{"id":1536,"date":"2014-11-12T15:50:20","date_gmt":"2014-11-12T22:50:20","guid":{"rendered":"https:\/\/blogs.mentor.com\/hyperblog\/?p=1536"},"modified":"2026-03-27T09:22:53","modified_gmt":"2026-03-27T13:22:53","slug":"length-matching-for-10ghz-links","status":"publish","type":"post","link":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/2014\/11\/12\/length-matching-for-10ghz-links\/","title":{"rendered":"Length matching for 10GHz links"},"content":{"rendered":"<p>For most busses, length-matching a group of signals to 5 mils is a bit of overkill.\u00a0 But, if length-matching to 5 mils is as easy for your layout personnel as length-matching to 100 mils, why not get the extra margin?\u00a0 However, for very fast serial links, length-matching the two sides of a differential pair is absolutely crucial.\u00a0 That is one of the key steps I discuss in my article &#8220;<a href=\"http:\/\/www.pcdandf.com\/pcdesign\/index.php\/current-issue\/241-designer-s-notebook\/9551-designers-notebook-1409\" target=\"_blank\" rel=\"noopener noreferrer\">Ten Steps to Ten GigHertz<\/a>&#8220;.<br \/>\nBut length-matching the total length to a tight tolerance isn&#8217;t the only length-matching requirement.\u00a0 Of course, the two halves of a differential pair need to be tightly length-matched so that both halves of the signal arrive at the same time.\u00a0 But it is also important that the two halves of the signal travel together as well &#8211;\u00a0in other words, the + and &#8211; signal should be in phase with one another throughout the route.\u00a0 That means at any given location, the trace lengths are matched.\u00a0 This is especially important at vias, where the matching of the signals is incredibly important to ensure that the signals pass through the vias in a purely differential mode, as this will limit the amount of energy radiated by the signals, as well as limit the amount of noise that the signals pick up.\u00a0 This is especially crucial for 10GHz signals where margins are very tight.<br \/>\nThis type of length-matching can be achieved by using phase-matching routing, like that implemented in Xpedition VX.\u00a0 My colleague Charles discussed this the other day in <a href=\"https:\/\/blogs.mentor.com\/xpedition\/blog\/2014\/10\/27\/pcb-routing-solutions-simplifying-the-tuning-process-part-2-manual-tuning\/\" target=\"_blank\" rel=\"noopener noreferrer\">his blog.\u00a0 Click here<\/a> to take a look if you are interested.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>For most busses, length-matching a group of signals to 5 mils is a bit of overkill.\u00a0 But, if length-matching to&#8230;<\/p>\n","protected":false},"author":71672,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"spanish_translation":"","french_translation":"","german_translation":"","italian_translation":"","polish_translation":"","japanese_translation":"","chinese_translation":"","footnotes":""},"categories":[13],"tags":[],"industry":[],"product":[],"coauthors":[],"class_list":["post-1536","post","type-post","status-publish","format-standard","hentry","category-news"],"_links":{"self":[{"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/posts\/1536","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/users\/71672"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/comments?post=1536"}],"version-history":[{"count":1,"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/posts\/1536\/revisions"}],"predecessor-version":[{"id":10444,"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/posts\/1536\/revisions\/10444"}],"wp:attachment":[{"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/media?parent=1536"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/categories?post=1536"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/tags?post=1536"},{"taxonomy":"industry","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/industry?post=1536"},{"taxonomy":"product","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/product?post=1536"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/coauthors?post=1536"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}