i need help to maesure the SNR of T/H circuit

[wael_wael]

db maesure

Hi every body,

what is the way of maesuring the SNR of the track/hold circuit. could some one help me.

bcs i dont know how to do it.

best regards

 

[yxo]

Hi!
You have to make fft or dft analysis and then SNR=20log(Asig/An)
Asig - amplitude of an input signal
An - RMS value of output noise with cuted harmoics and input signal. Or more simply, In Cadence you can use MDL calculator. It has the function of RMS

 

[wael_wael]

thank u so much but i need more details, i cant under stand what i have to do exactly:
first i do fft of the output signal than i find the amplitude of the input there(the amplitude should be compare to minimum level or to the noise??
the second step i not understand.
do u have any artcal about it??
best regards

 

[wael_wael]

pls, Could some one help me, i am still dont know the way
best regards

 

[ljy4468]

hi wael,

when you perform FFT, there is FFT output. (fft magnitude)

Then you can calculate SNR through that output file with MATLAB.

So if you want m-file, I can send you.

Thanks.

 

[wael_wael]

thank you so much for ur reply, now i have fft file of the ouput, so what is steps after that, how to calculate the SNR?
pls send the m-file i will be very thnkfull.
regards

 

[yxo]

what soft are you using? In cadence you can calculate SNR with a function in calculator

 

[ljy4468]

Here is a excel file and example for 256point fft.

You just fill fft_mag(db) (C4, C5, C6, C7.....) from output file.
then at I132, subtract fundamental bin.

In my example, G6 magnitude is 0dB, this is fundamental bin.

So subtract that.

Hope that it can help,
thanks.

Regards.

 

[wael_wael]

what soft are you using? In cadence you can calculate SNR with a function in calculator

Tanner, Tspice

Added after 8 minutes:

Here is a excel file and example for 256point fft.

You just fill fft_mag(db) (C4, C5, C6, C7.....) from output file.
then at I132, subtract fundamental bin.

In my example, G6 magnitude is 0dB, this is fundamental bin.

So subtract that.

Hope that it can help,
thanks.

Regards.

realy thank u so much, i have the fft magnitude in db bcs my simulator has the function of fft, but i have to subtract the fft magnitude with what that is my question (what is "the fundamental bin") do u mean the input frequency to the minimum level of the fft output . for the table i will do what u said but i need first understand the way.
thank u so much again and i hope one day i come to see ur country i have money friends from there
best regards