Convergence Criteria for Transversal Equalizers

This paper is concerned with certain aspects of the automatic equalization of low-noise, linear channels which are to be used for multilevel pulse-amplitude modulated ( P A M ) signals. T h e purpose of the equalizer is to compensate for the channel transfer characteristics in such a w a y that the over-all impulse response of the channel is a Nyquist-I type of pulse, 1 - 2 - 3 that is, as is illustrated in Fig. 1, a pulse with a central peak and uniformly spaced zeros with period T. If such an impulse response is achieved, a sequence of amplitude modulated impulses with period T can be transmitted and the sequence of amplitudes can be recovered at the receiver by simply sampling in synchronism with period T. Certain obvious questions such as how to achieve synchronism and * University of Washington, Seattle. 1775 1776 THE BELL SYSTEM TECHNICAL JOURNAL, OCTOBER 1968 Fig. 1 -- A Nyquist-I pulse with central sample and zeros at periodic sample times.