| 摘要 |
PROBLEM TO BE SOLVED: To realize a board frequency variable range and superior phase noise characteristic by connecting 1st and 2nd varactor diodes in parallel, in mutually revese directions in a variable capacitance circuit. SOLUTION: A control voltage Vcont is applied to a 1st varactor diode D2 via a resistor R2. Furthermore, the control voltage Vcont is applied to a 2nd varactor diode D3 via a resistor R3 to cause a reverse bias current to flow from the 2nd diode D3 via a resistor R4. The capacitance of the 1st varactor diode D2 is changed by a DC control voltage Vcont, to simultaneously change the capacitance of the 2nd diode D3, thereby controlling an oscillation frequency of a Colpitts oscillation circuit 2. In this case, the capacitance of a variable capacitance circuit 3 is combined sum of the capacitance in of a 1st circuit in parallel, consisting of a series circuit comprising a capacitor C1 and the diode D2 and the capacitance of a 2nd circuit, consisting of a series circuit comprising a capacitor C2 and the diode D3.
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