Miscellaneous active electrical nonlinear devices – circuits – and – Gating – Converging with plural inputs and single output
Reexamination Certificate
2001-11-28
2003-01-28
Callahan, Timothy P. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Gating
Converging with plural inputs and single output
C327S099000, C327S504000, C333S104000
Reexamination Certificate
active
06512409
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a signal switching circuit, for example a signal switching circuit suitable for use in a satellite broadcast receiving outdoor converter in which satellite broadcast signals of counterclockwise and clockwise circularly polarized waves are outputted arbitrarily to two output terminals.
2. Description of the Related Art
A conventional signal switching circuit will now be described with reference to
FIGS. 5 and 6
. First,
FIG. 5
illustrates a block configuration, in which a first signal, say, a satellite broadcast signal of a counterclockwise circularly polarized wave, is inputted to a first input terminal
51
and a second signal, say, a satellite broadcast signal of a clockwise circularly polarized wave, is inputted to a second input terminal
52
. These signals are inputted from a down converter (not shown).
The first signal is inputted through the first input terminal
51
to both a first terminal
55
a
of a first switch circuit
55
and a first terminal
56
a
of a second switch circuit
56
, while the second signal is inputted through the second input terminal
52
to both a second terminal
55
b
of the first switch circuit
55
and a second terminal
56
b
of the second switch circuit
56
. One of the two signals is selected in each of the switch circuits
55
and
56
and the selected signals are outputted respectively to third terminals
55
c
and
56
c
of the switch circuits
55
and
56
and are then outputted respectively to a first output terminal
53
and a second output terminal
54
.
The first and second switch circuits
55
and
56
are of the same configuration, which is illustrated in
FIG. 6
(only the first switch circuit
55
is shown). Two diodes
61
and
62
, which are connected together in series, are disposed between the first and third terminals
55
a,
55
c
in such a manner that their cathodes and anodes are located on the first terminal
55
a
side and the third terminal
55
c
side, respectively. A connection point between the two diodes
61
and
62
is connected to the anode of a diode
64
through a DC cut-off capacitor
63
, the cathode of the diode
64
being grounded high-frequencywise by means of a DC cut-off capacitor
65
.
Two diodes
66
and
67
, which are connected together in series, are disposed between the second and third terminals
55
b,
55
c
in such a manner that their cathodes and anodes lie on the second terminal
55
b
side and the third terminal
55
c
side, respectively. A connection point between the two diodes
66
and
67
is connected to the cathode of a diode
69
through a DC cut-off capacitor
68
, the anode of the diode
69
being grounded high-frequencywise by means of the DC cut-off capacitor
65
.
Voltage E is applied to the anodes of the diodes
62
and
67
through a resistor
70
. The cathode of the diode
61
, the anode of the diode
64
, and the cathode of the diode
69
are connected to a first voltage application terminal
74
through resistors
71
,
72
, and
73
, respectively. The cathode of the diode
66
and a connection point between the diodes
64
and
69
are connected to a second voltage application terminal
77
through resistors
75
and
76
, respectively. The voltage E is applied to the first and second voltage application terminals
74
,
77
while switching polarity by means of a change-over switch
78
of a two-circuit two-contact configuration.
When the voltage E is applied to the first voltage application terminal
74
and the second voltage application terminal
77
is grounded, the diodes
61
and
62
turn OFF and the diode
64
turns ON. Further, the diodes
66
and
67
turn ON and the diode
69
turns OFF. As a result, the second signal which has been inputted to the second terminal
55
b
is outputted to the third terminal
55
c.
At this time, the first signal which has been inputted to the first terminal
55
a
is not outputted.
When the first voltage application terminal
74
is grounded and the voltage E is applied to the second voltage application terminal
77
, the diodes
61
and
62
turn ON and the diode
64
turns OFF. Further, the diodes
66
and
67
turn OFF and the diode
69
turns ON. As a result, the first signal which has been inputted to the first terminal
55
a
is outputted to the third terminal
55
c.
At this time, the second signal which has been inputted to the second terminal
55
b
is not outputted.
Thus, the first signal inputted to the first input terminal
51
or the second signal inputted to the second input terminal
52
is outputted to the first output terminal
53
by the first switch circuit
55
.
Likewise, the first signal inputted to the first input terminal
51
or the second signal inputted to the second input terminal
52
is outputted to the second output terminal
54
by the second switch circuit
56
.
In the conventional configuration described above there are used six diodes for outputting the first or the second signal to the first output terminal
53
. Likewise, the same number of diodes are used for outputting the first or the second signal to the second output terminal
54
. As a result, not only the number of diodes used increases, but also the number of parts and wires for turning ON or OFF the diodes increases, with consequent complication of construction and difficulty in attaining the reduction of size.
SUMMARY OF THE INVENTION
The present invention has been accomplished in view of the above-mentioned points and it is an object of the invention to provide a signal switching circuit which permits the reduction in number of diodes used, thereby attaining the simplification of construction and the reduction of size.
For achieving the above-mentioned object, in a first aspect of the present invention there is provided a signal switching circuit comprising a first input terminal to which a first signal is inputted, a second input terminal to which a second signal is inputted, first and second output terminals from which the first or the second signal is outputted, first to fourth diode pairs each comprising two diodes which are connected together in series, the first to fourth diode pairs being disposed respectively between the first input terminal and the first output terminal, between the second input terminal and the first output terminal, between the first input terminal and the second output terminal, and between the second input terminal and the second output terminal, and first to fourth capacitor means connected respectively between diode-to-diode connection points in the respective diode pairs and the ground, wherein the first or the second diode pair is rendered conductive in an alternative manner, the third or the fourth diode pair is rendered conductive in an alternative manner, and a low pass filter for passing therethrough the corresponding first or second signal is constructed by residual inductance in each of the diode pairs thus rendered conductive and the associated capacitor means.
In a second aspect of the present invention there is provided, in combination with the above first aspect, a signal switching circuit wherein the first to fourth capacitor means are constructed by first to fourth strip lines respectively, one ends of the strip lines being connected respectively to the diode-to-diode connection points in the diode pairs, with the opposite ends thereof being made free, the length of each of the first and third strip lines is set shorter than a quarter wavelength of the first signal, and the length of each of the second and fourth strip lines is set shorter than a quarter wavelength of the second signal.
In a third aspect of the present invention there is provided, in combination with the above second aspect, a signal switching circuit wherein the two diodes in each of the diode pairs are connected together so that the directions of respective PN junctions are the same.
REFERENCES:
patent: 5327017 (1994-07-01), Fischer et al.
patent: 2000-224517 (2000-08-01), None
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Callahan Timothy P.
Englund Terry L.
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