Re: [oc] SNR Calculation using CADENCE SpectreS tool

[tcoffman_az@hotmail.com]

Hello Lokesh,

You've probably found the answer, but just in case:

Use the OCEAN command, sample and ocnPrint.

For example,
You have a bit stream from your sigma-delta that you'd like to post-
process in Matlab, but the Cadence produces too many points at the 
transitions of each pulse. I used that following command in the CIW:

ocnPrint( ?output "/users/you/filename" sample(VT( "/OUT1" ), 
20n,340u,"linear",78.125n) )

This sigma-delat has a sample clock of 12.8MHz, hence the 78.125n 
sampling. I sampled from 20n to 340u in linear steps and printed the 
results to a file, /users/you/filename. The bit stream is a transient 
voltage on node "/OUT1".


I hope this helps. It worked very well for me.

Regards,

Tim

----- Original Message ----- 
From: electronicszone@y...  
To: cores@o...  
Date: Fri, 3 Aug 2001 16:19:18 +0200 
Subject: [oc] SNR Calculation using CADENCE SpectreS tool 

> 
> 
> Dear Sir, 
>                        I am  working on a Sigma-delta ADC.          
>             Currently I am  working on CADENCE spectreS tool to 
> simulate the modulator.                                             
>                                                            I have a 
> second order modulator . The bandwidth of the input is 12.5MHz. The 
> oversampling ratio is only four (so sampling freq. is 100MHz). I am 
> working on a cascaded (MASH) modulator in which the second stage 
is 
> a 10-bit Pipelined ADC. The flash ADC inside the modulator is a 
> 4-bit one. Currently, I have designed the 2nd order modulator using 
> Switched capacitor filters.  Now, I want to calculate the Signal to 
> Noise ratio at the output of the Modulator.  Can you please help me 
> how to calculate SNR using CADENCE? Since, I have just started 
> working on CADENCE, i don't know much the features of this tool. 
> 				While doing its behavioral 
simulation in  MATLAB, i used the 
> PSD command in the MATLAB and since I know the input signal 
> frequency, I calculated the signal power and the rest as the Noise 
> power to get the SNR. I thought to use that SNR routine only (as i 
> used in MATLAB) to calculate the SNR of the output of the modulator 
> generated in CADENCE spectreS tool. But the problem is that this 
> tool, during its transient analysis, does not generate samples at 
> regular interval. So, i cant use the PSD command available in 
> MATLAB to calculate the PSD of the output of the modulator to 
> calculate the SNR. 
> 		Sir, please give me a suitable solution for the same. 
> waiting for a positive reply. 
>                                    Thanking You 
> Yours sincerely 
> Lokesh Kumath 
> 
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