Forum: GNU Radio DPSK Demodulation Output

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Charles Judah (Guest)
on 2009-02-18 20:00
(Received via mailing list)
Hello All,

My name is Charles and I'm a senior at California State University
Northridge. The team I am with is currently working on implementing a
digital communications scheme between a flying object and a ground based
station.

I am having issues with the Demodulation block of the DPSK (in DBPSK
mode).
The setup is, I read a binary file and send that directly into the DPSK
Modulator. I then immediately Demodulate this signal in the GRC window
and
put it into a file. This process is not the inverse of itself. The
output
file is unintelligle to me with a text editor and with a hex editor.

My question is, if I were to open and read a binary file of only
alternating
1s and 0s into the DPSK modulator then immediately feed that back into
the
demodulator, what format is the demodulator putting byte data back out?
Is
it padding the information with 0s? Any insight into "how" the
demodulation
block submits the byte data to the subsequent connecting block would be
greatly appreciated.
Johnathan C. (Guest)
on 2009-02-20 17:11
(Received via mailing list)
On Wed, 2009-02-18 at 09:59 -0800, Charles Judah wrote:

> My question is, if I were to open and read a binary file of only
> alternating 1s and 0s into the DPSK modulator then immediately feed
> that back into the demodulator, what format is the demodulator putting
> byte data back out? Is it padding the information with 0s? Any insight
> into "how" the demodulation block submits the byte data to the
> subsequent connecting block would be greatly appreciated.

The demodulator blocks output demodulated bits in what we call
"unpacked" form, which sends demodulated symbols in the LSBs of 1 byte
items.  In the case of dbpsk, these 1 byte items will have only the LSB
toggled to represent a decoded 1 or 0.

Johnathan
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