Can a square wave LO be used for the LTC5584 and LT5599 IQ demodulators?
Both the LTC5584 and the LTC5599 should ideally be driven by a sine wave at the LO input. If the LTC5599 is driven with a square wave, the accuracy of the 0/90 quadrature split gets affected, but the part contains gain and phase adjustment circuitry that can be programmed to correct for these errors.
The LTC5584, however, does not have this correction circuitry. Driving the LTC5584 with a square wave LO will degrade the EVM of a demodulated QAM signal and there are no means to correct for this degradation. Therefore, the LTC5584 requires a sine wave LO drive to achieve the specified quadrature performance.
