Linearity Improved Doherty Power Amplifier Using Composite Right/Left-Handed Transmission Lines

A Doherty power amplifier using composite right/left-handed transmission lines (CRLH-TL) is proposed for linearity improvement. The lambda/4 transmission line incorporating CRLH-TL is designed to suppress the second harmonic of the output of the main amplifier. The output power of the proposed power amplifier at the fundamental frequency (2.30 GHz) shows 31.0 dBm with 13 dBm input power excited. The Doherty power amplifier using CRLH-TL improves the linearity considerably compared to that without employing CRLH-TL.