SLAS748G March 2011 – January 2024 DAC3482
PRODUCTION DATA
The DAC3482 includes a Quadrature Modulator Correction (QMC) block. The QMC blocks provide a mean for changing the gain and phase of the complex signals to compensate for any I and Q imbalances present in an analog quadrature modulator. The block diagram for the QMC block is shown in Figure 6-25. The QMC block contains 3 programmable parameters.
Register qmc_gain(10:0) controls the I and Q path gains and is an 11-bit unsigned value with a range of 0 to 1.9990 and the default gain is 1.0000. The implied decimal point for the multiplication is between bit 9 and bit 10.
Register qmc_phase(11:0) control the phase imbalance between I and Q and is a 12-bit values with a range of –0.5 to approximately 0.49975. The QMC phase term is not a direct phase rotation but a constant that is multiplied by each "Q" sample then summed into the "I" sample path. This is an approximation of a true phase rotation to keep the implementation simple. The corresponding phase rotation corresponds to approximately +26.5 to –26.5 degrees in 4096 steps.
LO feed-through can be minimized by adjusting the DAC offset feature described below.