Direct-conversion quadrature modulator MMIC design with a new 90 degrees phase shifter including package and PCB effects for W-CDMA applications

A 1.9 GHz GaAs direct-conversion quadrature modulator MMIC adopting a new technique to generate 90/spl deg/; phase shift for W-CDMA applications is presented. This 90/spl deg/ phase shifter achieves a phase error less than 1.5/spl deg/ from 1.8 GHz to 2 GHz with extremely low implementation loss. The package and PCB interconnects are also analyzed using the 3-D EM simulation tool and transformed into the equivalent-circuit elements for co-simulation with the designed modulator MMIC. The dominant package and PCB effect is to degrade the sideband suppression, which is disadvantageous to the modulation quality.