Design and Validation of a Concurrent Dual-Band GaN Doherty Power Amplifier

Abstract

In the current era characterized by rapid advancements in wireless communication, the demand for high data rates, multi-band operation and low power consumption in communication systems like mobile base stations, poses significant challenges. To address these challenges, it is imperative to explore and devise new power amplifier (PA) solutions that conform to these stringent requirements. This thesis presents a comprehensive solution in the form of a dual-band Doherty PA (DB-DPA) to meet these pressing requirements. DPAs have gained considerable popularity due to their ability to achieve high back-off efficiency across a wide range of output power levels. The primary objective of this research is to design and simulate a symmetrical DB-DPA using state-of-the-art GaN-HEMT technology, for the frequency bands of 1.85 and 2.65 GHz. The load modulation network comprises a wideband combiner followed by a Chebyshev transformer. Subsequently, the designed DB-DPA is fabricated, measured, and the obtained results are presented and analyzed in detail. Through extensive measurements, this study demonstrates that the proposed DBDPA design delivers satisfactory performance in terms of drain efficiency (DE) and power gain for both the lower and upper-frequency bands of 1.85/2.65 GHz with a bandwidth of 100 MHz each. At a peak power of 47.9/47.3 dBm, the DB-DPA achieves a DE of 55.6/54.5%. Furthermore, at a 6 dB back-off level, the DB-DPA exhibits a DE of 41.2/44.6% and a gain of 19.5/15 dB for the desired frequencies. These characteristics position this design as a promising candidate for communication applications. The findings presented in this research emphasize the potential of the proposed DB-DPA design and provide a viable solution that meets the growing requirements of the wireless industry. The comprehensive investigation conducted through simulations and measurements contributes to the body of knowledge in the field and provides valuable insights for further advancements in DB-DPA design.