High efficiency class-E and compact Doherty power amplifiers with novel harmonics termination for handset applications

This paper presents high efficiency Class-E and compact Doherty power amplifiers (PAs) with novel harmonics termination for handset applications using a GaAs/InGaP heterojunction bipolar transistor (HBT) process. The novel harmonics termination circuit effectively reduces the insertion loss of the matching circuit, allowing a device with a compact size. The Doherty PA uses a lumped-element transformer which consists of metal-insulator-metal (MIM) capacitors on an IC substrate, a bonding-wire inductor and short micro-strip lines on a printed circuit board (PCB). The fabricated Class-E PA exhibits a power added efficiency (PAE) as high as 69.0% at 1.95 GHz and as high as 67.6% at 2.535 GHz. The fabricated Doherty PA exhibits an average output power of 25.5 dBm and a PAE as high as 50.1% under a 10-MHz band width quadrature phase shift keying (QPSK) 6.16-dB peak-to-average-power-ratio (PAPR) LTE signal at 1.95 GHz. The fabricated chip size is smaller than 1 mm². The input and output Doherty transformer areas are 0.5 mm by 1.0 mm and 0.7 mm by 0.7 mm, respectively.