Bandsplitting of video signals for 2-channel transmission

A system is described for reconstructing a wideband video signal at a receiver in which a wideband signal at a transmitter is split into two signals: a lowpass component and a highpass component. The highpass information is transmitted over an augmentation channel. The lowpass component transmitted over another channel is NTSC-compatible. The problem of how to accomplish the bandsplitting and recombination without introducing objectionable artifacts on either the NTSC-compatible portion or the reconstructed wideband signal is discussed. Complementary digital filters are considered for use in an exact reconstruction of the wideband signal. The reconstructed signal is treated as the wideband signal convolved with the impulse respond of a bandstop filter that introduces an amplitude distortion to the discrete Fourier transform of the digital wideband signal. It is shown that the amplitude distortion is virtually eliminated by applying an approximate inverse filter at the receiver. A technique for designing finite-impulse response (FIR) approximations of inverse digital filters is introduced and design examples shown.