Linear Doherty Power Amplifier with Enhanced Back-Off Efficiency Mode for LTE Applications

This paper presents a linear Doherty power amplifier (DPA) in microstrip technology designed at 1.7 GHz, for longterm evolution (LTE) applications. The DPA has been implemented using a low-cost GaAs HEMT with adoption of different drain bias voltage for main and auxiliary amplifiers to increase the overall gain. Measured performance of the proposed DPA across 1.48–1.83 GHz shows an output power of 31.5 dBm with 60% power added efficiency (PAE) at the 1-dB compression point (P1dB). The PAE is maintained higher than 50%, over 6 dB of output back-off range, and higher than 30% over 10 dB output power back-off. Moreover, the linearity performance of the designed DPA in terms of IMD3 is tested by applying a two-tone signal to the input of DPA which shows the IMD3 of less than -27 dBc at an output power of 31.5 dBm and -33 dBc at about 6 dB back-off power.