Highly Efficient 5.15-to 5.85-GHz Neutralized HBT Power Amplifier for LTE Applications

A highly efficient fully integrated 5.15- to 5.85-GHz GaAs HBT differential power amplifier (PA) is implemented for long-term evolution (LTE) handset applications considering LTE licensed-assisted access. A simple and practical output network, based on an on-chip transformer, is proposed to achieve low loss. A neutralization technique to mitigate the parasitic base-collector capacitance is also adopted to improve PA performances. The implemented PA achieved a high gain of 26.6-28.1 dB and saturated power of 30.5-31.1 dBm with a high peak power-added efficiency of 40.4%-44.5% under a continuous-wave signal test across 5.15-5.85 GHz. When tested with 20- and 40-MHz bandwidth quadrature phase-shift keying LTE signals, the PA showed an adjacent channel leakage ratio of -33 dBc up to output powers of 24.1-24.4 and 22.2-22.8 dBm, respectively.This work was supported in part by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education under Grant 2016R1D1A1A09919288 and in part by the Human Resource Program in Energy Technology of the Korea Institute of Energy Technology Evaluation and Planning from the Ministry of Trade, Industry and Energy, South Korea, under Grant 20154030200730