Triband 1.2/1.8/2.7 GHz doherty power amplifier using novel output combining network

This paper presents a new topology for a triband Doherty power amplifier (DPA). It utilizes a triband impedance inverter, realized using a T-network, to synthesize a triband power combining network. This approach enables Doherty load modulation around three separate operating frequencies with suitable fractional bandwidths. For proof of concept, a demonstration DPA operating at 1200, 1800, and 2700 MHz was designed, using 10-W GaN HEMT transistors as main and peaking devices. Peak drain efficiencies of 55.3%, 66% and 46% are measured at output powers of 41.3 dBm, 42.7 dBm and 40.8 dBm in the three operation bands, respectively. At 6-dB output power back-off, drain efficiencies of 63.5%, 50% and 40% are attained. Fractional bandwidths of 16.6%, 13.37% and 7.46% are obtained at each of the above mentioned operation bands in order.