set the parameters of the fourier component from analogLib

Hi all,
I am designing a Sample and hold circuit. I am using cadence for all
the schematics and simulations(spectre).

I need to calculate SFDR (Spurious Free Dynamic Range), THD and SNR
for the S&H, I added the fourier component FOUR0 from analogLib into
to my schmetic, and then do "check and save"
CIW shows "Schematic check completed with no errors."

However, when I did the transient simulation in ADE, it show "Cadence?
Analog Distributed Processing option: Job `job' failed with exit
status = 1"

What does it mean? How to setup the parameters of FOUR0?

How to calculate the SFDR (Spurious Free Dynamic Range), THD and SNR
of the sample and hold circuit?

Thanks!
Tony

 

Tony wrote, on 02/09/09 01:51:

Tony,

All that tells me was that the job failed.

Did you enter any parameters on the fourier component? What does the spectre
output log say - that's far more likely to tell you useful information than just
the fact that the job failed for some reason - it might even tell you _why_ it
failed!

Regards,

Andrew.

 

Hi Andrew,
Thanks for your suggestion, I checked the output log, it says

Error found by spectre during transient analysis `tran'.
ERROR (CMI-2384): FOUR0: the Period of fundamental frequency is
longer than simulation interval.

then I changed the Period of fundamental frequency, and now it works
fine.

one more question:
my circuits work now, how to measure THD and SFDR with this FOUR0?
where can I see the results of FOUR0?

Kind Regards,
Tony

 

Tony wrote, on 02/10/09 01:48:

Tony,

You should be able to find the spectral data via the results browser. From this
you could either compute the THD by hand, or you could just use the standard
calculator THD function on the transient results - the fourier analysis should
(I think) have improved the timestep placement so that the accuracy of the
post-processing DFT approach would be improved.

Do you have access to the "Designer's Guide to SPICE and Spectre" by Ken
Kundert? There's a good chapter in there for fourier analysis.

Andrew.

 

Hi Andrew,

Thanks for you help. I 've solved the problem and I can see the
results of THD now.
Sure, I am reading chapter 5 of the book "Designer's Guide to SPICE
and Spectre", It is helpful to me.

Kind Regards,
Tony