Contact US

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

matching of transformer coupled circuit

matching of transformer coupled circuit

matching of transformer coupled circuit

dear forum,

I´m using a passive circuit with two coils (one at each end) for relaying a signal between an RFID tranceiver and a transponder. The system operates at 13.56 MHz.
So far I only use a series resistor and a series capacitor for resonance frequency in the passive relay circuit. The distance between the two coils is only 2 -3 cm, and I have connected it by twisting a copper wire.

I´m wondering if I have to macth each end of the passive circuit to 50 ohm? (or to each other) to avoid reflections?
Any opinions on this?

RE: matching of transformer coupled circuit

While I can't picture your circuit exactly, I expect that if you go through the RLC calculations you'll see that 50 ohms will severely detune your resonator (very low Q) and you'll have poor coupling between the two antennas.  

Matching the transceiver and transponder antennas to each other might give some improvement; think of it as a transformer.  

At 13.56 MHz your wavelength is extremely long (about 22 meters) so reflections over 2-3 cm will not be a problem.  

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


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