A GaAs direct-conversion 1/4π shifted QPSK modulator IC with 0-28 dB variable attenuator for 1.9 GHz personal handy phone system

We have developed a GaAs direct-conversion 1/4/spl pi/ shifted QPSK modulator IC equipped with variable attenuators for controlling the output power level of the 1.9 GHz personal handy phone system (PHS). The IC was successfully demonstrated showing state-of-the-art performance with the image rejection ratio of more than 36 dB at a low input power of -10 dBm in the 1.9 GHz frequency range. By using the "Gate Current Control method by Pull-down FET's" (GCCPF), the equipped attenuators vary the output power from 0 dB to -28 dB by 4 dB step. The IC operates at a 2.7 V supply with the power dissipation of 259 mW. The 2.6/spl times/4.6 mm/sup 2/ chip with about 400 elements was fabricated by a 0.5 /spl mu/m WNx-gate BPLDD GaAs MESFET process.