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Tunable filter for AD9958

Question asked by RMLEARNEY on Jun 10, 2011
Latest reply on Jun 14, 2011 by DSB

Hi all,


Just wondering whether anyone here can help me in my amateur journey into DDS circuit design?


I've finally settled on the AD9958 as my DDS and have made some headway in using a PIC to program it, but I've begin to wonder about reconstruction filters on the output side of the AD9958.


I've looked over the LTC6603 from Linear, which looks like a good tunable 9th-order filter with dual inputs (for the dual outputs of the AD9958).


So my question is this -


Would I have to go: DDS Output -> 1:1 Matching Transformer -> LTC6603 Input -> Filtered Output


Or is there a circuit design that could go straight from DDS Output to LTC6603 input without a matching transformer. In other words, do I need a matching transformer between the output of the AD9958 and the differential input of the LTC6603?


Many thanks in advance,