Hello, I apologize in advance If I sound not right. To follow up on my inquiry: Well, I get to know how to find the bandwidth, as our constellation modulator uses some root raised cosine filter, it needs to have a roll-off factor which in another way excess bandwidth. Bw=(1+alpha)*T = (1+0.7)*(62500 symbol rate)= 106.25Khz. As the sampling rate is 2Mhz, SPS 32 and in QPSK 2bit inserted at once then the data rate would be 106.25Khz /2 = 53.125Khz am I right? if I am right then for the BPSK data rate would equal to bw as 1 bit per sec?
For BW calculation I think it is right but date rate I not sure. Thank for your all support. On Sat, Feb 15, 2020 at 3:04 PM Müller, Marcus (CEL) <muel...@kit.edu> wrote: > Please reply to the mailing list, not only to me privately. Thank you. > On Sat, 2020-02-15 at 02:17 +0100, Md. Atiqur Rahman wrote: > > Hello, I apologize in advance If I sound not right. > > To follow up on my inquiry: > > Well, I get to know how to find the bandwidth, as our constellation > > modulator uses some root raised cosine filter, it needs to have a > > roll-off factor which in another way excess bandwidth. Bw=(1+alpha)*T > > = (1+0.7)*(62500 symbol rate)= 106.25Khz. As the sampling rate is > > 2Mhz, SPS 32 and in QPSK 2bit inserted at once then the data rate > > would be 106.25Khz /2 = 53.125Khz am I right? if I am right then for > > the BPSK data rate would equal to bw as 1 bit per sec? > > > > For BW calculation I think it is right but date rate I not sure. > > Thank for your all support. > > > > On Fri, Feb 14, 2020 at 10:29 PM Md. Atiqur Rahman < > > atiq....@gmail.com> wrote: > > > Hello, > > > > > > Yes, you got me totally. The 'time sink', I am referring to as > > > timing diagram and about showing frequency as the signal changing > > > over time, hence signals have a certain frequency. > > > > > > ''Are you perhaps mixing up bandwidth and frequency? Or maybe > > > symbol > > > rate?'' yes I am confused in this two-term, bandwidth, of course, > > > the range of frequency where the frequency of that generated > > > signal. I am mostly like to calculate things to understand a > > > certain topic but understanding them practically I have a gap on > > > that. As like how pulse shaping really determined the bandwidth of > > > the signal. > > > > > > ''Regarding bandwidth: Bandwidth of a linear modulation (without > > > Bias) is > > > always fully defined by the pulse shaping filter. You have one of > > > these > > > in your system!'' > > > The first GRC flow graph I attached by followed the PSK > > > demodulation documentation, but all I really need to understand is > > > the baseband signal with its associates(data rate sampling rate, > > > symbol rate, bw and frequency)by digital modulation system. The > > > root raised filter is used for 'polyphase clock sync' but how I > > > insert a pulse shaping filter as associated with a roll of > > > factor(excess bw). As Excess BW is 0.7, symbol rate 62.5 k, sps is > > > 32 then how can I determine BW? > > > > > > I am going to read your suggested sections and will come back. > > > > > > Thank you so much for your support, I really appreciate it. > > > > > > On Fri, Feb 14, 2020 at 9:42 PM Müller, Marcus (CEL) < > > > muel...@kit.edu> wrote: > > > > Hello, > > > > > > > > > I need the basic baseband signal (low frequency) but it would > > > > be a > > > > 0Hz frequency? > > > > > > > > Yes, as said, it would be a band-limited signal around 0 Hz. > > > > That's the > > > > definition of baseband signal. > > > > > > > > I'm not sure what you mean with > > > > > > > > > timing diagram is showing the signal has some certain frequency > > > > > > > > A timing diagram (not _quite_ sure what that is) shows no > > > > frequency. > > > > > > > > Are you perhaps mixing up bandwidth and frequency? Or maybe > > > > symbol > > > > rate? (But you already have some calculations of symbol rate, so > > > > I'm > > > > really not sure