Sean. Cant say that I have ever attempted to pass 2.5 Ghz thru a via. We design our boards so the "high speed" stuff never passes thru vias. If you need to use them for High Speed then I would recommend using blind and buried vias since they inhibit much less capacitive and inductive properties. Unfortunately, the effects of the vias has been mainly guess work by RF engineers. ( I know I am going to receive some heat for this) I recommend reading the article that Doug Brooks wrote ( I said Bill Brooks before) about the effects of vias on transmission lines. His data was measured from actual board designs using a TDR. But his measurements were not at 2.5 Ghz.
Mike Reagan EDSI Frederick MD ----- Original Message ----- From: Sean James <[EMAIL PROTECTED]> To: Protel EDA Forum <[EMAIL PROTECTED]> Sent: Tuesday, November 27, 2001 2:41 PM Subject: Re: [PEDA] Vias & trace length > My design is 2.5Ghz, so via length is critical. > Sean James > PCB Designer > Telecast Fiber Systems, Inc. > 102 Grove Street > Worcester, MA 01605 > (TEL) 508.754.4858 x33 > (FAX) 413.541.6170 > ----- Original Message ----- > From: "Mike Reagan" <[EMAIL PROTECTED]> > To: "Protel EDA Forum" <[EMAIL PROTECTED]> > Sent: Tuesday, November 27, 2001 12:39 PM > Subject: Re: [PEDA] Vias & trace length > > > > > > > > > > Is there any way to get Protel to add vias to an overall trace length? Ex. > A > > via going from top to bottom thru an .062" board would add .062" to a > total > > trace length (PCAD/ACCEL does this). > > > > Sean, > > I don't think .062 inch for any digital signal under 500 mhz makes any > > difference. The actual capacitance of the via will pose more of a problem > > than the trace length. Actual measurements made by Bill Brooks > > www.ultracad.com and contributing editor to PCD magazine shows no > relevant > > impedance changes with vias placed in a trace. There are little hic-cups > in > > the impedance but it really doesn't change much. I wish protel would > give > > me a calculation of the capacitance with the via included. A trace > length > > is irrelevant unless it approaches a critical length for the signal, but > > loss can become a bigger factor. > > Question; Why don't you use Acell PCAD? personally I think it sucks > > > > > > Mike Reagan > > EDSI > > Frederick MD > > > * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/proteledaforum@techservinc.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
