| 摘要 |
PURPOSE:To obtain a stereo demodulated signal where the distortion due to adjacent broadcasting waves, the outband noise of a composite signal, etc. is reduced, by controlling switching of multistage attenuation outputs of the composite signal by a signal having 2N-fold frequency of the carrier frequency of the composite signal. CONSTITUTION:The composite signal is inputted from a terminal 11 and is applied to resistance attenuators 12 and 12' which divide the voltage to 2N-number of stages, and outputs attenuated in many stages are outputted to analog switches 13 and 13'. These signals are switched successively through switches 13 and 13' controlled by a timing signal, which is generated by a timing signal generator 18 on a basis of a timing reference signal generator 19 having 2N-fold frequency of the carrier wave of the composite signal, and are outputted to buffer amplifiers 14 and 14'. Outputs of amplifiers 14 and 14' are taken out as right and left sound signals from output terminals 16 and 16' through LPFs 15 and 15'. In this case, the switch 13 is switched to outputs of the attenuator 12 in order from the output of the smallest attenuation quantity and is next switched to them in order from the output of the largest attenuation quantity by the timing signal of the timing signal generator 18, and the switch 13' is switched to those of the attenuator 12' in order from the output of the largest attenuation quantity and is next switched to them in order from the output of the smallest attenuation quantity similarly, and this operation is repeated with the carrier frequency of the composite signal.
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