I should add that the pwb is designed with a ground plane 4mils from the diff pair.
On Mon, Nov 29, 2021 at 12:57 PM Istvan Novak < [email protected]> wrote: > This message originated outside of DISH and was sent by: > [email protected] > > Hi Charles, > > Having a trace shorted to ground at one end and leaving open at the other > end creates a quarter-wave resonator. > > If for sake of example the propagation delay on the particular layer is > 160ps/", 250mils has 40ps and the period at the quarter-wave resonance is > 4*40ps=160ps, which is around 6GHz. At that frequency (and increasingly as > we approach that frequency) the insertion loss, reflection and crosstalk > will be higher. Whether this creates a problem, depends on the signaling > speed and signaling budget. > > Best regards, > > Istvan Novak > > Samtec > > > On 11/29/2021 1:55 PM, Charles Grasso wrote: > > Hello all and I hope your Thanksgiving went well! > > I am seeking some guidance on the effect (detrimental or otherwise) on > adding short (say 250mils) ground fingers in between high speed > differential > pairs at their source. i.e at the IC pin field. The ground finger only has > a via > at the entrance to the pin field and not at the final destination 250 mils > away. > > Does anyone know of (or have experience of ) any issues this may cause? > > > -- > > Charles Grasso > > Dish Technologies > > (c) 303-204-2974 > > (h) 303-317-5530 > > (e ) [email protected] > > (e2) [email protected] > - > ---------------------------------------------------------------- > > This message is from the IEEE Product Safety Engineering Society emc-pstc > discussion list. To post a message to the list, send your e-mail to < > [email protected]> > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieee-pses.org/emc-pstc.html > > Attachments are not permitted but the IEEE PSES Online Communities site at > http://product-compliance.oc.ieee.org/ can be used for graphics (in > well-used formats), large files, etc. > > Website: http://www.ieee-pses.org/ > Instructions: http://www.ieee-pses.org/list.html (including how to > unsubscribe) <http://www.ieee-pses.org/list.html> > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > Scott Douglas <[email protected]> > Mike Cantwell <[email protected]> > > For policy questions, send mail to: > Jim Bacher <[email protected]> > David Heald <[email protected]> > > - > ---------------------------------------------------------------- > > This message is from the IEEE Product Safety Engineering Society emc-pstc > discussion list. To post a message to the list, send your e-mail to < > [email protected]> > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieee-pses.org/emc-pstc.html > > Attachments are not permitted but the IEEE PSES Online Communities site at > http://product-compliance.oc.ieee.org/ can be used for graphics (in > well-used formats), large files, etc. > > Website: http://www.ieee-pses.org/ > Instructions: http://www.ieee-pses.org/list.html (including how to > unsubscribe) <http://www.ieee-pses.org/list.html> > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > Scott Douglas <[email protected]> > Mike Cantwell <[email protected]> > > For policy questions, send mail to: > Jim Bacher <[email protected]> > David Heald <[email protected]> > -- Charles Grasso Dish Technologies (c) 303-204-2974 (h) 303-317-5530 (e ) [email protected] (e2) [email protected] - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
