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US 6,307,448 B1Granted
Frequency-variable-type filter, antenna duplexer, and communication apparatus
AssigneeMurata Manufacturing Co., Ltd.
InventorsMasayuki Atokawa, Yasuo Yamada
Life of this patent
Estimating the term…
Abstract
There is provided a frequency-variable-type filter, comprising: a voltage control terminal; at least one resonator; a switching device for being switched on/off by a control voltage supplied to the voltage control terminal; and the switching device being in the off-state, when a control circuit as an external circuit which is electrically connected to the voltage control terminal has high impedance at 0 V.
Claims18
A frequency-variable-type filter, comprising:
- a voltage control terminal;
- at least one resonator;
- a switching device which is switched on/off by a control voltage supplied to the voltage control terminal;
- and
- a control circuit electrically connected to the voltage control terminal;
- wherein said control has a high impedance and imposes a negative voltage on said switching device in response to a 0 V input voltage to said control circuit, thereby placing the switching device in the off-state.
3 more elements
A communication apparatus, comprising:
- a frequency-variable-type filter comprising a voltage control terminal;
- at least one resonator;
- and a switching device which is switched on/off by a control voltage supplied to the voltage control terminal;
- and
- a control circuit which supplies a control voltage to the voltage control terminal to perform voltage control of the frequency-variable-type filter;
- wherein the control circuit has high impedance and imposes a negative voltage on the switching device in response to a 0 V input voltage to said control circuit, thereby placing the switching device in the off-state.
3 more elements
A communication apparatus, comprising:
- a frequency-variable-type filter comprising a voltage control terminal;
- at least one resonator;
- and a switching device which is switched on/off by a control voltage supplied to the voltage control terminal;
- and
- a control circuit which supplied a control voltage to the voltage control terminal to perform voltage control of the frequency-variable-type filter;
- the switching device being in the off-state and the control circuit having a high impedance in response to a 0 V input voltage to said control circuit;
- wherein the impedance of the control circuit is 100 kΩ or more when the control circuit has a high impedance at a 0 V input voltage.
4 more elements
A communication apparatus, comprising:
- a frequency-variable-type filter comprising a voltage control terminal;
- at least one resonator;
- and a switching device which is switched on/off by a control voltage supplied to the voltage control terminal;
- and
- a control circuit which supplies a control voltage to the voltage control terminal to perform voltage control of the frequency-variable-type filter;
- the switching device being in the off-state and the control circuit having a high impedance in response to a 0 V input voltage to said control circuit;
- wherein the control circuit has a transistor.
4 more elements
A communication apparatus, comprising:
- a frequency-variable-type filter comprising a voltage control terminal;
- at least one resonator;
- and a switching device which is switched on/off by a control voltage supplied to the voltage control terminal;
- and
- a control circuit which supplies a control voltage to the voltage control terminal to perform voltage control of the frequency-variable-type filter;
- the switching device being in the off-state and the control circuit having a high impedance in response to a 0 V input voltage to said control circuit;
- wherein the control circuit has a field-effect transistor.
4 more elements
A communication apparatus, comprising:
- a frequency-variable-type filter comprising a voltage control terminal;
- at least one resonator;
- and a switching device which is switched on/off by a control voltage supplied to the voltage control terminal;
- and
- a control circuit which supplies a control voltage to the voltage control terminal to perform voltage control of the frequency-variable-type filter;
- the switching device being in the off-state and the control circuit having a high impedance in response to a 0 V input voltage to said control circuit;
- wherein the resonator is a dielectric resonator.
4 more elements
Dependencies are inferred from the claim text.