User Generated Signals


#1

Hello,

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

i =
q =
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


#2

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


#3

On 29/03/11 01:04 AM, Yulong Y. 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/TutorialsWritePythonApplications
http://gnuradio.org/redmine/wiki/gnuradio

Hope this helps,


Etienne Robillard

Company: Green Tea Hackers Club
Occupation: Software Developer (and CEO)
E-mail: removed_email_address@domain.invalid
Work phone: 450-936-2123
Website (Company): https://gthc.org/
Website (Blog): https://gthc.org/blog/
PGP public key fingerprint: F2A9 32EA 8E7C 460F 1728 A1A7 649C 7F17
A086 DDEC

During times of universal deceit, telling the truth becomes a
revolutionary act. – George Orwell

If a free society cannot help the many who are poor, it cannot save the
few who are rich. – John F. Kennedy


#4

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.