AONE-CHIP AUTOMATICEQUALIZER FORECHOREDUCTIONINTELETEXT
S. Vromans · 1981
Theory, implementation andtest results ofanautomatic equalizer forechoreduction inTeletext are described. Short echoes neednotbeparticularly annoying intheTVpicture, buttheycancompletely disturb Teletext data, transmitted inthefield retrace intervals. Theechoes maybecaused byreflections fromobstacles orimproper cable terminations. Toreduce theechoes thevideo signal ispassed through anadaptive transversal filter. Automatic coefficient adjustment utilizes analgorithm that isbased onaproperty oftheTeletext signal. Aspecific training waveforn isnotneeded. Analog implementation permits integration ononechip. Therefore, aLaguerre filter (cascade oftapped first-order phase-shifters), analog correlators andtapweight multipliers havebeendeveloped. Coefficient values arestored ascharges onintegrated dielectric capacitors.