Algorithm and Structure to Cancel Signal Distortion in ATSC Digital TV System

In this paper we propose the 8 VSB (8 Vestigial Side Band) method which is decided as the standard of modulators for next generation digital TV System. In developing digital TV System, one of the difficult problems is how digital signal can be transmitted to the receiver without any phase & amplitude distortion. But, phase & amplitude error is liable to occur by imperfect design, circumstance variation and device degradation. These characteristics result in distortion of I, Q signal of modulator and interference in adjacent channels. In particular, the interference in modulator with a high power amplifier results in serious problems in adjacent channels. Here we analyzed problems of phase & amplitude error which are occurred when 8 levels digital signals are modulated to IF signal. And we suggested phase & amplitude error compensation algorithm and discussed the results for adaptation of the algorithm. This paper is directed to a phase and amplitude compensation apparatus and method for a digital modulator. An object of the paper is to maintain the optimum operating state of the modulator, preferably, provided in a digital television repeater.