Same as Title, What Modulation Scheme does RFX400 can perfom?
If I draw a flow graph like below:
http://dl.dropbox.com/u/11382666/02_RXTX/TX.grc.png
What Modulation Scheme is used by default?
Can I change it?
On Wed, 2011-01-12 at 01:57 +0900, Songsong G. wrote:
Can I change it?
Songsong,
The modulation can be anything you want it to be. It’s a little
confusing if you aren’t used to thinking about DSP and SDR. The USRP+RFX
will happily output the raw samples you put into it, and it’s up to you
to encode them with a reasonable modulation. The same works for receive.
If you FM modulate your data, it will be FM modulated when it goes out
on the air. If you AM modulate it, it will be AM modulated.
For another example, the process to AM demodulate a signal is just a
complex-to-magnitude transform (i.e., y=|x|). So you can use
gr.complex_to_mag as an AM demodulator. There are existing blocks to do
FM demodulation as well. They can be found in gnuradio-companion under
“Modulators”. Any other modulation scheme you can come up with can be
used as well, if you can mathematically describe it and code it up.
Take a look at the examples in gnuradio/gnuradio-examples/python/usrp
for an idea as to what I’m talking about. The AM and FM receivers are a
good place to begin.
–n
On 01/11/2011 11:57 AM, Songsong G. wrote:
Same as Title, What Modulation Scheme does RFX400 can perfom?
Any modulation scheme you can think of that can be represented
efficiently as a series of
mathematical operations producing a baseband waveform that is then
up-converted by the
RFX2400 to the final frequency.
In SDR, the hardware doesn’t “know” anything about modulation or
demodulation, that’s up to the
software. The only limitation of the hardware is the bandwidth of the
resulting waveform.
The daughtercards typically anti-alias bandwidth limit the waveforms to
about 25-30MHz or so, on
the analog mixer inputs/outputs.
–
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
Thank you for your anwer 
Then, in short,
Does the flow graph I mentioned use carrier freq. 450 MHz or not?
From the file source, it is just a baseband signal
2011/1/12 Marcus D. Leech [email protected]