A Novel Digital-Intensive Hybrid Polar-I/Q RF Transmitter Architecture

A novel digital-intensive hybrid transmitter (TX) architecture is presented, combining conventional inphase and quadrature (I/Q) with constrained phase modulation. The proposed architecture utilizes an RF-DAC with phase modulated RF clock and adjusted I/Q components. By incorporating phase modulation the quadrature component is kept small while the inphase component approaches the complex signal envelope. Compared to a digital-quadrature TX architecture this results in a significantly reduced average and peak RF-DAC cell utilization. Therefore, the RF-DAC can be operated in less back-off at higher average output power and drain efficiency. The phase modulation is constrained in order to relax the phase modulators system requirements. Compared to a digital polar TX architecture utilizing an RF digital phase-locked loop with two-point phase modulation, this results in reduced frequency modulation and digital-controlled oscillator tuning range requirements. In addition, the design effort is further shifted from analog to digital domain in order to better exploit the benefits of CMOS technology scaling.