and
FIG. 21
is an enlarged view showing the joint portion between two circuit boards.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred embodiments according to the present invention will be described hereunder with reference to the drawings.
FIG. 1
is a cross-sectional view showing a satellite broadcast reception converter according to an embodiment,
FIG. 2
is a cross-sectional view of the satellite broadcast reception converter, which is taken along from another side,
FIG. 3
is a perspective view showing a waveguide,
FIG. 4
is a front view of the waveguide,
FIG. 5
is a perspective view showing a dielectric feeder,
FIG. 6
is a front view showing the dielectric feeder,
FIG. 7
is a an exploded view of the dielectric feeder,
FIG. 8
is a diagram showing the state that the dielectric feeder is fixed to the waveguide,
FIG. 9
is a diagram showing the difference between two dielectric feeders,
FIG. 10
is an exploded perspective view showing a shield case, a circuit board and a short cap,
FIG. 11
is a back-side view of the shield case,
FIG. 12
is a diagram showing the state that the circuit board is fixed to the shield case,
FIG. 13
is a cross-sectional view taken along A—A line of
FIG. 12
,
FIG. 14
is a diagram showing a part mount face of a first circuit board,
FIG. 15
is a diagram showing the positional relationship between a phase converter of the dielectric feeder and a minute radiation patter,
FIG. 16
is a cross-sectional view showing the fixing state of the waveguide and the circuit board, the short cap,
FIG. 17
is a diagram showing the relationship between a correcting portion of a waterproof cover and a radiation pattern,
FIG. 18
is a diagram showing a modification of the correcting portion,
FIG. 19
is a block diagram showing a converter circuit,
FIG. 20
is a diagram showing a layout state of circuit parts, and
FIG. 21
is an enlarged view of the joint portion between two circuit boards.
The satellite broadcast reception converter according to this embodiment comprises first and second waveguides
1
,
2
, first and second dielectric feeders
3
,
4
which are supported at the tip portions of the waveguides
1
,
2
respectively, a shield case
5
, first and second circuit boards
6
,
7
fixed in the shield case
5
, a pair of short caps
8
for closing the rear open ends of the respective waveguides
1
,
2
, a waterproof cover
9
for covering these parts, etc.
As shown in
FIGS. 3 and 4
, the first waveguide
1
is achieved by rolling a metal flat plate in a cylindrical form and joining the metal flat plate thus rolled, and then fixing the joint portion of the metal flat plate by plural caulking portions
1
a
. The interval between the respective caulking portions
1
a
is set to about a quarter wavelength of the wavelength λg in waveguide. The first waveguide
1
has a substantially circular shape in section, and four parallel portions
1
b
are formed on the peripheral surface thereof so as to be located at angular intervals of about 90 degrees in the peripheral direction. Each parallel portion
1
b
extends in the longitudinal direction parallel to the center axis of the first waveguide
1
, and a snap pawl
1
c
is extensively equipped to the rear end of each parallel portion
1
b
. Further, a stopper pawl
1
d
is formed at some midpoint of each of two confronting parallel portions
1
b
, and the stopper pawls
1
d
are disposed to project into the inside of the first waveguide
1
. The second waveguide
2
has the entirely same construction as the first waveguide
1
. The duplicative description thereof is omitted below, however, it has a caulking portion
2
a
, a parallel portion
2
b
, a snap pawl
2
c
and a stopper pawl
2
d.
Both the first dielectric feeder
3
and the second dielectric feeder
4
are formed of synthetic resin material having a low dielectric dissipation factor. In this embodiment, polyethylene (dielectric constant ∈≅2.25) which is inexpensive is used in consideration of the price. As shown in
FIGS. 5
to
7
, the first dielectric feeder
3
is constructed by a first split body
3
a
having a radiation portion
10
and a second split body
3
b
comprising an impedance converter
11
and a phase converter
12
. The radiation portion
10
is designed in a conical shape which expands like a horn, and a circular through hole
10
a
is formed at the center portion of the radiation portion
10
. An engaging projection
10
b
is equipped on the inner peripheral surface of the through hole
10
a
, and the first split body
3
a
is subjected to mold opening with the engaging projection
10
b
set as a parting line in the injection molding process. Further, an annular groove
10
c
is formed on the end face of the expanded tip portion of the radiation portion
10
, and the depth of the annular groove
10
c
is set to about a quarter wavelength of the wavelength λ of the electric waves propagating in the annular portion concerned.
The impedance converter
11
has a pair of curved surfaces
11
a
which are narrowed in an arcuate shape toward the phase converter
12
, and the cross-sectional shape of each curved surface
11
a
is approximately represented by a quadratic curve. The end face of the impedance converter
11
is substantially circular, and four flat fixing faces
11
b
are formed at an angular interval of about 90 degrees on the peripheral edge of the end face. Further, the impedance converter
11
is equipped with a cylindrical projection
13
at the center of the end face thereof, and an engaging recess portion
13
a
is formed on the outer peripheral surface of the projection
13
. When the projection
13
is inserted into the through hole
10
a
to make the end face of the impedance converter
11
abut against the rear end face of the radiation portion
10
, the engaging recess portion
13
a
and the engaging projection
10
b
are snap-jointed to each other in the through hole
10
a
, thereby unifying the first split body
3
a
and the second split body
3
b.
At this time, when the length from the rear end face of the radiation portion
10
to the engaging projection
10
b
is represented by A and the length from the end face of the impedance converter
11
to the engaging recess portion
13
a
is represented by B, the dimension A is set to be slightly longer than the dimension B. Therefore, at the time of the snap-joint between the engaging recess portion
13
a
and the engaging projection
10
b,
there occurs force acting to press the rear end face of the radiation portion
10
against the end face of the impedance converter
11
, and the first split body
3
a
and the second split body
3
b
are unified into one body with no rattle. Further, the annular groove
13
b
is formed on the tip face of the projection
13
, so that both the annular grooves
10
c
and
13
b
are concentrically arranged at the time when the first split body
3
a
and the second split body
3
b
are unified.
