[SI-LIST] Re: VSWR using the TDR Measurements.
- From: "Yuriy Shlepnev" <shlepnev@xxxxxxxxxxxxx>
- To: "'padma gundala'" <pgundala2001@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Sat, 17 Jan 2009 15:37:51 -0800
Padma,
To compute voltage standing wave ratio (VSWR), you have to calculate the
reflection coefficient in the frequency-domain first (see details in any
textbook on microwave circuits). The result of TDR is the time-domain
reflection. The frequency-domain reflection coefficient can be computed as a
ratio of Fourier transforms (DFT or FFT) of the time-domain response and
stimulus (ramped step).
Note that if TDR converted into the impedance profile, it provides scalar
values of the characteristic impedance at a particular spatial location
averaged over some frequency band. The local impedance values do not contain
information about the system and thus cannot be used to compute the
reflection coefficient and VSWR (an exception is the infinite non-dispersive
and lossless transmission line).
Best regards,
Yuriy Shlepnev
www.simberian.com
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of padma gundala
Sent: Saturday, January 17, 2009 8:56 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] VSWR using the TDR Measurements.
Hi Folks,
=
I am trying to use the Characteristic impedence value that I obtained from
the TDR measurements, at TrisePps to calculate the VSWR(I cannot use a
network analyser, don't have microprobes).
=
I was going to plug in the Z0 value into reflection coefficient formula and
then into VSWR Formula.
=
Do you think that this a right approach to calculate the VSWR. If so how do
I=account for the VSWR to change with frequency.
=
Thanks for any thoughts.
=
Padma
=
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