Designer’s Guide Community

mohammadreza

Junior Member

Offline

Posts: 19

Cadence Convergence Error
Jul 27^th, 2010, 4:25am

I am simulating an RF Power Amplifier in Cadence, SpectreRF environment. I am controlling the supply current by a seperate voltage applied to a transistor. For some values that I choose, I face with convergence error, both in PSS and Transient. However, when I remove my mathcihng network and replace it by a real load value that I had designed, I face no errors.

Is there any way for setting the options correctly so that I don't lose accuracy and have my expected result? I have tried the Moderate and ven liberal presets but the moderate one faces error as well and the liberal one is completely away.

Back to top

IP Logged

mohammadreza Junior Member Offline Posts: 19	Re: Cadence Convergence Error Reply #1 - Jul 27^th, 2010, 5:08am Thanks, I didn't see any HB-engine. Just shooting and flexible balance. I chose flexible balance and it worked. About the Q, since I need to operate between 2.4GHz and 2.49GHz, I chose 300. Is that fine? thanks
Back to top	IP Logged

mohammadreza Junior Member Offline Posts: 19	Re: Cadence Convergence Error Reply #2 - Jul 27^th, 2010, 5:29am thanks! decreasing the Q helped run the simulation successfully with the moderate accuracy.
Back to top	IP Logged

pancho_hideboo

Senior Fellow

Offline

Posts: 1424
Real Homeless

Re: Cadence Convergence Error
Reply #3 - Jul 27^th, 2010, 7:16am

pancho_hideboo wrote on Jul 27^th, 2010, 4:30am:

Maybe your matching network has very high Q.
High Q could cause convergence failure for time domain solver.

Use HB-engine not Shooting-Newton-engine in PSS of Cadence Spectre.

mohammadreza wrote on Jul 27^th, 2010, 5:08am:

I didn't see any HB-engine.
Just shooting and flexible balance.
I chose flexible balance and it worked.

See http://www.designers-guide.org/Forum/YaBB.pl?num=1258711290/1#1

mohammadreza wrote on Jul 27^th, 2010, 5:08am:

About the Q, since I need to operate between 2.4GHz and 2.49GHz, I chose 300.
Is that fine?

BW_3dB=f0/Q=2.445GHz/300=8.15MHz. It is too narrow.

You have to have broad BW_3dB which is far broader than 90MHz.
So set Q lesser than 27.

Also see the followings.
http://www.designers-guide.org/Forum/YaBB.pl?num=1207009725/2#2
http://www.designers-guide.org/Forum/YaBB.pl?num=1278414763/18#18

mohammadreza wrote on Jul 27^th, 2010, 5:29am:

decreasing the Q helped run the simulation successfully with the moderate accuracy.

Your case summaries are followings.

For Q>=300, Shooting-Newton-PSS with accuracy of moderate can not converge.
For Q<30, Shooting-Newton-PSS with accuracy of moderate can converge.

For Q>=300, HB-PSS with accuracy of moderate can converge.
For Q<30, HB-PSS with accuracy of moderate can converge.

Are the aboves correct ?

Back to top

« Last Edit: Jul 28^th, 2010, 6:28am by pancho_hideboo »

Kita━━━━━━(ﾟ∀ﾟ)━━━━━━ !!!!!
http://www7.plala.or.jp/ungeromeppa/flash/kita.html
http://www.youtube.com/watch?v=mjIxGh55bMM&feature=related

IP Logged

mohammadreza Junior Member Offline Posts: 19	Re: Cadence Convergence Error Reply #4 - Jul 28^th, 2010, 5:41am Yes, that's right
Back to top	IP Logged