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Update: Correction in Matlab code for raised cosine filter

by Krishna Sankar on May 25, 2008

Thanks to the keen observation by Mr. Phan Minh Hoang, I was notified that the Matlab/Octave scripts provided along with the topic raised cosine filtering was not behaving properly.

Reason: I was not taking care of the division by zero when creating the raised cosine filter taps. :(

The equation for raised cosine filter is

is the excess bandwidth parameter and takes values from 0 to 1.

I was not taking care of the division by zero in the above equation. I updated the code to explictly handle the division by zero case where:

(a) for and

(b) for

(Thanks to the article in RFDesign.com, The care and feeding of digital, pulse-shaping filter, Ken Gentile)

The updated posts are:

1. Raised cosine filter for transmit pulse shaping

2. Eye diagram with raised cosine filtering

Thanks again Mr. Phan Minh Hoang. :)

In case you find errors and inconsistencies in the article and/or simulation models, kindly let me know.

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{ 9 comments… read them below or add one }

ABHIJEET October 5, 2012 at 7:46 pm

hi, i need matlab code for ofdm transmission using pulse shaping filter like raised cosine filter


Avatar of Krishna Sankar Krishna Sankar October 6, 2012 at 6:42 am

@ABHIJEET: I do not have that code, but you can refer to posts related to OFDM under

But, why do wish to do raised cosine filtering with ofdm?


rasi October 8, 2009 at 7:53 am

in matlab using the inbuilt functions i generated random signal and modulated using QPSK and then transmitted adding awgn. After receiving and demodulating i m geeting zero bit error rate. Is it because of i have to use some other equations for QPSK and how can we change the frequency values and BW for the modulation. Please help me!!


Avatar of Krishna Sankar Krishna Sankar October 9, 2009 at 5:39 am

@rasi: Try increasing the noise power and see whether you are getting non-zero BER. If not there might be some typos in the code. You may also refer to the post


dima January 30, 2009 at 7:13 pm

cum sa scriu cosinus la patrat de un oarecare X, in softul MATLAB


Avatar of Krishna Sankar Krishna Sankar January 31, 2009 at 6:40 am

@dima: Can you please translate to english your query


jhony May 30, 2008 at 3:32 am

can you guide me to a site or some sources from where i can get help for the code written in c++ for digital communication?


Avatar of Krishna Sankar Krishna Sankar May 29, 2008 at 7:18 pm

Ofcourse, we can do the simulations in C++ (or any most other programming languages). The advantage with Matlab is that it is easier to code and debug compared to C.

In Matlab, Y = A*B where A and B are matrices is a one-liner.
Imagine how many lines of code we need to write for the same operation in C?


Jhony May 29, 2008 at 1:15 pm

i hope u r doing fine… why dont we do the simulations in c++??? i mean is it possible to simulate QPSK in c++?


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