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andy2000a
Joined: 18 Jul 2001
Posts: 767
Helped: 7
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 29 Aug 2003 9:16 adc sfdr |
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How to simulation SNDR on hspice ?? someone said use .Four Fin
and will find THD , SNDR=THD
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rfsystem
Joined: 25 Feb 2002
Posts: 858
Helped: 96
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29 Aug 2003 22:01 finding enob of adc |
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So Hspice means pure analog simulation. So you get a anlog vector of a digital signal. So you have to convert to 1bit per sample. So write the vector as asci. Read into Matlab. Convert to 1bit and sample at the right point. So you get much shorter vectors than the Hspice result because for each period of the sample clock you have 100s of time samples placed irregular. Compose from the 1bit vectors a integer number vector. Then make the analysis in Matlab with the help of the toolboxes.
With mixed mode spice simulators supporting some HDL you can write the same stuff running as analysis bench withhin the simulation. But I think it is not possible in Hspice.
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andy2000a
Joined: 18 Jul 2001
Posts: 767
Helped: 7
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05 Sep 2003 2:12 sfdr inl |
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I use hspice simulation THD ..
1. use ideal DAC convert ADC output to analog signal
2. use .four freq v(out)
and use THD equation
ENOB = (THD- 1.76 ) /6.02
but simulation THD is small , ENOB looke like very small ..
someone said hspice must be choose correct cycle time for FFT simulation
I don't know know to write ENOB code for matlab
if I use hspice simulation ADC .. I can write down ADC output value
but how to simulation INL/DNl/ENOB by matlab ??
and ADC need how many cycle ? or just only need 1 cycle A/C convert ?
can you give me matlab code ?
thank you
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rfsystem
Joined: 25 Feb 2002
Posts: 858
Helped: 96
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08 Sep 2003 21:48 sfdr in adc |
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Sorry, I did not have the code. I heard about it because of the troubles users have with postprocessing spice results.
Indeed, you need to use a rectangular window for FFT and put in a integer number of sines. Then after some decay time of initail transients you will be free of spectral leakage. So ENOB is calculated from the ratio of sine power to every other signal power. I don not know the exact formular, but it is not a simple THD.
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bastos4321
Joined: 01 Jan 1970
Posts: 341
Helped: 24
Location: space
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08 Sep 2003 22:58 adc enob code |
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The algorithm to calculate INL and DNL using the histogram method is presented here.
Joey Doernberg, Hae-Seung Lee and David A. Hodges, “Full-Speed Testing of A/D Converters”, IEEE Journal of Solid State Circuits, Vol. SC-19, No. 6, pp. 820-827, December 1984
BAstos
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