[USRP-users] LFTX output amplitude (Michael Rahaim)

Marcus Müller marcus.mueller at ettus.com
Fri Dec 12 10:00:39 EST 2014


Hi Mike,

On 12/12/2014 03:50 PM, Michael Rahaim via USRP-users wrote:
> Hi Ian,
>
> Thanks for the reply. I'm not extremely familiar with the details of
> the hardware implementation within the USRP - Am I correct in saying
> that the CORDIC processor implements the interpolation on the FPGA
> within the USRP motherboard and the LFTX implements the complex
> multiplication of the up sampled signal with the carrier?
>
No, not quite: the CORDIC is the sine-generating part of the
downconverter/upconverter. Interpolation is mathematically just "padding
with zeros", and you need a filter after that to get rid of images.

The point that Ian tried to make is: for a phase value of 0, the
CORDIC-mixer is just an I/Q passthrough. For any phase value !=0, it
mixes I and Q.


Greetings,
Marcus




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