A Highly Linear X-Band GaN HEMT Transformer-Based Doherty Power Amplifier

Abstract

This thesis presents an X-band Transformer-based Doherty Power Amplifier(PA) with a phase linearizer. Doherty PA used Cree inc. 6 W GaN HEMT bare die and implemented on 7-layer PCB. The phase linearizer compensates a phase distortion of Doherty PA. X-band Conventional Doherty PA is designed at 10 GHz for performance comparison with the X-band Transformer-based Doherty PA. The Conventional Doherty PA used Cree inc. 6 W GaN HEMT bare die and has been implemented using RT/Duroid 5880 10 mil thick substrate. The continuous wave (CW) measurement results show the peak output power of 40.3 dBm with a 40 V drain supply voltage at 10 GHz, the peak drain efficiency (DE) of 51% and the peak power added efficiency (PAE) of 40.3%. And the DE and PAE at 6 dB output power back-off are 41% and 33% respectively. X-band Transformer-based Doherty PA has been measured. The CW measurement results show the peak output power of 39.6 dBm with a 40 V supply at 9.56 GHz. The peak DE is 50.4% while the peak PAE is 38.5%. The DE and the PAE of the amplifier is still as high as 40% and 32.5% respectively at 6 dB output power back-off.