Comb filter, chrominance and luminance signal separating circuit for modifying the level-frequency characteristic of the luminance signal

Claim 1

A color video signal processing circuit for separating chrominance and luminance signals from a color video signal, the circuit comprising; an input terminal through which the color video signal is supplied, signal separating means containing a delay device for delyaing the color video signal suppplied through said input terminal by at least substantially one horizontal period so as to form a substraction-type comb-filter including said delay device between said input terminal and a frist intermediate terminal and an addition-type combfilter including also said delay device between said input terminal and a second intermediate terminal, level modifying means connected to said first intermediate terminal for providing a gain of zero decibels for first signal components of the signal at said first intermediate terminal residing in a low range in the frequency band which is lower than the frequency band of the chrominance signal, a gain of more than zero decibels for second signal components of the signal at said first intermediate terminal residing in a middle range in the frequency band which is lower than the frequency band of the chrominance signal, and a minimum gain for third signal components of the signal at said first intermediate terminal residing in a high range in the frequency band which is lower than the frequency band of the chrominance signal and a frequency range higher than said high range, adding means for adding an output of said level modifying means to a signal obtained at said second intermediate terminal, first output means for deriving a separated chrominance signal from said first intermediate terminal, and second output means for deriving a separated luminance signal from said adding means.