Circuitry for approximating the control signal for a BTSC spectral expander

摘要

Apparatus for approximating a signal k(b) useful in controlling a Broadcast Television Systems Committee (BTSC) expander circuit where k(b)=R(b+1)/(b+51) and b is the root-mean-square (RMS) value of an applied signal. In order to generate the control signal k(b), the signal, b, is scaled by a first coefficient. The signal, b, is squared and scaled by a second coefficient. The scaled signal and the squared and scaled signal are combined with a constant value to produce a signal approximating the signal k(b).