| 摘要 |
PURPOSE:To suppress automatically the carrier leakage caused at modulation by detecting a carrier leakage quantity by a carrier leak detection circuit in a modulator using an analog multiplier thereby controlling a bias voltage. CONSTITUTION:A modulation signal through an input bias voltage control section 6 and a carrier VC from a carrier oscillator 4 are inputted to an analog multiplier 3 and an output VAM to be modulated being modulated by the analog multiplier 3 is sent to an output terminal 5. A detection circuit 7 adds the modulated wave output VAM including the carrier leakage and the carrier VC of the carrier oscillator 4 to detect the carrier leakage component by using the synchronizing detection. In inputting it to a bias voltage controlled section 6, the input offset voltage caused by the change in the external environment is cancelled by adjusting the input bias of the analog multiplier 3 thereby controlling automatically the carrier leakage caused at modulation.
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