Efficiency-enhanced Doherty amplifier with extended bandwidth based on asymmetrical drain voltage

This paper presents design and implementation about an asymmetrical-Doherty-power-amplifier (A-DPA). The back-off efficiency and operating bandwidth are improved through considering knee-voltage (Vknee) effect and impedance-transformation-ratio (ITR) of inverter. The A-DPA is fabricated with NXP's 7th Generation Si LDMOS device BLF7G27-75P accompanied by the proposed combining network. Within a bandwidth of 300MHz, measurements perform drain efficiency of η ≧ 41 % and Gain of 14.1±0.6 dB over 7dB output power back-off for continuous wave signal. With linearization, the ADPA shows ACLR ≦ −45.8 dBc with drain efficiency η ≧ 41.4% in 2.25∼2.55 GHz under WCDMA signal with 7.8 dB PAPR at average power of 43 dBm. This is the widest bandwidth of DPA with high drain efficiency at output power 7 dB back-off using Si LDMOS packaged devices to the best of the authors' knowledge.