On Wed, Jul 17, 2013 at 12:35 AM, tom sutherland <[email protected]> wrote: > I want to QAM16 encode a band limited (0-3khz) signal on one computer. I > want to connect this computer to another computer running a QAM16 Decoder > program. The QAM16 encoded signal needs to be able to be sent over the audio > channel(single channel) of the computer. How can take the complex output of > the QAM16 module and "mix" it so that it can be sent over a single audio > channel? Need also to demodulate it on the other side. > > Thanks...Tom
To maintain the phase information, you need to move the entire signal from complex baseband (where it's centered at 0 and has information on both sides) to some frequency that is purely in the positive frequency. This probably means interpolating the signal first to give you room to move it, then multiplying it with a complex sinusoid at the new center frequency to do the actual frequency shift. Then take the real part (complex_to_real block). Regarding the upsampling and shift, if you're brave, you can try using the pfb_synthesizer_ccf block with 3 channels. Put a null source into channels 1 and 3 and your original signal into channel 2. That would upsample the signal by a factor 3 and place your signal in the right place (channel 0 spans 0 Hz, channel 1 is in the positive freq and channel 2 is in the negative freq). Probably easiest to start with an interpolating filter and doing the frequency shift using a complex multiply, though. Tom _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
