Re: [BLACKBOX] Another LibVector question

From: [at]} <Robert>
Date: Sat, 28 Mar 2009 09:49:08 +0000

----boundary-LibPST-iamunique-1769054787_-_-
Content-type: text/plain

Wojtek Skulski wrote:
> It is truly confusing. The correlator adds its latency to the correlated
> waveform. The latency is equal to 1/2 the FIR length. But the Conv
> function adds the correlator length to the correlated wave.
>
> All the indices are now mismatched with respect to the original
> feature in the ADC waveform.

 > It is confusing at best. Any comments why it should be so?


Read the Docu extract I sent as a bitmap (*carefully*)!

(The extract was for Complex, for Real just ignore the Conjugations.)

The Docu explains how much the 'Correlation' output is offset, and why.

The 'Convolution' output is not offset.

Since, in your case, both functions return the same numbers these comments may
seem contradictory, but they are different functions with different meanings and
different purposes. Confusion, I contend, is generated by mentally mixing them.


If you want to eliminate the 'Filter settling times' then do:

z := Vec.Conv (x, h);
z := Vec.Take (LEN (x), Vec.Loose (ASH (LEN (h), -1), z));

This will line up z with x if the length of the filter h is odd. If it is even,
bad luck!, but you will be within half a sample.


Sometimes one wants the settling time data, sometimes one does not. If the
library function removed it you would not be able put it back when you wanted
to. This way you have the option.

Cheers

Robert

----
To unsubscribe, send a message with body "SIGNOFF BLACKBOX" to LISTSERV{([at]})nowhere.xy----boundary-LibPST-iamunique-1769054787_-_-
Content-type: application/rtf
Content-transfer-encoding: base64
Content-Disposition: attachment; filename="rtf-body.rtf"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----boundary-LibPST-iamunique-1769054787_-_---

Received on Sat Mar 28 2009 - 10:49:08 UTC