×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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

Limit to square wave output frequency?

Limit to square wave output frequency?

Limit to square wave output frequency?

(OP)
I'm by trade a structural guy but I want to build a small cyclotron as a hobby project using rare earth permanent magnets. I want to use off the shelf RF equipment to produce the ion excitation and I'm wondering if it's easy or even possible to produce a square wave output at 10-20 MHz? It seems kind of fast to do anything but sinusoidal but maybe not. Can anyone give me a yes or no?
Thanks
-Todd

RE: Limit to square wave output frequency?

A square wave is just like a normal sinusoidal wave except that it has plenty of odd harmonics (each at the appropriate amplitude).

For example, if you're looking to create a square wave of 20MHz, then your circuits need to be able to handle at least 60MHz to produce a waveform that even looks slightly like a square wave.  A 'nice' 20 MHz square wave would require harmonics well above 100 MHz.

The issue for you isn't really creating a nice 20 MHz square wave (that's easy) - the issue is creating a nice 20 MHz square wave that is capable of driving your cyclotron (I assume that is what you're up to...).

Which leads to the next question:

Are you sure you want a square wave?

Circular motion and sin waves are one in the same.  If you're using the 10-20 MHz wave to drive the cyclotron, then you likely just need a nice easy sin wave (from any HF transmitter).

If you're going to be using much power, then choose an ISM frequency like 13.56 MHz (check the regs).

 

RE: Limit to square wave output frequency?

And unless you're licensed, randomly spitting out RF is illegal

TTFN

RE: Limit to square wave output frequency?

(OP)
Well I have been looking around for square wave generators and it seems there are some that will do what I want and are tunable. Is it possible to just amplify that signal without losing the form of the wave?
Also to IRstuff I'm planning on having a faraday cage around my project, so hopefully the Feds won't show up at my garage.
thanks for the help
-Todd

RE: Limit to square wave output frequency?

A faraday cage isn't a perfect device.  If you will be generating squarewaves for your experiment remember that the odd harmonics of the fundimental may have substantial energy.  One thing to keep in m ind is that Ham operators talk around the world on a few hundred miliwatts and less.

I remain,

The Old Soldering Gunslinger

RE: Limit to square wave output frequency?

What does a cyclotron load look like?  Capacitive?  What are the voltage and curent requirements?  As mentioned before, ham gear may be just the ticket, modified for your square wave.  Are you sure you want a square wave?  If so, what rise time is needed?

RE: Limit to square wave output frequency?

If your cyclotron needs a bit of power at 20MHz, as I suspect it will, and you are driving it with anything resembling a square wave then you have a serious shielding issue on your hands.  A 20MHz square wave from a fast source will have significant amplitude harmonics well into the hundreds of MHz.  

For a faraday cage to be effective it needs to be electrically continuous with all joints soldered/ welded/ sealed with finger-stock or RF gaskets, everywhere and have a filtered power entry.  A metal box grounded is not a faraday cage and will pass lots of radiation at the higher frequencies.  Eg, a riveted metal box with rivets every 4" is ineffective as a shield above say 500MHz due to the tiny gaps formed by sheet buckling between the rivets.

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