Matching device and antenna matching circuit
A battery portion (BAT) or another type of voltage shift portion is provided for shifting a control voltage (V 2 ) in a direction which causes the anode potential of a variable-capacitance diode (VD) to be a negative potential and superimposes its battery voltage (Vb) on the control voltage (V 2 ). Specifically, the battery portion (BAT) is inserted in a direction which causes the control voltage (V 2 ) to be decreased and operates such that [control voltage (V 2 )−battery voltage (Vb)] is applied to the anode terminal of the variable-capacitance diode (VD). Then, the voltage applied to the variable-capacitance diode (VD) is [control voltage (V 2 )−control voltage (V 1 )−battery voltage (Vb)]. Thus, the variable capacitance range of the variable-capacitance diode (VD) is increased.
1. A matching device comprising:
a variable-capacitance diode configured to change an impedance of a circuit including an external element;
a first control signal line for applying a first control voltage, the first control signal line being connected to a cathode terminal of the variable-capacitance diode;
a second control signal line for applying a second control voltage, the second control signal line being connected to an anode terminal of the variable-capacitance diode; and
a voltage shift portion inserted in the second control signal line, the voltage shift portion shifting the second control voltage so that the anode potential of the variable-capacitance diode becomes a negative potential.
2. The matching device according to claim 1 , wherein the voltage shift portion comprises a chemical battery.
3. The matching device according to claim 1 , further comprising:
a first rectifier circuit connected to the first control signal line, the first rectifier circuit rectifying a first alternating-current signal to generate the first control voltage supplied to the first control signal line; and
a second rectifier circuit connected to the second control signal line, the second rectifier circuit rectifying a second alternating-current signal to generate the second control voltage supplied to the second control signal line.
4. The matching device according to claim 3 ,
wherein the voltage shift portion comprises a constant voltage diode which generates a constant voltage when applied with a reverse bias voltage, and
a bias supply circuit for supplying the constant voltage diode with the reverse bias voltage derived from the first alternating-current signal or the second alternating-current signal.
5. The matching device according to claim 4 , wherein said bias supply circuit comprises a level shift circuit and a voltage-multiplying rectifier circuit for deriving the reverse bias voltage from the first alternating-current signal or the second alternating-current signal.
6. The matching device according to claim 5 , wherein said reverse bias voltage is derived from the first alternating-current signal.
7. The matching device according to claim 5 , wherein said bias supply circuit is connected to the anode of the constant voltage diode via a voltage divider.
8. The matching device according to claim 3 ,
wherein the voltage shift portion comprises a transformer configured to supply the second alternating-current signal to the second rectifier circuit after inverting the polarity of the second alternating-current signal.
9. The matching device according to claim 3 ,
wherein the first and second alternating-current signals are pulse width modulation signals.
10. The matching device according to claim 1 , further comprising a pair of stabilizing resistors connected respectively to said anode and cathode terminals of said variable-capacitor diode for stabilizing said first and second control voltages.