Home > Community > Blogs > RF Design > spectre rf mmsim 12 1 preview of coming attractions
Login with a Cadence account.
Not a member yet?
Create a permanent login account to make interactions with Cadence more convenient.

Register | Membership benefits
Get email delivery of the RF Design blog (individual posts).


* Required Fields

Recipients email * (separate multiple addresses with commas)

Your name *

Your email *

Message *

Contact Us

* Required Fields
First Name *

Last Name *

Email *

Company / Institution *

Comments: *

MMSIM 12.1 SpectreRF -- Preview of Coming nport Attractions! Part 2

Comments(5)Filed under: Virtuoso Spectre, Virtuoso Spectre Simulator GXL, Spectre, Spectre RF, Harmonic Balance, spectreRF, MMSIM, Circuit simulation, ADE-L, RF Simulation, Analog Simulation, ADE, RF, RF spectre spectreRF, simulation, spectre spectreRF, nport, nport settings, analog, HB, analog/RF, Wilsey


MMSIM 12.1 contains many new features to aid RF designers.  Many of these changes are described in my Part 1 blog post.

I've saved my favorite for last....here's a preview of the changes to the nport component in MMSIM12.1.

1.  The Edit Object Properties/Add Instance form has been revised for better usability. 

2. For most S-parameter files, only the S-Parameter file name and the number of ports need to be specified.  (See the red boxes in the GUI below).  The default settings for all of the other properties are suggested.

     nport1a gui

3.  When you select the Browse and select s-data file button, the following GUI appears and allows you to browse and select the desired s-parameter data file.  Once you do that, the filename is populated into the GUI..

nport 12.1 browse and select

4. The causality check is more robust.

5. The impulse response is adaptively sampled and is automatically cached so that it can be re-used in subsequent simulations. The cache location can be specified so that multiple users can share the same caching directory. The two options that control caching are located in the ADE options; Simulation -- Options -- Analog.

nport cache

nportirreuse enables caching of the impulse response.  Keep this at the default to save time.

nportirfiledir controls the location of the cached impulse response files. The default (blank) sets the location to /home/<username>/.cadence/dfII/mmsim. When a directory name is specified in the nportirfiledir option, the impulse response files are cached in the specified directory. This can be a shared directory between users, as long as all the users have write permissions in that directory.

6. Improved error messages makes troubleshooting problematic s-parameter files much easier!

  • The S-Parameter file is examined for common problems like discontinuities in the data, or imaginary part at DC, and this information is sent to the Spectre output file.
  • Passivity and Causality violations reported in the spectre output logfile have more useful information.

7. New Touchstone formats supported:

  • Touchstone 1 file format with multiple impedances. 
  • Touchstone 2 file format.

I'm sure you'll agree that the new nport is much easier to use in MMSIM12.1.

Have fun simulating!

Best Regards,



P.S.  Make sure you are using IC6.1.5 ISR14 or later to see these new features in the environment. 


By Frank Wiedmann on November 21, 2012
The new nport indeed brings big improvements. We compared simulation results with those of corresponding Sonnet broadband models and got very good matching in transient simulation. Unfortunately, the new nport does not yet work reliably for shooting pss. Depending on the circuit, the simulation results may be completely wrong in this case. An enhanced version that also works for shooting pss has been promised to us for next year.

By Tawna on November 21, 2012
Hi Frank,  the nport is optimized to work with the Harmonic Balance engine.  We don't recommend using it with the shooting engine at this time.   You are correct that R&D is working on improving the nport for the shooting engine.  Best regards,   Tawna

By Frank Wiedmann on November 22, 2012
For us at Rohde & Schwarz, shooting pss is pretty important. You can find some details at www.cadence.com/.../RohdeSchwarz_cs.pdf .

By Tawna on November 23, 2012
Hi Frank,
I have no doubt that shootin g PSS with  nports is important for you and many other customers.  
Do you have CCRs filed requesting enhancements to nport/Shooting PSS?  Please feel free to contact me offline to discuss this.
best regards,

By Tawna on November 23, 2012
Hi Frank,
We are aware that nport w/ shooting pss improvements are very important to you and many other customers.
It is something that R&D is/will be working on.
Please work with your Support AE regarding the CCRs you’ve filed on this issue.
You are welcome to contact me offline should you have other questions/comments about this.
Best regards,

Leave a Comment

E-mail (will not be published)
 I have read and agree to the Terms of use and Community Guidelines.
Community Guidelines
The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.