The DSPLib contains two different DDS/Mixer implementations. These will be referred to as the dds_mixer and dds_mixer_lut. They both differ in their implementations of the DDS and hence do not have identical outputs. The dds_mixer solution is available only on AI Engine (AIE), while the dds_mixer_lut is available on both AIE and AIE-ML. The dds_mixer_lut has modes that enable higher SFDR figures for the signal generator than the dds_mixer. Both implementations have three different modes of operation. The mode of the component is driven by template parameter TP_MIXER_MODE.
In DDS Only mode (MIXER_MODE_0), there is a single output port that contains the sin/cosine components corresponding to the programmed phase increment. The phase increment is a fixed uint32 value provided as a constructor argument, where 2^31 corresponds to Pi (180 degrees phase increment). The number of samples sent through the output port is determined by the TP_INPUT_WINDOW_SIZE parameter. The output port can be a window interface or a stream interface depending on the use of TP_API.
Mixer inputs are enabled with the TP_MIXER_MODE template parameter. There are two modes that have the mixer functionality enabled.
- In
MIXER_MODE_1, a single input port is exposed, and the input samples are complex multiplied by the DDS output for the given phase increment. - In
MIXER_MODE_2, two input ports are exposed for multi-carrier operation, with the first behaving as inMIXER_MODE_1, and the second input port getting complex multiplied with the complex conjugate of the DDS signal then accumulated to the result of the first complex multiply operation.