Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Junction field effect transistor
Reexamination Certificate
2001-12-27
2003-07-01
Crane, Sara (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Junction field effect transistor
C257S342000, C257S728000, C257S664000, C257S724000, C333S103000, C333S262000, C333S204000
Reexamination Certificate
active
06586786
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high frequency switch or the like, of which main object is to switch a high frequency signal in a radio circuit of radio communication equipment such as a portable telephone.
2. Description of the Prior Art
High frequency switch circuits are often used to switch transmit/receive signals in radio circuits of radio communication equipment such as a portable telephone using TDMA systems.
Hereinafter, an example of conventional high frequency switch circuits described above will be described with reference to a drawing.
FIG. 13
shows an equivalent circuit diagram of an example of conventional high frequency switch circuits.
In
FIG. 13
, the anode of a first diode D
1301
is coupled to a transmitting terminal
1301
through a first capacitor element C
1301
. Further, a control terminal
1302
is coupled to the anode side of the first diode D
1301
through an inductor element L
1301
and a resistor element R
1301
. Also, the anode of a second diode D
1302
is coupled to a receiving terminal
1303
through a second capacitor element C
1302
, and the cathode of the second diode is connected to ground. Further, one end of a first transmission line TL
1301
, which has an electrical length of ¼ wavelength at the operating frequency, is connected also to the anode side of the second diode D
1302
. The other end of the first transmission line is connected to the cathode of the first diode D
1301
, and also coupled to an antenna terminal
1304
through a third capacitor element C
1303
. Here, in order to decrease the variety of components to be used and thereby to reduce cost, usually, diodes having the same characteristics are used for the first diode D
1301
and the second diode D
1302
.
The operation of the high frequency circuit configured as described above will be described.
In transmitting, when a positive voltage is applied to the control terminal
1302
, the first diode D
1301
and the second diode D
1302
are turned on. At this time, the capacitor elements C
1301
, C
1302
, and C
1303
block components of direct current. A transmit signal passes through the capacitor C
1301
from the transmitting terminal
1301
and is transmitted to the antenna terminal
1304
through the first diode D
1301
and the capacitor element C
1303
. Herein, the transmission line TL
1301
operates as a ¼ wavelength resonator having one end grounded, because the second diode D
1302
is turned on. Therefore, the impedance of lines in the side of the antenna terminal
1304
becomes infinite and therefore no transmit signal is transmitted to the receiving side.
In receiving, no voltage is applied to the control terminal
1302
, and therefore both the first diode D
1301
and the second diode D
1302
are in the OFF state. Thus, a receive signal is transmitted to the receiving terminal
1303
from the antenna terminal
1304
through the capacitor element C
1303
, the transmission line TL
1301
, and the capacitor element C
1302
.
PIN diodes are mainly used for the first diode D
1301
and the second diode D
1302
, which are used for switching. However, generally, diodes have a tradeoff relationship that a diode of low ON resistance has a large capacitance between the cathode and anode terminals and a diode having a small inter-terminal capacitance in the OFF state has a high ON resistance.
Therefore, if importance is attached on isolation during receiving and therefore a diode having a small inter-terminal capacitance is selected to achieve high isolation, the signal path produces a large loss during transmitting because of the large ON resistance of the diode.
On the other hand, when importance is attached on insertion loss during transmitting and therefore a diode of a low ON resistance is selected, then there is a problem that the increased inter-terminal capacitance reduces isolation to result in a large loss produced by the signal path during receiving.
BRIEF SUMMARY OF THE INVENTION
The present invention has been achieved in view of such problems, and has an object to provide a high frequency switch favorably reducing loss produced in signal paths both during transmitting and during receiving.
One aspect of the present invention is a high frequency switch, comprising:
a transmitting terminal;
a receiving terminal;
an antenna terminal;
a first diode having an anode electrically connected to said transmitting terminal and a cathode electrically connected to said antenna terminal;
a second diode having an anode connected through a transmission line of ¼ wavelength to the antenna terminal which is electrically connected to said receiving terminal, and having the side of a cathode grounded; and
a control terminal provided to a node between said transmitting terminal and said first anode,
wherein said first and second diodes have a tradeoff relationship between ON resistance thereof and capacitance between said anode and said cathode, and
the ON resistance of the first diode is lower than the ON resistance of the second diode, and the capacitance of the second diode in the OFF state is smaller than the capacitance of the first diode in the OFF state.
Another aspect of the present invention is the high-frequency switch,
wherein a diode having a ON resistance of not higher than 1&OHgr; is used for said first diode and a diode having an inter-terminal capacitance of not larger than 0.8 pF in the OFF state is used for said second diode.
Still another aspect of the present invention is the high frequency switch,
wherein a diode having a ON resistance of not higher than 0.8&OHgr; is used for said first diode and a diode having an inter-terminal capacitance of not larger than 0.5 pF in the OFF state is for said second diode.
Yet still another aspect of the present invention is the high frequency switch,
Still yet another aspect of the present invention is the high frequency switch, further comprising a capacitor element or a parallel circuit of LC connected in series with said second diode.
A further aspect of the present invention is a high frequency switch, comprising:
a laminated component having a plurality of dielectrics laminated therein;
a transmitting terminal, a receiving terminal, an antenna terminal, a control terminal, a ground terminal, and an electrode pattern for connecting a part, which are provided on the surface of said laminated component;
a first diode having an anode electrically connected to said transmitting terminal and having a cathode electrically connected to said antenna terminal; and
a second diode having an anode connected through a transmission terminal of ¼ wavelength to the antenna terminal which is electrically connected to said receiving terminal, and having the side of a cathode grounded, said first and second diodes being mounted on the surface of said laminated component,
wherein said first and second diodes have a tradeoff relationship between ON resistance thereof and capacitance between said anode and said cathode, and
the ON resistance of the first diode is lower than the ON resistance of the second diode, and the capacitance of the second diode in the OFF state is smaller than the capacitance of the first diode in the OFF state.
A still further aspect of the present invention is the high frequency switch,
wherein said high frequency switch is configured by using the laminated component.
A yet further aspect of the present invention is a two-band type of high frequency switch, comprising:
a second high frequency switch for use in a second frequency band higher than the first frequency band; and
a divider for sharing the same antenna between said first high frequency switch and said second high frequency switch by multiplexing and demultiplexing said first frequency band and second frequency band, the antenna terminal of said first high frequency switch and the antenna terminal of said second high frequency switch being electrically connected to each other,
wherein the high frequency switch is used for said first high frequency switch and said second high freque
Ishizaki Toshio
Kitazawa Shoichi
Tanaka Masaharu
Yamada Toru
Crane Sara
Im Junghwa
Matsushita Electric - Industrial Co., Ltd.
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