×
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

ADS question

ADS question

ADS question

(OP)
Hi,

I am simulating an LNA for NF. I loaded the antenna S parameters to the input port. But when running the simulation there was a problem "No DC convergence" I am using a spice model for the main transistor. Simulating the LNA with 50R is ok, but the problem comes when loading the antenna S11 into the port 1.

Does anyone have an idea of what´s going on?

Thanks.

RE: ADS question

Sounds like you are using the non-linear analyzer.  Did you remember to include the bias lines/dc voltages/DC blocks?

www.MaguffinMicrowave.com

Maguffin Microwave wireless design consulting

RE: ADS question

(OP)
Hi,

yes, I used the DC blocks, it´s a good point.

When I used a 50R input port the circuit works perfectly, without problems. When I replace the 50R by a S1p file then ADS says "No DC convergence". Strange!!!

I you have any other ideas they will be welcome!

Thanks.

RE: ADS question

What happens if you put a (virtual) high value resistor, like 100K ohms, between the input and ground? Just to give the algorithm something to work with. This is based on the assumption that your antenna element is essentially an open circuit at DC.  

RE: ADS question

(OP)
Hi,

I have tried that but it didn´t work.

I have attached the ADS file in case you have time and can have it a look. When I load the input with a 50R port the circuit works fine, but when I load the antenna impedance then there are some problems, before I had the "no DC convergence" then I changed the way to import the antenna impedance and now it has some problems at one frequency, strange!

 

RE: ADS question

Well if 50R works and 100K doesn't, then as a first step perform a log-scale binary search pattern to see where it stops working. If it requires 5K (for example) instead of 100K, then at least it might help you to get started again.

 

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