Talk:Raised-cosine filter

message: "The care and feeding of digital, pulse-shaping filters" is no longer available at the link address. But I've found it here:
https://www.nonstopsystems.com/radio/pdf-hell/article-raised-cosine.pdf
(though there is no guarantee it will stay there... so I didn't change the article)  — Preceding unsigned comment added by 190.50.122.151 (talk) 03:29, 6 March 2019 (UTC)
thread_title:  Broken Link 

message: It seems that the roll-off parameter is more commonly known as alpha. Temblast (talk) 11:29, 24 June 2011 (UTC)
thread_title:  Alpha or beta? 

message: The bug can be found in the python code:
ax.set_xticks([-3,-2,-1,0,3,2,1])
ax.set_xticklabels(["-3T","-2T","-T","0","T","2T","3T"])
It should probably be:
ax.set_xticks([-3,-2,-1,0,1,2,3])
ax.set_xticklabels(["-3T","-2T","-T","0","T","2T","3T"])  — Preceding unsigned comment added by 81.230.178.57 (talk) 10:44, 12 August 2011 (UTC)
replies: text: Corrected. Thanx. --ElectroKid (talk • contribs) 22:00, 28 August 2011 (UTC)
thread_title:  The Raised-cosine-impulse.svg picture has label bugs on the time axis. 

message: I use transmitting, on a voice channel, digital data [high/low] as 'raised-cosine square waves' to eliminate the high harmonics. The transitions (edges) of these square waves follow the cosine function. I do this wave shaping by an analog circuit (using diodes or transistors, as done in some old sine-wave generator ICs).
My question is:
Could I find this technique on a Wikipedia page?
Searching the expression 'raised-cosine square wave' leads me always to pages related to 'raised-cosine filter' instead.
Thank you.
KerimF (talk) 18:21, 19 November 2016 (UTC)
thread_title:  The Raised-Cosine Square Waves 

message: This is a matter of consistency within Wikipedia and even within this article.
There are textbooks that present the Nyquist–Shannon sampling theorem with misleading scaling by leaving off the sample period T scaler from the sampling function
:  T \cdot \mathrm{III}_T(t) = T \sum_{n=-\infty}^{\infty} \delta(t - nT) 
which requires them to put the T factor in the passband gain of the reconstruction filter.  But we normally consider the gain of the filter, H(f), to be dimensionless.  This requires the impulse response h(t) to have dimension of 1/time, and this is confirmed when examining the convolution integral.
In addition, in this article it says:
:As \beta approaches 0, the roll-off zone becomes infinitesimally narrow, hence:
::\lim_{\beta \rightarrow 0}H(f) = \mathrm{rect}(fT)
:where \mathrm{rect}(.) is the rectangular function, so the impulse response approaches \mathrm{sinc}\left(\frac{t}{T}\right). Hence, it converges to an ideal or brick-wall filter in this case.
This is actually dimensionally correct, but disagrees with earlier expressions of H(f) having passband gain ot T.
So I am fixing this, and we'll see how long it lasts.  If someone insists on reverting the scaling back (to be more compatible with some of the textbooks) then you should get them to change it at Nyquist–Shannon sampling theorem and at Zero-order hold.  But as I will leave it, this article will be consistent with the other two. 96.237.136.210 (talk) 06:02, 25 March 2017 (UTC)
replies: text:  I just checked and this correction also makes this article consistent with Root-raised-cosine filter.  That confirms the correction. 96.237.136.210 (talk) 06:12, 25 March 2017 (UTC)
thread_title:  Scaling and dimensional issue...