| Thread Links | Date Links | ||||
|---|---|---|---|---|---|
| Thread Prev | Thread Next | Thread Index | Date Prev | Date Next | Date Index |
|
RX bandwidth filter and TX edge filter should naturally be lower for PAM4 – about half the bandwidth or NRZ – otherwise crosstalk generation and sensitivity
are unnecessarily high. These filters should include phase, not just magnitude as in moore_01_0311. Phase is significant in the time domain. It is still multiplication, but with complex
values. For the RX filter phase and magnitude we can assume Butterworth filter, which has a rather simple transfer function (see Wikipedia or more professional sources)
and is an approximation for realizable filters. As for the TX filter, can anyone suggest which filter is adequate? Is there a justification for 2nd order and are the poles real or complex conjugate? </Adee> From: Mellitz, Richard [mailto:richard.mellitz@xxxxxxxxx]
Should filters be different per port type? …Rich From: Mellitz, Richard [mailto:richard.mellitz@xxxxxxxxx]
Perhaps a convenient way to look at TX/RX filtering is convolution of the following. 1.
Tx Voltage Amplitude scaling (for NEXT, FEXT, and THRU not coding which will be done in a later algorithm ) 2.
Tx edge filter (moore_01_0311) 3.
Rx bandwidth filter (moore_01_0311) 4.
Tx/Rx block return loss filters (gamma,moore_01_0311) The first three are a straight convolution and with is multiplication in the frequency domain.
The lasts is a chain matrix convolution of RL under worst +1 or -1 reflection coefficient phase conditions and in the frequency domain may look like this sdd21=sdd21.*(1.-gamma_rx)./(1.- sdd11.*gamma_tx + sdd22.*gamma_rx +sdd21.^2.*gamma_tx.*gamma_rx -sdd11.*sdd22.*gamma_tx.*gamma_rx); …Rich |