Re: Digital modulation 'constellation modulator' output.

[Fabian Schwartau]

Hi,
take a look at the second page of the schematic of the Red Pitaya:
http://downloads.redpitaya.com/doc/Red_Pitaya_Schematics_STEM_125-10_V1.0.pdf
It has an ADC and a DAC. The signal going into the ADC will show up in
the source block in GNU Radio, while the signal going into the sink
block in GNU Radio will come out of the DAC. Simple as that.
Best regards,
Fabian

Am 13.06.20 um 12:40 schrieb Khalilur Rahman:
> Hello Fabian,
> I hope you are doing great!
> '' from Gnu Radio in PC digital modulation is done, the generated signal
> sink through Red Pitaya(FPGA). We are only concerned about processing
> the baseband signal by Gnu radio with Red Pitaya. From GitHub we found
> one SDR project. The 'sink' for red pitaya is also available on that
> project, so we don't need to make one. Now we are confused as the analog
> signal sink to Red pitaya how does it processing it? I mean the signal
> as an input to red pitayas CPU should be digital. ''
> Thank you
> 
> Best regard 
> Khalil
> 
> 
> On Sat, 13 Jun 2020 at 11:29, Fabian Schwartau <fabian@opencode.eu
> <mailto:fabian@opencode.eu>> wrote:
> 
>     Hey Khalil,
> 
>     first of all: every signal is digital within the computer. What you
>     probably mean is what this signal represents. The output of a modulator
>     usually represents an anlog signal. It is of type float (or complex
>     float) and each sample represents for example a voltage. I don't
>     understand what you are supposed to do with that signal after that. When
>     you say you need to "sink this signal though an embedded processor" you
>     mean an external physical device? If that is the case you need some sort
>     of sink in GNU Radio, like an audio sink, which will convert you digital
>     signal into an analog audio signal (DAC).
>     If you want to process the signal further, e.g. by filtering it, you can
>     do that in GNU Radio.
>     Hope that helps,
>     Fabian
> 
>     Am 13.06.20 um 10:40 schrieb Khalilur Rahman:
>     > Hello Guys,
>     > I was studying the digital modulation in regards to GNU Radio. I have
>     > one confusion which I really need to get over with.
>     >
>     > Let say, I am using BPSK modulation for processing low-frequency
>     > baseband  I- signal. After the digital modulation, the output I-signal
>     > is digital or analog type? Yes, as baseband signal it is
>     > obviously analog. I mean the output type of constellation
>     modulator. If
>     > I put a time sink it will show as an analog signal but my study
>     partner
>     > said it is digital. Same with QPSK or QAM. I know this is very basics
>     > but I did not find any answer.
>     > We need to generate baseband from GNU Radio and sink this signal
>     through
>     > an embedded processor for further signal processing. If the
>     > constellation modulator gives an analog signal then we have to first
>     > convert signal through ADC. We are very much new on GNU Radio.
>     >
>     > Thank you in advance.
>     >
>     > Best regards 
>     > Khalil
> 
>