How to calculate SNR & SNDR in cadence spectre?

snr calculation in cadence

Hi~~~

I design a sigma delta ADC , and simulate it power spectrum density like attached file.
How do i calculate the SNR and SNDR in cadence spectre environment?
Is SNR only just look the picture to find difference between highest and noise floor ?

thanks~~!!

snr calculator

The SNDR can be calculated by the calculator in spectreRF. For the SNR, you need to exclude the distortion products shown in the spectrum. Remember, it is not the distance from signal peak to noise floor -- this distance is usually called SFDR (spurious free dynamic range). Only knowing the noise floor is not sufficient, you also need to know how many FFT points are within your signal-bandwidth and multiply the noise floor (convert back to absolute number, not DB) by the number of in-band FFT points.

snr and sndr

willyboy19 said:

The SNDR can be calculated by the calculator in spectreRF. For the SNR, you need to exclude the distortion products shown in the spectrum. Remember, it is not the distance from signal peak to noise floor -- this distance is usually called SFDR (spurious free dynamic range). Only knowing the noise floor is not sufficient, you also need to know how many FFT points are within your signal-bandwidth and multiply the noise floor (convert back to absolute number, not DB) by the number of in-band FFT points.

Click to expand...

thank you willyboy~
could you please tell me how should i calculate the SNDR in spectre calculator.
or where i can find any reference about it.
thanks a lot~~!!

spectre snr

willyboy19 said:

The SNDR can be calculated by the calculator in spectreRF. For the SNR, you need to exclude the distortion products shown in the spectrum. Remember, it is not the distance from signal peak to noise floor -- this distance is usually called SFDR (spurious free dynamic range). Only knowing the noise floor is not sufficient, you also need to know how many FFT points are within your signal-bandwidth and multiply the noise floor (convert back to absolute number, not DB) by the number of in-band FFT points.

Click to expand...

Could you please explain a little more how coz there is no SNDR function in the spectreRF calculator.

spectre sndr

The spectrum function allows you to compute SNDR (it is called SINAD).

how to calculate snr of spectra

wpchan05 said:

The spectrum function allows you to compute SNDR (it is called SINAD).

Click to expand...

Hi,

Sorry my friend I cant find this function. Where to find it ?

Here is the fuctions that in my Calculator.

snr and sndr sigma delta

Oops! The spectrum function is available on IC61 only.

calculate the dynamic range from power spectrum

wpchan05 said:

Oops! The spectrum function is available on IC61 only.

Click to expand...

Aha !
I've got IC5141 with mmsim6.1.

delta sigma snr calculator

Hi

May I know how you got the power spectrum density curve plotted from Cadence calculator?

Thanks

Re: delta sigma snr calculator

hiiiiiiii

I'm working on sigma Delta ADC
CAN ANY1 PLEASE HELP ME ON WORKING WITH CADENCE SPECTRE FOR snr CALCULATION

TRANSIENT ANALYSIS DON E WITH
FIN=50HZ (OSR=64) (SINE WAVE)
FS=12800HZ=CLK FREQUENCY

HOW MANY CYCLES I SHOULD RUN THIS TRANSIENT ANALYSIS??

wats d funda of skipstart,skipstop, strobeperiod
& HOW TO CHOOSE

STROBEPERIOD?
SKIPSTART?
SKIPSTOP?
IN ORDER TO CALCULATE snr
PLEASE HELP ME IN FIGURING OUT THESE VALUES...

In IC5141 version, Spectre doesn't provide SNR directly.
You need to enter the MDL mode which is activated by waveview status.
the commend as below
/> wavescan -expr mdl

then the calculation window will be shown.
you can find one commend "SNR" in the function window.
But, this commend can't be directly used so u need to create a math equation.

Re: snr calculation in cadence

chungming said:

Hi~~~

I design a sigma delta ADC , and simulate it power spectrum density like attached file.
How do i calculate the SNR and SNDR in cadence spectre environment?
Is SNR only just look the picture to find difference between highest and noise floor ?

thanks~~!!

Click to expand...

To find snr you should give input greater than bw/2 and to for sndr less than bw/3.

you can find snr and sndr by important your transient simulation in to matlab by .txt or .csv file.
use this code below remember to adjust signal and noise points according to your input and BW.

N = 65536;
F = [-N/2:N/2-1]/N;
F_s = 240e6;
F = F_s.*F;
y = blackmanharris(N).*bit1(1:N);




Y = abs(fftshift(fft(y,N)));
Y = Y.^2/N.^2;
Y = Y.*2;
Y(N/2+1) = Y(N/2+1)./2;

figure(7);
semilogx(F, 10*log10(Y)); % FFT of Quantizer output on a semilog plot
xlabel('Frequency');
ylabel('Power (dB)');
title('FFT of given Quantizer Output');
axis([0 F_s -140 0]);
%grid on;


% Noise Calculation
noise = 0;
for i = N/2+1 : N/2+548
noise = noise + Y(i);
end

% Signal Retrieval
signal =0;
for i2 = -5:5
signal = signal + Y(N/2+53+ i2);
end

noise = noise - signal;

% SNR Calculation
SNR = signal/noise;

SNR_dB = 10*log10(SNR);
ENOB = (SNR_dB - 1.76)/6.02;

Re: snr calculation in cadence

Hi Friends
What is in cadence?
What formula should I use to find out snr or sndr
In general, what should we do?

Thanks