I will use an AD9652 ADC in first nyquist zone feeded by a zero IF downconverter, the input signal will be boosted by a HMC900LP5E Aliasing/VGA device, my current implementation foresee an ADC input stage that can handle both a double transformer as implemented in the EVM and AC coupled directly to the output of the VGA, by only unmounting/mounting transformers and resistors. The RF module is a mezzanine that can change in future, so the input stage can be easly modified. The double transformer implementation adopt the EVM circuit with differential input instead of a single-end and a AC capacitors of 2.2uF terminated to 400ohm as required by the HMC900. I wish to understand if i can use the double trasformer implementation also if is not required the balun function, for this specific mezzanine implementation, in particular I have some doubt that the double transformer will work well for frequency near to the DC as riquired in a zero IF, can someone help me ?
Obviously i need the best input quality as possible.