[skyworld]

Hi,

My design has an interleaved data stream input, i.e. i1, q1, i2,
q2, ... , in, qn; I have to de-mux these stream as i1, i2, ..., in and
q1, q2, ..., qn and send I/Q data to seperate DACs. When I observe I/Q
output, I found there are spurs in DAC outpt waveform. Very strangely,
these spurs are occurred only with special DAC input clock. For
example, when input DAC clock ranges from 24MHz to 30MHz and from
50MHz to 60MHz I can see spur with I output, in other frequencies,
there is no spur. For Q output, the spur occurred when DAC clock works
from 30MHz to 40Mhz. other frequency is ok. I am sure the input clock/
data to mux/DAC is ok, but I don't know why there are spurs to output
and why these spurs only happened in some specical frequency. Can
anybody help me? Thanks very much.


skyworld