Chrominance signal limiter

Abstract

A filter separates a composite video input signal into luminance and chrominance signal components. DC signals are combined with the luminance signal to produce four control signals, first and fourth ones of which have an AC component inversely proportional to the luminance signal, second and third ones of which having an AC component directly porportional to the luminance signal, each having a respective DC component. The DC components of the first and third control signals are regulated in proportion to a first reference voltage, V1, and the DC components of the second and fourth ones of the control signals are regulated in proportion to a second reference voltage V2. Cascade connected complementary non-additive mixers limit excursions in a first sense of the chrominance signal to the lesser in that sense of the first and second control signals and limits excursions in a second sense of the chrominance signal to the lesser in that sense of the third and fourth control signals to thereby provide a limited chrominance output signal. The luminance and chrominance signals are combined to provide a composite video output signal limited to a range defined by the reference voltages V1 and V2 and in which the chrominance component of the output signal is limited symmetrically with respect to the luminance signal level, thereby reducing even order harmonic distortion of the chrominance signal under limiting conditions.

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