>Bern and Stan,

>My signal processing is a little rusty, but I believe that a

>multiplication in the frequency domain is a correlation in the time

>domain. So the process is to fft the signal and the raised cosine,

>multiply the 2 together and then take the inverse fft, and that should be the correlation you are

>looking for. For this to work quickly, you need your signal lengths to be

>a power of 2 and I think you will need to use the same lengths for both.

>You can do the fft of the raise cosine and save it, so you only need to

>do that calculation once.

>Bill

Well - just to be picky-- multiplication in one domain corresponds to _convolution_ in the other domain. Similar to correlation though.

In any case if you have time domain processing available you really don't want to do the transforms- just too many gotchas.

correlation _should_ do the job.

Stan

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>Bern and Stan,

>My signal processing is a little rusty, but I believe that a multiplication

>in the frequency domain is a correlation in the time domain. So the

>process is to fft the signal and the raised cosine, multiply the 2 together

>and then take the inverse fft, and that should be the correlation you are

>looking for. For this to work quickly, you need your signal lengths to be

>a power of 2 and I think you will need to use the same lengths for both.

>You can do the fft of the raise cosine and save it, so you only need to do

>that calculation once.

>Bill

Well - just to be picky-- multiplication in one domain corresponds to

_convolution_ in the other domain. Similar to correlation though.

In any case if you have time domain processing available you really

don't want to do the transforms- just too many gotchas.

correlation _should_ do the job.

Stan

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From: Stan Bischof (Richard S) <rsb@soco.agilent.com>

Date: Mon, 1 May 2006 13:31:42 -0700 (PDT)

To: lbill@us.ibm.com

Subject: Re[2]: [vrf] Raised Cosine

>Bern and Stan,

>My signal processing is a little rusty, but I believe that a multiplication

>in the frequency domain is a correlation in the time domain. So the

>process is to fft the signal and the raised cosine, multiply the 2 together

>and then take the inverse fft, and that should be the correlation you are

>looking for. For this to work quickly, you need your signal lengths to be

>a power of 2 and I think you will need to use the same lengths for both.

>You can do the fft of the raise cosine and save it, so you only need to do

>that calculation once.

>Bill

Well - just to be picky-- multiplication in one domain corresponds to

_convolution_ in the other domain. Similar to correlation though.

In any case if you have time domain processing available you really

don't want to do the transforms- just too many gotchas.

correlation _should_ do the job.

Stan

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Stan Bischof Agilent Technologies 707-577-3994 stan_bischof@agilent.com

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