Sorry a correction.
> To convert this complex signal to a real, one has to do > this according to the following formula, isn't it? > > x(t) = Yc(t)Cos(2*pi*fc*t) - Yi(t)Sin(2*pi*fc*t) where > > Yc(t) -> Inphase signal, Yi(t) -> Quadrature signal, fc -> Carrier frequency, > x(t) -> real signal. > > I looked at the block "complex_to_real" and it outputs the Inphase component > as the real signal. Is it because, "fc" is 0Hz as the signal being at > > baseband? Won't we lose essential information by dropping the Quadrature > component. What about the > reverse operation? > > I want to mulitply this real signal with a PN sequence and then pass the > result > on to a costas loop which takes a complex input. I want to know how can we > > get a complex signal from a real one. Is there a block that does that? > > The book "Communication Systems" by Simon Haykin 2nd edition says, > - The complex envelope g_complex(t) equals a frequency shifted version > > of the pre-envelope g+(t) as shown > g_complex(t) = g+(t)*exp(-j2*pi*fc*t), where fc-> > carrier frequency. > and the pre-envelop is defined as, g+(t) = g_real(t) + j*g_hilbert(t). > > My problem is that we are working at OHz. How do I go ahead with this? > > If this what I need to do to get what I want then is there a > block that does it all? > > Thanks, > Peng. > > P.S. - I am sorry but I thought to make sure before I go ahead so that > I don't spend time doing things that may be unnecessary. > > > > On Sat, Jun 13, 2009 at 5:23 PM, Eric Blossom <[email protected]> wrote: > >> On Sat, Jun 13, 2009 at 02:31:59AM +0200, Sebastiaan Heunis wrote: >> > Jason >> > >> > From what I've picked up, you need two external sampled signals to get >> > an I-Q signal. With the TV tuner daughterboard, you automatically get >> > two signals. You just need to set the mux accordingly. When you use >> > a BasicRX, you need to feed the same signal to both inputs and use a >> > mux value of 0x32103210. >> >> If you use the standard interfaces, you don't have to do anything. You >> always get a valid complex baseband signal. >> >> The daughterboard code knows which boards have a single real output >> and which have quadrature inputs. In the single real case (e.g., >> TVRX), the library configures the mux such that it feeds the single >> input into the I side of the DDC and connects a constant zero into the >> Q side. The output of the DDC is always complex. In the case of >> daughterboards with quadrature output, one input is connected to the >> I input of the DDC and the other is connected to the Q input. >> >> See http://gnuradio.org/trac/wiki/UsrpRfxDiagrams >> >> Eric >> >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> [email protected] >> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> > >
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