A high-efficiency Class-F power amplifier using double CRLH-TL for LTE application

This paper describes a special form of metamaterials CRLH-TL (Composite Right/Left-Handed Transmission Line) applied to the design of high-efficiency Class-F power amplifier (Class-F PA). Due to CRLH-TL's dull-band characteristic, the CRLH-TL used to the Class-F power amplifier design can not only simplify the topology of PA circuit, but improve power additional efficiency (PAE) and realized the dual-band Class-F PA. The dull-band quarter-wavelength (λ/4) open-circuit CRLH-TL stub working at 5.2GHz and 7.8 GHz is proposed and firstly applied in input and output harmonic control networks for the Class-F PA, thus reducing the device sensitivity to second and third harmonic impedance terminations. As a result, a miniaturized and highly-efficient Class-F PA is obtained. Using a 10-W Cree GaN HEMT device, greater than 77% PAE has been measured from 2.570GHz to 2.620GHz, with output powers of 40.5-41.1dBm and second and third harmonic power ratios below -30.1dBc and -29.2dBc, respectively. To the best of the author's knowledge, the 82% efficiency represents the best performance obtained from a long-term evolution (LTE) band PA.