GATE CURRENT CONTROL METHOD BY PULL-DOWN FETS FOR 0-28-DB GAAS VARIABLE ATTENUATOR IN DIRECT-CONVERSION MODULATOR-IC FOR 1.9-GHZ-PHS

We have developed 3 GaAs direct-conversion x 14 shifted QPSK modulator IC equipped with variable attenuators for controlling the output powe r level of the 1.4 GHz Personal Handy Phone system in Japan (PHS), The IC was successfully demonstrated showing state-of-the-art performance with the image rejection ratio of more than 36 dBc at a law input pow er of -10 dBm in 1.9 GHz frequency range. By using the ''Gate Current Control method by Pull-down FETs'' (GCCPF), the equipped attenuators v ary the output power from 0 dB to -28 dB by 4 dB step. The TC operates at a 7.7 V supply with power dissipation of 259 mW. The 2.6 x 4.6 mm( 2) chip with about 400 elements was fabricated by a 0.5 mu m WNx-gate BPLDD GaAs MESFET process.