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Simulators >> Circuit Simulators >> track and hold circuit DFT analysis
https://designers-guide.org/forum/YaBB.pl?num=1178736051

Message started by vhdl00 on May 9^th, 2007, 11:40am

Title: track and hold circuit DFT analysis
Post by vhdl00 on May 9^th, 2007, 11:40am

Hi, I was trying to do DFT analysis to my track and hold circuit. How to chose the sample points? The sample frequency has to be the same as Clock? I am considering using coherent sampling.

Thanks for any inputs.

-steve

Title: Re: trank and hold circuit DFT analysis
Post by ywguo on May 10^th, 2007, 12:53am

Hi,

If that is a track-and-hold at the front-end of ADC, I think that the sampling frequency should the same as the clock. I would choose the sampling points where the output has settled. If using HSPICE, the print step of .tran can be set equal to the cycle of clock. Then print the output using .print card. Try to run a DFT using Matlab. Sometimes we also using .FFT card in HSPICE. However, I am not clear how to set the sampling point accurately. :(

Yawei

Title: Re: trank and hold circuit DFT analysis
Post by vhdl00 on May 10^th, 2007, 6:35am

Thanks for your response. Yawei.

I was confused after I tried import output data to matlab, we have to choose sampling points to do fft.

I was trying to use the sampling frequnecy same as clock, seems OK. Just want to know if there are some other ways?

thanks again

-Steve

Title: Re: track and hold circuit DFT analysis
Post by ywguo on May 12^th, 2007, 1:19am

Steve,

Yes, you have to choose sampling points to do DFT after importing the data into matlab if the print step of .tran is not equal to the clock cycle. However, I set the print step of .tran equal to the clock cycle.

Does sampling frequency in your post mean sampling frequency of FFT?

Yawei

Title: Re: track and hold circuit DFT analysis
Post by vhdl00 on May 12^th, 2007, 6:02am

Yawei,
The sampling frequency I was talking is the one in post-simulation processing FFT in matlab. I will just used your suggestion to set the step size in simulation the same as the clock frequency.

Thanks again,

-Steve