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Thread Subject:
Frequency Analysis

Subject: Frequency Analysis

From: Shane

Date: 15 Aug, 2013 14:03:09

Message: 1 of 6

I have some sample data and I can extrapolate the main frequency 20505Hz but the signal repeats 17Hz and this frequency does not show up. Here is a link to my data file and code. Can anyone help me get the 17Hz to show up in my frequency analysis.

https://dl.dropboxusercontent.com/u/12589/009-diff.lvm

https://dl.dropboxusercontent.com/u/12589/lvm_import.m

https://dl.dropboxusercontent.com/u/12589/lvm_import_shane.m

Subject: Frequency Analysis

From: dpb

Date: 15 Aug, 2013 14:31:22

Message: 2 of 6

On 8/15/2013 9:03 AM, Shane wrote:
> I have some sample data and I can extrapolate the main frequency 20505Hz
> but the signal repeats 17Hz and this frequency does not show up. Here is
> a link to my data file and code. Can anyone help me get the 17Hz to show
> up in my frequency analysis.
...

What was sample rate and more importantly, sample duration?

--

Subject: Frequency Analysis

From: Shane

Date: 15 Aug, 2013 15:33:21

Message: 3 of 6

The sample rate was 250kHz and the duration was 5 seconds

Subject: Frequency Analysis

From: dpb

Date: 15 Aug, 2013 19:16:28

Message: 4 of 6

On 8/15/2013 10:33 AM, Shane wrote:
> The sample rate was 250kHz and the duration was 5 seconds

A 17 Hz signal therein can have at most 85 cycles as compared to ~2k*5
for the dominant. The comparative energy at the two is thus likely
miniscule -- you can try to lowpass filter if a log scale doesn't bring
it out on baseband analysis.

--

Subject: Frequency Analysis

From: Godzilla

Date: 16 Aug, 2013 02:53:08

Message: 5 of 6

dpb <none@non.net> wrote in message <kuj9ed$8vf$1@speranza.aioe.org>...
> On 8/15/2013 10:33 AM, Shane wrote:
> > The sample rate was 250kHz and the duration was 5 seconds
>
> A 17 Hz signal therein can have at most 85 cycles as compared to ~2k*5
> for the dominant. The comparative energy at the two is thus likely
> miniscule -- you can try to lowpass filter if a log scale doesn't bring
> it out on baseband analysis.
>
> --

also, what is the signal-to-noise ratio?

Subject: Frequency Analysis

From: Shane

Date: 16 Aug, 2013 11:18:07

Message: 6 of 6

i'm not sure what the signal to noise ratio is

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