The phase converter
12
is designed to be continuous with the tapered portion of the impedance converter
11
, and functions as a 90-degree phase shifter for converting a circularly-polarized wave incident into the first dielectric feeder
3
to a linearly-polarized wave. The phase converter
12
is formed of a plate member having a substantially uniform thickness, and plural notches
12
a
are formed at the tip portion thereof. The depth of each notch
12
a
is set to about a quarter wavelength of the wavelength λg in waveguide, and the end face of the phase converter
12
and the bottom surfaces of the notches
12
a
serve as two reflection faces which are orthogonal to the travel direction of the electric waves. Further, elongated grooves
12
b
are formed on the both the side surfaces of the phase converter
12
.
As shown in
FIG. 8
, the first dielectric feeder
3
thus constructed is supported by the first waveguide
1
, the radiation portion
10
of the first split body
3
a
and the projection
13
of the second split body
3
b
are projected from the open end of the first waveguide
1
, and the impedance converter
11
and the phase converter
12
of the second splitter
3
b
are inserted and fixed in the first waveguide
1
. At this time, the respective fixing faces
11
b
of the impedance converter
11
are press-fitted to the four corresponding parallel portions
1
b
formed on the inner peripheral surface of the first waveguide
1
, and also both the side surfaces of the phase converter
12
are press-fitted to the two parallel portions
1
b
which are disposed at an angular interval of 180 degrees so as to face each other, whereby the second split body
3
b
can be simply fixed to the first waveguide
1
with high positional precision. Further, the stopper pawls
1
d
formed on the two parallel portions
1
b
bite into the elongated grooves
12
b
of the phase converter
12
, so that the second split body
3
b
can be surely prevented from falling off the first waveguide
1
.
The second dielectric feeder
4
has the same basic construction as the first dielectric feeder
3
in that it is constructed by a first split body
4
a
having a radiation portion
14
and a second split body
4
b
comprising an impedance converter
15
and a phase converter
16
, and a projection
17
of the second split body
4
b
is inserted and fixed in a through hole
14
a
of the first split body
4
a
, however, it is different from the first dielectric feeder
3
in the following two points. A first difference point resides in that the phase converters
12
,
16
are different in length. Comparing the length L
1
of the phase converter
12
of the first dielectric feeder
3
and the length L
2
of the phase converter
16
of the second dielectric feeder
4
, they are set to satisfy the relation of L
1
>L
2
. A second difference point resides in that the second split bodies
3
b
,
4
b
are different in color. For example, the second split body
3
b
of the first dielectric feeder
3
is achieved by performing injection molding with the original color of raw material, and the second split body
4
b
of the second dielectric feeder
4
is achieved by performing injection molding after the raw material is colored with red, blue or the like.
That is, among the constituent parts of the first dielectric feeder
3
and the second dielectric feeder
4
, both the first split bodies
3
a,
4
a
are common parts, and both the second split bodies
3
b,
4
b
are different parts which are different in length and color between the phase converters
12
,
16
thereof. The reason why the phase converters
12
,
16
are different in length will be described later. If the second split bodies
3
b,
4
b
are designed to be different in color, erroneous insertion of both the second split bodies
3
b,
4
b
can be simply and surely checked by viewing the colors of the projections
13
,
17
exposed from the end faces of the first split bodies
3
a,
4
a
when the first and second dielectric feeders
3
,
4
are mounted on the corresponding first and second waveguides
1
,
2
as shown in FIG.
9
.
As shown in
FIGS. 10
to
13
, the shield case
5
is achieved by subjecting a metal flat plate to press working, and a pair of connectors
18
are secured to a slant surface
5
a
formed at one side portion of the shield case
5
. A pair of through holes
19
and plural open holes
20
are formed in the flat top plate of the shield case
5
, and plural support portions
21
are formed at the peripheral edge of each through hole
19
having a circular shape and bent toward the outside of the shield case
5
in the vertical direction. Further, plural pier portions
5
b
are formed in the top plate of the shield case
5
so as to be surrounded by the respective open holes
20
, and plural fitting pawls
22
are formed at the outer edges of the pier portions
5
b
and bent toward the inside of the shield case
5
in the vertical direction. In addition, plural recess portions
23
are formed on the back surfaces of the pier portions
5
b
of the shield case
5
, and the recess portions
23
are formed in an elongated shape along the outer edges of the open holes
20
.
A first circuit board
6
is formed of material such as polytetrafluoroethylene or the like of fluorocarbon resin group having a low dielectric constant and a low dielectric loss, and it is designed to be larger in outer shape than the second circuit board
7
. Plural through holes
6
a
are formed at suitable positions of the first circuit board
6
. The second circuit board
7
is formed of material such as glass-added epoxy resin or the like which has a lower Q-value than the first circuit board
6
, and a through hole
7
a
is formed in the second circuit board
7
. Each of the first and second circuit boards
6
,
7
is provided with a ground pattern
24
,
25
atone side thereof, and each ground pattern
24
,
25
is soldered to the shield case
5
by using solder
26
filled in each recess portion
23
. In this case, if the ground patterns
24
,
25
of both the circuit boards
6
,
7
are overlaid on the back surface of the top plate of the shield case
5
under the state that cream solder is filled in each recess portion
23
in advance and then the cream solder is melted in a reflow furnace or the like, both the circuit boards
6
,
7
can be simply and surely grounded to the shield case
5
. At this time, if a part of each recess portion
23
is exposed to the outside from the outer edge portion of each circuit board
6
,
7
as shown in
FIGS. 12 and 13
, defects such as lack of solder, etc. can be easily visually checked, and thus deficient solder can be easily supplemented.
