GaN polar transmitter design for base-station applications

In this paper a comparative study of 10 watt GaN polar transmitters for base-station application is carried out. Two main topologies are compared and studied. In the first topology, the drain of the transistor is modulated with the pulse format of the signal´s envelope, and in the modified topology, the gate of the transistor is modulated with the pulse format of the signal´s envelope. The transmitters are compared for two main parameters, the power efficiency and the signal quality. After a brief description of both topologies, their advantages and disadvantages are described, especially in terms of efficiency and signal quality. A LTE signal with the bandwidth of 1.4 MHz, the PAPR of 7.2 dB and the sampling rate of 64 is used for comparison purposes. Using the LTE signal, the polar architecture with modulated drain bias is able to achieve an SNDR of 42 dBc and the drain efficiency of 44%, while an SNDR of 35 dBc and the drain efficiency of 53% are obtained for the modified polar transmitter with the gate bias modulation.