To obtain the RF modulator not causing a disturbing wave because a harmonic of an audio subcarrier is not in existence in the vicinity of a video carrier by generating directly the audio carrier by a 2nd oscillator, applying FM modulation to an audio signal with the carrier with the oscillating frequency and adding the modulated signal and the video carrier at an adder.
A signal received from an input terminal 21 is given to a video processing circuit 22, where the signal is subject to video processing and the result is given to a mixer 23. The mixer 23 receives a video carrier from a 1st oscillator 24, mixes the carrier with the video signal and provides an output of the mixed signal to an adder 27. On the other hand, an audio signal received from an input terminal 30 is given to an FM modulator 31, where an audio carrier with a frequency oscillated directly from a 2nd oscillator 32 and the audio signal are FM-modulated and the result is given to other terminal of the adder 27, where the modulated signal is added to the mixed signal. An output of the adder 27 is given to a low pass filter 28, where harmonics of the sum are eliminated and the result is outputted from an output terminal 29. Thus, no harmonics nor negative audio carrier waves are outputted.
KAMIMOTO RIYUUICHI
HIBINO YASUHIRO
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