Let's say that I have a set of S parameter data in the form rho+angle. The
parameters are S11(ant) for an antenna, S11(cable) and S21(cable) are for
the cable. S12(cable) and S21(cable) are assumed equal.

S11(system) is for the antenna and cable connected together. How would the
S11(system) be calculated?

As a first stab at it, I would calculate:
S11(system)=S11(ant) * S21(cable) * S12(cable)

Is that valid, and/or does S11(cable) need to be included?

Thanks

oops...I have changed the wording in a couple of places, and restated
problem below:

Let's say that I have a set of S parameter data in polar form. The
parameters are S11(ant) for an antenna, S11(line) and S21(line) are for
the transmission line. S12(line) and S21(line) are assumed equal.

S11(system) is for the antenna and cable connected together. How would the
S11(system) be calculated?

As a first stab at it, I would calculate:
S11(system)=S11(ant) * S21(line) * S12(line)

Is that valid, and/or does S11(line) need to be included?

Thanks

Wayne wrote:
Is that valid, and/or does S11(line) need to be included?

Where are your ports? One at the source and one
at the load?
--
73, Cecil http://www.w5dxp.com

"Cecil Moore" wrote in message
t...
Wayne wrote:
Is that valid, and/or does S11(line) need to be included?

Where are your ports? One at the source and one
at the load?
--
73, Cecil http://www.w5dxp.com

Cecil--
The s-parameter threads caused me to resurrect some test data that was taken
(by an RF engineer) before I retired. I never looked at the data other than
to see if the antenna system components met specification.

So, I have s parameters for each component taken with the latest/greatest
HP/Agilent VNA at the time. For coax cables, the VNA was connected to each
end of the coaxial cable for the measurements. Antenna data was taken with
one port of the VNA connected to the antenna input, which was a SMA
connector. The antenna was a s-band cavity antenna with a 1/4 wave probe.
The components were all 50 ohm nominal. Hopefully, this answers your
questions.

I'm curious about how to use the s-parameters for components to calculate
the "system" s-parameters. The original question is about a single antenna
fed by a transmission line, but I will probably try to analyze more
complicated hookups later.

Thanks
Wayne

Wayne wrote:
I'm curious about how to use the s-parameters for components to calculate
the "system" s-parameters. The original question is about a single antenna
fed by a transmission line, but I will probably try to analyze more
complicated hookups later.

If I correctly understand what you say, you have the trivial
one-port case of the antenna and the two-port case for the
transmission line. HP's Ap Note 95-1 might be the place to
start in understanding a basic analysis.

http://www.tm.agilent.com/data/stati...-1/an-95-1.pdf
--
73, Cecil http://www.w5dxp.com

"Cecil Moore" wrote in message
...
Wayne wrote:
I'm curious about how to use the s-parameters for components to calculate
the "system" s-parameters. The original question is about a single
antenna fed by a transmission line, but I will probably try to analyze
more complicated hookups later.

If I correctly understand what you say, you have the trivial
one-port case of the antenna and the two-port case for the
transmission line. HP's Ap Note 95-1 might be the place to
start in understanding a basic analysis.

http://www.tm.agilent.com/data/stati...-1/an-95-1.pdf
--
Yes, the measurements are one-port for the antenna and 2 ports for the line.
My question was asked after looking at the referenced website, and trying to
apply the information.

So, to avoid having to return to previous messages:
Can the S11 of a line connected to an antenna be calculated as:
S11(system)=S11(antenna) * S21(line) * S12(line) ?

Thanks
Wayne

So, to avoid having to return to previous messages:
Can the S11 of a line connected to an antenna be calculated as:
S11(system)=S11(antenna) * S21(line) * S12(line) ?

Thanks
Wayne

Check out http://www.rfcafe.com/references/electrical/s-h-y-z.htm
The usual method would be to convert the S matrices to ABCD
matrices then perform matrix multiplication on the cascaded
ABCD parameters. You then convert the resultant ABCD matrix to
an S matrix.
http://www.mathworks.com/access/help...oogle+ Search

Frank