The first and second circuit boards
6
,
7
can be not only soldered to the shield case
5
, but also fixed to the back surface of the top plate of the shield case
5
by using the respective fitting pawls
22
. In this case, if the respective fitting pawls
22
of the shield case
5
are inserted into the respective through holes
6
a
,
7
a
of the circuit boards
6
,
7
and then bent toward the plate surface side of the first circuit board
6
, both the circuit boards
6
,
7
could be fixed to the shield case
5
. Particularly, paying attention to the first circuit board
6
which is larger in size than the second circuit board
7
, suitable places containing the center portion and the peripheral edge portion are pressed against the back surface of the top plate of the shield case
5
by the plural fitting pawls
22
, so that warp of the first circuit board
6
can be surely corrected.
As shown in
FIGS. 14 and 15
, a pair of circular holes
27
are formed in the first circuit board
6
, and first to third bridging portions
27
a
to
27
c
are formed in each circular hole
27
. Under the state that the first circuit board
6
is fixed in the shield case
5
, both the circular holes
27
are coincident with the respective through holes
19
of the shield case
5
. The first bridging portion
27
a
and the second bridging portion
27
b
cross each other at an angle of about 90 degrees, and the third bridging portion
27
c
intersects to both the first and second bridging portions
27
a
,
27
b
at an angle of about 45 degrees. The respective bridging portions
27
a
to
27
c
at the left side of FIG.
14
and the respective bridging portions
27
a
to
27
c
at the right side of
FIG. 14
are located to be linearly symmetrical with each other with respect to the line P passing through the center of the first circuit board
6
. The opposite side to the ground pattern
24
side of the first circuit board
6
serves as a part-mount surface, and an annular earth pattern
28
is formed around each of the circular holes
27
on the part-mount surface. These earth patterns
28
are conducted to the ground pattern
24
through the through holes, and four fixing holes
29
are formed at angular intervals of about 90 degrees in the circumferential direction in each earth pattern
28
. Each fixing hole
29
is designed in a rectangular shape, and the four fixing holes
29
at the left side of FIG.
14
and the four fixing holes
29
at the right side of
FIG. 14
are located to be linearly symmetrical with each other with respect to the line P.
On the part-mount surface of the first circuit board
6
are formed a pair of first probes
30
a
,
30
b
located on both the first bridging portions
27
a
, a pair of second probes
31
a
,
31
b
located on both the second bridging portions
27
b
and a pair of minute radiation patterns
32
a
,
32
b
located on both the third bridging portions
27
c
by pattern formation. Accordingly, the respective pairs of the first probes
30
a
,
30
b
, the second probes
31
a
,
31
b
and the minute radiation patterns
32
a
,
32
b
at the right and left sides are located to be linear symmetrical with respect to the line P. In the following description, the minute radiation pattern
32
a
at the right side of
FIG. 14
is referred to as a first minute radiation pattern, and the minute radiation pattern
32
b
at the left side of
FIG. 14
is referred to as a second minute radiation pattern.
The short cap
8
is achieved by subjecting a metal plate to press working, and a flange portion
8
a
is formed at the open end side having a bottom-present shape as shown in FIG.
10
. Four fixing holes
33
are formed in the flange portion
8
a
at angular intervals of about 90 degrees in the circumferential direction, and each fixing hole
33
is designed in a rectangular shape. The short cap
8
functions as an terminal face for closing the open end of the rear portion of each of the waveguides
1
,
2
, and the short cap
8
and the first, second waveguide
1
,
2
are unified through the first circuit board
6
as shown in FIG.
16
. That is, the respective snap pawls
1
c
,
2
c
of the first and second waveguides
1
,
2
are inserted through the fixing holes
29
of the first circuit board
6
and projected to the back surface side thereof, and the respective fixing holes
33
of the short caps
8
are snapped into the snap pawls
1
c
,
2
c
, whereby the first circuit board
6
is pinched and fixed between the waveguides
1
,
2
and the pair of short caps
8
. At this time, cream solder is coated on the earth pattern
28
of the first circuit board
6
in advance, and by melting the cream solder in a reflow furnace after the snap-in of the short caps
8
, the short caps
8
are soldered to the earth pattern
28
of the first circuit board
6
.
As described above, the first circuit board
6
is fixed in the shield case
5
, and the first waveguide
1
and the second waveguide
2
are fixed vertically to the first circuit board
6
so as to penetrate from the first circuit board
6
through the through holes
19
of the shield case
5
and project to the outside. In this case, both the waveguides
1
,
2
abut against the respective support portions
21
formed at the peripheral edges of the through holes
19
, and these support portions
21
prevent undesired deformation such as inclination or the like of the waveguides
1
,
2
. The open portion of the shield case
5
at the opposite side to the projecting side of the waveguides
1
,
2
is covered (not shown).
Returning to
FIGS. 1 and 2
, the respective parts such as both the waveguides
1
,
2
, both the dielectric feeders
3
,
4
, the shield case
5
, etc. described above are accommodated in the waterproof cover
9
, and the pair of connectors
18
are projected from the waterproof cover
9
to the outside. The waterproof cover
9
is formed of dielectric material having excellent weather resistance such as polypropylene, ASA resin or the like, and the radiation portions
10
,
14
of the dielectric feeders
3
,
4
are disposed to face the front surface portion
9
a
of the waterproof cover
9
. A pair of projecting walls
34
are equipped substantially at the center of the front surface portion
9
a
, and both the projecting walls
34
extend to pass over the gap between the first and second waveguides
1
,
2
. These projecting walls
34
function as a correcting portion, and they can correct the radiation pattern of the electric waves incident to the waveguides
1
,
2
in accordance with the volume ratio of the projecting walls
34
because the phase of electric waves passing through the waterproof cover
9
is delayed by the projecting walls
34
. Accordingly, as shown in
FIG. 17
, the radiation pattern can be corrected from a shape indicated by a broken line (in case of no projecting wall
34
) to a shape indicated by a solid line, and thus a miniaturized reflection mirror (dish) is available. A thick portion
35
achieved by making the front surface portion
9
a
of the waterproof cover
9
thicker substantially at the center portion of the front surface portion
9
a
may be used as the correcting portion as shown in
FIG. 18
in place of the projecting walls
34
.
