Complex-->real


#1

I have a complex stream that I’ve bandpass filtered so that it only
contains the positive frequencies. I want to turn this into
a real signal. In the reverse direction, you use a hilbert transform,
right? But how do you do it in the reverse direction?
Do I just do a complex-to-float, and take the one that’s “real”, and
ignore the other one?

Left his complex arithmetic brain in his other pants…


Marcus L.
Principal Investigator, Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org


#2

On Sun, Feb 15, 2009 at 05:50:24PM -0500, Marcus D. Leech wrote:

I have a complex stream that I’ve bandpass filtered so that it only
contains the positive frequencies. I want to turn this into
a real signal. In the reverse direction, you use a hilbert transform,
right? But how do you do it in the reverse direction?
Do I just do a complex-to-float, and take the one that’s “real”, and
ignore the other one?

You can do that, or use gr_complex_to_real() which I would prefer for
coid readability. In my textbooks, the baseband to passband relation is
often described as

s(t) = Re{ x(t) exp(j 2 pi fc t) }

which is exactly what you’d be doing then (x(t) being the complex
baseband signal).

Cheers,
MB