On 4 Jan 2007 22:19:51 -0800, "ilam" wrote:

+++Dear all,
+++
+++I am new to RF world, would like to know how to use VNA to measure
+++absolute power?
+++
+++Please share your knowledge
+++
+++Thanks
+++Ilam
**********

Don't like doing your homework for you but if you really need a
helping hand maybe this link will help from Agilent.

http://eesof.tm.agilent.com/docs/icc...arBasics_1.pdf

Also I may suggest AN215A from Motorola as another source of info.
This can be found in the Motorola RF Aplications book. Should be a
part of most universities Engineering library.

I am not so sure what you intend to measure in Absolute Power? That is
somewhat vague. Absolute Power out? Absolute Power Dissapated? so
forth and so forth.

A VNA is best used to determine complex impedances of the input and
the output in terms called S-Parameters. S-parameters can be generated
for two, three, four or more ports. Often most used is two port
parameters. In two port parameters you generete four terms, S11, S21,
S12, and S22. S-parameters are logrithmic voltage ratios expressed in
dBs. These are complex vector quantities. These four readings give you
all the information needed about the DUT (Device Under Test).

S11 is the input complex reflection coefficient.
S21 is the forward complex transmission coefficient.
S12 is the reverse complex transmission coefficient.
S22 is the output complex refelction coefficient.

The nicety of these measurements is that they can be moved to the
Smith Chart for starting points for matching networks as well as
feedback networks for nuetralization.

james