[SI-LIST] Re: Impedance measurement
- From: steve weir <weirsi@xxxxxxxxxx>
- To: bharathrajupcb@xxxxxxxxxxx
- Date: Thu, 01 Nov 2007 09:43:55 -0700
While it is possible to use an IA that has sufficient bandwidth to
obtain apparent impedance at the test port, a TDR / TDT or VNA are the
instruments of choice for evaluating transmission channels. Think of
the IA as a poor man's1 port VNA.
Steve
Bharathkumar Raju wrote:
> Dear All,
> Is it possible to measure the impedance of USB D+ & D- signal traces
> of an unassembled PCBA, using HP 4249 impedance analyser? One end of the
> traces are left open and I measure the impedance across the pair at the other
> end. By measuring Zsc & Zoc I hope we can calculate the CI.
> Measuring with other end of the traces connected together (Zsc) seem
> to be easy and we get consistant results. What are the issues in using HP
> 4249 or similar impedance analysers in measuring impedance of open ended
> untermintaed traces (Zoc)? I request the experts to guide me in measuring Zoc
> accurately using impedance analysers.
> Bharath
>
>
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