[SI-LIST] VNA Question
- From: JP <edpc108@xxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Sun, 1 Jun 2003 18:27:13 +0100 (BST)
Hello SIers,
This is a basic VNA question, yet I don't have
clarity.
In theory, S parameters are obtained by perfectly
matching the relavant port impedances.
For instance, considering a 2 port system,
b1 = S11*a1 + S12*a2
b2 = S21*a1 + S22*a2
bi - reflected voltage
ai - incident voltage
S21 is obtained by ensuring a2 = 0, which implies
perfect match at port 2.
=> S21 = b2/a1
In reality, however DUT impedances need not be 50ohms
and is often not known. How does VNA ensure
a2(reflected component at port2) equals zero ?
Does VNAs have the mechanism to measure mismatch
and account automatically?
Thanks in advance,
Jayaprakash.
=====
Balachandran Jayaprakash
Celestijnenlaan,
3/61, 3001, Heverlee,
Leuven, Belgium.
Mobile: +32-472-630120
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