Is there any way to set up the 9958 so that new FTWs sent to a DDS will start at zero crossings?
The only way I could think for now is to apply a feedback mechanism. Such an ADC awaiting at the output side of the DDS. That ADC would then be connected to an MCU which is also controlling the DDS. The MCU would allow FTW modification when it detects that the output of the DDS is near zero crossing.
Yes, actually there is a way to implement an FSK/PSK modulator to switch on zero crossings. An application note by David Brandon and Jeff Keip is a very good reference for this. Here's the link:
Efficient FSK/PSK Modulator Uses Multichannel DDS to Switch at Zero Crossings
Hope this helps.
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