A 9 dB back-off dual-band asymmetric Doherty power amplifier using dual peaking amplifiers for reactance compensation

This paper proposes a dual-band asymmetric Doherty power amplifier (ADPA) with 9 dB power back-off range using dual parallel peaking amplifiers to realize reactance compensation for wideband operation at two frequency bands. To achieve dual-band amplification, the specific phase delays of the carrier and peaking output matching networks (OMNs) required on the two target frequency bands were determined using the phase delay period repeatability principle combined with the Doherty impedance transformation first. Then, the carrier and peaking OMNs were designed according to the desired phase delay. More specifically, two parallel peaking amplifiers using the low-order impedance transformation network were combined to generate the desired compensating reactance at the back-off power range for wideband operation. For verification, a dual-band ADPA operating over 2.35-2.75 and 3.2-3.6 GHz frequency bands was designed and measured. Experimental results show that, for the two frequency bands, the efficiencies at saturation are 53.6%-64.3% and 48%-67.8%, with the 9 dB back-off efficiencies reaching 41.5%-53.3% and 40.5%-52.8%, respectively. When stimulated by a 20 MHz modulated signal, the designed ADPA can achieve the adjacent channel leakage ratio of -48 dBc after linearization.