[SI-LIST] Re: TO define the "Preemphasis"

  • From: "DoraBabu - CTD, Chennai." <dbabu@xxxxxxxxxxxxxxx>
  • To: lincj@xxxxxxxxxxxxxxxxxxx, hpc@xxxxxxxxxx
  • Date: Fri, 5 Jul 2002 21:57:08 +0530


Got it from Xilinx Signal Integrity glossary : 

Pre emphasis is magnitude boosting of high frequency spectral components
before launching the signal (wave) onto the Transmission Line. Transmission
Lines embedded in most standard PCB materials (FR4, Rogers 43xx, Nelco and
Rogers) suffer varying degrees of dispersion and loss in the 1 gigahertz
spectrum. This is mostly due to conductance losses (leakage from the copper
trace to any other conducting structure) and Skin Effect. Dispersion is a
phenomenon whereby spectral components travel at different velocities. The
waveform looks smeared when it arrives at the receiver. 
Both of these "characteristics" play into a diminished and poorly received
signal. By boosting the high freq. spectral components, the magnitude of
these components can be diminished as the wave travels through the
Transmission Line, but since it starts out larger than the lower frequency
components, the composite signal arrives at the receiver looking the way it
was intended. 

Pre Emphasis is done by simply increasing the maximum amplitude of the
signal for one bit period. If the signal is 1 bit in duration, the amplitude
is allowed to rise to a value which is some percentage greater in magnitude.
At this point, if the signal is to stay at the same logic state, the driver
sends a decreased magnitude signal, or nominal logic level. Every time a
transition occurrs, the greater magnitude level is used. For all times after
this that the same level is to be transmitted, the nominal magnitude is
used. 

--Regards
Dorababu

-----Original Message-----
From: Miller [mailto:lincj@xxxxxxxxxxxxxxxxxxx]
Sent: Friday, July 05, 2002 5:38 PM
To: hpc@xxxxxxxxxx
Cc: SI_LIST (E-mail)
Subject: [SI-LIST] Re: TO define the "Preemphasis"



You can also check xilinx's Multi-Gigahertz Signaling FAQ
http://www.xilinx.com/xlnx/xil_prodcat_product.jsp?title=si_gigfaq

Best Regards

Miller Lin


------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List archives are viewable at:     
                //www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages 
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
  
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List archives are viewable at:     
                //www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages 
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
  

Other related posts: