This is exactly what i was looking for. Thank you so much. On Wed, 26 Feb 2020, 9:22 am Moses Browne Mwakyanjala, <mbkit...@gmail.com> wrote:
> Hello, > That comes down to baseband signal and passband as shown below. > Traditionally, we only quote positive frequencies. For example, for the > SRRC pulse you mentioned, the baseband signal extends from -Rs(1+alpha)/2 > to +Rs(1+alpha)/2. Thus, we say the baseband bandwidth is Rs(1+alpha)/2. > When transmitting over the air, we have a passband signal which extends > from Fc -Rs(1+alpha)/2 to Fc +Rs(1+alpha)/2 where Fc is the carrier > frequency. In this case, the positive bandwidth is Rs(1+alpha), which is > twice the bandwidth at baseband. As a general rule, passband frequency (the > frequency you transmit over the air) is twice the baseband signal. > Regards, > Moses. > PS- The attached pdf is quite a good introduction to gnuradio and signal > processing basics. > [image: image.png] > > On Wed, Feb 26, 2020 at 5:09 AM Md. Atiqur Rahman <atiq....@gmail.com> > wrote: > >> Thank you for your reply with the details. >> I do already read from the GNU Radio tutorial but wasn't fully sure. >> The equation now clear, just want to make sure one point from you. >> After the modulation(e.g qpsk) signal upconverted to RF, then the signal >> bandwidth still will be the same? >> >> Thank you again. >> >> >> On Wed, Feb 26, 2020 at 12:31 AM Moses Browne Mwakyanjala < >> mbkit...@gmail.com> wrote: >> >>> I saw your post on the gnuradio mailing list. >>> The constellation modulator block uses a Square-Root Raised-Cosine >>> filter with occupied bandwidth (double-sided a.k.a passband) given by BW = >>> (1 + alpha)Rs, where Rs is the symbol rate. The bit rate for M-ary linear >>> modulation is given by Bit Rate = Rs*Log(M)base2. Thus, for BPSK you will >>> achieve Bit Rate = Rs, and for QPSK it will be Bit Rate = 2 * Rs. >>> The transmission over-the-air is called passband, which for the SRRC >>> filter is given as described above. >>> You could read more on the SRRC filter from this Wikipedia article: >>> https://en.wikipedia.org/wiki/Root-raised-cosine_filter >>> You could get more information here: >>> https://wiki.gnuradio.org/index.php/Tutorials >>> >>> Good luck. >>> >>> >> >> -- >> Sincerely, >> Md Atiqur Rahman >> >>
