Hi Farah, One quick correction. The characteristic impedance of a parallel plate 100 mil wide and 40 mil dielectric thickness (Er=4) is about 76 ohms. I meant to go back and verify, but I got a little trigger-happy with my mouse. Best regards, George -----Original Message----- From: Haddadin, Farah [mailto:Farah.Haddadin@xxxxxxxxx] Sent: Tuesday, December 02, 2003 5:20 AM To: George Tang Subject: RE: [SI-LIST] Re: Dielectric Constant - thin materials - DC to 10GHz Thanks again George. Farah -----Original Message----- From: George Tang [mailto:gtang@xxxxxxxx] Sent: Monday, December 01, 2003 8:05 PM To: Haddadin, Farah; si-list@xxxxxxxxxxxxx Subject: RE: [SI-LIST] Re: Dielectric Constant - thin materials - DC to 10GHz Hi Farah, You can also use a TDR to measure propagation delay, but that requires some numerical processing to determine Er as a function of frequency. The standing wave method is quite accurate, since it requires the forward and reflected wave to be in phase. Regards, George -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Haddadin, Farah Sent: Monday, December 01, 2003 8:51 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Dielectric Constant - thin materials - DC to 10GHz Hello everyone, I am looking for a fixture that is capable of measuring permittivity of thin materials from DC - 10GHz. There are two issues here: 1) The wide band of frequency: do I have to create two fixtures: one for low frequency and one for high? 2) The thickness of the material to be tested: I was told that the thickness of the material should roughly be: 20/sqrt(Er) [mm]. For example, for a permittivity of 4, the thickness of the material under test should be 10 mm. This is a conservative thickness estimator, but the thickness of the materials of my interest is 0.1mm - 1mm. I would greatly appreciate it if someone can point me to an existing fixture or methodology to test such thin materials for the frequency range mentioned above. Also, is there any reading material on the web on how to create fixtures? Thank you, Farah ------------------------------------------------------------------ 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