Wonderful explaination! I spend a lot of time to explain this bad design habit in digital world to the engineers in China. And this time I found a confidant. Thanks Steve. Shaopeng AE Consultant Mentor Graphics Electronic Technology Co., Ltd. Tel: +86-10 - 5930 4050 Cell: +86-136 1105 7707 Fax: +86-10-6808 0319 E-mail: peng_shao@xxxxxxxxxx Address: RM1512, CanWay Building, No.66 NanLiShi Lu, Beijing, China 100045 -----邮件原件----- 发件人: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] 代表 steve weir 发送时间: 2011年10月24日 18:20 收件人: si-list@xxxxxxxxxxxxx 主题: [SI-LIST] Re: "Ground" strips between LVDS pairs Bad habits die hard. One bad habit you want to break for certain is copying magical mystery folklore design techniques. At audio frequencies shield traces work great. They are wonderful for keeping junk out of high impedance Op-Amps. High speed digital transmission lines are a different animal. As has been covered on this reflector many times: Inserting guard traces is usually ineffective and can actually create a tuned coupler. The most effective way to isolate signals that run over a reflection plane is to minimize the height over the plane and maximize the separation between aggressors and victims. If you can't meet your cross talk numbers that way, consider altering your stack-up, routing layer assignments, etc. One option always is co-planar wave guides. If you know how to design them, then you can pull out that option when it is appropriate. Steve On 10/24/2011 2:56 AM, Jason Young wrote: > Dear Experts, > Often on boards with LVDS signals, for instance connecting an LVDS > transmitter to a LCD panel, I see thin 'ground' strips running between the > differential microstrips. These strips have a sprinkling of vias connecting > them to the reference plane on layer 2. Either end generally has a via and > they extend most of the way between the source and termination. I'm told the > reason is to reduce crosstalk between the pairs. Can someone please explain > this reasoning? > Yours > Jason > Ps. Sorry for using the 'G' word. > > ------------------------------------------------------------------ > 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 technical documents are available at: > http://www.si-list.net > > List archives are viewable at: > //www.freelists.org/archives/si-list > > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > > > -- Steve Weir IPBLOX, LLC 150 N. Center St. #211 Reno, NV 89501 www.ipblox.com (775) 299-4236 Business (866) 675-4630 Toll-free (707) 780-1951 Fax ------------------------------------------------------------------ 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 technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list 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 technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu