Doherty Linear Power Amplifiers for Mobile Handset Applications

Two Doherty amplifiers are designed in MMIC form, which are fabricated using a commercial InGaP/GaAs HBT foundry process. The one is classical Doherty type amplifier with the size ratio of the main device and auxiliary device of 1(N = 1), and the other is an extended Doherty with the size ratio of 3(N = 3). The input and output circuits are made using a hybrid circuit, forming power amplifier modules. The efficiencies are improved about 18.8% at Pout = 23 dBm, about 5 dB backed-off point, from the size ratio N = 1 amplifier, and about 21% at Pout = 18.6 dBm, about 10 dB backed-off point, from the size ratio N = 3 one. We have extended the technology to the fully integrated power amplifier chip. The amplifier shows an output power of 22.5 dBm and a power-added efficiency (PAE) of 21.3% at an error vector magnitude (EVM) of 5%, measured with 54 Mbps 64-QAM-OFDM signals at 5.2 GHz