ron miller wrote: > > > A paper by IBM a couple years back showed that skin effect dominates > up to about 1 Ghz > at which point the loss(s-11) takes a big slope upward, more than > double the slope below > 1 Ghz. On a linear(freq) vs log(db) scale the slope is constant about > and below the break-point > at 1 Ghz. > > However, losses are not well documented by the laminate manufacturers > and while one may > specify loss at 1 Ghz another at 10 Ghz etc, there is no > concensus.about how the loss varies with > frequency and by manufacturer and their various grades of epoxy glass. > . > A standards body should probably measure the S-parameters for several > laminates and manufacturers. > > Ron Miller > > > > Alex Horvath wrote: > >>Exactly, it seems to be fairly common misconception that skin effect losses >>always dominate. Dielectric losses are proportional to frequency, although >>they start out lower they will always exceed skin effect losses between 500 >>and 1Ghz or so. The biggest factor affecting this seems to the resin content >>of the PCB. >> >>I'd like to hear more about the properties of the resin, if it can be >>manipulated for less loss and what are the tradeoffs. I wasn't able to find >>out much about resin properties on the web. >> >>Thanks >>steve weir <weirsp@xxxxxxxxxx> wrote: >>Stuart, for common dielectrics, somewhere in the high hundreds of MHz >>dielectric loss overtakes loss from skin effect. >> >>Steve. >>At 05:16 PM 11/24/2003 -0500, Stuart Brorson wrote: >> >> >>>True enough, but aren't the dielectric losses in FR-4 more or less >>>frequency independent (i.e. to the <10% level that the dielectric >>>function is constant)? >>> >>>Anyway, Tom is right: you need to consider the frequency variation of >>>both Dk (the dielectric function) and Df (the dielectric loss >>>function). However, both are typically dominated by skin effect >>>losses, particular in the GHz range. >>> >>>Stuart >>> >>> >>> >>> >>>>To make the answer complete you need also to include dielectric losses >>>> >>>> >>>which >>> >>> >>>>also are frequency dependent. >>>> >>>>Tom Dagostino >>>>Teraspeed Consulting Group LLC Teraspeed Consulting Group LLC >>>>2926 SE Yamhill St. Device Modeling Division >>>>Portland, OR 97214 13610 SW Harness Lane >>>>Beaverton, OR 97008 >>>>http://www.teraspeed.com 503-430-1065 >>>>tom@xxxxxxxxxxxxx >>>> >>>> >>>>-----Original Message----- >>>>From: si-list-bounce@xxxxxxxxxxxxx >>>>[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Stuart Brorson >>>>Sent: Monday, November 24, 2003 1:22 PM >>>>To: andyk@xxxxxxxxxx >>>>Cc: si-list@xxxxxxxxxxxxx >>>>Subject: [SI-LIST] Re: Dielectric constant for FR4 at above 1Ghz >>>>frequency >>>> >>>> >>>>If I am not mistaken, your question is equivalent to this one: Is the >>>>dielectric function constant over the 1 MHz -- 1 GHz range? The >>>>answer is: It is not constant, but varies by several percent or more >>>>over that range for many FR-4s. (FR-4 is not a single material, but >>>>is a family of materials, each different depending upon your PCB >>>>vendor, and whatever batch of materials he was shipped on any >>>>particular day.) >>>> >>>>However, the bigger problem for you to think about is the loss due to >>>>the skin effect in your copper traces. The skin effect losses vary as >>>>the square root of the frequency, IIRC. The frequency-dependent loss >>>>due to the skin effect dominates over the frequency variation of the >>>>FR-4's dielectric constant. >>>> >>>>Here are some references: >>>> >>>>http://www.tdasystems.com/library/appnotes/siml0803.pdf >>>>http://signalintegrity.com/Pubs%5Cnews%5C4_5.htm >>>> >>>>Stuart >>>> >>>> >>>> >>>> >>>>>Hi all, >>>>> >>>>>I am designing a high speed PCB at over 1Ghz frequency using FR4 >>>>> >>>>> >>>material= >>> >>> >>>>>. >>>>>I am wondering how much the dielectric constant will be affected by the >>>>>frequency over 1Ghz as compared to 1Mhz? >>>>> >>>>>Thank you >>>>> >>>>>Regards, >>>>>Andy >>>>> >>>>> >>>------------------------------------------------------------------ >>>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.org >>> >>>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 technical documents are available at: >>http://www.si-list.org >> >>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 technical documents are available at: >> http://www.si-list.org >> >>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 >> >> >> >> >> -- Ronald B. Miller, Microwave/SI Engineer RAIL = NOISE + REFLECTIONS Gigahertz Data Div of MI Corp. \\ // \\ // 7180 Thornton Avenue \\// \\// Newark, CA 94560 ->JITTER<- EYE ->JITTER<- tel 510-793-4744, //\\ //\\ fax 510-742-6686 // \\ // \\ www.ghzdata.com RAIL = NOISE + REFLECTIONS ------------------------------------------------------------------ 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.org 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