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Re: [Discuss-gnuradio] USRP Custom Filter Taps
From: |
Daniel Garcia |
Subject: |
Re: [Discuss-gnuradio] USRP Custom Filter Taps |
Date: |
Thu, 5 Oct 2006 17:51:49 -0700 (PDT) |
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.