On Feb 21, 5:35*am, Bob <sten...@yahoo.com> wrote:
> On 21 Feb, 08:14, c...@claysturner.com wrote:
>
>
>
>
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> > On Feb 20, 4:38*pm, Bob <sten...@yahoo.com> wrote:
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> > > On 20 Feb, 20:41, Mark <makol...@yahoo.com> wrote:
>
> > > > > So now I see something,,,notice the small peak to the left of the
> > > > > cursor on the second and fourth traces. Should this not be the same as
> > > > > the peaks beside it?
>
> > > > remember you are looking at the RRC filter..which is only 1/2 the
> > > > picture
>
> > > > pass this output though another RRC filter so that you have the full
> > > > RC filter and you will see what the receiver sees...
>
> > > > the Rx and Tx have matched filters and the NYquist filter is both of
> > > > them in cascade,
>
> > > > you are looking 1/2 way through the cascade..
>
> > > > Mark
>
> > > Hi Mark,
>
> > > The pulses you see on the first link is what happens when I pass the
> > > data through the RRC on the TX link. On the demod side links 2 and 3
> > > are when the data from the modulator is passed through idential RRCs.
> > > So, in effect I already have the RC response at the receiver. But is
> > > it correct...that's what I would like to know?
>
> > > Bob- Hide quoted text -
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> > > - Show quoted text -
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> > Hello Bob,
>
> > The feeding of pulses into the RRC filter (via convolution) assumes
> > your pulses become Kronecker deltas. Don't feed rectangular pulses,
> > instead feed spikes into the RRC filter. Then after going through two
> > of these in sucession, you will see a nice looking signal. You are
> > currenly getting a bunch of ringing resulting from the rectangular
> > pulse's response comingled (convolved) with the RRC's response. For
> > simplifying the testing, just try an RC filter and look at its output.
> > Two RRCs convolved is an RC. Try it!
>
> > IHTH,
>
> > Clay- Hide quoted text -
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> > - Show quoted text -
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> Hi Clay,
>
> I did already try it. I fed the output of one RRC into another and
> you're correct...I did get a nice RC pulse output.
> In the test case, this was done for spikes well seperated. However,
> for real test data, I don't have much choice as I have strings of 1's
> and in most cases very few 0's between them. In this case, what are my
> options?
>
> Regards
> Bob- Hide quoted text -
>
> - Show quoted text -

Hello Bob,

The overall RC response does two major things for you. First it limits
your spectral splattering by effectively making your spectral shape
fit inside of a rectangular window[1]. And second you have periodic
zeroes so your ISI is kept down to a minimum. Look at your data's eye
pattern and make sure the eye is open enough at the decision points to
tell your ones from your zeroes. The data under a low S/N is going to
look bad.

IHTH,
Clay

[1] The rectangular shape ideally will have vertical sides made up as
pieces of cosines. But a practical implementation will have other
distortion as you will end up limiting your impulse repsonse's
duration to something finite.