The satellite broadcast reception converter according to this embodiment receives electric waves transmitted from two adjacent satellites (first satellite S
1
and second satellite S
2
) which have been launched to the sky, and the first and second satellites S
1
and S
2
respectively transmit left-handed and right-handed circularly-polarized wave signals. The circularly-polarized wave signals are converged by the reflection mirror, pass through the waterproof cover
9
and then are incident into the first and second waveguides
1
,
2
. For example, the left-handed and right-handed circularly-polarized wave signals transmitted from the first satellite S
1
are incident from the end faces of the radiation portion
10
and the projection
13
into the first dielectric feeder
3
, and propagate from the radiation portion
10
through the impedance converter
11
to the phase converter
12
in the first dielectric feeder
3
. Thereafter, the circularly polarized wave signals are converted to linearly-polarized waves in the phase converter
12
, and then incident into the first waveguide
1
. That is, the circularly-polarized wave corresponds to the rotating composite vector between two linearly-polarized waves that are equal in amplitude and have a phase difference of 90 degrees therebetween. Therefore, when the circularly-polarized wave propagates in the phase converter
12
, the electric waves having the phase difference of 90 degrees are set to be in phase. For example, the left-handed circularly-polarized wave is converted to the vertically-polarized wave, and the right-handed circularly-polarized wave is converted to the horizontally-polarized wave.
At this time, since the plural annular grooves
10
c
,
13
b
having the depth of about λ/4 wavelength are formed on the end face of the first electric feeder
3
, the electric waves reflected from the end face of the radiation portion
10
and the bottom surfaces of the annular grooves
10
c
,
13
b
are inverted in phase and canceled, so that the reflection components of the electric waves directing to the end face of the radiation portion
10
are greatly reduced. In addition, since the radiation portion
10
is designed like a horn expanding from the open end of the front side of the first waveguide
1
, the electric waves can be efficiently converged to the first dielectric feeder
3
and also the length in the axial line direction of the radiation portion
10
can be shortened.
The impedance converter
11
is equipped between the radiation portion
10
of the first dielectric feeder
3
and the phase converter
12
, and the cross-sectional shape of each of the pair of curved surfaces
11
a
formed in the impedance converter
11
is continuously designed by an approximate quadratic curve, whereby the thickness of the first dielectric feeder
3
is converged to gradually decrease from the radiation portion
10
to the phase converter
12
. Therefore, not only the reflection components of the electric waves propagating in the first dielectric feeder
3
can be effectively reduced, but also the phase difference to the linearly-polarized wave is increased even when the length of the portion extending from the impedance converter
11
to the phase converter
12
is shortened. From this viewpoint, the overall length of the first dielectric feeder
3
can be also greatly shortened.
Further, since the notches
12
a
having the depth of about λg/4 wavelength are formed on the end face of the phase converter
12
, the electric waves reflected from the bottom surfaces of the notches
12
a
and the end face of the phase converter
12
are inverted in phase and canceled, so that impedance mismatch at the end face of the phase converter
12
can be overcome.
The left-handed and right-handed circularly-polarized wave signals transmitted from the first satellite SI are converted to the vertically and horizontally polarized wave signals in the phase converter
12
of the first dielectric feeder
3
as described above, and then travel to the short caps
8
in the first waveguide
1
. The vertically-polarized wave is detected by the first probe
30
a
, and the horizontally-polarized wave is detected by the second probe
31
a
. Likewise, the left-handed and right-handed circularly polarized wave signals transmitted from the second satellite S
2
travel from the end faces of the radiation portion
14
and the projection
17
into the second dielectric feeder
4
, and the left-handed circularly polarized wave is converted to the vertically polarized wave in the phase converter
16
of the second dielectric feeder
4
while the right-handed circularly polarized wave is converted to the horizontally polarized wave. These vertically and horizontally polarized waves travel to the short caps
8
in the second waveguide
1
, and the vertically polarized wave is detected by the first probe
30
b
while the horizontally polarized wave is detected by the second probe
31
b.
Here, the first and second minute radiation patterns
32
a
,
32
b
are formed on the first circuit board
6
. Since the first minute radiation pattern
32
a
intersects to each axial line of the first and second probes
30
a
,
31
a
at an angle of about 45 degrees and the second minute radiation pattern
32
b
intersects to each axial line of the first and second probes
30
b
,
31
b
at an angle of about 45 degrees, disturbances of the electrical fields of the vertically polarized wave and the horizontally polarized wave in the waveguides
1
,
2
can be suppressed by the first and second minute radiation patterns
32
a
,
32
b
respectively, and isolation between the vertically polarized wave and the horizontally polarized wave can be kept. Further, each of the first and second minute radiation patterns
32
a
,
32
b
is designed in a rectangular shape which is asymmetrical with respect to the axial line of each of the probes
30
a
,
31
a
,
30
b
,
31
b
, and the size (area) thereof is set to a relatively small value. Therefore, the reflection at the first and second minute radiation patterns
32
a
,
32
b
can be reduced with keeping the isolation between the vertically polarized wave and the horizontally polarized wave.
The first and second minute radiation patterns
32
a
,
32
b
are located on the first circuit board
6
so as to be linearly symmetrical with each other with respect to the line P. Therefore, as is apparent from
FIG. 15
, the first minute radiation pattern
32
a
is substantially orthogonal to the phase converter
12
of the first dielectric feeder
3
, and the second minute radiation pattern
32
b
is substantially parallel to the phase converter
16
of the second dielectric feeder
4
. In this case, as compared with the electrical field distribution in the second waveguide
2
in which the second minute radiation pattern
32
b
is substantially parallel to the phase converter
16
, the electrical field distribution in the first waveguide
1
in which the first minute radiation pattern
32
a
is substantially orthogonal to the phase converter
12
is deteriorated. Therefore, the deterioration of the electrical field distribution is corrected by increasing the dimension in the axial line direction of the phase converter
12
. That is, as described above, the length L
1
of the phase converter
12
of the first dielectric feeder
3
and the length L
2
of the phase converter
16
of the second dielectric feeder
4
are set to satisfy the relationship: L
1
>L
2
(see FIG.
