Re: [Discuss-gnuradio] User Generated Signals

[Syed Faisal Shah]

Jonathan,

I am new to GNU radio as well but have been using the gr_sig_source_c
class. This class generates a complex quadrature sinusoid with
cosine(x) as real part and sine(x) as imaginary part. Doing some code
hacking in gnuradio-core/src/lib/general/gr_sig_source_c.cc, you can
see that irrespective of the input argument SIN_WAVE or COS_WAVE the
program always calls 'sincos' method of class gr_fxpt_nco. Now,
'sincos' is defined as follows:

output[i]   = gr_complex(
gr_fxpt::cos (d_phase) * ampl, gr_fxpt::sin (d_phase) * ampl);

So, this is how you get cos in the real part and sin in the imaginary
part. One word of caution here, the file gr_sig_source_c.cc is machine
generated meaning it is generated by gr_sig_souce_x.t file. In case you
would like to modify, do not modify .cc file rather change .t file.

I hope it will be helpful.

Regards

Faisal
 
> >
> 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 .... "
> >