Modulators – Frequency modulator
Patent
1991-03-12
1992-10-20
Grimm, Siegfried H.
Modulators
Frequency modulator
332127, 358330, 358 23, 360 30, H04N 980
Patent
active
051573598
ABSTRACT:
An FM modulator includes a base clock generating circuit (7) receiving an incoming video signal for generating an AFC reference frequency signal having a frequency and phase corresponding to a horizontal synchronizing signal of the incoming video signal, a first carrier reset pulse having the same frequency as the horizontal synchronizing signal and a second carrier reset pulse whose frequency is an integer mutliple of that of the horizontal synchronizing signal. The second reset pulse is generated at a timing speed lagged behind the first reset pulse. The FM modulator further includes an adder (3) for adding the first reset pulse to the incoming video signal for lowering the DC level at the leading edge portion of the horizontal synchronizing signal, and an oscillator (9, 9a, 9b, 10, 10a, 10b) whose oscillation frequency is changed dependent on the DC level of the output signal from the adder to produce a carrier FM modulated by the video signal. The oscillator is reset by the second reset pulse.
REFERENCES:
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Iwamura Soichi
Nogami Hiroaki
Asher Robert M.
Conlin David G.
Grimm Siegfried H.
Sharp Kabushiki Kaisha
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