Pre-emphasis sampling mode filter for SECAM TV colour coder - operates on chrominance subcarrier signal by digital sampling to achieve specified transfer function

摘要

The filter has an 'inverted bell' response, intended for use with the chrominance signal of a SECAM colour television encoder. The filter operates by sampling, preferable digitally, and has a transfer function of the form (G(z)=a+bz power -1+cz power -2. The sampling frequency is four times the frequency of the chrominance sub-carrier in the PAL colour television system. The filter includes a first delay element (15) whose input is connected to the first inputs (20,18) of two adders (21,17) - one via a further delay line (19). The first adder output is fed directly to one input of a subtractor (28), while the second adder output passes via further processing circuitry to the second subtractor input. The subtractor output then forms the final output of the filter circuit.