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Re: Baseband signals frequency,amplitude,data rate determination.

From: Md. Atiqur Rahman
Subject: Re: Baseband signals frequency,amplitude,data rate determination.
Date: Fri, 14 Feb 2020 21:24:00 +0100

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) <address@hidden> 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,

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 ;)

Md Atiqur Rahman
Hochschule Bremen

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