| 摘要 |
PURPOSE: To prevent noises from being mixed into reproduced audio and video signals by mixing a sine wave FM signal, which has a specified distortion rate and the attenuation rate of a higher harmonic wave out of the band, with a base band signal in a prescribed ratio. CONSTITUTION: The FM signal is defined as the sine wave signal for which the distortion rate is less than 0.7% and the attenuation rate of the higher harmonic wave out of the band is more than 40dB, and it is mixed by a mixing circuit 4 within the range for which the mixing ratio of the FM signal with the base band signal is from 7.5% to 12.5%. Besides, concerning the sine wave FM signal component of the mixing signal, the distortion rate is less than 1.5% and the attenuation rate of the higher harmonic wave out of the band is more than 35dB. The circuit 4 is composed of an adder 4a and an inverter 4b and the adder 4a is composed of resistors R2 and R3 , with which the mixing ratio of the audio sine wave FM signal with the video base band signal is set, and an operational amplifier Op1 . Besides, the inverter 4b returns the mixing signal inverted by the amplifier Op1 to a non-inverted signal by using an operational amplifier Op2 . Then, the mixing signal is modulated to a rectangular wave FM signal by a rectangular wave FM modulation circuit 5. |
