Re: Baseband signals frequency,amplitude,data rate determination.
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) 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
Re: Baseband signals frequency,amplitude,data rate determination.
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) 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 ;) > > smime.p7s Description: S/MIME cryptographic signature
Re: Baseband signals frequency,amplitude,data rate determination.
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) 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
Re: Baseband signals frequency,amplitude,data rate determination.
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 ;) smime.p7s Description: S/MIME cryptographic signature
