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# IP3, IP2 simulation in cadence

Last post Mon, Apr 16 2012 1:31 PM by Tawna. 1 replies.
 Started by lijulia 13 Apr 2012 05:04 PM. Topic has 1 replies and 2408 views
• #### Fri, Apr 13 2012 5:04 PM

• lijulia
• Joined on Fri, Mar 5 2010
• Posts 7
• Points 105
 Hi, I am simulating the RF+mixer_LO gen ( with div4 circuit inside ), what is the best way to simulate the ip3 and ip2 for the whole chain?flo=2.8G, div_ratio=4frf1=720M, frf2=721M I tried hb with sweeping the input power,  but get the wired result, what should I put in the LO and RF ports? Or I can use rapid IP3, IP2 simulation method?or anything else?  Thanks for your help
• Post Points: 20
• #### Mon, Apr 16 2012 1:31 PM

• Tawna
• Joined on Thu, Jul 10 2008
• Snohomish, WA
• Posts 212
• Points 5,625
Re: IP3, IP2 simulation in cadence

Hi Julia,

I assume that you are simulating a receiver rather than a transmitter.

If your circuit has a divider, you may want to look at the following solution on Cadence Online Support:

11571722 (COS) Guidelines for simulating frequency dividers in spectreRF

The shooting engine is designed for strongly nonlinear circuits such as ring oscillators and circuits that have frequency dividers.    For information on whether to use the Shooting Newton vs the Harmonic Balance engine, see support.cadence.com Solution 11310266: When to use shooting Newton vs. harmonic balance . http://support.cadence.com/wps/mypoc/cos?uri=deeplinkmin:ViewSolution;solutionNumber=11310266

You will also need to set your tolerances appropriately in order to get accurate results also make sure you set enough harmonics.   For circuits with a divider, you should set tstab to 5X the period (after the divider) and set saveinit=yes (so you can verify that your circuit has settled).   The number of harmonics chosen for the nonlinear signal should be at least 5X the divide ratio.

If you are using harmonic balance, I recommend looking at

11603066 (COS) How to simulate a combination of a frequency tripler and divider with SpectreRF HB analysis

If you are a newer user to SpectreRF, I strongly encourage reading the following blog posts:

There are also a number of workshops/tutorials (again, if you are a newer user).  SpectreRF AppNotes and Tutorials....Still One of our Best Kept Secrets!

Best regards,

Tawna

Best regards, Tawna Wilsey Staff Support AE, Global Customer Support Cadence Design Systems, Inc.
• Post Points: 5