9
), that is, the length of the phase converter
12
is set to be longer, thereby preventing occurrence of a phase difference between the linearly-polarized waves traveling in the first waveguide
1
.
The reception signals detected by the first probes
30
a
,
30
b
and the second probes
31
a
,
31
b
are frequency-converted to IF frequency signals by a converter circuit mounted on the first and second circuit boards
6
,
7
and then output therefrom. As shown in
FIG. 19
, the converter circuit comprises a satellite broadcast signal input terminal portion
100
for receiving satellite broadcast signals transmitted from the first satellite S
1
and the second satellite S
2
and leading these signals to subsequently-connected circuits, a reception signal amplifying circuit portion
101
for amplifying and outputting the satellite broadcast signals input, a filter portion
102
for attenuating an image frequency band of the satellite broadcast signals input, a frequency converting portion
103
for frequency-converting the satellite broadcast signals output from the filter portion
102
, an intermediate frequency amplifying circuit portion
104
for amplifying the signals output from the frequency converter
103
, a signal selecting means
105
for selecting and outputting a satellite broadcast signal amplified by the intermediate frequency amplifying circuit portion
104
, first and second regulators
106
,
107
for supplying a power voltage to the respective circuit portions such as the reception signal amplifying circuit portion
101
, the filter portion
102
, the signal selecting means
105
, etc.
Satellite broadcast signals of left-handed and right-handed circularly polarized waves of 12.2 GHz to 12.7 GHz are transmitted from the first satellite S
1
and the second satellite S
2
, and these satellite broadcast signals are converged and input to the satellite broadcast signal input terminal portion
100
by the reflection mirror of the outdoor antenna device. The satellite broadcast signal input terminal portion
100
has the first and second probes
30
a
,
31
a
for detecting the left-handed and right-handed circularly polarized wave signals transmitted from the first satellite S
1
and the first and second probes
30
b
,
31
b
for detecting the left-handed and right-handed circularly polarized wave signals transmitted from the second satellite S
2
. As described above, the left-handed and right-handed circularly polarized wave signals transmitted from the first satellite S
1
are converted to the vertically polarized wave and the horizontally polarized wave and detected by the first and second probes
30
a
,
31
a
. The first probe
30
a
outputs a left-handed circularly-polarized wave signal SL
1
, and the second probe
31
a
outputs a right-handed circularly-polarized wave signal SR
1
. The left-handed and right-handed circularly polarized waves transmitted from the second satellite S
2
are converted to the vertically polarized wave and the horizontally polarized wave and then detected by the first and second probes
30
b
,
31
b
respectively. The first probe
30
b
outputs a left-handed circularly-polarized wave signal SL
2
, and the second probe
31
b
outputs a right-handed circularly polarized wave signal SR
2
.
The reception signal amplifying circuit portion
101
has first to fourth amplifiers
101
a
,
101
b
,
101
c
,
101
d
. The first amplifier
101
a
receives the right-handed circularly-polarized wave signal SR
1
, the second amplifier
101
b
receives the left-handed circularly-polarized wave signal SL
1
, the third amplifier
101
c
receives the left-handed circularly-polarized wave signal SL
2
and the fourth amplifier
101
d
receives the right-handed circularly-polarized wave signal SR
2
to amplify these signals up to a desired level and output them to the filter portion
102
.
The filter portion
102
has first to fourth band eliminating filters
102
a
,
102
b
,
102
c
,
102
d
. The first and fourth band eliminating filters
102
a
and
102
d
attenuate the frequency band of 9.8 GHz to 10.3 GHz which corresponds to the image frequency bands of the first intermediate frequency signal FIL
1
and the fourth intermediate frequency signal FIL
2
, and the second and third band eliminating filters
102
b
,
102
c
attenuate the frequency band of 16.0 GHz to 16.5 GHz which corresponds to the image frequency bands of the second intermediate frequency signal FIH
1
and the third intermediate frequency signal FIH
2
. After the right-handed circularly-polarized wave signal SR
1
passes through the first band eliminating filter
102
a
, the left-handed circularly-polarized wave signal SL
1
passes through the second band eliminating filter
102
b
, the left-handed circularly-polarized signal SL
2
passes through the third band eliminating filter
102
c
and the right-handed circularly-polarized wave signal SR
2
passes through the fourth band eliminating filter
102
d
, these signals are led to the frequency converter
103
.
The frequency converter
103
has first to fourth mixers
103
a
,
103
b
,
103
c
,
103
d
, a first oscillator
108
and a second oscillator
109
. The first oscillator
108
(oscillation frequency=11.25 GHz) is connected to the first mixer
103
a
and the fourth mixer
103
d
. The satellite broadcast signal output from the first band eliminating filter
102
a
is frequency-converted to the first intermediate frequency signal FIL
1
of 950 MHz to 1450 MHz in the first mixer
103
a
, and the satellite broadcast signal output from the fourth band eliminating filter
102
d
is frequency-converted to the fourth intermediate frequency signal FIL
2
of 950 MHz to 1450 MHz in the fourth mixer
103
d
. The second oscillator
109
(oscillation frequency=14.35 GHz) is connected to the second mixer
103
b
and the third mixer
103
c
. The satellite broadcast signal output from the second band eliminating filter
102
b
is frequency-converted to the second intermediate frequency signal FIH
1
of 1650 MHz to 2150 MHz in the second mixer
103
b
, and the satellite broadcast signal output from the third band eliminating filter
102
c
is frequency-converted to the third intermediate frequency signal FIH
2
of 1650 MHz to 2150 MHz in the third mixer
103
c.
