A Novel Hybrid Polar-I/Q Modulation Method relaxing RF Phase Modulator Design Requirements

A novel modulation scheme enabling a seamless transition between digital-intensive quadrature and polar transmitter architectures by combining inphase / quadrature (I/Q) with phase modulation is presented. Uy incorporating phase modulation the digital-quadrature RF digital-to-analog converter (DAC) input codewords peak to average power ratio is reduced. Therefore, the quadrature RF-DAC can be operated in a lower back-off region resulting in higher average output power and drain efficiency. Simulation results for LTE uplink transmission including the novel modulation scheme in combination with a drain efficiency model for a shared-cell, switched-capacitor RF-DAC are shown. Compared to a digital-quadrature transmitter the average output power and efficiency can be increased, approaching the digital-polar limit while showing significantly lower tuning-range requirements on the phase modulation path.