Irregular Power Spectrum Density when decomposing spectrum with autoregressive model

[yosukeT]

Hello.

I need help.

Now I'm trying to decompose spectrum for calculating Heart Rate Variability (HRV) with AR coefficient in LabVIEW Advance Signal Processing Toolkit.

Already I can decompose spectrum.

However, sometimes I have calculated irregular spectrum ,which are attached in this discussion, depending on AR order.

Have you ever calculated such irregular spectrum?

If you have ever seen the irregular spectrum pattern, please give me a solution.

the calculation program which I made could be wrong, But I’d like to ask your opinion.

Sincerely.

yosukeT