The AD7011 is a complete low power, CMOS, /4 DQPSK modulator with single +5 V power supply. The part is designed to perform the baseband conversion of I and Q transmit waveforms in accordance with the American Digital Cellular Telephone system (TIA IS-54). The on-chip /4 Differential Quadrature Phase Shift Keying (DQPSK) digital modulator, which includes the root raised cosine filters, generates I and Q data in response to the transmit data stream. The AD7011 also contains ramp control envelope logic to shape the I and Q output waveforms when ramping up or down at the beginning or end of a transmit burst. Besides providing all the necessary logic to perform /4 DQPSK modulation, the part also provides reconstruction filters to smooth the DAC outputs, providing continuous time analog outputs. The AD7011 generates differential analog outputs for both the I and Q signals.