AD9963 DAC configuration


I need to transmit a 8MHz GMSK signal from AD9963 DAC. Until now we have been using it to transmit 2MHz GMSK and there were no problems. However when we started to transmit higher symbol rate I noticed large IQ imbalance at the DAC output.

I used sine wave output from our FPGA to debug the DAC performance and indeed, I saw a degradation of the IQ imbalance.

Using our FPGA debug tools I checked that the sine wave before DAC is Ok, but the analog output suffers from imbalance.

I'm afraid that there are some problems with DAC configuration.

We are using 64MHz sample clock, no interpolation filters used.

The data is sampled using DDR clock option.

Can you please send me recommended registers configuration for the above options.