From: Larry Miller ([email protected])
Date: Fri Jun 23 2000 - 11:47:16 PDT
A matched coax feed is self-shielding. Indeed, radiation out of the coax via
the outer conductor is the classical indication that you have a mismatched
> -----Original Message-----
> From: Dorin Oprea [SMTP:[email protected]]
> Sent: Friday, June 23, 2000 11:03 AM
> To: [email protected]
> Subject: Re: [SI-LIST] : Merits of low dielectric constant
> I believe the signal loop area is the key of this puzzle (no losses in
> consideration). A lower dielectric permitivity allows getting the same
> value within a smaller spacing between the conductor and the reference
> (shield). Smaller distance between the two conductors means smaller loop
> and therefore, less EM radiation = energy loss (Henry Ott) and also
> inductance value.
> Smaller L and smaller C means also faster transportation medium (coax
> but L/C is still the same.
> Hassan Ali wrote:
> > I attended a presentation by a high-frequency (1GHz < f < 65GHz) coaxial
> > cable vendor, and the presenter claimed that their cables use a material
> > with a very low dielectric constant and therefore are ideal for
> > application as they give rise to low capacitive loading. He gave a
> > showing the capacitance (I think per unit length) decreasing as you
> > dielectric constant. This claim, however, perplexed me as I don't know
> how a
> > cable's capacitance per unit length would give rise to a capacitive
> > All I know from my transmission line classes, a lossless transmission
> > with Z0 = sqrt(L/C) would transmit signals exactly the same way
> > of the value of the p.u.l. capacitance C as long as the ratio L/C is
> > maintained. Am I missing something here?
> > Thanks.
> > Hassan.
> > --
> > Hassan Ali <[email protected]>
> > Equipment & Network Interconnect, Nortel Networks
> > 2 Brewer Hunt Way, Kanata ON, K2K 2B5 Canada
> > Tel: 613-765-1410 (ESN 395) Fax: 613-765-5512 (ESN 395)
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