On 24 December 2012 19:23, Brooke Clarke <brooke@...> wrote:
Hi:
The most accurate way of characterizing S11 or S22 is to use a scalar network analyzer with a bridge and precision air
line. The cal load is a precision load that's just slightly off from 50.0 Ohms but how much off doesn't matter.
It's far more accurate than a VNA.
I don't claim to know much about scaler network analyzers, so what I
say might be wrong.
I don't see how you can consider a *scaler* network analyzer able to
characterise S11 and S22, since both S11 and S22 require both
magnitude and phase information.
I believe the things you refer which have an impedance close to, but
not exactly 50 Ohms are generally known as sliding loads, though I
suppose they might have other names.
I do have a few precision airlines which are machined very accurately.
I've got a couple of 50 Ohm ones, and a couple which are stepped from
50 Ohms to 25 Ohms. These are part of VNA *verification* kits, so they
need to be very accurate.
I understand the weak point of calibration kits is the loads - hence
sliding loads are used at higher frequencies.
Dave