The intermediate frequency amplifying circuit portion
104
has first to fourth intermediate frequency amplifiers
104
a
,
104
b
,
104
c
,
104
d
which respectively receive the first to fourth intermediate frequency signals output from the frequency converter
103
to amplify the intermediate frequency signals to predetermined level, and outputs the signals thus amplified to the signal selecting means
105
. That is, the first intermediate frequency signal FIL
1
is input to the first intermediate frequency amplifier
104
a
, the second intermediate frequency signal FIH
1
is input to the second intermediate amplifier
104
b
, the third intermediate frequency signal FIH
2
is input to the third intermediate frequency amplifier
104
c
and the fourth intermediate frequency signal fIL
2
is input to the fourth intermediate frequency amplifier
104
d
, and the output signals therefrom are led to the signal selecting means
105
.
The signal selecting means
105
includes first and second composite circuits
110
,
111
and a signal switching control circuit
112
. The first signal composite circuit
110
combines the first intermediate frequency signal FIL
1
and the second intermediate frequency signal input thereto with each other and leads the composite signal to the signal switching control circuit
112
. Likewise, the second signal composite circuit
111
combines the third intermediate frequency signal FIH
2
and the fourth intermediate frequency signal FIL
1
input thereto with each other and leads the composite signal to the signal switching control circuit
112
. The signal switching control circuit
112
selects one of the composite signal of the first intermediate frequency signal FIL
1
and the second intermediate frequency signal FIH
1
and the composite signal of the third intermediate frequency signal FIH
2
and the fourth intermediate frequency signal FIL
2
, and outputs the composite signal thus selected to the first output terminal
105
a
and the second output terminal
105
b
, respectively. This switching control will be described later.
The first and second output terminals
105
a
,
105
b
are connected to different satellite broadcast receiving TV sets (not shown), and a control signal for controlling the signal selecting means
105
and a voltage for operating each circuit portion are supplied from each of the satellite broadcast receiving TV sets. For example, superposition of a control signal of 22 kHz on a DC voltage of 15V discriminates selection of the composite signal of the intermediate frequency signals FIL
1
and FIH
1
or the composite signal of the intermediate frequency signals FIL
2
and FIH
2
. That is, the satellite broadcast receiving TV sets supply the control signals to be superposed on the supply voltage to the output terminals
105
a
,
105
b
when selecting reception of the right-handed circularly-polarized wave signal SR
1
and the left-handed circularly-polarized wave signal SL
1
transmitted from the first satellite S
1
or reception of the right-handed circularly-polarized wave signal SR
2
and the left-handed circularly-polarized wave signal SL
2
transmitted from the second satellite S
2
. These voltages are input from the first output terminal
105
a
through a high-frequency preventing choke coil
113
to the signal switching control circuit
112
, and likewise the voltages are input from the second output terminal
105
b
through a high-frequency preventing choke coil
114
to the signal switching control circuit
112
.
The first voltage and the second voltage are input through the high-frequency preventing choke coils
113
and
114
to first and second regulators
106
,
107
respectively, and the first and second regulators
106
,
107
supplies the power voltage (for example, 8V) to the respective circuit portions. Therefore, the first and second regulators
106
,
107
are designed in the same construction, and a voltage stabilizing circuit is constructed by an integrated circuit. The output terminals of the first and second regulators
106
,
107
are connected through backflow preventing diodes
115
,
116
to the power supply voltage output terminal
117
. Accordingly, even when only one of the satellite broadcast receiving TV sets operates, the power supply voltage is supplied to the respective circuit portions. Further, the first and second output terminals
105
a
,
105
b
are connected through the regulators
106
,
107
to the power supply voltage output terminal
117
respectively, and thus for example the control signal supplied from the first output terminal
105
a
is prevented from being input to the signal switching control circuit
112
by using the inter-element isolation of the first and second regulators
106
,
107
. Likewise, the control signal supplied from the second output terminal
105
b
is prevented from being input to the signal switching control circuit
112
.
As shown in
FIG. 20
, the constituent parts for RF circuitry at the front stage from the frequency converter
103
are mounted on the first circuit board
6
while the constituent parts for IF circuitry at the rear stage from the intermediate frequency amplifying circuit portion
104
are mounted on the second circuit board
7
, and the first circuit board
6
and the second circuit board
7
are partially overlapped with each other and jointed integrally with each other.
In this case, signal lines for the right-handed circularly-polarized wave signals SR
1
, SR
2
of the first satellite S
1
and the second satellite S
2
are laid out at the outermost side of the first circuit board
6
, and signal lines for the left-handed circularly-polarized wave signals SL
1
, SL
2
of the first satellite S
1
and the second satellite S
2
are laid out at the inner side of the layout of the former signal lines. The right-handed circularly-polarized wave signals SR
1
, SR
2
at the outside are frequency-converted to the first and fourth intermediate frequency signals FIL
1
, FIL
2
of 950 MHz to 1450 MHz by the first and fourth mixers
103
a
,
103
d
connected to the first oscillator
108
, and the left-handed circularly-polarized wave signals SL
1
, SL
2
at the inside are frequency-converted to the second and third intermediate frequency signals FIH
1
, FIH
2
of 1650 MHz to 2150 MHz by the second and third mixers
103
b
,
103
c
connected to the second oscillator
109
. That is, the first oscillator
108
and the second oscillator
109
are arranged at the center portion of the first circuit board
6
, and the first oscillator
108
is connected through an oscillation signal line
36
to the first mixer
103
a
and the fourth mixer
103
d
at the outside while the second oscillator
109
is connected through an oscillation signal line
37
to the second mixer
103
b
and the third mixer
103
c
at the inside.
As shown in
FIG. 21
, intermediate frequency signal lines
38
for the intermediate frequency wave signals FIL
1
, FIL
2
, FIH
1
, FIH
2
output from the respective mixers
103
a
to
103
d
on the first circuit board
6
are connected to the intermediate frequency amplifying circuit portion
104
on the second circuit board
7
through connection pins
39
, and the ground pattern
24
formed on the first circuit board
6
and the ground pattern
25
a
formed on the part-mounting face of the second circuit board
7
are brought into contact with each other at the overlap portion between the first circuit board
6
and the second circuit board
7
. A lead pattern
40
confronting the ground pattern
25
a
is formed on the second circuit board
7
, the lead pattern
40
is connected to the intermediate frequency amplifying circuit portion
104
of the second circuit board
7
through a through hole
41
, and the connection pin
39
is soldered to the intermediate frequency signal line
38
and the lead pattern
40
at both the ends thereof. Accordingly, the oscillation signal line
36
for connecting the first oscillator
108
to the first and fourth mixers
103
a
,
103
d
at the outside and the intermediate frequency signal lines
38
for leading the intermediate frequency signals FIL
1
to FIL
4
from the respective mixers
103
a
to
103
d
to the intermediate frequency amplifying circuit portion
104
can be intersected to each other at the overlap portion between the first circuit board
6
and the second circuit board
7
with keeping the ground.
