On Sun, Jul 3, 2011 at 3:25 AM, John Andrews <gnu.f...@gmail.com> wrote:
> Hi Tom, > > > >> Are you doing this in your own top-level block (dsss from the looks of it) >> or under a current GNU Radio directory like gnuradio-core where the >> gr_firdes currently is? >> > Yes, I am doing this in my own top-level directory named 'dsss' > (abbreviation for direct sequence spread spectrum) > >> >> You haven't mentioned adding anything to the Makefile so that it is built >> properly. If you are working under gnuradio-core/src/lib/general, you'll >> also want to add your .h and .i files to general.i so that it get's >> compiled. >> > > I added the names to Makefile.am like I added the remaining names of files. > The Makefile.am has been adapted from howto-write-a-block. The C++ part gets > compiled without any problem but when importing in python it throws an > undefined_variable_dsss_firdes_Z*** type of error, which according to my > previous experience occurs with wrong SWIG interface problem. I am pretty > sure I am having a SWIG related issue here. > Ok, it _sounds_ like you are doing everything correctly. In my experience with this stuff, it usually comes down to a small typo somewhere. You can post your files here (.i, .h, and Makefile) so others to maybe have a look to see if there's anything incorrect in them. > Also, just curious, what application are you interested in that requires a >> raised cosine filter? And couldn't you just create a root raised cosine >> filter and convolve the the taps against themselves to make the raised >> cosine taps? >> > > I am developing a BPSK based Direct sequence spread spectrum Tx/Rx and at > the transmitter i wanted to use a raised cosine filter when interpolating > from symbol to N samples before sending it to the USRP. I am not sure if > this is the preferred method but I haven't found any documentation related > to DSSS that mentions pulse-shaping. > >> >> Tom >> > There is definitely some work on pulse shaping of DSSS systems. I believe, though, that they all use root raised cosine filters. This is done at both the transmitter and receiver so that the received signal has gone through two root raised cosine filters to make the raised cosine filter, which is a Nyquist filter. Tom
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