QPSK modulators for digital cellular communication

Two quaternary-phase-shift-keying (QPSK) modulator ICs are described. These devices use a dual conversion architecture and image rejection techniques to integrate the modulation and upconversion functions of a digital cellular transmit chain. They feature low power dissipation and wideband operation while maintaining suppression of higher harmonics. For 2nd through 4th harmonics, 30 dBc of suppression are guaranteed. For the 5th harmonic and higher harmonics, 50 dBc are required. The modulation carrier is suppressed by greater than 30 dB as well. A sleep state dissipating less than 60 mW can be activated by applying a voltage to a single pin. A second version of the modulator includes an on-chip 90-degree phase shifter. Both devices are packaged in surface-mount small-outline packages.<
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