| 摘要 |
PURPOSE:To prevent overmodulation when a sub-signal with a high level is inputted by detecting the level of the sub-signal and changing the sub-signal in phase by a variable phase shifter in response to the detected output so as to synthesize the output of the phase shifter and the sub-signal by means of a synthesis means. CONSTITUTION:The sub-signal SC is amplified by an amplifier 1, the amplitude of the sub-signal is detected by a detector 5 and fed to a differential amplifier 6. The amplifier 6 compares the detected voltage of the detector 5 with a prescribed voltage by a variable resistor 7 and a voltage proportional to the difference is outputted. When the difference is negative, the signal is absorbed by a diode 8 and when the difference is positive, the signal is fed to a variable phase shifter 9. The phase shifter 9 changes the output of the amplifier 1 in phase according to the level of the voltage difference and applies it to a hybrid 10. The output of the amplifier 1 and the output of the phase shifter 9 are synthesized by the hybrid 10 and the result is fed to a sub-signal modulator to prevent overmodulation from being caused. |
