[SI-LIST] Re: Return loss measurement - odd result - why?
- From: ronald miller <ron@xxxxxxxxxxx>
- To: dotter@xxxxxxxxxxxxx
- Date: Wed, 23 May 2007 23:50:27 -0700
Hi Dotter
It is not possible to get realisitic measurements through a balun except
over a very narrow
bandwidth and then only with a balun optimized to the narrow band you need.
For wideband use a differential TDR (Tektronix) and then convert to the
frequency domain
or you can use ADS to model lumped elements to match the time response
and then simulate
in the frequency domain to get accurate results.
4 port network analyzer can work if youi can get it calibrated properly
but the parasitics of
connecting to a PCB can give unreliable results.
Ron Miller
dotter wrote:
>Hi,
>I've been making return loss measurements of balun coupled ADC input
>using spectrum analyser with tracking gen and a return loss bridge.
>
>The return loss shows a regular "oscillation" of amplitude vs frequency
>of about 10dB with an extremely regular period of 100MHz across a
>bandwidth of about 1GHz.
>
>Is this an artifact? It seems extremely stable and unrelated to any
>clocks in the circuit.
>Any ideas what would cause this?
>
>Apologies if this is too far OT!
>
>Dotter
>
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--
Ronald Miller
Ghz Data, Signal Integrity Consulting
7721 Sunset Ave.
Newark CA 94560
tel 510-793-4744
cell 510-377-9380
fax 510-742-6686
www.ghzdata.com
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