[Discuss-gnuradio] sample_rate and bandwidth parameter

[Maria]

Dear all,

I have a question related to the parameters Samp Rate (Sps) and Bandwidth which can be found on the UHD USRP source and sink GNU radio blocks.

If I want to calculate the bandwidth of a modulated signal (QPSK for example), the standard equation to use is usually:

B = (1+roll-off)*sample_rate

However, I have checked that the bandwidth in GNU radio is calculated by:

B = (1+roll-off) * Bandwidth /number_symbols

Where Bandwidth is the USRP block parameter and number_symbols is 4 in this case (QPSK). Therefore, the Samp Rate parameter from the
UHD USRP source and sink GNU radio blocks does not have to do with the calculation of the signal bandwidth in frequency domain. I would be really glad if someone can explain to me the difference between these two parameters ("Samp rate" and "Bandwidth"). I have already read the documentation but I still do not really understand it.

Thank you very much and sorry for the I guess basic question.

Best regards,

Maria Jesus