A Baseband Hybrid Digital Transmission Scheme

A baseband hybrid digital transmission scheme is studied, and it is shown that the low- and high-frequency cutoffs in analog repeaters extremely degrade signal waveforms. Solutions studied are a combination of dc-constrained coding and modification of amplitude-frequency characteristics for low-frequency distortion, and a combination of flat amplitude equalization and simple phase equalization for high-frequency distortion. It is shown that these solutions reduce waveform distortions by a factor of ten. A solution of the control problem for automatic gain control (AGC) is also presented.