According to the satellite broadcast reception converter of the above-described embodiment, the respective snap pawls
1
c
,
2
c
formed at the open ends of the first and second waveguides
1
,
2
are inserted into the respective fixing holes
29
of the first circuit board
6
, and the respective fixing holes
33
of the short caps
8
are snapped into the snap pawls
1
c,
2
c
. Therefore, the first circuit board
6
can be pinched and fixed between the waveguides
1
,
2
and the short caps
8
through the simple work of fixing the short caps
8
to the snap pawls
1
c
,
2
c
by utilizing characteristic of springs (spring elasticity) of the waveguides
1
,
2
formed of sheet metal. Therefore, as compared with the conventional technique of fixing a circuit board and a short cap in a shield case by using plural screws, the number of parts and the number of working steps can be greatly reduced, so that the manufacturing cost of the satellite broadcast reception converter can be reduced. Further, cream solder is coated on the earth pattern
28
of the first circuit board
6
in advance, and the cream solder is melted under the state that the short caps
8
are snapped into the snap pawls
1
c,
2
c
and temporarily fixed. Therefore, the short caps
8
can be simply soldered to the earth pattern
28
of the first circuit board
6
.
Further, the parallel portions
1
b
,
2
b
extending in the axial line direction are formed at four confronting places on the peripheral surface of the waveguides
1
,
2
, and the snap pawls
1
c
,
2
c
are extensively formed at the tips of the respective parallel portions
1
b
,
2
b
. Therefore, the snap pawls
1
b
,
2
b
can be inserted in the corresponding fixing holes
29
of the first circuit board
6
with no rattle, and the relative positioning between each of the probes
30
a
,
30
b
,
31
a
,
31
b
formed on the first circuit board
6
and the waveguide
1
,
2
can be surely performed.
Further, the first circuit board
6
is fixed in the shield case
5
, and the waveguides
1
,
2
are inserted in the through holes
19
formed in the shield case
5
so as to project to the outside, so that the waveguides
1
,
2
and the shield case
5
which are different parts can be unified into one body through the first circuit board
6
. Therefore, the waveguides
1
,
2
to which high dimensional precision is required can be separated from the shield case
5
, and the management of the dimensional precision of the waveguides
1
,
2
can be enhanced. In this case, the support portions
21
are formed and bent at the peripheral edge of the through holes
19
of the shield case
5
, and the base portions of the waveguides
1
,
2
abut against the support portions
21
, so that undesired deformation such as inclination of the waveguides
1
,
2
or the like can be prevented by the support portions
21
.
In the above embodiment, the converter having the first and second waveguides
1
,
2
for receiving two satellite broadcasts is described. However, it is needless to say that the present invention is applicable to a converter having one waveguide for receiving one satellite broadcast.
Further, according to the satellite broadcast reception converter of the above-described embodiment, the dielectric feeder
3
,
4
formed of synthetic resin supported on the waveguide
1
,
2
is constructed by the first split body
3
a
,
4
a
having the radiation portion
10
,
14
projected from the open end of the waveguide
1
,
2
, and the second split body
3
b
,
4
b
having the phase converter
12
,
16
fixed in the waveguide
1
,
2
, and the first split body
3
a
,
4
a
and the second split body
3
b
,
4
b
are unified into one body by inserting the projection
13
,
17
of the second split body
3
b
,
4
b
into the through hole
10
a
,
14
a
formed at the center of the first split body
3
a
,
4
a
. Therefore, the volume (volumetric capacity) of each of the first split body
3
a
,
4
a
and the second split body
3
b
,
4
b
as a single body can be reduced, so that occurrence of surface sink and bubbles can be suppressed. In addition, the dielectric feeder
3
,
4
is divided at the joint portion between the through hole
10
a
,
14
a
and the projection
13
,
17
, and the dividing face is located at a position far away from the center of the first split body
3
a
,
4
a
at which the electric field intensity is largest, so that the electrical adverse effect caused by the division can be suppressed.
The second split body
3
b
,
4
b
is equipped with the impedance converter
11
,
15
which is narrowed in an arcuate shape from the open end of the waveguide
1
,
2
to the phase converter
12
,
16
, the projection
13
,
17
is provided on the end face of the impedance converter
11
,
15
, and the first split body
3
a
,
4
a
and the second split body
3
b
,
4
b
are jointed to each other at the end face of the impedance converter
11
,
15
. Therefore, the reflection components of the electric waves propagating from the radiation portion
10
,
14
through the impedance converter
11
,
15
to the phase converter
12
,
16
can be greatly reduced. In addition, the phase difference to the linearly polarized wave is large even when the length of the portion extending from the impedance converter
11
,
15
to the phase converter
12
,
16
is shortened, so that the overall length of the waveguide
1
,
2
can be greatly shortened.
With respect to the first dielectric feeder
3
, the engaging projection
10
b
is formed on the inner wall surface of the through hole
10
a
and the engaging recess portion
13
a
is formed on the outer wall surface of the projection
13
so that the engaging projection
10
b
and the engaging recess portion
13
a
are snap-jointed to each other. The snap-joint is also used for the second dielectric feeder
4
. Therefore, even when there is somewhat dimensional dispersion between the projection
13
,
17
and the through hole
10
a
,
14
a
, both can be simply and surely jointed to each other. At this time, with respect to the first dielectric feeder
3
, representing the length from the rear end face of the radiation portion
10
to the engaging projection
10
b
by A and representing the length from the end face of the impedance converter
11
to the engaging recess portion
13
a
by B, the relationship of A>B is set, so that the engaging projection
10
b
and the engaging recess portion
13
a
can be surely snap-jointed to each other with no rattle. It is true of the second dielectric feeder
4
.
