[SI-LIST] Re: Measuring characteristic impedance of transformer

Dear Padma,

What do you mean by characteristic impedance of a transformer? In case of a 
transmission line it is that impedance of a load that makes the input impedance 
of the transmission line equal to that load impedance and no reflection exists.

Kind regards
Boris Traa
System design engineer EMC

It's the currents that make circuits work or fail.

Philips Applied Technologies/EMC center
Room 2.020
High Tech Campus 26
5656AE Eindhoven, The Netherlands
Tel: ++ 31 40 27 43766
Fax: ++ 31 40 27 42224
E-mail:  boris.traa@xxxxxxxxxxx


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On 
Behalf Of padma gundala
Sent: 2009 Jun 26 6:34 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Measuring characteristic impedance of transformer

Hi,

We are measuring the characteristic impedance of transformer.(TDR)
Path is

SMA- 50 ohms trace- 1:1 transformer- 1:4 transformer- 200ohms (resistor 
soldered across)

We find as soon as the co-ax is connected to the SMA, immediately a standing 
wave exisists on the co-ax i.e insteAd of measuring 50ohms measures the 174 
ohms)

And the complete wave(volt ) even at the transformer, pcb traces shits upwards.
Can anyone explain this phenomena.
We also tried measuring a 68 ohms inductor alone+pcb trace.
the co-ax measures 50ohms , no standing wave on the co-ax.

Would like some input from anyone who tried this.

Thanks,
Padma




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