CertusPro-NX SerDes/PCS Usage Guide
Preliminary Technical Note
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All rights reserved. CONFIDENTIAL
Figure 8.3 shows the typical backplane application with Rx equalizer. Despite the signal distortion at the input of the
receiver, Rx equalizer corrects for the distortion and produces a clean waveform. CTLE reduces the low frequency
component from the received signal, which attenuates by a lower amount on the transmission line. The high frequency
component of the received signal can also be amplified by CTLE sometimes. The DFE is similar to the Tx equalizer,
usually implemented by multi-tap FIR. The combination of CTLE and DFE tolerates more channel loss than either
equalizer alone, when they have been tuned properly.
PCB, Connectors, Cables
Transmitter
Receiver with
Rx Equalizer
Signal at
Transmitter side
Signal at
Receiver side
Signal after
Receiver Equalization
Figure 8.3. Typical Backplane Application with Rx Equalizer
CertusPro-NX device implements both Tx equalizer and Rx equalizer for multiple protocols supporting. Tx equalizer is
based on 3-tap FIR, while the Rx equalizer is based on CTLE and 1-tap DFE. Below sections descript the detailed usage
of CertusPro-NX Tx equalizer and Rx equalizer.
Tx Equalization
Figure 8.4 shows the block diagram of transmit equalizer. Both pre-cursor ratio (C
-1
) and post-cursor ratio (C
+1
) are
negative and
,
C
–
1
C
0
C
+
1
1 UI Delay 1 UI Delay
input
output
Pre-Cursor
Ratio
Post-Cursor
Ratio
Figure 8.4. Transmit Equalizer Block Diagram
Table 8.1. Description of Tx Voltage Levels
The amplitude of the first bit of a repeated bitstream (given 00001111
pattern).
The amplitude between the first and the last bits in a repeated bitstream.
The amplitude of the last bit of a repeated bitstream (given 00001111 pattern).
Full-scale amplitude (given 01010101 pattern).
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