[SI-LIST] Re: Open Termination
- From: Geoff Stokes <gstokes@xxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Wed, 15 Sep 2004 11:35:27 +0100
There is a total confusion here.
The characteristic impedance of a transmission line is totally different
from the characteristic impedance of a wave in a medium. It's not entirely
an accident that the units of V/I and E/H are the same, i.e., ohms, but the
situation is completely different: the transmission line parameter applies
to the voltage between the metal conductors for signal and return and the
current on them; the wave is described the electric and magnetic fields E
and H.
> -----Original Message-----
> From: Ahmed El-Sanhoury [mailto:rd-ahsanh@xxxxxxxxxxxxxx]
> Sent: 15 September 2004 09:35
> To: si-list@xxxxxxxxxxxxx; si_monkey2@xxxxxxxxx
> Subject: [SI-LIST] Re: Open Termination
>
>
> si_monkey2
>
> I'm afraid that there is misunderstanding point, so i will try to =
> declare it:
>
> 1- When saying "open termination offers infinite impedance"
> means Load =
> Impedance ZL=3D infinite impedance.=20
> 2- According to that the input impedance of transmission line
> Zin equals =
> directly the characteristic impedance Zo.
> 3- If the transmission line media is air, the Zo =3D 120pi
> =3D 120x3.14 =
> =3D 377ohm.
> 4- so in this case Zin equals also 377 ohm.
>
> According the above i can modify your statement "Open end line is =
> exposed to air has about 377 ohms"
> to " Open end line which go through the air has about 377 ohm".
>
> Thanks
> Senior Eng A.Sanhoury
> IEP R&D Bahgat Group
> www.bahgat.com
> > ----------
> > From:
> si-list-bounce@xxxxxxxxxxxxx[SMTP:si-list-bounce@xxxxxxxxxxxxx] =
> on behalf of Sitar Moniker[SMTP:si_monkey2@xxxxxxxxx]
> > Reply To: si_monkey2@xxxxxxxxx
> > Sent: Wednesday, September 15, 2004 12:48 AM
> > To: si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Open Termination
> >=20
> > In SI and HSDD books, they assume that open termination offers =
> infinite impedance. My understanding is open end line is
> exposed to air =
> which has about 377 ohms.=20
> > =20
> > 1) How do you get infinite impedance for unterminated line?=20
> > =20
> > 2) Is there any intuitive way to show that voltage at the open end =
> doubles- other than using math: ref. coeft. =3D +1?
> > =20
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