Mux on usrp Tx side

GNU Radio
1

I understand the purpose of the mux on the rx side of the usrp.

I have a question regarding the tx side of the usrp.
In particular, it is not clear to me what the purpose of the mux
is on the tx side.
My understanding is that the samples from the USB (say complex)
are interpolated by N in the FPGA, then further interpolated
by 4 in the DAC chip (to reach 128Msps), then digitally up-converted and
then digital-to-analog converted.

where is the Mux in this chain? and what does the default value 152
represent?

Thanks
Achilleas

2

After a bit of digging I think I partially
answered my questions.

Just to make sure I have it right:

There are 2 complex interpolators implemented in the FPGA (say int0, and
int1). There are 4 real (ie, 2 complex) upconverters implemented in the
DAC chips (say dac0, dac1, dac2, dac3). The mux routes the I and Q
of int0 and int1 to the appropriate dacs.

Is it true that dac0,1 are hardwired to the TXA side of the USRP and
dac2,3 to the TXB?

Also, is the second complex interpolator used only if nchannels = 2 ?

Thanks
Achilleas

3

On Sat, Jun 09, 2007 at 09:43:02AM -0400, Achilleas A.
wrote:

Is it true that dac0,1 are hardwired to the TXA side of the USRP and
dac2,3 to the TXB?

Also, is the second complex interpolator used only if nchannels = 2 ?

Thanks
Achilleas

Yes. You have it right.

Eric