what you mean.) > > > > > > > > Regarding bandwidth: Bandwidth of a linear modulation (without > > > > Bias) is > > > > always fully defined by the pulse shaping filter. You have one of > > > > these > > > > in your system! > > > > > > > > Best regards, > > > > Marcus > > > > > > > > PS: > > > > > https://www.analog.com/media/en/training-seminars/design-handbooks/Software-Defined-Radio-for-Engineers-2018/SDR4Engineers.pdf > > > > might be a good place to start; you have gaps in understanding of > > > > chapters 2.1–2.3, 2.7, and 4.1–4.2, it seems. It'll be very hard > > > > for > > > > you to understand what your equalizer and synchronizers do. > > > > > > > > > > > > On Fri, 2020-02-14 at 21:24 +0100, Md. Atiqur Rahman wrote: > > > > > Thank you for the clarification. I will update it to 3.8 > > > > soon. > > > > > However, baseband is the main signal which will be converted to > > > > RF signal by means of upconverter. I have a SDR device(red- > > > > pitaya), in which two digitally modulated baseband signals(I-Q) > > > > will come out separately and later on with RF front end it will > > > > be mixed with high frequency. That is the main idea. Hence, > > > > first, I need the basic baseband signal (low frequency) but it > > > > would be a 0Hz frequency? That I have no idea of. The timing > > > > diagram is showing the signal has some certain frequency, then it > > > > would be 0? > > > > > Would you please give me some details. Thank you so much. > > > > > > > > > > ps: WX block insertion was a mistake. I didn't realize it until > > > > you mentioned it. As I am going to write a report on my work as > > > > well, it is great to know that now the graph can be export. Is > > > > there any updates also for extracting GRC flow graph from > > > > file>screen capture as well? > > > > > > > > > > On Fri, Feb 14, 2020 at 9:01 PM Müller, Marcus (CEL) < > > > > muel...@kit.edu> wrote: > > > > > > Hi Md. Atiqur, > > > > > > > > > > > > On Fri, 2020-02-14 at 20:43 +0100, Md. Atiqur Rahman wrote: > > > > > > > For a QPSK modulation technique, I choose to set > > > > constellation point 1 to -1, hence 1.4142 would be amplitude > > > > > > > > > > > > Ah, you're confusing the magnitude of the complex number with > > > > the > > > > > > amplitude of the I and Q component. > > > > > > > > > > > > So, yes, the magnitude of (1 + 1j), (1 - 1j), (-1 + 1j) and > > > > (-1 -1j) > > > > > > are 1.41, but the real and imaginary parts are still +-1. > > > > > > > > > > > > > but in the timing diagram, it looks less than that. > > > > > > > > > > > > So, that's correct :) > > > > > > > > > > > > > Another point is, as my sampling rate is 2Mhz, and samples > > > > per symbol are 32, hence 62.5K is the symbol rate, what will be > > > > my baseband signal frequency? > > > > > > > > > > > > 0 Hz. That's what "baseband" means. > > > > > > > > > > > > > > > > > > Best regards, > > > > > > Marcus > > > > > > > > > > > > PS: As someone occasionallly advising students, I'd recommend > > > > > > you clean up your flow graph; there's blocks in there you've > > > > commented > > > > > > out that you can never use (WX can't coexist with QT GUI). > > > > Also, try to > > > > > > make it as linear as possible, so to make it really easy to > > > > follow the > > > > > > "sample flow" optically. This is the Nr. 1 debugging hint for > > > > GRC > > > > > > beginners, and it really helps a lot when talking about a > > > > flow graph. > > > > > > > > > > > > Also, by the way, you're using a legacy GNU Radio. We've > > > > released GR > > > > > > 3.8, and you're still on 3.7.; the new GNU Radio has fewer > > > > bugs, and > > > > > > vector export for GRC figures, which is important to anyone > > > > writing a > > > > > > thesis with GRC flow graph pictures ;) > > > > > > > > > > > > > > > > > > > -- > > > Sincerely, > > > Md Atiqur Rahman > > > Hochschule Bremen > > > > > -- Sincerely, Md Atiqur Rahman Hochschule Bremen
