RX Equalizer (DFE and LPM)

Versal Adaptive SoC GTY and GTYP Transceivers Architecture Manual (AM002)

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1.3 English

A serial link bit error rate (BER) performance is a function of the transmitter, the transmission media, and the receiver. The transmission media or channel is bandwidth-limited and the signal traveling through it is subjected to attenuation and distortion.

There are two types of adaptive filtering available to the GTY and GTYP receiver depending on system-level trade-offs between power and performance. Optimized for power with lower channel loss, the GTY and GTYP receiver has a power-efficient adaptive mode named low-power mode (LPM), see Figure 1. For equalizing lossier channels, decision feedback equalization (DFE) mode is available. See Figure 2 for the GTY and GTYP transceiver.

DFE mode allows better compensation of transmission channel losses by providing a closer adjustment of filter parameters than when using a linear equalizer. However, DFE mode cannot remove the pre-cursor of a transmitted bit; it only compensates for the post cursors. A linear equalizer allows pre-cursor and post-cursor gain. The RX DFE mode is a discrete-time adaptive high-pass filter. The TAP values of DFE mode are the coefficients of this filter that are set by the adaptive algorithm.

Figure 1. LPM Mode
Figure 2. DFE Mode