Video de-peaking circuit in luminance channel in response to AGC signal

Claim 1

In a color television receiver of the type including signal translating stages for processing radio frequency and intermediate frequency signals, a luminance channel for processing luminance signals, a chrominance channel for processing chrominance signals, an image reproducing kinescope, an output stage coupled between said luminance channel and said image reproducing kinescope and apparatus for developing an AGC voltage to control the gain of said signal translating stages as an inverse function of the amplitude of a received signal, said luminance channel including a peaking circuit for accentuating high frequency components of said luminance signals, the combination therewith of: means coupled intermediate said luminance channel peaking circuit and said kinescope at said output stage and being also responsive to said AGC voltage but for automatically de-emphasizing said accentuated high frequency components of said luminance signals, also as an inverse function of said received signal amplitude; said means being independently operative of said peaking circuit and so configured and arranged that the degree of de-emphasis provided said accentuated high frequency components of said luminance signals increases with decreases in received strength to reduce the presence of higher frequency noise in a reproduced image under weak signal conditions while the degree of de-emphasis provided said accentuated high frequency components of said luminance signals decreases with increases in received signal strength where the signal-to-noise ratio of an incoming signal is correspondingly greater; said means including an impedance path for bypassing said accentuated high frequency components of said luminance signals away from said image reproducing kinescope, said AGC varying the impedance of said path in the same direction as variations in said received signal strength, said impedance path comprising the series connection of a capacitive and inductive reactance and a variable resistance, said capacitive and inductive reactance being selected so as to pass said accentuated high frequency components of said luminance signals with said resistance being controllably varied in the same direction as variations in said AGC voltage to change the loading of said output stage in the frequency range of said high frequency components of said luminance signals, also as an inverse function of received signal strength.