Schematic EP2S60 DAC and ADC

Good morning !!

I am are currently working on a project and we will wish to have more information concerning the schematic of the card of development stratix II EP2S60.

We would like to know why you use a transformer ADT1-1WT 75Ohm while impedance of SMA is 50Ohm (figure 1)?

Because it is necessary that one thus sends a signal in a coaxial cable 50 Ohm (figure 1) without loss of impedance are what one would not have had to put a transformer 50 Ohm.

And also, why do you use two transformers of different impedance. One is 50 Ohm, (ADT2-1T) other is 75ohm (ADT1-1WT) .(figure 2)

Best regards.