Re: [Discuss-gnuradio] I&Q on same or separate channels?

[Brian Padalino]

On Dec 13, 2007 4:35 PM, George Nychis <address@hidden> wrote:
> Hi all,
>
> For the in-band code, I'm noticing that it seems like the FPGA is
> packing two I's or two Q's, and not an I and a Q.  If you take a look at
> the following plot of a 10MHz sine wave, you will see what I mean.  The
> left plot is using the legacy receiver, the right side is using an
> in-band receiver:
> http://www.andrew.cmu.edu/user/gnychis/sines.png
>
> This boils down to the following code:
> http://gnuradio.org/trac/browser/gnuradio/branches/features/inband-usb/usrp/fpga/inband_lib/rx_buffer_inband.v
>
> I'm guessing that Thibaud's original assumption was that I and Q are
> packed in a single channel to be read from.  With a single data channel,
> the code will only read from channel 0.  Is this incorrect?  If so, this
> explains the behavior we're seeing.
>
> If I and Q are on separate channels, are they synchronized?

They are on separate channels, synchronized and are instantiated here:

    
http://gnuradio.org/trac/browser/gnuradio/branches/features/inband-usb/usrp/fpga/toplevel/usrp_inband_usb/usrp_inband_usb.v#L235

How do you feel you want to handle it?

Brian