Forum: GNU Radio User Generated Signals

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887f5f74c658b6aa92953f463a0f4bce?d=identicon&s=25 Jonathan Shan (Guest)
on 2007-04-07 06:17
(Received via mailing list)
Hello,

I am trying to transmit and receive a signal that the user defines. I am
following the directions written by Eric Blossom on independently
generating signals and then transmitting them.
"
   u = usrp.sink_c(...)

   i = <generate I somehow>
   q = <generate Q somehow>
   f2c = gr.float_to_complex()
   fg.connect(i, (f2c, 0))
   fg.connect(q, (f2c, 1))
   fg.connect(f2c, u)
"

i = [1000, .... , 923]   // 16 values in this array, one period of
cosine
q = [0, .....,  -383]   // calculated using hilbert transform, 16 values
isrc = gr.vector_source_f(i, 1)
qsrc = gr.vector_source_f(q, 1)
fg.connect(isrc .... ....)

The signal "i" is supposed to be a cosine wave.

When I connect f2c to gr.filesink, I see a cosine wave. However, the
received signal looks like noise centered around 51.

Also: why is the waveform of gr.sig_source_c(SIN_WAVE, offset = 0) a
cosine wave? I got this by using gr.file_sink, and looking at the
odd=real
values. file_sink output = "REAL IMAG REAL IMAG .... "

Any help would be appreciated.

Jonathan Shan
887f5f74c658b6aa92953f463a0f4bce?d=identicon&s=25 Jonathan Shan (Guest)
on 2007-04-09 06:55
(Received via mailing list)
On Sat, 7 Apr 2007, Jonathan Shan wrote:

>  fg.connect(q, (f2c, 1))
>  fg.connect(f2c, u)
> "
>
> i = [1000, .... , 923]   // 16 values in this array, one period of cosine
> q = [0, .....,  -383]   // calculated using hilbert transform, 16 values
>
> When I connect f2c to gr.filesink, I see a cosine wave. However, the received
> signal looks like noise centered around 51.
>

I tried changing the number of samples in i, q to larger values. Same
result. I also tried setting the transmit gain to max.

I think the problem is modulation / de-modulation. But what is
usrp.tune(carrier_freq) for? I can transmit and receive correctly
gr.sig_source_c just using usrp.tune on both ends.

Jonathan Shan
80d6dbc6036aff7e6d5aa940a5974f62?d=identicon&s=25 Yulong Yang (Guest)
on 2011-03-29 07:05
(Received via mailing list)
Hello,

I am a senior student that also studying GNU Radio. I have found your
post about generating signal and transmit on gnuradio mailing list
(though it is written in 2007).

I am wondering if you could give me some hints on generating signal and
transmit using USRP? I am new to gnu radio and have not figured out
where to start.

I have already looked through gr_sig_source_c.cc but find no luck. My
goal is to generate a sine, 2 sinc and 1 16QAM signal and transmit to
another USRP device. (I am using USRP2)

I will really appreciate your help. Thank you.
81744a252d12eafacd5969eb9d7f14af?d=identicon&s=25 Etienne Robillard (Guest)
on 2011-03-29 13:21
(Received via mailing list)
On 29/03/11 01:04 AM, Yulong Yang wrote:
> I have already looked through gr_sig_source_c.cc but find no luck. My
>
i found the tutorials on the wiki quite instructive and well-written:

http://gnuradio.org/redmine/wiki/gnuradio/Tutorial...
http://gnuradio.org/redmine/wiki/gnuradio

Hope this helps,

--
Etienne Robillard

Company: Green Tea Hackers Club
Occupation: Software Developer (and CEO)
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