Linearized asymmetrical GaN Doherty power amplifier with 100 MHz instantaneous bandwidth at 3.5GHz

This paper presents a linearized Doherty power amplifier (PA) operating over 100 MHz instantaneous bandwidth at 3.5 GHz. To maintain high efficiency at large back-off output power and achieve improved load modulation, the Doherty PA is designed by using unequal sized GaN devices. An uneven power divider is also utilized to deliver more input power to the peaking amplifier. Experimental results show that, for a 100 MHz modulated signal, the Doherty PA can achieve the efficiency of 42% at about 9 dB back-off output power of 39.5 dBm. The adjacent channel leakage ratio is about -25 dBc and can be improved to about -47 dBc by using digital pre-distortion technique.