Further, the radiation portion
10
,
14
is designed in a conical shape which expands forwardly from the open end of the waveguide
1
,
2
, and the end face of the impedance converter
11
,
15
is jointed to the rear end face of the radiation portion
10
,
14
. Therefore, the dividing face vertical to the travel direction of the electric waves propagating in the dielectric feeder
3
,
4
can be reduced, and the reflection of the electric waves at the dividing face can be suppressed.
In the above-described embodiment, the description is made on the two-satellite-broadcast reception converter having the first and second waveguides
1
,
2
and the first and second dielectric feeders
3
,
4
. However, it is needless to say that the present invention is applicable to a one-satellite-broadcast reception converter having one waveguide and one dielectric feeder mounted therein.
According to the present invention, the following effects can be achieved.
First, the snap pawls are formed at the open end of the waveguide formed of sheet metal, the snap pawls are inserted in the fixing holes formed in the circuit board, and the short cap for closing the open end of the waveguide is fixed to the snap pawls, whereby the circuit board is pinched and fixed between the waveguide and the short cap. Therefore, the number of parts and the number of working steps can be greatly reduced, so that the manufacturing cost of the satellite broadcast reception converter can be reduced.
Secondly, the dielectric feeder of synthetic resin is constructed by the first split body having the radiation portion projected from the open end of the waveguide and the second split body having the phase converter fixed in the waveguide, and the first and second split bodies are unified by inserting the projection equipped to the second split body into the through hole formed at the center of the first split body. Therefore, the volume (volumetric capacity) of each of the first and second split bodies as a single body can be reduced, so that occurrence of surface sink and bubbles can be reduced. In addition, the dielectric feeder is divided at the joint portion between the through hole and the projection, and the dividing face thereof is located at a position far away from the center of the first split body at which the electric field intensity is largest, so that the electrical adverse effect caused by the division can be suppressed.
Claims
- 1. A satellite broadcast reception converter, comprising:a circuit board having at least one probe; at least one waveguide formed of sheet metal disposed vertically to said circuit board; and at least one short cap having a bottom for closing an open end of said waveguide, wherein said waveguide is equipped with snap pawls at the open end thereof and said circuit board has fixing holes formed therein, said snap pawls being inserted into said fixing holes of said circuit board to thereby fix said short cap to said snap pawls, whereby said circuit board is pinched and fixed between said waveguide and said short cap.
- 2. The satellite broadcast reception converter according to claim 1, wherein said short cap is soldered to an earth pattern formed on said circuit board.
- 3. The satellite broadcast reception converter according to claim 1, wherein said waveguide is equipped with parallel portions extending in an axial line direction of said waveguide at four confronting positions on a peripheral surface of said waveguide, and said snap pawls are respectively formed at tip portions of said parallel portions.
- 4. The satellite broadcast reception converter according to claim 1, further comprising a shield case having a through hole for accommodating said circuit board and said short cap, wherein said waveguide is inserted through said through hole formed in said shield case to project to an outside of said shield case, and said circuit board is fixed in said shield case.
- 5. The satellite broadcast reception converter according to claim 4, wherein said shield case is formed of sheet metal, and equipped with support portions for supporting a peripheral surface of said waveguide, said support portion being formed and bent at a peripheral edge of said through hole.
- 6. A satellite broadcast reception converter, comprising:at least one waveguide that is closed at one end thereof and opened at another end thereof; at least one probe projecting in a center axis direction of said waveguide; and at least one dielectric feeder that is supported by said waveguide and formed of synthetic resin, wherein said dielectric feeder comprises a first split body having a radiation portion projecting from the open end of said waveguide and a second split body having a phase conversion portion fixed in said waveguide, and a projection equipped to said second split body is inserted in a through hole formed at a center portion of said first split body to unify said first split body and said second body into one body.
- 7. The satellite broadcast reception converter according to claim 6, wherein said second split body is equipped with an impedance converter which is narrowed in an arcuate shape from the open end of said waveguide to said phase converter, said projection is equipped to an end face of said impedance converter and said first and second split bodies are jointed to each other at the end face of said impedance converter.
- 8. The satellite broadcast reception converter according to claim 7, wherein an engaging projection is formed on an inner wall surface of said through hole, and an engaging recess portion is formed on an outer wall surface of said projection, said engaging projection and said engaging recess portion being snap-jointed to each other.
- 9. The satellite broadcast reception converter according to claim 8, wherein when a length from a rear end face of said radiation portion to said engaging projection is represented by A and a length from the end face of said impedance converter to said engaging recess portion is represented by B, A and B are set to satisfy the relation of A>B.
- 10. The satellite broadcast reception converter according to claim 7, wherein said radiation portion is designed in a conical shape which expands from the open end of said waveguide, and the end face of said impedance converter is jointed to a rear end face of said radiation portion.
Priority Claims (2)
Number |
Date |
Country |
Kind |
2001-289731 |
Sep 2001 |
JP |
|
2001-289791 |
Sep 2001 |
JP |
|
US Referenced Citations (4)
Number |
Name |
Date |
Kind |
6043789 |
Suzuki et al. |
Mar 2000 |
A |
6426729 |
Yoshida et al. |
Jul 2002 |
B2 |
6437753 |
Yuanzhu |
Aug 2002 |
B2 |
6445260 |
Miyazaki et al. |
Sep 2002 |
B1 |
Foreign Referenced Citations (4)
Number |
Date |
Country |
42 07 503 |
Sep 1993 |
DE |
0 899 812 |
Mar 1999 |
EP |
10126114 |
May 1998 |
JP |
2001-57507 |
Feb 2001 |
JP |