Method and apparatus for adaptive equalization in the presence of large multipath echoes
The performance of a multiphase and/or multiple amplitude receiver, such as a 64/256 quadrature amplitude modulation (QAM) receiver, is improved in the presence of single and multiple echoes. A moving window adaptive decision feedback equalizer (DFE) is provided according to the adaptive equation Cn(k+1)=Cn(k)&#8722;&Dgr;&middot;W(k)&middot;En(k)&middot;Xn(k), where &Dgr; (delta) is the step size, Cn(k) is the tap value of tap n for the k symbol, En(k) is the error output at the symbol k, Xn(k) is the received signal for pre-cursor taps (FFE) and past decision output for post-cursor taps (DFE), and W(k) is the sliding window function at symbol k. In the adaptation process, some coefficients are fixed while other taps are being adapted. In particular, the adaptation is focused on a group of taps which correspond to received echoes. By only adjusting these taps, no interference or noise is introduced to the decision making device in the digital receiver and therefore, the effect of noise and echoes on the adaptation control is substantially reduced.
General Instruments Corporation
H
H03H
inventional
Qin Shlomo
Zhang Ovadia