A 6-/12-dB back-off reconfigurable Doherty-like load modulated balanced amplifier with compact area and wide bandwidth

Abstract

This article presents a Doherty-like Reconfigurable Load Modulated Power Amplifier (R-LMBA) topology, which enables a broadband 6-/12-dB power back-off (PBO) reconfiguration by rearranging the bias voltages of the sub-amplifiers with compact area. The proposed R-LMBA guarantees proper phase differences among the three sub-PAs across the entire operating frequency band without the need for a bulky phase shifter that is adopted in conventional LMBAs. The design equations for the R-LMBA are proposed and analyzed in detail. A proof-of-concept PA has been designed in 0.1 μm GaAs pHEMT process to verify the proposed concept. In Mode-1, from 30 to 40 GHz, it achieves saturated output power (Psat) of 27.7–29.1 dBm with peak power added efficiency (PAE) of 28.5–34.4%, and 16.8–22.1% PAE at 6-dB PBO with its best 1.29 × efficiency enhancement over a Class-B counterpart. In Mode-2, it exhibits 28 dBm Psat with 30% peak PAE, and a PAE of 25%/13.6% at 6-/12-dB PBO, which is 1.67 × /1.81 × over an ideal Class-B PA. Besides, in Mode-1/-2, the PA demonstrates 21.3/20.3 dBm average output power (Pavg) and 17.9%/22.1% average PAE (PAEavg) with −28.1/-23.8 dB error vector magnitude (EVM) and −29.1/-25.9 dBc adjacent channel leakage ratio (ACLR) under 6-Gb/s 64-QAM modulated signal at 35 GHz.