This page contains block diagrams of the USRP and RFX2400 daughterboard. I generated these by aggregating information from a number of places. I'm not sure they're 100% correct. So, use them at your own risk.

I've annotated a few corrections. -eb

Here is a block diagram of the transmit and receive signal paths in the USRP:

http://gnuradio.org/images/usrp_dia_75.jpg

Block diagram of the digital down-conversion and decimation stage:

Right idea, except that there is effectively a single complex multipler. I.e., I2+jQ2 = (I1+jQ1) * exp(jwt).
The effect of the NCO and multiplier are implemented using the CORDIC algorithm.

http://gnuradio.org/images/ddc_75.jpg

Block diagram of the digital up-conversion stage:

Right idea, except that there is effectively a single complex multipler. I.e., I2+jQ2 = (I1+jQ1) * exp(jwt).

http://gnuradio.org/images/duc_75.jpg

Block diagram of RFX2400 transmit signal path:

In the diagram, G=gain and N=noise figure (dB) at 2.4 GHz

http://gnuradio.org/images/rfx2400_tx_75.jpg

Block diagram of RFX2400 receive signal path:

In the diagram, G=gain and N=noise figure (dB) at 2.4 GHz

http://gnuradio.org/images/rfx2400_rx_75.jpg

If anyone's interested in updating or correcting these diagrams, the OpenOffice? source file is source:gnuradio/trunk/usrp/doc/usrp_rfx_diagrams.odp. The originals were exported as JPG, and then imagemagick was used to convert them to a reasonable size for web viewing. (If you do update these images, please send them and the updated source file to eb@comsec.com for posting.)