A new design approach of Rat-Race coupler based compact GaN HEMT power amplifier towards flat high efficiency over broadband

Abstract

This paper presents a high efficiency Rat-Race Coupler based compact GaN HEMT power amplifier (PA) design over broadband for high power transmitter in wireless communication. The rat-race coupler integrated PA Compact design is proposed for the first time as per author best knowledge. The design methodology used a higher order two open stubs and a rat-race coupler (RRC) at input/output sections to control harmonics impedances. The RRC is used to enhance the i/o power, and efficiency over broadband, which provides a good insertion loss, and consumes the least power and non-crucial impedance bandwidth for the normalized frequency band of interest. As a proof of concept, a PA is fabricated using a monolithic microwave integrated circuit (MMIC) 0.15 µm gallium nitride high electron mobility transistor (GaN HEMT) process. The measured result shows that the designed PA achieves a flat power added efficiency (PAE) of 65 % − 74 %, output power (Pout) of 44.8 dBm − 46 dBm, and drain efficiency (DE) of 72 % − 85 %, over a record wide frequency of 1.8 GHz − 3.6 GHz, which is the highest one among all reported harmonic tuned PAs.