**From:** Dan Swanson (*dswanson@bartleyrf.com*)

**Date:** Fri Jun 23 2000 - 08:19:28 PDT

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Hassan,

The bigger consideration for high frequency operation

is the cross-section dimensions and modes. At some point the

cable (or connector) cross-section will support higher order modes.

Any small discontinuity along the transmission path can and will

launch higher order modes.

To get a feel for dimensions and useful freq range you can think

about the frequency range of typical connectors. An N connector

is good up to 10 or 12 GHz. 7mm is good up to 18 GHz I think.

An SMA or 3.5 mm is good up to 22GHz or so. 2.4mm goes

up to 40GHz.

Dan

Dan Swanson Email: d.swanson@ieee.org

Bartley R.F. Systems TEL: 978-241-1091

38 Water Street FAX: 978-388-7077

Amesbury, MA 01913

-----Original Message-----

From: Hassan Ali [SMTP:hali@nortelnetworks.com]

Sent: Friday, June 23, 2000 9:37 AM

To: si-list

Subject: [SI-LIST] : Merits of low dielectric constant

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 high-speed

application as they give rise to low capacitive loading. He gave a formula

showing the capacitance (I think per unit length) decreasing as you decrease

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 loading.

All I know from my transmission line classes, a lossless transmission line

with Z0 = sqrt(L/C) would transmit signals exactly the same way regardless

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 <hali@nortelnetworks.com> 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)**** To unsubscribe from si-list or si-list-digest: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu ****

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**Next message:**Ingraham, Andrew: "RE: [SI-LIST] : Merits of low dielectric constant"**Previous message:**Bob McCowan: "RE: [SI-LIST] : Merits of low dielectric constant"**Maybe in reply to:**Hassan Ali: "[SI-LIST] : Merits of low dielectric constant"**Next in thread:**Ingraham, Andrew: "RE: [SI-LIST] : Merits of low dielectric constant"

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