×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

*
*
*
*

Thanks. We have received your request and will respond promptly.

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Measurement of S-Parameters

thread239-85752

Measurement of S-Parameters

Measurement of S-Parameters

(OP)
In the measurement setup , I was going through the theory and I don't understand where the 2 comes from in the equation to find the S parameter S21. ( ie. S21 = 2V2/VG1)  Why is it there??

RE: Measurement of S-Parameters

If your reference impedance is normallized to 1 ohm the s21
is (v2/vg1)^2 as I recall. Maybe you have a misprint.

RE: Measurement of S-Parameters

The above answer was not correct, This would represent the "power". The formal definition for S21 is b2/a1 when a2=0 (ie. the output port is connected to the reference impedance). Therefore, If the device is matched at input and output, VG1=a1, and V2=b2, so S21=V2/VG1.

RE: Measurement of S-Parameters

My point is that this is because of normalization of amplitude. From book:
Reinhold ludwig & Pavel Bretchko
"RF Circuit Design Theory and Applications"
Page 171-172
You can find solution there.
By the way, I have a question here,too. Does somebody know why we should normalize here? I feel confuing for the normalization factor in those formulas.

RE: Measurement of S-Parameters

When you perform calcualtions based on voltage & currents such as when using ABCD parameters, normallizing to 1 ohms really cleans up the equations. You can renormilize to the real port impedances when you are finished.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login

Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now
Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close