How to measure absolute power using VNA?
 

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

How to measure absolute power using VNA?
 

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

Go to the S21 function. Your S21 power is read in dB... remember to
always use the appropriate attenuators as those VNAs are very expensive
and usually have a lower input power maximum of a watt or two.

The statements above are generalities... you should refer to the
operation manual for the exact VNA you will be using.

www.telstar-electronics.com

How to measure absolute power using VNA?
 

"Telstar Electronics" wrote in message
ups.com...
Go to the S21 function. Your S21 power is read in dB...

That would be "dBm" I think. Logarithmic power measurements have to be
referred to some reference power lever since dB is the logarithm of a ratio.
The one I see most often is dB above 1 milliwatt.

Also "S21" is a voltage transmission coefficient in the "scattering
parameter matrix" characterizing a 2-port network.

--
Regards,
Leland C. Scott
KC8LDO

How to measure absolute power using VNA?
 

"ilam" wrote in message
oups.com...
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


Does your VNA have the capabilities of measuring SWEPT power? Look for this
in the manual and I think you will be on the right track.I've never done it
but I think I have seen something in the manual about it.

How to measure absolute power using VNA?
 

Telstar Electronics wrote:
Go to the S21 function. Your S21 power is read in dB... remember to
always use the appropriate attenuators as those VNAs are very expensive
and usually have a lower input power maximum of a watt or two.

The statements above are generalities... you should refer to the
operation manual for the exact VNA you will be using.

www.telstar-electronics.com

One thing I forgot to mention... make sure you have a termination
(dummy load) on the output port. This load is generally quite small no
matter how much power you're measuring... in the several-watt range.
This is because of all the attenuation on the input port as I stated
before.

www.telstar-electronics.com

How to measure absolute power using VNA?
 

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