Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – For high frequency device
Reexamination Certificate
2002-09-27
2004-10-05
Jackson, Jerome (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
For high frequency device
C257S698000, C257S700000, C257S531000, C257S532000
Reexamination Certificate
active
06800935
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to switching circuits for passing or blocking a signal using switching diodes that are turned on or off.
2. Description of the Related Art
FIG. 6
shows the configuration of a known switching circuit. Two conductive patterns
22
and
23
for transmitting signals are formed on an insulating substrate
21
. One end of the conductive pattern
22
is provided with a connection land
22
a
, and one end of the conductive pattern
23
is provided with a connection land
23
a
. The connection lands
22
a
and
23
a
oppose each other. A switching diode
24
is mounted on the insulating substrate
21
. An anode terminal
24
a
is connected to the connection land
22
a
by soldering, and a cathode terminal
24
b
is connected to the connection land
23
a
by soldering.
When the switching diode
24
is turned on by a voltage switching circuit (not shown), a signal input to the conductive pattern
22
is transmitted to the other conductive pattern
23
through the switching diode
24
. When the switching diode
24
is turned off, signal transmission is blocked.
In the known switching circuit having the switching diode
24
, whose equivalent circuit is shown in
FIG. 7
, the switching diode
24
has a junction capacitance Cj at a PN junction, an inductance La at the anode terminal
24
a
, an inductance Lb at the cathode terminal
24
b
, and a stray capacitance Cs between the terminals
24
a
and
24
b
. As shown in
FIG. 8
, when the switching diode
24
is turned off, the switching diode
24
has the same characteristics as those of a high-pass filter. Thus, the switching diode
24
transmits a high-frequency signal S without greatly attenuating the signal.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to increase the signal blocking effect when a switching diode is turned off.
In order to achieve the foregoing objects, a switching circuit is provided according to the present invention. The switching circuit includes an insulating substrate including two signal transmission lines: a switching diode mounted, in series between the two signal transmission lines, on the insulating substrate, wherein an anode terminal and a cathode terminal are connected to the two signal transmission lines, and the switching diode is turned on or off; and a conductive pattern formed, below the switching diode, on a mounting face of the insulating substrate on which the switching diode is mounted, wherein the conductive pattern is grounded. Accordingly, there are stray capacitances between the conductive pattern and both ends of the anode terminal of the switching diode and stray capacitances between the conductive pattern and both ends of the cathode terminal of the switching diode. These stray capacitances and the inductance at each terminal form a low pass filter. When the switching diode is turned off, the transmission characteristics between the signal transmission lines are such that attenuation can be performed at high frequencies. Accordingly, a high-frequency signal can be sufficiently attenuated.
The conductive pattern may extend to both sides of the switching diode in the direction orthogonal to a direction in which the two terminals of the switching diode are connected with each other, and the conductive pattern may be grounded at both sides of the switching diode. The entire conductive pattern can be sufficiently grounded. As a result, the value of each stray capacitance between the conductive pattern and each terminal can be stabilized.
A ground conductor may be formed on a face opposite to the mounting face of the insulating substrate. Through holes connected to the conductive pattern may be provided at both sides of the switching diode. The conductive pattern may be connected to the ground conductor through the through holes. This eliminates the need to increase the area of the conductive pattern. Thus, a larger area of the mounting face of the insulating substrate can be used for the other circuit wiring.
REFERENCES:
patent: 3138768 (1964-06-01), Evans
patent: 5656874 (1997-08-01), Kato et al.
patent: 6020853 (2000-02-01), Richards et al.
patent: 1071221 (2001-01-01), None
patent: 09-036603 (1997-02-01), None
“The Application of Acoustic Charge Transport Technologies to Wideband Communication Systems;” Ward C.R. et al.; Proceedings of the National Telesystems Conference (NTC); Washington; May 19-20, 1992; New York, IEEE, U.S.A.; pp. 15-1 through 15-12.
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
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