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dft error with a valid transient waveform

Aldo2

Hello,

I want to calculate the dft of a transient waveform.

Thought vtime('tran "/out") is a valid waveform (it can be plotted with no error), I get the following error message:

*WARNING* yvector wrong type.

expression evaluation failed: val is not legal.
expression evaluation failed: dft(vtime('tran "/out") 100n 200n 1024 "Rectangular" 1 "default" 1.0 )
"(\"putprop\" 0 t nil (\"*Error* putprop: first arg must be either symbol, list, defstruct or user type\" nil))"

I tried also with VT("/out"), but the same error appeared.

I am using ic 615isr20121027 and mmsim 15.10.602

Thank you

Best regards,

Aldo

  • Hi Aldo,

    Have you by any chance set the output format to "psf with floats" on the Options->Save Options (in the Output Format choice at the bottom)? If so, this is a limitation - the DFT implementation doesn't support single-precision floating point numbers for the y-values. 

    You need to pick psf, psfxl or sst2. The only reason to use "psf with floats" (or psfbinf) would be to save disk space - but it does have this limitation (CCR 1607385) currently.

    Assuming that's what you're seeing that is!

    Regards,

    Andrew.

  • Hi Andrew,
    I selected "psf with floats" trying to have a faster post-processing.
    Is psfxl the fastest format? What about fsdb?

    Thank you
    Best regards
    Aldo

  • Hi Aldo,

    psfxl is intended to be the format for faster reading of the data into ViVA. fsdb is mainly there to support use with third-party tools (it's not our format), and so I wouldn't necessarily want to suggest that (I don't know how universal the support is, especially as you're using an older version). Once the data is read in, it should really matter which format was picked (other than if you only have single precision numbers). One issue with psfbinf is that you only get about 7 decimal significant digits.

    Generally speak if you only have small numbers of points, it doesn't matter that much. If you have millions of points, and/or tens or hundreds of thousands of signals, pick psfxl. I'd also suggest using IC617 rather than IC615 if you're concerned about performance.

    Andrew.

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