VNA Sandbox User Guide
Version 2B
calibration
In vector network analysis you are interested in impedances
of components and circuits. At high frequencies almost any
length of cable will act as an impedance transformer, thus
altering the impedance you actually see. Furthermore at
even higher frequencies many cables become lossy, which
influences gain and impedance plots.
Luckily these cables act as linear elements and can be
'calibrated-out' by linear algebra. Do not be afraid, the
instrument will do this for you, but it should be fed with
some well known impedances for every frequency of
interest before you start the actual measurement. Therefore
before using the instrument you should perform a
calibration on the whole set-up, including the cables,
connectors, etc. for the frequency range you want to use in
your measurement.
The instrument stores this set of calibration data, and since the egiQ VNA is very
temperature stable, you will not have to perform this calibration routine very often.
But, changing cables, connectors or frequency range means
that you most renew the calibration. Avoid bending cables
to much after calibration. (depending on the quality of the
cable of course)
The well known impedances the egiQ VNA uses for this are
an Open Connection (O) a Short Circuit (S) a load resistor of
50Ω (L) a Through (T) and a “No Connection” in order to
calibrate the insulation between ports (I).
On the egiQ VNA-Sandbox the calibration circuits are 11
(open), 12 (short), 13 (load and insulation) and 14
(through).
The calibrating process is straight forward, you will find it
step by step below. You will find the process for the 1-port
and the 2-port measurements. You will need cables with UFL connectors when using the
egiQ VNA-Sandbox.
Again: during the calibration process, use the very same cables and connectors you are going to use
in the actual measurement! Not calibrating the whole set-up will lead to very confusing results!
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