Echo Canceling for xDSL Applications
Original Publication Date: 2004-Apr-25
Included in the Prior Art Database: 2004-Apr-25
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So far, xDSL CO (extended Data Subscriber Line Central Office) chipsets use a bfilter (balancing filter) scheme with a pure resistive hybrid for analog echo canceling (Figure 1). The disadvantage of this method is that two inputs, a receive filter and a bfilter (RX and BF), are required, and a mismatch in the two paths can cause performance degradation. Especially a high gain stage inside the BF can cause high noise and distortion. Therefore, it is proposed to use more sophisticated hybrid impedances plus a simple high pass/low pass filter (hp/lp) to reach a better echo attenuation so that the output of the hybrid can be connected to newer AFE (Analog Front End) pins with lower power consumption, which have a very low max volt peak tolerance. The BF noise source is thereby removed.