| 摘要 |
PURPOSE:To eliminate the need of a DC offset adjusting process by detecting a base band signal based on a reference signal and the output signal of a high- frequency amplifying means and AC-amplifying the detected output signal. CONSTITUTION:An amplifying means 25 is constituted of a capacitor 26 for AC coupling and operational amplifier 27 and the output of the means 25 is inputted to an automatic gain controller AGC. In the base band signal to be detected by means of a phase detector, beats, the frequency of which is the frequency difference between carriers and a reference signal, are produced. Since the energy mean values above and below the vibration center of the beats are roughly equal to each other, no level shift takes place even when AC-amplification is performed and the occurrence of a DC offset is eliminated. |
