Wireline High-Speed TX Pre-emphasis FIR Filter Response.

[JohnLai]

Hello, Folks,

An online tutorial (Intel SI Fundamentals Short Course - Equalization) shows an TX Pre-emphasis FIR filter has such frequency response:



The green line in the above figure shows that there is a dip at 6.4GHz for the 6.4Gb/s data transmission. I do not understand why there is such a dip at 6.4GHz since this is exactly what the frequency components are needed for transmitted data. I am also expecting the pre-emphasis should be a high-pass filter like a passive CTLE due to the low-pass characteristics for wireline channels.

Could someone please explain it to me.

Thank you.

 

[alvays]

Hi

that's the sampling frequency or delay time. From FFT of power spectrum, no power for that point.
you can get examples by check RZ and NRZ FFT

Hello, Folks,

An online tutorial (Intel SI Fundamentals Short Course - Equalization) shows an TX Pre-emphasis FIR filter has such frequency response:

View attachment 87276

The green line in the above figure shows that there is a dip at 6.4GHz for the 6.4Gb/s data transmission. I do not understand why there is such a dip at 6.4GHz since this is exactly what the frequency components are needed for transmitted data. I am also expecting the pre-emphasis should be a high-pass filter like a passive CTLE due to the low-pass characteristics for wireline channels.

Could someone please explain it to me.

Thank you.

 

[JohnLai]

alvays,

Thank you for pointing that out. That makes sense to me.