Re: [Discuss-gnuradio] Real Signal to I/Q Samples

[Marcus D. Leech]

On 06/21/2011 05:33 PM, Tom Hendrick wrote:

Hello all, I am helping a colleague with the USRP center frequency tuning functionality and it is my understanding the signal must contain I and Q values centered at 0Hz.

A real valued signal is generated independently by another program and is fed to a GRC script.  Is it easy/possible to make a GRC script downshift the signal to 0 Hz and convert to I and Q values or is there perhaps an example of this already?

Thank you in advance- Tom

I've attached an example that uses a narrow-band, real-only signal source, with everything running at an arbitrary sample rate of 150Ksps.

It uses a Hilbert transform, followed by a decimate-by-two bandpass filter.

Without the bandpass filter, there will still be a residual "image" frequency in the complex output of the Hilbert transform, and since we're
  decimating by two anyway, I thought I'd put in a bandpass filter.

-- 
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org

hilbert.grc
Description: application/gnuradio-grc

hilbert.py
Description: Text Data