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

Easier way to realize a 2FSK LO in Xband

Easier way to realize a 2FSK LO in Xband

Easier way to realize a 2FSK LO in Xband

My current solution is Generate it at DDS and then modulate on L-band, then up-convert to X-band. This solution need a lot of components include a dds, two PLL, two Mixer and lots of amplifiers and filters and attenuators.
Because the 2FSK modulation is two simple, I'm wonder if there is some simpler method to go. Maybe switch between two normal X-band oscillator.
PS, the jitter should be less than 20 ns, the switch time should be less than 20 ns, the spur suppression should be greater than 60dBc, the phase noise should below -80dBc/Hz@1KHz.

Thank you

RE: Easier way to realize a 2FSK LO in Xband

Back in the old days (1970s smile ), experimentors would sometimes (often?) directly apply the baseband modulating signal to the microwave oscillator. Perhaps the oscillator (likely a Gunn diode in those days) was slightly sensitive to applied voltage. Or they'd put somnething in the resonant oscillator chamber. They'd directly shift the frequency of the x-band oscillator.

This approach was also related to AFC techiques. With appropriate design, the hardware can do both at once.

The data rates used by those experiments were quite low.

RE: Easier way to realize a 2FSK LO in Xband

The AFC is more like a frequency fine tune method with switch time of several us. My LO has 240MHz adjust range with step of 1MHz. So if I can use MOS SPDT between two Fractional-N PLL with the speed of 20ns with isolation of 60dB, the circuit is greatly simplified. But during rise-fall time the isolation is gradually changed, the smearing effect is a big problem, the total setup time is very long. I haven't seen prior art using several cascade switches to conquer the trade off of rise-fall time to isolation.

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