This configuration is a typical interface between a high speed DAC and a quadrature modulator. The two 50Ohm resistors provide a current return path for the DAC output and set the DC bias for the modulator input while the 100Ohm resistor helps limit the differential output swing (modulator input swing).

There are several ways to calculate the DAC output swing. The attached file shows two of them.

This configuration is a typical interface between a high speed DAC and a quadrature modulator. The two 50Ohm resistors provide a current return path for the DAC output and set the DC bias for the modulator input while the 100Ohm resistor helps limit the differential output swing (modulator input swing).

There are several ways to calculate the DAC output swing. The attached file shows two of them.