| 摘要 |
PROBLEM TO BE SOLVED: To provide an impedance conversion circuit for automatically adjusting input/output impedance matching of a crystal filter while a computer takes in the result of pass characteristic measurement of the crystal filter. SOLUTION: The computer adjusts capacitance of a varactor diode 12 connected in series with a transformer 3 according to a control voltage applied to a control terminal 10 of the varactor diode to adjust the overall inductance of the transformer 3 and the varactor diode 12. Thus, it is possible to adjust the resonance frequency of a parallel resonance circuit comprising the transformer 3, the varactor diode 12, and a capacitor 4 with respect to an input signal frequency. This is also applicable to output impedance matching for the crystal filter 5 by a resonance circuit employing a transformer 7, a capacitor 6, and a varactor diode 14. Thus, the computer controls the input/output impedance matching circuit of the crystal filter to automatically adjust the input/output impedance matching. COPYRIGHT: (C)2004,JPO
|
