On Thu, Oct 05, 2006 at 05:51:49PM -0700, Daniel Garcia wrote: > Matt Ettus wrote: > >Yes, you can change the filter taps in the FPGA. See the halfband (HB) > > verilog code. > > Thanks! I'll take a look. > > >> I read on a previous thread that it is possible to invert the spectrum of > >> the sampled signal so that the tuned frequency would be the FM carrier. > >> The end result being a stream from the USRP where 0 Hz is the center > >> frequency of the audio carrier the the video carrier is at 4.5 MHz. Is > >> this possible? The advantage here is that the base-band audio does not > >> need to be shifted before FM demodulation; also the video carrier does not > >> need to be shifted before demodulation (AM).
> >Not sure what you're looking for here. > After thinking about it, I'm not sure either. I figured I can to > tune to FM carrier to the center frequency (0Hz), set the decimation > to 4 (16 MS) and the video carrier is at -4.5MHz. Unfortunately, my > USB/computer can't handle can't handle the 16 MS rate. I was hoping > to avoid translating the signal by placing the FM signal at > 0Hz. Since my PC can't handle that data rate, I'm just going to > concentrate on the NTSC. > -Daniel > > As an aside: It would be nice to have something like the GC4014 > on-board the USRP. In my application it could be used to tune the > video and audio signals on separate receiver channels without using > up resources on the PC (and also reduce the need for a faster > interface in some cases). Not sure if there's enough room on the > FPGA though. The cost of extracting and decimating the audio portion of the full signal in s/w is pretty small. Have you tried just setting decimation to 8 giving 8MS/s complex? Why are you concerned about anything at 16MS/s? The 8 MS/s signal will have both the audio and video in it. A small amount of filtering would separate the two streams in software. Eric _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
