[SI-LIST] Re: Coaxial TEM Cutoff Frequency
- From: c deibele <deibele@xxxxxxx>
- To: gtang@xxxxxxxx
- Date: Thu, 11 Dec 2003 17:12:16 -0500
i disagree george.
this is a difficult question to be answered in just an email, but the
higher order modes associated with a transition can start to propagate.
at this point, the cutoff frequency happens. this can be associated
with tem, te or tm
-craig
George Tang wrote:
>Hi Merrick,
>
>Coaxial in TEM mode has no cutoff frequency, if you assume lossless. Of
>course, as you go higher in frequency, the lossless assumption will break
>down and the TEM mode model will not be valid due to an electric field
>component in the direction of propagation. But as far as cutoff frequency
>goes, coaxial in TEM mode does not have a cutoff as defined in TE or TM
>modes in waveguides.
>
>Regards,
>
>George
>
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx
>[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Moeller, Merrick
>Sent: Thursday, December 11, 2003 11:58 AM
>To: Si-List (E-mail)
>Subject: [SI-LIST] Coaxial TEM Cutoff Frequency
>
>
>Experts,
> I have been searching for a hand calculation of cutoff frequency
>for a coaxial contact. I have been able to find many for coaxial cable.
>However,
>I do not know the assumptions that are being made to derive these equations.
>Cutoff Frequency = 7.5/SQRT(er)(D+d)
>or
>Cutoff Frequency= ((2*c)/(PI*sqrt(er)))*1/(D+d)
>
>D = Sheild inner diameter
>d = Conductor outer diameter
>
>Any insight?
>
>Thanks,
>Merrick
>
>
>
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--
Craig Deibele, PhD PE
Spallation Neutron Source
Oak Ridge National Laboratory
PO Box 2008 MS 6473
701 Scarboro Road Room 301
Oak Ridge, TN 37830
deibele@xxxxxxx
office: +1 865.574.1969 cell: +1 865.384.2057 fax: +1 865.241.6739
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