GaN HEMT Doherty Amplifiers for W-CDMA and WiMAX Base Station Applications

摘要

Two types of Doherty amplifiers for mobile communication base stations have been developed using GaN HEMTs biased at drain voltage of 50V At first, a 2.1GHz-band Doherty amplifier demonstrating a saturated output power (Psat) of 57.5dBm (560W) was designed, and then a 2.5GHz-band Doherty amplifier exhibiting a Psat of 54dBm (250W) was developed. Both Doherty amplifiers showed the drain efficiency of more than 50% at 6dB back-off power. The Doherty networks were designed with accurate large signal models and the measured results were in good agreement with the simulated results. We investigated the linearity using digital pre-distortion system, and the drain efficiency of more than 46% was obtained at 8dB back-off power achieving ACLR of less than -54dBc with common W-CDMA 2-carrier signal with peak to average power ratio of 7.8dB. These superior characteristics of GaN HEMT Doherty amplifiers showed good suitability for the base station transmitter system.